Drum unit

Abstract

To remove a deposit on a photosensitive drum and remove a deposit on a charging roller.SOLUTION: A drum unit comprises: a drum frame 100 which is movable with respect to the main body housing of an image forming device and attachably / detachably supports a developing cartridge; a photosensitive drum 51 supported by the drum frame 100; a cleaning roller which comes in contact with the photosensitive drum 51 and recovers deposits on the photosensitive drum 51; a charging roller 200 which comes in contact with the photosensitive drum 51 to thereby charge the photosensitive drum 51; a charging roller cleaner 300 which comes in contact with the charging roller 200 and remove deposits on the charging roller 200; and a first bearing 510. The first bearing 510 supports one axial end portion of the charging roller 200 and one axial end portion of the charging roller cleaner 300. The charging roller 200 and the charging roller cleaner 300 can be fit into the drum frame 100 while the first bearing 510 is mounted.SELECTED DRAWING: Figure 8

Description

Technical Field

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[0001] The present disclosure relates to a drum unit including a photosensitive drum, which is movable with respect to the main body housing of an image forming apparatus.

Background Art

[0002] Conventionally, as a drum unit, there is known one including a charging roller for charging a photosensitive drum and a cleaning roller for removing deposits such as toner and paper dust on the photosensitive drum (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, although deposits on the photosensitive drum can be removed by the cleaning roller, when deposits adhere to the charging roller, the deposits on the charging roller cannot be removed, and there is a problem that the charging performance of the charging roller deteriorates.

[0005] <00000??]]Therefore, an object of the present disclosure is to remove deposits on the photosensitive drum and deposits on the charging roller.

Means for Solving the Problems

[0006] To solve the above problems, a drum unit according to a first aspect of the present disclosure is movable with respect to the main body housing of an image forming apparatus and includes a drum frame, a photosensitive drum, a cleaning roller, a charging roller, a charging roller cleaner, and a first bearing. The drum frame detachably supports a developing cartridge having a developing roller. It should be noted that there seems to be a typo in the original text where "

発明が解決しようとする課題

発明が解決しようとする課題

課題を解決するための手段

課題を解決するための手段

発明が解決しようとする課題

課題を解決するための手段

[0007] According to the first embodiment, deposits on the photosensitive drum can be removed by the cleaning roller, and deposits on the charging roller can be removed by the charging roller cleaner. Furthermore, since the charging roller and the charging roller cleaner can be mounted on the drum frame while mounted on the first bearing, the assembly work of the drum unit can be easily performed.

[0008] Furthermore, the drum unit of the second embodiment is the drum unit of the first embodiment, further comprising a conductive first spring that presses the charging roller against the photosensitive drum by pressing the first bearing, and the first bearing may be conductive.

[0009] According to the second embodiment, a voltage can be applied to the charging roller and the charging roller cleaner via the first spring and the first bearing.

[0010] Furthermore, the drum unit of the third embodiment is the drum unit of the second embodiment, further comprising a second bearing that supports the other axial end of the charging roller and the other axial end of the charging roller cleaner, and a second spring that presses the charging roller against the photosensitive drum by pressing the second bearing, wherein the drum frame comprises a support frame that supports the first bearing, the second bearing, the first spring and the second spring, and the first bearing and the second bearing may be in contact with the support frame in the axial direction.

[0011] According to the third embodiment, since the first bearing and the second bearing are in axial contact with the support frame, the first bearing and the second bearing can be positioned axially with respect to the support frame.

[0012] Furthermore, the drum unit of the fourth embodiment is the drum unit of the third embodiment, wherein the electrostatic roller cleaner comprises a rotatable cleaner shaft extending in the axial direction and a helical elastic member located on the outer circumferential surface of the cleaner shaft, the elastic member in contact with the electrostatic roller, wherein when the electrostatic roller cleaner rotates, the helical elastic member presses the electrostatic roller to the other side in the axial direction, so that the other end of the electrostatic roller in the axial direction is pressed against the second bearing, and the elastic member receives a reaction force from the electrostatic roller, whose axial movement is restricted by the second bearing, toward one side in the axial direction, so that the one end of the cleaner shaft in the axial direction is pressed against the first bearing.

[0013] According to the fourth embodiment, when the charging roller cleaner rotates, the charging roller can be pressed against the drum frame via the second bearing and support frame, thereby positioning the charging roller axially with respect to the drum frame. Furthermore, when the charging roller cleaner rotates, the charging roller cleaner can be pressed against the drum frame via the first bearing and support frame, thereby positioning the charging roller cleaner axially with respect to the drum frame.

