This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2020-192243 (filed on Nov. 19, 2020), the entire contents of which are incorporated herein by reference.
The present disclosure relates to an image carrier unit and an image forming apparatus including the same. The image carrier unit includes an image carrier, a cleaning member that makes contact with the image carrier so as to clean a surface thereof, and a demountable image carrier protective cover that protects the image carrier.
There is conventionally known an image carrier unit including a photosensitive drum (image carrier) on which an electrostatic latent image is formed and a charging device that charges the photosensitive drum. The charging device includes a charging roller that makes contact with the photosensitive drum so as to charge the photosensitive drum, a cleaning roller (cleaning member) that makes contact with the charging roller so as to clean the charging roller, and a biasing member that biases the charging roller toward the photosensitive drum.
In the image carrier unit configured as above, when stored in contact with the photosensitive drum for a long period of time, the charging roller might be permanently deformed under a contact pressure. There might also occur a phenomenon (bleeding phenomenon) in which a rubber component of the charging roller adheres to a surface of the photosensitive drum. As a result, there has been a fear of occurrence of charging abnormality of the photosensitive drum, which might adversely affect an image being formed.
To solve these problems, a method has been proposed in which the photosensitive drum and the charging roller are held in a separated state from each other, and there is known, for example, a configuration in which in an integral process cartridge including a charging roller biased into contact with a photosensitive drum by an elastic member, a charging roller separation member is provided that is capable of separating the charging roller from the photosensitive drum.
There is also known a photosensitive member protective cover that is demountably mounted to and protects a photosensitive cartridge including a photosensitive drum and a charging roller that makes contact with the photosensitive drum so as to charge the photosensitive drum. The photosensitive member protective cover includes a drum protective portion that protects the photosensitive drum and a separation portion that separates the photosensitive drum from the charging roller.
An image carrier unit according to one aspect of the present disclosure includes an image carrier, a first cleaning member, a unit frame, and an image carrier protective cover and is mountable/demountable with respect to a main body of an image forming apparatus. The image carrier includes a cylindrical main body portion and a pair of flange portions attached to both ends of the main body portion, and a toner image is formed on a surface of the main body portion. The first cleaning member rotates in contact under a prescribed pressure with an outer circumferential surface of the main body portion so as to remove residual toner remaining on the surface of the main body portion. The unit frame rotatably supports the image carrier and the first cleaning member. The image carrier protective cover is mountable/demountable with respect to the unit frame and protects the image carrier. The image carrier protective cover includes a cover main body that extends in an axial direction of the image carrier and protects the image carrier and a side surface portion that is disposed on one end side of the cover main body, and on the side surface portion, an image carrier holding portion is formed that is inserted into one of the pair of flange portions and performs positioning of the image carrier with respect to the unit frame. While performing the positioning of the image carrier, the image carrier holding portion releases a pressure contact state between the image carrier and the first cleaning member.
With reference to the appended drawings, the following describes an embodiment of the present disclosure.
The image forming portions Pa to Pd include photosensitive drums 1a, 1b, 1c, and 1d, respectively, that are provided therein to carry visible images (toner images) of the respective colors. Moreover, an intermediate transfer belt 8 that rotates in a counterclockwise direction in
The sheet S on which a toner image is to be transferred is contained in a sheet cassette 16 disposed in a lower part in the image forming apparatus 100, and the sheet S is conveyed to the secondary transfer roller 9 via a paper feed roller 12a and a registration roller pair 12b.
Next, a description is given of an image forming procedure performed in the image forming apparatus 100. Upon an input of an image forming instruction from a host apparatus such as a personal computer, the photosensitive drums 1a to 1d are first started to rotate by a main motor (not shown), and a surface of each of the photosensitive drums 1a to 1d is uniformly charged by a charging roller 21 (see
Each of developing devices 3a to 3d is filled with a prescribed amount of toner of a corresponding one of the respective colors of magenta, cyan, yellow, and black. In a case inhere a percentage of toner in a two-component developer filled in each of the developing devices 3a to 3d falls below a predetermined value due to after-mentioned toner image formation, the developing devices 3a to 3d are replenished with toner from toner containers 4a to 4d, respectively. The toner in the developer is supplied onto each of the photosensitive drums 1a to 1d by a developing roller 25 (see
Further, by each of primary transfer rollers 6a to 6d, a prescribed transfer voltage is applied between itself and a corresponding one of the photosensitive drums 1a to 1d, and thus the toner images of magenta, cyan, yellow, and black on the photosensitive drums 1a to 1d are primarily transferred on the intermediate transfer belt 8. These images of the four different colors are formed in a prescribed positional relationship predetermined for formation of a prescribed full-color image. After that, residual toner remaining on the surface of each of the photosensitive drums 1a to 1d is removed by a corresponding one of cleaning devices 7a to 7d in preparation for subsequent formation of a new electrostatic latent image.
