JPH10228154A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image footing device capable of easily removing the soil of an electrifying member in one or two or more electrifiers provided with respect to an image carrier, without increasing the scale of the image forming device in particular and complicating its structure, in the above-mentioned electrifiers. SOLUTION: In the device (laser beam printer), an auxiliary electrifier 2 facing the surface of the photoreceptor 1 (image carrier) whose surface is moved is provided with the electrifying member 21 which has a smooth surface 211a facing the photoreceptor 1 and to which an electrifying voltage is applied from a power source 13 and further, an electrifying member driving device 22 which can bring the surfaces S1 and S2 contributing to an electric discharge for the photoreceptor 1, of the smooth surface 211a of the electrifying member 21 into contact with the moving surface of the photoreceptor 1 and relatively slide the surfaces S1 and S2 against the surface of the photoreceptor 1.

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 such as a copying machine and a printer.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer, an electrophotographic system is usually adopted, and the surface of an electrostatic latent image carrier is uniformly charged. In response, image exposure is performed to form an electrostatic latent image, and this latent image is developed into a visible image. The visible image is immediately transferred to a transfer material such as transfer paper and fixed, or transferred to an intermediate image carrier (intermediate transfer member) as in a color image forming apparatus. Is transferred onto a transfer material and is sometimes fixed.

In charging the surface of the electrostatic latent image carrier or charging the intermediate image carrier to transfer a visible image to the intermediate image carrier, a charging device is used. Various types of charging devices have been proposed,
As a charging member, a charging member that partially contacts the surface of the image carrier and charges by discharging from a discharge contributing surface outside the contact portion, or a predetermined distance from the surface of the image carrier. In a charging device that employs a charging member that is disposed in close proximity and charges by discharge from the discharge contributing surface, foreign matters such as toner for development, paper dust, and glue adhere to the discharge contributing surface for some reason. This may prevent smooth and uniform discharge due to the dirt and may cause image noise.

[0004] For example, a so-called cleanerless type in which a developer remaining on an electrostatic latent image carrier without being transferred to a transfer material is recovered simultaneously with development in a developing device without using a dedicated cleaner. An image forming apparatus of this type is known. In this type of image forming apparatus, after a visible image is transferred from an electrostatic latent image carrier to a transfer material or to an intermediate image carrier, an electrostatic latent image carrier is In an image forming apparatus provided with a dedicated cleaner for removing the transfer residual developer from the image carrier due to foreign matters such as transfer residual developer, paper dust, and glue remaining on the body, the cleaner passes through the cleaner. Often, the discharge contributing surface of the charging member is stained by the developer, paper powder, or the like.

At present, as means for solving such a problem, a cleaning device for the charging member is added to the charging device, the pressing force of the charging member to the image carrier is reduced, or both are separated. It has been proposed to make it easier for the transfer residual developer and the like to pass between the charging member and the image carrier, thereby suppressing generation of stain on the charging member.

[0006]

However, it is not possible to add such a cleaning device to the charging device, to reduce the pressing force of the charging member against the image bearing member, or to provide a device for separating the charging member from the image bearing member. In addition, there is a problem that the size of the image forming apparatus is increased, the structure is complicated, and the manufacturing cost is increased.

Accordingly, the present invention provides one or more charging devices provided for an image bearing member without causing contamination of a charging member in the charging device without causing an extra large size or complicated structure of the image forming apparatus. Another object of the present invention is to provide an image forming apparatus which can be easily removed.

[0008]

The image forming apparatus of the present invention for solving the above-mentioned problems is provided with one or two or more charging devices facing the surface of the image carrier whose surface moves. One or more of them have a charging member having a smooth surface facing the image carrier and to which a charging voltage is applied, and further the charging member has a smooth surface facing the image carrier. The image forming apparatus further includes a charging member driving device capable of bringing a surface contributing to discharge into contact with a moving surface of the image carrier and sliding relative to the surface of the image carrier.

According to the image forming apparatus of the present invention, the electrostatic latent image carrier is uniformly charged prior to image exposure, and an image is exposed to the charged area to form an electrostatic latent image. The electrostatic latent image is developed into a visible toner image, and the visible toner image is transferred to a transfer target such as a transfer material or an intermediate image carrier. In any case, finally, the visible toner image is transferred to a transfer material and fixed.

