JPH11249526A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of correctly and inexpensively detecting, a positional deviation detecting mark for performing correcting for the positional deviation of a transporting belt or an intermediate transfer belt. SOLUTION: This device is allowed to set the circumference length of the transporting belt 14 as integer multiple of circumference of photoreceptors 8M, 8C, 8Y and 8k, and the circumference of the driving roller 14a for the transporting belt 14 to the same as the respective circumference of the photoreceptor 8M, 8C, 8Y and 8K, and to detect a register mark (positional deviation detecting mark) provided on the transporting belt 14, by the photosensor 18 as the absolute position on the transporting belt 14 in one picture element. In such a manner, the register mark (positional deviation detecting mark) for performing the positional deviation correction of the transporting belt 14, is correctly and inexpensively detected.

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 copying machine, a printer, a facsimile, etc., which forms an image using an electrophotographic system, and more particularly, to a plurality of image forming apparatuses such as a tandem type color copying machine and a color printer. The present invention relates to an image forming apparatus comprising the above image forming means and capable of correcting color misregistration of images of different colors formed by each image forming means.

[0002]

2. Description of the Related Art In recent years, color processing of documents processed in offices and the like is rapidly progressing, and image forming is performed by using an electrophotographic system such as a copying machine, a printer, and a facsimile which handles these documents. Devices are also rapidly becoming colored.

At present, these image forming apparatuses tend to have higher image quality and higher speed with higher quality and quicker office processing in offices and the like. An image forming apparatus that can meet such demands has, for example, an image forming unit for each color of magenta (M), cyan (C), yellow (Y), and black (K), and is formed by each image forming unit. Various types of so-called tandem-type color image forming apparatuses for performing multi-transfer of images of different colors onto a transferred transfer material or an intermediate transfer body to form a color image have been proposed and commercialized. .

[0004] As this kind of tandem type color image forming apparatus, for example, there is one as shown in FIG.

This tandem type color image forming apparatus is
A magenta image forming unit 13M for forming a magenta (M) image, a cyan image forming unit 13C for forming a cyan (C) image, and a yellow image forming for forming a yellow (Y) image A unit 13Y;
Black image forming unit 13 for forming a black (K) color image
K of four image forming units.
Image forming units 13M, 13C, 13Y, 13K
Are horizontally arranged with a certain distance DMC, DMY, DMK from each other.

Further, the four image forming units 13M and 13 of magenta, cyan, yellow and black are used.
C, 13Y, and 13K, each of the image forming units 13M, 13M in a state where a transfer material P such as paper is electrostatically attracted.
A transfer belt 14 as an endless transfer material carrier for transferring the transfer material P over transfer portions C, 13Y, and 13K.
Is arranged. The transport belt 14 is a driving roller 14
a and is suspended between the driven rollers 14a and 14b, and moves in the direction of the arrow R14 by the rotational driving of the driving roller 14a.

[0007] The four image forming units 13M, 13C, 13 of the above-mentioned magenta, cyan, yellow and black colors
Y and 13K have the same configuration.
Image forming units 13M, 13C, 13Y, 13K
Then, as described above, magenta, cyan,
It is configured to sequentially form yellow and black toner images.

[0008] Image forming units 13M, 13C, 13
Y and 13K are respectively electrophotographic photosensitive drums (hereinafter, referred to as
8M, 8C, 8Y, 8K)
The surfaces of these photoconductors 8M, 8C, 8Y, 8K are respectively provided with chargers (scorotrons) 10M, 10C, 10Y,
After being uniformly charged by 10K, the exposure devices 7M, 7C, 7Y, and 7K scan and expose laser light for image formation in accordance with image information to form an electrostatic latent image.

Each of the exposure devices 7M, 7C, 7Y, 7K includes a laser diode 1, a polygon mirror 2, a scanner motor 3, an fθ lens 4, a photodetector 5, and a reflection mirror 6, as shown in FIG. The laser light L emitted from the laser diode 1 is scanned by a polygon mirror 2 rotated by a scanner motor 3, and the photoconductors 8M, 8C, 8Y, and 8K are respectively passed through an fθ lens 4, a photodetector 5, and a reflection mirror 6. Expose.

