JP2016035545A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that can suppress a filter member provided in a pressure relief opening from clogging, and a process cartridge and an image forming apparatus that include the developing device.SOLUTION: There is provided a developing device 5 including: a developing roller 51 that carries a two-component developer G on its surface and makes a surface movement to supply a toner to a latent image on the surface of a photoreceptor in a developing area; a housing 59 that forms a developer storage part accommodating the developer G to be supplied to the developing roller 51 and has a through-hole 61 formed therein; and a filter 60 that prevents the developer G from being discharged from the through-hole 61, where the through-hole 61 is formed opposite to a position on the upstream side of a retention position before agent release on the surface of the developing roller 51 and on the downstream side of an airflow generation part 511; the developing device brings the developer G carried at the retention position before agent release before performing reverse control into contact with the filter 60 by the reverse control, the reverse control causing the developing roller 51 to make a surface movement in the direction reverse to that during a developing operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and a process cartridge and an image forming apparatus including the developing device.

  Conventionally, developing devices using a two-component developer including toner and a magnetic carrier have been widely used (for example, Patent Documents 1 and 2). This type of developing device includes a plurality of magnetic poles inside, and a developer carrying member whose surface moves endlessly by rotating. The developer is carried on the surface of the developer carrying member, and the toner in the developer is applied to the latent image formed on the surface of the latent image carrying member in the development area where the developer carrying member faces the latent image carrying member. By supplying, the latent image on the latent image carrier is developed.

  A developer carrying member is disposed in a developing container that forms a developer containing portion for containing the developer, and an opening is provided in the developing container so that a part of the surface of the developer carrying member is exposed in the developing region. It has been. Further, a developer conveying member that circulates the developer is disposed in the developer accommodating portion, and a part of the circulated developer is circulated while the developer is circulated in the developer accommodating portion where the developer conveying member is disposed. Is supplied to the surface of the developer carrying member. The developer supplied to the surface of the developer carrier from the inside of the developer container is regulated to an amount toward the development region at a regulation position where the developer regulation member and the developer carrier are opposed to each other, and is conveyed to the development region. Thereafter, the developer that has consumed the toner after passing through the developing region is separated from the surface of the developer carrying member, collected in the developer accommodating portion, and circulated together with other developers.

  Patent Documents 1 and 2 include a pressure release opening for discharging the air in the developer accommodating portion to the outside of the apparatus, and a filter member for suppressing toner from being discharged from the opening by suppressing the passage of toner. A configuration with is described.

  In order to cope with high-speed output in the developing device, it is necessary to increase the surface movement speed of the developer carrier, but if the surface movement speed of the developer carrier is increased, the air pressure in the developer container may increase. is there. This is considered to be due to the following reasons.

That is, when the surface of the developer carrying member exposed in the developing region serving as the opening of the developing container returns into the developing container, the air flow generated so as to be accompanied by the developer carrying member moving at high speed is the developer. It flows into the developing container together with the surface of the carrier.
On the other hand, with respect to the surface of the developer carrying member from the developing container toward the developing region, the developer blocks the space between the developer regulating member and the developer carrying member at the regulating position. Airflow that flows out to the opening together with the surface is difficult to occur.
When the developing container is in a substantially sealed state except for the opening in the developing region, it is difficult to generate an airflow flowing out from the opening, even though the airflow flows in from the opening. The air pressure in the agent container rises.

  When the air pressure in the developer container rises, the toner leaks together with the air from a slight gap between the developer carrier and the developer container toward the development area, or a gap between the members forming the developer container, and the toner. There is a risk of scattering. Toner scattering is a cause of problems such as contamination of the output image and failure due to contamination in the image forming apparatus, and thus must be suppressed.

  As described in Patent Documents 1 and 2, if the pressure relief opening and the filter member are provided, air is discharged from the pressure relief opening to the outside of the apparatus when the air pressure in the developer containing portion rises. Therefore, it is possible to suppress an increase in the atmospheric pressure in the developer accommodating portion. As a result, it is possible to suppress the occurrence of toner scattering due to an increase in the air pressure in the developer accommodating portion.

  However, in the conventional developing device, the toner whose passage through the pressure release opening is suppressed by the filter member remains attached to the inner surface of the developer accommodating portion of the filter member, and the attached toner accumulates and reaches the filter member. Clogging sometimes occurred.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device capable of suppressing clogging of a filter member provided in a pressure relief opening, and a process cartridge including the developing device. And an image forming apparatus.

  According to the present invention, a two-component developer composed of a toner and a carrier is carried on the surface, and the surface moves to form a latent image on the surface of the latent image carrier in the development region facing the latent image carrier. Forming a developer carrying member for supplying toner and a developer containing portion for containing the developer to be supplied to the developer carrying member, and discharging the gas in the developer containing portion to the outside of the device; A developer container formed with a pressure relief opening that suppresses an increase in the atmospheric pressure, a filter member that is provided in the pressure relief opening and prevents the developer from being discharged from the pressure relief opening, In the developing device, the developer carrying member is movable in the direction opposite to the surface moving direction during the developing operation, and the developer carrying member is moved in the direction opposite to the surface moving direction during the developing operation. A reverse movement control means for moving the surface, the pressure release opening is On the upstream side in the surface movement direction of the agent separation portion on the surface of the developer carrier, the upstream side in the surface movement direction with respect to the pre-agent separation stay position where the developer stays on the surface of the developer carrier, and The reverse operation control is formed so that the surface of the developer carrying member that has passed through the developing region is opposed to a position on the downstream side in the surface movement direction with respect to the developer carrying member entering portion that enters the developing container. Means reversely controls the surface of the developer carrying member in a direction opposite to that during the developing operation, and the developer carried at the staying position before the agent separation before the reverse control is applied to the filter member. It is made to contact.

