JP2003186303A - Gap-assuring member, developing device using the gap- assuring member, charging device and process cartridge detachable from image-forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gap-assuring member for stably maintaining a gap or a distance, between a rotary cylindrical member and a member arranged on the cylindrical member at a prescribed distance, and to provide a developing device and an electrifying device of an image-forming apparatus, using the gap assuring member. <P>SOLUTION: A support-engaging part 51b of the gap assuring member 51 is engaged with a journal part 11a<SB>1</SB>of a charging sleeve 11a through a circular hole 51a, and a circular-arc end 51c is contacted on a photoreceptor drum 4, to maintain the interval between the photoreceptor drum 4 and the electrifying sleeve 11a to be a prescribed gap. An extension part 51d, extending to the upstream side of the rotary direction of the photoreceptor drum 4, is formed on the circular-arc end 51c off the gap assuring member 51, and a circular-arc shape of the circular-arc end 51c is formed of a smaller- diameter than the outer peripheral diameter of the photoreceptor drum 4, so that the gap between both the members is maintained at a stable posture contacted on the photoreceptor drum 4 at two points, and toppling of the gap-assuring member 51 is prevented. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gap guarantee member for keeping a gap between a rotary member and a member facing it at a predetermined gap, a developing device and a charging device for an image forming apparatus using the gap guarantee member. The present invention also relates to a process cartridge that can be attached to and detached from an image forming apparatus.

Here, the image forming apparatus is an apparatus for forming an image on a recording medium by using an electrophotographic image forming process, and is, for example, an electrophotographic copying machine, an electrophotographic printer (for example, an LED printer, a laser beam printer). Etc.), an electrophotographic facsimile machine, an electrophotographic word processor, and the like.

As the process cartridge, an electrophotographic photosensitive member which is an image carrier, a charging means, a developing means,
A cartridge that is integrally formed with a cleaning unit and is detachable from the main body of the image forming apparatus, or
At least one of a charging unit, a developing unit, and a cleaning unit and an electrophotographic photosensitive member are integrally made into a cartridge so as to be attachable to and detachable from the main body of the image forming apparatus, or at least the developing unit or at least the charging unit and the electrophotographic photosensitive member. And a cartridge that can be attached to and detached from the main body of the image forming apparatus.

[0004]

2. Description of the Related Art An image forming apparatus using an electrophotographic image forming process uniformly charges a photosensitive drum, which is an image carrier, and forms a latent image by selectively exposing the photosensitive drum, The latent image is visualized with a developer, then the developer image is transferred to a recording medium, and heat or pressure is applied to the transferred developer image to fix the developer image on the recording medium. I am recording.

This type of image forming apparatus involves replenishment of the developer and maintenance of various process means. As means for facilitating the replenishment work and maintenance of the developer,
A process cartridge system is adopted in which the photosensitive drum, the developing means, the charging means, the cleaning means, and the like are collectively formed into a cartridge, and the cartridge can be attached to and detached from the apparatus main body.

In such a process cartridge type image forming apparatus, the developing sleeve for supplying the developer to the photosensitive drum is fixed between the photosensitive drum and the photosensitive drum so that the developer can be appropriately supplied. Are arranged at intervals. Further, also in a charging device that uniformly charges the photoconductor drum, it is important to keep the distance between the photoconductor drum and the charging means constant.

As a method for maintaining a constant gap between such a photosensitive drum and another member such as a developing sleeve,
A cylindrical gap assurance member called a spacer roller is provided at the end of the developing sleeve or the like, and the thickness of the spacer roller controls the gap between the photosensitive drum and the developing sleeve. Then, one of the spacer rollers is urged by the urging force of a spring or the like so as not to separate from the contact portion of the spacer roller due to vibration or the like.

[0008]

However, in the prior art for maintaining a constant gap between both members by using the above-mentioned cylindrical gap guarantee member called a spacer roller,
There were the following problems.

That is, in the system using a cylindrical gap assurance member such as a spacer roller, when the rotation direction of the photosensitive drum and the rotation direction of the developing sleeve and the charging means are forward,
The spacer roller also rotates following that direction, and the gap between them can be maintained without any problem. However, when the rotation direction of the photoconductor drum and the rotation direction of the developing sleeve or the charging unit come into contact with each other by a counter, the peripheral speed difference between the photoconductor drum and the development sleeve or the charging unit becomes larger than when rotating in the forward direction. The spacer rollers will be severely scraped, and it will not be possible to keep the spacers in an appropriate gap. In the worst case, the spacer rollers are scraped and locked by the powder, the torque increases, and it becomes difficult to maintain the gap.

Therefore, the present invention has been made in view of the above-mentioned unsolved problems of the prior art, that is, the distance between a rotating cylindrical member and a member arranged at a predetermined distance from the cylindrical member. It is an object of the present invention to provide a gap assurance member that can stably maintain a gap.

Furthermore, according to the present invention, the gap between the image bearing member and the developing unit and the gap between the image bearing member and the charging unit in the image forming apparatus can be reliably and stabilized without being affected by the peripheral speed difference between the members. To provide a developing device and a charging device that can be held in a fixed posture and contribute to the improvement of image quality, and a process cartridge that is detachable from the main body of the image forming apparatus and that includes the developing device or the charging device. The purpose is.

[0012]

In order to achieve the above object, the gap assurance member of the present invention is a gap assurance device which defines a distance between a rotating cylindrical member and a member arranged at a predetermined distance from the cylindrical member. In the member, the gap assurance member includes an engaging portion that engages with the member and an arcuate end portion that contacts the outer peripheral surface of the cylindrical member, and the arcuate shape of the arcuate end portion is the cylindrical member. It is characterized in that it is formed with a diameter smaller than the outer peripheral diameter of.

The gap assurance member of the present invention defines the gap between the rotating first cylindrical member and the second cylindrical member arranged with a predetermined gap from the first cylindrical member. In the above-mentioned gap assurance member, at least an engaging portion that rotatably engages with one of the cylindrical members and an arcuate end portion that comes into contact with the outer peripheral surface of the other cylindrical member are provided. The arc shape of the portion is characterized by being formed with a diameter smaller than the outer peripheral diameter of the cylindrical member against which the gap assurance member is pressed.

In the gap assurance member of the present invention, the arcuate shape of the arcuate end of the gap assurance member is 0.01 mm to 1 mm from the outer diameter of the cylindrical member against which the gap assurance member is pressed.
It is preferable that it is formed with a small diameter, and it is preferable that the gap ensuring member is brought into contact with the cylindrical member with a pressing force. Furthermore, when both members are cylindrical members, it is preferable that the peripheral surface moving direction of the first cylindrical member and the peripheral surface moving direction of the second cylindrical member are counter directions, and the arcuate end portion is It is preferable to have an end portion that extends upstream in the rotation direction of the other cylindrical member.

