JPH10142898A - Electrifier for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of an abnormal image due to electrification unevenness occurring when an electrifying roller case is pressed in the press- contact direction of an electrifying roller with a photoreceptor. SOLUTION: When first and second pressurizing arms 41 and 42 exert a pressing force on the electrifying roller case 16, to bring the electrifying roller 2 into press-contact with the photoreceptor 10, pressurizing springs 18 and elastic members 8 are compressed together to exert pressing forces F2 and F3 against the pressing force F1 by the pressurizing arms 41 and 42. Even if the pressing force F1 is excessive, a part of the excessive pressing force is absorbed because the pressurizing springs 18 and the elastic members 8 are compressed, so that the electrifying roller 2 comes into well-balanced press-contact with the photoreceptor 10. Further, a cleaning pad 25 is not greatly curved because the excessive pressing force is not exerted. Thus, the contact unevenness of the cleaning pad 25 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device of an image forming apparatus provided with pressing means for pressing a charging roller against a photosensitive member by applying a pressing force to a charging roller case for rotatably holding the charging roller.

[0002]

2. Description of the Related Art In recent years, an image forming apparatus such as a copying machine or a facsimile machine has an image forming unit in which a photosensitive member, a developing device, a charging device, and the like are housed in an integrated case, thereby making the entire image forming device compact. There is something that was made to be. Many charging devices incorporated in such an image forming unit use a charging roller to attach ions or electrons to the surface of a photoreceptor, thereby charging the surface to a constant potential. FIG. 8 shows an example of a charging device using such a charging roller.

In this charging device, shaft portions on both sides of a charging roller 51 are held by a charging roller case 53 via bearings 52 so as to be vertically movable, and between each bearing 52 and the inner surface of the charging roller case 53. Each of the springs 54 is interposed. Above the charging roller case 53, a pair of pressing arms 55, 55 for pressing are provided, and by depressing each of the pressing arms 55, the charging roller case 53 is pressed downward, and a spring is provided. 5
4, 54 are compressed and the charging roller 5
1 is pressed against the surface of the photoreceptor 56, and the surface of the photoreceptor 56 is charged while the charging roller 51 rotates with the rotating photoreceptor 56.

As shown by a virtual line in FIG. 8, a charging device includes a charging roller 51 on a lower surface of a charging roller case 53.
In some cases, a cleaning member 57 made of a sponge or the like that cleans the surface of the charging roller 51 is attached to the surface facing the surface of the charging roller 51 when the surface of the charging roller 51 slides. When the charging roller case 53 is further pressed down by the pressing arms 55 even after the charging roller 51 is pressed against the surface of the photosensitive member 56, the cleaning member 5
By contacting the surface of the charging roller 51 with the surface of the charging roller 51 and slidingly contacting the surface, it is possible to clean the adhered matter such as the toner adhered to the surface.

[0005]

However, since the charging device incorporated in the image forming unit tends to be made of resin for many parts in consideration of weight reduction and reuse of materials, for example, When the charging roller case is formed of a synthetic resin, a problem may occur. That is, in FIG. 8, when the pressing arms 55, 55 on both sides are pushed down and both ends of the charging roller case 53 are pressed downward, when the charging roller case 53 is made of resin, both ends thereof are lowered. Easy to bend in a folded state.

As a result, both ends of the charging roller 51 come into strong contact with the photosensitive member 56, and a nip having a certain width is formed between the charging roller 51 and the photosensitive member 56 at both ends. In the central portion in the direction, a portion having a small nip width may be formed, or a non-contact portion may be formed in some cases, so that the photosensitive member 56 may not be uniformly charged, which may cause inconvenience. .

On the other hand, in the case of a charging device in which the cleaning member 57 is attached to the lower surface of the charging roller case 53, if both ends of the charging roller case 53 bend downward by pressing down the pressing arm 55, the charging device is attached to the lower surface. Since the cleaning member 57 is also deformed in accordance therewith, the cleaning member 57 does not make uniform contact with the charging roller 51 in the longitudinal direction.

