JPH11295948A - Belt driving device and image forming device provided with same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt driving device capable of precisely and appropriately correcting the positional fluctuation in the width direction (meandering) of an endless belt. SOLUTION: This driving device is provided with a steering module 29 driving a steering motor 20 as a drive source, for correcting the positional fluctuation in the sideways of the endless belt, an edge sensor 13 for detecting the edge position in the sideways of the endless belt, a storing part 28 for storing edge shape data of the endless belt, and a controller 19a for controlling the operation of the steering module 29 by comparing the detection data of an edge position by the edge sensor 13 and the edge shape data stored in the storing part 28, and driving the steering motor 20 based on the comparison result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt driving device having a function of correcting a positional change of an endless belt in a width direction and an image forming apparatus having the same.

[0002]

2. Description of the Related Art Conventionally, among image forming apparatuses such as copying machines and printers, there is a color image forming apparatus that forms a multi-color (color) image using an endless intermediate transfer belt, a photoreceptor belt, or a paper transport belt. is there. In addition, this type of color image forming apparatus includes a tandem type color image forming apparatus that individually includes image forming units corresponding to, for example, yellow, magenta, cyan, and black on an endless belt such as an intermediate transfer belt. There is a device.

In general, in a belt driving device in which an endless belt is supported by a predetermined number of rolls and one of the rolls is used as a driving roll to run the endless belt, the running endless belt is moved in a width direction (a direction orthogonal to the belt running direction). ), So-called belt meandering (belt walk) occurs. In the tandem type color image forming apparatus, for example, when the images of the respective colors are superimposed and transferred on the endless intermediate transfer belt in the tandem-type color image forming apparatus, the relative positional shift of the images of the respective colors, and thus the color shift and the like, may occur. It causes color unevenness and the like. Therefore, in order to obtain a high-quality output image (color image), it is necessary to appropriately correct the meandering of the belt.

Therefore, as a meandering correction method of the belt,
Several techniques have been proposed so far. One of the typical techniques is a method of controlling the meandering of a belt by tilting a roll supporting an endless belt (hereinafter, referred to as a "steering method"). It has been known. In this steering system, the force applied to the belt is smaller than in the system in which the meandering of the belt is forcibly suppressed by ribs, guides, etc.
There is an advantage that high reliability can be obtained.

As a prior art employing the above-mentioned steering method, for example, Japanese Patent Laid-Open Publication No. Hei 3-288167 discloses a mark provided on an endless belt detected by a CCD sensor to detect the meandering of the belt. A technique for controlling the inclination of a roll (hereinafter, referred to as “first related art”) is disclosed. In addition, Japanese Patent Publication No. 63-64792
Japanese Patent Application Laid-Open No. 9-12173 and Japanese Patent Application Laid-Open No. 9-12173 disclose a technique (hereinafter, referred to as a "second conventional technique") in which a sensor detects the direction of deviation of an endless belt and controls the roll inclination based on the detection result. Each is disclosed. further,
Japanese Patent Application Laid-Open No. H8-106237 discloses a technique in which the edge position of an endless belt is detected in an analog manner by a displacement sensor, and the roll inclination is controlled based on the detection result (hereinafter, referred to as "third conventional technique"). Is disclosed.

[0006]

However, the first problem is to be solved.
The third prior art has the following problems. First, in the first prior art, one mark is provided on an endless belt, and the mark is read by a CCD sensor for each rotation of the belt to perform steering control. Position fluctuation cannot be detected and controlled finely, and there is a problem that control response is poor with respect to meandering of the belt. It is also conceivable to provide a plurality of marks on the endless belt in order to increase control responsiveness. However, it is generally very difficult to provide a plurality of marks with high accuracy on an endless belt, and in such a case, the position accuracy of the marks themselves greatly affects the quality of steering control.