In the gap guarantee member of the present invention, the material of the gap guarantee member is polyether sulfone (PES), polyphenylene sulfide (PPS), polyamide (P).
It is preferably A) or polyacetal (POM).

Further, the developing device of the present invention is a developing device for an image forming apparatus in which at least a developing sleeve is arranged around an image carrier, and a gap between the developing sleeve and the image carrier is provided. A gap assurance member that regulates a constant amount is provided, and the gap assurance member includes an engagement portion that rotatably engages with the developing sleeve and an arcuate end portion that contacts the outer peripheral surface of the image carrier. The circular arc shape of the circular arc end is formed to have a diameter smaller than the outer peripheral diameter of the image carrier on which the gap assurance member is pressed.

The charging device of the present invention is a charging device for an image forming apparatus in which at least charging means is arranged around an image carrier, and a gap between the charging means and the image carrier is constant. A gap assurance member for restricting the gap is provided, and the gap assurance member includes an engagement portion that engages with the charging unit and an arcuate end portion that contacts the outer peripheral surface of the image carrier. The arcuate shape of the arcuate end portion is characterized in that it is formed with a diameter smaller than the outer diameter of the image carrier on which the gap assurance member is pressed.

The charging device of the present invention is a charging device for an image forming apparatus in which at least a charging device is arranged around the image carrier, and a charging device holding member for holding the charging device and the image carrier. A gap assurance member that regulates the gap between the two is fixed between the contact portion and the contact portion, and the gap assurance member contacts the engaging portion that engages with the charging unit holding member and the outer peripheral surface of the image carrier. And a circular arc shape of the circular arc end is formed with a diameter smaller than an outer peripheral diameter of the image carrier on which the gap assurance member is pressed.

Further, the process cartridge of the present invention has at least a developing device around the image carrier,
In the process cartridge mountable to the main body of the image forming apparatus, a gap assurance member is provided between the developing sleeve of the developing device and the image carrier to regulate the gap therebetween, and the gap assurance member includes The developing device includes an engaging portion that rotatably engages with the developing sleeve, and an arcuate end portion that comes into contact with the outer peripheral surface of the image carrier. The arcuate shape of the arcuate end portion is pressed by the gap ensuring member. In the process cartridge mountable to the image forming apparatus main body, the process cartridge having a diameter smaller than the outer diameter of the image carrier, and having at least a charging device around the image carrier. A gap assurance member is provided between the charging unit of the apparatus and the image carrier to regulate the gap therebetween, and the gap assurance member is provided with an engagement portion that engages with the charging unit and the image. Bearer An arcuate end portion that contacts the outer peripheral surface of the body, and the arcuate shape of the arcuate end portion is formed with a diameter smaller than the outer peripheral diameter of the image carrier on which the gap assurance member is pressed. Is characterized by.

Further, the process cartridge of the present invention is a process cartridge which can be mounted on the main body of an image forming apparatus and has at least a developing device and a charging device around the image carrier, and the developing sleeve of the developing device and the image carrier. And a second gap assurance member that regulates the gap between the two to a constant amount, and a second gap that regulates the gap between the charging unit of the charging device and the image carrier to a constant amount. A gap assurance member is provided, and the first gap assurance member includes an engaging portion that rotatably engages with the developing sleeve and an arcuate end portion that contacts the outer peripheral surface of the image carrier. The second gap assurance member includes an engaging portion that engages with the charging unit and an arcuate end portion that comes into contact with the outer peripheral surface of the image carrier. Circle of arcuate end of gap assurance member Shape, together, characterized in that it is formed with a diameter smaller than the outside diameter of the image bearing member.

[0021]

According to the present invention, it is possible to stably maintain a distance and a gap between a rotating cylindrical member and a member arranged at a predetermined distance from the cylindrical member. Furthermore, it is possible to maintain a stable gap between the cylindrical members that rotate with each other, and it is possible to maintain the gap without rotating like the conventional spacer rollers. Even when they abut, the gap between both cylindrical members can be reliably and stably guaranteed.

Further, in the gap assurance member of the present invention,
By forming the arcuate shape of the arcuate end contacting the cylindrical member with a diameter smaller than the outer diameter of the pressed cylindrical member, the cylindrical member is always in contact with the cylindrical member at two points at the upper and lower ends in the rotation direction. The rotating cylindrical member can be contacted while maintaining a stable posture, and the gap between the two can be surely guaranteed.

By using the gap assurance member of the present invention between the photoconductor drum and the developing sleeve or between the photoconductor drum and the charging sleeve in the image forming apparatus, the photoconductor drum and the developing sleeve and the photoconductor drum are charged. The gap between the sleeves can be surely guaranteed without being affected by the difference in peripheral speed between the sleeves, which contributes to the improvement of image quality.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings.

The overall structure and image formation of the image forming apparatus in which the process cartridge of the present invention is detachably mounted will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing an overall configuration of a full-color laser beam printer which is an embodiment of an image forming apparatus to which a process cartridge of the present invention is detachably mounted.

The image forming apparatus 1 shown in FIG. 1 includes a photosensitive drum 4 (4Y, 4M, 4C, 4Bk) which is an image carrier.
Image forming portions 2 (2Y, 2M, 2C, 2Bk) arranged side by side so as to form developer images of respective colors on the top.
And an intermediate transfer belt 6a for temporarily transferring the developer images formed on the photoconductor drums 4 (4Y, 4M, 4C, 4Bk), and the developer image on the belt 6a as recording paper, OH
An intermediate transfer device 6 including a secondary transfer roller 6e that is a transfer unit that transfers a recording medium p such as a P sheet or cloth, a fixing device 7, and the recording medium p are sequentially conveyed to the intermediate transfer device 6 or the fixing device 7. Transporting means 3 (3a-3
i) is provided.

Photoreceptor drum 4 (4Y, 4M, 4C, 4B
image forming unit 2 (2Y, 2M, 2C, 2Bk) including k)
Is composed of an optical scanning system A (AY, AM, AC, ABk) and a process cartridge B (BY, BM, BC, BBk), and in the case of the 4-drum full color system, as shown in FIG. ), Magenta (M), cyan (C), and black (Bk) are arranged in parallel. Each process cartridge BY, BM,
Photoconductor drums 4Y, 4M, 4 held by BC, BB
Optical scanning system AY, AM, A facing C, 4Bk
C and ABk are respectively arranged, and the optical scanning system A (AY,
After the developer image is formed on the photoconductor drum 4 (4Y, 4M, 4C, 4Bk) for each color by the image signal from the AM, AC, ABk), the transfer roller 5 (5Y, 5M, 5).
C, 5Bk), the developers of the respective colors are superposed and transferred onto the intermediate transfer belt 6a running in the direction of the arrow in the figure.

