JP2002108168A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of faulty image quality caused by uneven rotation and vibration and also fluctuation of velocity in an image forming device. SOLUTION: The image forming device is provided with a conveying body freely rotatably disposed and carrying and conveying an object, a driving means driving the conveying body, a traction drive decelerating mechanism transmitting a driving force of the driving means to the conveying body, a velocity fluctuation detecting means detecting the velocity fluctuation of the conveying body and a drive controlling means controlling the driving means so as to correct the deviation of the conveying position of the conveying body based on the detection result of the velocity fluctuation detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine and a printer, and more particularly to an improvement in an image forming apparatus of a type in which two or more color toner images are superimposed to obtain a color image.

[0002]

2. Description of the Related Art Conventionally, as an intermediate transfer type image forming apparatus, for example, a photosensitive drum on which a toner image corresponding to an electrostatic latent image is formed and carried, and a toner image on the photosensitive drum is intermediately transferred. An intermediate transfer belt, a primary transfer device on which the toner image on the photosensitive drum is transferred to the intermediate transfer belt, and a secondary transfer device for transferring the toner image transferred on the intermediate transfer belt to a sheet at a time. A device provided with a secondary transfer device is known. In this type of image forming apparatus, in order to obtain a full-color image, a process of forming a toner image on a photosensitive drum and a primary transfer process of the toner image are repeated by the number of colors. For example, when a full-color image is formed by superimposing four color toner images, yellow, magenta, cyan, and black toner images are sequentially formed on the photosensitive drum, and these toner images are sequentially primary-transferred to an intermediate transfer belt. You. On the other hand, the intermediate transfer belt rotates at the same cycle as the photosensitive drum while holding the yellow toner image that has been primarily transferred first, and the magenta, cyan, and black toner images are sequentially placed on the intermediate transfer belt. The image is transferred over the image.

In this type of image forming apparatus, for example, a driving roll of an intermediate transfer belt is connected to a driving source such as a motor via a reduction device including a gear train, a timing belt, and a timing pulley. Rotational unevenness and vibration are generated from these meshing portions, and there is a problem that an image primarily transferred on the intermediate transfer belt has horizontal stripe unevenness called color shift or banding.

To solve such a problem, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 2306302 proposes a technique for preventing the above-described color shift and banding by adopting a traction drive reduction mechanism that does not use gears or pulleys as a reduction device for a photosensitive drum.

[0005]

Incidentally, in the above-described image forming apparatus, a secondary transfer roll for forming a transfer nip area between an intermediate transfer belt and a secondary transfer device is generally used as a secondary transfer device. A cleaner for removing residual toner remaining on the intermediate transfer belt after the transfer is provided. In such a configuration, when a full-color image, that is, a superimposed image is formed, the secondary transfer roll and the cleaner transfer the final color toner image to the intermediate transfer belt so as not to affect the image being formed. Until the image is transferred, these members are separated from the intermediate transfer belt and are brought into pressure contact with the intermediate transfer belt only at the time of secondary transfer or cleaning.

However, when a secondary transfer roll or a cleaner is brought into pressure contact with the intermediate transfer belt, the driving resistance is increased by that amount, so that the speed of the intermediate transfer belt is temporarily reduced, and at this time, the next image formation is started. If started, there was a technical problem that color shift occurs in the next image.

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problems, and it is an object of the present invention to prevent the occurrence of poor image quality due to rotation unevenness and vibration and also prevent the occurrence of poor image quality due to speed fluctuation. It is intended to provide an image forming apparatus that can be used.

[0008]

That is, the present invention provides a transporter which is rotatably disposed and carries an object,
A driving unit that drives the carrier, a traction drive reduction mechanism that transmits a driving force of the driving unit to the carrier, a speed variation detecting unit that detects a speed variation of the carrier, and a speed variation detecting unit. And a drive control unit for controlling the drive unit so as to correct the transfer position of the transfer body based on the detection result.

