JP2015169894A - Rotation unit, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation unit which is capable of suppressing inclined contact of a contact member with an opposite member even in a configuration in which a shaft on one side and a shaft on the other side have different diameters, and to provide a process cartridge and image forming apparatus.SOLUTION: The rotation unit such as a development device has a shaft provided on a first contact member holding side plate such as a side part on one side of a development case, and a shaft provided on a second contact member holding side plate, with the diameters of the shafts being different. The shaft center O2 of a second shaft 52b as a small diameter shaft is provided on a first load part S1 side rather than a shaft center O1 of a first shaft 52a as a large diameter shaft in the view from the shaft direction of a contact member such as a development roller 5a, the first load part S1 being a location which applies load for an opposite member holding member from the large diameter shaft when the first contact member holding side plate and the second contact member holding side plate start to rotate by energization force by energization means such as a compression spring, with a contact part R between the contact member and an opposite member as a supporting point.

Description

  The present invention relates to a rotation unit, a process cartridge, and an image forming apparatus.

  A developing roller carrying toner as a one-component developer is brought into contact with the photosensitive drum on the electrostatic latent image formed on the surface of the photosensitive member, and the toner is attached to the electrostatic latent image on the surface of the photosensitive drum. An image forming apparatus that performs development is known.

  Patent Document 1 describes an image forming apparatus in which a developing roller of a developing device is rotatably supported on a photosensitive unit holding a photosensitive member so that the developing roller contacts and separates from the photosensitive member. Specifically, shaft portions are formed below the support portions that rotatably support the developing rollers on both side plates of the developing case of the developing device as the rotating unit, and these shaft portions are used as bearings of the photosensitive unit. The developing device is rotatably supported on the photoconductor unit by being fitted into each. Then, the developing device is biased toward the photosensitive member by a spring as a biasing means, whereby the developing device is rotated with the shaft portion as a fulcrum, and the developing roller is brought into contact with the photosensitive member with a predetermined contact pressure.

  It is described that the shaft portions provided on both side plates of the case of the developing device are protrusions protruding from the side plate of the developing case by bosses or driving pins.

  The developing case of the developing device is formed of resin, and when the shaft portion is formed of a boss, it is formed integrally with the developing case by injection molding. On the other hand, when the shaft part is formed with a driving pin, each side plate of the developing case is provided with a fitting hole in which the driving pin is fitted, and the shaft part is formed by fitting each driving pin into the fitting hole. Is done.

  The photoconductor unit has a photoconductor frame formed of resin, and a photoconductor, a charging device, a cleaning device, and the like are held on the frame. The photoconductor frame includes a first face plate portion that is orthogonal to the axial direction of the photoconductor and holds one end of the photoconductor in the axial direction, and is orthogonal to the axial direction of the photoconductor and the other axial end of the photoconductor. The second face plate portion for holding the face plate and a stay portion extending in parallel to the axial direction connecting the face plate portions. Both side plates of the case of the developing device face each face plate portion of the photoconductor frame from the inside, and each shaft portion is fitted into a bearing provided on each face plate portion to support the developing device on the photoconductor unit. .

  When both the shaft portions are formed as bosses integrally formed with the developing case by injection molding, first, the developing device is inclined with respect to the shaft of the photosensitive member, and one shaft portion is inserted into the bearing. Next, the developing device is assembled to the photosensitive unit by inserting the shaft portion into the bearing while elastically deforming the face plate portion to which the shaft portion is not inserted outward. Thus, when the shaft portion is a boss formed integrally with the developing case by injection molding, it is necessary to fit the shaft portion into the bearing while elastically deforming one of the face plate portions of the photoconductor frame outward. , There was a problem in assembly.

  On the other hand, when both shaft portions are driven pins, the developing device can be assembled to the photosensitive unit by inserting the driven pins into the bearings of the face plate portion from the outside and fitting them into the fitting holes of the developing case. In this case, the developing device can be assembled to the photoreceptor unit without elastically deforming the face plate portion of the photoreceptor frame. This makes it possible to easily assemble the developing device to the photosensitive unit as compared with the case where both shaft portions are bosses formed integrally with the developing case by injection molding. However, in the configuration in which both shaft portions are driven pins, the number of parts is increased, leading to an increase in cost.

  Therefore, the present applicant is developing a developing device in which the shaft portion of one side plate of the developing case is a boss formed integrally with the developing case by injection molding, and the shaft portion of the other side plate is driven and pinned. In this developing device, first, the developing device is inclined with respect to the shaft of the photosensitive member, and a shaft portion formed integrally with the developing case by injection molding is inserted into a bearing on one face plate portion. Next, the developing device can be assembled to the photoreceptor unit by inserting the driving pin into the bearing of the other face plate portion from the outside and fitting it into the fitting hole of the case of the developing device. Also in the developing device under development, the developing device can be assembled to the photoconductor unit without elastically deforming the face plate portion of the photoconductor frame outward. Further, by using one of the shaft portions as a boss formed integrally with the developing case by injection molding, the number of driving pins can be reduced, and the cost of the apparatus can be suppressed.

  However, when the developing device under development described above is used, there is a problem in that a problem that an image defect such as image omission or image density decrease occurs in an image near both ends in the axial direction. As a result of diligent research on the above-mentioned problem as described later, the present applicant has found that the above-mentioned problem occurs when the developing roller shaft is inclined with respect to the shaft of the photosensitive member due to the shaft portions having different diameters. It was.

  Further, the above-mentioned problem is that a developing device in which spacers are provided at both ends in the axial direction of the developing roller, the developing roller is brought into contact with the photosensitive member via the spacer, and the developing roller is provided with a predetermined gap with respect to the photosensitive member. Can occur in the same way. A similar problem occurs in a two-component developing system using a two-component developer having toner and carrier.

  In addition to the developing device, for example, a cleaning device, a transfer device, or the like is provided with a contact member (a cleaning member in the cleaning device, a transfer member in the transfer device) that contacts the mating member, and rotates to the image forming apparatus main body, etc. Also in the freely provided rotating unit, if the diameter of the rotating shaft is different between the one side and the other side in the axial direction, the contact member is inclined with respect to the counterpart member and affects the image.

  The present invention has been made in view of the above background, and the purpose of the present invention is to make the abutting member tilt and abut against the mating member even in a configuration in which one shaft portion and the other shaft portion have different diameters. And a rotation unit, a process cartridge, and an image forming apparatus.

  In order to achieve the above object, the invention of claim 1 holds the first contact member holding side plate that holds one axial direction of the contact member that contacts the counterpart member, and the other axial direction of the contact member. The second abutting member holding side plate, the first abutting member holding side plate and the second abutting member holding side plate, the abutting member of the first abutting member holding side plate and the second abutting member holding side plate. The shaft is provided at a position different from the holding portion for holding the member, and is rotatably attached to a counterpart member supporting member that supports the counterpart member, and the biasing means is provided so that the contact member abuts the counterpart member. In the rotation unit used in the image forming apparatus biased by the shaft portion, the shaft portion provided on the first contact member holding side plate and the shaft portion provided on the second contact member holding side plate are different from each other, Small diameter when viewed from the axial direction of the contact member The shaft center of the small diameter shaft portion, which is the shaft portion of the larger diameter, and the shaft member of the large diameter shaft portion, which is the shaft portion of the larger diameter, and the counterpart member of the contact member by the biasing force of the biasing means. When the first abutting member holding side plate and the second abutting member holding side plate are about to rotate with the abutting portion as a fulcrum, a load is applied to the mating member support member from the large diameter shaft portion. It is characterized in that it is provided on one load part side.

  According to the present invention, even when the one shaft portion and the other shaft portion have different diameters, it is possible to prevent the contact member from inclining and contacting the counterpart member.