Further, the image forming apparatus 1 is detachably mounted with a paper feed cassette 3a for accommodating and storing a plurality of recording media p, and the recording media fed from the paper feed cassette 3a by a pickup roller 3b. p is separated one by one by the retard roller pair 3c, and the conveyance rollers 3d, 3
It is conveyed to the registration roller pair 3g by f. The registration roller pair 3g stops rotating when the recording medium p is conveyed.
The skew is corrected by being abutted against the nip of g.

After that, the recording medium p is sent out from the registration roller pair 3g to the secondary transfer roller 6e at a predetermined timing, and the developer image on the intermediate transfer belt 6a is transferred onto the recording medium p. After that, the recording medium p on which the developer image is transferred is conveyed to the fixing device 7 and fixed there, and is discharged by the discharge roller pair 3h and 3i, and is stacked on the discharge tray 8 on the apparatus main body 1.

Next, the optical scanning system A (AY, AM, AC,
ABk) together with the image forming unit 2 (2Y, 2M, 2C, 2
Bk) is a process cartridge B (BY, B
M, BC, BBk) will be described. Since the process cartridges BY, BM, BC, and BBk have the same configuration, one process cartridge B will be described below as an example.

In the process cartridge B, as shown in FIG.
The developing means 12 and the transfer opening are provided. In this embodiment, a two-component developer containing magnetic carrier powder is used, and as the photoconductor drum 4, a commonly used organic photoconductor or the like can be used. When a material having a surface layer having a resistance of 10 ² to 10 ¹⁴ Ω · cm or an amorphous silicon photoconductor is used, charge injection charging can be realized, which is effective in preventing ozone generation and reducing power consumption. . In addition, it becomes possible to improve the charging property. Therefore, in this embodiment, the photoconductor drum 4 in which the negatively charged organic photoconductor is provided on the aluminum drum base is used.

The charging means 11 is a magnetic brush charger using a magnetic carrier. The charging means 11 has a fixed magnet 11b in a hollow cylindrical charging sleeve 11a which is rotatably supported. Charging sleeve 11a
Is driven to rotate in the direction of the arrow in the figure, and after transferring the developer image formed on the photoconductor drum 4 to the intermediate transfer belt 6a, acts to take in the developer remaining on the photoconductor drum 4.

As the developing means 12, in the present embodiment, a method of developing a two-component developer in a contact state (two-component non-contact development) is adopted, and a developing means for two-component magnetic brush development is shown. . The developing sleeve 12a has a hollow cylindrical shape and is rotatably supported, and a fixed magnet 12b is disposed in the developing sleeve 12a. Development sleeve 1
2a is rotationally driven in the same direction as the rotation direction of the photosensitive drum 4 in the direction of the arrow shown in the figure, and its peripheral surface moves in the opposite direction to the moving direction of the peripheral surface of the photosensitive drum 4. Development sleeve 1
2a is urged toward the photoconductor drum 4, but the photoconductor drum 4 and the developing sleeve 12a are not in contact with each other.
A gap of about 1.0 mm is provided so that the developer can be developed while being in contact with the photosensitive drum 4.

The developer mixed with the carrier is supplied by agitation screws 12d and 12e in a casing partitioned by longitudinal partition walls 14d excluding both ends. The developer supplied from a developer supply container (not shown) drops to one end side of the stirring screw 12d and is stirred while being sent in one direction in the longitudinal direction, passes through a portion without the partition wall 14d on the other end side, and passes through the stirring screw. It moves to one end side at 12e, then is agitated while being fed by the agitation screw 12e through the part without the partition wall 14d on the one end side, and circulates in the developing container 12c.

The developing process for developing the electrostatic latent image formed on the photosensitive drum 4 by the two-component magnetic brush method using the developing means 12 and the developer circulation system will be described below.

First, the developer drawn up by the magnetic poles of the magnet 12b as the developing sleeve 12a rotates is conveyed, and the regulating blade, that is, the developer blade 12 disposed perpendicularly to the developing sleeve 12a.
It is regulated by f, and a thin layer is formed on the developing sleeve 12a. Here, when the thin-layered developer is conveyed to the main developing pole, magnetic brushes form ears. The electrostatic latent image on the photoconductor drum 4 is developed by the developer formed in the shape of the spikes, and then the developer on the developing sleeve 12a is returned to the developing container 12c by the repulsive magnetic field.

A DC voltage and an AC voltage are applied to the developing sleeve 12a from a power source (not shown). Generally, in the two-component developing method, when an AC voltage is applied, the developing efficiency is increased and the image is of high quality, but conversely fogging is likely to occur. Therefore, normally, by providing a potential difference between the DC voltage applied to the developing sleeve 12a and the surface potential of the photosensitive drum 4, it is possible to prevent the developer from being attached to the non-image area during development.

The developer image formed on the photosensitive drum 4 is
As shown in FIG. 1, the photosensitive drum 4 is rotated to be transferred to a portion facing the transfer charging roller 5 (5Y, 5M, 5C, 5Bk), and is transferred by the intermediate transfer device 6 to the intermediate transfer belt 6.
is transferred to a. The endless intermediate transfer belt 6a of the intermediate transfer device 6 is configured by being wound around a driving roller 6b, a driven roller 6c and a secondary transfer counter roller 6d, and the intermediate transfer belt 6a is rotated in the direction of the arrow in FIG. . Further, the transfer charging roller 5 is provided in the circulation path of the intermediate transfer belt 6a.
Y, 5M, 5C and 5Bk are photosensitive drums 4Y, 4M and 4
The transfer charging rollers 5 (5Y, 5M, 5C, 5Bk) are arranged to face C and 4Bk, respectively, and the photosensitive drums 4 (4Y, 4M, 5Y, 5M, 5C, 5Bk) are arranged from the inside of the intermediate transfer belt 6a.
4C, 4Bk) while being supplied with power from a high-voltage power supply while generating a pressing force in the direction of 4C, 4Bk), the photosensitive drum 4 is charged from the back side of the intermediate transfer belt 6a with a polarity opposite to that of the developer.
The developer images on (4Y, 4M, 4C, 4Bk) are sequentially transferred onto the upper surface of the intermediate transfer belt 6a.

The intermediate transfer belt 6a may be made of polyimide resin. The material of the intermediate transfer belt 6a is not limited to the polyimide resin, but a dielectric such as a polycarbonate resin, a polyethylene terephthalate resin, a polyvinylidene fluoride resin, a polyethylene naphthalate resin, a polyether ether ketone resin, or a polyether sal. A plastic such as a phon resin or a polyurethane resin, or a fluorine-based or silicon-based rubber can be preferably used.

