JPH1145037A - Image forming device and cleaning device for process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of an image carrier by making the abutting pressure of a cleaning blade, coming into contact by pressing with the position in the circumferential direction of the image carrier with which the vicinities of both ends of an electrifying roller come into contact, smaller than that with a part except the position in the circumferential direction. SOLUTION: A cleaning blade 6 is constituted in such a manner that it is attached to a supporting member 13 made of a rigid material such as metal by integrated molding and in an abutting edge on the image carrier, wherein the thickness of the edge is defined as (d), as a whole. The edge of the blade 6 is formed to make the thickness of a fixed part smaller than the thickness (d). In such a case, the thin part of the top end edge is formed to be thin up to the part near the supporting member 13, as a whole. In other words, the abutting pressure of the cleaning blade 6 coming into contact by pressure with the position in the circumferential direction of the image carrier, with which the vicinities of both ends of the electrifying roller come into contact, is smaller than that with the part except the position in the circumferential direction. Thus, the abutting pressure of the cleaning blade 6 against the easily shaved part of the image carrier is selectively low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrostatic transfer process, such as an electrostatic copying machine and a printer, and a process cartridge for the same.

[0002]

2. Description of the Related Art FIG. 12 is a schematic side sectional view of a main part showing a typical example of such an image forming apparatus, which will be briefly described below. In the image forming apparatus, there is provided a cylindrical image carrier 1 having an axis perpendicular to the paper surface and rotating in the direction of arrow a in the drawing.

Around the image carrier 1, a primary charging means for uniformly charging the photosensitive layer on the surface of the image carrier in the direction of rotation, and applying an image signal to the charged surface to form an electrostatic latent image Exposure means for forming an image, developing means for applying toner to the formed latent image to make it visible as a toner image, a transfer site for transferring this toner image to a transfer material, and removing residual toner on the image carrier Cleaning means and the like are provided.

1, a process cartridge 11 is formed by integrally mounting the image carrier 1, the charging roller 2 serving as a primary charging unit, the developing device 5 serving as a developing unit, and a cleaner 8 in a housing 9. . It is assumed that the process cartridge 11 is detachably mounted to an image forming apparatus main body (not shown), and the image carrier 1 is mounted on the apparatus main body while the image carrier 1 is mounted on the apparatus main body. It is assumed that the transfer roller 10 comes into contact with the transfer roller 10.

The operation of the above-described apparatus is briefly described below. A charging bias is applied to the charging roller 2 by a power source S to uniformly charge the surface of the image carrier. An electrostatic latent image is formed by applying an image signal 12 such as reflected light from an original and an image-modulated laser beam to the uniform charged surface by means (not shown).

When the electrostatic latent image reaches the developing site where the developing device 5 is arranged as the image carrier 1 rotates, the toner in the developing device rotates in the direction of arrow b.
Then, the thickness of the toner layer is regulated by the blade 4 and adheres to the latent image on the image carrier to be visualized as a toner image.

Further, when the toner image on the image carrier reaches a transfer portion where the transfer roller 10 is in contact with the image carrier 1, by this time, the transfer material is transferred to the transfer portion in time with the toner image. P is conveyed and supplied, and at the same time, a transfer bias is applied to the transfer roller, and the toner image on the image carrier side is transferred to the transfer material P by the action of the electric field thus formed.

The transfer material P having completed the transfer is separated from the image carrier 1 and conveyed to a fixing portion (not shown) provided on the apparatus main body side. Further, at the time of transfer, the residual toner remaining on the image carrier 1 without transferring to the transfer material proceeds as it is and reaches the cleaner 8, is scraped off from the image carrier 1 by the cleaning blade 6, and is cleaned by the rake sheet 7. Is guided to the toner storage section in the inside.

The primary charging roller 2 in such an image forming apparatus has an elastic conductive layer 19 disposed around a conductive core 18 as shown in an enlarged sectional view in FIG. And a resistance layer 20 is formed thereon.
FIG. 14 is a main part side view showing the charging roller opposed to the image carrier 1 in the image forming apparatus. As shown in FIG. Are supported by the bearing 21 and the bearing 21
The charging roller 2 is moved by the spring 22 in contact with the image carrier 1.
Is pressed against. The charging bias is applied to the spring 22 or the core 18 from a power source (not shown).

