JP2000227735A - Belt driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a belt from running on a roller in an image forming device. SOLUTION: This device used for the image forming device is provided with a belt 6 equipped with the elastic body guide member 7 at an end part on the rear side is extended around the roller 1, and an auxiliary belt 13 extended between the roller 1 end part and the freely rotated auxiliary roller 12 and abutting on the elastic body guide member 7. Then, the conditional expression θa<θb, is supposed to be satisfied, (in expression, θa is, showing angle formed by progress direction of auxiliary belt 13 right before being wound by roller 1 and progressing direction of belt 6 right before being wound by roller 1, θb is, showing angle formed by tangent direction on roller periphery at point that end edge of elastic body guide member 7 is, beginning to overlap sectional plane roller 1 main body part and progressing direction of belt 6 right before being roller 1).

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 such as a transfer / transport belt, a photoreceptor belt, and an intermediate transfer belt used in an image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction peripheral thereof.

[0002]

2. Description of the Related Art Conventionally, an apparatus for forming an image on a sheet, such as a copying machine, a printer, and a facsimile, has a structure in which a drum or a belt having an endless cross section is rotated. The belt having an endless cross section used in these mechanisms is, for example, a transfer conveyance belt, a photoreceptor belt, an intermediate transfer belt, or the like. The transfer conveyance belt is generally used for a full-color machine, and the belt carries a toner image and rotates while electrostatically adsorbing and conveying a sheet. Y (yellow), M (magenta), and C (cyan) , BK (black), by bringing the sheet into contact with the respective photosensitive drums in order, thereby transferring a toner image onto the sheet to form a full-color image. The photoreceptor belt forms a latent image by irradiating a photoconductive surface with light, and carries toner by electrostatic force on the latent image to form a toner image. The intermediate transfer belt once bears the toner image that has been exposed on the photoconductor, and then transfers the toner image to a sheet in the course of rotation. There is also known an image forming apparatus using a direct recording method in which a toner image is formed directly on a sheet on a transfer belt or on an intermediate transfer member.

[0003] In any of the apparatuses for driving these belts, the belt is generally stretched over two or more rollers, at least one of which is a driving roller. The driven roller is often a tension roller that applies tension to the belt. Here, high-precision parallelism is required between these rollers. If they are not parallel, the belt shifts in the axial direction according to the rotation of the belt, and the belt meanders, causing not only poor image quality such as color misregistration but also damage to the belt.

In order to alleviate the requirement for high-precision parallelism with respect to the roller shaft, a belt having an elastic guide member at an end on the back surface is used. FIG. 4 is a side view showing a driving roller portion of a conventional belt driving device for preventing the belt from meandering by an elastic guide member. Also, FIG.
FIG. 5 is a cross-sectional view of the drive roller of FIG. A belt 6 is in frictional contact with the drive roller 1. Reference numeral 7 denotes an elastic guide member adhered to both end portions of the belt 6. The belt 6 and the driving roller 1 rotate in the direction of the arrow shown in the figure. In the belt driving device provided with such an elastic guide member 7, a portion where the belt 6 is in contact with the roller 1,
When the elastic guide member 7 is hooked on the side surface of the roller 1, the belt can be prevented from being shifted.

However, since the friction between the elastic guide member 7 and the end of the roller 1 has a high friction coefficient of 0.3 or more, the meandering force of the belt 6 is generated, and the elastic guide member 7
When the roller and the end of the roller 1 contact each other, the elastic guide member 7 is pushed out in the radial direction of the roller, and eventually the elastic guide member 7 rides on the roller 1, and the belt 6 meanders and breaks.

Here, it has been empirically known that the belt 6 easily rides on the roller 1 at the P portion where the elastic guide member 7 enters the roller portion. This is because, for example, the speed direction of the roller end surface in the vicinity of the point B of the P
This is the Phb direction perpendicular to the radial direction at the point. Therefore, the elastic guide member at the point B receives a frictional force in the Phb direction from the contacting roller end face, and a component of the force at right angles to the traveling direction Pg of the elastic guide member is a component of the belt. This is the force that causes the ride. That is, the smaller the angle θb between the advancing direction Pg of the belt immediately before the roller is applied and the tangential direction Phb of the outer periphery of the roller at the point B where the upper end of the elastic guide member starts to overlap the roller end, the smaller the cause of the belt running up. Becomes smaller.

