JPH07261500A - Color electrophotographic device - Google Patents

Abstract

PURPOSE:To provide a color electrophotographic device capable of preventing a photoreceptor from being scratched at the time of image forming operation or the maintenance time. CONSTITUTION:In the device, the plural number of the image forming unit 13 composed of the developing means provided with the toner of the color different from the photoreceptor are used. The color image is synthesized by rotationally moving the image forming unit group 14 as a whole. At the time of shifting, replacing the image forming unit or the image forming time, the intermediate transfer body is located in the refuge position, and at the time of image forming, it is movable to the image forming position 17. By this way, at the time of the rotation of the image forming unit group, the intermediate transfer body is prevented from coming into collision with the image forming unit, hence the photoreceptor is prevented from the damage. Furthermore, the photoreceptor is prevented from the damage due to the collision of the intermediate transfer body and the photorecepor at the time of replacing the intermediate transfer body.

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 facsimiles and the like.

[0002]

2. Description of the Related Art As a conventional example, the inventors of the present invention filed Japanese Patent Application No. 5-1
The configuration will be described using the color electrophotographic apparatus filed in Japanese Patent No. 78998. FIG. 5 is an overall configuration diagram of the conventional color electrophotographic apparatus.

In the center, four sets of fan-shaped image forming units 101Bk for black, cyan, magenta, and yellow are provided.
01C, 101M, and 101Y form an image forming unit group, and are arranged in an annular shape. 102 is a photoconductor, 103
Is a charger, 104 is a developer hopper, 105 is a cleaner,
Reference numeral 106 is an electrode roller. Image forming units 101Bk, 101C, 101M, 101 arranged in an annular shape
Y is supported by a support (not shown), and is driven by a moving motor 107 that is a moving means as a whole, and is rotatably movable around a cylindrical fixed shaft 108 that does not rotate. Each image forming unit can be sequentially located at an image forming position 111 facing a transfer roller 110 supporting the intermediate transfer belt 109. Image forming position 111
Is also the exposure position by the signal light 112. Reference numeral 113 denotes a laser exposure device, which generates a signal light 112 by a laser beam that is modulated by a signal input to the printer unit, which passes through an optical path formed between the image forming units 101M and 101Y in FIG. , A window 1 opened in a part of the shaft 108
The light enters the mirror 115 fixed inside the shaft 108 through 14a and 114b, is reflected, and is irradiated on the photoconductor 102 of the image forming unit at the image forming position 111 to form a latent image. In the state of FIG. 5, the image forming unit 101Bk for black is used.
Act on.

Next, the operation of this apparatus when forming a color image will be described. First, the image forming unit is located as shown in FIG. 5, and the image forming unit 101Bk for black is used.
Is in the imaging position 111 as shown. Black signal light is input to the image forming unit 101Bk by the laser exposure device 113, and an image is formed with black toner. At the same time as the image is formed, the black toner image is transferred to the intermediate transfer belt by the action of the transfer roller 110. Immediately after all the black toner images have been transferred, the entire image forming unit group 101Bk, 101C, 101M, 101Y is driven by the moving motor 107 to integrally rotate and move,
The image forming unit 101C rotates exactly 90 degrees and stops at the position where it reaches the image forming position vicinity 111. After the image forming unit 101C arrives at the image forming position 111, the laser exposure apparatus uses the cyan signal and the image forming unit 1 is moved to the image forming unit 1 as before.
The signal light is input to 01C to form and transfer a cyan toner image. At this time, the intermediate transfer belt 109 makes one revolution, and the writing timing of the cyan signal light is controlled so that the next cyan toner image is positionally aligned with the previously transferred black toner image. Same operation as above
Magenta and yellow are also performed, and toner images of four colors are positionally aligned and superposed on each other to form a color image. After the final transfer of the yellow toner image, the four color toner images are transferred onto the paper 116 at the same timing as the second toner image.
It is collectively transferred by the action of the transfer roller 117. The toner image transferred onto the sheet is fixed by the fixing device 118.

[0005]

With such a configuration, 2
When color printing was continued for about 00 sheets, the surface of the photoconductor 102 of each image forming unit 101 began to be scratched gradually, and streaks appeared in the image.

