JPH09160324A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a color image of high image quality free of color slippage by improving the carrying capability of a transfer belt, improving the adherence of the transfer belt to image forming bodies, and carrying the transfer face at constant speed. SOLUTION: The device with cleaners 15 develops color toner images onto the plurality of drum-like image-forming bodies, arranged in parallel, by means of developing units, transfers the developed color toner images onto the transfer belt 18 in order, thereby superimproving the color toner images. The transfer belt 18 has arrangement rollers 20A-20D arranged inside common tangent to the outside diameters of the adjacent drum-like image-forming bodies, and the drum-like image-forming bodies rotate following the drive of the transfer belt 18.

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 color toner image using a plurality of image forming members.

[0002]

2. Description of the Related Art Many color image forming apparatuses for forming a color image by superposing toner images on a plurality of image forming bodies employ an electrophotographic image forming method. FIG. 1 shows a main part of one type of color image forming apparatus.

In FIG. 1, A, B, C, and D are image forming units arranged in parallel in the order of image processing, and are units for forming single-color toner images of yellow, magenta, cyan, and black, respectively. .

Each image forming section includes a drum-shaped image forming body 1, a charging unit 2, an exposing unit 3, a developing unit 4, and a cleaning unit 5 as shown in an image forming unit A for forming a yellow toner image. Each is provided with forming means. With such a configuration, first, a yellow toner image is formed on the image forming body 1 of the image forming unit A. This toner image is transferred to the transfer paper P conveyed by the transfer belt 8 in the direction of the arrow by the operation of the transfer device 7.

During this time, in the image forming section B, a magenta toner image is formed on the image forming body, and the transfer paper P
Is transferred in a manner superimposed on the yellow toner image. Similarly, a cyan toner image is superimposed by the image forming unit C, and a black toner image is superimposed by the image forming unit D, so that a color toner image is formed on the transfer paper P. The transfer paper P on which the color toner image is formed in this manner is continuously conveyed to the fixing device 6 by the transfer belt 8 to fix the toner image, and the copying is completed.

[0006]

In superposing the above-mentioned single color toner images, first, the transfer paper P is surely brought into close contact with the peripheral surface of each image forming body at the transfer portion.
Secondly, it is necessary that the toner image previously transferred by the transfer paper P is conveyed at an accurate timing with respect to the rotation cycle of the image forming body of the next image forming portion, and therefore the transfer belt 8 is It is necessary to contact the image forming body with an appropriate pressure contact force and at the same time, convey the image forming body at a constant speed.

[0007] The same applies to a method in which a toner image is sequentially superimposed on a transfer belt to form a color toner image, and then the toner images are collectively transferred onto transfer paper.

With respect to such a problem, Japanese Patent Laid-Open No. Sho-6 has already been published.
3-118772,62-2999977,62-141
No. 574 has been proposed, but none of them has given a large frictional resistance to the transfer belt to lower the transportability thereof, and thus has not been proposed yet for practical use.

The present invention has been made to solve the above problems. That is, the transportability of the transfer belt is improved, and the adhesion of the transfer belt to the image forming body is improved,
Furthermore, by conveying the transfer surface at a constant speed,
It is an object of the present invention to provide a color image forming apparatus capable of forming a high quality color image without color shift.

[0010]

The above object can be achieved by adopting the following constitution.

A color toner image is developed and formed by a developing device on a plurality of drum-shaped image forming members arranged in parallel, and the developed color toner image is sequentially transferred onto a transfer belt to form the color toner image. In a color image forming apparatus having a cleaning device, the transfer belt is arranged inside a common tangent line of the outer diameters of two adjacent drum-shaped image forming bodies, and the drum-shaped image forming body is provided. Is a color image forming apparatus which is driven to rotate by driving the transfer belt.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color image forming apparatus according to the present invention will be described with reference to FIGS.

FIG. 2 is a diagram for explaining the invention according to claim 1, and shows an outline of an apparatus I of a type for directly transferring a toner image on an image forming body onto a transfer sheet.

In FIG. 2, four sets of image forming sections 10A, 10B, 10C and 10D are arranged in parallel in the horizontal direction substantially in the center of the main body of the apparatus, and below each of the image forming sections, image transfer onto a transfer sheet is performed. And transfer transfer means for controlling the transfer.

