JPH09197752A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain precise color slurring correction by precisely detecting a color smear in main scanning and subscanning directions. SOLUTION: A color slurring detecting sensor device is constituted of an illuminating fluorescent lamp 36 for illuminating a carrying belt 12, a first return mirror 37 for reflecting/returning reflected light, that is, light which is from the fluorescent lamp 36 and reflected by the carrying belt 12, a second return mirror 38 for reflecting/returning the reflected light from the first return mirror 37 and an image forming lens 40 for forming an image on a CCD line sensor 39 with the reflected light from the second return mirror 38. The CCD line sensor 39 is arranged at an inclination of an angle of θ with the main scanning direction of the carrying belt 12. Grid-like inspection patterns printed on the carrying belt 12 at electrophotographic process stations for each color are detected at an angle of θ by the CCD line sensor 39, to detect the color slurring in the main scanning and subscanning directions.

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 color electrophotographic printer, a digital color copying machine, and a color electrophotographic facsimile apparatus, and in particular, it is provided with a color misregistration detection sensor for detecting color misregistration of various colors. Image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus,
JP-A-63-271275 is known. As shown in FIG. 6, the image forming stations 2C and 2C are provided with developer (toner) of cyan, magenta, yellow, and black on the transfer belt 1 that conveys the transfer material.
M, 2Y and 2BK are arranged. The image forming stations 2C, 2M, 2Y and 2BK are connected to the photosensitive drums 3C and 3C, respectively.
M, 3Y, and 3BK are arranged, and a primary charger for uniformly charging around the photosensitive drum, scanning optical devices 4C, 4M, 4Y, and 4BK as latent image forming means, and latent images by toner. A developing device that visualizes the image, a cleaner, and a transfer charger are arranged. The image forming stations 2C, 2M, 2Y and 2BK are provided on both sides of the transfer belt 1 at regular intervals with a cross-shaped registration mark 5 for example.
a, 5b are printed, and the registration marks 5a, 5b are
The mark detecting device including the lamps 6a and 6b, the condenser lenses 7a and 7b, and the CCD sensors 8a and 8b is used to detect the image position of each color, and the position shift element between the images of each color is corrected based on the detection output. It is configured.

[0003]

In this conventional device, C
Since the CD sensors 8a and 8b are arranged in the main scanning direction, the color misregistration in the main scanning direction (direction orthogonal to the transfer belt 1 conveying direction) can be detected, but the sub-scanning direction (transfer belt 1 conveying direction). The color misregistration is superimposed on the misregistration in the sub-scanning direction due to the eccentricity of the driving roller of the transfer belt 1, the jitter of the driving system, the uneven feeding, and the like due to the arrangement error of the scanning optical devices 4C, 4M, 4Y, and 4BK. Therefore, the color shift in the sub-scanning direction cannot be accurately corrected. In particular, in the case of eccentricity of the drive roller with periodicity, even if the misregistration is corrected from the error amount read as the sub-scanning position error, the phase at that location can be adjusted, but at other locations, the color in the sub-scanning direction can be adjusted. The color shift in the sub-scanning direction cannot be accurately corrected as a whole.

Therefore, according to the first and second aspects of the present invention, not only the color misregistration detection in the main scanning direction but also the color misregistration detection in the sub-scanning direction can be accurately performed except for the influence of the carrying accuracy of the carrying system. (EN) An image forming apparatus capable of accurately correcting color misregistration in the main scanning direction and the sub-scanning direction, and further confirming the conveyance accuracy of a conveyance system.

[0005]

According to the first aspect of the present invention,
Electrostatic latent image carrier, charging means for charging the electrostatic latent image carrier, exposure means for exposing the electrostatic latent image carrier charged by the charging means to form an electrostatic latent image, and exposing means An electrophotographic process station equipped with a developing means for developing the electrostatic latent image formed in step 1 to visualize it, and a transfer means for transferring the image visualized by the developing means to a transfer medium conveyed by the conveying means. In the image forming apparatus corresponding to various colors and arranged along the conveying means, the conveying means provides inspection patterns of various colors for detecting color misregistration in the main scanning direction and the sub-scanning direction in each electrophotographic process station. A CCD line is printed on a member to be conveyed, and the inspection patterns of various colors are arranged along the main scanning direction at the position of the conveying means on the downstream side of the electrophotographic process station arranged on the most downstream side of the conveying means. The CCD line sensor of the color misregistration detection sensor is arranged at an angle of θ with respect to the main scanning direction so that the inspection patterns of at least two colors can be detected simultaneously. The color misregistration is corrected based on the color misregistration detection outputs in the main scanning direction and the sub scanning direction.

As a result, the CCD line sensor can detect the color misregistration in the main scanning direction for each color and the color misregistration in the sub-scanning direction between the colors.

According to a second aspect of the invention, in the image forming apparatus according to the first aspect, the member to be conveyed by the conveying means is a conveyor belt.

[0008]

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

As shown in FIG. 1, an endless belt 12 is wound around a central portion of a main body case 11 around a driving roller 13, a driven roller 14 and tension rollers 15a and 15b to transfer a transfer sheet, which will be described later, as a transfer medium. It forms a transport means. Then, four electrophotographic process stations 161 are provided at the upper position facing the conveyor belt 12.
, 162, 163, and 164 are arranged in series at a predetermined interval.

Each of the electrophotographic process stations 16
1, 162 and 163 are yellow (Y), magenta (M), and cyan (C) electrophotographic process stations required for color printing, and the electrophotographic process station 164 is for black (K) for black printing. It is an electrophotographic process station and is arranged in the order of yellow, magenta, cyan, and black from upstream to downstream in the transport direction of the transport belt 12.

Each of the electrophotographic process stations 16
1 to 164 are photosensitive drums 171 as electrostatic latent image holders.
, 172, 173, 174 are provided, charging devices 181, 182, 183, 184, which are charging means, and laser scanning devices 191, 192, 193, which are exposure means, are provided around the respective photosensitive drums 171, 172, 173, 174. 19
4, developing devices 201, 202, 203, which are developing means,
204, transfer rollers 211, 212, 2 which are transfer means
13 and 214 and cleaning devices 221, 222 and 2
23 and 224 are arranged.

The transfer rollers 211, 212, 213,
214 is arranged to face the photosensitive drums 171, 172, 173 and 174 with the conveyor belt 12 interposed therebetween. The laser scanning devices 191, 192, 193, 19
4 is toner boxes 231, 232, 23 for replenishing toner to the developing devices 201, 202, 203, 204.
It is placed vertically adjacent to 3, 234.

At the bottom of the main body case 11, paper feed cassettes 24 and 25 are provided in two stages, upper and lower. Then, the transfer paper is picked up one by one from the upper paper feed cassette 24 by the paper feed roller 26 and sent out, and the transfer belt 1 is passed through the transfer roller 27, the guide 28, and the registration roller 29.
It is designed to be sent to the upper two. Further, the transfer paper is picked up one by one by the paper feed roller 30 from the paper feed cassette 25 in the lower stage and sent out.
2, transport roller 27, guide 28, registration roller 29
It is adapted to be delivered onto the conveyor belt 12 via the.

An adsorption device 33 for electrostatically adsorbing the transfer paper on the transfer belt 12 so as not to shift the transfer paper is provided at the tip of the transfer belt 12, and the transfer paper sent from the paper feed cassettes 24 and 25 is transferred to the transfer belt 12. At the same time, it is charged and brought into close contact with the conveyor belt 12. Each of the electrophotographic process stations 161 to 164 is adapted to perform color printing by sequentially superposing and transferring images of yellow, magenta, cyan, and black onto the transfer paper conveyed by the conveyor belt 12. Then, the transfer paper on which the color printing is finished is finally heated and fixed by the heat fixing device 34 and then discharged to the outside.

In this apparatus, when information for forming an image is input from an external host computer, for example, the paper feed roller 26 picks up the transfer paper from the paper feed cassette 24, and the picked-up transfer paper is conveyed by the transport roller 27.
And the registration roller 29 adjusts the timing, and then the sheet is sent onto the conveyor belt 12. Then, the transfer sheet is electrostatically adsorbed on the conveyor belt 12 by the adsorption device 33 and moves together with the conveyor belt 12 without causing a positional deviation during conveyance.

On the other hand, the image information is supplied to each of the laser scanning devices 191 to 194 as information corresponding to each color. For example, the image information of yellow is the laser scanning device 19
1, the laser scanning device 191 emits a laser beam according to the image information, and the photosensitive drum 171 uniformly charged by the charging device 181 is exposed to form an electrostatic latent image. Then, the electrostatic latent image on the photosensitive drum 171 is developed with the yellow toner by the developing device 201 to be visualized, and the yellow toner image is transferred onto the transfer paper on the conveying belt 12 by the transfer roller 211. Photosensitive drum 171 after transfer
The cleaning device 221 cleans the residual toner, and the charge is removed by a charge removing lamp (not shown) to prepare for the next electrophotographic process.

Similarly, image information of magenta, cyan, and black is supplied to laser scanning devices 192 to 194, respectively, and the conveyor belt 1 is fed by magenta, cyan, and black electrophotographic process stations 162, 163, and 164.
The magenta, cyan, and black toner images are sequentially transferred and transferred onto the yellow image on the transfer paper on 2. In this way, a color image is printed on the transfer paper, and the transfer paper is heated and fixed by the heat fixing device 34 and then discharged.

In this apparatus, since images of respective colors of yellow, magenta, cyan, and black are superposed for color printing, color misregistration when superposing the respective colors becomes a problem. Therefore, it is required to detect and correct the color shift.
Therefore, a color shift occurs at a position below the conveyor belt 12 between the drive roller 13 and the tension roller 15a, which is located on the downstream side of the black electrophotographic process station 164 arranged on the most downstream side of the conveyor belt 12. The detection sensor device 35 is arranged.

As shown in FIG. 2, the color misregistration detecting sensor device 35 illuminates a fluorescent lamp 36 for illuminating the conveyor belt 12 over the entire main scanning direction, and the light from the fluorescent lamp 36 causes the conveyor belt 12 to emit light. The first folding mirror 37, which reflects and reflects the reflected light diffused and reflected by the first folding mirror 3
Second folding mirror 3 that reflects the reflected light from 7 and returns it
8. The reflected light from the second folding mirror 38 is CCD
It is composed of an image forming lens 40 for forming an image on the line sensor 39. The CCD line sensor 39 is the conveyor belt 1.
2 is arranged at an angle of θ with respect to the main scanning direction so that the position on the line tilted at an angle of θ with respect to the main scanning direction can be detected.

Each of the electrophotographic process stations 16
In order to detect color misregistration in the main scanning direction and the sub-scanning direction, as shown in FIG. 3, 1 to 164 are grids on the conveyor belt 12 in which the directions of the respective colors coincide with the main scanning direction and the sub-scanning direction. The inspection pattern 41 in the shape of a circle is printed. Each of the electrophotographic process stations 161 to 16
Inspection pattern 41 printed by 4 directly on the conveyor belt 12
4, the line in the main scanning direction is yellow Y, magenta M, cyan C, black B in the sub scanning direction.
K, yellow Y, ... are alternately printed, and a plurality of short lines of the same color in the sub-scanning direction are printed at predetermined intervals on the lines of each color, and a large number of crosses of the same color are formed on the lines of each color. Is making. The CCD line sensor 39 is shown in FIG.
As shown by the detection line 42, the angle θ is set so that at least two color lines in the main scanning direction can be detected simultaneously.

In such a structure, in order to detect the color misregistration in the main scanning direction and the sub scanning direction of the printed image by each of the electrophotographic process stations 161-164, the driving roller 13 is rotationally driven to move the conveyor belt 12. The grid-like inspection pattern 41 is directly printed on the transport belt 12 by each of the electrophotographic process stations 161-164. Then, the CCD line sensor 39 reads the inspection pattern 41 on the conveyor belt 12.

For example, assuming that the CCD line sensor 39 is now arranged in parallel with the main scanning direction, as shown in FIG. 5, the line of magenta M is detected after the time t1 has elapsed after the line of yellow Y was detected. Then, the cyan C line is detected after the lapse of time t2, and the black B is detected after the lapse of time t3.
Detect the K line. Further, a short line printed in the direction orthogonal to the line of each color, that is, in the sub-scanning direction is also detected.

For example, if the line of yellow Y is used as a reference line, the line of magenta M in the sub-scanning direction shifts by + Δym in the main scanning direction, the line of cyan C in the sub-scanning direction shifts by -Δyc in the main scanning direction, and black. It can be detected that the line of BK in the sub-scanning direction is displaced by + Δybk in the main scanning direction. That is, the color misregistration of each color in the main scanning direction can be detected. Further, the line of magenta M in the main scanning direction should be originally located. + Δt1 is deviated in the sub scanning direction from the line indicated by the alternate long and short dash line in the figure, and the line of cyan C in the main scanning direction should be originally located. The line in the main scanning direction of the black BK should be displaced by -Δt2 in the sub-scanning direction with respect to the line shown by the one-dot chain line in the figure, and the line in the main-scanning direction of black BK should be originally located + Δt3 in the sub-scanning direction with respect to the line shown by the one-dot chain line in the figure. The deviation can be detected. That is, the color shift of each color in the sub-scanning direction can be detected.

However, this color misregistration in the sub-scanning direction is only when the conveyor belt 12 conveys at a constant speed evenly, and the conveyor belt 12 causes eccentricity of the driving roller 13 and jitter of the driving system. This color shift is not appropriate when the speed is partially changed due to uneven feeding. That is, if the CCD line sensor 39 is arranged parallel to the main scanning direction, it is not possible to accurately detect the color shift of each color in the sub scanning direction.

On the other hand, in this embodiment, the CCD line sensor 39 is inclined by the angle θ with respect to the main scanning direction. Therefore, as shown in FIG.
Can simultaneously read the yellow Y main scanning direction line, the magenta M main scanning direction line, and the cyan C main scanning direction line. As a result, the same detection line 4
21. Yellow Y main scanning direction line and magenta M
Distance ta between the detection positions P1 and P2 of the main scanning direction line
The distance tb between the detection positions P1 and P3 of the yellow Y main scanning direction line and the cyan C main scanning direction line can be detected. The distances ta and tb indirectly indicate the intervals in the sub-scanning direction between the yellow Y main scanning direction line, the magenta M main scanning direction line, and the cyan C main scanning direction line. Therefore, the color shift in the sub-scanning direction of each line in the main scanning direction can be detected from the interval in the sub-scanning direction.

As described above, the detection line 421, which is a line simultaneously detected by the CCD line sensor 39, detects the interval in the sub-scanning direction of each color at the same time, and thereby the color shift in the sub-scanning direction of the line in the main scanning direction of each color is detected. Since the speed can be detected, even if the speed of the conveyor belt 12 partially changes due to the eccentricity of the driving roller 13, the jitter of the driving system, the uneven feeding, etc., the effect is removed and the color misregistration of each color in the sub-scanning direction is eliminated. Can be accurately detected.

Regarding the color misregistration in the main scanning direction, as in the prior art, the misregistration amount of a line of magenta M in the subscanning direction with respect to a line of a certain color, for example, yellow Y in the subscanning direction, and cyan C. By detecting the line shift amount in the sub-scanning direction and the line shift amount of black BK in the sub-scanning direction, the color shift in the main scanning direction can be accurately detected.

As described above, since the color misregistration in the main scanning direction and the subscanning direction can be accurately detected, if the misregistration elements of the electrophotographic process stations 161 to 164 are corrected based on the detection information, the main scanning direction and the subscanning direction can be corrected. Color shift correction in the sub-scanning direction can be accurately performed.

When attention is paid to the line of cyan C in the main scanning direction in FIG. 4, the detection line 421 of the CCD line sensor 39 detects the line of cyan C in the main scanning direction at position P3, and after a lapse of a certain time. Detection line 422
In the position P4, a line of cyan C in the main scanning direction is detected. In the detection line 423 after a certain period of time, a line of cyan C in the main scanning direction is detected at a position P5. The line 424 detects the line of cyan C in the main scanning direction at the position P6.

Therefore, the distance between the positions P3 and P4, the position P
If the distance between 4 and P5 and the distance between positions P5 and P6 are measured, the feed amount of the conveyor belt 12 in a fixed time can be sequentially detected, so that the feeding accuracy of the conveyor belt 12 can be confirmed. That is, if the speed partially changes due to the eccentricity of the driving roller 13, the jitter of the driving system, the uneven feeding, and the like, the changing state of the speed can also be detected.

In this embodiment, the grid-shaped inspection pattern 41 is printed directly on the conveyor belt 12. However, the invention is not limited to this, and it is printed on the transfer paper conveyed by the conveyor belt 12. However, the inspection pattern of the transfer paper may be detected by the color shift detection sensor device. In this case, the color misregistration detection sensor device is arranged between the final stage black electrophotographic process station and the drive roller 13, that is, above the conveyor belt 12.

[0032]

As described above, according to the first and second aspects of the present invention, C of the color misregistration detection sensor arranged along the main scanning direction.
Since the CD line sensor is arranged at an angle θ with respect to the main scanning direction so that at least two color inspection patterns can be detected at the same time, the color misregistration detection in the main scanning direction is, of course,
Color misregistration in the sub-scanning direction can be detected accurately without the influence of the conveyance accuracy of the conveyance system. This makes it possible to correct color misregistration in the main scanning direction and the sub-scanning direction, and also to confirm the conveyance accuracy of the conveyance system. it can.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view of a main part showing a configuration of a color shift detection sensor device according to the same embodiment.

FIG. 3 is a diagram showing a color misregistration inspection pattern according to the first embodiment.

FIG. 4 is a partial enlarged view of an inspection pattern for explaining color misregistration detection in the sub-scanning direction in the same embodiment.

FIG. 5 is a partially enlarged view of an inspection pattern for explaining color misregistration detection in a main scanning direction and a sub scanning direction when a CCD line sensor is arranged parallel to the main scanning direction.

FIG. 6 is a perspective view showing a conventional example.

[Explanation of symbols]

 12 ... Conveying belt (conveying means) 161 to 164 ... Electrophotographic process station 171 to 174 ... Photosensitive drum (electrostatic latent image holder) 181 to 184 ... Charging device (charging means) 191 to 194 ... Laser scanning device (exposure means) ) 201-204 ... Developing device (developing means) 211-214 ... Transfer roller (transfer means) 35 ... Color shift detection sensor device 39 ... CCD line sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Iketani 570, Ohito, Ohito-cho, Takata-gun, Shizuoka Tech Co., Ltd. Inside the Ohito Works (72) Inventor, Mikio Yamamoto 570, Ohito, Ohito-cho, Takata-gun, Shizuoka Tech Co., Ltd. Ohi office

Claims (2)

[Claims] 1. An electrostatic latent image holder, charging means for charging the electrostatic latent image holder, and exposure for exposing the electrostatic latent image holder charged by the charging means to form an electrostatic latent image. Means, developing means for developing the electrostatic latent image formed by the exposing means to visualize it, and transfer means for transferring the image visualized by the developing means to a transfer medium conveyed by the conveying means. In an image forming apparatus in which a plurality of electrophotographic process stations corresponding to various colors are arranged along the conveying means, various colors for detecting color misregistration in the main scanning direction and the sub scanning direction in each electrophotographic process station. The inspection pattern of 1. is printed on the member conveyed by the conveying means, and the inspection patterns of various colors are mainly run to the position of the conveying means downstream of the electrophotographic process station arranged on the most downstream side of the conveying means. At least two CCD line sensors of the color shift detection sensor are detected by a color shift detection sensor composed of CCD line sensors arranged along the scanning direction.
The color inspection pattern is arranged at an angle θ with respect to the main scanning direction so that it can be detected at the same time, and the color misregistration is corrected based on the color misregistration detection output from the color misregistration detection sensor in the main scanning direction and the sub-scanning direction. An image forming apparatus characterized by the above. 2. The image forming apparatus according to claim 1, wherein the member conveyed by the conveying means is a conveyor belt.