  ADVANTAGE OF THE INVENTION According to this invention, there exists the outstanding effect that it can suppress that clogging arises in the filter member provided in the pressure release opening part.

FIG. 3 is a schematic cross-sectional view of the developing device at a position including a filter. 1 is a schematic configuration diagram illustrating an entire printer according to an embodiment. FIG. 3 is an enlarged configuration diagram illustrating one of image forming units. The block diagram which shows an example of the principal part structure of the control system which performs forward / reverse rotation control of a developing sleeve. The graph which shows the result of having compared the internal pressure rise after passing 20 sheets by the presence or absence of reverse rotation control.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of a tandem type color printer (hereinafter simply referred to as “printer 100”) in which a plurality of photoconductors are arranged in parallel will be described.
FIG. 2 is a schematic configuration diagram illustrating the entire printer 100 according to the present embodiment.
As shown in FIG. 2, in the toner container housing portion 31 above the printer 100 main body, four toner containers 32 (Y, M, C, K) corresponding to the respective colors (yellow, magenta, cyan, black) are provided. The printer 100 is detachably (replaceable).

  An intermediate transfer unit 15 is disposed below the toner container housing 31. Image forming portions 6 (Y, M, C, K) corresponding to the respective colors (yellow, magenta, cyan, black) are arranged in parallel so as to face the intermediate transfer belt 8 of the intermediate transfer unit 15.

FIG. 3 is an enlarged configuration diagram illustrating one of the four image forming units 6 (Y, M, C, and K) included in the printer 100. The four image forming units 6 (Y, M, C, and K) have substantially the same configuration except that each of the handled toner colors is different. Therefore, “Y” that indicates the color of the toner to be used will be described below. , “M”, “C”, and “K” are appropriately omitted.
As shown in FIG. 3, the image forming unit 6 includes a photosensitive member 1 as a latent image carrier, a charging roller 4 as a charging unit disposed around the photosensitive member 1, a developing device 5 as a developing unit, a cleaning unit. A cleaning device 2 as a means is provided. Furthermore, a static elimination means (not shown) is provided. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photoreceptor 1, whereby toner images of respective colors are formed on the photoreceptor 1.

  The image forming unit 6 constitutes a process cartridge that integrally supports the photosensitive member 1, the developing device 5, the charging roller 4, the cleaning device 2, and a charge eliminating unit (not shown), and is detachable from the printer 100 main body. Yes. By using the process cartridge, the exchangeability of the developing device 5 provided in the image forming unit 6 is improved.

  The photoreceptor 1 shown in FIG. 3 is rotationally driven in a clockwise direction in FIG. 3 by a drive motor (not shown). Then, the surface of the photoreceptor 1 is uniformly charged at a position facing the charging roller 4 (charging process).

  The surface of the photoreceptor 1 that is uniformly charged at a position facing the charging roller 4 reaches the irradiation position of the laser beam L emitted from the exposure device 7 shown in FIG. A corresponding electrostatic latent image is formed (exposure process). In the exposure process, the exposure device 7 disposed below the image forming units 6 (Y, M, C, K) transmits the laser light L based on the image information to the image forming units 6 (Y, M, C). , K) is irradiated toward the surface of the photoreceptor 1 (Y, M, C, K). Specifically, the exposure device 7 emits a laser beam L from a light source, and scans the laser beam L with a polygon mirror that is rotationally driven, while each photoconductor 1 (Y, M, C, K) is irradiated on the surface.

  The surface of the photoreceptor 1 on which the electrostatic latent image is formed reaches a position facing the developing roller 51 provided in the developing device 5, and the electrostatic latent image is developed at this position to form toner images of each color. (Development process).

The surface of the photoreceptor 1 on which the toner image is formed reaches a position facing the primary transfer bias roller 9 with the intermediate transfer belt 8 interposed therebetween, and the toner image on the photoreceptor 1 is placed on the intermediate transfer belt 8 at this position. Transferred (primary transfer process). At this time, a small amount of untransferred toner remains on the photoreceptor 1.
The surface of the photoreceptor 1 that has passed the position facing the primary transfer bias roller 9 reaches the position facing the cleaning device 2, and untransferred toner remaining on the photoreceptor 1 at this position is mechanically removed by the cleaning blade 2a. (Cleaning process).
The surface of the photoreceptor 1 that has passed through the position facing the cleaning device 2 finally reaches the position facing the unillustrated neutralization device, and the residual potential on the photoreceptor 1 is removed at this position.

  In this way, a series of image forming processes performed on the respective photoreceptors 1 of the four image forming units 6 is completed.