After the transfer of the developer image, the photosensitive drum 4 (4
The transfer residual developer remains on the surface of Y, 4M, 4C, 4Bk). If this residual transfer developer is passed through the charger as it is, the charging potential of only the residual image portion may be lowered, or a phenomenon (ghost) may occur in which the previous image portion appears thin or dark on the next image. . Even if the transfer residual developer passes under the charged magnetic brush that is in contact with the photosensitive drum 4,
In most cases, the shape of the previous image remains unchanged. Therefore, as the photoconductor drum 4 rotates, it is necessary to take the transfer residual developer that has reached the charging area into the magnetic brush charger 11 and erase the history of the pre-image. Here, the transfer residual developer on the photosensitive drum 4 often has a mixture of positive and negative polarities due to peeling discharge at the time of transfer. Considering the ease, it is desirable that the transfer residual developer is positively charged.

In this embodiment, the conductive brush 13 is brought into contact with the photosensitive drum 4 between the intermediate transfer device 6 and the magnetic brush charger (11), and a bias having a polarity opposite to the charging bias is applied. The positive transfer residual developer is the conductive brush 13
After passing through the negative transfer residual developer, the negative transfer residual developer is temporarily captured by the conductive brush 13 and is neutralized.
Sent to the top. This makes it easier for the residual transfer developer to be taken in the direction of the magnetic brush.

Next, the frame structure of the process cartridge configured as described above will be described.

FIG. 3 is an external perspective view of the process cartridge as seen from the front upper side, FIG. 4 is an external perspective view of the process cartridge as seen from the rear lower side, and FIG. 5 is a rear view of the process cartridge. 6A and 6B are a front view and a rear view of the developing unit constituting the process cartridge, showing a state in which the front cover 16a and the rear cover 16b of the process cartridge are removed. . In the mounting direction of the process cartridge to the apparatus main body, the front side is the front or the front,
The back side is referred to as the rear or the rear, and the top of the process cartridge refers to the top in the mounted state of the process cartridge.

Process cartridge B (BY, BM, B
C, BBk), a charging sleeve 11a, a regulating blade 11c, a conductive brush 13 and the like are integrated by a charging frame 15 into a developing unit D in which the photosensitive drum 4 and the developing means 12 are integrally formed by a developing frame 14. The charging unit C configured as described above is assembled for each unit (see FIG. 2). Further, the front cover 1 from both ends in the longitudinal direction
6a and the rear cover 16b (see FIGS. 3 and 4) position and connect the developing unit D and the charging unit C.

The developing frame 14 is, as shown in FIG.
Lower part 14f having seat portions 14e for accommodating the stirring screws 12d and 12e on both sides of the partition wall 14d and for mounting the regulating blade 12f, and the process cartridge B
The side portion 14g forming the exterior portion on the left side when viewed from the mounting direction, and the rear end plate portion 14h ((b) of FIG. 6) as shown in FIG. 3, FIG. 4 and FIG. Front end plate 14
i ((a) of FIG. 6).

The rear end plate portion 14h of the developing frame 14 (see FIG. 6)
(B)) is formed with a hole 14j for allowing the cylindrical shaft portion 26a (FIG. 7) of the charging unit C to rotate via a bearing, and further includes a driving side drum flange 37 of the photosensitive drum 4. A hole 14k to be inserted is provided. Further, the front end plate portion 14i ((a) of FIG. 6) is provided with a hole 14m having the same diameter as the hole 23a of the charging frame 15, and further has a hole 14n for holding the non-driving side drum flange of the photosensitive drum 4. It is provided. The photosensitive drum 4 rotatably supported by the rear end plate portion 14h and the front end plate portion 14i of the developing frame 14.
Has a driving side drum flange 37 fitted and fixed to one end of a drum cylinder provided with a photosensitive layer on the outer periphery of a hollow cylindrical aluminum cylinder, and a non-driving side drum flange fitted and fixed to the other end. The side drum flange is held by the front end plate portion 14i, the drive side drum flange 37 is held by the rear end plate portion 14h, and the drive side drum flange 37 has a coupling convex portion that is a convex portion in the axial direction from the end face center portion. 37a is provided.

As shown in FIG. 2, the charging unit C comprises a charging sleeve 11a, a regulating blade 11c and a conductive brush 13 which are integrally formed by a charging frame 15.
The charging frame 15 constitutes a part of the exterior of the process cartridge B, as shown in FIGS. The lower edge 15a of the charging frame 15 is, as shown in FIG. 2 and FIG.
It is parallel to the photoconductor drum 4 in the longitudinal direction at a distance close to the photoconductor drum 4. Then, the charging frame 15
2, has a vertical wall 15b extending upward from the lower edge 15a to form the exterior of the process cartridge B, and is curved at the upper portion to provide a corner portion 15c. The top plate portion 15d is provided in a substantially horizontal direction.
The charging frame 15 has a substantially key-shaped cross section, and the top plate portion 15d
Is a space below, and member attachment portions 15e and 15f (FIGS. 3 and 4) are integrally formed at both ends in the longitudinal direction. In addition, in FIG. 2, the lower edge 15 a of the charging frame 15 is a transfer opening 15 that opens the photosensitive drum 4.
An opening / closing shutter 15n is provided in the transfer opening 15m.

At the front end of the charging frame 15, as shown in FIG. 7 (a side view of the charging unit C as seen from the left in FIG. 2), the charging sleeve bearing 22 and the rear end cover 23 are fastened together. It is screwed on. A gear unit 24 is screwed and fixed to the rear end. The charging sleeve 11a held by the charging frame 15 has journal portions 11a1 formed on both sides thereof with a reduced diameter, and rotatably held by the charging sleeve bearing 22 and the gear unit 24.

As shown in FIGS. 2 and 7, the metal regulating blade 11c has a charging sleeve 11a at its tip.
Is fixed to the support sheet metal 11d along the longitudinal direction of the charging sleeve 11a with a gap. This support sheet metal 11d
Has a groove-shaped cross section and is attached to the member attaching portions 15e and 15f at both ends of the charging frame 15.

The charging unit C has a swing center S shown in FIG.
The developing frame 14 is swingably supported about C.
Therefore, as shown in FIG. 7, the gear case 26 of the gear unit 24 fixed to the rear end of the charging frame 15 in the longitudinal direction.
A cylindrical shaft portion 26a is provided on the swing center SC, and the swing center SC is provided on the rear end cover 23 in the longitudinal direction.
A cylindrical hole 23a is provided on the top.