In such technical means, examples of the object in the present invention include a toner image and a sheet such as paper. Further, as the carrier, for example, an image carrier such as a photoconductor or an intermediate transfer body to which a toner image formed on the image carrier is temporarily transferred as a carrier that carries and transports a toner image as an object. For example, as an object that carries and conveys a sheet as an object, there is a sheet conveying body. Here, the invention of the present application is directed to a mode in which the speed is likely to fluctuate due to the presence of a member (for example, a cleaner) which is provided so as to be able to contact and separate from the carrier, that is, the object is a toner image and the carrier is Is particularly effective in the embodiment in which is the intermediate transfer member. Further, the configuration of the transporting body may be appropriately selected, such as a drum shape or a belt shape, as long as it is rotatably disposed.

[0010] The driving means is for driving the carrier, and may be, for example, a motor. Further, the traction drive reduction mechanism may be appropriately selected from various types as long as the traction drive reduction mechanism transmits power by the rheological characteristics of an oil film formed on the contact surface in the friction transmission device.

Further, the speed fluctuation detecting means may directly detect the speed fluctuation of the carrier, as long as the speed fluctuation of the carrier can be detected, or may include a shaft for driving the carrier. The speed variation of the transport member may be indirectly detected by detecting the speed variation of the driving member.

Further, the drive control means controls the drive means based on the detection result of the speed fluctuation detection means so as to correct the transfer position shift of the transfer body. Specifically, the drive control means Is accelerated or decelerated to correct the transport position deviation of the transport body.

In a preferred embodiment, the object is a toner image and the carrier is an intermediate transfer member to which a toner image formed on an image carrier is temporarily transferred. From the viewpoint of reliably preventing an image shift when transferring the toner image from the body to the intermediate transfer body, the intermediate transfer body of the toner image on the image carrier is based on the detection result of the speed fluctuation detecting means. It is preferable to provide a timing control means for controlling the arrival timing of the data. As a method of controlling the arrival timing, for example, a method of adjusting the arrival timing by increasing or decreasing the speed of the intermediate transfer body, or a method of adjusting the arrival timing by changing the image formation timing on the image carrier And the like.

According to another aspect of the present invention, there is provided a carrier rotatably disposed and carrying an object, driving means for driving the carrier, and traction for transmitting the driving force of the driving means to the carrier. It is characterized by comprising a drive mechanism and speed fluctuation detecting means for detecting a speed fluctuation of the carrier.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. FIG. 1 shows an embodiment of a color image forming apparatus to which the present invention is applied. In FIG. 1, the color image forming apparatus according to the present embodiment includes an image input unit 1 that reads a document and outputs an image signal, and an image output unit 8 that forms an image on a sheet based on the image signal. ing. The image input unit 1 irradiates light from a light source 3 to a document (not shown) placed on the upper surface of a transparent document table 2, and reflects light reflected from the document to a lens 6 via reflection mirrors 4 and 5. Make it incident. The lens 6 converges the incident light and forms an image on a charge-coupled device 7 such as a CCD. The charge-coupled device 7 separates the incident light into red (R), green (G), and blue (B) colors and outputs RGB signals as image signals.

As shown in FIG. 2, the image output unit 8 converts the RGB signals supplied from the image input unit 1 into yellow (Y), magenta (M), cyan (C), and black (K). The image processing unit 8a converts the image signal (YMCK signal) into the image signal and stores it. Then, the image signal output from the image processing unit 8a is input to the image writing timing control unit 101, and is used when the image writing unit 9 modulates the laser beam L. The modulated laser beam L is deflected by a polygon mirror 10a constituting an optical scanning device provided in the image writing unit 9, and a main scan for writing an image is performed at a constant cycle.
Reference numeral 10b is a motor for rotating the polygon mirror 10a.

On the optical path of the laser beam L, there is arranged an SOS sensor 11 for sending a scanning start (SOS) signal indicating the start of main scanning when the laser beam L is irradiated. The laser beam L is reflected by the reflection mirror 1.
The light is reflected at 2 and irradiates the outer peripheral surface of the photosensitive drum 13,
The main scanning is performed in the axial direction of the photosensitive drum 13. By repeating this main scanning at a constant cycle, a predetermined color (Y, M,
C or K) electrostatic latent images are sequentially written.

When an electrostatic latent image is written on the photosensitive drum 13, development is immediately performed by the developing unit 15. Here, the developing device 15 is provided for each of the developing sleeves 1 of Y, M, C, and K.
5a to 15d, and supplies toner of a color corresponding to the written electrostatic latent image to the photosensitive drum 13 to develop the electrostatic latent image. Then, the toner images formed in this manner are sequentially superimposed on the intermediate transfer belt 16 which is always in contact with the outer periphery of the photosensitive drum 13 and are primarily transferred.

