JPH0736246A - Color electrophotographic device - Google Patents

Abstract

(57) [Summary] [Object] To provide a small-sized and high-performance color electrophotographic apparatus having a simple structure and capable of obtaining a beautiful color image. A plurality of image forming units each including a developing unit having a toner having a color different from that of an electrostatic image carrier are used. The entire image forming unit group is rotationally moved so that each group can be sequentially moved to the same image forming position. At the image forming position, the image forming unit is subjected to image exposure by signal light incident from the outside of the image forming unit group and image formation is performed, and the toner image is transferred to the facing intermediate transfer belt. The signal light passes between the image forming units, reaches the exposure position through the central mirror of the image forming unit group. A color electrophotographic apparatus in which the image forming units at the image forming positions are sequentially changed and the toner images of the respective colors are superposed and transferred on the intermediate transfer belt in position.

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 yellow, magenta, cyan and black on a transfer material is used. As a method of forming this color image, toner images of respective colors are sequentially formed on one photoconductor, the transfer material wound around a transfer drum is rotated to repeatedly face the photoconductor, and each of the colors of the colors sequentially formed there is formed. A transfer drum method in which toner images are transferred in an overlapping manner, and a plurality of image forming units are arranged side by side, and a toner image of each color is sequentially transferred to a transfer material conveyed by a belt or the like through each image forming unit position. In general, the continuous stacking method is used.

An example of a color image forming apparatus using the former transfer drum system is disclosed in Japanese Patent Laid-Open No. 1-252982.

FIG. 3 shows an outline of the overall configuration of this conventional example, and the configuration and operation will be briefly described below. In FIG. 3, reference numeral 101 denotes a photoconductor, which is opposed to the photoconductor and is the charger 1.
02, a developing unit 103, a transfer drum 104, and a cleaner 105 are provided. The developing unit 103 includes a Y developing device 106 for forming a yellow toner image, an M developing device 107 for magenta color, and a C developing device 10 for cyan color.
8, and a K developing device 109 for black color, which is rotated as a whole so that each developing device sequentially faces the photoconductor 101 to be in a developable state.

During operation, the transfer drum 112 and the photoconductor are opposed to each other and rotate at a constant speed in the directions of the arrows.

First, when the operation starts, the photosensitive member 101 rotates in the direction of the arrow, and the surface of the photosensitive member 101 is uniformly charged by the charger 102.

Thereafter, on the surface of the photosensitive member, a laser beam 110 modulated with a signal for forming a first color yellow image is formed.
And a latent image is formed. Further, this latent image is first developed by the yellow developing device 106 facing the photoconductor to form a yellow toner image. By the time the formed yellow toner image reaches the position facing the transfer drum 104, one sheet of paper as a transfer material already sent from the paper feeding unit 111 is already on the outer periphery of the transfer drum 104 with the leading end claw portion. The toner image is formed by being gripped by 112 and wound, and the toner image is formed at a predetermined timing so that the yellow toner image on the photoconductor faces and meets the predetermined position.

After the yellow toner image on the photoconductor is transferred to the paper by the action of the transfer charger 113, the surface of the photoconductor is cleaned by the cleaner 105 to prepare for the formation of the next color image. Subsequently, magenta, cyan, and black toner images are also formed in the same manner, but at that time, the developing unit 103 makes each developing device, which is used according to the color, face the photoconductor to be in a developable state. The diameter of the transfer drum is large enough so that the longest sheet of paper can be wound and the developing unit can be exchanged between images of each color.

Laser beam 110 for image formation of each color
The irradiation is performed with a timing such that the toner images of the respective colors on the photoconductor and the toner images already transferred to the paper on the transfer drum are aligned and face each other as the toner rotates. In this way, the four color toner images are transferred to the transfer drum 10.
4 is transferred onto the paper in a superimposed manner to form a color image on the paper. After the toner images of all colors have been transferred, the paper is peeled from the transfer drum 104 by the peeling claw 114, and the upper toner image is fixed by the fixing unit 116 via the conveyance unit 115 and is discharged to the outside of the apparatus. The above is a brief description of the configuration and operation of the conventional example.

On the other hand, as an example of a color image forming apparatus using a continuous transfer system, there is JP-A-1-250970. In this example, four image forming stations each including a photoconductor, an optical scanning unit, and the like are arranged to form an image of four colors, and a sheet conveyed on a belt passes under the respective photoconductors. The toner images are overlaid.

Further, as another method for forming a color image by superposing toner images of different colors on a transfer material, the toner images of respective colors sequentially formed on the photoconductor are once superposed on the intermediate transfer material, Finally, a method of collectively transferring all of the above to a transfer material is disclosed in JP-A-2-212867.

