JP2006030711A - Belt drive control device and image forming apparatus provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt drive control device for controlling rollers for driving or supporting a belt without applying movement to the radial direction or thrust direction of the rollers, and to provide an image forming apparatus provided with the belt drive control device. <P>SOLUTION: A belt drive unit provided with a plurality of motors 1, 1-a, 1-b, a plurality of rollers 2-a, 2-b, 2-c and an endless belt 4 stretched around the motors 1, 1-a, 1-b and the rollers 2-a, 2-b and constituted so as to drive the endless belt 4 by transmitting the driving force of the motors 1, 1-a, 1-b includes: a meandering detector 5 for detecting the meandering quantity of the endless belt 4; a plurality of rollers 2-a, 2-b arranged in parallel so that at least one of the rollers acts as a driving roller; and a rotational speed changing means 9 for changing the rotational speed of the driving rollers 2-a, 2-b to control the rotation of the driving rollers 2-a, 2-b by the rotational speed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a belt drive control device that corrects meandering of an endless belt stretched around a plurality of support members, and an image forming apparatus such as a copying machine, a printer, and a facsimile equipped with the belt drive control device.

Conventionally, an endless belt is used as an intermediate transfer belt, a photosensitive belt, or a paper conveying belt in an image forming apparatus such as a copying machine or a printer. Generally, it is known that an endless belt is supported by a plurality of rollers, and the endless belt is caused to travel by rotationally driving any one of the rollers (see, for example, Patent Documents 1 to 4).
During the travel of the endless belt, a phenomenon of moving in the belt width direction (roller axis direction) may occur, which is called belt meandering. This belt meandering phenomenon is particularly a problem in a color image forming apparatus. The color image forming apparatus includes an image unit having yellow, magenta, cyan, and black colors.
This image unit transfers an image of each color in an overlapping manner onto an intermediate transfer belt or transfer paper conveyed by the belt. At this time, if there is a relative positional shift in each color image, the color shift or color unevenness of the image occurs. Therefore, in order to obtain a high-quality output image, it is necessary to correct the meandering of the belt.
Accordingly, several belt meandering correction techniques have been proposed. These are roughly divided into two techniques: a technique for inclining a roller and a technique for regulating movement in the belt width direction. As a technique for inclining the former roller, there are Patent Document 1 and Patent Document 2.
Patent Document 1 discloses a technique for correcting the meandering of a belt by a load difference between right and left of a tension applying roller that applies tension to the belt. Patent Document 2 discloses a technique for detecting the inclination between a moving direction of a belt wound around a roller and a predetermined moving direction and correcting the inclination with a steering roller.
As the latter technique for regulating the movement in the belt width direction, there are Patent Document 3 and Patent Document 4 in addition to the detents in the ribs and guides that are recognized as known techniques.
Patent Document 3 discloses a technique in which a roller having a larger diameter is stopped by changing the diameter of the roller on the left and right. Patent Document 4 discloses a technique for generating a force in the direction opposite to the belt bias by decreasing the diameter toward the outer side of the roller.
JP 2002-296972 A JP 2003-312885 A Japanese Patent Laid-Open No. 06-278894 JP-A-11-0779457

However, in the prior art in which the roller is inclined, there is a problem of causing a transfer abnormality because the contact between the photosensitive drum and the intermediate transfer belt is not uniform. Further, in the conventional technology that regulates the movement in the belt width direction, there is a problem that the belt is damaged due to the contact of the rib or the guide.
Furthermore, as a problem common to both technologies, there is a problem that hinders smooth driving of the belt because force is applied in directions other than the rotation direction of the belt.
Accordingly, an object of the present invention is to provide a belt drive control device that controls a roller without moving in the radial direction or thrust direction of a roller that drives or supports the belt in consideration of the above-described circumstances, and an image including the belt drive control device, for example, It is to provide a forming apparatus.

In order to solve the above-mentioned problem, the invention described in claim 1 includes a plurality of rollers including a driving roller and a driven roller, a motor for driving the driving roller, and an endless belt stretched around the plurality of rollers. A belt driving device that drives an endless belt by driving a driving motor with a motor, wherein the driving roller includes a plurality of divided driving rollers arranged on the same axis, and at least one of the divided drives. The roller is driven by the motor, and the meandering detector for detecting the meandering amount of the endless belt, and the change value of the rotational speed of the divided driving roller is calculated based on the meandering amount detected by the meandering detector. A rotation speed changing means; and a control means for controlling the rotation speed of the divided drive roller based on the control information calculated by the rotation speed changing means. And it features.
According to a second aspect of the present invention, in the first aspect, one of the plurality of divided drive rollers is coupled to the motor, and the other is coupled to a brake.
According to a third aspect of the present invention, in the first or second aspect, a driven roller is disposed between the plurality of divided drive rollers.
A fourth aspect of the present invention is characterized in that in the first, second, or third aspect, a means for detecting the speed in the rotational direction of the endless belt is provided.
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, an encoder is attached to each of the divided drive rollers.

