Photoconductor unit and image forming apparatus

Abstract

To prevent a lubricant from entering a sliding part between a charging roller and a separation holding member.SOLUTION: A charging roller including a rotation shaft and an elastic layer formed around the rotation shaft, the charging roller being in contact with the photosensitive member to charge the photosensitive member, a bearing rotatably holding the rotation shaft of the charging roller, a fitting portion rotatably fitted to the rotation shaft of the charging roller, and an engaging portion that rotates integrally with the fitting portion and is rotatable between an engaging position where the engaging portion engages with the rotation member of the photosensitive member and a releasing position where the engaging portion releases engagement with the rotation member of the photosensitive member, the space keeping member includes a projected portion provided between the engaging portion and the bearing so as to project from the engaging portion toward the bearing and provided at a position spaced from a rotation shaft of the charging roller with respect to a radial direction of the charging roller.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a photosensitive unit that can be attached to an image forming apparatus that uses an electrophotographic process, and to an image forming apparatus that includes the same. [Background technology]

[0002] In order to facilitate maintenance, some image forming apparatuses have a detachable photoconductor unit that integrates a photoconductor and a process means that acts on the photoconductor. Image forming apparatuses employing this type of system employ a contact charging system in which a charging roller having an elastic layer is brought into contact with the photoconductor by the biasing force of a spring or the like to charge the photoconductor.

[0003] In such a contact charging method, if the photosensitive unit is left in contact with the charging roller and photosensitive member for a long period of time, the part of the charging roller that was in contact with the photosensitive member may become deformed, which may result in poor image formation.

[0004] Therefore, Patent Document 1 discloses a configuration in which the photosensitive body and the charging roller are separated from each other in a state in which a spacing member fitted onto the rotating shaft of the charging roller engages with a gear provided on the photosensitive body, and the spacing member is rotated by the rotation of the photosensitive body, causing the separated charging roller to come into contact with the photosensitive body.

[0005] Furthermore, Patent Document 2 discloses a configuration in which a spacing member that brings the photosensitive member and the charging roller into contact with each other and retracts the contact is supported on the rotation shaft of the charging roller, and the photosensitive member and the charging roller can be retracted from contact at any timing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-95532 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-311690 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in a configuration in which a spacing member is supported on the rotating shaft of the charging roller, if an adhesive such as grease enters the sliding portion between the rotating shaft of the charging roller and the spacing member, the adhesive increases the rotational load torque of the charging roller.

[0008] An object of the present invention is to prevent adhesive substances such as grease from entering the sliding portion between the charging roller and the spacing member, and to prevent an increase in the rotational load torque of the charging roller due to the adhesive substances entering the sliding portion. [Means for solving the problem]

[0009] A representative configuration of the present invention is a photosensitive member unit detachable from an image forming apparatus, the photosensitive member having a rotating member to which a driving force is input and which is driven to rotate, a rotating shaft, and an elastic layer formed around the rotating shaft, the charging roller having contact with the photosensitive member to charge the photosensitive member, a bearing for rotatably holding the rotating shaft of the charging roller, a fitting portion rotatably fitted to the rotating shaft of the charging roller, an engagement position that rotates integrally with the fitting portion and engages with the rotating member of the photosensitive member, and the rotating member of the photosensitive member. and a separation maintaining member that maintains a separation state in which the photosensitive body and the charging roller are separated at the engagement position and releases the separation state at the release position to allow contact between the photosensitive body and the charging roller, wherein the separation maintaining member is provided between the fitting portion and the bearing, protruding from the fitting portion toward the bearing, and has a protrusion that is provided at a position spaced from the rotation axis of the charging roller in the radial direction of the charging roller. [Effects of the Invention]

[0010] According to the present invention, it is possible to prevent adhesive substances such as grease from entering the sliding portion between the charging roller and the spacing member, and to prevent an increase in the rotational load torque of the charging roller due to the adhesive substances entering the sliding portion. [Brief explanation of the drawings]

[0011] [Figure 1] Schematic cross-sectional view of an image forming apparatus [Figure 2] Perspective view of a photosensitive unit [Figure 3] Cross-sectional view of the photoconductor unit [Figure 4] (a) (b) Perspective views of the vicinity of the spacing member in the spacing-maintaining state [Figure 5] 1 is a perspective view of the vicinity of the spacing member in the released state; FIG. [Figure 6] FIG. 10 is a perspective view of the vicinity of a spacing member of a comparative example. [Figure 7] Cross-sectional view of the vicinity of the spacing member of the comparative example [Figure 8] Cross-sectional view of the vicinity of the spacing member of the comparative example [Figure 9] FIG. 1 is a perspective view of a spacing member according to a first embodiment; [Figure 10] Cross-sectional view of the vicinity of the spacing member of Example 1 [Figure 11] FIG. 10 is a perspective view of a spacing member according to a second embodiment; [Figure 12] 10 is a perspective view of the vicinity of the spacing member in the separation release state according to the second embodiment; [Figure 13] 10 is a perspective view of the vicinity of the spacing member in the spacing-maintaining state according to the second embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Components with the same reference numerals in the drawings have the same configuration or function, and redundant explanations thereof will be omitted as appropriate. Furthermore, unless otherwise specified, the dimensions, materials, shapes, and relative positions of the components described in the following embodiments are not intended to limit the scope of the present invention to those components alone.

