JPH10307453A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which a remaining developer does not exist at an exposing position on an image carrier and the cost can be reduced and which can be made compact. SOLUTION: This image forming device is provided with an electrifying and recovering roller 32 which is brought into contact with an image carrier 12 on the upstream side of an exposing position. The roller 32 is provided with a first electrode 38 and a second electrode 40 which are brought into alternately slidably contact with the surface of the image carrier 12. An optional point on the image carrier 12 is brought into contact with at least the three electrodes of a first electrode 38, a second electrode 40 and the electrode 38 in this order, the surface of the carrier 12 is uniformly electrified by bringing it into the first contact with the electrode 38, a remaining toner is recovered by bringing it into the succeeding contact with the electrode 40 and the carrier 12 is uniformly electrified again by bringing it into the second succeeding contact with the electrode 38.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic cleanerless image forming apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, an electrostatic latent image formed on the surface of an image carrier by a developing device is developed with toner, and at the same time, toner remaining on the image carrier after the previous transfer is removed. A cleaner-less type for recovery is known.

For example, in Japanese Patent Application Laid-Open No. Hei 5-210300, in a cleanerless image forming apparatus, residual toner charged to a polarity opposite to the charging polarity of an image carrier is once collected by a charging roller and charged to an original polarity. After that, the toner is returned to the image carrier and collected by the developing device, or a cleaning roller is disposed between the transfer unit and the charging unit to collect the residual toner once, and the collected residual toner is more than an allowable amount. A method in which the image carrier is gradually returned onto the image carrier is proposed.

For example, Japanese Patent Application Laid-Open Nos. 4-371975 and 4-371776 propose a system in which a disturbance brush is provided in addition to a charging brush to disperse residual toner on an image carrier.

[0005]

However, in the above-described conventional cleanerless image forming apparatus, since the residual toner exists on the image carrier between the charged area and the developing area, an electrostatic latent image is formed at the time of image formation. Exposure to form the image is blocked by the residual toner, the surface of the image carrier is not uniformly charged, and the reproduced image has image defects such as light and shade patterns, halftone roughness, positive and negative memories. There's a problem. In addition, a method has been proposed in which a roller or a brush for temporarily collecting residual toner is separately provided in addition to the charging means so that the residual toner does not exist in an exposure area during image formation. If such a configuration is adopted, there is also a problem that it becomes an obstacle in reducing the cost and size of the apparatus.

Further, in an image forming apparatus of a type in which a residual pressure is collected by pressing a cleaner blade against an image carrier, foreign matters such as glue adhered to the surface of the image carrier are mechanically removed, and the image carrier is cleaned by the cleaner blade. Prevents filming of the image carrier (a phenomenon in which additives contained in paper and resin components in the toner adhere to and accumulate on the surface of the image carrier to form a film) by gradually shaving the photosensitive layer of the body However, in the cleaner-less type image forming apparatus, problems such as image noise generated every rotation cycle of the image carrier due to foreign matters such as glue and image noise due to filming of the image carrier are caused.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to expose an image carrier and a surface of a uniformly charged image carrier according to image information. Exposure means for forming an electrostatic latent image by means of a developer, contact developing means for visualizing the electrostatic latent image with a developer, and transferring the developer image visualized on the surface of the image carrier to a transfer-receiving member An image forming apparatus comprising: a transfer unit that transfers the developer remaining on the image carrier after the transfer by the contact developing unit. A contact charge recovery means for contacting the contact charge recovery means, the contact charge recovery means having a first electrode and a second electrode alternately slidingly contacting the surface of the image carrier; At least a first electrode and a second electrode during passage through the area of contact with the means The first electrode is set so as to be in contact with the three electrodes in order, and at any point on the image carrier during image formation, the surface of the image carrier is uniformly charged by the first contact with the first electrode, and the image is formed after transfer. A second electrode to which the developer remaining on the carrier is charged to the same polarity as the charge polarity of the image carrier, and then a voltage having the same polarity as the charge potential of the image carrier and a smaller absolute value is applied thereto , The residual developer is temporarily recovered, and then the surface of the image carrier is uniformly charged again by the second contact with the first electrode.

Further, in this image forming apparatus, during non-image formation, a voltage having the same polarity as the charge potential of the image carrier and having an absolute value larger than the same is applied to the second electrode of the contact charge recovery means to temporarily The collected developer is returned to the image carrier, and a voltage having the same polarity as the charge potential of the image carrier and a smaller absolute value is applied to the contact developing device to collect the developer from the image carrier to the contact developing device. can do.