Further, in this structure, since the intermediate transfer member and the photosensitive member are maintained while they are in contact with each other, the surface of the intermediate transfer member is rubbed against the surface of the photosensitive member when the intermediate transfer member 109 is replaced, and the external surface is damaged. However, there is a problem in that the light from the illuminates the photoconductor directly and deteriorates the photoconductor.

In view of the above problems, an object of the present invention is to provide a color electrophotographic apparatus which is less likely to damage the surface of the photoconductor and has good maintainability.

[0008]

In order to achieve the above-mentioned object, the present invention comprises a photoconductor that rotates at least and a developing means having toners of different colors, respectively. A plurality of movable image forming units for forming color toner images; an image forming unit group in which the plurality of image forming units are arranged side by side in a ring shape and rotatable; and a toner image formed on the photoconductor. A color electrophotographic apparatus including an intermediate transfer member that receives the image, an image forming position that is composed of a single exposure position and a single transfer position, and that forms an image by contact between the image forming unit and the intermediate transfer member. In the color electrophotographic apparatus, the intermediate transfer member is retracted to a position where the intermediate transfer member does not come into contact with the photoconductor of the image forming unit at least during the rotational movement of the image forming unit group.

[0009]

The structure and operation of the color electrophotographic apparatus using the intermediate transfer belt unit as the intermediate transfer member of the present invention will be described with reference to FIG. Reference numeral 1 is an exterior casing of the color electrophotographic printer, and the right end face side in the drawing is the front face. Reference numeral 1A denotes a printer front plate, and the front plate can be freely opened and closed and raised and closed around the hinge shaft 1B on the lower side with respect to the printer outer casing 1. 1 when the front plate 1A is tilted down and opened
It is shown by a dotted line. The operation of attaching / detaching the intermediate transfer belt unit 2 to / from the printer, the maintenance of the printer inside such as a paper jam, and the like are performed by tilting the front plate 1A open to largely open the inside of the printer. The attachment / detachment operation of the intermediate transfer belt unit 2 is designed so as to be perpendicular to the direction of the rotation axis generatrix of the photoconductor. The intermediate transfer belt unit 2 includes a transfer belt 3, a first transfer roller 4,
Second transfer roller 5, cleaner roller 6, scraper 7,
Waste toner reservoir 8, waste toner full detector 9, backup roller 10, position detector 11, tension roller 12,
Consists of. Details will be described later.

Black, cyan, magenta, and
Four pairs of fan-shaped image forming units 13 for each color of yellow
Bk, 13Y, 13M and 13C are image forming unit groups 14
And are arranged in an annular shape as shown in the figure. Each image forming unit has a hinge shaft 1 attached to the printer left side plate 1C of FIG.
It can be attached to and detached from a predetermined position of the image forming unit group 14 by opening it around D. The image forming unit 13 is properly mounted in the printer so that the mechanical drive system and the electric circuit system on both sides of the image forming unit side and the printer side are coupled to each other via a mutual coupling member (not shown). Mechanical
Electrically integrated.

Image forming unit 1 arranged in an annular shape
3Bk, 13C, 13M and 13Y are supports (not shown)
The image forming unit group as a whole is driven by a moving motor 15 which is a moving unit, and is rotatably movable around a cylindrical shaft 16 which is fixed and does not rotate. At the time of image formation, each image forming unit can be sequentially positioned at the image forming position 17 facing the first transfer roller 4 supporting the intermediate transfer belt 3 by rotational movement. The image forming position 17 is also an exposure position by the signal light 18.

