JP4751680B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and the like, and a two-component developing type developing apparatus and a process cartridge employed therein.

  2. Description of the Related Art Conventionally, developing devices using a two-component developer (hereinafter referred to as a developer) composed of toner and a magnetic carrier have been widely used. FIG. 2 shows a schematic configuration diagram of an example of the developing device. The developing device shown in FIG. 2 includes a rotatable sleeve 2 containing a magnetic field generating means 2 a having a plurality of magnetic poles fixedly arranged, developer agitating and conveying members 5 and 6 for agitating and conveying the developer, and a sleeve 2. A doctor 4 is provided as a restricting member for restricting the amount of developer carried. In this developing device, the developer agitated and conveyed by the developer agitating / conveying members 5 and 6 is pumped and carried on the surface by the magnetic force of the magnetic field generating means 2 a included in the sleeve 2, and a developing region facing the photoreceptor 40. And the toner is supplied to the latent image on the photoreceptor 40 for development. The developer that has consumed the toner after development is released from the surface of the sleeve 2 into the developing device, stirred with the developer in the developing device by the developer agitating and conveying members 5 and 6, and pumped up again on the surface of the sleeve 2. repeat. The magnetic field generating means 2a includes a developing pole 2b (S pole) facing the closest position between the sleeve 2 and the photosensitive member 40 so as to repeat such a cycle. In addition, a magnetic pole 2c (N pole), a magnetic pole 2d (S pole), a magnetic pole 2e (S pole), and a magnetic pole 2f (N pole) are provided in this order in the developer transport direction. Among these, the adjacent magnetic pole 2d and magnetic pole 2e have the same magnetic characteristics, and when the magnetic force is weakened by the repulsive magnetic field formed by them, the developer is released from the surface of the sleeve 2 into the developing device. The magnetic pole 2e is disposed in the vicinity of the developer agitating / conveying member 5, and has a function as a pumping electrode for pumping and carrying the developer. Further, the magnetic pole 2e and the adjacent magnetic pole 2f are configured to have different polar magnetic characteristics and have a function of carrying and transporting the pumped developer. FIG. 3 shows the lines of magnetic force formed by the pumping magnetic pole 2e and the adjacent magnetic pole 2f of the magnetic field generating means 2a. FIG. 4 shows the state of the developer pumped up by the magnetic lines of force. As shown in FIGS. 3 and 4, in this developing device, the developer at the top of the developer conveyed to the developer agitating / conveying member 5 is pumped to the surface of the sleeve 2 by the magnetic force of the pumping magnetic pole 2e, and the pumped development is performed. The agent is pumped and conveyed by the magnetic force formed by the magnetic pole 2e and the adjacent magnetic pole 2f. Further, the developer carried on the sleeve 2 is regulated so that the thickness of the developer becomes an appropriate amount by the doctor 4 disposed opposite to the magnetic pole 2f while being conveyed.

  Further, as the developer agitating and conveying member 5 used in the developing device, a screw-like member that is supported at both longitudinal ends and is rotatable is widely used. Further, the developer agitating / conveying member 5 has been made of metal to resin from the direction of weight reduction. Resin-made ones are more likely to wobble at the center in the longitudinal direction due to the weight of the developer compared to metal ones, and there may be some differences in the bulk of the developer depending on the location. Furthermore, the height of the developer may partially vary depending on the pitch of the screw blades.

  When the bulk of the developer stirred and conveyed by the developer agitating / conveying member is sufficiently higher than the uppermost part of the rotation radius of the developer agitating / conveying member, the uppermost part of the developer is the shake or blade of the developer agitating / conveying member. Therefore, there is almost no partial difference in bulkiness. Further, since the uppermost portion of the developer is close to the surface of the sleeve 2, a sufficient amount of developer is pumped up.

