JPH0530860U - Fixing device - Google Patents

Abstract

(57) [Summary] (Correction) [Construction] In a heat fixing device using a pressure belt, a plurality of rollers that hang the belt have a minimum diameter in the central portion and gradually increase in diameter toward both ends. It includes a roller and a roller having a maximum diameter in the central portion and gradually decreasing toward both ends. [Effect] It is possible to prevent the endless belt from laterally shifting and meandering with respect to the fixing roller.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a fixing device in an electrophotographic apparatus such as a copying machine.

[0002]

[Prior Art]

 The electrostatic latent image formed on the photoconductor by irradiating optical information according to the subject is converted into a toner image in the developing process and transferred onto a transfer material such as paper or resin film. The transfer material carrying the toner image is separated from the photoconductor and guided to the fixing device to fix the toner image. In general, a fixing device includes a fixing roller having a built-in heater, a pressure device such as a roller or an endless belt that conveys a transfer material between the fixing roller and a toner image to heat and fix the toner image, and a peripheral device around them. It is composed of related members such as a peeling claw and a discharge roller that are operably arranged.

[0003]

[Problems to be solved by the device]

 When an endless belt is used as a pressure device for the fixing roller, the time to press the transfer material, that is, the contact time of the endless belt with the fixing roller is relatively long compared to the case of the pressure roller, so that the temperature and pressure are not changed. Although there is an advantage that it can be lowered, there is a problem that the endless belt comes into contact with other members due to lateral displacement or meandering, and the endless belt is turned up or caught and damaged.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a fixing device that prevents lateral displacement and meandering of the endless belt with respect to the fixing roller.

[0005]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention provides a fixing roller that is heated by a heater and a plurality of rollers that convey the transfer material between the fixing roller and the fixing roller for fixing the toner image formed on the transfer material. In a fixing device including a looped endless belt, the plurality of rollers on which the looped endless belt is looped has a roller having a minimum diameter at the center and a diameter gradually increasing toward both ends, and a roller at the center. And a roller having a maximum diameter and gradually decreasing toward both ends. Particularly preferably, the endless belt has a width wider than that of each roller around which the belt is wound, and the belt is configured to press the edge of each roller.

[0006]

[Action]

 The endless belt has a maximum diameter at its center and a gradually decreasing diameter toward both ends. On the roller side of the so-called reverse-crown type, which has a gradually increasing diameter toward, it receives a series of repeated forces in opposite directions in the thickness direction so as to dent. These forces correct the deviation of the belt, and the forces in any of these directions act toward each other toward the center of the belt in the width direction, so that lateral displacement and meandering of the belt with respect to the rollers are suppressed.

[0007]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a preferred embodiment of the present invention. In the drawing, reference numeral 1 is a heat fixing roller arranged inside an electronic copying machine, and a transfer material, for example, paper is sandwiched between the fixing roller 1. The endless belt device 2 is provided as a pressurizing device that presses in contact with. The fixing roller 1 is usually a hollow aluminum roller whose surface is coated with an anti-offset material such as Teflon, and a rod-shaped heater is disposed inside the hollow. Further, the endless belt 3 of the belt device 2 is hung on a plurality of support rollers, three support rollers 4, 5 and 6 in the illustrated example, and the upper running portion of the belt 3 between the rollers 4 and 5 is the fixing roller 1. Press against the peripheral surface of.

The fixing roller 1 is rotatably provided on a fixed side plate 7 of the electrophotographic apparatus, and is rotated in a direction indicated by an arrow A when actuated by a driving device (not shown). Arranged around the fixing roller 1 are a peeling claw 8 for preventing the transfer material from winding around the roller, an oil applying device 9 for supplying offset preventing oil to the fixing roller, a cleaning blade 11, and a surface temperature detector 12. Has been done. Reference numeral 13 is a guide plate for conveying the transfer material conveyed from the photosensitive drum to the fixing device, and 14 is a discharge roller for the transfer material.

