JP2010128340A - Tandem type photoreceptor unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tandem type photoreceptor unit for easily exchanging a photoreceptor drum, and to provide an image forming apparatus with the tandem type photoreceptor unit. <P>SOLUTION: Drum supporting holes 32 are respectively formed at positions where they are opposed to each other on a first inside plate 24 and a second inside plate 25 of a drum unit 4. A first bearing member 90 and a second bearing member 91 are respectively fit in the drum supporting holes 32. The right end of the photoreceptor drum 5 is supported by the first inside plate 24 through the first bearing member 90, and the left end of the photoreceptor drum is supported by the second inside plate 25 through the second bearing member 91. The first bearing member 90 includes a first flange part 94 abutting on the inside surface of the first inside plate 24. The second bearing member 91 includes a second flange part 99 abutting on the outside surface of the second inside plate 25. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tandem photoreceptor unit and an image forming apparatus including the same.

As an electrophotographic color printer, a so-called tandem type printer is known in which photosensitive drums corresponding to yellow, magenta, cyan, and black are arranged in parallel.
As this tandem type color printer, one in which four photosensitive drums can be integrally attached to and detached from a main body casing has been proposed (for example, see Patent Document 1).

  The configuration according to this proposal includes a drum subunit that holds each photosensitive drum, and a pair of side plates that sandwich the drum subunit from both sides in the axial direction of the photosensitive drum. A developing cartridge that holds the developing roller is detachably mounted between both side plates corresponding to each drum subunit. The drum subunit, the developing cartridge, and the pair of side plates are detachably attached to the main casing as a drum unit.

Both end portions of the drum shaft of the photosensitive drum protrude outward from both side surfaces of the drum subunit. Each side plate has four shaft holes formed at regular intervals in the direction in which the photosensitive drums are arranged. Positioning of each drum shaft (photosensitive drum) is achieved by inserting the end of the drum shaft into each shaft hole.
JP 2007-72422 A

If the surface of the photosensitive drum is damaged or adhered, the image formed on the paper is disturbed. For this reason, if the surface of the photosensitive drum is damaged or adhered during the assembly or use of the color printer, it is necessary to replace the photosensitive drum.
However, in the color printer according to the above proposal, since both end portions of the drum shaft of each photosensitive drum are inserted into the pair of side plates, when it is necessary to replace one photosensitive drum after assembling the drum unit, The photosensitive drum alone cannot be removed from between the pair of side plates, and the drum subunits must be separated by removing the pair of side plates from all the drum subunits. Therefore, it takes time to replace the photosensitive drum. Further, since one side plate must be attached to each of the four drum subunits after replacement of the photosensitive drum, this reassembly takes time.

  An object of the present invention is to provide a tandem type photoconductor unit and an image forming apparatus including the tandem type photoconductor unit, in which the photosensitive drum can be easily replaced.

  In order to achieve the above object, the invention described in claim 1 is a tandem type photoconductor unit, which is arranged on a plurality of photosensitive drums arranged in parallel to each other and a central axis of each of the photosensitive drums. A shaft, a first side plate disposed on one side in the axial direction with respect to the photosensitive drum and having a first through hole formed at a position facing each photosensitive drum in the axial direction, and the photosensitive drum A second side plate disposed opposite to the first side plate on the other side in the axial direction and having a second through-hole formed at a position facing the photosensitive drum in the axial direction, and the first through-hole. A first bearing member fitted to each of the second through holes, and a second bearing member fitted to each of the second through holes, and the photosensitive drum includes a cylindrical drum body and the one side of the drum body. Fitted to the end And an earth member disposed in the drum body, the shaft passes through the flange member, one end of the shaft projects to the one side from the flange member, and the other end of the shaft The first bearing member is in contact with the ground member, and the first bearing member is in contact with a shaft holding portion that holds the one end portion of the shaft, a flange holding portion that holds the flange member, and an inner surface of the first side plate. The second bearing member includes a second end holding portion that holds the other end portion of the photosensitive drum, and a second flange portion that contacts the outer surface of the second side plate. It is characterized by having.

According to a second aspect of the present invention, in the first aspect of the invention, the first bearing member has a claw portion that is locked to an outer surface of the first side plate. Yes.
The invention according to claim 3 is the invention according to claim 1 or 2, wherein the first side plate and the second side plate are made of a metal material, and the first through hole and the second through hole are The first side plate and the second side plate are formed by performing press working using the same press die.

According to a fourth aspect of the invention, in the third aspect of the invention, the first through hole and the second through hole are formed by punching the first side plate and the second side plate from the other side, respectively. It is characterized by being formed by.
Moreover, the invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein inner surfaces of the first through hole and the second through hole have four linear portions, The four straight portions are in contact with a virtual circle virtually set in the first through hole and the second through hole, and are arranged at equiangular intervals with respect to the center of the virtual circle, and the first bearing The member has a diameter larger than the diameter of the virtual circle, has a first insertion portion inserted into the first through hole, and the second bearing member has a diameter larger than the diameter of the virtual circle. And having a second insertion portion to be inserted into the second through hole.

The invention according to claim 6 is the invention according to claim 5, wherein the inner surfaces of the first through hole and the second through hole connect two linear portions orthogonal to each other, and It includes four curved portions that bulge outward in the radial direction.
According to a seventh aspect of the invention, in the invention of the fifth or sixth aspect, the four straight portions include two horizontal straight portions extending in a parallel direction of the photosensitive drum, the parallel direction, and the axis. It is characterized by including two vertical straight lines extending in a direction orthogonal to the direction.

The invention according to claim 8 is an image forming apparatus, wherein the apparatus main body and the tandem type according to any one of claims 1 to 7 are detachably attached to the apparatus main body. And a photoreceptor unit.
The invention according to claim 9 is the invention according to claim 8, further comprising a pressing member that presses the photosensitive drum from the other side toward the one side, and the photosensitive drum receives the pressing member. The force is larger than the force that the shaft receives from the ground member.

  According to the first and eighth aspects of the present invention, the first through hole and the second through hole are formed in the first side plate and the second side plate of the tandem type photoconductor unit at positions facing each other. A first bearing member and a second bearing member are fitted in the first through hole and the second through hole, respectively. One end of the photosensitive drum is supported on the first side plate via the first bearing member, and the other end is supported on the second side plate via the second bearing member. The 1st bearing member has the 1st collar part contact | abutted to the inner surface of a 1st side plate. On the other hand, the 2nd bearing member has the 2nd collar part contact | abutted to the outer surface of a 2nd side plate.