In the charging device, the surface of the charging member facing the image carrier is formed smooth, and the charging member driving device discharges the smooth surface of the charging member to the image carrier. Can be brought into contact with the moving surface of the image carrier, and can be slid relatively to the surface of the image carrier. It can be easily rubbed off by the relative sliding contact with the surface of the carrier, and the discharge-contributing surface can be kept clean so that the image carrier and the deposits on the image carrier can be charged as desired. it can.

Further, it is not necessary to add a cleaning device for the charging member, to reduce the pressing force of the charging member against the image carrier, or to separately provide a device for separating the charging member from the image bearing member. Can be removed, so that the image forming apparatus does not need to be particularly large and the structure is not complicated. The charging device may be a contact charging device or a proximity charging device.

In the contact charging device, the charging member is brought into contact with the surface of the image carrier at a part of a smooth surface facing the surface of the image carrier, and is separated from the surface of the image carrier outside the contact portion. A case where the discharge contributing surface is formed in a portion can be exemplified. In addition, the proximity charging device can be exemplified by a case where the charging member is disposed close to the surface of the image carrier at a predetermined distance from a part of a smooth surface facing the surface of the image carrier.

In any case, the charging member may be a sheet-shaped charging member or a roller. In the sheet-shaped charging member referred to in the present invention, the charging portion directly contributing to the charging is supported by the supporting portion, and the whole is sheet-shaped, the blade-shaped, the whole is literally the sheet-shaped, and the film-shaped. Things etc. are included.

When a sheet-shaped charging member is employed in the contact charging device, the charging member can be supported in a cantilever manner, and can be partially brought into contact with the image carrier. Further, when the discharge contributing surface of the charging member is disposed at a position for discharging, whether it is a contact charging device or a proximity charging device, the maximum distance between the discharge contributing surface and the surface of the image carrier is a passive energy. There may be a case where the distance is set to be equal to or longer than the distance at which discharge occurs at the minimum discharge voltage according to the law.

When a sheet-shaped charging member is employed,
The sheet-shaped charging member can be a flexible sheet-shaped charging member having an elastic restoring force. In this case, as the charging member driving device, the charging member is pressed, and the elastic restoring force is used. A charging device including a cam device having a cam capable of bringing a discharge contributing surface of the charging member into contact with a moving surface of the image carrier and sliding relative to the surface of the image carrier; By applying an electrostatic attraction force to the photoconductor, the discharge contributing surface of the charging member can be brought into contact with the moving surface of the image carrier and slid relative to the surface of the image carrier. Including an electrostatic attraction force applying device, acting on the charging member, bringing the discharge contributing surface of the charging member into contact with the moving surface of the image carrier, and
Examples include a solenoid type driving device which can slide relatively to the surface of the image carrier.

In the contact charging device, when a roller is used as the charging member, the charging member driving device rotates the roller charging member such that its peripheral speed is different from the image carrier surface moving speed. In the proximity charging device, when a roller-type charging member is employed, the roller charging member is used as the charging member driving device. A driving unit that is driven to rotate differently from the speed,
And a drive unit for bringing the roller charging member into contact with and separating from the image carrier.

In any case, the charging member driving device is configured to repeatedly contact the discharge-contributing surface of the charging member with the surface of the image carrier while the surface of the image carrier is moving. What to drive, timing outside of image formation, for example, timing of pre-operation of the image carrier before image formation, timing between images when forming several images, post-operation of image carrier after image formation The driving of the charging member so that the discharge contributing surface of the charging member is brought into contact with the surface of the image carrier at the timing or the like, the timing of a predetermined operation on the image forming apparatus, for example, the exterior cover of the printer main body. The charging member is driven so that the discharge contributing surface is brought into contact with the surface of the image carrier and slid at the timing of opening and closing, the timing of replacement of components, and the like.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a schematic configuration of a laser beam printer that performs reversal development, which is an example of an image forming apparatus according to the present invention. In the laser beam printer, an image carrier having a thin film layer made of an organic photoconductive material (OPC) formed on the outer peripheral surface of a cylindrical body, that is, a drum-shaped organic photoconductor 1 is provided at a substantially central portion. The photoconductor 1 is negatively charged, and is rotationally driven in a direction indicated by an arrow a in the figure by a driving device (not shown).