  However, when the toner concentration becomes low or the charge amount of the developer decreases, and the bulk of the developer becomes low, the uppermost part of the developer is shaken by the developer agitating / conveying member or screw blades. It becomes easy to be influenced by the pitch, and a partial difference in the bulk of the developer as described above occurs. Further, since the uppermost part of the developer is far from the surface of the sleeve 2 and the magnetic force of the pumping magnetic pole 2e is weakened, the pumping amount of the developer is reduced, and further, the difference in the distance from the sleeve 2 to the uppermost part of the developer, that is, The difference in the bulk of the developer greatly affects the pumping amount. As the overall volume of the developer becomes lower in this way, a difference in the partial volume of the developer due to the developer agitating / conveying member occurs, and this difference appears as a difference in the pumping amount as it is on the image. A trace of the stirring and conveying member such as pitch unevenness appears.

  In Patent Document 1, the second regulating member that presses the pumped developer against the sleeve upstream of the regulating member that regulates the height of the developer with respect to the rotation direction of the sleeve and downstream of the developer stirring and conveying member. There has been proposed an apparatus for providing the above. FIG. 8 shows a schematic configuration diagram of the developing device of Patent Document 1. In FIG. In this developing device, the developer layer carried on the sleeve is pressed against the sleeve by the second regulating member and leveled, so that there is no trace of pitch unevenness formed on the sleeve, and the developer layer becomes uniform. By further restricting it to the required height with a restricting member, it is transported to the development area, thereby eliminating pitch unevenness.

JP 2002-258605 A

  In the developing device of Patent Document 1, when a large amount of developer is pumped up on the sleeve upstream from the second regulating member, a uniform developer layer can be conveyed to the developing region. However, if the toner density is further reduced, or the developer charge amount is reduced in a high-temperature and high-humidity environment, and the bulk of the developer is greatly reduced, the second upstream upstream of the second regulating member. In some cases, the regulating member may not be able to pump up enough developer to level out the developer. For this reason, the second restricting member does not act, and the unevenness of the developer layer cannot be eliminated and the pitch unevenness may occur.

  The present invention has been made in view of the above background, and an object of the present invention is a developing device capable of developing without unevenness due to the shake and pitch of the developer stirring and conveying member in the two-component developing device, A process cartridge and an image forming apparatus are provided.

In order to achieve the above object, the invention of claim 1 is fixedly disposed with a casing for containing a two-component developer composed of toner and a magnetic carrier, a developer agitating and conveying member for agitating and conveying the two-component developer. A latent image carrier comprising a rotatable non-magnetic sleeve containing magnetic field generating means having a plurality of magnetic poles, and pumping and carrying the two-component developer agitated and conveyed by the developer agitating and conveying member onto the surface of the sleeve And a developer carrying member conveyed to a region opposite to the developer, and a downstream of the developer pumping pole and adjacent to the developer pumping pole among the plurality of magnetic poles of the magnetic field generating means in the sleeve rotation direction. The region upstream of the magnetic pole is extended in the radial direction of the sleeve to the outside of the sleeve surface, and above the two-component developer stirred by the developer stirring and conveying member. Where than the lowest position remote from the sleeve surface, pumping surface facing the said sleeve is a non-magnetized surface an auxiliary magnetic field generating means, an upstream side with respect to the rotational direction of the sleeve of the pumping auxiliary magnetic field generating means The magnetic field generating means has a magnetic pole having the same polarity as the developer pumping pole .
According to a second aspect of the present invention , in the developing device of the first aspect , the magnetic flux density of the pumping auxiliary magnetic field generating means is equal to or higher than the magnetic flux density of the developer pumping pole of the magnetic field generating means. It is.
According to a third aspect of the present invention, in the developing device according to the first or second aspect , the pumping auxiliary magnetic field generating means is disposed on a casing outer wall of the developing device.
According to a fourth aspect of the present invention, in the process cartridge in which the image carrier and the developing device are integrally configured and detachable from the main body of the image forming apparatus, the developing device of the first, second or third aspect is used as the developing device. It is characterized by adopting.
According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier that carries an electrostatic latent image; and a developing device that converts the electrostatic latent image into a toner image. The present invention is characterized in that two or three developing devices are employed.
According to a sixth aspect of the present invention, there is provided a casing containing a two-component developer composed of toner and a magnetic carrier, a developer agitating / conveying member for agitating and conveying the two-component developer, and a magnetic field having a plurality of magnetic poles fixedly arranged. Consisting of a rotatable non-magnetic sleeve containing the generating means, the two-component developer agitated and conveyed by the developer agitating and conveying member is pumped up and carried on the sleeve surface, and conveyed to a region facing the latent image carrier In the developing device including the developer carrier, the region between the developer pumping pole and the magnetic pole adjacent to the downstream of the pumping pole in the sleeve rotation direction is outside the sleeve surface in the radial direction of the sleeve. The sleeve is opposed to the sleeve at a position farther from the sleeve surface than the lowest position on the upper surface of the two-component developer stirred by the developer stirring and conveying member. Is provided with a pumping auxiliary magnetic field generating means having a non-magnetized surface, and the upstream side of the pumping auxiliary magnetic field generating means with respect to the rotation direction of the sleeve has a magnetic pole of the same polarity as the developer pumping pole of the magnetic field generating means. It is characterized by.

