JP4239345B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color image forming apparatus, and more particularly to an image forming apparatus configured to perform writing on a plurality of image forming units using a light emitting element head array (hereinafter referred to as LED) as one writing device.
[0002]
[Prior art]
Conventionally, in a color image forming apparatus, an image forming unit is provided for each color of magenta, cyan, yellow, and black. Each of the image forming units includes a photosensitive drum, a charger for charging the photosensitive drum, a developing unit for storing each color toner, and an LED as an exposure unit for writing image information. ing. Then, a path of a recording medium such as a sheet is arranged so as to connect the transfer sections of the plurality of image forming sections, and the toner image is transferred from each image forming section to the recording medium so as to carry the color image. A recording medium to be printed is fixed through a fixing device to create a color copy.
[0003]
[Problems to be solved by the invention]
In the color image forming apparatus, it is necessary to dispose LEDs in order to write image information on the photosensitive drum of the image forming unit corresponding to each color. However, the LED is a very expensive component, and when four color image forming units are provided in one image forming apparatus, incorporating four LEDs reduces more than half of the manufacturing cost of the image forming apparatus. Will occupy. Therefore, in order to reduce the manufacturing cost of the color image forming apparatus, it is required to reduce the LED price ratio.
[0004]
The present invention is intended to solve the problems of the conventional color image forming apparatus as described above, and enables writing on a plurality of photosensitive drums using one LED (light emitting element head array). The object is to provide a device.
[0005]
[Means for Solving the Problems]
According to the present invention, four image forming units each including a charger, a photosensitive drum, a developing device, and a transfer roller are arranged in an annular shape to form a color toner image of four colors and transfer it to a sheet. An exposure unit that exposes the photosensitive drum of each image forming unit with a light emitting element head array is provided inside the ring so as to be rotatable about a support shaft, and the exposure unit is provided in the image forming unit. A series of image forming operations by forming an electrostatic latent image on each photosensitive drum by sequentially moving the photosensitive drum to correspond to the photosensitive drum, and transferring the color toner image formed on each photosensitive drum sequentially on the paper. It is characterized by performing . Furthermore, a distance corresponding to at least the entire length of the sheet is provided between the transfer position of the image forming unit and the transfer position of the next image forming unit.
[0006]
With the configuration as described above, in the color image forming apparatus of the present invention, by using one LED in common for a plurality of image forming means, the cost of the LED can be reduced, and the cost can be reduced. The image forming apparatus can be configured. In addition, by configuring the interval between the image transfer portions of each image forming unit to correspond to at least the length of the paper, it is possible to perform the LED image writing operation on the photosensitive drum in a stable state. Become.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The configuration of the image forming apparatus of the present invention will be described with reference to the illustrated example. The example shown in FIG. 1 shows the configuration of the color image forming apparatus 1, and the image forming unit 2 corresponds to the formation of yellow, magenta, cyan and black images as four color toner images. Two photosensitive drums 3Y, 3M, 3C and 3B are arranged, and the transfer roller 4 is arranged so as to sandwich the paper conveyed along the paper conveyance path 9 with respect to each photosensitive drum. The distance L between the image transfer portions of the respective colors is set to be slightly larger than the length as a recording medium, for example, when using the A4 horizontal feed method, the horizontal width of the A4 size. For each of the photosensitive drums 3Y, 3M,..., An exposure device 5 is provided at the central portion of the apparatus so as to be able to move in a swinging manner via a support shaft 6. On the other hand, images are sequentially written. When the yellow writing transfer is completed on the photosensitive drum 3Y, the trailing edge of the sheet is out of the nip position between the photosensitive drum 3Y and the transfer roller 4, so that the exposure device 5 is turned to the photosensitive drum 3M and the photosensitive drum Magenta writing transfer is performed on the drum 3M. Subsequently, when writing on the photosensitive drum 3M is completed, the exposure unit 5 is turned to the photosensitive drum 3C to perform cyan writing transfer, and after that, the exposure unit 5 is turned to the photosensitive drum 3B and finally is transferred. Black writing is performed.
[0008]
In the image forming apparatus 1, as in a general image forming apparatus or printer, a plurality of photosensitive drums 3 Y, 3 M,. The color toner images formed in the above are transferred in an overlapping manner. Then, after the three types of images are transferred to the paper, the paper on which the black image is transferred from the photosensitive drum 3B in the final stage is fixed through the fixing device 19, and the color copy is discharged. As the sheet conveying device in the image forming unit 2, any conventionally known conveying mechanism can be used. In addition, as will be described later, the sheet is held on the sheet carrying belt by electrostatic means. It can be conveyed while Further, it is also possible to use a method in which the color toner images are transferred in an overlapping manner at each image forming unit using the intermediate transfer belt, and the toner image is transferred from the intermediate transfer belt to the paper in the final stage and then fixed through the fixing device 19. Is possible.
