JPH05232776A - Image forming device - Google Patents

Abstract

PURPOSE:To generate good image with less chromatic misconvergence in a color image forming device by enhancing the accuracy in the position coordination of the decomposed color image. CONSTITUTION:A photo-sensitive substance belt 15 is set over rotary rollers 16, 17, and between them a back plate 18 having a curvature is provided. The belt 15 is furnished directly under its peripheral edge with a convex guide member 41, revolved while a fitted sliding state is kept with a guide groove 40 which is formed in the back plate 18 to serve as reference, and transported with the motion restrained while receiving a force to shift the belt always in the width direction to the specific side of its side line through the action of the tension strength due to a tension roller 19, and there is less risk of dislocation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION As an image forming method for obtaining a color image using electrophotography, a latent image is repeatedly formed and developed according to the number of separated colors of an original image read by a color scanner on an image forming body. There is a color image forming apparatus that obtains a color image by superposing a color toner image on the formed body and then transferring the color toner image. In such an image forming apparatus, a belt-shaped image forming body is used as an image forming body, and the number of separated colors (for example, three colors of yellow, magenta, cyan, or four colors including black) is provided around the forming body. There is one in which an appropriate exposure device and developing device are provided. The present invention relates to a color image forming apparatus including the belt-shaped image forming body.

[0002]

2. Description of the Related Art As an image forming method for obtaining a color image using an electrophotographic method, for example, JP-A-60-75850 and JP-A-60-7676 are known.
6, same 60-95466, same 60-95458, same 60-158475, Japanese Patent Application 2-27
There are 2546. A tension roller is attached to a belt-shaped image forming body in which a photoconductor is applied or vapor-deposited on a flexible belt, and the tension roller is rotated while maintaining a sliding contact state with respect to a reference back plate member. As a result, in the color image forming apparatus configured to convey the belt-shaped image forming body while always keeping the surface at a constant position, the belt-shaped image forming body is surrounded by a charger, an exposure device, and a color separation number. An image forming means including a plurality of developing devices accommodating different color toners (yellow, magenta, cyan, black) is arranged, and the image forming means are arranged at a constant interval around a belt-shaped image forming body which rotates. It is common to do. Image forming methods of the image forming apparatus having the belt-shaped image forming body include a one-pass method and a multi-turn method. The former is a method for forming an image by repeating latent image formation and development according to the number of separated colors while the belt-shaped image forming body makes one rotation and the forming body makes many rotations. However, in both cases, due to the meandering of the belt on the left and right, it is difficult to align the next separated color image with the immediately preceding separated color image without color shift.

[0003]

Although the following description will be given by the one-pass method, the multi-rotation method, which is the only exposure apparatus configuration, is also effective. In a color image forming apparatus, for example, by forming a registration mark on a belt-shaped image forming body, detecting the registration mark by a sensor, and sequentially starting exposure from a plurality of exposure devices arranged based on the detection, It is conceivable to start latent image formation at the same point on the image forming body.

However, in the color image forming apparatus described above, the registration mark formed on the belt-shaped image forming body is read by a single sensor or a plurality of sensors to determine the timing of starting the exposure from each exposure apparatus. Requires that the distance between the sensor and the exposure device and the arrangement distance between the plurality of exposure devices be positioned with strict accuracy. However, in practice, the array spacing of these multiple sensors and exposure devices must be set with strict mechanical accuracy (at the time of filing of this application, ± 0.3 to 0.5 mm).
Even if it is positioned, if you do not deal with the lateral displacement due to the meandering of the left and right belts, you will lack the painting dragon dot.

Further, in the color image forming apparatus which forms the color toner image by superposing the toner images on the image forming body as described above, the exposure start position on the belt-shaped image forming body is formed from a plurality of exposing devices. Has a problem that the image quality of the color toner image is deteriorated when the deviation cannot be set in a unit of one pixel, for example, about 80 μm or less. The problem now is the use of belt-like imagers, so alignment control is more difficult than with drum-like imagers.

In view of the above-mentioned problems of the prior art, the present invention ensures that the arrangement interval of the exposure apparatus positioned with strict mechanical accuracy works stably for the alignment of the separated color images, that is, a plurality of times. Provided is a color image forming apparatus for the purpose of guarding lateral deviation and flexure of a belt-shaped image forming body, which causes a shift of an exposure start point of latent image formation and a color shift resulting from the repetition of latent image formation. Especially.

[0007]

SUMMARY OF THE INVENTION The present invention for achieving the above object is to rotate a belt-shaped image forming body to a specific side of a side line while keeping the state in which the forming body is always aligned. In addition to the above, the laser scanning is performed from the side of the specific side line that is width-shifted, so that the starting point of the laser scanning is limited to a certain line. That is, the starting point of the laser scanning start is to be secured on the line on the belt-shaped formed body parallel to the specific side line. Further, this means can be applied to the one-pass method and the multi-turn method.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the main structure of a color copying machine which is a color image forming apparatus provided with a belt-shaped image forming body as an embodiment of the present invention. This color copying machine is roughly classified into an image reading system A and an image forming system B.
It consists of The image forming system B of the color image forming apparatus according to the present exemplary embodiment includes a plurality of charging units, a plurality of exposing units, and a plurality of developing units in which toners of four different colors are loaded around the belt-shaped image forming body. Image forming means is arranged, and a yellow image, a magenta image, a cyan image, and a black toner image are superposed by one rotation of the belt-shaped image forming body to form a color image.

