JPH09281769A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a synchronous driving rotation at a circumferential speed equal to those of plural photoreceptor drums by making use of the carrying force of an intermediate transfer belt. SOLUTION: In this image forming device, the contact surfaces of a belt member 10 with the peripheries of the photoreceptor drums 21 are formed by the installation of guiding rollers 14, the length along the periphery of the drum, of the contact surface, corresponding to the diameter of the drum is properly selected from the product of the radius (r) of the drum by the drum center angle (w) of the contact surface and the pressing force of the belt on the surface of the drum and further, a bias voltage applied to each transfer electrode 26 are properly selected respectively as well, so that the transmission efficiency of the carrying force of the belt member 10 with respect to the drums 21 is increased to surely drive/rotate the plural drums 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus for forming a color toner image using a plurality of image forming members.

[0002]

2. Description of the Related Art Many color image forming apparatuses for forming a color image by superposing toner images on a plurality of image forming bodies employ an electrophotographic image forming method. FIG. 1 shows a main part of one type of color image forming apparatus.

In FIG. 1, A, B, C, and D are image forming units arranged in parallel in the order of image processing, and are units for forming single-color toner images of yellow, magenta, cyan, and black, respectively. .

Each image forming section includes a drum-shaped image forming body 1, a charging unit 2, an exposing unit 3, a developing unit 4, and a cleaning unit 5 as shown in an image forming unit A for forming a yellow toner image. Each is provided with forming means. With such a configuration, first, a yellow toner image is formed on the image forming body 1 of the image forming unit A. This toner image is transferred to the transfer paper P conveyed by the transfer belt 8 in the direction of the arrow by the operation of the transfer device 7.

During this time, in the image forming section B, a magenta toner image is formed on the image forming body, and the transfer paper P
Is transferred in a manner superimposed on the yellow toner image. Similarly, a cyan toner image is superimposed by the image forming unit C, and a black toner image is superimposed by the image forming unit D, so that a color toner image is formed on the transfer paper P. The transfer paper P on which the color toner image is formed in this manner is continuously conveyed to the fixing device 6 by the transfer belt 8 to fix the toner image, and the copying is completed.

[0006]

In superposing the above-mentioned single color toner images, first, the transfer paper P is surely brought into close contact with the peripheral surface of each image forming body at the transfer portion.
Secondly, it is necessary that the toner image previously transferred by the transfer paper P is conveyed at an accurate timing with respect to the rotation cycle of the image forming body of the next image forming portion, and therefore the transfer belt 8 is It is necessary to contact the image forming body with an appropriate pressure contact force and at the same time, convey the image forming body at a constant speed.

[0007] The same applies to a method in which a toner image is sequentially superimposed on a transfer belt to form a color toner image, and then the toner images are collectively transferred onto transfer paper.

However, in such a case, it is difficult to drive and rotate all of the plurality of image forming members in synchronism with the peripheral speed of the transfer belt, and the transfer belt itself has a slight peripheral speed unevenness. It was said that it was not suitable for forming high-quality images.

Further, in a system in which a color toner image is formed on a transfer belt and transferred onto a transfer sheet at a time, it is difficult to convey the transfer sheet in a horizontal direction, and therefore, in terms of a layout of the apparatus and handling. There is also a problem, and there is also a problem that maintenance work becomes difficult because the structure is complicated by providing a plurality of image forming units.

As a result of solving these problems and improving the present invention, it is an object of the present invention to provide a color image forming apparatus capable of obtaining a high quality copy, easing the layout of the apparatus, and facilitating maintenance. .

[0011]

The above object is to provide a plurality of sets of image forming units in which a drum-shaped image forming body and a charging means, an image exposing means and a developing means are arranged around the image forming body. In a color image forming apparatus in which toner images formed on respective image forming bodies are sequentially superposed on an intermediate transfer body to form a color toner image, and the color toner images are collectively transferred onto a transfer material, the intermediate transfer body is stretched. A belt member,
The image forming units are arranged in parallel on one surface of the belt member, and the image forming members form a contact surface with the belt member via a contact surface forming member, and the power transmitted from the belt member. A color image forming apparatus (invention according to claim 1) characterized in that each of the image forming members is driven and rotated by an adhesion force formed by applying a transfer bias voltage, and a drum-shaped image forming member and the image forming member. A plurality of sets of image forming units each having a charging unit, an image exposing unit and a developing unit are provided around the image forming body, and the toner images formed on the respective image forming bodies are sequentially superposed on the intermediate transfer body to form a color toner. In a color image forming apparatus that forms an image and collectively transfers the color toner image onto a transfer material, the intermediate transfer member is a belt member stretched in a vertical direction, and each of the image forming units includes the belt. The image forming members form a contact surface with the belt member through a contact surface forming member, and the color toner images formed on the belt member are arranged above or below the member. This is achieved by a color image forming apparatus (invention according to claim 6) characterized in that the image is transferred onto a transfer material conveyed in the horizontal direction.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention according to claims 1 and 6 will be described with reference to FIGS.

