JP2004302138A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a color image good in color reproducibility and high in image quality by accurately detecting the mutual deviation of visible images in plural colors, accurately correcting the deviation and accurately superposing the visible images in plural colors on top of one another. <P>SOLUTION: As for detection pattern marks 27Y to 27BK formed on a transfer belt 13, sides 27Ya to 27BKa parallel to the main scanning direction and sides 27Yb to 27BKb orthogonal to the main scanning direction are detected by using a mark detecting sensor 28 which moves with rotation. Then, the detection pattern marks 27Y to 27BK can be accurately detected without being affected by the ruggedness of a dot, and the deviation is accurately corrected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color image forming apparatus that obtains a color image by superimposing visible images of a plurality of colors.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus for obtaining a color image, various methods have been adopted in order to reduce the size of the apparatus, increase the process speed, or achieve high-precision color superposition. For example, each time a toner image of three primary colors (yellow, magenta, and cyan) and, in some cases, four colors including black is formed on one photosensitive drum, transfer to paper is repeated three or four times. A method for obtaining a color image. Alternatively, an image forming unit for forming a single-color toner image on each photosensitive drum is provided for four colors including three primary colors or black in the paper transport direction, and the color toner images are superimposed on the paper to form a color image. A so-called tandem system that forms Alternatively, an image exposing device and a developing device of four colors including three primary colors or black for forming an electrostatic latent image on one photosensitive drum are provided, and toner images of each color are superimposed on the photosensitive drum. There is a multi-developing method for forming a color image and collectively transferring it to paper or the like.
[0003]
Regardless of these various image forming methods, a color image forming apparatus that superimposes toner images of a plurality of colors is capable of assembling accuracy, processing accuracy, mounting position errors of an exposure device or an image forming unit for each color, or a sheet as a transfer target medium. In some cases, the toner images of a plurality of colors may be displaced relative to each other due to uneven conveyance speed, and may not be accurately overlapped.
[0004]
Conventionally, in order to increase the overlay accuracy by correcting the relative misregistration of the toner images of a plurality of colors, in the tandem system, a line parallel to the main scanning direction and a main scanning direction are used by using an image forming unit of each color. After a detection pattern consisting of a line that is oblique to both the sub-scanning direction and a line that is oblique to the sub-scanning direction is formed on the transfer belt by shifting by a predetermined distance, this detection pattern is applied to the optical fiber sensor or line as the transfer belt travels. There is a device that detects using a fixed photodetector such as a sensor or a CCD (Charge Coupling Device), and corrects a positional deviation of a toner image formed by each color image forming unit based on the detected deviation amount ( For example, see Patent Document 1.)
[0005]
[Patent Document 1]
JP-A-8-278680 (pages 8, 9; FIG. 7)
For example, in Patent Document 1, as shown in FIG. 7, detection patterns 3a and 3b on the transfer belt 1 conveyed in the direction of arrow m are detected by a fixed photodetector 2, and the detection patterns 3a and 3b are detected. , The relative difference between the respective distances 4a and 4b crossing is detected to detect the deviation of each toner image in the main scanning direction. However, in Patent Literature 1, since the photodetector 2 is fixed, detection patterns 3a and 3b using oblique lines are required. However, these oblique lines have a certain area as shown in FIG. A detection error occurs because the image is constituted by dots, which are groups of collected toner. That is, irregularities are formed at the ends of the straight lines of the detection patterns 3a and 3b, and these irregularities are particularly remarkable in oblique lines, and the detection of the respective detection patterns 3a and 3b is started at the positions (A) and (B). In this case, the reading positions of the oblique lines are (C) and (D), respectively. As a result, if there is no unevenness, the relative difference between the distances 4a and 4b is (e), but the relative difference becomes (f) because of the unevenness due to the dots, and it becomes impossible to detect an accurate shift amount. Therefore, it has been impossible to perform an appropriate shift correction even though the shift amount is detected, resulting in a problem that overlay accuracy is reduced, color reproduction of a color image is impaired, and image quality is reduced.