An auxiliary charging device 2, a main charging device 3, a developing cleaning device 4, and a transfer roller 5 are sequentially arranged around the photosensitive member 1 along the rotation direction thereof. An image exposure device 6 using a beam is provided. Further, a paper feed cassette 7 is provided below the developing / cleaning device 4, and the transfer paper SH stored in the paper feed cassette 7 is provided.
Is pulled out by the paper feed roller 8 at a predetermined timing.

Transfer paper S pulled out of paper feed cassette 7
H is guided by a guide and conveyed to the timing roller pair 9. Further, a fixing roller pair 10 is disposed above the transfer roller 5, and a sheet discharging roller pair 11 and a sheet discharging tray 12 are provided following the fixing roller pair 10. In addition, a power supply 13 is provided at one corner at the bottom of the device.

The main charging device 3 includes a charging brush roller 31
The charging brush roller 31 includes a photosensitive member 1
In order to charge the surface of the photoreceptor prior to image exposure for forming an electrostatic latent image to be described later, the photoreceptor is rotationally driven by a driving device (not shown), and a predetermined voltage is supplied from the power supply 13. Applied. The voltage applied to the charging brush roller 31 may be a DC voltage having a constant value, or a voltage obtained by superimposing an AC component on the DC voltage. Although not limited thereto, here, -1350 [V] and-
A DC voltage of 300 [V] is alternately applied by switching operation of switching elements in the power supply. The application of such an alternating voltage makes it possible to uniformly charge the surface of the photoreceptor and significantly reduce charging unevenness as compared with the case where only a DC voltage is applied.

As shown in FIG. 2, the auxiliary charging device 2 includes a flexible sheet-shaped charging member 21 and a charging member driving device 22 having elastic restoring force as a whole. The sheet-shaped charging member 21 includes a belt-shaped charging unit 211 arranged in contact with the surface of the photoconductor 1 and a support unit 212 that supports the charging unit 211.
Consists of The support portion 212 is a flexible leaf spring member having a high elastic restoring force. The downstream end in the photosensitive member surface moving direction a is cantilevered at a fixed position, and the charging portion 211 is provided at the upstream end. I support it. The charging unit 211 has a surface facing the photoconductor 1 formed on a smooth surface 211 a (see FIG. 3), and a part of the charging unit 211 is disposed in contact with the surface of the photoconductor 1.

As shown in FIGS. 1 and 2, the charging member driving device 22 includes a rotating cam 221 that contacts the support portion 212 of the charging member 21 from above and a mechanism 222 that links the cam to rotation of the photosensitive member. In. The cam 221 is formed by cutting off a part of the outer peripheral surface of a member having a circular cross section in parallel with the rotation center line of the cam to form a flat surface fs. The cam 221 is driven to rotate in conjunction with the rotation of the photosensitive member 1. Outer curved surface cs and flat surface fs
Can alternately contact the support portion 212.

The support portion 212 is pressed downward by the contact of the outer peripheral curved surface cs of the cam 221 with the support portion 212, and the support portion 212 is pressed downward as shown in FIG.
And the position shown in FIG. In the state illustrated in FIG. 3A, the charging unit 211 contacts the photoconductor at a downstream portion P1 in the surface movement direction a of the photoconductor 1, and contacts the photoconductor with a protruding portion having a protruding amount L upstream of the photoconductor 1. It has a discharge contributing surface S1 that is separated from one surface by a predetermined distance to perform a discharge according to the Passien rule. Further, when the cam 221 rotates and its flat surface fs comes into contact with the support portion 212, the support portion 21
2 is elastically restored to the position shown in FIGS. 2 (B) and 3 (B). In the state shown in FIG. 3B, the charging unit 211
The photoconductor 1 contacts the photoconductor at an upstream portion P2 in the surface movement direction a of the photoconductor 1, and the photoconductor 1
It has a discharge contributing surface S2 that is separated from the surface by a predetermined distance and discharges according to the Passien rule.

That is, as the cam 221 rotates,
The discharge contributing surfaces S1 and S2 reciprocate along the photoconductor surface moving direction, and when switching from the position shown in FIG. 3A to the position shown in FIG. When the surface slides and rubs on the surface of the photoconductor and switches from the position shown in FIG. 3B to the position shown in FIG. Rubbed,
Thus, dirt due to the attached toner and the like on the discharge contributing surface is cleaned.

