JP2020003540A - Image formation apparatus - Google Patents

Abstract

To suppress locking of a screw and leakage of a developer caused thereby even in a state in which uneven distribution of the developer is caused owing to transportation of a developing device after shipping.SOLUTION: An image formation apparatus comprises a first motor capable of driving and rotating a first carrying screw arranged in a supply chamber and supplying a developer in the supply chamber to a developing sleeve and a second carrying screw arranged in a collection chamber and carrying a developer in the collection chamber having been collected after development; and a second motor capable of driving and rotating a developing sleeve, the first carrying screw being arranged at the same position with a top part of the second carrying screw during use of the developing device or at a higher position. A control part can execute, in initial driving of the developing device, a developer warm-up mode in which the first carrying screw and second carrying screw are rotated by the first motor for a predetermined time without rotating the developing sleeve by the second motor.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an image forming apparatus that forms an image on a recording material by an electrophotographic method, an electrostatic recording method, or the like.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus has been widely applied as a copying machine, a printer, a plotter, a facsimile, and a multifunction peripheral having a plurality of these functions. As an image forming apparatus of this type, an apparatus in which a developing device develops an electrostatic image formed on a photosensitive drum using a two-component developer mainly composed of a non-magnetic toner and a magnetic carrier is widely used. are doing. The developing device frictionally charges the toner and the carrier by rotating the conveying member and conveying the developer while stirring the toner in a circulation path in the developing container. The charged toner and carrier are supplied to a developing sleeve having a built-in mag roller by a conveying member, and are conveyed by the developing sleeve to a region facing the photosensitive drum to be subjected to development. The developer after the development is separated from the developing sleeve, returned to the circulation path, stirred and conveyed in the circulation path by the conveying member, and supplied to the developing sleeve again. As described above, when the developer is agitated and transported by the rotation of the transporting member, which is a rotating member, the developer aggregates due to vibration when the developing device is shipped and transported to the customer, and the developer in the circulation path. May increase the load applied when the transport member rotates. When the load applied to the rotation of the transport member increases, the transport member may not be able to rotate and may be locked, or the developer may leak from the circulation path to the outside of the developing container.

  In order to prevent an increase in the load applied when the transport member rotates, in the developing device containing the one-component developer, whether the rotation load of the agitator exceeds a predetermined value in order to detect the occurrence of aggregation or deviation of the developer. An image forming apparatus that detects whether or not the image forming apparatus is known is known (see Patent Document 1). In this image forming apparatus, when the rotational load of the agitator of the developing device exceeds a predetermined value, the agitator is driven by alternately rotating and inverting to drive the agitator to loosen the aggregation and deviation of the developer in the developing container. Execute the loosening sequence. According to this image forming apparatus, it is possible to eliminate the aggregation and bias of the developer contained in the developing container, reduce the load on the conveying member and the driving system thereof, and prevent the rotation of the conveying member from being locked. Can be.

JP-A-11-119526

  However, in the image forming apparatus described in Patent Document 1 described above, since a developing device for a one-component developer is applied, a rotation lock of a conveying member may not be prevented in a developing container for a two-component developer. is there. That is, in the developing device for a two-component developer, the first chamber for supplying the developer to the developing sleeve and the second chamber for collecting the developer from the developing sleeve form a developer circulation path, and the first chamber Is provided with a first transfer screw, and a second transfer screw is provided in the second chamber. When the aggregation of the developer, the bias of the developer in the circulation path, or the like occurs with respect to the first and second transport screws, the load applied to each transport screw cannot be reduced only by rotating the transport screw forward and reverse. There was a fear. Further, when the first transport screw is positioned at the same height or higher than the second transport screw, if the second transport screw is locked, the rotation of the first transport screw passes through the developing sleeve. The developer that has reached the second chamber may not be collected in the second chamber. In this case, the developer that is not collected in the second chamber may leak out of the developing container.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of suppressing screw locking and leakage of developer accompanying the screw even when the developer is biased due to transportation after shipment of the developing device.

  The image forming apparatus of the present invention has an image carrier, and a developer containing toner and a carrier, and a second chamber that forms a circulation path of the developer between the first chamber and the first chamber. A developing container, a developer carrying member that carries and rotates the developer contained in the developing container, rotates the electrostatic latent image formed on the image carrying member with toner, and is disposed in the first chamber. A first conveying unit that stirs and conveys the developer in the first chamber by rotation to supply the developer to the developer carrier; and a first conveying unit disposed in the second chamber and collected from the developer carrier after development. A developing device having a second conveying unit that stirs and conveys the developer in the second chamber by rotation; a first driving unit that can rotationally drive the first conveying unit and the second conveying unit; A second driving unit capable of driving the carrier to rotate, and the first driving unit And a control means for controlling the second drive means, wherein the first transport means has an uppermost portion at the same height position or a higher position as the uppermost portion of the second transport means when the developing device is used. The control unit is configured to control the first transport by the first driving unit for a predetermined time without rotating the developer carrier by the second driving unit during the initial driving of the developing device. A mode for rotating the means and the second transport means can be executed.

  ADVANTAGE OF THE INVENTION According to this invention, even in the state where a bias arises in a developer by the transportation after shipment of a developing device, lock of a screw and the leakage of the developer accompanying it can be suppressed.

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment. FIG. 2 is a cross-sectional view illustrating a developing device of the image forming apparatus according to the first embodiment. FIG. 2 is a vertical longitudinal sectional view illustrating a developing device of the image forming apparatus according to the first embodiment. FIG. 2 is a schematic block diagram illustrating a control system of the image forming apparatus according to the first embodiment. FIGS. 3A and 3B are vertical vertical cross-sectional views illustrating a developing device of the image forming apparatus according to the first exemplary embodiment, wherein FIG. 3A illustrates a case where the developer is biased toward an ascending communication portion, and FIG. It is a case where it is biased. FIGS. 6A and 6B are horizontal vertical cross-sectional views illustrating a developing device of an image forming apparatus according to a modification of the first embodiment, where FIG. 7A illustrates a case where the developer is biased toward an ascending communication portion, and FIG. This is the case where the position is biased toward the section. 6 is a flowchart illustrating a procedure for executing a developer familiarization mode in the image forming apparatus according to the first embodiment. 6 is a graph illustrating a relationship between a time from when the power of the image forming apparatus is turned on and a driving speed of each unit in the developing apparatus of the image forming apparatus that does not execute the developer familiarization mode. (A) shows the case where the developer in the developing device is not biased, and (b) shows the case where the developer in the developing device is biased. 4 is a graph illustrating a relationship between a time from when the power of the image forming apparatus is turned on and a driving speed of each unit in the developing device of the image forming apparatus according to the first embodiment. FIG. 4A is a cross-sectional view illustrating a modified example of the developing device of the image forming apparatus according to the first embodiment. FIG. ) Is a case where the supply chamber and the recovery chamber are arranged side by side in the horizontal direction. FIG. 10 is a vertical vertical sectional view illustrating a periphery of an outlet of a developing device of the image forming apparatus according to the second embodiment. When the developer is discharged from the discharge port in the developing device of the image forming apparatus according to the second embodiment, (a) the relationship between the developer surface height and the discharged amount of the developer, (b) the developer flow rate and the development It is a graph which shows the relationship with a liquid surface height. 9 is a graph illustrating a relationship between an output value of a toner density sensor and a toner density in a developing device of an image forming apparatus according to a third embodiment. 13 is a flowchart illustrating a procedure for executing a developer familiarization mode in the image forming apparatus according to the third embodiment.

