JPH0311382A - Fixing device - Google Patents

Abstract

PURPOSE:To eliminate the horizontal deviation of a belt and to prevent the jamming of a transfer material and the blurring of an image by providing the belt so that it can move and stop in normal and reverse directions with respect to the conveying direction of the transfer material and appropriately moving the belt. CONSTITUTION:In a belt type fixing device, the belt 3 is provided so that it can move and stop in the normal and reverse directions with respect to the conveying direction of the transfer material P. When or before the leading edge of the transfer material P is inserted in a nip, the belt 3 starts to move in the forward direction and when or after the leading edge of the material P is offered to a conveying device 9, the belt 3 is stopped. After the trailing edge of the material P passes the nip, the belt 3 is moved in the reverse direction to return to a home position. Thus, the horizontal deviation of the belt is eliminated and the jamming of the transfer material P and the blurring of the image are not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fixing device in an electrophotographic apparatus such as an electronic copying machine or an electrophotographic printer.

[Prior Art] Conventionally, a roller fixing device, an open fixing device, a flash fixing device, a belt fixing device, and the like are known as heat fixing devices in electrophotographic apparatuses.

Among these, the belt fixing device is particularly effective in terms of thermal efficiency and prevention of wrinkles in electrophotographic apparatuses using large transfer materials. As shown in FIG.
Endless belt 103 supported by and 102
is pressed against the outer peripheral surface of the heating roller 104, and the heating roller 10
4 and the endless belt) 103 in the forward direction at approximately the same circumferential speed, and the heating roller 104 and the endless belt 103
An apparatus is known that performs fixing by transporting a transfer material while nipping it in a nip between the transfer material and the transfer material.

Further, as shown in FIG. 4, an immovable bell 106 is brought into pressure contact with the outer peripheral surface of the heating roller 105, and the transfer material is pressed against the outer peripheral surface of the heating roller 105.
An apparatus is known in which the toner is conveyed and fixed by the frictional force of the heating roller 105 while sliding on the surface of the heated roller 106.

[Problems to be Solved by the Invention] Among such conventional devices, the device shown in FIG.
The problem is that the endless bell 103 tends to shift laterally as it is used, and even worse, its edges protrude from the support roller or roll up. In addition, the belt must be in the form of a seamless loop, and is quite expensive, especially if it is a wide belt intended for large-sized transfer materials. Furthermore, belt 10
3 has a structure in which the belt contacts the heating roller in turn over its entire length, so the part of the belt that has moved away from the heating roller as it moves cools down until it contacts the heating roller again, and when it comes into contact with the heating roller again, the part of the belt that has left the heating roller cools down. It has some problems in terms of thermal efficiency, such as the ability to absorb heat.

On the other hand, in the apparatus shown in FIG. 4, there are problems with conveyance of the transfer material, such as the transfer material not sliding smoothly on the belt 106 and clogging of the transfer material. There is a problem in that misalignment with the heating roller 105 occurs, causing blurring or running of the toner image on the transfer material.

The present invention was made in view of the above-mentioned problems, and it is possible to easily create a belt fixing device that is inexpensive and has good thermal efficiency even for large transfer materials, does not cause lateral deviation of the belt, and does not cause image distortion if the transfer material becomes clogged. The challenge is to provide it in a form that is

[! ! Means for Solving the Problem] In order to solve the above problem, the fixing device according to the present invention transfers the toner image by bringing a belt into pressure contact with a heating roller and passing a transfer material carrying a toner image through the nip between the belt. A fixing device of a type that fixes onto a material includes a supply device that supplies transfer material to the nip, and a conveyance device that receives the transfer material discharged from the nip and conveys it downstream, and The belt is provided so as to be movable in the forward direction and the reverse direction with respect to the conveying direction of the material, and can be stopped, and the forward movement of the belt is started when or before the leading edge of the transfer material is inserted into the nip, and the transfer material is moved in the forward direction. The belt is stopped when or after the leading edge of the transfer material is provided to the conveying device, and the belt is moved in the opposite direction to return to its original position after the trailing edge of the transfer material passes through the nip. It is characterized by

