JP2015222356A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent misregistration from being worsened due to correcting misregistration.SOLUTION: An image forming apparatus includes: first image forming means which forms a toner image of a first color; second image forming means which is arranged downstream of the first image forming means and forms a toner image of a second color; an image carrier to which the toner images of the first and second colors are transferred; first and second detection means arranged in different positions in a moving direction of the image carrier, to detect a position of an end of the image carrier; and misregistration correction means which executes misregistration correction for controlling the position where the toner image of the first color is formed, on the basis of the position of the end of the image carrier detected by the first and second detection means, so that the toner image of the first color is aligned with the toner image of the second color, on the image carrier. The control means does not execute misregistration correction when the amount of inclination of the image carrier is within a predetermined range.

Description

  The present invention relates to an image forming apparatus that forms an image.

  Conventional electrophotographic printers transfer Y, M, C, and K toner images formed on Y, M, C, and K drums onto an intermediate transfer member to form a color toner image in which the colors overlap. To do. The color toner image is transferred and fixed on a sheet. When the intermediate transfer belt is always driven to rotate straight without meandering, the toner image formed on each drum is transferred to the same position. When the intermediate transfer belt meanders, the toner image formed on each drum is transferred to different positions according to the amount of meandering, and color deviation occurs in the output image. As a technique for correcting the color misregistration caused by the meandering of the intermediate transfer belt, the misregistration detects the amount of inclination of the intermediate transfer belt in the belt main scanning direction (width direction) and corrects the image forming position deviation in the main scanning direction. A correction technique has been proposed (Patent Document 1).

JP 2009-25626 A

  However, if the misregistration is always corrected using the detected belt tilt amount, the color misregistration may become large when the belt is slightly tilted. In general, the amount that a human can recognize as a color shift is about 10 μm or more. When correcting a color misregistration of 10 μm or less, the color misregistration amount of 10 μm or less may be originally increased due to a detection error of the detection unit, an arithmetic error of the arithmetic device, an accuracy of the laser control device, or the like. .

  On the other hand, by increasing the detection accuracy of the detection unit, the calculation system of the calculation device, and the accuracy of the laser control device, it is also possible to prevent the color misregistration amount of 10 μm or less from being increased conversely. However, for this purpose, it is necessary to increase the accuracy of each device, which increases the cost of each device.

  In view of the above, an object of the present invention is to reduce the deterioration of the positional deviation by performing the positional deviation correction, and to form a high-quality output image in which the quality degradation due to the color deviation is less likely to occur.

  In order to achieve the above object, an image forming apparatus of the present invention includes a first image forming unit that forms a first color toner image, and a second color toner image that is disposed downstream of the first image forming unit. Second image forming means to be formed, and an image carrier onto which the first color toner image formed by the first image forming means and the second color toner image formed by the second image forming means are transferred And first and second detection means that are arranged at different positions in the moving direction of the image carrier and detect the position of the end of the image carrier, and the first color toner image on the image carrier. The formation position of the toner image of the first color is controlled based on the position of the edge of the image carrier detected by the first and second detection means so that the positions of the toner images of the two colors match. To perform misalignment correction And means, wherein, when the inclination of the image bearing member is within a predetermined range characterized in that it does not perform the positional deviation correction.

  According to the present invention, it is possible to form a high-quality output image in which it is possible to reduce the deterioration of the position shift by performing the position shift correction and to prevent the quality from being deteriorated due to the color shift.

1 is a diagram illustrating a configuration of an image forming apparatus. FIG. 6 is a diagram for explaining steering control of an intermediate transfer belt and inclination detection of the intermediate transfer belt. FIG. 3 is a diagram illustrating a configuration of a sensor that detects the position of an end portion of an intermediate transfer belt. It is a figure explaining position shift correction. It is a figure explaining the range of the inclination amount which implements position shift correction. It is a figure explaining the control flow concerning position shift correction.

Example 1
Hereinafter, embodiments in which the present invention is applied to an electrophotographic image forming apparatus will be described.

<Configuration example of image forming apparatus>
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to the present exemplary embodiment.

  A document 100 is placed on the document table glass 101. The document 100 placed on the document table glass 101 is irradiated with illumination 103. The light reflected by the original 100 passes through mirrors 104, 105, and 106 and is imaged on the CCD 109 by the optical system 108. The CCD 109 is composed of a three-line CCD line sensor of R (red), B (blue), and G (green). Further, the motor 102 drives the first mirror unit 137 holding the illumination 203 and the mirror 104 at a speed V, and drives the second mirror unit 107 including the mirrors 105 and 106 at a speed 1 / 2V. By driving the first mirror hot water 137 and the second mirror unit 107 in this manner, the entire image of the original 100 is read.

