JPH11237778A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device capable of obtaining all the time a color image which is free of color slippage and has stable, high image quality irrespective of, for example, a change in environment temperature, even in a high-speed color image forming device. SOLUTION: In the color image forming device having an arrangement of latent-image forming means 13 (Y, M, C, and K) for forming latent images on a belt photoreceptor 10, in the form of an endless belt and an arrangement of developing devices 14 (Y, M, C, and K) for developing the latent images on the belt photoreceptor 10, a sensor which is a registration sensor for detecting registration marks M2 formed on the belt photoreceptor 10 for the correct superimposition of toner images in colors and also serves as a seam detection sensor for detecting the position of the seam of the belt photoreceptor 10 is set, and on the belt photoreceptor 10 is a seam detection mark M1 which can be detected by the sensor 19 and has a different shape from the registration marks M2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image writing apparatus in an electrophotographic color image forming apparatus, and more particularly, to a copying machine in which a plurality of latent image forming means and developing means are arranged around an endless belt image carrier. And a color image forming apparatus such as a printer and a facsimile.

[0002]

2. Description of the Related Art As a developing method of an electrophotographic apparatus, there are known a normal developing method used for a normal electrophotographic copying machine and the like, and a reversal developing method used for a digital printer and a digital electrophotographic copying machine. The reversal development method generally uses a laser diode or the like as a light source, and develops a latent image formed on the image carrier by charging and exposure with a toner charged to the same polarity as the charged polarity of the photoconductor to form a toner image. It is a method. For example, when the charge polarity of the image carrier is negative, the polarity of the toner is also negative, and development is performed using a potential difference caused by exposure to form a toner image on the image carrier. After the development, the transfer material is charged to a polarity opposite to that of the toner by a transfer device using corona discharge or the like, and the toner image on the image carrier is transferred by the transfer material. Then, AC
After lowering the potential of the transfer material by corona discharge or DC corona discharge and reducing the adhesive force between the transfer material and the image carrier,
The transfer material is separated from the surface of the image carrier, and the process proceeds to the next process.

[0003]

Conventionally, there has been known an image forming apparatus having an endless belt-shaped image carrier. When the endless belt-shaped image carrier is usually manufactured, a seam is present.

In order not to form an image at the seam, it is necessary to detect the position of the seam and to form an image at a position other than the seam.

[0005] Some color image forming apparatuses having at least an endless belt-shaped image carrier require a registration sensor in order to accurately overlap images of a plurality of colors.

Since this color image forming apparatus has an endless belt-shaped image carrier, it is necessary to detect the position of the seam as described above and to form an image at a position other than the seam.

However, if the registration sensor and the seam detection sensor for detecting the position of the seam are separately installed in the apparatus, there is a problem in space.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a color image forming apparatus having a high-speed operation which always performs color misregistration irrespective of a change in environmental temperature. It is an object of the present invention to provide a color image forming apparatus capable of obtaining a stable and high-quality image without any problem.

[0009]

According to a first aspect of the present invention, there is provided a color image forming apparatus for forming a latent image on an endless belt-shaped image carrier, comprising: an endless belt; In a color image forming apparatus in which a plurality of developing devices for developing a latent image on an image carrier are arranged, a registration mark formed on the endless belt-shaped image carrier in order to accurately overlap toner images of a plurality of colors. A sensor which is a registration sensor for detecting, and also serves as a seam detection sensor for detecting a position of a seam of the endless belt-shaped image carrier, is detectable by the sensor on the endless belt-shaped image carrier. A seam detection mark having a form different from that of the registration mark is formed.

According to a second aspect of the present invention, in the first aspect, the seam detection mark and the registration mark have different widths in the sub-scanning direction.

[0011] The invention described in claim 3 is the invention according to claim 1 or 2.
Wherein the seam detection mark is formed of a paint, and the registration mark is formed of a developer in a developing device.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of an embodiment of the present invention, the structure of a color printer of the present invention and its operation will be described with reference to FIG.
Will be described with reference to the cross-sectional configuration diagram of FIG.

FIG. 1 is a sectional view showing a color printer to which a developing device and an image forming apparatus of the present embodiment are applied.

This color printer superimposes each color toner image sequentially formed on an image carrier, transfers the color image once on a recording paper in a transfer section, and forms a color image. This is a color image forming apparatus of a method of peeling off from a surface of a carrier.