[0013] Example 1 A photosensitive unit according to a first embodiment and an image forming apparatus including the same will be described with reference to FIGS. 1 to 10. FIG.

[0014] First, the overall configuration and operation of the image forming apparatus will be described using Fig. 1. Then, a separation mechanism that keeps the charging roller and the photosensitive member separated and a mechanism that automatically releases the separation mechanism when a driving force is input from the image forming apparatus main body and the photosensitive member is driven will be described in detail.

[0015] (Overall configuration and operation of image forming apparatus) 1 is a schematic cross-sectional view of an image forming apparatus according to this embodiment. The image forming apparatus 1 of this embodiment is a tandem type image forming apparatus that employs an intermediate transfer system and is capable of forming full-color images using an electrophotographic system.

[0016] The image forming apparatus 1 of this embodiment includes image forming units that form toner images of the respective colors of Y (yellow), M (magenta), C (cyan), and K (black). The configurations and operations of these image forming units are essentially the same except for the different colors of toner they use. Therefore, hereinafter, unless a distinction is required, the suffixes Y, M, C, and K indicating an element for one of the colors will be omitted and the element will be described generally.

[0017] The image forming unit has a photosensitive drum 12 as an image carrier, which is a drum-shaped (cylindrical) electrophotographic photosensitive member (photosensitive member). The photosensitive drum 12 is rotated by a driving force transmitted from a driving means (not shown) provided in the image forming apparatus main body.

[0018] In the image forming unit, the following devices are arranged around the photosensitive drum 12 in the rotational direction thereof in this order. First, a charging roller 13, which is a rotatable roller-shaped charging member, is arranged as charging means. Next, the surface of the photosensitive drum 12 is arranged to receive exposure from a laser scanner 22, which is an exposure device, serving as exposure means (electrostatic latent image forming means). Next, a developing device 20 is arranged as developing means. Toner is supplied to the developing device 20 from a toner bottle 21, which serves as a toner storage container, via a toner transport path (not shown). Next, a primary transfer roller 31, which is a roller-shaped primary transfer member, serving as primary transfer means, is arranged. Next, a cleaning blade 14, which serves as a member for cleaning the photosensitive drum, is arranged.

[0019] In addition, in the image forming section, a cleaning roller 15, which is a roller-shaped charge cleaning member serving as a cleaning means for the charge member, is disposed in contact with the charge roller 13. In this embodiment, the charge roller 13 is brought into contact with the surface of the photosensitive drum 12 with a predetermined pressing force by a biasing means such as a spring, and rotates in accordance with the rotation of the photosensitive drum 12.

[0020] In this embodiment, the cleaning roller 15 is brought into contact with the surface of the charging roller 13 with a predetermined pressing force by a biasing means such as a spring, and rotates in accordance with the rotation of the charging roller 13.

[0021] The image forming apparatus 1 also has an intermediate transfer belt 30 formed of an endless belt as an intermediate transfer body so as to come into contact with each photosensitive drum 12 of each image forming unit. The intermediate transfer belt 30 is wound around a plurality of support rollers (tension rollers) with a predetermined tension. The above-mentioned primary transfer rollers 31 are disposed on the inner circumferential surface (back surface) of the intermediate transfer belt 30 at positions facing each photosensitive drum 12. The primary transfer rollers 31 are pressed against the photosensitive drums 12 via the intermediate transfer belt 30, forming primary transfer portions (primary transfer nip portions) where the intermediate transfer belt 30 and the photosensitive drums 12 come into contact. The primary transfer rollers 31 rotate in accordance with the rotation of the intermediate transfer belt 30.

[0022] Furthermore, a secondary transfer roller 32, which is a roller-shaped secondary transfer member serving as secondary transfer means, is disposed on the outer circumferential surface side (front surface side) of the intermediate transfer belt 30, facing the secondary transfer opposing roller 33. The secondary transfer roller 32 is pressed against the secondary transfer opposing roller 33 via the intermediate transfer belt 30, forming a secondary transfer portion (secondary transfer nip portion) where the intermediate transfer belt 30 and the secondary transfer roller 32 come into contact. Furthermore, a belt cleaning device 40 serving as intermediate transfer body cleaning means is disposed on the outer circumferential surface side of the intermediate transfer belt 30, facing the tension roller 35. The intermediate transfer belt 30 is formed endlessly from a dielectric resin such as polyimide.

[0023] In addition, the image forming apparatus 1 is provided with a feed / convey roller 51 for a recording material P such as recording paper, a fixing device 70 for fixing a toner image onto the recording material P, and the like.

[0024] During image formation, the surface of the photosensitive drum 12, which is driven to rotate, is uniformly charged to a predetermined potential of a predetermined polarity by the charging roller 13. In this embodiment, a voltage is applied to the charging roller 13 from a high-voltage power supply (charging power supply), not shown, causing discharge on the surface of the photosensitive drum 12, thereby charging the surface of the photosensitive drum 12.

