JPH08305184A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device in which the size of the device and the number of parts are reduced and the time required for image formation is shortened. CONSTITUTION: The image forming device comprises photoreceptor drums (image carriers) 1a-1d, a transfer-material carrying belt 8 for carrying a transfer material by being driven by a driving roller 15 and driven roller 14, and a fixing device which is arranged on the downstream side of the transfer-material carrying belt 8 in the direction of the movement. In the device, the driven roller 14 and driving roller 15 are also used as transfer charge rollers. This reduces the length of the transfer-material carrying belt 8 by an amt. from L1 to L2, reducing a transfer-material carrying path, and therefore, shortens the time required for the image formation. Also, because the need for a transfer charge, for which the driven roller and driving roller serve, is eliminated, the number of parts is reduced and the size of the device is also reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally forms a visible image (toner image) on an image carrier by an electrophotographic recording system or an electrostatic recording system and transfers the toner image onto a transfer material to form an image. And an image forming apparatus that conveys a transfer material by a conveying belt, and includes a full-color or mono-color electrophotographic recording type copying machine or printer.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus adopting an electrophotographic recording system forms a latent image on a photosensitive drum, which is an image carrier, by utilizing light, magnetism, electric charge, etc., and visualizes this latent image. And an image forming portion for obtaining a visible image, a transfer material conveying means for conveying the transfer material to a transfer position of the image forming portion, and a fixing means for fixing the image transferred on the transfer material onto the transfer material. And have.

The transfer material transfer means is a transfer material transfer belt (hereinafter referred to as a belt-shaped transfer member) from the viewpoint of transferability.
A transport belt is simply used, and the transport belt transports a transfer material (hereinafter, referred to as recording paper) to a transfer position and further to a fixing device. At this time, the recording sheet is held and conveyed on the conveyor belt by electrostatic attraction. The conveyor belt has at least one drive roller and at least one conveyor belt.
It moves by being stretched between two driven rollers.

When a plurality of image forming units are provided, the driving roller is further downstream of the most downstream image forming unit and upstream of the fixing means, and at least one driven roller. Are arranged on the upstream side of the most upstream image forming unit. The conveyor belt is stretched with a constant force between the driving roller and the driven roller, and the conveyor belt is kept at a constant speed without slack between the rollers, and is located at the most downstream side from the most upstream side image forming unit. To the image forming unit.

Further, the recording paper is electrostatically adsorbed to the conveyor belt as described above, and is conveyed to each image forming portion while being securely held on the conveyor belt, and the toner images of the respective colors are transferred to the recording paper, A full-color image is formed by fixing the toner image by the fixing unit.

A schematic structure of a conventional full-color image forming apparatus will be described with reference to FIG.

FIG. 3 is a schematic view of a conventional full-color image forming apparatus. In a main body 18 of the image forming apparatus, four image forming sections Pa, Pb, P of a first, a second, a third and a fourth are formed.
c and Pd are arranged in parallel. In addition, the image forming apparatus main body 18
Below the first to fourth image forming portions Pa to Pd from the cassette 3 containing the transfer material (recording paper) inside to the fixing device 7, recording is performed through these image forming portions Pa to Pd. An endless belt-shaped transport belt 8 that moves in a circulating manner to transport the paper is provided. The conveyor belt 8 is a thin belt made of a dielectric material, and is stretched by a driven roller 9 arranged on the upstream side of the recording sheet conveying path and a driving roller 10 arranged on the downstream side of the recording sheet conveying path.

Thus, the conveyor belt 8 is driven by the drive roller 1.
3 is driven endlessly in the direction of arrow A in FIG. 3, the conveyor belt 8 carries the recording paper fed from the cassette 3 and synchronized by the registration roller pair 11, and carries it. The image forming units Pa, Pb, Pc, and Pd are sequentially conveyed.