In the case of the charging roller having the above-described structure, the resistance layer 20 is usually formed with a coating having a thickness of about several tens to several hundreds of μm. It is formed in a shape.

For this reason, the charging roller as described above is
When it is brought into contact with the image carrier as shown in FIG. 14, a minute gap of several to several tens μm is formed near the bulging portion at the end, as indicated by the symbol h. Therefore, when a high-voltage charging bias is applied, a discharge is generated in the minute gap according to Paschen's law. In addition, even in a portion where good contact does not exist where no gap exists as described above, a similar discharge is inevitably generated in a portion where the charging roller and the image carrier at both ends are close to each other.

Therefore, when the image bearing member and the charging roller are brought into contact with each other, the image bearing member is exposed to the discharge generated at the minute gap portion and both end portions as described above. This leads to deterioration of characteristics, and this portion is more easily scraped than other portions.

In order to avoid such a problem, the resistance layer 20
Is formed, the both ends where the sag is formed are cut, and if a charging roller having a shape without sag is used as shown in FIG. 15, the resistance layer does not exist on both sides of this roller. In particular, when a flexible material such as a sponge is used as the conductive layer, it deforms and tends to bulge outward, and this portion forms a minute gap with the image carrier. As shown by, discharge occurs intensively. Therefore, even in such a configuration, the image carrier is easily scraped off at the colored portions shown.

[Problems to be solved by the invention]

The present invention has been made in order to cope with such a situation. In the present invention, the influence of the cleaning member on the image carrier at the circumferential portion on the image carrier side where the portions near both ends of the charging roller contact each other is described. It is an object of the present invention to provide an image forming apparatus or a cleaning device for a process cartridge which is capable of forming a small image as much as possible to prevent local shaving of the surface of an image carrier and perform good image formation for a long period of time. It is assumed that.

[0015]

In order to achieve the above object, the present invention relates to an image carrier, a charging roller to which a charging bias is applied while being in contact with the image carrier, and a transfer residual toner on the image carrier. And a cleaning member for removing the cleaning roller, the contact pressure of the cleaning member that presses against the circumferential position of the image carrier where the portions near both ends of the charging roller contact with each other, and the contact pressure other than the circumferential position. A cleaning device (1) for an image forming apparatus characterized by being smaller than a contact pressure, or at least an image carrier, a charging roller to which a charging bias is applied while being in contact with the image carrier, and An image carrier in which the vicinity of both ends of the charging roller abuts on a process cartridge detachable from the image forming apparatus main body provided with a cleaning member for removing the transfer residual toner. Wherein the contact pressure of the cleaning member pressed against the circumferential position is smaller than the contact pressure at positions other than the circumferential position. The cleaning device (3), wherein the cleaning member is a cleaning blade in (1) or (2), or the contact pressure of the cleaning blade on the image carrier in (3). A cleaning means for reducing the thickness of a portion of the blade corresponding to the circumferential position of the image carrier on which the vicinity of both ends of the charging roller abuts is smaller than the thickness of other portions. (4) Or in the above (3), means for reducing the contact pressure of the cleaning blade with the image carrier is provided by: The cleaning device (5), wherein a free length of a portion corresponding to a circumferential position of the image carrier with which the vicinity of both ends of the electric roller abuts is longer than free lengths of other portions; In the method (3), the means for reducing the contact pressure of the cleaning blade against the image carrier is a surface of a portion of the blade corresponding to the circumferential position of the image carrier where the vicinity of both ends of the charging roller abuts. A cleaning device (6) or an image carrier, wherein the roughness is increased.
In an image forming apparatus provided with a charging roller to which a charging bias is applied while abutting on the charging roller and a cleaning member for removing transfer residual toner on the image bearing member, the image bearing member in which a portion near both ends of the charging roller abuts on A cleaning device for an image forming apparatus, wherein a friction coefficient of a pressure contact surface of a cleaning member pressed against a circumferential position is made smaller than a friction coefficient of a pressure contact surface of a cleaning member other than the circumferential position. 7) Or, detachable from the image forming apparatus main body including at least the image carrier, a charging roller to which a charging bias is applied while being in contact with the image carrier, and a cleaning member for removing transfer residual toner on the image carrier. In the process cartridge, the cleaning roller is pressed against the circumferential position of the image carrier where the portions near both ends of the charging roller abut. A cleaning device (8) for a process cartridge detachable from an image forming apparatus main body, wherein a friction coefficient of a pressing surface of the member is made smaller than a friction coefficient of a pressing surface of the cleaning member at a position other than the circumferential position. ) Or (7) or (8) above
Means for reducing the coefficient of friction between the cleaning blade and the image carrier, a portion of the blade corresponding to the circumferential position of the image carrier in contact with the vicinity of both ends of the charging roller has a low friction coefficient. A cleaning device (9), which is formed by coating or bonding a material;
Alternatively, in the above-mentioned (7) or (8), the means for reducing the friction coefficient between the cleaning blade and the image carrier may be such that the blade is positioned at a position in the circumferential direction of the image carrier where the vicinity of both ends of the charging roller abuts. The cleaning device (10), characterized in that a lubricant having a higher lubricity than other circumferential positions is applied, or the cleaning member (1) or (2), A cleaning device (11),
Alternatively, in the above (11), the means for reducing the contact pressure of the fur brush with the image carrier corresponds to the circumferential position of the image carrier where the vicinity of both ends of the charging roller of the fur brush abuts. In the cleaning device (12) or the device (11), the contact density of the fur brush on the image bearing member is reduced, in which the density of implanted hairs at the portion is made smaller than the density of implanted hairs at other portions. The means
A cleaning device (13) characterized in that the fur brush has a thinner fur at a portion corresponding to a circumferential position of the image carrier where the vicinity of both ends of the charging roller abuts, than a fur at other portions. Or means for reducing the contact pressure of the fur brush against the image carrier in the above (11), wherein the fur brush has a circumferential position on the image carrier at which both ends of the charging roller abut. A cleaning device (14), wherein the length of the fur of the part corresponding to (c) is shorter than the length of the fur of the other part.
Alternatively, in the above (11), the means for reducing the contact pressure of the fur brush with the image carrier corresponds to the circumferential position of the image carrier where the vicinity of both ends of the charging roller of the fur brush abuts. The cleaning device is characterized in that a spherical treatment is applied to each tip of fur at a portion to be cleaned.

