JP4663282B2 - Belt conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a belt conveyance device in an electrophotographic apparatus or the like, and is suitable for application to a copying machine or a printer.

In recent image forming apparatuses, it is necessary to realize printing with a displacement of pixel positions of several hundred μm or less in order to improve the printing accuracy. At that time, in the image forming apparatus using the intermediate transfer belt, the displacement of the printing position occurs due to the deviation of the belt traveling speed. The fluctuation in the belt running speed is caused by the eccentricity of the belt drive shaft, the belt thickness deviation, or the like.
In order to solve these problems, it is necessary to design and assemble a mechanism that does not cause eccentricity, and further, many cost increasing factors are required, such as man-hours at the time of assembling, improvement of part accuracy for improving time and accuracy.
In order to solve this, there are means such as marking on the belt and changing the rotational speed of the photosensitive member and the timing of writing by reading the amount of deviation of the marking position. As an effective means, it is considered that the belt running speed is measured and control is performed so that the speed becomes constant.
As a conventional technique, a method for correcting a positional deviation by performing position detection using a registration mark (for example, refer to Patent Document 1), a method for measuring data for one round of a belt, creating a correction value, and suppressing fluctuations (for example, Patent Document 2).
JP 2000-047546 A JP 2000-047547 A

However, in order to measure the belt running speed, it is necessary to print a mark on the belt. In order to accurately measure the speed over the entire circumference of the belt, it is necessary to write a high-resolution mark. Marking with can not be performed with very high resolution.
The present invention has been made in consideration of the above-mentioned circumstances, and in order to keep the belt running speed constant, a belt that realizes image output with suppressed image quality degradation using a commonly used encoder. An object is to provide a transport device.

In order to solve the above-mentioned problem, the invention described in claim 1 is characterized in that an endless intermediate transfer belt in an electrophotographic image forming apparatus is bridged between a driving roller and a pulley, and the intermediate transfer belt is driven by the driving roller. In the belt conveying device for running, the first detecting means for detecting the belt running speed based on the rotation information from the first encoder arranged coaxially with the driven roller that abuts on the intermediate transfer belt and rotates around, A second detecting means for detecting a belt traveling speed based on rotation information from a second encoder arranged coaxially with the driving roller; a ratio between the resolution of the first encoder and the resolution of the second encoder; The difference between the product value of the output of the first encoder and the output of the second encoder is obtained, and the difference is added to the output of the first encoder. In the a first correction means for correcting the output of the encoder, based on the detection result of the first detection means detected by the rotation information from the output of the first encoder corrected by said correction means And a control means for controlling the rotational speed of the drive roller so that the belt running speed of the intermediate transfer belt is constant .
According to a second aspect of the present invention, in the belt conveying device according to the first aspect, the driven roller is arranged in a straight portion on the endless belt.
According to a third aspect of the present invention, in the belt conveyance device according to the first aspect, the resolution of the first encoder on the intermediate transfer belt and the resolution of the second encoder on the driving roller are an integer ratio. It is characterized by becoming.
According to a fourth aspect of the present invention, in the belt conveying device according to the third aspect of the present invention, the belt conveyance device further includes a slip detection unit that detects the slip of the roller from the output ratio of the first encoder and the output ratio of the second encoder. It is characterized by that.
According to a fifth aspect of the present invention, an image forming apparatus includes the belt conveyance device according to any one of the first to fourth aspects.