On the other hand, in the second prior art, a pair of sensors are arranged in the width direction of the endless belt at a predetermined distance (gap) from the belt edge, respectively. When steering control is performed by detecting the direction in which the endless belt is shifted, the endless belt repeats reciprocating motion between a pair of sensors. Therefore, the meandering of the endless belt could not be finely controlled. Further, in principle, it is also possible to increase the accuracy of steering control by setting the distance from the belt edge to the sensor short. However, in consideration of dimensional tolerances in processing and assembling parts, there is a limit in shortening the distance from the belt edge to the sensor, so that the meandering of the endless belt cannot be accurately corrected.

Further, in the third prior art, when the edge position of the endless belt is detected in an analog manner by a displacement sensor, the detection result includes an error component due to the edge shape of the endless belt. Even with the steering control, there is a problem that the meandering of the endless belt is not properly corrected due to the influence of the error component.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has an endless belt and a predetermined number of rolls for supporting the endless belt. In a belt driving device in which any one of them is used as a driving roll and the endless belt runs by rotating the driving roll, a driving means for driving the endless belt in order to correct a position variation in a width direction, and an edge in a width direction of the endless belt. Detecting means for detecting the position, storing means for storing edge shape data of the endless belt, and comparing the detected data of the edge position by the detecting means with the edge shape data stored in the storing means, and based on the comparison result, And a control means for controlling the driving of the driving means.

In the belt driving device having the above-described configuration, when the position fluctuation in the width direction of the endless belt is corrected by driving the driving unit, the data of the edge position detected by the detecting unit and the edge shape data stored in the storing unit are used. Are compared by the control means. At this time, for example, by taking the difference between the edge position detection data and the edge shape data, the position fluctuation component due to the edge shape of the endless belt can be removed from the edge position detection data by the detection means. As a result, the drive control by the control unit is performed in a form in which an error component due to the edge shape of the endless belt is eliminated, so that the position fluctuation (meandering) of the endless belt can be more appropriately corrected.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating a configuration example of an image forming apparatus to which the present invention is applied. In FIG. 1, an intermediate transfer belt 1 comprising an endless belt
Are supported with a predetermined tension by a driving roll 2, a steering roll 3, a secondary transfer roll 4, and driven rolls 5, 6, and 7. Further, on the intermediate transfer belt 1, yellow (Y),
Image forming units 8, 9, 10, and 11 corresponding to each color of magenta (M), cyan (C), and black (K) are sequentially arranged.

Each of the image forming units 8, 9, 10, 1
Reference numerals 1 denote photosensitive drums 8a, 9a, 10a, and 11a rotatably supported by an apparatus body frame (not shown).
And an image writing section 8 for exposing and scanning the surface of each of the photosensitive drums 8a, 9a, 10a, 11a with a laser beam or the like.
b, 9b, 10b, and 11b. Further, around each of the photosensitive drums 8a, 9a, 10a, 11a,
According to the drum rotation direction (clockwise direction in the figure), the chargers 8c, 9c, 10c, 11c, the developing devices 8d, 9d,
10d, 11d, primary transfer rolls 8e, 9e, 10e,
11e and cleaners 8f, 9f, 10f, 11f are arranged in order.

Further, a belt home sensor 12 and an edge sensor 13 are arranged on the traveling path of the intermediate transfer belt 1. Of these, the belt home sensor 12 is
It detects a mark or the like provided at one location in the circumferential direction of the intermediate transfer belt 1 and is arranged upstream of the yellow (Y) image forming unit 8 in the belt traveling direction x. The edge sensor 13 detects the edge position of the intermediate transfer belt 1 and is arranged downstream of the black (K) image forming unit 11 (in front of the steering roll 3) in the belt traveling direction x.

The paper 14 to be image-formed is accommodated in a paper feed cassette (not shown), and is fed one by one by a pickup roll 15 provided on the paper feed side of the paper feed cassette. The fed sheet 14 is conveyed by a predetermined number of roll pairs 16 along a path shown by a broken line in the figure, and is sent to a press-contact position of the secondary transfer roll 4.