  In these inventions, the development agitated from the sleeve surface to the developer agitating / conveying member in a range in which the region between the developer pumping pole and the magnetic pole adjacent downstream is extended outward from the sleeve surface in the radial direction of the sleeve. A pumping auxiliary magnetic field generating means having a non-magnetized surface on the surface facing the sleeve is provided at a position farther from the lowermost position of the top surface of the agent. FIG. 5 shows lines of magnetic force formed by the developer pumping pole 2e, the magnetic pole 2f adjacent downstream and the pumping auxiliary magnetic field generating means 7 when such a pumping auxiliary magnetic field generating means is provided. FIG. 6 shows the state of the developer pumped up by these lines of magnetic force. The magnetic force of the pumping auxiliary magnetic field generating means 7 acts on the developer in the vicinity of the area where the pumping auxiliary magnetic field generating means 7 is arranged, and the developer in the vicinity of this area is raised and raised. That is, the developer is opposed to the region between the developer pumping pole 2e and the adjacent magnetic pole 2f, and the developer stirred by the developer stirring / conveying member is lifted from the bottom toward the sleeve surface, and the volume is simulated. To be close to the sleeve 2. When the bulk of the entire developer is originally high, the sleeve 2 pumps up the developer directly from the top of the developer conveyed to the developer agitating / conveying member 5, and further, the developer spiked by the pumping auxiliary magnetic field generating means 7 The developer is pumped up from the top. When the bulk of the developer becomes low, the developer is pumped up from the uppermost part of the developer that is raised by the pumping auxiliary magnetic field generating means 7 and close to the sleeve 2. The uppermost part of the developer that is raised by the pumping auxiliary magnetic field generating means 7 is not directly affected by the shake of the developer agitating / conveying member or the blade pitch of the screw, so there is little unevenness, and accordingly the pumping amount is uneven. Less. Further, since the developer is pumped up from the developer that has been lifted up and close to the sleeve 2, the pumping amount is stabilized and pitch unevenness is eliminated. Therefore, even if the bulkiness of the entire developer fluctuates, the pumping amount without unevenness due to the shake and pitch of the developer agitating / conveying member can be obtained, and accordingly, development without unevenness can be performed.

