JP7753017B2 - Photoconductor unit - Google Patents

Description

The present invention relates to a photosensitive unit that can be installed in an image forming apparatus that uses an electrophotographic process.

To facilitate maintenance, electrophotographic image forming devices are known that use a replaceable photoreceptor unit, which integrates a photoreceptor and a charging roller that charges the photoreceptor. Furthermore, many image forming devices that use this type of system use a contact charging method, in which a charging roller with an elastic layer is brought into contact with the photoreceptor using the biasing force of a spring or the like to charge the photoreceptor.

In this type of contact charging system, if the photosensitive unit is left in contact with the charging roller and photosensitive member for an extended period of time, the part of the charging roller that was in contact with the photosensitive member can become deformed, resulting in defective images when images are formed.

To prevent such image defects, a known configuration is to ship the photosensitive unit with a spacer sandwiched between the photosensitive element and the charging roller, and then remove the spacer before installing the photosensitive element in the image forming device body.

However, this configuration poses the problem of requiring the user to take the time to remove the spacer when installing the photosensitive unit into the image forming device body.

Patent Document 1 therefore discloses a configuration in which, when installing a photosensitive unit in an image forming apparatus, the photosensitive body rotates to bring the separated charging roller into contact with the photosensitive body without the user having to remove the spacer. Specifically, the configuration separates the photosensitive body and charging roller while a fan-shaped engaging portion at the tip of a spacing member fitted onto the rotational shaft of the charging roller engages with a photosensitive body gear mounted coaxially with the photosensitive body. When the spacing member rotates as the photosensitive body rotates, the photosensitive body gear and spacing member disengage, bringing the photosensitive body and charging roller into contact.

However, with the configuration described in Patent Document 1, between the time the photosensitive unit is shipped and the time it is installed in the image forming apparatus main body, for example during transport, vibrations can be applied to the photosensitive unit, causing the photosensitive member to rotate. As a result, the rotation of the photosensitive member can cause the spacing member to come off, potentially resulting in unintended contact between the photosensitive member and the charging roller.

Patent Document 2 describes a configuration in which, when the photosensitive element and the charging roller are separated, an engaging portion of a spacing member is engaged with the gear of the photosensitive element and the engaging portion is pressed against the gear. With this configuration, the engaging portion is pressed against the gear, making it difficult for the gear to rotate.

Japanese Patent Application Publication No. 11-95532 JP 2016-133775 A

However, before the photosensitive unit is attached to the image forming apparatus main body, strong vibrations may be applied to the photosensitive unit, causing the spacing member to move together with the charging roller in a direction away from the photosensitive member. As a result, with the configuration of Cited Document 2, when a force is applied that moves the spacing member together with the charging roller in a direction away from the photosensitive member, if the engagement portion separates from the photosensitive member gear, the spacing member, which has become free to rotate, may rotate and release the separated state.

The object of the present invention is to provide a photosensitive unit that can prevent the photosensitive element and charging roller from being unintentionally released from their separated state, even when a force acts on the engaging portion of the spacing member to move it away from the photosensitive element gear when the photosensitive element and charging roller are separated by the engagement between the engaging portion of the spacing member and the photosensitive element gear.

The present invention provides a photosensitive member unit that can be installed in an image forming apparatus, the photosensitive member unit comprising: a rotatable photosensitive member; a rotatable charging roller that contacts the photosensitive member to charge the photosensitive member; a charging roller bearing member that is attached to a rotation shaft of the charging roller and rotatably supports the charging roller; a biasing member that is provided on the charging roller bearing member and biases the charging roller toward the photosensitive member; a gear provided at a first end in the rotation axis direction of the photosensitive member; a spacing member that is provided on the rotation shaft of the charging roller and has an engaging portion that engages with the gear and separates the charging roller and the photosensitive member; and a spacing member that guides the charging roller bearing member biased by the biasing member so that the charging roller separates from the photosensitive member when the engaging portion and the gear are engaged, and a guide portion that guides the charge roller bearing member that is urged by the urging member so that the charge roller contacts the photosensitive body when the engagement portion and the gear are not engaged; a first side wall that is disposed at the first end in the rotational axis direction of the photosensitive body; a second side wall that is disposed at the second end in the rotational axis direction of the photosensitive body; and a connecting portion that connects the first side wall and the second side wall, and supports the photosensitive body rotatably on the first side wall and the second side wall, wherein, when the shortest distance between the end face of the charge roller bearing member urged by the urging member when the engagement portion and the gear are engaged and the first side wall is A, and the amount of engagement between the engagement portion and the gear when the engagement portion and the gear are engaged is B, A<B is satisfied.

According to this invention, when the photosensitive element and the charging roller are separated by the engagement between the engagement portion of the spacing member and the photosensitive element gear, even if a force acts to move the engagement portion of the spacing member in a direction away from the photosensitive element gear, it is possible to prevent the separation between the photosensitive element and the charging roller from being unintentionally released.

1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment. FIG. 2 is a cross-sectional view showing a schematic configuration of a drum unit according to the first embodiment. FIG. 4 is a partial perspective view showing a contact state of the drum unit according to the first embodiment, with a regulating portion omitted; FIG. 4 is a partial perspective view showing a contact state of the drum unit according to the first embodiment, with a regulating portion, a spacing member, and a frame omitted; FIG. 4 is a partial perspective view showing the drum unit in a separated state according to the first embodiment, with the regulating portion omitted; FIG. 4 is a partial perspective view showing the drum unit in a separated state according to the first embodiment, with a regulating portion and a frame omitted; 5A and 5B are schematic cross-sectional views showing the spacing member according to the first embodiment in a spaced state and a state in which the spaced state is released, respectively; FIG. 10 is a partial perspective view showing a separated state of the drum unit according to the reference example . 1A is a partial perspective view of a drum unit according to a reference example , showing a separated state with the frame omitted; FIG. 1B is a partial perspective view showing a photosensitive drum and a frame; FIG. 10A is a partial side view showing a separated state of the drum unit according to the reference example , and FIG. 10B is a cross-sectional view taken along the line XX in FIG. 10A and 10B show, respectively, (a) the direction of the torque acting when the abutting portion abuts against the abutted portion in the reference example , and (b) the relationship between the force direction acting on the spacing member and the normal vector at the abutting portion. FIG. 2 is a perspective view showing a spacing maintaining portion according to an embodiment of the present invention in the first embodiment. FIG. 2 is a perspective view showing a spacing maintaining portion according to an embodiment of the present invention in the first embodiment. FIG. 10 is a cross-sectional view showing the configuration of a modified example of the present invention. FIG. 10 is a cross-sectional view showing the configuration of a modified example of the present invention.