[0014] Furthermore, the drum unit of the fifth embodiment is a drum unit of the third or fourth embodiment, wherein the first bearing has a first contact surface that contacts the support frame in the axial direction, and a first projection that protrudes from the first contact surface, which limits the first bearing from coming off the support frame.

[0015] According to the fifth embodiment, the first projection can prevent the first bearing from coming off the support frame. Furthermore, when the first bearing is pushed axially by the electrostatic roller cleaner during rotation, the first projection becomes even less likely to come off the support frame.

[0016] Furthermore, the drum unit of the sixth embodiment is a drum unit of any one of the third to fifth embodiments, wherein the second bearing has a second contact surface that contacts the support frame in the axial direction, and a second projection that protrudes from the second contact surface, the second projection for preventing the second bearing from coming off the support frame.

[0017] According to the sixth embodiment, the second projection can prevent the second bearing from coming off the support frame. Furthermore, when the second bearing is pushed axially by the charging roller during the rotation of the charging roller cleaner, the second projection becomes even less likely to come off the support frame.

[0018] Furthermore, the drum unit of the seventh embodiment is a drum unit of any one of the third to sixth embodiments, wherein the first bearing is a first boss that supports the first spring and has a first boss that extends in the pressing direction which is the direction in which the charging roller is pressed against the photosensitive drum, and the support frame has a first portion that faces the first boss in the pressing direction, and one of the first boss and the first portion may have a convex portion, and the other may have a recess into which the convex portion fits.

[0019] According to the seventh embodiment, the first bearing can be positioned in a direction perpendicular to the pressing direction.

[0020] Further, the drum unit of the eighth aspect is any one of the drum units of the third aspect to the seventh aspect, the second bearing is a second boss that supports the second spring, and the second boss has a second boss that extends in a pressing direction that is the direction in which the charging roller is pressed against the photosensitive drum. The support frame has a second portion facing the second boss in the pressing direction, and one of the second boss and the second portion may have a convex portion, and the other may have a concave portion into which the convex portion fits.

[0021] According to the eighth aspect, the second bearing can be positioned in a direction perpendicular to the pressing direction.

Advantages of the Invention

[0022] According to the present disclosure, deposits on the photosensitive drum can be removed, and deposits on the charging roller can also be removed.

Brief Description of the Drawings

[0023] [Figure 1] It is a diagram showing an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] 2]It is a diagram showing a state where the drum unit is pulled out of the main body housing. [Figure 3] It is a diagram showing an enlarged structure around the charging roller unit. [Figure 4] It is a perspective view showing the drum unit. [Figure 5] It is a perspective view showing the first bearing, the second bearing, the first spring, the second spring, etc. [[ID=]33] [Figure 6] It is a diagram showing the relationship between the convex portion of the support frame and the boss of each bearing. [Figure 7] It is a cross-sectional view of the drum unit and a cross-sectional view showing an engagement portion between the support frame and each bearing. [Figure 8] It is an enlarged cross-sectional view showing one end side in the axial direction of FIG. 7. [Figure 9] It is an enlarged cross-sectional view showing the other end side in the axial direction of FIG. 7.

Embodiments for Carrying Out the Invention

[0024] Hereinafter, one embodiment of this disclosure will be described in detail with reference to the drawings as appropriate. As shown in Figure 1, a color printer 1, which is an example of an image forming apparatus, comprises a main body housing 2, and a supply unit 3, an image forming unit 4, a fixing unit 8, and a transport unit 9, all located inside the main body housing 2. The main body housing 2 has an output tray 21 on its upper surface.

[0025] The supply unit 3 includes a supply tray 31 for holding sheets S and a supply mechanism 32 for supplying the sheets S in the supply tray 31 to the image forming unit 4.

[0026] The image forming unit 4 comprises an exposure device SC, a drum unit 5, four developing cartridges 6, and a transfer unit 7.

[0027] The exposure apparatus SC is equipped with a light source and polygon mirrors, etc. (not shown). The exposure apparatus SC exposes the surface of the photosensitive drum 51 with a light beam shown by a dashed line.

[0028] The drum unit 5 is movable relative to the main housing 2 between the storage position shown in Figure 1 and the extension position shown in Figure 2. The drum unit 5 comprises a drum frame 100, four photosensitive drums 51, and four electrostatic roller units 52.