FIG. 2 is a schematic diagram showing a specific configuration of the edge sensor 13. 2, at one end of the intermediate transfer belt 1, the one end of a contact 13b is held in a pressed state by the pulling force of a spring 13a.
In this case, the pressing force of the contact 13b by the spring 13a is set to an appropriate magnitude that does not deform the intermediate transfer belt 1. The contact 13b is rotatably supported at an intermediate portion thereof by a support shaft 13c, and a displacement sensor 1 is provided at the other end of the contact 13b at the support shaft 13c.
3d is disposed in a facing state.

In the edge sensor 13, the movement of the intermediate transfer belt 1 in the width direction y at the time of meandering of the belt is replaced by the movement (oscillating operation) of the contact 13b which presses against the belt edge. At this time, the contact 13
Since the output level of the displacement sensor 13d fluctuates in accordance with the movement (displacement) of b, the position fluctuation of the belt edge can be detected based on the sensor output.

Next, an operation procedure when a color image is formed by using the image forming apparatus having the above configuration will be schematically described. First, when the intermediate transfer belt 1 is caused to travel in the x direction by the rotation of the drive roll 2, each image forming unit is driven based on a mark detection signal (belt home signal) output from the belt home sensor 12 during the running of the belt. At 8, 9, 10, and 11, image writing is started in order. Next, on the intermediate transfer belt 1, the respective color images of yellow, magenta, cyan, and black are sequentially superimposed and transferred (primary transfer), thereby forming one color image. Thereafter, the color image is transferred to the intermediate transfer belt 1.
Is transported to the secondary transfer roll 4 along with the travel of the printer, where the color image on the intermediate transfer belt 1 is collectively transferred (secondarily transferred) to the paper 14. Paper 1 with color image transferred
4 is sent to a fixing device 18 by a paper transport system 17, where an image fixing process (heating, pressurizing, etc.) is performed, and
It is discharged to a tray (not shown).

In such a series of image forming operations, if the position of the intermediate transfer belt 1 is meanderingly shifted in the width direction (lateral direction), each of the image forming units 8, 9, 1 is shifted.
Due to 0 and 11, a relative shift occurs in the position of the image transferred on the intermediate transfer belt 1, and this appears as color shift or color unevenness of the output image (color image). Therefore, in order to correct the meandering of the intermediate transfer belt 1, a structure for tilting the steering roll 3 is incorporated.

FIG. 3 is a schematic diagram showing a basic configuration for correcting meandering. In FIG. 3, a steering control device 19 controls a driving state of a steering motor 20 serving as a driving source for meandering correction, and outputs a motor control signal (motor drive signal) to the steering motor 20. As the steering motor 20,
A stepping motor or the like capable of controlling the rotation angle and the rotation speed with high accuracy is used. Further, the belt home sensor 12 and the edge sensor 13 described above are connected to the steering control device 19.
2 and a belt edge signal from the edge sensor 13, respectively.

On the other hand, as a mechanical structure for tilting the steering roll 3, a swing arm 21 and an eccentric cam 22 are provided. The swing arm 21 is rotatably supported at its intermediate portion by a support shaft 23. Further, one end of the steering roll 3 is rotatably connected to one end of the swing arm 21, and the eccentric cam 22 is held in pressure contact with the other end of the opposite arm. This eccentric cam 22
Rotates by driving the steering motor 20.

The edge sensor 13 may employ any configuration as long as the edge sensor 13 generates an output corresponding to a change in the position (meandering) of the intermediate transfer belt 1. For example, as shown in FIG. 4, an LED (Light Emitting Diode) 13 passes through an edge portion of the intermediate transfer belt 1.
e and the light amount sensor 13f are arranged in a facing state, and the LED 13
The sensor output level may be changed in accordance with the amount of light emitted from e and incident on the light amount sensor 13f.

