JP5305127B2 - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing apparatus for changing a height of a developer accumulated in the vicinity of a developer discharge port in response to the quantity of the developer within the apparatus, discharging the increased quantity of the developer when the quantity of the developer is increased within the apparatus, simplifying a constitution, and properly exchanging the developer within the apparatus, and an image forming apparatus with the developing apparatus. <P>SOLUTION: A supply downstream end wall surface 80 is provided so as to accumulate the developer in the vicinity of the developer discharge port 94 within a supply/transfer path 9. The developer discharge port 94 is provided so as to pass the developer attaining the height of the developer discharge port 94 among the accumulated developer T accumulated on the supply downstream end wall surface 80. An opening width W as a horizontal width of the developer discharge port 94 is configured so as to prevent the developer from attaining a discharge port upstream end 94f even if the developer attains a discharge port downstream end 94e among both ends of the developer discharge port 94 in the horizontal direction when the height of the accumulated developer T is maximized. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a developing device used for a copying machine, a facsimile, a printer, and the like, and an image forming apparatus using the developing device.

  Conventionally, an image forming apparatus including a developing device using a two-component developer including toner and a magnetic carrier has been widely used. As an image forming apparatus of this type, the toner density of the developer is kept within a predetermined range by supplying toner from the toner container as necessary to the developer in the developing apparatus that consumes toner with development. There is something to keep in. In such a configuration, the carrier in the developer is hardly consumed and used repeatedly, and therefore the carrier deteriorates as the image is output. Specifically, the coating film on the carrier surface is scraped by mechanical stress or the toner component is spent on the carrier surface. When the carrier is deteriorated, the ability to charge the toner of the carrier is gradually reduced, causing problems such as background stains, image density reduction, abnormal image density unevenness and toner scattering. For this reason, in this type of image forming apparatus, a service person regularly visits the user to exchange carriers. For this reason, maintenance costs are incurred, and the unit price for image formation is high.

  In Patent Document 1 and Patent Document 2, a premix developer in which a carrier and toner are mixed is supplied to the developer in the developing device to restore the toner density, and an increased amount of developer is removed from the developing device. A developing device to be discharged is described. In such a configuration, a new carrier in the premix developer is replenished to the developer in the developing device while the carrier that has become old due to the discharge of the developer is gradually discharged from the developing device. Then, the carrier replacement work can be omitted by replacing the carrier in the developer gradually with a new one by such discharge and replenishment.

In the developing device of Patent Document 1, a sensor for detecting the amount of developer is provided in a developer transport path through which the developer circulates in the developing device, and a shutter mechanism for opening and closing the developer discharge portion. In normal operation, the shutter is closed so that the developer is not discharged, and when the sensor detects that the volume of the developer exceeds a certain level, the shutter opens and the developer is discharged. ing. However, in this method, the configuration becomes complicated and the cost increases.
In the developing device of Patent Document 2, the developer is provided on the side wall on the downstream side of the position where the developer is supplied to the developing roller of the supply conveyance path that conveys the developer in the axial direction of the developing roller while supplying the developer to the developing roller. The developer is discharged out of the developing device from the developer discharge port. A circulation opening that communicates with the circulation conveyance path that delivers the developer to the upstream end of the supply conveyance path is provided downstream of the position where the developer discharge port is provided. In this developing device, when the premix developer is supplied and the amount of developer in the developing device increases, the bulk of the developer in the supply conveyance path increases. At this time, the developer that reaches the height of the developer discharge port at the position where the developer discharge port is provided is discharged from the developer discharge port to the outside of the developing device, and is not discharged at the position where the developer discharge port is provided. The developer is fed to the circulation conveyance path through the circulation opening. Further, in the state where the volume of the developer in the supply conveyance path does not change, the developer does not reach the height of the developer discharge port at the developer discharge port, so the developer is not discharged, and the supply conveyance path The developer that reaches the downstream side of the toner is sent to the circulation conveyance path.
In such a developing device, the increased amount of developer supplied by the premix developer is discharged from the developer discharge port, so that the carrier in the developer in the device is gradually replaced with a new one. Can continue. Further, since the developer is not discharged in a state where the volume of the developer in the supply conveyance path does not change, it is possible to prevent the developer amount in the developing device from decreasing. Further, when the volume of the developer reaches the height of the developer discharge port at the position of the developer discharge port, the developer that has reached the height of the developer discharge port is naturally discharged from the developer discharge port to the outside of the apparatus. . For this reason, a complicated developer discharging mechanism including a sensor and a shutter as in the developing device described in Patent Document 1 is not required, and it is possible to prevent the configuration from becoming complicated and costly.

Japanese Patent No. 2891845 JP 2000-112238 A

  However, as in Patent Document 2, in the case where the developer reaching the height of the developer discharge port is naturally produced from the developer discharge port to the outside of the apparatus, the amount of developer in the developing device does not increase. However, the developer may be discharged. The developer transported in the developer transport path may jump and be discharged due to the momentum of the transport, or when the transport member that imparts transport force to the developer is a transport screw, the rotating force of the developer. . As described above, when the developer jumps and is discharged, even if the developer in the developing device is in an appropriate amount or less than the appropriate amount, the jumped developer may be discharged. . This is a state in which the developer is discharged even though the amount of developer in the developing device has not increased. If the developer is discharged from the developer discharge port even though the developer is in an appropriate amount or less, the amount of developer in the developing device falls below the required amount, and the development on the latent image carrier is performed. The supply of the agent might become unstable. If the supply of the developer to the latent image carrier becomes unstable, abnormal images such as missing images may occur.

As a result of intensive studies by the present inventors, it was found that the developer can be prevented from jumping out and discharged by retaining the developer near the developer discharge port in the developer conveyance path. This is due to the following reason.
First, by retaining the developer in the vicinity of the developer discharge port, the momentum of the developer conveyed in the developer conveyance path can be suppressed in the vicinity of the developer discharge port, and the developer can be prevented from jumping. I can do it. Further, by retaining the developer, the developer that contacts the transport screw is suppressed by the weight of the developer above it, and the developer can be prevented from jumping by the rotating force of the transport screw. I can do it.
Further, by arranging the developer discharge port so that the developer that has reached the height of the developer discharge port out of the retained developer that is the retained developer is passed, the amount of developer in the entire developer conveyance path When the volume of the staying developer increases in accordance with the increase in the developer, the increased amount of developer can be discharged.

However, the developing device in which the developer discharge port is disposed so that the developer stays in the vicinity of the developer discharge port and the developer that has reached the height of the developer discharge port of the retained developer passes therethrough. Then, the developer discharge port may be clogged and the developer may not be discharged.
The reason why the developer is clogged in the developer discharge port can be considered as follows.
FIG. 27 is an enlarged explanatory view near the developer discharge port 94. In FIG. 27, the front side in the figure with respect to the developer discharge port 94 is the supply conveyance path, and the hatched portion in the figure indicates the developer. The arrow L direction in FIG. 27 is the developer conveyance direction in the supply conveyance path, and the developer in the supply conveyance path is developed by passing the developer discharge port 94 from the front side to the back side in FIG. The developer is discharged to a discharge conveyance path that conveys the toner to the outside.
FIG. 27A is an explanatory diagram showing the positional relationship between the developer discharge port 94 and the staying developer T in a steady state where there is no change in the developer amount in the developing device. As shown in FIG. 27A, the uppermost portion of the staying developer T is substantially the same height as the discharge port lower end portion 94 u of the developer discharge port 94. In this state, the developer is not discharged and circulates in the developing device. In FIG. 27B, the developer is replenished in the developing device in the state of FIG. 27A, the amount of developer in the developing device increases, and the volume of the staying developer T at the position of the developer discharge port 94 is increased. FIG. 10 is an explanatory diagram showing a positional relationship between the developer discharge port 94 and the staying developer T in a state where the amount of increase is increased. As the developer amount in the developing device increases, the bulk of the staying developer T increases at the position where the developer discharge port 94 is provided in the supply conveyance path as shown in FIG. At this time, the staying developer T that has reached the height of the developer discharge port 94 passes through the developer discharge port 94 and is discharged to the outside of the developing device as indicated by an arrow N in FIG. At this time, the stagnant developer T, which has increased in volume due to an increase in the developer amount, is naturally collapsed and developed when the part of the developer discharge port 94 that is higher than the lower end portion 94u of the discharge port becomes a certain height. It passes through the agent discharge port 94 and is discharged.
In the state shown in FIG. 27 (b), if the replenishment amount per hour is larger than the discharge amount per hour indicated by the arrow N in the figure, the staying developer near the developer discharge port 94 is larger. The bulk of T is further increased, and the state shown in FIG. FIG. 27C shows a state in which the discharge port lower end portion 94u is covered with the staying developer T from the discharge port downstream end portion 94e to the discharge port upstream end portion 94f. That is, in the horizontal direction, the stagnant developer T having an increased volume has reached the discharge port downstream end portion 94e and the discharge port upstream end portion 94f, which are both end portions of the developer discharge port 94.
FIG. 28 shows a schematic view of the vicinity of the developer discharge port 94 in the state of FIG.

As shown in FIG. 28, the developer discharge port 94 communicates the adjacent supply conveyance path 9 and the discharge conveyance path 2 with the discharge partition wall 135 interposed therebetween. Further, the developer discharge port 94 has a depth corresponding to the thickness of the discharge partition wall 135, the discharge port upper end portion 94t is the upper surface of the developer discharge port 94, the discharge port lower end portion 94u is the bottom surface, and the discharge port upstream end portion. 94f and the outlet downstream end 94e form a wall surface. Then, a part of the developer that has entered the developer discharge port 94 from the supply conveyance path 9 is put on the discharge port lower end portion 94 u that is the bottom surface of the developer discharge port 94.
In the discharge port lower end portion 94u in the state of FIG. 27C, as shown in FIG. 28, the width from the discharge port upstream end portion 94f to the discharge port downstream end portion 94e, which is the opening width of the developer discharge port 94 in the horizontal direction. The staying developer T exists in the supply conveyance path 9 in a wider range. At this time, the developer is present in the entire area in the horizontal direction at the discharge lower end portion 94u which is the bottom surface of the developer discharge port 94. In such a state, the developer on the lower discharge end portion 94u causes the developer on the lower side by the weight of the upper developer and the force received from the wall surfaces of the discharge outlet upstream end portion 94f and the discharge outlet downstream end portion 94e. Will be packed under pressure. Further, since the developer in the supply conveyance path 9 in the vicinity of the developer discharge port 94 is the staying developer T, the movement of the developer is small and the developer is in a packed state at the developer discharge port 94. Since it is difficult to apply an external force due to conveyance, the developer once packed is not easily collapsed from the developer discharge port 94 and is easily fixed.
In the area where the developer is fixed, the developer discharge port 94 is closed. At this time, it is possible to pass through the developer discharge port 94 above the area where the developer is fixed, but the developer is also packed and fixed on the fixed developer. Then, when the developer is in the packing state, the region where the developer is fixed spreads from the bottom to the top in order, and the fixed developer eventually closes the entire developer discharge port 94, and the developer There arises a problem that the discharge port 94 is clogged.

  If replenishment of the developer continues in a state where the developer discharge port 94 is clogged and the developer cannot be discharged, the amount of the developer in the developing device continues to increase without being replaced. Then, the air pressure in the developing device rises, and the developer is ejected from a gap that normally does not allow the developer to pass, leading to contamination in the image forming apparatus equipped with the developing device. Furthermore, the amount of developer in the developer device may exceed the amount of developer that can be accommodated in the developer device, leading to damage to the developer device.

27 and 28, the staying developer T exists in a wider range than the width from the discharge port upstream end portion 94f to the discharge port downstream end portion 94e at the discharge port lower end portion 94u of the developer discharge port 94. The phenomenon that the developer is clogged in the developer discharge port 94 due to the above has been described.
The same phenomenon occurs when the developer reaches the upper end portion of the developer discharge port 94, that is, in a range where the developer discharge port 94 is wider than the width from the discharge port upper end portion 94t to the discharge port lower end portion 94u. This can occur even in the presence of the agent T.
In a state where the staying developer T reaches the discharge port upper end portion 94t, the developer on the discharge port lower end portion 94u that is the bottom surface of the developer discharge port 94 is discharged to the discharge port upper end portion 94t that is the upper surface of the developer discharge port 94. And a packing state due to pressure sandwiched in the vertical direction from the outlet lower end 94u. When the developer that has been packed in response to the pressure in the vertical direction is fixed to the discharge port upper end portion 94t and the discharge port lower end portion 94u, the region where the developer is fixed in the horizontal direction expands from the vicinity where the developer is fixed. The developer discharge port 94 is clogged. Since the packing is in the height direction, it may collapse due to some impact, but the broken developer spreads on the discharge port lower end portion 94u, and the discharge port upstream end portion 94f and the discharge port downstream end portion 94e described above. The packing state receives pressure from the wall surface of the toner and leads to fixing of the developer.

  In addition, such a problem is not limited to a developing device using a two-component developer, and the developer is replenished by the developer replenishing means, and the increased amount of the developer in the developing device is discharged. This is a problem that may occur even in a developing device using a one-component developer as long as the developing device has a configuration of discharging from the outlet.

  The present invention has been made in view of the above problems, and the object thereof is that the volume of the developer staying in the vicinity of the developer discharge port varies depending on the amount of developer in the apparatus, A developing device that discharges an increased amount of developer when the amount of developer in the device increases, a developing device that can easily replace the developer in the device with a simple configuration, and the developing device Is provided.

