JP3209534U - Member mounted on photosensitive drum, end member, bearing, photosensitive drum unit, process cartridge, and image forming apparatus - Google Patents

Abstract

A member that does not require a lubricant between an end member and a bearing is provided. An end member 13 having a cylindrical body having an outer peripheral surface that is attached to an end of a photosensitive drum and serves as a sliding surface 14b, the sliding surface 14b being an arithmetic average in either direction. The roughness Ra is 0.5 μm or more. [Selection] Figure 5

Description

  The present invention relates to an image forming apparatus such as a laser printer and a copying machine, and a member, an end member, a bearing, a photosensitive drum unit, and a process cartridge mounted on a photosensitive drum provided in the image forming apparatus.

2. Description of the Related Art Image forming apparatuses such as laser printers and copiers include an image forming apparatus main body and a process cartridge that is detachably attached to the main body.
The process cartridge is a member for transferring contents to be represented such as characters and figures to a recording medium such as paper, and is provided with a photosensitive drum unit on which the contents to be transferred are formed. Accordingly, the process cartridge is also provided with various means for forming the content to be transferred on the photosensitive drum unit. Examples of various means include means for performing development, charging, and cleaning.

The photosensitive drum provided in the photosensitive drum unit is a cylindrical member, and is rotated around the axis of the cylinder when operating. In order to rotate the photosensitive drum in this way, a gear provided on the image forming apparatus main body side via a drive shaft is provided on a member (end member) provided at the end of the photosensitive drum. The driving force is transmitted to.
In such a system, particularly in a color machine having a plurality of photosensitive drums, there is a concern about color misregistration, color unevenness, etc. due to insufficient rotation accuracy, so it is necessary to provide a high-precision gear on the end member. .

  In order to cope with this problem, the following two types of driving methods are increasingly applied. According to these driving methods, the above-described problems can be solved without requiring a high-precision gear, and the same effect can be achieved not only in a color machine but also in a monochrome machine.

  The first driving method is a method of transmitting a driving force to the photosensitive drum by passing a through shaft through the photosensitive drum and using a key groove or the like. According to this driving method, a high-precision gear for receiving a driving force from the image forming apparatus main body is not necessary. However, since a through-shaft is required, it is difficult to assemble, and there is a problem in that it takes time to replace a photosensitive drum that is a consumable item.

  The second driving method is a method in which a driving force is directly transmitted to a coupling provided in an end member provided on the photosensitive drum without using a through shaft. There are several types of driving methods. Among them, a type using a sliding surface made of resin as an axis while receiving a driving force by a coupling provided on the end member, or a sliding type made of resin. There is a form that uses the moving surface as an axis. According to the type using a sliding surface made of resin as an axis (including an auxiliary type), the rotational driving force transmission accuracy is high, and the assembly and replacement of the photosensitive drum are easy.

  For example, Patent Document 1 discloses a technique using a sliding surface made of resin while receiving a driving force by a coupling.

Japanese Patent No. 4415532

  Here, in a type using a sliding surface made of resin as in Patent Document 1, a bearing may be provided so as to face and receive the sliding surface of the end member. The bearing includes an annular portion arranged to cover the sliding surface of the end member.

Conventionally, when the photosensitive drum unit is rotated, frictional heat is generated between the bearing and the sliding surface (side surface) of the end member, and the end member and the bearing are melted or welded by the frictional heat. It happened.
In order to solve such a problem, a lubricant such as grease has been supplied to the sliding surface.

  However, when the lubricant is used, there is a possibility that the lubricant may run out, or the lubricant may flow out and contaminate the photosensitive drum. As a result, development failure occurs, and proper printing is not performed, and as a result, the function as the photosensitive drum is also impaired. In addition, from the viewpoint of manufacturing, a step of applying a lubricant is required, which causes a problem of reduction in productivity and increase in cost. That is, in order to solve such problems in terms of quality and manufacturing, there is a demand for an aspect that does not require a lubricant.

  In particular, with the recent increase in printing speed, the rotational speed of the photosensitive drum is increased, whereby the sliding speed between the end member and the bearing tends to increase, and no lubricant is required. There is a further need.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a member that does not require a lubricant between an end member and a bearing, an end member, a bearing, a photosensitive drum unit, a process cartridge, and an image forming apparatus.

  The above object of the present invention is achieved by the following configuration.

(1) A member provided with a cylindrical body having an outer peripheral surface which is attached to an end portion of a photosensitive drum and serves as a sliding surface.
The sliding surface is a member having an arithmetic average roughness Ra in any direction of 0.5 μm or more.
(2) The member according to (1) above, wherein the sliding surface has a sharpness Ku of 2.8 or less.
(3) The member according to (1) or (2), wherein the sliding surface has an axial inclination.

(4) An end member attached to the end of the photosensitive drum,
The end member whose said end member is a member in any one of said (1)-(3).

(5) a cylindrical photosensitive drum;
A member provided with a cylindrical body having an outer peripheral surface which is attached to an end portion of the photosensitive drum and serves as a sliding surface;
With
The sliding surface of the member is a photosensitive drum unit in which an arithmetic average roughness Ra in any direction is 0.5 μm or more.
(6) The photosensitive drum unit according to the above (5), wherein the sliding Ku of the sliding surface of the member is 2.8 or less.
(7) The photosensitive drum unit according to (5) or (6), wherein the sliding surface of the member has an axial inclination.

