JP2003114560A - Image forming device and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and a process cartridge that output a satisfactory image free of an image defect, such as retransfer ghost, with an inexpensive configuration in a color cleaner-less system having a plurality of image forming stations. SOLUTION: In the image forming device having the electrophotographic image forming stations, a developing roller 5 is rotated so that the movement of the developing roller 5 is opposite to the movement of the surface of the photoreceptor drum 1 at the position where the photoreceptor 1 and the developing roller 5 face each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a laser beam printer or an electrophotographic copying machine, and a process cartridge detachably mountable to the main body of the apparatus, and more particularly to a cleanerless system having a plurality of developing devices. The present invention relates to a color image forming apparatus and a process cartridge.

[0002]

2. Description of the Related Art Conventionally, in image forming apparatuses such as electrophotographic copying machines and laser beam printers, generally, a charging process for uniformly and uniformly charging an image carrier such as a photosensitive drum, and an image carrier after charging. Exposure process to write an electrostatic latent image, development process to attach toner to the electrostatic latent image to develop it as a toner image, transfer process to transfer the toner image on the image carrier to a transfer material such as paper, transfer An image is formed by a series of image forming processes including a fixing process for fixing the toner image on the material and a cleaning process for removing the residuals such as transfer residual toner remaining on the surface of the image carrier after the toner image is transferred. There is.

In the above-mentioned cleaning process, the transfer residual toner collected by the cleaning device is stored in a disposal container and then disposed.

Therefore, in recent years, a cleanerless process has been proposed in which the above-mentioned cleaning device is omitted, the image forming apparatus is downsized, and maintenance such as discarding transfer residual toner is unnecessary. In one form of this cleanerless process, the developing device causes the toner to adhere to the exposed portion of the image bearing member where the surface potential is attenuated by reversal development, and at the same time, removes the residue remaining in the non-exposed portion. Collected.

That is, after the transfer process, the residue remaining on the image carrier without being transferred is the surface potential of the image carrier and the developing bias applied to the developer carrier after passing through the charging process. Difference (hereinafter referred to as "back contrast")
Is collected by the developing device by electrostatic force. This is seen in the cleanerless process of monochrome laser printers.

Specifically, in the case of a one-component developer composed of a negatively chargeable toner, the image carrier is uniformly charged to −600 V in the charging step, and corresponds to the image portion of the image carrier in the exposure step. The exposed portion is exposed to attenuate the surface potential so that the exposed portion becomes −200 V, and a DC voltage of −400 V is applied as a developing bias to the developer carrying member in the developing step. Remains on the image bearing member as it is in the exposed portion corresponding to the image portion, but is collected in the developing device due to the back contrast in the non-exposed portion, and the transfer residual toner is collected without a cleaning device. It can be reused as a developer.

In the recent laser beam printer market, color laser printers have become the mainstream.

What is needed therefor is an inexpensive and compact color printer, similar to a monochrome printer. Therefore, it has become necessary to construct a simple electrophotographic system.

[0009]

However, when the cleanerless system used in the monochrome electrophotographic system in the prior art as described above is applied to the full-color electrophotographic system, the following problems occur. It was

FIG. 1 is a schematic sectional view of a conventional image forming apparatus. In the case of the above-described negatively chargeable toner, a positive charge is applied to the transfer material in the transfer step in order to transfer the toner to the transfer material, and the negatively charged toner is transferred to the transfer material. Therefore, most of the transfer residual toner is usually positively charged, but it is negatively charged by passing through the charging step and remains on the photosensitive drum.

Therefore, the negative toner remaining on the image portion of the photosensitive drum is developed while remaining on the image portion of the photosensitive drum, and the negative toner remaining on the non-image portion is collected by the developing device. This is not a problem in the monochrome cleanerless because the toner remaining in the image portion is the toner of the same color.

However, in the color electrophotographic system,
Since a plurality of colors are used, there arises a problem of difference in color tone of the transfer residual toner.

FIG. 2 shows a mechanism of transfer residual toner in a second color image forming station of the color electrophotographic system.

In the color electrophotographic system, the toner image formed on the photosensitive drum of each image forming station is sequentially transferred onto a transfer material (for example, paper or OHP sheet) carried and conveyed by a belt-like transfer material conveying means. It will be transferred in layers.

In the image forming apparatus having such a structure, for example, the toner transferred onto the transfer material at the previous station adheres to the photosensitive drum of the next station when it reaches the next station. So-called re-transfer may occur, and it may be included in the transfer residual toner of the next station (in FIG. 2, the toner of the positive polarity on the drum after transfer corresponds).

