JPH0948533A - Belt meandering corrector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the occurrence of color discrepancy and image discrepancy with high accuracy by correcting the meandering of a belt at a speed within a specified range, based on the detected meandering of the belt detected by a belt meandering detector. SOLUTION: Around a middle transcriber unit, the first position detector 40 for detecting the lateral position of a middle transcribing belt 20 and the second position sensor 41 for reading the position in carriage direction of the middle transcribing belt 20 are provided. When the middle transcribing belt 20 meanders, it shifts either in H direction or in L direction orthogonal to the carriage direction. The position of the primary transcription front roller 27 regarded as shifting neither in H direction nor in L direction is made the temporary stable position. The position of the middle transcribing belt 20 can be corrected in H direction or L direction by biasing one end of the primary transcription front roller 27. A controller corrects the position of the primary transcription front roller 27 by the output of the first and second position sensors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt meandering correction device for correcting belt meandering. In particular, in the field of electrophotographic image forming apparatuses, the present invention relates to a belt meandering correction apparatus that corrects the meandering of a belt that forms an image on its surface.

[0002]

2. Description of the Related Art Conventionally, a belt meandering correction device for correcting belt meandering has been proposed. Particularly, in the field of electrophotographic image forming apparatuses, a belt meandering correction device for correcting meandering of a belt photosensitive member, an intermediate transfer belt, a fixing belt, etc. is proposed. Various types of belt meandering correction devices have been proposed, but many belt meandering correction devices that correct the belt position by changing the inclination angle of one of the suspension rollers supporting the belt are proposed. Has been done.

[0003]

However, since the conventional belt meandering correction device detects only the position of the belt in the direction perpendicular to the conveying direction and corrects the angle of the suspension roller, high-accuracy correction is possible. could not. In particular, when a toner image is superposed on a belt photosensitive member or an intermediate transfer belt to form a color image, if the belt position is largely moved by the correction mechanism while the toner images are superposed, the toner image is formed. In some cases, the images were misaligned and overlapped with each other, causing color misregistration and image misregistration.

Further, while the belt meandering correction device is inactive due to power off or trouble, the belt is replaced or the position of the belt or the suspension roller is changed, so that The horizontal position may shift significantly. In such a case, when the belt meandering correction device is turned on or when the trouble recovers and the belt starts to be conveyed, the belt conveyance is started in a state in which the lateral position is largely deviated, so that the meandering becomes large. . In particular, when a toner image is superposed on a belt photosensitive member or an intermediate transfer belt to form a color image, the toner images are misaligned and superposed, which may cause color misregistration or image misregistration.

In view of the above problems, an object of the present invention is to provide a belt meandering correction device with high accuracy and with less color misregistration and image misregistration.

[0006]

In order to solve the above problems, a meandering correction device of the present invention includes a belt moving device for moving a belt in a direction perpendicular to a belt conveying direction and a belt moving device perpendicular to the belt conveying direction. A belt meandering detection device for detecting the meandering of the direction, and a control device for controlling the belt moving device so as to correct the meandering of the belt at a speed within a predetermined range based on the meandering of the belt detected by the belt meandering detection device. Have.

Further, the meandering correction device of the present invention comprises a belt moving device for moving the belt in a direction perpendicular to the belt conveying direction, and a belt meandering detecting device for detecting the meandering in the direction perpendicular to the belt conveying direction. Based on the path change device that changes the belt conveyance path and the belt meandering detection device, the belt meandering is corrected by different control depending on the belt conveyance path changed by the path changer device. Thus, a control device for controlling the belt moving device is provided.

Further, the meandering correction device of the present invention conveys the belt in the forward direction and in the backward direction opposite to the forward direction, and moves the belt in a direction perpendicular to the direction in which the belt is conveyed. Based on the belt moving device, the belt meandering detection device that detects the meandering in the direction perpendicular to the belt conveying direction, and the belt meandering detected by the belt meandering detection device, different control depending on the belt conveying direction, And a control device that controls the belt moving device so as to correct the meandering of the belt.

Further, the meandering correction device of the present invention has a belt meandering detecting device for detecting meandering in a direction perpendicular to the belt conveying direction, and a suspension member having at least one shaft and suspending the belt around the belt. A shaft tilt angle correction device that moves the belt in a direction perpendicular to the conveying direction by changing the shaft tilt of the suspension member, a tilt detection unit that detects the tilt of the shaft of the suspension member, and a belt meandering detection device. The control device controls the belt moving device so as to correct the meandering of the belt based on the detected meandering of the belt and the tilt of the shaft of the suspension member detected by the tilt detecting means.

Further, the image forming apparatus according to the present invention includes an image carrying belt for carrying an image on its surface and carrying it in a predetermined carrying direction, a suspension member for suspending the belt around it, and a carrying direction of the belt. A belt moving device that moves the belt in a direction perpendicular to the belt, a belt meandering detection device that detects meandering in a direction perpendicular to the belt transport direction, and a predetermined mean based on the belt meandering detected by the belt meandering detection device. The control device controls the belt moving device so as to correct the belt meandering at a speed within the range.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a cross-sectional view of an electrophotographic image forming apparatus 100. The electrophotographic image forming apparatus 100 is an electrophotographic printer that receives data from a host computer to form an image, and mainly includes a photoconductor unit 1, an intermediate transfer body unit 2, an optical system unit 3, and a developing unit 4. The sheet feeding cassette 5, the copy sheet conveying unit 6, and the fixing device 7.

The photoconductor unit 1 contains a photoconductor 10 and an image forming element such as a charging device and a cleaner disposed around the photoconductor 10, and after cleaning the photoconductor 10 with the cleaner, It is uniformly charged by the charging device.

The print head 3 contains a laser diode, a scanning optical system, etc., and controls the laser diode based on the data from the host computer.
An electrostatic latent image is formed on the photoconductor 10 that is uniformly charged.

The developing unit 4 is provided rotatably around the developing unit shaft 11. Also, the developing unit 4
The developing devices 4Y, 4M, 4C, and 4K are housed in the developing device 4, and the selected developing device faces the photoconductor 10 by the rotation of the developing unit 4. The developing device facing the photoconductor 10 develops the electrostatic latent image formed on the photoconductor 10 to form a toner image.

The paper feed cassette 5 feeds the print paper P stored therein at a predetermined timing and conveys it to the facing portion of the timing rollers 30 and 31.

Next, the detailed structure of the intermediate transfer body unit 2 will be described. FIG. 2 is a cross-sectional view showing the structure of the intermediate transfer body unit 2. The intermediate transfer body unit 2 mainly includes the intermediate transfer belt 20, a driving roller-21, a biasing roller-22, and
Secondary transfer counter roller 23, intermediate transfer belt cleaner 25, primary transfer roller 27, primary transfer roller 28
It is composed of The intermediate transfer belt 20 has a circumference of 64.
An endless belt with a width of 0 mm and a width of 350 mm, made of polycarbonate. The size of the intermediate transfer belt 20 is at least 50 mm or more, preferably 100 mm or more in both the main scanning direction and the sub-scanning direction when the maximum size of A4 size paper is used as the print paper P.

The intermediate transfer belt 20 is a drive roller-2.
1, energizing roller 22, secondary transfer opposing roller 23, 1
The pre-transfer roller 27 and the primary transfer roller 28 are stretched and suspended.
Is in contact with The surface of the drive roller 21 is made of a rubber material, and the drive is transmitted from the main motor 15 via a drive transmission device (not shown) such as a gear and a timing belt. Rotate in the direction of. Drive low
The rotation of the LA-21 is transmitted to the intermediate transfer belt 20, and the intermediate transfer belt 20 is conveyed in the counterclockwise direction at substantially the same speed as the rotation speed of the photoconductor 10. Also, the energizing roller-22
Is urged in the direction of arrow a, and the intermediate transfer belt 2
It is stretched so that 0 is not loose between the rollers. For this reason, the rotation of the drive roller -21 is caused by the rotation of the intermediate transfer belt 20.
Be efficiently transmitted to.

The primary transfer roller 28 is biased in the direction of arrow b to bring the intermediate transfer belt 20 and the photosensitive member 10 into contact with each other, and a primary transfer bias voltage is applied. The toner image formed on the photoconductor 10 is transferred to the intermediate transfer belt 20 by the primary transfer bias voltage applied to the primary transfer roller 28. Intermediate transfer belt 2
The toner image transferred onto the transfer roller 0 is conveyed to a portion facing the secondary transfer roller 24 while being attached to the intermediate transfer belt 20. Secondary transfer roller 24 of the intermediate transfer belt 20
The secondary transfer facing roller 23, which is grounded,
Is provided. A secondary transfer bias is applied to the secondary transfer roller 24 so that the secondary transfer roller 24 can be pressed against and separated from the intermediate transfer belt 20. In addition, the secondary transfer roller 24
Is a drive motor provided separately from the main motor 15.
16 includes a drive transmission device (not shown) such as a gear, a pulley, and a timing belt from the drive motor 16.
Drive is transmitted via the. The secondary transfer roller-2
4 changes the drive voltage of the intermediate drive motor 16 from that of the main motor 15 or changes the gear ratio of the drive transmission device to change the gear ratio of the drive transmission device at a peripheral speed higher than that of the intermediate transfer belt 20 in the direction of the arrow in the figure. It can be rotated. Secondary transfer roller-2
Reference numeral 4 performs press contact separation in association with the conveyance of the print paper P, and contacts the secondary transfer counter roller 23 via the intermediate transfer belt 20 during press contact. In addition, the intermediate transfer belt 20
The number and the arrangement of the suspension rollers are not limited to the form of this embodiment, and may be set according to the form of the image forming apparatus.