Next, the principle of the meandering correction of the intermediate transfer belt 1 by the tilting operation of the steering roll 3 will be described with reference to FIG.
This will be briefly described with reference to FIG. First, as shown in FIG. 5A, in a state where the eccentric cam 22 stops at a predetermined angle and the steering roll 3 is held substantially horizontal (the inclination is almost zero) corresponding to the stop angle, the vehicle travels. It is assumed that the intermediate transfer belt 1 does not move (meander) in the width direction y.

From this state, as shown in FIG.
When the eccentric cam 22 is rotated counterclockwise in the figure by driving the steering motor 20, the swing arm 21 swings in the θ1 direction according to the amount of eccentricity of the eccentric cam 22. As a result, one end of the steering roll 3 is lifted by the swing arm 21, so that the steering roll 3 is inclined according to the amount of lifting. At this time, the intermediate transfer belt 1 wound around the steering roll 3 moves to the roll end lifted by the swing arm 21.

On the other hand, as shown in FIG.
When the eccentric cam 22 is rotated clockwise by driving the steering motor 20, the swing arm 21 swings in the θ2 direction according to the amount of eccentricity of the eccentric cam 22. As a result, one end of the steering roll 3 is pushed down by the swing arm 21, so that the steering roll 3 is inclined according to the amount of pushing down. At this time, the intermediate transfer belt 1 wound around the steering roll 3 moves to a side opposite to the roll end pushed down by the swing arm 21.

Accordingly, the position change of the intermediate transfer belt 1 in the width direction y is detected by the above-described edge sensor 13, and based on the detection result, the steering motor 20 is driven to appropriately control the inclination of the steering roll 3. By doing
The meandering of the intermediate transfer belt 1 can be corrected.
However, in order to properly correct the meandering of the intermediate transfer belt 1, the belt position fluctuation (meandering) is accurately detected, and based on the detection result, the inclination of the steering roll 3 is finely set under optimum conditions (control). There is a need to.

Therefore, in the present embodiment, a configuration as shown in FIG. 6 is employed as a steering control system for controlling the inclination of the steering roll 3. In the figure, a controller 19a constitutes one functional unit in the steering control device 19 described above.
It controls the inclination of the steering roll 3 in an actual image forming operation (image forming mode). The controller 19a mainly includes the compensator 24 and the motor driver 2
5, an A / D (analog / digital) converter 26, an operation unit 27, and a storage unit 28. The steering module 29 is a mechanical mechanism including the steering roll 3, the swing arm 21, and the eccentric cam 22 described above.
The belt module 30 is a mechanical mechanism including the above-described intermediate transfer belt 1 and rolls (2, 5, 6, 7) for running the intermediate transfer belt 1.

The compensator 24 determines a gain and a frequency characteristic based on the information of the belt position fluctuation amount w (r, n) as the input information, and converts the gain and the frequency characteristic into the information of the position fluctuation amount w (r, n). The control information of the corresponding steering amount s (r, n) is output to the motor driver 25. here,
“R” is the number of turns of the belt, and “n” is an address corresponding to the running direction of the belt. In contrast, motor driver 2
Numeral 5 is for driving the steering motor 20 according to the control information sent from the compensator 24, and the roll inclination angle θ (t) in the steering module 29 is controlled by this motor drive. In the present embodiment, since the stepping motor is employed as the steering motor 20, the control information s (r, n) sent from the compensator 24 corresponds to the number of motor steps.

On the other hand, the A / D converter 26 converts the analog detection signal E (r, n) output from the edge sensor 13 into a digital signal, and supplies the digitized detection signal to the arithmetic unit 27. It is. On the other hand, the arithmetic unit 27 generates edge data e (rn) by averaging the digital signal supplied from the A / D converter 26, that is, belt edge detection data.

The storage unit 28 stores edge shape data p (n) of the intermediate transfer belt 1 in a table format (hereinafter, referred to as an “edge shape table”). The edge shape table is created in advance in a mode different from a normal image forming mode, such as when manufacturing an image forming apparatus, when replacing the intermediate transfer belt 1, or when performing regular maintenance of the image forming apparatus. The table creation procedure at that time will be described later in detail.