  According to the present invention, a belt surface speed is measured by using a commonly used encoder, and even when slippage occurs on a roller pressed against the belt surface, the influence is minimized. Since the belt traveling speed is kept constant, image output with reduced image quality can be realized.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments according to a belt conveying device of the invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a partial configuration of a general image forming apparatus to which the belt conveyance device of the present embodiment is applied.
Recently, with the increase in the speed and color of an image forming apparatus, the charging, exposure, and transfer of four colors (black, yellow, magenta, and cyan) are repeated four times for one conventional photosensitive drum. A system has been adopted in which charging, exposure, and transfer of each color are individually performed by a photoconductor of a book, and each toner is superimposed on an intermediate transfer belt to form an image.
Such an image forming apparatus includes four photoconductors, an intermediate transfer belt, a paper conveying device, and the like as shown in FIG.
In FIG. 1, reference numerals 11 to 14 denote photoreceptors, which are yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), cyan (hereinafter referred to as C), and black (hereinafter referred to as K) during color image formation. A color image is formed by superimposing the four colors.
Since the photoconductors 11 to 14 perform image formation corresponding to each color of YMCK, image information is written from the respective laser scanning units. Although detailed description is omitted here, output image information based on electric charges is formed on the photosensitive member by irradiating the photosensitive member with laser light in this way, and toner images are formed by attaching toner.
The toner images formed on the photoconductors 11 to 14 are transferred to the intermediate transfer belt 21, and a color image in which the respective color images are superimposed on the intermediate transfer belt 21 is formed.

The intermediate transfer belt 21 is supported by a belt conveyance drive roller (drive roller) 22 and pulleys (driven pulleys) 23 and 24 that are driving sources of the intermediate transfer belt, and is rotated by the belt conveyance drive roller 22.
The color image formed on the intermediate transfer belt 21 is then transported by the transport belt 31 and transferred onto the paper transported by the pulley 24 and the secondary transfer drive roller 32, and is omitted in this drawing. Through a process such as fixing, an output image is formed on the paper.
In such an image forming apparatus, even if each of the photoconductors 11 to 14 rotates at a constant speed, if the speed of the intermediate transfer belt 21 varies, each photoconductor transferred onto the intermediate transfer belt 21. The transfer position of the toner from the bodies 11 to 14 is shifted, which causes image deterioration.
The configuration shown in FIG. 2 is intended to detect the belt rotation speed by attaching an encoder on the drive shaft of the belt transport drive roller or on the shaft of another belt transport drive roller. 2A is a side view and FIG. 2B is a top view.
The belt conveyance drive roller 101 is rotationally driven by a motor or the like, and the intermediate transfer belt 110 applied to the pulleys 102 and 103 rotates. At this time, the encoder 120 attached to the rotation shaft of the belt conveyance drive roller 101 also rotates at the same time, and outputs according to the rotation speed of the intermediate transfer belt 110.

However, when the encoder 120 is attached to the rotation shaft of the belt conveyance drive roller 101, the encoder 120 has a rotational speed even when the speed of the surface of the intermediate transfer belt is constant due to the eccentricity of the attachment of the encoder 120, the belt thickness deviation, or the like. Will occur.
Therefore, as shown in FIG. 3, a roller is pressed against the belt surface, and an encoder is arranged on the roller shaft. 3A is a side view and FIG. 3B is a top view.
The roller 221 is pressed against the belt surface between the belt conveyance driving roller 201 and the pulley 202, and the encoder 220 is attached on the rotation shaft of the roller 221.
As the belt conveyance drive roller 201 rotates, the intermediate transfer belt 210 rotates, and the driven roller 221 in contact with the intermediate transfer belt 210 also rotates. At this time, the encoder 220 attached on the rotating shaft of the driven roller 221 is also rotated at the same time, so that an encoder output corresponding to the belt rotational speed can be obtained.
As described above, the driven roller 221 is pressed against the horizontal portion of the intermediate transfer belt 210 as shown in FIG. 3, so that the surface speed of the intermediate transfer belt 210 can be measured.
This configuration measures the belt speed on the surface to be transferred from the photoconductor, so that belt movement speed information can be acquired without being affected by belt thickness deviation or eccentricity of the belt drive shaft or the like. Become.
Also, since the conveying roller supports the belt, it cannot be made too small in diameter, but there is no restriction on the driven roller that presses against the intermediate transfer belt, so it can be made small in diameter. The influence can also be reduced.
Furthermore, in addition to the encoder 302 attached to the driven roller 301 in contact with the belt surface as shown in FIG. 4, an encoder 311 is also attached on the shaft of the belt conveyance drive roller 310, and outputs from the two encoders 302 and 311 are calculated. In comparison with the device 320, whether or not the driven roller 301 pressed against the belt surface has slipped is detected by the output ratio of the two encoders 302 and 311. If slip has occurred, the shaft of the belt conveying drive roller 310 is detected. The output of the encoder 302 is corrected using the output of the encoder 311 above.