In order to achieve the above object, the invention according to claim 1 is characterized in that the developer is carried on the surface and rotated, and the toner is supplied to the latent image on the surface of the latent image carrier at a position facing the latent image carrier. A developer carrying member for developing the developer and a developer carrying member for carrying the developer, and supplying the developer to the developer carrying member while supplying the developer to the developer carrying member. A developer transport path for transporting the developer, and developer replenishing means for replenishing the developer to the developer transport path, and the volume of the developer according to an increase or decrease in the amount of the developer in the entire developer transport path. In a developing device provided with a developer discharge port for discharging the developer to the outside of the apparatus at a predetermined height in a position in the developer transport path where the developer increases or decreases, the developer discharge port in the developer transport path A developer retaining means for retaining the developer in the vicinity, and the developer discharge port is blocked by the developer retaining means; Provided so as to pass the residence developer developer that has reached the height of the developer discharge port of, reaching該滞distillate developer to the developer discharge port, and the bulk of該滞distillate developer maximum In this state, the opening width in the horizontal direction of the developer discharge port is set so that the developer does not reach both end portions of the developer discharge port in the horizontal direction.
According to a second aspect of the present invention, there is provided a developer for carrying and developing a developer on the surface thereof, supplying toner to the latent image on the surface of the latent image carrier and developing it at a position facing the latent image carrier. Development that includes a carrier and a developer conveying member that conveys the developer, and that conveys the developer while supplying the developer to the developer carrier in a developer supply region that supplies the developer to the developer carrier. The developer having a developer transport path and developer replenishing means for replenishing the developer to the developer transport path, and the developer volume increases or decreases in accordance with the increase or decrease in the amount of the developer in the entire developer transport path In a developing device provided with a developer discharge port for discharging the developer to the outside of the device at a predetermined height in the conveyance path, the developer stays in the vicinity of the developer discharge port in the developer conveyance path A developer retaining means, and the developer discharge port is a reservoir of the retained developer retained by the developer retaining means. Provided so as to pass the developer that has reached the height of the developer discharge opening, in a state in which reaches該滞distillate developer to the developer discharge port, the bulk of該滞distillate developer is maximized, the The opening width in the height direction of the developer discharge port is set so that the developer does not reach the upper end portion of the developer discharge port.
According to a third aspect of the present invention, there is provided a developer for carrying and developing a developer on the surface, supplying the toner to the latent image on the surface of the latent image carrier and developing it at a position facing the latent image carrier. Development that includes a carrier and a developer conveying member that conveys the developer, and that conveys the developer while supplying the developer to the developer carrier in a developer supply region that supplies the developer to the developer carrier. The developer having a developer transport path and developer replenishing means for replenishing the developer to the developer transport path, and the developer volume increases or decreases in accordance with the increase or decrease in the amount of the developer in the entire developer transport path staying at a predetermined height position in the transport path, in the developing device having a developer discharge port for discharging the developer to the outside of the apparatus, in the vicinity of the developer discharge port of the developer conveying path developer A developer retaining means, and the developer discharge port is a reservoir of the retained developer retained by the developer retaining means. Provided so as to pass the developer that has reached the height of the developer discharge opening, in a state in which reaches該滞distillate developer to the developer discharge port, the bulk of該滞distillate developer is maximized, horizontal Horizontal opening of the developer discharge port so that the developer does not reach both end portions of the developer discharge port in the direction and the developer does not reach the upper end portion of the developer discharge port. The width and the opening width in the height direction of the developer discharge port are set.
According to a fourth aspect of the present invention, there is provided a developer that rotates by supporting a developer on the surface and supplying toner to the latent image on the surface of the latent image carrier at a position facing the latent image carrier. Development that includes a carrier and a developer conveying member that conveys the developer, and that conveys the developer while supplying the developer to the developer carrier in a developer supply region that supplies the developer to the developer carrier. The developer having a developer transport path and developer replenishing means for replenishing the developer to the developer transport path, and the developer volume increases or decreases in accordance with the increase or decrease in the amount of the developer in the entire developer transport path In a developing device provided with a developer discharge port for discharging the developer to the outside of the device at a predetermined height in the conveyance path, the developer stays in the vicinity of the developer discharge port in the developer conveyance path A developer retaining means, and the developer discharge port is a reservoir of the retained developer retained by the developer retaining means. Provided to allow the developer reaching the height of the developer discharge port to pass therethrough, when continuously developing the maximum number of images that can set a full-color image, or continuously with the maximum number of images with an image area ratio of 1% or less In the case of developing, the opening width in the horizontal direction of the developer discharge port is set so that the developer does not reach both end portions of the developer discharge port in the horizontal direction.
According to a fifth aspect of the present invention, there is provided a developer that rotates by supporting a developer on the surface and supplying toner to the latent image on the surface of the latent image carrier at a position facing the latent image carrier. Development that includes a carrier and a developer conveying member that conveys the developer, and that conveys the developer while supplying the developer to the developer carrier in a developer supply region that supplies the developer to the developer carrier. The developer having a developer transport path and developer replenishing means for replenishing the developer to the developer transport path, and the developer volume increases or decreases in accordance with the increase or decrease in the amount of the developer in the entire developer transport path In a developing device provided with a developer discharge port for discharging the developer to the outside of the device at a predetermined height in the conveyance path, the developer stays in the vicinity of the developer discharge port in the developer conveyance path A developer retaining means, and the developer discharge port is a reservoir of the retained developer retained by the developer retaining means. Provided to allow the developer reaching the height of the developer discharge port to pass therethrough, when continuously developing the maximum number of images that can set a full-color image, or continuously with the maximum number of images with an image area ratio of 1% or less In the case of development, an opening width in the height direction of the developer discharge port is set so that the developer does not reach the upper end portion of the developer discharge port.
The invention of claim 6 is the developing device according to claim 1, 2 , 3, 4 or 5 , wherein the developer conveying path is configured to supply the developer to the developer carrying body while supplying the developer carrying body. A supply conveyance path that conveys the developer along the axial direction, and a circulation conveyance path that conveys the developer that has reached the downstream end in the conveyance direction of the supply conveyance path to the upstream end in the conveyance direction of the supply conveyance path, A developer discharge port is provided in the vicinity of the downstream end of the supply conveyance path in the developer conveyance direction.
The invention of claim 7 is the developing device according to claim 1, 2 , 3 , 4, 5 or 6 , wherein the developer conveying path supplies the developer to the developer carrying member while carrying the developer. A supply conveyance path for conveying the developer along the axial direction of the body, a circulation conveyance path for conveying the developer that has reached the downstream end in the conveyance direction of the supply conveyance path to the upstream end in the conveyance direction of the supply conveyance path, The developer separated from the surface of the developer carrier after passing through the portion facing the latent image carrier is collected, and along the axial direction of the developer carrier, and in the same direction as the supply conveyance path A recovery transport path that transports the developer transported to the most downstream side in the transport direction of the supply transport path and the most downstream side in the transport direction of the recovery transport path. Along the axial direction of the developer carrier, and the supply conveyance path is reversed. The developer is transported in the direction and supplied to the upstream end in the transport direction of the supply transport path.
The invention of claim 8 is characterized in that, in the developing device of claim 1, 2 , 3 , 4 , 5, 6 or 7 , the fluctuation range of the bulk density of the developer is suppressed to 15% or less. To do.
According to a ninth aspect of the present invention, there is provided the developing device according to the first, second, third , fourth, fifth , sixth, seventh or eighth aspect , wherein the developer passing through the developer discharge port from the developer transport path is developed by the developing device. The developer conveying path and the discharge conveying path are adjacent to each other with a partition wall interposed therebetween and communicated with each other at the developer discharging port. When the developer to be discharged through the developer discharge port is stacked on the lower surface of the developer discharge port formed by the thickness of the partition wall at the lower end, the discharge of the developer is hindered. The thickness of the partition wall forming the lower surface of the developer discharge port is set so that the amount of developer in the developing device does not increase.
According to a tenth aspect of the present invention, in the developing device according to the first, second, third , fourth, fifth , sixth, seventh , eighth or ninth aspect , the developer that has passed through the developer discharge port from the developer conveyance path is provided. A developer conveying path that conveys the developer outside, the developer conveying path and the discharge conveying path are adjacent to each other across a partition wall, and communicate with each other at the developer discharging port; the developer discharging port; The thickness of the partition wall at the lower end of the opening is set to 2 [mm] or less.
According to an eleventh aspect of the present invention, in the developing device according to the first, second, third , fourth, fifth , sixth, seventh , eighth, ninth, or tenth development, the development that has passed through the developer discharge port from the developer transport path A developer transport path for transporting the developer to the outside of the developing device, the developer transport path and the discharge transport path are adjacent to each other across a partition wall, and communicate with each other at the developer discharge port. The shape of the partition wall at the portion forming the lower end of the opening of the discharge port is an angular shape with an apex at the top or an R shape with an upward projection.
According to a twelfth aspect of the present invention, at least a latent image carrier, charging means for charging the surface of the latent image carrier, and formation of a latent image for forming an electrostatic latent image on the latent image carrier. And a developing unit for developing the electrostatic latent image into a toner image, wherein the developing unit is defined as claim 1, 2, 3, 4, 5, 6, 7, 8 , 9, 10 or 11 is used.

In the developing device having the configuration according to claim 1, the developer discharge port so that the developer does not reach both end portions of the developer discharge port in the horizontal direction in a state where the bulk of the staying developer is maximized. Since the opening width in the horizontal direction is set, it is possible to prevent the staying developer from being present in a wider range than the width from one end to the other end in the horizontal direction of the developer discharge port. Thereby, it is possible to prevent the developer from being packed by receiving pressure from the discharge port upstream end portion 94f and the discharge port downstream end portion 94e, and to prevent the developer from sticking.
Further, in the developing device having the configuration according to the second aspect, the developer discharge port is arranged so that the developer does not reach the upper end of the developer discharge port in a state where the bulk of the staying developer is maximized. Since the opening width in the height direction is set, it is possible to prevent the staying developer from being in a range wider than the width from the lower end portion to the upper end portion of the developer discharge port. Accordingly, it is possible to prevent the developer from being packed by receiving pressure from the discharge port upper end portion 94t and the discharge port lower end portion 94u, and to prevent the developer from sticking.
Furthermore, in the developing device having the configuration of claim 3, the developer is prevented from reaching the both end portions of the developer discharge port in the horizontal direction in a state where the bulk of the staying developer is maximized. Since the opening width in the horizontal direction of the discharge port is set, the staying developer does not exist in a range wider than the width from one end portion to the other end portion of the developer discharge port in the horizontal direction. Thereby, it is possible to prevent the developer from being packed by receiving pressure from the discharge port upstream end portion 94f and the discharge port downstream end portion 94e, and to prevent the developer from sticking. Furthermore, since the opening width in the height direction of the developer discharge port is set so that the developer does not reach the upper end portion of the developer discharge port, it is wider than the width from the lower end portion to the upper end portion of the developer discharge port. The staying developer does not exist in the range. Accordingly, it is possible to prevent the developer from being packed by receiving pressure from the discharge port upper end portion 94t and the discharge port lower end portion 94u, and to prevent the developer from sticking.

According to the first to twelfth aspects of the present invention, it is possible to prevent the developer discharge port from being clogged by preventing the developer from sticking with a simple configuration in which the opening width of the developer discharge port is set. And there is an excellent effect that a good developer can be exchanged.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of a tandem type color laser copier (hereinafter simply referred to as “copier 500”) in which a plurality of photoconductors are arranged in parallel will be described.
FIG. 1 is a schematic configuration diagram of a copying machine 500 according to the present embodiment. The copier 500 includes a printer unit 100, a paper feeding device 200 on which the printer unit 100 is placed, a scanner 300 fixed on the printer unit 100, and the like. An automatic document feeder 400 fixed on the scanner 300 is also provided.

  The printer unit 100 includes an image forming unit including four sets of process cartridges 18Y, 18M, 18C, and 18K for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). 20 is provided. Y, M, C, and K attached to the numbers of the respective symbols indicate members for yellow, cyan, magenta, and black (the same applies hereinafter). In addition to the process cartridges 18Y, 18M, 18C, and 18K, an optical writing unit 21, an intermediate transfer unit 17, a secondary transfer device 22, a resist roller pair 49, a belt fixing type fixing device 25, and the like are disposed. .

The optical writing unit 21 includes a light source (not shown), a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of a photoreceptor to be described later with laser light based on image data.
The process cartridges 18Y, 18M, 18C, and 18K include a drum-shaped photosensitive member 1, a charger, a developing device 4, a drum cleaning device, a static eliminator, and the like.

Hereinafter, the yellow process cartridge 18 will be described.
The surface of the photoreceptor 1Y is uniformly charged by a charger as charging means. The surface of the photoreceptor 1 </ b> Y that has been subjected to charging processing is irradiated with laser light that has been modulated and deflected by the optical writing unit 21. Thereby, the potential of the surface of the photoreceptor 1Y of the irradiation part (exposure part) is attenuated. Due to the attenuation of the surface potential, an electrostatic latent image for Y is formed on the surface of the photoreceptor 1Y. The formed electrostatic latent image for Y is developed by the developing device 4Y as developing means to become a Y toner image.
The Y toner image formed on the Y photoconductor 1Y is primarily transferred to an intermediate transfer belt 110 described later. The surface of the photoreceptor 1Y after the primary transfer is cleaned of the transfer residual toner by a drum cleaning device.
In the Y process cartridge 18Y, the photoconductor 1Y cleaned by the drum cleaning device is discharged by the charge eliminator. Then, it is uniformly charged by the charger and returns to the initial state. The series of processes as described above is the same for the other process cartridges 18M, 18C, and 18K.

Next, the intermediate transfer unit will be described.
The intermediate transfer unit 17 includes an intermediate transfer belt 110, a belt cleaning device 90, and the like. Further, it also includes a tension roller 14, a driving roller 15, a secondary transfer backup roller 16, four primary transfer bias rollers 62Y, M, C, and K.
The intermediate transfer belt 110 is tensioned by a plurality of rollers including the tension roller 14. Then, it is endlessly moved clockwise in the drawing by the rotation of the driving roller 15 driven by a belt driving motor (not shown).
The four primary transfer bias rollers 62Y, 62M, 62C, and 62K are disposed so as to be in contact with the inner peripheral surface side of the intermediate transfer belt 110, respectively, and receive primary transfer bias from a power source (not shown). Further, the intermediate transfer belt 110 is pressed toward the photoreceptors 1Y, 1M, 1C, and 1K from the inner peripheral surface side to form primary transfer nips. In each primary transfer nip, a primary transfer electric field is formed between the photoreceptor 1 and the primary transfer bias roller 62 due to the influence of the primary transfer bias.
The above-described Y toner image formed on the Y photoconductor 1Y is primarily transferred onto the intermediate transfer belt 110 due to the influence of the primary transfer electric field and nip pressure. On the Y toner image, the M, C, K toner images formed on the M, C, K photoconductors 1M, C, K are sequentially superposed and primarily transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) that is a multiple toner image is formed on the intermediate transfer belt 110.
The four-color toner image superimposed and transferred onto the intermediate transfer belt 110 is secondarily transferred onto a transfer sheet (not shown) as a recording medium at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt 110 after passing through the secondary transfer nip is cleaned by a belt cleaning device 90 that sandwiches the belt with the driving roller 15 on the left side in the drawing.

Next, the secondary transfer device 22 will be described.
Below the intermediate transfer unit 17 in the figure, a secondary transfer device 22 is disposed in which a paper conveying belt 24 is stretched by two stretching rollers 23. The paper transport belt 24 is moved endlessly in the counterclockwise direction in the drawing in accordance with the rotational drive of at least one of the stretching rollers 23. One of the two stretching rollers 23 arranged on the right side in the drawing sandwiches the intermediate transfer belt 110 and the paper transport belt 24 between the secondary transfer backup roller 16 of the intermediate transfer unit 17. It is out. By this sandwiching, a secondary transfer nip is formed in which the intermediate transfer belt 110 of the intermediate transfer unit 17 and the paper transport belt 24 of the secondary transfer device 22 are in contact with each other. A secondary transfer bias having a polarity opposite to that of the toner is applied to the one stretching roller 23 by a power source (not shown). By applying this secondary transfer bias, the four-color toner image on the intermediate transfer belt 110 of the intermediate transfer unit 17 is electrostatically moved from the belt side toward the one stretching roller 23 side in the secondary transfer nip. A next transfer electric field is formed. The transfer paper fed into the secondary transfer nip so as to synchronize with the four-color toner image on the intermediate transfer belt 110 by a registration roller pair 49 to be described later has four colors affected by the secondary transfer electric field and nip pressure. The toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to one of the stretching rollers 23 as described above, a charger for charging the transfer paper in a non-contact manner may be provided.

  In the paper feeding device 200 provided at the lower part of the copying machine 500 main body, a plurality of paper feeding cassettes 44 in which a plurality of transfer sheets can be stacked and stored in a bundle of sheets are arranged so as to overlap each other in the vertical direction. It is installed. Each paper feed cassette 44 presses the paper feed roller 42 against the uppermost transfer paper in the paper bundle. Then, by rotating the paper feed roller 42, the uppermost transfer paper is sent out toward the paper feed path 46.

