JP2659191B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus that forms image information on, for example, a transfer body using an electrophotographic method or the like.

[Prior Art] The present applicant has proposed a number of color image forming apparatuses for obtaining a full-color image by juxtaposing a plurality of image carriers (photosensitive drums and the like) (JP-A-58-23074, JP-A-58-23074). 1983-95361
JP-A-58-95362, JP-A-58-154856, JP-A-58-154856
8-207021, JP-A-59-31976, JP-A-59-46659
No., JP-A-59-50460, JP-A-59-42879, etc.).

[Problems to be Solved by the Invention] In the image forming apparatus of this type, a superposition shift (color shift) between respective colors at the time of multiple transfer is a very large problem.

In order to solve this problem, the present applicant has proposed to improve the color misregistration by a mechanical configuration (Japanese Patent Laid-Open No. 59-15 / 1984).
No. 5870, JP-A-59-155869, JP-A-59-155871, JP-A-59-204069, JP-A-59-155870, JP-A-59-16
No. 8467, JP-A-59-182139).

Although these proposals have greatly improved the color misregistration, there is still a problem in terms of stably moving the mechanical structure within 0.15 mm, which is the tolerance of the color misregistration.

For example, finer and slight instability such as belt running stability, reproducibility of photosensitive drum attachment / detachment, horizontal sink in LBP (laser beam printer) and vertical sink instability, As it was completed, it became a new problem. In addition, the relationship between the main body, the optical system, the photosensitive drum, and the like, which has been adjusted once at the time of installing the main body, can also be determined by, for example, moving the main body to another location when the floor shape is not the same plane. Causes distortion. In doing so, a very complicated and difficult readjustment must be performed.

On the other hand, proposals for adjusting the image forming timing for each color have already been made (JP-A-59-163971, JP-A-58-16397).
226559). Proposals for measuring the amount of color misregistration on an image have already been made (JP-A-52-2604, JP-A-53-2160).
5, JP-A-53-49514, JP-A-56-1557367, JP-A
58-14752).

However, none of these proposals has proposed an organic system in which the detected color shift amount is fed back to the writing unit. Therefore, at present, there is no device capable of improving color misregistration with high accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of solving the above-described problems in an image forming apparatus and forming an image at a predetermined position on a predetermined member with extremely high accuracy.

[Means for Solving the Problems] The present invention relates to an image forming unit for forming an image on an image carrier, and a control unit for controlling the image forming unit to form a registration mark image on the image carrier. A moving body having a fixed registration mark and moving so as to transfer a registration mark image formed on the image carrier at a transfer position; and a position of the registration mark image transferred on the moving body. Detecting means for detecting a position of the fixed registration mark; calculating means for calculating a displacement amount between the fixed registration mark and the registration mark image based on an output of the detecting means; and the calculating means Correction means for correcting the position of the image formed on the image carrier based on the positional deviation calculated by the above.

[Operation] According to the present invention, a registration mark is transferred onto a moving body at a predetermined interval during image transfer, and the fixed registration mark and the image registration mark on the moving body are constantly observed during image formation. Image formation is corrected based on this observation result. Thereby, a stable image is formed.

Embodiment The present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a color printer in which photosensitive drums are arranged side by side.

1Y, 1M and 1C are photosensitive drums for forming yellow, magenta and cyan images, respectively. Motor 3 is warm
The worm wheels 2Y, 2M, 2C are driven via 4Y, 4M, 4C, and thus the photosensitive drum and the worm wheel are integrally driven in the directions of arrows 5Y, 5M, 5C in the figure. Optical box 6Y, 6M, with built-in laser light source and polygon scanner
6C emits laser light raster lines 7Y, 7M, 7C, thereby exposing the photosensitive drums 1Y, 1M, 1C, respectively.

A well-known Carlson process is arranged around the photosensitive drums 1Y, 1M, and 1C, but is omitted in FIG.

The intermediate transfer belt 8 disposed below the photosensitive drums 1Y, 1M, 1C is suspended by rollers 9, 10, and is transported in the direction of arrow 11. Photosensitive drum 1 by Carlson process
The Y, M, C images formed on Y, 1M, 1C (the original color image is obtained by combining them) are sequentially transferred onto the intermediate transfer belt 8 by corona transfer or pressure transfer. Further, the image is retransferred to the transfer paper 12 between the pair of rollers 10 and 13 having a predetermined pressing force, and a color image (33a, 33b, 33c,...) Is obtained. The two-dimensional image pickup devices 14 and 15 as position detection means in the present invention are made of CCD, MOS, or the like, and the registration marks located on both sides of the belt 8 are centered on the imaging points 14a and 15a as the belt 8 moves. Is read through lenses 18 and 19. 16a, 16b, 17a, and 17b are fixed registration marks semi-permanently printed on the belt 8, and 34a, 34b, 35a, and 35b.
Is an image registration mark formed on the belt 8 during image formation. In this example, the fixed registration marks are indicated by circles and the image registration marks are indicated by crosses for easy understanding. However, the present invention is not limited to this.

The optical boxes 6Y, 6M, and 6C are provided with attitude control motors, respectively. One of them is an optical path length adjusting motor 20Y, 20
M and 20C change the optical path length (for example, 21C) of the laser light from the laser light source of the optical box 6 to the drum.

The optical box rotating motors 22Y, 22M, and 22C rotate the optical box 6 about the rotation axes of the motors 20Y, 20M, and 20C, and rotate, for example, the raster line 7C in the direction of the arrow 23.

FIG. 2 shows a part of a circuit for producing a horizontal synchronization (H-SYNC) and a vertical synchronization (V-SYNC) signal of each color.

FIG. 2 shows a circuit for finely adjusting the H-SYNC and V-SYNC signals for yellow (Y), magenta (M) and cyan (C), and the signals input thereto have a known circuit configuration. It is obtained by a sequence controller (JP-A-59-163971, JP-A-59-226559, etc.).

The fine adjustment circuit receives TOP (Y), TOP (M), TOP (C) signals of coarse vertical timing (image forming timing in the belt conveyance direction) of each color from the sequence controller, and coarse horizontal timing (belt conveyance direction) of each color. BD (Y), BD of image formation timing in the direction perpendicular to
(M) and BD (C) signals are input.

Further, the delay amount to be fine-tuned in the belt conveying direction is a margin register MR (YV), MR (MV), or DELAY (YV), DELAY (MV), or DELAY (CV) signal, respectively.
Stored in MR (CV). Similarly, the Delay amount to be finely adjusted in the direction perpendicular to the belt conveyance direction is DELAY (YH), DEL
AY (MH), DELAY (CH) signal as margin register MR
(YH), MR (MH), and MR (CH).

For example, the program counter PC (YV) calculates a vertical synchronization signal V-SYNC-Y for Y (hereinafter the same) from the BD (Y) signal, the TOP (Y) signal, and the value of the margin register MR (YV). Are output at a desired timing. Similarly, the horizontal synchronizing signal H-SYNC-Y (hereinafter the same) H-V-SYNC-M, V-SYNC-C and Y
SYNC-M and H-SYNC-C are obtained, and each color image is superimposed on the same image position on the conveyor belt 8.

FIG. 3 is a diagram for illustrating a method of adjusting one optical box 6 of each color (the same applies to other colors).

The optical path adjusting motor 20 is a pulse motor, and is fixed to a stay 23 integrally formed with the main body frame. The collar 24a is fitted in the holes 25 and 26 at the ends of the optical box 6. Color
A stopper 24b is integrally attached to the lower end of 24a, and supports the optical path box 6 from below.

A rotation stopper 24C is integrally attached to the middle of the collar 24a, and is fitted into the hole 27 of the stay 23. Thus, rotation of the collar 24a is prevented.

The shaft 20b of the motor 20 is provided with a male screw, the inner periphery of the collar 24a is provided with a female screw, and the shaft 20b is screwed into the collar 24a. Assuming that these screws are both right-handed screws, the optical box 6 is raised by rotating the shaft 20b in the direction of the arrow 28, and the optical box 6 is rotated by rotating the shaft 20b in the direction opposite to the arrow 28. Descend. As a result, the optical path length 21 changes, and as a result, the image size 29 changes.

On the other hand, the pulse motor 22 is fixed to the stay 30,
A tension coil spring 31 is mounted between the stay 30 and the optical box 6. The rotor 22C of the motor 22 is provided with a female thread, into which a male threaded shaft 22b is screwed. The shaft 22b moves forward and backward by the rotation of the rotor 22c of the motor 22.

The proximal end of the shaft 22b is fixed to the optical box 6, so that the rotation of the motor 22
The scanning line 32 can be tilted with respect to the generatrix of the photosensitive drum 1.

Next, how the color shift is corrected will be described for a cyan image. Other colors are substantially the same.

FIGS. 4, 5, 6, and 7 show the imaging points 14a and 15a on the belt 8 in FIG. 1 as viewed from above.

In FIG. 4, an image 33 is formed on the belt 8, and cross image registration marks 34 and 35 are formed outside the image area (on both sides of the image 33) by electrophotography (at the same time as the image). Fixed registration marks 16, 17 indicated by circles
Is semi-permanently printed on the belt 8. In the figure, the arrow
The belt 8 advances in the direction of 11.

The imaging devices 14 and 15 receive the marks 16, 17, 34 and 35 at the timing when the registration marks 34 and 35 (16 and 17) should pass through the imaging points 14a and 15a (fixed) based on the sequence signal from the sequence controller. Is imaged. FIG. 4 shows a case where the marks 34 and 35 reach the imaging point later than the ideal timing. Accordingly, the delay amount 36 is detected from the mark image pickup signal at the timing at which the signal should pass, and the delay (CV) shown in FIG.
The timing of the V-SYNC-C signal is advanced by advancing the phase of the signal and decreasing the value of the margin register MR (CV). By doing so, the color shift is corrected.

FIG. 5 shows a case where the image 33 is shifted laterally with respect to the belt 8.

In this case, the lateral deviation amount 37 between the fixed registration mark 16 and the image registration mark 34 is detected by a signal from the image sensor, and the value of the register MR (CH) is reduced by the DELAY (CH) signal based on the lateral deviation amount. Then, the timing of the H-SYNC-C signal is advanced. Thereby, the lateral displacement can be corrected.

FIG. 6 shows a case where the center line of the drum 1c and the optical scanning line 32 do not coincide with each other and are inclined.

In this case, a straight line connecting the two image registration marks 34 and 35 and a straight line connecting the fixed registration marks 16 and 17 are inclined θ.
Is detected by a signal from the image sensor, and the scanning line 32 is rotated by the detected θ in the direction of the arrow 23b. That is,
In FIG. 3, the pulse motor 22 is rotated to rotate the shaft 22b.
Is retracted, the center line of the drum 1c and the optical scanning line 32 can be matched.

FIG. 7 shows a case where the image magnification is incorrect. In FIG. 7, the amount of deviation 38, 39 between the image registration marks 34, 35 and the fixed registration marks 16, 17 is detected by a signal from the image sensor, and the error amount of the image magnification is determined from this by the length 40 (registration mark 34). The distance is determined as a ratio between 41 and 35 (the distance between the fixed registration marks 16 and 17).

Based on the obtained ratio, a similar triangle having a constant ratio between the height (optical path length 21) and the base (image size 29) of the triangle in FIG. The amount is calculated, and the image magnification can be corrected by rotating the shaft 20b of the pulse motor 20 in the direction of the arrow 28 based on the calculated value.

As described above, any form of color shift can be corrected. Obviously, the same applies to other colors.

FIG. 12 shows a configuration of a reading unit that detects the position of a registration mark based on a signal from a two-dimensional sensor (CCD) as an image sensor, and shows a portion corresponding to the registration mark on one side of the belt 8. .

The Y, M, and C signals of three colors are output from the image sensor 14, and the output signals of each color are amplified by the amplifiers 50, 51, and 52, and are converted into image signals by the binarization circuits 53, 54, and 55. Therefore, the output signals (1), (2), and (3) of these binarizing circuits can obtain the image signals of the registration marks corresponding to the respective colors of Y, M, and C.

Since all the fixed registration marks on the belt 8 are indicated by black circles, the fixed registration marks can be detected (imaged) by the image sensor 14.

The registration mark detection (imaging) signal obtained for each color is stored in each of the image memories 56, 57, 58. The timing of the storage is not shown in FIG. 12, but is, of course, when a portion in which the image registration mark of each color and the fixed registration mark are recorded in an overlapping manner in the reading range below the image sensor.

Based on the registration mark data stored in the image memory, the "+" mark and the "O" mark are used to detect the amount of deviation between the "+" mark as the image registration mark of each color and the "O" as the fixed registration mark. Are separated by the pattern matching circuits 59, 60, 61. That is, in each matching circuit, the same pattern data as the “+” mark from the pattern ROM 2 and the same pattern data as the “○” mark from the pattern ROM 1 are registered with the registration mark data (“+” mark) from each image memory. Data and “○” mark data) to separate the “+” and “○” registration mark information,
Output. Then, based on each registration mark information from each matching circuit, each of the center position calculation circuits 62, 63, 64 calculates the center position of the “+” and “「 ”registration marks.

FIG. 13 shows a correction unit that corrects various deviations based on the registration mark center position signal obtained by the reading unit. Y,
The M and C shift amount calculation units 70, 71, and 72 determine the direction of the image registration mark “+” from the fixed registration mark “○” to the image registration mark “+” based on the output signal from each center position calculation circuit of the reading unit ( For example, how many mm) is shifted is calculated as a shift amount, and the shift amount is obtained as X, Y coordinate position data based on a fixed registration mark. That is, the calculation results are obtained as “Y shift amount”, “M shift amount”, and “C shift amount”.

Similarly, a circuit block 73 for detecting the amounts of Y, M, and C shifts of the image pickup device 15 on the opposite side (consisting of a reading unit shown in FIG. 12 and a Y, M, and C amount shift detecting unit of FIG. 13) ), The Y, M and C deviation amount detection signals for the registration marks on the opposite side of the belt 8 are output.

Y, M, and C shift amount detection signals between two registration marks on one side of the belt 8 from the Y, M, and C shift amount calculation units 70, 71, and 72 and the other side of the belt 8 from the same block 73. Y, M between the two registration marks
And the C shift amount detection signal are supplied to a bus shift correction amount calculation circuit 7.
4. Input to the interval deviation / magnification deviation correction amount calculation circuit 75 and the inter-station timing correction amount calculation circuit 76.

The bus deviation correction amount calculation circuit 74 outputs a signal for controlling the pulse motor 22 (Y, M, C) based on an input signal (Y, M, and C deviation amount detection signals on both sides of the belt 8).
The bus deviation as shown in the figure is corrected.

The interval shift / magnification shift correction amount calculation circuit 75 is a circuit for controlling the pulse motor 20 (Y, M, C) based on the input signal and for finely adjusting the direction perpendicular to the belt conveying direction.
A DELAY (YH, MH, CH) signal is output as the lay amount, and for example, as shown in FIG. 7, a magnification shift (by control of the pulse motor 20) and a laser writing start position (by DELAY (YH, MH, CH)) (Interval shift) is corrected.

The inter-station timing correction amount calculation circuit 76 should be finely adjusted in the belt conveyance direction based on the input signal.
A DELAY (Yv, Mv, Cv) signal is output as a delay amount, and for example, an image writing timing as shown in FIG. 4 is corrected.

 Another embodiment of the present invention is shown in FIG.

FIG. 8 shows an example in which the continuous roll paper 42 is used as a transfer material.

Although there is essentially no difference from the first embodiment, the registration mark is preferably cut off after image formation.

 FIG. 9 shows still another embodiment of the present invention.

In this embodiment, the belt 8 is made up of the cut sheets 43a, 43a.
Used as carrier for b and 43c. It is desirable that the registration mark is outside the area of the cut sheet.

 10 and 11 show still another embodiment of the present invention.

These show specific examples of the drum support shown in FIG. One end of the drum 1C is rotatably supported by a bearing 44.The bearing 44 is pushed by a pulse motor 45 whose shaft moves forward and backward, and is pulled by a coil spring 46 which urges the shaft in the opposite direction. I have. This is the same principle configuration as the pulse motor 22 and the coil spring 31 shown in FIG.

When the scanning line 32 is inclined as shown in FIG. 10, at the transfer position, the line corresponding to the scanning line 32 becomes like 32b, and as a result, the shift angle θ is observed at the registration mark imaging position.

In this case, when the pulse motor 45 is rotated to rotate the drum center line by θ / 2 as shown in FIG. 11, the line 32b at the transfer position becomes a right angle to the image moving direction, and the image registration mark is You will be in the right posture.

Although a laser and a polygon scanner are used in the embodiments, the present invention is not limited to this. For example, an original image may be formed as in Japanese Patent Publication No. 55-6225. In addition, LCD shutter array, LED
An array or an ion flow modulation charger may be used.

Also, it is not limited to the color image forming apparatus,
If a monochrome printer requires high accuracy, it can be applied.

[Effects of the Invention] According to the present invention, all distortions and errors of a formed image can be constantly and continuously corrected, and in particular, color shift of a color image forming apparatus can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a color printer in which photosensitive drums are arranged side by side as an embodiment of the present invention, FIG. 2 is a circuit diagram for producing horizontal and vertical synchronization signals of each color, and FIG. 4, 5, 6, and 7 are diagrams showing imaging points on the belt, FIGS. 8 and 9 are perspective views showing another embodiment of the present invention, 10 and 11 are diagrams showing a specific example of a drum support mechanism, and FIGS. 12 and 13 are circuit block diagrams for correcting color misregistration.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yoichi Kubota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Ken Miyagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Miyake 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 56) References JP-A-57-167034 (JP, A) JP-A-63-286865 (JP, A) JP-A-59-229970 (JP, A) Japanese Utility Model Application Sho 63-188662 (JP, U)

Claims (12)

(57) [Claims] 1. An image forming means for forming an image on an image carrier, a control means for controlling the image forming means to form a registration mark image on the image carrier, and a fixed registration mark, A moving body that moves so as to transfer a registration mark image formed on the image carrier at a transfer position, a position of the registration mark image transferred onto the moving body, and a position of the fixed registration mark. A calculating means for calculating a positional shift amount between the fixed registration mark and the registration mark image based on an output of the detecting means, based on the positional shift amount calculated by the calculating means. And a correcting means for correcting the position of the image formed on the image carrier by using the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein two or more image carriers are arranged in parallel. 3. The image forming apparatus according to claim 1, wherein said movable body is an intermediate transfer body. 4. The moving body according to claim 1, wherein the moving body is a continuous paper supplied continuously.
An image forming apparatus according to any one of the preceding claims. 5. The apparatus according to claim 1, wherein said moving body is a conveying means for conveying a transfer material for transferring an image formed on an image carrier and a registration mark image. 3. The image forming apparatus according to claim 2. 6. The image forming means has writing means for writing a light beam for forming the image on the image carrier, and the correction means controls a writing timing of the light beam by the writing means. The image forming apparatus according to claim 1, wherein: 7. The apparatus according to claim 1, wherein said correction means is provided on said image carrier.
An image forming apparatus according to any one of the preceding claims. 8. An image forming apparatus according to claim 1, wherein said detecting means is provided on both sides of said transferring means. 9. The image processing apparatus according to claim 1, wherein said correcting means corrects a position of an image on said image carrier based on an image forming timing in a moving direction of said transfer means.
Item 3. The image forming apparatus according to Item 2 or 2. 10. The apparatus according to claim 1, wherein said correction means corrects the position of the image on said image carrier based on an image forming timing substantially perpendicular to the moving direction of the transfer means. Or the image forming apparatus according to claim 2. 11. The apparatus according to claim 1, wherein said correction means corrects the rotation of the position of the image on the image carrier based on a direction perpendicular to the moving direction of the transfer means.
Item 3. The image forming apparatus according to Item 2 or 2. 12. An image forming apparatus according to claim 1, wherein said correction means corrects the position of the image on said image carrier based on the magnification of the image.