[0025] After the surface of the photosensitive drum 12 is uniformly charged, the surface of the photosensitive drum 12 is scanned and exposed by a laser scanner 22 based on image information signals, forming an electrostatic latent image (electrostatic image) on the photosensitive drum 12. The latent image formed on the photosensitive drum 12 is developed into a toner image by the developing device 20 using toner as a developer. In this embodiment, the normal charging polarity of the toner is negative. The developing device 20 has a developing sleeve as a developer carrier that carries the toner and transports it to a position facing the photosensitive drum 12 (developing position). The developing sleeve is driven to rotate. During development, a predetermined developing voltage (developing bias) is applied to the developing sleeve from a high-voltage power supply (not shown) as a developing power supply.

[0026] The toner image formed on the photosensitive drum 12 is transferred (primary transfer) to the surface of the intermediate transfer belt 30 by the action of the primary transfer roller 31 in the primary transfer section. At this time, a primary transfer voltage (primary transfer bias) having a polarity opposite to the polarity of the toner charged during development (positive polarity in this embodiment) is applied to the primary transfer roller 31 from a primary transfer power supply (high-voltage power supply) not shown. When a full-color image is formed, the above-mentioned operation is performed in each image forming section, and the toner images of each color, Y (yellow), M (magenta), C (cyan), and K (black), formed on each photosensitive drum 12, are transferred onto the intermediate transfer belt 30 in a sequentially overlapping manner.

[0027] After the transfer, a small amount of residual toner remaining on the photosensitive drum 12 is removed by a cleaning blade 14 serving as a cleaning member and collected in a collection section.

[0028] Meanwhile, recording materials P are fed one by one from a paper feed cassette 50 and conveyed to a pair of registration rollers 60. The pair of registration rollers 60 then convey the recording material P between the intermediate transfer belt 30 and a secondary transfer roller 32 in synchronization with the toner image on the intermediate transfer belt 30. The color toner image on the intermediate transfer belt 30 is transferred (secondarily transferred) to the surface of the recording material P by the action of the secondary transfer roller 32 at the secondary transfer section. As the recording material P passes through the secondary transfer section, a secondary transfer voltage (secondary transfer bias), which has a polarity opposite to the polarity of the toner charged during development, is applied to the secondary transfer roller 32 from a secondary transfer power supply (high-voltage power supply) (not shown). After transfer, the small amount of residual toner remaining on the intermediate transfer belt 30 is removed and collected by a belt cleaning device 40, and the intermediate transfer belt 30 is prepared for the next image formation. The toner image transferred onto the recording material P is fixed by heating and pressure applied by a fixing unit 70. The recording material P on which the image has been fixed is discharged onto a discharge tray 90 by a pair of discharge rollers 80 .

[0029] (drum cartridge) Next, the configuration of the drum cartridge 10 as a photosensitive unit will be described with reference to FIGS.

[0030] The drum cartridge 10 of this embodiment integrally holds a photosensitive drum 12 as a photosensitive member, a charging roller 13 as a charging member, a cleaning roller 15 as a charge cleaning member, and a cleaning blade 14 as a cleaning member in a drum container 11 as a frame. The drum cartridge 10 is detachable from the image forming apparatus 1 by sliding it along the longitudinal direction (the axial direction of the photosensitive drum) from the image forming apparatus 1, and can be replaced for maintenance or the like.

[0031] 2 and 3, the photosensitive drum 12 is rotatably held about a rotation axis via a bearing (not shown) in the drum container 11. The photosensitive drum 12 is provided with a coupling 122 that receives a driving force from a motor (not shown) that serves as a drive source provided in the image forming apparatus. The photosensitive drum 12 is driven to rotate by the driving force received from the motor via the coupling 122.

[0032] A cleaning blade 14 is fixed to the drum container 11 as a cleaning member for cleaning the surface of the photosensitive drum 12. The cleaning blade 14 is provided so as to contact the surface of the photosensitive drum 12. The cleaning blade 14 is provided so as to contact the surface of the photosensitive drum 12 in a counter direction to the rotation direction of the photosensitive drum 12 during image formation. A recovery unit is provided near the cleaning blade 14 to recover transfer residual toner removed from the surface of the photosensitive drum 12 by the cleaning blade 14. A toner transport screw 18 is provided near the cleaning blade 14 as a transport unit to transport the toner recovered in the recovery unit and out of the drum cartridge 10 (photosensitive unit). The toner transported out of the drum cartridge 10 by the toner transport screw 18 is collected in a recovered toner container (not shown) provided in the image forming apparatus.

[0033] A gear 121 serving as a rotating member is provided at one end of the photosensitive drum 12 in the longitudinal direction. The gear 121 is fixed to the end of the photosensitive drum 12 in the longitudinal direction so as to rotate integrally with the photosensitive drum 12 around the rotation axis of the photosensitive drum 12. The gear 121 is connected to the toner transport screw 18 by a drive transmission member (not shown). When the photosensitive drum 12 rotates, the rotational force of the gear 121, which rotates integrally with the photosensitive drum 12, is transmitted to the toner transport screw 18 by the drive transmission member, thereby rotating the toner transport screw 18. As the toner transport screw 18 rotates, the residual toner collected in the collection section is transported out of the drum cartridge 10.