Therefore, the cylindrical shaft portion 26 of the charging unit C is
With a being inserted into the hole 14j ((b) in FIG. 6) of the rear end plate portion 14h of the developing frame 14, the cylindrical fitting hole 23a of the charging unit C is inserted into the hole 14m of the front end plate portion 14i of the developing frame 14. According to. Then, when the rear cover 16b (FIG. 5) on the back side as viewed from the mounting direction of the process cartridge B is aligned so as to coincide with the end of the developing frame 15, it projects in the longitudinal direction on the inner side of the rear cover 16b. The outer circumference of the hollow cylindrical shaft support portion 16b1 (see FIG. 7) is fitted into the hole 14j of the developing frame 14, and at the same time, the inner circumference thereof is fitted into the cylindrical shaft portion 26a of the charging unit C. Further, the support shaft 27 that fits into the hole 14m provided in the front end plate portion 14i of the developing frame 14 and projects (see FIG. 6A and FIG. 7).
Fits into the hole 23a of the charging unit C. As a result, in the charging unit C, the cylindrical shaft portion 26a on one end side is rotatably supported by the rear cover 16b, and the hole 23a on the other end side is rotatably supported by the developing frame 14.

The upper part of the developing frame 14 is shown in FIG.
Further, as shown in FIG. 3, the top plate 17 is fixed by abutting the peripheral edges of the inside of the guide portion 14a on the upper side plate 14g and the front and rear end plate portions 14h and 14i.

As shown in FIG. 2, spring seats 17a are provided on the top plate 17 at two locations in the longitudinal direction, and the compression coil springs 18 held by the spring seats 17a are attached to the top plate 17a.
And the top plate portion 15d of the charging frame 15 are contracted. As a result, the charging unit C has the compression coil spring 1
The spring force of 8 urges the rocking center SC clockwise in FIGS. 2 and 9. The charging sleeve 11a is also urged in the clockwise direction in the same manner. However, as will be described later, the gap assurance members 51 (FIGS. 7 and 7) provided in the journal portions 11a1 formed at both ends of the charging sleeve 11a, respectively. 9), the distance from the photosensitive drum 4 is maintained at a predetermined distance.

As shown in FIGS. 2, 8 and 9, the developing sleeve 12a is attached to the developing frame 14 so as to be swingable about the pressing center SLv. As shown in FIGS. 9 and 10, the developing sleeve 12a is rotatably held on the swing arm 32 by the journal portions 12a1 having reduced diameters on both sides thereof. The swing arm 32 is
At the lower portion thereof, both end plate portions 14 of the developing frame 14
It is swingably supported by a support shaft 33 press-fitted in the longitudinal direction with respect to h and 14i. A bearing hole 32a is provided substantially right above the supporting shaft 33 of the swing arm 32,
A stopper portion 32b is provided above it. The spring seat 32c is provided on a line substantially perpendicular to a line connecting the center of pressure SLv, which is the center of the support shaft 33, and the center of the bearing hole 32a. The stopper portion 32b prevents the swing arm 31 from turning to the right in FIG. 9 by hitting the developing sleeve cover 36 during assembly and disassembly. In the assembled process cartridge B, the stopper portion 32b and the developing sleeve cover 36 are not in contact with each other.

The journal portion 12a1 at both ends of the developing sleeve 12a is rotatably held in the bearing hole 32a of the swing arm 32, and the spring seat 32c and the spring seat 14p provided on the end plate portions 14h and 14i of the developing frame 14 are provided. A compression coil spring 35 is contracted between them. As a result, the developing sleeve 12a is rotated by the compression coil spring 35 toward the photosensitive drum 4 and is pressed about the pressing center SLv. Here, in the reduced-diameter journal portions 12a1 on both sides of the developing sleeve 12a, as shown in FIGS. 8 and 9, a clearance guarantee for maintaining the clearance between the photosensitive drum 4 and the developing sleeve 12a at a predetermined interval. A member 61 is provided.

As shown in FIG. 8, the developing sleeve 12a has a developing sleeve gear 19b fixed to one end of the journal portion 12a1. This developing sleeve gear 19b is, as shown in FIG. 5 and FIG.
It meshes with 9a. The developing unit driving gear 19a is a developing unit coupling 20 which is a rotational driving force receiving member of the developing unit.
And a cylindrical hole in the center of the back side of the developing unit coupling 20. The developing unit coupling 2 is attached to a shaft portion (not shown) provided in the longitudinal direction on the rear end plate portion 14h of the developing frame 14.
0 of the cylindrical holes are rotatably fitted. The developing unit drive gear 19a further includes a gear 19c via a gear 19c.
d, 19e are driven to rotate, and stirring screws 12d, 12
Rotate e. The charging sleeve 11a is connected to the charging unit coupling 25 via gears 24a and 24b in the gear unit 24.

On the other hand, the apparatus main body is provided with a drive unit (not shown) for the process cartridge B. This drive unit has a (photosensitive drum) coupling convex portion 37a, a charging unit coupling 25, and a charging unit coupling 25 of the process cartridge B. This is a drive unit having three couplings that respectively engage with the developing section couplings 20. These three couplings are driven by three independent drive sources. Therefore, the photosensitive drum 7, the charging sleeve 11a, and the developing sleeve 12a of the process cartridge B are driven independently of each other.

Next, the (guaranteed) gap assurance member 51 for maintaining the distance between the charging sleeve 11a and the photosensitive drum 4 at a predetermined distance will be described with reference to FIGS. 7, 9 and 10.

As shown in FIG. 7, the gap guarantee member 51 (for charging) for keeping the gap between the charging sleeve 11a and the photosensitive drum 4 at a predetermined distance is provided in the journal portions 11a1 at both ends of the charging sleeve 11a. As shown in FIGS. 9 and 10, the gap assurance member 51 is provided in each of the support engagement portions 5 having a circular hole 51a for inserting the journal portion 11a1 of the charging sleeve 11a.
1b and an arcuate end 5 having an arcuate shape formed with a diameter smaller than the outer circumference of the cylindrical member with which the other end abuts.
1c and a support-engaging portion 5
The journal portion 1 of the charging sleeve 11a is provided in the hole 51a of 1b.
1a1 is rotatably fitted, and the arcuate end 51c is brought into contact with the outside of the image area of the photosensitive drum 4. At this time, since the charging unit C holding the charging sleeve 11a is biased in the clockwise direction by the compression coil spring 18 as shown in FIGS. 2 and 9, the charging sleeve 11a and the gap assurance member 51 are also. The gap guarantee member 51 is pressed against the outer surface of the photoconductor drum 4 by being biased clockwise by the biasing force of the compression coil spring 18.