Thus, for example, the first bearing member is attached to one end of the photosensitive drum, and after the first bearing member is fitted into the first through hole of the first side plate, the second bearing member is moved to the second side plate. The other end of the photosensitive drum is held by the second bearing member so that the photosensitive drum is attached to the first side plate and the second side plate.
Further, by removing the second bearing member from the second through hole of the second side plate, the fixing of the other end of the photosensitive drum is released, so that the photosensitive drum and the first bearing member are connected to the first side plate of the first side plate. It can be removed integrally from one through hole. Therefore, it is not necessary to release the holding of the remaining photosensitive drums by the first side plate and the second side plate in order to replace one photosensitive drum. As a result, the photosensitive drum can be easily replaced.

  An earth member is disposed in the drum body of the photosensitive drum. A shaft is disposed on the central axis of the photosensitive drum. The shaft penetrates through the flange member, one end of the shaft projects to one side of the flange member, and the other end is in contact with the ground member. As a result, the drum body of the photosensitive drum can be grounded via the ground member and the shaft.

According to invention of Claim 2, the 1st bearing member has a nail | claw part. The claw portion is locked to the outer surface of the first side plate. Accordingly, the first bearing member is fixed in a state where the first side plate is sandwiched between the first flange portion and the claw portion. As a result, it is possible to prevent the first bearing member from dropping from the first through hole.
According to invention of Claim 3, a 1st side plate and a 2nd side plate consist of metal materials. And a 1st through-hole and a 2nd through-hole are formed by the press work using the same press type | mold with respect to a 1st side plate and a 2nd side plate, respectively. Therefore, the first through hole of the first side plate and the second through hole of the second side plate can be formed with the same accuracy. Moreover, since it is not necessary to prepare the press die for 1st side plates and the press die for 2nd side plates separately, the processing cost of a 1st side plate and a 2nd side plate can be reduced.

  According to invention of Claim 4, a 1st through-hole and a 2nd through-hole are formed by punching a 1st side plate and a 2nd side plate from the other side, respectively. Thereby, the corner | angular part which the inner surface of the 1st through-hole of a 1st side plate and the inner surface of a 1st side plate make is curving, and becomes what is called a sagging surface. Therefore, the first bearing member can be smoothly fitted to the first through hole from the inner surface side of the first side plate. Moreover, the corner | angular part which the inner surface of the 2nd through-hole of a 2nd side plate and the outer surface of a 2nd side plate make is curving, and becomes a so-called sagging surface. Therefore, the second bearing member can be smoothly fitted to the second through hole from the outer surface side of the second side plate.

  According to invention of Claim 5, the inner surface of a 1st through-hole and a 2nd through-hole has four linear parts, respectively. The four straight portions are in contact with a virtual circle virtually set in the first through hole and the second through hole, and are arranged at equiangular intervals with respect to the center of the virtual circle. That is, the first through hole and the second through hole are formed in a substantially square shape having four straight portions.

  The first bearing member has a first insertion portion that is inserted into the first through hole. The first insertion portion has an outer peripheral surface having a diameter larger than the diameter of a virtual circle virtually set in the first through hole. Accordingly, when the first insertion portion is inserted into the first through hole, the outer peripheral surface of the first insertion portion is deformed along the four straight portions, and is pressed against each straight portion of the first through hole. Therefore, the first bearing member can be fitted to the first through hole without any play.

Further, when a temperature change occurs in the tandem type photosensitive unit and a stress caused by a difference in expansion between the first bearing member and the first side plate is applied to the first bearing member, the first insertion in the first bearing member is performed. When the portion other than the contact portion between the portion and the straight portion is deformed, the stress can be absorbed. As a result, damage to the first bearing member can be prevented.
Further, four inner straight portions parallel to the four straight portions are formed on the inner surface of the first insertion portion in accordance with the deformation of the first insertion portion. One end portion (flange member) of the photosensitive drum held by the first insertion portion is in contact with and supported by any of the four inner straight portions. As a result, the one end portion of the photosensitive drum can be accurately positioned.

  The second bearing member has a second insertion portion that is inserted into the second through hole. The second insertion portion has an outer peripheral surface having a diameter larger than the diameter of a virtual circle virtually set in the second through hole. Accordingly, when the second insertion portion is inserted into the second through hole, the outer peripheral surface of the second insertion portion is deformed along the four straight portions, and is pressed against each straight portion of the second through hole. Therefore, the second bearing member can be fitted into the second through hole without any play.

Further, when a temperature change occurs in the tandem type photoreceptor unit and a stress due to a difference in expansion between the second bearing member and the second side plate is applied to the second bearing member, the second insertion in the second bearing member is performed. When the portion other than the contact portion between the portion and the straight portion is deformed, the stress can be absorbed. As a result, it is possible to prevent the second bearing member from being damaged.
In addition, four inner straight portions parallel to the four straight portions are formed on the inner surface of the second insertion portion in accordance with the deformation of the second insertion portion. The other end of the photosensitive drum held by the second insertion portion is in contact with and supported by one of the four inner straight portions. As a result, the other end portion of the photosensitive drum can be accurately positioned.

  According to the invention described in claim 6, the inner surfaces of the first through hole and the second through hole each include four curved portions. Each curved portion connects two linear portions orthogonal to each other, and bulges outward in the radial direction of the virtual circle. As a result, spaces are generated in the first through hole and the second through hole between the first bearing member and the second bearing member and the four curved portions, respectively. Therefore, when the first bearing member and the second bearing member are deformed radially outward of the virtual circle, the deformation can be allowed in the space, so that the first bearing member and the second bearing member are damaged. This can be further prevented.

  According to the seventh aspect of the present invention, the four straight portions include two horizontal straight portions extending in the parallel direction of the photosensitive drums, and two vertical straight portions extending in the direction perpendicular to the parallel direction and the axial direction. . Therefore, by arranging the two horizontal straight portions of each first through hole and each second through hole on two straight lines extending in the parallel direction of the photosensitive drum, each first through hole and each second through hole are arranged. They can be formed at the same position in the vertical direction. As a result, the photosensitive drums held in the first through hole and the second through hole via the first bearing member and the second bearing member, respectively, can be arranged at the same position in the vertical direction.

  Further, the first straight holes and the second through holes are formed with vertical straight portions on one side in the parallel direction of the photosensitive drums spaced apart from each other in the parallel direction. Two through holes can be formed at equal intervals in the parallel direction. Therefore, it is possible to make the pitch between the photosensitive drums held in the first through hole and the second through hole through the first bearing member and the second bearing member constant, respectively.

