JP2003173067A - Color image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate degradation in color image quality which results from color deviation, by correcting a speed change caused by a variation in the thickness of a carrying belt or a variation in the thickness of an intermediate transfer belt. <P>SOLUTION: A color image forming device 400 that directly forms an image on a transfer sheet placed on the endless carrying belt 201 is provided with a device 600 that controls the number of the rotations of a drive motor for the carrying belt according to a variation in the thickness of the carrying belt in its longitudinal direction. Also, in a color image forming device 500 that forms an image on the endless intermediate transfer belt 501 and transfers the formed image to a transfer sheet, the control device 600 copes with a variation in the thickness of the intermediate transfer belt 501 in its longitudinal direction in order to control the number of the rotations of a drive motor for the intermediate transfer belt. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem type color image forming apparatus having a plurality of photoconductors used in an electrophotographic copying machine, a printer or the like, and the speed of a transfer sheet conveying belt or an intermediate transfer belt. The present invention relates to a color image forming apparatus that performs control.

[0002]

2. Description of the Related Art As an example of a conventional color image forming apparatus,
There are a 4-cycle color output device using a single photoconductor and a so-called tandem type color image forming device using a plurality of photoconductors. In the former case, the device can be made relatively small, but the number of color outputs per unit time is small. On the other hand, in the latter, although the number of output sheets is large, the apparatus cannot be configured compactly, and it is difficult to align each color. Further, the tandem type color image forming apparatus includes a method of directly transferring to a final transfer member and a method of final transferring via an intermediate transfer member.
The direct transfer method is a method in which an image is formed by directly passing four image forming units for yellow, magenta, cyan, and black onto a final transfer member (transfer paper) placed on a conveyor belt and conveyed. . On the other hand, in the intermediate transfer method, once an image is formed by passing four image forming units for yellow, magenta, cyan, and black through an intermediate transfer member (intermediate transfer belt), and then the final transfer from this intermediate transfer member. It is a method of transferring onto a member (transfer paper).

An image in which a color image is obtained by placing these final transfer members on a conveyor belt and passing them through respective image forming portions one after another, or passing an intermediate transfer member (intermediate transfer belt) one after another through each image forming portion. In the forming apparatus, it is essential that the transport belt and the intermediate transfer belt maintain a constant moving speed, and if speed fluctuations occur during image formation, color misregistration occurs and the image quality of color images is significantly degraded. become.

Therefore, a technique disclosed in Japanese Patent Laid-Open No. 63-81370 is known in order to keep the conveyor belt speed constant. In this technique, a pickup roller for speed detection is brought into contact with the back surface of the conveyor belt, the rotation of the pickup roller that rotates with the movement of the belt is detected by a shaft encoder, and this detected speed is fed back to the PLL servo control circuit to determine the drive speed. The speed is controlled so that it is always equal to the predetermined speed.

[0005]

However, according to the above-mentioned prior art, it becomes possible to correct the speed fluctuations of the conveyor belt and the intermediate transfer belt due to various mechanical factors. If slippage occurs between the surfaces, speed fluctuation may be caused. To solve this, it is possible to increase the winding angle of the belt and the pickup roller to prevent slippage between the speed detection roller and the belt surface, but this will be affected by the belt thickness and the correct surface It becomes difficult to detect the speed. Further, since the speed detection unit is provided, the structure becomes complicated and the cost may increase. Further, the speed fluctuation is not corrected by following the change in the thickness of the transport belt or the intermediate transfer belt. The present invention has been made in view of such a situation, and corrects the speed fluctuation caused by the change of the belt thickness among various factors that cause the speed fluctuation of the conveyor belt and the intermediate transfer belt, and corrects the color misregistration. It is to eliminate the deterioration of the image quality of the color image due to.