  The paper feed path 46 that receives the transfer paper delivered from the paper feed cassette 44 includes a plurality of transport roller pairs 47 and a registration roller pair 49 provided near the end in the paper feed path 46. Then, the transfer paper is conveyed toward the registration roller pair 49. The transfer sheet conveyed toward the registration roller pair 49 is sandwiched between the rollers of the registration roller pair 49. On the other hand, in the intermediate transfer unit 17, the four-color toner image formed on the intermediate transfer belt 110 enters the secondary transfer nip as the belt moves endlessly. The registration roller pair 49 sends out the transfer paper sandwiched between the rollers at a timing at which the transfer paper can be brought into close contact with the four-color toner image at the secondary transfer nip. Thereby, in the secondary transfer nip, the four-color toner image on the intermediate transfer belt 110 is in close contact with the transfer paper. Then, it is secondarily transferred onto the transfer paper and becomes a full color image on the white transfer paper. The transfer paper on which the full-color image is formed in this manner exits the secondary transfer nip as the paper transport belt 24 moves endlessly, and then is sent from the paper transport belt 24 to the fixing device 25.

  The fixing device 25 includes a belt unit that moves the fixing belt 26 endlessly while being stretched by two rollers, and a pressure roller 27 that is pressed toward one roller of the belt unit. The fixing belt 26 and the pressure roller 27 are in contact with each other to form a fixing nip, and the transfer paper received from the paper transport belt 24 is sandwiched therebetween. Of the two rollers in the belt unit, the roller that is pressed from the pressure roller 27 has a heat source (not shown) inside, and heats the fixing belt 26 by the generated heat. The heated fixing belt 26 heats the transfer paper sandwiched in the fixing nip. The full color image is fixed on the transfer paper by the influence of the heating and the nip pressure.

  The transfer paper subjected to the fixing process in the fixing device 25 is stacked on the stack portion 57 provided outside the left side plate in the drawing of the printer housing, or forms a toner image on the other surface. To the secondary transfer nip described above.

  When a document (not shown) is copied, for example, a bundle of sheet documents is set on the document table 30 of the automatic document feeder 400. However, when the original is a single-sided original that is closed in a main form, it is set on the contact glass 32. Prior to this setting, the automatic document feeder 400 is opened with respect to the copying machine main body, and the contact glass 32 of the scanner 300 is exposed. Thereafter, the single-bound original is pressed by the closed automatic document feeder 400.

  When a copy start switch (not shown) is pressed after the document is set in this way, the document reading operation by the scanner 300 starts. However, when a sheet document is set on the automatic document feeder 400, the automatic document feeder 400 automatically moves the sheet document to the contact glass 32 prior to the document reading operation. In the document reading operation, first, the first traveling body 33 and the second traveling body 34 start traveling together, and light is emitted from a light source provided in the first traveling body 33. Then, the reflected light from the document surface is reflected by a mirror provided in the second traveling body 34, passes through the imaging lens 35, and then enters the reading sensor 36. The reading sensor 36 constructs image information based on the incident light.

  In parallel with such a document reading operation, each device in each of the process cartridges 18Y, 18M, 18C, 18K, the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 starts driving. Based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled, and Y, M, C, and K toner images are formed on the respective photoreceptors 1Y, 1M, 1C, and 1K. Is done. These toner images become four-color toner images superimposed and transferred on the intermediate transfer belt 110.

  Further, almost simultaneously with the start of the document reading operation, the paper feeding operation is started in the paper feeding device 200. In this paper feeding operation, one of the paper feeding rollers 42 is selectively rotated, and the transfer paper is sent out from one of the paper feeding cassettes 44 accommodated in the paper bank 43 in multiple stages. The fed transfer sheets are separated one by one by the separation roller 45 and enter the reverse feeding path 46, and then conveyed toward the secondary transfer nip by the conveyance roller pair 47. In some cases, paper feeding from the manual feed tray 51 is performed instead of such paper feeding from the paper feeding cassette 44. In this case, after the manual feed roller 50 is selectively rotated to feed the transfer paper on the manual feed tray 51, the separation roller 52 separates the transfer paper one by one and feeds it to the manual feed path 53 of the printer unit 100. Make paper.

  When the copier 500 forms a multicolor image composed of toners of two or more colors, the intermediate transfer belt 110 is stretched so that the upper stretched surface thereof is substantially horizontal, and all the upper stretched surface is placed on the upper stretched surface. Photoconductors 1Y, 1M, 1C, and 1K are brought into contact with each other. On the other hand, when forming a monochrome image consisting of only K toner, the intermediate transfer belt 110 is tilted to the lower left in the drawing by a mechanism (not shown) and the upper stretched surface is set to Y, M, C. The photoconductors 1Y, 1M, and 1C are separated. Of the four photoconductors 1Y, 1M, 1C, and 1K, only the K photoconductor 1K is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, not only the photosensitive member 1 but also the developing device 4 is stopped, and each member of the photosensitive member 1 and the developing device 4 and the developer in the developing device 4 are unnecessarily consumed. To prevent.

  The copier 500 includes a control unit (not shown) composed of a CPU and the like that controls each device in the copier 500, and an operation display unit (not shown) composed of a liquid crystal display, various key buttons, and the like. . The operator sends a command to the control unit by a key input operation on the operation display unit, so that one of the three modes is selected from the three-sided print mode, which is a mode for forming an image only on one side of the transfer paper. You can choose one. The three single-sided printing modes include a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode.

FIG. 2 is an enlarged configuration diagram illustrating the developing device 4 and the photosensitive member 1 included in one of the four process cartridges 18Y, 18M, 18C, and 18K. Since the four process cartridges 18Y, 18M, 18C, and 18K have substantially the same configuration except that the colors of the toners to be handled are different, the subscripts Y, M, C, and K added to “4” in FIG. Is omitted.
As shown in FIG. 2, the surface of the photosensitive member 1 is charged by a charging device (not shown) while rotating in the direction of arrow G in the drawing. The charged surface of the photoreceptor 1 is supplied with toner from the developing device 4 to a latent image on which an electrostatic latent image is formed by laser light emitted from an exposure device (not shown), thereby forming a toner image.

The developing device 4 has a developing roller 5 as a developer carrying member for supplying toner to the latent image on the surface of the photoreceptor 1 while moving the surface in the direction of arrow I in the drawing. The developing roller 5 includes a rotatable developing sleeve, and a magnetic body (not shown) including a plurality of magnetic poles is disposed therein. The magnetic material is necessary for holding the developer on the surface of the developing roller 5.
Further, a supply screw 8 is provided as a supply conveyance member that conveys the developer in the depth direction of FIG. 2 along the axial direction of the development roller 5 while supplying the development roller 5 with the developer.
A doctor blade 12 as a developer regulating means for regulating the developer supplied to the developing roller 5 to a thickness suitable for development is provided on the downstream side of the surface moving direction from the portion facing the supply screw 8 of the developing roller 5. ing.
A collection conveyance path 7 that collects the developed developer that has passed through the developing area and separated from the surface of the developing roller 5 on the downstream side in the surface movement direction from the developing area that is the portion of the developing roller 5 facing the photoreceptor 1. Faces the developing roller 5. The collection conveyance path 7 is a collection conveyance member that conveys the collected developer collected in the same direction as the supply screw 8 along the axial direction of the developing roller 5, and a spiral collection screw 6 arranged in parallel to the axial direction. I have. A supply conveyance path 9 provided with the supply screw 8 is arranged in the lateral direction of the developing roller 5, and a collection conveyance path 7 provided with the collection screw 6 is arranged in parallel below the development roller 5.
The developer can be separated from the developing roller 5 by setting the magnetic body in the developing sleeve described above to a state where there is no magnetic pole only at a position where the developer is desired to be separated. Yes. Further, a magnetic body having a magnetic pole arrangement in which a repulsive magnetic field is formed at a location to be separated may be used.

  The developing device 4 is provided with a stirring conveyance path 10 in parallel with the collection conveyance path 7 below the supply conveyance path 9. The agitating / conveying path 10 is arranged in parallel to the axial direction as an agitating / conveying member that conveys the developer along the axial direction of the developing roller 5 to the front side in the drawing, which is opposite to the supply screw 8 while stirring the developer. A helical stirring screw 11 is provided.

The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a first partition wall 133 as a partition wall. In the first partition wall 133, the supply conveyance path 9 and the agitation conveyance path 10 are partitioned at both ends on the front side and the back side in the drawing, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other. doing.
The supply conveyance path 9 and the recovery conveyance path 7 are both partitioned by the first partition wall 133, but an opening is provided at a location where the supply conveyance path 9 and the recovery conveyance path 7 of the first partition wall 133 are partitioned. Absent.
In addition, the two developer conveyance paths of the agitation conveyance path 10 and the recovery conveyance path 7 are partitioned by a second partition wall 134 as a partition member. The second partition wall 134 has an opening on the front side in the figure, and the agitation transport path 10 and the collection transport path 7 communicate with each other.
The supply screw 8, the recovery screw 6 and the stirring screw 11, which are developer conveying members, are made of resin or metal screws, and each screw has a diameter of φ22 [mm] and the screw pitch is 50 [mm]. The winding, the recovery screw 6 and the stirring screw 11 are one roll of 25 [mm], and the number of rotations is all set to about 600 [rpm].

The developer thinned by the doctor blade 12 made of stainless steel on the developing roller 5 is transported to a developing area which is a portion facing the photosensitive member 1 for development. The surface of the developing roller 5 is V-grooved or sandblasted, and is made of an Al or SUS element tube of φ25 [mm], and the gap between the doctor blade 12 and the photoreceptor 1 is about 0.3 [mm].
The developer after the development is collected in the collection conveyance path 7, conveyed to the front side of the cross section in FIG. 2, and to the agitation conveyance path 10 through the opening of the first partition wall 133 provided in the non-image area portion. Developer is transferred. The toner is supplied to the stirring and conveying path 10 from a toner replenishing port 95 (described later) provided on the upper side of the stirring and conveying path 10 near the opening of the first partition wall 133 on the upstream side in the developer conveying direction in the stirring and conveying path 10. Supplied.

Next, the circulation of the developer in the three developer conveyance paths will be described.
FIG. 3 is a perspective sectional view of the developing device 4 for explaining the flow of the developer in the developer transport path. Each arrow in the figure indicates the moving direction of the developer.
4 is a schematic diagram of the flow of the developer in the developing device 4. Like FIG. 3, each arrow in the drawing indicates the moving direction of the developer.

In the supply conveyance path 9 that has been supplied with the developer from the agitation conveyance path 10, the developer is conveyed downstream in the conveyance direction of the supply screw 8 while supplying the developer to the developing roller 5. Then, the excess developer that is supplied to the developing roller 5 and is not used for development and is transported to the downstream end in the transport direction of the supply transport path 9 is supplied to the stirring transport path 10 from the surplus opening 92 of the first partition wall 133 ( Arrow E) in FIG.
On the other hand, the developer supplied to the developing roller 5 is used for development in the developing region, and then separated / separated from the developing roller 5 and delivered to the collection conveyance path 7. The collected developer that has been transferred from the developing roller 5 to the collection conveyance path 7 and conveyed to the downstream end in the conveyance direction of the collection conveyance path 7 by the collection screw 6 enters the stirring conveyance path 10 from the collection opening 93 of the second partition wall 134. Supplied (arrow F in FIG. 4).
The agitating and conveying path 10 agitates the supplied surplus developer and the recovered developer, conveys the agitating screw 11 to the downstream side in the conveying direction, and conveys it to the upstream side in the conveying direction of the supplying screw 8. It is supplied to the supply conveyance path 9 from the supply opening 91 of 133 (arrow D in FIG. 4).
In the agitating and conveying path 10, the agitating screw 11 agitates and conveys the collected developer, the surplus developer, and the toner replenished as necessary in the transfer unit in the direction opposite to the developer in the collecting and conveying path 7 and the supply conveying path 9. . Then, the agitated developer is transported to the upstream side in the transport direction of the supply transport path 9 communicating with the supply opening 91 on the downstream side in the transport direction. A toner concentration sensor composed of a magnetic permeability sensor (not shown) is provided below the agitation transport path 10, and a toner supply control device (not shown) is operated by the sensor output to supply toner from a toner storage portion (not shown). Is going.

  In the developing device 4 shown in FIG. 4, a supply conveyance path 9 and a collection conveyance path 7 are provided, and developer supply and collection are performed in different developer conveyance paths, so that the developed developer is supplied to the supply conveyance path 9. There is no contamination. For this reason, it is possible to prevent the toner concentration of the developer supplied to the developing roller 5 from decreasing toward the downstream side of the supply conveyance path 9 in the conveyance direction. Further, since the recovery conveyance path 7 and the agitation conveyance path 10 are provided and the developer recovery and agitation are performed in different developer conveyance paths, the developed developer does not fall during the agitation. Thereby, since the sufficiently stirred developer is supplied to the supply conveyance path 9, it is possible to prevent the developer supplied to the supply conveyance path 9 from being insufficiently stirred. In this way, the toner density of the developer in the supply conveyance path 9 can be prevented from decreasing, and the developer in the supply conveyance path 9 can be prevented from being insufficiently stirred. Can be constant.

As shown in FIG. 4, the developer moves from the lower part to the upper part of the developing device 4 only by the arrow D. The movement of the developer indicated by the arrow D is to push the developer into the downstream side of the agitation transport path 10 by the rotation of the agitation screw 11 so that the developer rises and supplies the developer to the supply transport path 9. .
Such movement of the developer gives stress to the developer and contributes to a decrease in the life of the developer.
When the developer is lifted from the bottom to the top, stress is applied to the developer, and the carrier film in the developer is scraped off and the toner is spent on the spot. Accordingly, the stability of the image quality is maintained. It will disappear.
Therefore, the life of the developer can be extended by reducing the stress of the developer in the movement of the developer indicated by the arrow D. By prolonging the life of the developer, it is possible to provide a developing device that prevents deterioration of the developer and is always stable in image quality without image density unevenness.

In the developing device 4 of the present embodiment, as shown in FIG. 2, the supply conveyance path 9 is disposed obliquely above the stirring conveyance path 10. By disposing it obliquely above, it is possible to reduce the developer stress in the movement of the developer indicated by the arrow D, compared to the case where the supply conveyance path 9 is provided vertically above the stirring conveyance path 10 and the developer is lifted. .
Further, in the developing device 4, the supply conveyance path 9 and the agitation conveyance path 10 are arranged obliquely so that the upper wall surface of the agitation conveyance path 10 is higher than the lower wall surface of the supply conveyance path 9 as shown in FIG. 2. It arranges so that it may become a position.
Lifting the supply conveyance path 9 vertically upward with respect to the stirring conveyance path 10 causes the developer to be stressed because the developer is lifted by the pressure of the stirring screw 11 against gravity. On the other hand, the developer present at the highest point of the agitating and conveying path 10 is placed at the bottom of the supplying and conveying path 9 by arranging the upper wall surface of the agitating and conveying path 10 to be higher than the lower wall surface of the supplying and conveying path 9. Since the point can flow without being against gravity, the stress applied to the developer can be reduced.
Note that a fin member may be provided on the shaft of the stirring screw 11 in a portion where the stirring transport path 10 and the supply transport path 9 communicate with each other on the downstream side of the developer transport path of the stirring transport path 10. This fin member is a plate-like member composed of a side parallel to the axial direction of the stirring screw 11 and a side perpendicular to the axial direction of the stirring screw. By scooping up the developer with this fin member, it is possible to more efficiently deliver the developer from the stirring conveyance path 10 to the supply conveyance path 9.