The electrostatic latent images formed on the surfaces of the photoconductors 8M, 8C, 8Y, and 8K are stored in the respective image forming units 13M, 13M.
C, 13Y, 13K developing units 9M, 9C, 9Y, 9K
Are developed with magenta, cyan, yellow, and black toners to form visible toner images, and these visible toner images are transferred to the transfer chargers 12M,
The toner images are sequentially transferred to the transfer material P held on the conveyor belt 14 by the charging of 12C, 12Y, and 12K. Paper tray 1
The transfer material P in 6 is fed one by one by a feed roller 20 or the like.

The transfer material P on which the magenta, cyan, yellow and black toner images have been transferred is conveyed to a fixing device 15 after being separated from a conveying belt 14, and is pressed by the fixing device 15. Heated and subjected to fixing process,
The transfer material P on which the color image has been fixed is supplied to the discharge tray 17.
The paper is ejected on top.

Further, residual toner and the like adhering to the surfaces of the photoconductors 8M, 8C, 8Y and 8K are removed by the cleaning devices 11M, 11C, 11Y and 11K.

The above-described conventional tandem type color image forming apparatus includes a plurality of image forming units 13M, 13C,
Since one image is formed using 13Y and 13K, a color image can be formed at a considerably high speed.

However, when the speed of image formation is increased, the image forming units 13M, 13C, 13Y,
The alignment of images formed at 13K, that is, color registration (hereinafter referred to as “registration”) frequently deteriorates, and it becomes impossible to maintain high image quality. Therefore, it is impossible to achieve both high image quality and high speed. It was extremely difficult. This is because the position and size of each image forming unit itself and the position and size of each component in the image forming unit are delicate due to a change in the internal temperature of the color image forming device and an external force applied to the color image forming device. Due to the change. Of these, changes in the internal temperature of the apparatus and external forces are unavoidable.For example, daily operations such as recovery of paper jams, replacement of parts by maintenance, and movement of the color image forming apparatus require external force to the color image forming apparatus. Will be added.

Therefore, a plurality of image forming units for forming a visible image corresponding to the image information and also forming a visible image of a position detection mark (hereinafter referred to as a registration mark),
A moving member that sequentially moves and passes through a transfer area for transferring a visible image corresponding to image information formed by each image forming unit or a visible image of a registration mark, and a moving member provided in the transfer area on the downstream side in the moving direction of the moving member. And a registration mark detecting unit for detecting a registration mark transferred onto the moving member, wherein each of the image forming units is configured to correct a transfer image shift based on a detection signal output from the registration mark detecting unit. An image forming apparatus configured to be controlled has already been proposed.

[0016]

However, in the above-mentioned conventional image forming apparatus, since an expensive CCD is generally used for the registration mark detecting means for detecting the registration mark, the cost of the image forming apparatus is high. There was a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of accurately and at low cost obtaining registration misregistration data which is important in performing registration correction.

[0018]

In order to achieve the above object, the present invention provides an image forming method in which toner images formed on a plurality of electrophotographic photosensitive drums are transferred onto a transfer material in a superimposed manner. An endless transport belt that transports the transfer material to a transfer site of the toner image, a driving roller that drives the transport belt, and detecting a position shift of the transport belt on the transport belt. And a control unit for performing a displacement correction control of the transport belt based on detection data of the displacement detection mark detected by the detection unit. Means, the circumferential length of the conveyor belt is an integral multiple of the circumference of the electrophotographic photosensitive drum, and the circumference of the drive roller of the electrophotographic photosensitive drum The same circumference, said control means, the detection data of the position displacement detection mark detected by said detecting means is characterized by detecting a detection data of the absolute position on the conveyor belt in one pixel unit.

Further, the control means performs position deviation correction control of the transport belt based on the detection data detected a plurality of times.

