JPH07219300A - Color electrophotographic device - Google Patents

Abstract

PURPOSE:To provide a compact color electrophotographic device having a simple constitution, capable of obtaining a beautiful color image, and being excellent in maintainability. CONSTITUTION:The group of plural image forming units having toner whose color is different, is wholly rotatively moved, and the respective units are successively moved to the same image forming position. At the image forming position, the image is formed by signal light 13 in the image forming units 1BK, 1C, 1M and 1Y, and the toner image is transferred to an opposed intermediate transfer belt 32. When the toner image on the belt 32 passes a transferring position other than the transferring time, all the image forming units have moved rotating, so that they do not exist at the transferring position. While the toner image on the belt 32 passes the transferring position, the group of the image forming units moves rotating. A photoreceptor 9 and the belt 32 are made to perform the action to come into contact with and to separate from each other at the part on the belt 32, where the toner image is not formed. By controlling the timing of restarting the movement after stopping the rotative movement of the group of the image forming units halfway, the timing of making the belt 32 come into contact with the photoreceptor 9 at the time of completing rotative movement is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic apparatus applicable to color printers, color copying machines, color fax machines and the like.

[0002]

2. Description of the Related Art Generally, in order to form a color image by electrophotography, a method of forming a color image by superposing toner images of respective colors of yellow, magenta, cyan and black on a transfer body is adopted. In recent years, in order to reduce the size of such an apparatus and simplify the maintenance, a plurality of image forming units as shown in JP-A-62-287264 are held on a rotary support, and one exposure is performed. There has been proposed an apparatus for forming a color image on a paper wound around a transfer body while replacing the image forming unit with respect to the means. Hereinafter, an example of such a device will be described with reference to FIG.

In FIG. 3, 101 is four image forming units 102a, 10a of cyan, magenta, yellow and black.
A rotating frame for rotatably supporting 2b, 102c, and 102d, which is held by a support shaft 103 and rotates at the timing of development.

The respective units containing the four color toners have the same structure, and only the toners are different. The structure of this image forming unit and the image forming process will be described in detail with respect to the image forming unit 102a stopped at the image forming position in FIG.

The image forming unit 102a has a sensitized photosensitive drum 108 of an organic photoconductor, a primary charger 110, and a cleaner unit 111. On the other hand, a semiconductor laser (not shown) is provided outside the image forming unit 102a, and the signal light output from the laser is axially formed on the photosensitive drum 108 by the polygon 106 rotated at a constant speed by the motor. Exposure scanning. In FIG. 3, 1
Reference numeral 07 is a lens system, and 104 is a mirror for changing the traveling direction of the laser light.

The signal light output from the semiconductor laser according to the image signal of each color exposes the photosensitive drum 108 uniformly charged by the charger 110 to form an electrostatic latent image.
Then, the electrostatic latent image is developed by the developing device 109 to form a toner image on the photosensitive drum 108. On the other hand, the transfer material is fed by the feed roller 114 and is evenly wound around the surface of the transfer drum 112. The toner image formed on the photoconductor drum 108 is transferred onto the transfer material wound around the transfer drum 112 by the transfer charger 113 provided inside the transfer drum 112.

After the transfer, the toner remaining on the photosensitive drum 108 is collected by the cleaner unit 111. Photoconductor drum 10 whose surface is cleaned by the cleaner unit 111
After being statically removed by the static elimination lamp 105, 8 stops rotating.

After the above-described image forming operation is completed, the rotary frame 101 is rotated by 90 ° and each unit is rotated by 90 °, so that the unit 10 is set at the lowermost image forming position.
Instead of 2a, the unit 102b moves, stops, and is fixed.

Next, an image is created using the unit 102b. For this, the semiconductor laser is modulated according to the image signal corresponding to the toner color of the unit 102b, and the unit 1
After the latent image is formed on 02b, development is performed and the transfer drum 11
The toner image that has already been transferred onto the transfer material wound around 2 is transferred in an overlapping manner. The following process is unit 1
This is the same as the case of 02a.

In this way, the image forming process is performed for each of the four units, and the toner images of four colors are superposed on the transfer material held on the transfer drum 112 to form a color image. The transfer material on which the color image is formed is separated from the transfer drum 112 by the separation claw 115. Thereafter, the transfer material is conveyed on the conveyor belt 116, the toner image is fixed by the fixing device 117, and then the transfer material is ejected onto the tray 118.