The intermediate transfer belt cleaner 25 has a cleaning blade 26 which can be brought into contact with and separated from the intermediate transfer belt 20. The cleaning blade 26 is made of an elastic member such as silicon rubber, and is pressed against the intermediate transfer belt 20 with a total contact force of 200 g during pressing to remove residual toner on the intermediate transfer belt 20.

The pre-primary transfer roller 27 is constructed so that one end is an axis and the other end is tilted in the + s and -s directions. Roller before primary transfer-2
By controlling the deviation of 7, the lateral movement of the intermediate transfer belt 20 can be controlled. In this embodiment, the pre-primary transfer roller 27 is controlled to be displaced, but the present invention is not limited to this, and one or a plurality of other suspension rollers may be selected and used.

FIG. 3 is an enlarged sectional view showing a displacement mechanism of the pre-primary transfer roller 27, and FIG. 4 shows a main part of the displacement mechanism of the pre-primary transfer roller 27. It is an expansion perspective view. The displacement mechanism of the pre-primary transfer roller 27 will be described with reference to FIGS. 3 and 4.

The displacement mechanism of the pre-primary transfer roller 27 mainly includes a stepping motor 51, a motor gear 52, a drive gear 53, a drive pulley 54, a drive wire 55, idle pulleys 56 and 57, and a bearing holder 58. , A bearing 59.

The stepping motor 51 can rotate in both directions by a designated angle, and a motor gear 52 is provided on its rotation shaft. The rotation of the stepping motor 51 is transmitted to the drive gear 53 via the motor gear 52. The stepping motor 51 is
The motor gear 52 can be rotated 50 steps in the + s direction and 50 steps in the -s direction. However,
Here, the range of steps is + s, 10 steps, -s
Only 10 steps are used in the direction. Drive gear 5
3 is provided with an integrally molded drive pulley 54. The drive pulley 54 rotates integrally with the rotation of the drive gear 53. Drive pulley 54 and idle pulley 5
A drive wire 55 is wound around the loops 6 and 57, and the drive wire 55 is conveyed by the rotation of the drive pulley 54. The bearing holder 58 is fixed to the drive wire 55 so as to be located between the bearing 59 idle pulleys 56 and 57, and is moved in the + S direction and the −S direction by the drive wire 55.

The bearing holder 58 has a bearing 59.
Thus, the shaft portion 27a of the pre-primary transfer roller 27 is held, and the shaft portion 27a of the pre-primary transfer roller 27 rotates the stepping motor 51 one step by the movement of the bearing holder 58. Each time it is moved, it is displaced by 16 μm.

Further, as shown in FIG. 4, a bearing 60 is provided on one shaft portion 27b of the pre-primary transfer roller 27, and a slide bearing 63 and a bearing 59 are provided on the other shaft portion 27a. It is provided. Bearing 60, slide bearing 6
The pre-primary transfer roller 27 of the bearing 3 and the bearing 59 rotatably holds the shaft 27a and the shaft 27b.

The slide bearing 63 is fitted in a restriction hole 64 provided in the shaft displacement direction restriction plate 61, and is movable along the restriction hole 64. The bearing 60 is loosely supported by a bearing holding plate 65. With this configuration, when the slide bearing 63 moves along the regulation hole 64, the pre-primary transfer roller 27 moves the bearing 6
Inclining with 0 as the fulcrum. Therefore, by driving the stepping motor 51, the shaft portion 27a is displaced with the bearing 60 as a fulcrum. Further, the direction and range of the deviation of the pre-primary transfer roller 27 can be regulated by the shape of the regulation hole 64.

The direction of deviation of the roller 27 before the primary transfer is
As shown in the explanatory view of FIG. 5, it is most effective to deviate the wrapping angle of the intermediate transfer belt 20 with respect to the pre-primary transfer roller 27 in the direction perpendicular to the bisector thereof.

When the pre-primary transfer roller 27 is displaced from the parallel position, a force for laterally moving the intermediate transfer belt 20 is generated. That is, the stepping motor 51
By displacing the pre-primary transfer roller 27, the intermediate transfer belt 20 can be laterally moved and the position can be adjusted. In this embodiment, the roller is inclined by knitting only one end of the pre-primary transfer roller 27, but both ends of the roller are knitted and the roller is inclined. You may comprise so that it may be made.

FIG. 6 is a perspective view of the intermediate transfer body unit 2. The intermediate transfer body unit 2 includes a driving roller 21, a biasing roller 22, a secondary transfer facing roller 23, a primary transfer pre-roller 27, and a primary transfer between the side plate 70 and the side plate 71. The roller 28 is rotatably arranged, and the intermediate transfer belt 20 is stretched.

Around the intermediate transfer body unit 2, a first position detecting sensor 40 for detecting the lateral position of the intermediate transfer belt 20 and a second position detecting sensor 40 for reading the position of the intermediate transfer belt 20 in the conveying direction. A position detection sensor 41 is provided. The first position detection sensor 40 includes the light emitting element 4
0a and the light receiving element 40b are provided, and the light emitting element 40
The light emitted by a is detected by the light receiving element 40a. Further, in the present embodiment, the laser type parallel light linear sensor made by OMRON (setting resolution 2.2 μm) is used as the first position detecting sensor 40, but any other sensor capable of detecting the position may be used. On the other hand, the second position detection sensor 41 is a reflective photosensor in which a light emitting element 41a and a light receiving element 41b are integrally incorporated, and the light emitting element 41a illuminates an object and the reflected light is detected by the light receiving element 41b. Is configured.

FIG. 7 is a block diagram of a control circuit of the image forming apparatus 100. The first CPU 45, based on inputs from the host computer, the operation panel, the second CPU 46, etc., the main motor, the print head 3, the intermediate transfer belt cleaner 25, the timing rollers 30, 31 ,.
It controls each element such as the secondary transfer roller 24 and the primary transfer roller 28.

The second position detecting sensor 41 is the second CPU
The output value of the second position detection sensor 41 is connected to the second CPU 46. Second CPU 46
Detects a timing mark M formed on the side plate 71 side of the intermediate transfer belt 20 from the output value of the second position detection sensor 41 and generates a timing signal.

The first position detecting sensor 40 is connected to the second C sensor via the amplifier unit 47 and the digital panel meter 48.
Connected to PU. The output value of the first position detection sensor 40 is amplified by the amplifier unit 47, converted into a 5-level digital signal by the digital panel meter 48, and sent to the second CPU 46.

FIG. 8A is an explanatory view showing the relationship between the light receiving width of the light receiving portion 40c of the first position detecting sensor 40 and the intermediate transfer belt 20. Light receiving portion 4 of the first position detection sensor 40
0c receives the light of the light emitting element 40a and outputs a voltage signal proportional to the amount of received light. Light emitting element 40a and light receiving section 40
A part of the intermediate transfer belt 20 is inserted between c to block a part of the light emitted from the light emitting element 40a to the light receiving section 40c. Therefore, the light receiving unit 40c outputs a signal of a voltage corresponding to the amount of light received in the portion not covered by the intermediate transfer belt 20.

FIG. 8b is a graph showing the relationship between the light receiving width of the light receiving portion 40c and the voltage output from the first position detecting sensor 40. From this graph, it can be seen that the output voltage from the first position detection sensor 40 changes corresponding to the position of the intermediate transfer belt 20. In the present embodiment, the direction in which the output value of the first position detection sensor 40 increases is the H direction,
The direction that becomes smaller is the L direction.

Table 1 shows the relationship between the voltage signal of the first position detecting sensor 40 and the determination level.

[0038]

[Table 1]

The reference potential in Table 1 is the position detection sensor 40.
8b shows the boundary value of the voltage signal, and the reference position shows the position of the intermediate transfer belt 20 corresponding to the reference potential from the graph of FIG. 8b. Also, the number written between the reference positions indicates the distance between the reference positions. The voltage signal from the first position detection sensor 40 is amplified by the amplifier unit 47 and then input to the digital panel meter 48. The digital panel meter 48 converts the voltage signal into a five-level digital signal [HH, H, M, L, LL] (hereinafter referred to as a judgment level) with the reference potential of Table 1 as a boundary, and outputs the digital signal. .

This determination level is input to the second CPU 46. The timing signal from the second position detection sensor 41 and the intermediate transfer belt drive signal from the first CPU 45 are also input to the second CPU 46.

On the other hand, at the output port of the second CPU 46,
A motor driver 49 that drives the stepping motor 51 and an amplifier unit 47 are connected. 2nd C
The stepping motor 51 is driven by the drive signal output from the PU 46 to the motor driver 49, and the light emission of the light emitting element 41a of the first position detection sensor 40 is controlled by the ON / OFF signal output to the amplifier unit 47. In the present embodiment, since the light emitting element 41a that outputs laser light is used, the laser light is controlled to be emitted only during measurement in order to ensure safety.

When the intermediate transfer belt 20 meanders, the intermediate transfer belt 20 moves in the H direction or the L direction which is a direction orthogonal to the conveying direction. On the other hand, when the intermediate transfer belt 20 is stably conveyed and does not meander, it does not move in the H direction or the L direction.
The position of the roller 27 before primary transfer at this time is set to a stable position. However, in reality, the belt conveyance conditions do not become completely stable because the belt conveyance conditions change due to changes in environmental conditions and changes over time such as wear of suspension rollers and deterioration of the belt itself. Therefore, here, the position of the pre-primary transfer roller 27, which is considered not to move the intermediate transfer belt 20 in the H direction or the L direction, is set to the temporary stable position. This temporary stable position changes as the conveyance state of the intermediate transfer belt 20 changes.