The intermediate transfer belt 16 is supported by a drive roll 17 and support rolls 18 and 19 so that the intermediate transfer belt 16 can run or rotate in the belt circumferential direction. Then, on the side opposite to the photosensitive drum 13 with the intermediate transfer belt 16 interposed therebetween,
A transfer unit 20 composed of a corotron for applying a charge having a polarity opposite to that of the toner to the intermediate transfer belt 16 and transferring the toner image to the intermediate transfer belt 16 is provided. A color toner image is formed on the intermediate transfer belt 16 by superimposing the Y, M, C, and K images.

The intermediate transfer belt 16 is rotated by a driving roll 17 at the same speed in a direction opposite to the rotation direction of the photosensitive drum 13. As shown in FIG.
The belt drive motor 123 for rotating the photosensitive drum 13 is provided separately from a motor (not shown) for rotating the photosensitive drum 13, and is configured to rotate using a different drive signal. In the present embodiment, since the photosensitive drum 13 and the intermediate transfer belt 16 are driven independently, even if the rotational speed of the intermediate transfer belt 16 is increased or decreased to be different from the rotational speed of the photosensitive drum 13 On the other hand, the rotation speed of the photosensitive drum 13 is substantially constant without being affected. A drive control mechanism of the intermediate transfer belt 16 by the belt drive motor 123 will be described later.

As shown in FIG. 3, a mark M having a light reflectance different from that of the intermediate transfer belt 16 is formed on the side of the surface of the intermediate transfer belt 16. This mark M
Is detected by a mark sensor 22 arranged opposite to the intermediate transfer belt 16, and the mark sensor 22
Outputs the belt reference signal TR0 shown in FIG. Then, the position of the intermediate transfer belt 16 at that time is set as a reference position.

In FIG. 1, reference numeral 23 denotes a cleaner for removing residual toner on the intermediate transfer belt 16, and reference numeral 25 denotes a secondary transfer roll for transferring the toner image on the intermediate transfer belt 16 to a sheet. The cleaner 23 and the secondary transfer roll 25 are disposed so as to be able to freely contact and separate from the intermediate transfer belt 16, and until the final color toner image passes through the cleaner 23 or the secondary transfer roll 25.
These are separated from the intermediate transfer belt 16.

The paper stacked on the paper feed tray 26 is taken out one by one by a paper feed roll 27, and the secondary transfer roll 25 and a support roll (backup roll) 1 are taken out.
9 is supplied to the nip portion. At that time, the paper is charged by the secondary transfer roll 25 to the polarity opposite to that of the toner. Thus, the toner on the intermediate transfer belt 16 is secondarily transferred to the sheet at the nip. Thus, the sheet on which the color toner image has been secondarily transferred from the intermediate transfer belt 16 is sent to the fixing device 28 where the toner image is fixed.

As shown in FIG. 2, the image output section 8 is provided with a main controller 102. The main controller 102 generates various control signals for controlling each section of the color image forming apparatus. The main controller 102 is connected to a control unit 100 for controlling the rotation speed of the intermediate transfer belt 16 and an image writing timing control unit 101. The belt reference signal TR0 output from the mark sensor 22 is input to the main controller 102, the control unit 100, and the image writing timing control unit 101. The image writing timing control unit 101 controls the belt reference signal TR0
The rising edge of the SOS signal input from the SOS sensor 11 is counted from the rise of the signal, and when the count value reaches a predetermined value, a latent image writing start signal (image indicating the start of writing in the sub-scanning direction) (Forming start signal). Then, the image writing timing control unit 10
1, after counting a predetermined number of pixel clocks from the rise of the latent image writing start signal, reads out the Y, M, C, and K signals stored in the image processing unit 8a and sequentially outputs the signals to the image writing unit 9; Writing of the latent image in the main scanning direction of the line is started.

