JP2002341624A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact color image forming device realizing high-speed printing without changing the electrophotographic processing speed of a color image forming device using electrophotographic technology. SOLUTION: Relation among the number N1 of developing devices, the number N2 of image holding bodies, the number N3 of 1st transfer points where toner is transferred to an intermediate transfer body from the image holding body, and the number N4 of 2nd transfer points where the toner is transferred to a recording medium from the intermediate transfer body is set to N1>N2=N3>N4.

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, and more particularly to a color image forming apparatus utilizing an electrophotographic process.

[0002]

2. Description of the Related Art A color image forming apparatus using an electrophotographic technique includes three primary colors of yellow (Y), magenta (M) and cyan (C) for forming a color image to be printed, and black (K). An exposure device, which is a latent image forming device, which is controlled in accordance with the four color image information, exposes a photoreceptor, which is a latent image holding member, to form an electrostatic latent image of each of the above colors. A color image is formed by developing using a developing device having a developer (toner) of a color corresponding to the above, forming a toner image of each color on a photoreceptor, and superimposing and synthesizing the toner image of each color. I do. One of the color image forming apparatuses using the electrophotographic technique is an apparatus using an intermediate transfer member. The apparatus using the intermediate transfer member superimposes the toner image of each color formed on the photoreceptor four times on the intermediate transfer member for each color to form a color image, and transfers the color image to the recording medium at one time. Then, a color image is obtained by fixing.

[0003] The time required for the process of forming a full-color image according to the prior art will be described with reference to FIG. The vertical axis in FIG. 3 shows the items of each process of exposure, development, first transfer, and second transfer, and the horizontal axis shows the time required for each process. The length t of each cell in FIG. 3 corresponds to the time required for forming one image. Since the intermediate transfer member is rotated at a constant speed to form a full-color image, the length t of all cells, that is, the time t Are equal. In the prior art, the process from exposure of four colors of toner, yellow (Y), magenta (M), cyan (C), and black (K) to the first transfer proceeds in series. About four times as long as printing is required.

[0004]

There is an increasing demand for color image forming apparatuses to reduce the time required for full-color printing, that is, to increase the speed. In a conventional color image forming apparatus using an intermediate transfer member, yellow (Y), magenta (M), cyan (C), and black (K) are developed for each color on a photoreceptor. The toner image is transferred to a transfer member, and a four-color toner image is superposed on the intermediate transfer to form a full-color image.

[0005] Therefore, in order to shorten the full-color printing time, it is necessary to increase the speed of the electrophotographic process. However, all of the processes related to the electrophotographic process, such as shortening of a latent image forming time by an exposure device and development time by a developing device, are required. It is necessary to increase the speed of the components, which results in an increase in the size and cost of parts and devices.

An object of the present invention is to provide a small-sized color image forming apparatus capable of high-speed printing without changing the electrophotographic process speed of a color image forming apparatus using the above-described electrophotographic technology.

[0007]

In a color image forming apparatus according to the present invention, a plurality of first transfer points for transferring a toner image from a photosensitive member onto an intermediate transfer member are provided at a plurality of positions, and different color toner images are simultaneously formed on the intermediate transfer member. Thus, the required number of rotations of the intermediate transfer member is reduced to perform full-color printing, thereby shortening the color image forming time.

In the color image forming apparatus of the present invention, a latent image is formed on the image carrier using an exposure device, and the formed latent image is developed by a developing device having toners of different colors. Transfer the transferred toner image to the intermediate transfer member,
By repeating the above process a plurality of times, a color image in which a plurality of toner images are superimposed is formed on an intermediate transfer body, and the formed color image is transferred to a recording medium and fixed when the image holding body and the intermediate transfer body are fixed. By providing a plurality of first transfer points between the bodies and simultaneously transferring color toner images of different colors, full-color printing time is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color image forming apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a color image forming apparatus according to the present embodiment. In this color image forming apparatus, two photosensitive belts 2-1 and 2-2 serving as image holding members are vertically arranged in a housing 1. On the left side of FIG. 1 with respect to the two photosensitive belts 2-1 and 2-2, a transfer drum 6 as an intermediate transfer body, a transfer device 12, a paper feed device 10 for a recording medium such as a sheet, and a registration roller 11 , A recording medium guide 18 and a fixing device 14 are arranged, and the right side in FIG. 1 is filled with toner of four different colors of yellow (Y), magenta (M), cyan (C) and black (K). Equipment 5Y, 5M, 5C, 5K
Has been arranged. Below the developing devices 5M and 5K, two exposing devices 4 for forming latent images on the photosensitive belt 2-1 and the photosensitive belt 2-2 are arranged, and further under the developing device 5M, a sheet as a recording medium is stored. The paper feed cassette 9 is placed.