By displacing one end of the pre-primary transfer roller 27 from the temporarily stable position in the + s or -s direction,
The position of the intermediate transfer belt 20 can be corrected in the H direction or the L direction. One end of the pre-primary transfer roller 27 is displaced from the temporarily stable position in the + s or -s direction to form an angle θ.
When the roller 27 is inclined by only .theta.
Therefore, the roller 27 before the primary transfer is the intermediate transfer belt 20.
Also, the direction in which is conveyed is inclined by the angle θ. Due to this inclination, the intermediate transfer belt 20 moves in a direction perpendicular to the conveying direction. When the roller before primary transfer 27 is arranged in + s, the moving direction is in the H direction,
When knitting in the s direction, it moves in the L direction.

Further, when the movement amount Δd of the intermediate transfer belt 20 is expressed by a general formula, Δd ≧ L when the circumferential length of the intermediate transfer belt 20 is L and the inclination angle of the pre-primary transfer roller 27 is θ. × tan θ.

FIG. 9 is an operation control flowchart of the electrophotographic image forming apparatus 100. The control program of this operation control flowchart is mainly incorporated in the first CPU 45 and controls the operation of the electrophotographic image forming apparatus 100.

When the main switch of the electrophotographic image forming apparatus 100 is turned on, the operation control flowchart starts, and initial setting is performed in S10. When the initial setting is completed, warm-up is started in S20 and S30 is started.
At, the driving of the intermediate transfer belt 20 is started. When the driving of the intermediate transfer belt 20 is started, the first CPU
An intermediate transfer belt drive signal is sent from 45 to the second CPU 46. When it is determined in S40 that the warm-up is completed, the driving of the intermediate transfer belt 20 is stopped in S50, and the preliminary operation is completed.

Next, in S60, an internal timer is started, and it is determined in S70 whether or not there is a print command from the host computer. If there is no print command, the process proceeds to S90, waits until the timer ends, and then S60.
Return to

If there is a print command from the host computer in S70, the process proceeds to S80 and a print operation subroutine is executed. When the print operation subroutine of S80 ends, the process proceeds to S90, waits until the timer ends, and then returns to S60.

FIG. 10 shows the print operation subroutine (S80) of the operation control flowchart shown in FIG.

When the print operation subroutine of S80 is entered in the operation control flowchart, the driving of the intermediate transfer belt 20 is started in S100, and the electrophotographic copying operation is performed in S110. Also here, when the driving of the intermediate transfer belt 20 is started, the first CPU 45 causes the second CPU
An intermediate transfer belt drive signal is sent to 46. S110
By the electrophotographic copying operation, the photoconductor unit 1, the intermediate transfer unit 2, the print head 3, the developing unit 4 and the like are controlled, and an electrophotographic process such as charging, exposure, development and primary transfer is executed. By such an electrophotographic image forming operation, a toner image is formed on the intermediate transfer belt 20.

Next, in S120, it is judged whether or not the electrophotographic image forming operation has been completed, and the electrophotographic image forming operation of S110 is repeated if necessary. For example, at the time of full-color image formation, four-color images are formed on the intermediate transfer belt 20, and the electrophotographic image forming operation is repeated until the image superposition is completed. When the end of the electrophotographic image forming operation is confirmed in S120, the secondary transfer and fixing operations are performed in S130, and the image is output. In S140, it is determined whether or not the predetermined print operation is completed, and if a plurality of print operations are designated, the operations from S110 to S130 are repeated a designated number of times to output a plurality of images. When all the printing operations are completed, the intermediate transfer belt 20 is sent in S150.
Drive is stopped and the process returns to the main flow chart.

FIG. 11 is a flow chart of the belt meandering correction operation control. The belt meandering correction operation control flowchart is stored in the second CPU and is executed in conjunction with the first CPU. Main switch turns on and the second CPU
When is activated, first, initial setting is performed in S210, and variables Sn (current stepping motor step position), St (read value of meandering correction table), Sc
(Stepping motor drive step number) and Ss (temporary stable position) are substituted with 0. Also, stepping motor 5
For 1, the initial phase is given. For example, when a four-phase stepping motor is used as the stepping motor 51, (HH, H, L,) for the four phases (A +, B +, A-, B-)
LL) is output. In addition, the output of the laser diode, which is the light emitting element 40a of the first position detection sensor 40, is turned off.
Then, the delay timer for stabilizing the output of the laser diode is initialized. Furthermore, a variable State0 indicating the previous determination level and a variable State1 indicating the current determination level
Is substituted with the central position M.

When the initial setting is completed, the process proceeds to S220, the intermediate transfer belt drive signal from the first CPU 45 is judged, the process waits until the intermediate transfer belt drive signal is transmitted, and when the intermediate transfer belt drive signal is transmitted. S230
Proceed to.

Next, in S230 and S240, the rising edge of the timing signal output from the second position detection sensor 41 for detecting the mark indicating the reference position provided on the intermediate transfer belt 20 is detected.

When the rising of the timing signal is detected in S230 and S240, the light emitting element 40a of the first position detecting sensor 40 is turned on in S250, and the process proceeds to S260.

Next, in S260, a timer delay of 1 second is set in order to stabilize the light emitting element 40a of the first position detection sensor 40.

When the timer in S260 times out, in S270, the current judgment level is read from the digital panel meter 48 and is substituted into the variable state1. When the reading from the digital panel meter 48 is completed, in S280, the first position detection sensor 40
The output of the light emitting element 40a is turned off.

Next, the stepping motor drive subroutine of S290 and the temporary stable position correction subroutine of S300 are executed. The contents of the stepping motor drive subroutine of S290 and the temporary stable position correction subroutine of S300 will be described later.

At S310, the current decision level variable
After substituting the value of state1 into the previous determination level variable state0, the process returns to S220 after waiting for the timing signal of the second position detection sensor 41 to be turned off in S320.

FIG. 12 is a stepping motor drive subroutine of S290 of the belt meandering correction operation control flowchart.

In the belt meandering correction operation control flowchart, when the stepping motor drive subroutine of S290 is called, the previous judgment level (variable state0) and the current judgment level (variable) of the meandering correction control table 1 of Table 2 are called at S350. The corresponding value is read from the intersection of state1) and variable St (read value of meandering correction table)
To.

[0062]

[Table 2]

The meandering correction control table 1 of Table 2 will be described below.

The symbols (+, −) attached to the numbers represent the rotation direction of the stepping motor 51. That is,
The + sign indicates the rotation of the stepping motor 51 in the + s direction, and the − sign indicates the −s of the stepping motor 51.
Indicates rotation in a direction.

C means to return the deviation angle of the pre-primary transfer roller 27 to the temporarily stable position, which changes depending on the rotation direction of the stepping motor 51 and the control state at that time.

Next, the meandering correction table 1 of Table 2 will be described.

When the previous determination level is M and the present determination level is M, the lateral position of the intermediate transfer belt 20 is at the target position M, and there is no need for position correction. Therefore,
The stepping motor 51 is not driven.

When the previous determination level is M and the present determination level is H, it means that the lateral position of the intermediate transfer belt 20 is deviated from the target position M to the H side, and therefore the target position M is returned. There is a need. In order to gradually return the lateral position of the intermediate transfer belt 20 to the target position M, the stepping motor 51 is rotated by one step to the-side. At this time, by setting the number of steps to 1, abrupt lateral movement of the intermediate transfer belt 20 can be suppressed. Further, if the temporary stable position is proper, the lateral position of the intermediate transfer belt 20 moves from the target position M to the H side even though it does not move from the target position M, which means that the temporary stable position is incorrect. It means that. Therefore, it is necessary to change the temporary stable position to the-side. This change is performed in a temporary stable position correction subroutine described later.

When the previous determination level is M and the present determination level is HH, it means that the lateral position of the intermediate transfer belt 20 is abruptly offset from the target position M to the H side. Therefore, it is determined that some unexpected situation has occurred, and the stepping motor 51 is urgently rotated by 6 steps to the minus side.

When the previous determination level is H and the present determination level is L, the lateral position of the intermediate transfer belt 20 jumps from the first level on the H side to the target position M and moves to the first level on the L side. It means that you have done it. Therefore, it is determined that the correction control is too effective and an overshoot has occurred, and for the time being, the pre-primary transfer roller 27 is returned to the temporarily stable position.

When the previous determination level is H and the present determination level is M, the lateral position of the intermediate transfer belt 20 on the H side has returned to the target position, so the roller before primary transfer 27
To the temporary stable position.

When the previous determination level is H and the present determination level is H, it means that the lateral position of the intermediate transfer belt 20 is continuously at the first level on the H side. Therefore,
It is necessary to gradually return the lateral position of the intermediate transfer belt 20 to the target position M. Therefore, the stepping motor 51 is rotated by one step to the-side. Here, the amount of movement of the stepping motor 51 is limited to one step to avoid abrupt lateral movement of the intermediate transfer belt 20.

When the previous determination level is H and the current determination level is HH, the lateral position of the intermediate transfer belt 20 is further deviated from the first level on the H side to the H side and the second position on the H side.
Means you have moved to a level. Therefore, more
It is necessary to prevent the target position M from moving away from the target position M toward the H side. Therefore, the stepping motor 51 is rotated to the minus side by 2 steps. Here, by limiting the movement amount of the stepping motor 51 to 2 steps,
The sudden lateral movement of the intermediate transfer belt 20 is avoided.

