JP2002189332A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that charge is applied only to a specified spot on an intermediate transfer belt when transfer of a small size is continued and the partial characteristic deterioration of the belt is caused, because the reference position mark of the belt is set as reference in the case of writing by superposing a plurality of colors in the conventional image forming device. SOLUTION: In the case of writing by superposing a plurality of colors, the reference position mark 4 is written on the intermediate transfer belt 3 in the first color first, and then an image is written after a fixed time. As for the second and succeeding colors, the mark 4 is detected and the image is written after a previously set time, thereby, the image is superposed on the image written in the first color. Thereafter, such operation is repeated to form a color image. Therefore, an image starting place is optionally set by writing the mark in the first color, and the deterioration of the belt is eliminated and the life thereof is prolonged by not only using the specified spot on the belt but also using all around.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile machine having a toner image carrier such as an intermediate transfer belt capable of overwriting a plurality of colors.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show an example of a conventional image forming apparatus. 1 is a laser writing unit, 2 is a photoreceptor, 3 is an intermediate transfer belt (toner image carrier), 4 is a reference position mark,
Reference numeral 5 denotes a mark detection sensor, 6 denotes a developing device, 7 denotes an intermediate transfer belt cleaning, 8 denotes a paper feeding device, 9 denotes a fixing device, and 10 denotes a paper discharging device.

FIG. 7 shows an operation sequence of a conventional image forming apparatus. A start signal (a start button of an operation unit (not shown) in a copying operation, a print request from a host (not shown) in a printer operation) initiates an image forming cycle in this apparatus. When a start signal is received, it is first determined by a command whether data to be transferred is one color or two or more colors.

In the case of one color, since there is no need to wait for the reference position mark, transfer of image data is started from the reading unit or the host 11 shown in FIG. At this time, a reference image area signal (hereinafter, referred to as SFGATE) is input from the reading unit or the host 11. The image data is created according to this signal, and the laser writing unit 1
Based on GATE and image data, it is converted into writing system timing (WFGA shifted by timing c as shown in FIG. 9).
TE is output) and output. This is the laser writing unit 1
And the image is transferred onto the intermediate transfer belt 3. At the same time, paper feeding is started in accordance with WFGATE, and the paper is transferred onto the paper. Thereafter, the paper is discharged.

[0005] In the case of two or more colors, a reference is required to overlap each color without shifting. Therefore, the reference position mark 4 on the intermediate transfer belt is detected by using the mark detection sensor 5, and an image is formed based on the detection signal. That is, in the case of two colors, the intermediate transfer belt 3 is rotated two times in the case of three colors, three times in the case of four colors, and four times in the case of four colors.
By forming an image from the mark reference signal, it is possible to obtain a superimposed image without positional displacement.

As shown in FIG. 10 and FIG.
Is detected, first, a reference image area signal (a signal shifted from the mark by a predetermined timing a; hereinafter, B
Called FGATE. ), And passes the BFGATE to the reading unit or the host 11. Based on the BFGATE, an SFGATE (a signal shifted by a timing b from the BFGATE) converted to the timing of the reading unit or the host 11 is generated, and the transfer of image data is started in accordance with the SFGATE. This is written on a photoreceptor by a laser writing unit 1 and transferred onto an intermediate transfer belt. Transfer is performed in the same manner by detecting the next mark.

When all the colors have been completed, paper feeding is started in accordance with an image area signal of a writing system timing (here, WFGATE with a signal shifted by c from SFGATE), and the paper is transferred onto the paper. Thereafter, the paper is discharged. The CPU 13 in FIGS. 8 and 10 controls the operation of the entire image forming apparatus including the above-described control.

[0008]

In the above-described conventional image forming apparatus, since the reference position mark 4 of the intermediate transfer belt 3 is used as a reference, if small size transfer is continued, electric charges are applied only to a specific portion on the belt. As a result, there is a problem that the characteristics of the belt are partially deteriorated.

According to the present invention, the mark can be arbitrarily set by writing a mark in the first color by using a mark in the first color. The purpose is to extend the life.