  In the present invention, the pumping auxiliary magnetic field generating means 7 for lifting the developer from the bottom and making it stand up away from the lowermost position of the upper surface of the developer stirred by the developer stirring and conveying member from the sleeve surface. Is provided. This is due to the following reason. When the developer agitating / conveying member pushes up the developer against gravity and supplies it to the sleeve, if the developer agitating / conveying member is at a low position, the distance to the sleeve becomes long and a sufficient pumping amount cannot be obtained. For this reason, a technique for providing a developer conveying magnet roller between the developer agitating and conveying member and the sleeve and conveying the developer from the developer agitating and conveying member to the sleeve is known (for example, JP-A-2-171787). No. 5 and Japanese Patent Publication No. 5-13316). This requires a driving device for rotating the developer conveying magnet roller, a magnet roller that requires a large number of magnetic poles for the permanent magnet, and the apparatus becomes complicated and large. In addition, it is provided between the developer agitating and conveying member and the sleeve, and includes a magnet that captures the developer pumped up from the developer agitating and conveying member by magnetic force. The developer captured by the magnet by the pumping magnetic pole in the sleeve is magnetically sleeved. A technique for attracting the surface is also known (see, for example, Japanese Patent Laid-Open No. 10-48951). In both cases, a magnet is provided at a position close to the sleeve between the developer agitating and conveying member and the sleeve, which may adversely affect the movement of the developer conveyed to the sleeve. It is difficult to select an appropriate position and magnetic force. On the other hand, in the present invention, unlike these, the pumping auxiliary magnetic field generating means 7 is provided at a position away from the lowermost position on the upper surface of the developer stirred by the developer stirring and conveying member from the sleeve surface. Since the pumping auxiliary magnetic field generating means 7 is provided at a position away from the sleeve surface in this way, the pumping auxiliary magnetic field generating means 7 can exhibit the above-described action without adversely affecting the movement of the developer conveyed to the sleeve. .

  According to the first to sixth aspects of the invention, in the two-component developing device, there is an excellent effect that the development without unevenness due to the shake and pitch of the developer stirring and conveying member can be performed.

  Hereinafter, an embodiment in which an image forming apparatus to which the present invention is applied is applied to an electrophotographic color printer (hereinafter referred to as a printer) will be described. FIG. 1 is a schematic diagram of the overall configuration of a printer according to an embodiment of the present invention. In this printer, four toner image forming units 12Y, C, M, and K of yellow, cyan, magenta, and black are arranged side by side to constitute a tandem image forming unit 10. In the tandem image forming unit 10, individual toner image forming units 12Y, C, M, and K are arranged in order from the left in the drawing. Here, the suffixes Y, C, M, and K of the respective symbols indicate members for yellow, cyan, magenta, and black, respectively. The individual toner image forming units 12Y, 12C, 12M, and 12K of the tandem image forming unit 10 include drum-shaped photoconductors 40Y, 40C, 40M, and 40K as latent image carriers.

  The toner image forming units 12Y, 12C, 12M, and 12K for the respective colors may be formed integrally and may be process cartridges that are detachable from the main body. These process cartridges can be pulled out from the printer body along guide rails (not shown) fixed to the printer body. The toner image forming means 12Y, C, M, and K can be loaded at predetermined positions by pushing the process cartridge into the printer main body.

  Here, the toner image forming units 12Y, 12C, 12M, and 12K have the same configuration and operation. Accordingly, the subscripts Y, C, M, and K of the respective symbols are omitted below, and the toner image forming unit 12 will be described. FIG. 2 is a schematic configuration diagram of the toner image forming unit 12. A charging device 17, a developing device 1, and a cleaning device 19 are sequentially arranged around the photosensitive member 40 that rotates clockwise in the drawing.

  An exposure device 4 as a latent image forming unit is provided below the tandem image forming unit 10. The exposure device 4 is configured to irradiate the surface of each photoconductor 40 with laser light based on image data.

  Immediately above the tandem image forming unit 10 are an intermediate transfer belt 11 and primary transfer rollers 13Y, 13C, 13M, and 13K for transferring the toner image formed on each photoconductor 40 onto the intermediate transfer belt 11. I have. Further, a plurality of rollers for supporting the intermediate transfer belt 11 are provided, and the intermediate transfer belt 11 can be rotated counterclockwise in the drawing. Further, a secondary transfer roller 15 as a secondary transfer device is provided on the opposite side of the support roller downstream of the primary transfer rollers 13Y, 13C, 13M, and 13K with respect to the driving direction of the intermediate transfer belt 11. Further, a belt cleaning device that removes residual toner remaining on the intermediate transfer belt 11 after image transfer is provided downstream of the secondary transfer position in the driving direction of the intermediate transfer belt 11.