First Embodiment
A first embodiment of the present invention will be described with reference to Figures 1 to 11. First, a schematic configuration of an image forming apparatus according to this embodiment will be described with reference to Figure 1.

[Image forming apparatus]
The image forming apparatus 1 is a tandem-type image forming apparatus employing an intermediate transfer system that is capable of forming full-color images using an electrophotographic system. That is, the image forming apparatus 1 has image forming units 10 for each color, namely, Y (yellow), M (magenta), C (cyan), and K (black), and these image forming units 10 for each color are arranged side by side in the rotation direction of an intermediate transfer belt 61, forming a so-called tandem configuration. The configuration and operation of each image forming unit 10 are substantially identical except that the toner colors used are different.

The image forming unit 10 has a photosensitive drum 11, which is a cylindrical electrophotographic photosensitive member (photoconductor). The photosensitive drum 11 is driven to rotate at a process speed (circumferential speed) of 100 mm/sec by a driving force transmitted from a driving means (not shown) provided in the apparatus main body 1a. In the image forming unit 10, a charging roller 12, a developing device 14, a primary transfer roller 17, and a drum cleaning device 15 are arranged around the photosensitive drum 11 in the direction of rotation, in that order. An exposure device 16 is arranged below each image forming unit 10. The image forming apparatus 1 also has an intermediate transfer belt 61, which is an endless belt that serves as an intermediate transfer body and contacts the photosensitive drum 11 of each image forming unit 10.

The charging roller 12, which serves as the charging means, is a rotatable roller-shaped charging member that is positioned in contact with the photosensitive drum 11 and charges the surface of the photosensitive drum 11. The exposure device (laser scanner device) 16, which serves as the exposure means, exposes the charged surface of the photosensitive drum 11 to light to form an electrostatic latent image on the surface of the photosensitive drum 11.

The developing device 14, which serves as a developing means, contains toner as a developer and uses the toner to develop the electrostatic latent image formed on the photosensitive drum 11 into a toner image. The developing device 14 has a developing sleeve 14a, which serves as a developer carrier, that carries the toner and transports it to the area facing the photosensitive drum 11 (developing position). The developing sleeve 14a is driven to rotate.

The primary transfer roller 17, which serves as the primary transfer means, is a roller-shaped primary transfer member that performs primary transfer of the toner image formed on the photosensitive drum 11 onto the intermediate transfer belt 61. The drum cleaning device 15 cleans any residual toner remaining on the photosensitive drum 11 after primary transfer.

The intermediate transfer belt 61 is made of a dielectric resin such as polyimide and is endless. The intermediate transfer belt 61 is wrapped around multiple support rollers (tension rollers) with a predetermined tension. The above-mentioned primary transfer rollers 17 are disposed on the inner surface (back surface) of the intermediate transfer belt 61, facing each photosensitive drum 11. The primary transfer rollers 17 are pressed against the photosensitive drums 11 via the intermediate transfer belt 61, forming a primary transfer portion (primary transfer nip portion) N1 where the intermediate transfer belt 61 and photosensitive drum 11 come into contact. The primary transfer rollers 17 rotate in conjunction with the rotation of the intermediate transfer belt 61.

A secondary transfer roller 35, a roller-shaped secondary transfer member serving as secondary transfer means, is disposed on the outer peripheral surface (surface side) of the intermediate transfer belt 61, facing the secondary transfer opposing roller 62. The secondary transfer roller 35 is pressed against the secondary transfer opposing roller 62 via the intermediate transfer belt 61, forming a secondary transfer portion (secondary transfer nip portion) N2 where the intermediate transfer belt 61 and secondary transfer roller 35 come into contact. The toner image transferred to the intermediate transfer belt 61 is secondarily transferred to the recording material P at the secondary transfer portion N2.

In addition, a belt cleaning device 70 serving as an intermediate transfer body cleaning means is disposed on the outer peripheral surface of the intermediate transfer belt 61, facing the tension roller 64. The belt cleaning device 70 cleans residual toner and other particles remaining on the intermediate transfer belt 61 after secondary transfer.

Next, the image formation operation will be described. During image formation, the surface of the rotationally driven photosensitive drum 11 is uniformly charged to a predetermined potential of a predetermined polarity by the charging roller 12. In this embodiment, only a DC voltage of -1300 V is applied to the charging roller 12 from a high-voltage power supply (charging power supply) (not shown), causing discharge on the surface of the photosensitive drum 11, which charges the surface of the photosensitive drum 11 to approximately -700 V.

After the surface of the photosensitive drum 11 is uniformly charged, the surface of the photosensitive drum 11 is scanned and exposed by the exposure device 16 based on image information signals, forming an electrostatic latent image (electrostatic image) on the photosensitive drum 11. Note that the image forming apparatus 1 of this embodiment is equipped with an image reading device 2, and the image information described above includes image information of a document read by the image reading device 2 and image information sent from an external terminal such as a personal computer connected to the image forming apparatus 1.

The electrostatic latent image formed on the photosensitive drum 11 is developed into a toner image by the developing device 14 using toner as a developer. In this embodiment, the normal charging polarity of the toner is negative. During development, a predetermined development voltage (development bias) is applied to the developing sleeve 14a from a high-voltage power supply (not shown) serving as a development power supply. The development voltage used is an oscillating voltage in which a DC voltage (DC component) and an AC voltage (AC component) are superimposed. Toner is supplied to the developing device 14 from a toner bottle 19 (toner storage container) via a toner transport path (not shown).