With this structure, the axial distance between the photosensitive drum 4 and the charging sleeve 11a is kept at a predetermined value by the gap guarantee member 51, and the photosensitive drum 4 and the charging sleeve 1 are held.
A predetermined gap is always provided between 1a. Therefore,
The transfer residual developer that is about to pass through the opposing portion of the charging sleeve 11a and the photosensitive drum 4 is charged with a charging bias by making the moving direction of the peripheral surface of the charging sleeve 11a opposite to the moving direction of the peripheral surface of the photosensitive drum 4. Can be captured.

Further, the arcuate end portion 51 of the gap assurance member 51.
In c, an extension portion 51d extending to the upstream side in the rotating direction of the photoconductor drum 4 that contacts is formed. This extension 51d
Is the rotation direction B of the charging sleeve 11a and the photosensitive drum 4
Although the rotation direction A is hit by a counter as shown in FIG. 10, it functions to prevent the gap guarantee member 51d from falling due to the rotation of the photosensitive drum 4.

Further, the arcuate end portion 5 of the gap assurance member 51.
By forming the circular arc shape of 1c with a diameter smaller than the outer peripheral diameter of the photoconductor drum 4, the gap assurance member 51 has the arcuate end portion 51c of the photoconductor drum 4 as shown in FIG.
The photoconductor drum 4 is abutted at two points on both the upstream and downstream sides in the rotation direction of. As a result, the gap assurance member 51 can contact the photosensitive drum 4 in a stable posture. At this time, the arcuate shape of the arcuate end portion 51c of the gap assurance member 51 is 0.1 mm to 1 m larger than the outer diameter of the photosensitive drum 4.
By setting m to be small, even if slight wear occurs in the gap assurance member 51 during use, the gap assurance member 51 will always have the arcuate end 51c at both the upstream and downstream ends in the rotational direction of the photosensitive drum 4. It is possible to contact the photosensitive drum 4 at two points of the part.

Next, a gap guarantee member 61 (for development) for keeping the gap between the developing sleeve 12a and the photosensitive drum 4 at a predetermined distance will be described with reference to FIGS. 8, 9 and 10.

The center of pressure SLv is applied to the developing frame 14.
Developing sleeve 12 swingably attached about
a is a reduced diameter journal portion 12 as shown in FIG.
A (developing) gap assurance member 61 is provided inside the swing arm 32 at a1. This gap assurance member 61 has a circular hole 61a for inserting the journal portion 12a1 as shown in FIG. The support engagement portion 61b and a plate-shaped body having an arc-shaped end portion 61c having an arc shape formed with a diameter smaller than the outer peripheral diameter of the cylindrical member with which the other end portion abuts are configured by a plate-shaped body. The journal portion 12a1 of the developing sleeve 12a is rotatably fitted in the hole 61a of the joining portion 61b, and the arcuate end portion 61c is brought into contact with the outside of the image area of the photosensitive drum 4. Further, the arcuate end portion 61c of the gap ensuring member 61 is formed with an extension portion 61d extending to the upstream side in the rotation direction of the photoconductor drum 4 in contact therewith. As a result, the gap assurance member 61 is brought into pressure contact with the end portion of the photosensitive drum 4 outside the image area, and a predetermined gap (0.2 to 1.0 mm) is provided between the developing sleeve 12a and the photosensitive drum 4. Hold.

As shown in FIGS. 9 and 10, the rotation direction C of the developing sleeve 12a and the rotation direction A of the photosensitive drum 4 are shown.
Is hit by a counter, but an extended portion 61d extending upstream in the rotation direction of the photoconductor drum 4 is formed at the arcuate end portion 61c of the gap ensuring member 61. It functions to prevent the gap ensuring member 61 from falling due to the rotation of the drum 4.

Further, the arcuate end portion 61 of the gap ensuring member 61 is provided.
By forming the circular arc shape of c with a diameter smaller than the outer peripheral diameter of the photosensitive drum 4, the gap assurance member 61 can be formed as shown in FIG.
As shown in FIG. 0, the two ends of the arcuate end portion 61c are in contact with the photosensitive drum 4 at two points on the upstream side and the downstream side in the rotational direction of the photosensitive drum 4. As a result, the gap assurance member 61 can contact the photosensitive drum 4 in a stable posture.

At this time, by setting the arcuate shape of the arcuate end portion 61c of the gap ensuring member 61 to be smaller than the outer peripheral diameter of the photosensitive drum 4 by 0.1 mm to 1 mm, slight wear during use can be prevented. Even when it occurs at 61, the gap assurance member 61 always contacts the photosensitive drum 4 at two points, that is, the arcuate end portion 61c, both upstream and downstream in the rotational direction of the photosensitive drum 4.

The gap guarantee member 51 and the gap guarantee member 6
1, the arcuate shape of the arcuate end portion 61c of the gap assurance member 61 and the arcuate shape of the arcuate end portion 51c of the gap assurance member 51 are set to be larger than the outer peripheral diameter of the photoconductor drum 4, as shown in FIG. The arcuate end portion 61c of the gap assurance member 61 and the arcuate end portion 51c of the gap assurance member 51 come into contact with the photoconductor drum 4 at one point, respectively, and the rotational frictional force with the photoconductor drum 4 is reduced. Along with the change, the contact point with the photosensitive drum 4 may be displaced, and the gap between the two members may be changed due to the deviation of the contact point, which is not preferable.

The gap guarantee member 51 and the gap guarantee member 6 are also provided.
The surface of the photosensitive drum 4 with which the arc-shaped end portions 51c and 61c of 1 contact is aluminum or a photosensitive layer, and the material of the gap assurance members 51 and 61 is polyether sulfone (PES) because of its good slidability with aluminum. ), Polyphenylene sulfide (PPS), polyamide (PA), or polyacetal (POM).

In the above description, the gap assurance member for the gap between the photosensitive drum 4 and the charging sleeve 11a and the cylindrical member such as the photosensitive drum 4 and the developing sleeve 12a has been described. Not limited to the gap, as shown in FIGS. 12 and 13, between the photosensitive drum 4 which is a rotating cylindrical member and the charging (or cleaning) brush 73 which is one of the charging means, the same as described above. The charging brush 7 is provided with the gap assurance member 71.
The distance between the charging (or cleaning) brush 73 and the photoconductor drum 4 is regulated so that the photoconductor drum 3 is brought into contact with the photoconductor drum 4 with a predetermined pressing force or a predetermined amount of penetration in the longitudinal direction. You can also