[0006]
[Problems to be solved by the invention]
In view of the above, an object of the present invention is to solve the above-described problem, and to accurately detect a relative position error between visible images of a plurality of colors when a visible image of a plurality of colors is superimposed, and perform appropriate misalignment correction. Accordingly, an object of the present invention is to provide an image forming apparatus that superimposes visible images of a plurality of colors with high accuracy, has good color reproducibility, and obtains a clear and high-quality color image.
[0007]
[Means for Solving the Problems]
The present invention, as a means for solving the above problems, holds one or more image carriers that hold a visible image and can travel in the sub-scanning direction, and scans in a main scanning direction orthogonal to the sub-scanning direction. One or a plurality of image forming means for forming the visible image or a position information image indicating the formation position of the visible image on the image carrier, and forming on the image carrier by traveling in the sub-scanning direction. A transfer medium on which the plurality of position information images to be transferred are transferred at predetermined intervals; and a main transfer information medium which is movably provided at a position facing the transfer medium and is transferred to the transfer medium. Detecting means for detecting the forming position in the scanning direction and the forming position in the sub-scanning direction at different positions; and the plurality of pieces of position information based on a relative difference between the plurality of position information images detected by the detecting means in the main scanning direction. Image formation in the main scanning direction The location relative correction is intended to provide a correction means for relatively correcting the subscanning direction forming positions of the plurality of position information image from the relative difference in the sub-scanning direction forming position of said plurality of position information image.
[0008]
According to another aspect of the present invention, there is provided an image holding member that holds an image and can move in a sub-scanning direction, and scans the image holding member in a main scanning direction orthogonal to the sub-scanning direction. A plurality of image forming means for forming the image or a position information image for displaying a formation position of the image at predetermined intervals; and movably provided at a position facing the image holding member, and formed on the image holding member. A detection unit that detects a main scanning direction formation position and a sub-scanning direction formation position of a plurality of position information images at different positions, and a relative position of the main scanning direction formation positions of the plurality of position information images detected by the detection unit The main scanning direction forming positions of the plurality of position information images are relatively corrected from the difference, and the sub-scanning direction forming positions of the plurality of position information images are obtained from a relative difference between the sub-scanning direction forming positions of the plurality of position information images. The relative It is intended to provide a positive correcting means.
[0009]
With the above configuration, the present invention accurately detects the main scanning direction forming position and the sub-scanning direction forming position of a plurality of images, and thereby performs accurate relative correction between the main scanning direction forming position and the sub-scanning direction forming position. It is an object of the present invention to provide an image forming apparatus which is capable of obtaining a clear and high-quality color image with high overlay accuracy and good color reproducibility.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a schematic configuration diagram showing an image forming unit 10 of a four-tandem tandem type full-color electrophotographic apparatus which is an image forming apparatus of the present invention. The image forming unit 10 includes four sets of yellow (Y) and magenta (M), each of which forms a single-color developed image using each toner of yellow (Y), magenta (M), cyan (C), and black (BK). ), Cyan (C), and black (BK) image forming stations 12Y, 12M, 12C, and 12BK are arranged in parallel along a transfer belt 13 that is a transfer medium that transports a sheet P.
[0011]
Since the image forming stations 12Y, 12M, 12C, and 12BK of the respective colors have the same configuration, they will be described with reference to the yellow image forming station 12Y disposed in the preceding stage, and the image forming stations 12M of the other colors will be described. Regarding 12C and 12BK, the same portions are denoted by the same reference numerals and suffixes indicating the respective colors, and description thereof is omitted.