A DC voltage of -1350 [V] is applied from the power source 13 to the charging member 21, more precisely, the charging portion 211 from the power source 13. FIG. 4 shows that the charging unit 211 has a DC voltage of -1350 [V].
2 shows the relationship between the position of removing the dirt on the charging unit 211 when the voltage is applied, the distance that can be secured with the surface of the photoconductor, and the surface potential of the photoconductor.

As can be seen from this figure, the discharge contributing surface S1
By setting the maximum gap distance h1 (h2) (see FIG. 3) between (S2) and the photosensitive member 1 to be equal to or greater than the distance at which discharge occurs at the minimum discharge voltage according to the Passien rule, the rotation axis direction of the photosensitive member 1 It can be seen that even if there is unevenness in the gap distance between the discharge contributing surface S1 (S2) and the photoreceptor 1, it is possible to discharge without any trouble and to maintain uniform and uniform charge and charge at a predetermined potential level. Here, the gap distance h1 (h2) is set to be such a distance.

The role of the auxiliary charging device 2 will be described later. The developing cleaning device 4 includes a hopper 41 that stores a negatively charged non-magnetic one-component toner T. In this developing device, a developing sleeve 42, which is driven to rotate in the direction of arrow b in the drawing and faces the photoreceptor 1, is disposed, and a rotating member 43 for supplying the toner T to the developing sleeve 42 is provided in a hopper behind the developing sleeve. Also, a stirring blade 44 for supplying toner and preventing aggregation is provided.

The developing sleeve 42 is configured to transport the toner T having the same polarity as the charged polarity of the photosensitive member 1 to the photosensitive member 1 in order to develop an electrostatic latent image described later, in other words, -100 [V] to -500 [V] (here -300 [V] from the power supply 13) such that an electric field in which the toner T travels from the developing sleeve 42 to the laser beam irradiation section (exposure section) on the photoconductor 1 is generated. ) Is applied. The rotating member of the developing cleaning device 4 is driven to rotate by a driving device (not shown).

The transfer voltage is applied to the transfer roller 5 from the power source 13 as the transfer voltage, but not limited thereto. Here, a transfer voltage having a polarity opposite to that of the toner and within a range of +1 [kV] to +5 [kV] is applied. The visible toner image on the photoconductor is electrostatically attracted to the transfer paper SH conveyed between the transfer roller 5 and the photoconductor 1 under the application of the transfer voltage, and the transfer is performed. it can.

The laser device 6 irradiates a laser beam BM to the surface of the photosensitive member 1 located between the charging brush 31 and the developing / cleaning device 4 in accordance with image information.
Thus, an electrostatic latent image is formed by generating a potential attenuating portion on the surface of the photoreceptor uniformly charged in advance. According to the laser beam printer described above, the photoreceptor 1 is driven to rotate during image formation, and the surface thereof is uniformly charged by the charging brush roller 31 under the influence of the charging by the auxiliary charging device 2. , Here -800
[V]. The charged area is exposed from the laser device 6 based on the image information to form an electrostatic latent image, and the electrostatic latent image is developed by the developing / cleaning device 4 to be a visible toner image. On the other hand, the transfer paper SH is pulled out of the paper supply cassette 7 by the paper supply roller 8 and conveyed to the timing roller pair 9 where the transfer paper SH is synchronized with the toner image on the photoconductor 1 and is transferred to the transfer roller 5 and the photoconductor 1. Is transferred to the transfer section. Thus, the visible toner image is transferred onto the transfer sheet SH by the transfer roller 5, and thereafter, the transfer sheet SH passes through the fixing roller pair 10 to fix the toner image thereon, and is discharged by the discharge roller pair 11. It is discharged onto the tray 12.

After the transfer, the transfer residual toner remaining on the photoreceptor 1 has a polarity opposite to the normal charge polarity due to the influence of the positive voltage application from the transfer roller 5 during transfer and the influence of paper dust and the like. When a positively charged toner is contained and arrives at the charging brush roller 31 as it is, the toner adheres to the roller 31 to which a negative voltage is applied, hinders the charging of the photoconductor 1 and causes a halftone image Image problems such as black streaks and roughness occur.