Further, in the developing device 4, the distance between the center A between the developing roller 5 and the supply conveyance path 9 is shorter than the distance B between the center between the development roller 5 and the agitation conveyance path 10. A conveyance path 10 is arranged. Thus, the developer can be supplied without difficulty from the supply conveyance path 9 to the developing roller 5, and the apparatus can be reduced in size.
Further, the stirring screw 11 is rotated counterclockwise as viewed from the front side in FIG. 2 (the direction of arrow C in the figure), and the developer is supplied by lifting the developer along the shape of the stirring screw 11. It is transferred to the conveyance path 9. As a result, the developer can be lifted efficiently, and the stress on the developer can be further reduced.

FIG. 5 is a cross-sectional explanatory view of the cross section at the rotation center of the supply screw 8 of the developing device 4 as viewed from the direction of arrow J in FIG. In the figure, H denotes a developing region in which the developing roller 5 that is a developer carrying member supplies toner to the photosensitive member 1 that is a latent image carrying member. The width in the axial direction of the rotation axis of the developing roller 5 in the developing area H is the developing area width α.
As shown in FIG. 5, the developing device 4 has a supply opening 91 that is a part for lifting the developer from the agitation conveyance path 10 to the supply conveyance path 9, and a surplus that drops the developer from the supply conveyance path 9 to the agitation conveyance path 10. Both of the openings 92 are provided in the development region width α.

FIG. 6 is a schematic diagram of the developer flow in the developing device 4 having a configuration different from that in FIG. 4.
The developing device 4 shown in FIG. 6 is provided with a supply opening 91 and a surplus opening 92 outside the developing region width α. Since the supply opening 91 is provided outside the developing region width α, the upstream side in the transport direction of the supply transport path 9 is longer than the developing roller 5 by the upstream region β of the supply transport path. Further, since the surplus opening 92 is provided outside the developing region width α, the downstream side in the transport direction of the supply transport path 9 is longer than the developing roller 5 by the region γ on the downstream side of the supply transport path.

On the other hand, in the developing device 4 having the configuration shown in FIG. 4, since the supply opening 91 is provided within the developing region width α, the upstream side in the transport direction of the supply transport path 9 is on the supply transport path than the developing device 4 in FIG. The flow side region β can be shortened. Further, since the surplus opening 92 is provided in the developing area width α, the downstream side in the transport direction of the supply transport path 9 can be made shorter by the area γ on the downstream side of the supply transport path than the developing device 4 in FIG.
4 is provided with the supply opening 91 and the surplus opening 92 within the developing region width α, the upper portion of the developing device 4 is higher than that of the developing device 4 shown in FIG. Space saving can be achieved.

Next, the position at which toner is supplied to the developer conveyance path including the supply conveyance path 9, the agitation conveyance path 10 and the collection conveyance path 7 of the developing device 4 will be described. FIG. 7 is an external perspective view of the developing device 4.
As shown in FIG. 7, a toner replenishing port 95 for replenishing toner is provided above the upstream end of the agitating and conveying path 10 including the agitating screw 11 in the conveying direction. Since the toner replenishing port 95 is provided outside the end portion in the width direction of the developing roller 5, it is outside the developing region width α.
The portion where the toner replenishing port 95 is provided is on an extension line in the conveyance direction of the supply conveyance path 9 and corresponds to a vacant space in the region γ on the downstream side of the supply conveyance path in FIG. Providing the toner replenishment port 95 in an empty space by providing the surplus opening 92 within the developing region width α makes it possible to reduce the size of the developing device 4.
Further, the toner replenishing port 95 is not limited to the position above the upstream end portion in the transport direction of the stirring transport path 10 and may be provided above the downstream end portion of the collection transport path 7.
Further, a toner replenishing port 95 may be provided directly above the collection opening 93 where the developer is transferred from the collection conveyance path 7 to the stirring conveyance path 10. Since the space directly above the collection opening 93 is also an empty space provided by providing the surplus opening 92 within the developing region width α, the toner replenishing port 95 is provided at this position to reduce the size of the developing device 4. Can be planned. Furthermore, since the developer is likely to be mixed in the collection opening 93 serving as a delivery unit, the developer can be more efficiently stirred by replenishing at this position.

As in the developing device 4 described with reference to FIG. 4, a supply opening 91 that transfers the developer from the downstream end in the transport direction of the stirring transport path 10 to the upstream end in the transport direction of the supply transport path 9, and the supply transport path 9 Since the surplus opening 92 for transferring the developer from the downstream end to the upstream end in the transport direction of the stirring transport path 10 is provided in the development region width α, the upper portion of the development device 4 is higher than the conventional development device 4. Space can be saved, and the space of the entire developing device 4 can be saved.
Also, by providing the toner replenishment port 95 in the empty space by providing the surplus opening 92 within the development region width α, the development device 4 can be downsized.
Further, the developer can be more efficiently stirred by replenishing the toner from above the recovery opening 93 that is a delivery portion of the developer from the recovery transport path 7 to the stirring transport path 10.
Further, by providing the developing device 4 as the developing means of the printer unit 100 of the copying machine as the image forming apparatus, it is possible to save the space of the entire apparatus.

A toner replenishment control device (not shown) that is a developer replenishing unit replenishes toner in a toner storage unit (not shown) to the developing device 4 from the toner replenishing port 95. In the developing device 4 of this embodiment, a developer including toner and a carrier is supplied from a toner supply port 95 of the developing device 4. Hereinafter, the developer in which the toner supplied to the developing device 4 and the carrier are mixed is referred to as premix toner.
In the developing device 4 of the present embodiment, the circulation conveyance path that conveys the excess developer that has reached the downstream end in the conveyance direction of the supply conveyance path 9 to the upstream end in the conveyance direction of the supply conveyance path 9 is the stirring conveyance path 10. In addition, the circulating and conveying member that applies a conveying force to the developer in the agitating and conveying path 10 that is a circulating and conveying path is the agitating screw 11. Further, the circulation opening provided near the downstream end in the conveyance direction of the supply conveyance path 9 and through which the passed developer is transferred to the agitation conveyance path 10 which is a circulation conveyance path is a surplus opening 92. In addition, the developing device 4 includes a developer discharge port 94 in the supply conveyance path 9 through which the developer that has passed is discharged to the outside of the developing device 4. The developer that has passed through the developer discharge port 94 is transferred to the discharge conveyance path 2, and is conveyed to the outside of the developing device 4 by rotating the discharge screw 2 a that is a discharge conveyance member, and is discharged from the developing device 4. Made. The discharge conveyance path 2 is provided on the downstream side in the conveyance direction of the supply conveyance path 9 so as to be adjacent to the supply conveyance path 9 with the discharge partition wall 135 interposed therebetween, and the developer discharge port 94 is connected to the supply conveyance path 9 and the discharge conveyance path 2. Are openings provided in the discharge partition wall 135 so as to communicate with each other.

FIG. 8 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path 9 of the developing device 4.
As shown in FIG. 8, the developing device 4 according to the present embodiment allows the developer that has reached the vicinity of the downstream end in the transport direction of the supply transport path 9 and does not enter the surplus opening 92 serving as the circulation opening to the developer discharge port. A supply downstream end wall surface 80 is provided as a developer retaining means for retaining in the vicinity of the surplus opening 92 that is in the vicinity of 94. The developer conveyed to the downstream end in the conveyance direction of the supply conveyance path 9 by the supply screw 8 abuts against the supply downstream end wall surface 80. Further, the developer discharge port 94 passes the developer that has reached the position of the developer discharge port 94 out of the retained developer that is located above the surplus opening 92 and is retained by the supply downstream end wall surface 80. Is provided. In other words, of the developer P that has reached the vicinity of the downstream end in the transport direction of the supply transport path 9, the surplus developer that cannot enter the surplus opening 92 and overflows from the surplus opening 92 is supplied to the supply downstream end wall surface 80. The retained developer T is blocked. Then, when the bulk of the staying developer T increases, the developer that has reached the developer discharge port 94 provided above the surplus opening portion 92 passes through the developer discharge port 94 as indicated by an arrow K. Then, the toner is discharged out of the developing device 4.
As shown in FIG. 8, the developer discharge port 94 is a rectangular opening, and the discharge port lower end portion 94 u is positioned above the supply screw 8.

  The amount of staying developer T includes the amount of developer that reaches the vicinity of the downstream end in the conveyance direction of the supply conveyance path 9 (arrow L in the figure), the amount of developer that passes through the excess opening 92 (arrow E in the figure), and Increase or decrease depending on the balance. In a state where the developing device 4 is driven, an amount of developer P required for circulation is always transferred from the supply conveyance path 9 to the agitation conveyance path 10 through the surplus opening 92. Then, the amount of developer reaching the vicinity of the downstream end in the conveyance direction of the supply conveyance path from the amount of developer (arrow E in FIG. 4) delivered from the supply conveyance path 9 to the stirring conveyance path 10 through the excess opening 92. In the state where there are more (arrow L in FIG. 4), the amount of the staying developer T increases, and in the opposite state, the amount of the staying developer T decreases. Further, in the state where the staying developer T is present, the necessary amount of developer required for circulation is always transferred to the agitating / conveying path 10 through the surplus opening 92, so that the development toward the agitating / conveying path 10 is performed. There is no shortage of dosage. That is, in the state where the staying developer T is present, the necessary amount of developer is supplied from the agitating / conveying path 10 to the supply / conveying path 9 as the necessary amount of developer is directed to the agitating / conveying path 10. This is a state in which the developer amount in the developing device 4 maintains the necessary amount.

Further, since the developer discharged out of the developing device 4 is the developer that has reached the position of the developer discharge port 94 in the staying developer T, the staying developer T reaches the position of the developer discharge port 94. If the amount is not enough, the developer is not discharged out of the developing device 4. At this time, since the staying developer exists in a state where the developer is not discharged out of the developing device 4, the amount of developer in the developing device 4 is maintained at a necessary amount.
In the developing device 4, the developer P transported in the supply transport path 9 undulates in a state where the amount of developer in the developing device 4 is not increased, and the bulk of the developer is partially increased. Even if this phenomenon occurs, it is possible to prevent the developer from being continuously discharged. Specifically, when the amount of the staying developer T increases even if the amount is small, the developer reaches the position of the developer discharge port 94, and when the portion where the bulk of the developer reaches the vicinity of the downstream end in the transport direction of the supply transport path 9, the excess opening The developer exceeding the amount of developer passing through the portion 92 is discharged from the developer discharge port 94. However, the amount of the staying developer T decreases when the portion where the bulk of the developer has reached the vicinity of the downstream end in the transport direction of the supply transport path 9, and the staying developer T is at the position of the developer discharge port 94. The bulk is not reached. Thereafter, even if the part where the bulk of the developer becomes high or the part where the volume becomes low reaches the vicinity of the downstream end in the transport direction of the supply transport path 9, the developer (volume) only increases or decreases. Will not be discharged. Further, if the amount of the staying developer T increases even if the amount is small, unless the developer reaches the position of the developer discharge port 94, the portion where the bulk of the developer is increased or decreased is near the downstream end in the conveyance direction of the supply conveyance path 9. However, the amount of the staying developer T (bulk) only increases or decreases, and the developer is not discharged. As described above, since the developer can be prevented from continuing to be discharged, the developer P conveyed in the supply conveyance path 9 undulates in a state where the amount of the developer in the developing device 4 has not increased. Even if the phenomenon that the bulk of the developer is partially increased occurs, the amount of developer in the developing device 4 can be maintained at the required amount. As described above, since the necessary amount of the developer P in the developing device 4 can be ensured, the developer can be stably supplied to the photoreceptor 1. As a result, the electrostatic latent image on the photoreceptor 1 can be favorably converted into a toner image, an abnormal image such as image omission can be prevented, and good image formation can be performed.

  The vicinity of the downstream end of the supply conveyance path 9 in the conveyance direction is, for example, the same position in the conveyance direction of the developer conveyance section 9 and the supply conveyance path 9 where the developer is transferred from the supply conveyance path 9 to the stirring conveyance path 10. It is a place. In other words, it is where the conveying force by the supply screw 8 ends and is a portion where the developer is blocked by the supply downstream end wall surface 80. By providing the developer discharge port 94 here, after the developer is transported by the supply screw 8, it is received by the supply downstream end wall surface 80, and finally reaches the height of the developer discharge port 94 among the staying developer. Can be discharged.

  FIG. 9 is a perspective explanatory view of the vicinity of the front end portion in a state where the stirring screw 11, the recovery screw 6, and the doctor blade 12 are removed from the developing device 4. FIG. 10 is an explanatory perspective view of the developing device 4 in the vicinity of the front side of the state where the supply screw 8 is further removed from the state of FIG. Further, FIG. 11 is a perspective explanatory view of the developing device 4 with the developing roller 5 further removed from the state of FIG. 12 is a perspective explanatory view of the developing device 4 when the developing device 4 in the same state as that in FIG. 11 is viewed from substantially the same direction as FIG.

The rotation direction of the supply screw 8 is clockwise (the direction of the arrow M) as shown in FIG. 2, and is rotated in the direction in which the developer is lifted and supplied from below. Here, when the developer is supplied to the developing roller 5 so that the rotation direction of the supply screw 8 is counterclockwise and the developer is sprinkled from above, the developer is supplied to the developing roller 5 while being scattered. On the other hand, when the rotation direction of the supply screw 8 is clockwise as shown in FIG. 2, the developer is supplied to the developing roller 5 so as to lift the developer from below the supply conveyance path 9 where the developer is accumulated. It becomes like this. The developer supply performance is more stable when the developer is supplied by lifting from the lower side than when the developer is supplied while being scattered. Therefore, in the developing device 4, the rotation direction of the supply screw 8 is set clockwise as shown in FIG. doing.
In particular, in the case where the developer supplied to the developing roller 5 is not returned to the supply conveyance path 9 but is collected to the collection conveyance path 7 as in the developing device 4 of this embodiment, the amount of developer goes downstream of the supply conveyance path 9. It decreases according to. For this reason, it is more excellent in terms of developer supply that the developer is drawn up from below and supplied to the developing roller 5.

Here, in the supply conveyance path 9, the developer in the supply conveyance path 9 jumps by the momentum of movement in the supply conveyance path 9 by being conveyed and the rotating force of the supply screw 8 that is a developer conveyance screw. . If the developer discharge port 94 is provided at a predetermined height of the supply conveyance path 9 in the developer conveyance path, the jumped developer flies and passes through the developer discharge port 94. May be discharged. When the developer jumps and is discharged, even if the developer transported through the position where the developer discharge port 94 in the supply transport path 9 is provided is in an appropriate amount or less than the appropriate amount, The jumped developer may be discharged. In such a state where the developer jumped off is discharged, the developer may be discharged from the developer discharge port even though the amount of the developer in the developing device 4 is not more than an appropriate amount. The amount of developer in the developing device 4 is less than the required amount, and the supply of developer to the photoreceptor 1 may become unstable. When the developer supply to the photosensitive member 1 becomes unstable, an abnormal image such as image omission occurs.
Note that the developer can be prevented from jumping in the vicinity of the developer discharge port 94 by retaining the developer in the vicinity of the developer discharge port 94 as in the present embodiment. However, even if the developer in the vicinity of the developer discharge port 94 is prevented from jumping, the developer at a location away from the developer discharge port 94 may jump and be discharged from the developer discharge port 94.