When the previous determination level is HH and the present determination level is LL, the lateral position of the intermediate transfer belt 20, which was at the second level on the H side, jumps over the target position M and the second level on the L side. Means to have moved to. Therefore, it is judged that the correction control is too effective and an overshoot has occurred,
The pre-primary transfer roller 27 is returned to the temporary stable position.

When the previous determination level is HH and the present determination level is L, the lateral position of the intermediate transfer belt 20, which was at the second level on the H side, jumps over the target position M and reaches the first position on the L side. Means you have moved to a level. Therefore, it is judged that the correction control is too effective and an overshoot has occurred,
The pre-primary transfer roller 27 is returned to the temporary stable position.

If the previous determination level is HH and the present determination level is M, it means that the lateral position of the intermediate transfer belt 20 on the H side has returned to the target position M. Return the roller 27 to the temporary stable position.

When the previous determination level is HH and the present determination level is H, it is determined that the lateral position of the intermediate transfer belt 20 which was at the second level on the H side is gradually returning to the target position M. Then, in order to see the subsequent state, the angle of the pre-primary transfer roller 27 is maintained as it is.

When the previous determination level is HH and the current determination level is HH, the lateral position of the intermediate transfer belt 20 is H.
Side is stable at the second level, or is moving further from the second level on the H side to the H side. In any case, in order to return to the target position M, it is necessary to control the stepping motor 51 to the L side. At this time, the movement amount is reduced by setting the movement step number to 1. This is to prevent the lateral position of the intermediate transfer belt 20 from abruptly moving when it is stable at the second level on the H side.

When the previous determination level is L and the present determination level is H, the lateral position of the intermediate transfer belt 20, which was at the first level on the L side, jumps over the target position M and reaches the first position on the H side. Since it means that the roller has moved to the level, it is determined that the correction control is too effective and an overshoot has occurred, and the angle of the pre-primary transfer roller 27 is returned to the temporary stable position.

When the determination level of the previous time is L and the determination level of this time is HH, the lateral position of the intermediate transfer belt 20, which was at the first level on the L side, jumps over the target position M to the second level on the H side. Since it means that the roller has moved to the level, it is determined that the correction control is too effective and an overshoot has occurred, and the angle of the pre-primary transfer roller 27 is returned to the temporary stable position.

When the previous determination level is LL and the current determination level is HH, the lateral position of the intermediate transfer belt 20, which was at the second level on the L side, jumps over the target position M and reaches the second position on the H side. Since it means that it has moved to the level, it is judged that the correction control is too effective and an overshoot has occurred.
The angle of the pre-transfer roller 27 is returned to the temporary stable position.

The numerical value set in this way is S350.
After the variable St is input to the variable St in S, it is determined in S360 whether the variable St is C, that is, whether or not the movement to the temporary stable position is instructed.

When St is C, in S370,
After substituting the difference between the variable Ss (temporary stable position) and the variable Sn (current stepping motor step position) into the variable Sc (stepping motor driving step number), S380
Proceed to.

If St is not C, the process proceeds to S400 and branches if the variable St is positive and if it is not positive.

When St is determined to be positive in S400, the process proceeds to S410, and the value obtained by adding St (the reading value of the meandering correction table) to Sn (the current step position of the stepping motor) is the movement of the stepping motor 51. It is determined whether or not the upper limit value of 10 is exceeded. If this value exceeds 10, the process proceeds to S420,
After the upper limit value is set by substituting 10-Sn into Sc (the stepping motor drive step number) so that the stepping motor 51 rotates to the upper limit value, S
Proceed to 380.

In S410, the sum of Sn and St is 10
When it is determined that the value is equal to or less than that, the process proceeds to S430, and St (the reading value of the meandering correction table) is directly substituted into Sc (the stepping motor driving step number). Then, it progresses to S380.

If it is determined in S400 that St is not positive, the process proceeds to S440, in which the sum of Sn and St is -10.
It is determined whether or not it falls below.

In S440, if Sn + St is less than -10, the process proceeds to S450, in order to rotate the stepping motor 51 to the lower limit value, -10-S.
Substitute n for Sc. Then, it progresses to S380.

In S440, if Sn + St does not fall below -10, the process proceeds to S460, St is substituted for Sc, and then the process proceeds to S380.

In S380, the stepping motor 51 is driven according to the value of Sc.

In this example, a stepping motor having a movable range upper limit value of +50 and a movable range lower limit value of -50 is used.
Although the upper limit value is set to +10 and the lower limit value is set to −10, a stepping motor having a different upper limit value of the movable range, a lower limit value of the movable range, and a minimum stepping angle may be used if necessary. Further, by reducing the minimum stepping angle, more precise control can be made possible.

Finally, in S390, the value of the variable Sn (current stepping motor step position) is set to St.
The value is updated to the sum of (the read value of the meandering correction table) and Sc (the stepping motor driving step number), and the process returns to the belt meandering correction operation control flowchart.

In this example, the target position M is set so that the lateral position of the belt returns to the target position M.
If it is only for meandering prevention, it is not necessary to set a target position in particular, and the conveyance of the belt may be stabilized at a predetermined position. However, the belt is always moving laterally. For this reason, if the conveyance is stabilized at a predetermined position, the stabilization position will gradually shift, and the limit position determined by the width of the suspension roller or the like and the meandering detectable range will be exceeded. In order to prevent this phenomenon, the lateral position of the belt is controlled to return to the target position M in this example.

FIG. 13 is a temporary stable position correction subroutine of the belt meandering correction operation control flowchart.

When the temporary stable position correction subroutine of S300 is called in the belt meandering correction operation control flowchart, first in S500, it is determined whether or not State0 (previous determination level) is M. If the result is No, the variable Ss indicating the temporary stable position is not corrected, and the process returns to the belt meandering correction operation control flowchart. If Yes, the process proceeds to S510.

In S510, the process branches depending on the value (LL, L, M, H, HH) of state1 (current determination level).

If state1 = L in S510,
After proceeding to S520 and incrementing the variable Ss by 1, the process returns to the belt meandering correction operation control flowchart. This is the intermediate transfer belt 20 that was at the target position M.
This is because the lateral position of is deviated to the L side, and it is necessary to correct the temporary stable position.

If state1 = H in S510,
After proceeding to S530 and decrementing the variable Ss by 1, the process returns to the main routine of the belt meandering correction operation control flowchart. This is because the lateral position of the intermediate transfer belt 20, which was at the target position M, is deviated to the H side, and it is necessary to correct the temporary stable position.

In S510, state1 = M or L
If L and HH, the process directly returns to the belt meandering correction operation control flowchart.

In this way, by executing the temporary stable position correction subroutine, it is possible to perform stable belt conveyance at the target position M without meandering.

FIG. 14 is a graph showing the result of the belt meandering positive control based on the present invention. The experimental conditions are: the circumference of the intermediate transfer belt 20: 640 mm, the width of the intermediate transfer belt 20: 350 mm, the transport speed of the intermediate transfer belt 20: 150 mm / sec, the tension of the intermediate transfer belt 20: 1 kgf, to the pre-transfer roller 27. Angle of intermediate transfer belt 20: 90 ° Material of roller 27 before primary transfer: Rubber (EPDM) Roller 27 before primary transfer Diameter: φ30 Minimum tilt amount: 16 μm / step Set the target value M of the lateral position of the intermediate transfer belt 20 to 2 m.
The experiment was conducted by setting m.

In this experimental example, the bearing 59 is set to be displaced by 16 μm every time the stepping motor 51 rotates one step, and the distance between the bearing 59 and the bearing 60 is set to 380 mm. Because there is. 1
The deviation angle θ of the pre-transfer roller 27 is tan θ = 0.016 / 380.

In the graph of FIG. 14, the lateral position change of the intermediate transfer belt 20 and the four-rotational deviation obtained as a result of this experiment are calculated, and the rotation of the intermediate transfer belt 20 is 1-4, 2-5,
It is plotted by dividing it into 3 to 6 ... The four-rotation deviation is a deviation of the lateral position measured value during four rotations of the intermediate transfer belt 20, and when a sudden belt deviation occurs, the four-rotation deviation becomes a large value.

From the graph of FIG. 14, the intermediate transfer belt 20
It can be seen that the position of is controlled to about 2 mm, and the deviation of four rotations is controlled to within about 60 μm, although there are some protrusion values.

In this experimental example, the intermediate transfer belt 2
The experiment was conducted by setting the target value of the lateral position of 0 to 2 mm, but this value can be appropriately set according to the configuration of the belt to be controlled and the shape of the lateral position detection sensor.

As is apparent from this graph, by using the present invention, the meandering of the belt can be corrected and the lateral moving speed of the belt can be suppressed to a certain level or less. If the lateral movement speed of the belt can be suppressed below a certain level, especially in the case of an intermediate transfer belt or an image bearing belt such as a belt photosensitive member, the positional deviation of dots between the images of each color, the straight line distortion, and the color misregistration may occur. It is possible to suppress such problems. For example, when a straight line is formed in the traveling direction of the intermediate transfer belt, when the intermediate transfer belt laterally moves, the imaged straight line is distorted, but by suppressing the lateral transfer speed of the intermediate transfer belt to a certain value or less Can be minimized. In particular, the resolution of the human eye is 8 Cycles
Since it is about / mm, converting this to a positional deviation is 6
It becomes 2.5 μm (1 mm / 16 lines), and if the positional deviation is within 60 μm, it is almost impossible to distinguish them. In this experimental example, the circumference of the intermediate transfer belt 20 is 6
Since it is 40 mm, the roller 27 before the primary transfer has an angle θ.
When the intermediate transfer belt 20 makes one round in the deviated state, tan θ = Δd / 640, where Δd is 27 μm, where Δd is the lateral movement amount of the intermediate transfer belt 20. 27 μm is much lower than the degradation of the human eye, so the intermediate transfer belt 2
No image distortion or color misalignment due to 0 lateral movement is discriminated.