Further, after the toner image formed on the electrophotographic photosensitive drum is primarily transferred onto an endless intermediate transfer belt, the toner image on the intermediate transfer belt is secondarily transferred by being superimposed on a transfer material. A driving roller for driving the intermediate transfer belt; a position detection mark provided on the intermediate transfer belt for detecting a position deviation of the intermediate transfer belt; Detecting means for detecting a detection mark, and control means for performing position deviation correction control of the intermediate transfer belt based on detection data of the position deviation detection mark detected by the detection means, The circumference is an integral multiple of the circumference of the electrophotographic photosensitive drum, and the circumference of the drive roller is the same as the circumference of the electrophotographic photosensitive drum,
The control means detects the detection data of the misregistration detection mark detected by the detection means as detection data of an absolute position on the intermediate transfer belt on a pixel-by-pixel basis.

Further, the control means performs position deviation correction control of the intermediate transfer belt based on the detection data detected a plurality of times.

(Operation) According to the structure of the present invention, the circumference of the conveyance belt or the intermediate transfer belt is set to an integral multiple of the circumference of the electrophotographic photosensitive drum, and the circumference of the drive roller of the conveyance belt or the intermediate transfer belt is set. Is set to be the same as the circumference of the electrophotographic photosensitive drum, and the registration deviation caused by the eccentricity of the electrophotographic photosensitive drum and the driving roller appears at a fixed position on the transport belt or the intermediate transfer belt, thereby detecting the misregistration. The detection data of the displacement detection mark detected by the means is detected as the detection data of the absolute position on the transport belt or the intermediate transfer belt in one pixel unit, and accurate displacement information is obtained from the detection data detected a plurality of times. Can be.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic configuration diagram showing an image forming apparatus (a tandem type color image forming apparatus in the present embodiment) according to an embodiment of the present invention. Note that the same members as those of the conventional image forming apparatus shown in FIGS. 5 and 6 are denoted by the same reference numerals, and redundant description will be omitted. In addition,
The image forming operation of the image forming apparatus according to the present embodiment is the same as that of the above-described conventional image forming apparatus, and a description thereof will be omitted in the present embodiment.

In this embodiment, each of the photoconductors 8M, 8C,
The circumferential length of the transport belt 14 that transports the transfer material P to 8Y and 8K is an integral multiple of the circumference of each of the photoconductors 8M, 8C, 8Y, and 8K, and the drive roller 14 that drives the transport belt 14
The circumference of a is formed to be equal to the circumference of each of the photoconductors 8M, 8C, 8Y, and 8K. Further, each photoconductor 8M, 8C, 8
Y, 8K and the drive roller 14a are driven by the same pulse signal output from the control device 21. With such a configuration, the displacement caused by the eccentricity of each of the photoconductors 8M, 8C, 8Y, and 8K and the drive roller 14a is reduced by
Appears in a fixed position on 4.

In this embodiment, each of the image forming units 13M, 13M is similar to the above-described conventional image forming apparatus.
A visible image corresponding to the image information is formed by 13C, 13Y, and 13K, and a plurality of registration marks 19 are formed on the transport belt 14 at an arbitrary cycle as shown in FIG. The registration mark 19 is detected by the photo sensor 18. The controller 21 controls each of the photoconductors 8M, 8C, 8 based on the detection of the registration mark 19 by the photo sensor 18.
Y, 8K, the rotation of the transport roller 14a, and the scanner motor 3 are controlled to correct a transfer image shift (details will be described later). The control device 21 includes a FIFO memory 21a,
It has an EEPROM 21b which is a nonvolatile memory.

Next, the registration mark 19 by the control device 21
The correction control of the displacement of the conveyor belt 14 by the detection of
This will be described with reference to the flowchart shown in FIG.

First, the conveyor belt 14 is set to an arbitrary reference point (step S1).
Data stored in the FIFO memory 21a
Is stored (copied) (step S2).

If the conveyor belt 14 is at the reference point during the image formation described above (step S3), the FI
The counter of the FO memory 21a is reset (Step S4).

The control device 21 determines whether the conveyor belt 14 has rotated a specified number of times. If the conveyor belt 14 has rotated a specified number of times, the detection data of the registration mark 19 stored in the FIFO memory 21a is stored in the EEPROM 21b ( Copy) (step S6).