[0006]

According to the invention of claim 1, an image is directly formed on a transfer sheet placed on an endless conveyor belt, or an image is formed and formed on an endless intermediate transfer belt. In a color image forming apparatus that transfers the formed image to a transfer sheet, the rotational speed of a drive motor for the conveyor belt or the intermediate transfer belt is controlled in response to a change in the thickness of the conveyor belt or the intermediate transfer belt in the length direction. A color image forming apparatus comprising means for

According to a second aspect of the present invention, in the color image forming apparatus according to the first aspect, the means for controlling the rotational speed of the drive motor for the conveyor belt or the intermediate transfer belt is the length of the conveyor belt or the intermediate transfer belt. Means for storing the thickness change data and the reverse thickness change data with respect to the direction, and the reverse thickness change data is read from the storage means for each rotation cycle of the conveyor belt or the intermediate transfer belt, and the conveyor belt based on the data is read. A color image forming apparatus comprising means for outputting a control signal of a drive motor for an intermediate transfer belt.

According to a third aspect of the present invention, in the color image forming apparatus according to the second aspect, the data of the reverse thickness change is read from the storage means for each rotation cycle of the conveyor belt or the intermediate transfer belt, and the conveyance is performed based on the data. The color image forming apparatus is characterized in that the means for outputting the control signal of the drive motor for the belt or the intermediate transfer belt includes means for digitally converting the control signal for the drive motor.

According to a fourth aspect of the present invention, in the color image forming apparatus according to any one of the first to third aspects, the means for controlling the rotational speed of the drive motor for the conveyor belt or the intermediate transfer belt is the conveyor belt or the intermediate belt. Color image formation characterized by detecting a marker provided on the conveyor belt or the intermediate transfer belt during rotation of the transfer belt and starting control of the rotational speed of the drive motor for the conveyor belt or the intermediate transfer belt in conjunction with this detection. It is a device.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram of a main part of a direct transfer type color image forming apparatus according to an embodiment of the present invention. The color image forming apparatus 400 includes four image forming units 101Y, 1 for yellow, magenta, cyan, and black.
This is a tandem type in which 01M, 101C and 101K are continuously arranged in parallel. The image forming unit 101Y for yellow has a charging unit 103Y that uniformly charges the surface of the photosensitive drum 102Y around the photosensitive drum 102Y, and an electrostatic latent image formed on the photosensitive drum 102Y. Developing device 104Y for developing a toner image into a toner image
A transfer unit 105Y for transferring the toner image onto the transfer paper 151, and the photosensitive drum 102 after the transfer of the toner image.
The cleaning unit 106Y and the like collect and store the residual toner remaining on Y. In addition, image forming units 101M and 101 for magenta, cyan, and black
C and 101K also have the same configuration.

Then, an electrostatic latent image of a yellow component color is formed on the photosensitive drum 102Y by the image forming unit 101Y, the electrostatic latent image is developed by the developing device 104Y to form a toner image, and then the toner is formed. Image transfer means 10
The image is transferred onto the transfer paper 151 on the transport belt 201 by 5Y. Then, an electrostatic latent image of magenta component color is formed on the photoconductor drum 102M by the image forming unit 101M, the electrostatic latent image is developed by the developing device 104M to be a toner image, and then the toner image is transferred. Means 105M
Are transferred to the transfer paper 151 in a laminated manner. After that, the same process is sequentially repeated in the image forming units 101C and 101K, and then the fixing roller 107 fixes the toner on the transfer sheet 151 to form a desired color image.

The conveyor belt 201 is a belt drive roller 2
03, is stretched by driven rollers 202 and 307, a marker 211 that reflects light is provided on the back surface, and an optical sensor 310 that detects the marker is installed. Before a series of image formation, the conveyor belt 201 starts running, but when the marker 211 is detected by the optical sensor 310, the above-mentioned image forming step is executed for the first time.
Further, the conveyor belt 201 is connected to a belt drive motor (not shown here), and the rotation speed of this motor is controlled by a belt drive motor controller described later.