1 is a schematic configuration diagram of a printer 1 according to an embodiment. FIG. 3 is a diagram illustrating a state in which an upper cover is opened with respect to a printer housing. Sectional drawing of an image forming unit. The perspective view of an image forming unit. The external view which simplified the developing device. FIG. 6 is a schematic diagram for explaining the behavior of the developing device after the developing roller comes into contact with the photosensitive member. (A) is a figure which shows the ideal positional relationship of a bearing and a shaft part. (B) is a figure which shows the positional relationship of an actual bearing and a shaft part. The figure explaining the conventional structure. FIG. 6 is a schematic diagram for explaining a locus of movement of the developing roller when the developing device rotates when the rotation center on one end side in the axial direction of the developing device is different from the rotation center on the other end side. The schematic diagram explaining the arrangement position of the 2nd axial part of this embodiment. The schematic diagram which shows the Example which provided the axial center O2 of the 2nd axial part in the contact part side with the bearing of a 1st axial part rather than the axial center O1 of a 1st axial part. Embodiment in which the contact portion S2 with the bearing of the second shaft portion is provided in the area of the circle U1 and on the line connecting the shaft center of the developing roller and the contact portion S1 of the bearing of the first shaft portion. FIG. FIG. 6 is a schematic diagram for explaining a locus of movement of both ends in the developing roller axial direction when the rotation center at one axial end of the developing device is on a line passing through the rotation center on the other end side and the axial center of the developing roller. The schematic diagram which shows the Example which made the contact part S2 with the bearing of a 2nd axial part correspond with the contact part S1 with the bearing of a 1st axial part. FIG. 3 is a perspective view showing the inside of a printer casing. The schematic diagram explaining the length of a long hole-shaped bearing.

  Hereinafter, an embodiment of an electrophotographic color printer (hereinafter simply referred to as a printer) 1 will be described as an image forming apparatus to which the present invention is applied.

  First, the basic configuration of the printer 1 will be described. FIG. 1 is a schematic configuration diagram of a printer 1 according to the embodiment. In the figure, the printer 1 includes four image forming units 7K, 7C, 7M, and 7Y for forming toner images of black, cyan, magenta, and yellow (hereinafter referred to as K, C, M, and Y). It has. These use different colors of K, C, M, and Y toners as image forming substances, but otherwise have the same configuration and are replaced when the lifetime is reached.

  An image forming unit 7K for forming a K toner image will be described as an example. As shown in FIG. 1, the image forming unit 7K includes a drum-shaped photosensitive member 6K as an image carrier, a drum cleaning device 3K, a charge eliminating device (not shown), a charging device 4K, and a writing head as a latent image forming unit. 70K, developing device 5K and the like. The image forming unit 7K is a process cartridge that can be attached to and detached from the printer body, and consumable parts provided in the image forming unit 7K can be replaced at a time.

  Note that the drum cleaning device 3K, the charging device 4K, and the developing device 5K do not have to be integrally supported by the process cartridge. That is, a configuration in which at least one device selected from the drum cleaning device 3K, the charging device 4K, and the developing device 5K is integrally supported as a process cartridge together with the photosensitive member 6 can be employed.

  The charging device 4K collects the charging roller 4aK rotating in the counterclockwise direction in the drawing while contacting the photosensitive member 6K rotated in the clockwise direction in the drawing by driving means (not shown) and the toner attached to the charging roller 4aK. And a collection roller 4bK. Then, by generating a discharge between the charging roller 4aK and the photosensitive member 6K, the surface of the photosensitive member 6K is uniformly charged.

  The writing head 70K has a plurality of light emitting elements such as LEDs and organic EL elements arranged in the axial direction of the photoreceptor 6K. The writing head 70K emits a light emitting element at a predetermined position based on image information and irradiates the photosensitive member 6K to expose the photosensitive member 6K, thereby forming an electrostatic latent image for K on the photosensitive member 6K. .

  The developing device 5K is provided with a developing roller 5aK as an abutting member that rotates while abutting on the photosensitive member 6K as a counterpart member, and the toner carried on the surface of the developing roller 5aK is transferred to the developing roller 5aK. In the developing area which is a contact portion between the photosensitive member 6K and the photosensitive member 6K, the photosensitive member surface is attached to the electrostatic latent image for K. By this adhesion, the electrostatic latent image for K is developed into a K toner image. Then, a K toner image is intermediately transferred from the photoreceptor 6K onto an intermediate transfer belt 8 described later.

  The drum cleaning device 3K removes transfer residual toner adhering to the surface of the photoreceptor after the intermediate transfer process.

  The static eliminator neutralizes residual charges on the photoreceptor 6K after being cleaned by the drum cleaning device 3K. By this charge removal, the surface of the photoreceptor 6K is initialized and prepared for the next image formation.

  The image forming unit 7K for K has been described so far, but the image forming units 7C, 7M, and 7Y for C, M, and Y also have C, M, and Y on the photoreceptors 6C, 6M, and 6Y by a similar process. M and Y toner images are formed.

  Below the image forming units 7K, 7C, 7M, and 7Y, a transfer unit 15 is disposed as a transfer unit that rotates the endless intermediate transfer belt 8 in a counterclockwise direction in the drawing. In addition to the intermediate transfer belt 8, the transfer unit 15 includes a driving roller 17, a driven roller 18, four primary transfer rollers 19K, 19C, 19M, and 19Y, a secondary transfer roller 14, a belt cleaning device 22, a cleaning backup roller 23, and the like. It has.

  The intermediate transfer belt 8 is rotatably stretched by a driving roller 17, a driven roller 18, a cleaning backup roller 23, and four primary transfer rollers 19K, 19C, 19M, and 19Y disposed inside the loop. Then, it is rotated in the same direction by the rotational force of the driving roller 17 that is driven to rotate counterclockwise in the figure by a driving means (not shown).

  The four primary transfer rollers 19K, 19C, 19M, and 19Y sandwich the intermediate transfer belt 8 that is moved endlessly in this manner between the photoreceptors 6K, 6C, 6M, and 6Y. By this sandwiching, primary transfer nips for K, C, M, and Y where the front surface of the intermediate transfer belt 8 and the photoreceptors 6K, 6C, 6M, and 6Y abut are formed.

  A primary transfer bias is applied to the primary transfer rollers 19K, 19C, 19M, and 19Y by a transfer bias power source (not shown). As a result, a transfer electric field is formed between the electrostatic latent images on the photoreceptors 6K, 6C, 6M, and 6Y and the primary transfer rollers 19K, 19C, 19M, and 19Y. In place of the primary transfer rollers 19K, 19C, 19M, and 19Y, a transfer charger, a transfer brush, or the like may be employed.

  When the Y toner formed on the surface of the photoconductor 6Y of the Y image forming unit 7Y enters the above-described primary transfer nip for Y as the photoconductor 6Y rotates, the photoconductor is exposed to light by the action of the transfer electric field and nip pressure. Primary transfer is performed from above the body 6Y onto the intermediate transfer belt 8. The intermediate transfer belt 8 on which the Y toner image has been primarily transferred in this way passes through the primary transfer nip for C, M, and Y along with the endless movement thereof, and thus is on the photoreceptors 6C, 6M, and 6Y. The C, M, and Y toner images are primarily transferred onto the Y toner image by sequentially overlapping them. A four-color toner image is formed on the intermediate transfer belt 8 by this primary transfer of superposition.

  The secondary transfer roller 14 of the transfer unit 15 is disposed outside the loop of the intermediate transfer belt 8 and sandwiches the intermediate transfer belt 8 with the driving roller 17 inside the loop. By this sandwiching, a secondary transfer nip is formed in which the front surface of the intermediate transfer belt 8 and the secondary transfer roller 14 come into contact with each other. A secondary transfer bias is applied to the secondary transfer roller 14 by a transfer bias power source (not shown). By this application, a secondary transfer electric field is formed between the secondary transfer roller 14 and the drive roller 17 connected to the ground.

  Below the transfer unit 15, a paper feed cassette 30 that stores a plurality of recording papers P in a stack of paper sheets is detachably attached to the housing of the printer 1. In the paper feed cassette 30, a paper feed roller 30a is brought into contact with the top recording paper P of the paper bundle, and the recording paper is rotated by rotating it in a counterclockwise direction in the drawing at a predetermined timing. P is sent out toward the paper feed path 31.

  A pair of registration rollers (not shown) is disposed near the end of the paper feed path 31. The registration roller pair stops the rotation of both rollers as soon as the recording paper P delivered from the paper feed cassette 30 is sandwiched between the rollers. Then, rotation driving is restarted at a timing at which the sandwiched recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 8 in the above-described secondary transfer nip, and the recording paper P is directed to the secondary transfer nip. Send it out.

  The four-color toner image on the intermediate transfer belt 8 brought into intimate contact with the recording paper P at the secondary transfer nip is batch-transferred onto the recording paper P under the influence of the secondary transfer electric field and nip pressure, and the recording paper Combined with the white color of P, a full color toner image is obtained. The recording paper P having a full-color toner image formed on the surface in this way is separated from the secondary transfer roller 14 and the intermediate transfer belt 8 by curvature when passing through the secondary transfer nip. Then, it passes through a post-transfer conveyance path 33 and is sent to a fixing device 34 to be described later.