With this configuration, the surface of the image carrier can be uniformly worn as viewed in the axial direction.
This contributes to a longer life.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a main portion for explaining the present invention, wherein reference numeral 1 denotes an image carrier, reference numeral 2 denotes a charging roller, and reference numeral 6 denotes a cleaning blade. As described above, the portion where the image carrier is easily scraped is a portion near both ends of the charging roller 2 as shown by a dotted line in the drawing.

Therefore, in this apparatus, the contact pressure between the edge of the contact of the cleaning blade 6 with the image carrier and the image carrier at the portion between the dotted lines is reduced.

FIG. 2 and FIG. 3 are side sectional views of the cleaning blade in this case. The cleaning blade 6 is attached to a support member 13 made of a rigid material such as metal by integral molding, and a contact edge of the cleaning blade 6 with the image carrier has a thickness of d as shown in FIG. It has become.

The thickness e of the edge of the blade 6 corresponding to the portion sandwiched by the dotted line is formed smaller than the thickness d. In the blade shown,
The thin portion at the leading edge is formed thin as a whole up to a portion close to the support member 13.

The range (as viewed in the longitudinal direction) where the blade edge is formed to be thin as described above will be examined. In the charging roller having the above-described configuration, the swelling of the sagging portion that occurs near both ends of the resistance layer 20 is caused by, for example, the resistance layer 20.
If the thickness of about 100μm, the longitudinal direction 1-2mm
The width is several hundred μm at the peak. In this case, the above-mentioned minute gap h is formed with a width of about 3 mm, although it depends on the swell amount.

Accordingly, the width of the portion where the contact pressure is reduced as described above is as described above in consideration of the processing of the charging roller 2 and the cleaning blade 6 with respect to the image carrier 1, mounting errors, and movement in the longitudinal direction. Even when the width of the minute gap h is about 3 mm, it is necessary to form a thin portion of about 13 mm on both sides of the gap width, that is, about 5 mm. Further, in order to reduce the contact pressure with a width of 13 mm, it is actually necessary to reduce the blade thickness in a longer range at the blade edge.

In the above-described roller in which the end portion of the charging roller is cut to remove the dripping portion, the discharge area width varies depending on the spring pressure and the conductive layer, but the discharge area width is 1 mm.
The thickness is usually about or less, and the thin part is about 11
It can be fixedly set to about mm. Of course, also in this case, in order to form the thin portion, it is necessary to further increase the length in the blade edge direction.