  As shown in FIG. 2, the intermediate transfer unit 15 includes an intermediate transfer belt 8, four primary transfer bias rollers 9, a secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14, an intermediate transfer cleaning device 10, and the like. Composed. The intermediate transfer belt 8 is stretched and supported by three tension rollers (12 to 14), and is counterclockwise indicated by an arrow in FIG. 2 by the rotational drive of one of the three tension rollers. It is moved endlessly in the direction of rotation. In the printer 100 of the present embodiment, the secondary transfer backup roller 12 is rotationally driven as a drive roller.

The four primary transfer bias rollers 9 (Y, M, C, K) respectively sandwich the intermediate transfer belt 8 with the photoreceptor 1 (Y, M, C, K) to form a primary transfer nip. Yes. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias roller 9 (Y, M, C, K).
The intermediate transfer belt 8 travels in the direction of the arrow and sequentially passes through the primary transfer nip of each primary transfer bias roller 9 (Y, M, C, K). In this way, in each primary transfer nip, the toner images of the respective colors on the respective photoreceptors 1 (Y, M, C, K) are primarily transferred to the intermediate transfer belt 8 so as to be superimposed on the intermediate transfer belt 8. A color image is formed.

The intermediate transfer belt 8 on which the color image is formed by superimposing and transferring the toner images of the respective colors reaches a position facing the secondary transfer roller 19. At this position, the secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a secondary transfer nip. The color image formed on the intermediate transfer belt 8 is transferred onto a transfer material P such as transfer paper conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the transfer material P remains on the surface of the intermediate transfer belt 8.
The intermediate transfer belt 8 that has passed through the secondary transfer nip reaches a position facing the intermediate transfer cleaning device 10. At this position, the untransferred toner on the intermediate transfer belt 8 is collected.
In this way, a series of transfer processes performed on the intermediate transfer belt 8 is completed.

The transfer material P transported to the position of the secondary transfer nip described above is transported from the paper feed unit 26 disposed below the main body of the printer 100 via the paper feed roller 27, the registration roller pair 28, and the like. It is a thing.
Specifically, a plurality of sheet-shaped transfer materials P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feeding roller 27 is driven to rotate counterclockwise in FIG. 2, the uppermost transfer material P in the paper feeding unit 26 is fed toward the rollers of the registration roller pair 28. . The transfer material P conveyed to the registration roller pair 28 is temporarily stopped at the position of the roller nip of the registration roller pair 28 that has stopped rotating. Then, the registration roller pair 28 is rotationally driven in time with the color image on the intermediate transfer belt 8, and the transfer material P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the transfer material P.

The transfer material P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the fixing device 20. The color image transferred on the surface is fixed on the transfer material P by the heat and pressure generated by the fixing roller and the pressure roller included in the fixing device 20.
The transfer material P on which the color image has been fixed by the fixing device 20 is discharged to the outside of the device through the pair of paper discharge roller pairs 29. The transfer material P discharged from the apparatus by the discharge roller pair 29 is sequentially stacked on the stack unit 30 as an output image.
In this way, a series of image forming processes in the image forming apparatus is completed.

Next, the developing device 5 provided in the image forming unit 6 will be described with reference to FIG.
The developing device 5 includes a developing roller 51 as a developer carrying member facing the photosensitive member 1, and a first developer containing portion 53 and a second developer as a developer containing portion for containing the developer supplied to the developing roller 51. And an agent container 54. Further, the developing device 5 includes a doctor blade 52 that is a layer thickness regulating member facing the developing roller 51, and includes two conveying screws disposed in the first developer accommodating portion 53 and the second developer accommodating portion 54. As a first conveying screw 55 and a second conveying screw 57. Furthermore, a density detection sensor 56 for detecting the toner density in the developer in the second developer storage unit 54 is provided. Each of these members is installed in a housing 59 which is a developing container.

The developing roller 51 includes a magnet fixed inside, a developing sleeve that rotates around the magnet, and the like. The first developer accommodating portion 53 and the second developer accommodating portion 54 accommodate a two-component developer G composed of a carrier and toner.
The first developer accommodating portion 53 and the second developer accommodating portion 54 are partitioned by a partition wall 58, and the partition wall 58 is in the axial direction of the transport screw of the first developer accommodating portion 53 (on the paper surface in FIG. 3). Opening portions (not shown) are provided at both ends in the (perpendicular direction). The first developer accommodating portion 53 and the second developer accommodating portion 54 communicate with each other through this opening, and the first conveying screw 55 and the second conveying screw 57 rotate, whereby the developer G is developed in the first developing state. The developer container 53 and the second developer container 54 are circulated.
Further, the second developer accommodating portion 54 communicates with the toner conveyance path 40 through an opening formed thereabove.