A transfer device 12, a recording medium peeling device 13, and an intermediate transfer body cleaning device 16 are arranged around the transfer drum 6, and a charging device 3, around the photosensitive belts 2-1 and 2-2.
An afterimage removing device 7 and a photoconductor cleaning device 8 are provided. The two photosensitive belts 2-1 and 2-2, which are image holding members, are driven by a driving device (not shown) via a photosensitive member driving roller 2a, and as shown by an arrow 21a, each of them is from the bottom to the top in FIG. Rotate towards. In order to make the rotational speeds of the upper and lower photosensitive belts equal, it is preferable that the number of the driving devices is one. Reference numerals 2b and 2c are photosensitive member driven rollers. The rotational force between the photoconductor 2-1 and the photoconductor 2-2 is 22.
a and the transfer drum 6 at two first transfer points 22b.
Is transferred to the transfer drum 6, and the transfer drum 6
At the first transfer position, the photosensitive drum 2-1 and the photosensitive drum 2-2 are driven at the same peripheral speed by the mechanical frictional force and the electrostatic attraction force,
It rotates in the direction shown by arrow 21b. As shown in FIG. 1, in the present embodiment, a plurality of first transfer points are provided, and the driving force of the intermediate transfer body by the photoconductor is increased to realize smooth rotation of the intermediate transfer body without slip.

Next, a printing process of a color image according to the present embodiment will be described with reference to FIG. First, photosensitive belt 2
-1 and the photosensitive belt 2-2 are uniformly charged by the charging device 3. Next, the exposure device 4 exposes the image and character information by a personal computer, an image scanner, or the like to the photosensitive belts 2-1 and 2-2 in dot units to form an electrostatic latent image on the photosensitive belt. After that, the electrostatic latent image on the photosensitive belt is developed by any of the developing devices 5Y, 5M, 5C, and 5K to become a toner image, and is sent to the first transfer positions 22a and 22b. The photosensitive belts 2-1 and 2-2 are supplied with a potential from a power supply (not shown), and the transfer drum 6 is connected to the ground. Therefore, the first transfer positions 22a, 22
b, due to these potential differences, the photosensitive belts 2-2, 2-2
, The toner image is transferred to the transfer drum 6.

The photosensitive belts 2-2 and 2-2 passing through the first transfer positions 22a and 22b are irradiated with light by an afterimage removing device 7 to erase the electrostatic latent image, and the surface potential of the photosensitive belt is kept below a certain level. Drop. After that, the first photosensitive member cleaning device 8
The residual toner remaining on the photosensitive belts 2-1 and 2-2 that has not been transferred by the transfer is cleaned, and a state in which the next toner image can be formed is obtained. The operation of one cycle described above is performed by the transfer drum 6
The developing devices 5Y, 5M, 5C,
The process is sequentially performed for 5K, and a multi-color toner image is formed on the transfer drum 6 by superimposing these single-color toner images.

On the other hand, a recording medium such as a sheet, an OHP sheet, etc.
The transfer device 12 transfers the single-color or multiple-color toner image formed on the transfer drum 6 to the recording medium. FIG. 1 shows the travel path 19 of the recording medium by a thick line. After the transfer of the toner image to the recording medium, the recording medium is peeled off from the transfer drum 6 by the recording medium peeling device 13, the toner is melted and fixed by the fixing device 14, and discharged to the discharge tray 17 on the upper surface of the main body by the discharge device 15. Paper. Further, after the transfer to the recording medium is completed, the toner remaining on the transfer drum 6 without being transferred is cleaned by the intermediate transfer body cleaning device 16 so that the next toner image can be superimposed.
Here, the developing roller 5a, the photosensitive member cleaning device 8, the transfer device 12, and the intermediate transfer member cleaning device 16 are configured to be movable so as to be brought into contact with the partner member only when necessary.

Further, although not shown in FIG. 1, the transfer device 12, the transfer drum 6, the photosensitive belts 2-1 and 2-2, and the developing device 5Y are located almost on the left side of FIG. , 5M, 5C, and 5K, a full-color image can be simultaneously printed on the front and back surfaces of the recording medium traveling on the recording medium traveling path 19 at high speed.

That is, as shown in this embodiment, a plurality of image carriers (photosensitive belts 2-1, 2-
2) and a plurality of exposure devices 4 for forming the electrostatic latent image
And a plurality of developing devices 5Y, 5M, 5C, and 5K arranged around the image holding member for attaching toner to the electrostatic latent image formed on the image holding member to visualize the electrostatic latent image, and on the image holding member. A color image forming apparatus having an intermediate transfer body (transfer drum 6) for temporarily holding the adhered toner and superimposing and synthesizing the toner, the number N1 of developing devices 5Y, 5M, 5C and 5K;
The number N2 of image carriers (photosensitive belts 2-1 and 2-2) and the number N3 of first transfer points 22a and 22b for transferring toner from the image carrier to an intermediate transfer member (transfer drum 6); Second transfer point 2 for transferring toner from intermediate transfer member to recording medium
The relationship between 3a and the number N4 was set as N1> N2 = N3> N4, and the time required to form a full-color image was shortened.

