JP2000162891A - Image forming device for forming multiple images - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the speed variation of an intermediate transfer belt caused by the circumferential speed variation of a photoreceptor drum, to reduce the deviation of a transfer position and color slurring and to form a high-quality image, without image deterioration by providing a driven roller with a frictional load member. SOLUTION: An intermediate transfer belt 6 is constituted of conductive polycarbonate resin, so as to reduce a friction coefficient μ between a photoreceptor drum 5 and the belt 6. Then, a driven roller 22 is pivotally supported to freely rotate with a driven roller shaft 23, and the shaft 23 is fixed in a device main body. A roller 22 and the shaft 23 are coupled with a torque limiter 24 and apply rotational load to the roller 22. Then, frictional force acting on a contact part between the drum 5 and the intermediate transfer body 6 is made weaker than the tensile force of the belt 6. Therefore, slippage is caused between the surface of the drum 5 and the belt 6, so that the circumferential speed variation of the drum 5 is not transmitted to the belt 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex image forming apparatus capable of forming a composite image by superimposing image information on a transfer material using an electrophotographic method or the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic method, an electrophotographic photosensitive member serving as an image carrier is charged by a charger, and the photosensitive member is irradiated with light according to image information to form a latent image. An image is formed, and an image obtained by developing the latent image with a developing device is transferred to a sheet material or the like to form an image.

On the other hand, a plurality of image carriers for each of these image forming processes are provided in accordance with the colorization of the image, and each of the color images of a cyan image, a magenta image, a yellow image, and preferably a black image is carried on each image carrier. A tandem-type image forming apparatus that forms a full-color image by superposing and transferring each color image on a sheet material at a transfer position of each image carrier at a transfer position of each image carrier has also been proposed.

The tandem type multiplex image forming apparatus has an image forming section for each color, which is advantageous for speeding up.

However, there is a problem in how well the registration (registration) of each image formed by different image forming units is performed. This is because the shift of the image forming positions of the four colors transferred to the sheet material finally appears as a color shift or a change in color tone.

FIG. 5 shows a color printing apparatus using four photosensitive drums. This apparatus has a printing paper cassette 15, a feeding roller 16 and a registration roller 17 in a transport section, and has a fixing roller 18 and a pressure roller 19 in a fixing section. In the image forming section, photosensitive drums 51 (K, Y, M, C) for forming toner images of black (K), yellow (Y), magenta (M), and cyan (C) are formed.
And a toner image forming member 3 that forms a toner image disposed around the photosensitive drum 51 on the surface of the photosensitive drum 51. The toner image forming member 3 in each photosensitive drum 51 is , An exposure unit 12, a developing unit 13, a cleaner 14, and the like, and are constituted by the same members. On the other hand, the present apparatus has an intermediate transfer belt 52 for intermediately transferring the toner image on the photosensitive drum 51 before transferring the toner image formed on each photosensitive drum 51 to the printing paper 7. .

In the above-described apparatus, when a print command is issued from a control unit (not shown) built in the apparatus, feeding of the printing paper 7 is started, and the feeding roller 1 is fed from the printing paper cassette 15.
The printing paper 7 is taken out by 6, and the printing paper 7 is temporarily stopped at the nip portion of the registration roller 17, and the transfer timing is set here.

On the other hand, each image forming section forms a toner image of each color on the surface of the photosensitive drum 51. Then, the toner image on the photosensitive drum 51 is sequentially transferred by the voltage of the first transfer roller 21 onto the surface of the intermediate transfer belt 52 which is in contact with the photosensitive drum 51 and is conveyed in the direction of arrow A by the drive roller 20. You. Thereafter, the printing paper 7 is transported by the registration roller 17 whose rotation has been resumed, and the toner image transferred to the intermediate transfer belt 52 is transferred to the second transfer roller 10.
Is transferred to the printing paper 7 by the above voltage to obtain a color toner image. The printing paper 7 is further sent to a fixing device, where the toner image is fixed by heat and pressure applied from the fixing roller 18 and the pressure roller 19.

Further, residual toner on the surface of the intermediate transfer belt 52 after being transferred to the printing paper 7 by the second transfer roller 10 is cleaned by the intermediate transfer belt cleaner 27. Reference numeral 28 denotes a tension roller that applies a tension force to the intermediate transfer belt 52. Reference numeral 29 denotes a color misregistration detection sensor for detecting a color misregistration amount of the toner image on the intermediate transfer belt 52 formed by the toner image forming member 3 of each color.

