JP3487715B2 - Transfer belt device for image forming apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to an image forming apparatus such as a printer or a facsimile apparatus, which uses a transfer belt when transferring a toner image on a photoconductor onto a transfer paper.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrostatic transfer system such as a copying machine, a printer or a facsimile machine, a bias roller as a transfer means is made to face a photoconductor through a transfer belt made of a medium resistance material or the like. A contact transfer method is known in which a transfer bias is applied when a transfer sheet is conveyed to a transfer position by a transfer belt, and a toner image is transferred onto the transfer sheet. In the conventional transfer belt device used in such a system, a transfer belt is stretched around a driving roller and a driven roller as seen in, for example, Japanese Utility Model Laid-Open No. 3-29947 and Japanese Unexamined Patent Publication No. 3-216689. There is.

Naturally, in such a configuration, due to the variation in the roller diameter of the drive roller and the variation in the belt thickness of the transfer belt, which are caused by dimensional errors during manufacturing,
The transfer paper transport speed is not uniform depending on the machine, resulting in variations from machine to machine. Further, it is desired that the linear velocities of the registration roller, the transfer belt, the fixing roller, and the photoconductor maintain a very delicate relationship. Therefore, JP-A-5
As disclosed in Japanese Patent Laid-Open No. 9-204069, a drive roller is provided in the linear transport portion of the transfer belt, which is different from the above.
Techniques have also been proposed for suppressing fluctuations in the transfer belt transport speed.

As described above, in the image forming apparatus using the transfer belt, the linear velocities of the registration roller, the transfer belt, the fixing roller, and the photoconductor are required to have very high accuracy. In particular, the linear velocity of the registration roller, the linear velocity of the photoconductor, the linear velocity of the transfer belt, and the linear velocity of the fixing are important, and the suitability of these linear velocity settings greatly affects the quality of the image. Specifically, image quality deterioration such as magnification error, magnification error deviation, image blur, and latent image blur is caused when the balance of the linear velocity difference is lost. By the way, among the linear velocities of these members and units, the linear velocities that must always be the same are the linear velocity of the photoconductor and the linear velocity of the transfer belt. If these two linear velocities are deviated, no matter how highly accurate the linear velocities of other members and units are controlled, magnification errors, magnification error deviations, image blurring, etc. will always occur, resulting in image quality deterioration. Cause of.
Of the two linear velocities, the linear velocity of the photosensitive member largely depends on the accuracy of the photosensitive member alone and the fluctuation of the driving load of the entire apparatus, and it is not so difficult to secure the target linear velocity at present. There is. On the other hand, the linear velocity of the transfer belt is as described in Japanese Utility Model Laid-Open No. 3-29947 and JP-A-3-216689.
In the configuration in which the transfer belt is driven by the drive roller wound around the back surface of the transfer belt as in the technique described in the publication, the accuracy is substantially determined by the accuracy of the drive roller diameter and the transfer belt thickness. Although it is relatively easy to finish the drive roller diameter with high precision in processing, it is very difficult to make the transfer belt thickness uniform over the entire surface and to finish with high precision.

As shown in FIG. 5, a transfer belt generally comprises a base material 100 made of medium resistance rubber coated with PTFE 101 in a thickness of about 10 to 20 μm. This is one of the reasons that it is difficult to obtain the desired thickness with a uniform structure. Another factor is that it is very difficult in processing to finish the medium resistance rubber thickness of the base material 100 as intended. Also, when the transfer belt thickness changes with time due to wear, elongation, etc., the transfer belt linear velocity naturally deviates from the target value. Further, if a drive roller is provided in the linear portion of the transfer belt as in the technique described in Japanese Patent Laid-Open No. 59-204069, the variation in the transfer belt thickness can be completely ignored, but the transfer belt is driven by the transfer belt and the drive roller. Since the frictional force is used, a driving member such as a driven roller is required to drive the transfer belt in the straight line portion, and a considerable pressing force is required to be applied. This is because it is necessary to provide a cleaning member represented by a cleaning blade, which is a driving load, around the transfer belt, and the transfer paper has entered the transfer portion formed by the nip portion between the photoconductor and the transfer belt. In order to accurately convey the transfer paper even after that, slip should not occur between the transfer belt and the driving roller, and the contact area between the transfer belt and the driving roller is very small in the linear path of the belt. Therefore, it is necessary to increase the pressing force in order to prevent the slip.