  Untransferred toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned from the belt surface by a belt cleaning device 22 that is in contact with the front surface of the intermediate transfer belt 8. The cleaning backup roller 23 disposed inside the loop of the intermediate transfer belt 8 backs up the cleaning of the belt by the belt cleaning device 22 from the inside of the loop.

  The fixing device 34 forms a fixing nip by a fixing roller 34a containing a heat source such as a halogen lamp (not shown) and a pressure roller 34b that rotates while contacting the fixing roller 34a with a predetermined pressure. The recording paper P fed into the fixing device 34 is sandwiched between the fixing nips such that the unfixed toner image carrying surface is brought into close contact with the fixing roller 34a. Then, the toner in the toner image is softened by the influence of heating and pressurization, and the full color image is fixed.

  After the recording paper P discharged from the fixing device 34 passes through the post-fixing conveyance path 35, the recording paper P is sandwiched between the post-fixing conveyance path 35 and the rollers of the paper discharge roller pair 36. The recording paper P sandwiched between the paper discharge roller pair 36 is discharged to the outside of the apparatus and is stacked on the stack portion that is the upper surface of the upper cover 50 of the housing.

  The upper cover 50 of the casing of the printer 1 is supported so as to be rotatable about the shaft member 51, and is opened with respect to the casing as shown in FIG. 2 by rotating counterclockwise in the figure. It becomes a state. Thereby, the upper part of the housing is greatly opened, and the image forming units 7Y, 1M, 1C, and 1K arranged in the housing are exposed. The image forming units 7K, 7C, 7M, and 7Y can be attached to and detached from the printer main body with the upper cover 50 opened with respect to the housing. Thereby, it is possible to improve the maintainability of each image forming unit 7 and the photoconductor 6 and the developing device 5 provided in the image forming unit 7.

  The write heads 70K, 70C, 70M, and 70Y are held by the upper cover 50, and are put out from the inside of the housing to the outside by opening the upper cover 50 with respect to the housing.

FIG. 3 is a cross-sectional view of the image forming unit 7.
As described above, the image forming units 7K, 7C, 7M, and 7Y have the same configuration. Therefore, in the following description, the color code is omitted.
The image forming unit 7 includes a photoconductor unit 40 including a photoconductor 6, a charging device 4, a drum cleaning device 3, and the like, and a developing device 5.
The photoconductor 6, the charging device 4, the drum cleaning device 3, and the like are held by a photoconductor frame 43 as a counterpart member support member of the photoconductor unit 40.

  The developing device 5 includes a developing case 56 that contains toner or the like therein, a developing roller 5a as a developer carrying member that carries toner, and a supply roller 5b as a developer supply member that supplies toner to the developing roller 5a. have. The developing device 5 includes a regulating blade 5d as a regulating member that regulates the thickness of the toner carried on the developing roller 5a, a conveying screw 5c as a conveying member that conveys toner, and an agitating member that agitates the toner. As an agitator 5f.

  An opening 56a is formed in the lower portion of the developing case 56 facing the photosensitive member 6, and the developing roller 5a is rotatably provided in the opening 56a. The developing roller 5a is made of a metal core, an elastic layer made of an elastic member or a foamed elastic member disposed on the outer periphery of the core, an acrylic resin, a silicone resin, or the like disposed on the outer periphery of the elastic layer. And a surface layer (resin coat layer). The developing roller 5a may not have a surface layer.

  The supply roller 5b is composed of a sponge roller in which an elastic layer made of a foamed elastic member is disposed on the outer periphery of a metal cored bar. Examples of the material for the foamed elastic member include flexible urethane foam, silicone, and foamed polymer. Moreover, you may use what adjusted the resistance value by adding a electrically conductive material to these materials. The supply roller 5b is in contact with the developing roller 5a, and a nip (hereinafter referred to as “supply nip”) is formed between the rollers 5a and 5b.

  The regulation blade 5d is made of, for example, a metal plate such as SUS having a thickness of about 0.1 mm. The front end of the regulating blade 5d is in contact with the surface of the developing roller 5a to form a nip (hereinafter referred to as “regulating nip”).

  When an instruction to start the image forming operation is given, the toner in the developing case 56 is stirred by the agitator 5f and supplied to the supply roller 5b by the conveying screw 5c. The toner supplied to the supply roller 5b is frictionally charged by the friction between the supply roller 5b and the developing roller 5a at the supply nip and supplied to the surface of the developing roller 5a.

  The toner carried on the developing roller 5a passes through the regulation nip of the regulation blade 5d, so that the thickness of the toner layer is regulated and at the same time frictionally charged. When the toner on the developing roller 5a is conveyed to a position (development area) facing the photosensitive member 6, the toner is applied on the photosensitive member 6 by the force of the electric field generated between the photosensitive member 6 and the developing roller 5a. A toner image is formed by transferring to an electrostatic latent image.

  A first shaft portion 52a and a second shaft portion 52b are provided on each side surface of the developing case 56, respectively. As shown in FIG. 3, the diameter of the 1st axial part 52a is larger than the diameter of the 2nd axial part 52b. The developing device 5 is supported by these shaft portions 52a and 52b so as to be rotatable in the A direction or the B direction in the drawing. For this reason, the developing roller 5a is configured to be movable in a direction approaching and separating from the photosensitive member 6. The developing device 5 is urged in the A direction by a compression spring 54 as an urging unit.

FIG. 4 is a perspective view of the image forming unit 7.
The photoconductor frame 43 includes a stay portion 42 that extends in the axial direction, and a face plate portion 41 that is provided at both axial ends of the stay portion 42 and is a surface perpendicular to the axial direction. The face plate portion 41 on one side of the photoconductor frame 43 is provided with a bearing 41b that receives the first shaft portion 52a. The first shaft portion 52a is fitted to the bearing 41b with a gap. Similarly, a bearing for receiving the second shaft portion 52b is also formed on the other face plate portion (not shown) of the photoconductor frame 43, and the second shaft portion 52b is fitted to the bearing with a gap. Thereby, the developing device 5 is attached to the photoreceptor unit 40 so as to be rotatable.

  Each face plate portion 41 of the photoconductor frame 43 is provided with a spring receiver 41a for receiving one end of the compression spring 54 (only one end side in the axial direction is shown in FIG. 4). The developing case 56 is also provided with a spring receiver 57a for receiving the other end of the compression spring 54. The compression spring 54 is attached in a compressed state to the spring receivers 41a and 57a. As a result, the developing device 5 is urged toward the photosensitive unit 40 by the compression spring 54 and rotates around the shaft portion 52, and the developing roller 5a is applied to the photosensitive member 6 by the urging force of the compression spring 54. Touch. Thereby, a nip (hereinafter referred to as “development nip”) is formed between the developing roller 5 a and the photosensitive member 6.

  It is desirable to apply the contact pressure of the developing roller 5a to the photosensitive member 6 as lightly as possible without causing image omission. This is because the following three main problems can be suppressed by increasing the contact pressure. First, the first problem is a problem due to an increase in driving torque. More specifically, the developing roller 5a is in contact with the photosensitive member 6, and has a certain friction coefficient in the contact state. For this reason, when the pressing force is increased, the friction is increased, so that a torque for rotating both of them is required. When the torque becomes high, a large motor and a current that generate a larger driving torque are required for driving, which causes a problem that the cost is increased and the apparatus is expanded.

  The second problem is a problem due to toner deterioration. More specifically, the toner layer formed on the developing roller 5a in the developing device rubs against the supply roller 5b, the regulating blade 5d, and the like, and also rubs against the photoreceptor 6. When a force such as rubbing is applied to the toner in the developing device, the toner is broken or the external additive on the surface of the toner is peeled off. As a result, so-called deterioration of the toner occurs, and the chargeability of the toner may change or the toner may be softly aggregated or fixed. As a result, there arises a problem that a density change (thin density) due to a charge change of the toner or a vertical streak of the image occurs due to soft aggregation or fixing of the toner on the regulating blade 5d. Further, as described above, when the contact pressure is high and the driving torque is high, heat is generated at that portion, and this heat becomes one factor that causes the deterioration of the toner.

