JPH03179476A - Electrophotographic system printer - Google Patents

Abstract

PURPOSE:To relax the permanent deformation of an endless belt and to prolong the life of the belt by providing a mechanism for releasing or relaxing tensile force applied to the belt and relaxing the tensile force of the belt other than the time for performing a printing action. CONSTITUTION:The endless belt 1 is supported by a driving roller 2a, follower rollers 2b and 2c and a tension roller 7. Since the tension roller 7 is pulled by a tensile force applying member at the time of performing the printing action, the tensile force is applied to the belt 1 and driven by the driving roller 2a. When the printing action is completed, a cam 12 is driven and a transfer device 17 rotates around the rotary shaft of the driving shaft 2a by the action of a spring 16 and the belt 1 is separated from a drum 3. At such a time, the projecting shaft part 7a of the tension roller 7 abuts on a stopper 9 and is held against the tensile force applying member 14 and a spring 15, so that tension which acts on the belt 1 is relatively released. Thus, the permanent deformation of the belt 1 is relaxed and the life thereof is prolonged.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to an electrophotographic printing apparatus.

[Background of the invention]

In electrophotographic printing devices, a transfer method using corona discharge has been used to transfer the toner image formed on the photoreceptor to the transfer target, but the transfer performance is poor in high humidity.
This method has the disadvantage that transfer defects tend to occur due to stains on the corona wire, wrinkles on the transfer target, and the like. As one example of this, it has been proposed to perform transfer by charging a belt, one surface of which is made of a dielectric material, and pressing the transfer object against the photoreceptor with the belt, but in the above method, In order to prevent transfer defects due to poor adhesion between the photoreceptor and the transfer target, the transfer target must be pressed against the photoreceptor with a predetermined force. FIG. 6 is a sectional view showing an example of the prior art.

The endless belt 1 is stretched between a driving roller 2a and a driven roller 2b, and is applied with a predetermined tension in order to bring the transferred object 6 into close contact with the photoreceptor 3, and presses the transferred object 6 against the photoreceptor 3. There is. Belt tension must be maintained properly to obtain proper transfer. However, the endless belt 1 is made of rubber whose surface is coated with 1ffi material.
Or, it is made of a polyester film, etc., and under conditions where constant tension is applied as described above, it will stretch over time, and the pressing force of the transfer target 6 against the photoreceptor 3 may decrease or it may partially This elongation causes undulations in the endless belt 1, causing problems such as uneven pressing force on the transfer target 6 and deteriorating transferability.

In order to prevent the above-mentioned problems, the prior art has the disadvantage that the endless belt 1 must be periodically replaced at relatively short intervals.

[Purpose of the invention]

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to reduce the elongation of endless belts.

[Summary of the invention]

Permanent deformation of the belt increases as the tension is applied,
In addition, focusing on the fact that tension is only required to be applied during the printing operation, we devised a way to reduce the tension on the belt at times other than during the printing operation to alleviate permanent deformation of the belt and extend the life of the belt.

[Embodiments of the invention]

Fig. 2 is a sectional view showing one embodiment of the present invention, Fig. 3 is a sectional view showing an embodiment of the present invention.
The figures are perspective views, with FIG. 1 showing the printing state and FIG. 2 showing the non-printing state.

In FIG. 1, the endless belt 1 has side plates 10.1
It is supported by a driving roller 2a, driven rollers 2b, 2C, and a tension roller luff, which are locked to the roller 1 through a bearing 13. During printing operation, the tension roller 7 is applied with ↓A force by the tension applying members 14 and 15. Since the endless belt 1 is pulled in the direction, tension is applied to the endless belt 1, and the endless belt 1 is driven in the ←B force direction by the driving roller 2a. When the paper 6 is supplied from the paper supply device (not shown) in the above state, the paper 6 is transferred to the charging device 1.
By 8! It is attracted to the electrified endless belt l and transported. In the process of pressing the paper 6 against the drum 3, the toner 5 is transferred onto the paper 6 and guided to a fixing device provided downstream of the transfer device 17.

When the printing operation is completed, the drive of the endless belt 1 is stopped, the cam 12 is driven, and the transfer device 17 is rotated around the rotation axis of the drive shaft 2a by the action of the spring 16, and the endless belt 1 is rotated around the rotation axis of the drive shaft 2a. More am. This state is shown in FIG. 2. In the above process, the driven roller 2b
, 2C1 and the cleaner unit 8 are connected to the side plate 1.
0.11, it moves around the drive roller 2a as the cam 12 is driven, but the tension roller 7
The protruding shaft portion 7a hits a stopper 9 provided outside the transfer device 17.

Since it is held against the tension applying member 14 and the spring 15, the tension acting on the endless belt l is relatively released. 7'' indicates the tension roller without the stopper 9, which is an embodiment of the present invention, and the tension roller 7' indicates the state in which the stress of the G-end belt 1 is released according to the present invention.

Since the permanent deformation of the endless belt 1 due to creep increases depending on the magnitude of the stress and the time during which the stress is applied, the endless belt 1 can be reduced by releasing the stress acting on the endless belt 1 in a non-printing manner as described above. This can alleviate permanent deformation and extend the lifespan.

[Application example of the invention] Fig. 4 is a sectional view showing an application example of the invention, and Fig. 5 is a cross-sectional view showing an application example of the invention.
FIG.

This application example is different from the method described in the embodiment in which the transfer device is released from the photoreceptor 3 at the end of printing, and only the tension roller 7 is moved by the cam 12 at the end of printing.
This device is designed to release the tension on the endless belt 1 and release the endless belt 1 from the three photoreceptors.

Furthermore, a tension release mechanism may be provided independently in addition to the mechanism for removing the transfer device from the photoreceptor 3.

〔Effect of the invention〕

According to the present invention, tension for normal transfer and belt running can be applied to the endless belt during printing, while the tension described on the left can be released during non-printing, thereby making it possible to alleviate the elongation of the endless belt over time. , it is possible to provide a printing device that has stable transferability over a long period of time.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing embodiments of the present invention, in which 1 is an endless belt, 2a is an opening roller, 2b and 2c are driven rollers, 3 is a photoreceptor, 5 is a toner, and 6 is a transfer target. body,
7 is a tension roller, 9 is a stopper, and 18 is a charging member.

Claims (1)

[Claims] 1. Two or more rollers arranged parallel to each other in the axial direction, an endless belt supported by the rollers and partially or entirely made of a dielectric material, and the endless belt. It has a charging member for charging the belt, and a photoreceptor disposed adjacent to the endless belt, and presses a transferred object electrostatically attracted to the endless belt and conveyed to the photoreceptor. A printing device including a device for transferring electrostatically charged toner carried on the surface of the photoreceptor to the transfer object,
An electrophotographic printing apparatus characterized by having a mechanism for releasing or weakening the tension applied to the endless belt. 2. The electrophotographic printing apparatus according to claim 1, wherein the tension of the endless belt is released or weakened during non-printing operations. 3. The electrophotographic printing apparatus according to claim 1, wherein the endless belt is released from the surface of the photoreceptor by an operation of releasing or weakening the tension of the endless belt. 4. The electrophotographic printing apparatus according to claim 1, wherein the action of releasing or weakening the tension of the endless belt is brought about by an action of releasing the endless belt from the surface of the photoreceptor.