The toner image formed on the photosensitive drum 11 is transferred (primary transfer) to the surface of the intermediate transfer belt 61 by the action of the primary transfer roller 17 at the primary transfer station N1. At this time, a primary transfer voltage (primary transfer bias), which is a DC voltage of opposite polarity (positive polarity in this embodiment) to the charge polarity of the toner during development, is applied to the primary transfer roller 17 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 station 10, and the toner images of yellow, magenta, cyan, and black formed on each photosensitive drum 11 are transferred onto the intermediate transfer belt 61 in a sequentially superimposed manner. After transfer, the small amount of residual toner remaining on the photosensitive drum 11 is removed by the drum cleaning device 15 and collected in a collection station 15b .

Meanwhile, recording material P is fed one sheet at a time from the feed cassette 20 and transported to the registration roller pair 23. The recording material P is, for example, a sheet of paper, plastic sheet, or the like. The registration roller pair 23 then transports the recording material P between the intermediate transfer belt 61 and the secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer belt 61.

The color toner image on the intermediate transfer belt 61 is transferred (secondary transfer) to the surface of the recording material P at the secondary transfer section N2 by the action of the secondary transfer roller 35. As this recording material P passes through the secondary transfer section N2, a secondary transfer voltage (secondary transfer bias), which is a DC voltage of opposite polarity to the toner charging polarity during development, is applied to the secondary transfer roller 35 from a secondary transfer power supply (high-voltage power supply) not shown. After transfer, any small amount of residual toner remaining on the intermediate transfer belt 61 is removed and collected by the belt cleaning device 70, preparing it for the next image formation.

The toner image transferred onto the recording material P is fixed by heating and pressurizing it at the nip between the heating roller 41 and pressure roller 42 of the fixing device 40, and is then discharged onto the discharge tray 51 by the discharge roller pair 50.

[Drum cartridge]
Next, the schematic configuration of the drum cartridge 100 as a photosensitive unit will be described with reference to Figures 2 to 4. In this embodiment, the drum cartridge 100 having the photosensitive drum 11 is detachable from the device main body 1a (Figure 1) so that it can be replaced for maintenance, etc. For example, the drum cartridge 100 can be detachable from the device main body 1a by moving it along its longitudinal direction (the direction of the rotation axis of the photosensitive drum 11) relative to the device main body 1a.

As shown in Figure 2, the drum cartridge 100 includes a photosensitive drum 11 as a photosensitive member, a charging roller 12, a cleaning roller 13 as a cleaning member, a drum cleaning device 15, and a resin spacing member 200. These are all held together by a drum container 30 as a frame.

The photosensitive drum 11 is held in the drum container 30 via bearings (not shown) so that it can rotate around the rotation axis. That is, as shown in FIG. 3, the drum container 30 has side walls 30a arranged on both sides of the rotation axis of the photosensitive drum 11, charging roller 12, and cleaning roller 13, and connecting portions 30b that connect the side walls 30a on both sides. Both ends of the photosensitive drum 11 in the rotation axis direction are rotatably supported by the side walls 30a on both sides of the rotation axis direction via bearings.

The photosensitive drum 11 is also provided with a coupling 39 (Figure 4) that receives driving force from a motor (not shown) provided in the device main body 1a as a drive source and rotates the photosensitive drum 11 when the photosensitive drum 11 is attached to the device main body 1a. When the drum cartridge 100 is attached to the device main body 1a, the coupling 39 is coupled with a coupling provided on the device main body 1a side, and driving force is transmitted from the motor provided in the device main body 1a.

The drum container 30 is also provided with a drum cleaning device 15, which includes a cleaning blade 15a, a recovery section 15b, and a toner transport screw 38. The cleaning blade 15a is fixed to the drum container 30 and comes into contact with the surface of the photosensitive drum 11 in a counter-direction to the rotation direction β of the photosensitive drum 11 during image formation, thereby cleaning the surface of the photosensitive drum 11.

The recovery unit 15b is located near the cleaning blade 15a and recovers residual toner removed from the surface of the photosensitive drum 11 by the cleaning blade 15a. The toner transport screw 38, which serves as a transport unit, transports the toner recovered in the recovery unit 15b and out of the drum cartridge 100. The toner transported out of the drum cartridge 100 by the toner transport screw 38 is collected in a waste toner container (not shown) located in the device main body 1a.

A gear 36 (Figures 3 and 4) is provided as a rotating member fixed to the longitudinal end (end in the direction of the rotational axis) of the photosensitive drum 11 so as to rotate integrally with the photosensitive drum 11 around the rotational axis of the photosensitive drum 11. That is, the gear 36 is provided on the rotational axis of the photosensitive drum 11 so as to rotate together with the photosensitive drum 11. The gear 36 rotates integrally with the photosensitive drum 11 when a driving force is input to the photosensitive drum 11 via a coupling 39. The rotational force of the gear 36 is transmitted to the toner transport screw 38. This rotates the toner transport screw 38, allowing the residual toner collected in the collection section 15b to be transported out of the drum cartridge 100.

The charging roller 12, which serves as a charging member, is a roller-shaped member having a rotating shaft 12a, which is a conductive support (core metal, core material), and one or more elastic layers 12b formed around the rotating shaft 12a. The charging roller 12 is brought into contact with the surface of the photosensitive drum 11 with a predetermined pressing force by a pressure spring 32 (Figure 4), which serves as a first biasing member, and rotates in conjunction with the rotation of the photosensitive drum 11.

Now, a more specific explanation will be given. The charge roller 12 is rotatably supported by having its rotation shaft 12a held by a charge roller bearing 31, which serves as a roller holder. The charge roller bearing 31 is also supported so as to be slidable relative to the drum container 30. Specifically, the charge roller bearing 31 is slidably guided in the direction toward the rotation axis of the photosensitive drum 11 by a slide guide portion 30c provided on the drum container 30. In the illustrated example, a groove 31a is formed in the charge roller bearing 31 along the sliding direction, and the slide guide portion 30c engages with this groove 31a, thereby guiding the charge roller bearing 31 in the direction toward the rotation axis of the photosensitive drum 11.

The charging roller 12, supported by the charging roller bearing 31, is movable in a direction toward the rotation axis of the photosensitive drum 11 on a plane perpendicular to the rotation axis of the photosensitive drum 11. This allows the charging roller 12 to move between a contact position where it contacts the surface of the photosensitive drum 11 and a spaced position where it is spaced apart from the surface of the photosensitive drum 11. The charging roller 12 charges the surface of the photosensitive drum 11 when a voltage is applied at the contact position.