  The third problem is a problem due to wear of the photoreceptor. More specifically, the developing roller 5a has a minute roughness on the surface in order to convey toner. Further, the peripheral speed on the surface of the developing roller 5a is generally faster than the peripheral speed on the surface of the photosensitive member in order to stabilize the density. Therefore, the surface of the developing roller is rubbed against the photoreceptor 6. For this reason, the surface of the photoreceptor is scraped with the passage of time. When the developing roller 5a is strongly pressed, the photoreceptor 6 is also quickly worn, and when the photoreceptor 6 is severely worn, a problem occurs that the image density is lowered.

  By applying the contact pressure of the developing roller 5a to the photosensitive member 6 as lightly as possible without causing image omission, the above three problems can be suppressed. That is, an increase in driving torque can be suppressed, and an increase in cost and expansion of the apparatus can be suppressed. Further, toner deterioration and photoconductor 6 wear can be suppressed, and a good image can be maintained over time.

FIG. 5 is a simplified external view of the developing device 5.
As shown in FIG. 5, the first shaft portion 52a provided on one side plate portion of the developing case 56 is a resin protrusion formed integrally with the resin developing case 56, and the first shaft portion 52a provided on the other side plate portion. The biaxial portion 52b is a metal driving pin. The other side plate portion of the developing case is provided with a fitting hole 56b into which the driving pin is fitted, and the second shaft portion 52b is formed by fitting the driving pin into the fitting hole 56b. .

  The first shaft portion 52a, which is a resin protrusion, has a lower rigidity than a metal. Therefore, if the diameter is the same as that of the metal second shaft portion 52b, the first shaft portion 52a may be deformed. Further, when the driving pin constituting the second shaft portion 52b is made of the same material and the same diameter as the first shaft portion 52a, it is necessary to manufacture a driving pin dedicated to this device, leading to an increase in the cost of the device. Therefore, in this embodiment, a general-purpose driving pin is used. Therefore, the diameter is shorter than that of the first shaft portion 52a.

  Further, in the present embodiment, the photosensitive body frame 43 in which the stay portion 42 and each face plate portion 41 are integrally molded with resin is used. This is because when the stay portion 42 and each face plate portion 41 are separated, an assembly tolerance between the stay portion and the face plate portion is generated. As a result, the positional accuracy between the photosensitive member 6 held by the photosensitive member frame 43 and the charging device 4, the drum cleaning device 3, and the developing device 5 may be deteriorated, and a high-quality image may not be formed. Therefore, in the present embodiment, the photoconductor frame 43 in which the stay portion 42 and each face plate portion 41 are integrally molded with resin is used.

  However, by using such a photoconductor frame, when the first shaft portion 52a and the second shaft portion 52b are resin protrusions that are integrally molded with the developing case 56, the following problems occur. That is, one of the first shaft portion 52a and the second shaft portion 52b can be inserted into the bearing 41b formed on the face plate portion 41 of the photoconductor frame 43 while the developing device 5 is inclined with respect to the axial direction. it can. However, the other cannot be inserted into the bearing 41b unless the face plate portion is deformed outward. Accordingly, there arises a problem that the assembling workability of the developing device 5 is poor.

  On the other hand, by setting both the first shaft portion 52a and the second shaft portion 52b as driving pins, the driving device is mounted on the photosensitive member frame 43, and then the driving pin is inserted from the bearing 41b of the photosensitive member frame 43. And fit into the developing case. Thus, the developing device 5 can be assembled to the photoconductor frame 43 without deforming the face plate portion of the photoconductor frame 43, and the assembling workability is improved. However, in this case, since the number of parts increases, there arises a problem that the cost of the apparatus is increased.

  In this embodiment, from such a background, the first shaft portion 52a is a resin protrusion, and the second shaft portion 52b is a driving pin. With this configuration, the developing device 5 can be assembled to the photoconductor frame 43 as follows. That is, first, the first shaft portion 52 a of the resin protrusion is inserted into the bearing 41 b of the photoconductor frame 43. Next, the developing device 5 is assembled to the photoconductor frame by inserting the driving pin from the bearing 41b of the photoconductor frame 43 and fitting it into the fitting hole of the developing case. In this way, the developing device 5 is assembled to the photoconductor frame without deforming the face plate portion 41 of the photoconductor frame 43 by using the first shaft portion 52a as a resin protrusion and the second shaft portion 52b as a driving pin. Can do. Therefore, assembling workability can be improved as compared with the case where both shaft portions are made of resin protrusions. Further, compared to the case where both shaft portions are driven pins, an increase in the number of parts can be suppressed, and an increase in the cost of the apparatus can be suppressed.

  Conventionally, the centers of the first shaft portion 52a of the resin protrusion and the second shaft portion 52b made of a driving pin are aligned. However, in this case, there is a problem that an image defect such as so-called image omission or image density reduction in which images are not formed at both ends in the axial direction occurs. As a result of earnest research on this defect, the present applicant has found the following.

FIG. 6 is a schematic diagram for explaining the behavior of the developing device 5 after the developing roller 5a contacts the photoconductor 6. FIG.
As described above, the developing device 5 applies a load by the compression spring 54 and presses the developing roller 5 a against the photosensitive member 6 in order to bring the developing roller 5 a into contact with the photosensitive member 6. Therefore, when the developing roller 5a hits the photosensitive member 6, the developing device 5 tries to rotate counterclockwise in the drawing with the contact portion R between the developing roller 5a and the photosensitive member 6 as a fulcrum by the compression spring 54. As a result, the shaft portions 52a and 52b are moved while taking a track whose radius is a line segment connecting the contact portion R between the photosensitive member 6 and the developing roller 5a and the center of the shaft portion from the compression spring 54. The urging power to do is added.

  The bearing 41b on which the shaft portions 52a and 52b are rotatably supported is made larger than the diameter of the shaft portion so that the shaft portions 52a and 52b can smoothly rotate within the bearing. For this reason, there is a gap of about 0.06 mm between the shaft portions 52a, 52b and the bearing 41b, for example. Accordingly, the shaft portions 52a and 52b move in the bearing 41b and are not positioned at the ideal positions as shown in FIG. 7A, but as shown in FIG. It hits the upper position. As a result, as shown in FIG. 8, the first shaft portion 52a abuts against the bearing 41b at the position S1 in the drawing, and the second shaft portion 52b having a diameter smaller than that of the first shaft portion 52a is indicated by S2 in the drawing. It strikes the bearing 41b at the position.

  The photosensitive member 6 and the developing roller 5a are not perfect circles, and the outer peripheral surface has some degree of fluttering with respect to the center of rotation. That is, the radius of the photosensitive member 6 and the developing roller is not constant in the circumferential direction with respect to the center of rotation. The amount of change is about 0.2 mm for the developing roller 5 a and about 0.05 mm for the photosensitive member 6. Therefore, when the developing roller 5a and the photosensitive member 6 are in contact with each other, the distance between the photosensitive member center and the developing roller center constantly changes. Since the distance connecting the center of the photosensitive member and the center of the developing roller changes, the developing device always rotates slightly in the directions of arrows A and B shown in FIG. 3 with the shaft portions 52a and 52b as fulcrums. While in contact with the photoconductor. Here, the rotation operation of the developing device is a reciprocal rotation operation within an angle range of several degrees.

  Conventionally, it has been considered that the developing device 5 at this time rotates around the centers O1 and O2 of the shaft portions 52a and 52b. Therefore, conventionally, as shown in FIG. 8, the center O1 of the first shaft portion 52a and the center O2 of the second shaft portion 52b are configured to coincide with each other. However, as a result of diligent research by the present applicant, it has been found that the developing device 5 is actually rotating around the position where the shaft portions 52a and 52b abut against the bearing 41b. In the present embodiment, the diameter of the first shaft portion 52a and the diameter of the second shaft portion 52b are greatly different. Therefore, when the center O1 of the first shaft portion 52a and the center O2 of the second shaft portion 52b are made to coincide with each other, the center position of the rotation on one end side in the axial direction of the developing device (the first shaft portion 52a is a bearing). The position that is in contact with 41b (S1) and the center position of rotation on the other end side (position in which the second shaft portion 52b is in contact with the bearing 41b) (S2) are greatly different.

FIG. 9 is a schematic diagram for explaining the locus of movement of the developing roller 5a when the developing device 5 is rotated when the rotation center on one end side in the axial direction of the developing device 5 is different from the rotation center on the other end side. FIG.
When the developing device 5 is rotated clockwise in the drawing so that the developing roller 5a moves in a direction away from the photosensitive member 6 from the position shown in FIG. One end side of 5a is located upstream of the standard position in the direction of movement of the photoreceptor surface. On the other hand, the other end side is located downstream of the standard position in the movement direction of the photoreceptor surface.

