JP2002156808A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device for preventing overlapped dirt, a stained dot and the excessive-transfer of half tone by eliminating a fine gap when a transfer paper enters a transfer part. SOLUTION: In the case of the color image forming device using a transfer belt at a secondary transfer process, a supporting roller 300 is bitten into an intermediate transfer belt 220, or the intermediate belt 220 is wound round the supporting roller 300 by using a depressing member 320. In the case of the color image forming device using a transfer roller at the secondary transfer process, the secondary transfer roller 330 is bitten into the intermediate transfer belt 220, or the intermediate transfer belt 220 is wound round the secondary transfer roller 330 by using the depressing member 320.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to a color image forming apparatus using an intermediate transfer member.

[0002]

2. Description of the Related Art In recent years, an electrophotographic color image forming apparatus capable of copying and printing a full-color image has been put to practical use. As a method of transferring an image to a transfer material in a color image forming apparatus, there are an intermediate transfer method and a direct transfer method. In the intermediate transfer method, yellow (Y), magenta (M), cyan (C), and black (B) are formed for each color on a photoconductor with reference to a reference mark on the intermediate transfer belt.
The images K) are sequentially superimposed and transferred on the intermediate transfer belt in the primary transfer area, and the full-color toner image on the intermediate transfer belt is collectively transferred to the transfer material in the secondary transfer area. In the direct transfer method, a color toner image is created by successively transferring images onto paper held on a transfer drum or the like. The direct transfer method has a simple structure and is low in cost, but it is difficult to perform stable image formation when transferring to paper a plurality of times because conditions are different depending on the resistance and moisture content of the paper. The intermediate transfer method has a feature that the image is transferred to paper only once, so that the image quality is stable and the paper type is compatible.

[0003] An important prerequisite for a copying machine is pre-transfer at the entrance when a transfer sheet enters a transfer section. In particular, in a color transfer machine and further in an intermediate transfer system, a plurality of overlapping images are collectively transferred, so that the influence of the pre-transfer is enormous. The main problems are overlapping dust, dot bleeding, and excessive transfer of halftone. This is caused by the fact that the transfer paper does not come into contact with the intermediate transfer belt first at the entrance of the transfer section, so that a discharge occurs in a very small gap and the image is disturbed. In the prior art, the paper is guided so as to enter the front side of the transfer portion, but the paper did not adhere to the intermediate transfer belt as expected.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, it is possible to eliminate a small gap when a transfer sheet enters a transfer section.
An object of the present invention is to provide a color image forming apparatus which eliminates excessive transfer of dust, blur, and halftone.

[0005]

According to a first aspect of the present invention, a plurality of images from a plurality of photoreceptors are superimposed on an intermediate transfer belt, and then a secondary transfer belt is formed. A color transfer device that collectively transfers onto a transfer material with an intermediate transfer belt, wherein a support roller of a secondary transfer belt abuts on the intermediate transfer belt upstream of an opposing roller in a state in which the secondary transfer belt is wound around and is supported. When the roller is not in contact with the intermediate transfer belt position, the intermediate transfer belt is bent by the support roller and the secondary transfer belt having a thickness of 0.5 to 5 mm biting into the intermediate transfer belt. The radius of the opposing roller: Rt, the thickness of the intermediate transfer belt: Tb, secondary transfer belt thickness: Tb2, support roller diameter: R2, distance between opposing roller center and support roller center: M, and the relationship of (Rt + Tb + Tb2 + R2) -M ≦ 0 is satisfied. Features A color image forming apparatus.

According to a second aspect of the present invention, there is provided a color transfer method in which a plurality of images from a plurality of photoreceptors are superimposed on an intermediate transfer belt and then collectively transferred to a transfer material by a secondary transfer belt and an intermediate transfer belt. An apparatus, having a member for pushing down the intermediate transfer belt side from the back side on the upstream side of the opposing roller to the support roller of the secondary transfer belt in a state where the secondary transfer belt is wound, and winding the intermediate transfer belt around the support roller. 2. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is wound around a secondary transfer belt.

According to a third aspect of the present invention, there is provided a color transfer apparatus in which a plurality of images from a plurality of photosensitive members are superimposed on an intermediate transfer belt, and then collectively transferred to a transfer material by a secondary transfer roller and an intermediate transfer belt. And the opposing roller radius: Rt,
Intermediate transfer belt thickness: Tb, secondary transfer roller diameter: R2,
When the distance between the center of the opposing roller and the center of the transfer roller is M,
In a transfer device having a relationship of (Rt + Tb + R2) -M≤0, the secondary transfer roller abuts on the intermediate transfer belt on the upstream side of the opposing roller, and the secondary transfer roller is moved from the belt position when it is not in abutment. A color image forming apparatus characterized in that the secondary transfer roller bites the toner by 0.5 to 5 mm.