The transfer toner of the preceding station is naturally a toner of a different color (the transfer toner of the preceding station is hereinafter referred to as retransfer toner). These are negatively charged by passing through the charging device, and the toner remaining in the non-image area is collected by the developing device, but the retransfer toner of a different color remaining in the image area on the photosensitive drum is developed. Part is not collected and remains in the image part as it is and developed, and appears in the image as a ghost with a different color.

In order to eliminate the ghost of the retransfer toner, it is necessary to prevent the retransfer toner in the image area in a process upstream of the developing process. As an example, there is known a process in which an auxiliary member such as a brush for temporarily collecting the transfer residual toner on the photosensitive drum is provided in front of the charging roller. However, the process becomes complicated and expensive.

The present invention has been made in view of the above-mentioned prior art, and an object of the present invention is to provide an image forming apparatus and a process cartridge which prevent color mixture during development.

Another object of the present invention is to provide an image forming apparatus and a process cartridge which prevent retransfer ghost.

Another object of the present invention is to provide an image forming apparatus and a process cartridge suitable for a cleanerless system which does not have a dedicated cleaner.

Another object of the present invention is to provide an image forming apparatus and a process cartridge in which residual developer on the image carrier is completely removed during development.

Another object of the present invention is to provide an image forming apparatus and a process cartridge in which the residual developer on the image bearing member is aligned in a regular polarity so that it can be easily collected during development.

[0023]

In order to achieve the above object, in an image forming apparatus according to the present invention, a first image carrier and a first charging member are used to form the first image carrier. A first charging unit for charging and a developer of a first color are carried and conveyed, and the electrostatic image formed on the first image carrier is transferred to the first image carrier.
A first image forming station including a first developer carrying member which develops with a developer of the color, and a second image carrying member,
Second charging means for charging the second image bearing member by a second charging member that is capable of contacting the second image bearing member;
A second developer carrying member carrying and carrying a developer of the second color and developing the electrostatic image formed on the second image carrying member with the second color developer. After the image of the developer of the first color is transferred to the image forming station and the image receiving member in the first image forming station, the second color is developed to the image receiving member in the second image forming station. Transfer means for transferring the image of the developer, the second developer carrying member is capable of collecting the residual developer from the second image carrying member at the same time as the developing operation. The developer of the second color carried by the developer carrier is provided in contact with the second image carrier, and the moving direction of the second developer carrier is the second direction at the developing position. In a direction opposite to the moving direction of the image carrier, and the second charging member is disposed on the second image carrier. Frictionally charging the distillate developer to normal polarity, characterized in that.

Alternatively, the first image bearing member, the first charging means for charging the first image bearing member, and the developer of the first color are carried and conveyed to the first image bearing member. A first image forming station including a first developer carrier that develops the formed electrostatic image with the developer of the first color, a second image carrier, and the second image. A second charging unit for charging the carrier and a developer of the second color are carried and conveyed, and the electrostatic image formed on the second image carrier is developed with the developer of the second color. A second image forming station having a second developer carrying member, and the second image after the image of the developer of the first color is transferred to the image receiving member at the first image forming station. The second image is transferred to the image receiving member at the forming station.
Transfer means for transferring the image of the developer of the color, the second developer carrying member is capable of collecting the residual developer from the second image carrying member at the same time as the developing operation, The second color developer carried on the second developer carrier is provided in contact with the second image carrier, and the moving direction of the second developer carrier is the developing position. In, the direction is opposite to the moving direction of the second image carrier.

It is preferable that the image receiving member has a conveying means for conveying the image receiving member from the first image forming station to the second image forming station.

The second developer carrying member is preferably provided in contact with the second image carrying member.

Further, it is preferable that the second developer carrying member is provided with an elastic layer.

Further, the second developer carrying member holds the residual developer on the second image carrying member in a nip portion between the second developer carrying member and the second image carrying member. It is preferable to collect it in the second developer carrying member by stopping it before the above.

It is preferable that a DC voltage is applied to the second developer carrying member without applying an AC voltage.

The developer of the second color is preferably a one-component developer.

It is preferable that the second charging member charges the second image carrier by using discharge.

Further, it is preferable that a DC voltage is applied to the second charging member without applying an AC voltage.

Further, it is preferable that the second charging member is rotatable with respect to the second image carrier with a peripheral speed difference.

The first developer carrying member is provided in contact with the first image carrying member, and the second developer carrying member is provided in contact with the second image carrying member. Is preferred.

It is preferable that each of the first and second developer carrying members has an elastic layer.

The first developer carrying member removes the residual developer on the first image carrying member in front of a nip portion between the first developer carrying member and the first image carrying member. The second developer carrying body collects the residual developer on the second image carrying body by collecting the residual developer on the second developer carrying body with the second developer carrying body. It is preferable that the toner is collected in the second developer carrier by damming it in front of the nip portion with the second image carrier.