In this color printer, a scorotron charger (hereinafter, referred to as a charger) 11Y, around a flexible endless belt-shaped photoreceptor (hereinafter, referred to as a belt photoreceptor) 10 as an image carrier. 11M, 11C, 11K, image exposure devices 13Y, 13M, 13C, 13K, developing devices 14Y, 1
The image forming units 4M, 14C, and 14K are arranged in a plurality of sets (four sets in the drawing) in tandem. However,
Image exposure device 13 (Y, M, C, K) as latent image forming means
Uses a laser beam scanning optical device.

The belt photoreceptor 10 is stretched over a driving roller 101 and rotating rollers 102 and 103, is tensioned by the action of a tension roller 104, and is locally brought into contact with a backup member 105 provided on the inner peripheral surface. While contacting, it rotates clockwise as shown. Backup member 1
Reference numeral 05 denotes a developer bearing member (hereinafter referred to as a developing sleeve) 141 (Y, M,
C, K) and the image exposure device 13 (Y, M, C,
K) is regulated.

At the start of image recording, the drive motor rotates and the belt photoreceptor 10 rotates clockwise through the drive roller 101 as shown in FIG. The application of the potential is started. The belt photoreceptor 10 is charged with an electric potential, and
In 3Y, exposure with an electric signal corresponding to the first color signal, that is, an image signal of yellow (Y) is started, and the rotation (sub-scanning) of the belt causes the photosensitive layer on the surface to form a yellow (Y) image of the developed image. A corresponding electrostatic latent image is formed. This latent image is developed by the developing device 14Y.
The developer adhered and conveyed onto 1Y is reversely developed in a non-contact state, and a yellow (Y) toner image is formed in accordance with the rotation of the belt photoconductor 10.

Next, the belt photoreceptor 10 is yellow (Y)
A potential is further applied to the toner image by the charging action of the charger 11M, and exposure is performed by an electric signal corresponding to the second color signal of the image exposure device 13M, that is, an image signal of magenta (M). The magenta (M) toner image is superimposed on the yellow (Y) toner image by non-contact reversal development using 14M.

By the same process, a cyan (C) toner image corresponding to the third color signal is further formed by the charger 11C, the image exposing device 13C, and the developing device 14C. Further, black (K) corresponding to the fourth color signal is obtained by the charger 11K, the image exposure device stage 13K, and the developing device 14K.
Are formed sequentially and a color toner image is formed on the peripheral surface within one rotation of the belt photoreceptor 10.

Developing devices 14Y, 14M, 14C and 14
In the developing operation by K, the developing sleeve 1
To 41Y, 141M, 141C and 141K, a DC bias having the same polarity as the charging of the belt photoreceptor 10 or a developing bias obtained by adding an AC to the DC bias is applied.
Non-contact reversal development is performed by a two-component developer attached on the developing sleeve 141 (Y, M, C, K), and toner is attached to an exposed portion on the belt photoconductor 10 with the conductive layer grounded.

In this way, the color toner image formed on the peripheral surface of the belt photoreceptor 10 is charged by the charger 11F, and then the charge is removed by the pre-transfer exposure device. The paper is fed out from paper feeding cassettes 20A, 20B or a manual paper feeding unit 20C by paper feeding means 21A, 21B, 21C, and is conveyed to a pair of registration rollers 23. The belt photoreceptor 1 is placed on the transfer paper fed in synchronization with the toner image area on the belt 10.
The toner image is transferred by a transfer device (transfer roller) 17 that is disposed opposite to the lower portion of the drive roller 101 for driving the zero.

Photo sensors 19A and 19B are provided at predetermined positions between the registration roller pair 23 and the transfer roller 17 and opposed to the belt photoreceptor 10 stretched between the drive roller 101 and the rotation roller 102. ing. Photosensors (color registration sensors) 19A and 19B detect a seam of the belt photoconductor 10 and a registration mark, which will be described later, formed on the belt photoconductor 10, and include a set of a light emitting unit and a light receiving unit. The sensor can be used for both of these two detections.

The transfer material (transfer paper) to which the toner image has been transferred is separated from the peripheral surface of the belt photoreceptor 10 along the curvature of the driving roller 101, and then conveyed to a fixing device 24, where the toner image is transferred. The toner is fused and fixed on the transfer paper by being heated and pressed, and is discharged from the fixing device 24.
The sheet is conveyed by a pair of sheet discharge rollers 25A, 25B, and 25C, and is discharged to a sheet discharge tray 26 provided at an upper portion with the toner image surface on the transfer sheet facing downward.

