JP2000198567A - Endless belt conveyor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the meandering and cambering of endless belts even if rollers make poor parallelism, by holding the circumferential length and tension of the endless belts constant. SOLUTION: For tensioning an endless belt 1 via the pressure force of a spring 7, a conveyor 100 uses two tension rollers, or a first tension roller 3 and a second tension roller 4 for taking up and letting off the endless belt 1 respectively. Even if an immovable roller 2 comes out of its normal position by some reason, stress is relaxed and belt meandering and cambering is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless belt conveying device used for an image forming apparatus or the like. More specifically, the present invention relates to an endless belt transport device that suppresses meandering of an endless belt.

[0002]

2. Description of the Related Art Conventionally, endless belt conveyors have been
For example, it is used for a sheet conveying system of an image forming apparatus, a transfer belt, a photosensitive belt, and the like. Generally, an endless belt conveying device in an image forming apparatus includes an endless belt and a plurality of rollers that stretch the endless belt. Then, the endless belt is run by the rotational driving of these rollers. As a result, the transfer material, the toner image, and the electrostatic latent image carried on the endless belt are conveyed.

As a specific example, there is a case where the tandem type color image forming apparatus is used in a sheet conveying system. In a tandem-type color image forming apparatus, different color toner images are transferred from a plurality of photoconductors to a sheet carried and conveyed on a sheet conveying belt, which is an endless belt, so that a color image is formed. What you get.

As described above, in the endless belt conveying device used in the sheet conveying system of the tandem type color image forming apparatus, when the meandering tendency of the sheet conveying belt increases, the toner image moves from the photosensitive member to an accurate position on the sheet. Cannot be transferred multiple times, causing image misregistration. Therefore, it is necessary to prevent meandering of the endless belt, and various techniques have been proposed.

[0005]

However, in an actual endless belt conveying apparatus, meandering is a very complicated phenomenon, and is unavoidable due to processing accuracy and the like. That is, when the forming accuracy of parts such as rollers and belts and the assembling accuracy of the entire apparatus are low, the parallel accuracy between the rollers that stretch the belt is also low. If the parallel accuracy between the rollers is low, the circumference and tension of the running endless belt are constantly changing. For this reason, even if various meandering prevention technologies that have been conventionally proposed are applied,
In some cases it did not work well.

The present invention has been made to solve the above-mentioned problems of the conventional endless belt conveying device. That is, an object of the present invention is to provide an endless belt transport device capable of maintaining the tension of the endless belt constant and suppressing meandering even when the parallel accuracy between the rollers is low.

[0007]

SUMMARY OF THE INVENTION An endless belt conveying device according to the present invention, which has been made to solve this problem, has an endless endless belt, a fixed roller that stretches the endless belt, and an endless belt that is stretched together with the fixed roller. The tension roller has two or more tension rollers that can move in a direction intersecting the axial direction, and tension applying means that applies tension to the endless belt by pressing the tension roller away from the fixed roller.

In this endless belt conveying device, the endless belt is stretched around a fixed roller and two or more tension rollers. Then, a constant tension is applied to the endless belt by the tension applying unit pressing each tension roller in a direction away from the fixed roller.

In the present application, the term "fixed roller" refers to a roller having no mechanism for positively changing the support positions at both ends. However, the support position may slightly deviate from the correct position due to dimensional tolerances, wear, distortion, etc. of the supporting members. On the other hand, the "tension roller" is a roller having at least one end provided with some mechanism for changing the support position. The tension roller can have a function of applying tension to the endless belt by pressing the tension roller from inside to outside.

In this endless belt transfer device, if the end of the fixed roller corresponding to the end of each tension roller receiving pressure from the tension applying means is shifted from the correct position for some reason, the following phenomenon occurs. Happens. That is, such a displacement tends to increase the circumference of the endless belt on the side. But endless belts do not stretch as easily. Therefore,
The end of the tension roller on that side slightly moves in a direction approaching the fixed roller against the pressing of the tension applying means. Thereby, the circumference and tension of the endless belt are maintained.

In this state, the meandering direction of the endless belt in the range from the fixed roller to the tension roller is opposite to that in the range from the tension roller to the fixed roller. As described above, the meandering direction is reversed in the vertical direction, so that the meandering amount as a whole is suppressed. Since two or more tension rollers are provided, the receiving of the endless belt from the fixed roller and the sending of the endless belt to the fixed roller are performed by separate tension rollers. As a result, the stress caused by the upper and lower meandering being in opposite directions is reduced, and the effect of suppressing meandering is large.