When performing image formation, the developing sleeve constituting the developing roller 51 rotates in the direction of the arrow in FIG. 3 (counterclockwise direction). The developer G carried on the developing roller 51 by the magnetic field formed by the magnet arranged in the developing sleeve moves on the developing roller 51 as the developing sleeve rotates.
The developer G in the developing device 5 is adjusted so that the ratio of toner in the developer (toner concentration) is within a predetermined range. Specifically, the toner stored in the toner container 32 is supplied into the second developer storage portion 54 by a toner supply device (not shown) according to the consumption of toner in the developing device 5.
The toner replenished in the second developer accommodating portion 54 is mixed and stirred together with the developer G by the second conveying screw 57 and the first conveying screw 55, and the first developer accommodating portion 53 and the second developer are mixed. It circulates through the accommodating part 54. In this circulation, the developer G moves in the first developer accommodating portion 53 and the second developer accommodating portion 54 in the direction orthogonal to the paper surface in FIG. The toner in the developer G is charged to the opposite polarity to the carrier due to frictional charging with the carrier, adsorbed to the carrier, and carried on the developing roller 51 together with the carrier by the magnetic field formed on the developing roller 51. The

The developing device 5 configured as described above operates as follows.
The developing sleeve of the developing roller 51 rotates in the arrow direction (counterclockwise direction) in FIG. 3 during a developing operation in which toner is supplied to the latent image formed on the surface of the photoreceptor 1 and development is performed. The developer G carried on the developing roller 51 by the magnetic field formed by the magnet inside the developing sleeve moves on the developing roller 51 as the developing sleeve rotates.

  The developer G carried on the developing roller 51 is conveyed in the direction of the arrow in FIG. 3 and reaches a position where the developing roller 51 and the doctor blade 52 face each other. The developer G on the developing roller 51 is transported to a developing area which is a position where the developing roller 51 and the photosensitive member 1 are opposed to each other after the developer amount is made appropriate at this position. Then, the toner is attracted to the electrostatic latent image formed on the photosensitive member 1 by the developing electric field formed between the developing roller 51 and the photosensitive member 1 in the developing region. The developer G remaining on the developing roller 51 after passing through the developing region reaches the agent separating portion 512 above the first developer containing portion 53 as the developing sleeve rotates, and is separated from the developing roller 51 at this position. Then, it is conveyed while being stirred in the first developer accommodating portion 53.

Next, features of the developing device 5 according to the present invention will be described.
FIG. 1 is a schematic cross-sectional view of the developing device 5 at a position including the filter 60 in the axial direction of the rotation shaft of the developing roller 51.

  In the housing 59 forming the two developer accommodating portions (53, 54) for accommodating the developer G supplied to the developing roller 51, the gas in the developer accommodating portion is discharged to the outside of the apparatus, and the atmospheric pressure in the developer accommodating portion. A through-hole 61 that is a pressure release opening that suppresses the rise of the pressure is formed. The through hole 61 is provided with a filter 60 that is a filter member that prevents the toner together with the gas from being discharged outside the apparatus.

The developer G is adsorbed around the developing roller 51 by a magnetic force. The developer G is conveyed by the rotation of the developing sleeve, which is a cylinder around the developing roller 51. In the developing area where the developing roller 51 and the photosensitive member 1 face each other, the toner in the developer G is used for development, and the developer G after passing through the developing area is accommodated in the housing 59 again.
In the developer carrying member entering portion where the surface of the developing roller 51 that has passed through the developing region enters the housing 59, the air flow generating portion 511 is formed by narrowing the gap between the housing 59 and the developing roller 51. In the developing device 5 of the present embodiment, the gap in the airflow generation unit 511 is 1.4 [mm].

  In the air flow generation unit 511, the developer G contacts the surface of the housing 59 facing the developing roller 51, and the surrounding air is also sucked into the housing 59 by the conveyance of the developer G. Due to this suction force, an air flow (hereinafter referred to as “suction air flow”) is generated in the air flow generation unit 511 from the outside air toward the housing 59. By generating a suction air flow at the downstream end of the developing sleeve 51 in the surface movement direction at the portion where the developing roller 51 is exposed from the housing 59, scattered toner released from the carrier in the vicinity of the developing region is sucked into the housing 59 together with air. It can be recovered. As a result, the developing device 5 can suppress the occurrence of toner scattering from the development area.

  The suction air flow increases the atmospheric pressure (internal pressure) in the housing 59. When the internal pressure of the housing 59 rises, the toner leaks together with air from a slight gap between the developing sleeve and the housing 59 toward the developing region, or a gap between the members forming the housing 59 and the like, which may lead to toner scattering. There is. As a configuration that suppresses an increase in the internal pressure of the housing 59, the developing device 5 includes a through hole 61 that allows the air in the housing 59 to escape to the outside, and the through hole 61 is covered with a filter 60.

  The magnet arranged in the developing sleeve has a plurality of magnetic poles in the rotation direction of the developing sleeve, and is adjacent to the magnetic poles at locations other than the agent separating portion 512 where the developer G is separated from the surface of the developing roller 51 that has passed through the developing region. The polarities are different from each other. On the other hand, in the agent separation part 512, adjacent magnetic poles have the same polarity. In the agent separating portion 512, the developer G supported by the magnetic force of the magnetic pole on the upstream side in the surface movement direction of the developing sleeve is the same polarity even if it is directed to the magnetic pole of the same polarity on the downstream side together with the surface of the developing sleeve moving on the surface. Is not carried by the magnetic pole on the downstream side due to the repulsion. At this time, the developer G on the surface of the developing sleeve is repelled by the repulsive magnetic field and separated from the surface of the developing sleeve as indicated by a broken arrow β in FIG. Or stays on the surface of the developing sleeve.

