JP4646213B2 - Image forming apparatus - Google Patents

Description

  In the present invention, toner images of different colors are formed on a plurality of image carriers, and the toner images are transferred onto an intermediate transfer member, and then the superimposed toner images on the intermediate transfer member are transferred to a recording medium. In addition, the present invention relates to an image forming apparatus that obtains a recorded image by directly superimposing and transferring a toner image on each image carrier onto a recording medium carried and conveyed by a recording medium carrier.

  An image forming apparatus of the above type configured as an electronic copying machine, a printer, a facsimile, or a complex machine of these is well known (for example, see Patent Document 1). As described above, the image forming apparatus includes an intermediate transfer type image forming apparatus that transfers a toner image on each image carrier to a recording medium via an intermediate transfer body, and a toner on each image carrier. There is a direct transfer type image forming apparatus that directly transfers an image to a recording medium. In any type of image forming apparatus, for example, the position of each toner image transferred to the intermediate transfer member or the recording medium may be shifted due to speed fluctuations on the surface of each image carrier, and color misregistration may occur in the superimposed toner images. There is. The main causes of the speed fluctuation on the surface of the image carrier include the eccentricity of the image carrier itself and the mounting eccentricity of the image carrier.

  In order to prevent the occurrence of the above-described color misregistration, various configurations have been conventionally proposed. However, the configuration according to the conventional proposal has a problem in that the control is complicated.

JP 2002-284561 A

  An object of the present invention is to provide an image forming apparatus capable of effectively suppressing color misregistration and forming a high-quality color image with simple control.

  In order to achieve the above object, the present invention comprises a plurality of image carriers, forms toner images of different colors on the respective image carriers, and transfers the toner images superimposed on an intermediate transfer member. In the image forming apparatus for transferring a superimposed toner image on the intermediate transfer member to a recording medium to obtain a recorded image, one of the plurality of image carriers is defined as a reference image carrier, and the reference image Each reference pattern obtained by transferring a plurality of toner images formed on at least one circumference on the carrier to the intermediate transfer body and at least one circumference on another image carrier. A time difference detecting means for detecting each pattern obtained by transferring the plurality of toner images formed on the intermediate transfer member, and calculating a sum of absolute values of the passing time differences between each reference pattern and each corresponding pattern; A position in the rotational direction of the reference image carrier; The total is calculated a plurality of times while changing the position of the other image carrier in the rotation direction, and the other image carrier is positioned relative to the position of the reference image carrier in the rotation direction when the sum is minimized. The position of the rotation direction is detected, and the reference pattern and the surface moving speed of the image carrier and the intermediate transfer member at the time of forming the pattern are the same as the image carrier and the intermediate transfer member at the time of normal image formation. The present invention proposes an image forming apparatus characterized in that the driving of the image carrier and the intermediate transfer member is controlled so as to be faster than the surface moving speed of the first image.

  Similarly, in order to achieve the above object, the present invention includes a plurality of image carriers, and forms toner images of different colors on the respective image carriers, and each of the toner images is carried on a recording medium carrier. In an image forming apparatus that obtains a recorded image by being transferred onto a recording medium that has been transported, one of the plurality of image carriers is defined as a reference image carrier, and the image is formed on the reference image carrier. Each of the reference patterns obtained by transferring a plurality of toner images formed over at least one circumference of the toner image onto the recording medium transporting body and the other image carrier are formed over at least one circumference of the reference pattern. It comprises a time difference detection means for detecting each pattern obtained by transferring a plurality of toner images to the recording medium conveyance body and calculating the sum of absolute values of the passage time differences between the respective reference patterns and the corresponding patterns. , Position of the reference image carrier in the rotational direction The total is calculated a plurality of times while changing the position of the other image carrier in the rotational direction, and the other image carrier of the reference image carrier relative to the rotational position of the reference image carrier when the sum is minimized. The position of the rotation direction is detected, and the reference pattern and the surface moving speed of the image carrier and the recording medium carrier at the time of forming the pattern are the same as the image carrier and the recording medium at the time of normal image formation. An image forming apparatus is proposed in which the driving of the image carrier and the recording medium carrier is controlled so as to be faster than the surface moving speed of the carrier.

  According to the present invention, it is possible to provide an image forming apparatus capable of effectively suppressing color misregistration and forming a high-quality color image by simple control.