[Function] With this configuration, the belt is connected to the rotation of the heating roller before or when the leading edge of the transfer material carrying the toner image on its upper surface is inserted into the nip between the heating roller and the belt by the supply device. Start moving forward. As a result, the transfer material inserted into the nip is conveyed while being sandwiched between the heating roller and the belt, and while passing through the nip, the toner image on the transfer material is melted by contact with the heating roller and fixed onto the transfer material. When or after the leading edge of the transfer material is provided to the conveyance device, the belt stops, and the transfer material slides on the belt and is conveyed by the frictional force of the heating roller and the conveyance force of the conveyance device. After the trailing edge passes through the nip,
Move the belt in the opposite direction and return the belt to its original position. A belt that has undergone lateral deviation when moving in the * direction will move so as to return to its original position where there is no lateral deviation when returning in the opposite direction.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1a to 1c show different operating states of an embodiment of the fixing device according to the present invention.

The symbol l is a heating roller that rotates in the direction shown by arrow A, and has polytetrafluoroethylene or silicone rubber known as Teflon on the outer surface of a hollow cylindrical body made of a metal with good thermal conductivity such as aluminum. In some cases, a release agent such as silicone oil is applied on top of the mold release agent.

A rod-shaped heater 2 is fixed inside the heating roller independently of the heating roller 1, and is controlled on and off by an appropriate temperature controller to maintain the temperature of the heating roller within a predetermined temperature range. . Reference numeral 3 denotes a wide flexible or elastic belt with a substantially uniform thickness stretched over a pair of support rollers 4.6, and in this example, by joining both ends 7 of the belt with ends. Although the belt 3 forms a loop, it may be an endless belt formed in advance. The belt 3 has a width approximately equal to the width of the heating roller 1, and its upper running portion touches the outer surface of the heating roller 1. surface contact with appropriate pressure. The contact length a of the belt 3 with respect to the heating roller 1 is determined in consideration of the set temperature of the heating roller 1, the conveying speed of the transfer material, the melting point of the toner to be fixed, and the like. The outer surface of the belt 3 is made of a material and/or has a surface roughness that causes less friction than the outer surface of the heating roller 1 with respect to the transfer material to be conveyed, so that when the belt 3 stops and only the heating roller l rotates, , the transfer material is configured to slide on the belt 3 and be transported by the frictional force with the heating roller 1 and the transporting force of the discharge roller. A support roller 4.6 that drives the belt 3 is provided so as to be movable in the forward and reverse directions with respect to the conveying direction of the transfer material, and can be stopped, and accordingly, the belt 3 is movable in the forward and reverse directions and can be stopped. It is set in.

Reference numeral 8 is a suction belt device for providing a transfer material carrying a toner image by a known electrophotographic system to a nip (gap) between the heating roller 1 and the belt 3;
It rotates in the direction shown by arrow B at approximately the same circumferential speed as heating roller 1. In some cases, the suction belt device 8 can be omitted, in which case the transfer material is provided between the nip by the transport force of the photosensitive drum in electrostatic contact for the transfer of the toner image. In this document, the term "supply position" refers to a means for supplying the transfer material to the nip, such as a suction belt device or a photosensitive drum.

Reference numeral Sl denotes a detector for detecting passage of the leading edge of the transfer material, and the forward/reverse operation or stopping of the belt 3 is controlled based on this detection signal.

Reference numeral 9 indicates a pair of conveying rollers (conveying device) that receives the transfer material discharged from the nip and conveys it downstream, and the pair of conveying rollers 9 rotates at approximately the same circumferential speed as the circumferential speed of the heating roller l. .

Reference numeral 10 indicates a peeling claw for peeling off the transfer material from the heating roller 1.