FIG. 2 is a schematic view of the essential parts of a color image forming apparatus of the intermediate transfer type. In FIG. 2, the color image forming apparatus 500 includes a paper feed tray that accommodates the transfer paper 151, and transfer rollers 304 and 305 that secondarily transfer the superimposed transfer toner image formed on the intermediate transfer belt 501 onto the transfer paper 151. It has a fixing roller 107 for fixing the secondary-transferred toner image, a plurality of conveying rollers, and the like, and is configured to send out the transfer paper 151 at a predetermined timing and convey it at a constant speed. On the other hand, the image forming units 101Y, 101M, 101C and 101K form an image by an electrostatic copying method, and the photosensitive drums 102Y, 102M and 102 are continuously arranged in parallel.
It is mainly composed of C and 102Bk. The photosensitive drums 102Y, 102M, 102C, 102Bk are surrounded by the photosensitive drums 102Y, 102M, 102B.
Charging means 103 for uniformly charging the surface of C, 102Bk
Y, 103M, 103C, 103Bk and the photosensitive drum 1
02Y, 102M, 102C, 102Bk optical writing means 110Y for forming a required electrostatic latent image according to image information,
110M, 110C, 110Bk and developing devices 104Y, 104M, 104C, 104BK for developing electrostatic latent images
And the photosensitive drums 102Y, 102M, 102 after development.
Cleaning means 106Y, 106M, 106C, 106Bk for cleaning toner remaining on C, 102Bk
Are arranged. That is, the color image forming apparatus is a tandem type in which the image forming units are continuously arranged in parallel, and the printing speed is increased and the apparatus is made compact.

Further, the photosensitive drums 102Y, 102M,
Immediately below 102C and 102Bk, the intermediate transfer belt 501
With respect to the photoconductor drums 102Y, 102M, 102C,
Primary transfer means 105Y, 105M, 105C, and 105Bk that primarily transfer the visualized toner image are arranged on 102Bk. The intermediate transfer belt 501 is an endless belt having a medium resistivity.

The operation of the image forming apparatus will be described. Based on the recorded information, the optical writing means 110Y, 11
At 0M, 110C and 110Bk, light is modulated and emitted corresponding to each reproduced color. On the other hand, the photosensitive drum 10
2Y, 102M, 102C and 102Bk rotate at a constant speed in the direction of the arrow in the figure, and charging means 103Y, 1
The surface is uniformly charged by 03M, 103C and 103Bk, and then exposed and scanned by the optical writing means. By this exposure, the photoconductor drums 102Y, 102M, 10
The electrostatic latent image corresponding to each reproduced color formed on 2C and 102Bk is a developing device 104Y containing toner of each reproduced color,
The toner image of each color is developed by 104M, 104C and 104BK. These toner images are formed on the photosensitive drums 102Y, 102M, 102C, 10
2Bk and the intermediate transfer belt 501 facing each other, 1
The next transfer means 105Y, 105M, 105C, and 105Bk successively transfer the images onto the intermediate transfer belt 501.

The intermediate transfer belt 501 is stretched by a belt driving roller 203, a transfer roller 304, and a driven roller 202, a marker 211 that reflects light is provided on the back surface, and an optical sensor 310 that detects the marker is installed. ing. Before a series of image formation, the intermediate transfer belt 501
Starts running, but the marker 211 is the optical sensor 31.
When detected by 0, the above-mentioned image forming process is executed for the first time. Further, the intermediate transfer belt 501 is connected to a belt drive motor (not shown), and the rotation speed of this motor is controlled by a belt drive motor control device 600 described later.

The toner image superposedly transferred onto the intermediate transfer belt 501 is conveyed to a portion facing the transfer roller pair 304, 305. Then, the toner image on the intermediate transfer belt 501 is secondarily transferred by the transfer roller pair 304 and 305 onto the transfer paper 151 fed from the paper feed tray. After that, the transfer paper 151 to which the toner image is transferred is conveyed to the fixing roller 107 and heated there to melt the toner image of each color to obtain a full-color image.