FIG. 2 shows an example of the configuration of the color image forming apparatus of the present invention. A belt member 10 used as an intermediate transfer member is vertically arranged at a substantially central portion of the apparatus main body. It is stretched around the barrel driving roller 11 and the driven roller 12, is tensioned by the tension roller 13, and is circulated counterclockwise by the rotation of the driving roller 11 and conveyed.

The belt member 10 has yellow (Y), magenta (M), cyan (C) and black (K) on one side opposite to the tension roller 13, respectively.
Image forming units 20 (Y), 20 for forming respective toner images
(M), 20 (C) and 20 (K) are arranged in parallel in the order from the upstream side of the conveyance, that is, from the lower side.

Each of the image forming sections 20 has a photoconductor drum 21 and a corona charger 22 arranged on the peripheral surface thereof.
An exposure optical system 23 and a toner hopper 24A are integrated into a developing device 24 and a cleaning device 25. Each photoconductor drum 21 is rotated by one rotation in the clockwise direction, and the corona charging device 22 discharges the photoconductor drum 21 on its peripheral surface. A uniform electric potential is applied to the photoconductor, and the photoconductor to which the uniform electric potential is applied forms an electrostatic latent image by exposure of the exposure optical system 23, and the latent image is visualized by the developing device 24 to sequentially specify a specific color. To form a toner image.

The yellow (Y), magenta (M), cyan (C), and black (K) toner images formed on the photoconductor drums 21 in the image forming units 20 are as follows.
By the discharge of the transfer electrode 26, the color toner images are sequentially transferred onto the belt member 10 and superposed to form a color toner image, and the color toner image is conveyed to an image transfer portion in the upper part of the apparatus. On the other hand, in parallel with this, the transfer paper is conveyed from the paper feed cassette 30 by the operation of the carry-out roller 31, is fed from the horizontal direction to the image transfer portion via the timing roller 32, and the transfer voltage of the transfer roller 33 is applied. The color toner image is transferred. Further, the transfer paper is separated from the belt surface by the charge removal of the separator 34 and is conveyed to the fixing device 36 via the adsorption type conveyance belt 35, and the toner is fused and the transfer paper which has been fixed passes through the discharge roller 37. The image is discharged onto the tray 38 and the image formation is completed.

FIG. 3 shows an example of the construction of an apparatus in which an image transfer section is provided in the lower part. The belt member 10 is circulated in the clockwise direction and conveyed, and each image forming section 20 is conveyed from the upstream side, that is, from the upper side to the yellow ( Y), magenta (M), cyan (C)
2 and black (K) are arranged in parallel, and the transfer paper is fed in the horizontal direction to the image transfer portion to receive the transfer of the toner image as in the embodiment shown in FIG.

The belt member 10 has a thickness of 0.5 to 2.0 mm.
An endless rubber belt made of silicone rubber or urethane rubber having a resistance value of 10 ⁸ to 10 ¹² Ω · cm, and a toner filming prevention layer having a thickness of 5 μm to 50 μm on the outside of the rubber substrate. It has a two-layer structure with fluorine coating. This layer also preferably has a similar semiconductivity. 0.1-0.5m thickness instead of rubber belt base
m, a semiconductive polyester, polystyrene, polyethylene, polyethylene terephthalate, or the like can also be used.

The belt member 10 is in external contact with each of a pair of guide rollers 14 arranged as contact surface forming members at vertically symmetrical positions facing the peripheral surface of each photosensitive drum 21, and between the guide rollers 14. A contact surface is formed between the belt surface and the corresponding peripheral surface of the photoconductor drum 21.

The belt member 10 exerts a frictional force on the peripheral surface of the photosensitive drum 21 at the contact surface by the urging force of the tension roller 13, and an electrostatic force generated by the discharge of the transfer electrode 26. Generates a strong contact force between the belt member 10 and the contact surface between the peripheral surface of the photosensitive drum 10 and the conveyance force of the belt member 10 driven by the drive roller 11 via the contact force. The photoconductor drums 21 are transmitted to the photoconductor drums 21, so that each of the photoconductor drums 21 is driven and rotated at a peripheral speed corresponding to the conveyance speed of the belt member 10.