  The image processing unit 110 processes the image information output from the CCD 109 and outputs it as a print signal to the printer control unit 111. The semiconductor lasers 112, 113, 114, and 115 emit laser light based on the output signal output from the printer control unit 111. Laser light emitted from the semiconductor lasers 112, 113, 114, and 115 scans the photosensitive drums 124, 125, 126, and 127 by the polygon mirrors 116, 117, 118, and 119 to form a latent image corresponding to the output image. . Developing units 123, 122, 121, and 120 develop the latent images formed on the photosensitive drums 127, 126, 125, and 124, and yellow (Y), magenta (M), cyan (C), and black (Bk). The toner image is generated. The yellow (Y), magenta (M), cyan (C), and black (Bk) toner images are transferred to the intermediate transfer belt 128 by the transfer rollers 151, 152, 153, and 154 to form a color toner image. The The intermediate transfer belt is rotated by a driving roller 173 driven by a belt driving motor (not shown). The intermediate transfer belt 128 is an endless belt wound around a plurality of rollers, and is an image carrier that carries a toner image.

  The paper fed from any of the paper cassettes 132, 133, 134 and the manual feed tray 131 passes through the registration roller 130 and is conveyed to a nip portion formed by the intermediate transfer belt 128 and the second transfer transfer roller 155. In this nip portion, the color toner image on the intermediate transfer belt 128 is transferred onto a sheet. The photo interrupter 129 is an ITOP sensor for generating a page synchronization signal. The aforementioned paper feed timing and the start of exposure scanning of the photosensitive drum of the laser are performed in accordance with a page synchronization signal (ITOP signal) generated by this ITOP sensor.

  The sheet on which the color toner image is transferred is conveyed to the fixing device 136, and the color toner image is fixed on the sheet by the fixing device 136. The fixing device 136 includes a fixing roller 141 incorporating a halogen heater and a pressure roller 140, and fixes a color toner image on a sheet by heat and pressure. The fixed sheet is discharged onto the discharge tray 135.

  Sensors 170 and 171 for detecting the position of the end of the belt are provided at the end of the intermediate transfer belt 128. The steering motor 172 is controlled based on the position of the belt end detected by the sensor 171. The attitude of the steering roller 173 is controlled by the steering motor 172, and the position of the belt is adjusted so that the belt position falls within a predetermined range.

  The steering control of the intermediate transfer belt and the inclination detection of the intermediate transfer belt will be described with reference to FIG. The driving roller 174 is rotationally driven in the direction 215 by the belt driving motor 202. The intermediate transfer belt 128 is rotated by the driving roller 174 and moves in the direction 216.

  The steering control performed by the steering motor 205 will be described.

  A case where the intermediate transfer belt 128 moves in the + α direction 220 will be described. The sensor 171 detects that the position of the end portion of the intermediate transfer belt 128 has moved in the + α direction 220. The steering control unit 213 controls the steering motor 172 based on the detection result, and moves the steering roller 173 in the + β direction so that the intermediate transfer belt 128 moves in the −α direction.

  A case where the intermediate transfer belt 128 moves in the -α direction 220 will be described. The sensor 171 detects that the position of the belt end is moving in the -α direction. The steering control unit 213 controls the steering motor 172 based on the detection result, and moves the steering roller 173 in the −β direction so that the intermediate transfer belt 128 moves in the + α direction.

  By repeatedly performing such control, control is performed so that the end position of the intermediate transfer belt 201 does not fall outside a predetermined range.

  Next, belt inclination detection will be described. The sensor 171 is used not only for steering control of the intermediate transfer belt 128 but also for detecting the inclination of the intermediate transfer belt 128. The sensor 170 is used only for detecting the inclination of the intermediate transfer belt. The misregistration control unit 212 calculates a geometrical value based on the position of the end of the intermediate transfer belt detected by the sensor 170 and the position of the end of the intermediate transfer belt detected by the sensor 171. Is used to calculate the belt tilt.

  FIG. 3 is a diagram illustrating the configuration of the sensors 170 and 171. A sensor flag 302 abuts against the end 301 of the intermediate transfer belt 128, and the sensor flag 302 moves according to the position of the end 301. By detecting the position of the sensor flag with the sensor 303, the sensors 170 and 171 detect the position of the end portion of the intermediate transfer belt 128.

  FIG. 4 is a diagram for explaining processing for correcting a positional deviation caused by meandering of the intermediate transfer belt 128.

  A yellow photosensitive drum 127, a magenta photosensitive drum 126, a cyan photosensitive drum 125, and a black photosensitive drum 124 are arranged from the upstream side in the moving direction of the intermediate transfer belt 128. A sensor 170 is disposed between the yellow photosensitive drum 127 and the magenta photosensitive drum, and a sensor 171 is disposed between the cyan photosensitive drum 125 and the black photosensitive drum 124.