FIG. 2 shows the black image forming unit 13Bk in detail. Since each image forming unit is composed of the same constituent members except the developer contained therein, the image forming unit 13Bk for black will be described and the other colors will be omitted for simplification of description. The same reference numerals are assigned to the same portions for each color, and when it is necessary to distinguish the configurations of the respective colors, the letters indicating the respective colors are attached to the reference numerals. In this explanation, the developing method disclosed by the inventors in Japanese Patent Application No. 4-50274 is used, but it goes without saying that any developing method may be used as long as it is used in a normal electrophotographic method. For example, a magnetic brush developing method, an elastic rubber roller developing method, a jumping developing method, an impression developing method and the like.
In FIG. 2, reference numeral 19 is an organic photosensitive member mainly composed of a polycarbonate-based binder resin using phthalocyanine as a photosensitive material, 20 is a non-rotating magnet fixed coaxially with the photosensitive member 11, and 21 is a conductive material for negatively charging the photosensitive member. Charging roller made of rubber, 18 is laser beam signal light, 22
Is an exposure window which is an opening of the image forming unit through which the laser beam enters the image forming unit, and 23 is a developer hopper. Inside the developer hopper 23, a ferrite carrier 24Bk having a particle size of 50 μm, the surface of which is coated with a silicone resin.
Two-component developer 26 in which 10% of a black toner 25Bk having a negative charge property in which a black pigment is dispersed in polyester resin is mixed
Bk is added and directly attached to the surface of the photoconductor 11 by the magnetic force of the magnet 20. 27 is a rotatable collection electrode roller made of aluminum, 28 is a non-rotating magnet fixed coaxially inside thereof, 29 is a scraper made of phosphor bronze for scraping the toner collected on the collection electrode roller, 30 is a collection electrode It is an AC high voltage power supply that applies a voltage to the roller. Reference numeral 31 is a cleaner for cleaning the toner remaining on the surface of the photoconductor 19 after the transfer. The photoconductor 19 has a diameter of 30 mm and a peripheral speed of 60 mm / s.
And rotate it in the direction of the arrow so that the collecting electrode roller 27 has a diameter of 16
The rotation speed was 60 mm / s and the rotation speed was 60 mm / s.

Next, referring to FIG. 3, the intermediate transfer belt unit 2
The configuration of will be described. The intermediate transfer belt unit 2 includes a unit housing 2a, a transfer belt 3, a first transfer roller 4 made of an aluminum roller, a second transfer roller 5 made of a conductive elastic rubber roller, and an aluminum member for cleaning a toner image remaining on the transfer belt. Cleaner roller 6, scraper 7 for scraping the collected toner, waste toner reservoir 8 for storing the scraped toner, waste toner full detector 9 for detecting that the amount of toner in waste toner reservoir 8 is full, It includes a backup roller 10 made of a conductive rubber facing the cleaner roller 6, a position detector 11 for detecting the transfer start position of the transfer belt, and a tension roller 12 for adjusting the tension of the transfer belt to prevent meandering. The intermediate transfer belt unit 2 is attachable / detachable to / from a predetermined storage portion in the printer outer casing 1 by folding down the printer front plate 1A in FIG. The intermediate transfer belt 3 has a thickness of 1
An endless belt-shaped semi-conductive (medium resistance) urethane having a thickness of 00 μm is used as a base material, and a surface layer is made of a film having a thickness of 100 to 200 μm using a fluororesin such as PFA / PTFE. Two transfer rollers 5, a backup roller 10, and a tension roller 12 are wound around and configured to be movable in the arrow Y direction. The medium resistance elastic layer of the second transfer roller 5 and the backup roller 10 has an electric resistance value obtained by mixing and dispersing carbon or metal oxide in an elastic material such as silicon rubber, Teflon rubber, chloroprene rubber, urethane rubber, EPDM. (Volume resistivity) is 1
It consists of a solid or foamed fleshy layer that has been treated to have a medium resistance of 0 ⁵ to 10 ¹⁷ Ωcm. Here, the peripheral length of the transfer belt is a length (62 mm) slightly longer than a half of the peripheral length of a photosensitive drum (diameter 30 mm), which will be described later, in the length (298 mm) in the longitudinal direction of A4 paper, which is the maximum paper size.
Is set to 360 mm. At this time, the circumferential length of the intermediate transfer belt 3 from the contact portion between the second transfer roller 5 and the third transfer roller 34 to the contact portion between the cleaner roller 6 and the backup roller 10 is shorter than the distance of 62 mm, 5
It is set to be 5 mm. Intermediate transfer belt 3
Is set to be 1.5% faster than the image forming speed of the image forming unit 13 (60 mm / s, which is equal to the peripheral speed of the photoconductor), in order to prevent the hollow transfer of the toner image.