On the surface of the developing roller 51 after the amount of the developer G to be carried passing through the position facing the doctor blade 52 is regulated, the height of the developer G is changed by changing the magnetic force acting by the surface movement. Although it changes, the amount of developer G carried per unit area does not change much. However, since the developer G stays on the upstream side of the agent separation portion 512, the developer G per unit area from the surface of the developing roller G on the upstream side with respect to this staying position (the staying position before agent separation). The loading amount of increases.
When a certain amount of developer G stays at the staying position before the agent separation, a part of the developer G staying by being pushed by the developer G conveyed later is disposed in the developing sleeve. It is pushed out of the range supported by the magnetized magnetic force. The developer G pushed out from the range supported by the magnetic force falls and separates from the surface of the developing sleeve, as indicated by a broken line arrow β in FIG.

  In the developing device 5 to which the present invention is applied, a through hole 61 provided with at least one filter 60 is disposed to face the developing roller 51. Further, as shown in FIG. 1, the through-hole 61 is located downstream of the air flow generation unit 511 and upstream of the position where the developer stays upstream of the agent separation unit 512 in the surface movement direction of the developing sleeve. It is formed so as to face the surface of the developing roller 51 on the side.

  An arrow α in FIG. 1 shows an outline of the path of the suction airflow. As shown in FIG. 1, the developing device 5 is configured such that the suction air flow generated in the air flow generation unit 511 due to the rotation of the developing sleeve is a position where the developer G on the upstream side of the agent separation unit 512 stays (retention before agent separation). It is configured to be discharged out of the housing 59 upstream of the position). Further, since the developer G stays on the upstream side of the agent separating portion 512, the airflow entering the housing 59 is difficult to flow into the first developer containing portion 53 and the second developer containing portion 54, and the suction airflow penetrates. The mechanism is easy to be discharged out of the housing 59 from the hole 61.

  As described above, the suction airflow carries the toner generated in the vicinity of the development area into the housing 59 together with the air. When the suction airflow passes through the through hole 61, most of the toner carried by the suction airflow is collected by the filter 60, so that it is hardly discharged out of the housing 59.

  However, since the toner collected and adhered to the filter 60 accumulates more and more, if it accumulates too much, the air itself that forms the sucked air current will not be discharged from the housing 59 through the through hole 61 where the filter 60 is located. In this case, since the air pressure inside the housing 59 is higher than the air pressure outside the housing 59, the toner is discharged together with the air from the gaps described above, and the toner scatters. Therefore, by periodically removing the toner adhering to the filter 60, the air permeability of the filter 60 can be maintained and the exhaust function in the through hole 61 can be prolonged.

  In the developing device 5 to which the present invention is applied, reverse rotation driving of the developing sleeve constituting the developing roller 51 is used as means for periodically removing the adhered toner. In other words, reverse rotation control is executed to rotate (reverse) the developing sleeve in the opposite direction (clockwise direction in FIG. 1) to the normal rotation (forward rotation) direction in which the developing operation is performed (counterclockwise direction in FIG. 1). To do. As a result, the developer G staying at the pre-agent separation stay position on the upstream side of the agent separation portion 512 is moved in the reverse direction (upstream side in the developing sleeve surface movement direction during the developing operation).

FIG. 4 is a block diagram illustrating an example of a main configuration of a control system that performs forward / reverse control of the developing sleeve. The control unit 300 as a control unit is provided corresponding to each of the four developing devices 5, but since the basic configuration is the same, the color-coded codes (Y, C, M, K) are assigned. The description is omitted. As illustrated in FIG. 4, the control unit 300 includes a central processing unit (CPU 301), a read only memory (ROM 302), a random access memory (RAM 303), and the like. In the present embodiment, a part (CPU 301, ROM 302, RAM 303, etc.) of the control unit 300 of each developing device 5 is shared among the plurality of developing devices 5.
4, the control unit 300 of the printer 100 includes a CPU 301, a ROM 302, a RAM 303, and the like.

The control unit 300 controls the driving of the developing drive motor 550 which is a driving source for the rotating operation of the developing sleeve, and rotates the developing sleeve constituting the developing roller 51 in the counterclockwise direction in FIG. Drive. On the other hand, when performing reverse rotation control, the developing sleeve is driven to rotate in the clockwise direction in FIG.
In the developing device 5 of the present embodiment, the height (distance) from the surface of the developing roller 51 to the surface of the filter 60 is set to 1 [mm] to 2 [mm]. It is set as appropriate depending on the height of the developer G carried on the 51.

  In the developing device 5, the developer G on the surface of the developing roller 51 is not brought into contact with the filter 60 during the forward rotation of the developing sleeve, and the developer G on the surface of the developing roller 51 is applied to the filter 60 only during the reverse rotation of the developing sleeve. It is the structure made to contact. Specifically, the configuration is as follows. That is, the distance from the surface of the developing roller 51 at a position facing the through hole 61 to the filter 60 is set to be larger than the height in the normal direction of the developer G passing through this position during the developing operation. . Further, the developer G that has stayed at the position before the agent separation during the developing operation passes this distance when the developer G passes through a position facing the through hole 61 on the surface of the developing roller 51 by reverse rotation control. It is set to be smaller than the height in the normal direction.

