Patent Grant
10191406
The present invention relates to a voltage applying device for applying a voltage to a member-to-be-charged such as an electrophotographic photosensitive member or a dielectric member, a process cartridge including the voltage applying device and detachably mountable to an apparatus main assembly of an electrophotographic image forming apparatus and the electrophotographic image forming apparatus including the voltage applying device, and relates to a rotatable member for use with a rotatable driving member provided in the process cartridge or the electrophotographic image forming apparatus.
The electrophotographic image forming apparatus forms an image on a recording medium (material) with use of an electrophotographic image forming type. As examples of the electrophotographic image forming apparatus, for example, an electrophotographic copying machine, an electrophotographic printer (e.g., a laser beam printer, an LED printer, etc.), a facsimile machine, a word processor and the like are included. The apparatus main assembly is an image forming apparatus portion excluding the process cartridge from the electrophotographic image forming apparatus. The recording medium is a material on which the image is formed by the electrophotographic image forming apparatus, and for example, paper, OHT sheet, cloth and the like are included. Further, an image display member of an image display apparatus such as an electronic blackboard (white board) is also included.
Conventionally, in the electrophotographic image forming apparatus, a process cartridge type in which a photosensitive member and a process means actable on the photosensitive member are integrally assembled into a cartridge (unit) and the cartridge is detachably mountable to an apparatus main assembly of the image forming apparatus is employed. According to this process cartridge type, maintenance of the image forming apparatus can be carried out by a user himself (herself) without relying on a service person, so that operativity was able to be remarkably improved. Therefore, this process cartridge type has been widely used in the image forming apparatus.
The process cartridge includes a photosensitive drum (electrophotographic photosensitive drum) which is an image bearing member as disclosed in Japanese Laid-Open Patent Application (JP-A) 2005-164756, which also discloses a constitution including a charging roller for imparting electric charges to the photosensitive drum, a developing roller for supplying a developer (hereinafter referred to as “toner”) and a cleaning means for removing the toner remaining on a photosensitive drum surface without being transferred.
The developing roller is rotated by receiving drive (driving force) from the apparatus main assembly and is contacted to the photosensitive drum, and thus continuously supplies the toner from a developer accommodating portion to the photosensitive drum surface. As rollers of the process cartridge, a plurality of rollers such as a developing roller and a charging roller are used, but any roller includes a solid metal shaft as a rotation shaft in general.
On the other hand, in order to reduce a cost, JP-A 2015-197145 discloses a constitution in which a cylindrical shaft manufactured by press work and including a seamed portion (hereinafter referred to as a “seam”) over an entire region with respect to an axial direction is used as a rotation shaft of a roller.
JP-A 2013-103234 discloses a constitution in which a gear which is a driving member is attached to a shaft end of a pressed rotation shaft and then the rotation shaft is rotated.
The present invention is further development of the above-described conventional constitutions.
A principal object of the present invention is to determine positions of a project and a driving member with respect to an axial direction of the rotation shaft with reliability or to suppress a positional fluctuation of the rotation shaft with respect to the axial direction of the rotation shaft by accurately determining the positions of the rotation shaft and the driving member with respect to the axial direction of the rotation shaft and thereby to suppress a rotational fluctuation of the rotation shaft.
According to an aspect of the present invention, there is provided a rotatable member for use with a rotatable driving member provided in a process cartridge or an electrophotographic image forming apparatus, the rotatable member comprising: a hollow cylindrical rotation shaft engageable with the rotatable driving member, wherein the rotation shaft includes a seam extending from one end to the other end thereof in an axial direction thereof, wherein the rotation shaft includes a transmitting surface engageable with the driving member and configured to receive a driving force for rotating the rotation shaft about the axial direction, and wherein the transmitting surface is twisted or inclined with respect to the axial direction.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Parts (a), (b) and (c) of
Parts (a) and (b) of
Parts (a) and (b) of
Parts (a) and (b) of
Embodiments of the present invention will be described with reference to the drawings. Incidentally, a rotational axis direction (axial direction) of a photosensitive drum refers to as a longitudinal direction.
