JPH0651578A - Photosensitive belt driving device - Google Patents

Abstract

PURPOSE:To enhance the effect of preventing the misregistration of images by suppressing the meandering and slipping of the photosensitive belt of the photosensitive belt driving device of an electrophotographic device. CONSTITUTION:A coating layer of a lubricating material is formed on the step part at the end of a driving roller 1 and the surface with which elastic material guide members 7a, 7b of the photosensitive belt 5 come into contact. The driving roller 1 and driven rollers 2, 3 are so installed that the error in the parallelism between the axes thereof is confined to <=0.2mm. The photosensitive belt 5 is extended under 2.5 to 12kgf tension. Then, the guide members 7a, 7b come into contact with the step part of the driving roller 1 and suppresses the increase of the meandering when the photosensitive belt 5 meanders. In addition, the slip is suppressed by the high tension, by which the misregistration of the images is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive belt driving device used in an electrophotographic apparatus such as an electrophotographic copying machine or an electrophotographic printer, and more particularly to prevention of meandering of the photosensitive belt.

[0002]

2. Description of the Related Art A color electrophotographic apparatus using an electrophotographic process completes a color toner image by transferring toner images of respective colors formed on a photoconductor, which is a primary recording medium, onto a secondary recording medium in an overlapping manner. A photosensitive drum or photosensitive belt is generally used as the photosensitive member.

A color electrophotographic apparatus using a photosensitive belt forms a latent image of each color on an endless photosensitive belt which is stretched around a driving roller and a driven roller and rotates, and a developing device for each color forms one color. In this system, the toner images of the respective colors obtained by sequentially developing the respective images are superposed on the transfer drum and transferred. Since a full-color electrophotographic apparatus employs a method of forming toner images of four colors and superposing the toner images, in general, in order to increase the printing process speed, development is performed on the first area surface of the photosensitive belt,
In many cases, a method of forming the next latent image on the second area surface is adopted.

In this system, paper or OH is used on the image surface for one color.
The length of the photosensitive belt is required for the length of the transfer medium such as the P sheet, and since the area for two image surfaces is required, the length of the transfer medium is required to be at least twice the length. Therefore, it becomes longer than the conventional monochromatic photosensitive belt,
There were the following technical problems.

Since the distance between the driving roller and the driven roller is increased due to the lengthening of the photosensitive belt, the error in the parallelism between the axes increases, and the error in the inner peripheral length of the left side region and the right side region of the photosensitive belt increases. The first deviation due to the deviation of the photosensitive belt or the deformation caused by the rotation of the photosensitive belt to which tension is applied.
A positional deviation (color misregistration) between this image and the second image occurs.
Further, even when the parallelism between the axes is maintained, slippage occurs between the driving roller and the driven roller and the photosensitive belt if the tension is insufficiently applied to the photosensitive belt, and the positional deviation of each color image occurs.

The relationship between the tension of the photosensitive belt and the slip is almost saturated when the tension is above a certain level, but a higher tension is more advantageous for the positional deviation of the image due to the slip. However, when there is an error in the parallelism between the axes of the driving roller and the driven roller, the photosensitive belt is biased regardless of its tension, and an elastic member provided on the back surface of the photosensitive belt to prevent meandering. The guide member comes into contact with the stepped portions of the drive roller and the driven roller, and the pressure contact force to the stepped portion on one side of the drive and driven rollers gradually increases, so that the elastic body guide member rides on the stepped portion. Then, the photosensitive belt tries to return to the anti-ride side where the tension is small because the tension on the side on which the guide member rides is large, but the guide member is made of an elastic material in order to improve bending resistance and flexibility. Since the drive roller uses a high friction material such as a rubber material to obtain the driving force, the photosensitive belt cannot return to the opposite riding side, and the riding of the photosensitive belt progresses at last. Then, there is a problem in that the load is suddenly increased by coming into contact with the supporting member and slipping occurs.

Incidentally, since the guide member on the back surface of the photosensitive belt is bent and rotated along the outer circumference of the roller having a diameter of 20 mm to 30 mm, a member having excellent bending resistance and flexibility is required. In particular, for the guide member, a rubber material such as chloroprene rubber is generally used in order to improve the adhesion between the photosensitive belt and the roller. The guide member has a hardness of 30 to 40 °, the drive roller is made of rubber material having a hardness of 65 to 70 °, and the driven roller is generally made of metal or plastic material. The height of the guide member is 0.5mm to 1.5mm, and the width is 2
mm to 5 mm. The photosensitive belt has a photosensitive layer formed on a film of a thermoplastic high molecular weight substance and has an inner peripheral length of 65.
It is an endless one having a width of 0 mm to 800 mm and a width of 200 mm to 300 mm, and is stretched around a driving roller and a driven roller and tension is applied by a tension spring.