[0029] The drum frame 100 is movably supported on the main body casing 2. The drum frame 100 rotatably supports each photosensitive drum 51. The drum frame 100 detachably supports the developing cartridge 6.

[0030] The four photosensitive drums 51 are arranged at intervals in the direction of conveying the sheet S. The electrostatic roller units 52 are positioned at locations corresponding to each of the four photosensitive drums 51.

[0031] The four developing cartridges 6 each contain toner of a different color. Each developing cartridge 6 has a developing roller 61 that supplies toner to the photosensitive drum 51. The developing roller 61 is in contact with the photosensitive drum 51.

[0032] As shown in Figure 3, the drum unit 5 further comprises a cleaning roller 53, a recovery roller 54, a cleaner 55, and a static eliminator 56. The drum frame 100 rotatably supports the cleaning roller 53 and the recovery roller 54 via bearings (not shown). The charging roller unit 52 comprises a charging roller 200, a charging roller cleaner 300, and a support frame 400. The support frame 400 is a component of the drum frame 100. The support frame 400 is made of, for example, resin. The support frame 400 rotatably supports the charging roller 200 and the charging roller cleaner 300 via a first bearing 510 and a second bearing 520, which will be described later.

[0033] The cleaning roller 53 is a roller capable of collecting deposits adhering to the outer surface of the photosensitive drum 51. The cleaning roller 53 comes into contact with the outer surface of the photosensitive drum 51. The deposits include toner, paper dust, and the like.

[0034] The recovery roller 54 is a roller capable of recovering deposits adhering to the outer surface of the cleaning roller 53. The recovery roller 54 is in contact with the outer surface of the cleaning roller 53.

[0035] The cleaner 55 is a component for scraping off deposits adhering to the outer surface of the recovery roller 54. The cleaner 55 is made of an elastic material such as a sponge and comes into contact with the outer surface of the recovery roller 54. The drum frame 100 has a recess 101 for accumulating the deposits scraped off by the cleaner 55.

[0036] The static eliminator 56 is a component that removes static electricity from the outer surface of the photosensitive drum 51 by irradiating the outer surface of the photosensitive drum 51 with light. The static eliminator 56 has, for example, an LED. The static eliminator 56 is positioned between the cleaning roller 53 and the transfer roller 74 (see Figure 1), which will be described later, in the rotational direction of the photosensitive drum 51.

[0037] The charging roller 200 is a roller for charging the photosensitive drum 51. The charging roller 200 contacts the outer surface of the photosensitive drum 51 and rotates in conjunction with the photosensitive drum 51. The charging roller 200 is positioned between the cleaning roller 53 and the developing roller 61 in the direction of rotation of the photosensitive drum 51. The charging roller 200 is positioned above the first axis X1, which is the center of rotation of the photosensitive drum 51.

[0038] The electrostatic roller cleaner 300 is a component for removing deposits adhering to the electrostatic roller 200. Specifically, the electrostatic roller cleaner 300 is capable of scraping off deposits on the electrostatic roller 200 onto the photosensitive drum 51. The electrostatic roller cleaner 300 contacts the outer surface of the electrostatic roller 200 and rotates in conjunction with the electrostatic roller 200.

[0039] The charging roller cleaner 300 is positioned above the second axis X2, which is the rotation center of the charging roller 200. The charging roller cleaner 300 is positioned on the developing roller 61 side of the line connecting the first axis X1 and the second axis X2. A portion of the charging roller cleaner 300 protrudes above the charging roller 200 in the vertical direction and in the direction perpendicular to the first axis X1, and faces the photosensitive drum 51 in the vertical direction. This allows any deposits scraped off by the charging roller cleaner 300 to fall onto the outer surface of the photosensitive drum 51. In this embodiment, the vertical direction is the same as the orthogonal direction perpendicular to the axial direction and the movement direction, which will be described later.

[0040] Furthermore, any material scraped off onto the photosensitive drum 51 by the electrostatic roller cleaner 300 may be collected into the developing cartridge 6 by the developing roller 61, or it may be collected by the belt cleaner BC, which will be described later, via the transport belt 73, which will be described later.

[0041] Returning to Figure 1, the transfer unit 7 comprises a drive roller 71, a driven roller 72, a conveyor belt 73, four transfer rollers 74, and a belt cleaner BC. The conveyor belt 73 is an endless belt. The drive roller 71 and the driven roller 72 are components for rotating the conveyor belt 73.