[0012]
The yellow image forming station 12Y has a photosensitive drum 14Y which is an image carrier and rotates and runs in the direction of arrow s which is the sub-scanning direction. Around the photoreceptor drum 14Y, a charging device 16Y, an exposure device 17Y, a developing device 18Y, a transfer charger 20Y, and a cleaning device 21Y, which are image forming means, are sequentially arranged. The transfer charger 20Y is disposed to face the photosensitive drum 14Y via the transfer belt 13. The exposure device 17Y selectively irradiates yellow (Y) light facing the yellow (Y) optical signal by scanning in a main scanning direction orthogonal to the rotational traveling direction of the photosensitive drum 14Y, and selectively irradiates the yellow (Y) light. An electrostatic latent image corresponding to yellow (Y) image information and an electrostatic latent image of detection pattern marks 27Y, 27M, 27C, and 27BK described later are formed on 14Y.
[0013]
The transfer belt 13 is stretched between the drive roller 13a and the tension roller 13b, and conveys the paper P in the sub-scanning direction, that is, the arrow t direction. The transport speed of the paper P by the transfer belt 13 is set to be equal to the peripheral speed of the photosensitive drums 14Y, 14M, 14C, and 14BK. A fixing device 24 is provided downstream of the transfer belt 13. Reference numeral 25 denotes a registration roller, and reference numeral 26 denotes a transfer belt cleaner.
[0014]
At the downstream end of the transfer belt 13, a movable mark detection sensor 28 is disposed to face. The mark detection sensor 28 detects a formation position in the main scanning direction and a formation position in the sub-scanning direction of the detection pattern marks 27Y, 27M, 27C, and 27BK, which are position information images formed at predetermined intervals on the transfer belt 13. The detection result by the mark detection sensor 28 is input to a calculation unit 30 that calculates an appropriate exposure timing. The result of calculation by the calculation unit 30 is input to an exposure control device 31 which is a correction means and controls the exposure devices 17Y to 17BK. Note that the calculation unit 30 may be configured integrally with the exposure control device 31.
[0015]
The mark detection sensor 28 includes a photo sensor 28c at the tip of an arm 28b that can rotate about a fulcrum 28a. The mark detection sensor 28 holds the detection pattern marks 27Y to 27Y while holding the arm 28b substantially parallel to the main scanning direction. 27BK is detected in the sub-scanning direction, and the detection of the detection pattern marks 27Y to 27BK in the main scanning direction is performed with the arm 28b substantially perpendicular to the main scanning direction. The rotation angle of the arm 28b is detected by the encoder 28d.
[0016]
The shift detection in the sub-scanning direction, which is the traveling direction of the sheet P, by the mark detection sensor 28 is performed as shown in FIG. 2 by detecting the sides 27Ya to 27Ya of the detection pattern marks 27Y to 27BK formed at predetermined intervals in parallel with the main scanning direction. This is performed by detecting an interval of 27 BKa. That is, when the interval detected by the mark detection sensor 28 is wider than the predetermined interval, the exposure control device 31 advances the exposure start timing of the subsequent image, and when the detected interval is narrower than the predetermined interval, the exposure control device 31 By delaying the exposure start timing of the image, the shift correction of the toner images of a plurality of colors is performed.
[0017]
As shown in FIG. 3, the shift detection in the main scanning direction, which is the scanning direction of exposure, by the mark detection sensor 28 is performed when the sides 27Yb to 27BKb of the detection pattern marks 27Y to 27BK that are orthogonal to the main scanning direction are detected. This is performed by detecting the rotation angle of the arm 28b. From FIG. 3, when the length of the arm 28b is L and the rotation angle θ of the arm 28b at the time of detection of the detection pattern marks 27Y and 27M is shifted by Δθ between the preceding detection pattern mark 27Y and the subsequent detection pattern mark 27M. Means that the image shift amount in the main scanning direction is (LΔθ). Accordingly, the exposure controller 31 corrects the deviation of the toner images of a plurality of colors by changing the installation angle of the folding mirrors (not shown) of the exposure devices 17Y to 17BK or adjusting the timing of irradiation of the polygon mirror. Do.