First, the reading system A will be described with reference to FIG. 1, which is a main structural view of a color copying machine.

In the reading system A, a document placed on the document table 11 is illuminated by a halogen lamp 121 mounted on a carriage 12 that slides in the horizontal direction. Mirrors 131 and 132 are attached to the movable mirror unit 13, and they slide in the same horizontal direction, and in combination with the mirror 122 attached to the carriage 12, the optical image of the document is sent to the lens reading unit 14. Derive.

The carriage 12 and the movable mirror unit 13 are driven via wires (neither shown) connected to a stepping motor, and the speed ratio of each is 2:
It is set to 1 and is slid in the same direction.

The lens reading unit 14 has a lens 141 and a color CCD 142 at an image forming position behind the lens 141. CC
The document is color-separated into color image data of blue image data (B), green image data (G) and red image data (R) by D142, and is output to the image processing means 50 described later.

The image processing means 50, as shown in FIG.
The D / D conversion units 501B, 501G, 501R, the complementary color conversion unit 502, the black component extraction unit 503, the masking unit 504, and the image memory unit 505.

The A / D converters 501B, 501G and 501R are CCD14
Converts color image data consisting of blue (B), green (G), and red (R) image data input from 2 or monochrome image data (BK) into image data of, for example, 256 gradation digital signals. And outputs it to the complementary color conversion unit 502 described later.

The complementary color conversion unit 502 performs complementary color conversion of the digital signal of the color image data among the digital signals converted by the A / D conversion unit 501 to obtain yellow (Y), magenta (M),
Cyan (C) image data is obtained.

The black component extraction unit 503, for example, removes undercolor (U
The image data of (Y), (M), and (C) obtained by the complementary color conversion unit 502 is converted into black (B _K )
Image data of.

The masking unit 504 is (Y) after UCR,
Color correction is performed on the image data of (M) and (C).

The image memory unit 505 is composed of (Y), (M) and (C) image data color-corrected by the masking unit 504 and (B _K ) image data extracted by the black component extracting unit 503. The color image data is stored.

That is, after the image processing means 50 performs complementary color conversion, black component extraction, and color correction, a yellow (Y) image signal as the first color and magenta (M) as the second color.
Image signal, a cyan (C) image signal as a third color, and a black (B _K ) image signal as a fourth color are output to laser writing systems 24-27, which are exposure units described later.

Next, with respect to the image forming system B, based on FIG. 1 which is a main configuration diagram of a color copying machine, FIG. 3 which is a perspective view of a belt-shaped image forming body and FIG. 4 which is an arrangement configuration diagram of a laser writing system unit. Explain.

The belt-shaped image forming body 15, that is, a belt-shaped image forming body (hereinafter referred to as a photoconductor belt) 15 in which a photoconductor is applied, vapor-deposited or mounted on a flexible belt is a rotating roller.
A back plate member 18 having a curvature is provided between the rotating rollers 16 and 17 while being stretched between the rotating rollers 16 and 17. Further, the photosensitive belt 15 is provided with a convex guide belt 41 immediately below its peripheral edge, and a concave guide groove of the back plate member 18 serving as a reference.
While rotating while keeping the mating sliding contact with 40,
Due to the balance of the tension strength by the tension roller 19, the photoconductor belt 15 is always regulated and conveyed while being subjected to the force of moving the photoconductor belt 15 to the specific side of its side line. In order to convey the photosensitive belt 15 in close contact with the rotating rollers 16, 17 and the tension roller 19, although not shown, the rotating rollers 16, 17 and the tension roller 19 are not shown.
It is needless to say that a concave guide groove may be provided on the surfaces of the rotating rollers 16 and 17 and the tension roller 19 in order to fit the convex guide belt 41 of the photoconductor belt 15 with the concave guide groove. With the above-described structure, the photosensitive member on the outer peripheral surface of the photosensitive belt 15 is always kept in a constant relation position with respect to the surface of the back plate member 18 even during conveyance, and the image forming surface having a stable curvature is vertically long and wide. Since it is possible to secure the structure, it is possible to arrange a plurality of image forming means having the same shape at a constant interval. Further, as shown in FIG. 3, the back plate member 18 is provided with a concave guide groove 40, and a convex guide belt 41 attached to the peripheral edge of the photosensitive belt 15 is fitted and slid into the guide groove 40. The means 20 to 23 and the developing means 28 to 31 and the photoconductor belt 15 can be kept at a constant distance, and a stable and good image can be formed as described later. It is preferable that the direction in which the photoconductor belt 15 approaches is opposite to the scanning reference side of the laser beam. The photoconductor belt 15 hits the guide groove 40 in a state of receiving the width-shifting restricting force, and is regulated in an equilibrium state, and the convex portion of the guide belt 41 of the hit belt 15 is stably maintained. Therefore, the reference for starting the laser scanning on the photoconductor belt 15 is provided on the side of the belt 15 which is close to the width. Further, although the tension roller 19 is used as the width adjusting means, one of the rotating rollers 16 and 17 can be used as the tension roller together.