  FIG. 1 is a schematic diagram showing an example of an intermediate transfer type image forming apparatus. The image forming apparatus shown here is wound around a drive roller 5 and other rollers 6, 7, and 8 and rotates in the direction of arrow A. An intermediate transfer body 4 composed of an endless belt to be driven is provided, and first to fourth process cartridges 1Y, 1C, 1M, and 1BK are arranged to face the intermediate transfer body 4. Each of the process cartridges 1Y to 1BK has first to fourth image carriers 3Y, 3C, 3M, 3BK made of a drum-shaped photoconductor, and the image carriers 3Y to 3BK are illustrated around the image carriers 3Y to 3BK. not charging device (see FIG. 2), a developing device and a cleaning device are disposed, respectively.

  When the image forming operation is started, the first image carrier 3Y is rotated in the clockwise direction in FIG. 1, and at this time, the image carrier 3Y is charged by the charging device. The charged surface is irradiated with light-modulated laser light L emitted from the exposure device 2, thereby forming an electrostatic latent image on the image carrier 3Y, and this latent image is visible as a yellow toner image by the developing device. Imaged. In this manner, the yellow toner image formed on the first image carrier 3Y is transferred onto the intermediate transfer body 4 driven in the direction of arrow A by the action of the primary transfer roller 9. Transfer residual toner adhering to the image carrier 3Y after the toner image transfer is removed by a cleaning device.

  In exactly the same manner, a cyan toner image, a magenta toner image, and a black toner image are formed on the other image carriers 3C, 3M, and 3BK, respectively, and these toner images are transferred to the intermediate transfer member 4 on which the yellow toner image is transferred. The images are sequentially transferred on top of each other. In this way, a superimposed toner image is formed on the intermediate transfer member 4.

  Further, a secondary transfer roller 10 is disposed at a position facing the driving roller 5 with the intermediate transfer member 4 interposed therebetween, and a recording medium P such as transfer paper fed from a paper supply unit (not shown) is indicated by an arrow B. As shown in FIG. 2, the sheet is fed between the intermediate transfer member 4 and the secondary transfer roller 10. When the recording medium P passes through the secondary transfer roller 10 in this way, the superimposed toner image on the intermediate transfer body 4 is transferred to the recording medium P by the action of the secondary transfer roller 10. The transfer residual toner adhering to the surface of the intermediate transfer body 4 after the toner image transfer is removed by the intermediate transfer body cleaning device 11.

  The recording medium P to which the toner image has been transferred passes through a fixing device (not shown), and at this time, the toner image on the recording medium is fixed by the action of heat and pressure.

  As described above, the image forming apparatus of the present example includes a plurality of image carriers, and forms toner images of different colors on the image carriers, and superimposes the toner images on the intermediate transfer member. The toner image is transferred and the superimposed toner image on the intermediate transfer member is transferred to a recording medium to obtain a recorded image.

  Figure 2 is a partial cross-sectional view showing the inner side configuration of the first process cartridge 1Y. As shown in this figure, the first image carrier 3Y is fixedly supported on an image carrier shaft 13Y via a flange 12Y, and the image carrier shaft 13Y is rotatable on a housing 15Y via a bearing 14Y. It is supported. Further, a charging roller 16Y, which is an example of a charging device that charges the image carrier 3Y, is rotatably supported by the casing 15Y. On the other hand, a motor MY is fixedly arranged on the back side of the image forming apparatus main body, and a drive shaft 17Y is instructed to be freely rotatable. The image bearing member gear is concentric with the image carrier 3Y on the drive shaft 17Y. 18Y is fixed. When the motor MY is operated, the motor gear 19Y is rotationally driven, and the rotation is transmitted to the drive shaft 17Y via the image carrier gear 18Y. The rotation is transmitted to the image carrier shaft 13Y via the drive side joint 20Y and the image carrier side joint 21Y detachably engaged therewith, and the rotation is transmitted to the image carrier 3Y via the flange 12Y. The In this way, the image carrier 3Y is rotationally driven in the clockwise direction in FIG. 1 as described above.

  The other process cartridges 1C, 1M, and 1BK are also configured in the same manner as shown in FIG. 2, and the image carriers 3C, 3M, and 3BK are also rotationally driven in the same manner as described above. As described above, in the image forming apparatus of this example, the image carriers 3Y, 3C, 3M, and 3BK are driven by independent motors. In FIG. 1, reference numerals 18 </ b> C, 18 </ b> M, and 18 </ b> BK are assigned to image carrier gears that transmit rotation to the second to fourth image carriers 3 </ b> C, 3 </ b> M, and 3 </ b> BK, respectively.

