JP2835524B2 - Fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in an electrophotographic apparatus such as an electrophotographic copying machine or an electrophotographic printer.

[Related Art] Conventionally, as a thermal fixing device in an electrophotographic apparatus, a roller fixing device, an oven fixing device, a flash fixing device, a belt fixing device, and the like are known. Among them, the belt fixing device is particularly effective in an electrophotographic apparatus using a large-sized transfer material in view of thermal efficiency and prevention of wrinkles. As shown in FIG. 3, an endless belt 103 supported by a pair of spaced rollers 101 and 102 is pressed against an outer peripheral surface of a heating roller 104, and the heating roller 104 and the endless belt are fixed to each other. An apparatus is known in which the transfer member 103 is moved in the forward direction at substantially the same peripheral speed, and is conveyed and fixed while nipping the transfer material at the nip between the heating roller 104 and the endless belt 103.

Further, as shown in FIG. 4, an immovable belt 106 is pressed against the outer peripheral surface of the heating roller 105 to transfer the transfer material to the belt 106.
There is known an apparatus which conveys and fixes by a frictional force of a heating roller 105 while sliding on the surface of the sheet.

[Problems to be Solved by the Invention] In such a conventional apparatus, in the apparatus shown in FIG. 3, the endless belt 103 is laterally shifted for removal with use, and the edge thereof protrudes from the support roller or extremely. There is a problem of being turned up. Also, the belt must be in the form of a seamless loop, which is quite expensive, especially for wide belts intended for large transfer materials. Furthermore, belt 10
3 is configured to contact the heating roller successively over its entire length, so that the belt portion that has separated from the heating roller as it moves moves cools down until it contacts the heating roller again, It has some problems in terms of thermal efficiency, such as depriving heat.

On the other hand, in the apparatus shown in FIG. 4, the transfer material sometimes does not slide smoothly on the belt 106, and there is a problem with the transfer of the transfer material such as clogging of the transfer material. There is a problem that a deviation occurs between the heating roller 105 and the toner image on the transfer material, causing a blur or a flow.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and is intended to provide a belt fixing device which is inexpensive and has good thermal efficiency even for a large-sized transfer material, has no lateral displacement of the belt, and does not cause clogging of the transfer material and blurring of an image. The challenge is to provide in a simple form.

Means for Solving the Problems In order to solve the above problems, a belt whose outer surface is formed of a material and / or surface roughness such that friction is smaller than the outer surface of the heating roller, and a belt, , A heating roller that forms a nip therebetween, a support roller that drives a belt, a supply device that supplies a transfer material to the nip, and a conveyance device that receives the transfer material discharged from the nip and conveys it downstream. A belt is provided so as to be movable and stopped in the forward and reverse directions with respect to the transfer direction of the transfer material, and when the leading edge of the transfer material is inserted into the nip or before it, the belt is moved in the forward direction. When the transfer is started, the belt is stopped when or after the leading edge of the transfer material is provided to the transport device, and only the heating roller is rotated, and the frictional force generated on the heating roller and the slip generated on the upper surface of the belt are caused. Transporting the transfer material in the nip, fixing the toner image on the transfer material, and moving the belt in the opposite direction after the trailing edge of the transfer material passes through the nip to return the belt to the original position. Features.

[Operation] With this configuration, when the leading edge of the transfer material carrying the toner image on the upper surface is inserted into the nip between the heating roller and the belt by the supply device, or before that, the belt rotates in order with the rotation of the heating roller. Start moving in the direction. 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 melts due to contact with the heating roller and is fixed on the transfer material. The belt stops when or after the leading edge of the transfer material is provided to the transport device, and the transfer material is transported while sliding on the belt by the frictional force of the heating roller and the transport force of the transport device. Next, after the trailing edge of the transfer material has passed through the nip, the belt is moved in the reverse direction to return the belt to the original position. The belt that has temporarily shifted in the forward direction moves so as to return to the original position without the side shift when returning in the reverse direction.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1a to 1c show different operation states of an embodiment of the fixing device according to the present invention. Reference numeral 1 denotes a heating roller that rotates in the direction indicated by arrow A. The heating roller has polytetrafluoroethylene or silicon rubber known as Teflon on the outer surface of a hollow cylindrical body made of a metal having good heat conductivity such as aluminum. In some cases, a release agent such as silicone oil is applied thereon. Inside the heating roller, a rod-shaped heater 2 is fixed independently of the heating roller 1, and is turned on and off by an appropriate temperature controller to urge the heating roller to maintain its temperature within a predetermined temperature range. . Reference numeral 3 denotes a wide flexible or elastic belt having a substantially uniform thickness stretched over a pair of support rollers 4 and 6, and in this example, the both ends 7 of the endless belt are joined together. Although a loop is formed, an endless belt that has been formed endlessly in advance may be used. The belt 3 has a width substantially equal to the width of the heating roller 1, and its upper running portion is in surface contact with the outer surface of the heating roller 1 at a suitable pressure. 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 surface roughness that causes less friction with respect to the transfer material to be conveyed than the outer surface of the heating roller 1.
Is stopped, and only the heating roller 1 rotates, the transfer material slides on the belt 3 and is conveyed by the frictional force with the heating roller 1 and the conveying force of the discharge roller. The support rollers 4 and 6 for driving the belt 3 are provided so as to be movable and stopable in the forward and reverse directions with respect to the transfer direction of the transfer material. It is provided in.