As shown in FIG. 3, the photoconductor belt 15 has a transparent hole or a light-transmissive film in a transparent hole on the upstream side in the main scanning direction at a predetermined distance from the bonded portion 151 of the photosensitive surface of the photosensitive belt 15. And a resist mark 152 that transmits laser light is attached. The registration mark 152 serves as a reference for determining the exposure start position in the main scanning direction and the sub-scanning direction by using the photosensors FS1 to FS4, which will be described later, as the detection of the bonded portion. As shown in the drawing, the back plate 18 has recesses formed at both ends thereof, and photosensors FS1 to FS4 are arranged in the recesses as light detecting means. Photosensors FS1 to FS4 register the exposure light from the exposure device as a registration mark.
The transmitted light is detected through 152. In addition, a reflection member is provided on the photosensitive belt 15 as a registration mark,
It goes without saying that the photo sensor may receive the reflected light from the exposure light.

Around the photosensitive belt 15, a plurality of charging means, a plurality of exposing means, four developing means loaded with toners of different colors, a transferring means and a cleaning means are arranged.

The charging means is provided to uniformly charge the photosensitive layer on the surface of the photosensitive belt 15 with a predetermined polarity, and is the existing chargers 20 to 23 such as a corona charger and a scorotron charger.

The exposing means are semiconductor laser writing system units 24-27, and expose the surface of the photosensitive belt 15 charged by the chargers 20-23 to form an electrostatic latent image.

The developing means is composed of four developing devices containing different color developers, for example, yellow (Y), magenta (M), cyan (C) and black (B _K ) color toners (developer), respectively. 28-31. Each of these developing devices 28-3
1. It has a function of developing an electrostatic latent image on the photosensitive belt 15 into a toner image by a non-contact developing method. Unlike the contact development method, this non-contact development method does not damage the previous toner image formed on the photoreceptor belt 15, and
Since the movement of 15 is not hindered, a good color image can be obtained.

The transfer means transfers the toner image formed on the photosensitive belt 15 onto the transfer material by the transfer device 32 such as a transfer corona discharger.

The cleaning means 33 has a cleaning blade 331 and a cleaning roller 332, and is brought close to the surface of the rotating roller 17 and brought into pressure contact with the surface of the photosensitive belt 15 only during cleaning, so that the surface of the photosensitive belt 15 is pressed.
Provided to clean 15.

The recovery box 34 is for recovering and storing the residual toner on the photosensitive belt 15 removed by the cleaning means 33 through the toner recovery tube 341.

In this embodiment, each process of the photoconductor belt 15, the charging devices 20 to 23, the developing devices 28 to 31 containing toner of each color, the cleaning means 33, and the toner collecting box 34, which constitute the above-mentioned image forming portion, is carried out. The parts are housed in an integrated cartridge 35 to be unitized, and can be collectively attached to and detached from the apparatus main body.

The color image forming process by the image forming system B having the above-mentioned structure is performed as follows.

First, when the image signal of the first color output from the image reading system A is input to the laser writing system unit 24, the semiconductor laser 241 in the laser writing system unit 24 produces a laser beam. The laser beam is rotationally scanned by the polygon mirror 243 rotated by the drive motor 242, and the fθ lens 244 and the mirror 24 are scanned.
5, passing through the cylindrical lens 246 and the dustproof glass 247, projected onto the peripheral surface of the photoconductor belt 15 that has been uniformly charged to a predetermined charge by the charger 20 to form a bright line.

On the other hand, in the sub-scanning direction, the photosensor FS1 detects the registration mark 152 corresponding to the specific position of the photosensitive belt 15, and the modulation of the semiconductor laser 241 by the image signal is started based on this detection signal. The main scanning line to be processed is determined. When the scanning is started, the laser beam is detected by the photo sensor FS1 in the main scanning direction, and the semiconductor laser 241 is started to be modulated by the image signal of the first color based on the detected signal and is modulated. The laser beam scans the surface of the photosensitive belt 15.
Therefore, the photosensitive belt 15 is uniformly charged by the main scanning by the laser beam and the sub-scanning by the conveyance of the photosensitive belt 15.
A latent image corresponding to the first color is formed on the surface of the. This latent image is developed by the developing device 28 containing the yellow toner, and a yellow toner image is formed on the surface of the photoconductor belt 15. After that, the photoconductor belt 15 is conveyed while holding the yellow toner image on its surface, and then the second belt is continuously fed.
Enter the color image formation.