[0011]

When an image is output by the above-mentioned device, the toner image on the transfer material is rubbed on the surface of the photosensitive drum during the movement for replacing the image forming unit. An image due to toner other than the colors was disturbed, and a good color image could not be obtained.

In view of the above problems, an object of the present invention is to provide a compact color electrophotographic apparatus which is free from disturbance of a toner image and has good maintainability.

[0013]

In order to achieve the above object, the present invention comprises an electrostatic image bearing member, each of which rotates at least, and a developing unit having a developer of a different color. A plurality of image forming units capable of forming toner images of different colors on the electrophotographic image carrier, and a transfer member capable of forming a color image by superposing the toner images of the plurality of colors formed by the image forming unit, Transfer means for transferring the toner image on the electrostatic image carrier to the transfer body at one transfer position; exposure means for performing image exposure at a single exposure position corresponding to the transfer position; Each of the image forming units, the moving means for rotationally moving the entire image forming unit group to sequentially position the image forming unit corresponding to the exposure position and the image forming position corresponding to the transfer position,
After the toner image of at least one color is formed on the transfer body, the toner image forming portion already transferred onto the transfer body except the toner image transfer step from the image forming unit to the transfer body is the transfer position. The color electrophotographic apparatus is characterized in that not all of the plurality of image forming units are located at the image forming position when passing through the image forming apparatus.

Further, according to the present invention, each of the electrostatic image bearing members rotates at least, and the developing means having a developer having a different color, and toner images of different colors are formed on the electrostatic image bearing member. A plurality of image forming units that can be formed, a transfer body that can form a color image by superposing toner images of a plurality of colors formed by the image forming unit, and a single transfer position on the electrostatic image carrier. A transfer unit that transfers a toner image to the transfer body, an exposure unit that performs image exposure at a single exposure position associated with the transfer position, and a plurality of image forming units that correspond to the exposure position. And a moving means for rotating and moving the entire image forming unit group so as to sequentially position the image forming positions corresponding to the transfer position, the first image forming unit formed on the transfer body by the first image forming unit. Color After the toner image is transferred, before the second color toner image formed by the second image forming unit is transferred, the transfer body having the first color toner image passes through the transfer position. Is provided, and the image forming unit group is rotationally moved during this moving period.

Further, the present invention comprises an electrostatic image bearing member, each of which rotates at least, and a developing means having a developing agent of a different color, and toner images of different colors are formed on the electrostatic image bearing member. A plurality of image forming units that can be formed, a transfer body that can form a color image by superposing toner images of a plurality of colors formed by the image forming unit, and a single transfer position on the electrostatic image carrier. A transfer unit that transfers a toner image to the transfer body, an exposure unit that performs image exposure at a single exposure position associated with the transfer position, and a plurality of image forming units that correspond to the exposure position. And a moving unit for rotating and moving the entire image forming unit group to sequentially position the image forming position corresponding to the transfer position, the image forming position of the image forming unit by the moving unit. The initiation and completion of the replacement operation against a color electrophotographic apparatus which is characterized in that while the portions where the toner image on the transfer member is not formed is passing through the transfer position.

Further, according to the present invention, each of the electrostatic image bearing members rotates at least, and developing means having a developer of a different color, and toner images of different colors are formed on the electrostatic image bearing member. A plurality of image forming units that can be formed, a transfer body that can form a color image by superposing toner images of a plurality of colors formed by the image forming unit, and a single transfer position on the electrostatic image carrier. A transfer unit that transfers a toner image to the transfer body, an exposure unit that performs image exposure at a single exposure position associated with the transfer position, and a plurality of image forming units that correspond to the exposure position. And a moving means for rotating and moving the entire image forming unit group so as to sequentially position the image forming position corresponding to the transfer position, and the moving means rotationally moves the image forming unit group. In the middle, a color electrophotographic apparatus characterized by all rotational movement by said moving means in a state of not located in the image forming position to stop and wait for the plurality of image forming units.