Subsequently, in a normal image forming mode,
The processing procedure of the steering control executed by the controller 19a will be described. First, the intermediate transfer belt 1
During the traveling of the vehicle, the belt edge position is continuously detected by the edge sensor 13, whereby continuous information corresponding to the change in the position of the belt edge is output from the edge sensor 13. However, the belt edge position information E (t) output from the edge sensor 13 includes both the position fluctuation W (t) due to the meandering of the belt and the position fluctuation P (t) due to the belt edge shape (unevenness). Becomes

On the other hand, the controller 19a takes in the detection data of the edge sensor 13 at a predetermined sample timing based on the belt home signal from the belt home sensor 12 described above, and converts the data into an A / D converter 26. Convert to digital signal.

At this time, the sample timing based on the belt home signal is set so that N pieces of detection data can be obtained while the intermediate transfer belt 1 makes one rotation. Further, the number of the detection data; N is set so as to satisfy a one-to-one relationship with the number of addresses corresponding to the running direction of the belt; n. By the way, the number of belt revolutions described above; r
Is incremented by one each time a belt home signal is output from the belt home sensor 12, whereas the address in the belt running direction; n is reset each time a belt home signal is output.

At this time, one detection data may be fetched at each sample timing. In such a case, however, there is a concern that noise components included in the individual detection data may appear as detection errors. You. Therefore, in the present embodiment, at each sample timing, a plurality of (m) data is fetched at a minute pitch of, for example, several tens of msec for one detection data. Then, the m pieces of detection data taken in at each sample timing are sequentially provided to the arithmetic unit 27, where the averaging process is performed.

Specifically, when, for example, five data (m = 5) are captured as detection data at the first (first) sample timing, the sum of these five data is divided by the number of data (5). And average this and the address; n
= 1. Then, by repeating the same processing for the detection data captured at the second and subsequent sample timings, N pieces of detection data e (r, n) corresponding to the address; n are obtained.

By averaging a plurality of data taken in at each sample timing in this way, noise components included in individual data are deleted (canceled).
, Accurate detection data e with few detection errors
(R, n) can be obtained.

Subsequently, in the controller 19a,
Edge position detection data e generated from the arithmetic unit 27
(R, n) is compared with the edge shape data p (n) stored in the storage unit 28. At this time, since the detection data e (r, n) is generated from the calculation unit 27 in a time series corresponding to the above-described sample timing, for example, the first generation of the detection data e (r, 1) ), The edge shape data p (1) stored in the storage unit 28 corresponding to the address information “1” is to be compared.

Although the value of r included in the detection data r (r, n) changes according to the number of rotations of the intermediate transfer belt 1, the edge shape data P (n) to be compared is r Selected regardless of value. That is, the same edge shape data is selected as a comparison target even if the values of n are the same even if the detection data has different values of r.

Here, in the comparison between the detected data e (r, n) and the edge shape data p (n) in the controller 19a, their difference is obtained by calculation. The difference data in this case is obtained from the position information E (t) of the belt edge detected by the edge sensor 13 as described above, from the position fluctuation component P due to the belt edge shape (unevenness).
Since the value is obtained by subtracting (t), the data corresponds to the position fluctuation component W (t) due to the meandering of the belt.

Therefore, in the controller 19a,
The position data based on the difference is compared with preset reference position data (REF) to calculate a belt position fluctuation amount w (r, n) with respect to the reference position. The position fluctuation amount w (r, n) is obtained by reversing positive (+) / negative (-) according to the direction of deviation of the belt from the reference position. Therefore, the steering amount s (r, n) is set based on the position fluctuation amount w (r, n), and the driving of the steering motor 20 is controlled based on the steering amount s (r, n). With the components removed
The meandering of the belt can be appropriately corrected.