Further, if the deviation of 1 dot of the formed image is set to be less than the discrimination limit, it is desirable to set Δd to 60 μm (1 dot in the case of a 400 dpi laser optical system).

FIG. 15 is a belt meandering correction operation control flowchart showing another example of the belt meandering correction operation control. This belt meandering correction operation control makes the control method at the start of belt conveyance different from the meandering correction control during normal copying, such as when the main switch is turned on and when a trouble such as jam processing or a failure of the image forming apparatus is recovered. By controlling the belt to approach the preset target position,
Further, it is possible to more accurately suppress the occurrence of color shift and image shift.

The contents of the meandering correction operation control flow chart shown in FIG. 15 are the operation determination subroutine of S610 and S
The rough adjustment end determination subroutine of 710 is added, and S7
11 is the same as the meandering correction operation control flowchart of FIG. 11 except that the contents of the temporary stable position correction subroutine of 00 are different. Therefore, the meandering correction operation control flowchart shown in FIG. 15 will be described, focusing on the parts different from the meandering correction operation control flowchart in FIG. 11.

When the second CPU is actuated by turning on the main switch or recovering from a trouble, initialization is performed in S600, and then an operation mode determination subroutine is entered in S610. Note that the meandering correction control may be previously performed, and S600 may be skipped when data such as the temporary stable position Sc has been updated.
However, if the inclination of the pre-primary transfer roller 27 may change due to a trouble recovery operation such as a jam processing due to the mechanical configuration, S600 should be executed. Because the roller 27 before the primary transfer
This is because the previous provisional stable position becomes meaningless at all when the inclination of changes.

FIG. 16 shows the contents of the operation mode determination subroutine.

When the operation mode determination subroutine is entered, S
At 800, the copy state is determined. This copy state is used when the main switch is turned on or when troubles such as jam clearance and maintenance are recovered in the course of the progress of the control program in the operation control flowchart of FIG.
It is a flag set to identify the copy operation mode.

If it is determined in S800 that the copy state is "when the main switch is ON", S81
0, the meandering correction control table used in step S350 in the stepping motor drive subroutine is
The meandering correction control table 2 is set. Table 3 shows an example of the meandering correction control table 2.

[0114]

[Table 3]

The meandering correction control table 2 is different from the meandering correction control table 1 described above only in the numerical value to which an underline is added. Specifically, when the previous determination level is H and the current determination level is H or HH, and when the previous determination level is HH and the current determination level is HH, similarly, the previous determination level is L. The number of drive steps is set to be large when the current determination level is L or LL, and when the previous determination level is LL and the current determination level is LL. By setting in this way, the image forming apparatus 10
Even if the lateral position of the intermediate transfer belt 20 is greatly deviated while 0 is stopped, the position can be quickly corrected during the preliminary operation. Further, at this time, since an image is not formed on the intermediate transfer belt 20, even if a rapid lateral movement occurs, it does not cause an image defect.

Next, in S820, the process before the primary transfer is started.
In order to indicate that the temporary stable position of the liner 27 is being roughly adjusted, the flag Send is set to "0" and then the process returns to the meandering correction operation control flowchart.

If it is determined in S800 that the copy state is "at the time of trouble recovery", the process proceeds to S810,
The meandering correction control table is set in the meandering correction control table 2, the flag Send is set to "0" in S820, and the process returns to the meandering correction operation control flowchart.

At S800, the copy state becomes
When it is determined that "during normal copying", the process proceeds to S830,
The meandering correction control table is set to the meandering correction control table 1, and the flag Send is set to "1" to indicate that the temporary stable position of the primary transfer roller 27 is found in S840. Return to the operation control flowchart.

After returning from the operation mode determination subroutine of FIG. 16 in this manner, steps S620 to S690 are executed. The contents of the steps from S620 to S690 are the same as the contents from S220 to S290 of the meandering correction operation control flowchart of FIG. 11, and therefore the description thereof is omitted here. The stepping motor drive subroutine of S690 has the same contents as the stepping motor drive subroutine of S290 shown in FIG. 12, but the meandering correction control table used in S350 includes the meandering correction control selected in the operation mode determination subroutine. Either the table 1 or the meandering correction control table 2 is used.

When the steps up to S690 are executed,
Next, the temporary stabilization subroutine of S700 is executed.

FIG. 17 is another example of the temporary stable position correction subroutine. The temporary stable position correction subroutine of FIG. 17 is a method of calculating the temporary stable position by averaging a plurality of measured values. By using this method, the accuracy can be further improved.

When the temporary stable position correction subroutine is entered, S
At 850, the counter Count.Ave is determined.
When this counter reaches 20, the routine proceeds to a routine (S860 to S900) for correcting the temporary stable position, and otherwise, a routine (S910 to S960) for changing the average level variable Sa according to the current determination level (state1). )
Go to.

If it is determined in S850 that the counter is less than 20, the process proceeds to S910, and a branch is made according to the variable state1 indicating the current determination level.

When state1 is M, the correction is not applied to Sa and the process directly proceeds to S960.

When state1 is LL, the average level variable Sa is decremented by 2 in S920, and then S96.
Go to 0.

When state1 is L, the average level variable Sa is decremented by 1 in S930, and then S960.
Proceed to.

When state1 is H, the average level variable Sa is incremented by 1 in S940, and then S96.
Go to 0.

When state1 is HH, the average level variable Sa is incremented by 2 in S950, and then S9
Proceed to 60.

In S960, the counter Count.Ave is 1
Is incremented only and the process returns to the meandering correction operation control flowchart.

Next, in S850, the counter Coun
When it is determined that the count value of t.Ave has reached 20, the process proceeds to S860. In S860, the counter Count.
By the time Ave reaches 20, state1 (judgment level)
The positive / negative of the average level variable Sa changed according to is determined.

When Sa is 0, the state 1 (determination level) is output evenly distributed in positive and negative during 20 times. Therefore, the temporary stable position is determined to be correct, and the variable Ss indicating the temporary stable position is determined. No correction is made and the process proceeds to S890.

If Sa is negative in S860, it is determined that the average determination level for the 20 times is negatively biased, the variable Ss indicating the temporary stable position is incremented by 1, and the process proceeds to S890.

If Sa is positive in S860, it is determined that the average determination level for the 20 times is positively biased, the variable Ss indicating the temporary stable position is decremented by 1, and the process proceeds to S890.

After the variable Sc is corrected according to the value of the variable Sa, the counter Coun is reset in S890 and S900.
After substituting 0 for t.Ave and Sa, the process returns to the meandering correction operation control flowchart.

As described above, when the temporary stable position is corrected based on the average value of a plurality of times, more stable control can be performed. Although the number of times of measurement is set to 20 in this embodiment, the number of times of measurement is not limited to this, and an appropriate number of times may be set.

When the temporary stable position correction subroutine ends,
Returning to the meandering correction operation control flowchart, next,
The rough adjustment end determination subroutine is executed.

The temporary stable position correction subroutine of FIG. 13 may be used for this control example, or the temporary stable position correction subroutine of FIG. 17 may be used for the first control example.

FIG. 18 shows the contents of the rough adjustment end determination subroutine.

In S710 of the meandering correction operation control flowchart of FIG. 15, when the rough adjustment determination subroutine is called, the process proceeds to S1000, in which the pre-primary transfer is performed based on the contents of the flag Send set in the operation mode determination subroutine of FIG. It is determined whether the temporary stable position of the roller 27 is being searched.

That is, when Send is not 0, that is, when the temporary stable position is found, the process returns to the meandering correction operation control flowchart as it is.

In S1000, if Send = 0, that is, if a temporary stable position is being sought, the process proceeds to S1010. In S1010, in step s112,
It is determined whether the movement of the intermediate transfer belt 20 in the one-sided direction is stable. In the present embodiment, in view of the design of the meandering correction control table, if the lateral position of the intermediate transfer belt 20 reaches the target level M twice in succession, the intermediate transfer belt 2
It can be determined that the lateral position of 0 is stable at the target position M, and the pre-primary transfer roller 27 is at the temporary stable position. Therefore,
If state0 = M and state1 = M, it is determined that the temporary stable position of the pre-primary transfer roller 27 has been found, and step S1020.
Proceed to. Alternatively, the process may proceed to S1020 after the elapse of a predetermined time or after the intermediate transfer belt 20 has rotated a predetermined number of times. In S1020, Send = 1 is set,
The process returns to the meandering correction operation control flowchart. .

If the determination result in S1010 is No, the process returns to the meandering correction operation control flowchart.

When the rough adjustment end determination subroutine ends, in S720, the current determination level variable state1 value is substituted into the previous determination level variable state0, and then S730.
In, the process returns to S620 after waiting for the timing signal of the second position detection sensor 41 to turn off.

By using this control example, the belt can be returned to a stable state when the power of the image forming apparatus is turned on or when the belt is operated when a jam or trouble is solved, so that a more stable image can be obtained. Obtainable.