The first transfer roller 4 is movable between a transfer position 4a and a retreat position 4b, and when it is located at the transfer position 4a by a drive source (not shown) controlled by an electric signal, the transfer belt 4 is moved. 3 can transfer the toner image formed in contact with the photoconductor 19, and when located at the transfer position 4b, the transfer belt 3 separates from the photoconductor 19 to a non-contact position. When transferring the toner image on the photoconductor 19,
A voltage of about +2.5 kV (100 μA) is applied to the first transfer roller 4 and the tension roller 12 by the high voltage power supply 32. When the first transfer roller 4 is brought into direct contact with the photoconductor 19 to transfer the toner image onto the intermediate transfer belt 3, a so-called “front jump” phenomenon occurs before the intermediate transfer belt 3 comes into contact with the photoconductor 19 and the image is disturbed. In addition, it becomes difficult to uniformly adjust the contact pressure between the first transfer roller 4 and the photoconductor 19. However, if the first transfer roller 4 is moved and the intermediate transfer belt 3 stretched between the two rollers is brought into contact with the photosensitive drum 19 as in the present invention, these problems do not occur.

When the intermediate transfer belt unit 2 is mounted on the printer body, the first transfer roller 4 prevents the intermediate transfer belt 3 from coming into contact with the photosensitive member 19 and the retracted position 4b in FIG.
It is in. When the intermediate transfer belt unit 2 is mounted on the printer body and the image forming operation is started, the first transfer roller 4
Moves to the transfer position 4a, and the transfer belt 3 moves about 1.0k.
It is pressed against the photosensitive member 19 with a force of g.

The second transfer roller 5 and the backup roller are both made of conductive rubber, and are grounded via a resistor 33 of 20 MΩ to prevent scattering of the color toner image during transfer.

The third transfer roller 34 made of aluminum is
It is pressed against the second transfer roller 5 via the intermediate transfer belt 3. During formation of a color image on the intermediate transfer belt 3, in order not to disturb the toner image on the belt,
A voltage of -1 kV is applied by the high voltage power supply 35a. Further, when the color toner image is transferred to the image receiving paper 36, a voltage of +3 kV is applied by the high voltage power supply 35b. Reference numeral 37 is a charge eliminating needle for preventing the toner image from being disturbed when the paper 36 is separated from the intermediate transfer belt 3. The third transfer roller 34 is configured to be rotatable 1.5% slower than the intermediate transfer belt 3 in order to prevent a hollow defect when transferring a toner image.

The cleaner roller 6 cleans the intermediate transfer belt 3. The intermediate transfer belt 3 is attached to the cleaner roller 6.
During formation of a color image on the upper surface, a voltage having the same polarity as the toner, that is, a negative voltage in this case, is applied from the high voltage power supply 38a in order to prevent the toner from being transferred from the intermediate transfer belt 3. When cleaning the toner remaining on the intermediate transfer belt 3, a positive voltage that electrostatically attracts the toner is applied by the high voltage power supply 38b.

FIG. 4 is a perspective view showing the structure of the position detector 11 using a photo interrupter provided inside the intermediate transfer belt unit 2. There is a detection hole 39 at the end of the intermediate transfer belt 3, and the position detector 11 determines the leading end position of the toner image by optically detecting the passage of the detection hole 39, and the position detector 11 determines the leading end position of the toner image on the intermediate transfer belt 3. This is a configuration for aligning color images.

Returning to FIG. 1, the description will be continued. Reference numeral 40 denotes a laser beam scanner section arranged on the upper side in the printer outer casing 1, and is composed of a semiconductor laser, a scanner motor 40a, a polygon mirror 40b, a lens system 40c and the like.
The pixel laser signal light 18 corresponding to the time series electric pixel signal of the image information from the scanner unit 40 passes through the optical path window 41 formed between the image forming units 13Bk and 13C of FIG. Axis 1 through the window 42 opened in the part
The exposure window 22 of the image forming unit 13Bk which is incident on the mirror 43 fixed in the image forming section 6 and is reflected at the image forming position 17
From the inside into the image forming unit 13Bk, and passes through the passage between the developer reservoir 23 and the cleaner 31 arranged in the upper and lower parts of the image forming unit to enter the exposed portion on the left side surface of the photosensitive drum 19. Scanning exposure is performed in the bus line direction.

Here, since the optical path from the optical path window 41 to the mirror 43 uses the gap between the image forming units 13Bk and 13C on both sides, the image forming unit group 1
There is almost no wasted space in 4. Also, mirror 4
Since 3 is provided in the central portion of the image forming unit group 14, it can be configured by a single fixed mirror, and has a simple configuration and easy alignment.