When the intermediate transfer belt 8 starts to rotate in the counterclockwise direction as a drive roller 10 is driven to rotate by a belt drive motor (not shown), at prescribed timing, the sheet S is conveyed from the registration roller pair 12b to the secondary transfer roller 9 provided adjacently to the intermediate transfer belt 8, and the full-color image is transferred thereon by the secondary transfer roller 9. The sheet S on which the toner images have been transferred is conveyed to the fixing portion 13. Residual toner remaining on a surface of the intermediate transfer belt 8 is removed by a belt cleaning unit 19.
The sheet S thus conveyed to the fixing portion 13 is heated and pressed by a fixing roller pair 13a so that the toner images are fixed on a surface of the sheet S. and thus the prescribed full-color image is formed thereon. A conveyance direction of the sheet Son which the full-color image has been formed is switched by a branch portion 14 branching off in a plurality of directions, and thus the sheet S is directly (or after being conveyed to a double-sided conveyance path 18 and thus being subjected to double-sided printing) discharged to a discharge tray 17 by a discharge roller pair 15.
Next, a description is given of the image forming portions Pa to Pd.
The charging device 2a includes the charging roller 21 that makes contact with the photosensitive drum 1a so as to apply a charging bias to a drum surface thereof and a charging cleaning roller 23 for cleaning the charging roller 21.
The developing device 3a, includes two stirring conveyance members 24 composed of a stirring conveyance screw and a supply conveyance screw and the developing roller 25, and toner carried on a surface of the developing roller 25 is caused to fly onto the surface of the photosensitive drum 1a so as to be used to develop the electrostatic latent image into a toner image.
The cleaning device 7a includes a rubbing roller 26 and a cleaning blade 28 that make contact with the surface of the photosensitive drum 1a so as to remove residual toner or the like remaining on the surface of the photosensitive drum 1a and a collection spiral 29 that discharges the toner or the like removed by the rubbing roller 26 and the cleaning blade 28 to an exterior.
Furthermore, the photosensitive drum 1a, the charging device 2a, and the cleaning device 7a are integrated as a unit. In each of the image forming portions Pa to Pd, corresponding one of the photosensitive drums 1a to 1d, a corresponding one of the charging devices 2a to 2d, and a corresponding one of the cleaning devices 7a to 7d form a unit, and such units formed in the image forming portions Pa to Pd, respectively, are hereinafter referred to as drum units (image carrier units) 40a to 40d.
Next, a description is given of the drum unit 40a used in the image forming apparatus 100.
As for the drum units 40b to 40d, descriptions thereof are omitted since they have similar configurations to that of the drum unit 40a. Furthermore, in the drawings referenced hereinafter, a longitudinal direction of the drum unit 40a (an axial direction of the photosensitive drum 1a) is referred to as an X direction, a width direction of the drum unit 40a orthogonal to the X direction is referred to as a Y direction, and a perpendicular direction orthogonal to the X direction and to the Y direction is referred to as a Z direction.
As shown in
The drum unit 40a is a consumable article subject to periodic replacement and thus is packaged, shipped, and stored alone. For this reason, as shown in
As shown in
In the drum unit 40a alone, an end part (flange portion 51a) of the photosensitive drum 1a on a side near the support frame 41b is not radially positioned and is swingable in a prescribed range. When the drum unit 40a is mounted in the main body of the image forming apparatus 100, the flange portion 51a is fitted to a main-body-side coupling (not shown), and thus positioning of the end part is achieved. Furthermore, when the drum protective cover 80 is mounted to the drum unit 40a, a drum holding portion 83 (see
The cleaning device 7a includes the rubbing roller (first cleaning member) 26, a toner regulation roller 27, the cleaning blade 28, and the collection spiral 29. The rubbing roller 26 is biased into pressure contact under a prescribed pressure with the photosensitive drum 1a by a first coil spring 30 (see
The rubbing roller 26 is rotated with a difference in velocity from the photosensitive drum 1a so that the surface of the photosensitive drum 1a is ground by use of residual toner containing an abrasive. The rubbing roller 26 and the cleaning blade 28 remove, together with the residual toner, moisture, a discharge product, and so on adhering to the surface of the photosensitive drum 1a.
