JPH11311905A - Transfer belt driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively restrain the meandering of a transfer belt with simple constitution. SOLUTION: This transfer belt driving device is arranged to partially come in contact with a photoreceptor drum 30 and drives the transfer belt 44, on the surface of which a color toner image is formed so as to circulate. The device is equipped with a secondary transfer upper roller 43 arranged inside the circulating belt 44, a motor 53 for driving the roller 43, and plural driven rollers arranged inside the circulating belt 44 and rotated with the circulation of the belt 44. The roller existing at a part where an angle formed by the belt 44 at an incoming side and an outgoing side to the roller is the acutest out of the plural driven rollers is a tension roller 42 freely moving in a direction crossing with the belt 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer belt driving apparatus, and more particularly to a transfer apparatus for an image forming apparatus which circulates and drives a transfer belt on which a toner image is formed. The present invention relates to a belt driving device.

[0002]

2. Description of the Related Art Some image forming apparatuses such as copiers and printers form a color image on paper by superposing a plurality of kinds of color toners. For example, in a full-color copying machine, an image reading unit that reads a document image, an image processing unit that separates the read document image into four color components of cyan, magenta, yellow, and black, and an electrostatic latent image is formed on the peripheral surface Photosensitive drum, an exposure unit for forming an electrostatic latent image for each color component on the peripheral surface of the photosensitive drum, and visualizing the electrostatic latent image formed on the photosensitive drum with a corresponding color toner. Four developing devices, a transfer belt on which toner images formed on the photosensitive drum are sequentially transferred to form a stacked color toner image, and a color toner image transferred on the transfer belt to be transferred onto paper 2 Some include a next transfer roller and a fixing device for heating and fusing and fixing the color toner image on the sheet.

The read original image is cyan, magenta,
First, an electrostatic latent image corresponding to cyan is formed on the peripheral surface of the photosensitive drum. The electrostatic latent image formed on the peripheral surface of the photosensitive drum is visualized by a developing device containing cyan toner, and the cyan toner image is transferred to the surface of the transfer belt. Thereafter, similarly, magenta, yellow, and black toner images are formed on the peripheral surface of the photosensitive drum and transferred to the transfer belt. As a result, toner images of each color are stacked on the surface of the transfer belt to form a color toner image.

Thereafter, the sheet is conveyed between the transfer belt and the secondary transfer roller, and the color toner image on the surface of the transfer belt is transferred onto the sheet by the secondary transfer roller. The sheet on which the color toner image has been transferred is further transported to the fixing device. The fixing device is provided with a heating roller having a built-in heater and a pressure roller that presses against the heating roller. The sheet is sandwiched between the heating roller and the pressure roller to melt and fix the color toner image and to fix the sheet. In the discharge direction.

In the above-described image forming apparatus, the transfer belt is circulated around a driving roller and a plurality of driven rollers. At this time, the plurality of driven rollers include upper and lower primary transfer rollers for causing the transfer belt to face the photosensitive drum, and secondary transfer rollers for transferring a color toner image formed on the transfer belt to a sheet. And

Further, the transfer belt must always be set to an appropriate tension, and if the tension is not appropriate, the image quality deteriorates. Therefore, in the conventional apparatus, a tension setting tension is set between the driven roller and the driven roller on the side where the belt is loosened between the driven roller and the driven roller, that is, on the side fed by the driving roller (downstream from the driving roller in the circulation direction). A roller is provided.

[0007]

Since the transfer belt is circulated around a roller that is long in the axial direction,
It is easy to meander due to the irregular diameter of the roller. Since the transfer belt is made of a resilient fluororesin-based material in which carbon is dispersed to make it semiconductive, when it is moved to one side in a meandering manner, the end in that direction is easily formed. There is a problem that it is bent.

This meandering can be suppressed to some extent by a tension roller, but with a conventional tension roller, the amount of movement has little effect on the extension of the transfer belt, and it is difficult to sufficiently suppress the meandering. An object of the present invention is to effectively suppress meandering of a transfer belt with a simple configuration.

[0009]

According to a first aspect of the present invention, there is provided a transfer belt driving device for circulating and driving a transfer belt having a part arranged so as to face a photosensitive drum and having a surface on which a toner image is formed. A driving roller disposed inside the circulating transfer belt, a driving device for driving the driving roller, and a plurality of driven rollers including a roller for causing a part of the transfer belt to face the photosensitive drum. It has. Then, of the plurality of driven rollers, the roller at the acute angle between the transfer belt on the entrance side and the transfer belt on the exit side with respect to the roller is a tension roller that can move in the direction intersecting the transfer belt.