Therefore, the drive roller is brought into contact with the surface of the transfer belt which is endlessly stretched, that is, the transfer belt is electrostatically adsorbed and conveys the transfer paper, and the transfer belt 2
At least one of the rollers that stretch the transfer belt is brought into contact with the surface of the transfer belt so that slip does not occur between the drive rollers, and a linear lower running path formed by another driven roller. A technique has been proposed in which a drive roller is arranged so as to be deformed toward the inside of the belt, and the transfer belt is wound around the outer peripheral surface of the drive roller. In this technique, the transfer belt is driven without slipping with the drive roller, and the transport speed at that time, that is, the linear speed of the transfer belt is determined only by the diameter and the number of rotations of the drive roller, and the linear speed due to the variation in the thickness of the transfer belt. Therefore, it is easy to maintain the balance of the linear velocity difference among the registration roller, the photoconductor, the transfer belt, and the fixing roller, and it is possible to prevent the occurrence of an abnormal image.

[0007]

However, even if such a technique is applied, the drive roller is likely to be contaminated with toner or paper dust, which may cause a slip between the transfer belt and the drive roller. Is difficult to maintain for a long time. Therefore, a configuration is proposed in which a member for cleaning the drive roller is added to maintain the performance for a long period of time.

However, in the above-mentioned technique, the replaceability, the mounting position, etc. of the cleaning member are not taken into consideration, and when the cleaning member becomes dirty due to its suitability over time, the original purpose may not be achieved. The solution of this point was desired.

[0009]

In order to solve the above-mentioned conventional problems, the transfer belt device of the image forming apparatus of the present invention according to claim 1 is stretched and driven by a plurality of rollers, An endless transfer belt that electrostatically attracts and conveys the transfer paper from the upstream side to the downstream side of the photoconductor is provided, and the driving roller of the plurality of rollers is a transfer paper suction and conveyance surface of the transfer belt. In the transfer belt device of the image forming apparatus in which the cleaning member is in contact with the driving roller surface, the cleaning member is held by a holder member that forms a part of a support case, and the holder member is It is characterized by being detachable from the support case.

A second aspect of the present invention is characterized in that the cleaning member for the drive roller is detachable from the holder member.

A third aspect of the present invention is characterized in that the cleaning member is brought into surface contact with the drive roller.

A fourth aspect of the present invention is characterized in that the cleaning member is a roller-shaped member that is driven while being in contact with the drive roller.

According to the fifth aspect of the present invention, the cleaning member is opposed to the transfer belt with the drive roller interposed therebetween, and 0 ° to 90 ° from the vertical center line of the drive roller.
It is characterized in that it is arranged within the angle range of.

According to a sixth aspect of the present invention, the angle formed by the horizontal plane of the line connecting the center of the cleaning member and the center of the drive roller is in the range of 0 ° to 90 °.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a first embodiment of the present invention, and illustration and description of other components involved in image formation based on an electrophotographic process are omitted. Although not shown, the necessary devices based on the image forming principle known as the Carlson process are arranged around the drum-shaped photosensitive member 1 in FIG. First, in synchronism with the movement of the toner image formed on the photoconductor 1 rotating at the linear velocity Vo in the direction of the arrow, the transfer paper P sent by the registration roller pair 5 is transferred by the photoconductor 1 and the transfer belt 2. It is conveyed to the part 6. The transfer paper P is a pair of registration rollers 5.
Is conveyed to the transfer unit 6 at a linear velocity VR determined by the diameter of the. Next, the transfer sheet P is electrostatically attracted to the charged transfer belt 2 at a predetermined timing, and the transfer sheet P is conveyed at the linear velocity Vb of the transfer belt 2. At this time, the linear velocity V of the photoconductor 1
It is desirable that there is a relationship of Vo = Vb <Vr between o, the speed Vb of the transfer belt 2 and the linear speed VR of the registration roller pair 5.

The transfer belt device has one driving roller 3,
The driven roller 3 and the driven rollers 4a, 4b, 4c are composed of three driven rollers 4a, 4b, 4c, the transfer belt 2, etc.
The transfer belt 2 is stretched endlessly between the drive roller 3 and
It is driven by the driving force of. That is, by rotating the driving roller 3 by a driving source (not shown), the transfer belt 2 in contact with the driving roller 3 is run at the speed of Vb. Transfer belt 2
Is in contact with the drive roller 3 on the same surface as the transfer paper P is electrostatically attracted to and conveyed by the transfer belt 2, and has a predetermined winding so as not to slip between the transfer belt 2 and the drive roller 3. The drive roller 3 is in contact with the corners.