The first and second developer carrying members are AC
It is preferred that the DC voltage be applied without the voltage being applied.

The first color developer and the second color developer are preferably one-component developers.

The first charging member charges the first image carrier by using discharge, and the second charging member charges the second image carrier by using discharge. Is preferred.

It is preferable that a DC voltage is applied to the first and second charging members without applying an AC voltage.

The first charging member is rotatable with respect to the first image carrier with a peripheral speed difference, and the second charging member is rotatable with respect to the second image carrier. It is preferred that they can be rotated with a difference.

Further, in the process cartridge according to the present invention, after the developer image of the first color is transferred to the image receiving member in the first image forming station, the image receiving member is transferred in the second image forming station. A process cartridge detachably mountable to the second image forming station of an image forming apparatus main body, which comprises a transfer means for transferring a developer image of a second color to the image carrier, and the image carrier by a charging member. And a developer carrier for carrying and conveying the developer of the second color and developing the electrostatic image formed on the image carrier with the developer of the second color. The developer carrying member is capable of collecting the residual developer from the image carrying member at the same time as the developing operation, and the developer of the second color carried by the developer carrying member is the image carrying member. It is provided in contact with the body and bears the developer. The moving direction of the body is opposite to the moving direction of the image carrier at the developing position, and the charging member frictionally charges the residual developer on the image carrier to a regular polarity. To do.

Alternatively, after the developer image of the first color is transferred to the image receiving member in the first image forming station, the developer image of the second color is transferred to the image receiving member in the second image forming station. A process cartridge attachable to and detachable from the second image forming station of an image forming apparatus main body including a transfer unit, the image carrier, a charging unit that charges the image carrier, and a developer of the second color. And a developer carrier for developing the electrostatic image formed on the image carrier with the developer of the second color. The residual developer can be collected from the image carrier, and the second developer carried by the developer carrier can be collected.
The color developer is provided in contact with the image carrier, and the moving direction of the developer carrier is opposite to the moving direction of the image carrier at the developing position.

It is preferable that the image forming apparatus main body has a conveying means for conveying the image receiving member from the first image forming station to the second image forming station.

The developer carrying member is preferably provided in contact with the image carrying member.

Further, it is preferable that the developer carrying member has an elastic layer.

Further, the developer bearing member is dammed to the developer bearing member by damming the residual developer on the image bearing member in front of the nip portion between the developer bearing member and the image bearing member. It is preferable to collect.

Further, it is preferable that a DC voltage is applied to the developer carrying member without applying an AC voltage.

The developer of the second color is preferably a one-component developer.

It is preferable that the charging member charges the image carrier by using electric discharge.

Further, it is preferable that a DC voltage is applied to the charging member without applying an AC voltage.

Further, it is preferable that the charging member is rotatable with respect to the image carrier with a peripheral speed difference.

With the above-described structure, in a cleanerless color system that collects images at the same time as development, it is possible to provide a good image with a simple structure, eliminating image defects such as retransfer ghosts.

[0054]

BEST MODE FOR CARRYING OUT THE INVENTION An image forming apparatus according to a preferred embodiment of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative positions, and the like of the components described in this embodiment are not intended to limit the scope of the present invention to them unless otherwise specified. Absent.

(First Embodiment) FIG. 3 shows a schematic structure of a tandem type color laser beam printer having a plurality of developing devices as an example of an image forming apparatus according to the present invention. It should be noted that this figure shows a vertical cross-sectional view of the transfer material 8, which is an image receiving member, along the transport direction.

Referring to FIG. 3, the color image forming apparatus has an endless transfer belt 9 which is a transfer material conveying means for carrying and transferring the transfer material 8, and a transfer belt 9.
Process cartridges P1, P2 as image forming stations for forming toner images of different colors in the respective moving directions of
P3 and P4 are arranged in series. The toners stored in the developing devices 4y, 4m, 4c, and 4k of each image forming unit are of different colors, and the basic operation is the same. Also,
The process cartridge is attachable to and detachable from the main body of the image forming apparatus.

Here, the image forming unit portions P1 to P4 as image forming means are composed of four image forming units of yellow (Y), magenta (M), cyan (C) and black (Bk). Has been done. The respective image forming unit sections are configured such that photosensitive drums 1y, 1m, 1c, and 1k, which are image bearing members, are arranged, and yellow toner, magenta toner, and cyan toner, which are one-component developers, are arranged on the outer peripheral portions thereof. , Developing devices (developing means) 4y, 4m, 4c, 4k having developing rollers 5y, 5m, 5c, 5k, which are developer carrying bodies for accommodating the black toners and carrying the toners, and 3y being exposure means Three
m, 3c, 3k, and charging rollers (charging members) 2y, 2m, 2c, 2k are provided. In addition, transfer rollers 6y, 6m, 6c and 6k as transfer means are provided at positions facing the respective photosensitive drums 1 with the transfer belt 9 interposed therebetween.
Is provided.