[0042] The transfer roller 74 is a component that transfers the image on the photosensitive drum 51 to the sheet S or the conveyor belt 73. The transfer roller 74 is positioned inside the conveyor belt 73 and sandwiches the conveyor belt 73 between itself and the corresponding photosensitive drum 51.

[0043] The belt cleaner BC has the function of cleaning deposits on the conveyor belt 73. The belt cleaner BC is located on the opposite side of the conveyor belt 73 from the photosensitive drum 51.

[0044] The fixing device 8 is a device that heat-fixes the toner image onto the sheet S. The fixing device 8 includes a heating roller 81 that heats the sheet S and a pressure roller 82 that sandwiches the sheet S between the heating roller 81 and the pressure roller.

[0045] The transport unit 9 is configured to transport the sheet S discharged from the fixing device 8 toward the outside of the main housing 2. The transport unit 9 includes a transport roller 91 and a discharge roller 92. The sheet S discharged from the fixing device 8 is discharged to the discharge tray 21 by the transport roller 91 and the discharge roller 92.

[0046] As shown in Figure 4, the drum frame 100 has the four support frames 400 mentioned above, as well as a first frame 110, a second frame 120, a third frame 130, and a fourth frame 140.

[0047] In the following explanation, the direction of movement of the drum unit 5 will be simply referred to as the "direction of movement." In the drawings, the direction indicated by the arrow showing the direction of movement will be referred to as "one side of the direction of movement," and the opposite side as "the other side of the direction of movement." One side of the direction of movement corresponds to the downstream side in the direction in which the drum unit 5 is pulled out from the main housing 2.

[0048] Furthermore, the axial direction of the electrostatic roller 200 shown in Figure 5 is simply referred to as the "axial direction." In the drawing, the direction indicated by the arrow showing the axial direction is referred to as "one side of the axial direction," and the opposite side is referred to as "the other side of the axial direction."

[0049] The first frame 110 is a frame that supports one axial end of each support frame 400 and each photosensitive drum 51. The second frame 120 is a frame that supports the other axial end of each support frame 400 and each photosensitive drum 51.

[0050] The third frame 130 is connected to one end of the first frame 110 and one end of the second frame 120 in the direction of movement. The fourth frame 140 is connected to the other end of the first frame 110 and the other end of the second frame 120 in the direction of movement. Each support frame 400 and each photosensitive drum 51 is located between the third frame 130 and the fourth frame 140 in the direction of movement.

[0051] As shown in Figures 7 and 8, the first frame 110 has a first metal frame 111 made of metal and a first resin frame 112 made of resin. One axial end of the photosensitive drum 51 is supported by the first metal frame 111 via a first drum bearing DB1. One axial end of the support frame 400 is fixed to the first metal frame 111 by screws or the like. The first metal frame 111 is positioned axially on the main body housing 2.

[0052] As shown in Figures 7 and 9, the second frame 120 has a second metal frame 121 made of metal and a second resin frame 122 made of resin. The other axial end of the photosensitive drum 51 is supported by the second metal frame 121 via a second drum bearing DB2. The other axial end of the support frame 400 is fixed to the second metal frame 121 by screws or the like. The second metal frame 121 is positioned axially on the main housing 2.

[0053] The electrostatic roller 200 comprises a shaft 210 and a roller portion 220. The shaft 210 is made of metal and extends in the axial direction. The roller portion 220 is made of a conductive and elastic material, such as conductive rubber. The roller portion 220 is positioned on the outer circumferential surface of the shaft 210 so as to cover the outer circumferential surface of the shaft 210. The roller portion 220 is in contact with the photosensitive drum 51.

[0054] As shown in Figure 5, the electrostatic roller cleaner 300 comprises a cleaner shaft 310 and an elastic member 320. The cleaner shaft 310 is made of metal. The cleaner shaft 310 extends in the axial direction.

[0055] The elastic member 320 is a conductive and elastic material, such as a conductive sponge. The elastic member 320 is a helical member located on the outer circumferential surface of the cleaner shaft 310. The elastic member 320 is in contact with the charging roller 200.

[0056] The electrostatic roller unit 52 further comprises a first bearing 510, a first spring 610, a second bearing 520, and a second spring 620. The first bearing 510 and the first spring 610 are conductive. In this embodiment, the first bearing 510 is made of a conductive resin, and the first spring 610 is made of metal.

[0057] The second bearing 520 and the second spring 620 may or may not be electrically conductive. In this embodiment, the second bearing 520 is made of a non-conductive resin, and the second spring 620 is made of metal.