On the other hand, the belt photoreceptor 10 from which the transfer paper is separated
In the cleaning device 18, the cleaning blade 181 rubs the surface of the belt photoreceptor 10, removes and cleans the residual toner, and continues forming the toner image of the next original image, or temporarily stops and waits I do. When the formation of the toner image of the next original image is subsequently performed, the belt photoconductor 10
Is exposed on the photoreceptor surface to remove the previous history.

FIG. 2 is a perspective view showing an embodiment of an image exposure apparatus (scanning optical apparatus), and FIG. 3 is a plan view of the image exposure apparatus.

The plurality of image exposure devices 13Y, 13M, 1
Since 3C and 13K have almost the same configuration, the image exposure apparatus 13 (Y, M, C, K) will be hereinafter referred to as the image exposure apparatus 13 as a representative.

In these figures, reference numeral 30 denotes an optical deflecting unit comprising a rotary polygon mirror (polygon mirror) 31, a drive motor, a dynamic pressure bearing and the like. 32 is an fθ lens, 33
Is a second cylindrical lens, 34 is a first cylindrical lens, 35 is a semiconductor laser, 36 is a collimating lens, 37 is an index mirror for timing detection,
Reference numeral 8 denotes an index sensor for detecting synchronization.

The light deflection unit 30 and the scanning optical system optical members 31 to 38 are arranged and fixed at predetermined positions in an image exposure apparatus main body (housing) 130. The upper opening of the housing 130 is closed by a lid member 131.

Light beam L emitted from semiconductor laser 35
Is converted into parallel light by the collimator lens 36, and then passes through the first cylindrical lens 34 of the first imaging optical system and enters the rotary polygon mirror 31. The reflected light from the rotating polygon mirror 31 is transmitted to an fθ lens 32 and a second cylindrical lens 33.
And scans the peripheral surface of the photosensitive drum 31 with a predetermined spot diameter at a predetermined pitch in the sub-scanning direction. The main scanning direction has already been finely adjusted by an adjustment mechanism (not shown). For synchronization detection for each line, the light beam before scanning is
The light is incident on the index sensor 38 via.

FIG. 4 is a perspective view showing the arrangement of the belt photoreceptor 10 and the photo sensors 19A and 19B.

An endless (endless) belt photoreceptor 10 having a seam has a double arrow direction (sub-scanning direction) as shown in the figure.
Is rotated. In the vicinity of both side edges of the belt photoreceptor 10, 2
The light reflection type photosensors 19A and 19B are arranged in parallel in the direction indicated by the arrow (main scanning direction).
The photo sensors 19A and 19B are seam detection sensors for detecting seams of the rotating belt photoreceptor 10 and forming an image in an area other than the seam so that an image is not formed in the seam area. is there.

Further, at least an endless belt photoconductor 1
In a color image forming apparatus having 0, a color registration sensor is required to accurately overlap images of a plurality of colors.

According to the first aspect of the present invention, the joint detection sensor (photo sensor) and the color registration sensor (photo sensor) can be detected by a pair of photo sensors 19A and 19B.

That is, as described above, in a color image forming apparatus requiring a seam detection sensor and a color registration sensor, separately installing each photosensor has a space problem.

Since each of the photosensors does not greatly differ in function, it is possible to integrally reduce the space in the apparatus occupied by the photosensors. However, a new problem arises when each photosensor is integrally formed.

The photosensors 19A and 19B in which the seam detection sensor and the color registration sensor are integrated detect the seam detection mark M1 of the endless belt photoconductor 10 and the registration mark M2 formed on the belt photoconductor 10. Then, each detection purpose is reached.

However, when each sensor is integrated, if the seam detection mark M1 and the registration mark M2 formed on the endless belt photoreceptor 10 are formed in the same form, which mark is used? Indistinguishable.

Therefore, the seam detection mark M1 and the registration mark M2 have different shapes, specifically, the widths in the sub-scanning direction are different. That is,
The width A of the seam detection mark M1 in the sub-scanning direction is about 2 mm
The width B of the registration mark M2 in the sub-scanning direction is set to 0.2 to
It was set to 0.5 mm. The shape of the registration mark M2 is not limited to the F-shaped pattern shown in the figure, and may be another appropriate shape.