According to a sixth aspect of the present invention, in the first to fifth aspects, the rotational speed changing means generates a driving roller rotational speed difference contour from a table in which the meandering amount of the belt and the divided driving roller rotational speed for meandering correction are associated with each other. And generating a target rotational speed of the divided driving roller.
A seventh aspect of the invention is characterized in that, in the first to sixth aspects, the divided drive roller position and the detection position of the meandering detector are the same position.
The invention according to claim 8 is the invention according to any one of claims 1 to 6, wherein the rotation speed changing means generates the rotation speed of the divided drive roller from the phase difference of the meandering cycle between the position of the divided drive roller and the detection position of the detector. It is characterized by that.
The invention according to claim 9 is an image forming apparatus using the belt drive control device according to any one of claims 1 to 8, wherein toner is attached to the endless belt and transferred onto transfer paper. .
The invention according to claim 10 uses the belt drive control device according to any one of claims 1 to 8, wherein the endless belt conveys the transfer paper and causes the toner on the photosensitive drum to adhere to the transfer paper. The image forming apparatus is characterized.

  According to the present invention, meandering can be suppressed without moving the belt in the thrust direction or radial direction by increasing the roller rotation speed in the belt meandering direction or increasing the roller load on the side opposite to the bias.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of a belt drive control device according to the present invention in which motors are arranged in parallel. The mechanical structure and operation will be described. In FIG. 1, two motors 1-a and 1-b are provided, and the drive roller 2 (2-a, 2-b) is driven by both motors.
The rotational speeds of the motors 1-a and 1-b are controlled by speed command signals from the control board 6. The independent driving rollers (divided driving rollers) 2-a and 2-b drive the endless belt 4 by the driving force of the two motors 1-a and 1-b, and transmit the driving force to the driven roller 3. .
At this time, the meandering detector 5 detects the meandering of the endless belt 4. As shown in FIG. 1, the meandering detector 5 detects the amount by which the meandering detection marker 13 (see FIG. 14) formed along the belt edge fluctuates in the belt width direction. The detected presence / absence of meandering and the amount of meandering are sent to the control board 6. The control board 6 corrects and determines the rotational speeds of the motors 1-a and 1-b from the detected meandering amount, and sends a motor speed command signal again.

FIG. 2 is a block diagram showing the belt drive control device as a system. In FIG. 2, the control means 7 drives the first motor 1-a and the second motor 1-b by giving respective speed command signals.
In other words, the meandering detector 5 for detecting the meandering amount of the endless belt 4 and the change values of the respective rotational speeds of the divided drive rollers 2-a and 2-b (optimal rotational speeds) based on the meandering amount detected by the meandering detector 5. ) And a control means 7 for controlling the rotation speed of the divided drive roller based on the control information on the rotation speed of each divided drive roller calculated by the rotation speed change means 9. .
The rotational driving forces of both motors 1-a and 1-b are transmitted to the endless belt 4 and driven. The meandering of the endless belt 4 is detected by a meandering detector 5 as shown in FIG. 14, which will be described later, and FFT analysis is performed by an FFT analysis means (frequency analysis means) 8 that analyzes the frequency component contained in the mechanical signal.
The amount of meandering for each frequency is calculated by FFT analysis, and this information is sent to the motor rotation speed changing means 9. The motor rotation speed changing means 9 processes at each frequency whether or not the amount of meandering is equal to or greater than a certain threshold value, and synthesizes all meandering components equal to or greater than the threshold value.
If meandering occurs in the drive roller 2-a on the first motor 1-a side at a certain time, the rotational speed of the first motor 1-a is increased in accordance with the meandering cycle, or the first A command (control information) for lowering the rotational speed of the second motor 1-b is output to the control means 7.
Furthermore, both may be combined. In addition, if meandering is present on the split drive roller 2-b on the second motor 1-b side at a certain time, is the rotation speed of the second motor 1-b increased in accordance with the meandering cycle? Alternatively, the rotational speed of the first motor 1-a is decreased.
Furthermore, both control methods may be implemented together. In this way, utilizing the fact that the meandering extracted by the FFT analysis means 8 is periodic, the rotational speed of the roller on the side opposite to the direction in which the belt approaches the meandering is relatively increased, and the meandering is suppressed by the difference in the right and left speeds. To do.
By arranging the motors 1, 1-a, 1-b as driving sources and the brakes as load generating sources in parallel, the shift of the endless belt 4 that occurs when the thickness changes in the width direction of the endless belt 4 is also eliminated. it can.