[0012]

Among the conventional examples as described above, in the transfer drum system, the transfer drum is used in order to superimpose the positions of the toner images of different colors. By rotating this transfer drum at the same speed with respect to the photoconductor and adjusting the timing of the leading edge of the image, the mutual positions of the toner images of the respective colors when forming a color image are matched. However, in the above-mentioned configuration, since it is necessary to wind the paper around the transfer drum, the diameter of the transfer drum needs to be a certain size or more, and the structure is very complicated, so that the device is large. Was becoming.

Further, strong paper such as postcards and cardboard cannot be used because it cannot be wound around the transfer drum.

On the other hand, the continuous transfer method has an image forming position corresponding to the number of colors, and a transfer drum is not required because it is sufficient to pass the paper through it one after another. A latent image forming means such as a laser optical system for forming a latent image is required corresponding to the number of colors, and the structure is very complicated and expensive in this portion. Furthermore, since there are a plurality of image forming positions, the relative positional relationship of the image forming portions of each color greatly affects the color misregistration.

In particular, it is necessary to accurately align the respective colors of the latent image by the latent image forming means.
As shown in the example of Japanese Patent Laid-Open No. 70, there has been a problem that a considerable ingenuity of an image exposure system as a latent image forming means and a complicated structure are required.

Further, Japanese Patent Laid-Open No. 2-2 using an intermediate transfer material
In the example disclosed in Japanese Laid-Open Patent Publication No. 12867, the size of the photoconductor becomes large so that a toner image of each color can be formed on one photoconductor by each color developing unit. For example, a belt-shaped photoconductor is required. It becomes. In addition, there is a problem that it is difficult to maintain the developing device for each color and the photoconductor. For example, each developing device requires image adjustment with the photoconductor during maintenance, and position adjustment with each developing device when the photoconductor is replaced.

In view of the above problems, it is an object of the present invention to perform color registration with a compact and simple structure that does not require a complicated transfer drum and does not require a complicated structure for aligning the image exposure system. (EN) An excellent color electrophotographic apparatus that can be accurately performed, has a simple structure of a toner image forming unit including a photoconductor and a developing unit, has a small size, and has good maintainability.

[0018]

In order to achieve the above object, each of the electrostatic image bearing members comprises at least a rotating electrostatic image bearing member and a developing means having a toner of a different color. A plurality of movable image forming units capable of respectively forming toner images of different colors, transfer means for transferring the toner images on the electrostatic image carrier to a transfer material at a single transfer position, and An exposure unit that performs image exposure at a single exposure position corresponding to the transfer position and each of the plurality of image forming units are sequentially positioned at image forming positions corresponding to the exposure position and corresponding to the transfer position. A transfer member for rotating the entire image forming unit group in order to urge the image forming unit group, and a mirror for guiding the light of the exposing unit to the exposure position at substantially the center of rotation of the image forming unit group. above The toner images made, transferred superimposed in alignment, a color electrophotographic apparatus which performs color image formation.

Further, according to the present invention, each of the electrostatic image bearing members includes at least a rotating electrostatic image bearing member and a developing unit having a toner of a different color, and toner images of different colors are formed on the electrostatic image bearing member. A plurality of movable image forming units, transfer means for transferring the toner image on the electrostatic image carrier to a transfer material at a single transfer position, and a single transfer position corresponding to the transfer position. Exposure unit for performing image exposure at the exposure position, and the entire image forming unit group for sequentially positioning each of the plurality of image forming units at the image forming position corresponding to the exposure position and corresponding to the transfer position. At least a part of a boundary portion between the image forming units adjacent to each other, which has moving means for rotating and moving, forms at least a part of an optical path for guiding the light of the exposing means to the exposing position, The toner images of different colors on wood, transferred superimposed in alignment, a color electrophotographic apparatus which performs color image formation.

[0020]

With the above construction, since a transfer drum having a complicated construction is not used, it is simple, and since image formation of each color including exposure and transfer is carried out at the same image forming position, the construction is simple and accurate. You can align different colors. Further, since the developing means and the photoconductor can be configured as a set for each color, the maintainability such as the replacement of the image forming unit which has been adjusted in advance becomes excellent.

Further, the structure for guiding the light for exposure to the inside of the image forming unit group allows the image forming unit group to be simple and occupy a small volume, thereby enabling downsizing.

[0022]

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, four sets of fan-shaped image forming units 1Bk, 1C, 1M, and 1Y for each color of black, cyan, magenta, and yellow in the center constitute an image forming unit group, and are arranged in an annular shape as shown in the figure. ing. 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 the configurations of the respective colors, the letters indicating the respective colors are attached to the reference numerals. The image forming unit 1 for black is shown in FIG.
Bk is shown in detail.