The transfer material conveying means in this image forming apparatus is an electrostatic transfer belt 9 which is suspended by a plurality of suitable rollers and runs. The transfer roller 6 is provided inside and around the electrostatic transfer belt 9. The suction roller 10 is provided. A plurality of transfer rollers 6 are provided as a part of a plurality of image forming units described later.

The attraction roller 10 of the electrostatic transfer belt 9 electrostatically attracts the transfer material 8 conveyed from the paper feeding section onto the electrostatic transfer belt 9 prior to image formation. Each of the image forming portions P1 to P4 has a transfer material 8 electrostatically adsorbed on the electrostatic transfer belt 9.
, The yellow toner image, the magenta toner image, the cyan toner image,
Images are formed at the same timing so that the black toner images are overlapped, and the images are sequentially superimposed and transferred.

The image forming procedure will be described below with respect to the image forming unit P.
The description will be focused on 1.

The surface photosensitive layer of the photosensitive drum 1y, which is rotationally driven by a driving means (not shown), has a charging bias of -1150V.
Is uniformly charged by the charging roller 2y. The charging bias was a DC voltage without an AC voltage, and the surface potential of the photosensitive drum 1y was set to -600V. That is, the photosensitive drum 1y is charged to a potential of approximately (applied DC voltage-discharge start voltage) due to the discharge phenomenon in the minute gap between the photosensitive drum 1y and the roller 2y. In the present embodiment, the discharge starting voltage was about 550V. An image forming signal of a yellow component is projected from the laser scanner on the charged surface of the photosensitive drum 1y to form an electrostatic latent image.

When this electrostatic latent image reaches the developing portion as the photosensitive drum 1y rotates, the developing roller 5y imparts a negatively-charged yellow toner to the latent image by the developing bias, and the latent image is inverted as a yellow toner image. It is developed. The yellow toner image is further sent to the transfer portion as the photosensitive drum 1y rotates.

The transfer material 8 on which the yellow toner image has been transferred and transferred is conveyed, and the transfer bias applied to the transfer roller 6y (electrostatic absorption plus polarity is preliminarily set on the transfer belt 9 in accordance with the timing of reaching a portion. ), The yellow toner image is transferred (transferred) onto the transfer material 8. The residual toner that does not contribute to the transfer and remains on the photosensitive drum 1y is charged by the charging roller 2y to a regular polarity (negative polarity) that can be collected by the developing device. The photosensitive drum is also negatively charged. Many of the residual toners on the photosensitive drum after the transfer have a polarity opposite to the regular polarity (minus polarity), but the charging roller 2y is charged using discharge to be strongly charged to the negative polarity. To be done.

In order to strongly and negatively charge the residual toner, the voltage applied to the charging roller 2y is preferably a DC voltage without an AC voltage. Because, when the applied voltage is a superimposed voltage of AC voltage and DC voltage, A
This is because the residual toner is discharged by the action of the C voltage.
Further, in order to more positively charge the residual toner on the photosensitive drum to the negative polarity, it is preferable that the surface layer of the charging roller 2y has a triboelectrification polarity that triboelectrically charges the toner to the negative polarity. That is, it is preferable to select the material of the surface layer of the charging roller 2y and the material of the toner so that the toner is negatively frictionally charged by the charging roller.

Then, with the residual toner remaining on the photosensitive drum, the photosensitive drum is irradiated with light according to the image information by the laser scanner. At the same time that the developing device develops the latent image, the residual toner charged to the regular polarity by the charging roller 2y is collected by the developing device. then,
The photosensitive drum 1y is already in the next image forming operation.

The transfer material 8 onto which the yellow toner image has been transferred is conveyed to the image forming portion P2 as the transfer belt 9 moves. By the time the transfer material 8 reaches the image forming portion P2, a magenta toner image is formed on the photosensitive drum 1m by the laser scanner 3m and the developing roller 5m, and this toner image is transferred by the transfer roller 6m as described above. The yellow toner image is superimposed and transferred. The transfer material 8 onto which the superimposed toner image has been transferred is conveyed to the image forming portion P3.

Similarly, in the image forming sections P3 and P4, the cyan toner image and the black toner image are formed on the photosensitive drums 1c and 1k by the laser scanners 3c and 3k and the developing rollers 5c and 5k, and the transfer rollers 6c and 6k. Thus, the superimposed toner images are sequentially superimposed and transferred, and the transfer process is completed.

The transfer material 8 that has been transferred reaches the fixing device 12, where it is heated and pressed to melt and mix the toner images to form a color image, which is fixed and fixed on the transfer material 8.
It is discharged outside the aircraft.