Reference numeral 34 denotes a third transfer roller disposed inside the printer front plate 1A and above the feeding roller 44. The nip portion where the intermediate transfer belt 3 and the third transfer roller 34 are in pressure contact with each other is a printer. A sheet conveying path is formed so that the sheet is fed by the sheet feeding roller 44 provided under the front plate 1A. The configuration of the third transfer roller 34 may be a conductive elastic roller such as the second transfer roller 5, but if a metal roller having a smooth surface is used, a color image is synthesized on the intermediate transfer belt 3. It is more desirable because it does not disturb the surface of the toner image.

The fixing rollers 45a and 45b are provided on the upper inside of the printer. The halogen lamp 4 is provided inside the fixing roller 45a.
6 is provided. A polyimide film 47 is stretched between 45a and 45b. This film 47
Is used for the purpose of producing the gloss of a color print. 48
Is a backup roller provided to face the fixing roller 45a, and 49 is a pair of discharge rollers arranged on the paper exit side.
The above is the description of the main configuration of the electrophotographic apparatus of the present invention.

Next, the structure and operation when the image forming unit 13 and the intermediate transfer belt unit 2 are replaced will be described. The state of FIG. 1 is a state in which image formation is being performed. This is a state in which the first transfer roller 4 has moved to the position 4a in FIG. 3 in order to transfer the toner image formed on the photoconductor 19 to the intermediate transfer belt 3. When the image forming unit group 14 rotationally moves or when the printer apparatus is stopped, the first transfer roller 4 is retracted to the position 4b. In this state, the photoconductor 19 does not contact the transfer belt 3. In this retracted state, the printer stops the printing operation and opens the printer front plate 1A so that the replacement of the intermediate transfer body unit 2 can be taken out. Even if the intermediate transfer belt unit 2 is moved in and out in this state, the photosensitive member 1 is still in operation.
1 and the intermediate transfer belt 3 are not strongly pressed against each other to damage them. At the same time, the image forming units 13 can be replaced by opening the printer left side plate 1C. When the other image forming unit 13 is replaced, the image forming unit group 14 is stopped by rotating 90 ° from this state.

The surface of the intermediate transfer belt 3 is gradually deteriorated due to toner adhesion and the like as it is used for a long period of time. When the deterioration of the belt becomes remarkable, the image is partially cut off or white or black streaks occur in the image. Therefore, it is desirable to replace the intermediate transfer belt before it deteriorates and affects the image. However, it is extremely difficult to automatically detect the deterioration phenomenon of the intermediate transfer belt in the printer device. In the present invention, as shown in FIG. 3, the intermediate transfer belt 3 is integrated with the waste toner reservoir 8 into a unit,
The waste toner is discarded at the same time when the intermediate transfer belt 3 is replaced. In such a configuration, the size of the waste toner reservoir may be designed to have a small mesh capacity so that the waste toner reservoir is filled with the waste toner before the life of the intermediate transfer belt expires.
In this way, the waste toner full detector 9 installed inside the waste toner reservoir detects the full toner before the intermediate transfer belt deteriorates and an image defect occurs, and instructs the user to replace the intermediate transfer belt unit 2. be able to. Such a structure is effective not only for the intermediate transfer belt that directly forms a toner image thereon, but also for an intermediate transfer member having a structure in which an image receiving paper is wound around the same.

With the above arrangement, the photosensitive member of the image forming unit and the intermediate transfer belt are not in contact with each other during the rotational movement of the image forming unit group, so that the photosensitive member is not damaged. Further, since the intermediate transfer body does not come into direct contact with the photosensitive body when the intermediate transfer body unit is replaced, the photosensitive body is not damaged during maintenance. Further, in this method, the exposure position on the photoconductor is stable as compared with a configuration in which the position of the intermediate transfer belt 3 is fixed and the image forming unit 13 is moved to the transfer position during image formation and brought into contact with the intermediate transfer belt. Then
This has the effect of improving the color registration accuracy when synthesizing color images.