According to the invention described in claim 9, the pressing member presses the photosensitive drum from the other side toward the one side. The force that the photosensitive drum receives from the pressing member is larger than the force that the shaft receives from the ground member.
The direction in which the photosensitive drum is pressed by the pressing member is such that the first flange of the first bearing member contacts the inner surface of the first side plate, and the second flange of the second bearing member is the outer surface of the second side plate. It is the same as the direction which contacts. Therefore, when the photosensitive drum is pressed by the pressing member, the first bearing member and the second bearing member are pressed toward the first side plate and the second side plate through the photosensitive drum, respectively. Since the second bearing member does not tilt with respect to the first side plate and the second side plate, the photosensitive drum can be stably supported.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1. Printer FIG. 1 is a side sectional view showing an embodiment of a printer as an example of an image forming apparatus of the present invention. In addition, when referring to a direction, the illustrated direction arrow is referred to (the same applies to other drawings). Here, the horizontal direction and the width direction are the same, and the vertical direction and the vertical direction are the same. The horizontal direction includes the width direction and the front-rear direction.

The printer 1 is a tandem color laser printer. The printer 1 includes a main body casing 2 as an example of an apparatus main body. A front cover 3 is provided on one side surface of the main casing 2 so as to be openable and closable.
A drum unit 4 as an example of a tandem type photoreceptor unit is provided in the main body casing 2. The drum unit 4 can be attached to and detached from the inside of the main body casing 2 through an attachment / detachment opening formed on the front surface of the main body casing 2 in a state where the front cover 3 is opened.

  In the drum unit 4, four photosensitive drums 5 are arranged in parallel along the front-rear direction in a rotatable state. Each photosensitive drum 5 is provided with a scorotron charger 6 and a developing roller 7 facing each other. Each photosensitive drum 5 is adjacent to a developing cartridge 8 that holds a developing roller 7 and stores toner (developer). The developing cartridge 8 is configured to be detachable from the drum unit 4. The toner of the developing cartridge 8 is carried on the surface of the developing roller 7.

  The surface of each photosensitive drum 5 is uniformly charged by the charger 6 and then exposed by a laser beam (see the broken arrow in the drawing) emitted from the scanner unit 9 provided on the upper portion of the main casing 2. Thereby, an electrostatic latent image based on the image data is formed on the surface of each photosensitive drum 5. The electrostatic latent image on each photosensitive drum 5 is visualized by toner carried on the surface of the developing roller 7 corresponding to each photosensitive drum 5, and a toner image is formed on the surface of each photosensitive drum 5. The Here, since the color of the toner stored in each developing cartridge 8 varies depending on each developing cartridge 8, the color of the toner image on each photosensitive drum 5 varies depending on each photosensitive drum 5.

  The sheets S are accommodated in the sheet cassette 10 disposed at the bottom of the main casing 2 in a state where they are stacked in the vertical direction. Of the sheets S stored in the sheet feeding cassette 10, the uppermost sheet S is fed forward by a sheet feeding roller 11 provided so as to face the front end portion of the sheet feeding cassette 10 from above. The fed sheet S rises while changing its direction from the front side to the rear side.

The raised sheet S enters between the pair of registration rollers 12. The pair of registration rollers 12 sends the paper S toward the rear conveyor belt 13 at a predetermined timing.
The conveyor belt 13 is endless, and four transfer rollers 14 are arranged in the inner region. The four transfer rollers 14 are arranged in parallel along the front-rear direction, and each transfer roller 14 faces the corresponding photosensitive drum 5 from below with the upper portion of the transport belt 13 interposed therebetween.

  The paper S sent out from the pair of registration rollers 12 is delivered to the upper part of the transport belt 13. And the conveyance belt 13 conveys the paper S to the back side in the upper part by rotating in the clockwise direction in FIG. The toner image on the surface of each photosensitive drum 5 is transferred onto the sheet S conveyed by the conveying belt 13 by the transfer bias applied to the transfer roller 14 and is sequentially superimposed. Here, since the color of the toner image on each photosensitive drum 5 differs depending on each photosensitive drum 5, the color images are formed on the paper S by superimposing the toner images for four colors on the paper S. Is done.

The sheet S on which the color image is formed is conveyed to the fixing unit 15 on the rear side by the conveying belt 13. Here, the toner image of each photosensitive drum 5 transferred onto the paper S is thermally fixed by the fixing unit 15. Thereafter, the sheet S is transported by the transport roller 16 and is lifted while changing its direction from the rear side to the front side, and is discharged to the sheet discharge tray 17 at the upper part of the main body casing 2.
2. Drum Unit FIG. 2 is a perspective view of the drum unit as viewed from the upper right front side, showing a state where one developing cartridge is attached and the other developing cartridges are detached. FIG. 3 is a plan view of the drum unit, showing a state where a pair of outer plates are removed from the drum unit.

As shown in FIG. 2, the drum unit 4 includes four photosensitive drums 5, four developing cartridges 8, four drum subunits 20, a front beam 21, a rear beam 22, and a first inner side as an example of a pair of first side plates. The plate 24 and the second inner plate 25 as an example of the second side plate, and the pair of the first outer plate 27 and the second outer plate 28 are integrated and slide with respect to the inside of the main casing 2 (see FIG. 1). It can be attached and detached freely.
(1) Drum subunits The four drum subunits 20 are arranged between the first inner plate 24 and the second inner plate 25 with a space in the front-rear direction. Each drum subunit 20 is made of resin, is elongated in the width direction, and is formed in a substantially triangular prism shape opened to the lower front side. Each drum subunit 20 holds the charger 6 shown in FIG. 1 and a cleaning member (not shown) for cleaning the surface of the photosensitive drum 5.
(2) Front beam The front beam 21 is made of resin. The front beam 21 is installed between the front end portions of the pair of first inner plate 24 and second inner plate 25.

The front beam 21 holds a support shaft 29. The support shaft 29 is disposed so as to penetrate the front beam 21 along the width direction, protrudes outward in the width direction from the front beam 21, and further, the first inner plate 24, the second inner plate 25, and the first outer plate. 27 and the second outer plate 28 and protrudes outward in the width direction.
A front side grip 30 is integrally formed at the center in the width direction on the front surface of the front beam 21. The near side grip 30 is substantially U-shaped in plan view, and each free end thereof is connected to the front beam 21.
(3) Rear beam The rear beam 22 is made of resin. The rear beam 22 is installed between the rear end portions of the pair of first inner plate 24 and second inner plate 25.

A rear side grip 31 is integrally formed at the center in the width direction on the upper surface of the rear beam 22. The rear gripping portion 31 is substantially U-shaped when viewed from the back, and each free end thereof is connected to the rear beam 22 so as to incline from the rear lower side to the front upper side and project obliquely upward from the rear beam 22. It has been.
(4) Inner plate FIG. 4 is a perspective view of the second inner plate viewed from the upper right front side.

The first inner plate 24 on the right side and the second inner plate 25 on the left side are produced by pressing a metal plate using the same press die and have the same shape. In the following description, the configuration of the second inner plate 25 will be described.
As shown in FIGS. 3 and 4, the second inner plate 25 is formed in a substantially elongated rectangular plate shape extending in the front-rear direction. The front end portion and the rear end portion of the second inner plate 25 are opposed to the front beam 21 and the rear beam 22 in the left-right direction, respectively.