[0017]

In the structure of the present invention, the toner image formed directly on the transfer member or on the transfer material held on the transfer member (hereinafter, both are referred to as a toner image on the transfer member). When the toner image transfer position from the photoconductor to the transfer body is passed, the photoconductor at the position in the image forming unit that can only contact the transfer body surface is not at the image forming position, that is, the transfer position. The toner image does not come into contact with any part of the image forming unit, and the toner image on the transfer body is not rubbed and disturbed. Further, normally, in order to prevent the toner image on the transfer body from being disturbed due to the contact between the photosensitive body and the transfer body, while the toner image on the transfer body passes through the transfer position,
Provide a mechanism that can separate the photoconductor and the transfer body,
Methods such as applying an electric field to prevent reverse transfer when contacting the photoconductor are used, but these methods require a complicated separation mechanism, a charger and a power supply to apply the electric field, and the sequence is also It gets complicated. On the other hand, in the configuration of the present invention, the contact between the transfer body and the image forming unit can be prevented by utilizing the rotational movement of the image forming unit group, so that the apparatus can be downsized and a complicated mechanism is added. do not have to. Furthermore, when the rotational movement of the image forming unit is started and completed, there is a temporary difference in peripheral speed between the photoconductor and the transfer body.Therefore, if these operations are performed in the portion where the toner image is formed, the toner image may be disturbed. However, in the present invention, both operations are performed in the portion where the toner image is not formed on the transfer body, so that the toner image is not disturbed. In addition, the circumference of the transfer body is made longer than the maximum image length to create a portion on the transfer body where a toner image is not formed, and the operation of replacing the photoconductor and the transfer body is performed at this portion. In order to perform all replacement operations of the image forming unit accompanied by rotational movement while the portion of the body on which the toner image is not formed passes the transfer position, the portion on which the toner image is not formed is made considerably long. Therefore, the peripheral length of the transfer body becomes long and the apparatus becomes large. On the other hand, in the present invention, immediately after the transfer of the toner image of the first color, the rotation of the image forming unit is started while the portion where the toner image is not formed passes the transfer position, and the image forming unit of the first color is started. After the photoconductor is separated from the transfer body and the toner image on the transfer body passes through the transfer position and the image forming unit is rotated and moved, the transfer body makes one round and the toner image is formed again. While the non-existing portion is passing the transfer position, the photosensitive member of the second color image forming unit is brought into contact with the transfer member to complete the rotational movement of the image forming unit, so that the toner image is formed on the transfer member. Since it is not necessary to lengthen the non-existing portion, the peripheral length of the transfer body is shortened, and the apparatus can be downsized. Further, since the rotational movement of the image forming unit is stopped midway and the timing of the rotational movement of the image forming unit can be controlled according to the position of the toner image on the transfer body, the image can be easily aligned and the transfer can be performed. It is possible to easily perform the operation of bringing the photoconductor into contact with the transfer body at a portion where there is no toner image on the body, that is, the operation of completing the rotational movement of the image forming unit.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color electrophotographic apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a color electrophotographic apparatus according to an embodiment of the present invention. First, black, yellow in the center,
Four sets of fan-shaped image forming units 1Bk, 1Y, 1M, and 1C for each color of magenta and cyan constitute an image forming unit group, and are arranged in an annular shape as shown in the drawing. Since each image forming unit is made of the same constituent member except for the developer contained therein, the image forming unit for black will be described and the other colors will be omitted for simplification of description. Note that, for each color, the same portions are denoted by the same reference numerals, and when it is necessary to distinguish each color, the reference numerals are attached to indicate the respective colors. FIG. 2 shows the black image forming unit 1B.
Details of k are shown.

In FIG. 2, 9 is an organic photoreceptor in which phthalocyanine is dispersed in a polycarbonate binder resin, 1
0 is a charging roller for negatively charging the photoconductor, 13 is a signal light by a laser beam, 14a is a first hopper containing a developer in which a carrier and toner are mixed, and 14b is a first hopper containing only toner. Two hoppers, 15 is an opening opened for replenishing toner, 16 is a lid for opening and closing the opening 15, 17 is an agitator for replenishing toner, and 18a and 18b are developers in the first hopper 14a. Is an agitator for transporting the toner to the developing portion.