  Further, when the developing device 5 is rotated counterclockwise in the drawing so that the developing roller 5a moves from the position shown in FIG. 9 to the photosensitive member 6, the one end side of the developing roller is more than the standard position. Located downstream of the photoreceptor surface movement direction. On the other hand, the other end side is located upstream of the standard position in the direction of movement of the photoreceptor surface. That is, the developing roller 5a moves around a line segment connecting the center of the photosensitive member 6 and the center of the developing roller 5a with the axial center of the developing roller 5a as a fulcrum.

  If the center of rotation of the developing device 5 is the same position on the one end side and the other end side, even if the developing device 5 is rotated by the deflection of the photosensitive member 6 or the like, the shaft of the developing roller is It remains parallel to the axis. However, as shown in FIG. 9, if the center of rotation of the developing device 5 is different between the one end side and the other end side, when the developing device 5 rotates due to the flare of the photosensitive member 6, the shaft of the developing roller 5. Is inclined with respect to the axis of the photoreceptor.

  In the cylindrical photosensitive member 6 and the cylindrical developing roller 5a, when the axis of the developing roller 5a is tilted with respect to the axis of the photosensitive member 6 as described above, the developing roller 5a is in contact with the photosensitive member 6 only at one point. Stop touching. That is, it is one point in the central portion in the developing roller axial direction. Actually, since the developing roller 5a is made of rubber, it is crushed and contacted to some extent due to its elasticity. Therefore, the contacting portion has a width instead of a single point, but it still tends to be non-contact at both ends in the axial direction. The contact pressure near the part also decreases. In the present embodiment, as described above, the contact pressure between the photosensitive member 6 and the developing roller 5a is applied as lightly as possible without causing image loss. As a result, as described above, even if the vicinity of both ends is not in contact, the contact pressure decreases to a level at which image loss occurs, and image loss occurs near both ends in the axial direction.

  As a result of such diligent research, the present applicant has found the cause of image omission at both ends in the axial direction. And in order to suppress such an image omission at both ends in the axial direction, the present embodiment is configured as follows.

FIG. 10 is a schematic diagram for explaining the arrangement position of the second shaft portion 52b of the present embodiment.
As shown in FIG. 8, the pivot point on the first shaft portion 52a side when the shaft center O1 of the first shaft portion 52a and the shaft center O2 of the second shaft portion 52b are matched, The amount of deviation from the pivot point on the second shaft portion 52b side can be approximated as follows. That is, when the radius of the first shaft portion 52a is r1 and the radius of the second shaft portion 52b is r2, the rotation fulcrum on the first shaft portion 52a side and the rotation fulcrum on the second shaft portion 52b side are The amount of deviation can be approximated as r1-r2. As shown in FIG. 8, the rotation fulcrum S2 on the second shaft portion side of the developing roller is a line connecting the center O1 of the first shaft portion and the rotation fulcrum S1 on the first shaft portion side. It ’s not on the minute. Therefore, although the actual amount of deviation is slightly larger than r1-r2, the difference between the actual amount of deviation and r1-r2 is small, so that the amount of deviation can be approximated by r1-r2. Therefore, if the amount of deviation is smaller than the approximate amount of deviation r1-r2, the photosensitive member surface movement at both ends of the developing roller is compared to the case where the axial centers of the first shaft portion 52a and the second shaft portion 52b are made coincident. Directional movement can be suppressed. Therefore, in the present embodiment, the contact portion S2 (the portion where the urging force of the compression spring 54 acts from the second shaft portion 52b to the photosensitive unit) with the bearing 41b of the second shaft portion 52b is represented by a circle U1 shown in FIG. Provide in the area. The circle U1 has a radius (r1-r2) centered on a contact portion S1 of the first shaft portion 52a with the bearing 41b (where the urging force of the compression spring 54 acts from the first shaft portion 52a to the photosensitive unit). The circle. Since the contact portion S2 is located at least in the region of the circle U1, the amount of deviation between the rotation fulcrum on the first shaft portion 52a side and the rotation fulcrum on the second shaft portion 52b side is set to (r1 -R2).

  Specifically, as shown in FIG. 11, the shaft center O2 of the second shaft portion 52b is closer to the contact portion S1 side with the bearing 41b of the first shaft portion 52a than the shaft center O1 of the first shaft portion 52a. Provide. Accordingly, the contact portion S2 can be positioned in the area of the circle U1, and the amount of deviation between the pivot point on the first shaft portion 52a side and the pivot point on the second shaft portion 52b side is determined as follows. (R1-r2) or less. Therefore, it is possible to suppress movement in the direction of movement of the photoreceptor surface at both ends of the developing roller as compared with the case where the axial centers of the first shaft portion 52a and the second shaft portion 52b are matched. As a result, it is possible to suppress a decrease in the contact pressure with the photoconductor near both ends in the axial direction of the developing roller 5a, and it is possible to suppress image omission near both ends in the axial direction.

  Also, as shown in FIG. 12, the contact portion S2 of the second shaft portion 52b with the bearing 41b is located within the area of the circle U1, and between the shaft center of the developing roller 5a and the bearing 41b of the first shaft portion 52a. It is preferable to provide on the line which connected contact part S1.

  FIG. 13 shows the movement of both ends in the axial direction of the developing roller 5a when the rotational center S2 on the other axial end side of the developing device 5 is on a line passing through the rotational center S1 on the one end side and the axial center of the developing roller 5a. It is a schematic diagram explaining the locus | trajectory. As shown in FIG. 13, when the rotation center S2 at the other axial end of the developing device 5 is on a line passing through the rotation center S1 at one end and the axial center of the developing roller 5a, the developing roller 5a is in the standard position. Even when the developing roller is rotated several times from the state in FIG. 4, there is almost no positional deviation between the one end side and the other end side in the axial direction. Specifically, the other end side whose rotation center is close to the standard position is slightly located downstream of the one end side in the photosensitive member moving direction. That is, in the case shown in FIG. 9, when the developing roller 5a moves to the axial center side of the photosensitive member 6 and moves to the side away from the axial center of the photosensitive member, both of them are on the one end side of the developing roller. The moving direction and the moving direction on the other end side are different from each other. As a result, the developing roller 5a is twisted (movement that rotates around the axial center of the developing roller). On the other hand, in the case shown in FIG. 13, when the developing roller moves to the axial center side of the photosensitive member and when it moves in a direction away from the axial center of the photosensitive member, one end side and the other end side of the developing roller are both Move in the same direction. As a result, the other end side of the developing roller with a slight movement amount is slightly inclined. Therefore, as shown in FIG. 12, the contact portion S2 of the second shaft portion 52b with the bearing 41b is located within the area of the circle U1, and the shaft center of the developing roller 5a and the bearing 41b of the first shaft portion 52a. By providing it on the line connecting the contact portion S1 with the photosensitive member, it is possible to prevent the developing roller 5a from being almost inclined with respect to the axis of the photosensitive member when the developing device rotates due to the photosensitive member flare or the like. As a result, it is possible to further suppress the decrease in the contact pressure with the photoconductor near the both ends in the axial direction of the developing roller, and it is possible to further suppress the image omission near the both ends in the axial direction.

  Further, as shown in FIG. 14, it is more preferable that the contact portion S2 of the second shaft portion 52b with the bearing 41b coincides with the contact portion S1 of the first shaft portion 52a with the bearing 41b. With such a configuration, the fulcrum on one end side in the axial direction when the developing device 5 rotates due to the photosensitive member fluff or the like can coincide with the fulcrum on the other end side. As a result, the developing roller 5a does not tilt with respect to the shaft of the photosensitive member 6, and the contact pressure between the developing roller 5a and the photosensitive member 6 can be maintained uniformly in the axial direction. As a result, a good image can be obtained without image omission.

FIG. 15 is a perspective view showing the inside of the housing of the printer 1.
As shown in FIG. 15, the housing 90 of the printer 1 is made of sheet metal, and the side plates 90 a of the housing 90 are provided with guide grooves 91 </ b> Y, M, C, and K for guiding the image forming unit 7. ing. The guide grooves 91Y, 91M, 91C, and 91K are formed by projecting a part of the side plate 90a of the sheet metal into the housing by drawing.