[0058] The main housing 2 is provided with a voltage application unit (not shown). The voltage application unit applies voltage to the charging roller 200 and the charging roller cleaner 300 via the first spring 610 and the first bearing 510.

[0059] The first bearing 510 rotatably supports one axial end of the charging roller 200 and one axial end of the charging roller cleaner 300. As shown in Figure 8, the first bearing 510 has a first roller support recess 511 that rotatably supports one axial end of the shaft 210 and a first cleaner support recess 512 that rotatably supports one axial end of the cleaner shaft 310. The shaft 210 is rotatable relative to the first roller support recess 511 with one end of the shaft 210 inserted into the first roller support recess 511. The cleaner shaft 310 is rotatable relative to the first cleaner support recess 512 with one end of the cleaner shaft 310 inserted into the first cleaner support recess 512.

[0060] As shown in Figures 8 and 5, the first bearing 510 further includes a first contact surface 513, a first projection 514, and a first boss 515. The first contact surface 513 is a surface that contacts the support frame 400 in the axial direction. The first contact surface 513 is perpendicular to the axial direction.

[0061] The first projection 514 is a projection that prevents the first bearing 510 from coming off the support frame 400. The first projection 514 protrudes from the first contact surface 513.

[0062] The first boss 515 is a boss that supports the first spring 610. The first boss 515 extends in the pressing direction, which is the direction in which the charging roller 200 is pressed against the photosensitive drum 51 by the first spring 610. The first boss 515 has a recess 516 on its tip surface. The recess 516 opens on the upstream side in the pressing direction and on both sides in the axial direction.

[0063] The first spring 610 is a spring that presses the electrostatic roller 200 against the photosensitive drum 51 by pressing against the first bearing 510. The first spring 610 has a coil spring-shaped spring body 611, an electrical contact 612, and a connecting portion 613. The spring body 611 is supported from the inside by a first boss 515. The electrical contact 612 contacts a main body electrode provided on the main body housing 2. The spring body 611 and the electrical contact 612 are connected via the connecting portion 613.

[0064] The support frame 400 has a first limiting surface 411 and a first hook 412 as shown in Figure 8, and a first portion 413 as shown in Figure 6.

[0065] As shown in Figure 8, the first limiting surface 411 is a surface that restricts the first bearing 510 from moving to one side in the axial direction. The first limiting surface 411 can contact the first contact surface 513 of the first bearing 510. The first limiting surface 411 is perpendicular to the axial direction.

[0066] The first hook 412 is a part for supporting the first bearing 510. The first hook 412 has an arm portion 412A and a claw portion 412B. The arm portion 412A extends in the pressing direction and is elastically deformable in the axial direction. The claw portion 412B protrudes axially toward the first bearing 510 from the downstream end of the arm portion 412A in the pressing direction. The claw portion 412B engages with the first projection 514 of the first bearing 510 in the pressing direction.

[0067] As shown in Figure 6, the claw portion 412B has an inclined surface F1 that contacts the first projection 514 of the first bearing 510 when the first bearing 510 is attached to the support frame 400. The first projection 514 has an inclined surface F2 that contacts the inclined surface F1 of the claw portion 412B when the first bearing 510 is attached to the support frame 400.

[0068] Each inclined surface F1, F2 is tilted so that as it moves upstream in the pressing direction, it is positioned on the other side in the axial direction. As a result, when the first bearing 510 is attached to the support frame 400, the first hook 412 is pushed and deformed to one side in the axial direction by the inclined surface F2 of the first projection 514, and then returns to its original shape, causing the first projection 514 to engage with the claw portion 412B.

[0069] The first part 413 is the portion facing the first boss 515 in the pressing direction. The first part 413 has a protrusion 414 that fits into a recess 516 (see Figure 5) of the first boss 515. The protrusion 414 fitting into the recess 516 restricts the movement of the first bearing 510 in directions perpendicular to the axial direction and the pressing direction. The first bearing 510 is also movable in the pressing direction and the axial direction relative to the protrusion 414.

[0070] The second bearing 520 supports the other axial end of the charging roller 200 and the other axial end of the charging roller cleaner 300. As shown in Figure 9, the second bearing 520 has a second roller support recess 521 that rotatably supports the other axial end of the shaft 210 and a second cleaner support recess 522 that rotatably supports the other axial end of the cleaner shaft 310. The shaft 210 is rotatable relative to the second roller support recess 521 with its other end inserted into the second roller support recess 521. The cleaner shaft 310 is rotatable relative to the second cleaner support recess 522 with its other end inserted into the second cleaner support recess 522.