The rubbing roller 26 has, for example, a structure in which a roller body 26b that is a foam layer made of an EPDM rubber and having an Asker C hardness of 55° is formed around a metallic rotary shaft 26a, The roller body 26b may be made of a material, without being limited to an EPDM rubber, such as any other type of rubber or a foamed rubber body, and such a material having an Asker C hardness in a range of 10° to 90° is used favorably.
The toner regulation roller 27 is disposed in contact under a prescribed pressure with the rubbing roller 26 and regulates an amount of toner adhering to a surface of the rubbing roller 26 so as to adjust a grinding amount of the surface of the photosensitive drum 1a.
The cleaning blade 28 is secured in contact with the surface of the photosensitive drum 1a at a location on an upstream side, in the rotation direction, of a position of contact with the charging roller 21. The cleaning blade 28 is formed of, for example, a blade made of a polyurethane rubber and having a JIS hardness of 78° and is mounted at a prescribed angle on its point of contact with respect to a tangential direction of the photosensitive drum 1a.
The collection spiral 29 conveys residual toner removed from the surface of the photosensitive drum 1a by the rubbing roller 26 and the cleaning blade 28. As shown in
The charging device 2a includes the charging roller (charging member) 21, the charging cleaning roller (second cleaning member) 23, and a charging housing 61. The charging device 2a is mountable/demountable with respect to the unit frame 41. The charging housing 61 is formed using a nonconductive resin so as to extend in an axial direction of the charging roller 21 and houses the charging roller 21 and the charging cleaning roller 23. The charging roller 21 is a conductive rubber roller composed of a metallic rotary shaft (first rotary shaft) 21a and an elastic layer 21b made of rubber and formed on an outer circumferential surface of the rotary shaft 21a. The charging roller 21 is brought into pressure contact under a prescribed nip pressure with the photosensitive drum 1a and thus rotates passively following rotation of the photosensitive drum 1a.
The charging cleaning roller 23 is composed of a rotary shaft (second rotary shaft) 23a and a cleaning portion 23b formed of a sponge-like elastic member and spirally wound on an outer circumferential surface of the rotary shaft 23a. The charging cleaning roller 23 is rotated in a state where the cleaning portion 23b is in contact with an outer circumferential surface of the charging roller 21, thus removing residual toner, paper dust, and so on adhering to the charging roller 21. A drive input gear (not shown) for transmitting a rotation drive force to the charging cleaning roller 23 is secured to an end part of the rotary shaft 23a of the charging cleaning roller 23 on the side near the support frame 41c.
On both end part sides of the charging roller 21 and the charging cleaning roller 23 in axial directions thereof, a pair of bearing members 63 is disposed to rotatably support the rotary shaft 21a of the charging roller 21 and the rotary shaft 23a of the charging cleaning roller 23. The bearing members 63 are made of a conductive resin.
A second coil spring 64 is disposed between the charging housing 61 and each of the bearing members 63. An upper end part and a lower end part of the second coil spring 64 are in contact with a lower part of the each of the bearing members 63 and a bottom surface of the charging housing 61, respectively. The second coil spring 64 biases the charging roller 21 toward the photosensitive drum 1a (upward) via the each of the bearing members 63. Under a biasing force of the second coil spring 64, the charging roller 21 is evenly brought into pressure contact with the surface of the photosensitive drum 1a and thus rotates passively following rotation of the photosensitive drum 1a.