Next, correction in the deviation direction of the meandering correction roller will be described. In the present invention, as shown in FIG. 2, the belt meandering is performed by displacing the pre-primary transfer roller 27, which is one of the rollers suspending the intermediate transfer belt 20, as a meandering correction roller. . When the rollers that suspend the intermediate transfer belt are truly parallel, the lateral movement characteristics when the belt meandering correction roller corrects the belt are the same regardless of the direction in which the meandering correction roller is displaced. However, it is difficult to actually make the rollers that suspend the intermediate transfer belt parallel to each other. When the suspended rollers are not truly parallel, each suspension roller generates a force that biases the belt in a direction according to the strain of each roller, and laterally moves the belt to either side. In order to prevent this lateral movement, the meandering correction roller is biased to take a temporary stable position.However, since the roller system itself has the characteristic of biasing the belt, the lateral movement amount depends on the deviation direction of the meandering correction roller. Change occurs.

FIG. 19 shows the deviation amount (tilt) of the steering roller for meandering correction (roller 27 before primary transfer in this embodiment) using the intermediate transfer belt 20 of the embodiment shown in FIG. 6 is a graph showing the results of measuring the lateral movement amount per one rotation of the belt when the amount) is changed. In the graph of FIG. 19, the horizontal axis represents the deviation amount (tilt amount) of the steering roller, and the vertical axis direction represents the lateral movement amount per belt rotation. As can be seen from this graph, the ideal movement characteristic is point-symmetrical with respect to the deviation amount of the steering roller, but in reality, it is offset in a specific direction. If the meandering correction is performed in such a state of the meandering correction mechanism, the operation of the belt in the lateral movement direction changes depending on the deviation direction of the steering roller. Further, when the steering roller is displaced in the direction in which the lateral movement amount of the belt is large with respect to the deviation amount of the steering roller, overshoot occurs in a small number of steps, and the lateral movement of the belt with respect to the deviation amount of the steering roller is caused. When the steering roller is deviated in the direction in which the movement amount is small, the target position of the belt may not be reached by the specified number of steps. This phenomenon is caused by multiplying the read value from the meandering correction table by the correction constant A or the correction constant B set according to the deviation direction of the steering roller, as shown in the graph of FIG. This can be prevented by performing the driving with the number of driving steps corrected to.

FIG. 20 shows a flow chart used when such a correction is performed. The flowchart of FIG. 20 is a modification of the stepping motor drive subroutine shown in FIG. Therefore, FIG.
The explanation will focus on the parts that are different from the above, and the common parts will be omitted.

In FIG. 20, the value of Sc is corrected before driving the stepping motor in accordance with the value of Sc (stepping motor driving step number) in S380. That is, in S330, whether the position of the pre-primary transfer roller 27 is on the plus side or the minus side with respect to the temporary stable position, that is, the value of Sn (current stepping motor step position) is Ss.
It is determined whether or not it is larger than (temporary stable position). If it is larger, the routine proceeds to S331, where Sc is multiplied by the correction constant B, and if it is larger, the routine proceeds to S332 where Sc is multiplied by the correction constant A. The correction constant A and the correction constant B are values obtained by an experiment, and as shown in the graph of FIG.
By multiplying by, the actual movement characteristic can be corrected to the ideal movement characteristic.

Further, the intermediate transfer belt 20 may be operated in a separated state during non-image formation in order to perform the alignment at a higher speed. FIG. 21 is a sectional view showing the structure of the intermediate transfer body unit 2 when the intermediate transfer belt 20 is separated.

The intermediate transfer belt 20 is suspended in the state of the first path at the time of normal image formation, and the primary transfer roller-2
It is pressed against the photoconductor 10 by 8. Drive roller
21 and the primary transfer roller 28 are 21 'and 2 respectively.
It can be moved to the 8'position. When the driving roller 21 and the primary transfer roller 28 move to the positions 21 'and 28', respectively, the intermediate transfer belt 20 is suspended in the state of the second path, and the pressing force to the photoconductor 10 is not applied. It will be canceled. In this state, when the secondary transfer roller 24 is moved to the position 24 'and the pressing of the cleaning blade 26 is released, the intermediate transfer belt 20 becomes ready to return. At this time, since there is nothing that comes into pressure contact with the intermediate transfer belt 20 from the outside, the intermediate transfer belt 20 can be moved at high speed in both forward and backward movements. Therefore, the belt can be aligned at high speed.

FIG. 22 is a subroutine for driving the intermediate transfer belt 20 in contact with and separated from it. This subroutine is S11 of the print operation subroutine shown in FIG.
It is included in 0, and the intermediary transfer belt 20 is brought into contact with and separated from the intermediate transfer belt 20 and driven.

Next, the belt contact / separation / driving subroutine will be described with reference to FIG. When a belt contact / separation / driving subroutine is entered in S110, the state is determined in S1100. Since the state is 1 in the initial setting state, the process proceeds to S1110.

In S1110, it is determined whether the time t1 for setting the belt drive timing has elapsed. When it is determined in S1110 that the time t1 has been up, the process proceeds to S1120, and when the time t1 is not up, the process returns to the main routine. The timer value t1 starts counting when the start of the transfer operation is set in the main routine.

Next, in S1120, the intermediate transfer belt 20 is driven in the forward direction, and in S1130, the driving roller 21 and the primary transfer roller 28 are moved to move the intermediate transfer belt 20 to the photosensitive member 10. Press against.

At S1140, the intermediate transfer belt 20
When a signal indicating that is pressed against the photoconductor 10 is detected, the process proceeds to S1150. In S1150, the transfer flag is set to 1. This flag indicates that the intermediate transfer belt 20
Indicates that it is in a transferable position.

In S1160, the timer value t1 is reset.

In S1170, the timer value t2 is set and counting is started. The timer value t2 corresponds to the time when the transfer operation is performed.

In S1180, the state flag is set to 2.

In step S1100, the state flag is set to 2
If it is determined to be, the process proceeds to S1190.

In S1190, it is determined whether or not the time t2 corresponding to the time for performing the transfer operation has elapsed. In S1190, if it is determined that the time t2 has timed up, the process proceeds to S1200, and if the time t2 has not timed up, the process returns to the main routine.

Next, in S1140, the drive roller is set.
21 and the primary transfer roller 28 are moved to separate the intermediate transfer belt 20 from the photoconductor 10.

In S1210, the intermediate transfer belt 20
When a signal indicating that is separated from the photoconductor 10 is detected, the process proceeds to S1150. In S1220, the transfer flag is set to 0. This flag indicates that the intermediate transfer belt 2
0 indicates that it is at a position separated from the photoconductor 10.

In S1230, the timer value t2 is reset.

In S1240, the state flag is set to 3.

In step S1100, the state flag is set to 3
If it is determined to be, the process proceeds to S1250.

In S1250, it is determined whether the image formation has been completed up to the fourth color. In S1250, 4
If it is determined that the image formation is completed up to the color, the process proceeds to S1260, the state flag is set to 1, and the process returns to the main routine.

If it is determined in S1250 that the image formation has not been completed up to the fourth color, the flow advances to S1270 to convey the intermediate transfer belt 20 at high speed. Next, when the second position detection sensor 41 detects the timing mark M on the intermediate transfer belt 20 in S1280, the driving of the intermediate transfer belt 20 is stopped in S1290.

Finally, in S1240, the state flag is set to 3, and the process returns to the main routine.

When the transport path of the intermediate transfer belt 20 changes as the intermediate transfer belt 20 comes into contact with and separates from each other, the positional relationship between the rollers that suspend the intermediate transfer belt 20 changes. Therefore, the roller before primary transfer-2 corresponding to the transport path
It is necessary to change the temporary stable position of 7.

FIG. 23 is a flow chart of belt meandering correction operation control when the path of the intermediate transfer belt 20 is changed.

This flowchart is partly different from the meandering correction operation control flowchart shown in FIG. 15 and is used instead. Therefore, here, in FIG.
Only the points different from the meandering correction operation control flowchart will be described.

23 is different from the meandering correction operation control flowchart shown in FIG. 15 only in that a route determination subroutine of S681 is newly added.

In S680, after turning off the output of the light emitting element 40a of the first position detection sensor 40, S681
At, a transport route determination subroutine for determining the transport route of the intermediate transfer belt 20 and correcting the temporary stable position is executed. Next, the stepping motor drive subroutine of S690 is executed.

FIG. 24 shows the contents of the route determination subroutine. In S1400, it is confirmed whether or not the conveyance path of the intermediate transfer belt 20 has been switched, and if it has not been switched, the process directly returns.

When it is confirmed in S1400 that the conveyance path of the intermediate transfer belt 20 has been switched, and when the transfer path has been switched from the first path to the second path, the flow proceeds to S1410.

In S1410, the temporary stable position Ss1 on the first path is subtracted from the variable Sn (current step position of the stepping motor) and the value is substituted for Sft (shift amount). As a result, how much Sn (the current step position of the stepping motor) deviates from Ss1 (the temporary stable position on the first path) is checked. Then, the temporary stable position Ss2 in the second path is substituted into the variable Ss of the temporary stable position to replace the data of the temporary stable position.

In S1420, the first route to the second route
Find the number of steps required to correct the temporary stable position for changes to the route. The value obtained by subtracting Ss1 (temporary stable position on the first route) from Ss2 (temporary stable position on the second route) is input to the variable Sc (stepping motor driving step number), and the process proceeds to S1450.

When it is confirmed in S1400 that the conveyance path of the intermediate transfer belt 20 has been switched, and when the second path has been switched to the first path, the process proceeds to S1430.

In S1430, the temporary stable position Ss2 on the second path is subtracted from the variable Sn (current step position of the stepping motor) and the value is substituted for Sft (shift amount). With this, it is checked how much Sn (the current step position of the stepping motor) deviates from Ss2 (the temporary stable position in the second path). Then, the temporary stable position Ss1 in the first path is substituted into the variable Ss of the temporary stable position to replace the data of the temporary stable position.