Further, in the image forming apparatus according to the present invention, a gap is provided between the first electrode and the second electrode, and an edge of each of the electrodes is provided at an entrance of a contact area between the image carrier and the contact charge recovery means. May slide on the surface of the image carrier.

[0010]

According to the image forming apparatus of the present invention,
The first electrode and the second electrode of the contact charge recovery unit alternately slide on the surface of the image carrier, and at least the first electrode, while any point on the image carrier passes through the contact area with the contact charge recovery unit.
The second electrode contacts the three electrodes in the order of the first electrode. At the time of image formation, at any point on the image carrier, the surface of the image carrier is first uniformly charged by contact with the first electrode, and the developer remaining on the image carrier after the previous transfer is removed. Is charged to the same polarity as the charging polarity. Subsequently, the above-mentioned arbitrary point comes into contact with the second electrode to which a voltage having the same polarity as the charge potential of the image carrier and a smaller absolute value is applied, and the charged residual developer is brought into contact with the second electrode. Based on the potential difference from the surface of the carrier, the attraction is made to the second electrode by electrostatic force and is temporarily collected. At this time, since the charged residual developer is collected, the surface potential of the image carrier is reduced by the amount of the charged charge of the residual developer, and the surface potential becomes uneven. Therefore, 2 with the following first electrode
By the second contact, the surface of the image carrier is uniformly charged again. As described above, by the three steps of charging, collecting, and recharging, in the next exposure area, there is no residual developer, and the image can be uniformly and uniformly exposed on the image carrier. The latent image can be reliably formed, and a clear image without a light and shade pattern can be obtained. Further, since the charging of the image carrier and the recovery of the residual developer can be performed only by the contact charge recovery means, the cost and the size can be reduced.

The residual developer collected on the second electrode as described above applies a voltage having the same polarity as the charge potential of the image carrier and an absolute value greater than the charge potential during non-image formation.
When applied to the electrodes, the electrodes are pulled back onto the image carrier by an electrostatic force based on a potential difference between the second electrode and the surface of the image carrier. On the other hand, a voltage having the same polarity as the charged potential of the image carrier and an absolute value smaller than that is applied to the contact developing means. Therefore, the residual developer returned on the image carrier is attracted to the contact developing means by electrostatic force and collected. As a result, the collected developer can be used again for development, so that the residual developer does not have to be discarded, and the developer can be used effectively.

Further, in the case where a gap is provided between the first electrode and the second electrode so that the edge of each electrode slides on the surface of the image carrier at the entrance of the contact area with the image carrier. In addition, foreign substances such as glue adhered to the image carrier can be removed, and filming of the image carrier can be prevented by gradually scraping the photosensitive layer of the image carrier, thereby preventing image noise.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an image forming apparatus 10 according to the first embodiment.
A drum-shaped photosensitive member 12 which is an image bearing member having a photosensitive layer made of C) formed on the surface thereof is rotatably provided in the direction of arrow a. Around the photoreceptor 12, a contact charge recovery device 14, a developing device 16, and a transfer roller 18 are sequentially arranged along the rotation direction, and a laser device 20 is disposed obliquely above the photoreceptor 12.

The laser device 20 irradiates a laser beam 22 on the surface of the photosensitive member 12 located between the contact charge recovery device 14 and the developing device 16 in accordance with image information, and uniformly charges the surface of the photosensitive member 12. Then, an electrostatic latent image is formed by causing a potential attenuating section in the image.

The developing device 16 is provided with a hopper 24 for storing a triboelectrically non-magnetic one-component toner T as a developer. The hopper 24 opens toward the photoreceptor 12, and holds the toner, which is rotatable in the direction of arrow b and has the same polarity (eg, minus) as the charging polarity of the photoreceptor 12, on the outer peripheral surface. The developing sleeve 26 conveyed to the photoconductor 12 while contacting the photoconductor 12 is brought into contact with the photoconductor 12. A bias of −100 to −500 V (−300 V in the present embodiment) is applied to the developing sleeve 26 so that an electric field is generated in which toner flows from the developing sleeve 26 to the laser irradiation portion of the photoconductor 12 during normal image formation. Is applied. This electric field causes the toner to adhere to the electrostatic latent image to be visualized, thereby forming a toner image. The hopper 24 has a supply roller 2 for supplying toner to the developing sleeve 26.
8 and a stirring blade 30 which rotates in a direction opposite to the developing sleeve 26 to prevent aggregation of the toner and supply the toner to the supply roller 28.