As shown in the example of the image forming section 10A, each of the image forming sections has a photosensitive drum 11 as an image forming body placed at the center thereof, and a charger 12, an exposing section 13, a developing unit 14 and a cleaning unit around the periphery thereof. Although the apparatus 15 is arranged, the developing device 14 has different toner colors for each image forming unit, and the image forming unit 10A has a yellow color, the 10B has a magenta color, the 10C has a cyan color, and the 10C has a cyan color.
For D, a developing device containing each black toner is used.

On the other hand, the transfer / transport means is composed of four transfer devices 1.
7A, 17B, 17C, 17D, and a transfer belt 1 of a belt member stretched around a driving roller 19A and a driven roller 19B.
8 and.

Each of the transfer devices is arranged so as to face the lower peripheral surface of each photoconductor drum to form an image transfer portion between the transfer belt 18 and the drum peripheral surface, and the transfer belt 18 is rotated by a driving roller 19A. Transfer the transfer paper P to the transfer unit,
Further, the transfer paper P that has completed the transfer is conveyed to the fixing unit 16.

Further, arranging rollers 20A, 20B, 20C which are rotatable on the inner peripheral surface of the transfer belt 18 near each transfer portion.
And 20D are provided, and the outer peripheral surface of the transfer belt 18 is brought into contact with the peripheral surfaces of the respective photosensitive drums in an arc shape by the upward pressing of the respective disposing rollers. The transfer belt 18 pressed against the drum surface is always in a tensioned state by the action of the tension roller 21.

When the transfer sheet P is carried out from the sheet feeding device (not shown) on the right side of the apparatus and detected by the sensor 22, the photosensitive drums of the respective image forming sections are rotated clockwise and the transfer belt 18 is rotated counterclockwise. To start rotating or carrying.

When the sensor 24A detects the leading edge of the transfer paper P, in the image forming section 10A, the charger 12 acts to apply an electric charge to the peripheral surface of the photoconductor drum 11, and then the second laser writing device separates the charge. A laser beam is projected from the exposure unit 13 that has received the image signal of the color of 1, that is, the yellow, and an electrostatic latent image corresponding to the image of the yellow is formed on the peripheral surface of the drum.

This latent image is converted into a yellow toner image by the developing device 14, and is transferred onto the transfer paper P fed by the timing roller 23 in synchronization with the image formation.

Similarly, when the sensor 24B detects the front end of the transfer paper P to which the yellow toner image has been transferred, the second color, that is, magenta toner image is formed on the drum peripheral surface in the image forming section 10B. The image is transferred onto the image surface of the transfer paper P that has been conveyed by the transfer belt 18.

The image forming units 10C and 10 will be continuously described below.
The cyan and black toner images are transferred in superposition by D, respectively, and as a result, a color toner image is synthesized on the transfer paper P.

The transfer sheet P, which has been transferred in this way, is fed to the fixing section 16 by the conveying action of the transfer belt 18, and is discharged via the discharge roller 25 to the discharge tray 26 on the left side of the apparatus.
Is discharged on top.

During this time, the transfer sheet P is attracted to the outer peripheral surface of the transfer belt 18 by the discharge of the attraction charger 27, so that the placement rollers 20A, 20B, 20C and 20D are placed.
Even if the sheet is bent by pressing the sheet, the adhesiveness is not lost and the sheet is conveyed in synchronization with the image forming timing.

On the other hand, with respect to the transfer belt 18, the placement rollers 20A, 20B, 20C and 20D are installed so that they are pressed against each other along the peripheral surface of each photoconductor drum, but since each placement roller can freely rotate. No large frictional resistance is generated, and therefore, it is always conveyed at a stable predetermined speed.

The transfer paper P, which has completed the transfer of the toner image, is neutralized by the static eliminator 28, erases the adsorption force, is easily separated from the transfer belt 18, and is fed to the fixing unit 16.

FIG. 3 is a diagram for explaining the invention according to claims 1 and 2, and is an outline of an apparatus II of a type in which a toner image on an image forming body is once transferred onto a belt member and then transferred onto a transfer sheet at once. Indicates. In this case, a transfer belt 118 capable of transferring a toner image is used as the belt member.

