JP2007171282A - Intermediate transfer body and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intermediate transfer body and an image forming apparatus, in which increase in the pressure of a spring is unnecessary, tolerance is small, the individual difference and horizontal deviation of belt tension can be reduced, the core set of a belt can be reduced, and the extending effect of belt life is obtained. <P>SOLUTION: In the intermediate transfer body 11 and the image forming apparatus 200, a roller shaft 57 is conductive, a pair of magnetic bodies 51 whose opposite magnetic poles are faced to each other around the roller shaft 57 and force generated on the roller shaft 57 by allowing a current to flow through the roller shaft 57 is used for the belt tension. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an intermediate transfer member of an image forming apparatus such as a copying machine, a printer, and a FAX, and further relates to an image forming apparatus using intermediate transfer.

In an image forming apparatus having an intermediate transfer member, it has been confirmed that when the belt tension of the intermediate transfer belt is increased, the color shift in the transfer process can be reduced. This is thought to be because the frictional force between the drive roller and the belt increases as the belt tension increases. Therefore, in the prior art, the belt tension has been secured by pressing a tension roller with springs attached to both ends against the belt.
However, this method has a problem that the belt tension cannot be increased due to the cracks at the end of the belt and the curl wrinkles. In addition, there is a problem in that the belt tension varies depending on the tolerances of the springs, and there is a difference in the left and right belt tension.
For example, it can be said that there is a solid difference in belt tension between an intermediate transfer member in which a tolerance upper limit spring is attached to both ends of the tension roller and an intermediate transfer member in which a tolerance lower limit spring is attached to both ends of the roller. Further, if one tolerance upper and lower limit springs are attached to both ends of the roller, a lateral deviation of the belt tension will occur. A normal spring has a larger tolerance as the applied pressure increases.For example, even if the belt can be released from the belt cracking and belt curl restrictions due to the belt depressurization method, etc., a high belt tension can be secured. As long as the belt tension is due to pressurization, a large solid difference or left-right deviation may occur. The difference in belt tension between solids leads to a decrease in the robustness of color misregistration, and the tension left-right deviation has the problem of causing belt misalignment.

In Patent Document 1, a tension roller and a driving roller are connected via a first gear train, a swinging gear, a second gear train, and a tension adjustment cam when the intermediate transfer belt is driven to rotate, thereby driving the intermediate transfer belt. The force presses the tension roller via the tension adjustment cam to apply tension to the intermediate transfer belt. When the intermediate transfer belt is not driven, the swinging gear is released from the second gear train by its own weight, and the tension roller is pulled by the tension spring. It is disclosed that the belt moves in a direction in which the belt tension is released by force. As a result, when the image forming apparatus is not performing an image forming operation, the intermediate transfer belt can be prevented from being stopped with tension applied, and the intermediate transfer belt can be prevented from being permanently deformed. It is possible to achieve a long life and obtain a stable image over a long period of time.
However, although this method is effective in releasing the belt tension when the intermediate transfer belt is not driven, it has a small tolerance and does not solve the problem of reducing individual differences in belt tension and left-right deviation. It was.

In addition, Patent Document 2 includes a layer including a material formed by dispersing a fiber-shaped conductive agent and a fiber-shaped inorganic filler having different resistance values in a binder resin. A sex belt is disclosed. As a result, the uniformity of the electric resistance is improved, the change in the electric resistance due to the environment is small, the image quality defect such as a color shift due to the belt tension change is not generated, and the high image quality can be stably supplied. A semiconductive belt (especially an intermediate transfer member and a transfer conveyance belt) can be provided.
However, although this method is effective against changes in electrical resistance due to the environment, it has a small tolerance and has not solved the problem of reducing individual differences in belt tension and lateral deviation.

Further, Patent Document 3 discloses a belt member provided with at least one guide member that regulates the belt shift on the inner peripheral surface side, a plurality of rollers provided with a guide portion that guides the guide member, and the plurality of rollers. Drive means for driving at least one of the plurality of rollers, wherein the belt member is stretched and rotated by the plurality of rollers, and one of the plurality of rollers is moved in the axial direction. A belt driving device is disclosed in which the other rollers are configured to freely move in the axial direction. Accordingly, it is possible to provide a low-cost belt driving device, a belt driving method, and an image forming apparatus in which the belt member can stably rotate and move without the guide member of the belt member riding on the guide portion of the roller. it can.
However, although this method has a function that allows the belt member to rotate and move stably, the tolerance is small, and it solves the problem of reducing individual differences in belt tension and lateral deviation. It wasn't.