  The intermediate transfer member 4 is also driven by an independent motor (not shown). The intermediate transfer member 4 is driven by a motor for driving each image carrier, for example, a motor for driving a fourth image carrier 3BK on which a black toner image is formed. The transfer body 4 can also be configured to be rotationally driven.

  In addition to the image carrier, the process cartridge of the present example includes a housing, a charging device, a developing device, and a cleaning device. Each process cartridge includes at least an image carrier and a charging device that charges the image carrier. Can be configured.

  As shown in FIG. 1, the image carrier gears 18Y, 18C, 18M, and 18BK are provided with markings mY, mC, mM, and mBK, and the image carrier that detects each marking is provided in the image forming apparatus main body. position sensor 22Y, 22C, 22M, 22BK are arranged. Each of the image carrier gears 18Y to 18BK constitutes a transmission member that transmits rotation from each motor to each image carrier, but a transmission member including a pulley or the like can also be used. When using the pulley, the marking is provided on the respective pulleys. Further, instead of marking, a projection is provided on each transmission member, and the projection can be detected by the image carrier position sensors 22Y to 22BK. Furthermore, instead of providing markings or protrusions on the transmission members for each image carrier, markings or protrusions may be provided on each image carrier itself so that they can be detected by an image carrier position sensor.

  In the image forming apparatus described above, speed fluctuations occur in the image carriers 3Y to 3BK due to the eccentricity of the image carriers 3Y to 3BK, the eccentricity of the image carrier gears 18Y to 18BK, and the phase difference between the speed fluctuations. As a result, color misregistration may occur in the superimposed toner image transferred onto the intermediate transfer member. In order to suppress the occurrence of such color misregistration, the image forming apparatus of this example is configured to be able to perform the following adjustment operation.

  First, one image carrier among the plurality of image carriers 3Y to 3BK is defined as a reference image carrier. Here, the fourth image carrier 3BK on which the black toner image is formed is determined as the reference image carrier. A plurality of toner images are formed on the circumferential surface of the reference image carrier 3BK so as to have an equal pitch in the circumferential direction over at least one circumference of the image carrier 3BK, and the plurality of toner images are intermediately transferred. Transfer to body 4. At this time, the formation of the toner image on the image carrier 3BK and the transfer of the toner image to the intermediate transfer body 4 are performed in the same manner as the normal image forming operation described above. FIG. 3 is a plan view showing the intermediate transfer member 4 in a developed state. Reference numerals B1, B2, B3... BN denote a plurality of toner images formed on the image carrier 3BK as described above on the intermediate transfer member 4, respectively. Each reference pattern obtained by transfer is shown. Here the N reference patterns are formed on the intermediate transfer member 4.

  On the other hand, on the peripheral surface of another image carrier, for example, the first image carrier 3Y on which a yellow toner image is formed, a plurality of toners so as to have an equal pitch in the circumferential direction over at least one circumference. An image is formed, and the toner image is transferred to the intermediate transfer body 4. In FIG. 3, reference numerals Y1, Y2, Y3... YN are assigned to N patterns obtained by transferring the plurality of toner images to the intermediate transfer body 4. In this case, the formation of the toner image on the image carrier 3Y and the transfer of the toner image to the intermediate transfer body 4 are also performed in the same manner as the normal image forming operation described above.

  The reference patterns B1 to BN and the patterns Y1 to YN shown in FIG. 3 are formed at the same timing in the circumferential direction of the intermediate transfer body 4 when it is assumed that there is no cause of color misregistration. The reference patterns B1 to BN and the patterns Y1 to YN are all formed to have the same pitch when it is assumed that there is no cause of color misregistration. Therefore, if the image carriers 3BK and 3Y and the image carrier gears 18BK and 18Y are not decentered, the pitches of the reference patterns B1 to BN transferred onto the intermediate transfer member 4 and the patterns Y1 to YN are all equal. And the positions of the reference patterns B1 to BN and the patterns Y1 to YN corresponding to the reference patterns in the circumferential direction of the intermediate transfer body coincide with each other. That is, the positions of the first reference pattern B1 in FIG. 3 and the corresponding first pattern Y1 in the circumferential direction of the intermediate transfer body 4 are the same, and similarly, the next reference pattern B2 and the next corresponding to the next reference pattern B1. The positions of the pattern Y2 in the circumferential direction of the intermediate transfer body 4 are matched, and the positions of the reference patterns B3... BN corresponding to each other and the positions of the patterns Y3. Actually, however, the positions of the reference patterns B1 to BN and the patterns Y1 to YN in the circumferential direction of the intermediate transfer body 4 due to the eccentricity of the image carriers 3BK and 3Y and the image carrier gears 18BK and 18Y, etc. As shown in FIG.