  In order to prevent such a problem, the developing device 4 has a path along which the developer flying as the supply screw 8 that is a developer conveying member rotates to convey the developer is directed toward the developer discharge port 94. A block member 3 is provided as a flying developer discharge preventing member for closing. The developer in the developing device 4 is provided with the block member 3, and the developer flying by the feeding operation of the supply screw 8 blocks the path toward the developer discharge port 94, thereby preventing the jumped developer from being discharged. It is possible to prevent the developer from being discharged even though the amount is not increased. Therefore, the necessary amount of developer in the developing device 4 can be secured, and the developer can be stably supplied to the photoreceptor 1. As a result, the electrostatic latent image on the photoreceptor 1 can be favorably converted into a toner image, an abnormal image such as image omission can be prevented, and good image formation can be performed.

  The block member 3 is an R-shaped resin member whose bottom surface follows the shape of the supply screw 8 above the supply conveyance path 9. Due to the R shape along the shape of the supply screw 8, the bottom surface of the block member 3 can be brought close to the supply screw 8 as a whole so as to cover the entire supply screw 8. For this reason, it is possible to cover the upper part of the supply screw 8 that causes the developer to jump up, and to prevent the developer jumped up by the supply screw 8 from flying and reaching the developer discharge port 94.

Further, as shown in FIG. 12, the block member 3 protrudes in the vicinity of the developer discharge port 94 of the supply conveyance path 9, and therefore the supply screw 8 on the upstream side in the conveyance direction of the supply screw 8 with respect to the block member 3. The supply conveyance path 9 where the block member 3 is provided is narrower than the conveyance path 9. Therefore, the developer amount with respect to the capacity of the supply conveyance path 9 is larger at the position where the block member 3 is provided than at the upstream side in the conveyance direction with respect to the position where the block member 3 is provided. For this reason, the developer rises between the side wall of the block member 3 and the discharge partition wall 135 in the vicinity of the downstream end of the supply conveyance path 9 in the conveyance direction where no conveyance force is applied to the developer. As a result, the supply screw 8 is buried in the developer, and the splashing of the developer due to the rotation of the supply screw 8 is suppressed, and the upper part of the wing portion of the supply screw 8 protrudes from the developer surface. The change in the surface level due to the splashing of the supply screw 8 that occurs sometimes is mitigated in the vicinity of the developer discharge port 94. For this reason, it is possible to discharge with high sensitivity to the increase or decrease of the developer in the developing device 4.
By providing such a block member 3, when the developer amount in the developing device 4 increases due to the supply of the developer and the bulk of the developer in the supply conveyance path 9 increases, the development corresponding to the increased amount is achieved. The developer overflows from the developer discharge port 94.

13 and 14 show the flow of the developer in the developing device 4 in a state where the amount of the developer in the developing device 4 is small, that is, in a state where the staying developer does not reach the position of the developer discharge port 94. It is explanatory drawing shown. 13 is a cross-sectional explanatory view of the developing device 4 in the vicinity of the downstream end in the transport direction of the supply transport path 9 as viewed from the same direction as FIG. 2, and FIG. It is. In the figure, P indicates a developer.
As shown in FIGS. 13 and 14, when the developer amount in the developing device 4 is small, the developer is smoothly supplied from the supply conveyance path 9 to the stirring conveyance path 10 which is a circulation conveyance path. As a result, the developer P does not overflow at the surplus opening 92 provided in the first partition wall 133 that is the boundary between the supply conveyance path 9 and the agitation conveyance path 10, and the bulk of the staying developer does not increase. For this reason, the developer is hardly led to the developer discharge port 94 for discharging the developer P to the outside of the developing device 4, and it is possible to prevent the developer from being discharged in a state where the amount of the developer is small.

15 and 16 show a state in which the amount of developer in the developing device 4 is large, that is, in a state where the bulk of the staying developer near the downstream end in the transport direction of the supply transport path 9 has reached the position of the developer discharge port 94. 5 is an explanatory diagram showing a flow of developer P in the apparatus 4. FIG. 15 is a cross-sectional explanatory view of the developing device 4 near the downstream end in the transport direction of the supply transport path 9 as viewed from the same direction as FIG. 2, and FIG. 16 is a side cross-sectional explanatory view as viewed from the same direction as FIG. It is.
As shown in FIGS. 15 and 16, when the amount of developer in the developing device 4 is large, the developer P is in the vicinity of the surplus opening 92 where the developer P moves from the supply conveyance path 9 to the stirring conveyance path 10. Stay. As a result, the developer P at the most downstream portion in the transport direction of the supply transport path 9 has no place to go, and the staying developer increases in volume upward. When the bulk rises to the height of the developer discharge port 94, the developer P passes through the developer discharge port 94 and is discharged to the discharge conveyance path 2, and the discharge screw 2 a in the discharge conveyance path 2 discharges the developing device 4. It will be discharged to the outside.

  The developing device 4 discharges the developer that has reached the height of the developer discharge port 94 when the volume of the staying developer near the downstream end in the transport direction of the supply transport path 9 exceeds the height of the developer discharge port 94. Therefore, it is possible to prevent the developer transporting the supply transport path 9 from being insufficient due to the discharge of the developer from the developer discharge port 94. Accordingly, a necessary amount of developer can be supplied from the supply conveyance path 9 to the developing roller 5, and the developer can be stably supplied from the developing roller 5 to the photosensitive member 1. For this reason, the electrostatic latent image on the photosensitive member 1 can be favorably converted into a toner image, an abnormal image such as image omission can be prevented, and good image formation can be performed.

In FIG. 14, the state in which the developer in the developing device 4 is small has been described. However, when the developer in the developing device 4 is not discharged and the developer amount is stable, the vicinity of the downstream end in the transport direction of the supply transport path 9 In this state, the developer is retained. Details of this state will be described below.
The developing device 4 is configured to discharge a part of the staying developer staying in the vicinity of the downstream end in the transport direction of the supply transport path 9 when the bulk exceeds a predetermined height (the height of the developer discharge port 94). It is. That is, the developer discharge port 94 and the discharge conveyance path 2 discharge the developer in which the bulk of the staying developer near the downstream end in the conveyance direction of the supply conveyance path 9 reaches the height of the developer discharge port 94. . Therefore, the developing amount in the developing device 4 becomes stable in a state where the staying developer exists in a volume that does not reach the height of the developer discharge port 94 near the downstream end in the transport direction of the supply transport path 9. . This is due to the balance between the amount of developer transported through the supply transport path 9 and reaching the downstream end in the transport direction, and the amount of developer delivered to the stirring transport path 10 through the supply transport path 9 surplus opening 92. As shown in FIG. 27A, the developer stays in the vicinity of the downstream end in the conveyance direction of the supply conveyance path 9 so as not to reach the height discharged by the developer discharge port 94.

From this state, when the premix toner is supplied by the toner replenishment control device and the amount of developer in the developing device 4 increases, the amount of developer delivered from the supply conveyance path 9 to the stirring conveyance path 10 (arrow E in FIG. 4). ), The amount of developer transported through the supply transport path 9 and reaching the downstream end in the transport direction (arrow L in FIG. 4) is larger. At this time, the amount of the developer staying in the vicinity of the downstream end in the transport direction of the supply transport path 9 increases, and the bulk thereof increases as shown in FIG. As a result, when the volume of the staying developer reaches the developer discharge port 94, the developer discharge port is used as a part of the developer that stays so that the bulk becomes lower than the position of the developer discharge port 94. The developer reaching 94 is discharged.
Note that the staying developer is difficult to jump, and the volume of the developer changes according to the increase or decrease of the developer amount in the developing device 4. Then, the developer is discharged when the volume of the staying developer exceeds a predetermined height (developer discharge port 94). Since the developer is discharged, the amount of developer in the developing device 4 can be accurately maintained within a certain range.
As a result, the amount of developer conveyed through the supply conveyance path 9 is stabilized, so that it is possible to prevent a shortage of developer conveying along the supply conveyance path, and a necessary amount from the supply conveyance path 9 to the developing roller 5 can be prevented. Developer can be supplied. For this reason, a stable developer can be supplied from the developing roller 5 to the photosensitive member 1, and the electrostatic latent image on the photosensitive member 1 can be favorably formed into a toner image. Can be prevented and good image formation can be performed.

In addition, the developer overflowed in the vicinity of the downstream end in the transport direction of the supply transport path 9, where the volume of the developer changes due to the change in the developer amount in the developing device 4, is discharged from the developer provided on the discharge partition wall 135. Since the developer is discharged through the outlet 94, the developer in the developing device 4 can be replaced with high accuracy with a simple structure.
Further, the development in which the supply conveyance path 9 and the agitation conveyance path 10 are provided so as to be adjacent in the vertical direction with the first partition wall 133 serving as the supply circulation partition wall interposed therebetween, and reaches the downstream end in the conveyance direction of the supply conveyance path 9. The agent is configured to move to the stirring and conveying path 10 through an excess opening 92 that is an opening provided so as to communicate the supply conveying path 9 and the stirring and conveying path 10. The bulk of the staying developer near the downstream end in the transport direction of the supply transport path 9 is determined by the amount of developer transported to the downstream end by the supply screw 8 per hour and the development passing through the excess opening 92 per time. It varies depending on the difference from the dosage. The amount of developer conveyed by the supply screw 8 or the amount of developer passing through the excess opening 92 per hour varies depending on the change in the amount of developer in the developing device 4, and the amount of developer in the developing device 4 increases. Since the bulk of the developer near the downstream end in the transport direction of the supply transport path 9 increases, the developer in the developing device 4 can be replaced with high accuracy with a simple configuration.

At least a part of the position of the supply transport path 9 in the developer transport direction overlaps with the developer discharge port 94 which is a discharge port opening of the developing device 4 and the surplus opening 92 which is a circulation opening. In the developing device 4 of this embodiment, as shown in FIGS. 4, 14, and 16, the developer discharge port 94 and the excess opening 92 are at the same position in the developer transport direction of the supply transport path 9. With such a configuration, the amount of developer delivered from the supply conveyance path 9 to the agitation conveyance path 10 and the amount of developer discharged out of the developing device 4 by retaining the developer in the vicinity of the surplus opening 92 are set. It becomes easy to balance.
Further, since the developer discharge port 94 is provided above the surplus opening 92, the developer discharge port 94 reaches the downstream end in the transport direction of the supply transport path 9 when the amount of developer in the developing device 4 is an appropriate amount. The developer passes only through the excess opening 92 located below, moves to the stirring conveyance path 10 and circulates in the developing device 4. When the amount of the developer in the developing device 4 increases and the bulk of the staying developer at the downstream end in the transport direction reaches the height of the developer discharge port 94 above, the developer exceeding the height is discharged. It passes through the outlet 94 and is discharged to the outside of the developing device 4. In this configuration, the developer discharge port 94 is arranged above the surplus opening 92, and the developer is supplied in a state where the amount of developer to be supplied to the stirring and conveying path 10 is not supplied to the stirring and conveying path 10. When the developer amount in the developing device 4 exceeds a predetermined amount while preventing the developer from being discharged out of the developing device 4, the developer can be discharged out of the device. Accordingly, it is possible to realize a configuration in which the developer is circulated through the excess opening 92 and the developer increased by the developer discharge port 94 is accurately discharged and the developer is replaced.

Further, in the one-way circulation developing device 4 including the supply conveyance path 9, the agitation conveyance path 10, and the collection conveyance path 7, the developer that reaches the downstream end in the conveyance direction of the supply conveyance path 9 does not contribute to development. It is an agent. In the one-way circulation developing device 4, it is suitable to discharge the developer increased by the replenishment of the premix toner at the position where the excess developer stays. This is due to the following reason.
Since the collection conveyance path 7 conveys the developer carried on the developing roller 5 and passed through the development region, even if the amount of the developer in the developing device 4 changes, almost no developer is conveyed in the collection conveyance path 7. There is no change, and the developer cannot be discharged due to an increase in the volume of the developer.
As the amount of developer in the developing device 4 increases, the amount of developer to be transported increases and the bulk of the agitation transport path 10 also increases. However, due to the jumping of the developer to be transported or unevenness in the transport amount, the developer is discharged even if the developer amount does not increase, and the required amount of developer cannot be delivered to the supply transport path 9. is there. For this reason, it is not appropriate to discharge the developer due to the increase in the volume of the developer in the stirring conveyance path 10. Further, the configuration of discharging in the middle of the supply conveyance path 9 may increase the volume of the developer even if the amount of the developer in the developing device 4 is not increased, and the downstream side in the conveyance direction from the discharged position. Is not suitable because the developer may be insufficient.
For this reason, the one-way circulating developing device 4 discharges the developer increased by replenishing the premix toner at the position where the developer that reaches the downstream end in the transport direction of the supply transport path 9 stays. Is suitable.

In the developing device 4 of the embodiment, the excessive opening 92 is larger than the developer discharge port 94, but the developer discharge port 94 may be larger than the excessive opening 92.
Further, in the above-described embodiment, FIG. 4 shows a configuration in which the developer discharging means discharges a part of the developer when the volume of the developer near the downstream end in the transport direction of the supply transport path 9 exceeds a predetermined height. The configuration applied to the developing device 4 having the configuration shown has been described. The configuration to which the characterizing portion of the present invention can be applied is not limited to that shown in FIG. 4, but can be similarly applied to the developing device 4 having the configuration shown in FIG.
In the above-described embodiment, the developing device using the two-component developer composed of the carrier and the toner as the developer has been described. The developing device to which the feature of the present invention is applied is not limited to a developing device using a two-component developer. A developing device using a one-component developer can be used as long as the developer is replenished by the developer replenishing unit and the developer discharging unit discharges the increased amount of developer in the developing device. Is applicable.

In the developing device 4 of the present embodiment, the developer that is supplied from the supply conveyance path 9 to the developing roller 5 and passes through the development region is not returned to the supply conveyance path 9 but is transferred to the collection conveyance path 7. It is a developing device with directional circulation. In such a one-way circulating developing device, when the developer is supplied, the bulk of the developer increases in the vicinity of the upstream end portion of the stirring conveyance path or in the vicinity of the downstream end portion of the supply conveyance path.
In the developing device 4 of this embodiment, a developer discharge port 94 is provided at the downstream end of the supply conveyance path 9. The developer transported from the upstream side of the supply transport path 9 by the supply screw 8 falls from the surplus opening 92 at the downstream end of the supply transport path 9 to the stirring transport path 10. At this time, when a developer exceeding the developer amount that can be dropped per unit time is conveyed, surplus developer hits the wall and rises upward, as shown in FIGS. 8 and 15. The developer reaching the discharge port 94 is discharged.

  The amount of developer discharged is preferably dependent on the volume of the developer in the developing device 4, but there is a possibility that the developer jumped up by the supply screw 8 will be discharged. Therefore, as shown in FIGS. 10 and 11, the developing device 4 according to the present embodiment has walls on the upstream side and the downstream side in the transport direction of the developer discharge port 94. Thereby, it is possible to suppress the developer splashed up by the supply screw 8 from being discharged, and to perform discharge depending on the volume of the developer.

Patent Document 1 describes the disadvantage that conventional overflow discharge causes the developer to be discharged more than necessary when the developing device is tilted. However, only the developer that has risen with the configuration of the present invention. Therefore, the developer is not discharged due to the inclination.
Further, in Patent Document 1, the developer is prevented from being discharged excessively by sensing the inclination and opening and closing the shutter. However, a certain amount of developer may be discharged during the time from the tilt until the shutter closes, and if a discharge port is provided at a position where a large amount of developer is discharged due to the tilt, other developers may be discharged. Depending on the factors, the discharge amount is likely to vary, and the developer capacity is not stable. Therefore, the developing device 4 of this embodiment can discharge the developer more appropriately.