In FIG. 2, 9 is an organic photoreceptor in which phthalocyanine is dispersed in a polycarbonate binder resin, 1
0 is a non-rotating magnet fixed coaxially with the photoconductor 9;
Is a charging roller for negatively charging the photoconductor, 13 is a laser beam scanning light, and 14 is a developer hopper.

In the developer hopper 14, a two-component developer 2 is prepared by mixing a toner carrier 25Bk with a ferrite carrier 24Bk having a particle size of 50 μm, the surface of which is coated with a silicone resin.
6Bk was added and magnetically attached to the surface of the photoconductor 9.
The toner used is one in which a pigment is dispersed in a polyester resin and an additive is further added.

Reference numeral 17 is a rotatable recovery electrode roller made of aluminum, 16 is a non-rotating magnet fixed coaxially therein, 18 is an AC high voltage power source for applying a voltage to the recovery electrode roller, and 19 is on the recovery electrode roller. It is a scraper made of polyester film that scrapes off toner. Photoconductor 9
Has a diameter of 30 mm and is rotated in the direction of the arrow at a peripheral speed of 60 mm / s. The recovery electrode roller 17 has a diameter of 16 mm and a peripheral speed of 60 mm.
It was rotated in the direction of the arrow at mm / s.

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 photoreceptor 9 was charged to −500V by the charging roller 11. The photoconductor 9 was irradiated with laser beam scanning light 13 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -100V.

A two-component developer 26 is formed on the surface of the photoreceptor 9.
BK was magnetically attached in the developer hopper 14.
Next, the surface of the photoconductor 9 was passed in front of the recovery electrode roller 17. When the photoconductor 9 passes through the uncharged area, the electrode roller 17
The AC high-voltage power supply 18 applied an AC voltage (frequency: 1 kHz) of 750 V 0-p (peak-to-peak 1.5 kV) on which a DC voltage of 0 V was superimposed. After that, -5
When passing through the surface of the photoreceptor 9 charged with 00V and having an electrostatic latent image written therein, 750V 0-p (peak-to-peak 1. An alternating voltage (frequency: 1.5 kHz) of 5 kV) was applied. Then, the toner attached to the carrier and the charged portion on the photoconductor 9 was collected by the electrode roller 17, and the negative-positive inverted toner image remained only on the image portion on the photoconductor 9. Electrode roller 17 rotating in the direction of the arrow
The carrier and toner adhering to was scraped off by the scraper 19 and returned to the developer hopper 14 again to be used for the next image formation.

In this way, a black toner image is obtained on the photosensitive member 9. The developing devices 1C, 1M, and 1Y other than black have the same configuration 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, 1C, 1M, and 1Y are supported by a support (not shown), and are driven by a moving motor 30 which is a moving means as a whole, and are rotatable about a cylindrical fixed shaft 31 that does not rotate. It has become. Each image forming unit sequentially includes a transfer roller 3 that supports an intermediate transfer belt 32, which will be described later.
3 may be located at an image forming position 50 opposite to 3.
The image forming position 50 is also an exposure position by the signal light 13.

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.
Which is generated by the image forming units 1M and 1Y of FIG.
The image forming unit which is incident on the mirror 5 fixed inside the shaft 31 through the windows 4a and 4b opened in a part of the shaft 31 through the optical path formed between It is irradiated onto the photoconductor 9 to form a latent image. In the state of FIG. 1, it acts on the black image forming unit 1Bk.

Here, since the optical path to the mirror 5 is along the wall surface of the image forming units on both sides, there is almost no portion wasted as an occupied area of the image forming unit group.
Further, since the mirror 5 is provided at the center of the image forming unit group, it can be configured with only one fixed mirror, which is simple and highly reliable for alignment and the like. .

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. Here, in this embodiment, the drive roller 34 and the roller 35
The distance between them is set so that the perimeter is slightly longer than the length of the A4 sheet in the longitudinal direction. The transfer roller 33 is lightly pressed against the photoconductor 9 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
The paper feed portions 36a and 36b
A paper transport path is formed so that the paper is fed from the.

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 discharging roller for discharging the paper after fixing.

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

Initially, the image forming unit is in the position as shown in FIG. 1 and the black image forming unit 1Bk is in the image forming position 50 as shown. It also faces the transfer roller 33. Laser exposure device 3
Causes the black signal light to be input to the image forming unit 1Bk,
Image formation is performed using black toner. At this time, 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 at the same time. , The black toner image is transferred to the intermediate transfer belt.
Immediately after the transfer of all the black toner images, the entire image forming unit group 1Bk, 1C, 1M, 1Y is driven by the moving motor 30 and integrally rotates and moves in the direction of the arrow in FIG. The image forming unit 1C rotates and stops at a position where the image forming unit 1C reaches the image forming position vicinity 50. During this period, the portion of the toner hopper 14 (see FIG. 2) other than the photoconductor of the image forming unit is located inside the rotation arc of the tip of the photoconductor, so that the intermediate transfer belt does not contact the image forming unit.

