JP2002014514A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the difference of the circulating speed of an intermediate transfer belt in a color image forming device. SOLUTION: This device is provided with a photosensitive drum, an electrifier uniformly electrifying the surface of the photosensitive drum, an exposure device forming an electrostatic latent image by radiating a laser beam corresponding to image data to the photosensitive drum electrified by the electrifier, a developing roller forming a toner image by supplying toner to the electrostatic latent image, an intermediate transfer belt 3 which is provided with reinforcing members 3a at the inner peripheral parts at both ends in a circulating direction and to which the toner image is transferred, and plural belt supporting rollers 2 over which the belt 3 is laid, so that the belt 3 is circularly moved, and both ends of which level difference parts D to avoid the interference with the member 3a are formed at by recessing as much as the thickness of the member 3a.

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 composite image by superimposing image information using electrophotographic technology or the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic technique, a photosensitive member 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. Is formed, and the latent image is developed by a developing device, and the visualized toner image is transferred to a sheet material or the like to form an image.

On the other hand, a plurality of image carriers on which such a series of image forming processes are developed in accordance with colorization of an image are provided, and each color image of a cyan image, a magenta image, a yellow image, and preferably a black image is provided. Is formed on each image carrier, and a full-color image is formed by superimposing and transferring each color image on a recording medium at a transfer position of each image carrier, or a toner image of each color is formed on the image carrier. A number of tandem-type color image forming apparatuses have been proposed in which, after formation, the images are sequentially transferred to an intermediate transfer member, and the superimposed full-color toner images are collectively transferred onto a recording medium.

[0004] Such a tandem type color image forming apparatus has an image forming section for each color, and is considered to be advantageous for speeding up.

Here, a conventional color image forming apparatus will be described.

FIG. 4 is a schematic view showing a conventional color image forming apparatus using a tandem system, and FIG. 5 is a perspective view showing an intermediate transfer belt in the color image forming apparatus shown in FIG.

The color image forming apparatus shown in FIG. 4 includes image forming units 15, 16 for forming toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. 17, an exposure unit 19 for outputting an image signal to form an electrostatic latent image on photosensitive drums 15a, 16a, 17a, 18a provided in the image forming units 15, 16, 17, 18; The intermediate transfer belt 20 formed on the photosensitive drum 15
a, a primary transfer roller 21 for transferring a toner image formed on 16a, 17a, 18a to the intermediate transfer belt 20;
A fixing device 22 for fixing the toner image transferred to the paper P; transferring the toner image on the intermediate transfer belt 20 to the paper P supplied from the paper cassette 23; It is to fix it.

[0008] Image forming units 15, 16, 17, 18
Inside is, for example, a yellow (Y) image forming unit 1.
Reference numeral 5 denotes a photosensitive drum 15a on which an electrostatic latent image is formed by a laser beam from the exposure device 19, a charger 15b for charging the outer peripheral surface of the photosensitive drum 15a to a predetermined potential, and a photosensitive member 15b. A developing roller 15c for applying toner to the electrostatic latent image formed on the drum 15a and visualizing the toner;
And a cleaner 15 for removing residual toner on the photosensitive drum 15a after transferring the toner image to the intermediate transfer belt 20.
d. The other image forming units 16, 17, and 18 have the same configuration.

Since the intermediate transfer belt 20 is made of a resin material such as polycarbonate and has a thin film-like cylindrical shape, a crack may occur from the end face due to a change with time, and the intermediate transfer belt 20 may be damaged. Therefore, in order to prevent this, as shown in FIGS. 4 and 5, reinforcing members 20a are attached to the inner peripheral portion and the outer peripheral portion of both ends of the intermediate transfer belt 20 along the circumferential direction.