In such a state, the charging roller 51
In addition to the insufficient cleaning of the surface of the charging roller 51, minute toner or the like remains on the surface of the charging roller 51, which causes uneven charging on the photoconductor 56 and easily causes an abnormal image. Further, when the cleaning member 57 has an extremely strong sliding contact with the charging roller 51 due to the above-described uneven contact, toner filming may occur on the charging roller 51 at the portion.

In such a case, in a conventional charging device, a serviceman has taken measures such as cleaning the charging roller and the like and replacing parts. Therefore, when such a state that a serviceman needs to be called frequently occurs, it is troublesome to deal with the situation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and does not cause an irregular image due to uneven charging when the charging roller case is pressed in a direction in which the charging roller is pressed against the photosensitive member. The purpose is to be.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a charging roller for charging a photosensitive member while being rotated while being pressed against a rotating photosensitive member, and the charging roller being rotatable. A charging roller case to be held; an urging means interposed between the charging roller case and the charging roller to urge the charging roller in a direction away from the charging roller case; and a charging roller for applying a pressing force to the charging roller case. A pressing means for pressing the charging roller against the photosensitive member by pressing the pressing means via the urging means, wherein an elastic member is provided between the charging roller case and the pressing means, and the pressing means is provided. Is applied to the charging roller case via the elastic member.

With this configuration, when the pressing means applies a pressing force to the charging roller case to press the charging roller against the photosensitive member, the urging means interposed between the charging roller case and the charging roller; The elastic member provided between the charging roller case and the pressing means is compressed together,
A force opposing the pressing force of the pressing means is applied. If the pressing means is excessively pressed, the elastic member is compressed together with the urging means to absorb a part of the excessive pressing force, so that the charging roller is pressed against the photosensitive member in a well-balanced manner. As a result, charging unevenness can be prevented.

In the charging device of the image forming apparatus, a cleaning member that slides on the surface of the charging roller and cleans the surface is provided on the charging roller in a pressing direction of the charging roller case by pressing means on the inner surface of the charging roller case. It is preferable to provide the charging roller over the entire length of the charging roller in the axial direction.

[0014] Then, when the pressing means applies a pressing force to the charging roller case to press the charging roller against the photosensitive member and press the cleaning member against the charging roller, the cleaning member presses excessively against the charging roller. Even in such a case, the urging means interposed between the charging roller case and the charging roller, and the elastic member provided between the charging roller case and the pressing means are both pressed by the pressing means. And a part of the pressing force of the pressing means is absorbed by compression.

Therefore, the cleaning member does not deform together with the charging roller case due to an excessive pressing force, so that the cleaning member contacts the charging roller substantially uniformly in the longitudinal direction. For this reason, no hit unevenness occurs, so that good cleaning properties can be obtained, thereby preventing charging unevenness and preventing occurrence of an abnormal image. Further, it is possible to prevent toner filming from occurring on the surface of the charging roller.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view partially showing the vicinity of a charging roller of a charging device of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 shows an image forming unit in which the charging device is housed in a cartridge. Perspective view, FIG. 3
FIG. 2 is a schematic configuration diagram showing the image forming unit together with a fixing device and the like.

In this image forming apparatus, as shown in FIG. 3, an image forming section is formed in a cartridge-shaped image forming unit 1, which can be detachably mounted on an apparatus main body (not shown). I have. A transfer / separation device 20 having a transfer roller 23 is provided below the image forming unit 1, and the transfer / separation device 20 can rotate about a rotation fulcrum 21. A pressure roller 31 is located on the left side of the transfer / separation device 20 in FIG.
And a heating roller 32 are provided.

The image forming unit 1 is made of synthetic resin.
As shown in FIG. 3, a storage case is formed by the photoreceptor surrounding case 6 and the upper cover 7, and inside the photoreceptor 1 as shown in FIG.
0, a charging roller 2 constituting a charging device, and a developing device 3
And a cleaning device 4, a toner recycle belt 5 for feeding the residual toner collected by the cleaning device 4 to the developing device 3, a toner conveying screw 11, an agent stirring member 12, and the like.