As described above, by selectively lowering the contact pressure of the cleaning blade with respect to the portion of the image carrier that is easily shaved, the wear amount of the image carrier can be made uniform over the entire length of the blade edge. It is effective in extending the life of the device. The same function and effect can be obtained with an adhesive-type cleaning blade, but it is difficult to locally adjust the thickness by centrifugal molding as a blade molding method. Therefore, the integrally molded cleaning blade as described above is appropriate. is there.

FIGS. 4 and 5 are front views of a cleaning blade showing another embodiment.
2 shows a state where the blade 6 is attached.
In FIG. 4, the free length f of the blade 6 in the portion of the support member 13 corresponding to the portion shown by hatching in FIG. 1 is longer than the free length g of the other portions. It is.

It will be readily understood that such a configuration makes it possible to reduce the contact pressure of the cleaning blade on the hatched portion, that is, on the portion of the image carrier that is easily shaved. Even in this case, it is needless to say that it is necessary to widen the f-part width having a longer free length than the necessary contact pressure reduction area.

In FIG. 5, a free length portion f is formed by uniformly cutting the portion inside the contact pressure reducing area. It can be easily understood that the same operation as that of the above embodiment can be obtained by such a configuration. In addition, the support member has a simple structure of the support member and is easy to mold the blade, and the setting of the contact pressure reducing area does not need to be set as precisely as in the above embodiment. Further, the cleaning blade can be adapted to both an adhesive type and an integral molding type.

FIG. 6 is a front view of a cleaning blade showing still another embodiment. In this case, a tape 14 having a small coefficient of friction, for example, made of PTFE or the like is attached to a portion of the blade 6 attached to the support member 13 corresponding to the hatched portion in FIG. Or it has a coating. The thickness of the tape or the coating is desirably 20 μm or less in consideration of the cleaning property of the boundary with the non-adhered portion, and is desirably 10 μm or less in view of the recent tendency to reduce the diameter of the toner.

With such a configuration, the contact pressure of the cleaning blade at a portion where the image carrier is easily shaved can be substantially reduced, and this is effective in extending the life of the image carrier. Further, in this case, only the necessary minimum length in the blade edge direction, for example, the thin portion width 13 mm, 11 m
m, it is possible to accurately control the abrasion reduction width.

FIG. 7 is a front view of a cleaning blade showing still another embodiment. In this method, for example, graphite fluoride is applied to the blade edge as a lubricant, and silicon resin fine particles 15 having better lubricating performance are applied to the blade edge corresponding to a portion where the image carrier is easily shaved. It has been applied. The lubricating material is not limited to the above-described one, and any material may be used as long as the lubricating property of the portion indicated by reference numeral 15 is better than those of the other portions.

With this configuration, it is effective to prevent the image carrier from being excessively scraped and to prevent the blade from being turned up.

FIG. 8 is a front view of a cleaning blade showing another embodiment. In this one,
The surface of the edge portion of the blade 6 corresponding to the part of the image carrier that is likely to slip is formed on the rough surface 17 to reduce the frictional force.

When viewed from the surface roughness, the contact surface of the blade other than the portion where the image carrier is easily scraped is almost zero in terms of the ten-point average roughness (R _z ). The surface roughness of the blade edge facing the surface portion of the image carrier that is easily shaved is formed as a rough surface with _Rz = 1 to 3 μm.

By forming such a rough surface,
The action of the roughened portion of the blade edge rubbing against the surface of the image carrier is reduced, so that excessive shaving of the image carrier is reduced, and the life of the image carrier can be extended.

The above-mentioned surface roughness is appropriate. If the surface roughness is larger than this, the toner that has reached the blade passes through, and if the surface roughness is smaller than this, the effect of alleviating rubbing is lost. It was confirmed that a rough surface was formed to such an extent as described above, and that the contact pressure was set at a linear pressure of 20 to 40 g / cm, whereby a good anti-scraping effect was obtained.

This embodiment is suitable for a case where the cleaning blade is formed integrally with the supporting member. According to this, at the time of molding, a rough mold surface is previously formed at a predetermined position in a mold for molding, and a material is injected, so that the rough surface position can be accurately set without special post-processing.