The intermediate transfer belt 20 is stretched around a belt drive roller 24, a belt support roller 25, a tension roller 26, and an idle roller 27.
A primary transfer roller 21 for transferring a toner image from the photosensitive drum 15a to the intermediate transfer belt 20 is disposed inside. Since the belt drive roller 24 needs to run stably without slipping due to contact between the outer peripheral surface and the inner peripheral surface of the intermediate transfer belt 20, a rubber material having a high friction coefficient is formed in a roll shape on the outer peripheral surface. . The belt support roller 25 is provided between the belt drive roller 24 and the intermediate transfer belt 20 to press the photosensitive drum 15a, and the tension roller 26 is provided to apply a predetermined tension to the intermediate transfer belt 20. I have.

In the color image forming apparatus having such a configuration, for example, first, the yellow (Y) photosensitive drum 15
A is uniformly charged by the charger 15b, and a laser beam is radiated based on the image information transmitted from the host computer (not shown) to the exposure device 19, thereby forming a yellow component color latent image. This latent image is visualized as a yellow toner image by the toner thinned on the developing roller 15c. The visualized toner image is transferred to the photosensitive drum 15
When a transfer voltage is applied to the primary transfer roller 21 from the inner surface of the intermediate transfer belt 20 that is traveling in contact with a (circle A in the drawing), the image is transferred onto the intermediate transfer belt 20.

During this time, a magenta (M) component latent image of the next color is formed, and a magenta toner image of magenta toner is visualized by the developing roller 15c. Then, the magenta toner image is transferred to the intermediate transfer belt 20 on which the transfer of the yellow toner image has been completed, and is superimposed on the yellow toner image.

Thereafter, image formation is performed on the cyan toner image and the black toner image in the same manner, and the superposition of the four color toner images on the intermediate transfer belt 20 is completed.

Then, after the toner image on the intermediate transfer belt 20 is transferred to the paper P taken out of the paper cassette 23 and conveyed by the secondary transfer roller 28, the paper P passes through the fixing device 22 and is Is fixed and discharged in the direction of arrow B.

After the toner image is transferred to the paper P,
Residual toner remaining on the intermediate transfer belt 20 without being transferred to the sheet P is removed by the belt cleaner 29.

[0016]

However, in the conventional color image forming apparatus as described above, the thickness of the belt for determining the revolving speed of the intermediate transfer belt is limited to the thickness of the belt provided at both ends where the reinforcing member is provided. Since there is a difference between the central portion and the non-centered portion, there is a difference in the circling speed between the central portion and both ends, resulting in image curvature and color shift (see FIG. 2A).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color image forming apparatus capable of preventing the occurrence of a difference in the rotation speed of the intermediate transfer belt.

[0018]

In order to solve this problem, a color image forming apparatus according to the present invention comprises an electrostatic latent image carrier and charging means for uniformly charging the surface of the electrostatic latent image carrier. Exposure means for irradiating the electrostatic latent image carrier charged by the charging means with laser light corresponding to image data to form an electrostatic latent image; and supplying toner to the electrostatic latent image to form a toner image. A developing member to be formed and a reinforcing member are provided at inner peripheral portions at both ends along the circumferential direction, and an intermediate transfer belt on which a toner image is transferred is wound around the intermediate transfer belt, and the intermediate transfer belt is rotated around the intermediate transfer belt. In addition, a plurality of rollers formed at both ends with a stepped portion which is recessed by the thickness of the reinforcing member and avoids interference with the reinforcing member are provided.