(Structure of Image Forming Apparatus)
The image forming apparatus 100 includes a photosensitive drum 1 as an image bearing member rotationally driven. At a periphery of the drum 1, a charging roller 2, an exposure device 102, a developing roller 5, a transfer roller 104 and a cleaning blade 6 are provided. The drum 1, the charging roller 2, the developing roller 5 and the cleaning blade 6 are integrally assembled as a process cartridge 7. The cartridge 7 is detachably mounted to a predetermined mounting portion 100B of an apparatus main assembly 100A in a predetermined operation procedure. That is, the cartridge 7 is a part of the image forming apparatus 100.
In the apparatus main assembly 100A, a fixing device 106, a feeding roller 105 as a feeding means of a transfer material P, and an electrical component substrate (not shown) for carrying out electrical control of the apparatus. The charging roller 2 is rotationally driven in contact with the surface of the photosensitive drum 1 with a predetermined pressing force, and a predetermined charging bias is applied from a charging bias voltage source (not shown) to the charging roller 2, so that the drum 1 is electrically charged to a predetermined polarity and a predetermined potential.
The developing roller 5 is rotationally driven in contact with the surface of the drum 1 with a predetermined pressing force and carries and feeds toner (developer) accommodated in a toner accommodating portion 31c, to a developing position which is a contact position with the drum 1, and thus supplies the toner to the photosensitive drum surface. As a result, on an electrostatic latent image formed on the drum 1, the toner is deposited, so that the electrostatic latent image is developed (visualized) as a toner image. To the developing roller 5, a predetermined developing bias is applied from a developing bias voltage source (not shown).
The transfer roller 104 is rotationally driven in contact with the surface of the drum 1 with a predetermined pressing force, and to the transfer roller 104, a predetermined transfer bias is applied from a transfer bias voltage source (not shown). Then, the toner image is transferred from the surface of the drum 1 onto the transfer material P fed to a transfer nip between the transfer roller 104 and the drum 1.
The transfer material P on which the toner image is transferred is fed to the fixing device 106, where predetermined pressure and heat are applied to the transfer material, whereby the toner image is fixed on the transfer material P. Thereafter, the transfer material P is discharged to an outside of the image forming apparatus 100 by a discharging roller pair 107. The cleaning blade 6 removes transfer residual toner remaining on the surface of the drum 1 after the transfer and collects the toner in a residual toner accommodating portion 21c. Subsequently, the above-described process is similarly repeated.
(Structure of Process Cartridge)
Next, a structure of the cartridge 7 will be described with reference to
On the other hand, the developing unit 4 is prepared by holding the developing roller 5 and a developing blade 12 by a developing (unit) frame 31 and by assembling these members into a unit. In the developing frame 31, the toner accommodating portion 31c is formed. The developing unit 4 is swingably supported by the cleaning unit 9 by supporting portions (not shown) provided at longitudinal end portions. Further, the developing unit 4 is rotationally urged by urging springs (not shown) about the supporting portions in a direction in which the developing roller 5 contacts the drum 1. At one longitudinal end portion of the cartridge 7, a drive inputting portion engaging with a drive imparting portion (not shown) provided in the apparatus main assembly 100A is provided, so that a rotational drive (rotational driving force) is transmitted to the drum 1 and the developing roller 5.
(Structure of Developing Unit)
Next a structure of the developing unit 4 will be described with reference to
The developing roller 5 which is one of the rotatable members has a constitution in which a rotation shaft 5a of metal is coated with an elastic layer (elastic material layer) 5b at a central portion thereof with respect to an axial direction. The developing roller 5 is rotatably supported at both end portions thereof by shaft supporting portions 43 and 44 provided on the developing frame 31. A gear 40 which is a rotatable driving member for driving the developing roller 5 engages with a one end portion 5c projecting further from the shaft supporting portion 43 toward an outside with respect to the axial direction (hereinafter, this portion is referred to as a “first shaft end portion”), and rotates integrally with the developing roller 5. An engaging constitution of the gear 40 with the developing roller 5 will be described later as a feature of the present invention.
The gear 40 engages with an input gear 41. The input gear 41 is provided with a coupling portion 41a on a side surface thereof, and the coupling portion 41a engages with a drive inputting portion (not shown) provided on the apparatus main assembly 100A side. The elastic layer 5b of the developing roller 5 is disposed so as to block an opening E communicating with the toner accommodating portion 31c (
Outside the sealing members 45 and 46 with respect to the axial direction, rollers 48 and 49 are engaged rotatably about the rotation shaft 5a. The rollers 48 and 49 are constituted so that inner diameters thereof are slightly larger than an outer diameter of the rotation shaft 5a and so that outer diameters thereof are slightly smaller than an outer diameter of the elastic layer 5b. The rollers 48 and 49 urge the drum 1 so that outer peripheral surfaces thereof contact the surface of the drum 1, whereby the developing roller 5 can be kept in a stable contact state with the drum 1.