(8) a cylindrical photosensitive drum;
A member provided with a cylindrical body having an outer peripheral surface which is attached to an end portion of the photosensitive drum and serves as a sliding surface;
A charging roller that is a cylindrical roller provided to be able to charge the photosensitive drum;
A developing roller that is a cylindrical roller for supplying a developer to the photosensitive drum;
With
The process cartridge in which the sliding surface of the member has an arithmetic average roughness Ra in any direction of 0.5 μm or more.
(9) The process cartridge according to the above (8), wherein the sliding Ku of the sliding surface of the member is 2.8 or less.
(10) The process cartridge according to (8) or (9), wherein the sliding surface of the member has an axial inclination.

(11) a cylindrical photosensitive drum;
A member provided with a cylindrical body having an outer peripheral surface which is attached to an end portion of the photosensitive drum and serves as a sliding surface;
A rotation drive shaft connected to the end and rotating the member and the photosensitive drum;
A bearing that has a hole defining an inner peripheral surface facing the sliding surface and supports the cylindrical body by inserting the cylindrical body of the member into the hole;
With
The image forming apparatus in which the sliding surface of the member has an arithmetic average roughness Ra in any direction of 0.5 μm or more.
(12) The image forming apparatus according to (11), wherein the sliding Ku of the member has a ku Ku of 2.8 or less.
(13) The image forming apparatus according to (11) or (12), wherein at least one of the sliding surface of the member and the inner peripheral surface of the bearing has an axial inclination.
(14) Any of the above (11) to (13), wherein the difference between the outer diameter of the part of the member where the sliding surface is provided and the diameter of the hole of the bearing is 0.06 mm or more and 0.5 mm or less. An image forming apparatus according to claim 1.

(15) A bearing including a cylindrical body having an inner peripheral surface which is attached to the image forming apparatus or the process cartridge and serves as a sliding surface.
The sliding surface is a bearing having an arithmetic average roughness Ra in any direction of 0.5 μm or more.
(16) The bearing according to (15), wherein the sliding surface has a point Ku of 2.8 or less.
(17) The bearing according to (15) or (16), wherein the sliding surface has an axial inclination.

(18) a cylindrical photosensitive drum;
A member provided with a cylindrical body attached to an end of the photosensitive drum and having an outer peripheral surface;
A charging roller that is a cylindrical roller provided to be able to charge the photosensitive drum;
A developing roller that is a cylindrical roller for supplying a developer to the photosensitive drum;
A bearing for supporting the cylindrical body by inserting the cylindrical body of the member into the hole having a hole defining an inner peripheral surface which is a sliding surface facing the outer peripheral surface;
With
A process cartridge in which the sliding surface of the bearing has an arithmetic average roughness Ra in any direction of 0.5 μm or more.
(19) The process cartridge according to the above (18), wherein a point Ku of the sliding surface of the bearing is 2.8 or less.
(20) The process cartridge according to (18) or (19), wherein the sliding surface of the bearing has an axial inclination.

(21) a cylindrical photosensitive drum;
A member provided with a cylindrical body attached to an end of the photosensitive drum and having an outer peripheral surface;
A rotation drive shaft connected to the end and rotating the member and the photosensitive drum;
A bearing for supporting the cylindrical body by inserting the cylindrical body of the member into the hole having a hole defining an inner peripheral surface which is a sliding surface facing the outer peripheral surface;
With
The image forming apparatus in which the sliding surface of the bearing has an arithmetic average roughness Ra in any direction of 0.5 μm or more.
(22) The image forming apparatus according to the above (21), wherein a point Ku of the sliding surface of the bearing is 2.8 or less.
(23) The image forming apparatus according to (21) or (22), wherein at least one of the sliding surface of the bearing and the outer peripheral surface of the member has an axial inclination.
(24) Any of the above (21) to (23), wherein a difference between an outer diameter of a portion of the member provided with the outer peripheral surface and a diameter of the hole of the bearing is 0.06 mm or more and 0.5 mm or less. The image forming apparatus described in 1.

In the above-described present invention, the higher the sliding speed on the sliding surface, the more effective. The sliding speed is preferably 3.2 m / min to 18.9 m / min, particularly preferably 10 m / min or more.
In the present invention, the sliding surface sharpness Ku is preferably 2.8 or less, and more preferably 2.6 or less.
The arithmetic average roughness Ra and the bitterness Ku in this specification are defined in JIS B 0601-1994 and JIS B 0601-2001.
In the present invention, the material of the bearing is not particularly limited, but is preferably polystyrene, polycarbonate, or polyacetal, and more preferably polyacetal.

In the present invention, a conventionally used lubricant such as grease is not used.
In the present invention, Ra of the portion of the member or bearing attached to the end portion of the photosensitive drum where the sliding surface is provided is 0.5 μm or more. Conventionally, the sliding surface has such roughness. There was no.