Further, the joint detection mark M1 is formed of a paint and the registration mark M2 is formed of a developer, so that each sensor is formed as a single integrated photosensor 19A, 19B. Also, each mark can be distinguished and detected, and the purpose of each sensor can be achieved.

The formation of the registration mark M2 is performed when power is turned on, when a control signal is generated based on information on temperature rise in the apparatus by the temperature sensor inside the apparatus, or when a manual setting is performed, or when non-image formation is performed. That is, the seam detection mark M1 formed at the seam of the belt photoconductor 10 is
A, 19B, after detecting, the charger 11 (Y,
M, C, K) and the image exposure device 13 (Y, M, C, K) are simultaneously performed to form four types of latent images on the rotating belt photoreceptor 10. However, development is not performed by the developing device 14 (Y, M, C), and four kinds of latent images are formed by the final developing device 14K to form a black toner image. Note that the formation of the toner image is not limited to black, and the photo sensor 19
If A and 19B can be detected, another developing device 14
(Y, M, C).

The toner images of the four types of registration marks M2 (Y, M, C, K) formed on the belt photoreceptor 10 shown in FIG. Unit 11 (Y, M, C, K), image exposure apparatus 1
3 (Y, M, C, K) and a developing device 14K. This registration mark M2 (Y, M, C,
K) are sequentially read by the photosensors 19A and 19B, and the registration mark M2 (Y, M, C,
K), the passage timing is measured, and a predetermined interval C1 = C2
= C3 is determined.

FIG. 5 is a plan view showing another shape of the registration mark M2 (Y, M, C, K) formed on the belt photoreceptor 10. FIG.

Each registration mark M2 (Y, M, C, K)
Are formed by four consecutive V-shapes. When the belt photoreceptor 10 rotates in the direction indicated by the arrow, the photo sensor 1
Reference numerals 9A and 19B generate detection signals at positions intersecting with the registration marks M2 (Y, M, C, K) on the scanning lines shown by broken lines in the figure. As an example, the registration mark M2
The four letter-shaped shapes of (Y) are the photo sensors 19A, 19A.
When passing through the optical paths of B respectively, a detection signal is generated, and the pitches D1, D2, D of the registration marks M2 (Y) are generated.
3 to calculate the average value and calculate the registration mark M2
The measurement accuracy is improved by setting the representative value of the passing position of (Y). Other registration marks M2 (M), M2
(C) and M2 (K) similarly form a plurality of squares.

Further, a pair of left and right photo sensors 19A and 19B are provided in a direction orthogonal to the rotation direction of the belt photoconductor 10, and a pair of left and right registration marks M2 (Y) are formed on the belt photoconductor 10. Then, registration mark detection in which the deviation error of the belt photoconductor 10 is corrected is obtained. Similarly, the other registration marks M2 (M), M2 (C), M2 (K) are formed in a pair on the left and right.

FIG. 6 is a detection circuit diagram including the photosensors 19A and 19B. The photosensors 19A and 19B are reflection-type optical sensors each including a light-emitting portion and a light-receiving portion, and detect a registration mark M2 formed on the endless belt-shaped belt photoconductor 10 in order to accurately superimpose images of a plurality of colors. It is a sensor that also serves as a seam detection sensor that detects the position of the seam of the belt photoconductor 10.

There is a difference between the reflectance of the surface of the belt photoconductor 10 illuminated by the light emitting portions of the photosensors 19A and 19B and the reflectance of the seam detection mark M1 and the U-shaped registration mark M2 on the belt photoconductor 10. There is. Specifically, the reflectance of the joint detection mark M1 and the registration mark M2 is set lower than the reflectance of the surface of the belt photoconductor 10. Alternatively, in the circuit of FIG. 6, the detection output of the light receiving portion of the joint detection mark M1 and the registration mark M2 is set to be lower than the detection output of the light receiving portion on the surface of the belt photoreceptor 10.

FIG. 7 shows a flowchart of the color registration correction algorithm. Hereinafter, the process of color resist correction will be described.

(1) Prior to image formation, color registration correction is started as required. First, power is turned on, and the belt photoconductor 10 is rotated.

(2) When the seam detection mark M1 painted on the seam of the rotating belt photoreceptor 10 passes through the photo sensors 19A and 19B near the transfer roller 17, a detection signal is issued, and the passage of the seam is detected. You.