The front end portion of the second inner plate 25 extends toward the front upper side. A support shaft insertion hole 51 through which the support shaft 29 is inserted is formed through the front end portion of the second inner plate 25.
The rear end portion of the second inner plate 25 is formed in a substantially L shape in side view. More specifically, the rear end portion of the second inner plate 25 is formed in a shape that inclines toward the rear upper side and extends further upward.

Further, a notch 53 having a shape cut out in a substantially V shape from the rear edge is formed at the rear end of the second inner plate 25. Specifically, the cutout 53 includes an upper end edge extending in the front-rear direction in a side view, a lower end edge inclined at a constant gradient upward in the front side, and a front end edge connecting the front end of the upper end edge and the front end of the lower end edge. It is formed in the shape to have. As shown in FIG. 1, the notch 53 receives the main body reference shaft 34 laid across the width direction on the rear side in the main body casing 2 in a state where the drum unit 4 is attached to the main body casing 2, and It abuts on the main body reference shaft 34 from above and from the front.
(4-1) Drum Support Hole FIG. 5 is an enlarged view of the peripheral portion of the drum support hole in the inner plate.

The second inner plate 25 is formed with four first through holes and drum support holes 32 as an example of second through holes. The drum support holes 32 are formed between the front end portion and the rear end portion of the second inner plate 25 at regular intervals in the front-rear direction.
As shown in FIG. 5, the inner surface of the drum support hole 32 has four straight portions 60 and four curved portions 61.

The four straight portions 60 are in contact with a virtual circle 62 (shown by a broken line in FIG. 5) virtually set in the drum support hole 32, and are arranged at equiangular intervals with respect to the center of the virtual circle 62. More specifically, the four straight portions 60 extend in the up-down direction and have two vertical straight portions 63 that face each other in the front-rear direction, and two horizontal straight portions 64 that extend in the front-rear direction and face each other in the up-down direction. Consists of.
The four curved portions 61 are formed in a shape that connects two linear portions 60 orthogonal to each other and bulges outward in the radial direction of the virtual circle 62. As a result, the drum support hole 32 is formed in a substantially quadrangular shape with each apex rounded in a side view.

Each drum support hole 32 is formed by punching the first inner plate 24 and the second inner plate 25 from the left side. Therefore, the portion around the drum support hole 32 on the inner side surface of the first inner plate 24 and the portion around the drum support hole 32 on the outer side surface of the second inner plate 25 are so-called sagging surfaces. On the other hand, a portion around the drum support hole 32 on the outer side surface of the first inner plate 24 and a portion around the drum support hole 32 on the inner side surface of the second inner plate 25 are so-called burr surfaces.
(4-2) Locking groove At the lower end edge of the second inner plate 25, a first bearing locking groove 70 and a clip locking groove 71 are formed at a position below each drum support hole 32.

The first bearing locking groove 70 is formed in a shape in which the second inner plate 25 is cut out in a substantially rectangular shape from the lower end edge at a position overlapping the center of the drum support hole 32 in the vertical direction.
The clip locking groove 71 is formed in a shape in which the second inner plate 25 is cut out from the lower end edge at a front position and a rear position with respect to the bearing locking groove 70.
A second bearing locking hole 72 is formed at a position above each drum support hole 32 in the second inner plate 25. The second bearing locking hole 72 is formed as a square hole penetrating the inner plate 23 at a position symmetrical to the first bearing locking groove 70 with respect to the center of the drum support hole 32. (5) Outer plate As shown in FIG. 2, the pair of first outer plate 27 and second outer plate 28 are made of, for example, fiber reinforced resin. The first outer plate 27 and the second outer plate 28 are substantially elongated rectangular plates in a side view as compared with the first inner plate 24 and the second inner plate 25, which are wider in the vertical direction and have substantially the same length in the front-rear direction. Is formed. The front end portion and the rear end portion of the first outer plate 27 and the second outer plate 28 face the front beam 21 and the rear beam 22 in the left-right direction, respectively.

  The front end portions of the first outer plate 27 and the second outer plate 28 are formed narrower in the vertical direction than the middle portions of the first outer plate 27 and the second outer plate 28, and their lower end edges are located on the front upper side. Inclined towards. Further, the rear end portions of the first outer plate 27 and the second outer plate 28 are formed narrower in the vertical direction than the middle portions of the first outer plate 27 and the second outer plate 28, and their lower end edges Is inclined upward toward the rear side.

At the rear ends of the first outer plate 27 and the second outer plate 28, a notch 53 is provided at a position facing the notch 53 (see FIG. 4) of the first inner plate 24 and the second inner plate 25 in the width direction. A notch 33 having substantially the same shape is formed. The notch 33 does not interfere with the main body reference shaft 34 when the drum unit 4 is attached to the main body casing 2.
(6) Photosensitive drum FIG. 6 is a cross-sectional view of the drum unit shown in FIG. 3 taken along line VI-VI. FIG. 7 is a perspective view showing a part of the photosensitive drum and the first bearing member.

As shown in FIG. 6, the photosensitive drum 5 includes a cylindrical drum main body 80 and two flange members 81 that are fitted to both ends of the drum main body 80 so as not to be relatively rotatable.
The outermost layer of the drum body 80 is formed of a positively chargeable photosensitive layer.
An earth member 82 and a shaft 83 are arranged at the right end in the drum main body 80.

The ground member 82 is made of, for example, a metal material such as phosphor bronze, and is disposed inside the main body portion 84 and an annular plate-like main body portion 84 extending along the circumferential direction of the drum main body 80 as shown in FIG. The elastic part 85 is provided.
Four claws 86 are arranged at equiangular intervals on the outer peripheral edge of the main body 84. Each claw 85 is in contact with the inner surface of the drum body 80.

One end of the elastic portion 85 is connected to the main body portion 84, and the other end extends in a spiral shape toward the central axis of the drum main body 80.
The shaft 83 is made of a metal material and is disposed on the central axis of the drum body 80. As shown in FIG. 6, the right end portion of the shaft 83 passes through a flange member 81 described below and protrudes to the right from the flange member 81. Further, the left end portion of the shaft 83 is inserted through the vortex center of the elastic portion 85 and is in contact with the elastic portion 85.

  The flange member 81 is made of a resin material, and a part thereof is inserted into both end portions of the drum main body 80. On the left end face of the left flange member 81, a coupling groove (not shown) is provided in which a drive transmission unit 105 (see FIG. 2) described later provided in the main body casing 2 is coupled. As a result, as shown in FIG. 1, with the drum unit 4 mounted in the main casing 2, the driving force from the drive transmission unit is transmitted to the photosensitive drum 5, and the photosensitive drum 5 can be driven to rotate. The flange member 81 has an outer diameter that is smaller than the diameter of the drum holding hole 32 formed in the first inner plate 24 and the second inner plate 25.