  Further, as shown in FIG. 4, each face plate portion 41 of the photoconductor frame 43 is provided with a positioning boss 44 for positioning the image forming unit 7 within the housing 90 of the printer 1. When the image forming unit 7 is mounted in the printer housing 90, the photosensitive member shaft 6 a and the positioning boss 44 located above the photosensitive member shaft 6 a are inserted into the guide groove 91. Then, the image forming unit 7 is positioned in the housing 90 by bringing the photosensitive member shaft 6 a into contact with a bottom portion (not shown) of the guide groove 91. By using the photosensitive member shaft 6a as a reference for positioning with respect to the housing 90, the positional deviation of the photosensitive members 6 of the respective colors with respect to the moving direction of the intermediate transfer belt 8 can be suppressed, and the color deviation can be suppressed. In addition, it is possible to suppress the deviation of the exposure position relative to the photoreceptor 6 from the specified position, and to suppress the color deviation.

  If only the photosensitive member shaft 6 a is inserted into the guide groove 91, the image forming unit 7 may rotate around the photosensitive member shaft 6 a in the housing 90. Therefore, in order to prevent rotation and maintain the posture, the positioning boss 44 is also inserted into the guide groove 91 to fix the posture of the image forming unit 7 in the housing.

  Each component constituting the printer housing 90 is accurate, but an assembly error occurs when the housing 90 is assembled, and the positional relationship between the side plate 90a on the one side in the axial direction and the side plate on the other side is increased. It may be slightly off. Further, depending on the location where the printer 1 is installed, the housing 90 may be twisted. Specifically, when the printer 1 is installed on a horizontal surface, the housing 90 is not twisted, but in some circumstances, such as a surface where the surface on which the printer 1 is installed is uneven, the housing 90 May twist. In particular, in a small printer that can be installed on a desk or the like, the installation surface is likely to be installed on a non-horizontal surface. If the housing 90 is twisted, the positional relationship between the side plate 90a on one side in the axial direction and the side plate 90a on the other side may be shifted.

  As described above, when the positional relationship between the side plate 90a on one side in the axial direction and the side plate 90a on the other side is shifted, the image forming unit 7 whose posture is fixed to the guide groove 91 of each side plate is twisted about the axial direction. Power is generated. Specifically, force is applied to the positioning boss 44 provided on each face plate portion 41 of the photoconductor frame 43, and each face plate portion 41 of the photoconductor frame 43 is twisted. At this time, when the bearing 41 b provided in each face plate portion 41 is a hole having substantially the same diameter as each shaft portion of the developing device 5, the developing device 5 is similarly twisted by the twist of each face plate portion 41. As a result, the developing roller 5a of the developing device 5 is inclined due to the twist of each face plate portion 41. On the other hand, the photosensitive shaft 6a that is a positioning reference and contacts the bottom of the guide groove 91 is not affected by the twist of each face plate portion 41 as described above. As a result, the developing roller 5a is inclined with respect to the photosensitive member shaft 6a, and as described above, the contact pressure with the photosensitive member 6 near both ends in the developing roller axial direction is lowered, and there is a possibility that image omission occurs.

  For this reason, it is preferable that the bearing that receives the first shaft portion 52a and / or the bearing that receives the second shaft portion 52b is an elongated hole extending in a direction in which the bearing is in contact with or separated from the photoreceptor 6. Thus, by making the bearing into a long hole, when the face plate portion 41 of the photoconductor frame 43 is kinked and the position of the bearing is deviated from the specified position, the shaft portion of the developing device moves inside the long hole-shaped bearing. Move relatively and keep the specified position. As a result, at least on the side where the shaft portion of the developing device 5 is held by the long hole bearing, even if the face plate portion 41 is twisted, the positional relationship of the developing roller 5a with the photosensitive member 6 does not change, and a predetermined value is obtained. The contact pressure can be maintained. Thereby, a bearing can suppress the fall of the contact pressure of the edge part by the side of a long hole, and a bearing can suppress omission of the image of the edge part by the side of a long hole.

  When the bearing is a long hole, the position of the shaft portion in the bearing varies due to the torsion of the face plate portion 41 as described above. Further, during the operation of the developing device, the shaft portion may move slightly in the bearing. Therefore, in this case, the bearing 41b can be located at any position within the range that the shaft portion can take in the long hole bearing due to the twist of the face plate portion 41 or the movement of the shaft portion due to the operation of the developing device. The length and position of the long hole 41b are set so that the contact portion S2 between the first shaft portion 52b and the second shaft portion 52b enters the circle U1.

  In the above description, the embodiment in which the present invention is applied to the contact-type developing device 5 that develops the developing roller 5a in contact with the photosensitive member 6 has been described. However, the present invention provides a non-contact type developing device in which the developing roller 5a is brought into contact with the photosensitive member 6 via a spacer or the like, and a predetermined gap is provided between the developing roller 5a and the photosensitive member 6 for development. Is also applicable. In this non-contact type developing device, if the rotation fulcrum on the first shaft portion 52a side and the rotation fulcrum on the second shaft portion 52b side are different and the developing roller 5a is inclined with respect to the shaft of the photosensitive member 6, the shaft The gap at both ends in the direction is wider than specified. As a result, the image density in the vicinity of both ends in the axial direction is reduced, or in the worst case, the developer does not come into contact with the photosensitive member 6 and image omission occurs in the vicinity of both ends in the axial direction. Therefore, by applying the present invention to such a non-contact type developing device, it is possible to suppress the inclination of the developing roller 5a with respect to the photoreceptor 6, and it is possible to suppress a decrease in image density and image omission at both ends in the axial direction. In the non-contact type developing device 5, both a one-component developer composed only of toner and a two-component developer composed of toner and carrier can be applied as a developer.

  Furthermore, the present invention can be applied not only to the developing device but also to a rotating unit such as a secondary transfer device or a cleaning device that is rotatably attached to the image forming apparatus main body. For example, in a cleaning device, it is rotatably attached to the apparatus main body, and is urged toward the photosensitive member by an urging means so that a cleaning member such as a cleaning blade is brought into contact with the photosensitive member. Even in such a configuration, the cleaning device is rotated by the shaft portion due to the deflection of the photosensitive member. At this time, if the diameters of the one axis in the axial direction and the other axis are different from each other and the centers of these shaft portions are coincident with each other, the one movement locus and the other movement locus of the cleaning member in the axial direction are mutually different. Different. As a result, the cleaning member is inclined with respect to the axis of the photoconductor, the contact pressure at both ends in the axial direction is lowered, and there is a possibility that a cleaning failure may occur. On the other hand, by applying the present invention, such an inclination of the cleaning member can be suppressed, and good cleaning properties can be maintained.

  Further, in the secondary transfer apparatus, the apparatus is rotatably attached to the apparatus main body, and is urged toward the intermediate transfer belt by the urging means so that a transfer member such as a secondary transfer roller is brought into contact with the intermediate transfer belt. When the paper enters the secondary transfer nip, the secondary transfer device rotates about the shaft as a fulcrum according to the paper thickness of the paper. At this time, if one axis in the axial direction and the other axis have different diameters, and the centers of these axes coincide with each other, one movement locus and the other movement locus of the transfer member are different from each other. . As a result, the transfer member is inclined with respect to the axis of the secondary transfer counter roller, the transfer pressure at both ends in the axial direction is lowered, and transfer failure may occur. On the other hand, by applying the present invention, it is possible to suppress such an inclination of the transfer member and maintain good transferability.

What has been described above is an example, and the present invention has a specific effect for each of the following aspects.
(Aspect 1)
The first abutting member holding side plate such as the side plate portion of the developing case that holds one axial direction of the abutting member such as the developing roller 5a that abuts the counterpart member such as the photosensitive member 6 and the other axial direction of the abutting member are held. Holding the second contact member holding side plate, the first contact member holding side plate and the second contact member holding side plate, and holding the first contact member holding side plate and the second contact member holding side plate. A compression spring is provided so that the shaft is provided at a position different from the holding portion, and is rotatably attached to a counterpart member support member such as a photoreceptor frame 43 that supports the counterpart member, and the contact member abuts the counterpart member. In a rotating unit such as the developing device 5 used in the image forming apparatus urged by the urging means such as 54, a shaft portion provided on the first contact member holding side plate and a second contact member holding side plate are provided. The shaft and the diameter are different from each other. When viewed from the axial direction of the member, the shaft center of the small-diameter shaft portion such as the second shaft portion 52b that is the small-diameter shaft portion is the large-diameter shaft such as the first shaft portion 52a that is the large-diameter shaft portion. The first abutting member holding side plate and the second abutting member holding side plate try to rotate with the abutting portion R of the abutting member with the mating member as a fulcrum by the urging force of the urging means rather than the axial center of the portion. When this is done, it is provided on the side of the first load portion (in this embodiment, the position where the first shaft portion 52a hits the bearing 41b) where a load is applied to the counterpart member support member from the large diameter shaft portion.