(3) The belt photoreceptor 10 is further rotated by a predetermined distance from the seam detection, and registration marks M2 (Y) and M2 are formed in the image forming area on the belt photoreceptor 10.
(M), M2 (C), and M2 (K) black toner images are formed. This image is formed by the charger 11 (Y, M, C, K), the image exposure device 13 (Y, M, C, K), and the developing device 14K.

(4) The rotation of the belt photoreceptor 10 causes the registration marks M2 (Y), M2 (M), M2
The black toner images of (C) and M2 (K) are
9A and 19B, each registration mark M2
The formation position of (Y, M, C, K) is detected, and a detection signal is sent to the control unit.

(5) The control unit performs a color registration algorithm process. FIG. 8 shows the photo sensor 19.
A, 19B registration mark (F-shaped pattern) M
FIG. 4 is a diagram showing a detection position and a detection signal of No. 2; A registration signal (a square pattern) M2 on the belt photoreceptor 10 is detected by the two photo sensors 19 to generate a detection signal,
Based on the pattern of the first color, the main scanning start point, the sub-scanning start point, the relative unit inclination, and the relative lateral magnification are detected to calculate the shift amount, and the color shift correction processing in the sub-scanning direction and the main scanning direction is performed. Do. Further, the writing timing at the time of image formation is corrected by the correction amount of the detected shift amount.

(6) Store the registration correction data in the NVRAM. The color misregistration data of the four colors of Y, M, C, and K is stored in the SRAM connected to the registration information storage FPGA.

(7) After the above color registration correction processing is completed, a normal image forming process is started, and a composite image of each color (Y, M, C, K) corrected for registration is output at the time of image output. .

In the above embodiment, the description has been made of the belt photoreceptor having a seam as the image carrier. However, the present invention is not limited to this, and the charging device, the image exposing device, the developing device, etc. The present invention is also applicable to a transfer belt having a seam in a tandem-structure color image forming apparatus including a plurality of image forming units. Alternatively, the present invention can be applied to a color image forming apparatus provided with an intermediate transfer member having a seam.

The present invention is not limited to the above-described embodiment, but includes an endless belt-shaped image carrier having a seam (including an electrostatic recording medium) and a plurality of developing devices (wet developing device, ion developing device, (Including a flow control system).

[0057]

According to the color image forming apparatus of the present invention, it is possible to always obtain a stable high-quality image without color misregistration irrespective of a change in environmental temperature, even in a high-speed color image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color printer equipped with a plurality of image exposure apparatuses according to the present invention.

FIG. 2 is a perspective view showing an embodiment of an image exposure apparatus.

FIG. 3 is a plan view of the image exposure apparatus.

FIG. 4 is a perspective view of an image exposure apparatus.

FIG. 5 is a plan view showing an arrangement of a belt photoconductor and a sensor.

FIG. 6 is a detection circuit diagram including a photosensor.

FIG. 7 is a flowchart of a color registration correction algorithm.

FIG. 8 is a diagram showing a detection position and a detection signal of a registration mark M2 by a photo sensor.

[Explanation of symbols]

Reference Signs List 10 Endless belt-shaped image carrier (belt photoconductor) 11Y, 11M, 11C, 11K Scorotron charger (charger) 13Y, 13M, 13C, 13K Image exposure device (latent image forming means) 14Y, 14M, 14C, 14K Development Apparatus 17 Transfer device (transfer roller) 19A, 19B Photosensor (seam detection sensor, color registration sensor) A Width of seam detection mark M1 in sub-scanning direction B Width of registration mark M2 in sub-scanning direction L Light beam M1 Seam detection mark M2 (Y, M, C, K) Registration mark (F-shaped pattern)

Claims (3)

[Claims] 1. A color image forming apparatus comprising: a plurality of latent image forming means for forming a latent image on an endless belt-shaped image carrier; and a plurality of developing devices for developing a latent image on the endless belt-shaped image carrier. A registration sensor for detecting registration marks formed on the endless belt-shaped image carrier in order to accurately superimpose toner images of a plurality of colors; and a seam for detecting a position of a seam of the endless belt-shaped image carrier. A color sensor, wherein a sensor serving also as a detection sensor is provided, and a seam detection mark having a form different from that of the registration mark is formed on the endless belt-shaped image carrier. Image forming device. 2. The color image forming apparatus according to claim 1, wherein the seam detection mark and the registration mark have different widths in the sub-scanning direction. 3. The color image forming apparatus according to claim 1, wherein the joint detection mark is formed by a paint, and the registration mark is formed by a developer in a developing device.