The right flange member 81 is supported by the first bearing member 90 so as to be rotatable with respect to the first inner plate 24. The left flange member 81 is supported by the second bearing member 91 so as to be rotatable with respect to the second inner plate 25.
(7) Bearing Member FIG. 8 is a perspective view showing a part of the photosensitive drum and the first bearing member. FIG. 9 is a perspective view showing the second bearing member.
(7-1) First Bearing Member The first bearing member 90 is formed of a resin material, and as shown in FIGS. 7 and 8, as an example of a flange holding portion and a first insertion portion formed in a cylindrical shape. A cylindrical portion 92, a cylindrical shaft holding portion 93 extending in the same direction as the cylindrical portion 92 inside the cylindrical portion 92, and a first annular plate-like shape extending outward from the peripheral edge on the left side of the cylindrical portion 92 A flange 94 is provided integrally.

  The cylindrical portion 92 has an outer diameter slightly larger than the inner peripheral surface of the drum holding hole 32 (see FIG. 4) formed in the first inner plate 24, and is slightly smaller than the outer peripheral surface of the right flange member 81. Has a large inner diameter. A sealing portion 95 that seals the right end portion of the cylindrical portion 92 is formed integrally with the cylindrical portion 92 on the right end surface of the cylindrical portion 92. In the center of the sealing portion 95, a shaft through hole 96 having the same diameter as the outer peripheral surface of the shaft 83 is formed.

  The shaft holding portion 93 has substantially the same inner diameter as the outer peripheral surface of the shaft 83. Further, the right end portion of the shaft holding portion 93 is connected to a portion around the shaft through hole 96 on the left side surface of the sealing portion 95. As a result, when the shaft 83 is held by the shaft holding portion 93 by a method such as press-fitting or integral molding, the right end portion of the shaft 83 is connected to the sealing portion 95 (first through the shaft through hole 96 of the sealing portion 95. 1 bearing member 90) protrudes to the right.

A locking portion 97 as an example of two claw portions protruding rightward from the first flange portion 94 is formed at a position facing the outer peripheral edge of the first flange portion 94. The locking portion 97 is formed in a bowl shape whose tip is bent toward the center of the cylindrical portion 92.
(7-2) Second Bearing Member The second bearing member 91 is made of a resin material, and as shown in FIG. 9, the other end side holding portion and a cylinder as an example of the second insertion portion formed in a cylindrical shape. The portion 98 and the annular plate-shaped second flange 99 that extends outward from the peripheral edge on the left side of the cylindrical portion 98 are integrally provided.

The cylindrical portion 98 has an outer diameter slightly larger than the inner peripheral surface of the drum holding hole 32 (see FIG. 4) formed in the second inner plate 25, and is slightly smaller than the outer peripheral surface of the left flange member 81. Has a large inner diameter.
(8) Attaching the Photosensitive Drum to the Drum Unit FIG. 10 is a perspective view as seen from the lower left front side of the drum unit. In the state where one photosensitive drum is attached to the drum unit, the left end of the photosensitive drum is the second end. The state inserted in the drum support hole of the inner side plate is shown. FIG. 11 is a perspective view of the drum unit as viewed from the lower left front side. In the state where one photosensitive drum is attached to the drum unit, the right end of the photosensitive drum is in the drum support hole of the first inner plate. The state arrange | positioned in the position which opposes is shown. FIG. 12 is a perspective view as seen from the lower left front side of the drum unit. In the state where one photosensitive drum is attached to the drum unit, the left end of the photosensitive drum is positioned on the first inner plate. Indicates the state. FIG. 13 is an enlarged cross-sectional view of a peripheral portion of the drum support hole in the inner plate, showing a state where the first bearing member is inserted into the drum support hole. FIG. 14 is a perspective view of the drum unit as seen from the upper right front side, and shows a state in the middle of attachment of a pair of outer plates.

As shown in FIG. 10, the photosensitive drum 5 is attached to the drum unit 4 by four drum subunits 20, a front beam 21, a rear beam 22, and a pair of inner plates 23 (first inner plate 24 and second inner plate 25). Is performed in an assembled state.
Specifically, first, the four drum subunits 20 are arranged at regular intervals in the front-rear direction. The front beam 21 is disposed with a front space with respect to the foremost drum subunit 20. Further, the rear beam 22 is arranged with a slight space behind the rearmost drum subunit 20.

Thereafter, the first inner plate 24 is disposed on the right side of the front beam 21, the four drum subunits 20, and the rear beam 22, and the second inner plate 25 is disposed on the left side thereof. Then, the inner plates 23 are assembled to the front beam 21, the four drum subunits 20, and the rear beam 22 through a plurality of screws (not shown).
After the inner plates 23 are assembled to the front beam 21, the four drum subunits 20, and the rear beam 22, the photosensitive drum 5 is attached. 10 to 14, only one photosensitive drum 5 is illustrated in order to avoid complication of the drawings.

First, as shown in FIG. 10, the first bearing member 90 is attached to the right end portion of the photosensitive drum 5. Specifically, as shown in FIG. 7, the right flange member 81 is inserted inside the cylindrical portion 92. Further, the left end portion of the shaft 83 is in contact with the elastic portion 85 of the ground member 82.
Thereafter, the left end (left flange member 81) of the photosensitive drum 5 is inserted from below in a posture inclined with respect to the drum support hole 32 of the second inner plate 25. Specifically, the photosensitive drum 5 is inclined such that its left end is relatively upward and its right end is relatively downward. Since the outer diameter of the flange member 81 is smaller than the diameter of the drum support hole 32, the left flange member 81 is smoothly inserted into the drum support hole 32.

  Then, as shown in FIG. 11, the posture of the photosensitive drum 5 is set to a posture parallel to the width direction while the left flange member 81 is inserted into the drum support hole 32. Specifically, the drum support hole 32 (second drum support hole 32 from the front side in FIG. 11) and the width direction of the second inner plate 25 through which the left end portion (left flange member 81) of the photosensitive drum 5 is inserted. The right end of the photosensitive drum 5 is disposed at a position facing the drum support hole 32 of the first inner plate 24 facing the first inner plate 24. As a result, the axial direction of the photosensitive drum 5 coincides with the width direction. In this state, the left flange member 81 is exposed leftward from the drum support hole 32 of the second inner plate 25.