In each of the image forming portions Pa to Pd, a toner image of each color is formed, and each toner image is transferred to the transfer charger 5a.
.About.5d, the full-color image is formed by being transferred and superposed on the recording paper. The recording sheet carrying the unfixed full-color image is sent to the fixing device 7, where the full-color image is fixed by heat and pressure, and then discharged to the outside of the apparatus main body 18 and stacked on the discharge tray 13. .

[0010]

However, in the conventional full-color image forming apparatus shown in FIG. 3, the conveying path of the recording paper is very long, which leads to an increase in size of the apparatus, an increase in image forming time, and an increase in the number of parts. There's a problem.

When forming a black-and-white image, the purpose can be achieved if substantially only the fourth image forming portion Pd is operated. However, in terms of the apparatus configuration, the other first to third image forming portions Pa to P
Since c is also driven or driven, life of the first to third image forming units Pa to Pc other than the fourth image forming unit Pd is shortened.

Further, the images of the first to third image forming portions Pa to Pc other than the fourth image forming portion Pd may be erroneously formed and the image quality may be deteriorated.

Further, it is difficult to shorten the image forming time only when forming a black and white image or reduce the black and white image forming cost.

The present invention has been made in view of the above problems, and its object is to reduce the size of the apparatus, reduce the number of parts and the image forming time, prolong the life of the apparatus, and improve the image quality. An object of the present invention is to provide an image forming apparatus capable of improving the productivity of black-and-white image formation.

[0015]

To achieve the above object, the invention according to claim 1 conveys a transfer material by being driven by at least one image carrier, one driving roller and at least one driven roller. In the image forming apparatus having a transfer material conveying belt for rotating and a fixing device arranged on the downstream side in the moving direction of the transfer material conveying belt, at least the driving roller or the driven roller located near the outermost image carrier. One of them is a transfer charging roller.

According to a second aspect of the present invention, in the first aspect of the invention, a transfer unit is configured to include the transfer / conveying belt, the driving roller, the driven roller and a charger, and the transfer charging roller and It is characterized in that the transfer unit can be selectively rotated about an axis center of the driving roller or the driven roller.

Further, the invention according to claim 3 is characterized in that, in the invention according to claim 2, at least the driving roller is a transfer charging roller.

[0018]

According to the first aspect of the present invention, the length of the conveying belt can be shortened by shortening the conveying path by using the drive roller or the driven roller for driving the transfer conveying belt also as the transfer charging roller. The image forming time can be shortened, and the transfer charger for the dual purpose is not required, so that the number of parts can be reduced and the apparatus can be downsized.

According to the invention of claim 2 or 3,
The following effects can be obtained.

1) When the image forming portion located above the driving roller is a black image forming portion, switching between the monochrome image forming mode and the full color image forming mode can be easily and easily performed without using a complicated mechanism. Can be done cheaply.

2) Even when a paper jam (jam) occurs when the transfer material is conveyed by the transfer material conveying belt during the formation of a full-color image, the jam treatment can be easily performed.

3) When the formation of an image other than the black image is completed during the formation of the full-color image, the full-color image forming mode can be switched to the monochrome image forming mode during the formation of the black image, so that the time required for the switching can be shortened. can do.

4) In the black-and-white image forming mode, since the image forming portions of colors other than black do not come into contact with the transfer material conveying belt, it is possible to extend the life of the image forming portions of other colors. Further, since it is possible to suppress the consumption of the image forming portions of other colors, it is possible to reduce the image forming cost in the monochrome image forming mode.

5) In the black-and-white image forming mode, an image of a color other than black is not erroneously formed, so that deterioration of image quality can be prevented.

6) By increasing the process speed in the black and white image forming mode, the image forming time can be further shortened as compared with the full color image forming mode, so that the productivity of the black and white image forming can be improved. it can.

[0026]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> The basic structure of the image forming apparatus according to this embodiment is the same as that of the full-color image forming apparatus shown in FIG. 3, and here, the first, second, third and fourth embodiments are used. The image forming units Pa, Pb, Pc and Pd will be described.

First, the image forming section P of the conventional image forming apparatus.
The configurations of a to Pd will be described with reference to FIG.