  As described above, as a result of intensive research on the reason why abnormal images such as image omission and image density reduction occur near the both ends in the axial direction in the developing device under development, the present applicant has found the following. That is, in the developing device under development, since the shaft portion made of the boss formed integrally with the developing case formed on one side plate portion of the developing case is made of resin, it has a certain diameter so as not to be deformed. . On the other hand, in order to suppress cost increase, the driving pin uses a general-purpose metal pin and has a diameter smaller than that of the resin boss. By using a highly rigid metal pin as the driving pin, even a diameter smaller than that of the resin boss does not cause deformation.

  As described above, during the image forming operation due to the deflection of the photosensitive member 6, the developing device 5 rotates with the first shaft portion 52 a of the resin boss and the second shaft portion 52 b of the driving pin as fulcrums. Conventionally, the developing device 5 has been considered that the developing device 5 rotates about the axis center of each shaft portion. For this reason, in the developing device 5 under development, as shown in FIG. 9, the center of the first shaft portion 52a of the resin boss having a large diameter and the second shaft portion 52b of the insertion pin having a small diameter is centered. It was configured to match. However, as a result of earnest research by the present applicant, it has been found that, in fact, as described with reference to FIGS. 6 to 9, the shafts 52a and 52b do not rotate around the shaft centers. It is.

  Specifically, as described above with reference to FIGS. 6 and 7, after the developing roller 5a has contacted the photosensitive member 6, the developing roller 5a and the photosensitive roller 6 are exposed to light by the biasing force of a biasing means such as a compression spring. The developing device 5 is rotated (rotated counterclockwise in FIG. 6) with the contact portion R with the body 6 as a fulcrum. As a result, as shown in FIG. 7, the shaft portions 52a and 52b come into contact with predetermined positions of the bearing 41b of the photoreceptor frame (in FIG. 7, diagonally right above the bearing 41b in the drawing). . Then, when the developing device 5 is rotated due to the deflection of the photosensitive member 6, the shaft portions 52 a and 52 b are not rotated around the shaft center of each shaft portion, but the shaft portions 52 a and 52 b are rotated. The present applicant has discovered that the bearing 41b has been pivoted around the abutting portion.

  The diameter of the first shaft portion 52a and the diameter of the second shaft portion 52b are different from each other. Therefore, when the axial center of the first shaft portion 52a and the axial center of the second shaft portion 52b are made to coincide with each other as in the prior art, as shown in FIG. 9, the rotation at one end side in the axial direction of the developing device is performed. The movement fulcrum and the rotation fulcrum on the other end side are greatly different. As described above, since the rotation fulcrum is different between the one end side and the other end side in the axial direction, as shown in FIG. 9, the developing device is rotated due to the flare of the photosensitive member during the image forming operation. At this time, the movement locus on one end side of the developing roller and the movement locus on the other end side are different from each other. Therefore, the positions of both ends in the axial direction of the developing roller are shifted to the upstream side or the downstream side in the photosensitive member surface movement direction with respect to the central portion in the axial direction. As a result, the contact pressure at both ends of the developing roller in the axial direction is lower than the specified contact pressure, and in the worst case, the developing roller is separated from the photoconductor. As a result, it has been found that image defects such as image omission and image density reduction occur near both ends in the axial direction.

  In the configuration in which the developing roller is brought into contact with the photosensitive member via the spacer, the positions of both ends of the developing roller in the axial direction are shifted to the upstream side or the downstream side in the photosensitive member surface movement direction with respect to the central portion in the axial direction. In the worst case, the developer does not come into contact with the photoreceptor. As a result, image defects such as image omission and image density decrease occur near both ends in the axial direction.

  In addition to the developing device, for example, in a cleaning device or a transfer device that is rotatably held by the main body of the image forming apparatus, when the diameter of one of the rotating shafts is different from the other, the contact that makes contact with the mating member The member comes into contact with the counterpart member at an angle, and various problems occur.

  (Aspect 1) is made based on the above-described background, and the axis of the small-diameter shaft portion such as the second shaft 52b having a small diameter is used as the axis of the large-diameter shaft portion such as the first shaft 52a having a large diameter. Rather than the center, the contact force between the contact member such as the developing roller 5a and the other member such as the photosensitive member 6 by the biasing force of the biasing means such as the compression spring 54 serves as a fulcrum for the side plate of the developing case 56 and the like. When the contact member holding side plate is about to rotate, the contact member holding side plate is provided on the first load portion side where a load is applied to the counterpart member support member from the large diameter shaft portion. (In this embodiment, it is provided on the contact portion S1 side of the first shaft portion 52a with the bearing 41b.) Thereby, one end side in the axial direction as compared with the case where the shaft centers of the shaft portions 52a and 52b are made to coincide. The shift of the rotation fulcrum between the first end and the other end can be reduced. As a result, when a rotating unit such as a developing device rotates about the small-diameter shaft portion and the large-diameter shaft portion as a fulcrum, the amount of deviation between the movement locus on one side of the rotation unit axial direction and the movement locus on the other side. Can be made smaller than when the shaft centers of the shaft portions 52a and 52b are made to coincide. Thereby, the inclination of the contact member with respect to the counterpart member when the rotation unit rotates with each shaft portion as a fulcrum can be suppressed.

  Therefore, when the rotating unit is a developing device, the contact pressure at both ends of the developer carrying member in the axial direction is reduced (in the configuration in which the developer carrying member is brought into contact with the latent image carrying member via the spacer, the development gap is widened). Can be suppressed as compared with the case where the axes of the axes 52a and 52b are made to coincide with each other, and image density reduction and image omission near both ends in the axial direction can be suppressed. Further, when the rotating unit is a cleaning device, it is possible to suppress a decrease in the contact pressure between the cleaning member and the mating member, and good cleaning properties can be obtained. In addition, when the rotation unit is a transfer device, it is possible to suppress a decrease in transfer pressure in the axial direction and to obtain good transferability.

(Aspect 2)
In (Aspect 1), the radius of the large-diameter shaft portion such as the first shaft portion 52a is r1, and the radius of the small-diameter shaft portion such as the second shaft portion 52b is r2, and from the axial direction of the contact member such as the developing roller 5a. When viewed, the first abutting member holding side plate such as the side plate portion on one side of the developing case and the second abutting member holding side plate that is the other side plate portion of the developing case will rotate with the abutting portion as a fulcrum. When the second load portion (in this embodiment, the contact portion S2 with the bearing 41b of the second shaft portion 52b) is applied to the counterpart member supporting member such as the photoconductor frame 43 from the small diameter shaft portion. Centering on one load part, it provided in the area | region of the circle | round | yen of radius (r1-r2).
With this configuration, as described with reference to FIGS. 10 and 11, the shaft center of the large-diameter shaft portion such as the first shaft portion 52a and the axis of the small-diameter shaft portion such as the second shaft portion 52b are used. Compared with the case where the center is matched, the amount of deviation between the pivot point on the one end side in the axial direction of the developing device 5 and the pivot point on the other end side in the axial direction can be reduced. Thereby, it is possible to prevent the contact member such as the developing roller from being inclined with respect to the counterpart member such as the photosensitive member. Thus, when the rotating unit is a developing device, the contact pressure at both ends of the developer carrying member in the axial direction is reduced (in the configuration in which the developer carrying member is brought into contact with the latent image carrying member via the spacer, the development gap is widened). ) Can be suppressed as compared with the case where the axes of the axes 52a and 52b are made to coincide with each other, and image density reduction and image omission near both ends in the axial direction can be suppressed. Further, when the rotating unit is a cleaning device, it is possible to suppress a decrease in the contact pressure between the cleaning member and the mating member, and good cleaning properties can be obtained. In addition, when the rotation unit is a transfer device, it is possible to suppress a decrease in transfer pressure in the axial direction and to obtain good transferability.