[0027]

【Example】

(Specific Embodiment 1) The operation of the color electrophotographic apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

The printer of FIG. 1 is in an image forming state. The operation of the image forming unit 13Bk will be described with reference to FIG.
The photoconductor 19 was charged to −450V by the charging roller 21. The photoconductor 19 was irradiated with the laser beam scanning light 18 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor is -5.
It was 0V. The two-component developer 26Bk was magnetically attached to the surface of the photoconductor 19 in the developer hopper 23. Next, the surface of the photoconductor 19 was passed in front of the recovery electrode roller 27. When the photoconductor 19 passes through the uncharged area, an AC high voltage power source 30 superimposes a DC voltage of +100 V on the electrode roller 27 and an AC voltage of 750 V0-p (peak-to-peak 1.5 kV) (frequency of 2 kHz). Wave) was applied. After that, when passing the surface of the photoconductor 19 charged with −450 V and having the electrostatic latent image written therein, the electrode roller 27
750V 0-p (peak-to-peak 1.5k) superposed with a DC voltage of -250V by an AC high voltage power supply 30.
V) AC voltage (rectangular wave of frequency 2 kHz) was applied. Then, the developer on the photoconductor 19 and the toner adhering to the non-image portion are collected by the electrode roller 27, and the negative-positive inverted toner image remains only on the image portion on the photoconductor 19.
The developer and toner attached to the electrode roller 27 rotating in the direction of the arrow were scraped off by the scraper 29, returned to the developer hopper 23, and used for the next image formation. Thus, a black toner image was obtained on the photoconductor 19. The same operation is performed for the developing devices 13C, 13M, 13Y other than black.

Next, returning to FIG. 1, the operation of the apparatus for forming a color image will be described. The image forming unit group 14 is in the position shown in FIG. 1, and the black image forming unit 13Bk is in the image forming position 17 as shown. At this time, the photoconductor 19 is in contact with the intermediate transfer belt 3. By the image forming process of the image forming unit described above, the black signal light is input to the image forming unit 13Bk by the laser exposure device 40, and the image formation is performed by the black toner. At this time and the intermediate transfer belt 3
Is set so as to be 1.5% faster than the speed of the photoconductor 19 in order to prevent the hollow transfer of the toner image, and is applied to the first transfer roller 4 and the tension roller 12 simultaneously with the image formation. The black toner image is transferred onto the intermediate transfer belt 3 by the action of the applied voltage. At this time, + 2.5k is applied to the first transfer roller 4 and the tension roller 12 as described above.
A DC voltage of V was applied.

Immediately after the transfer of all the black toner images, the first transfer roller 4 is moved from the position 4a shown in FIG. 3 to the position 4b.
To the position where the intermediate transfer belt 3 does not contact the image forming unit 13Bk. Next, the entire image forming unit group 14 is driven by the moving motor 15 and
The image forming unit 13C is rotated by 90 ° in the direction of arrow Q, and stops at the position where the image forming unit 13C reaches the image forming position 17. Toner hopper 23 other than the photoconductor of the image forming unit
The portion of the cleaner 31 is located inside the rotary arc indicated by the dotted line at the tip of the photoconductor 19. Further, the retracted position 4b of the first transfer roller 4 is located outside the dotted arc.
Therefore, the intermediate transfer belt 3 does not come into contact with the image forming unit during the rotational movement of the image forming unit group.

When the rotation of the image forming unit group 14 is completed and the image forming unit 13C reaches the image forming position 17, the laser exposure device 32 inputs the signal light to the image forming unit 13C with the cyan signal as before. Then, the cyan toner image is formed and transferred. By this time, the intermediate transfer belt 3 has made one rotation, and the signal from the position detector 10 shown in FIG. 4 is set so that the next cyan toner image is in position with the previously transferred black toner image. Based on this, the writing timing of the cyan signal light is controlled. During this time, the third transfer roller 34 is in contact with the intermediate transfer belt 3, but as described above, the surface of the third transfer roller is smooth and a voltage of -1 kV is applied so as to prevent the adhesion of toner. Therefore, the toner image on the transfer belt is not disturbed. The cleaner roller 6 is also in contact with the intermediate transfer belt 3,
The surface of the cleaner roller 6 is also smooth, and a voltage of -1 kV that prevents toner adhesion is applied, so that the toner image on the transfer belt is not disturbed.

The same operation as described above was carried out for magenta and yellow, and four color toner images were positionally aligned and superposed on the intermediate transfer belt 3 to form a color image. After the final transfer of the yellow toner image, the toner images of four colors were collectively transferred by applying a voltage of +3 kV to the third transfer roller 34 on the paper (not shown) fed from the paper feed cassette at the same timing. The toner image transferred onto the sheet is fixed by the fixing rollers 45a and 45b and then discharged.