The upper cover 7 is attached so as to cover the photoreceptor 10 and the case 6 around the photoreceptor, and prevents the hand of an operator or a service person from touching the photoreceptor 10 and the charging roller 2. . And this imaging unit 1
Is in a state where it is mounted on a predetermined position of the apparatus main body (FIG. 3).
(Position shown in FIG. 3), the photosensitive member 10 can be rotated in the direction of arrow A by a driving source (not shown).

As shown in FIG. 4, the charging roller 2 is a conductive rubber (e.g., epichlorohydrin rubber) 2b having a small hygroscopic property and a stable resistance value on the outer periphery of a metal core 2a.
And the conductive rubber 2b
By applying a high voltage to the cored bar 2a while the surface of the photoconductor 10 is in contact with the surface of the photoconductor 10 (FIG. 3),
Is uniformly charged.

Both ends of the core 2a of the charging roller 2 are
The bearings 14 and 15 are rotatably held by the bearings 14 and 15, respectively, and have vertically long projections 14a, 14a and 15a, 15a (all of which are shown in a simplified manner) on both left and right surfaces. Each of the protrusions is slidably fitted into a corresponding one of the vertically long guide grooves 16a formed in the charging roller case 16 so as to be movable in the vertical direction.

The bearings 14 and 15 and the charging roller case 1
As shown in FIG. 1, pressure springs 18, 18 are interposed between the inner surface 16c and the inner surface 16c of the photosensitive member 6, and the charging roller 2 is applied to the photoreceptor 10 via the bearings 14, 15 by the urging force thereof. It can be pressed by pressing force.

On the inner surface 16c of the charging roller case 16,
A cleaning pad 25 which is a cleaning member for slidingly contacting the surface of the charging roller 2 to clean the surface;
For example, with a double-sided tape or the like. The cleaning pad 25 includes a first pressure arm 41 and a second pressure arm 42, which will be described later, on the inner surface of the charging roller case 16.
The inner surface 16c facing the charging roller 2 in the pressing direction (arrow C) of the charging roller case 16 by (pressing means)
And over the entire length of the charging roller 2 in the axial direction.

Therefore, the charging roller 2 keeps in contact with the photoreceptor 10 during the charging operation, so that the surface of the photoreceptor 10 is liable to be stained by minute toner adhering to the surface of the photoreceptor 10 to cause uneven charging. By bringing the cleaning pad 25 into pressure contact with the cleaning pad 25, the entire surface of the cleaning pad 25 can be cleaned and the toner can be removed, so that charging unevenness that occurs when the charging roller 2 becomes dirty can be prevented.

Further, the charging roller case 16 and the first and second
Between the pressing arms 41 and 42, elastic members 8, which are, for example, springs, are provided via a plate-shaped intermediate member 9, and the pressing force from the first and second pressing arms 41 and 42 is applied. The intermediate member 9 and the elastic members 8 on both sides are applied to the charging roller case 16. The intermediate member 9
Are arranged parallel to the upper surface of the charging roller case 16, as is apparent from FIG.

As shown in FIG. 4, spring receivers 6a and 6a are formed on both ends of the inner surface 16c of the charging roller case 16 in the longitudinal direction and on the front and rear surfaces of the photoreceptor surrounding case 6, respectively.
Pushing springs 26, 26 are interposed between the charging roller case 6a and the charging roller case 16 respectively. Each push-up spring 26
If a circular convex portion is formed on at least one of the spring receiver 6a on the photosensitive member surrounding case 6 side and the inner surface 16c on the charging roller case 16 side and press-fit there, the charging roller 2 can be unitized. When removing in the state, the push-up spring 26 can be prevented from falling off.

Next, a contact / separation mechanism for bringing the charging roller 2 into and out of contact with the photosensitive member 10 will be described. The first and second pressure arms 41 and 42 both function as pressing means, and oscillates by pressing the upper surface of the charging roller case 16 at one end to press the charging roller 2 toward the photoconductor 10. A possible arm.

As shown in FIG. 2, the first pressure arm 41 and the second pressure arm 42 are fixed at the same phase in the rotation direction at an interval on an arm holding shaft 43. Both ends of the shaft 43 are rotatably supported by a body front side plate and a body rear side plate (not shown) of the image forming apparatus via bearings or the like. Therefore, when the arm holding shaft 43 is rotated clockwise or counterclockwise in the figure, the first and second pressing arms 41 and 42 simultaneously rotate in the same direction by the same amount.