[0034] 5, the charging roller 13 as a charging member is a roller-shaped member having a charging roller rotation shaft (conductive support) 13a as a rotation shaft and one or more elastic layers 13b formed around the charging roller rotation shaft 13a. The outer peripheral surface of the charging roller 13 contacts the photosensitive drum 12 as a photosensitive member to charge the photosensitive drum 12.

[0035] The charge roller 13 is rotatably supported by having its charge roller rotation shaft 13a held by a charge roller bearing 161 serving as a holder. A lubricant 19 (see FIG. 10 ), such as grease, is applied between the charge roller rotation shaft 13a and the charge roller bearing 161 to reduce sliding resistance between the charge roller rotation shaft 13a and the charge roller bearing 161.

[0036] The charge roller bearing 161 is supported so as to be slidable relative to the drum container 11. Specifically, the charge roller bearing 161 is supported so as to be slidable in a direction perpendicular to the rotation axis direction of the photosensitive drum 12 so that the charge roller 13 it supports can move in a direction in which it abuts against the photosensitive drum 12 or in a direction in which the charge roller 13 moves away from the photosensitive drum 12.

[0037] Furthermore, a charge roller pressure spring 163 is provided between the drum container 11 and the charge roller bearing 161 as a first biasing means. This charge roller pressure spring 163 biases the charge roller 13 in a direction (biasing direction) toward the photosensitive drum 12, in a direction perpendicular to the rotational axis direction of the photosensitive drum 12. Therefore, the charge roller 13 is pressed against the photosensitive drum 12 by the charge roller pressure spring 163 and is in contact with the photosensitive drum 12. As described above, a lubricant 19 such as grease is applied between the charge roller rotation shaft 13a and the charge roller bearing 161 to reduce sliding resistance. Therefore, it is possible to reduce the frictional resistance between the charge roller rotation shaft 13a and the charge roller bearing 161 due to the biasing force of the charge roller pressure spring 163.

[0038] 4(b), cleaning roller 15 as a charge cleaning member is a roller-shaped member having a rod-shaped support portion (metal core, core material) 15a as a rotation shaft and an elastic layer 15b formed around support portion 15a. The cleaning roller 15 cleans charge roller 13 by contacting its outer circumferential surface with charge roller 13.

[0039] The cleaning roller 15 serving as a charge cleaning member is rotatably supported by having its support portion (rotation shaft) 15a supported by a cleaning roller bearing 162 serving as a cleaning bearing. The cleaning roller bearing 162 is supported so as to be slidable relative to the charge roller bearing 161. Specifically, the cleaning roller bearing 162 is supported so as to be slidable relative to the charge roller bearing 161 in a direction perpendicular to the rotational axis direction of the charge roller 13. This allows the cleaning roller bearing 162 to move in a direction in which the cleaning roller 15 it supports comes into contact with the charge roller 13, or in a direction in which the cleaning roller 15 moves away from the charge roller 13.

[0040] Furthermore, a cleaning roller pressure spring 164 is provided between the charge roller bearing 161 and the cleaning roller bearing 162 as a second biasing means. This cleaning roller pressure spring 164 biases the cleaning roller 15 toward the charge roller 13 in a direction perpendicular to the rotational axis of the charge roller 13. Therefore, the cleaning roller 15 is pressed against and contacts the charge roller 13 by the cleaning roller pressure spring 164. In other words, the cleaning roller 15 is movable along the biasing direction of the cleaning roller pressure spring 164. Furthermore, in this embodiment, the biasing direction of the charge roller pressure spring 163, which is the first biasing means, and the biasing direction of the cleaning roller pressure spring 164, which is the second biasing means, are the same, but they may be different directions.

[0041] With the above configuration, when the photosensitive drum 12 receives a driving force from a drive source provided in the image forming apparatus and rotates, the charging roller 13 is rotated by the frictional force with the photosensitive drum 12. Furthermore, when the charging roller 13 rotates, the cleaning roller 15 is rotated by the frictional force with the charging roller 13. Furthermore, the toner transport screw 18 receives a driving force (rotational force) from the gear 121 and rotates.

[0042] (Spacing member) 4(a) and 4(b), a description will be given of a spacing member that maintains a state in which the photosensitive drum 12 and the charging roller 13 are spaced apart. Figures 4(a) and 4(b) are perspective views showing a spacing-maintaining state (separated state) in which the photosensitive drum 12 and the charging roller 13, and the charging roller 13 and the cleaning roller 15 are spaced apart by a spacing member 17.

[0043] The drum cartridge 10 serving as a photosensitive unit is provided with a spacing member 17 that maintains the spacing between the photosensitive drum 12 and the charging roller 13. The spacing member 17 maintains a clearance between the charging roller 13 and the photosensitive drum 12, for example, during transportation for distribution. The spacing member 17 also maintains a clearance between the charging roller 13 and the cleaning roller 15 by separating them.