  Next, the photosensitive drum 5 is moved to the right as a whole, and the first bearing member 90 mounted on the right end of the photosensitive drum 5 is fitted into the drum support hole 32 of the first inner plate 24. . Specifically, as shown in FIG. 13, the outer peripheral surface of the cylindrical portion 92 of the first bearing member 90 is inserted into the drum support hole 32 in a state of being deformed along the four linear portions 60 of the drum support hole 32. The In this state, a gap is formed between the outer peripheral surface of the cylindrical portion 92 and the curved portion 61. Further, on the inner peripheral surface of the cylindrical portion 92, four inner straight portions 100 parallel to the four straight portions 60 are formed in accordance with the deformation of the cylindrical portion 92. The flange member 81 on the right side of the photosensitive drum 5 held by the cylindrical portion 92 abuts on one of the four inner straight portions 100 and is rotatably supported. As a result, the right end portion of the photosensitive drum 5 is positioned.

In this state, the first flange 94 of the first bearing member 90 is in contact with the inner side surface (left side surface) of the first inner plate 24. Further, the two locking portions 97 of the first flange portion 94 are locked to the first bearing locking groove 70 and the second bearing locking hole 72 of the first inner plate 24.
Thereafter, as shown in FIG. 12, the second bearing member 91 is attached to the second inner plate 25 and the left end portion (left flange member 81) of the photosensitive drum 5. Specifically, the cylindrical portion 98 of the second bearing member 91 (see FIG. 9) is provided between the outer peripheral surface of the left flange member 81 exposed from the drum support hole 32 of the second inner plate 25 and the drum support hole 32. Is inserted. That is, similarly to the first bearing member 90, the outer peripheral surface of the cylindrical portion 98 of the second bearing member 91 is inserted into the drum support hole 32 in a state of being deformed along the four straight portions 60 of the drum support hole 32. . In this state, a gap is formed between the outer peripheral surface of the cylindrical portion 98 and the curved portion 61. Further, four inner straight portions parallel to the four straight portions 60 are formed on the inner peripheral surface of the cylindrical portion 98 along with the deformation of the cylindrical portion 98. The left flange member 81 of the photosensitive drum 5 held by the cylindrical portion 98 abuts on any of the four inner straight portions and is rotatably supported. In this state, the second flange 99 of the second bearing member 91 is in contact with the outer surface (left side surface) of the second inner plate 25. As a result, the left end of the photosensitive drum 5 is positioned.

  Then, the clip member 101 is attached to a portion of the shaft 83 that protrudes to the right side of the sealing portion 95 (see FIG. 8) of the first bearing member 90. The clip member 101 is formed in a substantially U-shape, and each free end portion thereof is bent and locked in the clip locking groove 71 of the first inner plate 90 as shown in FIG. Thereby, the attachment of the photosensitive drum 5 to the drum unit 4 is completed.

After the attachment of the four photosensitive drums 5 is completed, the outer plate 26 is disposed on the outer side in the width direction of each inner plate 23 as shown in FIG. Then, the first outer plate 27 and the second outer plate 28 with respect to the first inner plate 24 and the second inner plate 25, the front beam 21, the four drum subunits 20, and the rear beam 22 through screws (not shown). Is assembled. Thereby, the assembly of the drum unit 4 is completed.
3. As shown in FIG. 6, a ground member 82 and a shaft 83 are provided in the photosensitive drum 5. As described above, the claw 86 of the ground member 82 is in contact with the inner surface of the drum body 80 of the photosensitive drum 5, and the ground member 82 and the shaft 83 are in contact with each other. Electrically connected. Further, as shown in FIG. 12, a clip member 101 is attached to the right end portion of the shaft 83. Since each free end portion of the clip member 101 is locked in the clip locking groove 71 of the first inner plate 24, the shaft 83 and the first inner plate 24 are electrically connected. That is, the drum body 80 of the photosensitive drum 5 is connected to the first inner plate 24 through the ground member 82, the shaft 83, and the clip member 101 so as to be electrically conductive.

As shown in FIG. 1, in a state where the drum unit 4 is mounted in the main body casing 2, the main body reference shaft 34 enters the notches 53 (see FIG. 4) of the first inner plate 24 and the second inner plate 25. The first inner plate 24 and the second inner plate 25 can be grounded via the reference shaft 34. In addition, since the first inner plate 24 and the photosensitive drum 5 are electrically connected through the ground member 82, the shaft 83, and the clip member 101, the ground member 82, the shaft 83, the clip member 101, and the first inner plate. The photosensitive drum 5 can be grounded through the main body 24 and the main body reference shaft 34.
4). Main Body Casing (1) Attaching / Detaching of Drum Unit to Main Body Casing Referring to FIG. 1, when attaching drum unit 4 to main body casing 2, first, front cover 3 of main body casing 2 is opened. Then, when the drum unit 4 is moved rearward, the drum unit 4 is guided into the main body casing 2. When the notch 53 (see FIG. 4) of the first inner plate 24 and the second inner plate 25 contacts the main body reference shaft 34, further pressing of the drum unit 4 is restricted. Thereby, mounting | wearing with respect to the inside of the main body casing 2 of the drum unit 4 is completed.

The detachment of the drum unit 4 from the main casing 2 is the reverse of the above.
(2) Input of Driving Force to Photosensitive Drum As shown in FIG. 2, when the drum unit 4 is mounted in the main body casing 2, the photosensitive drum 5 is located at a position facing the left end of each photosensitive drum 5 in the width direction. A drive transmission unit 105 as an example of a pressing member for transmitting a driving force to each other is disposed. After the drum unit 4 is mounted in the main casing 2, each drive transmission unit 105 advances to the right and is connected to a coupling groove (not shown) provided on the left end surface of each left flange member 81. The As a result, the driving force can be transmitted from the drive transmission unit 105 to each photosensitive drum 5, and each photosensitive drum 5 can be driven to rotate.

Moreover, after each drive transmission part 105 is connected to the coupling groove of each flange member 81, each drive transmission part 105 advances further to the right. Thereby, the drum unit 4 is moved rightward as a whole via each flange member 81. Thereby, positioning of the drum unit 4 in the width direction is achieved. At this time, the force received by the photosensitive drum 5 (drum unit 4) by each drive transmission unit 105 is larger than the force received by the shaft 83 from the ground member 82 shown in FIG.
5). As described above, the drum support holes 32 are formed in the first inner plate 24 and the second inner plate 25 of the drum unit 4 at positions facing each other. A first bearing member 90 and a second bearing member 91 are fitted in each drum support hole 32. The right end of the photosensitive drum 5 is supported by the first inner plate 24 via the first bearing member 90, and the left end is supported by the second inner plate 25 via the second bearing member 91. The first bearing member 90 has a first flange 94 that abuts against the inner surface of the first inner plate 24. On the other hand, the second bearing member 91 has a second flange 99 that comes into contact with the outer surface of the second inner plate 25.