[0010]

In order to achieve the above object, in an image forming apparatus according to the present invention, a writing means using a laser beam as a light source, a photosensitive member for carrying a toner image in which an electrostatic latent image is visualized. And an image forming apparatus having a toner image carrier capable of transferring a toner image on a photosensitive member by superposing a plurality of times, when forming an image of two or more colors, a reference mark pattern is formed by using a color to be written first using a toner image. A writing control unit is provided for writing an image after writing on the carrier, and writing an image based on the mark pattern for the second and subsequent colors.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Note that the description here is limited to the case of two or more colors. For one color, there is no need to write the reference position mark. FIG. 1 is a diagram showing an intermediate transfer belt 3 for describing the present embodiment in principle, FIG. 2 is a block diagram showing a main part of an image forming apparatus according to the present embodiment, and FIG. 3 is a timing chart showing an operation. FIG. 4 is a flowchart showing the operation. In FIGS. 1 and 2, parts corresponding to those in FIGS. 5, 6, 8, and 10 are denoted by the same reference numerals, and redundant description is omitted.

Next, the operation will be described with reference to FIGS. Here, the intermediate transfer belt 3 as a toner image carrier has at least a reference image size (for example, A
It shall have a length twice or more of 4). In the first color, an image is written a fixed time after writing the reference position mark 4. For the second and subsequent colors, the reference position mark 4 is detected, and after a predetermined time, when the image is written, the image overlaps with the image written in the first color. Thereafter, this is repeated to form a color image (the time to start writing an image from the mark 4 for the second and subsequent colors (a in FIG. 3 is determined by the system configuration).

If a black mark 4 is written on a color of the same system as the intermediate transfer belt 3, for example, a black belt, there is a risk that an erroneous determination is made when the mark is detected. An erroneous determination can be prevented by bringing a color close to the intermediate transfer belt 3 and a color that is easy to determine as the first color. For example, the intermediate transfer belt 3
If the color is black, it is good to write in yellow (in general, in the case of full color, use four colors of black, yellow, magenta, and cyan).

According to the above, by writing a mark in the first color on the intermediate transfer belt 3, an image start position on the belt can be arbitrarily set. It can be used evenly, thereby reducing belt degradation and extending belt life.

[0015]

According to the first aspect of the present invention, the belt can be prevented from being partially degraded, and the life of the belt can be extended. According to the second and third aspects of the present invention, it is possible to reduce erroneous determination of mark detection, improve overlay accuracy, and obtain high image quality.

According to the fourth aspect of the present invention, the size of the toner image carrier such as the intermediate transfer belt when transferring a plurality of colors can be made appropriate.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an intermediate transfer belt for describing an embodiment of the present invention in principle.

FIG. 2 is a block diagram showing a main part of the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a timing chart showing an operation of the image forming apparatus according to the embodiment of the present invention.

FIG. 4 is a flowchart illustrating an operation of the image forming apparatus according to the embodiment of the present invention.

FIG. 5 is a diagram showing a configuration according to an embodiment of the related art.

FIG. 6 is a diagram illustrating a configuration according to an embodiment of the related art.

FIG. 7 is a flowchart showing an operation in the embodiment of the related art.

FIG. 8 is a block diagram illustrating a main part of an image forming apparatus according to an embodiment of the related art.

FIG. 9 is a timing chart illustrating an operation of the image forming apparatus according to the embodiment of the related art.

FIG. 10 is a block diagram illustrating a main part of an image forming apparatus according to an embodiment of the related art.

FIG. 11 is a timing chart illustrating an operation of the image forming apparatus according to the embodiment of the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser writing unit 2 photoreceptor 3 intermediate transfer belt (toner image carrier) 4 reference position mark 5 mark detection sensor 11 reading unit or host 13 CPU

Claims (4)

[Claims] A writing unit using a laser beam as a light source; a photosensitive member for carrying a toner image in which an electrostatic latent image is visualized; and a toner image bearing member capable of transferring a toner image on the photosensitive member by superimposing a plurality of times. In the image forming apparatus, when forming an image of two or more colors, a reference mark pattern is first written on the toner image carrier using a color to be written, and then an image is written. An image forming apparatus, comprising: a writing control unit that writes an image. 2. The image forming apparatus according to claim 1, wherein the color of the mark pattern is different from the color of the toner image carrier. 3. The image forming apparatus according to claim 1, wherein the color of the mark pattern has a complementary color relationship with the color of the toner image carrier. 4. The image forming apparatus according to claim 1, wherein the toner image carrier has a length at least twice as large as a reference image size.