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

Reference numeral S1 denotes a detector for detecting the passage of the leading end of the transfer material. The forward / reverse operation or stop operation of the belt 3 is controlled based on the detection signal.

Reference numeral 9 denotes a pair of conveying rollers (conveying device) that receives the transfer material discharged from the nip and conveys the transferring material downstream. The conveying roller pair 9 rotates at a peripheral speed substantially equal to the peripheral speed of the heating roller 1. .

Reference numeral 10 denotes a separation claw for separating the transfer material from the heating roller 1.

In such a configuration, when the transfer material P carrying the toner image on the upper surface is conveyed by the supply roller pair 8 and the leading end is detected by the detector S1, the controller receiving the signal from the detector S1 sends the belt 3 Is moved in the forward direction with the rotation of the heating roller 1 at substantially the same speed as the peripheral speed of the heating roller 1 (FIG. 1a). This forward movement of the belt 3 is started when or before the leading edge of the transfer material P is inserted into the nip. The transfer material P inserted between the nips is heated roller 1
The toner image on the transfer material is melted by the contact with the heating roller 1 and fixed on the transfer material while passing between the nips. The belt 3 stops when or after the leading edge of the transfer material P is gripped by the transport roller pair 9, and the transfer material P slides on the belt 3 by the frictional force of the heating roller 1 and the transport force of the transport roller pair 9. It is transported (Fig. 1b). Next, after the trailing edge of the transfer material P passes through the nip, the support rollers 4 and 6 are reversed, that is, the belt 3 is moved in the reverse direction as shown in FIG. 1c, and the belt 3 is shown in FIG. 1a. Return to the original position. The transfer material that has passed through the nip is transported further downstream by the discharge roller 9.

FIGS. 2a to 2c show another embodiment of the fixing device according to the present invention, in which the same parts as those shown in FIGS. 1a to 1c are denoted by the same reference numerals. In this example, the belt 3 is formed in a belt shape. One end 11 of the belt 3 is wound around the support roller 4 for about 3/4 turn, and then fixed to the outer circumference, and the other end 12 is fixed to the support roller 6. Unlike the example shown in FIGS. 1a to 1c, other substantial configurations and operations are the same as the above example. In particular, in this example, the belt is completely fixed at the end portions of the belt to the support rollers 4 and 6, so that the lateral displacement of the belt is completely prevented.

The forward or reverse rotation or stop of the belt 3 can be controlled in a sequence based on a signal from the detector S1, for example, by counting a constant pulse (of course, the detector S1).
The position of the transfer material is not limited to the position shown in FIG. 1a), or a detector capable of detecting the leading edge and the trailing edge of the transfer material is provided at the outlet of the nip and the inlet of the conveying roller pair 9 so as to determine the position of the transfer material. It is also possible to directly detect and control.

[Effects of the Invention] According to the above configuration, according to the fixing device of the present invention, unlike the conventional configuration in which the belt is moved only in one direction as shown in FIG. Since the contact area of the belt to be contacted is limited to a narrow range, the heat retention efficiency is high, and the belt does not need to be endless, and has a seam as shown in FIG. 3 or a loop as shown in FIG. It is inexpensive because it is possible to use one that is not.

[Brief description of the drawings]

1a to 1c are schematic side views showing different operation states of an example of the fixing device according to the present invention, and FIGS. 2a to 2c are schematic views showing operation states of another example of the fixing device according to the present invention. 3 and 4 are schematic side views showing a conventional fixing device. 1 ... heating roller, 3 ... belt, 4 ... support roller, 6 ... support roller, 8 ... supply roller pair, 9 ... discharge roller pair.

Claims (3)

(57) [Claims] A belt formed by pressing the outer surface of the belt to a material and / or surface roughness such that friction is smaller than that of the outer surface of the heating roller, and pressing the belt to form a nip therebetween. A roller, a support roller for driving a belt, a supply device for supplying the transfer material to the nip, and a transport device for receiving the transfer material discharged from the nip and transporting the transfer material downstream, and The belt is provided so as to be movable in the forward direction and the reverse direction with respect to the transport direction and can be stopped, and when the leading edge of the transfer material is inserted into the nip or before that, the belt starts to move in the forward direction, The belt is stopped when or after the leading edge is provided to the conveying device, and only the heating roller is rotated, and the frictional force generated on the heating roller and the slip generated on the belt upper surface cause the d. Transports the transfer material at the nip, fixes the toner image on the transfer material, moves the belt in the reverse direction after the trailing edge of the transfer material passes through the nip, and returns to the original position. A fixing device. 2. The fixing device according to claim 1, wherein the belt is an endless belt supported by a support roller capable of rotating forward and reverse, or a belt formed by joining both ends to form a loop. 3. The belt comprises an endless belt, one end of which is fixed to one of a pair of reversible rollers, and the other end of which is arranged along the circumference of the other roller. 2. The fixing device according to claim 1, wherein the fixing device is fixed.