FIG. 9 is a front view showing a configuration in which a fur brush is used as a cleaning member. The fur brush 25 implants the fur 24 on the shaft 23, arranges the fur 24 in the cleaning device so that the fur contacts the image carrier, rotates the fur 24, and scrapes off the residual toner on the image carrier. It is composed.

In the illustrated cleaning member, the fur on the side of the cleaning member 25 corresponding to the portion of the image carrier that is easily scraped, and the flocking density at the portion corresponding to the arrows k and m in the drawing are reduced. .

Since the shaving of the image carrier by the fur brush is almost proportional to the number of times of contact and the contact area with the image carrier, the above-described structure is used for a portion where the image carrier is easily shaved. Reduces the rubbing action of the fur brush
Excessive shaving of the specific portion of the image carrier can be alleviated to extend its life.

In the above case, the flocking density of the specific portion of the fur brush is reduced, but the point is that the portion of the fur opposed to the specific portion of the image carrier may be weakened in contact with the image carrier. Therefore, the same operation and effect can be obtained even if the thickness of the flocked portion in the range k and m is smaller than that of the fur in the other portion.

In the embodiment shown in FIG. 10, in the fur brush basically having the same structure as that shown in FIG. 9, the fur free length portion corresponding to the reference numerals k and m is used. The length is shorter than the other parts. It will be readily understood that such a configuration can reduce the contact pressure of the predetermined portion to the image carrier.

In the embodiment shown in FIG. 11, in the fur brush basically having the same structure as that shown in FIG. This is configured so that the surface of the image carrier is hardly damaged. Although not shown, the symbols k and m
It is also possible to configure the fur of the part with a material having a lower coefficient of friction than the fur of the other part. Such a method is effective in preventing the image carrier from being excessively scraped and extending the life thereof. Of course, it is also possible to apply two or more of the above means to one brush.

[0043]

As described above, according to the present invention,
In an image forming apparatus including an image carrier, a charging roller that comes into contact with the image carrier, and a cleaning member that comes into contact with the image carrier, a portion in the vicinity of an end of the charging roller comes into contact with a circumferential portion on the image carrier that makes contact. The contact pressure of the cleaning member on the image carrier may be smaller than the contact pressure on other parts,
Alternatively, since the friction is reduced, the amount of shaving on the surface of the image carrier can be made uniform as a whole, which has a remarkable effect on extending the life of the image carrier.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a relational arrangement of an image carrier, a charging roller, and a cleaning blade in an image forming apparatus.

FIG. 2 is a side view of a normally thick portion of a cleaning blade showing an embodiment of the present invention.

FIG. 3 is a side view of the thin-walled portion.

FIG. 4 is a front view of a cleaning blade showing another embodiment of the present invention.

FIG. 5 is a front view of a cleaning blade showing another embodiment.

FIG. 6 is a front view of a cleaning blade showing still another embodiment.

FIG. 7 is a front view of a cleaning blade showing still another embodiment.

FIG. 8 is a front view of a cleaning blade showing still another embodiment.

FIG. 9 is a front view of a fur brush showing another embodiment.

FIG. 10 is a front view of a fur brush showing still another embodiment.

FIG. 11 is a front view of a fur brush showing still another embodiment.

FIG. 12 is a schematic side sectional view of a process cartridge of an image forming apparatus suitable for applying the present invention.

FIG. 13 is a partially enlarged cross-sectional view showing a configuration of a charging roller.

FIG. 14 is a side view showing a state where the charging roller is arranged opposite to the image bearing member;

FIG. 15 is a partially enlarged cross-sectional view showing a configuration of a charging roller having another configuration.

FIG. 16 is a side view showing a state where the charging roller is arranged opposite to the image carrier;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image carrier 2 Charging roller 6 Cleaning blade 13 Support member 14 Low friction coefficient tape or coating layer 15 Low friction member 16 Lubricant 17 Low friction member 18 Core metal 19 Conductive layer 20 Resistance layer 21 Bearing 22 Spring h Micro gap

Claims (15)