Reference numeral 19 is a rotatable developing electrode roller made of aluminum, 20 is a non-rotating magnet which is coaxially fixed inside, 21 is an AC high voltage power source for applying a voltage to the developing electrode roller 19, and 22 is on the electrode roller 19. It is a magnetic blade that regulates the toner layer thickness. The diameter of the photoconductor 9 is 30 m
The electrode roller 19 was rotated at a peripheral speed of 60 mm / s in the arrow direction, and the electrode roller 19 was rotated at a peripheral speed of 60 mm / s in the arrow direction.

In the first hopper 14a, a two-component developer 26 is prepared by mixing a ferrite carrier 24Bk having a particle size of 50 μm, the surface of which is coated with a silicone resin, and a toner 25Bk.
Bk was added and magnetically attached to the surface of the photoconductor 9. The toner used is one in which a pigment or the like is dispersed in a polyester resin and an additive is further added.

In the second hopper 14b, 400 g of toner is hermetically stored when the image forming unit is assembled, and 5000 sheets of A4 monochromatic 5% originals can be output without supplying toner from outside the unit. ing.

Reference numeral 27 is a cleaner for cleaning the toner remaining on the surface of the photoconductor after transfer. The operation of the image forming unit configured as described above will be described below with reference to FIG.

The photosensitive member 9 is charged with the charging roller 10 at -700V.
Charged to. The photoconductor 9 was irradiated with the signal light 13 by the laser beam to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -100V.

The surface of the photoreceptor 9 is covered with a two-component developer 26B.
K was carried and passed in front of the rotating electrode roller 19.
At this time, when the photoconductor 9 passes through the uncharged area, an AC high voltage power source 21 superimposes a DC voltage of +100 V on the electrode roller 19 and an AC voltage of 750 V 0-p (peak-to-peak 1.5 kV) (frequency). (1.8 kHz) was applied. After that, when passing the surface of the photoconductor 9 charged to -700V and having the electrostatic latent image written therein, 750V0-p (peak-to-peak) in which a DC voltage of -400V is superposed on the electrode roller 19 by an AC high voltage power source 21. An AC voltage (frequency 1.8 kHz) having a peak of 1.5 kV was applied. Then,
On the photosensitive member 9, a negative-positive inverted toner image remained only in the image portion.

Thus, a black toner image is obtained on the photosensitive member 9. The image forming unit in FIG. 2 is a black image forming unit, and also shows the upper and lower positions of the image forming unit at the image forming position. Toner 25Bk in the figure
The second developer hopper 14b containing the developer is the first hopper 14a.
Since the cleaner 27 is located on the upper side of the cleaner, the toner can be smoothly replenished and cleaned without providing a feeding mechanism or a stirring mechanism for moving the developer or toner inside the toner hopper 14b or inside the cleaner. It can be performed. That is, in the toner hopper 14b, the toner is supplied to the vicinity of the opening 15 by the rotational movement of the unit and its own weight,
In the cleaner, the toner scraped off by the blade falls to the bottom of the cleaner by its own weight and separates from the photoconductor.

Further, 28 is a photoconductor cover for protecting the photoconductor 9 and is shown in FIG. 2 in an opened state for image formation. The photoconductor cover 28 covers the photoconductor when the image forming unit is located at a position other than the image forming position, and prevents the photoconductor from being contaminated and the inside of the machine from being contaminated by toner when the unit is rotationally moved.

The developing devices 1Y, 1M, and 1C other than black have the same structure and operate.

The configuration of the printer section will be described again with reference to FIG. Image forming unit 1B arranged in an annular shape
k, 1Y, 1M, and 1C are supported by a support body 6 and are driven by a moving motor 30 which is a moving means controlled by a control circuit 29 as a whole, and around a cylindrical fixed and non-rotating shaft 31. It can be rotated in the direction of the arrow. Each image forming unit has an image forming position 5 facing a transfer roller 33 that supports an intermediate transfer belt 32, which will be described later.
Moved to 0 and positioned. The image forming position 50 is an exposure position by the signal light 13, and is also a transfer position where the toner images of respective colors are transferred onto the intermediate transfer belt 32.

Reference numeral 3 denotes a laser exposure device, which is a signal light 13 by a laser beam modulated by a signal input to the printer section.
Of the image forming units 1Bk and 1Bk of FIG.
After passing through the optical path formed between the fan-shaped portions of C, the light enters the mirror 5 fixed inside the shaft 31 through the transparent window 4 opened in a part of the shaft 31, and is reflected to the image forming position 50. The photoconductor 9 of an image forming unit is irradiated with the latent image to form a latent image.
In the state of FIG. 1, it acts on the black image forming unit 1Bk. The exposure position on the photoconductor 9 was located almost opposite to the transfer position, and the peripheral length of the photoconductor from the exposure position to the transfer position was 47 mm.