In FIG. 3, in the device II, the above device is used.
Image forming units 110A, 110B, 1 for forming toner images of yellow, magenta, cyan, and black similar to I
10C and 110D are arranged in parallel, and the above-mentioned transfer belt 118 is arranged below them.

Each of the image forming sections forms a monochromatic toner image on the peripheral surface of each photoconductor drum 111 by the same process as in the apparatus I, and transfers the toner image in synchronization with each toner image. The color toner images are combined by being sequentially transferred onto the belt 118.

On the other hand, in parallel with this, the paper feed cassette 120
The transfer sheet P is unloaded from the sheet by the rotation of the sheet feeding belt 121, and is conveyed to the transfer section of the transfer unit 122.

At this time, the transfer paper P is fed by adjusting the paper feed timing by the action of the timing roller 123 so as to be synchronized with the toner image on the transfer belt 118, and receives the batch transfer of the toner images.

The transfer sheet P, which has received the toner images collectively transferred, is fed to the fixing section 116, and after fixing the toner image, it is ejected onto the sheet ejection tray 126 on the upper side of the apparatus through the sheet ejection rollers 125, while being transferred. The belt 118 is the cleaning device 12
At 4, the residual toner is removed.

As described above, in the method of collectively transferring to the transfer paper, the photosensitive drum 111 and the transfer belt 118 do not sandwich the paper between them and they are in close contact with each other, so that they do not slip. Therefore, it is possible to perform stable driving by frictional force, which is a more preferable configuration.

FIG. 4 is a diagram showing another embodiment of the present invention in an apparatus of the same type as the apparatus II described in FIG. 3 above. The transfer belt 118 exits the final black toner image forming portion 110D. Shows a skeleton in which the toner image of (1) is collectively transferred to the transfer paper P at the transfer portion configured by the transfer device 122. In FIG. 4, members having the same functions as those of FIG. 3 are designated by the same reference numerals, but the operation of these members is almost the same as that of FIG.

FIG. 5 is a diagram for explaining the invention according to claim 1 in more detail.

In FIG. 5, the arrangement roller 20 is arranged so as to arrange the transfer belt 118 inside the common tangent line TL of the outer diameters of the two adjacent drum-shaped image forming bodies, that is, the photosensitive drums 111. is there. That is, the transfer belt 11
Photosensitive drum 11 whose outer peripheral surface is a drum-shaped image forming body
Arrangement roller 20 is arranged so as to contact the peripheral surface of No. 1 in an arc shape. When the transfer belt 118 is driven in the direction of the arrow in the figure, the photoconductor drum 111 is driven to rotate in the clockwise direction of the arrow in the figure.

With this structure, the transfer belt is improved in transportability, and the adhesion of the transfer belt to the photosensitive drum is also improved, so that a high quality color image can be formed.

FIG. 6 is a diagram for explaining the invention according to claim 3.

In FIG. 6, at least one of the photosensitive drum 111, which is a drum-shaped image forming body, the driving roller 119A that rotationally drives the transfer belt 118, and the driven roller 119B that is rotationally driven by the transfer belt 118. In FIG. 6 of the present embodiment, an encoder is attached to the photoconductor drum 111 at the right end as shown. The rotation speed of the photoconductor drum 111 is sent to the CPU as an electric signal by the encoder, and it is detected whether the rotation speed is a predetermined rotation speed or not. Controlled. Then, it is converted into a motor drive current by the D / A circuit and supplied to the motor, and the motor maintains a predetermined rotation.

In this way, the present apparatus operates the driving roller 11
Since the rotation speed of the motor that drives 9A is controlled, the transfer belt 118 is conveyed at a constant speed, and it is possible to form a high-quality color image without color misregistration.

Of course, the detection of the rotation state is not limited to the above-mentioned photosensitive drum 111, but the drive roller 119A and the driven roller 1 can be detected.
19B is also acceptable.

The cleaning device used in this apparatus is
By using a fur brush, the frictional resistance can be reduced, the rotation and rotation of the photoconductor drum and the transfer belt can be made smoother, and drive unevenness can be reduced, enabling the formation of higher quality color images. .