The synergistic effect of the magnitude of the angle θb and the magnitude of the coefficient of friction of the elastic guide member 7 with respect to the roller end surface increases the force with which the belt rides on the roller. For example, when the elastic body guide member 7 is made of rubber and the roller 1 is made of aluminum, the friction coefficient becomes 0.5 or more. As a result, the elastic body guide member 7 rides on the roller 1.

In consideration of the above mechanism, the angle θb between the direction Phb of the force acting on the contact portion of the elastic guide member of the roller at the point B and the traveling direction Pg of the elastic guide member should be as small as possible. If possible, the vertical component of the force acting on the elastic body guide member at the P portion is reduced, and it is possible to prevent the elastic body guide member 7 from running over.

Here, the point B is a point where the speed direction of the roller end face and the speed direction of the elastic guide member are the most different at the point P, and other points at the point P are selected. In this case, the force in the running direction acts on the elastic guide member. That is, if the riding force at the point B is reduced, the riding force at other points of the portion P is also reduced.

On the other hand, from the viewpoint of reducing the friction between the elastic guide member and the roller end, the friction coefficient between the elastic guide member and the roller end is reduced by means of a coating member or the like, and the elastic guide member is applied to the roller. A belt drive device has been devised which prevents meandering by preventing running up (Japanese Patent Laid-Open No. 6-51578). In this apparatus, the coefficient of friction of an elastic guide member (for example, rubber) having an inherently high coefficient of friction is reduced by means of a coating member or the like, and the contact portion of the elastic guide member of the roller is also rubbed by a similar method such as coating. By lowering the coefficient, meandering of the belt is prevented.

However, this method has the drawbacks that the coating cost is high and the coating is easily peeled off because the elastic guide member is bent around the roller, and the life is short.

[0012]

In consideration of the above-mentioned problems of the conventional apparatus and the causes thereof, the present invention is to reduce the direction of the frictional force which causes the elastic guide member to ride on the elastic guide member. It is an object of the present invention to provide a belt meandering prevention device capable of reducing a vertical component of frictional force by biasing the belt meandering direction.

[0013]

In order to achieve the above-mentioned object, the present invention is applied to an image forming apparatus, wherein at least one belt provided with an elastic guide member at an end of a back surface is a driving roller. A belt driving device that stretches around one or more rollers and rotates the belt by the driving rollers, the auxiliary roller being rotatable with a roller end of at least one of the two or more rollers. And an auxiliary belt that comes into contact with the elastic guide member at a portion that hangs on the roller end portion, and the traveling direction Pha of the auxiliary belt just before hanging on the roller and immediately before hanging on the roller The angle θa formed by the traveling direction Pg of the belt and the tangential direction Phb of the outer periphery of the roller at the point where the edge of the elastic guide member begins to overlap the cross section of the roller main body is equal to the angle θa. A belt drive, characterized in that less than the angle θb of the traveling direction Pg immediately before the belt according to la.

According to the present invention, the direction Pha of the force acting on the elastic guide member contact portion of the auxiliary belt at the portion where the elastic guide member comes into contact with the auxiliary belt forms the traveling direction Pg of the elastic guide member. Since the angle θa is small, the vertical component of the force acting on the elastic body guide member at the contact portion becomes small, and it is possible to prevent the elastic body guide member 7 from running over.

Further, in the belt driving device described above, a portion of the auxiliary belt, which is applied to the roller end, is configured to be flat with the roller main body.