That is, the gap assurance member 7 for the charging brush
1 is a charging brush 7 as shown in FIGS.
3, a circular hole 71a and an elliptical elongated hole 7 formed so that a pair of shaft portions 72a, 72b (FIG. 12) provided at both ends of the brush frame 72 for holding 3 can be inserted respectively.
1b is a plate-like body having a supporting engagement portion 71c and an arc-shaped end portion 71d that abuts the photosensitive drum 4 with the other end portion having an arc shape. The shafts 72a and 72b of the frame body 72 are provided with holes 71a.
And the gap assurance member 71 fitted in the elongated holes 71b,
The arc-shaped end portion 71d is set on the mounting portion 15k of the charging frame 15 so as to come into contact with the photosensitive drum 4, and the gap guarantee member 71 is exposed to light by the spring 76 arranged between the gap guarantee member 71 and the charging frame 15. The body drum 4 is brought into contact with and pressurized. Then, by setting the arcuate shape of the arcuate end portion 71d of the gap assurance member 71 for the charging brush, which is in contact with the photoconductor drum 4, to be smaller than the outer peripheral diameter of the photoconductor drum 4, the gap assurance member 71 is formed. The portion 71d abuts on the photosensitive drum 4 at two points on the upstream and downstream sides of the photosensitive drum 4 in the rotational direction of the photosensitive drum 4, and the gap assurance member 71 can abut the photosensitive drum 4 in a stable posture. As a result, the charging brush 73 can be arranged on the photosensitive drum 4 with a predetermined pressure or a predetermined amount of penetration through the gap assurance members 71, 71.

Although the process cartridge type image forming apparatus has been described in the above-described embodiments, the present invention is not limited to the process cartridge type and, for example, the conventional process cartridge type is not used. Of course, it is also possible to use it for a type of image forming apparatus. Further, the present invention is not limited to the gap assurance member in the gap between the photosensitive drum and the other member, and is naturally effective for the gap assurance member of other rotating cylindrical member such as a transfer roller. Is.

[0073]

As described above, according to the gap assurance member of the present invention, the distance and the gap between the rotating cylindrical member and the members arranged at a predetermined distance from the cylindrical member are stably maintained. To enable that. Furthermore, it is possible to maintain a stable gap between the cylindrical members that rotate with each other, and it is possible to maintain the gap without rotating like the conventional spacer roller. In particular, the rotating direction of both cylindrical members is a counter. Even in the case of abutting, it is possible to reliably and stably guarantee the gap between both cylindrical members.

Further, in the gap assurance member of the present invention,
By forming the arcuate shape of the arcuate end contacting the cylindrical member with a diameter smaller than the outer diameter of the pressed cylindrical member, the cylindrical member is always in contact with the cylindrical member at two points at the upper and lower ends in the rotation direction. The rotating cylindrical member can be contacted while maintaining a stable posture, and the gap between the two can be surely guaranteed.

By using the gap assurance member of the present invention between the photoconductor drum and the developing sleeve or between the photoconductor drum and the charging sleeve in the image forming apparatus, the photoconductor drum and the developing sleeve and the photoconductor drum are charged. The gap between the sleeves can be surely guaranteed without being affected by the difference in peripheral speed between the sleeves, which contributes to the improvement of image quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of an image forming apparatus to which a process cartridge of the present invention is detachably mounted.

FIG. 2 is a vertical cross-sectional view of a process cartridge detachably mountable to the image forming apparatus of the present invention.

FIG. 3 is an external perspective view of the process cartridge of the present invention seen from the front upper side. FIG.

FIG. 4 is an external perspective view of the process cartridge of the present invention as viewed from the lower rear side. FIG. 6 is a right side view of the process cartridge.

FIG. 5 is a rear view of the process cartridge of the present invention.

6 (a) and 6 (b) are respectively a front view and a rear view of a developing unit constituting the process cartridge of the present invention.

FIG. 7 is a side view of the charging unit in the process cartridge of the present invention as viewed from the left side in FIG.

FIG. 8 is a side view of the developing unit in the process cartridge of the present invention as viewed from the right side in FIG.

FIG. 9 is a schematic view showing a relationship between a supporting portion of the developing sleeve, the developing sleeve, the charging sleeve, and the photosensitive drum in the process cartridge of the present invention.

FIG. 10 is a schematic view showing a gap assurance member of the present invention and its attachment.

FIG. 11 is a schematic view showing a gap assurance member and its attachment as a comparative example to the gap assurance member of the present invention.

FIG. 12 is a schematic cross-sectional view showing a gap assurance member for a charging brush and its attachment in the process cartridge of the present invention.

FIG. 13 is a schematic side view showing a gap assurance member for a charging brush and its attachment in the process cartridge of the present invention.

[Explanation of symbols]

1 Image forming apparatus 2 (2Y, 2M, 2C, 2Bk) Image forming unit A (AY, AM, AC, ABk) Optical scanning system B (BY, BM, BC, BBk) Process cartridge p Recording medium 3a Paper feed cassette 3b Pickup roller 3c Retard roller pair 3d, 3f Conveying roller 3g Registration roller pair 3h, 3i Discharging roller pair 4 (4Y, 4M, 4C, 4Bk) Photoconductor drum 5 (5Y, 5M, 5C, 5Bk) Transfer charging roller 6 Intermediate transfer Device 6a Intermediate transfer belt 6b Drive roller 6c Driven roller 6d Secondary transfer counter roller 6e Secondary transfer roller 7 Fixing means 8 Ejection tray C Charging unit SC Swing center 11 Charging means 11a Charging sleeve 11a1 Journal part 11b Magnet 11c Control blade 11d Support sheet metal D Development unit SLv Pressure center 12 Developer 12a Developing sleeve 12a1 Journal part 12b Magnet 12c Developing containers 12d, 12e Stirring screw 12f Developer blade 13 Conductive brush 14 Developing frame 14a Guide part 14d Partition 14e Seat 14f Lower part 14g Side part 14h Rear end plate part 14i Front end plate part 14p Spring seat 15 Charging frame 15a Lower edge 15b Vertical wall 15c Corner 15d Top plate 15e, 15f Member mounting part 15k Mounting part 15m Transfer opening 15n Open / close shutter 16a Front cover 16b Rear cover 17 Top plate 17a Spring seat 18 Compression coil Spring 19a Developing unit drive gear 19b Developing sleeve gear 20 Developing unit coupling 22 Charging sleeve bearing 23 Rear end cover 23a Hole 24 Gear unit 24a, 24b Gear 25 Charging unit coupling 26 Gear case 26a Cylindrical Part 27 Support shaft 32 Swing arm 32a Bearing hole 32b Stopper part 32c Spring seat 33 Support shaft 35 Compression coil spring 36 Developing sleeve cover 37 Drive side drum flange 37a Coupling convex part 51 (for charging) gap assurance member 51a Hole 51b Support Engagement portion 51c Arc-shaped end portion 51d Extension portion 61 (for development) Gap assurance member 61a Hole 61b Support Engagement portion 61c Arc-shaped end portion 61d Extension portion 71 (for charging brush) Gap assurance member 71a Hole 71b Long hole 71c Support Engaging portion 71d Arc-shaped end portion 72 Brush frame bodies 72a, 72b Shaft portion 73 Charging brush 76 Spring

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takato Ueno             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F-term (reference) 2H035 CA07 CD11 CD14                 2H071 BA04 BA05 BA16 BA22 BA27                       BA29 CA02 DA06 DA08 DA15                       EA06                 2H077 BA07 BA10 EA03                 2H200 FA09 FA12 GA12 GA14 GA16                       GA23 GA45 HA13 HA21 HB08                       HB12 HB22 JB13 JB17 JC03                       KA01 LA23 LA38

Claims (19)

[Claims] 1. A gap assurance member for defining a distance between a rotating cylindrical member and a member disposed at a predetermined distance from the cylindrical member, wherein the gap assurance member engages with the member. Portion and an arcuate end contacting the outer peripheral surface of the cylindrical member, and the arc shape of the arcuate end is formed with a diameter smaller than the outer peripheral diameter of the cylindrical member. Element. 2. The arcuate shape of the arcuate end of the gap ensuring member is formed with a diameter smaller by 0.01 mm to 1 mm than the outer diameter of the cylindrical member against which the gap ensuring member is pressed. The gap assurance member according to claim 1. 3. The gap assurance member according to claim 1, wherein the gap assurance member is in contact with the cylindrical member with a pressing force. 4. A gap assurance member that defines a gap between a rotating first cylindrical member and a second cylindrical member that is disposed with a predetermined gap from the first cylindrical member, wherein the gap assurance member comprises: At least an engaging portion that rotatably engages with one of the cylindrical members and an arcuate end contacting the outer peripheral surface of the other cylindrical member are provided, and the arcuate shape of the arcuate end guarantees the gap. A gap ensuring member having a diameter smaller than an outer diameter of the cylindrical member against which the member is pressed. 5. The arcuate shape of the arcuate end of the gap assurance member is formed to have a diameter smaller by 0.01 mm to 1 mm than the outer diameter of the cylindrical member against which the gap assurance member is pressed. The gap assurance member according to claim 4. 6. The gap ensuring member according to claim 4, wherein the gap ensuring member is in contact with the other cylindrical member with a pressing force. 7. The method according to claim 4, wherein the peripheral surface moving direction of the first cylindrical member and the peripheral surface moving direction of the second cylindrical member are counter directions. The gap guarantee member described. 8. The arc-shaped end portion has an end portion that extends to the upstream side in the rotational direction of the other cylindrical member, as claimed in any one of claims 4 to 7. Gap guarantee member. 9. The gap assurance member is arranged on the side of the cylindrical member having the smaller outer diameter in the first cylindrical member and the second cylindrical member, and the arcuate end portion contacts the cylindrical member having the larger outer diameter. The gap assurance member according to any one of claims 4 to 8, wherein the gap assurance member is arranged so that 10. The gap assurance member according to claim 4, wherein one of the first cylindrical member and the second cylindrical member is an image carrier. 11. The one of the first cylindrical member and the second cylindrical member is an image carrier, and the other is a developing sleeve or a charging sleeve. A gap guarantee member in item 1. 12. The material for the gap ensuring member is polyether sulfone (PES), polyphenylene sulfide (PPS), polyamide (PA) or polyacetal (POM).
The gap assurance member according to any one of 1. 13. A developing device for an image forming apparatus, wherein at least a developing sleeve is arranged around an image carrier, and a gap guarantee is provided between the developing sleeve and the image carrier to regulate a gap between the two constant. A member is provided, and the gap assurance member includes an engaging portion that rotatably engages with the developing sleeve, and an arcuate end portion that comes into contact with the outer peripheral surface of the image bearing member. The developing device, wherein the arcuate shape of the end portion is formed to have a diameter smaller than the outer peripheral diameter of the image carrier on which the gap assurance member is pressed. 14. A charging device for an image forming apparatus, wherein at least a charging means is disposed around an image carrier, and a gap guarantee is provided between the charging means and the image carrier to regulate a gap between the charging means and the image carrier uniformly. A member is provided, and the gap assurance member is
An arc-shaped end contacting with the outer peripheral surface of the image carrier, the arc-shaped end of the arc-shaped end against which the gap assurance member is pressed. A charging device having a diameter smaller than the outer diameter of the image carrier. 15. A charging device for an image forming apparatus, comprising at least a charging means arranged around an image carrier, and a gap between the charging means holding member holding the charging means and the image carrier. A gap assurance member that regulates a constant amount is disposed, and the gap assurance member has an engagement portion that engages with the charging unit holding member and an arcuate end portion that contacts the outer peripheral surface of the image carrier. The charging device is characterized in that the arcuate shape of the arcuate end portion is formed with a diameter smaller than an outer peripheral diameter of the image carrier on which the gap assurance member is pressed. 16. A process cartridge mountable on an image forming apparatus main body, comprising at least a developing device around an image carrier, wherein a gap between the developing sleeve of the developing device and the image carrier is constant. A gap assurance member for regulating is provided, and the gap assurance member includes an engaging portion that rotatably engages with the developing sleeve and an arcuate end portion that comes into contact with the outer peripheral surface of the image carrier. The process cartridge is characterized in that the arcuate shape of the arcuate end portion is formed with a diameter smaller than an outer peripheral diameter of the image carrier on which the gap assurance member is pressed. 17. A process cartridge mountable on an image forming apparatus main body, comprising at least a charging device around an image carrier, wherein a gap between the charging device of the charging device and the image carrier is constant. A gap assurance member for restricting is provided, and the gap assurance member includes an engaging portion that engages with the charging unit and an arcuate end portion that comes into contact with the outer peripheral surface of the image carrier. The process cartridge, wherein the arcuate shape of the arcuate end portion is formed with a diameter smaller than the outer peripheral diameter of the image carrier on which the gap assurance member is pressed. 18. A process cartridge attachable to an image forming apparatus main body, which has at least a developing device and a charging device around an image carrier, and a gap between the developing sleeve of the developing device and the image carrier. And a second gap assurance member that regulates the gap between the charging unit and the image carrier of the charging device. The first gap assurance member includes an engaging portion that rotatably engages with the developing sleeve, and an arcuate end portion that contacts the outer peripheral surface of the image carrier, and the second gap is provided. The assurance member includes an engagement portion that engages with the charging unit and an arcuate end portion that contacts the outer peripheral surface of the image carrier, and the arcuate end portions of the first and second gap assurance members. The circular arc shape of both parts is the outer circumference of the image carrier. A process cartridge, characterized by being formed with a smaller diameter than. 19. The process cartridge according to claim 17, wherein the charging means is a charging sleeve or a charging brush, or a charging means holding member.