The image forming sections Pa, Pb, Pc, and Pd have substantially the same structure, and the image forming sections Pa to Pd are photosensitive drums that are image carriers that are rotationally driven in the direction of arrow B in the figure. 1a, 1b, 1c and 1d are provided, and the photosensitive drums 1a to 1d are provided around the photosensitive drums 1a to 1d.
Primary chargers 2a, 2b, 2c, 2d for uniformly charging
Developing devices 4a, 4b, 4c, 4d for developing the electrostatic latent images formed on the respective photosensitive drums 1a-1d, and transfer chargers 5a, 5 for transferring the developed toner images of respective colors onto the recording paper.
b, 5c, 5d and cleaning devices 6a, 6b, 6c for removing the toner remaining on the photosensitive drums 1a-1d,
6d are sequentially arranged in the drum rotation direction (arrow B direction). An exposure lens system 12 including an imaging lens and a laser beam scanner is provided above each of the photosensitive drums 1a to 1d.

Incidentally, the developing devices 4a, 4b, 4c, 4d
Contains yellow, magenta, cyan, and black toners, respectively.

When the recording sheet is placed on the conveyor belt 8, the image forming process for the photosensitive drums 1a, 1b, 1c, 1d is sequentially performed as the conveyor belt 8 moves in the direction of arrow A. Be started. That is, the first image forming unit P
The photosensitive drum 1a of a has a yellow image, the photosensitive drum 1b of the second image forming portion Pb has a magenta image, the photosensitive drum 1c of the third image forming portion Pc has a cyan image, and a fourth image. A black image is shared and formed on the photosensitive drum 1d of the forming portion Pd.

By the movement of the conveyor belt 8, the recording paper sequentially passes under the photosensitive drums 1a to 1d of the first to fourth image forming portions Pa to Pd, and the fixing device 7 shown in FIG.
The toner images of the respective colors formed in the image forming portions Pa to Pd are sequentially transferred onto the recording paper by the transfer chargers 5a, 5b, 5c and 5d of the image forming portions Pa to Pd. Then, a full-color image is formed.

After passing through the final fourth image forming portion Pd, the recording paper is separated from the conveyor belt 8 and sent to the fixing device 7, where the fixing device 7 fixes the full-color image, and then the outside of the device. The sheet is discharged to the sheet discharge tray 13.

Next, details of the image forming portions Pa to Pd of the image forming apparatus of the first embodiment of the present invention will be described with reference to FIG. In FIG. 1, the same elements as those shown in FIG. 4 are designated by the same reference numerals, and description thereof will be omitted below.

In this embodiment, the driving roller and the driven roller of the conveyor belt 8 are connected to the first and fourth image forming portions Pa and P.
The transfer charging rollers 14 and 15 of d are used instead.

Thus, in the prior art, the distance between the center axes of the drive roller 10 and the driven roller 9 of the conveyor belt 8 was L1 as shown in FIG. 4, but in this embodiment, the same distance is L2.
It can be shortened to (= L1-L3-L4). Therefore, the length of the conveyor belt 8 is 2 × (L3 + L4) as compared with the conventional one.
Therefore, the device can be downsized as a whole.

Further, since the transport distance of the recording paper by the transport belt 8 is shorter than the conventional transport distance by (L3 + L4), the image forming time is also shortened.

Further, the image forming portion Pa, which has been conventionally required,
Since the transfer chargers 5a and 5d for Pd (see FIG. 4) are not necessary, the number of parts can be reduced.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. 2 is a detailed view of the image forming unit of the image forming apparatus according to the second embodiment of the present invention.

In this embodiment, the transfer belt 8 disposed below the photosensitive drums 1a to 1d, the transfer charging roller 14, the driving roller 15, and the transfer chargers 5b and 5c are connected to a transfer unit (indicated by a broken line in FIG. 2). (Shown) 16 as a unit, and when forming a black and white image, the driving roller 15 of the conveyor belt 8 also serves as a transfer charging roller, and the transfer unit 16 is rotated in the direction of the arrow E in the figure with its shaft center 17 as the rotation center. .