[0018]
Next, the operation will be described. When the warm-up is started after the power is turned on and the full-color electrophotographic apparatus is in a ready state, the image forming unit 10 first corrects the positional deviation of the toner images formed by the image forming stations 12Y to 12BK. That is, in each of the image forming stations 12Y to 12BK, the photoconductor drums 14Y to 14BK are uniformly charged by the charging devices 16Y to 16BK according to the rotation of the photoconductor drums 14Y to 14BK in the direction of the arrow s, and then the exposure devices 17Y to 17BK. Exposure scanning is performed to form the detection pattern marks 27Y to 27BK on the photosensitive drums 14Y to 14BK.
[0019]
Next, the latent images corresponding to the detection pattern marks 27Y to 27BK on the photosensitive drums 14Y to 14BK are developed by the developing devices 18Y to 18BK, and yellow (Y), magenta (M), and cyan (C) are formed on the photosensitive drums 14Y to 14BK. C), black (BK) detection pattern marks 27Y to 27BK are obtained. Further, the detection pattern marks 27Y to 27BK on the photosensitive drums 14Y to 14BK are transferred to the transfer belt 13 at predetermined intervals as shown in FIG.
[0020]
When the detection pattern marks 27Y to 27BK reach the position of the mark detection sensor 28 as the transfer belt 13 travels, the mark detection sensor 28 first detects the side 27Ya of the yellow (Y) detection pattern mark 27Y parallel to the main scanning direction. After obtaining the formation position in the sub-scanning direction, the detection pattern mark 27Y is rotated in the direction of the arrow u to detect a side 27Yb orthogonal to the main scanning direction of the detection pattern mark 27Y. The direction forming position is obtained, and the result is input to the calculation unit 30. Next, the mark detection sensor 28 is rotated in the direction opposite to the direction of the arrow u, and after detecting the side 27Ma of the detection pattern mark 27M of magenta (M) parallel to the main scanning direction to obtain a sub-scanning direction formation position. Is rotated again in the direction of arrow u to detect a side 27Mb of the detection pattern mark 27M orthogonal to the main scanning direction, and the main scanning direction forming position is obtained from the rotation angle θ of the mark detection sensor 28, and the result is calculated. Input to the unit 30.
[0021]
The calculation unit 30 calculates the shift amount (Δθ) between the formation positions of the detection pattern marks 27Y and 27M for yellow (Y) and magenta (M) in the sub-scanning direction from the transit times of the sides 27Ya and 27Ma parallel to the main scanning direction. And input to the exposure control device 31. Further, the calculation unit 30 determines the positions of the yellow (Y) and magenta (M) detection pattern marks 27Y and 27M in the main scanning direction based on the rotation angle of the arm 28b when the sides 27Yb and 27Mb perpendicular to the main scanning direction are detected. The shift angle Δθ is calculated and input to the exposure control device 31. Thereafter, using the yellow (Y) detection pattern mark 27Y as a reference, the shift amounts of cyan (C) and black (BK) are detected by the mark detection sensor 28 in the same manner as for magenta (M). Then, the shift amount (LΔθ) is calculated.
[0022]
The exposure control device 31 controls the exposure apparatus in accordance with the amount of deviation between the reference yellow (Y) detection pattern mark 27Y and the magenta (M), cyan (C), and black (BK) detection pattern marks 27M to 27BK. 17Y to 17BK are corrected and controlled.
[0023]
When the detection pattern marks 27M to 27BK are shifted in the sub-scanning direction, the exposure control device 31 adjusts the exposure start timing so that the intervals between the respective detection pattern marks 27M to 27BK become a predetermined interval. Correction. When the detection pattern marks 27M to 27BK deviate in the main scanning direction, the exposure control device 31 changes the installation angle of the folding mirror (not shown) to deviate the exposure start position and correct the mutual deviation.
[0024]
Thereafter, the detection pattern marks 27Y to 27BK are formed on the transfer belt 13 again, detected by the mark detection sensor 28, and the shift amount is calculated by the calculation unit 30, and the shift of the detection pattern marks 27Y to 27BK is mutually corrected. Make sure that At this time, if the deviation has not been corrected, the exposure control device 31 controls the exposure devices 17Y to 17BK again for correction. This correction control operation is repeated to confirm the deviation correction of the detection pattern marks 27Y to 27BK, and the deviation correction operation is ended. Thereafter, a normal color image forming operation is started.
[0025]
When the image forming operation is started, for example, in the yellow image forming station 12Y, the image forming process is sequentially performed according to the rotation of the photosensitive drum 14Y in the direction of the arrow s. The photoreceptor drum 14Y is uniformly charged by the charging device 16Y, and then exposed by the exposure device 17Y to form an electrostatic latent image corresponding to yellow (Y) image data. It is developed to form a yellow (Y) toner image. Similarly, in each of the magenta (M), cyan (C), and black (BK) image forming stations 12M, 12C, and 12BK, a toner image of each color is formed on each of the photosensitive drums 14M, 14C, and 14BK. You.
[0026]
On the other hand, paper P is supplied from a paper feeding device (not shown) in synchronization with the operation of forming the toner images of each color on the photosensitive drums 14 </ b> Y to 14 </ b> BK. After being moved, it is sent to the transfer belt 13.
[0027]
The sheet P sent to the transfer belt 13 is conveyed in the direction of arrow t as the transfer belt 13 travels while being electrostatically attracted to the transfer belt 13. While the paper P is conveyed in the direction of the arrow t, the yellow toner image, the magenta toner image, the cyan toner image, and the black toner image are sequentially multiplex-transferred at the positions of the transfer chargers 20Y to 20BK to form a full-color toner image. Then, the image is conveyed to the fixing device 24 and fixed, and then discharged to complete the image forming operation.
[0028]
On the other hand, after the paper P is peeled off, the transfer belt 13 is driven to rotate as it is, and the attached toner and paper dust are cleaned by the belt cleaner 26. After the transfer of the toner image, each of the photoconductor drums 14Y to 14BK is driven to rotate as it is, and the cleaning devices 21Y to 21BK clean the residual toner and paper dust, and wait for the next full-color image forming process.
[0029]
During the repetition of the image forming operation, the superposition of each toner image may be shifted due to a change in the surrounding environment. Therefore, the detection pattern mark is detected by the mark detection sensor 28 according to the instruction of the operator or at regular intervals. 27Y to 27BK are read, and a misregistration correction operation of the toner image is performed.
[0030]
With the above configuration, in the present embodiment, by using the mark detection sensor 28 that rotates, the detection including the sides 27Ya to 27BKa parallel to the main scanning direction and the sides 27Yb to 27BKb orthogonal to the scanning direction is performed. The pattern marks 27Y to 27BK can be read with high accuracy, and the detection pattern marks 27Y to 27BK made of dots can be detected with high accuracy. Accordingly, appropriate misalignment correction can be performed with high accuracy, superposition of toner images of a plurality of colors can be performed with high accuracy, and a high-quality color image with good color reproducibility can be obtained.
[0031]
Next, the present invention will be described with reference to a second embodiment shown in FIG. This embodiment is different from the first embodiment in the image forming method. In the present embodiment, a multi-developing image forming apparatus is used to correct the color misregistration of a multi-color toner image, and the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. I do.
[0032]
A photosensitive drum 41 having an organic or amorphous silicon photosensitive layer provided on the surface of a conductive aluminum tube, for example, is provided on the photosensitive drum 41 of the image forming unit 40 of the multi-developing system which is an image forming apparatus. Image formation is sequentially performed on the photosensitive drum 41 using the liquid developers of yellow (Y), magenta (M), cyan (C), and black (BK) along the rotation of the body drum 41 in the direction of the arrow v. First to fourth image forming units 42Y to 42BK, which are image forming means, are arranged.