  FIG. 4 is a graph showing the difference between the ideal position of the toner image on the intermediate transfer body 4 and the symbols GK and GY in FIG. 4 indicate the difference between the ideal position of the black toner image and the yellow toner image on the intermediate transfer body 4. Each difference is shown.

On the other hand, as shown in FIGS. 1 and 3, with respect to the moving direction A of the intermediate transfer member 4, it faces the surface portion of the intermediate transfer member 4 further downstream than the image carrier 3BK located on the most downstream side. First and second pattern detection sensors S1, S2 are provided. The positions of the pattern detection sensors S1, S2 in the intermediate transfer member surface movement direction are the same. Each of the reference patterns B1 to BN is detected by the first pattern detection sensor S1, each of the patterns Y1 to YN is detected by the second pattern detection sensor S2, and the detection signal is captured by the CPU 23, and each of the reference patterns B1 to BN is detected. The sum of the absolute values of the passing time differences between BN and the patterns Y1 to YN corresponding to the respective reference patterns is calculated. That is, as shown in FIG. 3, the first reference pattern B1 and the pattern Y1 corresponding to each other have a time difference detected by the first and second pattern detection sensors S1 and S2 as Δt1, and the next reference pattern The difference between the time when B2 and the next pattern Y2 corresponding thereto are detected by the first and second pattern detection sensors S1, S2 is Δt2. Similarly, the following reference patterns B3... BN and the respective patterns Y3... YN corresponding to the respective reference patterns B3... YN are time differences detected by the sensors S1 and S2 as Δt3. A total ΔTC of absolute values of the differences between the respective times is obtained.
ΔTC = | Δt1 | + | Δt2 | + | Δt3 | ... + | ΔtN | (1)
The reference patterns B1 to BN and the patterns Y1 to YN are detected by the sensors S1 and S2, and then removed from the intermediate transfer body 4 by the cleaning device 11 shown in FIG. The value of the total sum ΔTC is stored in a storage device. This series of operations is the first calculation operation.

  Next, while changing the position of the other image carrier 3Y in the rotational direction with respect to the position of the reference image carrier BK in the rotational direction, the total ΔTC is calculated a plurality of times in the same manner as described above, and each value thereof is calculated. Is stored in a storage device. The second and subsequent calculation operations are performed.

  More specifically, during the first calculation operation, the image carrier position sensors 22Y and 22BK shown in FIG. 1 rotate the image carrier and the intermediate transfer body 4 while the image carrier gears 18Y. , 18BK, when the markings mY, mBK are detected, toner images are formed on the reference image carrier 3BK and the other image carrier 3Y, and the toner images are transferred to the intermediate transfer member 4. Thus, reference patterns B1 to BN and patterns Y1 to YN are obtained. After the reference patterns B1 to BN and the patterns Y1 to YN are detected by the first and second pattern detection sensors S1 and S2 as described above, the image carrier position sensor 22BK performs marking mBK on the image carrier gear 18BK. Is detected, the reference image carrier 3BK is stopped. On the other hand, for the other image carrier 3Y, a predetermined time T1 elapses after the image carrier position sensor 22Y detects the marking mY of the image carrier gear 18Y, and the marking mY becomes the image carrier position sensor. the 22Y, at the time of passing by for example 20 °, to stop the image bearing member 3Y. Thereby, the position in the rotation direction of the reference image carrier 3BK and the position in the rotation direction of the other image carrier 3Y are different from each other by 20 °.

  In this state, the second calculation operation is started to calculate the value of the total ΔTC. Also in the second calculation operation, when the image carrier position sensor 22BK detects the marking mBK of the image carrier gear 18BK, the reference image carrier 3BK is stopped, but the other image carriers 3Y When the carrier position sensor 22Y detects the marking mY of the image carrier gear 18Y, the image carrier 3Y is stopped when 2 × T1 which is twice the predetermined time T1 has elapsed. As a result, the position of the reference image carrier 3BK and the other image carrier 3Y in the rotational direction is different from the initial state by 40 °. In this state, the third calculation operation is started to calculate the total ΔTC.