Since the stepped portion is formed at a portion where the roller interferes with the reinforcing member, the running speed of the intermediate transfer belt becomes equal over the entire area, and the occurrence of the difference in the revolving speed of the intermediate transfer belt is prevented. It becomes possible to do.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there is provided an electrostatic latent image carrier, a charging unit for uniformly charging the surface of the electrostatic latent image carrier, and a charging unit for charging the surface of the electrostatic latent image carrier. Exposure means for irradiating the electrostatic latent image carrier with laser light corresponding to image data to form an electrostatic latent image; developing means for supplying toner to the electrostatic latent image to form a toner image; A reinforcing member is provided at the inner peripheral portion at both ends along the direction, an intermediate transfer belt on which the toner image is transferred, and an intermediate transfer belt are wound around the intermediate transfer belt, and the intermediate transfer belt is rotated circumferentially. A color image forming apparatus having a plurality of rollers having a stepped portion that is recessed by a distance and avoids interference with a reinforcing member is formed at both ends, and a stepped portion is formed in a portion of the roller that interferes with the reinforcing member. So that the running speed of the intermediate transfer belt Over and equal, it has the effect that it is possible to prevent the occurrence of the difference between the circumferential speed of the intermediate transfer belt.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is a schematic diagram showing the structure of a color image forming apparatus according to an embodiment of the present invention, and FIG. 2 shows an intermediate transfer belt in the color image forming apparatus of FIG. 1 in comparison with a conventional intermediate transfer belt. 3 is an explanatory diagram for calculating the belt speed of the intermediate transfer belt in FIG.

In FIG. 1, the intermediate transfer belt 3 driven and driven by the belt drive roller 1 is wound around the belt drive roller 1, the belt support roller 2, and a tension roller 14 for applying tension to the intermediate transfer belt 3 in a closed loop. Then, the sheet P from the sheet cassette 10 disposed below the intermediate transfer belt 3 passes through the space between the secondary transfer roller 11 and the intermediate transfer belt 3 and passes through the fixing device 12. .

That is, above the intermediate transfer belt 3, an exposure device (exposure means) that irradiates a laser based on image information.
9 are arranged between the exposing device 9 and the intermediate transfer belt 3, yellow (Y), magenta (M), cyan (C),
Black (K) image forming units 5, 6, 7, 8 are sequentially arranged along the running direction of the intermediate transfer belt 3. The color toner image formed on the intermediate transfer belt 3 is transferred to the sheet P by nipping the sheet P between the secondary transfer roller 11 and the intermediate transfer belt 3, and the transferred toner image Is fixed on the sheet P by the fixing device 12.

A belt cleaning unit 4 for removing the toner image remaining on the intermediate transfer belt 3 without being transferred onto the paper P is provided between the image forming unit 5 and the belt support roller 2. .

The present invention is not limited to the present embodiment as long as it comprises a black or monochrome image forming unit and a color image forming unit for at least two colors, such as yellow.

Each of the image forming units 5, 6, 7, and 8 has the same structure as each other, and the photosensitive drums 5a, 6
a, 7a, 8a, and corona-type chargers (charging means) 5b for uniformly charging the surfaces of the photosensitive drums (electrostatic latent image carriers) 5a, 6a, 7a, 8a to a predetermined potential. 6
b, 7b, 8b and the residual toner are transferred to the photosensitive drums 5a, 6
cleaning blades 5c, 6c, 7c, 8c for removing from the surfaces of a, 7a, 8a and waste toner screws 5d, 6d, 7d for transporting waste toner scraped off by the cleaning blades 5c, 6c, 7c, 8c , 8d
And developing rollers (developing means) 5e, 6e, 7e, 8e for attaching toner to the electrostatic latent images formed on the photosensitive drums 5a, 6a, 7a, 8a and visualizing the electrostatic latent images; Supply rollers 5f, 6f, 7f, 8f for supplying toner from a toner tank (not shown) to the surfaces of the developing rollers 5e, 6e, 7e, 8e, and developing rollers 5e, 6e, 7
e and 8e are provided with thinning blades 5g, 6g, 7g and 8g which are made uniform in thickness and charged to a predetermined potential.