<First embodiment>
Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS. In the present embodiment, a tandem type full-color printer is described as an example of the image forming apparatus 1. However, the present invention is not limited to the tandem-type image forming apparatus 1 and may be another type of image forming apparatus, and is not limited to a full-color image forming apparatus, and may be a monochrome or mono-color image forming apparatus. Alternatively, the present invention can be implemented for various uses such as a printer, various printing machines, a copying machine, a facsimile, and a multifunction peripheral.

  As shown in FIG. 1, the image forming apparatus 1 includes an apparatus main body 10, a sheet feeding unit (not shown), an image forming unit 40, a sheet discharging unit (not shown), and a control unit 11. The image forming apparatus 1 can form a four-color full-color image on a recording material according to an image signal from a document reading device (not shown), a host device such as a personal computer, or an external device such as a digital camera or a smartphone. . The sheet S as a recording material is a member on which a toner image is formed, and specific examples thereof include plain paper, a sheet made of synthetic resin which is a substitute for plain paper, thick paper, and a sheet for an overhead projector.

In the present embodiment, a two-component developer having a magnetic toner and a non-magnetic carrier is used. The toner has a base made of a binder resin having a colorant, and an additive added to the base. In this embodiment, a negatively chargeable polyester resin is used as a resin forming the toner. If the particle size of the toner is too small, friction with the carrier is difficult, so that it is difficult to control the charge amount. If the particle size is too large, a fine toner image cannot be formed. For this reason, the volume average particle diameter is preferably 4 μm or more and 10 μm or less. In the present embodiment, a toner having a volume average particle diameter of 7 μm was used. As the carrier, a metal such as iron, nickel, cobalt, manganese, chromium, rare earth, or the like, or an alloy thereof, or an oxide ferrite which is not oxidized on the surface can be used. If the particle size of the carrier is too small, the carrier tends to adhere to the image carrier during development, and if it is too large, the carrier disturbs the toner image during development, so the weight average particle size is preferably from 20 to 60 μm. Preferably it is 30 to 50 μm. The resistivity is preferably 10 ⁷ Ωcm or more, more preferably 10 ⁸ Ωcm or more. In this embodiment, a ferrite carrier having an average volume particle size of 40 μm and a resistivity of 10 ⁸ Ωcm was used. In the present embodiment, 300 g of the developer is accommodated in the developing container, and the weight ratio of the developer and the carrier at the time of installation is 1: 9.

  The image forming unit 40 can form an image on the sheet S fed from the sheet feeding unit based on image information. The image forming unit 40 includes a process cartridge 50y, 50m, 50c, 50k, toner bottles 41y, 41m, 41c, 41k, exposure devices 42y, 42m, 42c, 42k, an intermediate transfer unit 44, and a secondary transfer unit 45. And a fixing unit 46. The image forming apparatus 1 according to the present embodiment corresponds to full color, and the process cartridges 50y, 50m, 50c, and 50k include yellow (y), magenta (m), cyan (c), and black (k). Are provided separately in the same configuration for each of the four colors. For this reason, in FIG. 1, each component of the four colors is shown with the same reference numeral followed by a color identifier. However, in other drawings and specifications, only the reference numeral may be used without adding the color identifier. is there.

  The process cartridge 50 includes a photosensitive drum 51 that carries a toner image and moves, a charging roller 52, a developing device 20, a pre-exposure device (not shown), and a cleaning blade 55. The process cartridge 50 is integrally unitized, and is configured to be detachable from the apparatus main body 10.

  The photosensitive drum 51 is rotatable and carries an electrostatic image used for image formation. The photosensitive drum 51 is formed by laminating an organic photoconductor layer (OPC) composed of three layers, an undercoat layer, a photocharge generation layer, and a charge transport layer, which are sequentially applied on the outer peripheral surface of an aluminum cylinder having a diameter of 80 mm. It is configured. The photosensitive drum 51 is rotatably supported at both ends by flanges, and is driven to rotate in a rotation direction R1 (see FIG. 2) by transmitting a driving force from a driving motor (not shown) to one end. . In the present embodiment, the case where a commonly used drum-shaped organic photoconductor is used as the photoconductor drum 51 has been described. However, the present invention is not limited to this, and an inorganic photoconductor such as an amorphous silicon photoconductor may be used. . Further, the image carrier is not limited to a drum-shaped photoconductor, and for example, a belt-shaped photoconductor may be used.

  The charging roller 52 is, for example, a rubber roller that has a length of 320 mm and is in contact with the surface of the photosensitive drum 51 and rotates by being driven, and uniformly charges the surface of the photosensitive drum 51. A DC voltage is applied to the charging roller 52 as a charging bias, and charges the photosensitive drum 51 via the charging roller 52. The exposure device 42 is a laser scanner, and emits a laser beam according to the image information of the separated color output from the control unit 11.

  The developing device 20 develops the electrostatic image formed on the photosensitive drum 51 with toner by applying a developing bias. The developing device 20 has a developing sleeve (developer carrier) 24. Details of the developing device 20 will be described later.

  The toner image developed on the photosensitive drum 51 is primarily transferred to the intermediate transfer unit 44. The surface of the photosensitive drum 51 after the primary transfer is neutralized by a pre-exposure device (not shown). The cleaning blade 55 is of a counter blade type and is in contact with the photosensitive drum 51 with a predetermined pressing force. After the primary transfer, the toner remaining on the photosensitive drum 51 without being transferred to the intermediate transfer unit 44 is removed by a cleaning blade 55 provided in contact with the photosensitive drum 51, collected, and prepared for the next image forming step. .

  The intermediate transfer unit 44 includes a plurality of rollers such as a driving roller 44a, a driven roller 44d, and primary transfer rollers 47y, 47m, 47c, and 47k, and an intermediate transfer belt 44b wound around these rollers and carrying a toner image. Have. The primary transfer rollers 47y, 47m, 47c, and 47k are disposed to face the photosensitive drums 51y, 51m, 51c, and 51k, respectively, abut the intermediate transfer belt 44b, and transfer the toner image on the photosensitive drum 51 to the intermediate transfer belt 44b. Transcribe.

  The intermediate transfer belt 44b contacts the photosensitive drum 51 to form a primary transfer portion with the photosensitive drum 51, and applies a primary transfer bias to transfer the toner image formed on the photosensitive drum 51 to the primary transfer portion. Primary transfer. By applying a primary transfer bias of positive polarity to the intermediate transfer belt 44b by the primary transfer roller 47, the respective toner images having the negative polarity on the photosensitive drum 51 are sequentially multiplex-transferred to the intermediate transfer belt 44b.

  The secondary transfer section 45 includes a secondary transfer inner roller 45a and a secondary transfer outer roller 45b. A full-color toner image formed on the intermediate transfer belt 44b is transferred to the sheet S by applying a positive secondary transfer bias to the outer secondary transfer roller 45b. The secondary transfer outer roller 45b abuts on the intermediate transfer belt 44b to form a secondary transfer portion 45 with the intermediate transfer belt 44b. The transferred toner image is secondarily transferred to the sheet S by the secondary transfer unit 45.