In the neighborhood of the other end portion 5d opposite on side from the first shaft end portion 5c of the rotation shaft 5a (hereinafter, the other end portion is referred to as a “second shaft end portion”), an electroconductive contact member 50 is provided so as to contact an outer peripheral surface of the rotation shaft 5a. The contact member 50 includes a contact portion 50a with the apparatus main assembly 100A side, and a bias is applied from the apparatus main assembly 100A side to the developing roller 5 through the contact member 50. Incidentally, the developing roller 5 can also employ a constitution in which the coating layer 5b of the rotation shaft 5a is a non-elastic material layer.
(Structure of Rotation Shaft 5a)
Next, a structure of the rotation shaft 5a of the developing roller 5 will be described with reference to
The rotation shaft 5a has a hollow cylindrical shape including a seam (connecting portion) 5e formed by subjecting a rectangular metal plate to press bending and then by bringing end surfaces, extending in the longitudinal direction, of the rectangular metal plate into contact with each other. By employing such a constitution, the rotation shaft 5a can be prepared with a lower cost and a lighter weight than those of a solid metal shaft. The rotation shaft 5a is provided with circumferentially projected portions 5f at one end surface arranged in the longitudinal direction and is provided with circumferentially recessed portions 5g at the other end surface, opposing the one end surface, arranged in the longitudinal direction. These projected portions 5f and recessed portions 5g are engaged with each other by closing a gap 5k therebetween with respect to the axial direction. As a result, torsion (twist) strength of the rotation shaft 5a can be enhanced. Accordingly, when the rotational drive is imparted to the rotation shaft 5a, it is possible to prevent the seam 5e from opening.
The structure of the above-described rotation shaft 5a is summarized as follows. The rotation shaft 5a has the hollow cylindrical shape. The rotation shaft 5a includes the seam (connecting portion) 5e extending from one end to the other end thereof with respect to an axial direction 0-0 (phantom line). The seam 5e is constituted by the recessed portions 5g and the projected portions 5f which are formed on one side and the other side thereof and is in the form such that he projected portions 5f on one side engage with the recessed portions 5g on the other side and that the projected portions 5f on the other side engage with the recessed portions on one side and thus one side and the other side of the seam 5e are connected with each other.
The first shaft end portion 5c is a plane perpendicular to an axis 0-0 of the rotation shaft 5a. Further, at a part of the first shaft end portion 5c, as shown in parts (b) and (c) of
A twist direction of the cut-away portion 5h is determined by the rotational direction of the rotation shaft 5a. In this embodiment, as shown in part (c) of
(Engagement Constitution (Structure) Between Developing Roller 5 and Gear 40)
Next, the engagement constitution between the developing roller 5 and the gear 40 will be described with reference to
Further, the gear 40 includes a shaft centering portion 40c having the same diameter as an inner diameter of the rotation shaft 5a. The shaft centering portion 40c engages with an inner peripheral surface of the rotation shaft 5a and determines the position of the rotation shaft 5a so that an axial center thereof aligns (overlaps) with the rotation shaft 5a. Further, the gear 40 includes a regulating surface 40e, and the regulating surface 40e contacts a regulating surface 31a of the developing frame 31, so that a position of the gear 40 relative to the developing frame 31 with respect to the axial direction is regulated.
Further, the gear 40 includes, on an outer peripheral surface of the shaft centering portion 40c, a gear portion 40a which is a drive receiving portion for receiving rotational drive from the apparatus main assembly 100A and a boss 40d perpendicular to the axis of the shaft centering portion 40c. In a state in which the gear 40 is engaged with the rotation shaft 5a, when the rotational drive is imparted from the gear portion 40a to the rotation shaft 5a, the rotational drive is transmitted to the rotation shaft 5a through the boss 40d. That is, the boss 40d acts as a drive transmitting portion.