  A fixing device 16 for fixing the toner image on the recording medium is provided above the secondary transfer device. The fixing device 16 is configured by pressing a pressure roller against a fixing roller.

  A paper feed unit 14 is provided at the bottom of the printer. The paper feed unit conveys the recording medium from the paper feed cassette to the secondary transfer area.

  Next, the operation of the printer will be described. Each photoconductor 40 is rotated by the individual toner image forming units 12M, Y, C, and K, and the surface of the photoconductor 40 is uniformly charged by the charging device 18 as the photoconductor 40 rotates. Next, the image data is irradiated with laser writing light from the exposure device 18 to form an electrostatic latent image on each photoconductor 40. Thereafter, toner is attached by each developing device 1 and the electrostatic latent image is visualized to form single color images of yellow, cyan, magenta, and black on each photoconductor 40, respectively. Further, the intermediate transfer belt 11 is rotated and conveyed by a drive motor (not shown), and the visible image is sequentially transferred onto the intermediate transfer belt 11 by the primary transfer rollers 13M, Y, C, and K. As a result, a composite color image superimposed on the intermediate transfer belt 11 is formed. On the other hand, the toner remaining on the surface of each photoconductor 40 after the image is transferred is removed by the cleaning device 19 to prepare for the next image formation.

  Further, the leading edge of the recording body is fed out from the paper feed cassette in the paper feed unit 14 at the timing of the image formation, and the secondary transfer roller 15 and the intermediate transfer belt 11 are connected with the timing of the image forming operation. It is conveyed during Here, the intermediate transfer belt 11 and the secondary transfer roller 15 form a so-called secondary transfer nip across the recording medium, and secondarily transfers the superimposed toner image on the intermediate transfer belt 11 onto the recording medium.

  The recording medium after the secondary transfer is sent to the fixing unit 16 where heat and pressure are applied by the fixing device to fix the transferred image and discharged outside the apparatus. On the other hand, the residual toner remaining on the intermediate transfer belt 11 is removed from the intermediate transfer belt 11 after image transfer by a belt cleaning device (not shown) to prepare for the next image formation.

  Next, the developing device 1 that is a characteristic part of the present embodiment will be described in detail. FIG. 7 is a schematic configuration diagram of the developing device 1 employed in the printer of the present embodiment. The developing device shown in FIG. 7 includes a rotatable nonmagnetic sleeve 2 containing magnetic field generating means 2a having a plurality of magnetic poles fixedly arranged, and screws 5 and 6 as developer agitating and conveying members for agitating and conveying the developer. And a doctor 4 as a regulating member for regulating the amount of developer carried on the sleeve 2 and a T sensor (not shown) for measuring the toner concentration in the developing device 1 and supplying the toner from the toner hopper. I have.

  The magnetic field generating means 2a is a magnet roller and has a plurality of magnetic poles. This magnet roller is formed by embedding a plurality of magnet blocks in a plastic roller. Further, a so-called plastic magnet in which magnetic powder is dispersed and kneaded in plastic resin powder (polymer compound) or rubber magnet is extruded or injection molded while applying a magnetic field, and then a magnet block is embedded in the development pole portion. You can also. As the magnetic field generating means 2a, a so-called six-pole magnetic pole having five magnets as shown in the figure was used. Specifically, a developing electrode 2b (S pole) is provided at a position facing the closest position between the sleeve 2 and the photoreceptor 40. A magnetic pole 2c (N pole), a magnetic pole 2d (S pole), a magnetic pole 2e (S pole), and a magnetic pole 2f (N pole) are provided in this order in the developer transport direction. In addition, although the thing of such a structure was used as the magnetic field generation | occurrence | production means 2a of this embodiment, you may use what comprised by 8 poles or 10 poles as needed.