Next, the operation at the time of the correction will be described.
For example, when the driven roller 301 is not slipped, if the output per time t of the encoder 302 attached to the driven roller 301 pressed against the belt surface is n, the encoder 311 on the shaft of the belt conveyance drive roller 310 Is N, and the ratio of the resolution of the encoder 302 and the resolution of the encoder 311 is x: 1,
N = x × n + Δn
The relationship holds. If slip occurs here,
N> x × n + Δn
Therefore, since the value of the driven roller 301 on the belt surface is smaller than the rotational speed of the belt conveyance drive shaft, it is determined that slip has occurred, and the value of the encoder 302 processed by the control processing device is set to (N−x × n). ) Is added to continue the speed control.
By realizing such an operation, even if the driven roller 301 pressed against the belt surface slips, the influence can be minimized.
By realizing the configuration and operation as described above, the speed of the belt surface is detected, control based on the speed information is realized, and image output that minimizes the deviation of the printed image due to belt speed fluctuations is achieved. It becomes possible.

1 is a diagram illustrating a partial configuration of a general image forming apparatus to which a belt conveyance device of an embodiment is applied. The figure which shows the belt conveyance apparatus of a structure which attaches an encoder on a belt conveyance roller drive shaft, and detects a belt rotational speed. The figure which shows the belt conveying apparatus of a structure which presses a roller to the belt surface and arrange | positions an encoder on the roller axis | shaft. The figure which shows a belt conveying apparatus provided with two encoder.

Explanation of symbols

11 to 14 Photoconductor, 21 Intermediate transfer belt, 22 Belt transport drive roller, 23, 24 Pulley, 31 Transport belt, 32 Secondary transfer drive roller, 101 Belt transport drive roller, 102, 103 Pulley, 110 Intermediate transfer belt, 120 Encoder, 201 Belt drive roller, 202, 203 Pulley, 210 Intermediate transfer belt, 220 Encoder, 221 Driven roller, 301 Driven roller, 302 Encoder, 310 Belt transport drive roller, 311 Encoder, 320 Arithmetic unit

Claims (5)

In a belt conveying apparatus that spans an endless intermediate transfer belt in an electrophotographic image forming apparatus between a driving roller and a pulley, and drives the intermediate transfer belt by driving the driving roller.
First detecting means for detecting a belt traveling speed based on rotation information from a first encoder disposed coaxially with a driven roller that is in contact with and rotates on the intermediate transfer belt;
Second detection means for detecting a belt traveling speed based on rotation information from a second encoder arranged coaxially with the drive roller;
The difference between the product of the ratio of the resolution of the first encoder and the resolution of the second encoder and the output of the first encoder and the output of the second encoder is obtained, and the difference is calculated as the first Correction means for correcting the output of the first encoder by adding to the output of the first encoder;
Based on the detection result of the first detection means detected by the rotation information from the output of the first encoder corrected by the correction means, the belt traveling speed of the intermediate transfer belt is constant. Control means for controlling the rotational speed of the drive roller;
A belt conveying device comprising:   2. The belt conveyance device according to claim 1, wherein the driven roller is disposed in a straight portion on the endless belt.   2. The belt conveyance device according to claim 1, wherein the resolution of the first encoder on the intermediate transfer belt and the resolution of the driving roller of the second encoder are an integer ratio. Belt conveyor.   4. The belt conveyance device according to claim 3, further comprising slip detection means for detecting slippage of the roller from an output ratio of the first encoder and an output ratio of the second encoder.   An image forming apparatus comprising the belt conveyance device according to claim 1.

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