The transfer roller 18 applies a voltage having a polarity opposite to that of the toner to the paper P conveyed in synchronization with the rotation of the photoconductor 12 from the back surface thereof to electrostatically attract the toner on the photoconductor 12. To transfer the toner image to the paper P. At this time,
There is toner remaining on the surface of the photoreceptor 12 without being transferred to the paper P, and the toner is charged to a polarity opposite to the original charging polarity (for example, plus) depending on the type of the paper P and a printing environment. Things are included. The sheet P to which the toner image has been transferred is discharged outside the image forming apparatus after the toner image is fixed while passing through a fixing device (not shown).

The contact charge recovery device 14 includes a charge recovery roller 32, a first power supply 34, and a second power supply 36. The charge recovery roller 32 is rotatably supported in the direction of arrow c, and is provided so that the outer peripheral surface thereof comes into contact with the surface of the photoconductor 12 between a transfer area by the transfer roller 18 and an exposure area by the laser device 20. Further, as shown in FIG. 2, the charge recovery roller 32 has a first electrode 38 and a second electrode 40 on an outer peripheral portion. First electrode 38 and second electrode 4
Numerals 0 extend in parallel with the axial direction of the charge collection roller 32, and are arranged alternately in the circumferential direction. Therefore, when the charge collection roller 32 is driven to rotate, the first electrode 38 and the second electrode 40 alternately slide on the surface of the photoconductor 12. Further, the first electrode 38 and the second electrode 40 are insulated from each other. The first electrode 38 is connected to the first power supply 34 via a shaft 42 at one end of the charge collection roller 32, and a voltage of, for example, -1150V is applied. On the other hand, the second electrode 40 is connected to the shaft 4 at the other end of the charge collection roller 32.
4 is connected to the second power supply 36 via the switch 4, and by switching the switch 46 in the second power supply 36, for example, during image formation,
A voltage of 300 V, for example, -1150 V is applied during non-image formation.

With respect to the charge recovery roller 32, at least any one of the first electrode 38 and the second electrode 4
The peripheral speed of the charge recovery roller 32 and the width of each of the electrodes 38 and 40 are set so as to contact three electrodes in the order of 0 and the first electrode 38. Specifically, as shown in FIGS. 3A and 3B, the peripheral speed V _{CC of} the charge recovery roller 32, the peripheral speed V _{PC of} the photoconductor 12, and the contact area between the charge recovery roller 32 and the photoconductor 12. Length L _NIP , width L ₁ of first electrode 38, width L of second electrode 40
_2, when the width L _S of the inter-electrode 46, the time t _NIP any point A on the photosensitive member 12 is required to pass through the contact area L _NIP is represented by the following formula (1).

[0019]

## EQU1 ## t _NIP = L _NIP / V _PC (1)

During this time t _NIP , at least the first electrode 3
8, the second electrode 40 and the first electrode 38 must be brought into contact with the arbitrary point A, but the first electrode 38 does not always come into contact at the entrance of the contact area, and in the worst case, There is also a possibility that the contact starts from where the first electrode 38 has passed. If the worst case, at least the three electrodes to said arbitrary point A is in contact with the order, the inter-electrode 46 within the time t _NIP, the second electrode 40, the inter-electrode 4
6, the first electrode 38, the inter-electrode 46, the second electrode 40, the inter-electrode 46, and the first electrode 38 need to pass through the contact area L _NIP . For this purpose, the time obtained by dividing the passing length at this time by the peripheral speed V _CC of the charge recovery roller 32 is the time t.
_Since it is only necessary to be shorter than _NIP , it can be expressed by the following equation (2).

[0021]

(L _S + L ₂ + L _S + L ₁ + L _S + L ₂ + L _S + L ₁ ) / V _CC ≦ t _NIP (2)

Here, in the worst case assumed above, the last first electrode 38 can be charged if slightly applied to the above-mentioned arbitrary point A. Can be rewritten into the following equation (3).

[0023]

(L _S + L ₂ + L _S + L ₁ + L _S + L ₂ + L _S ) / V _CC <t _NIP (3)

The following equation (4) is derived from the above equations (1) and (3).