That is, the photosensitive belt 15 on which the yellow toner image is formed is re-charged when it is conveyed to the next position of the charger 21, as in the case of the image signal of the first color described above. 21 is charged, and then the registration mark 152 corresponding to a specific position on the photoconductor belt 15 is attached to the photo sensor FS2.
Is detected, the modulation of the semiconductor laser of the laser writing system unit 25 by the image signal of the second color is started on the basis of this detection signal, and the laser beam generated by the semiconductor laser 251 in the laser writing system unit 25 is detected. The photoconductor belt 15 is rotated and scanned by a polygon mirror 253 rotated by a drive motor 252, passes through an fθ lens 254, a mirror 255, a cylindrical lens 256, and a dustproof glass 257, and is uniformly charged to a predetermined charge by a charger 21. A latent image is formed by being projected on the peripheral surface of the. The latent image is developed by the developing device 29 containing magenta toner as the second color. The magenta toner image is formed in the presence of the already formed yellow toner image.

Similarly, the photosensitive belt 15 on which the yellow and magenta toner images of the first and second colors have been formed and further conveyed is the same as in the case of the image signals of the two colors described above. , Is continuously uniformly charged by the charger 22,
A latent image is formed by the laser writing system unit 26, and is developed by a developing device 30 containing cyan toner to form a cyan toner image. Further, the photoconductor belt 15 on which the cyan toner image of the third color is formed is further conveyed and is uniformly charged by the charger 23 as in the case of the image signals of the second and third colors. A latent image is formed by the laser writing system unit 27, and a color toner image is formed by superposing the black toner images by developing with a developing device 31 containing black toner. That is, a color toner image is formed during one rotation of the photoconductor belt 15.

A direct current or an alternating current bias is applied to each of the developing devices 28 to 31, and reversal development (jumping development) is carried out in a non-contact manner on the photoreceptor belt 15 whose base is grounded.
Is to be done. For this non-contact development, either one-component developer or two-component developer can be used. When a one-component developer is used, it is not necessary to provide a toner concentration control means and the size can be reduced. However, the development method using a two-component developer is superior in terms of development stability, and therefore, color reproduction is improved. preferable.

As described above, the color toner image formed on the surface of the photoconductor belt 15 is supplied from the paper feed cassette 42 by the paper feed roller 36 and is transferred by the timing roller 37 to the transfer material which is in timing with the color toner image. Transcribed. The transfer unit 32 applies a high voltage power source having a polarity opposite to that of the toner to transfer the toner.

Thus, the transfer material on which the color toner image has been transferred is reliably separated by the photosensitive belt 15 which rapidly changes direction (small diameter curvature) along the driving roller 16 and melts the toner by the fixing means 38. After being fixed, the paper is discharged from the apparatus main body by the paper discharge roller 39.

On the other hand, after the transfer of the color toner image onto the transfer material, the photosensitive belt 15 is further conveyed in the clockwise direction,
Cleaning blade 331 and cleaning roller 332
The residual toner is removed and cleaned by the cleaning means 33 in the pressure contact state. After the cleaning is completed, a new image forming process is started again.

Next, the position adjustment (correction) for eliminating the positional deviation of each color of the color image will be described.

In the position adjustment in this embodiment, the image signal of a specific patch is output, and the yellow, magenta, cyan, and black colors of the specific patch are printed on the transfer material by the image forming method by the image forming system B described above. An image is created, and then the image of the specific patch is read by the image reading system A described above, the positional deviation of each color is detected and calculated, and the mirrors 245, 255, 265, 2 of each laser writing system unit 24-27 are detected.
Correct the positional deviation with 75 etc.

This correction is performed by (i) making the scanning lines in the main scanning direction by each laser writing system unit parallel (rewriting writing to be parallel), and (ii) making the interval between each laser writing system unit appropriate (sub-writing). Correct the scanning interval), (ii
i) The scanning width in the main scanning direction by each laser writing system unit is made constant, and (iv) the writing start position of each laser writing system unit in the main scanning direction is adjusted (correction of the deviation in the main scanning direction is performed).

First, the formation of a color image of a specific patch will be described.

As for the specific patch, an image is formed on both ends of one main scanning line by using the patch of the reference color with an arbitrary color (toner color) among the colors of yellow, magenta, cyan and black as a reference. , Images of other color patches are formed on both ends of the same main scanning line as the reference patch. That is, an image is formed on the transfer material P as a patch pair of a reference color patch and another color patch at both ends of the same scanning line. In this embodiment, as shown in FIG. 5, a black patch is used as a reference patch, and black (B _k ) and yellow (Y), and black (B _k ) and magenta.
An image is formed on the transfer material P using (M), black (B _k ) and cyan (C) as patch pairs. However, if the alignment of the laser writing system units 24 to 27 is proper (accurate) at this time, the patch pairs will be completely overlapped, but in FIG. It shows the state of being.