[0044] The spacing member 17 has a fitting portion 17a that fits rotatably onto the charge roller rotation shaft 13a, and is rotatably provided on the charge roller rotation shaft 13a. The spacing members 17 are provided on both ends of the charge roller rotation shaft 13a. In other words, the spacing members 17 are rotatable about the rotation axis of the charge roller 13 and are supported on both ends of the charge roller 13. Therefore, the spacing members 17 can move in conjunction with the movement of the charge roller 13. Note that the spacing members 17 provided on both ends of the charge roller rotation shaft 13a have the same configuration, and therefore this embodiment will be described using a diagram showing only one of the spacing members 17.

[0045] The fitting portion 17 a is rotatably fitted to the charge roller rotation shaft 13 a between the elastic layer 13 b of the charge roller 13 and the charge roller bearing 161 .

[0046] The spacing member 17 is provided with a first spacing maintaining portion 174 and a second spacing maintaining portion 175. The first spacing maintaining portion 174 is a spacing maintaining portion that abuts against the photosensitive drum 12 to separate the photosensitive drum 12 and the charging roller 13 while maintaining a clearance therebetween. Here, as shown in FIGS. 4(a) and 4(b), the first spacing maintaining portion 174 abuts against an end portion of the photosensitive drum 12 in the axial direction. The second spacing maintaining portion 175 is a second spacing maintaining portion that abuts against the cleaning roller 15 to separate the charging roller 13 and the cleaning roller 15 while maintaining a clearance therebetween. Here, the second spacing maintaining portion 175 abuts against the support portion 15a of the cleaning roller 15. The first spacing maintaining portion 174 and the second spacing maintaining portion 175 rotate integrally with the fitting portion 17a.

[0047] 4(a) and 4(b), the first separation maintaining portion 174 is sandwiched between the charging roller rotation shaft 13a and the gear 121 by the pressure (biasing force) of the charging roller pressure spring 163 serving as the first biasing means. Also, in the separation maintaining state, the second separation maintaining portion 175 is pressed against the cleaning roller 15 by the pressure (biasing force) of the cleaning roller pressure spring 164 serving as the second biasing means, and is sandwiched between the charging roller rotation shaft 13a and the support portion 15a of the cleaning roller 15.

[0048] This ensures that, for example, when the drum cartridge 10 is transported, the elastic layer 13b of the charging roller 13 and the photosensitive drum 12 are spaced apart, and further, the charging roller 13 and the cleaning roller 15 are spaced apart, ensuring a clearance between them.

[0049] The separation maintaining member 17 rotates integrally with the fitting portion 17a and has a first engaging portion 171 that is rotatable between an engaging position where it engages with the gear 121 of the photosensitive drum 12 and a releasing position where it releases the engagement with the gear 121 of the photosensitive drum 12. The separation maintaining member 17 maintains a separated state where the photosensitive drum 12 and the charging roller 13 are separated from each other at the engaging position (position shown in FIG. 4(a)). Furthermore, the separation maintaining member 17 releases the separated state at the releasing position (position shown in FIG. 5), allowing the photosensitive drum 12 and the charging roller 13 to come into contact with each other.

[0050] As shown in FIG. 4A , the first engagement portion 171 is provided on a side surface of the first separation maintaining portion 174 facing the gear 121 in the separation maintaining state. The first engagement portion 171 has gear teeth at the same pitch as the gear tooth surface pitch of the gear 121. That is, the first engagement portion 171 is included in the first separation maintaining portion 174 and is provided integrally with the first separation maintaining portion 174. In the separation maintaining state in which the photosensitive drum 12 and the charging roller 13 are separated, the first engagement portion 171 engages with the gear 121. In other words, in the separation maintaining state, the separation maintaining member 17 is located at a separation position where the first engagement portion 171 engages with the gear 121 as a rotating member, maintaining the separation state in which the photosensitive drum 12 and the charging roller 13 are separated. With this configuration, the separation maintaining member 17 maintains the separation state.

[0051] The spacing maintaining member 17 further has a second engaging portion (172) that rotates integrally with the fitting portion 17a and engages with the cleaning roller 15. Here, the second spacing maintaining portion 175 described above also serves as the second engaging portion. The spacing maintaining member 17 engages with the cleaning roller 15 at the engagement position (position shown in FIG. 4(a)) where the first engaging portion 171 engages with the gear 121, thereby maintaining a spaced apart state between the charging roller 13 and the cleaning roller 15. The spacing maintaining member 17 also disengages from the cleaning roller 15 at the release position (position shown in FIG. 5) where the first engaging portion 171 disengages from the gear 121, thereby canceling the spaced state and allowing the charging roller 13 and the cleaning roller 15 to come into contact with each other.

[0052] (Automatic release of the separation state) Next, the automatic release of the separation holding state will be described with reference to FIGS. 4(a), 4(b), and 5. FIG.

[0053] When the drum cartridge 10 held in the spaced state is attached to the image forming apparatus and the image forming apparatus is started up, the initial operation performed by the image forming apparatus inputs a driving force (rotational force) from the motor provided in the image forming apparatus to the photosensitive drum 12.