[0009]
As an image forming member (image forming unit) used in the image forming unit 2, for example, a device having a mechanism as shown in FIG. 2 can be configured. The image forming member 10 shown in FIG. 2 can be used as an image forming member for each color, and the developing device 12, the cleaning device 14, and the charger 11 are combined with the photosensitive drum indicated by reference numeral 3. Constitute. An exposure device 5 provided for writing an image on the photosensitive drum 3 is provided so as to be rotatable around a support shaft 6. The exposure device 5 supported by the support shaft 6 is provided for each photoconductor. An image corresponding to each color is written by moving in correspondence with the drum. In addition, as the exposure device 5, as in the apparatus generally used conventionally, LED light emitting elements are arranged in a line in the length direction of the photosensitive drum, and the LED elements are arranged according to image writing information. And the light is transmitted to the photosensitive drum to form an electrostatic latent image.
[0010]
The photosensitive drum 3 disposed in the image forming unit is uniformly charged by a charger 11 and irradiated with light of image information by an exposure device 5 to form an electrostatic latent image. Toner is supplied from the developing device 12 to the latent image to form a toner image. The toner image formed on the photosensitive drum 3 is transferred to a sheet by applying a predetermined potential from a transfer roller 4 that sandwiches the sheet, and the sheet is conveyed toward a transfer unit for the next color toner image. After transferring the color toner image from the photosensitive drum 3, the toner remaining on the surface of the drum 3 is removed by the blade 15 of the cleaning device 14 so as to cope with the next charging / exposure / development operations. To do. The mechanism combining the toner image creation and the developing device having the configuration shown in FIG. 2 can be configured according to the position where the image forming member 10 is arranged. The mechanism shown in FIG. 2 can be manufactured and applied as a mechanism that does not interfere with the paper conveyed along the paper conveyance path.
[0011]
In the cleaning device 14 disposed on the image forming member 10, for example, a mechanism can be provided in which the toner scraped off by the blade 15 is transported out of the apparatus by a conveying means 15 a such as a screw. In the developing device 12, toner is fed from the toner hopper to the developing roller 13 via the supply roller 13 a, and the toner formed as a thin layer on the developing roller is electrostatically charged at a position where it contacts the photosensitive drum 3. The latent image is attached to the latent image so as to be visualized as a single color toner image, and the color toner image is transferred to a sheet by applying a predetermined voltage to the transfer roller 4.
[0012]
Further, in the above-described embodiment and another embodiment to be described later, the positions of the four photosensitive drums 3Y, 3M,... Arranged in the image forming unit 2 are centered on the support shaft 6 that supports the exposure device 5, etc. As shown in FIG. 1, the photosensitive drums 3Y, 3M,... Are sent out from the paper feed tray 16 by the paper feed roller 17 and are fed by the transport roller device 18 to form an image forming unit. The image is written on the basis of the movement information of the paper supplied toward the image 2. For this purpose, the exposure device 5 is provided with means for swinging around the support shaft 6 at an equal angle, and each time an image is written on each photosensitive drum, a predetermined angle is provided. By moving the exposure unit 5, the photosensitive drum is positioned relative to the image writing unit. Then, after sequentially writing images from the photosensitive drum 3Y, black image writing is finally performed, and a series of image forming operations is completed. When starting the next image forming operation, the exposure device 5 is started from positioning with respect to the image forming member 10Y.
[0013]
In the example shown in FIG. 1, it is described that a sheet as a recording medium on which a color toner image is transferred from each image forming member 10 can be conveyed using an arbitrary conveying unit. On the other hand, for carrying the paper, for example, a paper carrying belt 20 as shown in FIG. 3 can be used. As the paper carrying belt 20, a belt that can electrostatically hold paper on the surface of the belt can be used as in the paper conveying belt device conventionally used in the image forming apparatus. It is also possible to use a means in which the electrodes are arranged in close contact with each other at right angles to the transport direction, a high voltage is applied to the electrodes, and the paper is carried on the belt surface by static electricity.
[0014]
The paper carrying belt 20 is disposed along each of the photosensitive drums 3Y, 3M,..., A roller corresponding to the lower roller of the transport roller device 26, a driving pulley 21, a guide pulley 22, Guide to the belt 20 in the return direction is performed via 22a. A sheet taken out from the sheet feeding tray 16 by the sheet feeding roller 17 is supplied to the sheet bearing belt 20 toward the sheet bearing belt 20 at the conveyance roller device 26, and an electrode of the intermediate transfer belt is supplied from the charger 28. The sheet is pressed and held on the belt surface by the pressing roller 27 while supplying power to the sheet.
[0015]
Then, the color toner images are transferred from the respective image transfer units to the paper held on the paper carrying belt 20 in an overlapping manner, and after the image transfer from the last photosensitive drum 3B is completed, the turning rollers 23, The paper that peels between the guide pulleys 22 and carries the color toner images in an overlapping manner is fixed through the fixing device 19. The action of peeling the paper from the paper carrying belt 20 can be performed by the peeling claw 25, but any other peeling means can be used.