In order to prevent the end of the intermediate transfer belt 3 from being damaged, a reinforcing member 3a (FIG. 2B) is attached to the inner and outer peripheral portions at both ends along the circumferential direction. ing. A belt driving roller 1, a belt supporting roller 2, and a tension roller 14 are disposed on the inner peripheral side of the intermediate transfer belt 3, and the intermediate transfer belt 3 is stretched around the belt. Further, the photosensitive drums 5a, 6a, 7a, 8
The primary transfer rollers 13Y, 13M,
13C and 13B are provided. The reinforcing member 3a
May be provided only on the inner peripheral side, and may not be provided on the outer peripheral side.

Since the belt drive roller 1 needs to run the intermediate transfer belt 3 made of polycarbonate without slipping, a urethane rubber material having a high frictional force is wound in a roll around an aluminum cored bar. . Belt support roller 2, tension roller 14, and primary transfer roller 1
Reference numerals 3Y, 13M, 13C, and 13B denote metal rollers, which are rotated following the movement of the intermediate transfer belt 3. The belt support roller 2 is grounded to regulate the flow of current applied to the secondary transfer roller 11, and the primary transfer rollers 13Y, 13M, 13C, and 13B are connected to the photosensitive drums 5a, 6a, 7a, and 8a. A voltage for transferring a toner image to the intermediate transfer belt 3 is applied.

Here, as shown in FIG. 2B, the belt driving roller 1, the belt supporting roller 2, the tension roller 14, and the primary transfer rollers 13Y, 13M, 13C, 13B are reinforced with the intermediate transfer belt 3 as shown in FIG. In order to avoid interference with the member 3a, step portions D that are recessed by an amount corresponding to the thickness of the reinforcing member 3a are provided at both ends. Note that FIG.
(B) shows the belt drive roller 1, but the other rollers have the same configuration.

Conventionally, as shown in FIG. 2A, at the end where the reinforcing member 20a is provided, the intermediate transfer belt 20 floats by the thickness of the reinforcing member 20a. Since the step portion D is formed as described above, the intermediate transfer belt 3 does not rise at the end.

In the above configuration, first, the surface of the photosensitive drum 5a is uniformly charged by the charger 5b in the image forming unit 5, and an electrostatic latent image is formed in accordance with the yellow component color image information output from the exposure unit 9. Is done. On the developing roller 5e, the yellow toner supplied from the supply roller 5f is triboelectrically charged by the thinning blade 5g and is uniformly formed into a thin layer.
The latent image on the photosensitive drum 5a adheres to the latent image on the photosensitive drum 5a due to the potential difference of the voltage applied between the developing roller 5e and the developing roller 5e, and this is visualized. The visualized yellow toner is transferred as a yellow toner image onto the intermediate transfer belt 3 by applying a high potential voltage to the primary transfer roller 13Y.

On the other hand, while the yellow toner image is being transferred to the intermediate transfer belt 3, the magenta image forming unit 6 also transfers the magenta component electrostatic latent image to the photosensitive drum 6a in the same manner as the yellow image forming unit 5. The magenta toner image is formed on the developing roller 6e, and then the magenta toner image is visualized by the magenta toner uniformly thinned. And
When a high potential voltage is applied to the primary transfer roller 13M,
The magenta toner image is transferred from the photosensitive drum 6a so as to be superimposed on the intermediate transfer belt 3 on which the transfer of the yellow toner image has been completed in the previous image forming unit 5.

Thereafter, image formation is similarly performed on the cyan toner image and the black toner image by the image forming units 7 and 8, and when a high potential voltage is applied to the primary transfer rollers 13C and 13B, the intermediate transfer belt The three color toner images are superimposed on 3.

Thereafter, when the sheet P taken out of the sheet cassette 10 and conveyed passes between the intermediate transfer belt 3 and the secondary transfer roller 11, the sheet P on the intermediate transfer belt 3
The combined toner images of the colors are collectively transferred to the paper P. The transferred toner image is heated and fixed on the sheet P by the fixing device 12, and is discharged out of the machine.