[0054] When the photosensitive drum 12 starts to rotate from the separation maintaining state shown in FIG. 4B in which the photosensitive drum 12 and the charging roller 13 and the charging roller 13 and the cleaning roller 15 are separated, the photosensitive drum 12 rotates in the direction of arrow A and the gear 121 rotates. Then, the first engagement portion 171 of the separation maintaining member 17 engaged with the gear 121 receives the rotational force of the gear 121 and rotates. As the separation maintaining member 17 rotates, the first separation maintaining portion 174 is released from being sandwiched between the charging roller rotation shaft 13a and the gear 121, and the separation is released as shown in FIG. 5. Furthermore, the second separation maintaining portion 175 is released from being sandwiched between the charging roller rotation shaft 13a and the support portion 15a of the cleaning roller 15, and the separation is released as shown in FIG. 5.

[0055] In this way, when the drum cartridge 10 maintained in the separation state is mounted on the image forming apparatus and the photosensitive drum 12 starts to rotate, the first engagement portion 171 of the separation member 17 engaged with the gear 121 of the photosensitive drum 12 rotates in response to the rotational force of the gear 121. When the first engagement portion 171 rotates in response to the rotational force of the gear 121, the separation state shown in Fig. 4(a) is released and the state becomes the separation release state shown in Fig. 5, completing the automatic release by the separation member 17.

[0056] (Protrusion of spacing member) 9 and 10, the spacing member 17 according to this embodiment has a protrusion 17b that protrudes from the fitting portion 17a toward the bearing between the fitting portion 17a and the charge roller bearing 161. The protrusion 17b is located at a position spaced apart from the charge roller rotation shaft 13a in the radial direction perpendicular to the axial direction of the charge roller 13.

[0057] The protrusion 17b is provided so as to protrude in the radial direction of the charging roller 13 beyond the diameter of the fitting portion 17a.

[0058] The protrusion 17b of the spacing member 17 abuts against the charging roller bearing 161, thereby maintaining a predetermined distance between the fitting portion 17a and the charging roller bearing 161.

[0059] At least at the engagement position (position shown in FIG. 4(a)) and the release position (position shown in FIG. 5), the protrusion 17b of the spacing member 17 abuts against the charge roller bearing 161 as shown in FIG.

[0060] Here, spacing member 17 according to Example 1 will be described in more detail in comparison with a spacing member of a comparative example. First, the spacing member of the comparative example will be described using Figures 6, 7, and 8, and then spacing member 17 according to Example 1 will be described using Figures 9 and 10.

[0061] (Comparative example of spacing member) As shown in Fig. 6, the spacing member 17 is rotatably fitted and held on the charge roller rotation shaft 13a. To show in detail the relationship between the charge roller rotation shaft 13a, the spacing member 17, the charge roller bearing 161, and the lubricant 19, the area B enclosed by the dotted circle in Fig. 6 will be described using Fig. 7.

[0062] 7, the spacing member 17 of the comparative example does not have the protrusion 17b described above, and the fitting portion 17a with the charge roller rotation shaft 13a faces the charge roller bearing 161. This raises the concern that the lubricant 19 applied between the charge roller rotation shaft 13a and the charge roller bearing 161 may overflow from the lubricant application portion 161a when the charge roller 13 is assembled, and enter the fitting portion 17a between the spacing member 17 and the charge roller rotation shaft 13a.

[0063] When the separation state is released, the charge roller rotation shaft 13a is rotatable relative to the fitting portion 17a of the spacing member 17, and the charge roller rotation shaft 13a rotates and rubs against the fitting portion 17a of the spacing member 17. The fitting portion 17a of the spacing member 17 is fitted to the charge roller rotation shaft 13a to accurately maintain the separation distance during separation. Therefore, if lubricant 19 enters between the rotating and rubbing charge roller rotation shaft 13a and the fitting portion (sliding portion) 17a of the spacing member 17, the load torque required to rotate the charge roller 13 may increase. If this rotation load torque of the charge roller 13 exceeds the frictional force between the photosensitive drum 12 and the charge roller 13, the charge roller 13 will no longer be able to rotate in response to the photosensitive drum 12, which may result in poor image quality.

[0064] To prevent the spilled lubricant 19 from reaching the fitting portion 17a of the spacing member 17, a configuration may be considered in which the lubricant application portion 161a of the charge roller bearing 161 is retracted from the fitting portion 17a of the spacing member 17, as shown in FIG. 8. However, in the configuration shown in FIG. 8, the bearing portion of the charge roller bearing 161 that supports the charge roller rotation shaft 13a of the rotating charge roller 13 is smaller than in the configuration shown in FIG. 7. Therefore, the configuration shown in FIG. 8 is not preferable from the perspective of durability of the charge roller bearing 161. Another possible configuration is to extend the bearing portion of the charge roller bearing 161 in the axial direction to increase the area that supports the charge roller rotation shaft 13a, but this would increase the space required in the longitudinal direction of the drum cartridge 10, which is not preferable from the perspective of space saving.

[0065] (Spacing member of Example 1) 9 and 10, the spacing member 17 of Example 1 has a protrusion 17b that is provided between the fitting portion 17a and the charge roller bearing 161 and that protrudes from the fitting portion 17a toward the bearing. The protrusion 17b is provided at a position spaced apart from the charge roller rotation shaft 13a in the radial direction of the charge roller 13. The protrusion 17b also protrudes beyond the diameter of the fitting portion 17a in the radial direction of the charge roller 13.