In the color image forming apparatus, considering the mechanical factors of the speed fluctuations of the conveyor belt and the intermediate transfer belt, there is a factor due to the deviation of the thickness of the conveyor belt and the intermediate transfer belt. In addition to the above, there may be eccentricity of the driving roller and eccentricity of the driving member of the roller, for example, gears. Here, the deviation of the belt thickness will be considered. It is desirable that the transport belt and the intermediate transfer belt have a uniform thickness over the entire circumference. However, in manufacturing, a thick portion t1 and a thin portion t2 are nonuniform (FIG. 3).
reference). Since the belt speed V is determined by V = NR (N: drive roller rotation speed, R = driving radius), the belt speed changes when R changes even when the rotation speed is constant. Therefore, the driving radius becomes R = r + 1 / 2t (r: radius of driving roller, t: belt thickness) (see FIG. 4), and when the belt thickness t is not uniform between t1 and t2, the conveyor belt, The speed of the intermediate transfer belt is not constant and causes fluctuation.

FIG. 5 is a diagram showing a change in the length of one belt with respect to the thickness when the endless conveyor belt or the intermediate transfer belt is unfolded in the circumferential direction. In the figure, the thickness t2 with respect to the reference thickness t.
It shows a change from (= + δt) to t1 (= −δt).
This change can be obtained by actual measurement, and the actual value is that there is a deviation of about ± 5 μm from t = 100 μm.

Such a relationship can be obtained as the belt speed (mm / sec) when the driving radius (belt thickness) changes in one belt revolution time, and the state of the change is shown by the curve A in FIG. As shown, the thickness increases with respect to the reference thickness t, and the thickness decreases from the direction toward δt −.
It is represented as a curve represented by a parameter in the direction toward δt. Therefore, in order to correct the speed fluctuation due to the change of the driving radius, the characteristic has the opposite characteristic to the curve A, that is, the reference thickness t.
With respect to the data shown by the curve B (inverse thickness change data), which is symmetric with respect to the x-axis and is expressed by the parameter from the direction of decreasing the thickness to −δt and the direction of increasing the thickness to + δt, A constant speed can be obtained by controlling the rotation speed of the drive motor.

FIG. 7 is a block diagram of the belt drive mechanism.
In the figure, the belt drive motor 205 is a drive transmission gear 20.
The rotation is transmitted to the belt driving roller 203 via 6, 204. Therefore, the rotation speed of the belt drive motor 205 is drive-controlled based on the data.

FIG. 8 is a block diagram showing the drive control of the belt drive motor. In FIG. 8, the data input unit 601 of the belt drive motor control device 600 is a parameter from the direction toward + δt where the thickness is thicker than the reference thickness t of the conveyor belt to the direction where −δt where the thickness is thinner. With respect to the characteristic represented by, the data of the characteristic represented by the parameter in the direction from −δt where the thickness becomes thin with respect to the reference thickness t to + δt where the thickness becomes thick is stored. Before a series of image formation, the transport belt or the intermediate transfer belt starts to run, but the marker 211 is set to the optical sensor 310.
At the same time or at a predetermined timing, the control circuit 602 reads out the data and drives the drive circuit 603 when detected by. The drive circuit 603 transmits a drive signal controlled by the data to the encoder 604, and the encoder 604 converts the drive signal into a digital signal and connects the belt drive roller 203 to the belt drive motor 20.
5 to control the rotation speed of the motor. At this time, the encoder 604 outputs the final signal based on the data to the control circuit 6
By returning to 02, the data is read again after one round of the belt, and the same operation is repeated.

According to this embodiment, the belt drive motor 2
When controlling 05, the program is executed at an arbitrary timing, and if the belt position and the motor rotation speed control start timing are deviated, the speed fluctuation correction becomes unsuccessful. However, in the conveyance belt 201 or a part of the intermediate transfer belt 501. A marker 211 is provided, and when this marker is detected by the optical sensor 310, data reading is executed at the same time or at a fixed timing, and the rotation speed of the motor is controlled by a digital signal. It can be lost.