Reference numeral 32 is an intermediate transfer belt having a thickness of 100 μm.
Endless belt-like semi-conductive urethane film as a base material, wound around a transfer roller 33 and a stainless steel roller 34 formed of urethane foam with low resistance treatment, and movable in the arrow direction. Has become. The peripheral length of the intermediate transfer belt 32 is 340 mm.
When a 4-size image is output, there is a portion on the intermediate transfer belt 32 where a 46 mm toner image is not formed between the trailing edge and the leading edge of the image.

The transfer roller 33 is lightly pressed against the photosensitive member 9 of the unit 1Bk at the image forming position via the intermediate transfer belt 32. A second transfer roller 35, which has the same structure as the transfer roller 33, is pressed against the roller 34 via the intermediate transfer belt 32 so as to be driven and rotated.

Intermediate transfer belt 32 and second transfer roller 35
A sheet conveying path is formed in the nip portion which is pressed against the sheet so that the sheet is fed from the sheet feeding section 36.

An optical position detection sensor 8 detects the image position on the intermediate transfer belt 32, and is provided at a position corresponding to a position 50 mm upstream from the transfer position in the belt traveling direction of the intermediate transfer belt 32. The length from the transfer position to the position detection sensor 8 is set so that the exposure can be started after the position detection sensor 8 detects the position of the image.
It is slightly longer than the circumference from the exposure position to the transfer position above.

Reference numeral 60 denotes a magnetic resistance type toner density sensor installed on the shaft 31.
First hopper 1 of the image forming unit when positioned in
It is located so that the toner density in 4a can be detected.

A belt cleaner 40 includes a belt cleaner for cleaning the intermediate transfer belt.

Reference numeral 44 is a fixing device for fixing the toner image on the paper after transfer, and 45 is a discharge roller for discharging the paper after fixing.

The above is the description of the main structures of the electrophotographic apparatus and the image forming unit of the present invention. Next, the operation of this apparatus when forming a color image will be described.

First, each image forming unit is in the position as shown in FIG. 1, and the image forming unit 1Bk for black is used.
Is positioned at the image forming position 50, and the toner density sensor 60 is positioned so as to be substantially in contact with the side wall of the image forming unit. This position 50 is also a position facing the transfer roller 33. Black signal light is input to the image forming unit 1Bk by the laser exposure device 3, the operation of the image forming unit is started, and an image is formed with black toner. Simultaneously with the start of image formation, the toner concentration sensor 60 starts detecting the toner concentration of the developer in the first hopper 14a,
According to the detection signal, when the toner in the first hopper 14a is insufficient, the agitator 17 pushes the lid 16 open to replenish the toner.

The image forming speed of the image forming unit 1Bk (equal to the peripheral speed of the photosensitive member) and the moving speed of the intermediate transfer belt are set to be the same, and at the same time when the image is formed, the transfer roller 33 acts. Then, the black toner image is transferred to the intermediate transfer belt 32. When the transfer of the black toner image is completed, the movement motor 30 starts the rotational movement of the image forming unit group before the tip of the black toner image on the intermediate transfer belt 32 reaches the transfer position. After that, while the black toner image on the transfer belt 32 is passing through the transfer position, the movement motor 3
0 rotates 70 ° in the direction of the arrow in FIG. 1 and stops. In addition,
Since the parts other than the photoconductor of the image forming unit are located inside the rotation arc of the tip of the photoconductor, the intermediate transfer belt does not come into contact with the image forming unit.