JP 2001-22188 A JP 2002-182488 A JP 2002-14570 A

Therefore, the present invention has been made in view of the above problems, and the problem is that it is not necessary to increase the pressure of the spring, the tolerance is small, and the belt tension individual difference and left-right deviation can be reduced. An intermediate transfer member and an image forming apparatus are provided. Another object of the present invention is to provide an intermediate transfer member and an image forming apparatus that have effects of reducing belt curl and extending the life of the belt.

The features of the present invention, which is a means for solving the above problems, are listed below.
The present invention relates to an intermediate transfer member having an endless belt and applying tension to the belt by pressing a roller accompanied by a spring against the belt. The intermediate transfer member is characterized in that a pair of magnetic members whose magnetic poles face each other are installed on each other, and a force generated in the roller shaft by applying a current to the roller shaft is used for belt tension.
The present invention is characterized in that the current can be controlled based on the result of color misregistration detection on the intermediate transfer member.
Further, the present invention is characterized in that an electric current flows through the roller shaft only when an image forming apparatus forms an image.
Furthermore, the present invention is characterized in that the pressure applied by the spring during non-image formation is equal to or greater than the minimum force that causes the belt to sag due to vibration during transportation or attachment / detachment.
In the invention, it is preferable that the roller with the spring has a damper that attenuates vibration of the roller.

The present invention is the intermediate transfer member, wherein the paired magnetic bodies are installed only at both end bearing portions of the roller shaft.
Further, the present invention is characterized in that the paired magnetic bodies are continuously installed in the roller axis direction to both ends of the roller axis.
Furthermore, the present invention is characterized in that the pair of magnetic bodies is installed inside the roller.
The present invention also provides an image forming apparatus having the above-described intermediate transfer member.

The present invention provides an intermediate transfer member and an image forming apparatus that do not require high spring pressure, have small tolerances, and can reduce individual differences in belt tension and left / right deviations. It became possible to do. In addition, it is possible to provide an intermediate transfer member and an image forming apparatus that have effects of reducing belt curl and extending the life of the belt.

The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

In the present invention, the belt tension is generated by applying a current to the tension roller, and the belt tension is adjusted by controlling the current based on a result read by a sensor that detects color misregistration on the intermediate transfer member. Is the method. In this method, a spring is required to adjust the belt tension, but it is not necessary to increase the pressure applied to the spring. The deviation can be reduced, and when the image is not formed, the current is not passed, which leads to a reduction in belt curl and an extension of the belt life.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of the present invention, which is an image forming apparatus 200 of a tandem type intermediate transfer system. The image forming apparatus 200 main body is provided with an endless belt-shaped intermediate transfer body 11 in the center. The intermediate transfer body 11 has a multi-layer structure, and the base layer is made of, for example, a fluororesin, PVD sheet, or polyimide resin with little elongation, and the surface is covered with a smooth coat layer such as a fluororesin. Then, as shown in FIG. 1, in the illustrated example, it is wound around the support rollers 10, 12, 34 and 35 so as to be able to rotate and convey counterclockwise in the drawing. In the illustrated example, an intermediate transfer body cleaning device 25 for removing residual toner remaining on the intermediate transfer body 11 after image transfer is provided on the left side of the support roller 10.
Further, on the intermediate transfer member 11 stretched between the support roller 12 and the support roller 35, four image forming units of yellow, cyan, magenta, and black are arranged side by side along the conveyance direction. A tandem image forming apparatus is configured. An exposure apparatus 4 is further provided below the tandem image forming apparatus as shown in FIG.
On the other hand, a secondary transfer device is provided on the side of the intermediate transfer body 11 facing the support roller 35. In the illustrated example, the secondary transfer device is configured by spanning a secondary transfer belt 100, which is an endless belt, between two rollers 111 and 112, and is pressed against the support roller 35 via the intermediate transfer body 11. Then, the image on the intermediate transfer body 11 is transferred to a sheet. Some secondary transfer devices use a secondary transfer roller. A fixing device 30 for fixing the transferred image on the sheet is provided on the secondary transfer device. The fixing device 30 is configured by pressing a pressure roller against a fixing roller.
The secondary transfer device is also provided with a sheet transport function for transporting the image-transferred sheet to the fixing device 30. Further, as the secondary transfer device, a transfer roller or a non-contact charger may be arranged. In such a case, it is difficult to provide this sheet conveying function together.