Each of the patch pairs described above uses the laser writing system units 24 to 27 before position adjustment to store image data so as to form patch images of the patch pair at the same position in both the main scanning direction and the sub scanning direction. (Not shown)
Stored in advance.

Further, when forming an image of a specific patch, by pressing a position adjustment button (neither is shown) of the operation panel provided on the apparatus main body, the normal mode of the color image forming process described above is performed. Switch to position adjustment mode. The position adjustment mode is a mode in which a patch image is called from the patch memory and image formation is performed by the normal color image forming method.

The operation of forming the patch image is started by pressing a copy button (not shown) provided on the operation panel. Then, as shown in FIG. 5, each patch pair is formed on the recording paper.

Subsequently, the transfer material P on which the color image of the above patch pair is drawn is placed on the original table 11, and when the copy button on the operation panel is pressed again, the halogen lamp 121 irradiates the transfer material P, The image is read by the reading unit 14 as image data. Then, the read image data is converted to A / by the image processing means 50 as shown in FIG.
Image processing is performed as a color image signal by D conversion, complementary color conversion, black component extraction, and color correction, and position adjustment is performed based on this image signal. Black component extraction at this time is 100% UCR
By performing the above, each patch can be separated.
That is, the read image signal is input to the patch pair detection unit 51 based on the position adjustment mode, and ( _Bk ) and (Y), ( _Bk ) and (M), ( _Bk ) and (C), Each patch pair is identified and the positional relationship is detected.

The positional deviation amount of each patch pair is calculated in the positional deviation calculation unit 52 from the positional relationship between the patches of each color identified by the patch pair detection unit 51 and the reference patch, and the amount of deviation is stored in the CPU's deviation memory unit. Then, based on this deviation amount, the ROM 53a
The correction amount is obtained from the CPUs 53 and 55, and the position of each laser writing system unit is adjusted. As the type of this positional deviation, the distances between the patches at both ends and the corresponding reference patches are different (the lines connecting the patches of each color are not parallel)
If the patch pair is shifted in the sub-scanning direction (the patch pair in the middle of FIG. 5), if the patch pairs have different lengths in the main scanning direction (main scanning width), the patch pairs are in the main scanning direction. There is a case where there is a deviation (patch pair in the lower part of FIG. 5). By correcting the positional relationship among these items, the above corrections (i) to (iv) are performed.

Here, the patch pair detecting section 51 will be described. It should be noted that since any of the patch pairs of (Bk) and (Y), (Bk) and (M), and (Bk) and (C) described above perform position shift detection and position correction in the same manner, In the embodiment detailed below, only the patch pair of (Bk) and (Y) will be described as an example.

FIG. 6A shows a case where the patch pair created by the above-mentioned position adjustment mode has all of the above-mentioned positional deviations. In the obtained image, the upstream side in the main scanning direction of the (Bk) patch is Bk ₁ , the downstream side in the main scanning direction is Bk _2, and similarly, the upstream side in the main scanning direction of the (Y) patch is Y.
₁ and the downstream side in the main scanning direction is Y ₂ .

The patch pair detecting section 51 identifies each patch pair from the image signal image-processed by the image processing means 50 for the patch pair on the transfer material P shown in FIG. 6, and detects the positional relationship described below. ..

X ₁ : distance in the sub-scanning direction from Bk ₁ to Y ₁ x ₂ : distance in the sub-scanning direction from Bk ₂ to Y ₂ y ₁ : distance in the main-scanning direction from Bk ₁ to Y ₁ y ₂ : Bk ₂ to Y _{2 in} the main scanning direction y _B : Bk ₁ to Bk ₂ distance where x ₁ and x ₂ are upstream of Bk ₁ and Bk _{2 in the} sub scanning direction, respectively. Value, the downstream side is a positive value, and similarly, when y ₁ and y ₂ are upstream of Bk ₁ and Bk _{2 in the} main scanning direction, respectively, a negative value and a downstream side are positive values.

Next, the position shift calculator 52 will be described.

In the position shift calculation section 52, the main scanning line L _{Bk of Bk} connecting Bk ₁ and Bk ₂ and the main scanning of Y connecting Y ₁ and Y ₂ are detected based on the value detected by the patch pair detecting section 51. The angle θ with the line L _Y is calculated.

In addition, L of the patch pair shown in FIG.
Under the assumption that _Bk and L _Y are parallel (θ = 0), L _Bk
And L _Y in the sub-scanning direction x ₁ '(= x ₂ '), Bk ₁ and Y ₁
Calculates a main scanning direction distance y ₁ 'and Bk ₂ and Y ₂ distance in the main scanning direction and y _2' to the (Figure 6 (b)).

Further, the L of the patch pair shown in FIG.
Under the assumption that _Bk and L _Y are parallel (θ = 0) and the distance between Y ₁ and Y ₂ is the same as the distance between Bk ₁ and Bk ₂ , Bk
A distance y ₁ ″ between ₁ and Y ₁ in the main scanning direction, and Bk ₂ and Y ₂
And a distance y ₂ ″ (= y ₁ ″) in the main scanning direction is calculated (FIG. 6D).