However, in this case, the transfer residual toner first arrives at the auxiliary charging device 2 as the photosensitive member 1 rotates.
Here, a DC voltage of -1350 [V] is applied to the charging member 21 of the auxiliary charging device 2 as described above, and both the transfer residual toner passing therethrough while charging the photosensitive member surface are removed. In this example, the charge is performed to about -900 [V]. Thus, the transfer residual toner charged to the opposite polarity is charged to the regular negative polarity, and is prevented from adhering to the charging brush roller 31 arriving after that, so that the photosensitive member can be charged by the brush roller 31 without any trouble.

The transfer residual toner is charged by the charging brush roller 3.
1 so that the so-called exposure kick or the like at the time of exposure by the laser device 6 is suppressed. When image formation is not continued, the transfer residual toner goes to the developing / cleaning device 4 as it is, but when image formation is continued, the laser device 6 applies the next image information to the surface of the photoconductor 1 in which the residual toner is dispersed. The corresponding laser beam BM is irradiated. The potential of a portion irradiated with the laser (hereinafter, referred to as an image portion) is attenuated with respect to a portion not irradiated with the laser (hereinafter, referred to as a non-image portion), whereby a new electrostatic latent image is formed.

When the newly formed electrostatic latent image reaches the position of the developing sleeve 42 of the developing and cleaning device 4 as the photosensitive member 1 rotates, it is developed under a developing bias. At the same time as the development, the transfer residual toner T located in the non-image portion is electrostatically attracted to the developing sleeve 42 by the difference between the potential of the non-image portion and the developing bias potential, and is collected.

As described above, the transfer residual toner is supplied to the developing device 42.
However, in practice, the transfer residual toner and the like adhere to the discharge contributing surface of the charging unit 211 of the charging member 21 in the auxiliary charging device 2 and become soiled. This occurs because the transfer residual toner or the like charged to the positive polarity due to the influence of the transfer voltage during transfer or the like is attracted to the charging unit 211 by Coulomb force. In a dirty state, the discharge by the charging unit 211 becomes non-uniform, and a portion of the charging brush roller 31 corresponding to a portion in which the discharge has failed is soiled, which causes image noise.

Here, the charging member driving device 22 is provided in the auxiliary charging device 2, and as described above, as shown in FIG. By reciprocating in the surface moving direction, the discharge contributing surfaces S1 and S2 can be rubbed against the surface of the photoreceptor to remove the dirt, and if there is dirt on the discharge contributing surface, the generated image noise is suppressed accordingly. it can.

In the above description, the charging member 21 is slid in contact with the photosensitive member in conjunction with the rotation of the photosensitive member.
Drive 1 is performed at a timing other than the time of image formation, for example, the timing of pre-rotation of the photoconductor before image formation, the timing between images when forming several images, and the post-rotation of photoconductor after image formation. It may be performed at a timing or the like, or may be performed at a predetermined operation on the printer, for example, at a timing of opening / closing an exterior cover of the printer main body or at a timing of replacing parts.

Further, the charging member 21 may be moved irregularly at an acceptable cycle. Cleaning at such a timing can be performed, for example, by operating the charging member driving device 22 under the control of the control unit CONT that controls the operation of the entire printer. Next, another example of the image forming apparatus according to the present invention will be described with reference to FIG. The image forming apparatus shown in FIG. 5 is also a laser beam printer. In the printer shown in FIG.
0 while the charging device 3 in the printer of FIG.
Is removed. The other points are the same as those of the printer shown in FIG. 1, and the same parts are denoted by the same reference numerals.

The auxiliary charging device 20 is the same as the auxiliary charging device 2 shown in FIG. 1, except that a cleaner blade 23 that contacts the photosensitive member 1 is added upstream of the charging member 21. Since the auxiliary charging device 20 is provided with the cleaner blade 23, the charging member 21 is less contaminated than the auxiliary charging device 2 shown in FIG. Therefore, by reciprocating the charging member 21 in the same manner as in the case 2 of the apparatus, dirt on the charging member can be sufficiently removed, and the photosensitive member 1 can be charged to a desired potential by only the charging member 21. The charging device 3 can be omitted.