[0071] As shown in Figures 9 and 5, the second bearing 520 further includes a second contact surface 523, a second projection 524, and a second boss 525. The second contact surface 523 is a surface that contacts the support frame 400 in the axial direction. The second contact surface 523 is perpendicular to the axial direction.

[0072] The second projection 524 is a projection that prevents the second bearing 520 from coming off the support frame 400. The second projection 524 protrudes from the second contact surface 523.

[0073] The second boss 525 is a boss that supports the second spring 620. The second boss 525 extends in the pressing direction. The second boss 525 has a recess 526 on its tip surface. The recess 526 opens on the upstream side in the pressing direction and also opens on both sides in the axial direction.

[0074] The second spring 620 is a spring that presses the electrostatic roller 200 against the photosensitive drum 51 by pressing against the second bearing 520. The second spring 620 is a coil spring. The second spring 620 is supported from the inside by the second boss 525.

[0075] The support frame 400 has a second limiting surface 421 and a second hook 422 as shown in Figure 9, and a second portion 423 as shown in Figure 6.

[0076] As shown in Figure 9, the second limiting surface 421 is a surface that restricts the second bearing 520 from moving to the other side in the axial direction. The second limiting surface 421 is in contact with the second contact surface 523 of the second bearing 520. The second limiting surface 421 is perpendicular to the axial direction.

[0077] The second hook 422 is a part for supporting the second bearing 520. The second hook 422 has an arm portion 422A and a claw portion 422B. The arm portion 422A extends in the pressing direction and is elastically deformable in the axial direction. The claw portion 422B protrudes axially toward the second bearing 520 from the downstream end of the arm portion 422A in the pressing direction. The claw portion 422B engages with the second projection 524 of the second bearing 520 in the pressing direction.

[0078] As shown in Figure 6, the claw portion 422B has an inclined surface F3 that contacts the second projection 524 of the second bearing 520 when the second bearing 520 is attached to the support frame 400. The second projection 524 has an inclined surface F4 that contacts the inclined surface F3 of the claw portion 422B when the second bearing 520 is attached to the support frame 400.

[0079] Each inclined surface F3, F4 is tilted so that it is positioned on one side in the axial direction as it moves upstream in the pressing direction. As a result, when the second bearing 520 is attached to the support frame 400, the second hook 422 is pushed and deformed on the inclined surface F4 of the second projection 524 on the other side in the axial direction, and then returns to its original shape, causing the second projection 524 to engage with the claw portion 422B.

[0080] The second part 423 is the portion facing the second boss 525 in the pressing direction. The second part 423 has a protrusion 424 that fits into the recess 526 (see Figure 5) of the second boss 525. The protrusion 424 fitting into the recess 526 restricts the movement of the second bearing 520 in directions perpendicular to the axial direction and the pressing direction. The second bearing 520 is also movable relative to the protrusion 424 in the pressing direction and the axial direction.

[0081] The electrostatic roller 200 and the electrostatic roller cleaner 300 can be mounted on the support frame 400 with the first bearing 510 and the second bearing 520 attached. When the electrostatic roller 200, the electrostatic roller cleaner 300, the first bearing 510, the second bearing 520, the first spring 610, and the second spring 620 are mounted on the support frame 400, the support frame 400 supports the first bearing 510, the second bearing 520, the first spring 610, and the second spring 620.

[0082] Next, we will explain the process by which the charging roller 200 and the charging roller cleaner 300 are positioned in the axial direction during image formation. As shown in Figure 9, during image formation, when the photosensitive drum 51 rotates, the charging roller 200 and the charging roller cleaner 300 rotate in accordance with the rotation of the photosensitive drum 51. When the charging roller cleaner 300 rotates, the helical elastic member 320 presses the charging roller 200 to the other side in the axial direction. As a result, the other end of the shaft 210 of the charging roller 200 in the axial direction is pressed against the bottom surface 521A of the second roller support recess 521 of the second bearing 520. In other words, the other end of the shaft 210 in the axial direction comes into contact with the bottom surface 521A of the second roller support recess 521. When the other end of the shaft 210 in the axial direction comes into contact with the bottom surface 521A of the second roller support recess 521, the movement of the charging roller 200 to the other side in the axial direction is restricted.