In such a configuration, when the transfer material P carrying the toner image on its upper surface is conveyed by the pair of supply rollers 8 and its leading edge is detected by the detector S1, the controller receives a signal from the detector S1 and moves the belt 3 is moved in the forward direction of the rotation of the heating roller L at approximately the same speed as the circumferential speed of the heating roller L (Fig. 1a), and this forward movement of the belt 3 causes the leading edge of the transfer material P to be inserted into the nip. Begins when or before. The transfer material P inserted between the nip is conveyed while being held between the heating roller 1 and the belt 3, and while passing between the nips, the toner image on the transfer material is melted by contact with the heating roller L and is deposited on the transfer material. It will be established. When or after the leading edge of the transfer material P is gripped by the pair of transport rollers 9, the belt 3 stops, and the transfer material P slides on the belt 3 due to the frictional force of the heating roller 1 and the transport force of the pair of transport rollers 9. transported (Fig. 1b). Then, after the trailing edge of the transfer material P has passed through the nip, the support roller 4.6 is reversed, i.e. the belt 3 is moved in the opposite direction as shown in FIG. The transfer material that has passed through the nip is conveyed further downstream by the discharge roller 9.

Figures 2a to 2C show another embodiment of the fixing device according to the invention, in which the same parts as in the example shown in Figures 1a to 1c are designated by the same reference numerals. In this example, the belt 3 is in the form of a belt, and the lower end 11 is fixed to the outer circumferential surface of the support roller 4 after being wrapped about 374 times around the outer circumferential surface, and the other end 12 is fixed to the support roller 6. Figure 1a to 1st
Unlike the example shown in FIG. c, the other substantial configurations and operations are the same as the above example. Particularly in this example, since the ends of the belt are fixed to the support rollers 4 and 6, sideways displacement of the belt is completely prevented.

The forward/reverse rotation or stopping of the belt 3 can be sequentially controlled by, for example, counting constant pulses based on the signal from the detector S1 (of course, the signal from the detector S1 is used as a reference).
t is not limited to the position shown in FIG. It is also possible to directly detect and control the position of.

[Effects of the Invention] With the above configuration, the fixing device according to the present invention
1! Unlike the conventional configuration in which the belt moves only in one direction as shown in I, there is no lateral deviation of the belt, and there is no additional
Since the contact area of the belt that should be in contact with the a-ra is narrow and limited, heat retention efficiency is good, and there is no need for the belt to be endless. It is inexpensive because it can be used without loops.

[Brief explanation of the drawing]

1a to 1c are schematic side views showing different operating states of an example of the fixing device according to the present invention; I
FIGS. 2C to 2C are schematic side views showing the operating state of another example of the fixing device according to the present invention, and FIGS. 3 and 4 are schematic side views showing the conventional fixing device. DESCRIPTION OF SYMBOLS 1... Heating roller, 3... Belt, 4... Support roller, 6... Support roller, 8... Supply roller pair, 9... Discharge roller pair.

Claims (3)

[Claims] (1) In a fixing device of a type in which a belt is pressed against a heating roller and a transfer material carrying a toner image is passed through a nip between the belt and the toner image is fixed on the transfer material, the transfer material is provided to the nip. It has a supply device and a conveyance device that receives the transfer material discharged from the nip and conveys it downstream, and the belt is provided so as to be movable in forward and reverse directions with respect to the conveyance direction of the transfer material and to be stoppable. , starting the forward movement of the belt at or before the leading edge of the transfer material is inserted into the nip, and moving the belt at or after the leading edge of the transfer material is provided to the transport device. The fixing device is characterized in that the belt is stopped, and after the trailing edge of the transfer material passes through the nip, the belt is moved in the opposite direction to return to its original position. (2) The fixing device according to claim 1, wherein the belt is an endless belt supported by a support roller capable of forward transfer, or a belt having both ends joined together to form a loop. (3) The belt consists of a band with an end, one end of which is fixed to one of a pair of rollers that can be forward-transferred, and the other end is placed along the circumference of the other roller; 2. The fixing device according to claim 1, wherein the fixing device is fixed.