After the image forming unit 1C arrives at the image forming position 50, as before, the laser exposure device inputs signal light to the image forming unit 1C with a cyan signal to form and transfer a cyan toner image. Be seen. At this time, the intermediate transfer belt makes one rotation, and the writing timing of the cyan signal light is controlled so that the next cyan toner image is positionally matched with the previously transferred black toner image. During this time, the second
The transfer roller 35 and the cleaner section 40 are slightly separated from the intermediate transfer belt so that the toner image thereon is not affected.

The same operation as described above is performed for magenta and yellow, 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 collectively transferred onto the paper sent from the paper supply unit 36a or 36b by the action of the second transfer roller 35 at the same timing. 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 single color mode, first, the image forming unit of a predetermined color is moved to the image forming position. 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.

Next, the maintenance of this device will be described. It is assumed that the developer of a specific color is consumed and runs out, and maintenance is performed. First, by rotating the image forming unit group by the action of the moving motor 30,
The image forming unit of the color of interest is moved to the upper position (the position of the image forming unit 1C in FIG. 1). Then, the cover 46 located above the apparatus main body is opened, and only the image forming unit of interest is taken out of the apparatus from there. Next, a new image forming unit of that color that has been adjusted in advance as an image forming unit is mounted.

Therefore, after mounting, image formation can be started without any adjustment. 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 makes it possible to perform accurate color registration with a simple configuration. In addition, the image forming means is completed independently as one image forming means for each color, so that the structure is simple, and the image forming means can be replaced for each color and the maintainability is excellent. Becomes

Therefore, in this configuration, since each image forming unit including the photoconductor can be independently adjusted externally, it is possible to easily replace a unit that has already been adjusted at the time of factory shipment on site.

Furthermore, in the present configuration, even when a color image is continuously formed, each photoconductor is paused while forming another color, so that a stable image is obtained without electrostatic fatigue. can get.

In the above embodiments, the specific structure of the image forming unit is used. However, even in the case of the image forming unit having the structure using the conventional developing method,
The essence and effects of the present invention remain unchanged.

[0048]

As described above, the present invention has a simple structure because a transfer drum having a complicated structure is not used, and since image formation for each color is performed at the same image forming position,
Accurate color registration can be performed with a simple structure. And since the image forming unit is completed as one image forming unit independently for each color, the configuration is simple,
Further, the maintainability such as the replacement of the image forming unit adjusted in advance for each color becomes excellent.

Further, the structure for guiding the light for exposure to the inside of the image forming unit group allows the image forming unit group to be simple, occupying a small volume, and being miniaturized.

[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]

 3 Laser exposure device 5 Mirror 1Bk, 1C, 1M, 1Y Image forming unit 9 Photoreceptor 32 Intermediate transfer belt 33 Transfer roller 35 Second transfer roller

Claims (2)

[Claims] 1. Each comprises at least a rotating electrostatic image carrier and a developing means having a toner of a different color, so that toner images of different colors can be formed on the electrostatic image carrier. A plurality of movable image forming units, a transfer means for transferring the toner image on the electrostatic image carrier onto a transfer material at a single transfer position, and a single exposure position associated with the transfer position. The image forming unit group is rotationally moved in order to sequentially position each of the exposure unit for performing image exposure and the plurality of image forming units at the image forming position corresponding to the exposure position and corresponding to the transfer position. A moving unit and a mirror that guides the light of the exposing unit to the exposure position are provided at substantially the center of rotation of the image forming unit group, and the toner images of different colors are aligned on the transfer material. Over and over Copy, color electrophotographic apparatus which performs color image formation. 2. Each comprises at least a rotating electrostatic image carrier and a developing means having a toner of a different color, and toner images of different colors can be formed on the electrostatic image carrier. A plurality of movable image forming units, a transfer means for transferring the toner image on the electrostatic image carrier onto a transfer material at a single transfer position, and a single exposure position associated with the transfer position. The image forming unit group is rotationally moved in order to sequentially position each of the exposure unit for performing image exposure and the plurality of image forming units at the image forming position corresponding to the exposure position and corresponding to the transfer position. At least a part of a boundary between the image forming units adjacent to the moving means, and at least a part of an optical path for guiding the light of the exposing means to the exposing position,
A color electrophotographic apparatus that forms a color image by transferring toner images of different colors onto a transfer material, aligning their positions and transferring them.