The height in the normal direction of the developer G on the surface of the developing roller 51 is the magnetic flux density in the normal direction of the magnetic field formed by the magnet inside the developing roller 51 and the developer G carried per unit area. Varies with the value of the quantity. Specifically, the value increases as the value of the magnetic flux density increases, and increases as the amount of the developer G carried per unit area increases. Therefore, if the magnetic flux density at the position facing the through hole 61 is not changed, the height of the developer G in the normal direction increases as the amount of the developer G carried per unit area increases.
Further, since the developer G stays in the staying part before the agent separation during the developing operation, the amount of the developer G carried per unit area is larger than the surface of the developing roller 51 at the position facing the through hole 61 at the time of forward rotation. It is increasing. For this reason, in the position facing the through hole 61 of the developing roller 51, the developing stayed at the staying position before the agent separation than when the developer G whose layer thickness is regulated by the doctor blade 52 passes during forward rotation. The developer G is higher when the agent G passes through this position during reverse rotation.

  The developer G staying at the staying position before the agent separation at the time of forward rotation can move together with the developing sleeve only at the time of reverse rotation. Therefore, by setting the distance from the surface of the developing roller 51 at a position facing the through hole 61 to the filter 60 to the above-described distance, the developer G on the surface of the developing roller 51 is applied to the filter 60 only at the time of reverse rotation. A configuration for contact can be realized.

  In the developing device 5, since the developer G on the surface of the developing roller 51 contacts the filter 60 only at the time of reverse rotation, the developer G carried on the surface of the developing roller 51 at the time of the developing operation in which the developing sleeve rotates forward is filtered 60. Do not touch. Thus, the filter 60 can be prevented from being covered with the developer G carried on the developing roller 51 during the developing operation, and air can be discharged from the through hole 61 during the developing operation.

  Further, in the developing device 5, when the developer is not operating, the controller 300, which is a reverse operation control means, moves the surface of the developing roller 51 in the direction opposite to that during the developer operation, that is, reverses the developing sleeve. Perform reverse rotation control. Thereby, the developer G on the surface of the developing roller 51 contacts the filter 60 when the developer G staying at the staying position before the agent separation during the developing operation passes the position facing the through hole 61. . By bringing the developer G carried on the developing roller 51 into contact with the filter 60, the toner adhered to the filter 60 can be removed by the developer G, and the filter 60 provided in the through hole 61 is clogged. This can be suppressed.

  Further, the developing device 5 of the present embodiment has a configuration in which the normal direction magnetic flux density on the surface of the developing roller 51 at the position facing the through hole 61 does not change between the forward rotation and the reverse rotation of the developing sleeve. However, it is good also as a structure which enlarges the value of the magnetic flux density of a normal line direction at the time of reverse rotation. When the value of the magnetic flux density in the normal direction is made larger at the time of reverse rotation than at the time of normal rotation, the height of the developer G passing through the position facing the through hole 61 at the time of normal rotation and the development staying at the stay position before the agent separation The difference from the height of the developer G when the agent G passes through the position facing the through hole 61 during reverse rotation becomes large. Accordingly, it is easy to realize a configuration in which the developer G does not contact the filter 60 during normal rotation, and the developer G contacts the filter 60 only during reverse rotation. A configuration in which the value of the magnetic flux density at the position facing the through hole 61 during reverse rotation can be increased by changing the angle of the magnet inside the developing roller 51 between forward rotation and reverse rotation.

Since most of the toner collected by the filter 60 is attached to the surface of the filter 60, the developer G staying upstream of the agent separating portion 512 by the reverse rotation control comes into contact with the toner on the surface of the filter 60. Is removed, and the air permeability of the filter 60 can be maintained.
Note that it is desirable that the developer G is not in contact with the filter 60 during normal rotation as in the developing device 5 of the present embodiment. If the carrier contained in the developer G continues to hit the filter 60, the carrier caught on the filter 60 may pass through the filter 60 and be discharged out of the housing 59. Of course, since the carrier should not be taken out of the housing 59, discharge of the carrier should be prevented. On the other hand, there is no problem because the frequency is low as long as it corresponds to the reverse control.

The frequency of executing the reverse rotation control is preferably executed before the toner has accumulated on the filter 60. Although how much toner is scattered varies depending on the specification conditions, the toner starts to accumulate on the filter 60 even under a condition where there is a lot of toner scattering after 100 to 200 sheets have passed.
Accordingly, the reverse rotation control of the developing roller 51 may be executed once every 100 sheets. In the developing device 5 of the present embodiment, the presence / absence of reverse rotation is controlled by the surface movement distance of the developing roller 51, and the reverse rotation control is performed once when the output of five sheets is performed four times.

  As long as the carrier does not pass through the filter 60 and is not discharged out of the housing 59, the reversal may be performed for each output, or in the case where the toner scattering is small, the frequency is once every 1000 sheets or more. Reverse rotation control may be executed. The frequency of reverse rotation control is determined in advance according to the type of filter 60 and the type of toner at what output the toner starts to accumulate on the filter 60, and the reverse rotation is performed before the toner starts to accumulate on the filter 60 according to the confirmation result. What is necessary is just to set suitably so that control may be performed.