The plurality of support rollers around which the endless belt 3 is stretched has a so-called crown-shaped roller having a minimum diameter in the central portion and gradually increasing toward both ends, and a maximum diameter in the central portion. It includes a so-called inverted crown-shaped roller that gradually decreases in diameter toward both ends. In the illustrated example, the roller 4 on the inlet side of the transfer material is a straight roller, the roller 5 on the outlet side is a crown-shaped roller, and the intermediate roller 6 is a reverse crown-shaped roller. The surfaces of the rollers 4, 5 and 6 are provided with friction reducing means such as Teflon coat in order to reduce the coefficient of friction with the belt 3, and when the belt is thermally expanded, the expansion in the width direction is reduced. It is designed to be slid against. The roller 4 is arranged so that the belt 3 is pressed against the fixing roller, and the transfer material conveyed between the fixing roller 1 and the belt 3 is pressed against the peripheral surface of the fixing roller 1. The fixing roller 1 may have a straight shape or an inverted crown shape complementary to the shape of the support roller 5.

The belt 2 has its center portion in the width direction bulged according to the shape of the roller 5 on the side of the roller 5 having a crown shape, and dents according to the shape of the roller 6 on the side of the roller 6 having a reverse crown shape. Each of them is repeatedly subjected to a force in the opposite direction in the thickness direction. These forces act so as to correct the deviation of the belt, and both act toward each other toward the center of the belt in the width direction, so that lateral displacement and meandering of the belt with respect to the roller are suppressed.

In order to prevent the lateral displacement of the belt more reliably, the endless belt 3 has a wider lateral width than the support rollers 4, 5, and both end portions of the endless belt 3 have support rollers 4, 5 as shown in FIG. , 6 has a width such that it projects a few mm to a few tens of mm outwardly in the axial direction from the edge E. The endless belt 3 is, for example, a heat-resistant belt made of silicon rubber or the like, on which a toner offset preventing means such as Teflon coat is applied, and it is preferable that the endless belt 3 has appropriate elastic contraction. A portion 30 (FIG. 2) in the vicinity of the edge projecting from the edge E of the supporting rollers 4, 5, 6 of 3 holds the edge E of the supporting roller with an appropriate pressure to prevent lateral displacement of the belt with respect to the supporting roller.

In the above description, the roller 4 has a straight shape, the roller 5 has a crown shape, and the roller 6 has an inverted crown shape. However, the present invention is not limited to this, and any one of a plurality of rollers supporting the belt 3 can be crowned. And a reverse crown is included. Further, the number of support rollers is not limited to three.

[0013]

[Effect of the device]

 As described above, according to the present invention, as the plurality of rollers for supporting the belt, the crown-shaped roller and the inverted crown-shaped roller are included to prevent the lateral displacement of the belt, and further, the belt width is set to be larger than the roller length. By setting a large value and pressing down the end of the roller with the belt's tightening force, the lateral displacement of the belt can be prevented more reliably.

[Brief description of drawings]

FIG. 1 is a side sectional view showing the internal structure of a fixing device according to an example of the present invention.

FIG. 2 is an explanatory view showing the shape of a support roller of FIG.

FIG. 3 is a front view showing a belt portion of FIG.

[Explanation of symbols]

 1 Fixing Roller 2 Endless Belt Device 3 Endless Belt 4 Support Roller 5 Support Roller 6 Support Roller

Claims (2)

[Scope of utility model registration request] 1. A fixing roller heated by a heater,
In a fixing device including an endless belt that is wound between a plurality of rollers that convey the transfer material between the fixing roller and the fixing roller to fix the toner image formed on the transfer material, the plurality of rollers that apply the endless belt are , A roller having a minimum diameter at the central portion and gradually increasing toward both ends, and a roller having a maximum diameter at the central portion and gradually decreasing toward both ends. Fixing device. 2. The endless belt has a width wider than that of each roller around which the endless belt is wound, and the endless belt is arranged so as to press the end edge of each roller.
The fixing device described.