Furthermore, a pressure spring 32 serving as a first biasing member is provided between the drum container 30 and the charge roller bearing 31. The pressure spring 32 biases the charge roller 12 in a direction toward the rotation axis of the photosensitive drum 11 in a plane perpendicular to the rotation axis of the photosensitive drum 11 (the biasing direction of the pressure spring 32). In other words, the pressure spring 32 biases the charge roller bearing 31 in the same direction as the sliding direction of the charge roller bearing 31. As a result, the charge roller 12 is pressed against the photosensitive drum 11 and comes into contact with it. In other words, the pressure spring 32 biases the charge roller 12 in a direction from the separated position toward the contact position.

The cleaning roller 13, which serves as a cleaning member, comes into contact with the charge roller 12 to clean its surface. The cleaning roller 13 is a roller-shaped member that has a rotating shaft 13a, which is a rod-shaped support portion (core metal, core material), and an elastic layer 13b formed around the rotating shaft 13a, and its outer surface comes into contact with the charge roller 12. The cleaning roller 13 is brought into contact with the surface of the charge roller 12 with a predetermined pressing force by a pressure spring 34 (Figures 3 and 4), which serves as a second biasing member, and rotates in response to the rotation of the charge roller 12.

Now, a more specific explanation will be given. The cleaning roller 13 is rotatably supported by the cleaning roller bearing 33, with its rotation shaft 13a supported by the cleaning roller bearing 33. The cleaning roller bearing 33 is also supported slidably relative to the charge roller bearing 31. Specifically, the cleaning roller bearing 33 is configured to be slidable in a direction toward the rotation axis of the charge roller 12, so that the cleaning roller 13 can move along a direction toward the rotation axis of the charge roller 12 in a plane perpendicular to the rotation axis of the charge roller 12. In this embodiment, the rotation axis of the charge roller 12 and the rotation axis of the spacing member 200, which will be described later, are common.

As a result, the cleaning roller 13 is movable between a roller contact position where it contacts the surface of the charging roller 12 and a roller separation position where it is separated from the surface of the charging roller 12. The cleaning roller 13 cleans the charging roller 12 at the roller contact position.

Furthermore, a pressure spring 34 is provided between the charge roller bearing 31 and the cleaning roller bearing 33 as a second biasing member. The pressure spring 34 biases the cleaning roller 13 in a direction (biasing direction) toward the rotational axis of the charge roller 12 in a plane perpendicular to the rotational axis of the charge roller 12. As a result, the cleaning roller 13 is pressed against the charge roller 12 and comes into contact with it. That is, the pressure spring 34 biases the cleaning roller 13 in a direction from the roller separation position toward the roller contact position. In other words, the cleaning roller 13 is supported by the cleaning roller bearing 33 so as to be movable along the biasing direction of the pressure spring 34. Furthermore, in this embodiment, the biasing direction of the pressure spring 32 and the biasing direction of the pressure spring 34 are approximately the same.

The cleaning roller 13 is also supported by the charging roller bearing 31 via the cleaning roller bearing 33 and the pressure spring 34. Therefore, as described below, when the charging roller 12 is moved in a direction away from the photosensitive drum 11 by the spacing member 200, the cleaning roller 13 moves in the direction of movement of the charging roller 12 in conjunction with this.

With the above configuration, when the photosensitive drum 11 receives a driving force from a drive source such as a motor provided in the device main body 1a and rotates, the charging roller 12 is rotated by the frictional force with the photosensitive drum 11. Furthermore, when the charging roller 12 rotates, the cleaning roller 13 is rotated by the frictional force with the charging roller 12. In addition, the toner transport screw 38 receives a driving force (rotational force) from the gear 36 and rotates.

[Spacer member]
Next, the spacing member 200 will be described with reference to Figures 3 to 7. Note that in Figures 3 to 7, a regulating portion 300, which will be described later with reference to Figure 8, is omitted. First, with reference to Figures 5, 6, and 7A, a spacing maintaining configuration in which the spacing member 200 maintains the photosensitive drum 11 and the charging roller 12, and the charging roller 12 and the cleaning roller 13, in a spaced-apart state, will be described.

[Configuration for maintaining spacing]
The drum cartridge 100 is provided with a spacing member 200 for separating the charging roller 12 from the photosensitive drum 11 and the charging roller 12 from the cleaning roller 13 to ensure clearance during transportation for distribution.

The spacing member 200 is provided on the rotation shaft 12a of the charge roller 12 so as to be able to swing freely. In this embodiment, the spacing member 200 is provided on each end of the rotation shaft 12a of the charge roller 12 so as to be able to swing around the rotation shaft 12a as the swing axis. In other words, the spacing member 200 is supported by the charge roller 12 so as to be able to swing around the rotation axis of the charge roller 12. Therefore, the spacing member 200 can move in conjunction with the movement of the charge roller 12. Note that the spacing members 200 on both ends of the charge roller 12 have the same configuration, and therefore the following description will be given using a diagram showing only one side.

The spacing member 200 has two spacing retainers 210, 220 and a swing support member 230. As described above, the swing support member 230 is fitted to the rotation shaft 12a of the charging roller 12 so that it can swing freely. This allows the spacing member 200 to be supported so that it can swing freely relative to the rotation shaft 12a. The spacing retainer 210 is disposed between the gear 36 provided on the photosensitive drum 11 and the rotation shaft 12a of the charging roller 12, separating the photosensitive drum 11 and the charging roller 12 while ensuring clearance. The spacing retainer 220 is disposed between the rotation shaft 12a of the charging roller 12 and the rotation shaft 13a of the cleaning roller 13, separating the charging roller 12 and the cleaning roller 13 while ensuring clearance.

The two separation retaining portions 210, 220 and the swing support portion 230 are integrally formed. Therefore, when the spacing member 200 is positioned in the first phase in the swing direction, the separation retaining portions 210, 220 maintain the photosensitive drum 11 and the charging roller 12, and the charging roller 12 and the cleaning roller 13, spaced apart (separation retaining state). On the other hand, when the spacing member 200 swings from the first phase to the second phase in the swing direction, the separation retaining state between the photosensitive drum 11 and the charging roller 12 and the separation retaining state between the charging roller 12 and the cleaning roller 13 are simultaneously released (separation released state), as described below.