In the endless belt conveying device of the present invention, a moving plate for supporting at least one side of the two or more tension rollers and transmitting the pressing force of the tension applying means to each tension roller is further provided. It is preferable to have a slide rail that defines the movement direction of the slide rail. In such a case, the moving plate presses the inside of the endless belt from the inside to the outside along the moving direction defined by the slide rail due to the pressing force of the tension applying means. And in the fixed roller,
When the end on the side corresponding to the moving plate is deviated from the correct position for some reason, the end of the tension roller on the corresponding side moves against the fixed roller along the moving direction of the slide rail against the pressing of the tension applying means. Move a little closer. Thereby, the circumference and tension of the endless belt are maintained.

Further, in the endless belt conveying device of the present invention, it is more preferable that the fixed roller is a driving roller that transmits a driving force to the endless belt. Generally, this is because the configuration can be simpler than the case where the tension roller is used as the driving roller.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. The present embodiment is an endless belt conveying device used for a sheet conveying belt, a transfer belt, and a photosensitive belt in an image forming apparatus such as a copy, a facsimile, and a printer.

FIG. 1 shows the entire configuration of an endless belt conveying device 100 according to an embodiment of the present invention. The endless belt transport device 100 of the present invention basically stretches an endless endless belt 1 with three rollers, a fixed roller 2, a first tension roller 3, and a second tension roller 4. The endless belt 1 has a spring 7 for pressing the first tension roller 3 and the second tension roller 4 away from the fixed roller 2, that is, from the inside to the outside of the endless belt 1.
This is for applying tension to the endless belt 1 by the elasticity of the spring 7.

The fixed roller 2 has no mechanism for positively changing the support positions at both ends. That is, one end of the shaft 21 is fixedly supported by the side plate 5 fixed to the main body. The other end is also fixed and indicated with respect to the main body. A drive motor 9 is provided at the other end. That is, the fixed roller 2 has a role of transmitting the driving force of the driving motor 9 to the endless belt 1.

On the other hand, the first tension roller 3 and the second tension roller 3
The support position of the tension roller 4 can be moved in a direction crossing the axial direction. Further, as described above, the spring 7 is pressed in a direction away from the fixed roller 2. More specifically, the spring 7 has one end 7
1 is fixed by being engaged with the engaging portion 51 of the side plate 5. The other end 72 is provided with an engaging portion 6
1 so that the movable side plate 6 can be moved in the moving direction by being engaged with the moving plate 1. In addition, the moving side plate 6
, One end of each shaft portion (31 and 41) of the first tension roller 3 and the second tension roller 4 is supported. Further, the moving side plate 6 is supported by the slide rail 8 provided on the side plate 5 at the above-mentioned spring engaging portion 61, and its moving direction is set in the axial direction of the first tension roller 3 and the second tension roller 4. It is defined in the direction of intersection. With the above-described mechanism, the first tension roller 3 and the second tension roller 4 can move their support positions in a direction intersecting the axial direction.

In the endless belt transfer device 100 having the above-described configuration, the first pressing force of the spring 7 causes the first
One side of the tension roller 3 and the second tension roller 4 is pressed in a direction away from the fixed roller 2. As a result, a constant tension is applied to the endless belt 1. In this state, when the drive from the drive motor 9 is transmitted to the fixed roller 2, the fixed roller 2 rotates, the endless belt 1 travels along with the rotation, and the first tension roller 3 and the second tension roller 4 also move. It follows and rotates.

Here, the endless belt conveying device 100
In the following, behavior when the position of the fixed roller 2 is deviated from a correct position due to some cause such as a reduction in molding accuracy of parts or assembling accuracy of a device, or wear of each part due to durable use will be considered. For this reason, it is assumed that the position of one end of the fixed roller 2 is shifted from the correct position 21A to a position 21A 'below the fixed position 2A as shown in FIG. Fixed roller 2
Is the end on the side corresponding to the end on which the tension rollers 3 and 4 are pressed by the spring 7. At this time, the endless belt conveying device 100
The following phenomena occur.