  The yellow photosensitive drum 127 forms a yellow patch toner image 402 (a) at the yellow temporary transfer position on the intermediate transfer belt. The black photosensitive drum 124 disposed downstream of the yellow photosensitive drum 127 forms a black patch toner image 403 at a black temporary transfer position on the intermediate transfer belt. The black patch toner image 403 is formed so as to overlap the leading edge and the trailing edge of the yellow patch toner image 402 (b).

  In FIG. 4, the main scanning direction is the width direction of the intermediate transfer belt 128 and is a direction that intersects the moving direction of the intermediate transfer belt 128.

  FIG. 4A is a diagram illustrating the positions of the yellow toner patch and the black toner patch when the intermediate transfer belt 128 is not inclined. When the intermediate transfer belt 128 is not inclined, the yellow patch 402 (b) and the black patch 403 are formed at the same position in the main scanning direction. That is, no positional deviation occurs between the yellow patch 402 (b) and the black patch 403 in the main scanning direction.

FIG. 4B is a diagram for explaining the positions of the yellow toner patch and the black toner patch when the intermediate transfer belt 128 is inclined.
It is assumed that the distance between the yellow photosensitive drum 127 and the black photosensitive drum 124 in the moving direction of the intermediate transfer belt 128 is d1 (mm) 405. The difference between the position of the end of the intermediate transfer belt 128 at the position of the yellow photosensitive drum 127 and the position of the end of the intermediate transfer belt at the position of the black photosensitive drum 124 is Δd1 (mm). To do. The amount of inclination of the intermediate transfer belt 128 can be obtained by Expression (1).
Δd1 (mm) / d1 (mm) (1)

Here, it is assumed that the difference between the position of the end of the intermediate transfer belt detected by the sensor 171 and the position of the end of the intermediate transfer belt detected by the sensor 172 is Δd2 (mm). Assume that the distance between the sensor 171 and the sensor 172 in the moving direction of the intermediate transfer belt is d2 (mm). The amount of inclination of the intermediate transfer belt 128 can be obtained by Expression (2).
Δd2 (mm) / d2 (mm) (2)
Both the equations (1) and (2) obtain the same amount of inclination of the intermediate transfer belt 128. Therefore, since the value obtained by equation (1) is the same as the value obtained by equation (2), equation (3) is established.
Δd1 (mm) / d1 (mm) = Δd2 (mm) / d2 (mm) (3)
From this equation (3), the positional deviation amount Δd1 in the main scanning direction with respect to yellow black due to the belt inclination can be obtained from equation (4).
Δd1 = (Δd2 × d1) / d2 (4)

  Therefore, the position deviation amount Δd1 (mm) can be obtained by detecting the position of the end portion of the intermediate transfer belt in the main scanning direction by each of the sensor 170 and the sensor 171. Δd1 (mm) represents the position of the yellow photosensitive drum 127 in the moving direction of the intermediate transfer belt in the main scanning direction of the intermediate transfer belt 128 and the position of the black photosensitive drum 124 in the moving direction of the intermediate transfer belt. 2 shows the difference from the position of the intermediate transfer belt in the main scanning direction. That is, the correction value for the yellow toner patch is shown.

  As shown in FIG. 4C, by correcting the formation position of the yellow toner patch in the main scanning direction based on Δd1 (mm), at the position of the black toner patch in the moving direction of the intermediate transfer belt, In this case, the position of the black toner patch can be matched with the position of the yellow toner patch in the main scanning direction.

  Note that magenta and cyan can be similarly processed by setting the value of d1 to a value corresponding to each color. That is, for magenta, the difference between the position of the magenta photosensitive drum 126 and the position of the black photosensitive drum 124 in the moving direction of the intermediate transfer belt is used as the value of d1. For cyan, the difference between the position of the cyan photosensitive drum 127 and the position of the black photosensitive drum 124 in the moving direction of the intermediate transfer belt is used as the value of d1.

  Thus, in this embodiment, the inclination of the intermediate transfer belt is obtained from the detection results of the two sensors. However, depending on the sensor, the signal component of detection of several μm may be equivalent to the noise level. When the misalignment is corrected based on the detection result due to noise, the misalignment may be worsened.

  Therefore, in the present embodiment, when Δd2 is equal to or smaller than a predetermined range, the positional deviation is not corrected. In this embodiment, when Δd2 is within a predetermined range (−10 μm to +10 μm), the positional deviation is not corrected.

  With reference to FIG. 5, the range of the tilt amount for performing the positional deviation correction in the present embodiment will be described.