Then, the transport belt 14 is moved 1 in the sub-scanning direction.
After moving by the number of pixels (step S7), the FIFO memory 2
The detection data is read from 1a, and the read detection data is set in the shift register (step S8).

When the photo sensor 18 detects the registration mark 19 (step S9), the least significant bit is shifted to 1 (step S10). When the registration mark 19 is not detected, the least significant bit is set to 0. (Step S11), the shifted value (data) is again
Writing to the FO memory 21a (Step S12).

That is, the greater the number of 1s in the detection data, the greater the number of times the registration mark 19 is detected. FIFO
The number of addresses in the memory 21a is equal to or more than the number of pixels in the sub-scanning direction of the conveyor belt 14. The number of bits is arbitrary, but the larger the number of bits, the more past detection data can be stored. FIF
The reading and writing counters of the O memory 21a are reset each time the conveyor belt 14 makes one rotation,
The registration mark detection data at any point above is
It is assumed that the data is stored at a fixed address of the O memory 21a.

Then, the position data of the registration mark 19 is calculated, and the photosensitive members 8M, 8C, 8Y, 8K,
a) When controlling the scanner motor 3 (step S13), position data of the registration mark 19 is calculated from a location where the number of detections is the largest based on past measurement data for the number of bits of the FIFO memory 21a, When the position of the conveyor belt 14 is shifted, the controller (registration controller) 21 corrects the position of the conveyor belt 14 (step S1).
4). If the positional deviation of the conveyor belt 14 is corrected in step S14, the correction control ends, and if not, the process returns to step S3 (step S15).

Since the detected data in the FIFO memory 21a disappears when the power of the image forming apparatus is turned off, it is stored in the nonvolatile memory EEPROM 21b or the like at an arbitrary time as described above, and When the power is turned on again, the detection data stored in the EEPROM 21b is written to the FIFO memory 21a.
However, each of the image forming units 13M, 13C, 13Y,
In the case where the past detection data and the future detection data obviously do not match, such as when a cartridge (CRG) integrated with 13K is replaced, the detection data in the FIFO memory 21a may be reset.

As described above, in the present embodiment, the misregistration caused by the position and size of each of the image forming units 13M, 13C, 13Y and 13K and the image forming unit 13
M, 13C, 13Y, 13K, the image forming members (photoconductors 8M, 8C, 8Y, 8K, scorotrons 10M, 10K,
C, 10Y, 10K, developing units 9M, 9C, 9Y, 9K)
The registration deviation caused by the subtle change in the position and size of the registration mark 1 appears at a fixed position on the conveyor belt 14, so that the registration mark 1
9 is stored in the FIFO memory 21a and compared with the detection data of the past several times to obtain accurate displacement information of the transport belt 14 at a low cost without using an expensive CCD for the detection means. Can be.

<Embodiment 2> In this embodiment, an image forming apparatus having the same configuration as that of Embodiment 1 is used, and the image forming operation is the same as that of the above-described conventional image forming apparatus. Then, the description is omitted.

The correction control of the transfer image shift by detecting the registration mark by the control device 21 of the present embodiment will be described with reference to the flowchart shown in FIG. In the present embodiment, steps S8 'and S1 in the flowchart shown in FIG.
Except for 0 'and S11', the configuration is the same as that of the above-described first embodiment. In this embodiment, steps S8 ', S10', S1
Descriptions other than 1 'will be omitted.

In this embodiment, in step S7, the transport belt 14 is moved by one pixel in the sub-scanning direction, and the data is stored in the FIFO memory 21a in which the detection data is not written every time the transport belt 14 moves by one pixel in the sub-scanning direction. When saving, F
The detection data read from the IFO memory 21a is set in an up / down counter (step S8 '). When the registration mark 19 is detected, the count is incremented by 1 (step S10'). The data is stored again in the FIFO memory 21a (steps S11 'and S12).

In the present embodiment, step S1
3. When the position data of the registration mark 19 is calculated in S14 to control the photoconductors 8M, 8C, 8Y, 8K, the transport roller 14a, and the scanner motor 3, the FIFO memory 2
The position data of the registration mark 19 is calculated from the position where the detection data 1a is the highest, and when the position of the conveyor belt 14 is shifted, the controller (register controller) 21 corrects the position error of the conveyor belt 14.

As described above, also in the present embodiment, accurate displacement information of the transport belt 14 can be obtained at low cost, as in the first embodiment.

In each of the above-described embodiments, the displacement of the transport belt 14 that transports the transfer material P to which a color image is to be transferred is corrected. The present invention can be similarly applied to the correction of the displacement of the intermediate transfer belt of an image forming apparatus having an intermediate transfer belt for secondary transfer to a transfer material.

[0043]

As described above, according to the present invention,
It is possible to accurately and inexpensively obtain registration deviation data, which is important when correcting the positional deviation of the transport belt that transports the transfer material or the intermediate transfer belt that performs the secondary transfer.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing registration marks of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating correction control of a positional deviation of the conveyance belt in the image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating control for correcting a position shift of a conveyance belt in the image forming apparatus according to the second embodiment of the present invention;

FIG. 5 is a schematic configuration diagram showing an image forming apparatus in a conventional example.

FIG. 6 is a view showing an exposure apparatus of an image forming apparatus in a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Laser diode 2 Polygon mirror 3 Scanner motor 4 fθ lens 5 Photodetector 6 Reflection mirror 7M, 7C, 7Y, 7K Exposure device 8M, 8C, 8Y, 8K Photoconductor (electrophotographic photoconductor drum) 9M, 9C, 9Y, 9K developing device 10M, 10C, 10Y, 10K charging device 11M, 11C, 11Y, 11K cleaning device 12M, 12C, 12Y, 12K transfer device 13M, 13C, 13Y, 13K image forming unit 14 transport belt 14a drive roller 15 fixing device 16 Paper feed tray 17 Discharge tray 18 Photosensor (detection means) 19 Registration mark (position shift detection mark) 21 Controller (control means) 21a FIFO memory 21b EEPROM

Claims (4)

[Claims] 1. An image forming apparatus for forming an image by superimposing and transferring toner images formed on a plurality of electrophotographic photosensitive drums provided on a plurality of electrophotographic photosensitive drums onto a transfer material. An endless transport belt that transports the transport belt, a drive roller that drives the transport belt, a displacement detection mark provided on the transport belt for detecting a displacement of the transport belt, and the displacement detection mark. Detecting means for detecting, and control means for performing position shift correction control of the transport belt based on the detection data of the position shift detection mark detected by the detecting means; The circumference of the photosensitive drum is an integral multiple of the circumference, and the circumference of the drive roller is the same as the circumference of the electrophotographic photosensitive drum, the control means,
The image forming apparatus according to claim 1, wherein detection data of the misregistration detection mark detected by the detection means is detected as detection data of an absolute position on the transport belt in units of one pixel. 2. The image forming apparatus according to claim 1, wherein the control unit performs a displacement correction control of the transport belt based on the detection data detected a plurality of times. 3. After the toner image formed on the electrophotographic photosensitive drum is primarily transferred onto an endless intermediate transfer belt, the toner image on the intermediate transfer belt is secondarily transferred by being superimposed on a transfer material. A driving roller for driving the intermediate transfer belt; a position shift detection mark provided on the intermediate transfer belt for detecting a position shift of the intermediate transfer belt; Detecting means for detecting a detection mark, and control means for performing position shift correction control of the intermediate transfer belt based on detection data of the position shift detection mark detected by the detection means, The circumference is an integral multiple of the circumference of the electrophotographic photosensitive drum, and the circumference of the drive roller is the same as the circumference of the electrophotographic photosensitive drum. The detection data of the position displacement detection mark detected by the detecting means, for detecting a detection data of the absolute position on the intermediate transfer belt in one pixel unit, that the image forming apparatus according to claim. 4. The image forming apparatus according to claim 1, wherein the control unit performs a displacement correction control of the intermediate transfer belt based on the detection data detected a plurality of times.