[0083] The axial force applied from the charging roller 200 to the second bearing 520 is received by the second metal frame 121 via the support frame 400. As a result, the charging roller 200 is positioned axially with respect to the second metal frame 121. This means that both the charging roller 200 and the photosensitive drum 51 are positioned axially with respect to the second metal frame 121, thus determining the region in the axial direction where the photosensitive drum 51 is charged.

[0084] On the other hand, when the spiral elastic member 320 presses the charging roller 200 to the other side in the axial direction, the electrostatic roller cleaner 300 receives a reaction force from the force applied by the elastic member 320 to the charging roller 200. In particular, when the axial movement of the charging roller 200 is restricted by the second bearing 520, the reaction force applied from the charging roller 200 to the electrostatic roller cleaner 300 becomes larger. When a reaction force is applied from the charging roller 200 to the electrostatic roller cleaner 300 toward one side in the axial direction, as shown in Figure 8, one end of the cleaner shaft 310 in the axial direction is pressed against the bottom surface 512A of the first cleaner support recess 512 of the first bearing 510. In other words, one end of the cleaner shaft 310 in the axial direction comes into contact with the bottom surface 512A of the first cleaner support recess 512.

[0085] The axial force applied from the electrostatic roller cleaner 300 to the first bearing 510 is received by the first metal frame 111 via the support frame 400. Therefore, the electrostatic roller cleaner 300 is positioned axially with respect to the first metal frame 111.

[0086] Based on the above, the following effects can be obtained in this embodiment. The cleaning roller 53 can remove deposits from the photosensitive drum 51, and the electrostatic roller cleaner 300 can remove deposits from the electrostatic roller 200. Furthermore, since the electrostatic roller 200 and the electrostatic roller cleaner 300 can be mounted on the drum frame 100 with the first bearing 510 and the second bearing 520 attached, the assembly of the drum unit 5 can be easily performed.

[0087] Since the first bearing 510 and the first spring 610 are conductive, a voltage can be applied to the charging roller 200 and the charging roller cleaner 300 via the first spring 610 and the first bearing 510.

[0088] Since the first bearing 510 and the second bearing 520 make axial contact with the support frame 400, the first bearing 510 and the second bearing 520 can be positioned axially relative to the support frame 400.

[0089] When the electrostatic roller cleaner 300 rotates, the electrostatic roller 200 can be pressed against the drum frame 100 via the second bearing 520 and the support frame 400, thereby positioning the electrostatic roller 200 axially with respect to the drum frame 100. Furthermore, when the electrostatic roller cleaner 300 rotates, the electrostatic roller cleaner 300 can be pressed against the drum frame 100 via the first bearing 510 and the support frame 400, thereby positioning the electrostatic roller cleaner 300 axially with respect to the drum frame 100.

[0090] The first projection 514 prevents the first bearing 510 from coming off the support frame 400. Furthermore, when the first bearing 510 is pushed axially by the electrostatic roller cleaner 300 during rotation, the engagement width between the first projection 514 and the claw portion 412B becomes maximum, making it even more difficult for the first projection 514 to come off the support frame 400.

[0091] The second projection 524 prevents the second bearing 520 from coming off the support frame 400. Furthermore, when the second bearing 520 is pushed axially by the charging roller 200 during the rotation of the charging roller cleaner 300, the engagement width between the second projection 524 and the claw portion 422B becomes maximum, making it even more difficult for the second projection 524 to come off the support frame 400.

[0092] The protrusion 414 of the support frame 400 fits into the recess 516 of the first boss 515, which restricts the movement of the first bearing 510 in a direction perpendicular to the axial direction and the pressing direction. Thus, the first bearing 510 can be positioned in a direction perpendicular to the axial direction and the pressing direction.

[0093] The protrusion 424 of the support frame 400 fits into the recess 526 of the second boss 525, which restricts the movement of the second bearing 520 in a direction perpendicular to the axial direction and the pressing direction. Thus, the second bearing 520 can be positioned in a direction perpendicular to the axial direction and the pressing direction.

[0094] This disclosure is not limited to the embodiments described above and can be used in various forms as illustrated below.

[0095] In the embodiment described above, the first boss 515 has a recess 516 and the first portion 413 has a protrusion 414. However, the disclosure is not limited thereto, and the first boss may have a protrusion and the first portion may have a recess. Similarly, the second boss and the second portion may have a protrusion and the second portion may have a recess.

[0096] The image forming apparatus is not limited to the color printer 1, but may also be a copier, a multifunction printer, or the like.