In this apparatus, the transfer belt is stretched over a driving roller and a plurality of driven rollers. Then, the drive roller is driven by a drive device such as a motor, and the transfer belt circulates. At this time, of the plurality of driven rollers, the roller at the portion where the transfer belt on the entrance side and the exit side with respect to the roller is the sharpest angle acts as a tension roller that is movable in the direction crossing the transfer belt. .

Here, since the angle between the entrance side and the exit side of the transfer belt with respect to the tension roller is an acute angle, the transfer belt moves relatively largely with respect to the amount of movement of the tension roller. The influence of the movement of the transfer belt on the transfer belt is greater than that of the conventional apparatus. The meandering of the transfer belt can be easily and effectively suppressed without using a special component or the like.

According to a second aspect of the present invention, in the transfer belt driving device of the first aspect, the tension roller is disposed so as to face the driving roller. In a conventional transfer belt driving device, a driving roller and a main driven roller are arranged to face each other, and a tension roller is provided between the two rollers. However, in the device according to the second aspect, since the tension roller is provided so as to face the drive roller, the tension roller serves as the main driven roller and the tension roller in the conventional device, and therefore, the configuration is accordingly reduced. It's easy.

According to a third aspect of the present invention, in the apparatus of the second aspect, the driving roller is disposed so as to face a secondary transfer roller for transferring a toner image on the transfer belt to a sheet. The plurality of driven rollers provided between the driving roller and the tension roller include upper and lower primary transfer rollers for causing the transfer belt to face the photosensitive member.

[0014]

FIG. 1 is a cross-sectional view of a full-color copying machine to which an embodiment of the present invention is applied. The copying machine 1 has a main body 10 and a document holder 11 mounted on the upper part of the main body 10 so as to be openable and closable. An original platen 15 on which an original is placed is disposed on the main body 10 at an upper portion thereof. Inside the main body 10, an image forming section 16 is provided substantially at the center of the upper part in the left-right direction. Also,
At a lower portion, a paper feed unit 17 for supplying a document to the image forming unit 16 is provided.

The paper supply section 17 is detachably attached to the main body 10 and is a paper supply cassette 18, 19, 2 for storing paper.
0, 21 and a bypass tray 2 provided on the right side thereof
2 is provided. Below the platen 15, a platen 15
An optical system 23 for reading the image information of the original placed on top is provided. The optical system 23 includes a light source 24 for irradiating light to the surface of the document placed on the document table 15,
A mirror 25 for deflecting light reflected from the original surface,
26, 27, a lens 28 for converging light from the mirror 27, and a CC for receiving the light converged by the lens 28 and generating an image data signal corresponding to the original image.
A color image sensor 29 such as a D sensor.

The image forming section 16 has a photosensitive drum 30 on the surface of which an electrostatic latent image is formed.
0, a main charging device 31, a blank lamp 32, developing devices 33, 34, 35, 36, and a transfer device 37.
And a cleaning device 38. Main charging device 3
Reference numeral 1 denotes a device for charging the surface of the photoconductor drum 30, which is disposed above the photoconductor drum 30. The blank lamp 32 is a lamp for removing electricity from a desired area on the surface of the photoconductor drum 30.
1 is disposed adjacent to the right side. Developing devices 33, 34, 35, and 36 for forming toner images on the photoconductor drum 30 are arranged from the left side of the photoconductor drum 30 downward from the main charging device 31 with a predetermined gap. Each of the developing devices 33, 34, 35, and 36 stores cyan, magenta, yellow, and black toners, respectively, and visualizes the electrostatic latent image formed on the photosensitive drum 30 by the respective color toners. . Also, the transfer device 3
Reference numeral 7 denotes a device for transferring the toner image on the photosensitive drum 30 to a sheet, and is disposed diagonally below and to the right of the photosensitive drum 30. The cleaning device 38 is a device for removing residual toner and the like on the surface of the photoconductor drum 30, and is disposed diagonally above and to the right of the photoconductor drum 30.

An exposure device 39 for forming an electrostatic latent image on the peripheral surface of the photosensitive drum 30 is provided diagonally above and to the left of the photosensitive drum 30. The exposure device 39 includes a laser unit 40 and a mirror 41 that deflects the laser light from the laser unit 40 to the peripheral surface of the photosensitive drum 30. The exposure device 39 rotates the photosensitive drum 30 based on an image data signal obtained from the color image sensor 29. An electrostatic latent image is formed on the surface. The laser light emitted from the exposure device 39 is configured to pass between the main charging device 31 and the developing device 33 and to irradiate the peripheral surface of the photosensitive drum 30.