[0066] 10, in the spacing member 17 of Example 1, the protrusion 17b ensures a distance from the lubricant application portion 161a to the fitting portion 17a. Therefore, even if the lubricant 19 spills out from the lubricant application portion 161a, the spilled lubricant 19 can be prevented from entering the fitting portion 17a, which is the sliding portion between the charge roller 13 and the spacing member 17. As a result, an increase in the rotational load torque of the charge roller 13 due to the lubricant 19 spilling out into the fitting portion 17a can be prevented.

[0067] It is preferable that the protrusions 17b be as long as possible in the longitudinal direction (axial direction) of the charge roller 13 while ensuring a predetermined fitting width for the fitting portion 17a of the spacing member 17. In this embodiment, the axial distance (fitting width) of the fitting portion 17a is set to 6.5 mm, and the axial distance of the protrusions 17b is set to 1.6 mm. It is also preferable that the protrusions 17b be positioned as far away as possible in the radial direction of the charge roller 13 as long as they do not come into contact with the cleaning roller bearing 162 supported by the charge roller bearing 161. In this embodiment, the protrusions 17b are configured circumferentially at a position 1 mm radially out from the charge roller rotation axis 13a.

[0068] Example 2 A photosensitive unit and an image forming apparatus including the same according to Example 2 will be described. Note that the configurations of the photosensitive unit and the image forming apparatus including the same according to Example 2 are the same as those of the above-described examples except for the spacing member 17, and therefore the description thereof will be omitted here.

[0069] (Spacing member of Example 2) 11 to 13, the spacing member 17 according to Example 2 will be described. Note that in the spacing member 17 according to Example 2, members having the same functions as those of the spacing member 17 according to Example 1 described above will be given the same reference numerals, and descriptions thereof will be omitted.

[0070] As shown in Fig. 11, the spacing member 17 according to the second embodiment has a configuration in which the protrusion 17b is partially cut away, compared to the spacing member 17 according to the first embodiment shown in Fig. 9. Specifically, the spacing member 17 does not have the protrusion 17b in the area facing the photosensitive drum 12 at the release position (the position shown in Fig. 12).

[0071] The position of the notched protrusion 17b of the spacing member 17 shown in this embodiment will be described. As shown in FIG. 12 , the spacing member 17 has the protrusion 17b cut out at a position facing the photosensitive drum 12 during normal operation when the separation is released. This ensures a clearance between the protrusion 17b and the photosensitive drum 12. If the diameter of the elastic layer 13b of the charging roller 13 is reduced to save space, the distance between the spacing member 17 and the photosensitive drum 12 becomes closer when the separation is released than before the diameter reduction. The spacing member 17 does not have the protrusion 17b in the area facing the photosensitive drum 12 at the release position (position shown in FIG. 12 ). This ensures a clearance between the photosensitive drum 12 and the spacing member 17. In other words, the provision of the notched protrusion 17b in part of the protrusion 17b ensures a clearance between the photosensitive drum 12 and the spacing member 17 at the release position (position shown in FIG. 12 ).

[0072] 12 and 13, the protrusion 17b is provided at a position facing at least the abutment surface 161b of the charge roller bearing 161. This makes it possible to reliably ensure that the distance between the lubricant application portion 161a and the fitting portion 17a is equal to or greater than a predetermined distance during separation and separation release.

[0073] The above-described configuration makes it possible to prevent the lubricant 19 from entering the sliding portion (fitting portion 17a) between the charge roller 13 and the spacing member 17. This makes it possible to prevent an increase in the rotational load torque of the charge roller 13 due to the lubricant 19 entering the sliding portion. As a result, it is possible to reduce the risk of charge roller slippage caused by an increase in the rotational load torque of the charge roller 13.

[0074] In the above-described embodiment, a photosensitive unit that can be attached to an image forming apparatus and an image forming apparatus equipped with the photosensitive unit are exemplified, but the present invention is not limited to this. For example, an image forming apparatus equipped with a photosensitive member and a charging roller may also be used, and similar effects can be obtained by applying the present invention to this image forming apparatus.

[0075] In the above-described embodiment, four image forming units are used, but the number of units used is not limited to this and may be set appropriately as needed.

[0076] In the above-described embodiment, a laser scanner is used as the exposure means, but the present invention is not limited to this and an LED array or the like may also be used.

[0077] In the above-described embodiment, a drum cartridge integrally including a photosensitive drum and a charging means and a cleaning means as process means acting on the photosensitive drum was used as an example of a photosensitive unit detachably attached to an image forming apparatus, but the present invention is not limited to this. For example, a process cartridge integrally including a photosensitive drum and a charging means, developing means, and cleaning means as process means acting on the photosensitive drum may be used. Furthermore, a process cartridge integrally including a photosensitive drum, a charging means, a developing means, or a cleaning means may be used.