When the photosensitive drum 11 and charging roller 12 are spaced apart, the spacing retainer 210 is sandwiched between the rotation shaft 12a of the charging roller 12 (the rotation shaft of the spacing member 200) and the gear 36 by the pressure (bias) of the pressure spring 32. When the charging roller 12 and cleaning roller 13 are spaced apart, the spacing retainer 220 is sandwiched between the rotation shaft 13a of the cleaning roller 13 and the rotation shaft 12a of the charging roller 12 by the pressure (bias) of the pressure spring 34.

As shown in FIG. 7(a), the spacing member 200's spacing retaining portion 210 has an engaging portion 211 that can engage with the gear 36. The engaging portion 211 has gear teeth 211a formed as engaging protrusions on the side surface that faces the gear 36 of the spacing retaining portion 210 in the spacing retaining state. The gear 36 also has engaging recesses 36a formed around its entire circumference on its outer circumferential surface that can engage with the gear teeth 211a. In other words, the engaging recesses 36a are formed between the gear teeth of the gear 36. The gear teeth 211a are formed at the same pitch as the engaging recesses 36a of the gear 36 (the gear tooth pitch of the gear 36). In the spacing retaining state in which the photosensitive drum 11 and the charging roller 12 are spaced apart, the gear teeth 211a of the engaging portion 211 engage with the engaging recesses 36a of the gear 36. With the engagement portion 211 engaged with the gear 36, which serves as a rotating member, the spacing member 200 holds the charging roller 12 in a spaced position, separating the photosensitive drum 11 and the charging roller 12, against the biasing force of the pressure spring 32.

The spacing member 200's spacing member 220 also has an engaging portion 221, which serves as a cleaning member engaging portion and is engageable with the rotating shaft 13a of the cleaning roller 13, which serves as a part of the cleaning member. The engaging portion 221 is provided on the side of the spacing member 220 that faces the rotating shaft 13a in the spacing member state, and is a recess with a radius of curvature substantially equal to the outer diameter of the outer surface of the cylindrical rotating shaft 13a. In the spacing member state in which the charge roller 12 and cleaning roller 13 are spaced apart, the engaging portion 221 engages with the rotating shaft 13a. In other words, with the engaging portion 221 engaged with the rotating shaft 13a, the spacing member 200 holds the cleaning roller 13 in a spaced position where the charge roller 12 and cleaning roller 13 are spaced apart, against the biasing force of the pressure spring 34.

The engaging portion 221 of the spacing retainer 220 is formed to engage with the rotating shaft 13a of the cleaning roller 13 when the engaging portion 211 of the spacing retainer 210 is engaged with the gear 36. Therefore, when the spacing member 200 is positioned in the first phase in the swinging direction, the engaging portion 211 engages with the gear 36, and the engaging portion 221 engages with the rotating shaft 13a. This maintains the charging roller 12 and cleaning roller 13 in a spaced-apart state. As a result, for example, when transporting the drum cartridge 100, the elastic layer 12b of the charging roller 12 is spaced apart from the photosensitive drum 11, and the charging roller 12 and cleaning roller 13 are also spaced apart, ensuring a clearance between them.

[Configuration of separation release]
3, 4, and 7(b), a description will be given of a separation release configuration that releases the separation maintained state between the photosensitive drum 11 and the charging roller 12, and between the charging roller 12 and the cleaning roller 13, using the spacing member 200. When a new drum cartridge 100 is mounted in the apparatus main body 1a (FIG. 1) and the image forming apparatus 1 (FIG. 1) is started, an initial operation performed by the image forming apparatus 1 inputs a driving force (rotational force) to the photosensitive drum 11 from a motor provided in the apparatus main body 1a.

When the drum cartridge 100 is installed in the device main body 1a, as shown in FIG. 7(a), the photosensitive drum 11 and the charging roller 12, and the charging roller 12 and the cleaning roller 13, are spaced apart. When the photosensitive drum 11 starts to rotate from this spaced apart state, the gear 36 rotates along with the rotation of the photosensitive drum 11, as shown in FIG. 7(b). The engaging portion 211, which is engaged with the gear 36, then receives the rotational force of the gear 36, causing the spacing member 200 to swing in the predetermined direction α (the direction of the arrow in FIG. 7(b)).

By swinging the spacing member 200 in the predetermined direction α in this way, the engagement portion 211 disengages from the gear 36, and the spacing retainer 210 is released from being sandwiched between the rotation shaft 12a of the charge roller 12 (the swing shaft of the spacing member 200) and the gear 36. As a result, the state in which the charge roller 12 is held in the spacing position is automatically released. In other words, the charge roller 12 comes into contact with the photosensitive drum 11. Note that if the spacing member 200 swings in the direction opposite to the predetermined direction α, the movement of the spacing member 200 is restricted, preventing the engagement portion 211 from disengaging from the gear 36.

Furthermore, when the spacing member 200 swings in the predetermined direction α, the engagement portion 221 disengages from the rotating shaft 13a of the cleaning roller 13, and the spacing retaining portion 220 is released from being sandwiched between the rotating shaft 12a of the charging roller 12 and the rotating shaft 13a of the cleaning roller 13. As a result, the cleaning roller 13 is automatically released from being held in the roller separation position. That is, in this embodiment, when the gear 36 rotates due to the initial operation of the image forming apparatus 1 after the drum cartridge 100 is installed in the apparatus main body 1a, the spacing member 200 swings in the predetermined direction α, and the spacing between the charging roller 12 and cleaning roller 13 is automatically released at the same time.

[Restriction of movement of spacing member]
(Reference example)
8 to 11 , a configuration that can prevent the engagement between the engaging portion 211 of the spacer member 200 and the gear 36 from accidentally disengaging will be described. In the reference example , a regulating portion 300 serving as a regulating means prevents the engagement between the engaging portion 211 of the spacer member 200 and the gear 36 from accidentally disengaging. Specifically, the regulating portion 300 regulates the movement of the spacer member 200 in a direction that increases the distance between the center of oscillation of the spacer member 200 and the center of rotation of the gear 36 (in a direction in which the charge roller bearing 31 is guided along the slide guide portion 30 c) so that the engagement between the engaging portion 211 and the gear 36 does not disengage.