[Example 1]
Next, a description will be given of a first embodiment (hereinafter, referred to as embodiment 1) having the features of the present invention.
FIG. 17 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path 9 in the state where the developer amount in the developing device 4 of Embodiment 1 is maximized. 17, 18, and 19 indicate a portion where the developer is not present in the developer discharge port 94.
In the developing device 4 of the first embodiment, the bulk of the staying developer T increases or decreases according to the increase or decrease of the developer amount in the entire developer transport path. Therefore, in the state where the developer amount in the developing device 4 is maximized, The bulk of the staying developer T is also maximized. In the developing device 4, as shown in FIG. 17, the developer discharge port 94 has a horizontal region w <b> 1 where the developer does not reach even when the bulk of the staying developer T is maximized. That is, an opening width W that is a width in the horizontal direction of the developer discharge port 94 is set so that the developer does not reach the discharge port upstream end portion 94f that is one end portion of the developer discharge port 94 in the horizontal direction. Yes.

FIG. 18 is an explanatory diagram of Comparative Example 1 in which the horizontal region w1 of FIG. 17 is not secured in a state where the bulk of the staying developer T is maximized. If the horizontal region w1 is not secured as in Comparative Example 1 in FIG. 18, the developer is regulated in the horizontal direction of the developer discharge port 94 as shown in FIG. Discharge is hindered, and the developer is easily clogged at the developer discharge port 94. Further, the staying developer T in the region indicated by the shaded portion T1 in FIG. 18 is not discharged from the developer discharge port 94 even though it exists above the discharge port lower end portion 94u of the developer discharge port 94. For this reason, in Comparative Example 1, there is a problem that the responsiveness of the developer discharge amount with respect to the increase in the developer amount in the developing device 4 is deteriorated.
On the other hand, in the developing device 4 of the first embodiment described with reference to FIG. 17, the developer is not regulated in the horizontal direction of the developer discharge port 94, and the developer is discharged well. Can be prevented from clogging at the developer outlet 94.

  Further, in the developing device 4 of Embodiment 1, as shown in FIG. 17, the developer discharge port 94 secures a height direction region h1 where the developer does not reach even when the bulk of the staying developer T becomes maximum. ing. That is, the opening height H that is the width in the height direction of the developer discharge port 94 is set so that the developer does not reach the discharge port upper end portion 94t that is the upper end portion of the developer discharge port 94.

FIG. 19 is an explanatory diagram of Comparative Example 2 in which the height direction region h1 of FIG. 17 is not secured in a state where the bulk of the staying developer T is maximized. If the height direction region h1 is not secured as in Comparative Example 2 in FIG. 19, the developer is regulated in the height direction in the same manner as in Comparative Example 1 where the developer is regulated in the horizontal direction. Therefore, the discharge of the developer is hindered, and the developer is easily clogged at the developer discharge port 94. Further, the staying developer T in the region indicated by the shaded portion T2 in FIG. 19 is not discharged from the developer discharge port 94 even though it exists above the discharge port lower end portion 94u of the developer discharge port 94. For this reason, in Comparative Example 1, there is a problem that the responsiveness of the developer discharge amount with respect to the increase in the developer amount in the developing device 4 is deteriorated.
On the other hand, in the developing device 4 of the first embodiment described with reference to FIG. 17, the developer is not restricted in the height direction of the developer discharge port 94, and the developer is discharged well. It is possible to prevent the developer from clogging at the developer discharge port 94.

The driving condition of the developing device 4 that maximizes the amount of developer in the developing device 4 is the maximum number of continuous images that can be set by the printer, and the maximum amount of white images that are less than 1% of the image area ratio. The case of continuous printing with the number of sheets is considered.
When the whole surface solid image is continuously printed, the toner concentration in the developer delivered from the developing roller 5 to the collection conveyance path 7 becomes very low, and a premix containing a toner with a low charge amount to supplement the consumed toner. Toner is replenished. When a large amount of toner having a low charge amount is contained, the toner and the carrier are in a tight state. When toner replenishment control is performed based on the detection result of the magnetic permeability sensor, the magnetic permeability sensor detects that there is non-magnetic toner in the space, so there is a lot of toner when there is a lot of space in the developer. Detect as you do. On the other hand, if the toner and carrier are in a tight state, it is detected that the toner is low and the carrier is high, so that the pre-contained amount including the amount of consumed toner and the amount of toner for improving the state of further increasing the carrier are included. Mick toner is replenished. As a result, the premix toner more than the required amount is replenished, and the amount of developer conveyed per unit time in the agitating and conveying path 10 is maximized, and the developer amount in the developing device 4 is also maximized as this state continues. May be.
On the other hand, when the entire white image is continuously printed, the toner contained in the developer in the developing device 4 continues to be stirred without being used, and the charge amount of the toner increases. As a result, the amount of charge per toner weight increases, so even if the potential of the latent image on the photoreceptor 1 is the same, the potential is offset by a small amount of toner, and the amount of toner attached to the photoreceptor 1 is reduced. To do. In the case where the pattern image is formed on the photosensitive member 1 and the toner replenishment control is performed based on the detection result of the P sensor that reads the pattern image, the toner replenishment is performed when it is detected that the image density of the pattern image is low. Therefore, in the case of the entire white image, since the premix toner is continuously supplied even though the toner is not consumed, the amount of developer in the developing device 4 may become maximum. Further, when the entire white image is continuously printed, the charge amount of the developer increases, and as a result, the volume of the developer increases, the developer amount increases, and the bulk per weight of the developer also increases. Due to the increase, the developer capacity in the developer device 4 may become maximum.
In the copying machine 500 of the present embodiment, the amount of developer in the developing device 4 is maximized when 999 continuous prints, which is the maximum number of images that can be set for the entire white image, are performed.
In an actual machine, continuous printing of a full white image can occur, for example, during continuous printing of a full-color image. When an image formed with a color other than the color of toner provided in a certain developing device is continuously printed, a developing device that does not use toner is also driven, so this developing device continuously prints a white image form on the entire surface. It becomes a state.

If the opening width W of the developer discharge port 94 is too wide, the discharge port upstream end portion 94f is positioned in a region where the momentum of the developer transported in the supply transport path 9 is not suppressed, and the jumped development is performed. The developer may be discharged from the developer discharge port 94. On the other hand, if the opening width W of the developer discharge port 94 is too narrow, the problem described in Comparative Example 1 may occur.
Further, in order to increase the opening height H of the developer discharge port 94, there is a limit because it is determined by the height of the casing of the developing device 4 even if the position of the discharge port upper end portion 94t is increased. Further, if the opening height H is increased by lowering the position of the lower end portion 94u of the discharge port, it is possible to discharge even when the bulk of the staying developer T is low, and the amount of staying developer T decreases and the staying developer T decreases. The function of preventing the developer from jumping due to T decreases. For this reason, if the opening height H is increased by lowering the position of the discharge port lower end portion 94u, the jumped developer may be discharged from the developer discharge port 94. On the other hand, if the opening height H of the developer discharge port 94 is too narrow, the problem described in Comparative Example 2 may occur.

Next, an example of a method for setting the opening width W and the opening height H of the developer discharge port 94 will be described.
The present inventors performed optimization using quality engineering, and set the values of the opening width W and the opening height H of the developer discharge port 94.
The following eight elements c1 to c8 were used as control factors in quality engineering.
c1: Number of rotations of supply screw c2: Height direction position of developer discharge port (c2 in FIGS. 9 and 13)
c3: Opening width W of the developer discharge port
c4: Opening height H of the developer discharge port
c5: Supply screw diameter at the position where the developer discharge port is provided c6: Ceiling width of the supply screw (c6 in FIGS. 11 and 13)
c7: Width of excess opening (c7 in FIGS. 8 and 12)
c8: Magnetic pole arrangement of the magnetic material in the developing roller These control factors c1 to c8 were verified by performing the following experiments at three levels.

[Experiment]
The present inventors replenish the developer by 10 [cc] from the toner replenishing port 95 of the empty developing device 4 and replenish the developer by 10 [cc], and then develop after driving the developing device 4 for one minute. An experiment for measuring the amount of developer discharged from the agent discharge port 94 was performed with different combinations of control factor levels.
FIG. 20 is a graph schematically showing the relationship between the replenishment amount and the discharge amount in this experiment.
In FIG. 20, the graph (1) shows that the developer is not discharged until the total amount of replenishment reaches 340 [cc], and after that, the amount of replenishment exceeds 340 [cc]. It shows a state of being discharged linearly. In the graph of (2), the developer is temporarily discharged before the total amount of replenishment reaches 340 [cc], and then the discharge stops, and the total amount of replenishment exceeds 340 [cc]. , 350 [cc] shows a state of being discharged linearly by the amount replenished. In the graph of (3), the developer is not discharged until the total amount of replenishment reaches 340 [cc], and after that, the amount discharged is less than the amount replenished over 340 [cc]. This shows a state where
As shown in the graph (2), the developer is temporarily discharged before the total replenishment amount reaches a predetermined amount. The developer is temporarily discharged by the developer jumping. It is thought that. Therefore, in such a developing apparatus, there is a possibility that the developer may be scattered when the developer amount is temporarily reduced. That is, it seems that the opening width W of the developer discharge port 94 is set too wide. Further, as shown in the graph of (3), when the total amount of replenishment amount reaches a predetermined amount and the discharge amount after discharge starts is smaller than the amount replenished exceeding the predetermined amount, the development in the developing device The discharge responsiveness to the increase in the amount of the agent is poor, and the developer discharge port 94 may be clogged. That is, it seems that the opening width W of the developer discharge port 94 is set too narrow.
On the other hand, the graph of (1) shows that since the developer is not discharged in a state where the amount of developer is less than 340 [cc], discharge due to jumping of the developer can be prevented. Further, it can be seen that when the developer amount exceeds 340 [cc], the developer is discharged linearly, and thus the discharge responsiveness to the increase in the developer amount in the developing device is good.
That is, it is desirable to combine the control factors so that the relationship between the developer replenishment amount and the developer discharge amount is as shown in the graph of (1).
To find the most suitable combination, if the experiment for all combinations, there are combinations of 3 ^eight, a large burden of the experiment. On the other hand, when verification based on quality engineering is performed, eighteen control factors and three levels of 18 experiments are performed, and optimization using quality engineering is performed based on the results of each experiment. Among these combinations, it is possible to obtain a combination of control factors in which the relationship between the developer replenishment amount and the developer discharge amount is closest to the graph of (1).
Since the control factor includes the opening width W of the developer discharge port and the opening height H of the developer discharge port, by finding the most suitable combination, the developer discharge port 94 The opening width W and the opening height H can be set.

After finding the most suitable combination of control factors by the above-described method, the developing device 4 set to the combination of the control factors is created, and the developer is developed under the condition that the developer amount in the developing device 4 is maximized. Experiment to drive.
At this time, the conditions for maximizing the developer amount may vary depending on the apparatus and the composition of the developer to be used, so verification is performed for the case of continuous printing of a full solid image and the case of continuous printing of a full white image. When the maximum number of continuous prints capable of inputting a full-color image or the maximum number of continuous prints capable of inputting a full-color white image are not clogged in the developer discharge port 94, In the state where the bulk of the staying developer T is maximized, the developer discharge port 94 is opened so that the developer does not reach the discharge port upstream end portion 94f which is one end portion of the developer discharge port 94 in the horizontal direction. It can be determined that the width H has been set. Similarly, the opening height of the developer discharge port 94 is set so that the developer does not reach the discharge port upper end portion 94t which is the upper end portion of the developer discharge port 94 in a state where the bulk of the staying developer T is maximized. It can be determined that H is set.

FIG. 21 is a graph showing the relationship between toner density and bulk density in the developing device 4.
The upper limit of the toner concentration of a normal developer is set so as not to exceed a coverage of 100 [%]. This is because when the coverage ratio exceeds 100%, the toners come into contact with each other, and the reversely charged toner increases, resulting in deterioration of scattering and background stains. The lower limit of toner density is set to the minimum toner density necessary to maintain the image density. In this embodiment, the toner density is set to 5 to 9 [wt%], and the change in bulk density at this time is 1.75 [g / cc] to 1.55 [g] as shown in FIG. / Cc].
In general, when the toner concentration is increased, the specific gravity of the toner is smaller than the specific gravity of the carrier, so that the bulk density of the developer is reduced and as a result, the amount (bulk) of the developer in the developing device is increased. If the fluctuation of the bulk exceeds 15 [%], the range of the allowable developer amount in the developing device 4 cannot be satisfied, and a malfunction such as an abnormal image may occur. Therefore, it is desirable to keep the fluctuation range of the bulk density of the developer within 15% in actual use. If the fluctuation range of the bulk density of the developer exceeds 15 [%], the balance of the developer in the developing device 4 may be lost. Specifically, when the amount of the developer is rapidly changed from a large amount to a small amount (toner density decrease), there is a possibility that the supply of the developer to the developing sleeve becomes insufficient and white spots may occur. On the other hand, if the amount of developer suddenly changes from a small amount to a large state, the developer may overflow (including clogging of the developer discharge port 94).
In order to prevent clogging of the developer due to the developer being in the packing state at the developer discharge port 94, which may occur when the bulk changes from a small amount of developer to a large state, The opening of the developer discharge port 94 may be enlarged, but there are restrictions on the layout. For this reason, in this embodiment, the fluctuation range of the bulk density is limited to 15 [%].

FIG. 22 is an explanatory view of the wall thickness forming the developer discharge port 94.
The developer discharge port 94 communicates the supply transport path 9 and the discharge transport path 2 adjacent to each other with the discharge partition wall 135 interposed therebetween. The thickness t of the discharge partition wall 135 was set to 2 [mm] or less.
If the thickness t of the discharge partition wall 135 of the discharge port lower end portion 94u is too thick, the developer stays on the discharge port lower end portion 94u when the developer is discharged, and the developer indicated by T3 in FIG. There is a possibility that it will not be discharged. When the developer stays as indicated by T3 as shown in FIG. 22, the developer stays accelerated from this point, and the developer discharge is inhibited. In the worst case, the developer amount in the developing device 4 is within the allowable range. May cause problems such as abnormal images.
In order to prevent such a problem, it is desirable that the thickness t of the discharge partition wall 135 of the lower end portion 94u of the discharge port is 2 [mm] or less.

The discharge partition wall 135 of the discharge port lower end portion 94u which is the lower end portion of the developer discharge port 94 has a thickness t, and the lower surface of the developer discharge port 94 is formed by this thickness. When the developer to be discharged through the developer discharge port 94 is stacked on the lower surface of the developer discharge port 94, the discharge of the developer is hindered and the amount of developer in the developing device 4 increases. There is a fear. Therefore, the thickness or shape of the discharge partition wall 135 that forms the lower surface of the developer discharge port 94 is set so that the developer discharge is not hindered and the amount of developer in the developing device 4 does not increase. It is desirable.
As such setting of the discharge partition wall 135, the thickness t of the discharge partition wall 135 forming the lower surface of the developer discharge port 94 may be set to 2 [mm] or less as described with reference to FIG.

  In addition, the thickness of the discharge partition wall 135 that forms the lower surface of the developer discharge port 94 is not limited, and the shape of the discharge partition wall 135 that forms the discharge port lower end portion 94u of the developer discharge port 94 is not limited. You may set to the shape where a developer is hard to pile up.

