JP2003255671A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably electrify a photoreceptor drum and also to improve the maintability of an image forming apparatus. <P>SOLUTION: In an electrifying device 56, an electrifying roller 69 coated with electrification accelerating particles 72 by an applicable roller 70 is made to abut on the photoreceptor drum 12. An electrifying device 55 is separately provided in addition to it, so that electrification is stabilized. A drum developing cartridge 2 is constituted by integrally assembly the photoreceptor drum 12 and a developing device 16 into a housing 15. The drum developing cartridge 2 is constituted so as to be freely attachable/detachable to/from an image forming apparatus main body M, so that is can be easily replaced by opening/ closing a door 65. <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 charging device used in an image forming apparatus such as a copying machine, a printer and a facsimile, and an image forming apparatus provided with the charging device.

[0002]

2. Description of the Related Art FIG. 6 shows a schematic structure of a laser printer as an example of a conventional image forming apparatus.

A laser printer 201 shown in FIG. 1 includes a process cartridge 202, a sheet feeding and feeding device for feeding and feeding a recording material (paper or transparent film) 220 in a sheet feeding cassette (not shown), a laser scanner, and a fixing device 227. Etc.

In the laser printer 201, a recording material 220 housed in a paper feeding cassette (not shown) arranged below the laser printer 201 is fed by a paper feeding roller 221, and a pair of conveying rollers in guides 222 and 223. The sheets 224 and 225 convey the sheet to the vicinity of the photosensitive drum 203, which is an image carrier. The recording material 220 is then conveyed by a registration roller (not shown) to the transfer nip portion between the photosensitive drum 203 and the transfer roller 219, and the toner image formed on the surface of the photosensitive drum is transferred by the charging roller 219. To be done.

A developing device 210, a charging device, a cleaning device 211 and the like are arranged around the photosensitive drum 203 in the process cartridge 202.

The developing device 210 includes a developing sleeve 209.
And doctor blade, toner container, and stirring member 21
The surface of the developing sleeve 209 is coated with toner.

The charging device has a charging roller 204, a bearing portion 206 that supports the shaft 205 of the charging roller 204, and a pressure spring 207 that urges the bearing portion 206 downward. End (upper end) is chassis 2
It is fixed at 08. A charging nip portion 204 a is formed between the photosensitive drum 203 and the charging roller 204.

The above-mentioned recording material 220 having the toner image transferred on its surface is conveyed to the fixing device 227 along the guide 226, where the toner image is fixed on the surface. The fixing device 227 has a fixing roller 228 having a built-in heater and a pressure roller 229.

The recording material 220, on the surface of which the toner image is fixed by the fixing device 227, is conveyed along guides 230 and 231 and is discharged by the discharge roller pair 232 and 233.
The paper is discharged onto the paper discharge tray 234.

Further, the writing of the image signal to the photosensitive drum 203 is performed by reflecting a laser beam 215 emitted from a laser optical system (not shown) by a polygon mirror 217 attached to a motor 218, so that a reflection mirror is formed. Through 216, the surface of the photosensitive drum 203 after charging is scanned. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 203.

In the above structure, the entire charging device is arranged in the process cartridge 202.

[0012]

In the image forming apparatus (laser printer) as described above, there is a strong demand for stable output of high quality images.

Therefore, it has become important to charge the charging device more stably than ever before. Further, usability is also required, and it is necessary to improve low running cost and maintainability.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an image forming apparatus which can perform more stable charging, and have low running cost and improved maintainability. .

[0015]

The invention according to claim 1 is
An image forming apparatus for forming an electrostatic latent image on a surface of an image bearing member charged by a charging device and developing the electrostatic latent image by a developing device, comprising at least two charging devices.
The image carrier and the developing device are unitized to form a cartridge that is detachable from the main body of the image forming apparatus.
It is characterized by

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, at least two charging devices are arranged inside the image forming apparatus main body and outside the cartridge. Is characterized by.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, at least one of the charging devices includes a container accommodating charging promoting particles and a surface of the image carrier. It is characterized by comprising: a charging roller in contact with the charging roller; and a coating means for coating the charging roller with the charging promoting particles.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the container, the charging roller, and the coating unit constitute a detachable charging cartridge, and the charging cartridge is attached. The charging roller is urged toward the image carrier by a biasing means and the charging roller having the surface coated with the charging promoting particles is brought into contact with the surface of the image carrier.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In addition, in each of the drawings, components denoted by the same reference numerals have similar configurations or actions, and repeated description thereof will be appropriately omitted.