According to a fourth aspect of the present invention, there is provided a color transfer apparatus, wherein a plurality of images from a plurality of photosensitive members are superimposed on an intermediate transfer belt and then collectively transferred to a transfer material by a secondary transfer roller and an intermediate transfer belt. 4. The color image forming apparatus according to claim 3, further comprising a member that pushes down the intermediate transfer belt side from the back side on the upstream side of the opposing roller, wherein the intermediate transfer belt is wound around the secondary transfer roller. 5. And

[0009]

FIG. 1 shows an example of a digital color printer using an image forming apparatus using a transfer belt for secondary transfer. An image forming apparatus main body 100 forms a color image by a conventionally known electrophotographic method. Image writing unit 1 for
20, an image forming unit 130, and a paper feeding unit 140. The image processing unit performs image processing based on the image signal, converts the image signal into black (BL), yellow (Y), magenta (M), and cyan (C) color signals for image formation, and transmits the signal to the image writing unit 120. I do. The image writing unit 120 is, for example, a laser scanning optical system device including a laser light source, a deflector such as a rotary polygon mirror, a scanning imaging optical system device, and a mirror group. It has a writing optical path and writes an image in accordance with each color signal on the photoconductor 210 provided for each color of the image forming unit 130.

The image forming section 130 includes photoconductors 210 for black (BL), yellow (Y), magenta (M), and cyan (C).
A PC photoreceptor is used. Around each photoconductor 210,
Charging device, an exposure portion of laser light from the writing portion 120, black,
Developing device 20 for each color of yellow, magenta and cyan
0, a primary transfer device 230, a cleaning device 300, a neutralization device, and the like. The developing device 200 has 2
A component magnetic brush development system is used.

The intermediate transfer belt 220 is interposed between each of the photosensitive members 210 and the primary transfer device 230.
From 10 toner images of each color are sequentially superimposed and transferred,
The toner image on the photoconductor 210 is carried. Then, after the transfer paper is fed from the paper feed unit 140, the transfer paper is carried on the secondary transfer belt 290 via the resist 280, and is transferred to the transfer paper when the intermediate transfer belt 220 and the secondary transfer belt 290 come into contact with each other. A color image is formed. Then, the transfer paper after the image transfer is fixed to the fixing device 1 by the secondary transfer belt 290.
The fixing device 150 conveys the image, and the image is fixed, so that a color image is obtained.

Referring to FIG. 1, the transfer paper exiting the resist 280 enters the nip between the intermediate transfer belt 220 and the secondary transfer belt 290 while contacting the guide plates above and below the entrance.
FIG. 2 is a schematic configuration diagram showing a positional relationship between the intermediate transfer belt 220 and the secondary transfer belt 290 according to the present invention. The support roller 300 cuts into the intermediate transfer belt 220 on the upstream side of the opposing roller 260, and has a sufficient prenip area on the upstream side of the bias roller 310. In this manner, by bringing the transfer paper into close contact with the image in the absence of the electric field from the bias roller 310, it is possible to prevent overlapping dust, bleeding of dots, and unevenness due to excessive transfer of halftone images.

FIG. 3 is a schematic diagram showing the positional relationship among the pressing member 320, the secondary transfer belt 290, and the intermediate transfer belt 220 according to the present invention. The difference from FIG. 2 is that the support roller 300 does not bite into the intermediate transfer belt 220 but is wound around the secondary transfer belt 290 from the inside of the intermediate transfer belt 220 by the guide of the pressing member 320. In this case, the same effect is obtained with respect to unevenness due to excessive transfer of the halftone image and dot bleeding, and at the same time, since there is a surface formed by the pressing member 320 immediately before the entrance portion, the pre-contact area increases, Further, it is possible to prevent the transfer paper from moving on and off the intermediate transfer belt 220 before the close contact nip. The pressing member 320 is made of a sheet metal or the like, and a fiber-like material such as a brush is planted in a close contact portion with the intermediate transfer belt 220 to improve slip.

FIG. 4 shows an example of a digital color printer using an image forming apparatus as in FIG. The difference from FIG. 1 is that a transfer roller is used for secondary transfer.

FIG. 5 shows a secondary transfer roller 330 according to the present invention.
FIG. 2 is a schematic configuration diagram illustrating a positional relationship between the image forming apparatus and an intermediate transfer belt 220. Although there are not many pre-contact areas as shown in FIG. 2, the secondary transfer roller 330 bites into the intermediate transfer belt 220 on the upstream side of the opposing roller 260, so that the adhesion of the wrapping part can be ensured, and overlapping dust and dot bleeding occur. In addition, unevenness due to excessive transfer of a halftone image can be prevented.