[0010]

However, in the above-described conventional configuration, since the toner image is transferred from each photosensitive drum 51 to the intermediate transfer belt 52 as described above, the intermediate transfer belt 52 and the photosensitive drum 51 Used in contact. Therefore, when the peripheral speed of the photosensitive drum 51 deviates from a predetermined speed and a speed difference occurs between the photosensitive drum 51 and the intermediate transfer belt 52, each photosensitive drum 5
Belt deflection occurs in the intermediate transfer belt 52 between the photoconductor drums 51 and the belt distance between the photosensitive drums 51 fluctuates, and the output image causes color misregistration of each color. Factors that cause the peripheral speed of the photoconductor drum 51 to deviate from the predetermined speed include a manufacturing error of the rotary shaft center.

As a result, the transfer position of the toner image transferred to the intermediate transfer belt 52 is shifted, and the resulting image is shaded due to the color shift, which causes a problem that the image quality is significantly deteriorated.

The above problem is very serious in forming a high-quality image without color misregistration in a digital color multiplex image forming apparatus.

Accordingly, an object of the present invention is to provide a multiple image forming apparatus in which the speed fluctuation between the photosensitive drum 51 and the intermediate transfer belt 52 is minimized, and the transfer position shift and, consequently, the color shift are reduced. I do.

[0014]

In order to solve the above-mentioned problems, the present invention provides a friction load member for applying a rotational load to a driven roller of an intermediate transfer belt driven roller provided at the uppermost stream of a photosensitive drum. With this configuration, the intermediate transfer belt driving roller and the intermediate transfer belt driven roller can make the intermediate transfer belt tension larger than the contact friction force between the photosensitive drum and the intermediate transfer belt. A multiple image forming apparatus capable of reducing fluctuations in the speed of the intermediate transfer drum due to fluctuations can be obtained.

The surface of the intermediate transfer belt driven roller is
Since the belt is formed by the high friction member, the belt slip on the surface of the intermediate transfer belt driven roller can be reduced, so that a multiple image forming apparatus that can reduce the intermediate transfer drum speed variation due to the photosensitive drum peripheral speed variation can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a plurality of photosensitive drums, an exposure unit for irradiating each of the photosensitive drums with light to form a latent image, and a photosensitive drum. A plurality of developing means for visualizing the latent images formed thereon, a transfer means for transferring the image visualized by the developing means to an intermediate transfer belt, a driving roller for driving the intermediate transfer belt, and an intermediate transfer A multiplexed image forming apparatus having a driven roller driven by a belt and superimposing images visualized on each of the photosensitive drums successively on a transfer material to form a composite image; , The intermediate transfer belt driving roller and the intermediate transfer belt driven roller
Since the tension of the intermediate transfer belt can be made larger than the contact frictional force between the photosensitive drum and the intermediate transfer belt, a multiplex image forming apparatus that can reduce the speed fluctuation of the intermediate transfer belt due to the circumferential speed fluctuation of the photoconductor drum can be obtained.

According to a second aspect of the present invention, in the first aspect of the invention, a high friction member is provided on the surface of the intermediate transfer belt driven roller, so that the intermediate transfer belt slides on the surface of the intermediate transfer belt driven roller. Can be reduced.

According to a third aspect of the present invention, in the first aspect of the present invention, the surface of the intermediate transfer belt driven roller itself is made to have a high friction so that the cost is not increased and the intermediate transfer belt driven roller surface is formed on the intermediate transfer belt driven roller surface. Of the intermediate transfer belt can be reduced.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a configuration diagram of a multiplex image forming apparatus according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a driven roller of the multiplex image forming apparatus according to an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a configuration diagram of a second driven roller of the multiple image forming apparatus according to an embodiment of the present invention.

First, an embodiment of the present invention will be described with reference to FIGS. The basic configuration of this printing apparatus is the same as that of the color printing apparatus described in the background art, so that the description is omitted here.