That is, as shown in the drawing, the driven roller 4c is arranged at a proper position on the lower running surface, and the driven roller 4c is also arranged.
The drive roller 3 is disposed in the vicinity of the upstream side of the transfer roller 3 so that the drive roller 3 and the driven roller 4c are displaced inside the original lower running surface of the transfer belt 2 so that the driven roller 4c moves downward. The vertical positional relationship is shifted so as to be displaced to the outside of the side traveling surface. Therefore, the transfer belt 2 is wound around the outer peripheral surface of the drive roller 3. 7 in the figure
Is an upper guide plate, 8 is a lower guide plate, 9 is a cleaning blade, and 11 is a fixing roller pair. Also, the drive roller 3
The diameter and the number of revolutions of the transfer belt 2 are the target speed Vb of the transfer belt 2.
Can be arbitrarily selected by. That is, the thickness of the transfer belt 2 has nothing to do with the speed Vb of the transfer belt 2, and the speed Vb of the transfer belt 2 is the same as the drive roller linear speed Vr determined by the diameter and the rotation speed of the drive roller 3.

Reference numeral 14 in the drawing is a case for accommodating and supporting the above-mentioned transfer belt device, and a holder 15 of the cleaning member 10 is detachably attached to the case 14.
The holder 15 of the cleaning member 10 can be attached to the case 14 by utilizing the elasticity of the molding material, for example, by a so-called “patching stop” structure. In order to attach the cleaning member 10 to the holder 15 and make it removable, for example, when the cleaning member 10 uses a nonwoven fabric 16, a double-sided tape 17 may be attached to the back surface in advance so that the adhesive member can be peeled off. . The cleaning member 10
The drive roller 3 may be divided into a plurality of parts in the longitudinal direction along the axial direction.

When the holder 15 to which the cleaning member 10 is attached is attached to the case 14, the nonwoven fabric 16 of the cleaning member 10 is attached.
Is pressed by the drive roller 3 and comes into contact with the surface of the drive roller 2 over a certain area. Therefore, when the drive roller 3 rotates, the nonwoven fabric 16 makes sliding contact with the surface of the drive roller 3, so that a force F acts on the cleaning member 10 in the tangential direction over the entire contact surface as shown in FIG. The surface is cleaned, and the target transfer belt linear velocity Vb is maintained for a long time without slipping the transfer belt 2.

The range in which the cleaning member 10 is brought into contact with the drive roller 3 is preferably set such that the angle from the vertical center line of the drive roller is 0 ° ≤θ1≤90 °, as shown in FIG. That is, if the cleaning member 10 is in the range of θ1 ≧ 90 °, the holder 15 cannot be removed by simply removing the holder 15 from the case 14 in the vertical direction. 0 ° ≧
When the cleaning member 10 is in the range of θ1, a tangential force is applied to the cleaning member 10 in the direction in which the holder 15 is disengaged from the case 14 when the drive roller 3 rotates, while 0 ° ≦ θ1 ≦ 90 °. If the cleaning member 10 is attached in the range of, the holder 15 can be detached and attached from the case 14 only in the vertical direction, the replacement workability is improved, and the cleaning member 10 does not come off during driving.

FIG. 3 is a schematic sectional view showing a second embodiment of the present invention. Similar to FIG. 1, only parts necessary for explaining the present invention are shown, and illustration and description of other components involved in image formation based on the electrophotographic process are omitted.

In this embodiment, the cleaning member 1 of the previous embodiment is used.
Instead of 0, a holder 18 having a cleaning roller 12 at its tip which rotates while being driven by the drive roller 3 and cleans the surface of the drive roller 3 is used. As a matter of course, the cleaning roller 12 is made of a material having a larger coupling force with the toner than that of the driving roller 3. Further, since a force acts between the cleaning roller 12 and the driving roller 3 in the direction connecting the centers of the cleaning roller 12 and the driving roller 3, the angle formed by the line connecting the cleaning roller 12 and the driving roller 3 and the horizontal plane is 0 as shown in the figure. The cleaning roller 12 is attached so that the range of ° ≦ θ3 ≦ 90 ° is satisfied. In the case of this embodiment, as shown in FIG. 4, both ends of the cleaning roller 12 are supported by the holders 18a having elasticity, and the removal uses the elasticity of the holders 18a (the supporting parts are tilted as indicated by arrows in the figure). You may do it. Other configurations,
Since the operation is the same as that of the previous embodiment, duplicate description will be omitted.