1 is a diagram illustrating a configuration of an image forming apparatus. It is a figure explaining the structure of a process cartridge. FIG. 3 is an exploded perspective view showing a photosensitive drum unit, a rotation drive shaft, and a bearing. 4A is a cross-sectional view taken along the line III-III in FIG. 3, and FIG. 4B is a combination thereof. Fig.5 (a) is the figure which showed the external appearance of the edge part member, FIG.5 (b) is an enlarged view of the Vb part of Fig.5 (a). FIG. 6A is a view showing the appearance of the end member of another example, and FIG. 6B is an enlarged view of the VIb portion of FIG. 6A. It is the figure which expanded and showed a part of FIG.4 (b).

  The above-mentioned operation and gain of the present invention will be clarified from embodiments for carrying out the invention described below. Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these embodiments.

The embodiment described below is characterized by the arithmetic average roughness Ra of the sliding surface of the end member attached to the end of the photosensitive drum that slides with the bearing.
FIG. 1 is a diagram for explaining one embodiment, and is a perspective view schematically showing an image forming apparatus 1. Examples of the image forming apparatus include a laser printer, a copying machine, and a facsimile. As can be seen from FIG. 1, the image forming apparatus 1 includes an image forming apparatus main body 2 and a process cartridge 3.

  The image forming apparatus main body 2 is a main part of the image forming apparatus 1, and has a rotation drive shaft 21 as will be described later, and includes other necessary components other than the process cartridge 3.

  The process cartridge 3 is a member on which an image to be transferred to a medium such as paper is formed, and is attachable to and detachable from the image forming apparatus main body 2 as indicated by an arrow A in FIG. FIG. 2 conceptually shows the configuration of the process cartridge 3.

  The process cartridge 3 has a housing 4 that forms the outline of the process cartridge 3, and various components are contained inside the housing 4. Specifically, the present embodiment includes a photosensitive drum unit 10 (see FIG. 3), a charging roller 5, a developing roller 6, a regulating member 7, a transfer unit 8, and a cleaning blade 9. When a medium such as paper moves along the line indicated by B in FIG. 2 inside the process cartridge 3, an image is formed on the medium.

  The photosensitive drum unit 10 is formed with characters, figures and the like to be transferred to a recording medium such as paper. FIG. 3 is an exploded perspective view of the rotation drive shaft 21 provided in the image forming apparatus main body 2, the bearing 22 provided in the image forming apparatus main body 2 or the process cartridge 3, and the photosensitive drum unit 10 provided in the process cartridge 3. It was. 4A shows a cross-sectional view along III-III in FIG. 3, and FIG. 4B shows a state in which the rotary drive shaft 21, the bearing 22, and the photosensitive drum unit 10 are combined in the cross section. The figure of was shown.

  As can be seen from FIGS. 3, 4 (a), and 4 (b), the photosensitive drum unit 10 includes a photosensitive drum 11, a flange 12, and an end member 13.

The photosensitive drum 11 is a member in which a photosensitive layer is coated on the outer peripheral surface of a cylindrical drum cylinder. The drum cylinder is configured by applying a photosensitive layer to a conductive cylindrical cylinder such as aluminum. The photosensitive layer to be formed is not particularly limited, and known ones can be applied depending on the purpose.
As will be described later, an end member 13 is disposed at one end of the photosensitive drum 11, and a flange 12 is provided at the other end.

  The flange 12 is a member formed of resin, and a fitting portion that is fitted inside the cylinder of the photosensitive drum 11 and a bearing portion that is arranged so as to cover one end surface of the photosensitive drum 11 are formed coaxially. Has been. The bearing portion has a disk shape that covers the end surface of the photosensitive drum 11, and is provided with a portion that receives a shaft (not shown) provided in the image forming apparatus main body 2. Further, a ground plate made of a conductive material is disposed on the flange 12, thereby electrically connecting the photosensitive drum 11 and the image forming apparatus main body 2.

  The end member 13 is an example of a member that is mounted on the photoconductive drum 11 and has a sliding surface that does not require a lubricant. Of the end of the photoconductive drum 11, the end opposite to the flange 12 is provided. It is a member attached to. The end member 13 receives the rotational driving force from the rotational driving shaft 21 of the image forming apparatus main body 2 to rotate the photosensitive drum unit 10 itself, and to other rollers (charging roller or the like) adjacent to the photosensitive drum unit 10. Has a function of transmitting the rotational force. Specifically, the end member 13 includes a cylindrical body 14, a gear portion 15 provided on the outer peripheral surface of the cylindrical body 14, and a connecting portion 16.

  The cylindrical body 14 is a bottomed cylindrical member having a bottom at one end, and includes a ring-shaped contact wall 14a erected on the outer peripheral surface thereof. The outer diameter of the cylindrical body 14 on the side where the bottom of the contact wall 14a is not provided is substantially the same as the inner diameter of the photosensitive drum 11, and as can be seen from FIGS. 4 (a) and 4 (b). The one end side of the cylindrical body 14 can be inserted and fitted into the photosensitive drum 11. As a result, the end member 13 can be fixed to the photosensitive drum 11. At this time, the photosensitive drum 11 is inserted to a depth at which the end surface of the photosensitive drum 11 is brought into contact with the contact wall 14a. At this time, an adhesive may be used for stronger attachment.

  In addition, a sliding surface 14b is formed on a portion of the outer peripheral surface of the cylindrical body 14 that protrudes without being inserted into the photosensitive drum 11 and on the side where the bottom is provided. As will be described later, the sliding surface 14b is a portion disposed so as to face the inner peripheral surface of the bearing 22.