<First Embodiment> FIG. 1 shows a schematic structure of an electrophotographic laser printer as an example of an image forming apparatus according to the present invention.

A laser printer (hereinafter referred to as "image forming apparatus") 1 shown in FIG. 1 is a drum developing cartridge (cartridge) in which a photosensitive drum 12 as an image carrier and a developing device 16 are integrated (unitized). 2 is configured. The drum developing cartridge 2 is attachable / detachable to / from the image forming apparatus main body M, and the attachment / detachment can be easily performed by the user.

The image forming apparatus 1 shown in FIG. 1 is provided with a drum developing cartridge 2, a charging device 3, an exposing device 20, a fixing device 28, a paper feed cassette 21 and the like in an image forming device body M.

The photosensitive drum 12, which constitutes a part of the drum developing cartridge 2, is rotationally driven in the direction of arrow R1 at a predetermined process speed by a driving means (not shown).

The surface of the rotationally driven photosensitive drum 12 is charged by a charging device 3 having a first charging device 3A and a second charging device 3B.

Each of the first and second charging devices 3A and 3B has a charging roller that is in contact with the surface of the photosensitive drum 12, that is, a first charging roller 7 and a second charging roller 11. Both ends of the charging rollers 7 and 11 in the longitudinal direction are rotatably supported by bearings 6 and 10. These bearings 6 and 10 are attached to the tip end portions of the compression springs 5 and 9, and the base end portions of the compression springs 5 and 9 are fixed to the convex portions 4 and 8 of the frame 3a. The charging rollers 7 and 11 are urged by the compression springs 5 and 9 to be pressed against the surface of the photosensitive drum 12 with a predetermined contact pressure,
The photosensitive drum 12 is driven to rotate as the photosensitive drum 12 rotates in the direction of arrow R1. A charging bias is applied to the charging rollers 7 and 11 by a charging bias applying power source (not shown), whereby the surface of the photosensitive drum 12 is uniformly (uniformly) charged to a predetermined polarity and potential. The frame 3a is fixed to the image forming apparatus main body M with screws (not shown).

The surface of the photosensitive drum 12 after charging is
An electrostatic latent image is formed by the exposure device 20.

The exposure device 20 has a laser oscillator (not shown), a polygon mirror 20a, a reflection mirror 19, etc., and the laser beam 18 generated from the laser oscillator based on image information rotates at a high speed. 20
a, the surface of the photosensitive drum 12 is illuminated by being reflected by the reflection mirror 19. As a result, the charge on the irradiated (exposed) portion of the surface of the photosensitive drum 12 is removed and an electrostatic latent image is formed.

The electrostatic latent image described above is developed by the developing device 16 housed in the drum developing cartridge 2.

The developing device 16 directs the developing sleeve 13, a regulating blade (not shown) for regulating the layer thickness of the developer coated on the surface of the developing sleeve 13, and the developer in the developing container toward the developing sleeve 13. It has the stirring member 14 which conveys. A developing bias is applied to the developing sleeve 13 by a developing bias applying power source (not shown), whereby toner of the developer on the developing sleeve 13 is attached to the electrostatic latent image on the photosensitive drum 12, and the electrostatic latent image is formed. Is developed as a toner image.

The toner image thus formed on the photosensitive drum 12 is transferred onto the recording material S by the transfer roller 17. The recording material S is housed in a paper feed cassette 21 attached to the lower part of the image forming apparatus main body M, and the paper feed roller 2
The sheet is fed by 2 and conveyed by the conveying rollers 23, 24 to the registration rollers (not shown) along the guides 25, 26. The recording material S is temporarily stopped by the registration roller, and thereafter, the registration roller rotates in synchronization with the toner image on the photosensitive drum 12, whereby the photosensitive drum 1
2 is supplied to the transfer nip portion between the transfer roller 17 and the transfer roller 17. On the recording material S supplied to the transfer nip portion, the toner image on the photosensitive drum 12 is transferred by the transfer bias applied to the transfer roller 17 by the transfer bias applying power source (not shown).