Similarly, the developing device used in this apparatus can reduce the rotational torque of the photosensitive drum by using the non-contact developing device, and reduce the driving unevenness of the photosensitive drum to obtain higher image quality. It is possible to form a color image.

FIG. 7 is a view for explaining a desirable form of this device.

In FIG. 7, the length of the common tangent line TL between two adjacent photoconductor drums 111 and the straight line passing through the center of rotation of the two adjacent photoconductor drums 111 is L2, the common tangent line TL and the placement roller 20. L1 is the length with the inner tip of
Then, L1 = 5 to 30 mm, L1 / L2 = 0.1
~ 0.5 is desirable. The nip length NL at which the photosensitive drum 111 is pressed against the transfer belt 118 at the transfer portion is preferably NL = 10 to 60 mm.

Further, as shown in the figure, the electrodes in the transfer part when transferring to the transfer paper are provided with a transfer device and a separator, and the static eliminator is designed to eliminate the static electricity from both sides of the belt as shown in the figure. However, the static eliminator may be omitted. Further, it is desirable to provide a suction charging device facing the placement roller so as to re-suck the transfer paper. At this time, it is desirable that the placement roller is grounded as a metal roller.

[0048]

The constitutions of the inventions according to claims 1 and 2 improve the transportability of the transfer belt, and in particular, the constitution of the invention according to claim 1 further improves the adhesion of the transfer belt to the photosensitive drum. It has the effect of enabling the formation of a high quality color image.

According to the third aspect of the present invention, the rotation speed of the motor for driving the driving roller is controlled, and the transfer belt is conveyed at a constant speed to form a high-quality color image without color misregistration. Has the effect of enabling

According to the fourth and fifth aspects of the invention, the rotation and rotation of the photosensitive drum and the transfer belt are made smoother to reduce drive unevenness, and it is possible to form a higher quality color image. Have.

As described above, according to the present invention, the transferability of the transfer belt is improved, the adhesion of the transfer belt to the image forming body is improved, and the transfer surface is conveyed at a constant speed, so that the color misregistration occurs. A color image forming apparatus capable of forming a high quality color image having no high quality is provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a relationship between an image forming body and a transfer / conveyance unit.

FIG. 2 is a diagram for explaining the invention according to claim 1;

FIG. 3 is a diagram illustrating an invention according to claims 1 and 2.

FIG. 4 is a diagram for explaining another embodiment of the invention according to claims 1 and 2.

FIG. 5 is a diagram for explaining the invention according to claim 1 in more detail.

FIG. 6 is a diagram illustrating an invention according to claim 3;

FIG. 7 is a diagram illustrating a desirable form of the present apparatus.

[Explanation of symbols]

 10A, 10B, 10C, 10D Image forming part 110A, 110B, 110C, 110D Image forming part 11,111 Photosensitive drum 14 Developing device 15,124 Cleaning device 18,118 Transfer belt 19A Driving roller 19B Driven roller 20,20A, 20B , 20C, 20D Arrangement roller NL Nip length P Transfer paper TL Common tangent

Claims (5)

[Claims] 1. A color toner image is developed and formed by a developing device on a plurality of drum-shaped image forming bodies arranged in parallel,
In a color image forming apparatus having a cleaning device that sequentially transfers the developed and formed color toner images onto a transfer belt and superimposes the color toner images, the transfer belt is provided outside the two drum-shaped image forming bodies adjacent to each other. A color image forming apparatus having an arrangement roller arranged inside a common tangent of diameter, wherein the drum-shaped image forming body is driven and rotated by driving of the transfer belt. 2. The color image forming apparatus according to claim 1, wherein the toner images are collectively transferred from the transfer belt onto the transfer paper. 3. Rotation control is performed by detecting a rotational state of at least one of a drive roller that rotationally drives the drum-shaped image forming body, the transfer belt, and a driven roller that is rotationally driven by the transfer belt. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is a color image forming apparatus. 4. The color image forming apparatus according to claim 1, wherein the cleaning device uses a fur brush. 5. The color image forming apparatus according to claim 1, wherein the developing device is a non-contact developing device.