With the above configuration, the switching between the black and white image forming mode and the full color image forming mode can be performed easily and inexpensively without using a complicated mechanism.

Further, when the transfer unit 16 is rotated about the shaft center 17 of the transfer charging roller / driving roller 15, the transfer belt 8 and the black photosensitive drum 1d are not phase-shifted, and the transfer is not performed. Since the positional relationship between the conveyor belt 8 and each of the image forming portions Pa to Pd is not disturbed by the rotation operation of the unit 16, it is possible to switch the monochrome image forming mode and the full color image forming mode with high accuracy.

Further, even when a paper jam (jam) is caused when the recording paper is conveyed by the conveyor belt 8 at the time of forming a full-color image, the jam treatment can be easily performed.

Further, in the configuration according to this embodiment, if the formation of an image other than the black image is completed during the formation of the full color image, the full color image formation mode can be switched to the monochrome image formation mode during the formation of the black image. Therefore, the time required for switching can be shortened.

In the black-and-white image forming mode, since the image forming portions Pa to Pc for the other three colors do not come into contact with the conveyor belt 8, the life of the image forming portions Pa to Pc for the other three colors is extended. Is possible. Further, in the black-and-white image forming mode, the cost can be reduced as compared with the full-color image forming mode because the image forming units Pa to Pc for the other three colors are not consumed.

Furthermore, image forming portions Pa other than black
The image of Pc is not erroneously formed, and the image quality is not deteriorated.

In addition, by increasing the process speed in the black and white image forming mode, the image forming time can be further shortened as compared with the full color image forming mode, and the productivity of the black and white image forming can be improved. .

[0048]

As is apparent from the above description, according to the present invention, the transfer material transporting means is driven by at least one image carrier, one driving roller and at least one driven roller to transport the transfer material. In an image forming apparatus having a belt and a fixing device arranged on the downstream side in the moving direction of the transfer material conveying belt, at least one of the driving roller and the driven roller, which is adjacent to the outermost image carrier, is transferred. A charging roller is used, and a transfer unit is configured by including the transfer / conveying belt, the driving roller, the driven roller, and a charging device, and the axis of the driving roller or the driven roller serving as the transfer charging roller is a rotation center. Since the transfer unit is selectively rotatable, the size of the device is reduced, the number of parts is reduced, the image formation time is shortened, the life of the device is extended, and the image quality is improved. There is an advantage that it is possible to improve the productivity of the upper and black-and-white image formation.

[Brief description of drawings]

FIG. 1 is a detailed cross-sectional view of an image forming unit of a full-color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a detailed sectional view of an image forming portion of a full-color image forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a conventional full-color image forming apparatus.

FIG. 4 is a detailed cross-sectional view of an image forming unit of a conventional full-color image forming apparatus.

[Explanation of symbols]

 1a to 1d Photosensitive drum (image bearing member) 5a to 5d Transfer charger 7 Fixing device 8 Transfer material conveying belt 9 Driven roller 10 Drive roller 14 Transfer charge roller / driven roller 15 Transfer charge roller / drive roller 16 Transfer unit 17 Transfer unit Center of rotation 18 Image forming apparatus main body

Claims (3)

[Claims] 1. A transfer material conveying belt which conveys a transfer material driven by at least one image carrier, one driving roller and at least one driven roller, and arranged on the downstream side in the moving direction of the transfer material conveying belt. In the image forming apparatus having the above-mentioned fixing device, at least one of the driving roller and the driven roller which is adjacent to the outermost image carrier is a transfer charging roller. 2. The transfer conveyance belt, the drive roller,
A transfer unit is configured to include the driven roller and a charger, and the transfer unit is selectively rotatable about an axis center of a drive roller or a driven roller that is the transfer charging roller. The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 2, wherein at least the driving roller is a transfer charging roller.