According to experiments, when the photosensitive drum 21 having a diameter of 30 to 100 mm is targeted, the width of the contact surface formed between the belt member 10 and the photosensitive drum 21, that is, the length along the peripheral surface of the drum. The product of the radius r shown in FIG. 4 and the center angle w of the drum formed by the contact surface is 15 to 6 (nip length).
The range of 0 mm is selected according to the drum diameter, and the pressing force of the contact surface against the drum surface of the belt member 10 is applied to the transfer electrode 26 at 100 to 500 N / m (N is Newton) per unit length in the drum axial direction. By setting the bias voltage to be applied within the range of 0.5 to 2 kV according to the drum diameter, it has been confirmed that the belt member 10 can transmit the driving force to the photoconductor drums 21 extremely efficiently. It was

Generally, the driving torque required to rotate the photosensitive drum 21 having a diameter of 30 to 100 mm is required to be in the range of 5 to 50 N, and therefore, the belt member 10 for driving the four image forming portions. The driving force is set to 25 to 25 in consideration of power loss due to additional belt cleaning means.
By setting it to 0N, it is possible to sufficiently drive and rotate each photosensitive drum 21. If it is less than 25N, the torque for rotating the photosensitive drum 21 becomes insufficient, and 250N
If it is larger, another driving force is required. Setting within the above range is a condition under which stable driving can be performed by electric force and frictional force.

A strong frictional force that does not cause a slip acting on the contact surface formed between the belt member 10 and the peripheral surface of the photoconductor drum 21 is generated when the voltage application to the transfer electrode 26 is released and the belt or The photosensitive drum 21 can be moved from its image forming position by being separated and retracted from one of the drums, and can be freely attached to and detached from the apparatus main body. The specific means will be described below.

The belt member 10 is provided with a mechanism for moving and retracting the tension roller 13 to a position indicated by a broken line, that is, a position inside the belt, as shown in FIG.
By the operation of the mechanism, the tension of the belt is reduced and the frictional force acting on the contact surface with each photoconductor drum 21 can be released all at once. As a result, each photosensitive drum 21
Can be moved in the axial direction of each rotary shaft 21A and can be easily attached and detached.

Alternatively, the corona charging device 22, the developing device 24, and the cleaning device 2 are left, leaving the exposure optical system 23 in which the photosensitive drum 21 is fixed and positioned as shown in FIG. 5B.
Together with 5, integrated into an image forming unit 200 capable of horizontally moving and retracting to a position shown by a broken line, that is, a position separated from the belt surface, and by the movement, the peripheral surface of the photosensitive drum 21 is separated from the belt surface, After that, the image forming unit 200 may be configured to move in the rotation axis direction of the photosensitive drum 21.

Alternatively, the photosensitive drum 21 is moved to the position shown by the broken line in the exposure optical system 23 as shown in FIG.
The image forming unit 20 capable of moving horizontally and retracting together with the corona charger 22, the developing device 24, and the cleaning device 25 in the direction away from the belt surface in the figure.
0, and the peripheral surface of the photoconductor drum 21 is separated from the belt surface by the movement thereof.
It is also possible to take out 0 while moving it further.

Further, in the embodiment shown in FIG. 6, the belt member 10 has a belt surface facing each image forming portion 20, and the tangential position between the driving roller 11 and the driven roller 12 ( The guide roller 14 is provided with a mechanism for horizontally moving from the inside of the tangential position to the outside together with the transfer and separation electrodes 26 and 27. By moving each of the electrodes 26 and 27 to the position indicated by the solid line, tension is further applied to the belt surface, and the contact surface and the image are formed on the peripheral surface of the photosensitive drum 21 installed outside the tangential position. The transfer area is structured.

Therefore, the belt member 10 is guided by the guide roller 14
By moving each of the electrodes 26 and 27, the belt surface can be returned to the tangential position, and as a result, the photoconductor drum 21 can release the frictional force received from the belt surface and move in the rotation axis direction. It is easy to put on and take off.

Further, in the belt member 10 shown in FIG. 7, the guide roller 14 and the transfer / separation electrodes 26 and 27 are integrated in a stretched state, and the rotary shaft 11A of the drive roller 11 is used as a fulcrum in a clockwise direction. The photoconductor drum 21 is rotated to the position shown by the broken line to release the frictional force of the belt member 10 with respect to the drum peripheral surface, and the photosensitive drum 21 is rotated in the direction of the rotation axis or at a right angle to the rotation axis. It is possible to attach and detach by moving to the left.