After the toner image is transferred, the residual toner remaining on the surface of the photosensitive drum 12 is removed by a cleaning device (not shown), and the photosensitive drum 12 is used for the next image formation.

On the other hand, the recording material S after the transfer of the toner image is conveyed to the fixing device 28 along the conveying guide 27, where it is heated and pressed by the fixing roller 29 and the pressure roller 30. The image is fixed.

The recording material S after the toner image is fixed is guided by the guide 3
1 and 32, and the sheet is discharged onto a sheet discharge tray 35 formed on the upper surface of the image forming apparatus main body M by sheet discharge rollers 33 and 34. This completes the image formation.

Next, the drum developing cartridge 2 according to the first embodiment will be described in detail with reference to FIG. This figure is an enlarged vertical sectional view of the drum developing cartridge 2 as viewed from the same direction as in FIG.

As shown in the figure, the drum developing cartridge 2 comprises a housing 15, a photosensitive drum 12 and a developing device 16 built in the housing 15. Developing device 16
Has a developing container 16a, a developing sleeve 13, a regulating blade (not shown), and a stirring member 14. The developing container 16a is provided with an opening 16b at a portion facing the surface of the photosensitive drum 12, and the developing sleeve 13 is rotatably arranged in the opening 16b. The developing sleeve 13 is arranged such that its surface faces the surface of the photosensitive drum 12, and the closest position between them is the developing position. The developing sleeve 13 is rotatably driven in the direction of the arrow in FIG. 2 by a driving unit (not shown) with the developer carried on the surface thereof, and the regulation blade regulates the layer thickness of the developer coated on the surface. . The developer whose layer thickness is regulated is rotated by the developing sleeve 13 so that the photosensitive drum 1
2 is conveyed to the developing position facing the surface, and the developing sleeve 1
Toner 3 is attached to the electrostatic latent image on the photosensitive drum 12 by the developing bias applied from the developing bias applying power source to develop the toner image as a toner image.

The stirring member 14 has a stirring fin 14a fixed to the stirring shaft, and the stirring shaft is rotationally driven in the direction of the arrow in the figure by a driving means (not shown). As a result, the agitating fin 14a rotates, agitates the developer in the developing container 16a, and moves the developer toward the developing sleeve 13.

A part of the housing 15 projects toward the photosensitive drum 12 side to form an arm 15a. The arms 15a are arranged at positions corresponding to both ends of the photosensitive drum 12 in the longitudinal direction, and a bearing portion (not shown) is provided at the tip of each arm 15a. By these bearings, the shaft 12a of the photosensitive drum 12
Is rotatably supported. Drum developing cartridge 2
The photosensitive drum 12, the developing sleeve 13, and the agitating member 14, which are the constituent members of the above, are all rotationally driven as described above. However, these are the drum developing cartridge 2 at a predetermined position of the image forming apparatus main body M. When it is mounted on, the image forming apparatus main body M is connected to a drive source (not shown).

By adopting the above-described structure, the drum developing cartridge 2 is a cartridge in which the photosensitive drum 12 and the developing device 16 are assembled in the housing 15 and which is attachable to and detachable from the image forming apparatus main body M as a whole. Can be configured.

<Second Embodiment> FIGS. 3 and 4 show an image forming apparatus according to a second embodiment. The figure is a vertical cross-sectional view of the image forming apparatus viewed from the front side.

The image forming apparatus 50 shown in these figures is an electrophotographic laser printer and uses the same drum developing cartridge 2 as in the first embodiment.
The same parts and configurations as those in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The image forming apparatus 50 shown in FIG. 3 is provided with a drum developing cartridge 2, charging devices 56 and 55, an exposure device 60, a sheet feeding cassette 65, a fixing device 28, etc. inside the image forming apparatus main body M. .

At the bottom of the image forming apparatus main body M, a paper feed cassette 65 is mounted. In the paper feed cassette 65,
A plurality of recording materials S are stored in a stacked state. The recording material S has its front end side placed on the intermediate plate 66. Middle plate 6
6, the base end side is swingably supported by the rotary bearing portion 66a, and the tip end side is biased upward by the compression spring 67. As a result, the topmost recording material S of the plurality of recording materials S has the tip of the separation claw 6 of the separation guide 68.
8a is contacted from below.