FIG. 6 is a schematic diagram showing the positional relationship among the pressing member 320, the secondary transfer roller 330, and the intermediate transfer belt 220 according to the present invention. 3, the intermediate transfer belt 220 is pressed down by the pressing member 320,
It is wound around the secondary transfer roller 330. Again,
The same effect is obtained with respect to blurring due to excessive transfer of a halftone image and dot bleeding. Further, by winding the intermediate transfer belt 220 around the secondary transfer roller 330, the pre-contact area can be increased, and furthermore, it is possible to prevent the transfer paper from moving before and after coming into contact with the intermediate transfer belt 220 before the close nip.

[0017]

As described above, in the color image forming apparatus of the present invention, a minute gap when the transfer paper enters the transfer portion is eliminated, thereby preventing overlapping dust, dot bleeding and excessive transfer of halftone. You can do it.

[Brief description of the drawings]

FIG. 1 is an example of a digital color printer using an image forming apparatus using a transfer belt for secondary transfer.

FIG. 2 is a schematic configuration diagram illustrating a positional relationship between an intermediate transfer belt and a secondary transfer belt according to the present invention.

FIG. 3 is a schematic configuration diagram illustrating a positional relationship among a pressing member, a secondary transfer belt, and an intermediate transfer belt according to the present invention.

FIG. 4 is an example of a digital color printer using an image forming apparatus using a transfer roller for secondary transfer.

FIG. 5 is a schematic configuration diagram illustrating a positional relationship between a secondary transfer roller and an intermediate transfer belt according to the present invention.

FIG. 6 is a schematic configuration diagram illustrating a positional relationship among a pressing member, a secondary transfer roller, and an intermediate transfer belt according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 image forming apparatus main body 120 image writing unit 130 image forming unit 140 paper feeding unit 150 fixing device 200 developing device 210 photoconductor 220 intermediate transfer belt 230 primary transfer device 240 cleaning device 250 tension roller 260 facing roller 270 drive roller 280 resist 290 Secondary transfer belt 300 Support roller 310 Bias roller 320 Depressing member 330 Secondary transfer roller 340 Conveyor belt

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Sadayuki Iwai 1-3-6 Nakamagome, Ota-ku, Tokyo Stock inside Ricoh Company (72) Inventor Kazuto Koyama 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh F term (reference) 2H030 AA01 AA06 AB02 AD05 BB42 BB46 BB53 2H032 AA05 BA09 BA23

Claims (4)

[Claims] 1. A color transfer device, comprising: superimposing a plurality of images from a plurality of photoconductors on an intermediate transfer belt; and transferring the images onto a transfer material at a time using a secondary transfer belt and the intermediate transfer belt. When the support roller of the transfer belt is in contact with the intermediate transfer belt on the upstream side of the opposing roller in a state where the secondary transfer belt is wound, the thickness of the support roller and the thickness of the secondary transfer belt relative to the intermediate transfer belt position when the support roller is not in contact Is 0.5-5m
The intermediate transfer belt is bent by cutting into m, the opposite roller radius: Rt, the intermediate transfer belt thickness: Tb, the secondary transfer belt thickness: Tb2, the support roller diameter: R2, the distance between the center of the opposite roller and the center of the support roller: A color image forming apparatus having a relationship of (Rt + Tb + Tb2 + R2) -M ≦ 0, where M is 2. A color transfer device, comprising: superimposing a plurality of images from a plurality of photoconductors on an intermediate transfer belt; and transferring the images onto a transfer material using a secondary transfer belt and the intermediate transfer belt. The support roller of the secondary transfer belt around which the transfer belt is wound has a member that pushes down the intermediate transfer belt side from the back side on the upstream side of the opposing roller, and the intermediate transfer belt is wound around the secondary transfer belt wound around the support roller. The color image forming apparatus according to claim 1, wherein: 3. A color transfer device, comprising: superimposing a plurality of images from a plurality of photoconductors on an intermediate transfer belt; and transferring the images onto a transfer material using a secondary transfer roller and an intermediate transfer belt. : Rt, thickness of the intermediate transfer belt: Tb, diameter of the secondary transfer roller: R2, distance between the center of the opposing roller and the center of the secondary transfer roller: M, (Rt + Tb + R2) −M ≦
In the transfer device having a relationship of 0, the secondary transfer roller abuts on the intermediate transfer belt on the upstream side of the opposing roller, and the secondary transfer roller is shifted from the non-contact belt position by 0.5 at the secondary transfer roller. A color image forming apparatus having a depth of about 5 mm. 4. A color transfer apparatus, comprising: superimposing a plurality of images from a plurality of photoconductors on an intermediate transfer belt; and transferring the images onto a transfer material by a secondary transfer transfer roller and an intermediate transfer belt. 4. The color image forming apparatus according to claim 3, further comprising a member that pushes down the intermediate transfer belt side from the back side on the upstream side of the intermediate transfer belt, wherein the intermediate transfer belt is wound around a secondary transfer roller.