Thereafter, the third transfer roller 34 is again set to -1k.
A voltage of V is applied to transfer the toner directly attached to the surface of the third transfer roller to the intermediate transfer belt 3, and then +3 kV is applied to the cleaner roller 6 together with the transfer residual toner remaining on the intermediate transfer belt 3. The toner was cleaned by applying the voltage of (1) and stored in the waste toner reservoir 8 in the intermediate transfer belt unit 2.

When such a printing operation was repeated for about 30,000 sheets, the discharged toner reservoir 8b became full, and the waste toner full detector 9 composed of an optical sensor output a signal that it was full. At this time, the intermediate transfer belt 3 was in a state where it could be used for printing about 10,000 more sheets, but the user was urged to replace the intermediate transfer belt unit 2 based on the signal from the full detector 9.

The intermediate transfer belt unit 2 in which the waste toner reservoir 8b is full of waste toner is replaced as follows. Although the image forming unit group 14 is in the state shown in FIG. 1, the first transfer roller 4 is retracted to the position 4b shown in FIG. Therefore, the photoreceptor 19 of the image forming unit 13Bk
Moves to a retracted position where the intermediate transfer belt unit 2 does not come into contact with the intermediate transfer belt 3, and the apparatus is stopped. The user opens the front plate 1A located on the front part of the apparatus main body and takes out the intermediate transfer belt unit 2 from there. Next, a new intermediate transfer belt unit, which has been adjusted in advance with a position detector, a waste toner full detector, etc., is mounted.
Therefore, after mounting the unit, image formation can be started without any adjustment. When the new intermediate transfer belt unit is mounted on the main body, the photoconductor 19 of the image forming unit 13Bk does not collide with the intermediate transfer belt 3 or the first transfer roller 4 and get damaged.

The above is the description of the configuration and operation of the embodiment.
In the above embodiments, a specific structure was used as the structure of the image forming unit. However, even in the case of an image forming unit having a structure using the conventional developing method or charging method, the essence and the effect of the present invention Does not change. Further, it goes without saying that such a structure is effective not only for the intermediate transfer belt that directly forms a toner image thereon, but also for an intermediate transfer body having a structure in which an image receiving paper is wrapped around the same. Nor.

[0037]

According to the present invention, since the intermediate transfer member and the image forming unit do not collide with each other when the image forming unit group is rotated, the photosensitive member is not damaged. Furthermore, when the intermediate transfer body unit is replaced, the intermediate transfer body and the photosensitive body do not collide with each other and the photosensitive body is not damaged. It is possible to obtain a color electrophotographic apparatus having a small and simple structure and good maintainability.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a positional relationship during image formation of a color electrophotographic apparatus of the present invention.

FIG. 2 is a configuration diagram showing a configuration 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 an intermediate transfer body unit of the present invention.

FIG. 4 is a configuration diagram showing a configuration of a position detector of the intermediate transfer member unit of the present invention.

FIG. 5 is a block diagram of a conventional color electrophotographic apparatus.

[Explanation of symbols]

 2 Intermediate Transfer Body Unit 3 Intermediate Transfer Belt 4 First Transfer Roller 5 Second Transfer Roller 6 Cleaning Roller 10 Backup Roller 12 Tension Roller 13 Image Forming Unit 14 Image Forming Unit Group 17 Image Forming Position 18 Laser Signal Light 19 Photoconductor 34th 3 transfer roller 40 laser exposure device 43 mirror

Claims (1)

[Claims] 1. A plurality of movable image forming units each of which comprises at least a rotating photoconductor and a developing means having a toner of a different color, and which forms a toner image of a different color on the photoconductor. An image forming unit group in which the plurality of image forming units are arranged side by side in a ring shape and rotatable, an intermediate transfer member that receives the toner image formed on the photosensitive member, a single exposure position and a single transfer position A color electrophotographic apparatus including an image forming position configured to contact the image forming unit and the intermediate transfer member to form an image, at least during rotational movement of the image forming unit group. A color electrophotographic apparatus having a configuration in which the intermediate transfer member is retracted to a position where it does not come into contact with the photosensitive member of the image forming unit.