  As a result, the first bearing member 90 is attached to one end portion of the photosensitive drum 5, and after the first bearing member 90 is fitted into the drum support hole 32 of the first inner plate 24, the second bearing member 91. Is fitted into the drum support hole 32 of the second inner plate 25 and the other end of the photosensitive drum 5 is held by the second bearing member 91, whereby the first inner plate 24 and the second inner plate 25. Attachment of the photosensitive drum 5 to the above is achieved.

  Further, by removing the second bearing member 91 from the drum support hole 32 of the second inner plate 25, the fixing of the other end of the photosensitive drum 5 is released, so that the photosensitive drum 5 and the first bearing member 90 are released. Can be integrally removed from the drum support hole 32 of the first inner plate 24. Therefore, it is not necessary to release the holding of the remaining photosensitive drums 5 by the first inner plate 24 and the second inner plate 25 in order to replace one photosensitive drum 5. As a result, the photosensitive drum 5 can be easily replaced.

  A ground member 82 is disposed in the drum body 80 of the photosensitive drum 5. A shaft 83 is disposed on the central axis of the photosensitive drum 580. The shaft 83 passes through the flange member 81, and a right end portion thereof protrudes to the right side of the flange member 81, and a left end portion thereof is in contact with the ground member 82. Thereby, the drum body 80 of the photosensitive drum 5 can be grounded via the ground member 82 and the shaft 83.

  Further, the first bearing member 90 has a locking portion 97. The locking portion 97 is locked to the first bearing locking groove 70 and the second bearing locking hole 72 of the first inner plate 24. Accordingly, the first bearing member 90 is fixed in a state where the first inner plate 24 is sandwiched between the first flange portion 94 and the locking portion 97. As a result, it is possible to prevent the first bearing member 90 from dropping from the drum support hole 32.

  The first inner plate 24 and the second inner plate 25 are made of a metal material. The drum support holes 32 are formed by pressing using the same press die for the first inner plate 24 and the second inner plate 25, respectively. Therefore, the drum support hole 32 of the first inner plate 24 and the drum support hole 32 of the second inner plate 25 can be formed with the same accuracy. Further, since it is not necessary to separately prepare a press die for the first inner plate 24 and a press die for the second inner plate 25, the processing cost of the first inner plate 24 and the second inner plate 25 can be reduced. Can do.

  The drum support hole 32 is formed by punching the first inner plate 24 and the second inner plate 25 from the left side. As a result, the corner formed by the inner surface of the drum support hole 32 of the first inner plate 24 and the inner surface (left side surface) of the first inner plate 24 is curved, forming a so-called sagging surface. Therefore, the first bearing member 90 can be smoothly fitted into the drum support hole 32 from the inner surface side of the first inner plate 24. In addition, a corner formed by the inner surface of the drum support hole 32 of the second inner plate 25 and the outer surface (left side surface) of the second inner plate 25 is curved to form a so-called sagging surface. Therefore, the second bearing member 91 can be smoothly fitted into the drum support hole 32 from the outer surface side of the second inner plate 25.

Each of the inner surfaces of the drum support holes 32 has four straight portions 60. The four straight portions 60 are in contact with a virtual circle 62 that is virtually set in the drum support hole 32, and are arranged at equiangular intervals with respect to the center of the virtual circle 62.
The first bearing member 90 has a cylindrical portion 92 that is inserted into the drum support hole 32. The cylindrical portion 92 has an outer peripheral surface having a diameter larger than the diameter of the virtual circle 62 that is virtually set in the drum support hole 32. As a result, when the cylindrical portion 92 is inserted into the drum support hole 32, the outer peripheral surface of the cylindrical portion 92 is deformed along the four straight portions 60 and presses against the straight portions 60 of the drum support hole 32. Therefore, the first bearing member 90 can be fitted to the drum support hole 32 without any play.

Further, when a temperature change occurs in the drum unit 4 and a stress due to a difference in expansion between the first bearing member 90 and the first inner plate 24 is applied to the first bearing member 90, the cylinder in the first bearing member 90 is When the portion other than the contact portion between the portion 92 and the straight portion 60 is deformed, the stress can be absorbed. As a result, the first bearing member 90 can be prevented from being damaged.
Further, four inner straight portions 100 parallel to the four straight portions 60 are formed on the inner surface of the cylindrical portion 92 as the cylindrical portion 92 is deformed. One end portion (flange member 81) of the photosensitive drum 5 held by the cylindrical portion 92 abuts on one of the four inner straight portions 100 and is rotatably supported. As a result, one end portion of the photosensitive drum 5 can be accurately positioned.

  The second bearing member 91 has a cylindrical portion 98 that is inserted into the drum support hole 32. The cylindrical portion 98 has an outer peripheral surface having a diameter larger than the diameter of the virtual circle 62 virtually set in the drum support hole 32. Thus, when the cylindrical portion 98 is inserted into the drum support hole 32, the outer peripheral surface of the cylindrical portion 98 is deformed along the four straight portions 60, and the outer peripheral surface of the cylindrical portion 98 is each linear portion of the drum support hole 32. Pressure contact with 60. Therefore, the second bearing member 91 can be fitted to the drum support hole 32 without any play.

Further, when a temperature change occurs in the drum unit 4 and a stress due to a difference in expansion between the second bearing member 91 and the second inner plate 25 is applied to the second bearing member 91, the cylinder in the second bearing member 91 is When the portion other than the contact portion between the portion 98 and the linear portion 60 is deformed, the stress can be absorbed. As a result, damage to the second bearing member 91 can be prevented.
In addition, along the deformation of the cylindrical portion 98, four inner straight portions parallel to the four straight portions 60 are formed on the inner surface of the cylindrical portion 98. The other end portion of the photosensitive drum 5 held by the cylindrical portion 98 abuts on any of the four inner straight portions and is rotatably supported. As a result, the other end portion of the photosensitive drum 5 can be accurately positioned.

  The inner surface of each drum support hole 32 includes four curved portions 61. Each curved portion 61 connects two linear portions 60 that are orthogonal to each other, and bulges outward in the radial direction of the virtual circle 62. As a result, spaces are generated in the drum support hole 32 between the first bearing member 90 and the second bearing member 91 and the four curved portions 61, respectively. Therefore, when the first bearing member 90 and the second bearing member 91 are deformed to the outside in the radial direction of the virtual circle 62, the deformation can be allowed in the space. Therefore, the first bearing member 90 and the second bearing Damage to the member 91 can be further prevented.

  The four straight portions 60 include two horizontal straight portions 64 that extend in the front-rear direction and two vertical straight portions 63 that extend in the vertical direction. Therefore, by arranging the two horizontal straight portions 64 of each drum support hole 32 on two straight lines extending in the front-rear direction, each drum support hole 32 can be formed at the same position in the vertical direction. As a result, the photosensitive drums 5 held in the drum support holes 32 via the first bearing member 90 and the second bearing member 91 can be arranged at the same position in the vertical direction.