In the charging devices 2 and 20, the charging member 21 is driven by a cam mechanism. However, as shown in FIG. 6, the charging member 21 may be reciprocated by a driving device 220 using a solenoid SOL. As shown, an AC voltage is applied to the charging member 21 from the AC power supply PW in the charging device 2, thereby changing the electrostatic attraction force to the photoreceptor 1 in accordance with the voltage application cycle, thereby causing the charging member 21 to vibrate. In this case, the dirt may be removed. However, in this case, the charging unit 211 is a sheet material in which carbon particles are dispersed in a semiconductive material of, for example, 10 ⁴ Ωcm to 10 ⁹ Ωcm, for example, a styrene elastomer so that an electrostatic attraction force is generated. In this case, the cam mechanism can be omitted.

Further, as shown in FIG. 8, in the charging device 2 shown in FIG. 1, a screw-type rotary cam 223 having spiral blades may be employed instead of the cam 221. The cam 223 acts so as to sequentially press the charging member 21 from one end to the other end, and start pressing the one end again. The rotating cam 223 includes the charging member 21.
Spiral blade 22 so that the force pressing the photosensitive member 1 against the photosensitive member 1 is made uniform at each portion in the direction of the rotation axis of the photosensitive member (in other words, the pushing amount of the charging member by the cam is made uniform).
3a is formed. So, in this example,
The spiral blades are arranged such that the pushing amount at the center of the charging member 21 is substantially equal to the pushing amount at the end of the charging member 21 and the pushing amount at both ends is substantially equal to the pushing amount at the central portion. 223a is formed.

In the case of the cam 221 shown in FIG. 1, the pressure contact force of the charging member 21 against the photosensitive member 1 tends to fluctuate at various portions in the axial direction of the photosensitive member along with the rotation of the cam, and the load variation on the photosensitive member 1 increases. However, when the rotating cam 223 is employed, the pressing force of the charging member 21 against the photoconductor 1 can be made uniform at each portion in the rotation axis direction of the photoconductor, and the load fluctuation on the photoconductor 1 can be reduced.

Although the rotary cam 223 has a spiral blade here, other members can be used instead of the cam 223 as long as the force for pressing the charging member can be made uniform in each part. In the case where any of the charging devices described above is adopted, a film-shaped charging member 24 may be used as the sheet-shaped charging member, for example, as illustrated in FIG. 9, instead of the charging member 21.

Further, instead of the charging members 21 and 24 and the above-mentioned various charging member driving devices, for example, a charging roller arranged in contact with the surface of the photosensitive member 1 is provided, and the peripheral speed of the charging roller is set to the photosensitive member surface moving speed. Even if a device for rotating and driving the charging roller is provided in a different manner, the surface dirt of the charging roller can be cleaned in the same manner as described above. In the image forming apparatus described above, the configuration is such that the charging member can be removed from one charging device. However, if necessary, a similar removal configuration can be employed for each of two or more charging devices.

The charging devices 2, 20 and the like capable of cleaning the charging members described above are contact charging devices. However, the present invention can be applied to a proximity charging device. Equipment can be adopted.

[0047]

As described above, according to the present invention,
With respect to one or more charging devices provided for an image carrier, an image forming apparatus that can easily remove stains on a charging member of the charging device without causing an extra large size or complicated structure of the image forming apparatus. Can be provided.

[Brief description of the drawings]

FIG. 1 shows an example of an image forming apparatus according to the present invention (printer).
It is a figure which shows schematic structure of.

FIG. 2A is an enlarged side view of an auxiliary charging device in the printer of FIG. 1, showing a state where the charging member is located at one position, and FIG. The state where it is in another position is shown.

3A is a partially enlarged view of FIG. 2A, and FIG. 3B is a partially enlarged view of FIG. 2B.

FIG. 4 is a diagram showing a relationship between a dirt removing position of a charging unit when a constant voltage is applied to a charging member, a distance that can be secured between the charging unit and the photoconductor surface, and a photoconductor surface potential in the auxiliary charging device shown in FIG. It is a figure showing a relation.

FIG. 5 is a diagram illustrating a schematic configuration of another example (printer) of the image forming apparatus according to the present invention.

FIG. 6 is a diagram showing another example of the auxiliary charging device.

FIG. 7 is a diagram showing still another example of the auxiliary charging device.

FIG. 8 is a diagram showing still another example of the auxiliary charging device.

FIG. 9 is a diagram showing still another example of the auxiliary charging device.