  In the developing device of the present embodiment, the uppermost surface of the developer agitated by the screw 5 is in a range in which the region downstream of the magnetic pole 2e and upstream of the magnetic pole 2f is extended outward from the sleeve surface in the radial direction of the sleeve 2. A pumping auxiliary magnetic field generating means 7 is provided at a position farther from the sleeve 2 than the lower position. Here, the lowermost position of the upper surface of the developer is the position of the upper surface of the developer when the volume of the developer is the lowest, and specifically, the higher volume of the developer when the toner concentration is 0%. May be used as the lowest position. As the pumping auxiliary magnetic field generating means 7, the surface facing the sleeve 2 is a non-magnetized surface, and the upstream surface with respect to the rotation direction of the sleeve 2 has the same polarity as the pumping magnetic pole 2 e adjacent to the upstream side with respect to the rotation direction of the sleeve 2. A magnet having a number of magnetic poles was used.

  FIG. 5 shows lines of magnetic force formed by the pumping magnetic pole 2e, the adjacent magnetic pole 2f, and the pumping auxiliary magnetic field generating means 7 when such a pumping auxiliary magnetic field generating means 7 is provided. FIG. 6 shows the state of the developer pumped up by these lines of magnetic force. The magnetic force of the pumping auxiliary magnetic field generating means 7 acts on the developer in the vicinity of the area where the pumping auxiliary magnetic field generating means 7 is arranged, and the developer in the vicinity of this area is raised and raised. That is, the developer agitated by the screw 5 is opposed to the region between the developer pumping pole 2e and the adjacent magnetic pole 2f, and is raised from the bottom toward the sleeve surface to make the volume pseudo-high. And close to the sleeve 2. When the bulk of the entire developer is originally high, the sleeve 2 draws the developer directly from the top of the developer conveyed to the screw 5, and further rises up by the pumping auxiliary magnetic field generating means 7 and comes close to the sleeve 2. The developer is pumped up from the top of the developer. When the bulk of the developer becomes low, the developer is pumped up from the uppermost part of the developer that is raised by the pumping auxiliary magnetic field generating means 7 and close to the sleeve 2. The uppermost part of the developer that is raised by the pumping auxiliary magnetic field generating means 7 is not directly affected by the shake of the developer agitating / conveying member or the blade pitch of the screw, so there is little unevenness, and accordingly the pumping amount is uneven. Less. Further, since the developer is lifted and pumped up from the developer close to the sleeve 2, even if the screw 5 is shaken by rotation, the pumping amount is stabilized and pitch unevenness is eliminated. Therefore, even if the bulkiness of the entire developer fluctuates, the pumping amount without unevenness due to the shake and pitch of the developer agitating / conveying member can be obtained, and accordingly, development without unevenness can be performed.

  Such a pumping auxiliary magnetic field generating means 7 can be arranged in the developing device 1. However, in this embodiment, as shown in FIG. 7, the development stirred by the screw 5 in a range in which the region downstream of the magnetic pole 2 e and upstream of the magnetic pole 2 f is extended outward from the sleeve surface in the radial direction of the sleeve 2. It arrange | positioned in the outer wall of the casing 9 in the place away from the sleeve 2 rather than the uppermost lowest position of an agent. By disposing on the outer wall of the casing 9 in this way, it is possible to avoid the developer from coming into direct contact with the pumping auxiliary magnetic field generating means 7, and the same performance as the initial state can be exhibited over time.

  Further, a magnet is used in which the upstream surface of the pumping auxiliary magnetic field generating means 7 has the same polarity as the pumping magnetic pole 2e close to the upstream side in the rotation direction of the sleeve 2 in the rotation direction of the sleeve 2. Therefore, the pumping auxiliary magnetic field generating means 7 generates a repulsive magnetic field with respect to the pumping magnetic pole 2e. This repulsive magnetic field distorts the magnetic field of the pumping auxiliary magnetic field generating means 7 and the pumping magnetic pole 2e, so that the developer is not raised on the upper part of the screw 5 but is raised in a wide range from the side to the upper part. Can be sprinkled. Therefore, it is possible to lift the developer having a low bulk to a position where the developer is brought close to the sleeve.