The SOS signal and the belt reference signal TR0 are input to the control unit 100. The control unit 100 determines the rotation cycle of the intermediate transfer belt 16 and the polygon mirror 10 based on the SOS signal and the belt reference signal TR0.
A phase difference from the rotation cycle a is calculated, and a correction signal representing a correction value P for increasing or decreasing the rotation speed of the intermediate transfer belt 16 is used as a reference based on the calculation result and a correction value for correcting the transfer deviation. Output to the clock generator 120.

Here, the reference clock generator 120 shown in FIGS. 2 and 3 is composed of a VCO (Voltage Control Oscillator) using a PLL (Phase Locked Loop), and has a frequency reference proportional to the input voltage. The clock is output to the drive motor control unit 121. Drive motor control unit 1
Reference numeral 21 supplies an excitation current having a frequency corresponding to the supplied reference clock to the belt drive motor 123. As the belt drive motor 123, a stepping motor, a DC brushless motor, or the like is used.

A traction drive reduction mechanism 130 is provided between the belt drive motor 123 and the drive roll 17 of the intermediate transfer belt 16 as a drive force transmission mechanism. The traction drive reduction mechanism 130 is shown in FIG.
As shown in FIG. 3, an outer casing 131, a casing 132 having a circular cross section disposed inside the casing 131, three planetary rolls 133 disposed inside the casing 132, A sun roll 134 is provided at the center of the three planetary rolls 133 so as to be in contact with each of the planetary rolls 133. The inside of the casing 132 is filled with traction grease (not shown).
Then, the sun roll 134 is connected to the belt drive motor 12.
3 and the planetary roll 133 is connected to the rotating shaft 17a of the drive roll 17 to form a reduction gear.

On the rotary shaft 17a of the drive roll, an encoder 140 comprising a disk 141 having a partly opened hole and a sensor 142 for detecting passage of the hole.
Is provided. In the present embodiment, the detection result of the encoder 140 is fed back to the drive motor control unit 121, and the rotation of the belt drive motor 123 is controlled so as to recover the lead or delay.

Further, a transfer start signal BTR indicating the transfer start timing output from the main controller 102 is input to the control unit 100 shown in FIG. 2 to output a correction signal for increasing or decreasing the rotation speed of the intermediate transfer belt 16 and The output stop timing is controlled.
That is, in the present embodiment, since the traveling speed of the intermediate transfer belt 16 is changed in the primary transfer non-image area as described later, the timing of starting the speed change and the timing of stopping the rotation change are determined based on the transfer start signal BTR. Control.

In this embodiment, since the traveling speed of the intermediate transfer belt 16 can be changed in the non-image area to be written, the latent image output from the image writing timing control section 101 is supplied to the control section 100. A write start signal is also input.

FIG. 3 shows that the image writing timing control unit 101 controls the belt reference signal T for the first color and the second color.
9 shows an example of timing from detection of R0 to start of writing of a latent image and an example of a transfer position shift in the sub-scanning direction after primary transfer. As shown in the figure, the scanning by the laser beam L is always performed, and the signal from the SOS sensor 11 is always generated at a constant cycle.
The latent image writing start signal rises and the writing of the latent image is started. Therefore, the image writing by the laser beam L is not performed until the latent image writing start signal rises. The laser beam L reaches the image forming area of the photosensitive drum 13 in the main scanning direction after a lapse of a predetermined image clock after the irradiation of the SOS sensor 11 is completed. For this reason, writing of an image in the sub-scanning direction is performed by the SOS sensor 1.
It starts at the fall of the signal from 1. Therefore, in the present embodiment, the fall of the signal from the SOS sensor 11 is used as a signal indicating the start of scanning in the sub-scanning direction.

The image writing timing control unit 10
As shown in FIG. 3, reference numeral 1 denotes the start of counting the number of times the SOS signal has fallen from the rise of the belt reference signal TR0 of the first color (for example, yellow). Raise the write start signal. Thus, writing of the first color latent image is started, and subsequently, the written latent image is developed with the first color toner. At the same time, SOS starts from the rise of the second color (for example, magenta) belt reference signal TR0.
The counting of the number of times of the signal falling is started, and when the number of falling of the SOS signal is counted N, the latent image writing start signal is raised. Thus, the writing of the second color latent image is started, and then the written latent image is developed with the second color toner. Thereafter, the latent images of the third color (for example, cyan) and the fourth color (for example, black) are similarly developed.