FIG. 23 is an enlarged schematic view of the vicinity of the developer discharge port 94 viewed from the upstream side of the supply conveyance path 9 in the conveyance direction.
As shown in FIG. 23, the shape of the discharge partition wall 135 in the portion forming the discharge port lower end portion 94u of the developer discharge port 94 is a square shape with the vertex O on the upper side. An inclined surface S is formed between the vertex O and the corner Q, and a discharge partition wall 135 is formed so that the vertex O is disposed on the supply conveyance path 9 side and the corner Q is disposed on the discharge conveyance path 2 side. To do. Further, it is desirable that the angle θ of the vertex O is an acute angle.
If the discharge port lower end portion 94u of the developer discharge port 94 is a flat surface, the developer is piled up on the flat surface portion, and depending on how the developer is aggregated, the developer is loaded so as to affect the discharge of the developer. There is a risk of blocking. On the other hand, by setting the shape of the discharge partition wall 135 at the portion forming the lower end portion 94u of the discharge port as shown in FIG. 23, the developer has its own weight along the slope S from the vertex O toward the corner portion Q. Fall. As a result, there is no space for developer to accumulate at the lower end 94u of the discharge port of the developer discharge port 94, and developer discharge is hindered due to the developer remaining at the lower end 94u of the discharge port. Can be prevented.
Further, the shape of the discharge partition wall 135 of the portion forming the discharge port lower end portion 94u that prevents the developer from staying in the discharge port lower end portion 94u is not limited to that shown in FIG. R) that is convex upward as shown in FIG. 24, or a shape such that the vertex O is on the discharge conveyance path 2 side and the corner Q is on the supply conveyance path 9 side as shown in FIG. Also good. In the case of the shape of FIG. 24 (b), the effect of preventing the retention of the developer is inferior compared to the shape shown in FIG. 23, but the developer is less likely to stack compared to the flat bottom outlet portion 94u, This has the effect of preventing the developer from staying.

[Example 2]
Next, a second embodiment (hereinafter referred to as embodiment 2) having the features of the present invention will be described.
In Example 1 shown in FIG. 17, the discharge port downstream end portion 94 e, which is the downstream end of the developer discharge port 94 of the supply transport path 9, is upstream with respect to the downstream end wall surface 80 in the developer transport direction. .
Here, as Example 2, a configuration in which the positions of the discharge port downstream end portion 94e and the downstream end wall surface 80 in the transport direction of the supply transport path 9 coincide with each other will be described. In addition, since it is common with Example 1 except the positional relationship of the discharge outlet downstream end part 94e and the downstream end wall surface 80, only a different point is demonstrated.
FIG. 25 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path 9 in a state where the developer amount in the developing device 4 of Example 2 is maximized. As shown in FIG. 25, in the developing device 4 of Example 2, the positions of the outlet downstream end portion 94e and the downstream end wall surface 80 in the transport direction of the supply transport path 9 coincide. In the first embodiment shown in FIG. 17, the developer that is not discharged from the developer discharge port 94 even though it is above the discharge port lower end portion 94u is located between the discharge port downstream end portion 94e and the downstream end wall surface 80. Exists. On the other hand, in the second embodiment shown in FIG. 25, the positions of the outlet downstream end portion 94e and the downstream end wall surface 80 coincide with each other. However, there is no developer that is not discharged from the developer discharge port 94. For this reason, the responsiveness of the discharge of the developer with respect to the increase and decrease of the developer amount in the developing device 4 becomes better.

[Modification]
The developing device 4 according to the above-described embodiment has a configuration in which the supply conveyance path 9 is provided above the stirring conveyance path 10 and the collection conveyance path 7. The developing device 4 to which the configuration in which the developer in the apparatus can be satisfactorily replaced as in the first and second embodiments can be applied is not limited to this configuration. Hereinafter, as a modification, a developing device in which three developer conveyance paths including a supply conveyance path 9, an agitation conveyance path 10, and a collection conveyance path 7 are provided at substantially the same height will be described. Since the configuration other than the shape of the developing device 4 is the same as that of the embodiment, only the developing device 4 which is a difference will be described.

FIG. 26 is a schematic configuration diagram of the developing device 4 according to a modification.
As shown in FIG. 26, the surface of the photosensitive member 1 is charged by the scorotron charger 103 while rotating in the direction of arrow G in the drawing. The charged surface of the photosensitive member 1 is supplied with toner from the developing device 4 to a latent image on which an electrostatic latent image is formed by a laser beam L irradiated from an exposure device (not shown) to form a toner image.

The developing device 4 has a developing roller 5 as a developer carrying member for supplying toner to the latent image on the surface of the photoreceptor 1 while moving the surface in the direction of arrow I in the drawing. Further, a supply screw 8 is provided as a supply conveyance member that conveys the developer in the depth direction of FIG. 26 while supplying the developer to the developing roller 5.
A doctor blade 12 as a developer regulating member that regulates the developer supplied to the developing roller 5 to a thickness suitable for development is provided on the downstream side of the surface moving direction from the portion facing the supply screw 8 of the developing roller 5. ing.
The developed developer that has passed through the developing section is collected downstream from the developing section, which is the facing portion of the developing roller 5 with respect to the photoconductor 1, and the collected developer is collected in the same direction as the supply screw 8. A recovery screw 6 is provided as a recovery transport member for transporting to the front. A supply conveyance path 9 having a supply screw 8 and a collection conveyance path 7 having a recovery screw 6 are arranged below the developing roller 5 in parallel. The two conveyance paths of the supply conveyance path 9 and the collection conveyance path 7 are partitioned by a second partition wall 134 as a partition member.

  The developing device 4 is provided with a stirring conveyance path 10 in parallel with the supply conveyance path 9 on the opposite side of the collection conveyance path 7. The agitating and conveying path 10 includes an agitating screw 11 serving as an agitating and conveying member that conveys the developer to the near side in the figure, which is in the opposite direction to the supply screw 8 while agitating the developer. The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a first partition wall 133 as a partition member. Both ends of the first partition wall 133 on the front side and the back side in the figure are openings, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other. The excess developer that is supplied into the supply conveyance path 9 and is not used for development and is conveyed to the downstream end in the conveyance direction of the supply conveyance path 9 and the collected development conveyed to the downstream end in the conveyance direction of the collection conveyance path 7 by the collection screw 6 The agent is supplied to the stirring conveyance path 10. The agitating and conveying path 10 agitates the supplied excess developer and the recovered developer and conveys them to the downstream side in the conveying direction of the agitating screw 11. Then, the developer is supplied into the supply conveyance path 9 on the upstream side in the conveyance direction of the supply screw 8 from the supply opening provided in the first partition wall 133.

The second partition wall 134 has an opening at the end in the drawing, which is the most downstream side in the transport direction of the recovery screw 6, and the supply transport path 9 and the recovery transport path 7 communicate with each other. The three conveying paths are in communication with the downstream end in the conveying direction of the collection screw 6, the downstream end in the conveying direction of the supply screw 8, and the upstream end in the conveying direction of the stirring screw 11.
Then, the recovered developer transported to the downstream end in the transport direction of the recovery transport path 7 is transferred to the supply transport path 9. Further, the collected developer and the developer that has not been supplied to the developing roller 5 that is conveyed by the supply screw 8 are transferred to the communicating agitating and conveying path 10.
In the agitating and conveying path 10, the agitating screw 11 agitates and conveys the collected developer, the surplus developer, and the toner replenished as necessary in the transfer unit in the direction opposite to the developer in the collecting and conveying path 7 and the supply conveying path 9. . Then, the agitated developer is transferred to the upstream side in the conveyance direction of the supply conveyance path 9 communicating with the downstream side in the conveyance direction. A toner concentration sensor 127 is provided below the agitating and conveying path 10, and a toner replenishment control device (not shown) is operated by sensor output to replenish toner from a toner bottle (not shown) to a transfer unit. Yes.
The casing of the developing device 4 includes an integrally formed lower casing 112 and upper casing 113 that are divided into upper and lower portions at the shaft portions of three conveying screws. The first partition wall 133 is a part of the lower casing 112, and the second partition wall 134 is held by the upper casing 113 and mated with the lower casing 112.
As the above-described toner replenishment control device, a system using a known MONO pump can be employed. According to this method, there are few restrictions on the installation location of the toner cartridge, which is advantageous for space allocation in the image forming apparatus. Further, since the toner can be replenished in a timely manner, it is not necessary to provide a large toner storage space in the developing device 4, and the developing device 4 can be downsized.

As shown in FIG. 26, the screw apex 114 of the supply screw 8 which is the uppermost part of the supply member is disposed below the rotation center 115 of the developing roller 5. In the developing device 4, an angle θ1 between a straight line connecting the rotation center 115 of the developing roller 5 and the screw apex 114 and a horizontal straight line passing through the rotation center 115 is set to 30 [°]. The angle θ1 depends on the diameter of the supply screw 8, but is preferably 10 [°] to 40 [°] in view of the layout because the developing device 4 is downsized.
The developer is supplied to the developing roller 5 by the magnetic poles provided in the developing roller 5 attracting the magnetic carrier in the developer. As described above, by arranging the screw apex 114 to be lower than the rotation center 115 of the developing roller 5, the weight of the developer does not affect the amount of the developer supplied to the developing roller 5, and the magnetic force The size contributes to the developer supply amount. Accordingly, since the developer is reliably supplied from above the developer conveyed in the supply conveyance path 9, the developing roller 5 can be used even if the bulk of the developer in the supply conveyance path 9 is not uniform in the conveyance direction of the supply screw 8. An appropriate amount of developer can be supplied.

In the conventional developing device in which the three developer transport paths are provided at the same height, the supply opening for delivering the developer from the stirring transport path 10 to the supply transport path 9 is provided outside the width of the development area. As a result, the agitation conveyance path 10 and the supply conveyance path 9 are in a state where the upstream end portion in the conveyance direction of the supply conveyance path 9 protrudes as compared with the developing roller 5 and the collection conveyance path 7.
In the developing device 4 of the modified example, since the supply opening is provided within the width of the developing region, the portion where the agitation conveyance path 10 and the supply conveyance path 9 protrude compared to the development roller 5 and the recovery conveyance path 7 is eliminated. Space saving of the developing device 4 can be achieved.
Further, like the developing device 4 of the modified example, by providing the collection conveyance path 7, the stirring conveyance path 10, and the supply conveyance path 9 at substantially the same height, the stress applied to the developer is reduced, and the length of the developer is increased. Life can be extended. In other words, by providing the three developer transport paths at the same height, it is not necessary to lift the developer upward in the developer transport path, so that stress applied to the developer can be reduced. As a result, the deterioration of the developer can be suppressed and stable image quality can be maintained.

As described above, according to the present embodiment, the developer is carried on the surface and rotated, and the toner is supplied to the latent image on the surface of the photoconductor 1 at a position facing the photoconductor 1 as the latent image carrier and developed. A developing roller 5 that is a developer carrying member, and a supply screw 8 that is a developer conveying member that conveys the developer. In the developer supply area for supplying the developer to the developing roller 5, the developer is supplied to the developing roller 5. As a developer replenishment means for replenishing the developer from the toner replenishment port 95 to the supply transport path 9 of the developer transport path for transporting the developer while being supplied, and the developer transport path including the supply transport path 9. And a toner replenishment control device shown in the figure, where the bulk of the developer increases or decreases in accordance with the increase or decrease in the amount of developer in the developing device 4 that is the amount of developer in the entire developer conveyance path. A developer discharge port 94 for discharging the developer to the outside of the apparatus at a predetermined height is provided. The developing device 4 includes a supply downstream end wall surface 80 which is a developer retaining means for retaining the developer in the vicinity of the developer discharge port 94 in the supply conveyance path 9, and the developer discharge port 94 is provided with the supply downstream end wall surface 80. The developer that has reached the height of the developer discharge port 94 among the accumulated developer T that has accumulated by the Of the discharge port downstream end portion 94e and the discharge port upstream end portion 94f, which are both ends of the outlet 94, even if the developer reaches the discharge port downstream end portion 94e, the developer does not reach the discharge port upstream end portion 94f. Thus, in order to set the opening width W that is the width of the developer discharge port 94 in the horizontal direction, the width of the developer discharge port 94 is wider than the width from the discharge port upstream end portion 94f to the discharge port downstream end portion 94e. State where the staying developer T exists It is not to become. Thereby, it is possible to prevent the developer from being packed by receiving pressure from the discharge port upstream end portion 94f and the discharge port downstream end portion 94e, and to prevent the developer from sticking. For this reason, it is possible to prevent the developer discharge port 94 from being clogged due to the widened area where the developer is fixed.
Further, in the state where the bulk of the staying developer T is maximized, the developer discharge port 94 is arranged in the height direction so that the developer does not reach the discharge port upper end portion 94t which is the upper end portion of the developer discharge port 94. By setting the opening height H, which is the width, the staying developer T exists in a wider range than the width from the discharge port lower end portion 94u, which is the lower end portion of the developer discharge port 94, to the discharge port upper end portion 94t. It will never be. Accordingly, it is possible to prevent the developer from being packed by receiving pressure from the discharge port upper end portion 94t and the discharge port lower end portion 94u, and to prevent the developer from sticking. For this reason, it is possible to prevent the developer discharge port 94 from being clogged due to the widened area where the developer is fixed.
Thus, in the developing device 4, it is possible to register that the developer is packed in the horizontal direction as well as in the height direction, so that the developer discharge port 94 can be prevented from being clogged. Therefore, in the developing device 4, the developer discharge port 94 can be prevented from being clogged with a simple configuration in which the opening width W and the opening height H of the developer discharge port are set. Can be done.
Further, the developing device 4 serves as a developer conveying path, a supply conveying path 9 that conveys the developer along the axial direction of the developing roller 5 while supplying the developer to the developing roller 5 that is a developer carrier, and a supply conveying path. And a stirring conveyance path 10 which is a circulation conveyance path for conveying the developer that has reached the downstream end in the conveyance direction of the path 9 to the upstream end in the conveyance direction of the supply conveyance path, and a developer discharge port 94 is provided as a developer in the supply conveyance path 9. By providing it in the vicinity of the downstream end in the transport direction, the excess developer that has not been supplied to the developing roller 5 and has reached the vicinity of the downstream end in the transport direction of the supply transport path 9 is retained as the retained developer T, and development is performed by increasing or decreasing the bulk The developer can be discharged from the agent discharge port 94. Accordingly, since the increase or decrease in the volume of the staying developer T or the discharge of the developer from the developer discharge port 94 does not affect the delivery of the developer to the developing roller 5, the developer is stably supplied to the developing roller 5. And good image formation can be performed.
Further, the developing device 4 serves as a developer conveying path, a supply conveying path 9 that conveys the developer along the axial direction of the developing roller 5 while supplying the developer to the developing roller 5 that is a developer carrier, and a supply conveying path. The agitating conveyance path 10 that is a circulation conveyance path for conveying the developer that has reached the downstream end in the conveyance direction of the path 9 to the upstream end in the conveyance direction of the supply conveyance path 9 and a portion facing the photosensitive member 1 that is a latent image carrier. A recovery conveyance path 7 that collects the developer separated from the surface of the developing roller 5 after passing and conveys the developer along the axial direction of the development roller 5 and in the same direction as the supply conveyance path 9 is provided. The transport path 10 is supplied with the excess developer transported to the most downstream side in the transport direction of the supply transport path 9 and the recovered developer transported to the most downstream side in the transport direction of the recovery transport path 7, and developed. Along the axial direction of the roller 5 and in a direction opposite to the supply conveyance path 9 By supplying the developer in the conveying direction upstream end of the supply conveyance path 9 and conveyed, it is possible to realize a one-way circulation of the developer.
Further, by suppressing the fluctuation range of the bulk density of the developer in the developing device 4 within 15%, the volume of the developer in the developing device 4 is prevented from exceeding the allowable developer amount range, Occurrence of problems such as abnormal images can be prevented.
Further, the developing device 4 includes a discharge conveyance path 2 that conveys the developer that has passed through the developer discharge port 94 from the supply conveyance path 9 that is a developer conveyance path to the outside of the development apparatus 4. The conveyance path 2 is adjacent to the discharge partition wall 135 and communicates with the developer discharge port 94. Further, the developer discharge port 94 is discharged to the lower surface of the developer discharge port 94 formed by the thickness of the discharge partition wall 135 of the discharge port lower end portion 94u which is the lower end portion of the developer discharge port 94. The thickness of the discharge partition wall 135 that forms the lower surface of the developer discharge port 94 is set so that the developer discharge does not hinder the developer discharge and the developer amount in the developing device 4 increases. To do. As a result, the developer remaining to be discharged at the lower end 94u of the discharge port can be prevented and the developer whose volume has been increased to the developer discharge port 94 can be discharged reliably, so that the developer in the developing device 4 can always be discharged. It can be kept constant, and the occurrence of problems due to insufficient or excessive developer can be prevented.
In addition, the developer transport path 9 includes a discharge transport path 2 that transports the developer that has passed through the developer discharge port 94 from the supply transport path 9 to the outside of the developing device 4, and the supply transport path 9, the discharge transport path 2, and the like. Is adjacent to the discharge partition wall 135, which is a partition wall, and communicates with the developer discharge port 94. The thickness of the discharge partition wall 135 of the discharge port lower end portion 94u, which is the lower end of the developer discharge port 94. By setting the thickness to 2 [mm] or less, it is possible to prevent the developer from staying at the lower end 94u of the discharge port and to prevent the discharge of the developer from being hindered.
Further, as shown in FIG. 23, the shape of the discharge partition wall 135 in the portion forming the discharge port lower end portion 94u which is the lower end portion of the developer discharge port 94 is a square shape with the vertex O on the upper side. May be set. As a result, the developer can be prevented from staying at the lower end 94u of the discharge port, and the discharge of the developer can be prevented from being hindered. Furthermore, as a shape for preventing the developer from staying at the lower end 94u of the discharge port, an R shape that protrudes upward may be used as shown in FIG.
Further, the photosensitive member 1 is a latent image carrier, the charger is a charging unit for charging the surface of the photosensitive member 1, and the latent image forming unit is for forming an electrostatic latent image on the photosensitive member 1. In the copying machine 500 as an image forming apparatus having the optical writing unit 21 and a developing unit for developing the electrostatic latent image into a toner image, the developing device 4 is used as the developing unit. Since the developer in the inside can be satisfactorily replaced, it is possible to prevent the occurrence of contamination in the apparatus of the copying machine 500 or breakage of the developing apparatus 4 and to perform good image formation.