  As the pumping auxiliary magnetic field generating means 7 of the present embodiment, specifically, one having a cross section of 4 mm × 3 mm and a magnetic force of 80 mT is used so that the magnetic flux density is equal to or larger than that of the pumping magnetic pole 2e. . It has been confirmed in actual machines that if the magnetic force of the pumping auxiliary magnetic field generating means 7 is smaller than the pumping magnetic pole 2e, it does not contribute to pumping.

  Further, if the pumping auxiliary magnetic field generating means 7 is within an angle range between the pumping pole 2e and the adjacent magnetic pole 2f, the effect of assisting the developer pumping is recognized. This is probably because the magnetic flux density in the tangential direction is high. Further, when the pumping auxiliary magnetic field generating means 7 is disposed at a position exceeding the above range, the developer does not easily stand up and no contribution to the pumping of the developer can be expected.

As described above, in the printer according to the present embodiment, the screw 5 is agitated in a range in which the region downstream of the developer pumping magnetic pole 2e and upstream of the adjacent magnetic pole 2f extends in the radial direction of the sleeve 2 to the outside of the sleeve 2 surface. A pumping auxiliary magnetic field generating means 7 having a non-magnetized surface on the surface facing the sleeve is provided at a position farther from the sleeve than the lowest position on the upper surface of the developer. The pumping auxiliary magnetic field generating means 7 lifts up the developer in the vicinity by the magnetic force to make it stand up, and makes the bulk pseudo close to the sleeve 2. Even when the bulk of the developer becomes low, the sleeve 2 draws and carries the developer from the uppermost portion of the protuberant developer. The uppermost portion of the developer spiked by the pumping auxiliary magnetic field generating means 7 is not directly affected by the shake of the developer agitating / conveying member and the blade pitch of the screw, and therefore there is little unevenness. Moreover, since the uppermost part is close to the sleeve 2, the pumping amount is also stabilized. For this reason, unevenness in the pumping amount is reduced, and development without unevenness due to the shake or pitch of the screw 5 can be performed.
Further, a magnet whose upstream surface with respect to the rotation direction of the sleeve 2 of the pumping auxiliary magnetic field generating means 7 has the same polarity as the pumping magnetic pole 2e is used. Therefore, the pumping auxiliary magnetic field generating means 7 generates a repulsive magnetic field with respect to the pumping magnetic pole 2e. This repulsive magnetic field distorts the magnetic field of the pumping auxiliary magnetic field generating means 7 and the pumping magnetic pole 2e, so that the developer is not raised on the upper part of the screw 5 but is raised in a wide range from the side to the upper part. Can be sprinkled. Therefore, it is possible to lift the developer having a low bulk to a position where the developer is brought close to the sleeve.
Further, by making the magnetic flux density of the pumping auxiliary magnetic field generating means 7 equal to or greater than that of the pumping magnetic pole 2e, the pumping auxiliary magnetic field generating means 7 can make the developer stand up efficiently.
The pumping auxiliary magnetic field generating means 7 is disposed on the outer wall of the casing 9. As a result, the developer can be prevented from coming into direct contact with the pumping auxiliary magnetic field generating means 7, and the same performance as the initial state can be exhibited over time.
In addition, since the photosensitive member 40 and the developing device 1 are integrally configured to be a process cartridge that can be attached to and detached from the main body of the image forming apparatus, maintenance can be facilitated.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a conventional developing device. FIG. 10 is a magnetic force diagram formed in a developer pumping area in a conventional developing device. Explanatory drawing of a mode that a sleeve pumps up a developing agent in the conventional developing device. FIG. 6 is a magnetic force diagram formed in a developer pumping region in the developing device of the present embodiment. Explanatory drawing of a mode that a sleeve pumps up a developing agent in the image development apparatus of this embodiment. FIG. 2 is a schematic configuration diagram of a developing device of the present embodiment. FIG. 2 is a schematic configuration diagram of a developing device according to Patent Document 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing apparatus 2 Sleeve 2a Magnetic field generating means 2b Developing pole 2c, 2d, 2f Magnetic pole 2e Pumping magnetic pole 4 Doctor 5, 6 Screw 7 Pumping auxiliary magnetic field generating means 8 Second developer regulating member 9 Casing 10 Tandem image forming section 11 Intermediate transfer Belt 12Y, C, M, K Toner image forming means 13Y, C, M, K Primary transfer roller 14 Paper feed unit 15 Secondary transfer roller 16 Fixing device 17 Charging device 18 Exposure device 19 Cleaning device 40 Photoconductor