In the reference example , as shown in Fig. 8 , the regulating portion 300 has an abutting portion 302 provided on the spacing member 200 and an abutted portion 301 provided on the drum container 30. As shown in Fig. 9A , the abutting portion 302 is provided so as to protrude from the end face of the spacing maintaining portion 210 in the direction of the rotation axis of the photosensitive drum 11. Therefore, the abutting portion 302 is provided outward of the photosensitive drum 11 in the direction of the rotation axis.

As shown in Figure 9(b), the abutted portion 301 is provided on the side wall 30a of the drum container 30 that faces the end of the photosensitive drum 11 in the rotational axis direction. Specifically, the abutted portion 301 is formed by protruding the portion of the side surface of the side wall 30a that is closer to the charge roller 12 than the portion that faces the end of the photosensitive drum 11 in the rotational axis direction inward (toward the charge roller 12) in the rotational axis direction. This abutted portion 301 is formed so that it abuts against the abutting portion 302 when the spacing member 200 moves in a direction that increases the distance between the oscillation center of the spacing member 200 and the rotation center of the gear 36 while the engaging portion 211 is engaged with the gear 36.

That is, the abutted portion 301 has an abutment surface 301a against which the abutting portion 302 abuts. The abutment surface 301a is formed on the side of the abutting portion 302 when the spacing member 200 is in the spacing-maintaining state, where the distance between the oscillation center of the spacing member 200 and the rotation center of the gear 36 is greater. Here, the spacing member 200 is provided so as to be able to swing freely relative to the rotation shaft 12a of the charge roller 12, and the oscillation center of the spacing member 200 and the rotation center of the charge roller 12 are approximately the same. In addition, the charge roller 12 is urged toward the photosensitive drum 11 by the pressure spring 32, and the spacing-maintaining portion 210 of the spacing member 200 is sandwiched between the rotation shaft 12a of the charge roller 12 and the gear 36 by the urging force of this pressure spring 32.

For this reason, in the reference example , the side of the spacing member 200 where the distance between the oscillation center of the spacing member 200 (the rotation center of the charging roller 12) and the rotation center of the gear 36 (the rotation center of the photosensitive drum 11) increases is opposite to the biasing direction of the pressure spring 32. Therefore, the abutting surface 301a is located in the opposite direction to the biasing direction of the pressure spring 32 with respect to the abutting portion 302 when the spacing member 200 is in the separation maintaining state. Therefore, when the abutting portion 302 abuts against the abutting surface 301a, movement of the spacing member 200 in the direction away from the gear 36 against the biasing force of the pressure spring 32 is restricted.

10(a) and (b), the distance between the abutting portion 302 and the abutted portion 301 in the separation-maintaining state, when the spacing member 200 is not moving in a direction that increases the distance between the center of oscillation of the spacing member 200 and the center of rotation of the gear 36, is defined as A. It is preferable that the distance A be greater than 0. That is, it is preferable that there is a gap between the abutting portion 302 and the abutted portion 301 in this state. The separation-maintaining state is a state in which the spacing member 200 holds the charge roller 12 in the separation position. Furthermore, the state in which the spacing member 200 is not moving in a direction that increases the distance between the center of oscillation of the spacing member 200 and the center of rotation of the gear 36 is a state in which the spacing-maintaining portion 210 of the spacing member 200 is pressed against the gear 36 and is not separated from the gear 36. In this state, when viewed from the direction of rotation of the gear 36, the distance A is smaller than the length (engagement amount B) over which the gear teeth 211a and the engagement recesses 36a overlap in the direction in which the gear teeth 211a protrude.

That is, as shown in Figures 10(a) and (b), in the separation-maintaining state, the relationship between the distance A between the abutting portion 302 and the abutting surface 301a and the engagement amount B between the gear 36 and the engaging portion 211 is such that the distance A is smaller in the sliding direction of the charge roller bearing 31 (the direction in which the charge roller bearing 31 is guided along the slide guide portion 30c). In other words, A < B. With this configuration, when the engaging portion 211 is engaged with the gear 36, the spacing member 200 is restricted from moving in a direction that increases the distance between the center of oscillation of the spacing member 200 and the center of rotation of the gear 36, so that the engagement between the engaging portion 211 and the gear 36 does not disengage.

For example, if the drum cartridge 100 is vibrated or dropped during transportation, there is a risk that the charging roller 12 will move away from the photosensitive drum 11 against the biasing force of the pressure spring 32. In this case, the spacing member 200 supported on the rotation shaft of the charging roller 12 will also move away from the photosensitive drum 11. However, because distance A is smaller than engagement amount B as described above, the abutting portion 302 abuts against the abutted portion 301 before the engagement between the engaging portion 211 and the gear 36 disengages, restricting the movement of the spacing member 200 and preventing the separation state from being released.

When the separation state is released, the gear 36 rotates together with the photosensitive drum 11, causing the spacing member 200 to swing, thereby disengaging the engagement portion 211 from the gear 36. At this time, the spacing member 200 is biased toward the photosensitive drum 11 together with the charging roller 12 by the pressure spring 32, so it moves toward the photosensitive drum 11 as the engagement portion 211 and gear 36 disengage. In other words, as the spacing member 200 swings, the abutting portion 302 provided on the spacing member 200 moves in a direction away from the abutted portion 301. Therefore, the abutting portion 302 does not interfere with the abutted portion 301, and the spacing member 200 swings, releasing the separation state.

In the reference example , the spacing member 200 is restricted from rotating in the direction opposite to the rotation direction (predetermined direction α) in which the spacing member 200 is automatically released from the position in the spaced state when the abutting portion 302 abuts against the abutted portion 301. For this reason, as shown in Figure 11 (a), the abutted portion 301 is formed so that when it abuts against the abutting portion 302, a reaction force P in the normal direction acting on the abutting portion 302 acts in a direction that causes the spacing member 200 to swing in the direction opposite to the predetermined direction α.

