JPH0442273A - Electrophotographic printer - Google Patents

Abstract

PURPOSE:To prevent the plastic deformation and the deterioration of quality of a transfer belt occurring by arranging a heat insulating member for heat insulation among the transfer belt, a heating roll, and a pressurizing roll. CONSTITUTION:The heat insulating means 11, 15 which cut off heat radiation are provided among the heating roll 2, the pressurizing roll 3, and the transfer belt 1. When a print operation is completed, the rotation of the transfer belt 1 is stopped, and when the fact that no material 12 to be transferred exists on a paper guide 10 is detected by a transferred material detecting member 13, a heat insulating material travel mechanism 14 is operated. Thence, a mobile heat insulating member 15 is moved from a position shown in dotted line be tween the heating roll 2 and the neighborhood of part A of the transfer belt 1 to a position shown in continuous line, which prevents the local temperature rise of the transfer belt 1 occurring with a fixed heat insulating member 11. In such a way, it is possible to prevent the plastic deformation in the neighbor hood of the part A and the deterioration of quality of the transfer belt 1 from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrophotographic printing apparatus having a transfer belt and a hot roll fixing device.

[Background of the invention]

The disadvantages of the prior art will be explained below with reference to FIG.

In an electrophotographic printing apparatus having a transfer belt, toner electrostatically adhered on the photoreceptor is transferred to the transfer material 12 as follows. The surface of the transfer belt 1 is charged by the corona charger 6, and the transferred material 1 is charged on the transfer belt 1.
2 is supplied. The transfer material 12 is electrostatically attracted to the surface of the transfer belt 1 and conveyed. Since the transfer belt 1 is always in contact with the photoreceptor 4 with a constant pressure, the transferred material 1
2 is also fixed on the photoreceptor 4 in the transfer area, and the toner on the photoreceptor 4 is electrostatically transferred onto the transfer material 12 by discharge from the transfer corona discharger 7. Thereafter, as the transfer belt 1 rotates, the charge on the transfer material 12 that leaves the photoreceptor 4 is as follows:
The charge is removed by the corona charge remover 8, and the electrostatic attraction force to the transfer belt 1 is weakened. The transfer material 12 separated from the transfer belt 1 passes over a paper guide 1o and is conveyed to a heat roll fixing device consisting of a heat roll 2 and a pressure roll 3.

As described above, since the transfer belt 1 also serves to convey paper to the heat roll fixing device, it is disposed close to the heat roll 2 of the heat roll fixing device. The transfer belt 1 is generally made of a polymer compound because of its electrical properties such as charging and insulating properties, its mechanical properties such as flexibility, and its ease of manufacture.

In conventional electrophotographic printing apparatuses, the heating roll 2 maintains a high temperature of approximately 180 to 190° C. not only during printing but also during printing standby or when the electrophotographic apparatus is standing up. During printing standby, the transfer bells 1 to 1 facing the high-temperature heat roll are stopped, so the heat radiation from the heat roll 2 is concentrated near the area A in the figure on the transfer belt 1. This caused problems such as plastic deformation and material deterioration. Said transfer bell 1-1
If plastic deformation or material deterioration occurs, poor adhesion between the photoconductor 4 and the transfer material 2 may cause paper jams, etc. due to poor adhesion between the transfer material 12 and the transfer belt 1, resulting in poor image quality and This causes serious problems in terms of reliability of the device and shortens the life of the transfer bell 1.

[Purpose of the invention]

An object of the present invention is to provide an electrophotographic printing apparatus that does not cause the above-mentioned problems in an electrophotographic transfer system using an endless transfer belt.

[Summary of the invention]

The present invention recognizes that one of the major causes of the above-mentioned problems with the transfer belt is that the transfer belt stops and faces the high-temperature heating roll during non-printing, and is exposed to heat radiation. By providing a heat insulating means to block heat radiation between the roll, pressure roll, and transfer belt, we focused on the fact that it is possible to prevent the temperature of transfer bells 1 through 1 from increasing. This is something that has been devised.

[Embodiments of the invention]

A specific embodiment of the present invention will be described below with reference to FIG.