An example of such a photosensitive belt driving device is described in Japanese Utility Model Laid-Open No. 63-76867.

[0009]

As described above, the photosensitive belt driving device in the conventional color electrophotographic apparatus prevents the photosensitive belt from meandering and slipping in order to obtain a high-quality color image without color misregistration. Therefore, various measures have been taken, but it has been difficult to configure the characteristics of the components so that the photosensitive belt can be prevented from both meandering and slipping.

An object of the present invention is to prevent meandering and slipping of the photosensitive belt in such a photosensitive belt driving device.

[0011]

According to the present invention, a photosensitive material layer is formed on the surface of a base material layer and has an endless shape having a width of 200 mm to 300 mm and an inner peripheral length of 650 mm to 800 mm, and both end portions of its back surface. In a photosensitive belt drive device in which a photosensitive belt provided with an elastic body guide member having a rubber shore hardness of 30 ° to 40 ° parallel to the above is stretched around a driving roller and a driven roller and rotated by the driving roller, the driving roller And the driven roller, the contact step with which the elastic guide member abuts is formed on the sliding surface having a friction coefficient of 0.02 to 0.30, and the parallelism error between the axes is set to 0.2 mm or less. The photosensitive belt is stretched around the driving roller and the driven roller with a tension of 2.5 kgf to 12 kgf.

[0012]

The friction coefficient between the step portion of the driving roller and the guide member of the photosensitive belt is reduced, and the parallelism error between the axes of the driving roller and the driven roller is specified to reduce the acting force of the guide member riding on the driving roller. As a result, even if the tension of the photosensitive belt is increased and stretched, the photosensitive belt can be prevented from riding on the driving roller. Since the photosensitive belt is stretched with high tension, the occurrence of slippage is reduced and the image position shift can be reduced.

[0013]

Embodiments of the present invention will be described with reference to FIGS.

In FIGS. 1 and 2, 1 is a driving roller, 2 and 3 are driven rollers, 4 is a supporting member for swingably supporting the driven roller 3, and 5 is the driving roller 1.
A photosensitive belt stretched around the driven rollers 2 and 3, and a tension spring 6 acting on the support member 4. The support member 4 and the tension spring 6 are provided in pairs on both end sides of the driven roller 3. 7a and 7b are rubber elastic guide members, and 8 is a transfer drum for completing a color toner image by transferring the toner images of the respective colors formed on the photosensitive belt 5 in an overlapping manner. Contact and rotate.

FIG. 3 is a partial sectional view showing a section taken along the line III-III in FIG. 2. The stepped portions on both ends of the driving roller 1 and the photosensitive belt 5 are shown in FIG.
The surface of the elastic body guide members 7a and 7b adhered to both side ends of the sliding member coating layer 9a having a small friction coefficient,
9b (thickness of 3 to 50 μm) is formed.

FIG. 4 shows an embodiment of the drive roller 1'in which the shape of the stepped portions at both ends of the drive roller 1 is modified, and the stepped portions at both ends are chamfered in an arc shape. Is different from The sliding material coating layer 9a is also formed on the stepped portions at both ends of the drive roller 1'and the elastic body guide member 7a.

5 to 7 are partially enlarged views for explaining the action of preventing the elastic body guide member 7a of the photosensitive belt 5 from riding on the stepped portion of the drive roller 1. As shown in FIG. The photosensitive belt 5 is rotated according to the rotation of the driving roller 1 and the driven rollers 2 and 3, and the driving roller 1 and the driven rollers 2 and 3 are rotated.
3 due to the parallelism error between the axes, the imbalance of the left and right tension spring forces, the difference in the left and right inner peripheral lengths of the photosensitive belt 5, etc.
The guide member 7a contacts the step (end surface) at the end of the drive roller 1. Here, in the combination where the abutting surfaces of the guide member 7a and the drive roller 1 have a high coefficient of friction as in the conventional device, the guide roller 7a partially rides on the drive roller 1 due to the straightness error of the guide member 7a. If this state continues, the guide member 7a will completely ride on the outer peripheral surface of the drive roller 1.