  The sliding surface 14b has a surface roughness Ra of 0.5 μm or more. FIG. 5A shows the end member 13 viewed from above in FIG. FIG. 5B is an enlarged view of a portion indicated by Vb in FIG. 5A and is a diagram for explaining the surface state of the sliding surface 14b. As can be seen from FIG. 5A and FIG. 5B, in this embodiment, the concave and convex portions extend in the direction along the rotation axis of the end member 13, and the concave and convex portions extend in the circumferential direction of the sliding surface 14b. It is set as the sliding surface 14b which has roughness so that may be arranged in parallel. Therefore, the surface roughness Ra in the direction indicated by C in FIG. 5B (the circumferential direction of the sliding surface 14b) is usually 0.5 μm or more, preferably 1.5 μm or more. On the other hand, the surface roughness Ra is preferably 500 μm or less. This is because if the surface roughness Ra is larger than this, it causes “rattle” during sliding.

  By making the sliding surface 14b into a surface having such roughness, the area where the sliding surface 14b substantially contacts the inner peripheral surface 22a of the bearing 22 can be reduced, and the sliding surface 14b and the bearing 22 can be reduced. Thus, it is possible to reduce the friction with the inner peripheral surface 22a, and thereby to prevent the end member 13 and the bearing 22 from melting and fusing without using a lubricant. In addition, it is considered that discharge of fine facets scraped off from the sliding surface by friction is promoted, and it is possible to prevent the facets from acting as an abrasive (a factor for increasing the dynamic friction coefficient).

  Furthermore, the point Ku of the sliding surface 14b is preferably 2.8 or less. “Pointing Ku” is a measure of the sharpness of the surface shape curved surface, and can characterize the spread of the surface height distribution. The sharpness Ku can be obtained by calculating the fourth moment of the surface shape curved surface, and is sometimes referred to as “crutosis of roughness curve”. By setting the point Ku on the sliding surface 14b to 2.8 or less, the surface height distribution is crushed (not pointed), and local friction can be reduced. As a result, even when no lubricant is used, the end member 13 and the bearing 22 can be prevented from melting and fusing. Further preferred end point Ku is 2.6 or less. On the other hand, the pointedness Ku is preferably 1 or more.

  Also, the outer diameter Da of the portion (hereinafter, also simply referred to as “sliding surface 14b”) provided with the sliding surface 14b of the cylindrical body 14 shown in FIG. 22 is preferably formed to be 0.06 mm or less smaller than the inner diameter of the portion (hole) into which the sliding surface 14b is inserted (hereinafter also referred to simply as the “inner diameter of the bearing”) Db. When at least one of the sliding surface 14b and the inner peripheral surface 22a of the bearing 22 has an inclination in the axial direction (so-called taper), the sliding surface is in a posture in which the end member 13 is inserted into the bearing 22 as described later. It is preferable that the difference between the diameter of the sliding surface 14b and the diameter of the inner peripheral surface 22a is 0.06 mm or more at each portion where 14b and the inner peripheral surface 22a face each other.

  The gear portion 15 is a gear provided between the contact wall 14a and the sliding surface 14b in the outer peripheral surface of the cylindrical body 14, and transmits a rotational force to the developing roller. In the illustrated embodiment, the gear portion 15 is a spur gear. However, the type of gear is not particularly limited and may be any gear that can achieve the purpose, such as a helical gear.

  The connecting portion 16 is a portion provided so as to protrude from the outer surface of the bottom of the cylindrical body 14. The connecting portion 16 has a function of transmitting a rotational force from the rotary drive shaft 21 to the photosensitive drum unit 10 by being connected to a rotary drive shaft 21 described later. Therefore, the connecting portion 16 has a shape such that the rotational force is efficiently transmitted from the rotation drive shaft 21 to the end member 13. The shape is not particularly limited as long as it has such a function. For example, a shape that is rectangular when the connecting portion is viewed in the direction of the rotation axis of the photosensitive drum unit 10 can be given.

  Such an end member 13 is preferably formed of a resin from the viewpoint of moldability. According to this, even if the shape is complicated, it can be manufactured by injection molding or the like. The rough surface provided in the sliding surface 14b is obtained by roughening a portion to which the sliding surface is transferred by cutting using a lathe / milling machine, grinding, shot blasting, or the like on an injection mold. Can do. Further, when the rough surface is formed, the concave and convex portions extend in the circumferential direction of the sliding surface 14b as described later, and the concave and convex portions are arranged in parallel in the direction along the rotation axis of the end member. In the case of forming a rough surface, undercut processing such as forcibly removing and a slide core can be used. It is also possible to form a rough surface in a spiral and remove the frame while rotating it. Furthermore, when the embossing process is performed on the injection mold, an etching process using an organic solvent can be used.

  In the present embodiment, as described above, in the sliding surface 14b, the concave portion and the convex portion extend in the direction along the rotation axis of the end member 13, and the concave and convex portions are arranged in parallel in the circumferential direction of the sliding surface 14b. A surface having roughness was used. However, in the present invention, the direction of the unevenness is not limited to this, and Ra may be 0.5 μm or more in any direction on the sliding surface. FIG. 6 shows another example of the end member 13 '. 6 (a) corresponds to FIG. 5 (a), FIG. 6 (b) corresponds to FIG. 5 (b), and FIG. 6 (b) shows an enlarged view of the portion VIb in FIG. 6 (a). It is a figure. In the end member 13 ′, only the surface property of the sliding surface 14 b ′ is different from that of the end member 13, and the other parts are common to the end member 13.