In S1440, the first route is switched from the second route.
Find the number of steps required to correct the temporary stable position for changes to the route. The value obtained by subtracting Ss2 (temporary stable position on the second route) from Ss1 (temporary stable position on the first route) is input to the variable Sc (stepping motor driving step number), and the process proceeds to S1450.

Next, in S1450, S1420.
Alternatively, the stepping motor 51 is driven according to the value of Sc (stepping motor driving step number) obtained in S1440.

In S1460, the value obtained by subtracting Sft (shift amount) from Ss (temporary stable position) is Sn.
Substitute in (current stepping motor step position) and return to the main routine.

By performing such correction control, it is possible to perform a stable meandering correction even if the conveyance path changes.

FIG. 25 is a belt contact / separation drive subroutine showing another example of control at the time of contact / separation of the intermediate transfer belt 20 and driving. The belt contact / separation drive subroutine shown in FIG.
Only the part of S1271 is different from the contact / separation drive subroutine shown in FIG. By S1271, the intermediate transfer belt 20 is
When they are separated, the moving direction is reversed and they are conveyed at high speed.

When the intermediate transfer belt 20 is moved back in this way, in order to return the intermediate transfer belt 20 deviated from the target position to the target position, the pre-primary transfer roller 27 is rotated by the angle θ.
When it is moved back in a tilted state, it moves laterally in the direction opposite to the direction of forward movement. Therefore, the intermediate transfer belt 20
It is necessary to perform the correction control different from that in the forward movement at the time of the backward movement. As the correction control when the intermediate transfer belt 20 moves backward,
A method of displacing the inclination of the pre-primary transfer roller 27 opposite to that in the forward movement can be considered.

FIG. 26 is a perspective view of the intermediate transfer member unit. As shown in FIG. 26, if the intermediate transfer belt 20 is tilted at an angle of −θ during the backward movement, the same correction as in the case of tilting the pre-primary transfer roller 27 at the angle of θ at the forward movement can be performed. .

Further, when the intermediate transfer belt 20 is moved back, the deviation direction and the lateral movement direction of the intermediate transfer belt 20 are opposite to those of the forward movement, so it is necessary to change the meandering correction table. Table 4 shows the meandering correction control table 3 used in the backward movement. The positive and negative values of the values of the meandering correction control table 3 are opposite to those of the meandering correction table 1 in forward movement shown in Table 2.

[0188]

[Table 4]

The meandering correction control table 3 has the same number of movement steps as the meandering correction control table 1 described above, but has the opposite phase only in the deviation direction.

FIG. 27 is a belt meandering correction operation control flowchart when the intermediate transfer belt 20 is reciprocated.

This flowchart is partly different from the meandering correction operation control flowchart shown in FIG. 15 and is used instead. Therefore, here, in FIG.
Only the points different from the meandering correction operation control flowchart will be described.

In contrast to the meandering correction operation control flowchart shown in FIG. 15, FIG. 27 shows the pre-primary transfer roll of S682.
La angle setting subroutine is newly added, and S
The content of the stepping motor drive subroutine of 690 is different.

In S680, the output of the light emitting element 40a of the first position detecting sensor 40 is turned off, and then S682.
At, the transfer direction of the intermediate transfer belt 20 is determined,
1 for changing the deviation angle of the roller 27 before the primary transfer
A pre-transfer next roller angle setting subroutine is executed. Next, the stepping motor drive subroutine of S690 is executed.

FIG. 28 shows the contents of the pre-primary transfer roller angle setting subroutine.

In S1500, it is confirmed whether or not the rotation direction of the intermediate transfer belt 20 has been switched, and if it has not been switched, the process directly returns.

At S1500, the intermediate transfer belt 20
If it is confirmed that the rotation direction of has been switched, S
Proceed to 1510.

In S1510, Ss (temporary stable position) is subtracted from the variable Sn (current stepping motor step position) and the value is substituted for Sft (shift amount). Thus, it is checked how much Sn (the current step position of the stepping motor) deviates from Ss (temporary stable position).

In S1520, the value of Sft is -2.
The value multiplied by is input to the variable Sc (stepping motor driving step number). By this step, the number of steps required to deviate the pre-primary transfer roller 27 from Ss (temporary stable position) to a target angle is obtained.

In S1530, the stepping motor 51 is driven according to the value of Sc (stepping motor driving step number) obtained in S1520.

At S1540, the value obtained by subtracting Sft (shift amount) from Ss (temporary stable position) is Sn.
Substitute in (current stepping motor step position) and return to the main routine.

FIG. 29 is a stepping motor drive subroutine of S690 of the belt meandering correction operation control flowchart shown in FIG.

This flowchart is partly different from the stepping motor drive subroutine shown in FIG. Therefore, here, only the difference from the meandering correction operation control flowchart of FIG. 12 will be described, and the same step numbers will be used for common parts.

When the stepping motor drive subroutine of S690 is called in the belt meandering correction operation control flowchart of FIG. 27, it is determined in S335 that the moving direction of the intermediate transfer belt 20 is forward or backward.

In the case of forward movement, the process proceeds to S337, selects the meandering correction control table 1 shown in Table 2 and proceeds to S350.
Since the steps after S350 are the same as those shown in FIG. 12, the description thereof is omitted here.

[0205] If it is determined in S330 that it is a return movement, S3
36, the meandering correction control table 3 shown in Table 4 is selected, and the process proceeds to S350.

Further, as in the meandering correction control table 3, when control is performed such that the number of movement steps is the same as in the forward movement at the time of the backward movement but only the deviation direction is in the opposite phase, the stepping as shown in FIG. It is possible to use one meandering correction control table by using a motor driving subroutine.

This flowchart is also used in the same way as the flowchart of FIG. 29, with some differences from the stepping motor drive subroutine shown in FIG. Therefore, here, only the difference from the meandering correction operation control flowchart of FIG. 12 will be described, and the same step numbers will be used for common parts.

When the stepping motor drive subroutine of S690 is called in the correction operation control flowchart of FIG. 27, the set value of the meandering correction control table 1 is read into St (read value of the meandering correction table) in S340.

Next, in S341, it is determined that the moving direction of the intermediate transfer belt 20 is forward or backward.

In the case of forward movement, the process proceeds to S360. S360
Subsequent steps are the same as those shown in FIG. 12, so description thereof will be omitted here.

If it is determined in S341 that the movement is returning, the process proceeds to S342, where the sign of the value of St is inverted to S36.
Go to 0. By performing such control, it is possible to cope with both reciprocating motion with only one meandering correction control table.

A method of performing meandering correction corresponding to the reciprocal movement of the intermediate transfer belt 20 other than the method of changing the control method between the forward movement and the backward movement as described above will be described.

FIG. 31 is a perspective view showing a modification of the intermediate transfer body unit shown in FIG. Therefore, the description will be focused on the parts different from those in FIG. 26, and the description of the common parts will be omitted.

In the intermediate transfer body unit shown in FIG. 31, the first position detection sensor 40 is provided with respect to the center of the intermediate transfer belt 20.
A third position detection sensor 75 is provided at a position symmetrical with respect to. Then, when the intermediate transfer belt 20 moves forward, the first position detection sensor 40 is used to
The third position detection sensor 75 is used when is moved back. When the intermediate transfer belt 20 moves back, the belt detection value of the third position detection sensor 75 outputs a value that is the reverse of the value detected by the first position detection sensor 40 used during the forward movement. When the meandering correction is performed on the detected value according to the flowcharts shown in FIGS. 11 to 13 and FIGS. 15 to 18, the angle of the pre-primary transfer roller 27 is set in the direction opposite to the forward movement. Therefore,
Even when the intermediate transfer belt 20 moves backward, the same meandering correction as when moving forward is performed.

Further, the control method is the same as that of the forward movement, and only the circuit configuration is changed to cope with the belt meandering correction at the backward movement.

FIG. 32 is a modification of the control circuit block diagram shown in FIG. Therefore, the description will be focused on the parts different from those in FIG. 7, and the description of the common parts will be omitted.

The control circuit block diagram of FIG. 32 is obtained by adding an inverter unit 80 to the circuit block diagram shown in FIG. The signal output from the first position detection sensor 40 via the amplifier unit 47 is input to the digital panel meter as it is during the forward movement, but is input to the digital panel meter via the inverter unit 80 during the backward movement. The inverter unit 80 reverses and outputs the detection value of the first position detection sensor 40. Therefore, when the intermediate transfer belt 20 moves back, the belt detection value becomes a value that is the reverse of the value when moving forward. This detected value is shown in FIG.
When the meandering correction is performed according to the flowcharts shown in FIGS. 13 and 15 to 18, the angle of the pre-primary transfer roller 27 is set in the direction opposite to the forward movement. Therefore, when the intermediate transfer belt 20 is moved backward, the same meandering correction as that in the forward movement is performed.

In this manner, by making the deviation angle of the meandering correction roller different during forward and backward movements of the belt, the meandering correction can be performed regardless of the forward and backward movements of the belt.

In this embodiment, the meandering correction device of the present invention is used for the intermediate transfer belt, but the present invention is not limited to this and may be applied to a belt photosensitive member or a fixing belt.

[0220]

According to the meandering correction device of the present invention, in addition to the position in the direction perpendicular to the belt conveying direction, the belt moving speed detected by the belt moving speed detecting device allows the belt to move in the direction perpendicular to the belt conveying direction. The moving speed can be set to a predetermined speed. For this reason, more accurate belt meandering correction is possible, and the movement of the belt during image formation is kept within a predetermined range to minimize color misregistration and image misregistration, and correction at the start of belt conveyance. Finer meandering correction control can be performed by increasing the speed and making corrections quickly.