  The rotation angle of the developing sleeve in the reverse rotation direction during the reverse rotation control needs to be rotated to the extent that the developer G staying on the upstream side of the agent separation portion 512 touches the filter 60. In the developing device 5 of the present embodiment, the rotation angle of the developing sleeve is set to rotate about 30 [°] to 40 [°] including variations. The rotation angle at the time of the reverse rotation control is a value determined by the distance between the position facing the filter 60 on the surface of the developing roller 51 and the agent separating portion 512 (the angle of the central angle of the developing roller 51).

FIG. 5 is a graph showing a result of comparing the increase in internal pressure after passing 20 sheets with and without reverse control in the developing device 5 shown in FIG.
As shown in FIG. 5, the initial increase in the internal pressure is small because the air permeability of the filter 60 is good, but the filter 60 becomes clogged as the number of sheets passing increases, and the internal pressure increases with time. However, as shown in the graph of “with reversal” in FIG. 5, when reverse rotation control is performed to prevent clogging of the filter 60 by reverse rotation, the air permeability of the filter 60 is maintained, and the internal pressure increases with time. Can be suppressed.

  As a configuration for removing the toner adhering to the filter member, a configuration in which the toner is removed by periodically vibrating the filter member is conceivable. However, in the case of such a configuration, a mechanism for vibrating the filter member is newly required, leading to high costs. On the other hand, the developing device 5 of the present embodiment is configured to execute the reverse rotation control by appropriately setting the distance between the filter 60 and the developing roller 51, so that a new mechanism is not required and the cost is high. It can also be suppressed.

  In the developing device 5 of the present embodiment, the through hole 61 is provided at a position where the suction air flow generated by the rotational movement of the developer G held by the developing roller 51 can be efficiently discharged, and is covered with the filter 60. Further, by executing the reverse rotation control, the developer G accumulated on the upstream side of the agent separating portion 512 can be brought into contact with the filter 60 and the toner adhering to the filter 60 can be removed. Further, a new mechanism for preventing clogging of the filter 60 is not required, and the life of the filter 60 can be extended at low cost.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A two-component developer composed of a toner such as developer G and a carrier is carried on the surface, moved on the surface, and on the surface of the latent image carrier in a development region facing the latent image carrier such as the photoreceptor 1. A developer carrier such as a developing roller 51 that supplies toner to the latent image, and a developer container such as a first developer container 53 and a second developer container 54 that store the developer supplied to the developer carrier. A housing 59 in which a pressure release opening such as a through hole 61 is formed to suppress a rise in air pressure in the developer accommodating portion by discharging a gas such as air in the developer accommodating portion to the outside of the apparatus. In the developing device such as the developing device 5 provided with a developing container and a filter member such as a filter 60 that is provided in the pressure opening and prevents the developer from being discharged from the pressure opening. The body also moves in the direction opposite to the direction of surface movement during development. The surface is movable, and includes a reverse operation control means such as a control means 300 for moving the developer carrying member in the direction opposite to the surface moving direction during the developing operation. The upstream side in the surface movement direction with respect to the staying position before developer separation where the developer stays on the surface of the developer carrier on the upstream side in the surface movement direction of the agent separation part such as the agent separation part 512 on the upper side, and the development region It is formed so that the surface of the developer carrier that has passed is opposed to a position that is on the downstream side in the surface movement direction with respect to the developer carrier entry portion such as the airflow generation portion 511 that enters the developer container, and reverse rotation control The means performs reverse rotation control to move the surface of the developer carrying member in the direction opposite to that during the developing operation, and contacts the developer held at the staying position before the agent separation before the reverse rotation control.
According to this, as described in the above embodiment, the developer stays in the staying position before the agent separation during the developing operation, and the developer carrier at the position facing the upstream pressure release opening also by this position. The amount of developer carried per unit area is larger than the surface. Then, the developer staying at the staying position before the agent separation is moved to the position facing the opening by reverse rotation control, so that the normal direction of the surface of the developer carrier at the position facing the depressurization opening The height of the developer becomes higher than that during the developing operation. By bringing the developer whose height is higher than that during the developing operation into contact with the filter member, the toner adhering to the filter member can be removed by the developer, and the filter member provided in the pressure release opening is clogged. Can be suppressed.

(Aspect B)
In the aspect A, the surface movement distance of the developer carrying member such as the developing roller 51 at the time of the reverse rotation control is the developer that was in the staying position before the agent separation on the upstream side of the agent separation portion 512 before the reverse rotation control is executed. It is equal to or longer than the surface movement distance at which the surface of the carrier reaches a position facing the filter member such as the filter 60.
According to this, as described in the above embodiment, the toner adhering to the filter member using the developer whose amount carried per unit area at the position upstream of the agent separating portion during the developing operation is increased. A configuration to be removed can be realized.

(Aspect C)
In any of the aspects A and B, the reverse rotation control is performed by moving the surface of the developer carrying member such as the developing roller 51 by a predetermined distance from the previous reverse rotation control by 100 sheets in the surface movement direction during the developing operation. To run after.
According to this, as described in the above embodiment, the control is performed to move the surface of the developer carrying member in the reverse direction before the toner starts to deposit on the filter member such as the filter 60, and the toner is deposited on the filter member. Thus, clogging can be prevented.