  As described above, the calculation operation is performed at least the number of times corresponding to one rotation of the image carrier 3Y while gradually changing the position of the other image carrier 3Y in the rotational direction with respect to the position of the reference image carrier 3BK in the rotational direction. Execute. At the start of each calculation operation, when the position in the rotation direction of the image carrier 3Y with respect to the position in the rotation direction of the image carrier 3BK is changed by 20 °, the calculation operation is performed at least 18 times. Thereafter, the CPU detects the position in the rotation direction of the other image carrier 3Y with respect to the position in the rotation direction of the reference image carrier 3BK when the sum ΔTC is the smallest, and the image carrier 3Y is rotated by the rotation of the motor MY. Is brought to its rotational position. The position of the reference image carrier 3BK in the rotation direction remains the same. In this way, while changing the position of the rotation direction of the other image carrier relative to the position of the rotation direction of the reference image carrier, the above-mentioned total calculation is performed a plurality of times, and the reference image when the total is the smallest is obtained. The position in the rotational direction of another image carrier relative to the position in the rotational direction of the carrier is detected.

  In exactly the same manner, a large number of toner images are formed on the reference image carrier 3BK and the other image carrier 3C, and each toner image is transferred to the intermediate transfer member 4 to obtain a reference pattern and a pattern. By detecting the first and second pattern detection sensors S1 and S2, the calculation operation for obtaining the sum ΔTC of the absolute value of the time difference is performed in the rotational direction of the image carrier 3C with respect to the position in the rotational direction of the reference image carrier 3Y. Repeat several times while changing the position. In this case as well, the position in the rotation direction of the image carrier 3C relative to the position in the rotation direction of the reference image carrier 3BK when the sum ΔTC is the smallest is detected, and the image carrier 3C is brought to the rotation position. .

  The above-described operation is also performed on another image carrier 3M, and the position of the image carrier 3M in the rotation direction is adjusted.

  As described above, after adjusting the positions of the image carriers 3Y to 3BK in the rotation direction, the above-described normal image forming operation is performed. As a result, the phase difference of the speed fluctuation of each image carrier can be eliminated, or this can be made extremely small, and the color misregistration of the superimposed toner image transferred onto the intermediate transfer body 4 can be eliminated. It is possible to reduce to such an extent that is ignored.

  As described above, in the image forming apparatus of this example, the first and second pattern detection sensors S1 and S2 and the CPU 23 use one of the plurality of image carriers as a reference image carrier. Each reference pattern obtained by transferring a plurality of toner images formed on the reference image carrier over at least one circumference thereof to the intermediate transfer member, and at least one of them on the other image carrier. A time difference that detects each pattern obtained by transferring a plurality of toner images formed over the circumference to an intermediate transfer member and calculates the sum of the absolute values of the passage time differences of each reference pattern and each corresponding pattern. It constitutes a detection means.

Here, the total time difference ΔTC in the above-described equation (1) is caused by the following factors.
Δtdr: Speed fluctuation of image carrier Δtreg: Shift deviation between reference pattern and pattern Δtsq: Deviation of skew between reference pattern and pattern Δtblt: Deviation due to deviation in thickness of intermediate transfer member

  The shift deviation is the deviation of the writing position of the electrostatic latent image on the image carrier, and the entire reference pattern is shifted by a certain amount in the circumferential direction of the intermediate transfer body 4 or the entire pattern is transferred to the intermediate transfer body 4. Means a time difference due to a certain amount of deviation in the circumferential direction. Further, as shown in FIG. 5, the above-described skew deviation is not perpendicular to the reference pattern B <b> 1 to BN or the patterns Y <b> 1 to YN but to the moving direction A of the intermediate transfer body 4. It means a time difference caused by tilting from the direction V as shown by an angle θ.

  The eccentricity of the drive roller 5 that drives the intermediate transfer member 4 shown in FIG. 1 can also be cited as a factor of color misregistration. This factor is the intermediate transfer from the outer peripheral length of the drive roller 5 and each of the image carriers 3Y to 3BK. This factor is not considered here because it can be removed by making the distance between the transfer positions for transferring the toner image to the body 4 the same.