[0024]

The effect corresponding to the invention of claim 1 is a method of directly forming an image on a transfer sheet placed on an endless transfer belt, or an image formed by forming an image on the endless transfer belt. In a color image forming apparatus of the type in which a sheet is transferred to a transfer sheet, it is possible to correct a speed variation caused by a change in the thickness of the transport belt or the transfer belt, and eliminate a deterioration in image quality of a color image due to a color shift. Effects corresponding to the inventions of claims 2 and 3: Since no special speed detecting device such as the speed detecting pickup roller is used, the device for correcting the speed fluctuation can be simply configured. Effect corresponding to claim 4 of the invention: Since the speed fluctuation correction can always be performed at accurate timing, it is possible to eliminate the deviation of the speed fluctuation correction due to the timing deviation.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of a direct transfer type color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a main part of an intermediate transfer type color image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing a change in thickness of a conveyance belt or an intermediate transfer belt in a length direction.

FIG. 4 is a diagram illustrating a change in belt speed with respect to a change in driving radius.

FIG. 5 is a diagram showing a change of a belt circumference length versus a thickness when a conveyance belt or an intermediate transfer belt is developed in a circumferential direction.

6A and 6B are diagrams showing a belt speed change diagram with respect to one round time of a conveyor belt or a transfer belt and a diagram symmetrical to the belt speed change diagram.

FIG. 7 is a configuration diagram of a transport belt or transfer belt drive mechanism.

FIG. 8 is a block configuration diagram of a belt drive motor control device.

[Explanation of symbols]

201 ··· Conveyor belt, 202 · · Driven roller, 203 · · Belt drive roller, 204 · · Drive transmission gear, 205 · · Belt drive motor, 211 · · Marker, 304 · · Transfer roller, 305 · · Transfer roller, 307, driven roller, 310
..Optical sensor, 501..Intermediate transfer belt, 600..Belt drive motor controller

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H030 AA01 AB02 AD16 BB02 BB21                       BB42 BB43 BB56                 2H200 FA04 GA12 GA23 GA33 GA44                       GA47 GB12 GB25 GB41 HA00                       HA02 HA28 HB12 HB22 JA02                       JB06 JB10 JB49 JB50 JC03                       JC19 JC20 LA12 LA27 PA11                       PB25

Claims (4)

[Claims] 1. A color method in which an image is directly formed on a transfer sheet placed on an endless conveyor belt, or an image is formed on an endless intermediate transfer belt and the formed image is transferred to the transfer sheet. In the image forming apparatus, a color is provided, which includes means for controlling the number of rotations of a drive motor for the conveyor belt or the intermediate transfer belt in response to a change in thickness of the conveyor belt or the intermediate transfer belt in the longitudinal direction. Image forming apparatus. 2. The color image forming apparatus according to claim 1, wherein the means for controlling the number of rotations of the drive motor for the conveyor belt or the intermediate transfer belt changes the thickness of the conveyor belt or the intermediate transfer belt in the longitudinal direction. Means for storing data and data for reverse thickness change, and data for reverse thickness change read from the storage means for each rotation cycle of the conveyor belt or intermediate transfer belt and driving of the conveyor belt or intermediate transfer belt based on the data A color image forming apparatus comprising means for outputting a motor control signal. 3. The color image forming apparatus according to claim 2, wherein the data of the reverse thickness change is read from the storage means for each rotation cycle of the conveyor belt or the intermediate transfer belt, and the conveyor belt or the intermediate transfer belt based on the data is read. 2. The color image forming apparatus according to claim 1, wherein the means for outputting the control signal for the drive motor includes means for converting the control signal for the drive motor into a digital signal. 4. The color image forming apparatus according to claim 1, wherein the means for controlling the rotation speed of the drive motor for the conveyor belt or the intermediate transfer belt is at the time of rotation of the conveyor belt or the intermediate transfer belt. A color image forming apparatus, which detects a marker provided on a conveyor belt or an intermediate transfer belt, and starts controlling the number of rotations of a drive motor for the conveyor belt or the intermediate transfer belt in conjunction with the detection.