By rotating the paper feed roller 22 in the direction of the arrow in the figure, the uppermost recording material S in the paper feed cassette 65 is separated from the next recording material S by the separation claw 68a and only one sheet is supplied. Will be sent. The fed recording material S is guided by the guide 2
Registration rollers (not shown) disposed in the vicinity of the photosensitive drum 12 by the conveyance rollers 23 and 24 in the rollers 5 and 26.
It is conveyed to and is temporarily stopped by this registration roller.

The recording material S temporarily stopped by the registration roller is then transferred to the photosensitive drum 12 and the transfer roller by the registration roller so as to match the timing with the toner image formed on the photosensitive drum 12 as described later. The toner image is supplied to the transfer nip portion between the toner image and the toner image 17 and transferred.

In the figure, the first charging device 56 is located above the photosensitive drum 12, and the second charging device 5 is located to the left.
5 are provided.

The first charging device 56 includes a housing 56a.
A charging roller 69 and a coating roller (coating means) 70 are built in the charging roller 69, and the charging accelerating particles 72 are stored in the charging roller 69.
It can be applied to the surface. The charge promoting particles 72 are filled in the housing 56a and sealed by the seal blades 73 and 74. The housing 56a of the first charging device 56 has a tip end portion of a compression spring (coil spring) 57 fixed to the upper portion thereof, and the base end portion of the compression spring 57 is located above the frame 5a.
It is fixed at 9. 4 to the left and right of the housing 56a
A book guide 58 is provided. As a result, the first charging device 56 can move in the vertical direction, and the compression spring 57 causes the charging roller 69 to stably press against the photosensitive drum 12 to form a charging nip portion having a predetermined width. It is supposed to do.

As described above, the first charging device 56 is configured as a cartridge in which the charging roller 69, the coating roller 70, and the charging accelerating particles 72 are built in the housing 56a (hereinafter, appropriately referred to as "charging cartridge"). .

On the other hand, the second charging device 55 has a charging roller 51. A bearing 52 that rotatably supports the charging roller 51 at both ends in the longitudinal direction is fixed to the tip end of a compression spring 53 whose base end is fixed to the protrusion 54 and is urged toward the photosensitive drum 12. There is. This allows
The charging roller 51 is pressed against the surface of the photosensitive drum 12 to form a charging nip portion. The frame 55a of the second charging device 55 is fixed to a part of the image forming apparatus main body M by screws (not shown).

The surface of the photosensitive drum 12 has a predetermined polarity and potential by applying a charging bias to the charging rollers 69 and 51 of the first and second charging devices 56 and 55 by a charging bias applying power source (not shown). It is uniformly charged.

The photosensitive drum 12 after charging is exposed by the exposure device 60.
Form an electrostatic latent image.

The exposure device 60 has a laser oscillator (not shown) that generates laser light based on image information.
The laser light 62 generated by the laser oscillator is generated by the motor 61.
The surface of the photosensitive drum 12 is scanned by being reflected by the polygon mirror 61 and the bending mirror 63 attached to a. As a result, an electrostatic latent image is formed on the photosensitive drum 12. The exposure device 60 including the laser oscillator, the motor 61a, and the polygon mirror 61 is arranged in the frame 59 described above.

The electrostatic latent image formed on the photosensitive drum 12 as described above is developed as a toner image by the developing device 16, and this toner image is conveyed from the paper feeding cassette 65 as described above. It is transferred onto the recording material S by the transfer roller 17. The recording material S after the transfer of the toner image is conveyed to the fixing device 28 along the conveyance guide 27, where it is heated and pressed to fix the toner image. The recording material S on which the toner image has been fixed is conveyed along the guides 31 and 32, and is ejected by the paper ejection rollers 33 and 34 onto a paper ejection stacker 64 as a paper ejection tray. This completes the image formation.

In the image forming apparatus main body M, the frame 59 is rotatable about the rotary bearing portion 59b, and the paper discharge stacker 64 is rotatable about the rotary bearing portion 64a. Further, a door 65 is provided on a portion of the right side wall of the image forming apparatus main body M in FIG. 3 corresponding to the drum developing cartridge 2, and the door 65 is provided with the rotary bearing 6.
It is rotatable about 5a.