As described above, the total sum ΔTC can be expressed by the following equation (2).
ΔTC = Δtdr + Δtreg + Δtsq + Δtblt (2)
From the equations (1) and (2), the following equation is obtained.
| Δt1 | + | Δt2 | + | Δt3 | ... + | ΔtN |
= Δtdr + Δtreg + Δtsq + Δtblt (3)
In formula (3), for Δtblt, a belt having a small thickness deviation such as polyimide has been developed in recent years, and the time difference due to the deviation of the thickness of the intermediate transfer member can be made almost zero. Therefore,
ΔTC = | Δt1 | + | Δt2 | + | Δt3 | ... + | ΔtN |
= Δtdr + Δtreg + Δtsq (4)
Can be expressed as

  Here, determining the position in the rotational direction of the other image carriers 3Y, 3C, 3M with respect to the position in the rotational direction of the reference image carrier 3BK is such that the total ΔTC is minimized. Means to minimize. Even if the position of the image carrier in the rotational direction is adjusted, Δtreg and Δtsq in the equation (4) cannot be reduced, and Δtreg and Δtsq are the temperatures of the optical elements of the exposure apparatus 2 shown in FIG. When it rises, it shows a large value.

The above-described adjustment operation of the position of the image carrier in the rotation direction is performed, for example, when the image forming apparatus starts up. At this time, if it takes a long time from the start of the adjustment operation to the end of the operation, the optical element of the exposure apparatus 2 is displayed at the time when the adjustment operation is started and at the latter half of the operation. The value of Δtreg and Δtsq in the equation (4) increases during the adjustment operation, which may deteriorate the adjustment accuracy. For example, assuming that the image forming speed during normal image forming operation is 100 mm / sec, the diameter of each image carrier is 30 mm, and the above-described calculation operation is performed 16 times for each of the image carriers 3Y, 3C, 3M. The time T required for operation is
T = (30 × π / 100) × 3 × 16≈45 seconds (5)
And it takes quite a long time. During this time, the values of Δtreg and Δtsq become large, and there is an unavoidable possibility that the adjustment accuracy will deteriorate.

  Therefore, in the image forming apparatus of the present example, as described above, the reference pattern and the surface movement speed of the intermediate transfer member when forming the pattern on the intermediate transfer member 4 are set so that the normal image forming speed is high. The driving of the image carrier and the intermediate transfer member is controlled so as to be faster than the surface moving speed of the image carrier and the intermediate transfer member. For example, a variable speed motor is used as a motor for driving each image carrier and a motor for driving the intermediate transfer member 4, and the speeds of the image carrier and the intermediate transfer member during the normal image forming operation and the adjustment operation are adjusted. Change it. Specifically, if the image forming speed during the adjustment operation is set to 200 mm / sec, the time required for the adjustment operation is 23 seconds, which is approximately half the time represented by the equation (5). For this reason, the adjustment work can be completed before Δtreg and Δtsq change, and deterioration of the adjustment accuracy can be prevented.

  As described above, the example in which the present invention is applied to the intermediate transfer type image forming apparatus has been described. FIG. 6 shows an example of a direct transfer type image forming apparatus. The image forming apparatus shown here has a plurality of support rollers 5, 6, 7, and 8 instead of the intermediate transfer body 4 shown in FIG. and a recording medium conveying member 104 formed of an endless belt which is wound. The recording medium conveyance unit 104 is driven in the direction of arrow A, and the recording medium P fed from a paper feeding unit (not shown) is carried by the recording medium conveyance unit 104 as indicated by arrow B. At this time, the toner images of the respective colors formed on the image carriers 3Y to 3BK are transferred onto the recording medium P. The recording medium P leaves the recording medium conveyance body 104 and then passes through a fixing device (not shown). At this time, the superimposed toner image on the recording medium P is fixed. Toner adhering to the recording medium conveying member 104 is removed by a cleaning device 11.

  In the case of the image forming apparatus shown in FIG. 6, the reference image carrier 3BK and a plurality of toner images formed on the other image carriers are transferred to the recording medium carrier 104 and the recording medium is conveyed. A reference pattern and a pattern are formed on the body. The other configuration of the image forming apparatus shown in FIG. 6 is the same as the configuration shown in FIGS. 1 to 5, and each pattern is finally removed by the cleaning device 11. The components corresponding to those shown in FIG. 1 are denoted by the same reference numerals as in FIG.