Then, a manner of drive transmission will be described with reference to part (b) of
When the gear 40 is rotated, the boss 40d contacts an end surface 5j which is a part of the end surface of the cut-away portion 5h and which is provided on a downstream side with respect to the rotational direction W (hereinafter, the end surface 5j is referred to as a drive transmitting portion), so that the rotational drive is transmitted to the developing roller 5. That is, the rotation shaft 5a includes the drive transmitting portion 5j; for receiving the rotational drive, in the neighborhood of the first shaft end portion 5c which is one end thereof. The drive transmitting portion 5j is provided as the end surface 5j twisted or inclined toward the downstream side with respect to the rotational direction W of the developing roller 5 with an increasing distance from the first shaft end portion 5c toward the second shaft end portion 5d which is the other end. That is, the end surface 5j is a surface twisted or inclined with respect to the axial direction of the rotation shaft 5a.
As described above, the rotation shaft 5a is provided so as to close the gap 5k between the projected portions 5f and the recessed portions 5g with respect to the axial direction, and therefore, even in the case where the drive is transmitted to the rotation shaft 5a, an increase in gap between the shaft centering portion 40c and the inner peripheral surface of the rotation shaft 5a is suppressed. As a result, a rotational fluctuation due to eccentricity is suppressed.
In the case where a load torque of the developing roller 5 is T and a pitch circle diameter of the gear portion 40a is D, at an engaging portion between the gear portion 40a and the input gear 41, a component force (component of force) A exerted on the gear portion 40a in the axial direction and a component force B in a circumferential direction are represented by the following formulas.
A=B tan α (1)
B=2T/D (2)
On the other hand, the rotation shaft 5a receives a force from the boss 40d at the drive transmitting portion 5j. When an outer diameter of the rotation shaft 5a is d and a helix angle of the drive transmitting portion 5j is θ, a component force a, in the axial direction, of a force by the boss 40d and a component force b in the circumferential direction are represented by the following formulas.
a=b tanθ (3)
b=2T/d (4)
Thus, when the drive is transmitted to the rotation shaft 5a, on the developing roller 5, the component force a in the axial direction acts in a direction in which the developing roller 5 is drawn to the gear 40. Then, the first shaft end portion 5c of the developing roller 5 contacts the positioning portion 40b, so that the position of the developing roller 5 relative to the gear 40 with respect to the axial direction is determined.
Further, on the gear 40, the component force A exerted by the input gear 41 in the axial direction and the reaction force a exerted by the developing roller 5 in the axial direction act. Both the forces act in a direction in which the gear 40 is drawn into the developing frame 31. As a result, the regulating surface 40e of the gear 40 contacts the regulating surface 31a, so that the position of the gear 40 relative to the developing frame 31 with respect to the axial direction is determined.
From the above-described relationships, the position of the developing roller 5 relative to the developing frame 31 with respect to the axial direction is determined through the gear 40. Further, when such a constitution is employed, the developing roller 5 can be rotated without bringing the second shaft end portion 5d into contact with the developing frame 31, so that rotation accuracy is not influenced even when an uneven portion such as a press work trace is formed on the second shaft end portion 5d. Accordingly, there is no need to smoothly process the second shaft end portion 5d after the press work, and therefore, the developing roller 5 can be manufactured inexpensively. Further, the rotation shaft 5a and the gear 40 attract each other during rotation so as not to loosened, and therefore, it is possible to suppress a rotational fluctuation and a positional fluctuation of the developing roller 5.
Incidentally, in this embodiment, even when the boss 40d which is a drive imparting portion and the drive transmitting portion 5j are disposed in any phases and even when these portions are provided in plural pairs, a similar effect can be obtained.
Also a constitution in which a so-called developer supplying roller not only supplying the toner from the toner accommodating portion 31c to the developing roller 5 but also peeling excessive toner off the developing roller 5 at the same time is provided depending on the process cartridge and is slid on and driven by the developing roller 5 has been known in general.
In part (a) of
In this embodiment, the present invention is applied to the rotation shaft 5a of the developing roller 5 which is one of the rotatable members, but is also similarly applicable to the rotation shaft 51a of the developer supplying roller 51. Similarly as in the case of the developing roller 5, an effect of suppressing a rotational fluctuation and a positional fluctuation of the developer supplying roller 51 can be obtained.