  The fixing section 46 includes a fixing roller 46a and a pressure roller 46b. When the sheet S is nipped and conveyed between the fixing roller 46a and the pressure roller 46b, the toner image transferred to the sheet S is heated and pressed to be fixed on the sheet S. After fixing, the sheet discharge unit feeds the sheet S conveyed from the discharge path, discharges the sheet S from a discharge port, and stacks the sheet S on a discharge tray, for example.

  An image forming operation in the image forming apparatus 1 configured as described above will be described. When the image forming operation is started, first, the photosensitive drum 51 rotates and the surface is charged by the charging roller 52. Then, a laser beam is emitted from the exposure device 42 to the photosensitive drum 51 based on the image information, and an electrostatic latent image is formed on the surface of the photosensitive drum 51. When the toner adheres to the electrostatic latent image, it is developed and visualized as a toner image, and is primarily transferred to the intermediate transfer belt 44b. After the primary transfer, the toner remaining on the photosensitive drum 51 without being transferred to the intermediate transfer unit 44 is removed by the cleaning blade 55.

  On the other hand, the sheet S is supplied in parallel with such a toner image forming operation, and the sheet S is transported to the secondary transfer unit 45 via the transport path in synchronization with the toner image on the intermediate transfer belt 44b. . The image is secondarily transferred from the intermediate transfer belt 44b to the sheet S, and the sheet S is conveyed to a fixing unit 46, where the unfixed toner image is heated and pressed to be fixed on the surface of the sheet S, and the apparatus main body 10 Is discharged from

  Here, in the present embodiment, the transport speed of the sheet S can be changed in two stages according to the basis weight of the sheet S on which an image is formed. Here, when the basis weight of the sheet S is less than 250 [g / m2], the first process speed is set to 320 [mm / S]. When the basis weight of the sheet S is not less than 250 [g / m2] and not more than 300 [g / m2], the second process speed is 160 [mm / S] lower than the first process speed. I have to. The A4 size print productivity at the first process speed is 70 ppm and the A4 size print productivity at the second process speed is 35 ppm.

  Next, the developing device 20 in the image forming apparatus 1 according to the present embodiment will be described in detail with reference to FIGS. The developing device 20 is detachable from the apparatus main body 10 and includes a developing container 30 for storing a developer, a first conveying screw 21, a second conveying screw 22, a developing sleeve 24, a regulating blade 25, a toner density sensor 26. The developing device 20 develops the electrostatic latent image formed on the photosensitive drum 51 with a developer. The developing container 30 has an opening 30 a at a position facing the photosensitive drum 51 so that the developing sleeve 24 is exposed.

  The developing container 30 has a partition wall 27 extending substantially horizontally in the longitudinal direction at a substantially central portion. The developing container 30 is vertically divided into a supply chamber (first chamber) 31 and a recovery chamber (second chamber) 32 by a partition wall 27, and the developer is stored in the supply chamber 31 and the recovery chamber 32. . That is, the supply chamber 31 is disposed so as to at least partially overlap the collection chamber 32 when the developing device 20 is viewed from above and below during use. Thereby, the first transport screw 21 is arranged such that the uppermost portion is at the same height position or higher than the uppermost portion of the second transport screw 22 when the developing device 20 is used. Here, the uppermost portion is, for example, an upper vertex of the spiral conveying blades 21b and 22b of each of the conveying screws 21 and 22.

  The supply chamber 31 supplies the developer to the developing sleeve 24. The recovery chamber 32 communicates with the supply chamber 31 to recover the developer from the developing sleeve 24 and agitate the developer. On the partition wall 27 between the supply chamber 31 and the recovery chamber 32, an ascending communication part 33 and a descending communication part 34 for vertically connecting the supply chamber 31 and the recovery chamber 32 are formed at both ends. The ascending communication part 33 assembles the developer recovered from the developing sleeve 24 in the recovery chamber 32 and the developer unloaded from the supply chamber 31 into the supply chamber 31. The descending communication part 34 assembles the developer that has passed through the supply chamber 31 without being supplied to the developing sleeve 24 in the supply chamber 31, into the recovery chamber 32.

  The first transport screw 21 is disposed in the supply chamber 31 substantially in parallel with the developing sleeve 24, and transports the developer in the supply chamber 31 (first chamber) while stirring by rotation. The first transport screw 21 is rotatably provided in the developer container 30 and has a shaft 21 a having magnetism, and a spiral that rotates integrally with the shaft 21 a and transports the developer inside the developer container 30 in the transport direction D <b> 1 by rotation. And a transfer wing 21b. The second transport screw 22 is disposed in the recovery chamber 32 substantially in parallel with the first transport screw 21, and rotates the developer in the recovery chamber 32 (second chamber) recovered from the developing sleeve 24 after development by the first transport screw. The screw 21 is conveyed while being stirred in the opposite direction. The second conveying screw 22 is rotatably provided in the developing container 30 and has a shaft portion 22a having magnetism, and a spiral that rotates integrally with the shaft portion 22a and conveys the developer inside the developing container 30 in the conveying direction D2 by rotation. And a carrier wing 22b in the shape of a letter. The developer is circulated between the supply chamber 31 and the recovery chamber 32 through the ascending communication part 33 and the descending communication part 34, which are communication parts at both ends of the partition wall 27, by the conveyance by the rotation of the conveyance screws 21 and 22. In the present embodiment, the shaft portions 21a and 22a rotate at 900 rpm to circulate the developer. The toner is agitated by the transport screws 21 and 22 and rubs against the carrier to be triboelectrically charged to a negative polarity.

  The image forming apparatus 1 includes a first motor (first driving unit) M1 that can rotationally drive each of the conveying screws 21 and 22 and a second motor (second driving unit) M2 that can rotationally drive the developing sleeve 24. Is provided. The first motor M1 is directly connected to the first transfer screw 21, and the first transfer screw 21 and the second transfer screw 22 are connected by a gear of 1: 1.07. The second motor M2 is directly connected to the developing sleeve 24. Each of the motors M1 and M2 uses a DC motor. In the present embodiment, there are two steady-state drive rotation speeds during image formation according to the process speed. In the case of the first process speed, the rotation speed of the first motor M1 is 890 [rpm], and the second The rotation speed of the motor M2 is 520 [rpm]. In the case of the second process speed, the rotation speed of the first motor M1 is 650 [rpm], and the rotation speed of the second motor M2 is 260 [rpm]. That is, the control unit 11 can change the rotation speed at which the first transport screw 21 and the second transport screw 22 are rotated by the first motor M1 in the predetermined shift range during image formation. In the present embodiment, separate motors M1 and M2 are used in order to independently drive each of the transport screws 21 and 22 and the developing sleeve 24. However, the present invention is not limited to this. . For example, a single motor may be used to switch the drive transmission system between the transport screws 21 and 22 and the developing sleeve 24 using a clutch or the like.