FIG. 3 is a block diagram showing a second embodiment of the belt drive control device according to the present invention, in which a motor and a brake are combined. In FIG. 3, one of the drive rollers (divided drive rollers) 2-a and 2-b is coupled to the motor 1 and the other is coupled to the brake 10.
The split drive rollers 2-a and 2-b are connected by a structure like a clutch, and the amount of transmission of the driving force of the motor 1 to the opposite split drive rollers 2-a and 2-b can be adjusted. If it is good.
This mechanism is used when the thickness of the endless belt 4 differs in the width direction. That is, when the endless belt 4 on the motor 1 side is thin and the endless belt 4 on the brake side is thick, the belt speed on the motor 1 side is constantly decreasing, so the drive roller rotation speed on the brake side is decreased.
FIG. 4 is a block diagram showing a third embodiment of the belt drive control device according to the present invention having driven rollers arranged in series in the axial direction. One or more of the rollers arranged in series are driven rollers.
The driven roller 2-c is coaxially sandwiched between the divided driving rollers 2-a and 2-b directly connected to the two motors 1-a and 1-b. The driven roller 2-c itself rotates with the endless belt 4 driven by the driving force given by the left and right divided driving rollers 2-a and 2-b without controlling the rotational speed.
By arranging the driven rollers 2-c in parallel in addition to the divided driving rollers 2-a and 2-b, it is possible to balance the difference in roller rotation speed, and to reduce the difference in speed between the left and right sides of the belt conveyance. Can do.

FIG. 5 is a block diagram showing a fourth embodiment of a belt drive control device according to the present invention provided with a belt rotation speed detector. In order to suppress meandering, motors 1-a and 1-b having different rotational speeds are used for one endless belt 4. The split driving rollers 2-a and 2-b are driven by respective motors.
Therefore, it is difficult to accurately estimate the surface speed of the endless belt 4 from the rotational speeds of the motors 1-a and 1-b. Therefore, the belt rotation speed detector 11 is attached to the endless belt 4 itself to check whether the surface speed is as intended.
At this time, when it is desired to increase the surface speed, the rotational speed of the motor is increased or the brake load is decreased so that the rotational speeds of the left and right divided drive rollers 2-a and 2-b are uniformly increased. Even if the load or the rotational speed difference changes, it is possible to adjust the control amount to the desired belt speed by detecting whether the desired belt speed is obtained.
On the other hand, when it is desired to reduce the surface speed, the rotational speeds of the motors 1-a and 1-b are reduced so that the rotational speeds of the left and right divided drive rollers 2-a and 2-b are uniformly reduced, or the brake Or increase the load.
FIG. 6 is a schematic perspective view showing the configuration of a belt drive control device according to the present invention in which an encoder is provided on a drive roller having a brake configuration. FIG. 7 is a schematic perspective view showing the configuration of the belt drive control device according to the present invention in which an encoder and a brake are provided on the driven roller 3 having a brake configuration arranged in series.
In FIG. 6, an encoder 12 that detects the rotational speed of the shaft is attached to at least one of the split drive rollers 2-a and 2-b. The encoder 12 may be an encoder integrated with the motor 1 and is attached to the motors 1, 1-a, 1-b shown in FIGS. 1, 3, and 5.
By constantly monitoring the rotational speeds of the motors 1, 1-a and 1-b, it is confirmed whether the rotational speed difference has become larger or smaller than the target. There is also a configuration in which an encoder is attached to a drive roller having a brake configuration.
Thus, by attaching the encoder 12 to the two divided drive rollers 2-a and 2-b connected by the clutch, the drive roller rotational speed or the rotational speed difference can be managed with high accuracy.

In FIG. 7, brakes 7-a and 7-b are provided on the driven rollers 3-a and 3-b divided in two, and encoders 12-a and 12-b are provided on the respective axes. There is one drive roller 2.
FIG. 8 is an explanatory diagram showing the phase difference between the meander detector and the drive roller speed change position according to the embodiment of the present invention. The meandering amount can be rephrased as a speed difference in the belt width direction. The rotation speed of the roller is the speed in the belt conveyance direction.
Therefore, by converting the speed difference in the width direction of the endless belt into the speed difference in the transport direction, the target rotational speed of the divided drive rollers 2-a and 2-b arranged in series to correct the meandering of the endless belt 4 is determined. it can. Here, a belt drive control device as shown in FIG. 1 will be described as an example.
FIG. 9 is a top view of the belt drive control device according to the present invention in which the motors of FIG. 1 are arranged in series. FIG. 10 is a schematic diagram showing an outline of a belt conveyance speed difference to be corrected. FIG. 9 illustrates the meandering amount generated with respect to the belt movement amount and the rotational speed difference to be changed.
At this time, the meandering amount with respect to the belt conveyance amount is detected as shown in the left graph of FIG. The left and right axes of the meandering amount correspond to the left and right in the belt width direction of FIG. At this time, the belt conveyance speed difference contour to be corrected is as shown in the right graph of FIG.
In the graph on the right, the left and right axes of the belt conveyance speed are the difference between the left belt conveyance speed and the right belt conveyance speed in FIG. Therefore, when the belt conveyance speed difference is larger on the left side, the motor rotation speed is changed so that the belt conveyance speed on the left side is higher than that on the right side.
Further, since the belt conveyance speed difference is obtained by multiplying the roller rotation speed by the driving roller radius, if the scale of the belt conveyance speed axis is changed, it can be directly used as the outline of the drive roller rotation speed difference.

FIG. 11 is a diagram for explaining the correspondence between the meandering amount and the rotational speed difference. For example, the motor rotation speed changing unit 9 or the control unit 7 creates the drive roller rotation speed difference contour with respect to the belt conveyance amount from the correspondence table between the meandering amount and the drive roller rotation speed difference as shown in FIG. By the way, this table may be generated at the time of product shipment or may be generated during operation of the product.
Since meandering of endless belt 4 has periodicity, a driving roller rotational speed difference profile is created in accordance with the period. Then, the left and right divided drive roller target rotational speeds are determined. By using the rotation speed difference table, it is possible to quickly generate a drive roller target rotation speed for attenuating the meandering amount that is a speed difference in the belt width direction.
The belt drive control device makes the drive roller position and the detection position of the detector the same position. This detector is arranged so as to detect in the normal direction of the divided drive rollers 2-a and 2-b arranged in series.
Further, among the divided drive rollers on which the endless belt 4 is hung, the place where the transmission force acts greatly is the position where the belt is hung on the divided drive roller. Therefore, it is preferable as the highest sensitivity to detect the meandering of this portion. By performing detection and control at the same position, a simple feedback control system can be realized.
In the belt drive control device, the rotation speed generation means generates a control rotation speed from the phase difference of the meandering cycle between the divided drive roller position and the detection position of the detector. In the case of the configuration as shown in FIG. 4, the section shown in FIG. 8 which is a side view is converted into a phase difference.
In the conversion method, the rotation speed of the driving roller is applied to the time passing through the section. Using this phase difference and the periodicity of meandering, meandering on the meandering detector is converted into meandering on the driving roller and used for controlling the rotational speed of the driving roller. By converting meandering at the detection position to meandering at the drive roller position, more precise control can be performed.

FIG. 12 is a schematic perspective view showing a configuration diagram of an image forming apparatus including an intermediate transfer belt according to an embodiment of the present invention. In this image forming apparatus, toner is attached to the endless belt 4 and transferred to the transfer paper 15. Reference numeral 11 denotes a photosensitive member, M denotes a motor, 2A denotes a driving roller, and M denotes a motor.
Detection and correction of meandering is performed automatically before transfer. In addition, since meandering has periodicity, it is preferable to have a structure in which information obtained by detecting and changing the motor speed can be stored even when the image forming apparatus is turned off. By suppressing meandering of the photoreceptor belt 4-b, transfer with little color shift can be performed.
FIG. 13 is a schematic perspective view showing a configuration of a four-tandem image forming apparatus according to an embodiment of the present invention. The endless belt 4 conveys the transfer paper 15 and causes the toner on the photosensitive drums 14-a, 14-b, 14-c and 14-d to adhere to the transfer paper 15.
Detection and correction of meandering is performed automatically before transfer. In addition, since meandering has periodicity, it is preferable to have a structure in which information obtained by detecting and changing the motor speed can be stored even when the image forming apparatus is turned off. By suppressing meandering of the transfer belt, transfer with little color misregistration can be performed.
FIG. 14 is a schematic perspective view illustrating a meandering detector. As described with reference to FIG. 1, the meander detector 5 detects the meander of the endless belt 4. As shown in FIG. 1, the meandering detector 5 detects the amount by which the meandering detection marker 13 fluctuates in the belt width direction. The detected meander is sent to the control board 6.
In short, instead of applying a force in the radial direction or thrust direction of the roller, the force or speed in the rotational direction is adjusted, and the rollers are arranged in parallel so that the meandering is controlled by the difference in rotational speed between the left and right rollers. .

The block diagram which shows 1st Embodiment of the belt drive control apparatus by this invention which has arrange | positioned the motor in series. The block diagram which shows a belt drive control apparatus as a system. The block diagram which shows 2nd Embodiment of the belt drive control apparatus by this invention which combined the motor and the brake. The block diagram which shows 3rd Embodiment of the belt drive control apparatus by this invention. The block diagram which shows 4th Embodiment of the belt drive control apparatus by this invention provided with the belt rotational speed detector. The schematic perspective view which shows the structure of the belt drive control apparatus by this invention which provided the encoder in the drive roller of the brake structure. The schematic perspective view which shows the structure of the belt drive control apparatus by this invention which provided the encoder in the drive roller of the brake structure. Explanatory drawing which shows the phase difference of the meandering detector which is embodiment of this invention, and a drive roller speed change position. The figure which looked at the belt drive control apparatus by this invention which has arrange | positioned the motor of FIG. 1 in series from the top. Schematic which shows the outline of the belt conveyance speed difference which should be corrected. The figure explaining the correspondence of the amount of meandering and a rotational speed difference. 1 is a schematic perspective view illustrating a configuration diagram of an image forming apparatus including an intermediate transfer belt according to an embodiment of the present invention. 1 is a schematic perspective view illustrating a configuration of a four-tandem image forming apparatus according to an embodiment of the present invention. The schematic perspective view explaining a meandering detector.

Explanation of symbols

1 motor 1-a motor, 1-b motor, 2-a drive roller arranged in parallel, 2-b drive roller arranged in parallel, 2-c driven roller arranged in parallel, 4 endless belt, 4a endless belt, 4b endless belt (Photosensitive belt), 5 meander detector, 7 control means, 8 FFT analysis means, 9 motor rotation speed changing means, 10 brake, 10-a brake, 10-b brake, 11 belt rotation speed detector, 12 encoder, 12-a encoder, 12-b encoder, 13 meandering detection marker, 14-a photosensitive drum, 14-b photosensitive drum, 14-c photosensitive drum, 14-d photosensitive drum, 15 transfer paper, 16 belt Speed detection marker,

Claims (10)

A plurality of rollers including a driving roller and a driven roller, a motor for driving the driving roller, and an endless belt stretched around the plurality of rollers, and driving the driving motor by the motor to drive the endless belt In the belt drive device
The drive roller is composed of a plurality of divided drive rollers disposed on the same axis, and has a configuration in which at least one of the divided drive rollers is driven by the motor,
The meandering detector for detecting the meandering amount of the endless belt, the rotational speed changing means for calculating the change value of the rotational speed of the divided drive roller based on the meandering amount detected by the meandering detector, and the rotational speed changing means And a control means for controlling the rotational speed of the divided drive roller based on the control information.   2. The belt drive control device according to claim 1, wherein one of the plurality of divided drive rollers is coupled to the motor, and the other is coupled to a brake.   The belt drive control device according to claim 1, wherein a driven roller is disposed between the plurality of divided drive rollers.   4. The belt drive control device according to claim 1, further comprising means for detecting a speed in a rotation direction of the endless belt.   The belt drive control device according to any one of claims 1 to 4, wherein an encoder is attached to each of the divided drive rollers.   The rotational speed changing means creates a drive roller rotational speed difference contour from a table in which the meandering amount of the belt and the divided drive roller rotational speed for meander correction are associated with each other, and generates a target rotational speed of the divided drive roller. The belt drive control device according to any one of claims 1 to 5, wherein   The belt drive control device according to any one of claims 1 to 6, wherein the divided drive roller position and the detection position of the meandering detector are the same position.   7. The rotation speed changing unit generates the rotation speed of the divided drive roller from a phase difference of a meandering cycle between the position of the divided drive roller and the detection position of the detector. The belt drive control device according to the item.   The image forming apparatus using a belt drive control device according to claim 1, wherein toner is attached to the endless belt and transferred onto transfer paper. The image forming apparatus using a belt drive control device according to claim 1, wherein the endless belt conveys transfer paper and causes toner on a photosensitive drum to adhere to the transfer paper. .

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