(Aspect D)
In either aspect A or B, the reverse rotation control is executed after the number of output sheets exceeds a threshold such as 100 sheets from the previous reverse rotation control.
According to this, as described in the above embodiment, the control is performed to move the surface of the developer carrying member in the reverse direction before the toner starts to deposit on the filter member such as the filter 60, and the toner is deposited on the filter member. Thus, clogging can be prevented.

(Aspect E)
At least a latent image carrier and a developing unit in an image forming apparatus such as a printer 100 including a latent image carrier such as the photosensitive member 1 that carries the latent image and a developing unit that develops the latent image on the latent image carrier. In a process cartridge such as the image forming unit 6 that is held on a common holding body as a single unit and is detachable from the main body of the image forming apparatus, the developing device according to any one of the aspects A to D is used as the developing unit. 5 or the like.
According to this, as described in the above embodiment, it is possible to improve the exchangeability of the developing device that can suppress the clogging of the filter member provided in the pressure relief opening.

(Aspect F)
Latent image formation such as at least a latent image carrier such as the photoreceptor 1, charging means such as a charging roller 4 for charging the surface of the latent image carrier, and an exposure device 7 that forms an electrostatic latent image on the latent image carrier. In the image forming apparatus such as the printer 100 having the developing means and the developing means for developing the electrostatic latent image, the developing means includes the developing device such as the developing device 5 according to any one of the aspects A to D.
According to this, as described in the above-described embodiment, it is possible to prevent clogging of the filter member provided in the pressure release opening, thereby preventing toner scattering from the developing device, and the apparatus using the scattered toner. Internal dirt and image quality deterioration can be prevented.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2a Cleaning blade 2 Cleaning apparatus 4 Charging roller 5 Developing apparatus 6 Image forming part 7 Exposure apparatus 8 Intermediate transfer belt 9 Primary transfer bias roller 10 Intermediate transfer cleaning apparatus 12 Secondary transfer backup roller 13 Cleaning backup roller 14 Tension roller 15 Intermediate transfer unit 19 Secondary transfer roller 20 Fixing device 26 Paper feed unit 27 Paper feed roller 28 Registration roller pair 29 Paper discharge roller pair 30 Stack unit 31 Toner container container 32 Toner container 40 Toner transport path 51 Developing roller 52 Doctor blade 53 First developer accommodating portion 54 Second developer accommodating portion 55 First conveying screw 56 Concentration detection sensor 57 Second conveying screw 58 Partition wall 59 Housing 60 Filter 61 Through hole 100 Printer 300 Gobe 301 CPU
302 ROM
303 RAM
511 Airflow generating section 512 Agent separating section 550 Development drive motor G Developer L Laser beam P Transfer material

JP 2012-189787 A JP 2007-248629 A JP2012-058609A

Claims (6)

A developer that carries a two-component developer comprising a toner and a carrier on the surface, moves the surface, and supplies the toner to the latent image on the surface of the latent image carrier in a development region facing the latent image carrier. A carrier,
A pressure is formed to form a developer accommodating portion that accommodates the developer to be supplied to the developer carrying member, discharge the gas in the developer accommodating portion to the outside of the apparatus, and suppress the increase in the atmospheric pressure in the developer accommodating portion. A developer container having an opening formed therein;
In a developing device comprising: a filter member provided at the pressure relief opening and preventing the developer from being discharged from the pressure relief opening.
The developer carrying member can move in the direction opposite to the direction of surface movement during the developing operation,
Reversing operation control means for moving the surface of the developer carrying member in the direction opposite to the surface moving direction during the developing operation,
The depressurization opening moves on the upstream side in the surface movement direction of the agent separation portion on the surface of the developer carrier relative to the pre-agent separation stay position where the developer stays on the surface of the developer carrier. So that the surface of the developer carrying member that has passed through the developing region faces the position that is on the downstream side in the surface moving direction with respect to the developer carrying member entering portion that enters the developing container. Formed,
The reverse operation control means performs reverse control to move the surface of the developer carrying member in a direction opposite to that during the developing operation, and removes the developer held at the staying position before the agent separation before performing the reverse control. A developing device which is brought into contact with the filter member. The developing device according to claim 1,
The surface movement distance of the developer carrier during the reverse rotation control is such that the surface of the developer carrier that was in the staying position before the agent separation before executing the reverse rotation control is a position facing the filter member. A developing device characterized in that it is at least a surface movement distance to reach. The developing device according to claim 1 or 2,
The developing device, wherein the reverse rotation control is executed after the developer carrying member has surface moved a predetermined distance in the surface movement direction during the developing operation from the previous reverse rotation control. The developing device according to claim 1 or 2,
A developing device, wherein the reverse rotation control is executed after the number of output sheets exceeds a threshold from the previous reverse rotation control. In an image forming apparatus comprising a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier, at least the latent image carrier and the developing unit are shared as a single unit. In the process cartridge that is held by the holding body and is detachable from the image forming apparatus main body,
A process cartridge comprising the developing device according to claim 1 as the developing means. At least a latent image carrier;
Charging means for charging the surface of the latent image carrier;
Latent image forming means for forming an electrostatic latent image on the latent image carrier;
In an image forming apparatus having developing means for developing the electrostatic latent image,
An image forming apparatus comprising the developing device according to claim 1 as the developing unit.

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