The photosensitive drum 1y is constructed by providing a photosensitive layer (for example, an organic optical semiconductor, amorphous silicon, etc.) on the surface of a conductive cylindrical drum substrate. The photosensitive drum 1 is rotationally driven by driving means (not shown),
The surface has a predetermined surface moving speed (hereinafter abbreviated as peripheral speed).
It is designed to move (rotate) in the direction of the arrow.

The charging roller 2y has a structure in which the outer peripheral surface of a cored bar is covered with an elastic body, and the surface of the elastic body is covered with the photosensitive drum 1y.
It is placed in contact with the surface.

The developing device 4y includes a developing roller 5y that is rotationally driven, a developing blade that regulates the layer thickness of the toner carried on the surface of the developing roller 5y, and a new roller that supplies new toner to the developing roller 5y. To remove old toner from the developing device, the toner supply roller 7 (see FIG. 4) that is rotated by the counter with respect to the developing roller is provided to the developing device 4y.
It is placed inside. The toner supply roller 7 is provided in pressure contact with the developing roller.

As the toner, either magnetic or non-magnetic toner can be used, and the manufacturing method thereof may be either polymerization or pulverization. The toner used in the present embodiment has a negative charging property that is normally charged negatively by friction.

The toner applied to the surface of the developing roller 5y and the layer thickness of which is regulated by the developing blade is applied with a developing bias (DC voltage) of -400V to the developing roller 5y by a power source (not shown), and thus the photosensitive drum The electrostatic latent image is developed as a toner image by being attached to the exposed portion on 1y.

On the other hand, residuals on the photosensitive drum such as transfer residual toner remaining on the surface of the photosensitive drum after the toner image is transferred are removed as follows.

The toner attached to the surface of the photosensitive drum from the developing device during development is negatively charged. At the time of transfer, the back surface of the transfer material is positively charged by the transfer roller 6 and the toner is transferred onto the transfer material by the electric field. At this time, since the photosensitive drum is also positively charged, a part of the toner is positively charged, and as a result, the toner remains on the photosensitive drum without being transferred to the transfer material.

The photosensitive drum 1 without being transferred onto the transfer material 8.
Some of the residue on the photosensitive drum left on the surface is positively and negatively charged. Those that are negatively charged are collected during development. However, in order to collect the positively charged residue on the photosensitive drum by back contrast during development, it is necessary to negatively charge the residual material on the photosensitive drum. This is performed at the same time that the surface of the photosensitive drum is negatively charged by the charging roller. In this way, the residue on the photosensitive drum is recovered to the original developing device.

However, in the secondary color station and the tertiary color station, when the developing roller rotates in the forward direction with respect to the photosensitive drum, the retransferred toner is collected by the developing device simultaneously with the development, as shown in FIG. Instead, they remain in the image portion as they are, which causes adverse effects on the image.

Therefore, in the present embodiment, the simultaneous development and recovery of the retransfer toner is performed as follows.

In this embodiment, as shown in FIG. 4, the photosensitive drum 1 and the developing roller 5 are provided in contact with each other, and the photosensitive drum 1 is rotated with respect to the moving direction of the surface of the photosensitive drum 1 rotating at a predetermined peripheral speed. At the contact portion between 1 and the developing roller 5, it is rotated in the opposite direction (arrow direction).

In this embodiment, the developing roller is rotated in the opposite direction (counter direction) at a peripheral speed of 170% of the peripheral speed of the photosensitive drum. By doing so, as shown in FIG. 4, a peripheral speed difference is provided between the surface of the photosensitive drum 1 and the surface of the developing roller 5, and a nip pressure is provided to mechanically stop the retransfer toner before the nip. The progress of the retransfer toner is hindered, and the developing device collects the retransfer toner.

The residue on the photosensitive drum collected by the developing roller 5 is agitated by the agitating member in the developing device 4 and mixed with other toner to be reused. Since toners of different colors are very small, they are mixed in the developing device to a level that causes no problem on the image.

Actually, image evaluation was carried out when the developing roller 5 was rotated in the forward direction and in the reverse direction with respect to the rotation direction of the photosensitive drum.

As a sample image, a pattern image as shown in FIG. 5 was used. In the area A, a 4 cm square solid black image is written, and in the area B, a halftone pattern is written. In the area A, the image forming pattern of only yellow was formed as the primary color, and in the area B, the image forming pattern of only magenta was formed as the secondary color.

As a result, when the yellow toner is not collected by the development, the image pattern of the area A appears in the area B, which causes an adverse effect on the image. Therefore, an image is output when the developing roller is rotated in the forward direction and in the reverse direction with respect to the photosensitive drum. It should be noted that the image adverse effect can be recognized as shown in FIG. 6, and the images are compared by the density of the area C and the tint difference of the area D. The results are shown in Table 1. O indicates that no difference in color tone could be confirmed, and X indicates that adverse image effects were confirmed in the image pattern.