  As can be seen from FIGS. 6A and 6B, the sliding surface 14b ′ of the end member 13 ′ extends in the direction along the circumferential direction of the end member 13 ′. It has a rough surface in which irregularities are juxtaposed in a direction along the rotation axis. Accordingly, the surface roughness Ra in the direction indicated by D in FIG. 6B (the rotation axis direction of the end member 13 ′) is 0.5 μm or more.

  Thus, regarding the sliding surface of the end member being Ra ≧ 0.5 μm, the direction is not particularly limited, and it may be satisfied in any direction.

  Next, the rotary drive shaft 21 and the bearing 22 shown in FIGS. 3, 4A, and 4B will be described. The rotation drive shaft 21 is a member provided in the image forming apparatus main body 2, and the bearing 22 is a member provided in the image forming apparatus main body 2 or the process cartridge 3.

  The rotation drive shaft 21 is a cylindrical member, and is arranged so that the rotation axis thereof is coaxial with the rotation axis of the photosensitive drum unit 10. Further, the rotation drive shaft 21 has a hole 21 a that can receive the connecting portion 16 of the end member 13 on a surface disposed to face the end member 13 of the photosensitive drum unit 10.

  The hole 21 a is formed so that the connecting portion 16 can be inserted and the rotational force of the rotary drive shaft 21 can be transmitted to the photosensitive drum unit 10 in the inserted posture. Accordingly, the rotational drive shaft 21 is disposed so that the end surface on the side where the hole 21 a is provided faces the end surface of the end member 13 of the photosensitive drum unit 20. On the other hand, the surface on the side where the hole 21 a is not provided in the end surface of the rotary drive shaft 21 is connected to a member that is a drive source of the image forming apparatus main body 2.

  As a result, a rotational force can be applied from the image forming apparatus main body 2 to the photosensitive drum unit 10 through the rotation drive shaft 21.

  In the present embodiment, the convex connecting portion 16 on the end member 13 side and the concave hole 21a on the rotary drive shaft 21 side are shown to be connected to each other, but the concave and convex portions are reversed. May be. Moreover, both may be connected by other connection means so that rotational force transmission is possible.

  The bearing 22 is a member that stably rotates the photosensitive drum unit 10, maintains the position of the photosensitive drum, and maintains an appropriate positional relationship with other rollers such as a developing roller. The shape is cylindrical as can be seen from FIGS. 3, 4A and 4B, and the opening on one side is slightly narrowed. The bearing 22 is prohibited from rotating and is disposed in the image forming apparatus main body 2 or the process cartridge 3, and the cylindrical shaft thereof is coaxial with the rotational drive shaft 21 and the rotational shaft of the photosensitive drum unit 10.

  Here, as described above, the inner diameter Db of the bearing 22 is preferably 0.06 mm or more larger than the outer diameter Da of the portion where the sliding surface 14b of the cylindrical body 14 is provided. When at least one of the sliding surface 14b and the inner peripheral surface 22a of the bearing 22 has an inclination in the axial direction (so-called taper), the sliding surface is inserted with the end member 13 inserted into the bearing 22 as described later. It is preferable that the difference between the outer diameter Da of the portion where the sliding surface 14b is provided and the inner diameter Db of the bearing 22 is 0.06 mm or more in each portion where 14b and the inner peripheral surface 22a face each other.

  Such a bearing 22 is preferably formed of a resin from the viewpoint of moldability. According to this, it can manufacture by injection molding etc.

  As shown in FIG. 4B, the photosensitive drum unit 10, the rotary drive shaft 21, and the bearing 22 are combined as follows. That is, the portion of the end member 13 of the photosensitive drum unit 10 that is provided with the sliding surface 14 b is inserted into the cylinder of the bearing 22. Accordingly, the sliding surface 14 b is disposed so as to face the inner peripheral surface 22 a of the bearing 22.

  At this time, when the difference between the outer diameter Da of the portion provided with the sliding surface 14b and the inner diameter Db of the bearing 22 is defined as described above, when the photosensitive drum unit 10 rotates as will be described later. As shown in FIG. 7 in which the portion indicated by VII in FIG. 4B is enlarged, a predetermined gap can be formed between the sliding surface 14b and the inner peripheral surface 22a. . Alternatively, even when the gap is not always formed due to the shake of the photosensitive drum unit 10 during the rotation, the chance of contact between the sliding surface 14b and the inner peripheral surface 22a may be reduced. it can. Thereby, when the photosensitive drum unit 10 rotates, the end member 13 and the bearing 22 can be further prevented from being melted or fused. In this embodiment, the sliding surface 14b is provided with an inclination in the axial direction. In this case, the difference between the outer diameter Da of the portion where the sliding surface 14b is provided and the inner diameter Db of the bearing 22 is the largest. The difference is preferably 0.06 mm or more, more preferably 0.12 mm or more, and even more preferably 0.25 mm or more at a small portion (in this embodiment, a portion represented by E in FIG. 7). By setting the difference between Db and Da to be larger, the chance of contact between the sliding surface 14b and the inner peripheral surface 22a is reduced, and the effect of suppressing the melting and fusion of the bearing 22 can be further increased. .