[0025]

V _CC / V _PC > (L ₁ + 2L ₂ + 4L _S ) / L _NIP (4)

For example, the contact area L _NIP = 2 mm, and the width of each of the first electrode 38, the second electrode 40, and the space 46 between the electrodes is L ₁
= L ₂ = L _S = 1 mm, the peripheral speed ratio between the photosensitive member 12 and the charge recovery roller 32 is given by the equation (4).

[0027]

V _CC / V _PC > (1 + 2 × 1 + 4 × 1) /2=3.5 (5)

## EQU1 ## Therefore, if the peripheral speed of the photosensitive member 12 (the system speed) V _PC and 38mm / sec, the peripheral speed V _CC of the charge collection roller 32 would be set greater than 133 mm / sec.

Next, referring to FIG.
The following describes the charging of the photoconductor 12 and the collection of the residual toner. In addition, the graphs shown below the arbitrary point A on the photoconductor 12 in FIGS. 3A to 3C respectively show the relationship between the surface potential at the point A and the time t.

An arbitrary point A on the photoconductor 12 on which the residual toner is loaded moves to a contact area with the charge collection roller 32 by the rotation of the photoconductor 12. Then, as shown in FIG. 3A, the first electrode 38 to which a voltage of -1150 V is applied.
When (I ₁ ) contacts the arbitrary point A, the surface of the photoconductor 12 is charged to about −700V. At the same time, of the residual toner, the positive polarity toner charged to the opposite polarity to the charging polarity of the photoconductor 12 is charged to the negative polarity having the same polarity as the charging potential of the photoconductor 12. At this time, the first electrode 38
Since the surface potential of the photoreceptor 12 is relatively positive with respect to the potential of the photoreceptor 12, the negative residual toner may not be collected by the first electrode 38 while being attracted to the photoreceptor 12 by the electrostatic force. Absent. The surface potential of the photoconductor 12 of -700 V includes the charge of the charged toner.

Subsequently, as shown in FIG. 3B, the second electrode 40 (II ₁ ) comes into contact with the arbitrary point A due to a speed difference between the photosensitive member 12 and the charge recovery roller 32. At the time of image formation, the charged potential of the photoconductor 12 (−700) is applied to the second electrode 40.
V-3 having the same polarity as that of V) and having an absolute value smaller than that of V-3.
00V is applied. As a result, the potential of the second electrode 40 is relatively positive with respect to the surface potential of the photoreceptor 12, so that the residual toner of negative polarity is attracted by the electrostatic force and collected on the second electrode 40. . At this time, since the charged residual toner is collected, the surface potential of the portion of the surface of the photoreceptor 12 on which the residual toner has been loaded decreases by an amount corresponding to the charge of the collected residual toner on an absolute value basis. Positive memory will be generated as it is. Then, the following -1150
By the second contact with the first electrode 38 (I ₂ ) to which the voltage of V is applied, the surface of the arbitrary point A on the photoconductor 12 is uniformly charged again.

As described above, at any point on the photoconductor 12, the residual toner is all recovered from the photoconductor 12 through the three steps of charging, collecting the residual toner, and recharging. The surface can be uniformly charged. As a result, in the next exposure area, the surface of the uniformly charged photoconductor 12 having no residual toner can be exposed, so that a desired electrostatic latent image can be surely formed. A clear image can be obtained without image disturbances such as light and shade patterns and halftone roughness caused by being blocked. In addition, since the charging, collecting, and recharging steps can be performed only by the single charging and collecting roller 32, this is advantageous in reducing cost and size.

Here, assuming that a solid black image having the largest residual toner amount is formed on A4 size paper, the setting conditions required for the charge recovery roller 32 will be exemplarily considered. When the developing toner amount is 0.8 mg / cm ² and the transfer efficiency is 90%, the residual toner amount is

[0034]

0.8 × (1−0.9) = 0.08 mg / cm ²

## EQU1 ## A4 size paper length is about 29cm
Then, per 1 cm width,

[0036]

## EQU7 ## 0.08 × 29 = 2.32 mg / cm

The remaining toner is present. On the other hand, the maximum value of the toner holding ability of the second electrode 40 is set to 1.
Assuming 2 mg / cm ² , the total width of the second electrode 40 required to collect all the residual toner is:

[0038]

(Equation 8) 2.32 ÷ 1.2 = 1.93 cm

## EQU1 ## Here, assuming that the widths of the first electrode 38, the second electrode 40, and the distance between the electrodes 46 are the same, the outer circumference of the charge collection roller 32 is

[0040]

## EQU9 ## 1.93 × 3 = 5.79 cm

## EQU1 ## Therefore, the outer diameter of the charge collection roller 32 at this time is

[0042]

## EQU10 ## 5.79 / π = 1.84 cm

Is as follows. Therefore, in this assumption,
It is sufficient that the outer diameter of the charge collection roller 32 is about 19 mm, and it can be seen that a compact design is possible.