  The developing sleeve 24 carries a developer having a non-magnetic toner and a magnetic carrier, and rotates and conveys it to a developing area Da facing the photosensitive drum 51. The developing sleeve 24 is made of, for example, a non-magnetic material such as aluminum or non-magnetic stainless steel. In this embodiment, the developing sleeve is made of aluminum having a diameter of 20 mm. Inside the developing sleeve 24, a roller-shaped magnet roller 24m is fixedly installed in a non-rotating state with respect to the developing container 30. The magnet roller 24m has a developing magnetic pole S1 and magnetic poles N3, N2, S2, and N1 for transporting the developer. The developer forms a magnetic brush by the magnetic field of the developing magnetic pole S1, and this magnetic brush develops the electrostatic latent image as a toner image with the charged toner while contacting the photosensitive drum 51 in the developing area Da. As the developer is transported by the first transport screw 21, the developer jumps up and is supplied to the developing sleeve 24. The developer is bound by the magnetic pole N2 because the magnetic carrier is mixed. Next, with the rotation of the developing sleeve 24, the developer passes through the magnetic pole S2 facing the regulating blade 25, and the developer is regulated to a predetermined amount. The regulated developer passes through the magnetic pole N1 and is supplied to the developing magnetic pole S1 facing the photosensitive drum 51. The developer that has passed the developing area Da and consumed the toner with respect to the electrostatic latent image is released from the magnetic binding force of the magnetic pole between the magnetic poles N3 and N2, and is peeled off from the surface of the developing sleeve 24. And collected in the collection chamber 32.

  The developing sleeve 24 is disposed in the opening 30 a so as to be partially exposed to face the photosensitive drum 51. The diameter of the developing sleeve 24 is 20 mm, and the diameter of the photosensitive drum 51 is 30 mm. The photosensitive drum 51 is driven to rotate so that the surface speed of the photosensitive drum 51 becomes the process speed. By setting the closest area between the developing sleeve 24 and the photosensitive drum 51 to a distance of about 260 μm, it is set so that the developer conveyed to the developing area Da can be developed while being in contact with the photosensitive drum 51. I have.

The regulating blade 25 faces the developing sleeve 24 on the upstream side of the developing area Da in the rotation direction R2 of the developing sleeve 24 in order to reduce the amount of the developer carried on the developing sleeve 24 and supplied to the electrostatic latent image. Are located. As the regulating blade 25, an aluminum plate-like member extending along the longitudinal axis is used. The regulating blade 25 is disposed on the developing container 30 side such that the tip of the blade faces the center of the developing sleeve 24 on the upstream side of the photosensitive drum 51 in the rotation direction R2 of the developing sleeve 24. As the developing sleeve 24 rotates, the developer on the developing sleeve 24 passes through the space between the tip of the regulating blade 25 and the developing sleeve 24 and is sent to the developing area Da. Therefore, by adjusting the gap between the regulating blade 25 and the surface of the developing sleeve 24, the amount of the developer carried on the developing sleeve 24 and conveyed to the developing area Da can be adjusted. In the present embodiment, the developer conveyance amount is set to 30 mg / cm ² . For this purpose, the distance between the regulating blade 25 and the developing sleeve 24 is preferably 200 to 1000 μm, more preferably 300 to 700 μm, and is set to 400 μm in the present embodiment.

  The toner density sensor 26 is installed at a position 3 [cm] from the innermost wall in the transport direction D2 of the collection chamber 32 and 9 [mm] from the lower surface of the collection chamber 32, and has a detection surface with a diameter of 8 [mm]. Is provided so as to protrude from the inner wall of the collection chamber 32 by 0.5 [mm]. The toner concentration sensor 26 is an inductance sensor that can detect the magnetic permeability of the developer inside the developing container 30 by applying a control voltage. That is, when the toner density increases, the carrier density near the detection surface relatively decreases, and when the toner density decreases, the carrier density near the detection surface relatively increases. Therefore, from the toner density conversion table using the signal value of the magnetic permeability, Calculate the actual toner density. The toner concentration sensor 26 is connected to the control unit 11 (see FIG. 4), detects the toner concentration of the developer conveyed in the collection chamber 32, and transmits a corresponding electric signal to the control unit 11. The development of the electrostatic latent image on the photosensitive drum 51 causes a decrease in the toner concentration of the developer in the developing device 20. The toner concentration sensor 26 provided opposite to the developer in the collection chamber 32 detects the toner of the developer. Detect concentration. The control unit 11 can execute automatic toner replenishment control (ATR) using the toner density sensor 26.

  As shown in FIG. 3, a hopper 41a that stores toner for replenishment is disposed above the developing device 20. The hopper 41 a includes a screw-shaped supply screw 35 at a lower portion, and one end of the supply screw 35 extends to a position of a supply port 29 provided at a front end of the developing device 20. The toner consumed by the image formation is supplied to the developing container 30 from the hopper 41a through the supply port 29 by the rotational force of the supply screw 35 and the gravity of the developer. In this manner, the supply developer is supplied from the hopper 41a to the developing device 20. The replenishment amount of the replenishment developer is roughly determined by the number of rotations of the supply screw 35, and the number of rotations is determined by a toner replenishment amount control unit (not shown). As a method of controlling the toner replenishment amount, a method of optically or magnetically detecting the toner density of the two-component developer, a method of developing a reference latent image on the photosensitive drum 51 and detecting the density of the toner image, and the like are described. Various methods are known and can be appropriately selected.

  As shown in FIG. 4, the control unit 11 is constituted by a computer, for example, a CPU 12, a ROM 13 for storing a program for controlling each unit, a RAM 14 for temporarily storing data, and an input / output for inputting and outputting signals to and from the outside. And a circuit 15 (I / F). The CPU 12 is a microprocessor that controls the entire control of the image forming apparatus 1, and is a main controller of the system controller. The CPU 12 is connected to the sheet feeding unit, the image forming unit 40, the sheet discharging unit, and the like via the input / output circuit 15, exchanges signals with each unit, and controls the operation. The ROM 13 stores an image forming control sequence and the like for forming an image on the sheet S. The RAM 14 is composed of, for example, a flash memory. The control unit 11 is connected to sensors such as the toner density sensor 26 and receives electric signals from each sensor. The control unit 11 is connected to a first motor M1, a second motor M2, and the like via a motor control unit 16, which is a driver, and can control each of the motors M1 and M2.

  Next, the initial installation of the developing device 20 shipped from the factory in the image forming apparatus 1 of the present embodiment will be described. In the present embodiment, the developing device 20 is shipped from a factory in a state of being installed in the image forming apparatus 1 (attached state, bundled state), carried into a customer or the like, and installed together with the image forming apparatus 1. In the image forming apparatus 1, the developing device 20 is supported in the same manner as during normal printing. That is, the developing device 20 is urged in the first direction X1 (see FIG. 2) and the second direction X2 (see FIG. 3). The first direction X1 (see FIG. 2) is a direction in which the developing device 20 is urged toward the photosensitive drum 51 in a horizontal direction orthogonal to the rotation axis direction of each of the transport screws 21 and 22. The second direction X2 (see FIG. 3) is a direction in which the conveying screws 21 and 22 are urged from the descending communication portion 34 toward the ascending communication portion 33 along the rotation axis direction of each of the screws. The developing device 20 is pressed by a spring in each of the first direction X1 and the second direction X2. As a result, the bearing (not shown) provided on the flange at the end of the developing sleeve 24 and the spacer (not shown) provided on the flange at the end of the photosensitive drum 51 via the bearing abut the developing sleeve. 24 and the photosensitive drum 51 form the closest area.