Here, the first color belt reference signal TR0
Assuming that the time from the rise of the first SOS signal to the fall of the first SOS signal is T1 and the cycle of the SOS signal is Tsos, the time from the detection of the first color belt reference signal TR0 to the start of latent image writing is “T1 + Tsos × N”. ". Further, assuming that the time from the rise of the second color belt reference signal TR0 to the fall of the first SOS signal is T2, the time from the detection of the second color belt reference signal TR0 to the start of latent image writing is “T2”. T2 + Tsos × N ”. Accordingly, the time lag TE from the rise of the belt reference signal TR0 to the writing of the latent images of the first color and the second color is:
“T2−T1” (where T1 <T2). As described above, the writing start timing of the latent image of the second color is "T2-T1" more than the writing timing of the latent image of the first color.
This time shift TE appears as a distance shift to a transfer start position provided on the intermediate transfer belt 16 as shown by arrows a and b in FIG.

The positional deviation LE between the writing start positions of the first and second colors on the photosensitive drum 13 is such that the speed fluctuation from the belt reference position to the latent image writing start position is zero, and the resolution of the laser beam L is X ( (dpi), the scanning line pitch D is 25.4 / X (mm). Therefore, the displacement LE of the latent image writing start position is given by LE = D ×
(T2-T1) / Tsos (mm). Therefore, if the second color toner image is transferred and superimposed on the first color toner image while leaving this state, a color shift of LE (mm) occurs at the maximum.

Here, with reference to the first color, the TR of the belt reference signal of the nth color (n = 2, 3, 4) is used.
Assuming that the time from the rise of 0 to the fall of the first SOS signal is Tn, the displacement LE from the second color to the nth color is expressed as follows. LE = D × (Tn−T1) / Tsos

Accordingly, in the present embodiment, before the second color toner image is superimposed on the first color toner image, the rotation speed of the intermediate transfer belt 16 is changed at a constant speed fluctuation rate within a predetermined time. After returning to the original speed, LE
The position deviation of the toner image on the intermediate transfer belt 16 resulting from the deviation of the writing start position corresponding to the above is corrected. Before the third color toner image and the fourth color toner image are superimposed, the write start position is similarly corrected.

FIG. 6 is a diagram for explaining the timing from the writing of the latent image on the photosensitive drum 13 to the transfer of the toner image to the intermediate transfer belt 16 in the present embodiment. In the color image forming apparatus according to the present embodiment,
The latent images of the first to fourth colors are written on the photosensitive drum 13 while the intermediate transfer belt 16 makes four revolutions. During the writing of the latent images of each color, the writing as shown in FIG. There is a time zone in which is not performed. Hereinafter, the time period from when the reference position of the intermediate transfer belt 16 indicated by the symbol A in FIG. 6 reaches a predetermined position to when the writing of the latent image is started is referred to as a “writing non-image area”.

In the color image forming apparatus according to the present embodiment, the toner image on the photosensitive drum 13 is transferred to the intermediate transfer belt 16 while the intermediate transfer belt 16 makes four rotations.
Between the transfer of the toner images of each color, there is a “transfer non-image area”, which is a time zone during which transfer is not performed, as indicated by reference numeral B in the figure.

In the present embodiment, a belt drive motor 123 for rotating the drive roll 17 and a motor for rotating the photosensitive drum 13 are separately provided, and the photosensitive drum 13 and the intermediate transfer belt 16 are separated by different drive sources. Therefore, if the rotation speed of the intermediate transfer belt 16 is changed in the non-transferred image area B, there is no effect on the toner image to be transferred. be able to. In addition, since the photosensitive drum 13 and the intermediate transfer belt 16 are separately rotated by different driving sources, even if the rotation speed of the intermediate transfer belt 16 is changed, the rotation speed of the photosensitive drum 13 is hardly affected. . Therefore, even if the speed of the intermediate transfer belt 16 is changed during the writing of the latent images of the second and subsequent colors, the latent image written on the photosensitive drum 13 is hardly affected.

By correcting the rotation speed of the intermediate transfer belt 16 by an amount corresponding to the transfer position deviation amount at the above timing, the time from the rise of the belt reference signal TR0 of the intermediate transfer belt 16 to the rise of the latent image writing start signal is obtained. The generated positional deviation is corrected, and the positional deviation of the leading end of each color toner image in the sub-scanning direction is corrected as shown in FIG.