[0078] In the above-described embodiment, a copier is used as an example of an image forming apparatus, but the present invention is not limited to this. For example, other image forming apparatuses, such as a printer or a facsimile machine, or other image forming apparatuses, such as a multifunction peripheral that combines the functions of these, may also be used. Furthermore, while the present invention is exemplified as an image forming apparatus that uses an intermediate transfer member, sequentially transfers toner images of different colors onto the intermediate transfer member in a superimposed manner, and then transfers the toner images carried on the intermediate transfer member to a recording material all at once, the present invention is not limited to this. It may also be an image forming apparatus that uses a recording material carrier, sequentially transfers toner images of different colors onto a recording material carried on the recording material carrier in a superimposed manner. Similar effects can be achieved by applying the present invention to these image forming apparatuses or to photosensitive units detachably attached to image forming apparatuses. [Explanation of symbols]

[0079] 1...Image forming device 10...Drum cartridge (photosensitive unit) 11...Drum container 12...Photosensitive drum (photoconductor) 13...Charging roller 13a...Charging roller rotating shaft (rotating shaft) 13b...Elastic layer 15...Cleaning roller (cleaning material) 17 ... Spacing member 17a ... fitting part (sliding part) 17b...Protrusion 19...Lubricant 121 ... Gear (rotating part) 122... Coupling 161 ...Charging roller bearing (bearing) 161a ... Lubricant application section 161b ...butting surface 162 ... Cleaning roller bearing (cleaning bearing) 163 ... Charging roller pressure spring 164 ... Cleaning roller pressure spring 171 ... first engagement portion 174 ... First spacing retaining portion 175 ... Second separation holding portion (second engagement portion)

Claims

1. A photosensitive unit detachable from an image forming apparatus, a photosensitive member having a rotating member to which a driving force is input and which is driven to rotate; a charging roller having a rotating shaft and an elastic layer formed around the rotating shaft, the charging roller contacting the photosensitive member to charge the photosensitive member; a bearing that rotatably holds the rotation shaft of the charging roller; a separation maintaining member having a fitting portion that is rotatably fitted to the rotation shaft of the charging roller, and an engaging portion that rotates integrally with the fitting portion and is rotatable between an engaging position where it engages with the rotating member of the photosensitive member and a releasing position where it releases the engagement of the photosensitive member with the rotating member, the separation maintaining member maintaining a separation state between the photosensitive member and the charging roller at the engaging position and releasing the separation state at the releasing position to allow the photosensitive member and the charging roller to come into contact with each other; Equipped with the spacing member is provided between the fitting portion and the bearing, protruding from the fitting portion toward the bearing, and has a protrusion provided at a position spaced apart from the rotation axis of the charging roller in the radial direction of the charging roller.

2. a lubricant is applied between the rotation shaft of the charging roller and the bearing; 2. The photosensitive unit according to claim 1, wherein the spacing member maintains a predetermined distance between the fitting portion and the bearing by causing the protrusion to abut against the bearing.

3. 2. The photosensitive unit according to claim 1, wherein the projection of the spacing member abuts against the bearing at least at the engagement position and the release position.

4. 2. The photosensitive member unit according to claim 1, wherein the spacing member does not have the protrusion in an area facing the photosensitive member in the release position.

5. 5. The photosensitive unit according to claim 4, wherein the protrusion is provided at a position facing at least the abutment surface of the bearing.

6. 2. The photosensitive unit according to claim 1, wherein the protrusion is provided so as to protrude beyond the diameter of the fitting portion in the radial direction of the charging roller.

7. 2. The photosensitive unit according to claim 1, wherein the fitting portion is rotatably fitted to the rotation shaft of the charging roller between the elastic layer of the charging roller and the bearing.

8. a rotatable cleaning member that comes into contact with the charging roller to clean the charging roller; a cleaning bearing that is movably held by the bearing and that rotatably holds the cleaning member, 2. The photosensitive unit according to claim 1, wherein the spacing maintaining member further has a second engaging portion that rotates integrally with the fitting portion and engages with the cleaning member, wherein the engaging portion engages with the cleaning member at the engaging position where it engages with the rotating member to maintain the charging roller and the cleaning member spaced apart, and the engaging portion disengages from the cleaning member at the releasing position where it disengages from the rotating member to release the spaced apart state, thereby allowing the charging roller and the cleaning member to come into contact with each other.

9. An image forming apparatus comprising the photosensitive unit according to any one of claims 1 to 8.

10. a photosensitive member having a rotating member to which a driving force is input and which is driven to rotate; a charging roller having a rotating shaft and an elastic layer formed around the rotating shaft, the charging roller contacting the photosensitive member to charge the photosensitive member; a bearing that rotatably holds the rotation shaft of the charging roller; a separation maintaining member having a fitting portion that is rotatably fitted to the rotation shaft of the charging roller, and an engaging portion that rotates integrally with the fitting portion and is rotatable between an engaging position where it engages with the rotating member of the photosensitive member and a releasing position where it releases the engagement of the photosensitive member with the rotating member, the separation maintaining member maintaining a separation state between the photosensitive member and the charging roller at the engaging position and releasing the separation state at the releasing position to allow the photosensitive member and the charging roller to come into contact with each other; Equipped with the spacing member is provided between the fitting portion and the bearing, protruding from the fitting portion toward the bearing, and has a protrusion provided at a position spaced apart from the rotation axis of the charging roller in the radial direction of the charging roller.

Images