  On the other hand, the bearing 22 has a function of holding the position of the photosensitive drum while the photosensitive drum unit 10 rotates, maintaining an appropriate positional relationship with other rollers such as a developing roller, and performing stable rotation. From such a point of view, the difference between the outer diameter Da of the portion where the sliding surface 14b is provided and the inner diameter Db of the bearing 22 is preferably 0.5 mm or less.

  As described above, when a part of the end member 13 is disposed in the bearing 22, the connecting portion 16 provided on the end member 13 projects through the opening of the bearing 22. By inserting the protruding connecting portion 16 into the hole 21a of the rotation drive shaft 21, the photosensitive drum unit 10 and the rotation drive shaft 21 are connected to each other so as to be rotatable.

  Returning to FIG. 2, the description of the process cartridge 3 will be continued. The charging roller 5, the developing roller 6, the regulating member 7, the transfer unit 8, and the cleaning blade 9, which are other configurations provided inside the housing 4 of the process cartridge 3, are as follows.

The charging roller 5 charges the photosensitive drum 11 by applying a voltage from the image forming apparatus main body. This is performed by the charging roller 5 rotating following the photosensitive drum 11 and contacting the outer peripheral surface of the photosensitive drum 11.
The developing roller 6 is a roller that supplies a developer to the photosensitive drum 11. Then, the electrostatic latent image formed on the photosensitive drum 11 is developed by the developing roller 6. The developing roller 6 contains a fixed magnet.
The regulating member 7 is a member that adjusts the amount of developer adhering to the outer peripheral surface of the developing roller 6 and imparts triboelectric charge to the developer itself.
The transfer unit 8 is a roller for transferring an image formed on the photosensitive drum 11 to a recording medium such as paper.
The cleaning blade 9 is a blade that contacts the outer peripheral surface of the photosensitive drum 11 and removes the developer remaining after the transfer by the tip.

  Each of the above rollers is housed inside the housing 4 so as to be rotatable. That is, each roller rotates inside the housing 4 as necessary to exert its function.

  Here, each roller and blade provided in the process cartridge 3 has been described. However, the members provided here are not limited thereto, and other members, parts, developer, etc. that are normally provided in the process cartridge. Is preferably provided.

  Next, the operation of the image forming apparatus 1 will be described. When the image forming apparatus 1 is operated, the process cartridge 3 including the above-described photosensitive drum unit 10 is inserted into the image forming apparatus main body 2 and attached as shown in FIG. 1, and is attached to the rotary drive shaft 21 and the bearing 22. Connect. And the rotational drive shaft 21 is rotated as needed. As a result, the photosensitive drum unit 10 rotates and can be charged by the charging roller 5.

  With the photosensitive drum unit 10 rotating in this way, laser light corresponding to image information is irradiated to the photosensitive drum 11 using various optical members, and an electrostatic latent image based on the image information is obtained. This latent image is developed by the developing roller 6.

  On the other hand, a recording medium such as paper is set in the image forming apparatus main body 2 and is conveyed to a transfer position by a feed roller, a conveyance roller, etc. provided in the image forming apparatus main body 2, and moves along a line B in FIG. To do. A transfer unit 8 is disposed at the transfer position. A voltage is applied to the transfer unit 8 as the recording medium passes, and an image is transferred from the photosensitive drum 11 to the recording medium. Thereafter, the image is fixed to the recording medium by applying heat and pressure to the recording medium. Then, the recording medium on which the image is formed is discharged from the image forming apparatus main body by a discharge roll or the like.

In the operation of the image forming apparatus, when the photosensitive drum unit 10 rotates, the end member 13 rotates inside the bearing 22. In the present invention, since the surface property of the sliding surface 14b is Ra ≧ 0.5 μm, the contact area between the sliding surface 14b and the inner peripheral surface 22a can be reduced, and the friction can be reduced.
That is, it is conceivable that the cause of melting in the prior art is that the contact area between the sliding surface and the inner peripheral surface is large, so that friction is increased and heat is easily generated. In contrast, the present invention can suppress this without using a lubricant by the above-described configuration.
In particular, in recent years, the rotational speed of the photosensitive drum unit 10 has been increased due to the increase in printing speed, and the effect of the present invention becomes remarkable.

  Further, if the lip Ku of the sliding surface 14b is 2.8 or less, the sharpness of the unevenness is suppressed, and therefore it is possible to further suppress the friction between the sliding surface 14b and the inner peripheral surface 22a.

  Furthermore, when the above-described difference in diameter is provided between the portion where the sliding surface 14b is provided and the bearing 22, contact between the sliding surface 14b and the inner peripheral surface 22a can be prevented or reduced. Therefore, the friction can be further prevented or reduced.

  The embodiment in which the sliding surface 14b having the above-described predetermined configuration is formed on the end member 13 side has been described above. However, the present invention is not limited to this in view of the effects of the present invention, and the same sliding surface as described above may be formed on the bearing side.

  The present invention will be further described in the following examples. However, the present invention is not limited to the embodiments.

  In the example, an end member having a changed surface roughness of the sliding surface was produced, and the melting and fusion were examined. This will be described in detail below.