The second pressure arm 42 has a cam abutting portion 42a extending at an end opposite to the side in contact with the charging roller case 16, and the lower surface thereof has an eccentric cam 44 having an eccentric shape shown in FIG. Contact. And the second pressure arm 4
The arm pressing spring 4 is provided between the upper surface of the cam contact portion 42a and the spring holder 46 fixed to the apparatus main body.
7, the cam contact portion 42a is pressed against the eccentric cam 44 by the urging force of the arm pressing spring 47.

With such a configuration, when the eccentric cam 44 is rotated by a driving means such as an electromagnetic clutch, the center of the shaft 45 that integrally supports the cam from the position where the eccentric cam 44 contacts the second pressing arm 42. The second pressing arm 42 swings in the direction indicated by the arrow E together with the arm holding shaft 43 in accordance with the change in the distance up to this distance, and is fixed to the arm holding shaft 43 as shown in FIG. The first pressure arm 41 also swings by the same amount in the same direction as the second pressure arm 42. Therefore, the first and second pressure arms 41,
When the upper surface of the intermediate member 9 shown in FIG. 1 is pressed by 42, the charging roller case 16 is lowered via the elastic members 8, 8, whereby the charging roller 2 is pressed against the photosensitive member 10.

Then, the first and second pressing arms 41,
If the pressure applied to the intermediate member 9 by the intermediate member 9 is weakened or separated from the upper surface of the intermediate member 9, the charging roller case 16 moves in the direction away from the photoconductor 10 by the urging force of the pair of springs 26, 26, and the charging roller 2 moves away from the photoconductor 10. In FIG. 2 (see also FIG. 3), reference numeral 19 denotes a holder of a static elimination lamp (not shown), which is formed of a highly rigid metal or the like. The holder 19 is fixed in a state parallel to the arm holding shaft 43.

Next, the image forming operation of the image forming apparatus thus configured will be briefly described. First, as shown in FIG. 3, the image forming unit 1 is set at a predetermined position in the apparatus main body, and the eccentric cam 44 is rotated by a predetermined amount to move the first and second pressing arms 41 and 42 in the direction of arrow E. The charging roller 2 is pressed against the photoreceptor 10 by rotating and pressing down the charging roller case 16 (the position shown in FIG. 6).

When the image forming operation is started in this state,
The surface of the photoconductor 10 is neutralized by irradiating a neutralizing light from a neutralizing lamp (not shown), and its surface potential is averaged to a reference potential of, for example, 0 to -150V. Next, a high voltage is applied to the charging roller 2 which is in contact with the surface of the photoconductor 10 to charge the photoconductor 10, and the surface potential is set to, for example, about -1100V. Then, the charged potential surface is exposed to light from an exposure unit to form a latent image portion having an image surface potential of, for example, 0 to -290 V.

When the photosensitive member 10 rotates in the direction indicated by the arrow A, the latent image portion is developed by the developing sleeve 13 of the developing device 3.
, The toner held on the surface of the developing sleeve 13 to which a bias of about -800 V is applied to the latent image portion, and the latent image portion is developed to form a toner image (visible image). ).

On the other hand, the transfer paper P is fed from a paper feed unit (not shown), and the leading end of the transfer paper P and the leading end of the toner image on the photoconductor 10 coincide with each other at the position of the transfer roller 23. The toner image on the photoconductor 10 is transferred to the transfer paper P by the transfer roller 23 with the timing adjusted by the registration roller pair 24. The transfer paper P is conveyed between the pressure roller 31 and the heating roller 32 of the fixing device 30, where the toner is fused (transferred) by heat and pressure, and is discharged to a paper discharge tray or the like outside the apparatus. Is done.

The residual toner remaining on the photoreceptor 10 after the image transfer is scraped off by the cleaning blade 33 of the cleaning device 4, and the surface of the photoreceptor 10 is in a state where the toner is hardly adhered. Move on to the image forming process. The residual toner collected by the cleaning device 4 is conveyed to the developer agitating section 27 of the developing device 3 by the recycle belt 5, and the developer agitating member 28
And supply to the developing sleeve 13 again for recycling. In FIG. 3, reference numeral 29 denotes a cleaning blade 33.
This is a holder for holding. The above is the basic operation of the image forming apparatus.