[Claims] 1. An image forming apparatus comprising: an image carrier; a charging roller to which a charging bias is applied while being in contact with the image carrier; and a cleaning member for removing transfer residual toner on the image carrier. The image forming apparatus according to claim 1, wherein a contact pressure of a cleaning member that presses against a circumferential position of the image carrier with which the portions near both ends contact is smaller than a contact pressure at a position other than the circumferential position. Cleaning device. 2. An image forming apparatus main body comprising at least an image carrier, a charging roller to which a charging bias is applied while being in contact with the image carrier, and a cleaning member for removing transfer residual toner on the image carrier. In the process cartridge, the contact pressure of the cleaning member that presses against the circumferential position of the image carrier where the both ends of the charging roller contact with each other may be smaller than the contact pressure at positions other than the circumferential position. A cleaning device for a process cartridge. 3. The cleaning device according to claim 1, wherein the cleaning member is a cleaning blade. 4. A means for reducing the contact pressure of the cleaning blade against the image carrier, the thickness of a portion of the blade corresponding to the circumferential position of the image carrier contacting the vicinity of both ends of the charging roller. 4. The cleaning device according to claim 3, wherein the thickness is smaller than the thickness of the portion. 5. A device for reducing the contact pressure of a cleaning blade against an image carrier, comprising: setting a free length of a portion of the blade corresponding to a circumferential position of the image carrier on which the vicinity of both ends of the charging roller abuts. 4. The cleaning device according to claim 3, wherein the length is longer than the free length of other portions. 6. A means for reducing the contact pressure of the cleaning blade against the image carrier, the surface roughness of a portion of the blade corresponding to the circumferential position of the image carrier contacting the vicinity of both ends of the charging roller. 4. The cleaning device according to claim 3, wherein the surface roughness is made larger than the surface roughness of other parts. 7. An image forming apparatus comprising: an image carrier; a charging roller to which a charging bias is applied while being in contact with the image carrier; and a cleaning member for removing transfer residual toner on the image carrier. The friction coefficient of the pressure contact surface of the cleaning member pressed against the circumferential position of the image carrier where the portions near both ends are in contact with each other is set to be smaller than the friction coefficient of the pressure contact surface of the cleaning member at positions other than the circumferential position. A cleaning device for an image forming apparatus. 8. An image forming apparatus main body including at least an image carrier, a charging roller to which a charging bias is applied while being in contact with the image carrier, and a cleaning member for removing transfer residual toner on the image carrier. In the process cartridge, the friction coefficient of the pressure contact surface of the cleaning member pressed against the circumferential position of the image carrier where the portions near both ends of the charging roller contact each other, the friction coefficient of the pressure contact surface of the cleaning member at positions other than the circumferential position A cleaning device for a process cartridge detachable from an image forming apparatus main body, wherein the cleaning device is smaller than the cleaning device. 9. A means for reducing the coefficient of friction between the cleaning blade and the image carrier includes a low friction coefficient at a portion of the blade corresponding to the circumferential position of the image carrier where the vicinity of both ends of the charging roller abuts. The cleaning device according to claim 7 or 8, wherein the material is coated or adhered. 10. A means for reducing the coefficient of friction between the cleaning blade and the image carrier, wherein the blade is provided with another circumferential position at the circumferential position of the image carrier at which both ends of the charging roller contact. The cleaning device according to claim 7 or claim 8, wherein a lubricant having higher lubricity is applied. 11. The cleaning device according to claim 1, wherein the cleaning member is a fur brush. 12. A means for reducing the contact pressure of the fur brush on the image carrier, wherein the flock density of a portion of the fur brush corresponding to the circumferential position of the image carrier in contact with the vicinity of both ends of the charging roller is reduced. The cleaning device according to claim 11, wherein the density is smaller than the density of the other portion. 13. A fur brush having means for reducing the contact pressure of the fur brush on the image carrier, the fur brush having a portion corresponding to the circumferential position of the image carrier on which the vicinity of both ends of the charging roller abuts. 12. The cleaning device according to claim 11, wherein the thickness is made smaller than the thickness of the fur in other parts. 14. A means for reducing the contact pressure of the fur brush on the image carrier, the fur brush being provided at a position corresponding to the circumferential position of the image carrier on which the vicinity of both ends of the charging roller abuts. The cleaning device according to claim 11, wherein the length is shorter than the length of the fur of the other part. 15. A means for reducing the contact pressure of the fur brush with the image carrier, the fur brush being located at a position corresponding to the circumferential position of the image carrier with which the vicinity of both ends of the charging roller abuts. The cleaning device according to claim 11, wherein each tip is subjected to spherical processing.