Next, at the time of non-image formation, the charge collection roller 3
The operation of discharging the residual toner collected in Step 2 onto the photoconductor 12 and collecting the residual toner in the developing device 16 will be described. At the time of non-image formation, as shown in FIG.
6 (see FIG. 1), a voltage having the same polarity as the charging potential of the photoconductor 12 and having an absolute value larger than that, for example, -1150 V, is applied to the second electrode 40. As a result, the surface of the photoconductor 12 becomes relatively positive with respect to the potential of the second electrode 40, so that the negative residual toner collected on the second electrode 40 is attracted by the electrostatic force, and 12 is returned.

The residual toner released on the photoreceptor 12 is
The developing sleeve 2 of the developing device 16 is rotated by the rotation of the photoconductor 12.
6 to the contact area. At this time, a bias of −300 V is applied to the developing sleeve 26, and the bias voltage is a voltage having the same polarity as the charging potential −700 of the photoconductor 12 and an absolute value smaller than that, and The developing sleeve 26 is relatively positive with respect to the surface potential. As a result, the negative residual toner on the photoconductor 12 adheres to the developing sleeve 26 by electrostatic force and is collected. The residual toner thus collected is stirred and mixed inside the developing device 16 and then used again for development. Therefore, it is not necessary to discard the residual toner, and the toner can be effectively used.

FIG. 5 shows the second electrode 4 of the charge collection roller 32.
6 is a chart showing the timing of switching between a residual toner recovery voltage of −300 V and a residual toner discharge voltage of −1150 V applied to 0. In the case of printing two or more sheets continuously, as shown in FIG. 5A, at least the time t (from the contact position with the charge collection roller 32 on the photoconductor 12 to the exposure position) is longer than the end of the exposure. Distance of photoconductor 12
(The time obtained by dividing by the peripheral speed of the exposure), the voltage for recovery is switched to the voltage for emission as soon as possible, and the voltage for emission is switched to the voltage for recovery as early as time t at least earlier than the start of the next exposure. As shown in FIG. 5B, similarly at the end of printing, the voltage is switched from the collecting voltage to the discharging voltage earlier than the end of the exposure by the time t at the earliest, and the switching to the collecting voltage is thereafter performed. The operation may be performed after all of the residual toner released on the surface 12 is collected by the developing device 16.

It should be noted that the specific numerical values and their positive / negative values in the above description, the charging polarity of the toner and the photoconductor are merely examples, and each numerical value and its polarity can be appropriately changed. The charge polarity of the body may be positive.

Next, another embodiment of the present invention will be described with reference to FIGS. Note that items that are not specified are the same as those of the image forming apparatus 10 according to the first embodiment.

In the image forming apparatus shown in FIG. 6, the first electrode 38 and the second electrode 40 are formed as a belt member 60, which is wound between two rollers 62, 64 and rotated to rotate the photosensitive member 12. It is designed to contact the surface. In the case of large-sized paper having a large amount of residual toner or toner having poor transfer efficiency, when the residual toner cannot be completely collected by the charge collection roller 32, the belt type is used to improve the residual toner collection ability. be able to.

In the image forming apparatus shown in FIG.
8 and the second electrode 40 are formed in a sheet shape and attached to a member 70 that reciprocates in the direction of the arrow.

In the image forming apparatus shown in FIG. 8, the first electrodes 38 and the second electrodes 40, each formed in a sheet shape, are alternately mounted on the outer periphery of the rotating shaft 80. The part is in sliding contact with the photoconductor 12. At this time, each electrode sheet is
The first electrode 38 and the second electrode 38
The sheet shape and arrangement are determined so that the electrodes 40 do not contact each other.

In the image forming apparatus shown in FIG. 9, a contact recovery roller 92 provided with a plurality of slits is provided around a wire 90 for corona discharge, and is brought into sliding contact with the photosensitive member 12 while rotating the roller 92. Things. In this case, since the surface of the photoconductor 12 is charged by corona discharge through the slit, the slit corresponds to the first electrode 38. Further, the portion forming the slit is the photosensitive member 1.
2 corresponds to the second electrode 40 that collects the residual toner by contacting the second electrode 40. Instead of the contact recovery roller 92, a belt member having a plurality of slits may be rotated around the wire 90.