The transfer position deviation can also be corrected by controlling the rotational speed of the polygon mirror in the non-image area A for writing.

In the color image forming apparatus according to the present embodiment, as described above, the cleaner 23 or the secondary transfer roll 25 is brought into pressure contact with the intermediate transfer belt 16 only during cleaning or secondary transfer. ing. Therefore, the load applied to the intermediate transfer belt 16 increases when they are pressed against each other, and the load applied to the intermediate transfer belt 16 decreases when they are separated after being pressed. Then, the running speed of the intermediate transfer belt 16 is reduced or increased in accordance with the load fluctuation, and a transfer position shift occurs. The load fluctuation of the intermediate transfer belt 16 occurs while the toner image on the photosensitive drum 13 is being transferred to the intermediate transfer belt 16 (during primary transfer), and when the latent image writing start signal rises, the primary transfer occurs. May occur before start.

During the primary transfer, a load change occurs during the transfer of the toner image on the photosensitive drum 13 to the intermediate transfer belt 16, and as shown in FIG. Occurs on the way. FIG. 8 exemplifies a transfer position shift when a load variation occurs during the primary transfer of the K color, and a maximum R position shift occurs after the transfer is completed. Accordingly, in the writing non-image area, by changing the rotation speed of the polygon mirror 10a, the correction of changing the timing of writing the latent image on the photosensitive drum 13 of the color in which the transfer position deviation has occurred (when the load increases, Correction to speed up the writing start timing, correction to delay the writing timing when the load decreases, or correction to change the speed of the intermediate transfer belt 16 in the transfer non-image area (intermediate transfer when the load increases) A correction for increasing the speed of the belt 16 and a correction for reducing the speed of the intermediate transfer belt 16 when the load decreases are performed. At this time, as shown in FIG. 9, the positional deviation amounts are distributed before and after in the sub-scanning direction with reference to the reference color transfer position. As the correction amount at this time, an appropriate value is calculated in advance from the transfer position deviation amount and the timing of occurrence of the load change, and is stored in the correction value memory. By distributing the displacement amount in this way, the image displacement amount of the entire image is reduced.

Until the primary transfer starts, a load change occurs between the rise of the latent image writing start signal and the primary transfer, so that the transfer start position of the intermediate transfer belt 16 with respect to the photosensitive drum 13 is shifted, and the transfer position is changed. The displacement occurs over the entire image as shown in FIG. Note that FIG.
Indicates a transfer position shift when a load change occurs between the rise of the K-color latent image writing start signal and the start of the primary transfer, and the maximum R at the leading and trailing ends in the sub-scanning direction of the transferred image. Misalignment has occurred.

Therefore, in the same manner as described above, in the writing non-image area, by controlling the rotation speed of the polygon mirror 10a, the correction for changing the timing of writing the latent image on the photosensitive drum 13 of the color in which the transfer position shift has occurred is corrected. Alternatively, control is performed to change the speed of the intermediate transfer belt 16 in the transfer non-image area. The correction amount at this time is different from the case during the primary transfer, and is the same as the maximum positional deviation amount. Also in this case, an appropriate correction value is calculated in advance from the transfer position deviation amount and the timing of the occurrence of the load change, and stored in the correction value memory. By correcting the transfer position shift amount in this way, the position shift amount of the entire image is reduced.

When the load fluctuation on the intermediate transfer belt 16 extends from the rise of the latent image writing start signal to the time during the primary transfer, the transfer during the primary transfer and the case until the start of the primary transfer are performed. Since a displacement occurs, in this case, the correction amount may be a combination of the above.

Next, a description will be given of a processing routine for correcting misregistration when a load change occurs in the intermediate transfer belt 16 based on the above principle.

FIG. 12 shows a routine for calculating a correction amount for correcting a displacement due to a load change. In step S1, it is determined whether or not the belt reference signal TR0 has risen. If it has, in step S2, the count value of the counter at that time is stored in the memory as the cycle of the latent image writing start signal. Then, in step S3, the counter is reset to restart the counting. In step S4, it is determined whether or not the cycle of the intermediate transfer belt 16 has changed, that is, whether or not the load has changed, by comparing the previously stored cycle with the currently stored cycle.