Further, by suppressing the moving speed in the direction perpendicular to the belt conveying direction to be equal to or lower than the resolution of the human eye, it becomes possible to prevent color misregistration and image misregistration from being recognized.

Further, when the belt is started to be conveyed, the axial tilt angle correction device is controlled so that a predetermined position in the direction perpendicular to the belt conveying direction approaches a preset target position, whereby image formation is started. The position correction can be completed before it is done. As a result, more stable belt conveyance can be realized, and color misregistration and image misregistration can be suppressed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electrophotographic image forming apparatus according to the present invention.

FIG. 2 is a sectional view showing a configuration of an intermediate transfer member unit.

FIG. 3 is a cross-sectional view showing a main part of a roller displacement mechanism according to the present invention.

FIG. 4 is an enlarged perspective view showing a main part of a roller displacement mechanism according to the present invention.

FIG. 5 is an explanatory view showing a direction of deviation of a roller according to the present invention.

FIG. 6 is a perspective view of an intermediate transfer member unit according to the present invention.

FIG. 7 is a block diagram of a control circuit of the image forming apparatus according to the present invention.

FIG. 8 is a graph showing the relationship between the belt position and the voltage signal from the sensor.

FIG. 9 is an operation control flowchart of the electrophotographic image forming apparatus according to the present invention.

FIG. 10 is a print operation subroutine of an operation control flowchart according to the present invention.

FIG. 11 is a belt meandering correction operation control flowchart according to the present invention.

FIG. 12 is a stepping motor drive subroutine of belt meandering correction operation control.

FIG. 13 is a temporary stable position correction subroutine of belt meandering correction operation control.

FIG. 14 is a graph showing a result of performing belt meandering positive control according to the present invention.

FIG. 15 is a flowchart showing another example of belt meandering correction operation control.

FIG. 16 is an operation mode determination subroutine of another example of belt meandering correction operation control.

FIG. 17 is another example of a temporary stable position correction subroutine of belt meandering correction operation control.

FIG. 18 is a rough adjustment end determination subroutine of another example of belt meandering correction operation control.

FIG. 19 is a graph showing a lateral movement amount per one rotation of the belt when the tilt amount of the steering roller is changed.

FIG. 20 is a stepping motor drive subroutine of belt meandering correction operation control.

FIG. 21 is a cross-sectional view showing a configuration of an intermediate transfer body unit when the intermediate transfer belt is separated.

FIG. 22 is a print operation subroutine of an operation control flowchart according to the present invention.

FIG. 23 is a flowchart of belt meandering correction operation control when the path of the intermediate transfer belt is changed.

FIG. 24 is a flowchart showing the contents of a route determination subroutine.

FIG. 25 is a belt contact / separation drive subroutine showing another example of control at the time of contact / separation of the intermediate transfer belt and driving.

FIG. 26 is a perspective view of an intermediate transfer member unit according to the present invention.

FIG. 27 is a flowchart of belt meandering correction operation control when the intermediate transfer belt 20 is reciprocated.

FIG. 28 is a flow chart showing the contents of a pre-primary transfer roller angle setting subroutine.

FIG. 29 is a flowchart showing the contents of a stepping motor drive subroutine.

FIG. 30 is a flowchart showing the contents of a stepping motor drive subroutine.

FIG. 31 is a perspective view showing a modified example of the intermediate transfer member unit.

FIG. 32 is a modification of the control circuit block diagram of the image forming apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor unit 2 Intermediate transfer body unit 3 Printhead 4 Developing unit 5 Paper feed cassette 6 Copy paper transport unit 7 Fixing device 10 Photoconductor 11 Developing unit shaft 15 Main motor 16 Drive motor 20 Intermediate transfer belt 21 Drive roll -Raler 22 Energizing Roller 23 Secondary Transfer Opposing Roller 24 Secondary Transfer Roller 25 Intermediate Transfer Belt Cleaner 26 Cleaning Blade 27 Primary Pre-Transfer Roller 28 Primary Transfer Roll Lar 30 Timing Roller 31 Timing Roller 40 First Position Detection Sensor 41 Second Position Detection Sensor 45 First CPU 46 Second CPU 47 Amplifier Unit 48 Digital Panel Meter 49 Motor Driver 51 Stepping Motor 52 Motor Gear 53 Drive Gear 54 Drive pulley 55 Drive Wire 56 Idle pulley 57 Idle pulley 58 Bearing holder 59 Bearing 60 Fixed bearing 61 Deflection direction regulation plate 63 Slide bearing 64 Regulation hole 65 Bearing holding plate 70 Side plate 71 Side plate 75 Third position detection sensor 80 Inverter unit 100 Electrophotographic imaging Equipment P Print paper

Claims (19)

[Claims] 1. A belt moving device for moving a belt in a direction perpendicular to a belt conveying direction, a belt meandering detecting device for detecting meandering in a direction perpendicular to the belt conveying direction, and a belt meandering detecting device. A belt meandering correction device having a controller that controls a belt moving device so as to correct the belt meandering at a speed within a predetermined range based on the belt meandering. 2. The belt meandering correction device according to claim 1, wherein the belt is suspended by a suspension member having at least one shaft. 3. The belt meandering device according to claim 2, wherein the belt moving device has an axial tilt angle correcting device for moving the belt in a direction perpendicular to the conveying direction by changing the tilt of the shaft of the suspension member. Correction device. 4. The belt meandering detection device detects the meandering of the belt based on a detection value of a belt position detection device that detects a predetermined position in a direction perpendicular to the belt conveying direction. The belt meandering correction device described. 5. The belt meandering device according to claim 4, wherein the control device controls the belt moving device so that a predetermined position in a direction perpendicular to the belt conveying direction approaches a preset target position. Correction device. 6. The belt meandering correction device according to claim 4, wherein the moving speed of the belt in the direction perpendicular to the conveying direction is detected based on the position detected by the belt position detection device. 7. The belt meandering correction device according to claim 1, wherein the control device controls the belt moving device by a preset meandering correction table. 8. The belt meandering correction device according to claim 7, wherein the belt meandering correction device has a plurality of preset meandering correction tables and can be switched according to an operating condition of the belt meandering correction device. 9. A meandering correction table having a larger amount of belt movement than a meandering correction table used during normal image formation is selected from among a plurality of meandering correction tables at the start of operation of the belt meandering correction device. The belt meandering correction device according to claim 8. 10. The belt meandering correction device according to claim 1, wherein the range of the moving speed of the belt in the direction perpendicular to the conveying direction is a speed of moving by 60 μm per one rotation of the image carrier belt. 11. A belt moving device for moving a belt in a direction perpendicular to a belt conveying direction, a belt meandering detection device for detecting meandering in a direction perpendicular to the belt conveying direction, and a route for changing a belt conveying route. The belt moving device is controlled to correct the belt meandering by different control based on the belt meandering detected by the changing device and the belt meandering detecting device according to the belt conveyance route changed by the route changing device. A belt meandering correction device having a control device. 12. A conveyor device for conveying the belt in a forward direction and a backward direction opposite to the forward direction, a belt moving device for moving the belt in a direction perpendicular to the belt conveying direction, and a belt conveyer. The belt meandering detection device that detects the meandering in the direction perpendicular to the direction and the belt meandering detection device that corrects the belt meandering with different control depending on the belt conveyance direction based on the belt meandering detected by the belt meandering detection device. A belt meandering correction device having a control device for controlling a moving device. 13. A belt meandering detection device for detecting meandering of a belt in a direction perpendicular to a conveying direction, a suspension member having at least one shaft and suspending the belt around the shaft, and an inclination of a shaft of the suspension member. By changing the angle, the shaft tilt angle correction device that moves the belt in the direction perpendicular to the transport direction, the tilt detection means that detects the tilt of the suspension member shaft, and the belt meandering and tilt detected by the belt meandering detection device. A belt meandering correction device having a controller for controlling the belt moving device so as to correct the belt meandering based on the inclination of the axis of the suspension member detected by the detecting means. 14. An image carrying belt which carries an image on its surface and is carried in a predetermined carrying direction, a suspension member which suspends the belt around it, and a belt which moves in a direction perpendicular to the carrying direction of the belt. A belt moving device, a belt meandering detection device that detects the meandering of the belt in a direction perpendicular to the conveying direction, and a belt meandering device that detects the meandering of the belt at a speed within a predetermined range based on the belt meandering detected by the belt meandering detection device. An image forming apparatus having a control device that controls a belt moving device so as to perform correction. 15. A belt meandering detection device detects belt meandering based on a detection value of a belt position detection device that detects a predetermined position in a direction perpendicular to the belt conveyance direction, and a control device detects the belt conveyance direction. The predetermined position in the direction perpendicular to
The belt meandering correction device according to claim 14, wherein the belt movement device is controlled so as to approach a preset target position. 16. The belt meandering correction device according to claim 15, wherein the belt meandering detection device detects a predetermined position in a direction perpendicular to the belt carrying direction at the time of starting the belt carrying. 17. The belt meandering correction device according to claim 16, wherein the belt is started to be conveyed when the belt meandering correction device is turned on or when the trouble is recovered. 18. The belt meandering correction apparatus according to claim 14, wherein the image forming apparatus is an electrophotographic image forming apparatus that forms an image on a photoconductor. 19. The belt meandering correction device according to claim 18, wherein the image carrying belt is an intermediate transfer belt on which an image formed on the photoconductor is transferred.