[0085]

[Table 1] As described above, the counter developing method in which the developing roller is rotated in the direction opposite to the rotating direction of the photosensitive drum was able to obtain a good image without adverse effects of tint.

As described above, in the present embodiment, in the cleanerless type color image formation, the surface of the developing roller is opposed to the developing roller and the photosensitive drum without using an auxiliary member such as a brush immediately after transfer and before charging. Is moved in the direction opposite to the moving direction of the photosensitive drum surface. As a result, the retransfer toner is mechanically blocked before the nip to inhibit the progress of the retransfer toner, and the developing device collects the retransfer toner. As a result, in a simple color cleaner-less system, it was possible to obtain a high quality image without the influence of retransfer toner.

Although the process cartridge in which the charging device, the developing device and the photosensitive drum are integrated is used in the present embodiment, the charging device or the developing device may be provided in the image forming apparatus main body. Each photosensitive drum may be provided in the main body of the image forming apparatus.

Further, an image system in which the image forming apparatus is combined with an image input means such as a scanner and a control means such as a computer or a server may be used.

(Second Embodiment) Next, a second embodiment according to the present invention will be described. In the second embodiment, the structure of the image forming apparatus and the structure of the developing apparatus are the same as those in the first embodiment, and therefore the description thereof will be simplified and the characteristic structure of the present invention will be described.

In the first embodiment, as the charging device, the charging roller which is driven by the photosensitive drum is used. However, in this embodiment, the surface of the charging roller is brought into contact with the surface of the photosensitive drum rotating at a predetermined peripheral speed and further rotated in the forward direction so that the peripheral speed is different, or the reverse direction is used. It shall be performed with a structure that rotates it.

In such a structure, even if the transfer residual toner adheres to the charging roller, the charging performance for the transfer residual toner does not deteriorate, and the transfer residual toner is easily frictionally charged to a desired polarity for a long period of time. As a result, no adverse effect on the image such as retransfer ghost occurs. In the experiments conducted by the present inventor, it has been found that a peripheral speed difference of 1% or more is effective, and the peripheral speed difference described above means a difference of 1% or more in peripheral speed. Is.

Next, the configuration of the present embodiment will be described.

FIG. 7 shows a schematic view of the apparatus main body. The cartridges P21, P22, P23, and P24 integrally house a photosensitive drum, a charging roller, a developing roller, and a toner container.

The charging roller 22 is rotated in the forward direction with respect to the rotation direction of the photosensitive drum, and the charging roller 22 is set to 1 with respect to the peripheral speed of the photosensitive drum.
It was rotated at a peripheral speed of 20%. In this way, by providing a peripheral speed difference between the surface of the photosensitive drum and the surface of the charging roller, contaminants such as toner on the surface of the charging roller are rubbed,
It is possible to effectively perform negative charging by frictional charging. Here, the negatively charged toner is
It moves to the surface of the photosensitive drum due to the potential difference between the charging roller and the photosensitive drum (for example, charging roller applied voltage 1250V, photosensitive drum potential −700V). Note that, as in the first embodiment, the charging roller charges the photosensitive drum by using electric discharge, and this discharge also tends to strongly charge the toner negatively.

The transfer residual toner (including the most transferred toner) that has been negatively charged is collected by the developing roller that rotates in the direction opposite to the moving direction of the surface of the photosensitive drum, is stored in the developing container, and the toner is collected by the stirring member. Be stirred. Since the retransfer toner is very small, the retransfer toner is mixed in the developing device to a level that causes no problem on the image.

The members used are the same as those used in the second embodiment. By adopting such a configuration, the same effect as that of the first embodiment can be obtained.

As a result, in a simple color cleanerless system, it is possible to prevent the transfer roller from being contaminated by the transfer residual toner on the charging roller and obtain a high quality image without the influence of the retransfer toner.

In each of the above-described embodiments, the same developing device is used in all the image forming stations, but in the image forming station for the first color,
Since the retransfer toner hardly adheres, the developing device of the image forming station for the first color is not limited to the developing device.

That is, in the image forming station for the first color, the developing roller can be rotated in the forward direction with respect to the rotating direction of the photoconductor, or the photoconductor and the developing roller are not in contact with each other and the developing roller on the developing roller is not in contact. Toner can also be made to fly to the photoconductor. However, when the toners of the other colors are easily conveyed to the image carrier of the first color by the transfer belt and the retransfer toners are easily attached to the image carrier of the first color, as in the first and second embodiments. Further, it is effective that the developing device of the image forming station for the first color is the same as the developing devices of the other stations.