When a start switch (not shown) is pressed, one of the support rollers 10, 34, and 35 is rotationally driven by a drive motor (not shown) and the other four support rollers are driven to rotate, and the intermediate transfer member 11 is rotated and conveyed. At the same time, each image forming means rotates the photoconductor 1 to form yellow, cyan, magenta, and black single-color images on each photoconductor 1. Then, along with the conveyance of the intermediate transfer body 11, the single color images are sequentially transferred to form a composite color image on the intermediate transfer body 11.
Also, when a start switch (not shown) is pressed, one of the paper feed rollers 27 of the paper feed table is selectively rotated, the sheet is fed out from one of the paper feed cassettes 26 provided in multiple stages in the paper bank, and one sheet is fed by the separation roller. The paper is separated and put into the paper feed path 29, transported by the transport roller, guided to the paper feed path 29 in the image forming apparatus main body, and abutted against the registration roller 28 and stopped. Then, the registration roller 28 is rotated in time with the composite color image on the intermediate transfer body 11, the sheet is fed between the intermediate transfer body 11 and the secondary transfer device, and is transferred by the secondary transfer device to be transferred onto the sheet. Record a color image on
The image-transferred sheet is conveyed by the secondary transfer device and sent to the fixing device 30. The fixing device 30 applies heat and pressure to fix the transferred image, and is then discharged by the discharge roller 32 and discharged. Stack on the tray 40. On the other hand, the intermediate transfer body 11 after the image transfer is removed by the intermediate transfer body cleaning device 25 to remove residual toner remaining on the intermediate transfer body 11 after the image transfer, and is prepared for re-image formation by the tandem image forming apparatus.

FIG. 2 is a schematic configuration diagram of the intermediate transfer unit. The endless belt-like intermediate transfer belt 11 is wound around the support rollers 10, 12, 34, and 35 so as to be able to rotate and convey counterclockwise in the drawing. Of the supporting rollers, the roller 34 is a driving roller, and also serves as a secondary transfer counter roller 36. The support roller 10 is a cleaning facing roller, and an intermediate transfer body cleaning device 25 for removing residual toner remaining on the intermediate transfer body 11 after the secondary image transfer is provided on the left. The support rollers 12 and 35 are driven rollers and have a function of stabilizing the primary transfer nip. In this configuration, the cleaning counter roller 10 also serves as a tension roller, and serves to apply a constant tension to the intermediate transfer belt 11. Four rollers 20 are provided as primary transfer rollers corresponding to the image forming means of yellow, cyan, magenta, and black. As a configuration of the cleaning device 25, residual toner is removed by bringing the cleaning blade 22 into contact with the belt at the position of the cleaning facing roller 10.

FIG. 3 is a schematic view showing securing of conventional belt tension by the tension roller 10. A compression spring 50 for tension is provided at both ends of the tension roller 10, and the belt tension is secured by pressing the tension roller against the belt with the pressure of the compression spring. It is known that when the belt tension is increased, the color shift is reduced.

FIG. 4 is a graph showing the relationship between the belt tension and the color misregistration amount. In consideration of the graph, as the belt tension increases, the frictional force between the driving roller and the belt increases, and the belt running performance is stabilized, so that the color shift is reduced. However, if the belt tension is increased, cracks at the end of the belt and winding of the belt tend to occur. Therefore, the film thickness of the belt and the belt tension are determined based on these trade-offs. At present, there is also an image forming apparatus that performs tension down as a measure for avoiding belt curling.
However, even in such a method, as long as the belt tension is ensured by the spring pressure, the following two points have an influence on the quality due to the crossing of the pressing force of the spring.
The first is the difference in belt tension. The intermediate transfer body in which the springs with the upper limit of tolerance of the spring pressure are installed on both ends of the tension roller and the intermediate transfer body with the springs of the lower limit of tolerance on the belt tension are different, and the amount of color misregistration is also in accordance with that. It varies from body to body, leading to a decrease in robustness. Moreover, when the spring pressure is large, the tolerance is usually set large. Therefore, when a high belt tension is applied, the variation in the color misregistration amount increases.
The second is the lateral deviation of the belt tension. This is also an effect of the spring tolerance. However, when the upper and lower tolerance springs are respectively installed on one side of the tension roller, there is a possibility that a lateral deviation of the belt tension occurs and the belt is shifted.