With this configuration, even when the belt is meandering in the thrust direction of the drive roller and the elastic guide member comes into contact with the auxiliary belt, the belt is not distorted and the elastic guide member is moved in a meandering manner. Can be stopped.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a transfer / conveying belt portion of a tandem color printer. In FIG. 1, 1 is a driving roller, 2 is a driven roller, 3 is a tension roller for applying tension to the belt, 4 is a supporting member for supporting the tension roller 3 so as to be able to swing, and 5 is an acting member. This is a tension spring. Reference numeral 6 denotes a transfer / conveying belt stretched around the drive roller 1, driven roller 2, and tension roller 3, reference numeral 7 denotes an elastic guide member made of an elastic material such as rubber, reference numeral 10 denotes Y (yellow), M (magenta), and C ( This is a photosensitive member that forms a toner image of each color of cyan) and BK (black).

The procedure for forming a full-color image on a sheet is as follows:
It is as follows. First, the sheet fed by the registration rollers 8a and 8b for controlling the sheet feeding timing is sucked on the belt 6 by the suction roller 9 to which a high voltage is applied. The toner images formed on the photoconductor 10 are sequentially transferred to the sheet on the belt 6 driven by the driving roller 1 in the order of Y, M, C, and BK. Finally, the sheet separated from the belt by the separation claw 11 is transported to the fixing device. Therefore, if the belt is displaced between the respective photoconductors, a color shift occurs in the image, and high precision is required for the belt conveyance.

FIG. 2 is a cross-sectional view of the drive roller unit of FIG. In the present embodiment, since the same operation is exerted by the same configuration at the other end of the roller (not shown), only the illustrated one end will be described. Now, elastic guide members are adhered to both side ends of the transfer and transport belt 6. An auxiliary belt 13 is disposed between the elastic guide member 7 and the driving roller 1.
Is stretched between the auxiliary roller 12 and the driving roller 1. The auxiliary roller 12 is configured to be freely rotatable,
With the rotation of the driving roller 1, the auxiliary roller 12 also rotates via the auxiliary belt 13. The sectional shape of the auxiliary belt 13 is
The roller end 20 has a concave shape that fits with the convex shape. With such a configuration,
The auxiliary belt 13 does not move in the roller axis direction.
In addition, the auxiliary roller 12 is also formed in a concave shape that is fitted and rotated with the convex type of the auxiliary belt 13, so that the auxiliary belt 13 is stretched and rotated stably.

Further, as shown in FIG.
The thickness of the auxiliary belt and the shape of the roller are such that the portion of the drive roller 1 on which the belt is stretched is flat with the portion 20 on which the belt 6 is stretched (hereinafter, this portion is referred to as a “roller body”). Is set. With such a configuration, the auxiliary belt 13 is stretched around the end of the driving roller 1, and has the same diameter as the roller main body.
The belt 6 is not distorted, and the elastic guide member 7 comes into contact with the auxiliary belt 13 in the thrust direction of the drive roller 1 so that the elastic guide member 7 comes into contact with the auxiliary belt 13.
Can stop the meandering of the belt 6.

FIG. 3 is an enlarged side view of the drive roller unit shown in FIG. With reference to FIGS. 2 and 3, a mechanism for preventing the guide member 7 from riding on the drive roller 1 according to the configuration of the present invention will be described. The transfer belt 6 tends to be shifted in the axial direction of the roller due to a parallelism error between the driving roller 1, the driven roller 2, and the tension roller 3 and a balance of the tension force of the tension roller 3. Both ends of the drive roller 1 (hereinafter referred to as "roller ends") and auxiliary rollers 12 provided in the vicinity of the transfer belt 6 in the vicinity thereof.
The auxiliary belt 13 is stretched between them, and the auxiliary belt rotates according to the rotation of the drive roller 1. Therefore,
When the transfer belt 6 is deviated in the axial direction, the elastic body guide member 7 comes into contact with the auxiliary belt 13 and tries to stop the deviation.

In this embodiment, the point A at which the elastic body guide member 7 starts to overlap the auxiliary belt 13 corresponds to the point B described in the conventional example. That is, according to the same principle as described in the conventional example, the angle θa formed by the traveling direction Pg of the elastic guide member 7 at the point A and the direction Pha of the force acting on the elastic guide member contact portion of the roller is reduced. This can prevent the elastic body guide member 7 from running over. Therefore, the size and position of the auxiliary roller 12 are defined so that θa in the drawing is reduced.