As shown in
Furthermore, on a side surface of the bearing member 63, there is formed the pressed portion 63c that is to be contacted by a pressure release rib 85 (see
The drum holding portion 83 is formed on an inner side of the side surface portion 82 of the drum protective cover 80. The drum holding portion 83 performs positioning of the flange portion 51a with respect to the support frame 41b in a state where the drum protective cover 80 is mounted to the drum unit 40a and releases a pressure contact state between the photosensitive drum 1a and the rubbing roller 26. Furthermore, the side surface portion 82 has an opening hole 82a formed therethrough for allowing the collection spiral 29 (see
The pressure release rib 85 is formed on an inner side of the cover main body 81 of the drum protective cover 80. The pressure release rib 85 extends over substantially an entire region of the cover main body 81 along the axial direction of the photosensitive drum 1a. At each of two locations on the pressure release rib 85 along an extending direction thereof, a pressing convex portion 85a is formed at a position to be opposed to the pressed portion 63c of the hearing member 63. In a state where the drum protective cover 80 is mounted to the drum unit 40a, the pressure release rib 85 releases a pressure contact state between the photosensitive drum 1a and the charging roller 21.
Next, a description is given of a mechanism for releasing a pressure contact state between the photosensitive drum 1a and the rubbing roller 26 by mounting the drum protective cover 80.
The frame positioning boss 83a cylindrically protrudes from an inner surface of the side surface portion 82. The frame positioning boss 83a fits in a cover positioning hole (first positioning hole) 42 (see
The flange positioning boss 83b cylindrically protrudes from a distal end surface of the frame positioning boss 83a. The flange positioning boss 83b fits in the flange positioning hole (second positioning hole) 52 (see
As shown in
This achieves positioning between the drum protective cover 80 and the support frame 41b and between the drum protective cover 80 and the photosensitive drum 1a, thus achieving positioning between the photosensitive drum 1a and the support frame 41b.
Here, the flange positioning boss 83b is displaced in such a direction (downward in
A bearing portion 31 that rotatably supports the rotary shaft 26a of the rubbing roller 26, on the other hand, is supported so as to be movable in the Y direction relative to the support frame 41b and is biased in a direction (downward in
Since the drum rotary shaft 53 is supported to the support frame 41c, a distance between a part of the photosensitive drum 1a on a side near the flange portion 51b (the right side in
Next, a description is given of a mechanism for releasing a pressure contact state between the photosensitive drum 1a and the charging roller 21 by mounting the drum protective cover 80.
In mounting the drum protective cover 80, first, the cover main body 81 is disposed to be opposed to the photosensitive drum 1a. Next, the drum protective cover 80 is slid gradually along the axial direction of the photosensitive drum 1a from the side near the flange portion 51a to the side near the flange portion 51b. Thus, as shown in
When the drum protective cover 80 is slid further from a state shown in
By the above-described separating operation, the charging roller 21 is brought into a state free from a pressure from the photosensitive drum 1a, which is a reaction to (resistance against) a pressing force of the second coil spring 64, namely, a pressing force in a separating direction from the photosensitive drum 1a in the approaching/separating direction. At this time, the charging roller 21 is brought into a state of being separated from a part of an inner circumferential surface (a lower surface in
Thus, it is possible to suppress a phenomenon in which the cleaning portion 23b of the charging cleaning roller 23 is deformed and remains in that state. This makes it possible to suppress deterioration in cleaning performance of the charging cleaning roller 23 and unstable passive rotation of the charging roller 21 due to friction of the cleaning portion 23b. While the description herein is of an operation in which the pressure release rib 85 presses down one of the hearing members 63 on one side (the left side in
In this embodiment, the drum protective cover 80 includes the drum holding portion 83 formed therein to perform positioning of a part of each of the photosensitive drums 1a to 1d on the side near the flange portion 51a. Furthermore, the flange positioning boss 83b of the drum holding portion 83 is provided so as to be displaced in the separating direction from the rubbing roller 26 relative to the frame positioning boss 83a. Thus, when the drum protective cover 80 is mounted to each of the drum units 40a to 40d, a corresponding one of the photosensitive drums 1a to 1d is held in a state where a part thereof on the side near the flange portion 51a is inclined in the separating direction from the rubbing roller 26, and thus it is possible to release a pressure contact state between the corresponding one of the photosensitive drums 1a to 1d and the rubbing roller 26.