  The positional deviation control unit 212 obtains an inclination amount (Δd2 / d2) from the outputs of the sensors 170 and 171. Then, the positional deviation control unit 212 determines whether or not to correct the positional deviation from the inclination amount. Further, when the positional deviation is corrected. If it is determined, the position deviation correction value 602 for each color is obtained from the amount of inclination.

  In FIG. 5, the y axis indicates the amount of inclination obtained by the positional deviation control unit 212, and the x axis indicates time. Even when the inclination of the intermediate transfer belt is not inclined, the inclination / inclination amount varies depending on the noise component of the sensor as indicated by the signal 612. In the sensors 170 and 171 used in the present embodiment, a voltage indicating an inclination amount within ± 5 μm is generated as a noise component. That is, when the tilt amount is within ± 5 μm, it cannot be determined whether it is a noise component or the intermediate transfer belt is tilted. When the amount of inclination calculated by the position deviation control unit 112 is within ± 5 μm, if position deviation correction is performed based on this amount of inclination, there is a possibility of correction depending on the noise component. In other words, there is a possibility that the positional deviation is worsened by performing the positional deviation correction. Therefore, in this embodiment, when there is a possibility that the voltage 602 is a noise component, control is performed so as not to perform misalignment correction. Generally, the amount that a human can recognize as a color shift is 10 μm or more. Therefore, in this embodiment, when the amount of inclination calculated by the positional deviation control unit 112 is within a range of ± 10 μm, positional deviation correction is not performed.

  Further, the range in which the tilt amount calculated by the misregistration control unit 112 exceeds ± 250 μm is the tilt amount where the tilt of the intermediate transfer belt cannot be designed. Therefore, in this embodiment, when the amount of inclination calculated by the positional deviation control unit 112 exceeds ± 250 μm, positional deviation correction is not performed.

  In the present embodiment, the range of the inclination amount for performing the positional deviation correction is not less than +10 μm and less than +250 μm and more than −250 μm and not more than −10 μm. In this way, by defining the range of the tilt amount for performing the positional deviation correction, it is possible to prevent the positional deviation from being deteriorated by performing the positional deviation correction.

  FIG. 6 is a diagram illustrating a control flow executed by the misregistration control unit 212. When the misalignment correction according to the belt inclination is started, the misalignment control unit 212 activates the sensor 170 and the sensor 171 to detect the position of the end of the belt (step 501). Then, based on the detection results of the sensors 170 and 171, the misregistration control unit 212 calculates the amount of inclination of the intermediate transfer belt (step 502). The positional deviation control unit 212 determines whether the calculated inclination amount is +10 μm or more and whether the calculated inclination amount is −10 μm or less (step 503). When the calculated inclination amount is a voltage indicating a range of ± 10 μm (No in Step 503), the positional deviation correction is not performed (S607). On the other hand, if the inclination amount is outside the range of ± 10 μm (step 503 Yes), it is determined whether the calculated inclination amount is +250 μm or less and whether the calculated inclination amount is −250 μm or more. (Step 604). When the calculated inclination amount is out of the range of ± 205 μm (step 604 Yes), an error status is generated (step 606), and no misalignment correction is performed (step 607). If the calculated tilt amount is out of the range of ± 205 μm (No in step 604), the position shift correction amount Δd1 of each color is calculated from the calculated tilt amount, and the position shift correction is performed on each color (step). 505).

128 Intermediate transfer belt 127, 126, 125, 124 Photosensitive drum 170, 171 Sensor

Claims (4)

First image forming means for forming a first color toner image;
A second image forming unit disposed downstream of the first image forming unit to form a second color toner image;
An image carrier onto which a first color toner image formed by the first image forming means and a second color toner image formed by the second image forming means are transferred;
First and second detection means arranged at different positions in the moving direction of the image carrier and detecting the position of the end of the image carrier;
The end of the image carrier detected by the first and second detection means so that the positions of the first color toner image and the second color toner image are aligned with each other on the image carrier. Misregistration correction means for executing misregistration correction for controlling the formation position of the toner image of the first color based on the position;
The image forming apparatus according to claim 1, wherein the control unit does not perform the positional deviation correction when an inclination amount of the image carrier is within a predetermined range.   The image forming apparatus according to claim 1, wherein the control unit does not perform the misregistration correction when an inclination amount of the image carrier is larger than a predetermined value. The image carrier is an endless belt and is wound around first and second rollers;
Control means for controlling the attitude of the first roller in order to adjust the inclination of the image carrier based on the position of the end of the image carrier detected by the first detector. The image forming apparatus according to claim 1 or 2.   The image forming apparatus according to claim 1, wherein the correction unit controls a formation position of the first color toner image in a width direction of the image carrier.

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