<Fabrication of an end member on which sliding surfaces having different rough surfaces are formed>
In Table 1 to be described later, a general grade of polyacetal resin (F20-03, manufactured by Mitsubishi Engineering Plastics) was used for the end member of Reference Example 1, and polystyrene was used for the bearing. As the end member of Reference Example 2, a resin (Mitsubishi Engineering Plastics, FL-2020) containing polyacetal containing 20% by weight of highly slidable fluororesin was used.

In Reference Example 1 and Reference Example 2, an end member was produced by injection molding using a conventional mold, and used as it was including the sliding surface.
On the other hand, in Examples 1 to 3 and Example 6, an end member is formed by injection molding using a conventional mold, and the surface of the sliding surface is cut using a cutting machine. The surface roughness in the circumferential direction was adjusted by changing the cutting conditions (feed, rotation speed, cutting angle of the cutting tool, etc.).
In Examples 4 and 5, the end member is formed by injection molding using a conventional mold, and the sliding surface is processed using an NC milling machine. The surface roughness is determined by the size of the processing tool and the engraving. The surface roughness in the axial direction was adjusted by changing the program.

<Measuring method of Ra and sharpness Ku of sliding surface>
A rough surface (Examples 1 to 3 and 6) having recesses and protrusions extending in the circumferential direction of the sliding surface and having unevenness arranged in parallel in the axial direction is a surface roughness measuring machine (Mitutoyo Corporation, SURF TEST-SV). -548) was used to perform contact measurements with a probe having a probe diameter of 5 μm. On the other hand, a rough surface (Examples 4 and 5) having concave and convex portions extending in the axial direction of the end member and having unevenness arranged in parallel in the circumferential direction of the sliding surface also uses the same surface roughness measuring machine as described above. It is possible to measure contact with a probe. However, in this example, this measuring machine would exceed the measurement range, so the level difference was measured in a non-contact manner using an image measuring machine (TESA, TESA VISIO 300).

<Method of evaluation>
The evaluation method is as follows. In each example, one type of print pattern was repeatedly printed, and 12000 pages were printed with a pause of 1 hour every 4000 pages, and the sliding surfaces of the end members after the experiment were visually evaluated. Moreover, evaluation in the middle of the test (4000 pages) was also performed. Furthermore, the image quality of the printed material output last was evaluated. In Reference Example 1, a lubricant was used between the sliding surface and the inner peripheral surface, but no lubricant was used in other examples. The sliding speed at this time was 13 m / min.

<Evaluation criteria>
The criteria for the visual evaluation of the sliding surface are as follows.
A: The sliding surface is not melted, and the sliding surface or the inner peripheral surface of the bearing is not scraped by friction.
○: The sliding surface is not melted, but a trace of the sliding surface or the inner peripheral surface of the bearing being scraped by friction is seen.
X: The sliding surface is melted, and a trace of the sliding surface or the inner peripheral surface of the bearing being scraped over the entire surface by friction is seen.
On the other hand, the image quality evaluation of the last printed material is as follows.
A: Image defect is not found.
○: Image defects are observed in an area of less than 5% of the printing area.
X: Image defects are observed in a region of 5% or more of the printing area.

<Result>
Table 1 shows the material of the end member, the presence / absence of lubricant, Db-Da, Ra, edge Ku, rough surface direction, and evaluation results. “Db−Da” in Table 1 is the difference between the outer diameter (Da) of the portion where the sliding surface of the end member is provided and the inner diameter (Db) of the bearing. Also, the “rough surface direction” means that the concave and convex portions extend in the circumferential direction of the sliding surface, and the rough surface having unevenness aligned in the axial direction is the “circumferential direction”, and the concave and convex portions in the axial direction of the end member The rough surface having the protrusions and recesses extending in parallel in the circumferential direction was defined as the “axial direction”.

参考例１と実施例１〜６との対比からわかるように、潤滑剤を用いなくても、摺動面をＲａ≧０．５μｍとすることにより、潤滑剤を用いた場合と同様の結果を得ることができた。また、かかる結果を得るための粗面方向は周方向及び軸方向のいずれでもよいこともわかった。従って、これ以外の方向のである、斜め方向、非連続形態（点状等）、シボ加工等のパターンを有する粗面、エンボス加工により形成される粗面でも、同様の効果があると考えられる。

As can be seen from the comparison between Reference Example 1 and Examples 1 to 6, even if no lubricant is used, by setting the sliding surface to Ra ≧ 0.5 μm, the same result as in the case of using the lubricant is obtained. I was able to get it. It was also found that the rough surface direction for obtaining this result may be either the circumferential direction or the axial direction. Therefore, it is considered that the same effect can be obtained even in a direction other than this, such as an oblique direction, a discontinuous form (such as a dot shape), a rough surface having a pattern such as embossing, or a rough surface formed by embossing.

  In addition, as can be seen from the comparison between Reference Example 2 and Example 1, the resin of the end member used in Reference Example 2 has excellent slidability, but Examples 1 to 5 However, the result is good and is equivalent to Example 6. Therefore, it can be seen that the surface roughness Ra is more important than the slidability of the resin itself.

  Further, as can be seen from Example 6, even if Db-Da is small, good results can be obtained by appropriately adjusting Ra.