Next, referring to FIG. 4, the charging cartridge (first charging device) 56 and the drum developing cartridge 2
The operation when the user or the service person replaces is explained.

First, a user or a service person rotates the frame 59 by lifting the frame 59 in the direction of arrow R2 around the rotary bearing 59b. At this time, the frame 59 comes into contact with the paper discharge stacker 64 and rotates it in the direction of arrow R3. In the open state of the frame 59 shown in FIG. 4, the charging cartridge 56 is urged in the falling direction by the compression spring 57.
Since the projection 59a is provided, the projection 59a is prevented from engaging with the charging cartridge 56 and easily coming off. The protrusion 59a is formed so as to be elastically deformed so that the user or a service person can easily take out the charging cartridge 56 from the frame 59.

Subsequently, the user or service person takes out the charging cartridge 56 from the open frame 59 in the direction of arrow K2. Then, the new charging cartridge 56 is attached by the reverse operation. After that, the frame 59 is rotated in the direction opposite to the direction of the arrow R2 to be closed, and the paper discharge stacker 64 is closed, so that the charging cartridge 5 is closed.
The exchange of 6 is completed.

On the other hand, in order to replace the drum developing cartridge 2, first, the door 65 is rotated about the rotary bearing 65a in the direction of arrow R4 and opened. With the door 65 open, the drum developing cartridge 2 is taken out in the direction of arrow K1. Then, the new drum developing cartridge 2 is mounted in the direction opposite to the arrow K1 direction. After that, the door 65 is closed and the replacement of the charging cartridge 2 is completed.

In the above, the example in which the charging cartridge 56 and the drum developing cartridge 2 are replaced has been described, but these can be easily replaced individually without affecting the other.

<Third Embodiment> FIG. 5 shows an image forming apparatus according to a third embodiment. The figure is a vertical cross-sectional view of the image forming apparatus viewed from the front side.

An image forming apparatus 80 shown in this figure is an electrophotographic digital copying machine, and uses a drum developing cartridge 81, first and second charging devices 82 and 91 similar to those in the second embodiment. is doing.

The image forming apparatus 80 shown in FIG. 5 includes a drum developing cartridge 81, first and second charging devices 82 and 91, an exposing device 90, a paper feeding cassette 100, and a fixing device inside the image forming device main body M. A document table 92 and a document table 102 are provided.

Paper feeding roller 101 in the main body M of the image forming apparatus
When is rotated in the direction of the arrow, the recording material S is fed from the paper feed cassette 100, and one sheet is separated, and the photosensitive drum 8 is separated by the conveyance roller and the registration roller (neither is shown).
3 is supplied to a transfer nip portion between the transfer roller 85 and the transfer roller 85.

Around the photosensitive drum 83, a developing sleeve 86, a first charging device 82, a second charging device 91, a transfer roller 85 and the like are arranged.

First charging device (charging cartridge) 82
Has the same configuration as the first charging device 56 of the second embodiment described above. That is, the charging roller 8 is provided in the housing.
4. A coating roller is built in so that the charging promoting particles can be coated on the charging roller 84.

A compression spring 88 is interposed between the upper portion of the charging cartridge 82 and the upper frame 90, and four guides are provided on the left and right sides of the housing.
The charging cartridge 82 is urged downward by a compression spring 88 while being guided by these four guides. As a result, the charging roller 84 is pressed against the surface of the photosensitive drum 83 with a predetermined contact pressure to form a charging nip portion having a predetermined width.

The frame 90 in which the above-described charging cartridge 82 is incorporated is rotatable about the rotary bearing portion 90a. An exposure device 104 is incorporated in the frame 90, and the exposure device 10
The laser beam 106 generated from the laser beam No. 4 is reflected by the reflection mirror 105 to expose the surface of the photosensitive drum 83 after charging.

The second charging device 91 has the same structure as the second charging device 55 of the second embodiment. That is, the charging roller 87 is rotatably supported by a bearing biased toward the photosensitive drum by the compression spring 89, and is pressed against the surface of the photosensitive drum 83 by a predetermined contact pressure to form a charging nip portion having a predetermined width. Is forming.

The above-mentioned photosensitive drum 83 and developing sleeve 8
The drum developing cartridge 81 having No. 6 is similar to that of the above-described second embodiment, and can be easily attached to and detached from the image forming apparatus main body M.