In this way, when forming an image, the position fluctuation in the width direction of the intermediate transfer belt 1 can be minimized by the tilting operation of the steering roll 3, so that when forming a color image, color misregistration is required. It is possible to obtain a high-quality output image without color or color unevenness.

Further, the position fluctuation (meandering) during one rotation of the intermediate transfer belt 1 can be finely controlled with high responsiveness.
It is possible to shorten the time until the first sheet of image is output (for example, FCOT (Fast Copy Output time) in a copying machine), and it is possible to stably perform meandering control against disturbances such as during sheet conveyance.

Next, a procedure for creating an edge shape table in the present embodiment will be described in detail. FIG. 7 is a flowchart showing the procedure for creating the edge shape table, and FIG. 8 is a diagram showing the state of the intermediate transfer belt 1 when the edge shape table is created. Note that a series of processes related to the creation of the edge shape table is executed by the steering control device 19, and the execution timing is the same as during normal image formation, such as when manufacturing an image forming apparatus or replacing a belt, as described above. Is set separately.

First, at the time of manufacturing an image forming apparatus or the like,
When the intermediate transfer belt 1 is stretched around a predetermined number of rolls, the edge position of the belt is slightly (for example, in units of several mm) from a preset reference position due to an error in the mounting position or the like.
It is shifted. Therefore, in step S1,
By driving the steering motor 20 based on the detection data from the edge sensor 13, the tilting operation of the steering roll 3 is controlled (steering control 1). However,
At this point, since the belt edge shape is unknown information, the steering control is performed using only the detection data of the edge sensor 13.

As a result, the edge position of the intermediate transfer belt 1 gradually approaches the reference position (REF) from the position when the belt is mounted as shown in FIG. 8 by the steering control 1 in step S1. In FIG. 8, the movement of the belt edge position including the fluctuation component due to the belt edge shape is indicated by a broken line, and the original movement of the belt not including the fluctuation component due to the belt edge shape is indicated by a solid line.

Subsequently, based on the detection data from the edge sensor 13, the moving amount (meandering amount) W of the intermediate transfer belt 1 is determined.
It is repeatedly determined whether or not (n) is within a preset allowable range Wa (step S2). When the moving amount W (n) of the intermediate transfer belt 1 falls within the allowable range Wa, the steering roll in that state is determined. The average value of the tilt angles of the steering roll 3 is calculated, and the tilt angle of the steering roll 3 is fixed using the calculated value (step S3). The tilt angle of the steering roll 3 fixed at this time is an angle in a state where the intermediate transfer belt 1 is running stably near the reference position.

Here, the reason why the inclination angle of the steering roll 3 is fixed while the intermediate transfer belt 1 is running stably near the reference position as described above will be described. First, when the inclination angle of the steering roll 3 is generally fixed, the intermediate transfer belt 1 moves in one direction at a constant rate (hereinafter, referred to as a walk rate) in the width direction as shown in FIG. However, the edge shape of the intermediate transfer belt 1 is
Since the straight line does not accurately become a straight line due to its assembly, the detection data of the belt edge position by the edge sensor 13 is measured in a form in which the edge shape (concavo-convex shape) of the belt itself is added. At this time, the inclination (walk rate) of the position change of the intermediate transfer belt 1 with respect to the time axis is a straight line (broken line in the figure).
This slope component (walk rate component)
Is subtracted from the detection data, the edge shape data of the intermediate transfer belt 1 can be calculated. However, when calculating the edge shape data, if the walk rate (belt movement rate) of the detection data of the original edge position is large, the distortion in calculating the edge shape data becomes large and the accuracy deteriorates.

FIG. 10 shows the result of measuring the error of the edge shape data with respect to the walk rate. From this figure, it can be easily understood that the smaller the walk rate (μm / cycle), the smaller the error in the edge shape data. For this reason, in the present embodiment, in calculating the edge shape data of the intermediate transfer belt 1, the walk rate is set to a predetermined level (0.5 m).
(m / cycle or less), steering control is performed to minimize errors due to the distortion.