The hardness of the guide members 7a and 7b which can effectively suppress the occurrence of image position deviation is rubber shore hardness considering the flexibility on the driving roller 1 and the driven rollers 2 and 3 and the friction due to the contact with the roller step portion. 30-40 ° is preferable, and the step portion of the driving roller 1 has a rubber shore hardness of 65-70 °.
Is preferred. The friction coefficient of the contact surface is preferably as small as possible, but 0.02 to 0.3 is practical in consideration of the material and form used.

In this embodiment, since the coating layer 9a of the sliding material having a small friction coefficient is formed on the surface layers of the driving roller 1 and the guide member 7a, the straightness error δ is smaller than that of the driving roller 1. Because of its high rigidity, it is absorbed by the elastic deformation of the guide member 7a, and it does not develop into riding. In addition, the radius of the stepped portion at the end of the drive roller 1 is 0.5.
By chamfering with a curvature of mm to 50 mm or an equivalent linear inclination, the straightness error δ of the guide member 7a is easily absorbed.

The drive roller 1'shown in FIG. 7 also has the same effect. That is, when the error is large, the guide member 7a is elastically deformed due to the deviation of the photosensitive belt 5, and a minute gap g is generated between the photosensitive belt 5 and the driving roller 1 ', and the driving roller 1'and the photosensitive belt 1'. When the tension between the five belts increases and the friction driving force increases, the photosensitive belt 5
Can move in a direction in which the tension is weak, that is, in the direction of arrow P so as to prevent riding.

FIG. 8 shows the relationship between the parallelism between the axes of the driving roller and the driven roller and the image position shift. In the conventional apparatus, even if the photosensitive belt is stretched so as to have a tension of 2.0 kgf, if the parallelism error between the axes of the drive roller and the driven roller exceeds 0.15 mm, the amount of positional deviation of the image will be large. Increase, the influence of the error increases. This tendency occurs with a small parallelism error as the tension increases. On the other hand, in the embodiment, when the photosensitive belt is stretched with a tension of 8 kgf, the positional deviation of the image can be suppressed even if the parallelism error between the axes is 0.25 mm or more.

FIG. 9 shows how an error in the parallelism between the axes of the driving roller and the driven roller affects the image position deviation when the tension of the photosensitive belt is changed. If the tension of the stretched photosensitive belt is 8 kgf or less, it is possible to suppress the occurrence of image misalignment even if the inter-axis parallelism error is 0.25 mm or more. However, the tension of the photosensitive belt is 1
When the parallelism error between the axes exceeds 0.15 mm in the stretched state of 0 kgf, the amount of positional deviation of the image tends to increase and the influence of the error increases. This is because the elastic guide member is deformed by excessive tension, and the correction force for restoring the deviation of the photosensitive belt is insufficient.

FIG. 10 shows the effect obtained by forming the slip coating layer 9 on the contact surface between the driving roller 1 and the photosensitive belt 5. In an apparatus having no sliding material coating layer 9, the photosensitive belt 5 stretched at 10 kgf has an increasing tendency for the amount of positional deviation of the image to increase when the parallelism error between the axes exceeds 0.15 mm. However, in the case where the sliding material coating layer 9 is formed on the abutting surface, the occurrence of image positional deviation can be stably suppressed even when the inter-axis parallelism error exceeds 0.25 mm when stretched with a tension of 10 kgf. be able to. Photosensitive belt 5
Even if the tension of 12 kgf is applied, if the parallelism between the axes is set to 0.2 mm or less, the image displacement amount can be suppressed within a predetermined range.

With respect to the tension of the stretched photosensitive belt 5, if the parallelism error between the drive roller 1 and the driven rollers 2 and 3 and the inner peripheral length error are strictly specified, the higher the tension is, the higher the effect of preventing the image position shift is. However, in order to effectively exert the strength (durability) of the photosensitive belt itself and the offset correction effect by the elastic body guide members 7a and 7b, the tension is set to 8 kgf or less. Is effective.