In the present invention, as shown in FIG. 5, a pair of magnetic bodies whose magnetic poles are opposite to each other are installed around the tension roller shaft, a current flows in the appropriate direction of the roller shaft, and the force generated by Fleming's left-hand rule Is used for belt tension. As a result, even when a high belt tension is ensured, it is not necessary to set a high spring pressure, the spring tolerance is smaller than that of the prior art, and the belt tension individual difference and left / right deviation due to the tolerance can be reduced. .
A simplified diagram of Fleming's left hand rule is shown in FIG. Further, in this configuration, the belt tension can be varied by the value of the current, and therefore, based on the result of color misregistration detection on the intermediate transfer member during image formation for the purpose of further reducing the color variation solid state variation. The current value can be controlled. Thereby, the solid difference of the belt tension mentioned by the effect of this invention can be made smaller.
In order to prevent belt end cracks and belt curling, the current is applied to the roller shaft only during image formation to reduce tension during non-operation. As a result, belt depressurization is performed at the time of non-image formation, so that there are effects of reducing belt curl and extending the life of the belt.

In addition, when the spring attached to the tension roller is installed with a pressure smaller than that of the prior art, if the belt is separated from the belt due to tension down during non-operation from the above description, the following operation is performed. When the image is tensioned up, the tension roller may ride on the anti-shift members at both ends of the belt. This may increase the vibration of the running belt and increase the color shift or damage the belt. Therefore, a spring for holding the tension roller on the belt is required.
Therefore, the smaller the spring pressure, the more likely it is to avoid the risk of belt end cracks and belt curling, but it occurs when the image forming apparatus and intermediate transfer member are transported or when the intermediate transfer member is attached or detached. The belt is pressurized with at least a force that does not cause deflection of the belt against possible vibration. This is to prevent the belt from riding on the anti-shift member. The lower limit of the pressing force is set to the minimum force that causes the belt to sag due to strong vibration that is considered to occur during transportation or attachment / detachment, so that the rollers of the intermediate transfer member are provided at both ends of the belt even when vibration occurs. There is no need to ride on the anti-slip member.

In addition, by adding a damper that attenuates vibration to the spring, the vibration of the tension roller can be kept small even when the tension is suddenly shifted from the tension-up state during image formation. It is possible to prevent the belt from climbing on the anti-shift member. For example, rubber parts are representative of inexpensive damper members. Since rubber is originally a viscoelastic body, it may actually be used in the form shown in FIG. As a result, even when the power supply is suddenly turned off at the time of image formation, vibration of the tension roller can be suppressed, and the roller of the intermediate transfer member can run on the detent prevention members at both ends of the belt by the vibration generated at that time. Disappear.

Further, there is a case where the center portion of the tension roller is bent as the belt tension increases. Therefore, in the case of belt tension in which no deflection occurs in the central portion of the tension roller, a force due to electric current is generated if the magnetic material 51 pair is installed with the magnetic poles opposite in the radial direction of the roller shaft. If the pair of the magnetic bodies 51 is installed only at the both end bearing portions, no large space is taken away by the magnetic bodies.

Also, in the case of belt tension that causes deflection at the center of the tension roller, if the magnetic body 51 that is continuous in the roller axial direction is installed in order to reduce the deflection, the tension roller causes the load to be evenly distributed by the current. Can be generated. That is, since the magnetic body described in the present invention is continuously installed up to both ends of the roller shaft in the roller shaft direction, the Lorentz force acts on the roller shaft as an evenly distributed force. The left-right deviation can be further reduced, and the deflection generated in the center portion of the tension roller can be reduced even when the belt tension is high.
In addition, in this case, a space is required for installing a magnetic material that is continuous in the axial direction. Therefore, if a magnetic material that is continuous in the axial direction is installed in the tension roller as shown in FIG. Can be planned. The tension roller is hollow, and a hollow cylinder is inserted into the tension roller, and a roller shaft (conductive) is passed through the cylinder. The cylinder and the outer wall of the roller are held by bearings at both ends of the roller. The inside tube is fixed.