As shown in FIG. 2, the transfer device 37 includes a circulating transfer belt 44, a secondary transfer upper roller (drive roller) 43 disposed inside the circulating transfer belt 44, and driven to rotate by a motor 53. A tension roller 42 disposed at a position facing the upper secondary transfer roller 43.
And The tension roller 42 has a roller shaft 42a supported by a bearing 55, as shown in detail in FIG. The bearing 55 is movable with respect to an elongated hole 10b formed in the frame 10a of the main body 10. Therefore, the tension roller 42 is movably supported in a direction crossing the transfer belt 44. The bearing 55 is constantly urged outward by a spring 56, and the transfer belt 44 is given an appropriate tension by the urging force of the spring 56.

Between the secondary transfer roller 43 and the tension roller 42, an upper primary transfer roller 45 and a lower primary transfer roller 46 are provided on the inner peripheral portion of the transfer belt 44. These rollers 45 and 46 are arranged at a predetermined interval, and press a part of the transfer belt 44 circulated between the rollers 45 and 46 against the peripheral surface of the photosensitive drum 30.

The upper primary transfer roller 45 is a pressing position where the transfer belt 44 is pressed against the peripheral surface of the photosensitive drum 30 together with the lower primary transfer roller 46, and a separation position where the transfer belt 44 is separated from the peripheral surface of the photosensitive drum 30. , And is configured to be moved by a cam mechanism (not shown) or the like. Further, the transfer device 37 is provided with a cleaning device 48 for cleaning the surface of the transfer belt 44. This cleaning device 48
A transfer cleaning roller 49 facing a cleaning blade 51 disposed between the lower primary transfer roller 46 and the upper secondary transfer roller 43;
And a toner collection unit 52.

The transfer device 37 includes a lower secondary transfer roller 54 that is in pressure contact with the upper secondary transfer roller 43 via a transfer belt 44. In such a transfer device 37,
Of the rollers disposed inside the transfer belt 44, all rollers except the secondary upper transfer roller 43
4 is a driven roller that rotates with the circulation. And
Of these driven rollers, the angle θ (see FIG. 2) between the entrance side and the exit side of the transfer belt 44 with respect to the tension roller 42 is the sharpest angle as compared with the corresponding angles of the other driven rollers.

Each of the paper feed cassettes 18, 1
A vertical transport path 61 for transporting paper from 9, 20, 21 toward the image forming unit 16 and a bypass transport path 62 for transporting paper from the bypass tray 22 toward the image forming unit 16 are provided. Each paper cassette 18, 19, 20,
Pickup rollers 63, 64, 6 for taking out the sheets stored therein are provided in the bypass tray 21 and the bypass tray 22.
5, 66, 67, and a pair of paper feed rollers 68, 69, 70, 71, 72 for feeding the sheets one by one to the transport path. In the vertical transport path 61, a pair of transport rollers 73, 7
4, 75, 76 are provided. The vertical transport path 61 and the bypass transport path 62 are connected to the upper secondary transfer roller 4 of the transfer device 37.
The third and second transfer rollers converge on the right side of the lower transfer roller 54, and are continuous with a paper feed path 77 that supplies a sheet to the transfer device 37. The paper feed path 77 is provided with a registration roller 84 for holding the paper conveyed from the paper feed unit 17 at a predetermined position.

On the left side of the secondary transfer upper roller 43 and the secondary transfer lower roller 54 of the transfer device 37, there is formed a paper discharge conveyance path 78 through which the paper on which the toner image has been transferred is conveyed. A fixing device 79 is disposed on the left side. The fixing device 79 includes a heating roller 8 having a built-in heater.
0 and a pressure roller 81 that is in pressure contact with the heating roller 80 are provided for nipping and transporting the sheet between the two rollers and for heating and fixing the toner image formed on the surface of the sheet.

A sheet discharge roller pair 82 is provided on the left side of the fixing device 79, and is configured to discharge sheets to a sheet discharge tray 83. Next, the operation will be described. When a document is placed on the document table 15 and a key for starting copying is pressed, the document placed on the document table 15 is irradiated with light by the optical system 23. Then, the reflected light is converted into an image data signal by the color image sensor 29. The image data signal is decomposed into an image of each color component by an image processing unit (not shown). First, an electrostatic latent image based on the cyan color component is formed on the photosensitive drum 30.
This electrostatic latent image is visualized by the developing device 33 containing the cyan toner.