Here, in order to superpose the toner images of a plurality of colors at predetermined positions on the intermediate transfer belt 3 without shifting, the rotation speed of the intermediate transfer belt 3 serving as a base for superposition is adjusted by the rotation speed of the intermediate transfer belt 3. Must be equal throughout.

FIG. 3 shows a model for calculating the belt speed.

For example, when the intermediate transfer belt 3 is traveling around by the belt drive roller 1, the speed V on the surface of the intermediate transfer belt 3 on which the toner image is superimposed is superposed.
Indicates that the radius of the belt driving roller 1 is r,
Assuming that the thickness of the belt drive roller 1 is t and the thickness of the belt drive roller 1 is R, V = 2πR (r + t). However, in the conventional device as shown in FIG.
When the thickness of the reinforcing member 20a is defined as s and the others are defined as described above, the peripheral speed V 'at the portion where a is adhered is V' = 2πR
(R + t + s), which is faster by the thickness of the reinforcing member, and the end portions of the intermediate transfer belt 3 have different surface velocities from the central portion. For this reason, the transfer image is curved, or the speed of the intermediate transfer belt 3 is affected by both ends and becomes higher than the prescribed speed as a whole, resulting in a shift in color superposition.

On the other hand, in the present embodiment, in all the rollers that support the intermediate transfer belt 3 in a stretch band, the stepped portion D is formed in a portion that interferes with the reinforcing member 3a. Becomes equal over the entire area, and it is possible to prevent a difference in the circulating speed in the intermediate transfer belt 3 from occurring. Thereby, an image of good quality without color shift and image curvature can be obtained.

[0040]

As described above, according to the present invention, since the stepped portion is formed at the portion where the roller interferes with the reinforcing member, the running speed of the intermediate transfer belt becomes equal over the entire area, and the intermediate transfer belt is moved. An effective effect that it is possible to prevent the occurrence of the difference in the circling speed in the belt can be obtained.

As a result, there is obtained an effective effect that it is possible to obtain an image of good quality without color shift and image curvature.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view in the width direction showing an intermediate transfer belt in the color image forming apparatus of FIG. 1 in comparison with a conventional intermediate transfer belt.

FIG. 3 is an explanatory diagram for calculating a belt speed of the intermediate transfer belt of FIG. 2;

FIG. 4 is a schematic view showing a color image forming apparatus using a conventional tandem system.

FIG. 5 is a perspective view showing an intermediate transfer belt in the color image forming apparatus of FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Belt drive roller 2 Belt support roller 3 Intermediate transfer belt 3a Reinforcing member 5a, 6a, 7a, 8a Photoconductor drum (electrostatic latent image carrier) 5b, 6b, 7b, 8b Charger (charging means) 5e, 6e, 7e, 8e Developing roller (developing means) 9 Exposure device (exposing means) 11 Secondary transfer roller 13Y, 13M, 13C, 13B Primary transfer roller 14 Tension roller D Step

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Yoshihara 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yuji Nagai 1006 Okadoma Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Kazuhiro Ogata 1006 Kadoma, Kazuma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (72) Inventor Hiroshi Kusuda 1006 Odaka, Kazuma, Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. BB42 BB46 BB53 2H032 AA05 AA15 BA09 BA23

Claims (1)

[Claims] An electrostatic latent image carrier, a charging unit for uniformly charging the surface of the electrostatic latent image carrier, and image data on the electrostatic latent image carrier charged by the charging unit. Exposure means for irradiating a corresponding laser beam to form an electrostatic latent image, developing means for supplying a toner to the electrostatic latent image to form a toner image, and inner peripheral portions at both ends along the circumferential direction And an intermediate transfer belt on which the toner image is transferred. The intermediate transfer belt is wound around the intermediate transfer belt, and the intermediate transfer belt is rotated circumferentially. The reinforcing member is recessed by the thickness of the reinforcing member. A color image forming apparatus comprising: a plurality of rollers each having a step portion for avoiding interference with a member formed at both ends.