The point B shown in FIG. 3 is a point at which the tip of the elastic guide member starts to overlap the roller end when the diameter of the roller body is the same as the diameter of the roller end. Pointing to. That is, when the roller end of the belt driving device according to the present invention is virtually configured without giving a special shape to the end as in the conventional example shown in FIG. It points to the point where it begins to contact the roller end, and therefore the present invention is specified in comparison with the prior art as shown in FIG.

That is, by making θb smaller than θa in FIG. 3, the vertical component of the frictional force acting on point A becomes smaller than the vertical component of the frictional force acting on point B shown in FIG. You can do it.

In the above embodiment, the belt driving device in which the driving roller portion includes the auxiliary belt and the auxiliary roller has been described. However, a belt driving device in which the above configuration is applied to another roller portion may be used. A belt driving device applied to a plurality of roller units may be used. In particular, when the change in the moving direction of the belt is remarkable in the roller portion, it is effective to apply the above configuration. Further, the belt driving device described above is a belt driving device in which the belt has elastic guide members at both ends thereof, and auxiliary rollers at both ends of the rollers, the auxiliary belt, and the like have been described. The present invention is effective even when these configurations are not provided at both ends of the roller and the belt but are provided only on one side. In other words, if the belt transports the recording paper, if the belt carries the recording paper at a position deviated from the traveling direction of the belt, the belt may always be biased in one direction. The configuration described above may be used only at the end opposite to the direction in which the belt is biased.

Although the belt driving device according to the present invention has been described as a transfer / conveying belt in a tandem color printer, the belt driving device according to the present invention is not limited to the above-described embodiment, but includes a photosensitive belt, an intermediate transfer belt, and a transfer belt. If the belt requires high precision, such as a conveyor belt, the effect is effective. Further, the image forming apparatus may be either color or monochrome, and is not limited to the electrostatographic system, but may be a direct recording system.

[0028]

As described above, according to the present invention, an auxiliary belt driven by a driving roller is provided in a driving roller portion, and the angle between the auxiliary belt and the elastic guide member is reduced, whereby the elastic guide member is formed. The force that pushes the belt at the moment when the belt contacts the roller end can be reduced, thereby preventing the guide member from riding on the roller.

Further, with the above configuration, meandering of the belt can be prevented, and there is no need to perform any processing on the elastic guide member. Therefore, a belt drive device which is inexpensive and has a long life can be provided. .

[Brief description of the drawings]

FIG. 1 is a side view showing a transfer / conveyance belt driving device according to the present invention.

FIG. 2 is an enlarged side view showing a driving roller unit of FIG. 1;

FIG. 3 is an enlarged sectional view showing a driving roller unit of FIG. 1;

FIG. 4 is a side view showing a driving roller unit of a conventional belt driving device.

FIG. 5 is a cross-sectional view showing a driving roller unit of a conventional belt driving device.

[Explanation of symbols]

1: drive roller, 2: driven roller, 3: tension roller, 4: support member, 5: tension spring, 6: transfer conveyance belt, 7: elastic guide member, 8: registration roller, 9: suction roller, 10: photosensitive Body, 11: separation claw, 12: auxiliary roller, 13: auxiliary belt, 20: roller body, 21:
Roller end

Claims (2)

[Claims] 1. A belt used in an image forming apparatus and having an elastic guide member at an end of a back surface is stretched around two or more rollers at least one of which is a driving roller, and the driving roller A belt driving device for rotating a belt, wherein the belt driving device is stretched between a roller end of at least one of the two or more rollers and a rotatable auxiliary roller, and is hung on the roller end. Θb <θb (θa; the angle between the traveling direction of the auxiliary belt immediately before the roller and the traveling direction of the belt immediately before the roller, θb <θb The angle between the tangential direction of the outer periphery of the roller at the point where the edge of the elastic guide member starts to overlap the cross section of the roller body and the traveling direction of the belt immediately before the roller is applied to the roller. A belt drive device characterized by satisfying the relationship. 2. The belt driving device according to claim 1, wherein a portion of the auxiliary belt that overlaps with the roller end portion is configured to be flat with the roller main body portion.