When the electrophotographic printing device finishes the printing operation, the rotation of the transfer belt 1 stops. When the transferred material detecting member 13 detects that there is no transferred material 12 on the paper guide 1o while the transfer bell l-1 is stopped, the heat insulating member moving mechanism 14 operates, and the movable heat insulating member 15 moves. heating roll 2;
It moves from the position shown by the dotted line to the position shown by the solid line between the area A of the transfer belt 1 where heat is concentrated, and prevents a local temperature rise of the transfer belt 1 together with the fixed heat insulating member 11. By preventing the temperature rise of the transfer belt 1, it is possible to prevent plastic deformation and material deterioration near the A section of the transfer belt 1 described in the prior art section, which has the effect of improving printing quality and reliability of the device. Moreover, the life of the transfer belt 1 can be extended.

It should be noted that the above-mentioned example has been described in which the heat insulation by the movable heat insulating member 15 is performed in a so-called printing standby state in which the main body of the electrophotographic printing apparatus is in a power supply state and the heat roll fixing device is heated. When the printing apparatus is started up, the heat insulating member moving mechanism 14 is controlled and the movable heat insulating member 15 is moved until the heat roll reaches a predetermined temperature, and even when the power is turned off after finishing printing.
Care has been taken to ensure proper insulation.

In the above embodiment, insulation between the heat roll fixing device and the transfer belt was achieved using only the insulation member, but in order to further enhance the insulation effect, well-known means such as a fan may be installed in the space near the insulation member. Supplementary measures for insulation, such as generating airflow and providing ventilation, may also be used.

Further, if thermal deterioration of the transfer belt 1 can be prevented with the movable heat insulating member 11 fixedly installed to such an extent that it does not impede the conveyance of the transferred material, the heat insulating member moving mechanism 14 used in the above embodiment can be used. , of course, can be omitted.

In addition, some heat roll fixing devices have a mechanism that releases the nip when the heat roll and pressure roll are not rotating, in order to prevent local deformation of the heat roll and pressure roll. Although this is well known, it goes without saying that this nip release mechanism may also be used as a moving mechanism for the movable heat insulating member, and the movable heat insulating member may be moved in conjunction with the nip release.

Furthermore, in this embodiment, the heat insulating member was shaped to cut off heat radiation, but it could also be shaped to almost seal the heat roll or transfer belt so as to prevent the transfer of heat due to convection from the heat roll. It's good as well.

In this embodiment, the heat roll is placed at the top and the pressure roll is placed at the bottom, but the heat roll may be placed at the bottom and the pressure roll is placed at the top.

〔Effect of the invention〕

According to the present invention, by taking heat insulating means such as arranging a heat insulating member between the transfer belt of the electrophotographic printing device and the hot roll fixing device, transfer is performed from a high temperature part such as the heating roll of the hot roll fixing device. By preventing local heat concentration on the belt 1- and preventing plastic deformation and deterioration of the transfer belt,
The effect of improving printing quality and reliability of the device can be obtained, and the life of the transfer belt can be extended.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of an electrophotographic printing apparatus according to the present invention, and FIG. 2 is a sectional view showing an electrophotographic printing apparatus according to the prior art. In the figure, 1 is a transfer belt, 2 is a heating roll, 3 is a pressure roll, 4 is a photoreceptor, 11 is a fixed heat insulating member, 2 is a transfer material, 13 is a transfer material detection member 14 is a heat insulating member moving mechanism , 15 is a movable heat insulating member. Patent applicant name Hitachi Koki Co., Ltd.

Claims (1)

[Claims] 1. A charged transfer belt attracts and conveys the transfer material,
In an electrophotographic printing apparatus that transfers a toner image on a photoreceptor to a transfer material, and conveys the transferred material using a transfer belt to a heat roll fixing device consisting of a heating roll and a pressure roll, the transfer belt and between the heating roll and the pressure roll,
An electrophotographic printing device characterized by disposing a heat insulating member for heat shielding. 2. The heat insulating member is located at a location where it does not interfere with the conveyance of the transferred material when the transfer belt is rotating, and is movable to a position where sufficient heating and cooling effects can be achieved when the transfer belt is stopped. The electrophotographic printing apparatus according to claim 1, characterized in that: 3. The heat roll fixing device has a nip release mechanism for the heating roll and the pressure roll, and the movement of the heat insulating member is performed in conjunction with the nip release mechanism. The described electrophotographic printing device.