If a load change occurs in the intermediate transfer belt 16, the difference between the previous cycle and the current cycle is calculated in step S5 to calculate the maximum value R of the transfer position shift amount. In step S6, the correction amount for correcting the transfer position deviation is calculated as described above, and stored in the correction amount memory. In step S7, it is determined whether or not the calculation of the correction amount when the dandruff variation has occurred for all four colors has been completed. If the calculation has not been completed for all four colors, the process returns to step S1 to repeat the above processing. .

By the above processing, the intermediate transfer belt 16
The correction amount when the load fluctuation occurs in each color is calculated for each color and stored in the correction memory.

FIG. 13 shows a routine for correcting the transfer position deviation by correcting the speed of the intermediate transfer belt 16. In step S 11, the clock is counted, and the intermediate transfer belt of the first color is counted. A time T1 from the rise of the 16 reference signals TR0 to the first fall of the SOS signal is measured. In the next step S12,
The count value n initialized to 0 is incremented, and the time Tn from the rise of the reference signal TR0 of the intermediate transfer belt 16 of the nth color to the fall of the SOS signal is counted in step S13. In step S14, the displacement amount LE of the n-th color based on the time T1 of the first color described above is calculated based on the above equation.

In step S15, it is determined whether or not the correction value for the n-th color calculated by the routine of FIG. 12 is stored in the correction value memory. If the correction value is stored, the correction value is set. In step S16, the position shift amount LE of the nth color is set so that the corresponding transfer position shift correction is performed.
Is corrected by the correction value.

In the next step S17, it is determined whether or not it is the timing for changing the speed of the intermediate transfer belt 16 in the above-described primary transfer non-image area or the like. Is input to the reference clock generator 120 to control the rotation speed of the belt drive motor 123 and correct the rotation speed of the intermediate transfer belt 16. That is, the correction amount P of the speed of the belt drive motor 123 that drives the intermediate transfer belt 16 is a coefficient for changing the frequency of the reference clock generated from the reference clock generation unit 120. The rotation speed of the intermediate transfer belt 16 is increased or decreased with respect to the initial steady speed by multiplying the result by the initial frequency and setting the result of the calculation as the frequency of the reference clock output from the reference clock generator 120.

In step S19, in the speed change area of the intermediate transfer belt 16 such as the primary transfer non-image area,
Control is performed to control the rotation speed of the belt drive motor 123 to return the rotation speed of the intermediate transfer belt 16 to a steady state speed. Then, in step S20, it is determined whether or not the speed change of the intermediate transfer belt 16 has been completed for all four colors, and if the processing has been completed for four colors, this routine is completed, and the processing has been completed for four colors. If not, the process returns to step S11 to repeat the above processing.

By performing the above processing, correction for increasing or decreasing the rotational speed of the intermediate transfer belt 16 in the non-image area of the primary transfer is performed. In this case, if the correction amount of the traveling speed is large, there is a concern that a slip may occur between the intermediate transfer belt 16 and the drive roll 17, so the correction amount is set as small as possible. Therefore, the intermediate transfer belt 1
The rotation speed 6 is increased or decreased over the entire speed change area by making maximum use of the speed change area of the intermediate transfer belt 16 such as the primary transfer non-image area.

In the color image forming apparatus having the above structure, the intermediate transfer belt 16 is provided in the non-image area for primary transfer.
If the rotation speed is changed, there is no effect on the transferred toner image. Further, since the photosensitive drum 13 and the intermediate transfer belt 16 are driven by separate motors,
Even if the speed of the intermediate transfer belt 16 is changed, the photosensitive drum 1
The speed of 3 is hardly affected. Accordingly, even if the speed of the intermediate transfer belt 16 is changed during the writing of the second and subsequent latent images, the latent image written on the photosensitive drum 13 is hardly affected. As described above, in the color image forming apparatus, it is possible to prevent a color shift of the transferred toner image without affecting the transferred toner image or the written latent image.

In particular, in this embodiment, if the intermediate transfer belt 16 is rotated at the correction speed over the entire primary transfer non-image area, the correction amount P of the rotation speed can be reduced. Thus, slip between the intermediate transfer belt 16 and the driving roll 17 can be prevented, and color deviation of toner can be reliably prevented.