Next, the positional relationship between the charging roller 2 and the charging roller case 16 of the image forming unit 1 and the first and second pressing arms 41 and 42 during each operation will be described with reference to FIGS. I do. FIG. 5 shows that the charging roller 2 is
0 shows a state where charging is not performed, and at this time, the first and second pressure arms 41 (FIG. 4), 42
Is rotated by the eccentric cam 44 to a position where the tip end is the highest, and a pair of push-up springs 26, 2
6 (FIG. 4), the charging roller case 16 is pushed upward away from the photoconductor 10, and
Are separated from the photoconductor 10.

During the charging operation, the eccentric cam 44 rotates to the position shown in FIG. 6, so that the first and second pressing arms 41 and 42 are moved to the positions shown in the figure according to the amount of eccentricity of the eccentric cam 44. It swings around the holding shaft 43 in the direction of arrow E. In this position, the charging roller case 16 is pushed down by the first and second pressure arms 41 and 42 against the urging force of the push-up spring 26 (FIG. 4). Accordingly, the charging roller 2 is pushed down by the front and rear pressure springs 18 (FIG. 4) via the front and rear bearings 14 and 15, and comes into pressure contact with the photoconductor 10 with a required pressing force. It becomes possible to rotate. In this state, the charging roller 2 charges the surface of the photoconductor 10. Note that, at the position shown in FIG.
Reference numeral 5 is located at a position distant from the charging roller 2.

Further, in the cleaning mode for cleaning the surface of the charging roller 2, the eccentric cam 44 rotates to the illustrated position as shown in FIG.
The pressing arms 41 and 42 further swing in the direction of arrow E about the arm holding shaft 43. As a result, the charging roller case 16 is further pushed down from the position shown in FIG. 6, so that the cleaning pad 25 comes into contact with the surface of the charging roller 2 as shown in the figure.

Therefore, the charging roller 2 is moved to the photosensitive member 10
When rotated in the direction of arrow B by the rotation in the direction of arrow A, the cleaning pad 2 pressed against its surface is rotated.
5 cleans and removes the toner adhering to the surface of the charging roller 2 by wiping it.
The above-described modes of the charging roller separation, charging, and charging roller cleaning are performed by the rotation of the eccentric cam 44 in accordance with the cam curve thereof.
When 42 swings, it is repeated alternately.

In the cleaning mode in which the cleaning pad 25 cleans the surface of the charging roller 2, the cleaning pad 25 comes into contact with the surface of the charging roller 2 so as to bite. , 42, the contact pressure of the cleaning pad 25 against the charging roller 2 becomes excessive.

In this case, the charging roller 2 which rotates while being pressed against the surface of the photoreceptor 10 becomes difficult to rotate due to the excessive pressing force received from the cleaning pad 25. Is more likely to occur. In this case, normal charging cannot be performed, and an abnormal image is generated. In addition, since the cleaning pad 25 comes into sliding contact with the charging roller 2 while being pressed against the charging roller 2 with an excessive contact pressure, toner filming occurs and charging performance is reduced.

However, the charging device of the image forming apparatus according to the present invention has a plate-like intermediate member 9 between the charging roller case 16 and the first and second pressing arms 41 and 42 as described with reference to FIG. Elastic members 8 and 8 are provided through
Since the pressing forces F1, F1 from the second pressing arms 41, 42 are applied to the charging roller case 16 via the elastic members 8, 8, the first and second pressing arms 4
Even if the pressing forces F1 and F1 applied by the cleaning rollers 1 and 42 are excessively large, an abnormal image or toner filming occurs because the cleaning pad 25 does not contact the charging roller 2 with an excessive contact pressure. Do not do.

That is, excessive pressing forces F 1, F 1 may be applied to the intermediate member 9 from the first and second pressing arms 41, 42 due to variations in component dimensions, mounting accuracy, and the like. However, the elastic members 8, 8 oppose the pressing force F1 via the intermediate member 9 to the force F3,
F3 is applied to the forces F2, F2 by the pressure springs 18, 18.
To work with.