  For this reason, the developing device 20 receives the force from the descending communication portion 34 toward the ascending communication portion 33 in the rotation axis direction of the transport screws 21 and 22 due to the vibration at the time of transportation of the image forming apparatus 1 and the developer is biased. There is a possibility that it will be. As a result, when the developing device 20 is initially installed after transportation, the developer distribution in the developing device 20 is such that the developer flows in both the supply chamber 31 and the recovery chamber 32 as shown in FIG. There is a possibility that it is biased toward the 33 side. In FIG. 5A, the broken lines in the supply chamber 31 and the recovery chamber 32 indicate the developer surface, and the arrows of the broken lines indicate the direction in which the developer circulates. The developer is biased in the axial direction.

  Further, without being limited to the present embodiment, the developer in the developing device 20 during transportation is biased vertically downward by gravity due to vertical vibration parallel to gravity, and each developer is transported by horizontal vibration perpendicular to the vertical direction. There may be a deviation in one of the rotation axis directions of the screws 21 and 22. The direction of rotation of each of the transfer screws 21 and 22 is determined depending on the center of gravity of the developing device 20 and the posture during transportation. For example, as shown in FIG. 5B, in both the supply chamber 31 and the recovery chamber 32, the developer may be biased toward the downward communication portion 34. Alternatively, as shown in FIGS. 6A and 6B, even in a developing device in which the supply chamber 31 and the recovery chamber 32 are installed in a horizontal direction (see FIG. 10B), In both the case 31 and the recovery chamber 32, the developer may be biased toward the upward communication portion 33 or the downward communication portion 34.

  In the present embodiment shown in FIG. 5A, the first transport screw 21 for supplying the developer to the developing sleeve 24 and the second transport screw 22 for collecting the developer from the developing sleeve 24 are provided as separate bodies. ing. In this case, when the transport screws 21 and 22 and the developing sleeve 24 are simultaneously driven, the developer in the supply chamber 31 provided with the first transport screw 21 flows into the collection chamber 32 via the developing sleeve 24. At this time, the recovery chamber 32 is in a state where the developer is already biased, and there is a portion where the developer completely fills the recovery chamber 32 in the rotation axis direction of the second transport screw 22. When the developer flows through the developing sleeve 24 in such a state, the load on the second conveying screw 22 temporarily increases, and when the screw lock or the developer conveying force on the surface of the developing sleeve 24 is weak, the developer is Can not be taken in normally, and there is a risk of inducing developer leakage.

  In this case, it is conceivable to execute the switching control of the forward / reverse rotation of the conveying member as described in Patent Document 1 described above. However, even if the switching control is executed, if the developer flows from the supply chamber 31, the amount of the developer in the collection chamber 32 increases, so that the loosening effect cannot be sufficiently exhibited, and the second transport screw The load on 22 cannot be reduced. Further, even if the switching control is performed, if a part of the collection chamber 32 is filled with the developer, the developer cannot be taken in normally, and the developer leaks from the opening 30 a of the developing container 30. It is difficult to avoid.

  Each of the cases shown in FIGS. 5B, 6A and 6B is the same as the case shown in FIG. 5A. That is, when the developer flows into the collection chamber 32 via the developing sleeve 24 in a portion where the developer is biased in the collection chamber 32 (that is, when the developer flows into the second conveyance screw 22 along a path indicated by a solid arrow). The load is temporarily increased in the area.

  Therefore, in the present embodiment, in order to avoid such a situation, when the developing device 20 is initially installed, the first transport screw 21 and the second transport screw 22 are driven at a predetermined speed for a predetermined time. A developer blend-in mode (mode) can be executed. Hereinafter, the developer familiarization mode will be described in detail. In this embodiment, when the image forming apparatus 1 is shipped from a factory in a state where the developing apparatus 20 is mounted on the image forming apparatus 1 and the image forming apparatus 1 is set in an initial installation mode at a customer or the like, the developing apparatus 20 is mounted. The case where the initial installation is performed at the same time is described.

  The developer familiarizing mode is such that, when the developing device 20 is initially installed (at the time of initial driving), the first motor M1 does not rotate the developing sleeve 24 by the second motor M2 for a predetermined time, and the first transport screw 21 and the This is a mode in which the second transfer screw 22 is rotated. The initial installation of the developing device 20 means that, for example, when the developing device 20 is shipped attached to the apparatus main body 10, the power of the image forming apparatus 1 is turned on for the first time at the loading destination and the developing device 20 is driven for the first time. Means when In the present embodiment, the control unit 11 can execute the developer familiarization mode at the time of initial installation of the developing device 20 after the developing device 20 is mounted on the apparatus main body 10 and shipped to a customer or the like. .

  In the present embodiment, the predetermined time for executing the developer familiarization mode is 5 seconds. Further, in the present embodiment, the rotation speed of the first motor M1 is set to 890 so that the rotation speed of the first conveyance screw 21 and the second conveyance screw 22 when the developer running-in mode is executed becomes the first process speed. [Rpm]. That is, the control unit 11 sets the rotation speed at which the first motor M1 rotates the first transport screw 21 and the second transport screw 22 to the maximum rotational speed in the speed change range when the developer blending mode is executed. As a result, downtime due to execution of the developer familiarization mode can be minimized, and a decrease in productivity can be suppressed.

  When the power of the image forming apparatus 1 is turned on, it is determined whether or not the timing of the initial installation in the developing device 20 is based on the state of the initial installation flag stored in the RAM 14 of the image forming apparatus 1. That is, at the time of shipment from the factory, the image forming apparatus 1 is shipped with the initial installation flag in the ON state in the RAM 14. Execute the medicine blending mode.

  Hereinafter, in the image forming apparatus 1 of the present embodiment, a procedure for executing the developer familiarization mode will be described with reference to a flowchart illustrated in FIG. The initial installation flag is written to the RAM 14 in the ON state at the time of shipment from the factory. When the power of the image forming apparatus 1 is turned on (step S1), the CPU 12 acquires an initial installation flag (step S2). The CPU 12 determines whether or not the initial installation flag is on (step S3).

  When determining that the initial installation flag is on (YES in step S3), the CPU 12 determines that the power is on for the first time after shipment from the factory. In this case, the CPU 12 controls the first motor M1 in accordance with the drive time and the motor drive speed, which are the parameters of the developer familiarization mode stored in the RAM 14, assuming that the developer in the developing device 20 may be biased. Then, a developer familiarization mode is executed (step S4). After executing the developer familiarization mode, the CPU 12 rewrites the initial installation flag of the RAM 14 to an off state (step S5), and ends the processing. As a result, when the power of the image forming apparatus 1 is turned on from the next time on, it is determined in step S3 that the initial installation flag is not in the on state (NO in step S3), and the process is terminated as it is, thereby avoiding downtime.

  After replacing the developing device 20 shipped in the mounted state with another developing device 20, the control unit 11 does not execute the developer familiarization mode when the developing device 20 is initially driven after the replacement. In this case, the first transport screw 21 and the second transport screw 22 are rotated by the first motor M1, and the developing sleeve 24 is rotated by the second motor M2. As a result, it is possible to avoid executing the developer familiarization mode more than necessary, to suppress the occurrence of downtime, and to improve the productivity.