After that, the position detection sensor 8 detects the image trailing edge of the black toner image on the intermediate transfer belt 32, and sends a signal for passing the image trailing edge to the control circuit 29. In response to the signal, the control circuit 29 instructs the stopped moving motor 30 to start moving again. Movement motor 3 that has resumed movement
0 means that the image forming unit 1Y is moved to the image forming position so that the photoconductor of the image forming unit 1Y and the intermediate transfer belt 32 come into contact with each other at the transfer position after the rear end of the black toner image on the intermediate transfer belt 32 has passed the transfer position. Positioning is performed at 50 and the rotational movement is completed. The image forming unit 1Y starts the rotation of the photoconductor and the developing electrode roller at the same time as the positioning. Next, the position detection sensor 8 detects the image front end of the black toner image on the intermediate transfer belt 32, and sends a signal for passing the image front end to the control circuit 29. In response to this signal, the control circuit 29 instructs the laser exposure device 3 to start exposure at a timing such that the front end of the yellow toner image matches the front end of the black toner image on the intermediate transfer belt 32, and the yellow image is formed. To start. The laser exposure device 3 which has received the instruction inputs the signal light to the image forming unit 1Y by the yellow signal as before, and the yellow toner image is formed and transferred. During this time, the second transfer roller 35 and the cleaner unit 40 are slightly separated from the intermediate transfer belt so that nothing acts on the toner image thereon.

The same operation as described above is performed for magenta and cyan, and four color toner images are positionally aligned and superposed on each other on the intermediate transfer belt to form a color image. After the final transfer of the cyan toner image, the four color toner images are collectively transferred onto the paper fed from the paper feed section 36 at the same timing by the action of the second transfer roller 35. The toner image transferred onto the paper is fixed by the fixing device 44. The sheet is then discharged to the outside of the apparatus via the discharge roller 45. The transfer residual toner remaining on the intermediate transfer belt is cleaned by the action of the cleaner unit 40 to prepare for the next image formation.

Next, the operation in the monochromatic mode will be described. In the monochromatic mode, first, the image forming unit of a predetermined color is moved to the image forming position and positioned. Next, the same color image formation and transfer to the intermediate transfer belt are performed in the same manner as before, and this time after transfer, the transfer is continued as it is, and the transfer is performed on the paper sent from the paper supply unit by the next second transfer roller. I will do it.

The above is the description of the configuration and operation of the embodiment.
According to the present invention, since the image formation of each color is performed at the same image forming position without using a transfer drum having a complicated configuration, the present invention can perform accurate color registration with a simple configuration, and The image forming unit is completed independently as one image forming unit for each color, the configuration is simple, and it is easy to replace each color. Become.

Further, in this configuration, since each image forming unit including the photoconductor can be independently adjusted externally, it is possible to easily replace, for example, a unit which has already been adjusted at the time of factory shipment without any adjustment on site. is there.

Since the photoconductor is covered except when the image is formed, the photoconductor is not damaged or soiled, and the interior of the device is not soiled by the scattering of the developer.

Further, in this configuration, since the size of the intermediate transfer member can be reduced, the apparatus can be downsized, and the registration of the toner images of respective colors on the intermediate transfer member can be easily and accurately aligned.

In the above embodiment, a color image is formed by superimposing the toner images of the respective colors on the intermediate transfer belt as the intermediate transfer member, but a drum is used as the intermediate transfer member and the toner images of the respective colors are superposed thereon. Even in a configuration in which a color image is formed at the same time, a transfer material such as paper is held on an intermediate transfer body in the form of a drum and a belt, and the toner images of respective colors are directly transferred onto the transfer material and sequentially superimposed. Even with the configuration for forming a color image, the essence and effects of the present invention do not change.

Further, in the above embodiment, the contact and separation operation of the photosensitive member and the intermediate transfer member was performed by utilizing the rotational movement of the image forming unit. However, in order to make this operation easy and reliable,
Even if a simple mechanism is used for separating, or a mechanism for changing the contact pressure and the amount of bite between the photoconductor and the intermediate transfer member without separation is used, the essence and the effect of the present invention do not change.

In the above embodiments, the two-component developing method in which the carrier and the toner are mixed is used as the developing method used in the image forming unit. However, even in the case of the one-component developing method using only the toner, the essence of the present invention is And the effect is the same.

[0052]

As described above, according to the present invention, since images of respective colors are all formed at the same image forming position, accurate registration of colors can be performed with a simple structure. While the toner image already transferred onto the intermediate transfer body passes through the transfer position, the image forming unit is rotationally moved, so that the toner image on the intermediate transfer body is not disturbed and the intermediate transfer body is not disturbed. The circumference of can be shortened. Since the rotational movement of the image forming unit is stopped midway and the timing is controlled, it is possible to easily separate and contact the photosensitive member and the intermediate transfer member in the portion of the intermediate transfer member where the toner image is not formed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a color electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an image forming unit used in a color electrophotographic apparatus according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional color electrophotographic apparatus.