Further, the elastic members 8, 8 are
Along with 8 and 18, a part of the displacement of the first and second pressing arms 41 and 42 in the pressing direction is absorbed by compressing. Therefore, it is possible to prevent the cleaning pad 25 from being pressed against the charging roller 2 with an excessive contact pressure, and to prevent the charging roller case 16 from being largely bent. It is possible to prevent occurrence of mining.

[0046]

As described above, according to the present invention, even if the pressing force of the pressing means against the charging roller case is excessive, the urging means interposed between the charging roller case and the charging roller can be used. The elastic member provided between the charging roller case and the pressing means is compressed together, and acts against the pressing force of the pressing means, and the urging means and the elastic member are compressed, Since a part of the excessive pressing force is absorbed, the charging roller is pressed against the photosensitive member in a well-balanced manner, so that charging unevenness can be prevented and an abnormal image can be prevented from being generated.

When the cleaning member for cleaning the surface of the charging roller is provided on the inner surface of the charging roller case facing the charging roller, the pressing force of the pressing means is excessive as described above. Also, since the urging means and the elastic member act against the pressing force to exert a force opposing the pressing force and absorb a part of the pressing force by compressing the charging roller case, the charging roller case may be greatly deformed. As a result, the charging roller contacts the photoconductor substantially uniformly over substantially the entire area in the longitudinal direction.

Therefore, since the charging roller does not slip on the photosensitive member and the cleaning member does not hit the charging roller, the charging unevenness is prevented, so that an abnormal image is not generated. Can be Further, it is possible to prevent toner filming from occurring on the surface of the charging roller. Further, since the cleaning property of the charging roller is improved, the life of the charging roller is prolonged and the life of the photoconductor is prolonged.

[Brief description of the drawings]

FIG. 1 is a front view showing a part of the vicinity of a charging roller of a charging device of an image forming apparatus according to an embodiment of the present invention in a partial cross section.

FIG. 2 is a perspective view showing an image forming unit in which the charging device is housed in a cartridge shape.

FIG. 3 is a schematic configuration diagram showing the image forming unit together with a fixing device and the like.

FIG. 4 is an exploded perspective view showing a configuration around a charging roller case of the image forming unit.

FIG. 5 is a schematic diagram showing a state where a charging device provided in the image forming unit in FIG. 3 is not performing a charging operation.

FIG. 6 is a schematic diagram showing a state where the charging device is performing a charging operation.

FIG. 7 is a schematic diagram showing a state in a cleaning mode for cleaning a charging roller of the charging device.

FIG. 8 is a front view showing an example of a charging device incorporated in a conventional image forming unit.

[Explanation of symbols]

 2: Charging roller 8: Elastic member 10: Photoconductor 16: Charging roller case 18: Pressure spring (biasing means) 25: Cleaning pad (cleaning member) 41: First pressure arm 42: Second pressure arm

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Watanabe 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Toshitaka Yamaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Share Inside Ricoh Company (72) Inventor Kenzo Tatsumi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Hiroshi Yoshinaga 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company ( 72) Inventor Takeo Suda 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Mayumi Ohori 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd.

Claims (2)

[Claims] 1. A charging roller for charging a photosensitive member while being rotated while being pressed against a rotating photosensitive member, a charging roller case for rotatably holding the charging roller, the charging roller case and the charging roller Biasing means interposed between and biasing the charging roller in a direction away from the charging roller case, and pressing the charging roller via the biasing means by applying a pressing force to the charging roller case. And a pressing unit for pressing the charging roller against the photoreceptor, an elastic member is provided between the charging roller case and the pressing unit, and a pressing force from the pressing unit is reduced. A charging device for an image forming apparatus, wherein the charging device is applied to the charging roller case via the elastic member. 2. The charging device according to claim 1, wherein a cleaning member that slides on the surface of the charging roller to clean the surface of the charging roller is provided by the pressing unit that presses the inner surface of the charging roller case. A charging device for an image forming apparatus, wherein the charging device is provided on a surface facing the charging roller in a pressing direction of a case over an entire length of the charging roller in an axial direction.