  Here, FIG. 8A shows the driving speed of the developing sleeve 24 and the first transport screw 21 when there is no bias of the developer in the developing device 20 at the time of initial installation in the image forming apparatus in which the developer blending mode is not executed. Is shown. As shown in the drawing, after the power of the image forming apparatus is turned on, during normal image formation, after the driving of the developing device 20 is started, the developing sleeve 24 and the first transport screw 21 start driving at the same time. . The developing sleeve 24 rises to the target speed at 100 [mS], and the first transport screw 21 rises to the target speed at 50 [mS]. Note that the first transport screw 21 and the second transport screw 22 are connected by gears and therefore have different rotation speeds, but both exhibit the same rotation behavior.

  On the other hand, in FIG. 8B, in the image forming apparatus that does not execute the developer familiarization mode, the drive speed of the developing sleeve 24 and the first transport screw 21 when the developer is biased in the developing device 20 at the time of initial installation is shown. Show. When the bias of the developer exists at the time of the initial installation, the developing sleeve 24 rises at 100 [mS] as in the normal image formation, whereas the second transport screw 22 has a heavy load, and the first transport screw 21 Takes longer than usual to get up. However, since the developing sleeve 24 is driven in the same manner as during normal image formation, the developer flows from the supply chamber 31 into the collection chamber 32 via the developing sleeve 24 while the first transport screw 21 is being started. Resulting in. As a result, the load on the second transport screw 22 increases at an accelerated rate, and the first transport screw 21 that is interlocked via the gears also receives the load. In the example shown in FIG. 8B, the first transfer screw 21 is locked at 310 [mS] and the driving speed is 0.

  On the other hand, as shown in FIG. 9, in the image forming apparatus 1 of the present embodiment, the first transport screw 21 is driven only for 5 seconds at the time of the initial installation, and is started up to the target speed of 890 [rpm], and 5 seconds. Stop later. At this time, as shown in FIG. 9, it takes 380 [mS] for the first transport screw 21 to rise to the target speed, which takes more time than during normal image formation. However, since the developing sleeve 24 is stopped, there is no inflow of the developer through the developing sleeve 24, so that the screw is not locked, and the operation which is the same as the normal operation even when the image is formed after the execution of the developer familiarization mode is performed. Can be realized.

  As described above, according to the image forming apparatus 1 of the present embodiment, the control unit 11 can execute the developer familiarization mode when the developing device 20 is initially driven. That is, when the power of the image forming apparatus 1 is turned on, the control unit 11 executes the developer familiarization mode, and does not rotate the developing sleeve 24 by the second motor M2, but the first motor M1 for a predetermined time. The transfer screw 21 and the second transfer screw 22 can be rotated. Accordingly, even when the developer in the developing device 20 is biased, the locking of the first transport screw 21 and the second transport screw 22 and the accompanying leakage of the developer can be suppressed.

  Further, according to the image forming apparatus 1 of the present embodiment, the control unit 11 performs the initial installation of the developing device 20 after the developing device 20 is shipped to a customer or the like with the developing device 20 mounted on the apparatus main body 10. The developer familiarization mode can be executed. Accordingly, even when the developer is biased due to the transportation after the shipment of the developing device 20, the locking of the first transport screw 21 and the second transport screw 22 and the leakage of the developer accompanying the lock can be suppressed.

  Further, according to the image forming apparatus 1 of the present embodiment, the control unit 11 replaces the developing device 20 shipped in the mounted state with another developing device 20, and then performs the initial driving of the replaced developing device 20. Do not execute the developer familiarization mode. As a result, it is possible to avoid executing the developer familiarization mode more than necessary, to suppress the occurrence of downtime, and to improve the productivity.

  In the image forming apparatus 1 of the above-described embodiment, the case where the supply chamber 31 is disposed directly above the collection chamber 32 has been described. However, the present invention is not limited to this. What is necessary is just to be able to divide into two accommodation rooms. However, in this case as well, the first transport screw 21 is arranged so that the uppermost portion is at the same height position or higher than the uppermost portion of the second transport screw 22 when the developing device 20 is used. In this case, for example, as shown in FIG. 10A, the supply chamber 31 and the recovery chamber 32 may be arranged so as to be shifted in the horizontal direction and the vertical direction orthogonal to the rotation axis direction of the developing sleeve 24. Alternatively, as shown in FIG. 10B, the supply chamber 31 and the recovery chamber 32 may be arranged in a horizontal direction orthogonal to the rotation axis direction of the developing sleeve 24.

  Further, in the image forming apparatus 1 of the above-described embodiment, after the developing device 20 shipped in the mounted state is replaced with another developing device 20, when the replaced developing device 20 is initially driven, the developer familiarization mode is executed. Although the case where no operation is performed has been described, the present invention is not limited to this. For example, even in such a case, the developer familiarization mode may be executed. In this case, even if the developer is biased in the developing device 20 after the replacement, it is possible to prevent the transport screws 21 and 22 from being locked.

  Further, in the image forming apparatus 1 of the above-described embodiment, the case where the developing device 20 is shipped with the developing device 20 attached to the apparatus main body 10 has been described, but the present invention is not limited to this. For example, even in the case of a single developing device 20 that is not mounted on the device main body 10, there is a case where the bias of the developer occurs due to transportation at the time of shipping. In order to prevent the lock of the transport screws 21 and 22 due to the bias of the developer in the single developing device 20, for example, the image forming device 1 is interlocked with the initial setting operation after the replacement of the developing device 20. In this case, the developer familiarization mode may be executed.

<Second embodiment>
Next, a second embodiment of the present invention will be described in detail with reference to FIGS. The second embodiment differs from the first embodiment in that the rotation speed of each of the transfer screws 21 and 22 during execution of the developer familiarization mode is different. However, the other configuration is the same as that of the first embodiment, so that the same reference numerals are used and the detailed description is omitted.

  In the first embodiment, when the developing device 20 is initially installed, only the transport screws 21 and 22 are driven at the first process speed for 5 seconds to prevent screw lock and leakage of the developer even when the developer is biased. It is to suppress. The first process speed corresponds to the highest driving speed of each of the transport screws 21 and 22, thereby minimizing downtime. On the other hand, in the case of driving at the first process speed, when the developing device 20 is provided with a discharge port for discharging the developer, the discharge amount may be larger than expected. Therefore, in the present embodiment, the driving speed of each of the transport screws 21 and 22 in the developer blend-in mode is driven at a lower driving speed than the maximum driving speed of each of the transport screws 21 and 22 during image formation. The bias of the developer is eliminated while suppressing the excessive discharge of the developer.

  Hereinafter, an operation (ACR) of exchanging the carrier with the image forming operation by discharging the developer from the discharge port 36 provided in the developing device 20 will be described. The developing device 20 frictionally charges the toner and the carrier by rotating the transport screws 21 and 22 and transporting the developer while stirring the developer in a circulation path in the developing container 30. As for the developer including the toner and the carrier, the carrier not consumed by the image formation continues to be circulated while receiving friction in the developing container 30, so that the charging performance of the carrier gradually decreases. For this reason, the two-component developer for replenishment in which a small amount of carrier is added to the replenishment toner is stored in the hopper 41a. Further, by discharging a surplus of the developer by overflowing a part of the conveyed developer through a discharge port 36 provided in the circulation path, the carrier in the developer is exchanged, and the average charging performance is improved. A configuration to secure it has been proposed.