FIG. 9 is a view showing a method of installing a magnetic body inside the roller. The intermediate cylinder 58 is fixed to a tension roller. The magnetic body 51 is bonded to the inner wall of the intermediate cylinder 58. The tension roller outer wall 60 can be rotated around the belt. The conductive shaft 59 is fixed. The intermediate cylinder 58 and the conductive shaft 59 are held by bearings, and the shaft can move in the direction in which force is generated (A part). Furthermore, the tension roller outer wall 60 and the intermediate cylinder 58 are held by bearings (B portion). If a pair of continuous magnetic bodies 51 is pasted on the inner wall of the inner cylinder as shown in FIG. 9, a force is generated when a current flows through the shaft.

Further, the image forming apparatus having the intermediate transfer member has high color misregistration, and is less likely to cause belt deviation, curl, and belt end cracks.

1 is a diagram illustrating an image forming apparatus of a tandem type intermediate transfer system. It is a schematic block diagram of an intermediate transfer part. It is the schematic which showed the conventional belt tensioning method. 6 is a graph showing the relationship between belt tension and color misregistration amount. It is the figure which showed the belt tension by electric current control. It is the figure which showed the simplification figure about Fleming's left-hand rule. It is the figure which showed the vibration suppression mechanism of the tension roller. It is the figure which showed the method by the continuous magnetic body installation. It is the figure which showed the method of installing a magnetic body inside a roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Exposure apparatus 10 Tension roller (support roller)
11 Intermediate transfer body 12 Support roller 20 Primary transfer roller 22 Cleaning blade 25 Intermediate transfer body cleaning device 26 Paper feed cassette 27 Paper feed roller 28 Registration roller 29 Paper feed path 30 Fixing device 32 Discharge roller 34 Support roller 35 Support roller 36 Secondary Transfer roller 40 Paper discharge tray 50 Compression spring 51 Magnetic body 52 Damper member 53 Conductive shaft (roller side)
54 Rubber member 55 Spring shaft (conductive)
56 Sheet metal (encloses rubber member)
57 Conductive shaft 58 Intermediate cylinder 59 Conductive shaft 60 Tension roller outer wall 100 Secondary transfer belt 111 Roller 112 Roller 200 Image forming apparatus

Claims (9)

In an intermediate transfer member having an endless belt and applying tension to the belt by pressing a roller with a spring attached thereto,
In the intermediate transfer member, the roller shaft is conductive.
Around the roller shaft, a magnetic material pair facing the opposite poles is installed,
An intermediate transfer member characterized in that a force generated in the roller shaft by applying an electric current to the roller shaft is used for belt tension. The intermediate transfer member according to claim 1,
The intermediate transfer member is characterized in that the current can be controlled based on the result of color misregistration detection on the intermediate transfer member. The intermediate transfer member according to claim 1 or 2,
The intermediate transfer member is characterized in that an electric current flows through a roller shaft only when an image is formed by an image forming apparatus. The intermediate transfer member according to any one of claims 1 to 3,
The intermediate transfer member is characterized in that the pressing force of the spring at the time of non-image formation is equal to or more than a minimum force that causes a slack in the belt due to vibration during transportation or attachment / detachment. The intermediate transfer member according to any one of claims 1 to 4,
The intermediate transfer member is characterized in that a roller accompanied by a spring has a damper that attenuates vibration of the roller. The intermediate transfer member according to any one of claims 1 to 5,
The intermediate transfer member is characterized in that the paired magnetic members are installed only at both end bearing portions of the roller shaft. The intermediate transfer member according to any one of claims 1 to 5,
The intermediate transfer member is characterized in that the pair of magnetic members are continuously arranged in the roller axis direction to both ends of the roller shaft. The intermediate transfer member according to claim 7,
The intermediate transfer member, wherein the pair of magnetic members is installed inside the roller. An image forming apparatus comprising the intermediate transfer member according to claim 1.

Images