  According to the present invention, melting and fusion due to friction between the end member of the photosensitive drum unit and the bearing can be suppressed without using a lubricant.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming apparatus main body 3 Process cartridge 10 Photoconductor drum unit 11 Photoconductor drum 12 Flange 13 End member (member)
14 Cylindrical body 14b Sliding surface 16 Connecting portion 21 Rotating drive shaft 21a Hole 22 Bearing

Claims (24)

A member provided with a cylindrical body having an outer peripheral surface which is attached to an end portion of a photosensitive drum and serves as a sliding surface,
The sliding surface is a member having an arithmetic average roughness Ra in any direction of 0.5 μm or more.   The member according to claim 1, wherein a point Ku of the sliding surface is 2.8 or less.   The member according to claim 1, wherein the sliding surface has an axial inclination. An end member attached to the end of the photosensitive drum,
The end member whose said end member is a member as described in any one of Claims 1-3. A cylindrical photosensitive drum;
A member provided with a cylindrical body having an outer peripheral surface which is attached to an end portion of the photosensitive drum and serves as a sliding surface;
With
The sliding surface of the member is a photosensitive drum unit in which an arithmetic average roughness Ra in any direction is 0.5 μm or more.   6. The photosensitive drum unit according to claim 5, wherein a point Ku of the sliding surface of the member is 2.8 or less.   The photosensitive drum unit according to claim 5, wherein the sliding surface of the member has an axial inclination. A cylindrical photosensitive drum;
A member provided with a cylindrical body having an outer peripheral surface which is attached to an end portion of the photosensitive drum and serves as a sliding surface;
A charging roller that is a cylindrical roller provided to be able to charge the photosensitive drum;
A developing roller that is a cylindrical roller for supplying a developer to the photosensitive drum;
With
The process cartridge in which the sliding surface of the member has an arithmetic average roughness Ra in any direction of 0.5 μm or more.   The process cartridge according to claim 8, wherein a point Ku of the sliding surface of the member is 2.8 or less.   The process cartridge according to claim 8, wherein the sliding surface of the member has an axial inclination. A cylindrical photosensitive drum;
A member provided with a cylindrical body having an outer peripheral surface which is attached to an end portion of the photosensitive drum and serves as a sliding surface;
A rotation drive shaft connected to the end and rotating the member and the photosensitive drum;
A bearing that has a hole defining an inner peripheral surface facing the sliding surface and supports the cylindrical body by inserting the cylindrical body of the member into the hole;
With
The image forming apparatus in which the sliding surface of the member has an arithmetic average roughness Ra in any direction of 0.5 μm or more.   The image forming apparatus according to claim 11, wherein a point Ku of the sliding surface of the member is 2.8 or less.   The image forming apparatus according to claim 11, wherein at least one of the sliding surface of the member and the inner peripheral surface of the bearing has an inclination in the axial direction.   14. The difference between the outer diameter of the portion of the member where the sliding surface is provided and the diameter of the hole of the bearing is 0.06 mm or more and 0.5 mm or less. Image forming apparatus. A bearing provided with a cylindrical body having an inner peripheral surface which is attached to an image forming apparatus or a process cartridge and serves as a sliding surface,
The sliding surface is a bearing having an arithmetic average roughness Ra in any direction of 0.5 μm or more.   The bearing according to claim 15, wherein a point Ku of the sliding surface is 2.8 or less.   The bearing according to claim 15 or 16, wherein the sliding surface has an axial inclination. A cylindrical photosensitive drum;
A member provided with a cylindrical body attached to an end of the photosensitive drum and having an outer peripheral surface;
A charging roller that is a cylindrical roller provided to be able to charge the photosensitive drum;
A developing roller that is a cylindrical roller for supplying a developer to the photosensitive drum;
A bearing for supporting the cylindrical body by inserting the cylindrical body of the member into the hole having a hole defining an inner peripheral surface which is a sliding surface facing the outer peripheral surface;
With
A process cartridge in which the sliding surface of the bearing has an arithmetic average roughness Ra in any direction of 0.5 μm or more.   The process cartridge according to claim 18, wherein a point Ku of the sliding surface of the bearing is 2.8 or less.   The process cartridge according to claim 18, wherein the sliding surface of the bearing has an axial inclination. A cylindrical photosensitive drum;
A member provided with a cylindrical body attached to an end of the photosensitive drum and having an outer peripheral surface;
A rotation drive shaft connected to the end and rotating the member and the photosensitive drum;
A bearing for supporting the cylindrical body by inserting the cylindrical body of the member into the hole having a hole defining an inner peripheral surface which is a sliding surface facing the outer peripheral surface;
With
The image forming apparatus in which the sliding surface of the bearing has an arithmetic average roughness Ra in any direction of 0.5 μm or more.   The image forming apparatus according to claim 21, wherein a point Ku of the sliding surface of the bearing is 2.8 or less.   23. The image forming apparatus according to claim 21, wherein at least one of the sliding surface of the bearing and the outer peripheral surface of the member has an inclination in the axial direction.   The image according to any one of claims 21 to 23, wherein a difference between an outer diameter of a portion of the member provided with the outer peripheral surface and a diameter of the hole of the bearing is 0.06 mm or more and 0.5 mm or less. Forming equipment.

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