In the above embodiment, the image receiving member is the transfer material, and the transfer material is carried by the transfer belt and conveyed to each image forming station. However, the image receiving member is used as the intermediate transfer belt and the intermediate image is transferred from each image forming station. After the toner images of the respective colors are superimposed and transferred to the transfer belt, the superimposed toner images may be collectively transferred from the intermediate transfer belt to the transfer material.

[0101]

As described above, according to the present invention, in a simple color cleanerless system for simultaneous recovery of development, by rotating the developer carrying member in the opposite direction to the moving direction of the surface of the image carrying member. It is possible to eliminate adverse effects on the image such as retransfer ghost.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a conventional image forming apparatus.

FIG. 2 shows a mechanism of transfer residual toner in a secondary color station of a color electrophotographic system.

FIG. 3 is a sectional view of the image forming apparatus according to the first embodiment.

FIG. 4 is a schematic diagram showing how retransfer toner is collected in the image forming apparatus according to the first embodiment.

FIG. 5 is a diagram showing a pattern image for confirming an image adverse effect.

FIG. 6 is a diagram showing a pattern image in which a retransfer ghost appears.

FIG. 7 is a sectional view of an image forming apparatus according to a second embodiment.

[Explanation of symbols]

1, 1y, 1m, 1c, 1k Photosensitive drum 2, 2y, 2m, 2c, 2k Charging roller 4, 4y, 4m, 4c, 4k Developing device 5, 5y, 5m, 5c, 5k Developing roller 6, 6y, 6m, 6c, 6k Transfer roller 7 Toner supply roller 8 Transfer material 9 Transfer belt 10 Adsorption roller 12 Fixing device P1, P2, P3, P4 Process cartridge (image forming unit)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/08 G03G 15/08 501Z 503 503A 507 507B F term (reference) 2H077 AA37 AC16 AD02 AD06 AD31 AD35 BA09 EA11 EA15 FA21 GA13 2H200 FA08 GA12 GA23 GA34 GA46 GA47 GA52 GB37 HA04 HA28 HB12 HB22 HB47 HB48 JA02 JB06 LA19 LA38 MC01 MC14 NA02 NA09 2H300 EA05 EB04 EB07 EB12 EF02 EF08 EG02 EG04 EG05 EG08 EJ09 EJ23 EJ29 EJ33 EL03 EM03 GG18 GG29 HH19 MM01 MM28 PP02

Claims (30)