  In summary, the image forming apparatus shown in FIG. 7 includes a plurality of image carriers 3Y to 3BK, forms toner images of different colors on the image carriers, and each toner image is recorded on a recording medium. It is configured to obtain a recorded image by being transferred onto a recording medium P carried and carried by the carrier 104, and one of the plurality of image carriers 3Y to 3BK is used as a reference image carrier. Each reference pattern obtained by transferring a plurality of toner images formed on at least one circumference on the reference image carrier 3BK to the recording medium carrier 104, and another image carrier Further, each pattern obtained by transferring a plurality of toner images formed over at least one circumference thereof to the recording medium conveyance body 104 is detected, and each reference pattern and the difference in transit time between the corresponding patterns are detected. Time to calculate the sum of absolute values When the sum is calculated a plurality of times while changing the position in the rotational direction of another image carrier relative to the position in the rotational direction of the reference image carrier 3BK. It is configured to detect the position in the rotation direction of another image carrier relative to the position in the rotation direction of the reference image carrier 3BK, and the image carriers 3Y to 3BK and the recording medium carrier 104 at the time of forming the reference pattern and the pattern. The drive of the image carrier and the recording medium carrier 104 is controlled so that the surface movement speed of the image carrier becomes faster than the surface movement speed of the image carrier and the recording medium carrier during normal image formation. Has been.

1 is a schematic diagram illustrating an example of an intermediate transfer type image forming apparatus. FIG. 2 is a schematic diagram of a process cartridge shown in FIG. 1 and a drive system that drives an image carrier of the process cartridge. FIG. 3 is a plan view showing a reference pattern and a pattern formed on an intermediate transfer member. Is a graph showing the difference between the ideal position of the toner image transferred on the intermediate transfer member. It is a figure explaining skew deviation. 1 is a schematic diagram illustrating an example of a direct transfer type image forming apparatus.

Explanation of symbols

3Y, 3C, 3M, 3BK Image carrier 4 Intermediate transfer member 104 Recording medium carrier P Recording medium

Claims (2)

A plurality of image carriers are formed, toner images of different colors are formed on the respective image carriers, and the toner images are transferred onto the intermediate transfer member, and the superimposed toner images on the intermediate transfer member are transferred. In an image forming apparatus that obtains a recorded image by transferring to a recording medium,
One of the plurality of image carriers is defined as a reference image carrier, and a plurality of toner images formed on the reference image carrier over at least one turn thereof are transferred to the intermediate transfer member. And detecting each reference pattern obtained by transferring a plurality of toner images formed on at least one circumference on the other image carrier to the intermediate transfer member, and detecting each reference pattern. A time difference detecting means for calculating a sum of absolute values of the passing time differences between the pattern and each pattern corresponding to the pattern, and changing the rotational position of the other image carrier relative to the rotational position of the reference image carrier; While performing the calculation of the sum a plurality of times, the position of the rotation direction of the other image carrier relative to the position of the rotation direction of the reference image carrier when the sum is the smallest, The reference pattern and the pattern The surface movement speed of the image carrier and the intermediate transfer body during formation is faster than the surface movement speed of the image carrier and the intermediate transfer body during normal image formation. An image forming apparatus that controls driving. A plurality of image carriers are provided, toner images of different colors are formed on the respective image carriers, and the respective toner images are transferred onto a recording medium that is carried and conveyed by the recording medium carrier. In an image forming apparatus for obtaining a recorded image,
One image carrier among the plurality of image carriers is defined as a reference image carrier, and a plurality of toner images formed on the reference image carrier over at least one turn thereof are applied to the recording medium carrier. Detecting each reference pattern obtained by transferring, and each pattern obtained by transferring a plurality of toner images formed on at least one circumference on another image carrier to the recording medium carrier, Each reference pattern and time difference detecting means for calculating the sum of absolute values of the passage time differences of the corresponding patterns are provided, and the position of the other image carrier in the rotational direction relative to the position of the reference image carrier in the rotational direction. The sum is calculated a plurality of times while changing the value, and the position in the rotation direction of the other image carrier relative to the position in the rotation direction of the reference image carrier when the sum is the smallest is detected. And the reference pattern and the The image carrier and the recording medium conveyance body at the time of forming the turn have a surface moving speed that is faster than the surface movement speed of the image carrier and the recording medium conveyance body at the time of normal image formation. An image forming apparatus that controls driving of a recording medium conveyance body.

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