The upper primary transfer roller 45 is a photosensitive drum 3
The transfer belt 44 is located at a pressure contact position close to the zero side, and the transfer belt 44 is pressed against the peripheral surface of the photosensitive drum 30 together with the primary transfer lower roller 46. As a result, the toner image formed of the cyan toner formed on the photosensitive drum 30 is transferred to the surface of the transfer belt 44 by the upper primary transfer roller 45 and the lower primary transfer roller 46.

When the toner image of the cyan toner is transferred to the transfer belt 44, an electrostatic latent image corresponding to magenta is formed on the photosensitive drum 30. The image is visualized. This toner image is similarly transferred onto the transfer belt 44. Hereinafter, similarly, the toner images of the respective color components of yellow and black are transferred onto the transfer belt 44 in a stacked state. When transferring toner images of each color component,
Synchronization is performed so that there is no image shift.

At the same time as these operations, the paper is conveyed from one of the paper feed cassettes 18, 19, 20, and 21 and the bypass tray 22, and is made to stand by the registration rollers 84 in the paper feed path 77. When the transfer of the color toner image onto the transfer belt 44 is completed, the secondary transfer upper roller 43 and the secondary transfer lower roller 54 are transferred from the registration roller 84.
And the color toner image formed in a stacked state on the surface of the transfer belt 44 is transferred onto the sheet by the secondary transfer lower roller 54. Thereafter, the sheet having the color toner image transferred to the surface thereof is conveyed to a fixing device 79 by a sheet discharge conveyance path 78, where the color toner image transferred to the sheet surface is heated and melt-fixed. Is discharged.

During this time, the upper primary transfer roller 45 is located at the pressing position, and the surface of the transfer belt 44 is pressed against the peripheral surface of the photosensitive drum 30 by the upper primary transfer roller 45 and the lower primary transfer roller 46. doing. In the above operation, the transfer belt 44 is circulated by being wrapped around each roller. However, the transfer belt 44 is always tensioned outward by the tension roller 42, whereby an appropriate tension is maintained. In particular, since the angle θ between the entrance side and the exit side of the transfer belt 44 with respect to the tension roller 42 is an acute angle, the tension roller 4
2 greatly affects the amount of belt tension. Therefore, the transfer belt 44 can be strongly set for a small amount of movement of the tension roller 42, and the meandering of the transfer belt 44 can be effectively suppressed.

[0029]

According to the present invention, since the tension roller for adjusting the tension of the transfer belt is provided at an acute angle portion on the belt path, it is possible to effectively apply tension to the transfer belt by moving the tension roller. As a result, meandering of the transfer belt can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a copier employing an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part thereof.

FIG. 3 is a diagram showing a configuration of a support portion of a tension roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier 10 Main body 15 Document table 16 Image forming part 17 Paper supply part 22 Bypass tray 23 Optical system 30 Photoconductor drum 33 Developing device 34 Developing device 35 Developing device 36 Developing device 37 Transfer device 39 Exposure device 43 Secondary transfer upper roller 44 Transfer Belt 45 Primary Transfer Upper Roller 46 Primary Transfer Lower Roller 54 Secondary Transfer Lower Roller 77 Paper Feeding Conveying Path 78 Paper Discharging Conveying Path 79 Fixing Device 80 Heating Roller 81 Pressure Roller 91 Control Unit 92 Operation Panel 93 Image Reading Unit 94 Image Processing Unit 95 Exposure Unit 96 Photoconductor Drive Unit 97 Feeding and Conveying System 98 Primary Transfer Roller Control Unit 99 Discharge Conveying Path

Claims (3)

[Claims] 1. A transfer belt driving device of an image forming apparatus for circulating and driving a transfer belt on a surface of which a toner image is formed, a part of which is arranged so as to face a photoreceptor drum, wherein: A drive roller disposed inside; a drive device for driving the drive roller; and a plurality of driven rollers including a roller for causing a part of the transfer belt to face the photosensitive drum. Among the driven rollers, the roller at the portion where the angle between the transfer belt on the entrance side and the transfer side on the roller is the sharpest is a tension roller movable in a direction intersecting with the transfer belt. Transfer belt drive. 2. The transfer belt driving device for an image forming apparatus according to claim 1, wherein said tension roller is disposed so as to face said driving roller. 3. The drive roller is arranged to face a secondary transfer roller for transferring a toner image on the transfer belt to a sheet, and is provided between the drive roller and a tension roller. The transfer belt driving device for an image forming apparatus according to claim 2, wherein the plurality of driven rollers include upper and lower primary transfer rollers for causing the transfer belt to face the photoconductor.