  In the present embodiment, the mixing ratio between the toner and the carrier of the two-component developer for replenishment is 9: 1 by weight. As shown in FIG. 11, a discharge port 36 is provided in a wall of the supply chamber 31 downstream of the developing sleeve installation area on the downstream side in the developer conveyance direction D <b> 1, and the developer is discharged from the discharge port 36. . When the amount of the developer in the developing device 20 increases in the developer supply step, the developer is discharged so as to overflow from the discharge port 36 in accordance with the increased amount. The discharge port 36 is formed at a position on the upstream side in the transport direction D1 from the position of the supply port 29. This is to prevent the replenished new developer from being discharged immediately.

  In the present embodiment, the conveying blade 21b in the portion facing the discharge port 36 is notched, so that the developer conveying force in the portion facing the discharge port 36 is reduced as compared with the area adjacent to the discharge blade 36, so that the development is performed. Allow the agent to stay and drain. In the transport direction D1, the length of the cutout portion of the transport blade 21b is 14 mm, and the length of the discharge port 36 is 10 mm. The center position of the cutout portion of the transport blade 21b in the transport direction D1 and the transport of the discharge port 36 are performed. It is installed so that the center position in the direction D1 matches. The lower edge of the discharge port 36 is located at a position of +3 mm with the upper part in the vertical direction from the center of the shaft portion 21a (see FIG. 3) of the first transport screw 21 being positive. Each of the transfer screws 21 and 22 is formed of a single spiral blade having an outer diameter of 18 mm, a shaft diameter of 6 mm, and a pitch of 40 mm. The clearance between the developing container 30 and the screw outer diameter is 1 mm in each direction.

  As shown in FIG. 12A, the amount of the developer discharged from the discharge port 36 is measured from the center of the shaft 21 a of the first transport screw 21 at a portion (opposed portion) facing the discharge port 36 in the developing container 30. Is determined by the height of the developer surface. As shown in FIG. 12B, the height of the developer surface from the center of the shaft 21 a of the first transport screw 21 at the portion facing the discharge port 36 in the developing container 30 is opposite to the position of the discharge port 36. It is determined by the flow rate of the developer flowing into the section. In a developing device having a configuration in which the first transport screw 21 and the second transport screw 22 are different from each other as in the present embodiment, the first transport screw 21 supplies the developer to the developing sleeve 24. The number decreases on the downstream side of D1. Since the second transport screw 22 collects the developer from the developing sleeve 24, the flow rate of the developer increases toward the downstream side. Here, when only the transport screws 21 and 22 are driven for a certain period of time in the developer familiarization mode, the developer does not flow from the first transport screw 21 to the second transport screw 22 via the developing sleeve 24. . For this reason, the flow rate of the developer in the opposite portion of the discharge port 36 temporarily increases, and there is a possibility that the developer may leak out of the discharge port 36 depending on conditions.

  In order to prevent this, in the present embodiment, the driving speed of each of the transport screws 21 and 22 is made slower than in the first embodiment, and even if only each of the transport screws 21 and 22 is driven by executing the developer adaptation mode, the discharge is performed. The flow rate of the developer flowing into the opposite portion of the outlet 36 is reduced. Therefore, in the present embodiment, only the transport screws 21 and 22 are driven at the second process speed for 5 seconds during execution of the developer familiarization mode. Here, in order to set the process speed to the second process speed, the rotation speed of the first motor M1 is set to 650 [rpm]. That is, the control unit 11 sets the rotation speed at which each of the transport screws 21 and 22 is rotated by the first motor M1 to a rotation speed lower than the maximum rotation speed in the speed change range when the developer running-in mode is executed. In particular, in the present embodiment, the control unit 11 sets the speed to the minimum rotation speed.

Here, the first embodiment and the second embodiment compare the amount of developer discharged from the discharge port 36 when the developer familiarization mode is executed when the developing device 20 is initially installed.
Table 1 shows the results.

  As shown in Table 1, in the case of the present embodiment, the developer surface height of the developer is suppressed as compared with that in the first embodiment, and the amount of the developer discharged from the discharge port 36 can be suppressed. In the case where the drive speed of each of the transport screws 21 and 22 is reduced as a method of reducing the developer flow rate as in the present embodiment, a decrease in the developer surface due to a mere decrease in the flow rate flowing into the discharge port 36 is avoided. effective. In this case, in addition to this effect, the degree of stagnation of the developer in the region may be reduced, and the elevation of the developer surface can be further suppressed.

  As described above, also by the image forming apparatus 1 of the present embodiment, the control unit 11 can execute the developer familiarization mode when the developing device 20 is initially driven. Accordingly, even when the developer in the developing device 20 is biased, the locking of the first transport screw 21 and the second transport screw 22 and the accompanying leakage of the developer can be suppressed.

  Further, according to the image forming apparatus 1 of the present embodiment, the control unit 11 sets the rotation speed at which the first motor M1 rotates each of the transport screws 21 and 22 to the maximum rotation speed in the speed change range during the execution of the developer adaptation mode. Set a lower rotation speed. For this reason, even if the developing container 30 has the discharge port 36 for discharging the carrier, the amount of the developer discharged from the discharge port 36 during the execution of the developer familiarization mode can be suppressed.

<Third embodiment>
Next, a third embodiment of the present invention will be described in detail with reference to FIGS. The present embodiment differs from the first embodiment in that the developer familiarization mode is executed based on the detection result of the toner density sensor 26. However, the other configuration is the same as that of the first embodiment, so that the same reference numerals are used and the detailed description is omitted.

  In the present embodiment, as described in the first embodiment, there is a correlation between the output value of the toner density sensor 26 as an inductance sensor and the developer toner density as shown in FIG. This correlation is stored in the ROM 13 as the above-mentioned toner density conversion table, and the actual toner density can be calculated using the signal value of the magnetic permeability which is the output value of the toner density sensor 26. In the present embodiment, the toner density sensor 26 is operated with a drive power supply of 6.8 [V] and a control voltage of 6 [V], and is output at 0 [V] to 5 [V]. The control voltage may be adjusted by control so that the output voltage falls within a predetermined range.

  Due to the characteristic that the toner density is calculated based on the carrier density near the sensor detection surface, if the carrier density near the sensor detection surface changes due to factors other than the toner density, even if the toner density does not change, the apparent toner Detected as a change in density. However, if the toner density is known in advance, it is possible to predict a change in carrier density near the sensor surface, that is, a bias of the developer, from the difference between the output result (detection value) of the toner density sensor 26 and the actual toner density. it can.

Here, tapping is performed by tapping the developing device 20 against the lower floor surface or the like in a direction in which the developing device 20 is set up with the downward communication portion 34 or the upward communication portion 33 down, and is mounted on the image forming apparatus 1 after a predetermined number of tappings. And the toner density sensor 26 detects the image. Then, the direction and the number of tappings, the presence or absence of a screw lock corresponding thereto, and the output value of the toner density sensor 26 were compared. Table 2 shows the results.