In the present embodiment, the traction drive reduction mechanism 130 is provided between the belt drive motor 123 and the drive roll 17 to transmit the driving force. Therefore, the gear train, the timing belt, the timing pulley, and the like are used. Vibration and speed fluctuation as in the case of using the toner can be prevented, and the color shift of the toner accompanying the vibration and the speed fluctuation can be reliably prevented.

In this embodiment, the intermediate transfer belt 16
In the primary transfer non-image area, the intermediate transfer belt 16
The example in which the transfer position deviation is corrected by increasing or decreasing the rotation speed of the polygon mirror 10a has been described. However, the present invention is not limited to this. The transfer position shift may be corrected by changing the latent image writing timing.

[0060]

As described above, according to the present invention,
The transport body is driven to rotate via the traction drive mechanism, and the transport position deviation of the transport body is corrected based on the detection result of the speed fluctuation detection means, preventing the occurrence of poor image quality due to uneven rotation and vibration. In addition, it is possible to prevent the occurrence of image quality failure due to speed fluctuation.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an embodiment of a color image forming apparatus to which the present invention is applied.

FIG. 2 is a control block diagram of the color image forming apparatus.

FIG. 3 is a timing chart showing the timing of image formation.

FIG. 4 is an explanatory diagram illustrating a drive system of an intermediate transfer belt.

FIG. 5 is an explanatory diagram of a traction drive mechanism.

FIG. 6 is a timing chart showing timings of writing and transferring a latent image.

FIG. 7 is a diagram showing a correction of an image tip position.

FIG. 8 is a diagram illustrating a shift of a transfer position in an image forming unit when a load change occurs during primary transfer of K color.

FIG. 9 is a diagram illustrating a shift amount of the transfer position after correcting the transfer position of FIG. 8;

FIG. 10 is a diagram illustrating a shift amount of a transfer position in an image forming unit when a load change occurs before writing a Y-color latent image.

FIG. 11 is a diagram illustrating a maximum color shift amount when a load change occurs before writing a Y-color latent image.

FIG. 12 is a flowchart of a correction amount calculation process for correcting a transfer position shift.

FIG. 13 is a flowchart of a process for correcting a transfer position shift by increasing or decreasing a rotation speed of an intermediate transfer belt.

[Explanation of symbols]

9 image writing unit, 11 SOS sensor, 13 photosensitive drum, 16 intermediate transfer belt, 17 drive roll,
22 mark sensor, 23 cleaner, 25 secondary transfer roll, 120 reference clock generator, 121 drive motor controller, 123 belt drive motor, 130 traction drive reduction mechanism, 140 encoder

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Fukada 2274 Hongo, Ebina-shi, Kanagawa F-term in Fuji Xerox Co., Ltd. (Reference) 2H027 DA17 DE01 DE07 EA03 EB04 EC06 EC09 ED02 ED24 EE01 EE03 EE05 2H030 AA01 AD17 BB42 BB46 BB53 BB56 2H032 AA05 AA15 BA09 BA23 2H071 BA03 CA01 CA05 CA09 DA09 DA15 DA26 DA31

Claims (4)

[Claims] 1. A transporter rotatably disposed and carrying an object, a driving unit for driving the transporter, and a traction drive reduction mechanism for transmitting a driving force of the driving unit to the transporter. A speed variation detecting unit that detects a speed variation of the transport body; and a drive control unit that controls the drive unit to correct a transport position shift of the transport body based on a detection result of the speed variation detecting unit. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the object is a toner image, and the carrier is an intermediate transfer to which a toner image formed on an image carrier is temporarily transferred. An image forming apparatus characterized by being a body. 3. The image forming apparatus according to claim 2, further comprising: a timing control unit configured to control a timing at which the toner image on the image carrier reaches the intermediate transfer body based on a detection result of the speed fluctuation detection unit. An image forming apparatus, comprising: 4. A transporter that is rotatably disposed and carries an object, a driving unit that drives the transporter, a traction drive reduction mechanism that transmits a driving force of the driving unit to the transporter. An image forming apparatus comprising: a speed change detecting unit configured to detect a speed change of the conveyance body.