The transfer electrodes 2 of each image forming section 20 other than the image forming section 20 used even when forming a monochrome image.
6 is discharged and all the photosensitive drums 21 are rotated at the same speed as the belt due to the adhesive force of the belt, so that the toner image on the belt is generated when passing through the abutting portion of the unused photosensitive drum 21. It is possible to prevent the toner image from being disturbed.

[0031]

According to the present invention, the intermediate transfer belt can drive a plurality of photoconductor drums synchronously at the same peripheral speed as the intermediate transfer belt by utilizing the conveying force thereof, and as a result, a toner image of a specific color can be formed. With the plurality of image forming units to be formed, it is possible to obtain a high-quality color image with no image shift (the invention of claim 1). Further, by improving the layout, it is possible to provide a color image forming apparatus which facilitates the transportability of the transfer paper, the jam processing, and the maintenance work of the photosensitive drum and the like (the invention of claim 6).

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between an image forming body and a transfer / conveyance unit.

FIG. 2 is a sectional configuration diagram of a color image forming apparatus (first) of the present invention.

FIG. 3 is a cross-sectional configuration diagram of a color image forming apparatus (2) of the present invention.

FIG. 4 is a main part diagram of the device (No. 1).

FIG. 5 is an explanatory view of a detachable type (first) of a photosensitive drum.

FIG. 6 is an explanatory diagram of a detachable type (second) of the photosensitive drum.

FIG. 7 is an explanatory view of a detachable type (part 3) of the photosensitive drum.

[Explanation of symbols]

 10 Belt Member 11 Drive Roller 12 Followed Roller 13 Tension Roller 14 Guide Roller 20 Image Forming Part 21 Photosensitive Drum 22 Corona Charger 23 Exposure Optical System 24 Developer 25 Cleaning Device 26 Transfer Electrode 27 Separation Electrode 30 Paper Feed Cassette 32 Timing Roller 33 transfer roller 34 separator 36 fixing device 200 image forming unit

Claims (10)

[Claims] 1. A toner formed on each of the image forming bodies, having a plurality of image forming portions each having a drum-shaped image forming body and a charging means, an image exposing means and a developing means arranged around the image forming body. In a color image forming apparatus in which images are sequentially superimposed on an intermediate transfer member to form a color toner image, and the color toner images are collectively transferred to a transfer material, the intermediate transfer member is a stretched belt member, The image forming units are arranged in parallel on one surface of the belt member, and the image forming members form a contact surface with the belt member via a contact surface forming member, and the power transmitted from the belt member. A color image forming apparatus wherein each of the image forming members is driven and rotated by an adhesion force formed by applying a transfer bias voltage. 2. The color image forming apparatus according to claim 1, wherein a transfer bias voltage is applied to each of the image forming bodies even when a monochromatic image is formed. 3. The driving force transmitted to each image forming body is 5
3. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is about 50 Newtons. 4. The driving force of the belt member is 25 to 250.
The color image forming apparatus according to claim 1, wherein the color image forming apparatus is a Newton. 5. The color image forming apparatus according to claim 1, wherein a width of a contact surface of the belt member with respect to the image forming body is 15 to 60 mm. 6. A toner formed on each of the image forming bodies, having a plurality of sets of image forming portions each having a drum-shaped image forming body and a charging means, an image exposing means and a developing means arranged around the image forming body. In a color image forming apparatus that sequentially superimposes images on an intermediate transfer member to form a color toner image and transfers the color toner images to a transfer material at once, the intermediate transfer member is a belt member stretched in a vertical direction. The image forming units are arranged in parallel in a vertical direction on one surface of the belt member, and the image forming members form a contact surface with the belt member via a contact surface forming member. A color image forming apparatus, wherein the color toner image formed on the upper part or the lower part is transferred onto a transfer material which is conveyed in the horizontal direction. 7. The color image forming apparatus according to claim 6, wherein each of the image forming bodies is attached and detached by moving in the rotational axis direction at a position separated from the belt member. 8. The color image forming apparatus according to claim 6, wherein each of the image forming bodies is detached by moving in a direction away from the belt member after retracting the image exposing means. 9. The image forming bodies are located outside a connecting position between the tension members at both ends, and move in the rotation axis direction by retracting the contact surface forming member inside the tangential position. The color image forming apparatus according to claim 6, wherein the color image forming apparatus is attached and detached. 10. The image forming members are detached by moving the belt member together with the contact surface forming member from the image forming members and then moving in the rotational axis direction or the direction perpendicular to the rotational axis. The color image forming apparatus according to claim 6.