  In Table 2, the bias level 0 is a state after the normal image forming operation, and there is no developer bias in the developing device 20. The output value of the toner density sensor 26 at the bias level 0 was 1.9 [V]. At the bias level 0, no screw lock of the transport screws 21 and 22 occurred due to the execution of the normal image forming operation.

  At the bias level 1, the first conveying screw 21 was tapped 80 times in the vertical direction with the descending communication part 34 facing downward. At the bias level 1, the developer is biased around the descending communication part 34 and there is almost no developer near the ascending communication part 33 and the toner density sensor 26. At 3 [V], it is extremely smaller than the bias level 0. At the bias level 1, screw lock of the transport screws 21 and 22 occurred due to execution of the normal image forming operation.

  At the deviation levels 2 to 5, the first conveying screw 21 was tapped 20 times, 40 times, 60 times, and 80 times in the vertical direction with the ascending communication portion 33 downward. At the bias level 2 and the bias level 3, the developer is biased in the vicinity of the ascending communication portion 33 due to tapping, but both are light and screw lock does not occur even in a normal image forming operation. At the bias level 4 and the bias level 5, the output of the toner density sensor 26 is large, and a screw lock occurs in a normal image forming operation.

  Therefore, in the present embodiment, when the output voltage of the toner density sensor 26 becomes 1.0 [V] or less or 4.0 [V] or more in a state where each of the transport screws 21 and 22 is stationary. It is determined that the bias of the developer, which is likely to cause screw lock, has occurred. When the bias of the developer occurs, the developer familiarization mode is performed. It should be noted that the magnitude of the voltage in this determination is merely an example, and is not limited to the numerical values shown here. Further, the threshold value of the output value of the toner density sensor 26 for executing the developer familiarization mode does not need to be a predetermined fixed value as described in the present embodiment, and may be a value adjusted in the factory or , A variable determined from other values.

  Next, a procedure for executing the developer familiarization mode in the image forming apparatus 1 of the present embodiment will be described with reference to a flowchart shown in FIG. It should be noted that the flowchart shown in FIG. 14 partially has the same processing as the flowchart shown in FIG. 7 in the first embodiment, and these similar processing has the same step numbers and detailed description is omitted. I do.

  When determining that the initial installation flag is on (YES in step S3), the CPU 12 determines that the power is on for the first time after shipment from the factory. Then, the CPU 12 acquires the output value V of the toner density sensor 26 (Step S10). The CPU 12 determines whether or not the obtained output value V satisfies 1.0 (V) <V <4.0 (V) (Step S11). If the CPU 12 determines that the obtained output value V does not satisfy 1.0 (V) <V <4.0 (V) (NO in step S11), the developer in the developing device 20 is biased. Judge that there is a possibility. Therefore, the CPU 12 controls the first motor M1 to execute the developer familiarization mode according to the drive time and the motor drive speed, which are the parameters of the developer familiarization mode stored in the RAM 14 (step S4). On the other hand, when the CPU 12 determines that the obtained output value V satisfies 1.0 (V) <V <4.0 (V) (YES in step S11), the CPU 12 terminates the processing as it is to reduce the downtime. Can be avoided.

  As described above, also by the image forming apparatus 1 of the present embodiment, the control unit 11 can execute the developer familiarization mode when the developing device 20 is initially driven. Accordingly, even when the developer in the developing device 20 is biased, the locking of the first transport screw 21 and the second transport screw 22 and the accompanying leakage of the developer can be suppressed.

  Further, according to the image forming apparatus 1 of the present embodiment, the control unit 11 switches whether or not to execute the developer familiarization mode based on the output value of the toner density sensor 26 when the developing device 20 is initially installed. Therefore, unnecessary downtime and discharge of the developer can be reduced.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Device main body, 11 ... Control part (control means), 20 ... Developing device, 21 ... 1st conveyance screw (1st conveyance means), 22 ... 2nd conveyance screw (2nd conveyance means) , 24: developing sleeve (developer carrier), 26: toner concentration sensor, 30: developing container, 31: supply chamber (first chamber), 32: collection chamber (second chamber), 51, 51c, 51k, 51m , 51y: photosensitive drum (image carrier), M1: first motor (first driving means), M2: second motor (second driving means).

Claims (8)

An image carrier;
A developer container containing a developer having a toner and a carrier and having a first chamber and a second chamber forming a circulation path of the developer between the first chamber; and a developer contained in the developer container. And a developer carrier that rotates and carries the electrostatic latent image formed on the image carrier with toner. The developer carrier is disposed in the first chamber, and the developer in the first chamber is agitated and rotated by rotation. A first transport unit that transports and supplies the developer to the developer carrier, and agitates and transports the developer in the second chamber that is disposed in the second chamber and that is collected from the developer carrier after development by rotation. A developing device having a second conveying unit;
A first driving unit that can rotationally drive the first conveying unit and the second conveying unit;
A second driving unit that can rotationally drive the developer carrier;
Control means for controlling the first drive means and the second drive means,
The first transporting means is arranged such that the uppermost part is at the same height position or higher than the uppermost part of the second transporting means when the developing device is used,
The control unit is configured to rotate the developer carrying member by the second driving unit during the initial driving of the developing device without rotating the developer carrier by the first driving unit for a predetermined time. A mode for rotating the transport means can be executed,
An image forming apparatus comprising: An apparatus main body to which the developing device can be attached and detached,
The control unit is capable of executing the mode at an initial drive of the developing device after the developing device is mounted in the device main body and shipped.
The image forming apparatus according to claim 1, wherein: After replacing the developing device shipped in the mounted state with another developing device, the control unit does not execute the mode during the initial driving of the other developing device, and the first driving unit executes the second driving device without executing the mode. Rotating the developer carrying member by the second driving unit while rotating the first conveying unit and the second conveying unit;
The image forming apparatus according to claim 2, wherein: The control unit is capable of changing the rotation speed of rotating the first transport unit and the second transport unit by the first driving unit in a predetermined speed change range during image formation, (1) setting a rotation speed at which the first conveyance unit and the second conveyance unit are rotated by the first driving unit to a maximum rotation speed in the shift range;
The image forming apparatus according to claim 1, wherein: The control unit is capable of changing the rotation speed of rotating the first transport unit and the second transport unit by the first driving unit in a predetermined speed change range during image formation, (1) setting a rotation speed at which the first conveyance unit and the second conveyance unit are rotated by the one driving unit to a rotation speed lower than a maximum rotation speed in the shift range;
The image forming apparatus according to claim 1, wherein: The control unit sets a rotation speed at which the first driving unit rotates the first conveyance unit and the second conveyance unit to a minimum rotation speed in the shift range when the mode is executed.
The image forming apparatus according to claim 5, wherein: The developing device has a toner concentration sensor that detects a toner concentration of a developer inside the developing container,
The control unit switches whether or not to execute the mode based on a detection value of the toner density sensor when the developing device is initially driven,
The image forming apparatus according to claim 1, wherein: The first chamber is disposed so as to at least partially overlap the second chamber when the developing device is viewed from above and below during use.
The image forming apparatus according to claim 1, wherein:

Images