However, even when the intermediate transfer belt 1 is running stably near the reference position, after the inclination angle of the steering roll 3 is fixed, the intermediate transfer belt 1 moves at a predetermined rate (0.5 mm / (less than cycle), it gradually deviates from the reference position (REF).

When the inclination angle of the steering roll 3 is fixed, the intermediate transfer belt 1 is caused to travel around the RL from that point on, and the position information of the belt edge at that time, that is, the detection data e (r, n) of the edge sensor 13 is obtained.
Is obtained (step S4). However, in this case, the number of belt rotations is two or more (RL ≧ 2). Further, the sample timing of the belt edge position by the edge sensor 13 is set so that N pieces of detection data per belt rotation can be obtained based on the belt home signal from the belt home sensor 12 as in the case of the steering control described above. Set.

Thus, for example, when the number of belt rotations is set to 3 (RL = 3) and the number of samples per belt is set to 10 (N = 10), the detection as shown in FIG. Data is obtained. Therefore, the edge shape data is calculated as follows using the detected data (step S5).

First, assuming that the data detected by the edge sensor 13 at the start of sampling is e (r ₁ , N), the walk rate WR per sample period can be obtained by the following equation ( ₁ ). Here, “r ₁ ” is the number of belt rotations immediately before the start of the creation processing of the edge shape table.

[0052]

(Equation 1)

Next, the walk rate component WR obtained by the above equation (1) is converted into the detection data e by the following equation (2).
By removing from the (r, n), only the edge shape component p (r, n) of the belt is extracted as shown in FIG.

[0054]

(Equation 2)

Next, by averaging the edge shape data for the RL circumference (three rounds in this example) using the following equation 3, as shown in FIG. Of the edge shape data p ₀ (n) is calculated. By this averaging process, the detection accuracy of the belt edge position using the edge sensor 13 can be improved.

[0056]

(Equation 3)

However, the average value of the edge shape data p ₀ (n) thus obtained is the reference value (REF =
0), which is a so-called DC offset component. Therefore, when the steering control is actually performed using the edge shape data p ₀ (n), the edge position of the intermediate transfer belt 1 is controlled in a state shifted from the reference position by a certain amount due to the offset component. Therefore, the offset component is removed using the following equation (4).

[0058]

(Equation 4)

As a result, as shown in FIG.
The average value of the edge shape data of the intermediate transfer belt 1 becomes substantially zero, and the edge shape data p (n) is stored in the storage unit 28 as data of the edge shape table.

On the other hand, the edge shape data p (n)
Is calculated, the inclination angle of the steering roll 3 remains fixed, so that the intermediate transfer belt 1 moves in one direction at a constant rate. Therefore, the position of the intermediate transfer belt 1 is shifted from the reference position (REF). Therefore, this time, the edge shape data p
Using (n), the same steering control as in image formation (steering control 2) is performed (step S6). Thereby, the edge position of the intermediate transfer belt 1 gradually approaches the reference position (REF).

Next, based on the detection data from the edge sensor 13, it is determined whether or not the moving amount W (n) of the intermediate transfer belt 1 has reached a predetermined allowable range Wb (W (n) <Wb).
(Step S7), and the intermediate transfer belt 1
When the movement amount W (n) falls within the allowable range Wb, that is, when the position of the intermediate transfer belt 1 returns to the reference position, the steering control enters a standby state (preparation completed) (step S8). Thus, a series of table creation processing is completed.

The values of "N" and "RL" can be arbitrarily changed, and the precision of steering control is improved by increasing the value of "N" (the number of controls and the number of samples). However, it goes without saying that increasing the value of “RL” improves the accuracy of the averaging process.

Further, the position fluctuation (meandering) in the width direction of the belt.
Is not limited to the one using the tilting operation of the steering roll 3, and for example, by moving any one of a predetermined number of rolls supporting the belt in the axial direction, Other means, such as those for correcting position fluctuations, may be employed.