  In addition, the drum support holes 32 are formed at equal intervals in the front-rear direction by forming the vertical straight portions 63 on one side in the front-rear direction of the drum support holes 32 at regular intervals in the front-rear direction. Can do. Therefore, the pitch between the drums of the photosensitive drum 5 held in the drum support hole 32 via the first bearing member 90 and the second bearing member 91 can be made constant.

The drive transmission unit 105 presses the photosensitive drum 5 from the left side toward the right side. The force that the photosensitive drum 5 receives from the drive transmission unit 105 is larger than the force that the shaft 83 receives from the ground member 82.
The direction in which the photosensitive drum 5 is pressed by the drive transmission unit 105 is the direction in which the first flange 94 of the first bearing member 90 contacts the inner surface of the first inner plate 24 and the second flange of the second bearing member 91. The portion 99 is the same as the direction in which the second inner plate 25 abuts on the outer surface. Therefore, when the photosensitive drum 5 is pressed by the drive transmission unit 105, the first bearing member 90 and the second bearing member 91 are directed toward the first inner plate 24 and the second inner plate 25 through the photosensitive drum 5, respectively. Since the first bearing member 90 and the second bearing member 91 are not inclined with respect to the first inner plate 24 and the second inner plate 25, respectively, the photosensitive drum 5 can be stably supported. .

FIG. 1 is a side sectional view showing an embodiment of a printer as an example of an image forming apparatus of the present invention. FIG. 2 is a perspective view of the drum unit as viewed from the upper right front side, showing a state in which one developing cartridge is attached and the other developing cartridges are detached. FIG. 3 is a plan view of the drum unit, showing a state where a pair of outer plates are removed from the drum unit. FIG. 4 is a perspective view of the second inner plate viewed from the upper right front side. FIG. 5 is an enlarged view of a peripheral portion of the drum support hole in the inner plate. 6 is a cross-sectional view of the drum unit shown in FIG. 3 taken along line VI-VI. FIG. 7 is a perspective view showing a part of the photosensitive drum and the first bearing member. FIG. 8 is a perspective view showing a part of the photosensitive drum and the first bearing member. FIG. 9 is a perspective view showing the second bearing member. FIG. 10 is a perspective view of the drum unit as viewed from the lower left front side. In the state where one photosensitive drum is attached to the drum unit, the left end of the photosensitive drum is inserted into the drum support hole of the second inner plate. Indicates the state. FIG. 11 is a perspective view of the drum unit as viewed from the lower left front side. In the state where one photosensitive drum is attached to the drum unit, the right end of the photosensitive drum faces the drum support hole of the first inner plate. The state arranged at the position is shown. FIG. 12 is a perspective view seen from the lower left front side of the drum unit, and shows a state in which the left end portion of the photosensitive drum is positioned on the first inner plate while one photosensitive drum is being attached to the drum unit. Show. FIG. 13 is an enlarged schematic cross-sectional view of a peripheral portion of the drum support hole in the inner plate, showing a state where the first bearing member is inserted into the drum support hole. FIG. 14 is a perspective view of the drum unit as viewed from the upper right front side, and shows a state in the middle of attachment of a pair of outer plates.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 2 Main body casing 4 Drum unit 5 Photosensitive drum 24 1st inner board 25 2nd inner board 32 Drum support hole 60 Linear part 61 Curved part 62 Virtual circle 63 Vertical linear part 64 Horizontal linear part 80 Drum main body 81 Flange member 82 Earth member 83 Shaft 90 First bearing member 91 Second bearing member 92 Cylindrical portion 93 Shaft holding portion 94 First collar portion 97 Locking portion 98 Cylindrical portion 99 Second collar portion 105 Drive transmission portion

Claims (9)

A plurality of photosensitive drums arranged in parallel with each other;
A shaft disposed on the central axis of each photosensitive drum;
A first side plate disposed on one side in the axial direction with respect to the photosensitive drum and having a first through hole formed at a position facing each photosensitive drum in the axial direction;
A second side plate disposed opposite to the first side plate on the other side in the axial direction with respect to the photosensitive drum, and having a second through-hole formed at a position facing each photosensitive drum in the axial direction;
A first bearing member fitted in each of the first through holes;
A second bearing member fitted in each of the second through holes,
The photosensitive drum is
A cylindrical drum body;
A flange member fitted to the one end of the drum body;
An earth member disposed in the drum body,
The shaft penetrates the flange member, one end of the shaft projects to the one side than the flange member, and the other end abuts the ground member,
The first bearing member is
A shaft holding portion for holding the one end portion of the shaft;
A flange holding portion for holding the flange member;
A first flange that contacts the inner surface of the first side plate;
The second bearing member is
A second end holding portion for holding the other end of the photosensitive drum;
A tandem type photosensitive unit having a second collar portion that abuts against an outer surface of the second side plate.   2. The tandem photoconductor unit according to claim 1, wherein the first bearing member has a claw portion that is locked to an outer surface of the first side plate. The first side plate and the second side plate are made of a metal material,
The first through hole and the second through hole are formed by pressing the first side plate and the second side plate using the same press die, respectively. Item 3. The tandem photoreceptor unit according to Item 1 or 2.   The tandem photoconductor unit according to claim 3, wherein the first through hole and the second through hole are formed by punching the first side plate and the second side plate from the other side, respectively. The inner surfaces of the first through hole and the second through hole have four straight portions,
The four straight portions are in contact with a virtual circle virtually set in the first through hole and the second through hole, and are arranged at equiangular intervals with respect to the center of the virtual circle,
The first bearing member has a diameter larger than the diameter of the virtual circle, and has a first insertion portion that is inserted into the first through hole,
The said 2nd bearing member has a larger diameter than the diameter of the said virtual circle, and has a 2nd insertion part inserted in a said 2nd through-hole. The tandem type photoreceptor unit described.   The inner surfaces of the first through hole and the second through hole include four curved portions that connect two linear portions orthogonal to each other and bulge outward in the radial direction of the virtual circle. The tandem type photoreceptor unit described.   The four straight portions include two horizontal straight portions that extend in the parallel direction of the photosensitive drums, and two vertical straight portions that extend in a direction perpendicular to the parallel direction and the axial direction. The tandem type photoreceptor unit described. The device body;
An image forming apparatus comprising: the tandem photosensitive unit according to claim 1, which is detachably attached to the apparatus main body. A pressing member that presses the photosensitive drum from the other side toward the one side;
The image forming apparatus according to claim 8, wherein a force received by the photosensitive drum by the pressing member is greater than a force received by the shaft from the ground member.

Images