(Aspect 3)
In (Aspect 2), the first load portion and the second load portion are configured to coincide with each other when viewed from the axial direction of the contact member such as the developing roller.
According to (Aspect 3), as described with reference to FIG. 14, the rotation fulcrum on the one axial end side of the rotation unit such as the developing device and the rotation fulcrum on the other axial end side are matched. be able to. Thereby, it is possible to prevent the contact member such as the developing roller from being inclined with respect to the counterpart member such as the photosensitive member. Thus, when the rotation unit is a developing device, in a configuration in which a developer carrier such as a developing roller abuts on the latent image carrier, the contact pressure with the latent image carrier such as a photoconductor is axially increased. Can be uniform. Further, when the developer carrier is opposed to the latent image carrier with a predetermined gap, the gap between the latent image carrier and the latent image carrier can be made constant in the axial direction. Thereby, it is possible to obtain a good image in which a decrease in image density and an image omission are prevented. When the rotating unit is a cleaning device, the contact pressure between the cleaning member and the mating member can be made constant in the axial direction, and good cleaning properties can be obtained. Moreover, when the rotation unit is a transfer device, good transferability can be obtained.

(Aspect 4)
In any one of (Aspect 1) to (Aspect 3), a large-diameter shaft portion such as the first shaft portion 52a is integrally molded with a first contact member holding side plate such as one side plate portion of the developing case 56 with resin. It is a resin shaft, and a small diameter shaft portion such as the second shaft portion 52 b is a metal member such as a driving pin that can be attached to and detached from a first contact member holding side plate such as one side plate portion of the developing case 56.
According to (Aspect 4), as described in the embodiment, the photoconductor frame 43 is compared with the case where both the large-diameter shaft portion and the small-diameter shaft portion are resin shafts integrally formed with the contact member holding side plate. Can be easily assembled. In addition, the number of parts can be reduced and the cost of the apparatus can be suppressed as compared with the case where the large-diameter shaft shaft and the small-diameter shaft shaft are made of metal members such as driving pins.

(Aspect 5)
In any one of (Aspect 1) to (Aspect 4), the counterpart member is a latent image carrier such as the photosensitive member 6, and the abutting member carries the developer on its surface and moves to the surface. Spacers provided at both ends in the axial direction of a developer carrier such as a developing roller or a developer carrier that conveys the developer to a development region facing the image carrier.
With this configuration, as described above, it is possible to obtain a good image in which a decrease in image density and an image loss are prevented.

(Aspect 6)
A latent image carrier such as a photoreceptor 6 that carries a latent image, and a developing device 5 that is rotatably held by a latent image carrier support member such as a photoreceptor frame 43 that supports the latent image carrier. In a process cartridge such as the image forming unit 7 that is configured to be detachable integrally with the image forming apparatus main body, the rotating unit according to any one of (Aspect 1) to (Aspect 5) Was used.
According to (Aspect 6), it is possible to suppress the contact member such as the developing roller 5a from inclining and contacting the latent image carrier such as the photosensitive member. As a result, when the rotating unit is a developing device, it is possible to provide a process cartridge capable of forming an image in which a decrease in image density near both ends in the axial direction and an image omission are suppressed. Further, when the rotating unit is a cleaning device, a process cartridge that can maintain good cleaning properties can be provided.

(Aspect 7)
In (Aspect 6), the rotating unit is a developing device.
According to (Aspect 7), as described above, it is possible to provide a process cartridge capable of forming an image in which a decrease in image density near both ends in the axial direction and an image omission are suppressed.

(Aspect 8)
In (Aspect 6) or (Aspect 7), the first bearing and / or the second shaft portion 52b that receives a large-diameter shaft portion such as the first shaft portion 52a of the latent image carrier support member such as the photoconductor frame 43, etc. The second bearing for receiving the small-diameter shaft portion is a long hole extending in the direction of the latent image carrier.
According to (Aspect 8), even when the latent image carrier supporting member such as the face plate portion 41 of the photoconductor frame is twisted, the shaft portion of the rotating unit such as the developing device 5 is located in the long hole bearing. It can move relatively and it can control that a rotation unit twists. Thereby, the twist of the rotating unit due to the twist of the latent image carrier support member can be suppressed, and the contact member such as the developing roller 5a can be prevented from being inclined with respect to the latent image carrier such as the photosensitive member 6. it can.

(Aspect 9)
An image including a rotating member such as the photosensitive member 6 and a rotating unit such as the developing device 5 that includes a contact member such as the developing roller 5a that contacts the rotating member and is rotatably supported with respect to the apparatus main body. In the forming apparatus, the rotating unit of any one of (Aspect 1) to (Aspect 5) is used as the rotating unit.
According to (Aspect 9), the abutting member can be prevented from inclining and abutting with respect to the rotation axis of the rotating member. Thereby, when the rotating unit is a developing device, it is possible to provide an image forming apparatus capable of forming an image with reduced image density near the both ends in the axial direction and an image missing. Further, when the rotating unit is a cleaning device, it is possible to provide an image forming apparatus capable of obtaining good cleaning properties. Further, when the rotation unit is a transfer device, it is possible to provide an image forming apparatus capable of obtaining good transfer properties.

1: printer 5: developing device 5a: developing roller 6: photoconductor 6a: photoconductor shaft 7: image forming unit 40: photoconductor unit 41: face plate portion 41b: bearing 43: photoconductor frame 44: positioning boss 52a first shaft Part 52b: second shaft part 54: compression spring 56: developing case 90: printer housing 90a: side plate 91: guide groove O1: shaft center O2 of the first shaft part O: shaft center R of the second shaft part R: photosensitive member Contact portion S1 with the developing roller Contact portion S2 between the first shaft portion and the bearing S2: Contact portion between the second shaft portion and the bearing

JP 2013-200552 A

Claims (9)

A first abutting member holding side plate that holds one axial direction of the abutting member that abuts the mating member;
A second contact member holding side plate for holding the other axial direction of the contact member;
The first abutting member holding side plate and the second abutting member holding side plate are positioned differently from the holding portion for holding the abutting member of the first abutting member holding side plate and the second abutting member holding side plate. And an image forming apparatus that is rotatably attached to a counterpart member support member that supports the counterpart member with a shaft portion provided on each of the shaft portions, and that is biased by a biasing means so that the contact member abuts the counterpart member. In the rotating unit used,
The shaft portion provided on the first contact member holding side plate and the shaft portion provided on the second contact member holding side plate have different diameters from each other,
When viewed from the axial direction of the abutting member, the biasing means is configured such that the axial center of the small-diameter shaft portion, which is the smaller-diameter shaft portion, is more than the axial center of the large-diameter shaft portion, which is the larger-diameter shaft portion. When the first abutting member holding side plate and the second abutting member holding side plate are about to turn with the urging force of the abutting portion of the abutting member as the fulcrum, the large diameter A rotating unit provided on the first load portion side where a load is applied to the mating member support member from the shaft portion. The rotating unit according to claim 1,
The radius of the large diameter shaft portion is r1, the radius of the small diameter shaft portion is r2,
When viewed from the axial direction of the contact member,
When the first abutting member holding side plate and the second abutting member holding side plate are about to rotate with the abutting portion as a fulcrum, a load is applied to the counterpart member supporting member from the small diameter shaft portion. A rotation unit characterized in that a load portion is provided in a circular region having a radius (r1-r2) with the first load portion as a center. The rotating unit according to claim 2,
A rotation unit configured so that the first load portion and the second load portion coincide when viewed from the axial direction of the contact member. The rotating unit according to any one of claims 1 to 3,
The large-diameter shaft portion is a resin shaft integrally molded with the first contact member holding side plate with resin,
The rotation unit, wherein the small-diameter shaft portion is a metal member that can be attached to and detached from the second contact member holding side plate. It is a rotation unit in any one of Claims 1 thru | or 4, Comprising:
The counterpart member is a latent image carrier;
The abutment member carries the developer on its surface and moves on the surface, thereby transporting the developer to the development area facing the latent image carrier, or the axial direction of the developer carrier A rotating unit characterized in that it is a spacer provided at both ends. A latent image carrier for carrying a latent image;
A rotation unit rotatably supported by the latent image carrier supporting member that supports the latent image carrier,
In the process cartridge configured to be detachable integrally with the image forming apparatus main body,
A process cartridge using the rotation unit according to claim 1 as the rotation unit. The process cartridge according to claim 6,
A process cartridge, wherein the rotating unit is a developing device. The process cartridge according to claim 6 or 7,
The first bearing that receives the large-diameter shaft portion and / or the second bearing that receives the small-diameter shaft portion of the latent image carrier supporting member is an elongated hole extending toward the latent image carrier. To process cartridge. A rotating member;
An image forming apparatus including a rotation unit that includes a contact member that contacts the rotation member and is rotatably supported with respect to the apparatus main body.
An image forming apparatus using the rotation unit according to claim 1 as the rotation unit.

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