11B, the abutment surface 301a of the abutted portion 301 is inclined in the direction opposite to the predetermined direction α with respect to the direction perpendicular to the biasing direction S of the pressure spring 32 (e.g., FIG. 9A). In other words , the abutment surface 301a is configured as a surface inclined with respect to the sliding direction of the charge roller bearing 31.

Specific explanation follows. The abutment surface 301a is an inclined surface such that when it comes into contact with the abutment portion 302, the normal reaction force P acting on the abutment portion 302 has a force component that rotates the spacing member 200 in the direction opposite to the direction in which the spacing member 200 rotates during automatic release (predetermined direction α). In other words, as shown in Figure 11(a), the normal reaction force P generates a torque T that rotates the spacing member 200 in the direction opposite to the predetermined direction α.

In the reference example , as shown in FIG. 11B , the normal direction N of the abutting surface 301a is oriented toward the cleaning blade 15a relative to the direction toward the rotation axis of the photosensitive drum 11 (i.e., the biasing direction S) in the sliding direction of the charging roller bearing 31. As shown in FIG. 2 , the cleaning blade 15a abuts against the photosensitive drum 11 in a counter-direction relative to the rotation direction. Furthermore, in order to clean the surface of the photosensitive drum 11 before charging the photosensitive drum 11, the cleaning blade 15a is disposed upstream of the charging roller 12 relative to the rotation direction of the photosensitive drum 11. The spacing member 200 oscillates in a predetermined direction α as the photosensitive drum 11 rotates in the rotation direction β. Therefore, the cleaning blade 15a is positioned in the opposite direction to the predetermined direction α relative to the spacing member 200. Therefore, in the reference example , the normal direction N of the abutting surface 301a is oriented toward the cleaning blade 15a relative to the biasing direction S.

If a large impact is applied to the drum cartridge 100, for example, during transportation, the following problem may occur. For example, deformation of the drum container 30 may cause the relationship between the distance A between the abutting portion 302 and the abutting surface 301a in the spaced-apart state and the engagement amount B between the gear 36 and the engaging portion 211 to be reversed. In other words, A may become greater than B.

However, by tilting the abutment surface 301a as described above, it is possible to prevent the separation state from being inadvertently released, even if, for example, A > B occurs and the gear 36 and engagement portion 211 temporarily separate. That is, when an impact causes the separation member 200 to move and the abutment portion 302 to come into contact with the abutment surface 301a, a normal resistance force P is generated in the abutment portion 302, causing it to rotate in the opposite direction to the direction in which the separation member 200 rotates during automatic release (predetermined direction α). This prevents the separation member 200 from rotating in the predetermined direction α, preventing the separation state from being released even if A > B occurs.

(Example of the present invention)
A feature of the present invention is that in addition to this configuration (a configuration in which the spacing member 200 is provided with an abutting portion 302, and the abutting portion 302 of the spacing member 200 abuts against the abutted portion 301 of the drum container 30), the spacing member 200 is further configured to prevent the spacing state from being released. Note that even if the spacing member 200 is configured without the abutting portion 302, a modified example that can prevent the spacing state from being released by having the configuration described below may be used. In this embodiment, as shown in FIG. 13 , the spacing member 200 has a supported portion 212 that is supported by the core of the charge roller 12 , and a connecting portion 213 (extension portion) that extends from the supported portion 212 along the core of the charge roller 12 and connects the supported portion 212 and the engaging portion 211. If the length of the connecting portion 213 is long, the connecting portion 213 is more likely to bend from the supported portion 212 . When an external force is applied to the photosensitive unit 100 , the connecting portion 213 may bend in a direction that moves the engaging portion 211 away from the gear 36. As a result, there is a risk that the engagement between the engaging portion 211 and the gear 36 may be released. To prevent this, in the separation-maintaining state, a protrusion 310 protruding from the charge roller bearing 31 abuts against the surface (opposite surface) of the separation maintaining portion 210 opposite the gear 36 in the biasing direction of the pressure spring 32 (first biasing member). The protrusion 310 is part of the charge roller bearing 31. In this embodiment, the protrusion 310 is configured to protrude from the charge roller bearing 31 , but is not limited to a protruding shape. It is not necessary for the protrusion 310 to be configured so that it partially protrudes from the charge roller bearing 31 , as long as it abuts against the separation maintaining portion 210. With this configuration, when vibration or impact is applied to the drum cartridge 100, the separation maintaining portion 210 can be prevented from separating from the gear 36 when the separation maintaining portion 210 is momentarily deformed. With this configuration, even if the separation maintaining portion 210 has low rigidity, the separation maintaining portion 210 can be prevented from separating from the gear 36 when vibration or impact is applied to the drum cartridge 100.

The configuration of the protrusion 311 will now be described with reference to FIGS. 12 and 13 . FIG. 12 is a perspective view of the drum cartridge 100. The protrusion 311 constitutes part of the charge roller bearing 31, and is therefore located further outward than the charge roller 12b in the direction of the rotational axis of the charge roller 12b. In other words, the protrusion 311 is integrally molded with the charge roller bearing 31. FIG. 13 is a diagram illustrating the relationship between the protrusion 311 and the separation retainer 210 in the separation retaining state. In this embodiment, when the engaging portion 211 and the gear 36 are engaged and the charge roller 12b is separated from the photosensitive drum 11 (separated state), the protrusion 311 abuts against the separation retainer 210. The configuration in which the protrusion 311 presses the separation retainer 210 with the biasing force of the pressure spring 32 prevents the engagement from being released even if a force is applied in the direction in which the engaging portion 211 moves away from the gear 36 during a shock. On the other hand, in this embodiment, the portion of the protrusion 311 that comes into contact with the spacing maintaining portion 210 is arc-shaped. By making the portion of the protrusion 311 that comes into contact with the spacing maintaining portion 210 arc-shaped, the contact area between the protrusion 311 and the spacing maintaining portion 210 can be reduced when the spacing maintaining member 200 rotates, and therefore the load that the protrusion 311 places on the rotation of the spacing maintaining portion 210 can be reduced. Furthermore, it is preferable that at least a portion of the protrusion 311 overlaps with the engaging portion 211 in the direction of the rotation axis of the charge roller 12. This configuration prevents the engaging portion 211 from separating from the gear 36. Note that in this embodiment, the distance A is shorter than the distance B.