[Claims] 1. A first image carrier, a first charging means for charging the first image carrier by a first charging member, and a first charging device.
A first developer carrier that carries and conveys a developer of the color of, and develops the electrostatic image formed on the first image carrier with the developer of the first color. An image forming station, a second image carrier, and a second charging member capable of contacting the second image carrier to charge the second image carrier.
And a second developer carrying member for carrying and carrying the second color developer and developing the electrostatic image formed on the second image carrier with the second color developer. A second image forming station, and the first image forming station to the image receiving member in the first image forming station.
Transfer means for transferring the image of the developer of the second color to the image receiving member at the second image forming station after transferring the image of the developer of the second color. At the same time as the developing operation, the agent carrier is used for the second
Residual developer can be collected from the image carrier, and the second color developer carried on the second developer carrier is provided in contact with the second image carrier, The moving direction of the second developer carrying member is opposite to the moving direction of the second image carrying member at the developing position, and the second charging member is arranged on the second image carrying member. An image forming apparatus characterized in that the residual developer is triboelectrically charged to a regular polarity. 2. The image forming apparatus according to claim 1, further comprising a conveying unit that conveys the image receiving member from the first image forming station to the second image forming station. 3. The second developer carrying member is provided in contact with the second image carrying member.
Alternatively, the image forming apparatus described in 2. 4. The image forming apparatus according to claim 3, wherein the second developer carrier comprises an elastic layer. 5. The second developer carrying member holds the residual developer on the second image carrying member in a nip portion between the second developer carrying member and the second image carrying member. 5. The image forming apparatus according to claim 3, wherein the image is collected in the second developer carrying member by being dammed in front of the second developer carrying member. 6. The image forming apparatus according to claim 3, 4 or 5, wherein a DC voltage is applied to the second developer carrying member without applying an AC voltage. 7. The image forming apparatus according to claim 3, wherein the developer of the second color is a one-component developer. 8. The image forming apparatus according to claim 1, wherein the second charging member charges the second image carrier by using discharge. 9. The image forming apparatus according to claim 8, wherein a DC voltage is applied to the second charging member without applying an AC voltage. 10. The image forming apparatus according to claim 1, wherein the second charging member is rotatable with respect to the second image carrier with a peripheral speed difference. 11. The first developer carrying member is provided in contact with the first image carrying member, and the second developer carrying member is provided in contact with the second image carrying member. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided. 12. The image forming apparatus according to claim 11, wherein the first and second developer carrying members each include an elastic layer. 13. The first developer carrying member retains the residual developer on the first image carrying member in a nip portion between the first developer carrying member and the first image carrying member. The second developer carrying member collects the residual developer on the second image carrying member by collecting the residual developer on the second image carrying member by damaging it in front of the second developer carrying member. 13. The image forming apparatus according to claim 11, wherein the image is collected in the second developer carrying member by damming it in front of a nip portion between the second developer carrying member and the second image carrying member. 14. The first and second developer carriers are A
14. The image forming apparatus according to claim 11, 12 or 13, wherein a DC voltage is applied without applying a C voltage. 15. The developer of the first color and the developer of the second color is
11. A one-component developer, wherein the developer is a one-component developer.
The image forming apparatus according to any one of 4 above. 16. The first charging member charges the first image carrier by using discharge, and the second charging member charges the second image carrier by using discharge. The image forming apparatus according to claim 1, wherein: 17. The image forming apparatus according to claim 16, wherein the first and second charging members are applied with a DC voltage without being applied with an AC voltage. 18. The first charging member is rotatable with a peripheral speed difference with respect to the first image carrier, and the second charging member is rotatable.
The image forming apparatus according to claim 1, wherein the charging member is rotatable with respect to the second image carrier with a peripheral speed difference. 19. A first image forming station transfers a developer image of a first color to an image receiving member, and then a second image forming station transfers a developer image of a second color to the image receiving member. A process cartridge attachable to and detachable from the second image forming station of an image forming apparatus main body including a transfer unit, comprising: an image carrier, a charging unit that charges the image carrier by a charging member, and the second color. And a developer carrier for carrying and carrying the developer and developing the electrostatic image formed on the image carrier with the developer of the second color. At the same time, the residual developer can be collected from the image carrier, and the developer of the second color carried by the developer carrier is provided in contact with the image carrier, The moving direction of the body is such that at the developing position, The process cartridge is in a direction opposite to a moving direction, and the charging member frictionally charges the residual developer on the image carrier to a regular polarity. 20. The process according to claim 19, wherein the image forming apparatus main body has a conveying unit that conveys the image receiving member from the first image forming station to the second image forming station. cartridge. 21. The developer carrier is provided in contact with the image carrier.
0 process cartridge. 22. The process cartridge according to claim 21, wherein the developer carrying member includes an elastic layer. 23. The developer carrying member is damped to the developer carrying member by damming the residual developer on the image carrying member in front of a nip portion between the developer carrying member and the image carrying member. 23. Collecting according to claim 21 or 22
The process cartridge described in 1. 24. The process cartridge according to claim 21, 22 or 23, wherein a DC voltage is applied to the developer carrying member without applying an AC voltage. 25. The process cartridge according to claim 21, wherein the developer of the second color is a one-component developer. 26. The process cartridge according to claim 19, wherein the charging member charges the image carrier by using electric discharge. 27. The process cartridge according to claim 26, wherein a DC voltage is applied to the charging member without applying an AC voltage. 28. The process cartridge according to claim 19, wherein the charging member is rotatable with respect to the image carrier with a difference in peripheral speed. 29. A first image carrier, first charging means for charging the first image carrier, and a developer of a first color are carried and conveyed to the first image carrier. A first image forming station including a first developer carrier for developing the formed electrostatic image with the developer of the first color, a second image carrier, and the second image. Second charging the carrier
And a second developer carrying member for carrying and carrying the second color developer and developing the electrostatic image formed on the second image carrier with the second color developer. A second image forming station, and the first image forming station to the image receiving member in the first image forming station.
Transfer means for transferring the image of the developer of the second color to the image receiving member at the second image forming station after transferring the image of the developer of the second color. At the same time as the developing operation, the agent carrier is used for the second
Residual developer can be collected from the image carrier, and the second color developer carried on the second developer carrier is provided in contact with the second image carrier, The image forming apparatus, wherein the moving direction of the second developer carrying member is opposite to the moving direction of the second image carrying member at the developing position. 30. After the first color developer image is transferred to the image receiving member at the first image forming station, the second color developer image is transferred to the image receiving member at the second image forming station. A process cartridge attachable to and detachable from the second image forming station of an image forming apparatus main body having a transfer unit, the image carrier, a charging unit for charging the image carrier, and the second color developer And a developer carrier that develops the electrostatic image formed on the image carrier with the developer of the second color. The residual developer can be collected from the image carrier, and the developer of the second color carried by the developer carrier is provided in contact with the image carrier, and the developer carrier moves. The direction is opposite to the moving direction of the image carrier at the developing position. A process cartridge characterized by being suitable for.