[0097] The elements described in the above-mentioned embodiments and modifications may be implemented in any combination. [Explanation of Symbols]

[0098] 1. Color printer 2 Main unit 5 Drum Units 6. Developing cartridge 51 Photosensitive drum 53 Cleaning roller 61 Developing roller 100 Drum Frames 200 Electrostatic Roller 300 Electrostatic Roller Cleaner 510 First bearing

Claims

1. A drum unit that is movable relative to the main housing of an image forming apparatus, A drum frame that detachably supports a developing cartridge having a developing roller, A photosensitive drum supported by the aforementioned drum frame, A cleaning roller that comes into contact with the photosensitive drum and is capable of collecting any deposits adhering to the photosensitive drum, A charging roller that contacts the photosensitive drum and charges the photosensitive drum, A charging roller cleaner that comes into contact with the charging roller and removes deposits adhering to the charging roller, A first bearing supports one axial end of the charging roller and one axial end of the charging roller cleaner, Equipped with, The charging roller and the charging roller cleaner can be mounted on the drum frame with the first bearing installed. The drum unit is characterized in that the drum frame supports four of the photosensitive drums.

2. A drum unit that is movable relative to the main housing of an image forming apparatus, A drum frame that detachably supports a developing cartridge having a developing roller, A photosensitive drum supported by the aforementioned drum frame, A cleaning roller that comes into contact with the photosensitive drum and is capable of collecting any deposits adhering to the photosensitive drum, A charging roller that contacts the photosensitive drum and charges the photosensitive drum, A charging roller cleaner that comes into contact with the charging roller and removes deposits adhering to the charging roller, A first bearing supports one axial end of the charging roller and one axial end of the charging roller cleaner, A first spring presses the charging roller against the photosensitive drum by pressing the first bearing, Equipped with, The charging roller and the charging roller cleaner can be mounted on the drum frame with the first bearing installed. The drum unit is characterized in that the pressing direction of the first spring is different from the direction in which the charging roller and the charging roller cleaner are aligned.

3. The drum unit according to claim 2, characterized in that the drum frame supports four of the photosensitive drums.

4. The system further includes a conductive first spring that presses the charging roller against the photosensitive drum by pressing the first bearing, The drum unit according to any one of claims 1 to 3, characterized in that the first bearing is electrically conductive.

5. A second bearing supports the other axial end of the charging roller and the other axial end of the charging roller cleaner, The device further comprises a second spring that presses the charging roller against the photosensitive drum by pressing the second bearing, The drum frame is The system comprises a support frame that supports the first bearing, the second bearing, the first spring, and the second spring, The drum unit according to claim 4, characterized in that the first bearing and the second bearing are in contact with the support frame in the axial direction.

6. The aforementioned electrostatic roller cleaner is A rotatable cleaner shaft extending in the axial direction, The cleaner shaft comprises a spiral elastic member located on the outer circumferential surface, the elastic member in contact with the charging roller, During the rotation of the aforementioned charged roller cleaner, The helical elastic member presses the charging roller to the other side in the axial direction, so that the other end of the charging roller in the axial direction is pressed against the second bearing. The drum unit according to claim 5, characterized in that the elastic member receives a reaction force to the force pressing the charging roller, so that one end of the cleaner shaft in the axial direction is pressed against the first bearing.

7. The first bearing is, The support frame has a first contact surface that contacts it in the axial direction, The drum unit according to claim 5 or 6, further comprising a first projection protruding from the first contact surface, the first projection for limiting the first bearing from disengaging from the support frame.

8. The second bearing is, The support frame has a second contact surface that contacts it in the axial direction, The drum unit according to any one of claims 5 to 7, further comprising a second projection protruding from the second contact surface, the second projection for limiting the second bearing from disengaging from the support frame.

9. The first bearing is, A first boss supporting the first spring, having a first boss extending in the pressing direction which is the direction in which the charging roller is pressed against the photosensitive drum, The support frame has a first portion that faces the first boss in the pressing direction, The drum unit according to any one of claims 5 to 8, characterized in that one of the first boss and the first portion has a protrusion, and the other has a recess into which the protrusion fits.

10. The second bearing is, A second boss supporting the second spring, the second boss extending in the pressing direction which is the direction in which the charging roller is pressed against the photosensitive drum, The support frame has a second portion that faces the second boss in the pressing direction, The drum unit according to any one of claims 5 to 9, characterized in that one of the second boss and the second portion has a protrusion and the other has a recess into which the protrusion fits.

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