Further, also the charging roller 2, a rotation shaft structure similar to that of the developing roller 5 in this embodiment and a structure for driving the developing roller are applicable. Also the charging roller 2 includes, as shown in part (b) of
A constitution according to Embodiment 2 will be described with reference to
The developing roller 5 includes a rotation shaft 5a having a circumferentially twisted end surface 5n in the neighborhood of a first shaft end portion 5c and provided with a hole 5m penetrating a rectangular metal plate. As is apparent from part (a) of
Further, as a drive imparting portion to the rotation shaft 5a, a snap-fitting portion 40g is provided on an outer peripheral surface of a shaft centering portion 40c so as to be perpendicular to an axis of the shaft centering portion 40c. When the gear 40 in engaged with the rotation shaft 5a, the shaft centering portion 40c is inserted into the first shaft end portion 5c while flexing the snap-fitting portion 40g, so that the snap-fitting portion 40g and the hole 5m are engaged with each other. In that state, when the rotational drive in the arrow W direction is imparted to the gear 40, the snap-fitting portion 40g contacts the fracture surface 5n (drive transmitting portion).
By the above-described constitution, similarly as in Embodiment 1, the rotation shaft 5a and the gear 40 can be fastened to each other without being loosened during the drive, and therefore, a rotational fluctuation and a positional fluctuation of the developing roller 5 can be suppressed. Further, the drive transmitting portion 5n is provided at the end surface defining the hole 5m, so that a true circle in the neighborhood of the first shaft end portion 5c can be formed with high accuracy. Further, helix (twist) strength of the rotation shaft 5a in the neighborhood of the hole 5m can be further enhanced. Further, similarly as the constitution described in Embodiment 1, the constitution in this embodiment is also applicable to the developer supplying roller 51 and the charging roller 2. Further, the end surface 5j in Embodiment 1 and the end surface 5n in this embodiment (Embodiment 2) were transmitting surfaces for transmitting thereto (or receiving) a driving force, for rotating the rotation shaft 5a about the axis, from the boss 40d or the snap-fitting portion 40g of the gear 40. However, the constitutions of Embodiments 1 and 2 are also applicable to an embodiment in which the drive transmitting direction is opposite to that in Embodiments 1 and 2. In this case, the end surface 5j and the end surface 5n are transmitting surfaces for transmitting the driving force to the boss 40d or the snap-fitting portion 40g in order to rotate the gear 40 by the driving force from the rotation shaft 5a. Further, the rotation shafts 5a and the supporting structures and the drive transmitting structures of the rotation shafts 5a in Embodiments 1 and 2 are applicable to a structure of the apparatus main assembly 100A and a structure of the electrophotographic image forming apparatus, not the process cartridge 7. For example, the structures are applicable to a feeding mechanism for feeding a sheet on which the toner image is to be transferred, a transferring mechanism for transferring the toner image onto the sheet or an intermediary transfer belt, a fixing mechanism for fixing the toner image on the sheet under application of heat and/or pressure to the sheet on which the toner image is transferred, and the like mechanism.
Here, the electrophotographic image forming apparatus also includes an image forming apparatus of a transfer type or a direct type, in which a latent image, such as an electrostatic latent image, a magnetic latent image or a resistance pattern latent image, is formed using an electrostatic recording dielectric member or a magnetic recording (magnetic) material as the image bearing member and is developed with the developer. Also in this case, such an image forming apparatus is referred to as the electrophotographic image forming apparatus.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2017-076570 filed on Apr. 7, 2017, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-076570 | Apr 2017 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 7162181 | Maeshima et al. | Jan 2007 | B2 |
| 9500977 | Matsuzaki et al. | Nov 2016 | B2 |
| 20050115043 | Maeshima et al. | Jun 2005 | A1 |
| 20110079952 | Ono | Apr 2011 | A1 |
| 20150277265 | Matsuzaki et al. | Oct 2015 | A1 |
| 20170219962 | Sasaki et al. | Aug 2017 | A1 |
| 20170371263 | Hayashida et al. | Dec 2017 | A1 |
| 20170371264 | Nonaka et al. | Dec 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 2005164756 | Jun 2005 | JP |
| 2011136833 | Jul 2011 | JP |
| 2013103234 | May 2013 | JP |
| 2015113229 | Jun 2015 | JP |
| 2015197145 | Nov 2015 | JP |
| Entry |
|---|
| Copending, unpublished U.S. Appl. No. 15/947,109, to Fumito Nonaka, filed Apr. 6, 2018. |
| Number | Date | Country | |
|---|---|---|---|
| 20180292766 A1 | Oct 2018 | US |