In the present embodiment, when the engaging portion 211 and the gear 36 are engaged and the charging roller 12b is spaced from the photosensitive drum 11 (separated state), the protrusion 311 is disposed in contact with the separation maintaining portion 210. Alternatively, the following configuration is also possible. That is, in the separated state, the protrusion 311 is disposed at a distance C (shortest distance) from the separation maintaining portion 210. Distance C is shorter than the aforementioned distance B (the amount of engagement between the engaging portion 211 and the gear 36). With this configuration, even if a force is applied to the engaging portion 211 in a direction away from the gear 36 and the engaging portion 211 moves in the direction away from the gear 36 when a shock is applied, the separation maintaining portion 210 can be prevented from coming into contact with the protrusion 311 and disengaging. Distance C is also shorter than distance B. Even with this configuration, the same effect as the above configuration can be obtained.

In this embodiment, the protrusion 311 has an arc shape, but it is not limited to this shape and may have other configurations in which the width decreases as it approaches the photosensitive drum 11.

(Modification of the present invention)
In this embodiment, the regulating portion is a plate-shaped protrusion protruding from the side wall 30a of the drum container 30. However, as shown in Figures 14 and 15, the side wall 30d of the drum container 30 may also serve as the regulating portion. That is, as shown in Figures 14 and 15, the end surface 31b of the charge roller bearing 31 serves as the abutting portion 302, and the side wall 30d of the drum container 30 serves as the abutted portion 301. When the engaging portion 211 is engaged with the gear 36 (the separation holding state in Figure 15), and the spacing member 200 moves in a direction in which the distance between the oscillation center of the spacing member 200 and the rotation center of the gear 36 increases (the direction in which the charge roller bearing 31 is guided along the slide guide portion 30c), the abutting portion 302 (the end surface 31b of the charge roller bearing 31) abuts against the abutted portion 301 (the side wall 30d of the drum container 30). Even with this configuration, it is desirable that the engagement amount B (the length over which the engaging portion 211 is engaged with the gear 36) between the gear 36 and the engaging portion 211 in FIG. 14 be greater than the distance A (shortest distance) between the abutting portion 302 (end surface 31 b of the charging roller bearing 31) and the abutted portion 301 (side wall 30 d of the drum container 30) in the spaced-apart state in FIG. 15.

As described above, even if vibration or impact is applied to the drum cartridge 100, causing a force to move the separation retaining portion 210 in a direction away from the gear 36, it is possible to prevent the engagement between the engaging portion 211 and the gear 36 from being disengaged. As a result, it is possible to reduce the risk of the separation retaining state between the photosensitive drum 11 and the charging roller 12, and further between the charging roller 12 and the cleaning roller 13, being unintentionally released.

1 Image forming apparatus 1a Apparatus main body 11 Photosensitive drum (photosensitive member)
12 Charging roller 12a Rotating shaft 13 Cleaning roller (cleaning member)
13a Rotating shaft (part of cleaning member)
30 Drum container (frame)
30a, 30d: Side wall 30b: Connecting portion 30c: Slide guide portion 31, 31A: Charging roller bearing (roller holding portion)
32 Pressure spring (first biasing member)
34 Pressure spring (second biasing member)
36 Gear (rotating member)
36a Engagement recess 100 Drum cartridge (photosensitive unit)
200, 200A Spacer member 210 Spacer holding portion 211 Engagement portion 211a Gear teeth (engagement protrusion)
220 Separation holding portion 221 Engagement portion (cleaning member engagement portion)
300, 300A Regulation part 301, 301A Abutted part 301a, 301Aa Abutment surface 302, 302A Abutment part

Claims (3)

A photosensitive unit that can be attached to an image forming apparatus,
a rotatable photoreceptor;
a rotatable charging roller that contacts the photoreceptor and charges the photoreceptor;
a charging roller bearing member attached to a rotation shaft of the charging roller and rotatably supporting the charging roller;
a biasing member provided on the charging roller bearing member and biasing the charging roller toward the photosensitive member;
a gear provided at a first end of the photosensitive member in a rotational axis direction;
a spacing member provided on a rotation shaft of the charging roller, the spacing member having an engaging portion that engages with the gear, for spacing the charging roller and the photosensitive member apart;
a guide portion that guides the charge roller bearing member urged by the urging member so that the charge roller separates from the photosensitive body when the engagement portion and the gear are engaged, and that guides the charge roller bearing member urged by the urging member so that the charge roller contacts the photosensitive body when the engagement portion and the gear are not engaged;
a frame including a first side wall disposed at a first end of the photosensitive member in a rotational axis direction, a second side wall disposed at a second end of the photosensitive member in the rotational axis direction, and a connecting portion connecting the first side wall and the second side wall, the frame rotatably supporting the photosensitive member on the first side wall and the second side wall;
Equipped with
When the shortest distance between the end surface of the charge roller bearing member urged by the urging member and the first side wall in a state in which the engaging portion and the gear are engaged is A, and the amount of engagement between the engaging portion and the gear in a state in which the engaging portion and the gear are engaged is B,
A photoreceptor unit characterized in that A<B is satisfied. a rotatable cleaning roller that contacts the charging roller to clean the charging roller;
a cleaning roller bearing member attached to a rotation shaft of the cleaning roller and rotatably supporting the cleaning roller;
a second biasing member provided on the cleaning roller bearing member for biasing the cleaning roller toward the charging roller;
a second guide portion that guides the cleaning roller bearing member urged by the second urging member so that the cleaning roller separates from the charging roller when the engagement portion and the gear are engaged, and that guides the cleaning roller bearing member urged by the second urging member so that the cleaning roller contacts the charging roller when the engagement portion and the gear are not engaged;
The photoreceptor unit according to claim 1 , further comprising: a driving force receiving portion for receiving a driving force for rotating the photosensitive member;
The photosensitive unit according to claim 1 or 2, characterized in that, when the engagement portion and the gear are engaged, as the driving force receiving portion receives the driving force and the gear rotates, the engagement portion and the gear transition from an engaged state to a disengaged state.