An intermediate transfer belt 6 and four photosensitive drums 5 (K, Y, M, C) are provided. Each photosensitive drum 5 has a black (K), yellow (Y), and magenta (M), respectively. , And a cyan (C) toner image. Further, the intermediate transfer belt 6 is made of a conductive polycarbonate-based resin, and reduces the coefficient of friction μ between each of the photosensitive drums 5. The driven roller 22 is rotatably supported by a driven roller shaft 23, and the driven roller shaft 23 is fixed to an apparatus main body (not shown). The driven roller 22 and the driven roller shaft 23 are connected to a torque limiter 24, and apply a rotational load to the driven roller 22. Then, the frictional force acting on the contact portion B between the photosensitive drum 5 and the intermediate transfer belt 6 was made smaller than the tension of the intermediate transfer belt.

That is, the photosensitive drum 5 and the intermediate transfer belt 6
The frictional force F acting between the two members can be expressed as F = μP, where P is the pressure contact force applied between the two members. When the radius of the driven roller 22 is R and the load torque is T, the intermediate transfer belt tension Ft on the surface of the driven roller 22 can be expressed as Ft = TR. The belt tension Ft of the intermediate transfer belt 6 is made larger than the value of the frictional force F (Ft
> F).

Therefore, even if a peripheral speed difference occurs between the surface of the photosensitive drum 5 and the intermediate transfer belt 6 and a frictional force F is generated at the contact portion B between these members, the frictional force F is larger than the frictional force F. Since the transfer belt tension Ft is large, slippage occurs between the surface of the photosensitive drum 5 and the intermediate transfer belt 6, and the fluctuation of the peripheral speed of the photosensitive drum 5 is not transmitted to the intermediate transfer belt 6.

FIG. 3 is a diagram showing a configuration in which a high friction member 26 such as urethane rubber is attached to the surface of a driven roller. With this configuration, the frictional force between the intermediate transfer belt 6 and the high friction member 26 is improved, and belt slip between the intermediate transfer belts can be reduced.

FIG. 4 is a configuration diagram in which the surface of the driven roller is provided with irregularities to increase the friction. With this configuration,
The frictional force with the intermediate transfer belt 6 is improved, and belt slip between the intermediate transfer belts can be reduced.

[0026]

As described above, according to the present invention, a plurality of photosensitive drums, an exposure means for irradiating each of the photosensitive drums with light to form a latent image, and a photosensitive drum formed on each of the photosensitive drums A plurality of developing means for visualizing the latent image, a transfer means for transferring the image visualized by the developing means to the intermediate transfer belt, a driving roller for driving the intermediate transfer belt, and a rotation driven by the intermediate transfer belt. And a driven roller, wherein a frictional load member is provided on the driven roller in a multiplex image forming apparatus which forms a composite image by sequentially superimposing images visualized on each of the photosensitive drums on a transfer material. The intermediate transfer belt driving roller and the intermediate transfer belt driven roller can increase the tension of the intermediate transfer belt more than the contact frictional force between the photosensitive drum and the intermediate transfer belt. Shooting drum speed multiple image forming apparatus capable of reducing variation is obtained, displacement transfer position, can thus have reduced color shift, to obtain a high-quality image image degradation is not.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a multiplex image forming apparatus according to an embodiment of the present invention;

FIG. 2 is a configuration diagram of a driven roller of the multiplex image forming apparatus according to the embodiment of the present invention;

FIG. 3 is a configuration diagram of a second driven roller of the multiple image forming apparatus according to the embodiment of the present invention;

FIG. 4 is a configuration diagram of a third driven roller of the multiple image forming apparatus according to the embodiment of the present invention;

FIG. 5 is a configuration diagram of a conventional multiple image forming apparatus.

[Explanation of symbols]

 Reference Signs List 5 photosensitive drum 6 intermediate transfer belt 22 driven roller 23 driven roller shaft 24 torque limiter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaya Shimada 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. AA27 AA37 AA51 AA61 AA75 BA43 FA05 FA18 GA02 GA38 GA52 HA04 HA48

Claims (3)

[Claims] A plurality of photoconductors; an exposing means for irradiating each of the photoconductors with light to form a latent image; and a plurality of developing devices for visualizing the latent images formed on each of the photoconductors. Means for transferring the image visualized by the developing means to a transfer belt, a driving roller for driving the transfer belt, and a driven roller driven and rotated by the transfer belt, A multiple image forming apparatus for forming a composite image by sequentially superimposing images visualized on each body on a transfer material, wherein the driven roller is provided with a friction load member. 2. The multiple image forming apparatus according to claim 1, wherein the surface of the driven roller is formed of a high friction member. 3. The multiple image forming apparatus according to claim 1, wherein said driven roller has a rough surface.