Accordingly, even in a case where the drum units 40a to 40d are stored for a long period of time, it is possible to suppress permanent deformation of the rubbing roller 26. As a result, it is possible to effectively suppress adhesion of a discharge product to the photosensitive drums 1a to 1d due to deterioration in rubbing performance or cleaning performance and adhesion of a toner external additive or the like to the charging roller 21.
Furthermore, in this embodiment, the drum protective cover 80 is provided with the pressure release rib 85 that separates each of the photosensitive drums 1a to 1d from the charging roller 21. Thus, when the drum protective cover 80 is mounted to each of the drum units 40a to 40d, the pressure release rib 85 presses down the pressed portion 63c of the bearing member 63, thereby enabling the each of the photosensitive drums 1a to 1d to be separated from the charging roller 21.
Accordingly, even in a case where the drum units 40a to 40d are stored for a long period of time, it is possible to suppress permanent deformation of the charging roller 21. As a result, it is possible to effectively suppress deterioration in charging performance and occurrence of a phenomenon (bleeding phenomenon) in which a rubber component of the charging roller 21 adheres to the respective surfaces of the photosensitive drums 1a to 1d.
Furthermore, when the drum protective cover 80 is demounted from each of the drum units 40a to 40d, the drum holding portion 83 is pulled out from the flange portion 51a, and when the drum units 40a to 40d are mounted in the main body of the image forming apparatus 100, each of the photosensitive drums 1a to 1d is brought into pressure contact with the rubbing roller 26. Furthermore, when the drum protective cover 80 is demounted, the pressure release rib 85 is separated from the pressed portion 63c, and thus each of the photosensitive drums 1a to 1d is brought into pressure contact with the charging roller 21.
As described above, by performing an operation of mounting/demounting the drum protective cover 80 to/from each of the drum units 40a to 40d, it is possible to bring into contact or separate a corresponding one of the photosensitive drums 1a to 1d with or from the charging roller 21 and the rubbing roller 26. Accordingly, it is possible to improve workability of replacing the drum units 40a to 40d while suppressing an increase in number of components used or a size increase.
Furthermore, the first bearing portion 63a of the bearing member 63, which supports the rotary shaft 21a of the charging roller 21, has such an elongated hole shape that the inner diameter R1 in the approaching/separating direction is longer than the inner diameter R2 in the direction orthogonal to the approaching/separating direction. Thus, when a pressure contact state between the photosensitive drum 1a and the charging roller 21 is released, the charging roller 21 is brought into a state free from a pressing force in the separating direction from the photosensitive drum 1a, positioned on an upper side in the first bearing portion 63a, and placed on the surface of the charging cleaning roller 23. Accordingly, it is possible to suppress deformation of the charging roller 21 caused by the charging cleaning roller 23 and deformation of the cleaning portion 23b of the charging cleaning roller 23 during transportation and storage of the drum units 40a to 40d.
Other than the above, the present disclosure is not limited to the foregoing embodiment and can be variously modified without departing from the spirit of the disclosure. For example, while the foregoing embodiment uses the charging cleaning roller 23 composed of the rotary shaft 23a and the cleaning portion 23b spirally wound on the outer circumferential surface of the rotary shaft 23a, a cleaning brush may be used in place of the charging cleaning roller 23.
Furthermore, regarding the bearing member 63, the drum protective cover 80, the drum holding portion 83, and the pressure release rib 85, their respective shapes and so on described above are also preferred examples and can be changed as appropriate depending on specifications or the like of the charging devices 2a to 2d or the drum units 40a to 40d.
Furthermore, while the foregoing embodiment has described an example in which the present disclosure is applied to the drum units 40a to 40d mounted in a color printer, the present disclosure is not limited thereto. Needless to say, the present disclosure is applicable in a completely similar manner also to a drum unit mounted in a monochrome printer, a color copy machine, a monochrome copy machine, a digital multi-functional peripheral, a facsimile, or the like.
The present disclosure is usable in an image carrier unit including an image carrier, a cleaning member that makes contact with the image carrier so as to clean a surface of the image carrier, and a demountable image carrier protective cover that protects the image carrier. By use of the present disclosure, it is possible to provide an image carrier unit that is capable of maintaining a state where a cleaning member is separated from an image carrier while suppressing an increase in number of components used and a size increase.
Number | Date | Country | Kind |
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2020-192243 | Nov 2020 | JP | national |