[0023]

In the transfer belt device of the image forming apparatus according to the first aspect of the present invention, since the holder supporting the cleaning member of the driving roller is detachable from the case,
When replacing the cleaning member, it is possible to replace the entire transfer belt device without taking out the transfer belt device from the main body of the image forming apparatus, and the replacement workability is greatly improved.

In the transfer belt device of the image forming apparatus according to the second aspect of the present invention, since the cleaning member and the holder of the driving roller are detachable, only the cleaning member can be exchanged in addition to the above-mentioned common effect, and therefore the exchange is possible. There is an effect that the cost of members can be reduced. Further, since only the cleaning member is a consumable component, there is an effect that the component disposal cost can be reduced and the environment can be addressed.

In the transfer belt device of the image forming apparatus according to the third aspect, since the cleaning member is in surface contact with the driving roller, in addition to the above-mentioned common effects, the cleaning ability is high and the target transfer belt linear velocity is high. Has the effect of making it easier to maintain for a long time.

In the transfer belt device of the image forming apparatus according to the fourth aspect, since the cleaning member is pressed against and driven by the driving roller, the load of the cleaning member can be reduced in addition to the above-described common effect, and thus the transfer can be performed. The torque for driving the belt device is reduced, and the load on the drive source is reduced, which contributes to cost reduction.

In the transfer belt device of the image forming apparatus according to the fifth aspect, since the cleaning member is attached within the range of 0 ° ≦ θ1 ≦ 90 ° from the vertical center line of the drive roller, in addition to the above common effects, There is an effect that the detachability of the cleaning member and the holder from the case can be improved.

In the transfer belt device of the image forming apparatus according to the sixth aspect, the angle formed by the line connecting the center of the cleaning member and the center of the drive roller with the horizontal plane is in the range of 0 ° to 90 °. In addition to the common effect, when the cleaning member is pressed against the drive roller, no force is applied to the cleaning member in the vertical direction, so that the cleaning member is not likely to come off from the case.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the embodiment of FIG.

FIG. 3 is a schematic cross-sectional view showing a second embodiment of the present invention.

FIG. 4 is a conceptual diagram showing an example in which both ends of a cleaning roller are supported by elastic holders in the embodiment of FIG.

FIG. 5 is a cross-sectional view of a general transfer belt.

[Explanation of symbols]

1 photoconductor 2 Transfer belt 3 drive roller 4 Driven roller 5 Registration roller pair 6 Transfer part 7 Upper guide plate 8 Lower guide plate 9 Cleaning blade 10 Cleaning member 11 Fixing roller pair 12 Cleaning roller 14 cases 15 holder 16 non-woven fabric 17 double-sided tape 18, 18a holder

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Claims (6)

(57) [Claims] 1. An endless transfer belt, which is stretched and driven by a plurality of rollers and electrostatically attracts and conveys a transfer sheet from the upstream side to the downstream side of a photosensitive member. In a transfer belt device of an image forming apparatus, in which a drive roller is in contact with a transfer paper suction and conveyance surface of the transfer belt, and a cleaning member is in contact with the drive roller surface, the cleaning member is provided in a support case. A transfer belt device of an image forming apparatus, characterized in that the transfer belt device is held by a holder member that forms a part, and the holder member is detachable from the support case. 2. The cleaning member for the drive roller is attachable to and detachable from the holder member.
Transfer belt device of the image forming apparatus. 3. The transfer belt device of the image forming apparatus according to claim 1, wherein the cleaning member is in surface contact with the drive roller. 4. The transfer belt device for an image forming apparatus according to claim 1, wherein the cleaning member is a roller-shaped member that is driven while being in contact with the drive roller. 5. The cleaning member is arranged so as to face the transfer belt with the drive roller interposed therebetween, and is arranged within an angle range of 0 ° to 90 ° from a vertical center line of the drive roller. The transfer belt device of the image forming apparatus according to claim 1. 6. The transfer of the image forming apparatus according to claim 4, wherein an angle formed by a line connecting the center of the cleaning member and the center of the driving roller with a horizontal plane is in the range of 0 ° to 90 °. Belt device.