[0016]
The example shown in FIG. 4 uses the intermediate transfer belt 30 to transfer the color toner images formed on the respective photoconductive drums on the intermediate transfer belt 30 that circulates and moves in an endless manner. What is held by the belt 30 is configured as an apparatus of a system for transferring to a sheet. As the intermediate transfer belt 30, for example, a belt made of a polyimide resin can be used in the same way as an intermediate transfer belt conventionally used in a color image forming apparatus. As shown in the figure, the intermediate transfer belt 30 is guided along the four photoconductor drums 3Y, 3M,..., And on the return side of the belt, a plurality of guide pulleys 32, 32a,. Will be guided. Then, the intermediate transfer belt 30 is driven at a predetermined speed by a driving pulley 31, and the exposure device 5 is sequentially moved with respect to the image writing portion of each photosensitive drum in accordance with the moving speed of the image writing portion of the belt. The image writing operation is performed.
[0017]
After the black image is transferred from the photosensitive drum 3 </ b> B to the intermediate transfer belt 30, a transfer roller 39 is disposed at a portion where the belt is turned by the turning roller 33, and the turning roller 33 and the transfer roller 39 Feed the paper so that it is in between. When the color toner image is transferred from the intermediate transfer belt 30, the paper taken out from the paper feed tray 16 by the paper feed roller 17 is sent to the image transfer unit by the transport roller device 18. Then, a voltage is applied from the back side of the paper by the transfer roller 39 to transfer the color toner image carried on the belt 30, peeled off by the peeling claw 35, and then sent to the fixing device 19 for color copying. Create Further, after transferring the color toner image from the intermediate transfer belt 30 to the paper, the toner remaining on the surface of the intermediate transfer belt 30 is removed by the blade 37 of the cleaning device 36, and the next charging / exposure / development operation is performed. To deal with.
[0018]
In the example using the paper carrying belt 20, conventionally known electrostatic paper carrying means may be used as long as the paper can be held on the belt surface by static electricity. As the intermediate transfer belt 30, a conventionally known transfer belt means can be arbitrarily used. Further, as a cleaning device for the intermediate transfer belt 30, it is possible to use a device having an arbitrary mechanism. Furthermore, in the above-described embodiment, one exposure unit 5 is directed to all of the photosensitive drums 3Y, 3M, 3C, and 3B. However, one LED is shared by the photosensitive drums 3Y, 3M, and 3C. In addition, another exposure device 5 can be arranged on the photosensitive drum 3B.
[0019]
【The invention's effect】
Since the image forming apparatus of the present invention is configured as described above, by using one LED in common for all the image forming means, the cost of the LED can be reduced and the cost can be reduced. The image forming apparatus can be configured. In addition, by configuring the interval between the image transfer portions of each image forming unit to correspond to at least the length of the paper, it is possible to perform the LED image writing operation on the photosensitive drum in a stable state. Become.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus of the present invention.
FIG. 2 is an explanatory diagram of a configuration of an image forming unit provided in the image forming apparatus.
FIG. 3 is an explanatory diagram of another configuration example of the image forming apparatus.
FIG. 4 is an explanatory diagram of another configuration example of the image forming apparatus.
[Explanation of symbols]
1 image forming apparatus, 2 image forming section, 3 photosensitive drum,
4 transfer roller, 5 exposure unit, 6 spindle, 9 paper transport path,
10 image forming member, 11 charger, 12 developing device,
13 developing roller, 13a supply roller,
14 cleaning device, 15 blade, 15a transporter,
16 paper feed tray, 17 paper feed roller, 18 transport roller device,
19 fixing device, 20 paper carrying belt, 21 driving pulley,
22 guide pulley, 23 turning roller, 25 peeling claw,
26 conveying roller device, 27 pressing roller, 28 charger,
30 intermediate transfer belt, 31 driving roller, 32 guide pulley,
35 peeling claw, 36 cleaning device, 37 blade,
38 Transfer section, 39 Transfer roller.

Claims (2)

Four image forming units each having a charger, a photosensitive drum, a developing device, and a transfer roller for forming and transferring four color toner images onto a sheet are arranged in an annular shape. In the image forming means, an exposure device that exposes the photosensitive drum of each image forming means by a light emitting element head array is provided to be rotatable about a support shaft, and the exposure device is provided on the photosensitive drum of each image forming means. A series of image forming operations are performed by sequentially moving correspondingly to form an electrostatic latent image on each photoconductive drum and sequentially transferring the color toner images formed on each photoconductive drum on a sheet. An image forming apparatus. The image forming apparatus according to claim 1, wherein a distance corresponding to at least the entire length of the sheet is provided between the transfer position of the image forming unit and the transfer position of the next image forming unit.

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