[Explanation of symbols]

 Reference Signs List 1 photoconductor (image carrier) 2 auxiliary charging device 21 charging member (sheet-shaped charging member) 211 charging portion 211a smooth surface S1, S2 discharge contributing surface 212 support portion 22 charging member driving device 221 rotating cam fs cam 221 flat surface cs outer peripheral curved surface of cam 221 222 interlocking mechanism 3 main charging device 31 charging brush roller 4 developing device 5 transfer roller 6 laser device 7 paper feed cassette SH transfer paper 8 paper feed roller 9 timing roller pair 10 fixing roller pair 11 discharge roller pair DESCRIPTION OF SYMBOLS 12 Paper discharge tray 13 Power supply CONT control part 20 Charging device 23 Cleaning blade 220 Charging member driving device SOL solenoid driving device PW Alternating current (AC) power supply 223 Rotating cam 223a Spiral blade of cam 223 24 Film charging member

Claims (12)

[Claims] 1. An image bearing member having a surface which moves is provided with one or more charging devices facing the surface, and one or more of the charging devices have a smooth surface facing the image bearing member. It has a charging member to which a charging voltage is applied having
Further, of the smooth surface of the charging member, a surface contributing to discharge to the image carrier is brought into contact with a moving surface of the image carrier,
The image forming apparatus further includes a charging member driving device that can slide relative to the surface of the image carrier. 2. The image forming apparatus according to claim 1, wherein the charging device is a contact charging device, and the charging member is brought into contact with the image carrier surface at a part of a smooth surface facing the image carrier surface, and the image outside the contact portion is provided. The image forming apparatus according to claim 1, wherein the discharge contributing surface is formed at a portion separated from a surface of the carrier. 3. The charging device is a proximity charging device, and the charging member is arranged such that a part of a smooth surface facing the surface of the image carrier is close to the surface of the image carrier at a predetermined distance. 2. The image forming apparatus according to 1. 4. An image forming apparatus according to claim 2, wherein said charging member is a sheet-shaped charging member. 5. When the discharge-contributing surface of the charging member is arranged at a position for discharging, the discharge is performed at a minimum discharge voltage according to the Passien's law when the maximum distance between the discharge-contributing surface and the surface of the image carrier is reduced. The image forming apparatus according to claim 4, wherein the distance is set to be equal to or longer than the distance that occurs. 6. An image forming apparatus according to claim 2, wherein said charging member is a charging member in the form of a roller. 7. The charging member is a sheet-shaped charging member,
The sheet-shaped charging member is a flexible sheet-shaped charging member having an elastic restoring force, and the charging member driving device presses the charging member and utilizes the elastic restoring force to contribute to discharge of the charging member. 3. The image forming apparatus according to claim 2, further comprising a cam device having a cam capable of bringing a surface into contact with a moving surface of the image carrier and sliding relative to the surface of the image carrier. 8. The charging member is a sheet-shaped charging member,
The sheet-shaped charging member is a flexible sheet-shaped charging member having an elastic restoring force, and the charging member drive device discharges the charging member by applying an electrostatic attraction force to the photosensitive member to the charging member. 3. An electrostatic attraction force applying device capable of bringing a contribution surface into contact with a moving surface of the image carrier and sliding relative to the surface of the image carrier.
The image forming apparatus as described in the above. 9. The charging member is a sheet-shaped charging member,
The sheet-shaped charging member is a flexible sheet-shaped charging member having an elastic restoring force, and the charging member driving device acts on the charging member to move the discharge contributing surface of the charging member to move the image carrier. 3. The image forming apparatus according to claim 2, further comprising a solenoid type driving device which can be brought into contact with the surface and slid relative to the surface of the image carrier. 10. The charging member driving device drives the charging member such that the discharge-contributing surface of the charging member is repeatedly brought into contact with the surface of the image carrier while the surface of the image carrier is moving. The image forming apparatus according to claim 1, wherein: 11. The charging member driving device drives the charging member such that the discharge contributing surface of the charging member is brought into contact with the surface of the image carrier and slid at a timing other than the time of image formation. 10. The image forming apparatus according to any one of 1 to 9. 12. The charging member driving device drives the charging member such that the discharge contributing surface is brought into contact with the surface of the image carrier at a predetermined operation timing of the image forming apparatus. 10. The image forming apparatus according to any one of 1 to 9.