Reference numeral 92 in the figure is a fixing device for fixing the toner image transferred onto the recording material S, and the recording material S after the toner image is fixed is discharged onto the discharge tray 103. Has become.

The present embodiment described above shows an example in which the present invention is applied to a copying machine as an image forming apparatus.
In the image forming apparatus main body M, the first and second charging devices 82,
91, and the photosensitive drum 83 and the developing device are unitized into a cartridge.

In this embodiment, the drum developing cartridge 81 is replaced by rotating the frame 90 in the main body M of the image forming apparatus in the direction of the arrow in the figure around the rotary bearing 90a. It is performed in a state of being separated from the surface of the photosensitive drum 83. In this embodiment, the drum developing cartridge 81 can be pulled out from the front side of the image forming apparatus main body M in this state. That is,
The drum developing cartridge 81 is attachable to and detachable from (taken in and out of) the front and rear direction of the image forming apparatus main body M (direction perpendicular to the paper surface). When the drum developing cartridge 81 is attached and detached, the drum developing cartridge 81 is retracted to the right in the figure so that the charging roller 87 of the second developing device 91 does not rub against the photosensitive drum 83. You can move in any direction.

With the above configuration, the drum developing cartridge 81 can be easily replaced by the user or the service person.

In the above-described first to third embodiments, the configuration in which the photosensitive drum and the developing device are formed as one unit is illustrated, but the configuration of the drum developing cartridge is not limited to these embodiments. Any other form may be used as long as the photosensitive drum and the developing device can be integrated to form a unit.

In the first to third embodiments, the first and second
However, the drum developing cartridge according to the present invention may be used in a configuration in which only one charging device or three or more charging devices are used.

Further, in the first to third embodiments, the charging device has been described as an example of the charging roller and further the charging roller used by coating the charging promoting particles. However, also for this, another method, for example, When the charging device using corona discharge is used, the drum developing cartridge of the present invention can be used.

[0076]

As described above, according to the present invention,
By making the image carrier and the developing device into a cartridge structure in which they are integrated, they can be easily replaced when they reach the end of their lives.

Further, by making the cartridge in which the image bearing member and the developing device are integrated and separated from other members, the product cost as the cartridge can be kept low.

Further, since the cartridge in which the image bearing member and the developing device are integrated is formed separately from other members, the number of parts as the cartridge can be reduced and the assembling accuracy can be improved. The reliability of the cartridge can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is an enlarged vertical sectional view of a drum developing cartridge.

FIG. 3 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to a second embodiment.

FIG. 4 is a diagram showing how to replace a drum developing cartridge and a charging cartridge in the image forming apparatus according to the second embodiment.

FIG. 5 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to a third embodiment.

FIG. 6 is a vertical sectional view showing a schematic configuration of a conventional image forming apparatus.

[Explanation of symbols]

1, 50, 80 Image forming apparatus 2, 81 Cartridge (drum developing cartridge) 3A Charging device (first charging device) 3B, 55, 91 Charging device (second charging device) 12,83 Image carrier (photosensitive drum) ) 16 developing device 56, 82 charging device (first charging device, charging cartridge) 56a container (housing) 57, 88 urging means (compression spring) 69, 84 charging roller (first charging roller) 70 coating means ( Coating roller) 72 Charge promoting particles

Claims (4)

[Claims] 1. An image forming apparatus for forming an electrostatic latent image on the surface of an image bearing member charged by a charging device and developing the electrostatic latent image by a developing device, wherein at least two charging devices are provided. An image forming apparatus, wherein a carrier and the developing device are unitized to form a cartridge that is attachable to and detachable from a main body of the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the at least two charging devices are arranged inside the image forming apparatus main body and outside the cartridge. 3. At least one of the charging devices comprises a container accommodating charging promoting particles, a charging roller in contact with the surface of the image carrier, and a coating for applying the charging promoting particles to the charging roller. An image forming apparatus according to claim 1 or 2, further comprising: 4. The container, the charging roller, and the applying unit constitute a detachable charging cartridge, and the charging cartridge is biased toward the image carrier by a biasing unit, and the charging cartridge is biased toward the image carrier. The image forming apparatus according to claim 3, wherein the charging roller coated with the charging promoting particles is brought into contact with the surface of the image carrier.