Further, in the color image forming apparatus of this embodiment shown in FIG. 1, four developing devices 5Y and 5 for yellow (Y), magenta (M), cyan (C) and black (K) are provided.
M, 5C, 5K, and a first image carrier (photosensitive belt 2).
-1) The above latent image is developed by two developing devices 5Y and 5M,
The latent image on the second image carrier (photosensitive belt 2-2) is
Developed by two developing devices 5C and 5K, and the first image is transferred from the two image carriers to the intermediate transfer member (transfer drum 6) at two locations.
The transfer of the toner at the transfer points (22a, 22b) was performed simultaneously to reduce the time for forming a full-color image.

FIG. 1 shows a combination of a photosensitive belt and an intermediate transfer member in the form of a drum and an image holding member.
Even when the intermediate transfer body is a belt-shaped image carrier and the image carrier is a combination of photosensitive drums, the time required to form a full-color image can be similarly reduced.

The time required for forming a full-color image in the embodiment shown in FIG. 1 will be described below with reference to FIG. In FIG. 2, the vertical axis indicates an item of each process, a column A indicates a process from exposure of yellow (Y) and magenta (M) to the first transfer on the first image carrier, and a column B indicates the process. Second
The process from the exposure of cyan (C) and black (K) to the first transfer is performed on the image carrier, and the column C shows the process of the second transfer. The horizontal axis in FIG. 2 indicates the time required for each process, and the length t of the cell indicates the time required for forming one image. In this embodiment, since the intermediate transfer member is rotated at a constant speed to form a full-color image, the lengths t of all the cells are equal. As shown in FIG. 2, in the present embodiment, after the Y process shown in column A is completed, the process of M is performed, and the process shown in column B is performed simultaneously with the process of column A.
After the end of the C process, the process of K is performed. After that, the second transfer in column C is performed. Thus, in the present embodiment, columns A and B
Since the processes in the columns are performed simultaneously, the time for forming a full-color image can be reduced.

[0019]

According to the color image forming apparatus of the present invention,
High-speed printing can be performed without changing the electrophotographic process speed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a color image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram of a full-color image forming time by the color image forming apparatus of FIG. 1;

FIG. 3 is an explanatory diagram of a full-color image forming time by a conventional color image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Housing, 2-1 and 2-2 ... Photosensitive belt, 2a ... Photoconductor drive roller, 2b, 2c ... Photoconductor driven roller, 3 ... Charging device, 4 ... Exposure device, 5Y, 5M, 5C, 5K ... Development 5a: developing roller, 6: transfer drum, 7: residual image removing device, 8: photoconductor cleaning device, 9: paper feed cassette, 10 ...
Paper feeding device, 11: registration roller, 12: transfer device, 1
3: Recording medium peeling device, 14: Fixing device, 15: Discharge device, 16: Intermediate transfer body cleaning device, 17: Discharge tray, 1
8: recording medium guide, 19: recording medium traveling path, 21a
... Rotating direction of photosensitive belts 2-1 and 2-2, 21b ... Rotating direction of transfer drum 6, 22a, 22b ... First transfer point, 2
3a: Second transfer point.

Continued on front page F term (reference) 2H030 AA06 AB02 BB23 BB42 BB46 2H200 FA17 GA24 GA47 GB12 GB25 HA12 JA02 JB12 JB13 JB16 JC02 JC04 JC09 JC12 KA07

Claims (6)

[Claims] A plurality of image holding members for holding an electrostatic latent image; a plurality of exposure devices for forming the electrostatic latent image; a plurality of developing devices arranged around the image holding member; A color image forming apparatus comprising: an intermediate transfer member for temporarily holding toner adhered to a body and superimposing and synthesizing the toner; a number N1 of developing units, a number N2 of image holders, and an intermediate transfer member from the image holder. The number N3 of first transfer points for transferring toner to
A color image forming apparatus, wherein the number N4 of second transfer points for transferring toner from an intermediate transfer member to a recording medium satisfies N1> N2 = N3> N4. 2. A color image forming apparatus according to claim 1, wherein
The image forming apparatus includes four developing devices for yellow (Y), magenta (M), cyan (C), and black (K). The first image carrier is developed by two developing devices, and the second image carrier is developed. Wherein the toner is transferred from the two image carriers to the intermediate transfer member at two transfer points. 3. The color image forming apparatus according to claim 1, wherein
A color image forming apparatus, wherein the intermediate transfer member has a drum shape, and the plurality of image carriers are photosensitive belts. 4. The color image forming apparatus according to claim 1, wherein
A color image forming apparatus, wherein the intermediate transfer member has a belt shape, and the plurality of image holding members are photosensitive belts. 5. The color image forming apparatus according to claim 1, wherein
A color image forming apparatus, wherein the intermediate transfer member has a belt shape, and the plurality of image carriers are photosensitive drums. 6. A color image forming apparatus according to claim 1, wherein
Driving the plurality of image carriers by one driving device;
A color image forming apparatus wherein a plurality of image carriers contact at a plurality of first transfer points to drive the intermediate transfer member.