[0033]
Each of the image forming units 42Y to 42BK has the same configuration except that the color of the liquid developer to be used is different from each other, but the yellow (Y) disposed upstream of the photosensitive drum 41 in the rotation direction. And the other image forming units 42M to 42BK will be denoted by the same reference numerals and suffixes indicating the respective colors, and the description thereof will be omitted.
[0034]
The yellow (Y) image forming unit 42Y includes a well-known corona charger or scorotron charger, and uniformly charges the surface of the photosensitive drum 41, and yellow (Y) modulated according to image information. The yellow (Y) light 43Y corresponding to the light signal is scanned in a main scanning direction orthogonal to the rotational traveling direction of the photosensitive drum 41 and selectively irradiated, and a yellow (Y) image is formed on the photosensitive drum 41Y. An exposure device 45Y for forming an electrostatic latent image corresponding to information and an electrostatic latent image of detection pattern marks 27Y, 27M, 27C, and 27BK described below is provided.
[0035]
Further, the yellow (Y) image forming unit 42Y supplies a yellow (Y) liquid developer to the electrostatic latent image formed on the photosensitive drum 41 by the developing roller 46Y, and controls the developing device 44Y that forms a toner image. Have.
[0036]
Downstream of each of the image forming units 42Y to 42BK around the photoconductor drum 41, a removing device 46 including a squeezing unit and a drying unit for removing the excess carrier liquid on the photoconductor drum 41 after development by the developing units 44Y to 44BK. Is provided. A transfer device 47 having an intermediate transfer roller 47a and a pressure roller 47b is provided downstream of the removing device 46 around the photosensitive drum 41.
[0037]
Between the removal device 46 around the photoconductor drum 41 and the transfer device 47, the sides 27Ya of the detection pattern marks 27Y, 27M, 27C, and 27BK formed on the photoconductor drum 41 at predetermined intervals are parallel to the main scanning direction. The same rotatable mark detection sensor 28 as in the first embodiment for detecting the sides 27Yb to 27BKb orthogonal to the main scanning direction is arranged opposite to the first embodiment. The detection result by the mark detection sensor 28 is input to the calculation unit 30, and the calculation result by the calculation unit 30 is input to an exposure control device 48 which is a correcting means and controls the exposure devices 45 Y to 45 BK.
[0038]
Downstream of the transfer device 47 around the photoconductor drum 41, a photoconductor cleaner 50 that removes toner remaining on the photoconductor drum 41 after the primary transfer of the toner image to the intermediate transfer roller 47a is provided.
[0039]
Next, the operation will be described. After the power is turned on, first, the positional deviation of the toner image is corrected. In accordance with the rotation of the photoconductor drum 41 in the direction of arrow v, the photoconductor drum 41 is uniformly charged by the charging devices 49Y to 49BK in the image forming units 42Y to 42BK, and then the detection pattern marks 27Y to 27BK are formed by the exposure devices 45Y to 45BK. An electrostatic latent image is formed, developed by the developing devices 44Y to 44BK, and detection pattern marks 27Y to 27BK are formed on the photosensitive drum 41 at predetermined intervals.
[0040]
When the detection pattern marks 27Y to 27BK reach the position of the mark detection sensor 28 due to the rotation of the photosensitive drum 41, the mark detection sensor 28 rotates similarly to the first embodiment, and sequentially turns yellow (Y) and magenta. The (M), cyan (C), and black (BK) detection pattern marks 27Y to 27BK detect sides 27Ya to 27BKa parallel to the main scanning direction and sides 27Yb to 27Yb orthogonal to the main scanning direction, and perform sub-scanning directions. The detection results of the formation position and the formation position in the main scanning direction are input to the calculation unit 30.
[0041]
The calculation unit 30 calculates the shift amount of the detection pattern marks 27Y to 27BK in the sub-scanning direction formation position and the shift amount of the detection pattern marks 27Y to 27BK in the main scanning direction and inputs the calculated shift amount to the exposure control device 31. The exposure control device 31 adjusts the exposure start timing of the exposure devices 45Y to 45BK according to the shift amount to correct the shift in the sub-scanning direction, and changes the installation angle of the folding mirror (not shown) in the main scanning direction. Correct the misalignment. Thereafter, the detection pattern marks 27Y to 27BK are formed again on the photosensitive drum 41, detected by the mark detection sensor 28, and the amount of displacement is calculated by the calculation unit 30, and the displacement of the detection pattern marks 27Y to 27BK is mutually corrected. Check that If the shift has not been corrected, the exposure control device 31 again controls the exposure of the exposure devices 45Y to 45BK, and after the shift correction operation is completed, starts a normal color image forming operation.
[0042]
When the image forming operation is started, the photosensitive drum 41 rotates in the direction of arrow v, and at the same time, the toner image forming operation is performed by each of the image forming units 42Y to 42BK, and first, the yellow (Y) image forming unit 42Y. Then, the photosensitive drum 41 is uniformly charged by the charging device 49Y, then an electrostatic latent image corresponding to the yellow (Y) image data is formed by the exposure device 45Y, and the yellow (Y) toner image is formed by the developing device 46Y. Is formed. Similarly, magenta (M), cyan (C), and black (BK) toner images are sequentially superimposed on the photosensitive drum 41 by the subsequent image forming units 42M to 42BK to form a full-color toner image. You.
[0043]
Thereafter, the toner image on the photosensitive drum 41 is removed of the excess carrier liquid via the removing device 46, reaches the transfer device 47, is primarily transferred to the intermediate transfer roller 47a, and is further transferred between the intermediate transfer roller 47a and the pressure roller 47b. Is transferred to a sheet P conveyed in the direction of arrow w, a full-color image is completed on the sheet P, and the image forming operation is completed.
[0044]
After the primary transfer of the toner image to the intermediate transfer roller 47a is completed, the photosensitive drum 41 is removed of the residual developer by the photosensitive member cleaner 50, and a series of image forming processes is completed, and the next color image forming process is awaited.
[0045]
While the image forming operation is repeated as described above, the detection pattern marks 27Y to 27BK are read by the mark detection sensor 28 by the instruction of the operator or at regular intervals, and the misregistration operation of the toner image is performed.
[0046]
With the above configuration, in the present embodiment, similarly to the first embodiment, the mark detection sensor 28 that rotates is provided, and the sides 27Ya to 27BKa parallel to the main scanning direction and orthogonal to the scanning direction. The detection pattern marks 27Y to 27BK composed of the sides 27Yb to 27BKb can be read with high accuracy, and the detection pattern marks 27Y to 27BK can be detected with high accuracy. Therefore, appropriate misalignment correction can be performed with high accuracy, the overlay accuracy of the toner images of a plurality of colors can be improved, and a high-quality color image with good color reproducibility can be obtained.
[0047]
The present invention is not limited to the above-described embodiment, and can be changed without departing from the spirit of the present invention. For example, the detecting means is a photo sensor of the mark detecting sensor 52 as shown in a modified example shown in FIG. The detection pattern marks 27Y to 27BK may be detected by reciprocatingly sliding the arm 52b supporting the 52a with the feed screw 52c substantially parallel to the main scanning direction in the direction of the arrow w. The mark detection sensor 52 detects a shift in the position where the position information image is formed in the main scanning direction based on the feed amount of the feed screw 52c. Further, the shape of the position information image is arbitrary, and the detection means is not limited to the photo sensor but may be a CCD or the like. A correction method for performing relative correction on the position information images of a plurality of colors is also arbitrary. Further, the position information image may be provided on either the rear side or the front side of the image holding member, or may be provided on both the rear side and the front side as required.