In the image forming apparatus shown in FIG. 10, first electrodes 38 and second electrodes 40 are alternately provided on the outer periphery of the charge collection roller 100 in a protruding manner.
A gap 104 is provided between zeros. Thereby, at the entrance of the contact area between the charge collection roller 100 and the photoconductor 12,
The edges of the electrodes 38 and 40 are in sliding contact with the surface of the photoconductor 12. The material of each of the electrodes 38 and 40 has a hardness equivalent to that of a conventional cleaner blade (for example, 7 mm).
0 °). By doing so, foreign matter 102 such as glue adhered to the surface of the photoconductor 12 can be removed, so that image noise in the photoconductor cycle can be prevented, and
By gradually shaving the second photosensitive layer by the electrodes 38 and 40, image noise due to photoconductor filming can also be prevented.

In the image forming apparatus of each embodiment described above, the residual toner temporarily collected by the second electrode is returned to the photosensitive member once and collected by the developing device. May be collected in a collecting device (not shown) by an electrical or mechanical method, or may be sent back from the collecting device to the developing device.

The present invention is not limited to a one-component developer composed only of toner, but can be applied to an image forming apparatus using a two-component developer composed of toner and carrier.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is an enlarged perspective view of a charge collection roller.

FIG. 3 is a diagram for explaining a state of charging of a photoconductor and collection of residual toner by a charge recovery roller.

FIG. 4 is a diagram illustrating a state in which residual toner is released from a charge recovery roller and collected by a developing sleeve.

FIG. 5 is a chart showing a timing of switching a voltage applied to a second electrode of a charge recovery roller.

FIG. 6 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment.

FIG. 7 is a schematic configuration diagram illustrating an image forming apparatus according to a third embodiment.

FIG. 8 is a schematic configuration diagram illustrating an image forming apparatus according to a fourth embodiment.

FIG. 9 is a schematic configuration diagram illustrating an image forming apparatus according to a fifth embodiment.

FIG. 10 is a schematic configuration diagram illustrating an image forming apparatus according to a sixth embodiment.

[Explanation of symbols]

10 image forming apparatus, 12 photoconductor (image carrier), 16
Developing device (contact developing means), 18 transfer roller (transfer means), 20 laser device (exposure means), 32 charge recovery roller (contact charging means), 38 first electrode, 40 second electrode.

Claims (3)

[Claims] 1. An image carrier, an exposure unit for exposing a surface of the uniformly charged image carrier in accordance with image information to form an electrostatic latent image, and developing the electrostatic latent image with a developer Contact developing means, and a transfer means for transferring a developer image visualized on the surface of the image carrier to a transfer-receiving body, wherein the developer remaining on the image carrier after transfer is subjected to the contact development. In the image forming apparatus, the contact charge recovery means is provided between the transfer means and the exposure means, the contact charge recovery means being in contact with the image carrier, and the contact charge recovery means alternately slides on the surface of the image carrier. A first electrode and a second electrode that are in contact with each other, and at least the first electrode and the second electrode are provided while an arbitrary point on the image carrier passes through a contact area with the contact charge recovery unit.
The electrode and the first electrode are set so as to be in contact with the three electrodes in this order.
At the first contact with the electrode, the surface of the image carrier is uniformly charged, and the developer remaining on the image carrier after transfer is charged to the same polarity as the charge polarity of the image carrier. The residual developer is temporarily recovered by contact with the second electrode to which a voltage of the same polarity and an absolute value smaller than that is applied, and then the surface of the image carrier is contacted by the second contact with the first electrode. An image forming apparatus characterized by being uniformly charged again. 2. During non-image formation, a voltage having the same polarity as the charge potential of the image carrier and an absolute value greater than the voltage is applied to the second electrode of the contact charge recovery means to temporarily recover the developer. Returning to the carrier, applying a voltage having the same polarity as the charging potential of the image carrier and an absolute value smaller than the voltage to the contact developing unit to recover the developer from the image carrier to the contact developing unit. The image forming apparatus according to claim 1, wherein: 3. A gap is provided between the first electrode and the second electrode, and an edge of each of the electrodes slides on the surface of the image carrier at an entrance of a contact area between the image carrier and the contact charge recovery means. The image forming apparatus according to claim 1, wherein: