JPH10268595A - Belt driving device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of forming a high-quality image having no color slurring, no irregular color and no unseemly stripe pattern by restraining the impactive vibration of an intermediate transfer belt by external force so that the intermediate transfer belt can stably travel. SOLUTION: When recording paper P passes through a secondary transfer fixing part 3a, impactive force acts on the intermediate transfer belt 3 (belt tensioning side span 3b and belt loosening side span 3C), so that the tensile force of the belt is suddenly increased on a belt tensioning side and the tensile force of the belt is suddenly decreased on a belt loosening side. Therefore, the impactive vibration is caused in a belt rotating direction. By preventing the tensile force of the belt on the belt tensioning side from being increased by a 1st tensile force fluctuation absorption means 4A and the tensile force of the belt on the belt loosening side from being decreased by a 2nd tensile force fluctuation absorption means 4B, the fluctuation of the tensile force of the belt 3 is restrained and the vibration of the belt 3 is absorbed.

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 for driving an endless belt stretched over a plurality of rollers including a driving roller, and uses the endless belt for a photoreceptor belt, an intermediate transfer belt, a paper transport belt, and the like. Electrophotographic copier,
The present invention relates to an image forming apparatus such as an electrophotographic printer, an ionography printer, an ink jet printer, and a facsimile apparatus, and more particularly, to a belt driving device and an image forming apparatus that suppress impact vibration.

[0002]

2. Description of the Related Art In a belt driving device for driving an endless belt stretched over a plurality of rollers, it is an important issue to run the endless belt at a stable speed, and in particular, various kinds of deterioration with time and temperature change. It is a fundamental problem to absorb the elongation and the slack generated in the endless belt due to a change in the use condition such as the above.

[0003] As a conventional belt driving device aiming at solving such a problem, for example, Japanese Patent Application Laid-Open No. Sho 61-2898 is disclosed.
Japanese Patent Publication No. 7-No. This belt driving device has an endless belt stretched over one driving roller and a plurality of driven rollers, and one tension roller is freely rotatable on a belt slack side (downstream of the driving roller) of the endless belt. The tension roller is in contact with and is displaceably supported by an elastic member.

In this belt driving device, if the endless belt is stretched or slack due to deterioration over time or temperature change and the belt tension on the slack side of the belt is to be reduced, the tension roller is displaced and the tension on the slack side of the belt is reduced. Suppress the drop. As a result, the extension and slack of the endless belt can be absorbed.

[0005] As another image forming apparatus to which a conventional belt driving device aiming at solving such a problem is applied,
For example, there is one disclosed in JP-A-5-224572.

FIG. 9 shows this image forming apparatus 10, in which a transfer backup roller 11A and a transfer pinch roller 11B, an idler roller 12, a steering roller 13, a plurality of backup rollers 14, a drive roller 15, And a belt photoreceptor 16 stretched over first and second tension rollers 17 and 18, and the first tension roller 17 on both sides of the transfer unit 11 serving as a disturbance source based on the supply of the recording medium has solid lines. Two-way arrow 1
The second tension roller 18 is movably supported in the direction of 7a, and is movably supported in the direction of the solid bidirectional arrow 18a, and is in contact with the belt photoreceptor 16. Further, the image forming apparatus 10 transfers the first tension roller 17 based on the detection of the position sensor 19 for detecting the position of the first tension roller 17 so that the first tension roller 17 is maintained at substantially the same position. A speed servo control circuit 20 for controlling the speed of the backup roller 11A, and a plurality of write heads 21 for forming latent images of respective colors on the belt photoconductor 16
And

In the image forming apparatus 10, the transfer unit 1
When the recording medium is fed into the transfer nip formed between the transfer backup roller 11A and the transfer pinch roller 11B, a braking force for stopping the movement of the belt photoconductor 16 is generated, and the belt tension side is generated. , The belt tension on the belt slack side tends to decrease sharply. When the belt tension on the belt tension side increases,
The displacement of the second tension roller 18 is suppressed, and when the belt tension on the belt slack side decreases, the position sensor 19
Detects the displacement of the first tension roller 17, the speed servo control circuit 20 increases the rotation speed of the transfer backup roller 11A to suppress a decrease in the belt tension, and maintains the first tension roller 17 at a fixed position. .

On the other hand, as a color image forming apparatus based on electrophotography, an apparatus provided with a heat-transfix type transfer fixing section in which a fixing section is integrated with a transfer section of an intermediate transfer belt is effective for high image quality and miniaturization. It is increasingly used as a thing.

In such a color image forming apparatus, image information separated into colors such as cyan, magenta, yellow, and black is written on a charged drum photoreceptor or the like and recorded as an electrostatic latent image. This is developed with each color toner. The toner image developed with each color toner is 1
The next transfer is superimposed on the intermediate transfer belt. The transferred toner image is transferred and fixed on the recording paper by the transfer fixing unit in the secondary transfer fixing step. According to the thermal transfix type transfer fixing unit, since the surface of the toner is clean and smooth, the same image quality as that obtained by printing is obtained, and since the fixing device is integrated,
There is an advantage that the size can be reduced.

In a color image forming apparatus provided with a transfer fixing unit, it is necessary to perform transfer fixing while bringing a recording sheet into contact with an intermediate transfer belt at a relatively high pressure. For this reason, when the recording paper enters the transfer fixing section, a braking force is generated to stop the belt running at the transfer fixing section, and the belt tension on the belt tension side rapidly increases, and the belt on the belt slack side is increased. The tension decreases sharply. As a result, impulsive vibration occurs in the belt, and the vibration propagates through the belt and is transmitted to the photoconductor during image formation or during primary transfer, causing local image deterioration. Also, when the recording paper comes off from the transfer / fixing section, a vibration phenomenon occurs due to the release of the braking force, which similarly causes image deterioration. For this reason, "color misregistration" that causes misregistration between the colors occurs, "color unevenness" that slightly changes the color tone, and very ugly stripes occur in the background color. There is a problem that various image deteriorations such as fraying are caused. Thus, the photoreceptor belt including the intermediate transfer belt,
It is important to suppress a vibration phenomenon of an image forming belt such as a paper transport belt.

[0011]

However, Japanese Patent Application Laid-Open No.
According to the conventional belt driving device disclosed in Japanese Patent No. 28987, even if the tension roller provided on the slack side of the belt is displaced to suppress the decrease in the belt tension on the slack side of the belt, the increase in the belt tension on the tight side of the belt is suppressed. Therefore, the belt tension on the belt tension side propagates to the belt slack side and cannot suppress the vibration phenomenon of the belt.For example, the impact generated when a transfer fixing unit having a high nip pressure is provided is provided. It is difficult to absorb such vibrations.

Further, according to the conventional image forming apparatus 10 disclosed in Japanese Patent Application Laid-Open No. 5-224572, the position of the tension roller 17 which is about to be displaced in response to a change in tension is detected, and the speed of the transfer backup roller 11A is reduced. Since the control is performed, the number of control parameters increases, the configuration becomes complicated, and a factor of speed fluctuation is given to the photoreceptor belt 16, and as a result, color unevenness may occur.

Accordingly, it is a first object of the present invention to provide a belt drive device capable of suppressing the impact vibration of the endless belt due to an external force and enabling the endless belt to run stably. Further, a second object of the present invention is to suppress a shocking vibration of an image forming belt such as a photoreceptor belt, an intermediate transfer belt, and a paper transport belt due to an external force, thereby enabling a stable running of the image forming belt. Another object of the present invention is to provide an image forming apparatus capable of forming a high-quality image having no color shift, uneven color, or ugly stripes.

[0014]

To achieve the first object, the present invention provides an endless belt stretched by a plurality of rollers including a driving roller at a predetermined speed in a predetermined direction by the driving roller. In the belt driving device, which conveys, the external force applied to the external force action point of the endless belt decreases or increases on the slack side of the endless belt with respect to the drive roller, and the tension fluctuation increases or decreases on the tight side. The slack side and the tension side are disposed in contact with the endless belt, and the slack side increases or decreases the transport route length of the endless belt, and the stretch side decreases or increases the transport route length. A first means for absorbing the fluctuation of the tension and maintaining a constant tension on at least one of the slack side and the tension side of the endless belt. Providing a belt driving apparatus characterized by having a spare second tension fluctuation absorbing means.

In order to achieve the second object, the present invention provides an image forming apparatus comprising: an endless photosensitive belt stretched by a plurality of rollers including a driving roller; An image forming apparatus that conveys at a speed and generates a tension fluctuation that decreases or increases on the slack side of the photosensitive belt and increases or decreases on the tight side with respect to the drive roller by the transfer operation of the transfer unit of the photosensitive belt. A support roller that supports the photosensitive belt on the slack side or the tension side and forms an image bearing area on the photosensitive belt where an image bearing operation is performed with the drive roller; and the support roller. The slack side and the tension side between the transfer belt and the transfer unit are disposed in contact with the photoreceptor belt, and the transport route length of the photoreceptor belt is increased on the slack side. A first and a second to reduce or increase the transport route length on the tension side to absorb the fluctuation of the tension and maintain a constant tension of at least the image bearing area of the photosensitive belt. An image forming apparatus having tension fluctuation absorbing means is provided.

In order to achieve the second object, the present invention provides a method for forming an endless paper transport belt stretched by a plurality of rollers including a driving roller in a predetermined image forming direction by the driving roller in a predetermined image forming direction. The recording medium is conveyed at a speed such that the recording medium is released from the release position of the paper conveyance belt by the traction force of the fixing unit on the paper conveyance belt, and the recording medium decreases or increases on the slack side of the paper conveyance belt with respect to the drive roller. An image forming apparatus that generates a tension fluctuation that increases or decreases on the tension side, supports the paper transport belt on the slack side or the tension side, and transfers a toner image to the recording medium between the driving roller and the driving roller. A support roller for forming a toner image transfer area on the paper transport belt; and the slack between the support roller and the release position. Side and the tension side are arranged in contact with the paper transport belt, by increasing or decreasing the transport route length of the paper transport belt on the slack side, and decreasing or increasing the transport route length on the tension side There is provided an image forming apparatus including first and second tension fluctuation absorbing means for absorbing the fluctuation in tension and maintaining the tension of at least the toner image transfer area of the sheet conveying belt constant.

In order to achieve the second object, the present invention provides a method for forming an endless intermediate transfer belt stretched by a plurality of rollers including a driving roller in a predetermined image forming direction by the driving roller in a predetermined image forming direction. The intermediate transfer belt is conveyed at a speed and decreases or increases on the slack side of the intermediate transfer belt with respect to the driving roller by the secondary transfer operation or the secondary transfer fixing operation of the secondary transfer portion of the intermediate transfer belt, and increases or decreases on the tight side. In the image forming apparatus which generates a decrease in tension fluctuation, the intermediate transfer belt is supported on the slack side or the tension side, and a toner image transfer area where a toner image is transferred between the intermediate transfer belt and the driving roller is formed on the intermediate transfer belt. A support roller formed on the intermediate transfer belt and disposed on the slack side and the tension side between the support roller and the secondary transfer unit; By increasing or decreasing the conveyance route length of the intermediate transfer belt on the slack side, and reducing or increasing the conveyance route length on the tension side, the tension fluctuation is absorbed to absorb at least the toner of the intermediate transfer belt. First to keep the tension of the image transfer area constant
And an image forming apparatus having a second tension fluctuation absorbing means.

[0018]

FIG. 1 is a schematic diagram of a color image forming apparatus to which a belt driving device according to an embodiment of the present invention is applied. The color image forming apparatus 100 is of a tandem type using the intermediate transfer belt 3, and includes a transparent document table 101 such as a platen glass on which a document (not shown) is placed, and a document table 101 on the document table 101. An image reading unit 102 that optically scans a placed document to read image data from the document, and converts the image data read by the image reading unit 102 into color image data of each color (black, yellow, magenta, and cyan). An image processing unit 103 that decomposes and performs predetermined image processing on each color image data; and a first unit that transfers a black (K) toner image based on each color image data after the image processing by the image processing unit 103. An image forming unit 110, a second image forming unit 120 for transferring a yellow (Y) toner image, and a third image for transferring a magenta (M) toner image Forming unit 1
30, a fourth image forming unit 140 for transferring a cyan (C) toner image, and each image forming unit 110, 1
A plurality of rollers (a driving roller 2A, a driven roller 2B, a leveling roller 2C, a first tension roller 2D, a second tension roller 2E, and a secondary transfer fixing roller 154A) are provided below 20, 20, and 140. A belt driving device 1 that drives the stretched endless intermediate transfer belt 3 and a secondary transfer fixing unit (a nip between the secondary transfer fixing rollers 154A and 154B) 3a on the intermediate transfer belt 3
, A registration roller 151 for feeding the recording paper P to the secondary transfer fixing unit 3a at a predetermined timing, and a secondary transfer fixing roller 154A around which the intermediate transfer belt 3 is stretched. And a secondary transfer fixing roller that is arranged to face the intermediate transfer belt 3 with the toner image primary-transferred to the intermediate transfer belt 3 and collectively secondary-transfers the toner image onto the recording paper P, and also fixes and discharges the toner image to a tray (not shown). 154B and a neutralizer 155 for neutralizing the intermediate transfer belt 3
And a cleaner 15 for cleaning the surface of the intermediate transfer belt 3
6 and a main control unit (not shown) for controlling the entire image forming apparatus 100.

Each image forming unit 110, 120, 13
Reference numerals 0 and 140 denote a photosensitive drum 111 and an exposure charger 11 for applying a predetermined charge to the photosensitive drum 111 before exposure.
2, an exposure section 113 for exposing the photosensitive drum 111 with a laser beam modulated based on the corresponding color image data to form an electrostatic latent image, and an electrostatic latent image formed on the photosensitive drum 111. Corresponding color (K, Y, M, C)
A developing unit 114 for developing with the toner of the type described above, a transfer charger 115 arranged at the primary transfer position of the toner image to apply a predetermined charge, a cleaner 116 for removing the toner remaining on the photosensitive drum 111, A static eliminator 117 for neutralizing the drum 111;

FIG. 2 shows the belt driving device 1. The belt driving device 1 is provided on a belt tension side span 3b between the driving roller 2A and the secondary fixing transfer roller 154A, and a first tension fluctuation absorbing unit 4A that absorbs vibration of the intermediate transfer belt 3; A belt slack side span 3c between the driving roller 2A and the secondary fixing transfer roller 154A,
Second tension fluctuation absorbing means 4B for absorbing the vibration of the intermediate transfer belt 3, a rotation drive mechanism 5 for rotating and driving the drive roller 2A, and a belt drive control unit 6 for controlling the drive of the belt 3
And

The first tension fluctuation absorbing means 4A is provided on both sides of the tension roller 2D and the tension roller 2D, and has a predetermined spring constant to press the tension roller 2D against the belt 3, rubber, etc. Elastic member 2d
d. Second tension fluctuation absorbing means 4B
Like the first tension fluctuation absorbing means 4A, the tension roller 2E is provided on both sides of the tension roller 2E.
An elastic member 2ee such as a spring or rubber for pressing E against the belt 3.
It is composed of The first and second tension fluctuation absorbing means 4A and 4B absorb the vibration energy of the belt 3 to reduce the fluctuation of the belt tension. Therefore, the tension rollers 2D and 2E have a structure that is as light as possible. It preferably has a small moment of inertia. For the same reason, the elastic members 2dd and 2ee have as small a rigidity as possible and have a predetermined spring constant so that a sufficient pressing force can be applied to the belt 3.

The rotation drive mechanism 5 includes a first inertia 50 attached to one shaft end 2aa of the drive roller 2A.
A and a second inertia 50B attached to a secondary transfer fixing roller 154A on which the intermediate transfer belt 3 is stretched.
A rotation number detector 51 such as a rotary encoder attached to the shaft end 2aa and detecting the rotation number of the drive roller 2A; and a drive motor 52 for rotatingly driving the drive roller 2A.
And a winding transmission mechanism 53 for transmitting the driving torque of the driving motor 52 to the driving roller 2A. The winding transmission mechanism 53 includes a large pulley 53a attached to one shaft end 2aa of the drive roller 2A, a small pulley 53b attached to an output shaft of the drive motor 52, and both pulleys 53a.
a and a timing belt 53c wound between 53a and 53b.

The first inertia 50A attached to the shaft end 2aa of the drive roller 2A has a function of smoothing a high frequency rotation speed fluctuation generated by a drive system gear or the like, and also performs secondary transfer fixing. The second inertia 50B attached to the roller 154A has an effect of smoothing a high-frequency rotation speed fluctuation generated when the recording sheet P passes through the nip between the secondary transfer fixing rollers 154A and 154B. ing. In particular, these inertia 50A, 50A are used to smooth the speed fluctuation at a high frequency (for example, 20 Hz or more) which cannot be corrected by the feedback control.
B is necessary. Also, low frequency fluctuations generally result in large displacements, so feedback control is an effective method to suppress them. However, the first and second inertia 50A, 50
B needs to be designed in a well-balanced manner with the control parameters in order to avoid the resonance point, but this can be sufficiently achieved by a so-called control design, which is a conventional technique.

The belt drive controller 6 includes a rotation speed detector 51
The belt drive control is performed so that the belt 3 runs at a predetermined speed by performing feedback control of the rotation speed of the drive motor 52 based on the rotation speed detection signal from the motor.

Next, the operation of the color image forming apparatus 100 will be described. (1) Overall Operation When a main control unit (not shown) inputs a belt drive start signal to the belt drive control unit 6, the belt drive control unit 6 drives the drive motor 52 to start traveling of the intermediate transfer belt 3. , The belt 3 is controlled so that the belt 3 runs at a predetermined speed. When the image reading unit 102 scans an original and reads image data, the image processing unit 103 performs color separation on the image data read by the image reading unit 102 and performs predetermined image processing on the color-separated image data. Is applied. Exposure unit 1 of each image forming unit 110, 120, 130, 140
Reference numeral 13 exposes the photosensitive drum 111 charged by the exposure charger 112 to a laser beam corresponding to image data of each color by the image processing unit 103 to form an electrostatic latent image. The developing device 114 develops the electrostatic latent image formed on the photosensitive drum 111 with toner corresponding to each color. When the photosensitive drum 111 rotates and the developed toner image is carried to the primary transfer position, the toner image of each color is sequentially transferred onto the intermediate transfer belt 3 by the charge provided by the transfer charger 115, and the full-color toner It becomes an image. The intermediate transfer belt 3 on which the final toner image has been transferred is a secondary transfer fixing unit 3
a, the recording paper P sent from a paper feeding device (not shown) and waiting at the registration rollers 151 is rotated by a predetermined timing when the registration rollers 151 rotate at a predetermined timing. Transported to On the recording paper P, the toner image is
After being transferred and fixed by the next transfer / fixing rollers 154A and 154B, the sheet is discharged to a discharge tray (not shown). In this way, a full-color image is copied. After the transfer, the intermediate transfer belt 3 is neutralized by a neutralizer 155 and cleaned by a cleaner 156.

(2) Operation for Suppressing Vibration Due to Impulsive Disturbance FIGS. 3A and 3B are diagrams for explaining the operation of the belt driving device 1. FIG. 3A shows the recording paper P entering the secondary transfer fixing unit 3a. FIG. 5B shows the time, and FIG.
It is a figure which shows the time of exiting from. When the recording paper P enters the nip portion between the secondary transfer fixing rollers 154A and 154B, the secondary transfer fixing roller 1 to which a high pressing force is applied is applied.
54A and 154B exert a force to separate them from each other. With this force, a sudden braking force acts on the running of the belt 3. On the other hand, the drive roller 2A tends to continue to rotate normally by the feedback control. For this reason, the belt tension on the belt tension side 3b between the driving roller 2A and the secondary transfer fixing roller 154A sharply increases, and
The belt tension of the belt slack side span 3c between the driving roller 2A and the secondary transfer fixing roller 154A sharply decreases. Also, the phenomenon of a sudden increase in belt tension in the belt tension side span 3b caused by the entry of the recording paper P into the nip portion always has a balance point, so the direction must be changed somewhere and the direction will be reversed at the next moment. A large force will act on it. During this time, the driving roller 2A continues to drive the belt 3 normally, so that the belt slack side span 3c
In this case, a phenomenon occurs in which the belt tension decreases and the moving speed rapidly decreases. Of course, since such a tension phenomenon always has a balance point, as in the case of the belt tension side span 3b, the direction always changes somewhere, and the force acts in the opposite direction at the next moment. Therefore, the first and second
If the tension fluctuation absorbing means 4A, 4B is not provided or is not disposed at an appropriate position, the speed of the belt 3 is suddenly suddenly reduced at the belt slack side span 3c, and the reaction of Then, a vibration phenomenon occurs in which the speed of the belt 3 is returned to temporarily increase. The above phenomenon is caused by the fact that the leading edge of the recording paper P is
When the recording paper P enters the nip portion between the rollers 154B and 154B, it occurs in a step response manner.
During the nip, the roller 154A and 154B are stabilized in a state where a force for pushing and spreading the roller is applied. Therefore,
As in the present invention, the first and second tension fluctuation absorbing means 4
By providing A and 4B, as shown in FIG.
The tension roller 2D of the first tension fluctuation absorbing means 4A disposed in the belt tension side span 3b is displaced rightward in the figure to prevent the belt tension in the belt tension side span 3b from increasing and to loosen the belt. The tension roller 2E of the second tension fluctuation absorbing means 4B disposed in the side span 3c is displaced in the lower right direction in the drawing to prevent a decrease in belt tension. As a result, the vibration of the belt 3 is absorbed, and the position fluctuation of the belt 3 is reduced.

On the other hand, when the recording paper P is
In the case of slipping out of the nip portion between 54A and 154B, as shown in FIG. 3 (b), the load suddenly decreases, so that the tension roller 2 of the first tension fluctuation absorbing means 4A.
D is displaced to the left in the figure and the elastic strain energy stored in the elastic member spring 2dd is rapidly released.
The moving speed of the belt 3 about the secondary transfer fixing roller 154A tends to increase rapidly. Naturally, at the next moment, a so-called vibration phenomenon, which suddenly slows down, occurs. However, as shown in FIG. 3 (b), the tension roller 2E of the second tension fluctuation absorbing means 4B is displaced in the upper left direction in FIG. 3 to attempt to absorb the energy released by the first tension fluctuation absorbing means 4A. Therefore, the belt tension of the slack side span 3c is kept constant, and the speed thereof is also kept constant.

Next, effects of the image forming apparatus 100 will be described with reference to the drawings.

FIGS. 4 and 5 show the measurement results of the comparative example. This comparative example has a configuration in which the second inertia 50B and the second tension fluctuation absorbing means 4B are removed from the configuration shown in FIG. FIG. 4 shows the results of measuring the speed fluctuation occurring in the belt slack side span 3b when the recording paper P enters and exits the transfer fixing unit 3a.
FIG. 5 shows a measurement of a positional change occurring in the belt slack side span 3b when the recording paper P enters and leaves the transfer fixing unit 3a. In FIG. 4, the vertical axis represents the speed fluctuation dv / V (%) in the belt running direction, and the horizontal axis represents time (s). In FIG. 5, the vertical axis represents the position variation dx (mm) in the belt running direction, and the horizontal axis represents time (s). 4 and 5, the spike-like impact that appears first is when the recording paper P enters, and the spike-like impact that appears next is when the recording paper P comes out. From FIG. 4, it can be seen that the speed variation at the time of entry and exit is about 2%, and from FIG. 5, the position variation at the time of entry and exit is about 0.04 mm.

FIGS. 6 and 7 show the measurement results of the apparatus according to the present invention. This device has a second configuration in the configuration of the comparative example.
Is added to the inertia 50B. FIG. 6 shows the speed fluctuation as in FIG. 4, and FIG. 7 shows the position fluctuation as in FIG. From FIG. 6, it can be confirmed that the spike-like speed fluctuation at the time of entry and exit is greatly attenuated to 1%, and the frequency is greatly reduced. From FIG. 7, it can be seen that the frequency of the position change is also greatly reduced, but the magnitude of the position change does not change much unlike the case of the speed.

FIG. 8 shows the measurement results of the apparatus 1 of FIG.
This is a measurement of the position variation as in FIG. From FIG. 8, the position fluctuation is about 0.3 μm, which is two orders of magnitude smaller than that of the comparative example in FIG. 5, and the spike-like vibration generated when the recording paper P enters or exits is completely eliminated. You can see that you can do It should be noted that even in the configuration in which the second inertia 50B is removed from the device 1 of FIG.
A result similar to that of FIG. 8 is obtained.

(A) Since the tension fluctuation absorbing means 4A and 4B are provided on the tension side and the slack side of the belt 3, respectively, it is possible to suppress an impulsive position fluctuation and to prevent a color shift or the like. it can. (B) By adding inertia 50A and 50B,
High-speed fluctuations in speed can be suppressed, and color unevenness and stripes can be prevented. (C) By the feedback control of the driving roller 2A, steady position fluctuations can be suppressed, and color misregistration can be further prevented in combination with the tension fluctuation absorbing means 4A, 4B. (D) Since a color shift, color unevenness, stripe pattern, and the like can be prevented, a good full-color image can be formed. (E) The second tension fluctuation absorbing means 4B mainly absorbs the shocking vibration of the belt 3 in the belt slack side span 3c. Since the impact vibration of the belt 3 can be isolated without being transmitted to the photosensitive drum 111 by the second tension fluctuation absorbing means 4B, the impact vibration is applied to the image formed on the photosensitive drum 111. The effect can be reduced. (F) Tension rollers 2D, 2E and elastic members 2dd, 2
Since the tension fluctuation absorbing means 4A and 4B made of ee are provided and the inertia 50A and 50B are simply added, it is possible to prevent color shift, color unevenness, and the like without increasing the size and complexity of the image forming apparatus 100. .

The present invention is not limited to the above embodiment, but various embodiments are possible. For example, the present invention may be applied to an image forming apparatus using the belt 3 shown in FIG. 1 as a photoreceptor belt or a sheet conveying belt. In the case of an image forming apparatus using the belt 3 shown in FIG. 1 as a paper transport belt, the recording paper electrostatically attracted to the paper transport belt is transported to a toner image transfer area, and a toner image is formed on the recording paper in the toner image transfer area. After the transfer, the recording paper is conveyed to the fixing unit by the paper conveyance belt.However, depending on the size of the recording paper, when the leading edge of the recording paper reaches the fixing unit, or when the rear end of the recording paper is on the paper conveyance belt There is. In this case, since the sheet feeding speed of the fixing unit is faster than the rotation speed of the sheet conveying belt, the traction force of the fixing unit acts on the sheet conveying belt as an external force. Even in such a case, by arranging the first and second tension fluctuation absorbing means 4A and 4B at predetermined positions, it is possible to absorb shocking vibration due to external force. Also, the first to fourth image forming units 11
0, 120, 130 and 140 are arranged on the slack side of the belt between the drive roller 2A and the second tension fluctuation absorbing means 4B.
It may be arranged on the belt tension side between the driving roller 2A and the first tension fluctuation absorbing means 4A.

[0034]

As described above, according to the belt driving device of the present invention, even if an impact force is applied to the endless belt by an external force, the belt tension side and the belt tension side are absorbed by the first and second tension fluctuation absorbing means. Since the vibration is absorbed by reducing the tension fluctuation on the slack side, the endless belt can run stably.

According to the image forming apparatus of the present invention, even if an impact force acts on the photoreceptor belt due to the transfer operation, the first and second tension fluctuation absorbing means provide a belt tension side and a belt slack side. Since the vibration is absorbed by reducing the tension fluctuation, the photosensitive belt can run stably, and a high-quality image free from color shift, color unevenness, and ugly stripes can be obtained.

Further, according to the image forming apparatus of the present invention, even if an impulsive force acts on the paper transport belt due to the pulling force of the fixing unit, the belt tension side and the belt slack are absorbed by the first and second tension fluctuation absorbing means. Since the fluctuation in the tension on the side is reduced to absorb the vibration, the paper transport belt can run stably, and a high-quality image free from color shift, color unevenness, and ugly stripes can be obtained.

According to the image forming apparatus of the present invention,
Even if an impulsive force acts on the intermediate transfer belt by the next transfer operation or the secondary transfer fixing operation, the first and second tension fluctuation absorbing means reduce the tension fluctuation on the belt tension side and the belt slack side to vibrate. As a result, the intermediate transfer belt can run stably, and a high-quality image having no color shift, uneven color, or ugly stripes can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is a perspective view of a belt driving device according to the present invention.

3A and 3B are diagrams for explaining the operation of the belt driving device according to the present invention, in which FIG. 3A illustrates a state in which a recording sheet enters a secondary transfer fixing unit, and FIG. FIG. 7 is a diagram illustrating a state where the sheet exits from a next transfer fixing unit.

FIG. 4 is a diagram showing a measurement result of a speed fluctuation of a comparative example.

FIG. 5 is a diagram illustrating a measurement result of a position change in a comparative example.

FIG. 6 is a diagram showing measurement results of speed fluctuation according to the present invention.

FIG. 7 is a diagram showing a measurement result of a position change according to the present invention.

FIG. 8 is a diagram showing a measurement result of position fluctuation according to the present invention.

FIG. 9 is a configuration diagram of an image forming apparatus to which a conventional belt driving device is applied.

[Explanation of symbols]

 Reference Signs List 1 belt drive device 2A drive roller 2aa shaft end portion 2B driven roller 2C leveling roller 2D, 2E tension roller 3 intermediate transfer belt 3a secondary transfer fixing portion 3b belt tension side span 3c belt slack side span 4A first tension fluctuation absorption Means 4B Second tension fluctuation absorbing means 5 Rotation drive mechanism 50 Rotation speed detection unit 51 Drive motor 52 Winding transmission mechanism 52a Large pulley 52b Small pulley 52c Belt 6 Belt drive control unit 100 Image forming apparatus 101 Document table 102 Image reading Unit 103 Image processing unit 110 First image forming unit 111 Photoconductor drum 112 Exposure charger 113 Exposure unit 114 Developing unit 115 Transfer charger 116 Cleaner 117 Static eliminator 120 Second image forming unit 130 Third image forming Unit 140 fourth Image forming unit 150 sheet conveying path 151 registration rollers 154A, 154B 2 transfer fixing roller 155 discharger 156 Cleaner P recording paper

Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 21/00 350 G03G 21/00 350

Claims (17)

[Claims] An endless belt stretched by a plurality of rollers including a driving roller is conveyed at a predetermined speed in a predetermined direction by the driving roller, and the driving is performed by an external force applied to an external force application point of the endless belt. A belt driving device that generates a tension fluctuation that decreases or increases on the slack side of the endless belt with respect to the roller and increases or decreases on the tension side, wherein the belt drive device is disposed in contact with the endless belt on the slack side and the tension side. By increasing or decreasing the transport route length of the endless belt on the slack side, and reducing or increasing the transport route length on the tension side, the tension fluctuation is absorbed to absorb the tension fluctuation and the tension side and the tension of the endless belt. First to maintain a constant tension on at least one of the sides
And a second tension fluctuation absorbing means. 2. A tension roller having a predetermined moment of inertia and said elastic member having a predetermined spring constant and pressing said tension roller against said endless belt. The belt driving device according to claim 1, comprising: 3. The belt driving device according to claim 1, wherein at least one of the plurality of rollers has a moment of inertia for suppressing high-frequency vibration of the endless belt. 4. A belt drive according to claim 1, wherein said drive roller is driven by feedback control based on detection of a rotation speed of at least one of said plurality of rollers or a movement speed of said endless belt. apparatus. 5. An endless photosensitive belt stretched by a plurality of rollers including a driving roller is conveyed by the driving roller in a predetermined image forming direction at a predetermined image forming speed,
In the image forming apparatus, the transfer operation of the transfer unit of the photoconductor belt causes the tension of the drive roller to decrease or increase on the slack side of the photoconductor belt and increase or decrease on the tension side. Alternatively, a support roller that supports the photosensitive belt on the tension side and forms an image bearing area on the photosensitive belt where an image bearing operation is performed with the drive roller; and the support roller and the transfer unit. The slack side and the tight side are arranged in contact with the photoreceptor belt, and the slack side increases or decreases the transport route length of the photoreceptor belt, and reduces the transport route length on the stretch side. Alternatively, the first and second tension fluctuations that absorb the fluctuation of the tension and increase the tension of at least the image bearing area of the photosensitive belt to be constant. Image forming apparatus characterized by having a yield means. 6. The first and second tension fluctuation absorbing means includes a tension roller having a predetermined moment of inertia, and the tension roller having a predetermined spring constant and pressing the tension roller against the image carrier belt. 6. The image forming apparatus according to claim 5, comprising an elastic member. 7. An image forming apparatus according to claim 5, wherein at least one of said plurality of rollers is provided with a moment of inertia for suppressing high frequency vibration of said image carrier belt. 8. The apparatus according to claim 5, wherein said drive roller is driven by feedback control based on detection of a rotation speed of at least one of said plurality of rollers or a movement speed of said image carrier belt. Image forming device. 9. An endless paper transport belt stretched by a plurality of rollers including a drive roller is transported by the drive roller in a predetermined image forming direction at a predetermined image forming speed, and is recorded on the paper transport belt. When the medium is released from the release position of the paper transport belt by the pulling force of the fixing unit, a tension fluctuation that decreases or increases on the slack side of the paper transport belt and increases or decreases on the tension side with respect to the drive roller. In the image forming apparatus, the paper transport belt is supported on the slack side or the tension side, and a toner image transfer area for transferring a toner image to the recording medium between the drive roller and the driving roller is formed on the paper transport belt. A support roller, and the paper transport bell on the slack side and the tension side between the support roller and the release position. The paper transport belt is arranged to increase or decrease the transport route length of the paper transport belt on the slack side, and reduce or increase the transport route length on the tension side to absorb the tension fluctuation and transport the paper. An image forming apparatus comprising first and second tension fluctuation absorbing means for maintaining a constant tension in at least the toner image transfer area of the belt. 10. A tension roller having a predetermined moment of inertia and said elasticity for pressing said tension roller against said sheet transport belt with said predetermined spring constant. The image forming apparatus according to claim 9, further comprising a member. 11. An image forming apparatus according to claim 9, wherein at least one of said plurality of rollers is provided with a moment of inertia for suppressing high-frequency vibration of said sheet conveying belt. 12. The image according to claim 9, wherein said drive roller is driven by feedback control based on detection of a rotation speed of at least one of said plurality of rollers or a movement speed of said paper transport belt. Forming equipment. 13. An endless intermediate transfer belt stretched by a plurality of rollers including a driving roller is conveyed by said driving roller in a predetermined image forming direction at a predetermined image forming speed, and a secondary image of said intermediate transfer belt is formed. The secondary transfer operation or the secondary transfer fixing operation of the transfer unit decreases or increases on the slack side of the intermediate transfer belt with respect to the drive roller;
An image forming apparatus that generates a tension fluctuation that increases or decreases on a tension side, wherein the intermediate transfer belt is supported on the slack side or the tension side and a toner image transfer area where a toner image is transferred between the driving roller and the toner image transfer area. A support roller that is formed on the intermediate transfer belt, and is disposed in contact with the intermediate transfer belt on the slack side and the tension side between the support roller and the secondary transfer unit, and the slack side on the slack side. By increasing or decreasing the transport route length of the intermediate transfer belt and reducing or increasing the transport route length on the tension side, the tension fluctuation is absorbed to keep the tension of at least the toner image transfer area of the intermediate transfer belt constant. An image forming apparatus comprising: first and second tension fluctuation absorbing means for maintaining the first and second tension fluctuations. 14. A tension roller having a predetermined moment of inertia, said first and second tension fluctuation absorbing means, said elastic roller pressing said tension roller against said intermediate transfer belt with said predetermined spring constant. The image forming apparatus according to claim 13, further comprising a member. 15. An image forming apparatus according to claim 14, wherein at least one of said plurality of rollers is provided with a moment of inertia for suppressing high-frequency vibration of said intermediate transfer belt. 16. The secondary transfer section includes a pair of transfer rollers, and a transfer roller of the pair of transfer rollers on which the intermediate transfer belt is stretched suppresses high frequency vibration of the intermediate transfer belt. The image forming apparatus according to claim 14, wherein the inertia moment is added. 17. An image according to claim 14, wherein said drive roller is driven by feedback control based on detection of a rotation speed of at least one of said plurality of rollers or a movement speed of said intermediate transfer belt. Forming equipment.