[0048]
【The invention's effect】
As described above, according to the present invention, since accurate displacement correction can be obtained by highly accurate detection of the position information image, the overlay accuracy of the visible images of a plurality of colors can be improved, and high color reproducibility can be achieved. A high quality color image can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an image forming unit of a color electrophotographic apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic explanatory view showing a mark detection sensor and a detection pattern mark according to the first embodiment of the present invention.
FIG. 3 is a schematic explanatory view showing detection of a deviation of a detection pattern mark by the mark detection sensor according to the first embodiment of the present invention.
FIG. 4 is a schematic explanatory view showing a detection pattern mark formed on the transfer belt according to the first embodiment of the present invention.
FIG. 5 is a schematic configuration diagram illustrating an image forming unit of a color electrophotographic apparatus according to a second embodiment of the present invention.
FIG. 6 is a schematic configuration diagram illustrating a mark detection sensor according to a modified example of the invention.
FIG. 7 is a schematic explanatory view showing displacement detection by a conventional fixed photodetector.
FIG. 8 is a schematic explanatory view showing a detection error by a conventional photodetector.
[Explanation of symbols]
10. Image forming unit
12Y to 12BK: Image forming station
13 ... Transfer belt
14Y-14BK: Photoconductor drum
16Y-16BK: Charging device
17Y-17BK ... Exposure equipment
18Y to 18BK: Developing device
20Y ~ 20BK ... Transfer charger
24 ... Fixing device
27Y-27BK ... Detection pattern mark
28… Mark detection sensor
28b ... arm
28c Photo sensor
28d ... Encoder

Claims (6)

One or more image carriers that hold a visible image and are capable of traveling in the sub-scanning direction;
One or more image forming means for scanning in the main scanning direction orthogonal to the sub-scanning direction to form a position information image indicating the visible image or the visible image forming position on the image carrier;
A transfer receiving medium that travels in the sub-scanning direction and transfers a plurality of position information images formed on the image holding member at predetermined intervals;
Detecting means movably provided at a position facing the transfer-receiving medium, and detecting, at different positions, a formation position in the main scanning direction and a formation position in the sub-scanning direction of the plurality of position information images transferred to the transfer receiving medium When,
The main scanning direction formation positions of the plurality of position information images are relatively corrected from a relative difference between the main scanning direction formation positions of the plurality of position information images detected by the detection unit, and the plurality of the position information images are A color image forming apparatus comprising: a correction unit that relatively corrects the formation positions of the plurality of position information images in the sub-scanning direction based on a relative difference between the formation positions in the sub-scanning direction. An image holding member that holds an image and can travel in the sub-scanning direction;
A plurality of image forming units that scan in a main scanning direction orthogonal to the sub-scanning direction and form a position information image that indicates a formation position of the image or the image on the image carrier at a predetermined interval;
Detecting means movably provided at a position facing the image holding member, and detecting a main scanning direction forming position and a sub-scanning direction forming position of a plurality of position information images formed on the image holding member at different positions; ,
The main scanning direction formation positions of the plurality of position information images are relatively corrected from a relative difference between the main scanning direction formation positions of the plurality of position information images detected by the detection unit, and the plurality of the position information images are A color image forming apparatus comprising: a correction unit that relatively corrects the formation positions of the plurality of position information images in the sub-scanning direction based on a relative difference between the formation positions in the sub-scanning direction. 3. The color image forming apparatus according to claim 2, wherein the image or the position information image formed on the plurality of image forming units is a visible image. 4. The color as claimed in claim 1, wherein said detection means rotates to detect a main scanning direction forming position and a sub-scanning direction forming position of said plurality of position information images. Image forming device. 5. The color image forming apparatus according to claim 4, wherein said detecting means has an encoder for measuring a rotation amount of said detecting means. 4. The apparatus according to claim 1, wherein the detection unit moves in parallel with the main scanning direction to detect a main scanning direction forming position and a sub-scanning direction forming position of the plurality of position information images. The color image forming apparatus according to any one of the above.

Images