That is, such a displacement of the fixed roller 2 tends to increase the circumferential length of the endless belt 1 on the side. However, since the endless belt 1 is not easily stretched, the corresponding end of the tension rollers 3 and 4 slightly moves in a direction (arrow B direction) approaching the fixed roller 2 against the pressing of the spring 7. . Thereby, the circumferential length and the tension of the endless belt 1 are maintained.

In this state, the endless belt 1
, The meandering direction is opposite (the direction of arrow C and the direction of arrow D) in the range from the fixed roller 2 to the first tension roller 3 and the range from the second tension roller 4 to the fixed roller 2. Since the directions of the meandering are reversed in the vertical direction as described above, the meandering amount as a whole is suppressed.

Further, the endless belt conveying device 100
In this case, since the first and second tension rollers are provided, the receiving of the endless belt 1 from the fixed roller 2 and the feeding of the endless belt 1 to the fixed roller 2 are performed by different tension rollers. Is being carried. As described above, the upper and lower sides of the endless belt 1 whose meandering directions are opposite to each other are shared by the two tension rollers. For this reason, the stress caused by the upside-down tendency of meandering is alleviated, and the effect of suppressing meandering is large.

FIG. 3 is a graph showing the relationship between the torsion angle of the roller and the amount of meandering in this type of endless belt conveyor. In FIG. 3, the solid line indicates the case of the endless belt transport device 100. On the other hand, the broken line shows the case of an endless belt transport device having one tension roller. Here, the “twist angle” refers to the twist angle between the fixed roller and the tension roller. FIG.
As can be seen from the figure, in the case of the endless belt transport device 100, the change in the amount of meandering when the twist angle of the roller changes is suppressed as compared with the case where the tension roller is one.

As described in detail above, the endless belt transport device 100 according to the present embodiment includes the two tension rollers of the first tension roller 3 and the second tension roller 4, so that the fixed roller The stress caused when the upper endless belt 1 is twisted for some reason and causes the upper and lower endless belts 1 to meander in opposite directions is reduced. Thereby, the effect of suppressing meandering is secured. The constant roller 2 has a role as a driving roller for transmitting a driving force to the endless belt 1. Therefore, the configuration can be simpler than using the tension roller as the drive roller.

Such an endless belt transport device 100
Can be suitably used for the sheet transport system 201 of the tandem image forming apparatus 200 shown in FIG. 4, for example. The tandem type image forming apparatus 200 includes four image forming units 2.
The toner images formed by 00C, 200M, 200Y, and 200K are superimposed on a sheet conveyed by the sheet conveying system 201 to form an image. By using the endless belt conveyance device 100 having the above-described configuration for the paper conveyance system 201, meandering can be suppressed while maintaining the circumferential length and tension of the endless belt 1. For this reason, image shift of the toner image transferred onto the paper is suppressed.

The present embodiment is merely an example, and does not limit the present invention. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof. For example, the present invention is applicable not only to a tension roller but also to a system having two fixed rollers and four rollers.

[0027]

As is apparent from the above description, according to the present invention, meandering is suppressed without excessive stress while maintaining the circumferential length and tension of the endless belt even when the parallel accuracy between the rollers is low. An endless belt transport device is provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an endless belt transport device according to an embodiment.

FIG. 2 is a model diagram illustrating an operation of meandering suppression in the endless belt conveyance device according to the embodiment.

FIG. 3 shows the relationship between the torsion angle and the meandering amount, and the relationship between the endless belt conveyance device and the tension roller according to the present embodiment.
It is a graph shown in comparison with this endless belt conveyance device.

FIG. 4 is an overall configuration diagram of the tandem image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Endless belt 2 Fixed roller 3 1st tension roller 4 2nd tension roller 5 Side plate 6 Moving side plate 7 Spring 8 Slide rail 9 Drive motor 100 Endless belt conveyance device

Claims (3)

[Claims] 1. An endless endless belt, a fixed roller which stretches the endless belt, and two or more tension rollers which stretch the endless belt together with the fixed roller and are movable in a direction intersecting the axial direction. And a tension applying means for applying a tension to the endless belt by pressing the tension roller away from the fixed roller. 2. The endless belt conveying device according to claim 1, wherein said moving plate supports said two or more tension rollers and transmits a pressing force of said tension applying means to each tension roller. And a slide rail for defining a moving direction of the endless belt. 3. The endless belt conveying device according to claim 1, wherein the fixed roller is a driving roller that transmits a driving force to the endless belt.