FIG. 11 shows the relationship between the tension of the photosensitive belt 5 and the image position deviation (color deviation). In the conventional device, the tension is set to about 1.5 kgf or less in order to suppress the occurrence of the deviation of the photosensitive belt, and both the deviation of the photosensitive belt and the image position deviation (color deviation) are satisfied. No area was obtained. According to the present invention, with respect to the belt deviation, even if the tension of the photosensitive belt 5 is increased to about 12 kgf and stretched, the drive roller 1 and the elastic body guide members 7a, 7b are also stretched.
Can be maintained well by appropriately maintaining the contact condition of 1 and the parallelism between the driving roller 1 and the driven rollers 2 and 3, and therefore the photosensitive belt 5 can be kept in a range of 2.5 kgf to 12 kg.
By setting to f, a region that satisfies both the deviation of the photosensitive belt and the image position deviation (150 μm or less) can be obtained.

[0026]

According to the present invention, the friction coefficient between the step portion of the driving roller and the guide member of the photosensitive belt is reduced, and the parallelism error between the axes of the driving roller and the driven roller is specified so that the guiding member rides on the driving roller. By increasing the tension of the photosensitive belt by stretching the photosensitive belt, the photosensitive belt is prevented from riding on the drive roller, and the photosensitive belt is stretched with high tension to prevent slippage. It is possible to reduce the positional deviation of the image.

[Brief description of drawings]

FIG. 1 is a side view of a photosensitive belt driving device showing an embodiment of the present invention.

FIG. 2 is a plan view of the photosensitive belt driving device shown in FIG.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a partially longitudinal front view showing a modified example of the driving roller in the photosensitive belt driving device according to the present invention.

FIG. 5 is a partial enlarged view for explaining a riding-up prevention action in the photosensitive belt driving device according to the present invention.

FIG. 6 is a partial enlarged view for explaining a riding-up preventing action in the photosensitive belt driving device according to the present invention.

FIG. 7 is a partially enlarged view for explaining a running-up preventing action in the photosensitive belt driving device according to the present invention.

FIG. 8 is a tension characteristic diagram of the photosensitive belt in the photosensitive belt driving device.

FIG. 9 is a tension characteristic diagram of the photosensitive belt in the photosensitive belt driving device.

FIG. 10 is a tension characteristic diagram of the photosensitive belt in the photosensitive belt driving device.

FIG. 11 is a tension characteristic diagram of the photosensitive belt in the photosensitive belt driving device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive roller 2,3 Driven roller 5 Photosensitive belt 7a, 7b Elastic body guide member 8 Transfer drum 9 Sliding material coating layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeharu Kitagishi 1-1-1, Higashitaga-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Taga factory (72) Inventor Mitsuo Suzuki 1-chome, Higashi-taga-cho, Hitachi, Ibaraki 1-1 No. 1 inside Hitachi Ltd. Taga Factory (72) Inventor Tomio Hayano 1-1-1 Higashi Taga-cho Hitachi City Ibaraki Pref. Inside Hitachi Ltd Taga Factory

Claims (4)

[Claims] 1. A rubber shore hardness of 30 ° to 30 mm, which is an endless shape having a width of 200 mm to 300 mm and an inner peripheral length of 650 mm to 800 mm, in which a photosensitive material layer is formed on the surface of a base material layer. In a photosensitive belt driving device in which a photosensitive belt having a 40 ° elastic body guide member is stretched around a driving roller and a driven roller and rotated by the driving roller, the driving roller and the driven roller are the elastic body. The contact step with which the guide member abuts is formed on the sliding surface having a friction coefficient of 0.02 to 0.30 and the parallelism error between the axes is 0.2.
The photosensitive belt driving device is set to be less than or equal to mm, and the photosensitive belt is stretched around the driving roller and the driven roller with a tension of 2.5 kgf to 12 kgf. 2. A photosensitive belt driving device, wherein the contact step portions of the driving roller and the driven roller are arcuate in section with a radius of 0.5 mm to 50 mm. 3. The photosensitive belt driving device according to claim 1, wherein the contact step portion is covered with a sliding material. 4. A rubber shore hardness of 30 °, which is an endless shape having a width of 200 mm to 300 mm and an inner peripheral length of 650 mm to 800 mm in which a photosensitive material layer is formed on the surface of a base material layer and which is parallel to both end portions of its back surface. In a photosensitive belt driving device in which a photosensitive belt having a 40 ° elastic body guide member is stretched around a driving roller and a driven roller and rotated by the driving roller, the photosensitive belt is 2.5 kgf to 8 kgf. A photosensitive belt driving device, which is stretched around the driving roller and a driven roller by a tension.