[Explanation of symbols]

 1Bk, 1C, 1M, 1Y Image forming unit 3 Laser exposure device 5 Mirror 6 Support 8 Position detection sensor 9 Photoconductor 13 Signal light 28 Photoconductor cover 32 Intermediate transfer belt 33 Transfer roller 35 Second transfer roller 50 Image forming position 60 Toner density sensor

Claims (5)

[Claims] 1. An electrostatic image carrier, each of which rotates at least, and a developing unit having a developer having a different color, and toner images of different colors can be formed on the electrostatic image carrier. A plurality of image forming units, a transfer member capable of forming a color image by superposing toner images of a plurality of colors formed by the image forming unit, and a toner image on the electrostatic image bearing member at a single transfer position. A transfer means for transferring to the transfer body; an exposure means for performing image exposure at a single exposure position corresponding to the transfer position; and a plurality of image forming units respectively corresponding to the exposure position and A moving unit that rotates and moves the entire image forming unit group to sequentially position the image forming units corresponding to the transfer position, and forms the toner image of at least one color on the transfer body, and then forms the image. When the toner image forming portion already transferred onto the transfer body passes through the transfer position except in the step of transferring the toner image from the knit to the transfer body, all of the plurality of image forming units are in the image forming position. Color electrophotographic device characterized by not being located. 2. The structure according to claim 1, wherein at least the portion of the image forming unit other than the electrostatic image carrier does not come into contact with the transfer body when the image forming unit group is rotationally moved. Color electrophotographic device. 3. An electrostatic image bearing member, each of which rotates at least, and a developing unit having a developer of a different color, and toner images of different colors can be formed on the electrostatic image bearing member. A plurality of image forming units, a transfer member capable of forming a color image by superposing toner images of a plurality of colors formed by the image forming unit, and a toner image on the electrostatic image bearing member at a single transfer position. A transfer means for transferring to the transfer body; an exposure means for performing image exposure at a single exposure position corresponding to the transfer position; and a plurality of image forming units respectively corresponding to the exposure position and A first color toner formed on the transfer body by the first image forming unit, and a moving unit that rotates and moves the entire image forming unit group to sequentially position the image forming positions corresponding to the transfer position. Statue After the transfer, before the transfer of the second color toner image formed by the second image forming unit, a transfer period in which the transfer body having the first color toner image passes through the transfer position is provided, A color electrophotographic apparatus, wherein the image forming unit group is rotationally moved during this moving period. 4. An electrostatic image bearing member, each of which rotates at least, and a developing unit having a developer of a different color, and toner images of different colors can be formed on the electrostatic image bearing member. A plurality of image forming units, a transfer member capable of forming a color image by superposing toner images of a plurality of colors formed by the image forming unit, and a toner image on the electrostatic image bearing member at a single transfer position. A transfer means for transferring to the transfer body; an exposure means for performing image exposure at a single exposure position corresponding to the transfer position; and a plurality of image forming units respectively corresponding to the exposure position and Moving means for rotating and moving the entire image forming unit group so as to sequentially position the image forming position corresponding to the transfer position, and the moving means inserts the image forming unit into the image forming position. The initiation and completion of the e operation, a color electrophotographic apparatus which is characterized in that while the portions where the toner image on the transfer member is not formed is passing through the transfer position. 5. An electrostatic image bearing member, each of which rotates at least, and a developing unit having a developer of a different color, and toner images of different colors can be formed on the electrostatic image bearing member. A plurality of image forming units, a transfer member capable of forming a color image by superposing toner images of a plurality of colors formed by the image forming unit, and a toner image on the electrostatic image bearing member at a single transfer position. A transfer means for transferring to the transfer body; an exposure means for performing image exposure at a single exposure position corresponding to the transfer position; and a plurality of image forming units respectively corresponding to the exposure position and A moving unit that rotates and moves the entire image forming unit group to sequentially position the image forming units corresponding to the transfer position, and the moving unit rotates the image forming unit group, Color electrophotographic apparatus rotating movement by said moving means in a state where all of the image forming unit number is not located at the image forming position, characterized in that the stop-wait.