1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 2 is a schematic configuration diagram of a developing device and a photoreceptor. FIG. 3 is a perspective cross-sectional view of the developing device for explaining the flow of the developer. FIG. 3 is a schematic diagram of a developer flow in a developing device. Cross-sectional explanatory drawing of a developing device. FIG. 5 is a schematic diagram of a developer flow in a developing device having a shape different from that in FIG. 4. FIG. FIG. 3 is an enlarged schematic view near the downstream end in the transport direction of a supply transport path of the developing device. FIG. 5 is a perspective explanatory view of the vicinity of the front end in a state where the stirring screw, the recovery screw, and the doctor blade are removed from the developing device. FIG. 10 is an explanatory perspective view of the vicinity of the near side in a state where a supply screw is removed from the developing device shown in FIG. 9. FIG. 11 is a perspective explanatory view of the vicinity of the near side in a state where the developing roller is removed from the developing device shown in FIG. 10. FIG. 12 is an explanatory perspective view when the developing device shown in FIG. 11 is viewed from a direction different from FIG. 11. Cross-sectional explanatory drawing of the developing device in a state where the developer amount is small. Side surface explanatory drawing of the image development apparatus of a state with little developer amount. Cross-sectional explanatory drawing of the developing device in a state where the amount of developer is large. Side surface explanatory drawing of the image development apparatus of a state with much developer amount. FIG. 4 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path in a state where the developer amount in the developing device of Embodiment 1 is maximized. FIG. 6 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path in a state where the amount of developer in the developing device of Comparative Example 1 is maximized. FIG. 10 is an enlarged schematic view near the downstream end in the transport direction of the supply transport path in a state where the amount of developer in the developing device of Comparative Example 2 is maximized. The graph which shows typically the relationship between the replenishment amount and discharge | emission amount of an experiment. 6 is a graph showing the relationship between toner density and bulk density in the developing device 4; Explanatory drawing of the wall thickness which forms a developer discharge port. Explanatory drawing of the discharge partition wall set to the shape where developer is hard to pile up. Explanatory drawing of the other example of the discharge partition wall set to the shape where developer is hard to pile up, (a) is R shape, (b) is the square shape by which the vertex was arrange | positioned at the discharge side. FIG. 10 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path in a state where the amount of developer in the developing device of Embodiment 2 is maximized. FIG. 6 is a schematic explanatory diagram of a developing device and a photoreceptor according to a modified example. An enlarged explanatory view of the vicinity of the developer discharge port, (a) is a steady state in which there is no change in the developer amount in the developing device, and (b) is an increase in the volume of the staying developer T at the position of the developer discharge port. State (c) is a state in which the lower end of the discharge port is covered with the staying developer from the downstream end of the discharge port to the upstream end of the discharge port. The schematic diagram which looked at the developer discharge port vicinity of the state of FIG.27 (c) from upper direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Discharge conveyance path 2a Discharge screw 4 Developing device 5 Developing roller 6 Collecting screw 7 Collection conveyance path 8 Supply screw 9 Supply conveyance path 10 Stirring conveyance path 11 Stirring screw 12 Doctor blade 14 Stretching roller 15 Driving roller 16 Secondary 16 Transfer backup roller 17 Intermediate transfer unit 18 Process cartridge 20 Image forming unit 21 Optical writing unit 22 Secondary transfer device 23 Tension roller 24 Paper transport belt 25 Fixing device 26 Fixing belt 27 Pressure roller 80 Downstream end wall surface 90 Belt cleaning device 91 Supply opening 92 Surplus opening 93 Recovery opening 94 Developer discharge port 94e Discharge port downstream end portion 94f Discharge port upstream end portion 94t Discharge port upper end portion 94u Discharge port lower end portion 95 Toner replenishment port 100 Printer unit 110 Intermediate transfer belt 133 First partition wall 134 Second finish Cut wall 135 Discharge partition wall 500 Copying machine

Claims (12)

A developer carrying member that rotates by carrying a developer on the surface, and supplies toner to the latent image on the surface of the latent image carrying member at a position facing the latent image carrying member;
A developer transport member that transports the developer while supplying the developer to the developer carrier in a developer supply region that includes a developer transport member that transports the developer and supplies the developer to the developer carrier; ,
Developer replenishing means for replenishing the developer in the developer transport path,
A developer discharge port for discharging the developer to the outside of the apparatus at a predetermined height at a location in the developer conveyance path where the bulk of the developer increases or decreases according to the increase or decrease of the developer amount in the entire developer conveyance path. In the provided developing device,
Developer retaining means for retaining the developer in the vicinity of the developer discharge port in the developer conveying path is provided, and the developer discharge port is configured to discharge the developer out of the retained developer retained by the developer retaining means. Provided to allow the developer to reach the height of the outlet,
The development is performed so that the developer does not reach both ends of the developer discharge port in the horizontal direction in a state where the staying developer reaches the developer discharge port and the bulk of the staying developer is maximized. A developing device characterized in that an opening width in a horizontal direction of the agent discharge port is set. A developer carrying member that rotates by carrying a developer on the surface, and supplies toner to the latent image on the surface of the latent image carrying member at a position facing the latent image carrying member;
A developer transport member that transports the developer while supplying the developer to the developer carrier in a developer supply region that includes a developer transport member that transports the developer and supplies the developer to the developer carrier; ,
Developer replenishing means for replenishing the developer in the developer transport path,
A developer discharge port for discharging the developer to the outside of the apparatus at a predetermined height at a location in the developer conveyance path where the bulk of the developer increases or decreases according to the increase or decrease of the developer amount in the entire developer conveyance path. In the provided developing device,
Developer retaining means for retaining the developer in the vicinity of the developer discharge port in the developer conveying path is provided, and the developer discharge port is configured to discharge the developer out of the retained developer retained by the developer retaining means. Provided to allow the developer to reach the height of the outlet,
The developer discharge port so that the developer does not reach the upper end of the developer discharge port when the staying developer reaches the developer discharge port and the bulk of the staying developer is maximized. The developing device is characterized in that the opening width in the height direction of is set. A developer carrying member that rotates by carrying a developer on the surface, and supplies toner to the latent image on the surface of the latent image carrying member at a position facing the latent image carrying member;
A developer transport member that transports the developer while supplying the developer to the developer carrier in a developer supply region that includes a developer transport member that transports the developer and supplies the developer to the developer carrier; ,
Developer replenishing means for replenishing the developer in the developer transport path,
A developer discharge port for discharging the developer to the outside of the apparatus at a predetermined height at a location in the developer conveyance path where the bulk of the developer increases or decreases according to the increase or decrease of the developer amount in the entire developer conveyance path . In the provided developing device,
Developer retaining means for retaining the developer in the vicinity of the developer discharge port in the developer conveying path is provided, and the developer discharge port is configured to discharge the developer out of the retained developer retained by the developer retaining means. Provided to allow the developer to reach the height of the outlet,
In a state where the staying developer reaches the developer discharge port, and the bulk of the staying developer is maximized, the developer does not reach both end portions of the developer discharge port in the horizontal direction, and The horizontal opening width of the developer discharge port and the opening width of the developer discharge port in the height direction are set so that the developer does not reach the upper end of the developer discharge port. A developing device.   A developer carrying member that rotates by carrying a developer on the surface, and supplies toner to the latent image on the surface of the latent image carrying member at a position facing the latent image carrying member;
A developer transport member that transports the developer while supplying the developer to the developer carrier in a developer supply region that includes a developer transport member that transports the developer and supplies the developer to the developer carrier; ,
Developer replenishing means for replenishing the developer in the developer transport path,
A developer discharge port for discharging the developer to the outside of the apparatus at a predetermined height at a location in the developer conveyance path where the bulk of the developer increases or decreases according to the increase or decrease of the developer amount in the entire developer conveyance path. In the provided developing device,
Developer retaining means for retaining the developer in the vicinity of the developer discharge port in the developer transport path is provided. Provided to allow the developer to reach the height of the outlet,
When the maximum number of continuous images that can set a full-color image is continuously developed, or when images with an image area ratio of 1% or less are continuously developed with the maximum number of images, the developer is applied to both ends of the developer discharge port in the horizontal direction. A developing device characterized in that an opening width in a horizontal direction of the developer discharge port is set so as not to reach.   A developer carrying member that rotates by carrying a developer on the surface, and supplies toner to the latent image on the surface of the latent image carrying member at a position facing the latent image carrying member;
A developer transport member that transports the developer while supplying the developer to the developer carrier in a developer supply region that includes a developer transport member that transports the developer and supplies the developer to the developer carrier; ,
Developer replenishing means for replenishing the developer in the developer transport path,
A developer discharge port for discharging the developer to the outside of the apparatus at a predetermined height at a location in the developer conveyance path where the bulk of the developer increases or decreases according to the increase or decrease of the developer amount in the entire developer conveyance path. In the provided developing device,
Developer retaining means for retaining the developer in the vicinity of the developer discharge port in the developer transport path is provided. Provided to allow the developer to reach the height of the outlet,
The developer does not reach the upper end of the developer discharge port when the maximum number of continuous images that can set a full-color image or when the image area ratio is 1% or less is continuously developed with the maximum number of images. The developing device is characterized in that an opening width in the height direction of the developer discharge port is set. The developing device according to claim 1, 2 , 3, 4 or 5 .
The developer conveyance path includes a supply conveyance path that conveys the developer along the axial direction of the developer carrier while supplying the developer to the developer carrier, and a conveyance conveyance downstream end of the supply conveyance path. A circulating conveyance path for conveying the reached developer to the upstream end in the conveyance direction of the supply conveyance path,
A developing device, wherein the developer discharge port is provided in the vicinity of a downstream end of the supply conveyance path in the developer conveyance direction. The developing device according to claim 1, 2 , 3 , 4, 5 or 6 .
The developer conveyance path includes a supply conveyance path that conveys the developer along the axial direction of the developer carrier while supplying the developer to the developer carrier, and a downstream end in the conveyance direction of the supply conveyance path. Collects the developer that has separated from the surface of the developer carrier after passing through the circulating conveyance path for conveying the reached developer to the upstream end in the conveyance direction of the supply conveyance path, and the portion facing the latent image carrier. And a recovery transport path that transports along the axial direction of the developer carrier and in the same direction as the supply transport path,
The circulation conveyance path is supplied with the developer conveyed to the most downstream side in the conveyance direction of the supply conveyance path and the developer conveyed to the most downstream side in the conveyance direction of the recovery conveyance path, and receives the development. A developing device characterized in that the developer is conveyed along the axial direction of the agent carrier and in the opposite direction of the supply conveyance path and is supplied to the upstream end in the conveyance direction of the supply conveyance path. The developing device according to claim 1, 2 , 3 , 4 , 5, 6 or 7 .
A developing device characterized in that the fluctuation range of the bulk density of the developer is suppressed to 15% or less. The developing device according to claim 1, 2 , 3 , 4 , 5 , 6, 7 or 8 .
A discharge conveyance path for conveying the developer that has passed through the developer discharge port from the developer conveyance path to the outside of the developing device;
The developer transport path and the discharge transport path are adjacent to each other across a partition wall, and communicate with each other at the developer discharge port.
The developer to be discharged through the developer discharge port is stacked on the lower surface of the developer discharge port formed by the thickness of the partition wall at the lower end of the opening of the developer discharge port. A developing device characterized in that the thickness of the partition wall that forms the lower surface of the developer discharge port is set so that the discharge of the agent is inhibited and the amount of developer in the developing device does not increase. The developing device according to claim 1, 2 , 3 , 4 , 5 , 6 , 7, 8, or 9 .
A discharge conveyance path for conveying the developer that has passed through the developer discharge port from the developer conveyance path to the outside of the developing device;
The developer transport path and the discharge transport path are adjacent to each other across a partition wall, and communicate with each other at the developer discharge port.
A developing device characterized in that a thickness of the partition wall at the lower end of the opening of the developer discharge port is set to 2 [mm] or less. The developing device according to claim 1, 2 , 3 , 4 , 5 , 6 , 7 , 8, 9 or 10 .
A discharge conveyance path for conveying the developer that has passed through the developer discharge port from the developer conveyance path to the outside of the developing device;
The developer transport path and the discharge transport path are adjacent to each other across a partition wall, and communicate with each other at the developer discharge port.
The developing device characterized in that the shape of the partition wall forming the lower end of the opening of the developer discharge port is a square shape with an apex upward or an R shape with an upward projection. At least a latent image carrier;
Charging means for charging the surface of the latent image carrier;
Latent image forming means for forming an electrostatic latent image on the latent image carrier;
In an image forming apparatus having developing means for developing the electrostatic latent image into a toner image,
An image forming apparatus using the developing device according to claim 1, 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9, 10, or 11 as the developing means.

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