The respective values of x ₁ , x ₂ , y ₁ , y ₂ , y _B detected by the above patch pair detecting section 51 and the position shift calculating section 52
Θ, x ₁ '(= x ₂ '), y ₁ ', y ₂ ', y ₁ ”calculated in
For each value of (= y ₂ ″), a correction amount by a motor described later is obtained by using a table value in the ROM 53a, and a CPU 53 described later,
The correction amount is input to 55. The CPUs 53 and 55 perform the adjustment (correction) of the positions (i) to (iv) based on the shift amount input from the patch pair detection unit 51 and the position shift calculation unit 52 described above.

Of the position adjustments (corrections) in this embodiment
(i) and (ii) are the laser writing system units 24-27.
This is done by moving the mirrors 245, 255, 265, 275 of.

First, here, the laser writing system unit 2
The configuration of 4, 25, 26 and 27 will be described based on FIG. 7. Since the laser writing system units 24, 25, 26, 27 all have the same configuration and function, the laser writing system unit 24 corresponding to a yellow image will be described here as an example.

An image signal is input to the laser writing system unit 24, and the laser beam generated by the semiconductor laser 241 is rotationally scanned by the rotating polygon mirror 243, and the fθ lens 244, the mirror 245, and the cylindrical lens 2
An image is formed on the photosensitive belt 15 via 46. On the other hand, the beam detect detector 249 detects the laser beam generated from the semiconductor laser 241 via the mirror 248.

Next, the mirror 245 is shown in FIGS.
Based on.

The mirror 245 is integrally formed with one end held by a holding member 245a. The holding member 245a is
It is pivotally supported on the support 245b by a rotating shaft 245c,
It is rotatable with the mirror 245. The support 245b has one end rotatably supported by a bearing (not shown) of the apparatus body by a support shaft 245d, and the other end supported by a shaft 245e of a motor M1 which is a pulse motor provided in the apparatus body. Has been done.

The rear surface of the mirror 245 is fixed to the shaft 245f of the motor M2, which is a pulse motor,
The male threaded shaft 245f is moved forward and backward by the rotation of the rotor M2a of the female threaded motor M2. The motor M2 is provided on the support 245b, and the support 2
With the support shaft 245d of 45b and the shaft 245e of the motor M1 as the rotation shafts, they rotate integrally with the support body 245b. That is, the rotation of the motor M1 causes the mirror 245 to support the support shaft 245.
d around the shaft 245e of the motor M1 in the direction B, and the mirror M245 is rotated by the rotation of the motor M2.
It can be rotated in the A direction around c. Further, the motors M1 and M2 are rotated by a driving unit 54 controlled by the CPU 53 with a pixel clock CLK described later in a direction to correct the deviation amount described below by an amount for correcting the deviation amount.

First, (i) parallelism adjustment (correction for making the scanning lines in the main scanning direction parallel by each laser writing system unit) will be described.

In order to make L _Bk and L _Y parallel, the CPU 5
3 is based on θ calculated by the position shift calculator 52,
It suffices if = 0. That is, the CPU 53
A signal is sent to the drive unit 54 to rotate the rotor M2a of the motor M2 shown in FIGS.
The angle θ formed by L _Bk and L _Y can be set to 0 by swinging in the direction A around the rotation axis 245c. At this time,
The amount of swinging of the mirror 245 can be finely adjusted by controlling the amount of rotation of the rotor M2a using the pixel clock CLK according to the angle θ formed by L _Bk and L _Y.
That is, the scanning lines in the main scanning direction by the laser writing system units are made parallel to each other within the accuracy of one scanning (see FIG. 6B).

Next, (ii) misalignment adjustment in the sub-scanning direction (correction to make the intervals between the laser writing system units suitable) will be described.

Therefore, in order to overlap L _Bk and L _Y , in the pair patch shown in FIG. 6B, L _Y must be moved to the upstream side in the sub-scanning direction. The movement of the L _Y, performed by controlling the drive unit 54 which receives a signal from the CPU 53, rotates the motor M1 which is shown in FIGS. That is, by rotating the motor M1, the mirror 245 can be rotated about the support shaft 245d and the shaft 245e, and L _Y can be overlapped with L _Bk (correction of deviation in the sub-scanning direction). The amount of deviation in the sub-scanning direction is x ₁ ′ calculated by the position deviation calculator 52. At this time, the rotation amount of the motor M1 can be finely adjusted by controlling the amount of rotation of the motor M1 by using the pixel clock CLK according to the shift amount x ₁ ′.

On the other hand, position adjustment (correction) in this embodiment
Of the positions (iii) and (iv), the beam detect detecting circuit 60, the registration mark detecting circuit 61, the CPU 55, the clock synchronizing circuit 56, and the counter 57 shown in FIG.
To use.

As shown in FIG. 7, the beam detect detection circuit 60 outputs the output signal from the beam detector 249, which receives the laser light incident through the mirror 248, to a rectangular beam detect signal BD based on an arbitrary set value. Is output.