Further, in the present embodiment, an example of application to an image forming apparatus using the endless intermediate transfer belt 1 has been described. However, the present invention relates to an endless photosensitive belt, a sheet conveying belt, and the like. The present invention can be similarly applied to the used image forming apparatus, and can also be applied to a belt drive of another apparatus other than the image forming apparatus.

[0065]

As described above, according to the belt driving device of the present invention, in order to correct the position fluctuation of the endless belt in the width direction, the control means uses the detection data of the edge position by the detection means. In controlling the driving of the driving means, using the edge shape data stored in the storage means,
Since the position fluctuation component (error component) due to the edge shape of the endless belt can be removed from the edge position detection data, the position fluctuation of the endless belt can be more appropriately corrected without being affected by the belt edge shape. It becomes possible. Thus, for example, in a color image forming apparatus using an endless belt, it is possible to obtain a high-quality output image without color shift or color unevenness.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a schematic diagram showing a specific configuration of an edge sensor.

FIG. 3 is a schematic diagram showing a basic configuration for correcting meandering.

FIG. 4 is a schematic diagram showing another configuration example of the edge sensor.

FIG. 5 is a diagram illustrating the principle of meandering correction.

FIG. 6 is a configuration diagram of a steering control system adopted in the embodiment of the present invention.

FIG. 7 is a flowchart illustrating a procedure for creating an edge shape table.

FIG. 8 is a diagram showing a belt position change state when an edge shape table is created.

FIG. 9 is a diagram illustrating a state in which the position of the belt fluctuates when the inclination angle of the roll is fixed.

FIG. 10 is a diagram illustrating a measurement result when an error of edge shape data with respect to a movement ratio of a belt is measured.

FIG. 11 is a schematic diagram showing a procedure for calculating edge shape data.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Intermediate transfer belt, 2 ... Drive roll, 3 ... Steering roll, 4 ... Secondary transfer roll, 5, 6, 7 ... Follower roll, 13 ... Edge sensor, 19a ... Controller, 20
... Steering motor, 21 ... Swing arm, 22 ... Eccentric cam, 27 ... Calculation unit, 28 ... Storage unit

Claims (8)

[Claims] 1. An endless belt and a predetermined number of rolls for supporting the endless belt. One of the predetermined number of rolls is used as a drive roll, and the endless belt runs by rotation of the drive roll. In the belt driving device, a driving unit that drives the endless belt to correct a position change in a width direction, a detection unit that detects an edge position in a width direction of the endless belt, and stores edge shape data of the endless belt. Storage means for comparing the edge position detection data by the detection means with the edge shape data stored in the storage means, and controlling the drive means based on the comparison result. A belt drive device characterized by the above-mentioned. 2. The edge shape data stored in the storage unit is calculated based on a detection result of the detection unit in a state where the endless belt is moved in a width direction at a constant rate. The belt driving device according to claim 1, wherein: 3. The belt driving device according to claim 2, wherein the rate at which the endless belt moves in the width direction is set to 0.5 mm or less per belt circumference. 4. When calculating the edge shape data,
3. The belt driving device according to claim 2, wherein the endless belt is caused to travel over two or more turns, and a detection result obtained by the detection unit is averaged. 5. The driving means includes a steering roll that supports the endless belt together with the predetermined number of rolls, and corrects a positional change in the width direction of the endless belt by a tilting operation of the steering roll. By fixing the angle,
3. The belt driving device according to claim 2, wherein the endless belt is moved in a width direction at a constant rate. 6. A method for correcting edge shape data for one round of a belt obtained by the averaging process so that an average value thereof is about 0, and storing the corrected edge shape data in the storage means. The belt driving device according to claim 4, wherein: 7. An inclination angle of the steering roll,
6. The endless belt is fixed in a state in which the endless belt is running stably near a preset reference position.
A belt drive as described. 8. An image forming apparatus comprising the belt drive device according to claim 1. Description: