JP2004361850A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of protecting an image carrier and suppressing the occurrence of a stripe image. <P>SOLUTION: The image forming apparatus is constituted by laying an endless belt type image carrier 40 on a plurality of rollers 41 to 45, and is set so that the surface hardness of the rollers 41 to 45 on which the image carrier 40 is laid may be lower than the back hardness of the image carrier 40. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus that suspends an endless belt-shaped image carrier with a plurality of rollers.
[0002]
[Prior art]
2. Description of the Related Art An image forming apparatus including an image carrier including an endless belt-shaped photoconductor and an intermediate transfer belt, and forming a full-color image by superimposing four color toner images of cyan, magenta, yellow, and black is widely known. .
[0003]
[Problems to be solved by the invention]
By the way, if a roller for suspending a belt-shaped image carrier (for example, an intermediate transfer belt) has a high hardness, that is, if the roller is hard, the back surface of the image carrier is damaged by the rotation operation, and when it progresses, a stripe ( In particular, it may appear as a concave streak (see the cross-sectional view of FIG. 3, reference numeral 40 denotes an intermediate transfer belt, 40a denotes a scratch on the back surface, and 40b denotes a streak on the front surface). As a result, there is a problem that streaky shading occurs in a halftone image or a solid image on a transfer material.
Similarly to the above-described problem, the rougher the surface roughness of the suspended roller, the more easily the back surface of the image carrier is damaged, and the more likely a streak image is generated. In particular, when the surface hardness of the roller is softer than the back surface hardness of the image carrier, this is not so problematic. However, when the surface hardness of the roller is harder than the back surface hardness of the image carrier, it is significantly deteriorated.
The above two problems appear more remarkably in the case of a resin material such as a fluorine-based resin often used as an intermediate transfer belt than in the case where the image carrier is made of a metal material such as nickel.
[0004]
Here, as a cleaning method of the intermediate transfer belt, a known blade cleaning method, a bias cleaning method, and the like are widely used. However, the blade cleaning method has a good cleaning property, but has a large load variation at the time of the contact / separation operation. In addition, there is a restriction on the layout that it cannot be arranged above the image forming apparatus in terms of toner scattering and toner collection.
Therefore, when it is desired to reduce the load fluctuation at the time of the contact / separation operation or when it is desired to dispose the cleaning means above, a method without using a cleaning blade such as a bias cleaning method is adopted. In the case of this method, paper dust and paper additives adhering to the intermediate transfer belt in the secondary transfer portion directly enter the contact portion (primary transfer nip portion) with the photosensitive member without being blocked by the blade. As a result, the surface of the photoreceptor is apt to be damaged due to these effects.
When the concave streaks 40b are generated on the surface of the intermediate transfer belt 40 as described above, scratches on the surface of the photoreceptor are also uneven in a streak shape (the surface portion of the photosensitive belt 1 corresponding to the concave streak 40b of the intermediate transfer belt 40 is Scratches are small: see FIG. 4), and the streak image becomes more prominent.
The present invention has been made in view of such a background, and an object of the present invention is to provide an image forming apparatus capable of protecting an image carrier and suppressing generation of a streak image.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an image forming apparatus in which an endless belt-shaped image carrier is suspended by a plurality of rollers, wherein the surface hardness of the suspended rollers is smaller than the back surface hardness of the image carrier. The most important feature is an image forming apparatus set low.
According to a second aspect of the present invention, in the image forming apparatus in which the endless belt-shaped image carrier is suspended by a plurality of rollers, among the suspended rollers, at least the surface hardness is higher than the back surface hardness of the image carrier. An image forming apparatus having a surface roughness of 0.4 μm or less in arithmetic average roughness (Ra) is the most main feature.
According to a third aspect of the present invention, there is provided an image forming apparatus according to the first or second aspect, wherein the image carrier is an intermediate transfer belt made of a resin material such as a fluorine-based resin.
The invention according to claim 4 is the image forming apparatus according to claim 3, wherein the cleaning means for the intermediate transfer belt is a blade rescreening means.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a front view showing a schematic configuration of a printer as an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a photosensitive belt and an intermediate transfer belt in the printer of FIG. This printer includes a photosensitive belt 1 as a latent image carrier wound around a plurality of support rollers. The photoreceptor belt 1 is driven to rotate in a clockwise direction, around which a charger 10, an optical writing unit 20, four developing devices 30, an intermediate transfer belt 40 as an intermediate transfer member, a photoreceptor cleaning device 50, and the like are provided. Are located. An organic photosensitive layer is formed on the surface of the base material of the photosensitive belt 1.
When an image forming operation (printing operation) is performed by the printer, a high voltage is applied to the charger 10 so that the photosensitive belt 1 is uniformly charged. Then, in an image signal processing unit (not shown), color image information, for example, a color image signal sent from an external computer is converted into an optical writing signal and sent to the optical writing unit 20. In the optical writing unit 20, a laser as a light source is controlled based on the optical writing signal, and Black (K), Cyan (C), and Magenta (M) are transmitted via a polygon mirror, an f / θ lens, and a reflection mirror. , Yellow (Y) image signals are written, and an electrostatic latent image is formed on the photosensitive belt 1.
The electrostatic latent image on the photosensitive belt 1 is developed for each color by each developing device 30 having each color toner. As a result, a toner image is formed on the photosensitive belt 1 for each color. At a contact portion between the photoreceptor belt 1 and the intermediate transfer belt 40, a charge having a polarity opposite to that of the toner is applied to the primary transfer bias roller 41 (FIG. 2), so that the toner image on the photoreceptor belt 1 is transferred to the intermediate transfer belt. It is transferred onto 40.
By repeating this toner image formation and transfer operation four times, a four-color superimposed color toner image is formed on the intermediate transfer belt 40. The color toner image on the intermediate transfer belt 40 is transferred by a paper transfer roller 70 as a secondary transfer member onto transfer paper as a recording material sent from a paper feed cassette 60 by conveyance rollers 61 and 62. The transfer paper onto which the color toner image has been transferred is conveyed to the fixing device 80, and the toner image is fused and fixed.
[0007]
Next, a specific configuration of the present invention will be described. As shown in FIG. 2, the intermediate transfer belt 40 as an image carrier in the present invention includes five primary transfer bias rollers 41, a driving roller 42, a cleaning opposing roller 43, a secondary transfer opposing roller 44, and a tension roller 45. It is suspended by rollers and rotates in the direction A in FIG. The intermediate transfer belt 40 is made of a fluorine resin material having a plurality of layers, and each of the five rollers 41 to 45 is made of a rubber material such as EP rubber having a thickness of about 2 mm on the peripheral surface of a metal core. The surface hardness is set to be lower than the back surface hardness of the intermediate transfer belt 40.
By making the surface hardness of the suspended roller lower than the back surface hardness of the image carrier, that is, by making it softer, it is possible to prevent the back surface of the image carrier from being damaged and to suppress generation of a streak image.
By forming the image carrier as an intermediate transfer belt made of a resin material such as a fluorine-based resin, even when a resin material whose back surface is more easily damaged than a metal material is used as the material of the image carrier, the back surface of the image carrier is Can be prevented from being damaged, and generation of a streak image can be suppressed.
In the above-described configuration, all the rollers that suspend the intermediate transfer belt 40 are made of a rubber material. However, for example, when any of the rollers is made of a metal or the like having a hardness higher than the back surface of the intermediate transfer belt 40 due to cost reduction or the like. Is set so that at least the surface roughness of the roller is 0.4 μm or less in arithmetic average roughness (Ra). That is, by smoothing the surface roughness of the suspended roller, it is possible to prevent the back surface of the image carrier from being damaged, and to suppress the occurrence of a streak image. In particular, when the surface hardness of the roller is harder than the back surface hardness of the image carrier, the effect is remarkable.
Although the color image forming apparatus using the intermediate transfer belt 40 as the image carrier has been described as an example, the photosensitive belt 1 may be used as the image carrier. Further, as the image carrier, a photosensitive belt in a monochrome image forming apparatus that does not use an intermediate transfer belt may be applied.
[0008]
2, the intermediate transfer belt cleaning device 46 contacts a brush roller 46-1 that contacts the intermediate transfer belt 40, a bias roller 46-2 that is biased and contacts the brush roller 46-1, and a bias roller 46-2. The intermediate transfer belt 40 includes a blade 46-3 and a recovery coil 46-4 for recovering the waste toner scraped off by the blade 46-3. It is configured to be able to move in and out of contact. Even in such a bladeless cleaning device, it is possible to prevent the streak image from becoming more prominent.
By using the blade rescreening means as the cleaning means for the intermediate transfer belt, even if the photoreceptor surface is more easily damaged by the influence of paper dust and paper additives, the surface of the intermediate transfer belt may be concave. Since no stripes are generated, the state of the surface of the photoconductor is not uneven, and the generation of image stripes can be suppressed.
[0009]
【The invention's effect】
According to the first aspect of the present invention, the surface hardness of the suspended roller is made lower than the back surface hardness of the image carrier, that is, by making it softer, the back surface of the image carrier is prevented from being damaged, and the generation of a streak image is prevented. Can be suppressed.
According to the second aspect of the present invention, by smoothing the surface roughness of the suspended roller, it is possible to prevent the back surface of the image carrier from being damaged, and to suppress generation of a streak image. In particular, when the surface hardness of the roller is harder than the back surface hardness of the image carrier, the effect is remarkable.
According to the third aspect of the present invention, the above effects can be obtained even when the back surface of the image carrier is more easily damaged than a metal material.
According to the fourth aspect of the present invention, even in the case of the blade rescreening means in which the surface of the photoreceptor is more easily damaged due to the effect of paper powder or paper additives, concave streaks are not generated on the surface of the intermediate transfer belt. The state of the photoreceptor surface is not uneven, and the generation of image streaks can be suppressed.
[Brief description of the drawings]
FIG. 1 is a front view showing a schematic configuration of a printer as an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a photosensitive belt and an intermediate transfer belt in the printer of FIG. 1;
FIG. 3 is a diagram showing a problem of the conventional example.
FIG. 4 is a diagram showing a problem of the conventional example.
[Explanation of symbols]
Reference Signs List 1 photoreceptor belt, 40 intermediate transfer belt, 41 primary transfer bias roller, 42 drive roller, 43 cleaning opposing roller, 44 secondary transfer opposing roller, 45 tension roller, 46 intermediate transfer belt cleaning device

Claims (4)

An image forming apparatus in which an endless belt-shaped image carrier is suspended by a plurality of rollers, wherein the surface hardness of at least one roller is set lower than the back surface hardness of the image carrier. In an image forming apparatus in which an endless belt-shaped image carrier is suspended by a plurality of rollers, among the suspended rollers, at least a roller whose surface hardness is higher than the back surface hardness of the image carrier has an arithmetic average roughness. An image forming apparatus wherein (Ra) is 0.4 μm or less. 3. The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer belt made of a resin material such as a fluorine-based resin. 4. The image forming apparatus according to claim 3, wherein the cleaning unit for the intermediate transfer belt is a blade rescreening unit.

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