The registration mark detection circuit 61 outputs a rectangular registration signal RL based on the peak value or an arbitrary set value of the output signal from the photosensor FS1 by the transmitted light that has passed through the registration mark by optical scanning with a laser. To do. The optical scanning by the laser for detecting the registration mark 152 does not have to be performed over the entire area, and may be limited to the area including the registration mark 152 based on the detection of the belt position by the reference mark or the encoder.

The CPU 55 outputs the output signal of the image signal with reference to the beam detect signal BD and the registration signal RL, and at the same time calculates the deviations y ₁ ', y ₂ ' of the main scanning width calculated by the position deviation calculator 52. Deviation amount y ₁ ″ in the main scanning direction,
Each deviation is corrected based on y ₂ ″.

The clock synchronization circuit 56 outputs a pixel clock synchronized with the output signal from the CPU 55.
An oscillation circuit 561 that generates a reference pixel clock, a frequency divider 562 that adjusts the frequency of the reference pixel clock, and a delay circuit 56 that generates a multiphase clock in which the phase of the reference clock is delayed.
3, a synchronization detection circuit 564 that detects the clock most synchronized with the phase of the output signal from the CPU 55, a clock selection circuit 565 that is synchronized from the output signal from the synchronization detection circuit 564 and the output signal from the delay circuit 563, and from the CPU 55 Output signal,
The pixel clock CLK from the clock selection circuit 565 is used by the CPU 55
And a counter 57 that outputs based on the output signal from the. That is, the counter 57 outputs the clock CLK for a predetermined time (time corresponding to the main scanning width of the image) after receiving the output signal from the CPU 55. An image signal is output based on this pixel clock CLK.

First, (iii) main scanning width adjustment (correction for making the scanning width in the main scanning direction constant by each laser writing system unit) will be described.

[0075] Adjustment of the main scanning width in the main scanning direction, by using the y ₁ 'and y _2' calculated by the positional deviation calculation unit 52, y
_{1 '-y 2'<0 (} Bk 1, if from the distance between the Bk ₂ Y _1, towards the distance between Y ₂ is long) if earlier the dot clock of the writing system, conversely, y ₁ '-y _{If 2} '> 0 (when the distance between Y ₁ and Y ₂ is shorter than the distance between Bk ₁ and Bk ₂ ), the pixel clock of the writing system is delayed so that the main scanning direction between Y ₁ and Y _{2 is} increased. Is the same as the distance between Bk ₁ and Bk _{2 in} the main scanning direction.

A high-frequency oscillator circuit 561 in the clock synchronization circuit 56 shown in FIG. 10 is a high-frequency clock and, for example, is a high-frequency oscillator circuit and oscillates a reference pixel clock. Further, the frequency divider 562 can change the frequency of the reference pixel clock of the high frequency oscillation circuit 561 by changing the frequency division ratio. This frequency division ratio is calculated by using y ₁ 'and y ₂ ' calculated by the position shift calculator 52,
In U55 (y ₁ ') - is (y _2') = 0 and becomes as set.

That is, the reference pixel clock is advanced,
The delaying adjustment can be performed by changing the frequency of the reference pixel clock given to each laser beam. Thus, the Y ₁ by changing the frequency
The distance between Y _{2 in} the main scanning direction and the distance between Bk ₁ and Bk _{2 in} the main scanning direction can be matched.

Next, description will be given of (iv) misalignment adjustment in the main scanning direction (correction for aligning the writing start position of each laser writing system unit in the main scanning direction).

The CPU 55 takes time t from the detection of the beam detect signal BD to the detection of the registration signal RL.
_i (i = 1, 2, 3, ...) Is clocked a plurality of times, and the average time t _a obtained by averaging these is stored in the register. Further, the deviation amount y ₁ ″ calculated in the main scanning direction in the position deviation calculation unit 52 is calculated and stored based on the scanning speed of the laser writing system unit 24. The deviation amount y _r is stored.
_{If 1} "is a positive value, this deviation time _tr is a positive value,
If y ₁ ″ is a negative value, t _r is a negative value. Then, the CPU 55 described above causes a new beam detect signal at the time of image formation.
After the BD is detected, the average time t _a is delayed by the stored shift time t _r (that is, delayed by t _a + t _r ).
Output the output signal. As a result, the deviation in the main scanning direction can be adjusted (corrected).

As described above, in the position adjustment mode, the adjustments (corrections) of the above (i) to (iv) can be performed with respect to the positional deviations of the above.

That is, each of the yellow, magenta, and cyan laser writing system units is adjusted to the correct position with respect to the reference black laser writing system unit, and no color shift occurs in the obtained color image on the recording paper. ..

When this position adjustment is completed, the position adjustment mode is released by pressing the position adjustment button on the operation panel again, and image formation is performed in the normal image formation mode.