Claims (6)

A casing that contains a two-component developer composed of toner and a magnetic carrier, a developer agitating and conveying member that agitates and conveys the two-component developer, and a non-rotatable non-rotating material that includes a magnetic field generating means having a plurality of magnetic poles fixedly arranged A developer carrying member comprising a magnetic sleeve and pumping and carrying the two-component developer agitated and conveyed by the developer agitating and conveying member to the surface of the sleeve and conveying the developer to a region opposite to the latent image carrier. In the developing device,
Of the plurality of magnetic poles of the magnetic field generating means with respect to the sleeve rotation direction, a region downstream from the developer pumping pole and upstream from the magnetic pole adjacent to the downstream of the developer pumping pole is positioned in the radial direction of the sleeve from the sleeve surface. A surface facing the sleeve is a non-magnetized surface in a range extending outward and further away from the sleeve surface than the lowest position of the upper surface of the two-component developer stirred by the developer stirring and conveying member. A pumping auxiliary magnetic field generating means is provided ,
A developing device characterized in that the upstream side of the pumping auxiliary magnetic field generating means with respect to the rotation direction of the sleeve has a magnetic pole having the same polarity as the developer pumping pole of the magnetic field generating means . 2. The developing device according to claim 1 , wherein the magnetic flux density of the auxiliary pumping magnetic field generating means is equal to or higher than the magnetic flux density of the developer pumping pole of the magnetic field generating means. 3. The developing device according to claim 1, wherein the pumping auxiliary magnetic field generating means is disposed on an outer wall of the casing of the developing device. 4. A process cartridge comprising an image carrier and a developing device which are integrally formed and detachable from an image forming apparatus main body, wherein the developing device according to claim 1, 2 or 3 is adopted as the developing device. . In an image forming apparatus comprising: an image carrier that carries an electrostatic latent image; and a developing device that converts the electrostatic latent image into a toner image.
4. An image forming apparatus comprising the developing device according to claim 1, 2 or 3 as the developing device.   A casing that contains a two-component developer composed of toner and a magnetic carrier, a developer agitating and conveying member that agitates and conveys the two-component developer, and a non-rotatable non-rotating material that includes a magnetic field generating means having a plurality of magnetic poles fixedly arranged. A developer carrying member comprising a magnetic sleeve and pumping and carrying the two-component developer agitated and conveyed by the developer agitating and conveying member to the surface of the sleeve and conveying the developer to a region opposite to the latent image carrier. In the developing device,
  The region between the developer pumping pole and the magnetic pole adjacent to the downstream side of the pumping pole with respect to the sleeve rotation direction extends in the radial direction of the sleeve to the outside of the sleeve surface, and the developer stirring and transporting A pumping auxiliary magnetic field generating means in which the surface facing the sleeve is a non-magnetized surface at a position farther from the sleeve surface than the lowest position on the upper surface of the two-component developer stirred by the member;
An image forming apparatus characterized in that the upstream side of the pumping auxiliary magnetic field generating means with respect to the rotation direction of the sleeve has a magnetic pole having the same polarity as the developer pumping pole of the magnetic field generating means.

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