In this embodiment, the black laser writing system unit is used as a reference, but the present invention is not limited to this, and any of yellow, magenta, and cyan laser writing system units may be used as a reference. Further, the position of the laser writing system unit serving as a reference may be adjusted by the operator himself.

Further, although the above-mentioned position adjustment may be performed only once, more accurate position adjustment can be performed by performing the position adjustment a plurality of times.

Further, in the present embodiment, the patches are formed at both ends of one scanning line, but it is not always necessary to form them at both ends, and it is sufficient that the positional deviation between the patch and the reference patch can be detected. However, more accurate position adjustment can be achieved by creating patches near both ends of the scanning line. It goes without saying that the positional deviation may be detected by creating a line instead of creating a patch.

Further, although the image reading system A of the apparatus main body is used for reading each patch pair image in this embodiment, the reading system A may be provided separately from the apparatus main body. Furthermore, in this embodiment, in the image adjustment mode,
Each patch pair was formed on the transfer material, but the reading means was arranged on the peripheral surface of the photoconductor belt, and each patch pair formed on the photoconductor belt (not only the toner image but also a fixed one) Needless to say, the position of each patch pair may be detected by directly reading. Further, in the present embodiment, the traveling regulation of the belt 15 is performed by the convex guide member 41 of the belt and the groove-shaped member 40 of the back plate, but regulation by other methods is also possible. For example, a flange (flange) is attached to the ends of the rotating rollers 16 and 17, and the tension is set so that the belt is pressed against the flange so as to be in equilibrium. May be regulated by The scanning reference of the laser is taken on the side where the belt abuts this collar.

[0087]

As described above, Japanese Patent Application No. 2-272546 discloses a plurality of exposure devices in a color image forming apparatus in which an image forming means including a plurality of exposure devices is arranged around a moving image forming body. Position is corrected to maintain the parallelism of the main scanning line,
In addition, for the purpose of correcting the deviation of the laser scan line width in the main scanning direction and preventing the exposure start point of latent image formation corresponding to the number of colors from deviating, the color deviation can be performed with a high accuracy of 1 dot width. The aim is to provide a color image forming apparatus that can prevent such a problem. That is, the detecting means for detecting the specific pattern output by the exposure device, the calculating means for calculating the positional deviation between the exposure devices of the specific pattern detected by the detecting means, and the positional deviation calculated by the calculating means. In order to prevent color misregistration by having control means for controlling the position of each of the exposure devices based on
It was not always possible to achieve the intended purpose due to the meandering of the rotating photoreceptor belt. According to the present invention, by sliding a convex guide member installed on the lower portion of the photoconductor belt in a specific line groove of the back plate member, the photoconductor belt is moved in a specific direction of the back plate and rotated. , Prevents misalignment of the separated color image due to the meandering of the photoconductor belt, maintains stable registration accuracy, and performs laser scanning from the belt edge mark in the specific direction that has been aligned to write in the main scanning direction. Determine the timing. Thus, the invention of Japanese Patent Application No. 2-272546 can be reinforced to exert a synergistic effect.

[Brief description of drawings]

FIG. 1 is a main configuration diagram of a color copying machine.

FIG. 2 is a block diagram of image processing means.

FIG. 3 is a perspective view of a photosensitive belt.

FIG. 4 is a layout configuration diagram of a laser writing system unit.

FIG. 5 is a diagram showing a patch pair on a recording sheet created in a position adjustment mode.

FIG. 6 is a diagram showing a positional relationship between a Bk patch and a yellow patch, which are reference patches.

FIG. 7 is a diagram showing a yellow laser writing system unit.

FIG. 8 is a perspective view showing a mirror of a laser writing system unit.

FIG. 9 is a block diagram for adjusting the parallelism of scanning lines and the deviation in the sub-scanning direction.

FIG. 10 is a block diagram for adjusting the width and deviation in the main scanning direction.

FIG. 11 is an explanatory diagram of the present invention.

[Explanation of symbols]

 14 Lens reading unit 15 Photoconductor belt 24, 25, 26, 27 Laser writing system unit 50 Image processing unit 51 Patch pair detection unit 52 Position deviation calculation unit 53, 55 CPU 54 Drive unit 56 Clock synchronization circuit 60 Beam detect detection circuit 61 Registration Mark detection circuit 152 Registration mark 245, 255, 265, 275 Mirror 249 Beam detect detector A Reading system B Image forming system FS1, FS2, FS3, FS4 Photo sensor M1, M2 Pulse motor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number for FI G03G 15/01 112 Z 7818-2H 15/04 116 9122-2H 21/00 119 H04N 1/04 D 7251-5C

Claims (2)

[Claims] 1. In a color image forming apparatus in which an image forming unit including a plurality of exposure devices is arranged around a moving image forming body, a belt-shaped image forming body is moved in a specific direction in a state in which a widthwise movement is restricted. An image forming apparatus characterized by. 2. The image forming apparatus according to claim 1, wherein an end portion of the belt-shaped image forming body on which the scanning reference of the laser beam is regulated is used.