JP2586842Y2 - Fixing device - Google Patents

Description

[Detailed description of the invention]

[0001]

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

[0002]

2. Description of the Related Art An electrostatic latent image formed on a photoreceptor by irradiating light information corresponding to a subject is converted into a toner image in a developing process, and is transferred onto a transfer material such as paper or a resin film. The transfer material carrying the toner image is separated from the photoreceptor and guided to a fixing device to fix the toner image. In general, a fixing device includes a fixing roller having a built-in heater, and a pressing device such as an endless belt or a roller for transporting a transfer material between the fixing roller and performing heat fixing of a toner image. And related members such as a peeling claw and a discharge roller which are operably disposed.

[0003]

In the case of using an endless belt as a pressing device for the fixing roller, the time for pressing the transfer material, that is, the contact time of the endless belt for the fixing roller, is relatively shorter than in the case of the pressure roller. It has the advantage of being able to lower the temperature and pressure due to its long length, but it has the problem that the endless belt comes in contact with other members due to lateral displacement or meandering and is turned up or caught and damaged. have.

[0004] 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 the endless belt from laterally shifting and meandering with respect to a fixing roller.

[0005]

In order to solve the above problems, the present invention provides a fixing roller heated by a heater,
In a fixing device including an endless belt hung between a plurality of rollers that convey the transfer material between the fixing roller and the fixing roller to fix a toner image formed on the transfer material, the plurality of rollers that hang the endless belt include: A straight-shaped roller positioned at the entrance side of the transfer material and arranged so as to press the endless belt against the fixing roller; , And a roller located between the roller located on the entrance side and the roller located on the exit side has a minimum diameter at the center and gradually increases toward both ends. And the endless belt has a wider width than each of the rollers around which the endless belt is wound, and is arranged such that the endless belt presses the edge of each roller.

[0006]

The endless belt has a minimum diameter at the center so that the center of the endless belt expands on the so-called crown-shaped roller side where the center portion on which the belt is hung has a maximum diameter and gradually decreases toward both ends. Then, on the side of the so-called inverted crown-shaped roller, which gradually increases in diameter toward both ends, a force in the opposite direction in the thickness direction is repeatedly and successively received so as to be depressed. These forces correct the bias of the belt, and the forces in any of these directions act so as to be attracted toward the center in the width direction of the belt, so that lateral displacement and meandering of the belt with respect to the rollers are suppressed.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 shows a preferred embodiment of the present invention.
In the drawing, reference numeral 1 denotes a heat fixing roller disposed inside the electrophotographic apparatus, and an endless belt device 2 as a pressing device that presses a fixing member 1 with a transfer material, for example, paper.
Is provided. The fixing roller 1 is generally formed by coating a surface of a hollow aluminum roller with an anti-offset material such as Teflon, and has a bar heater disposed in the hollow. The endless belt 3 of the belt device 2
Denotes a plurality of support rollers, three support rollers 4 in the illustrated example,
The upper running portion of the belt 3 is pressed against the peripheral surface of the fixing roller 1 between the rollers 4 and 5.

[0008] The fixing roller 1 is a fixed side plate 7 of an electrophotographic apparatus.
And is rotatable in a direction shown by an arrow A when actuated by a driving device (not shown). Around the fixing roller 1, a peeling claw 8 for preventing the transfer material from being wound around the roller, an oil applying device 9 for supplying offset preventing oil to the fixing roller, a cleaning blade 11, a surface temperature detector 12, and the like are arranged. ing. Reference numeral 13 denotes a guide plate for conveying the transfer material conveyed from the photosensitive drum to the fixing device, and reference numeral 14 denotes a discharge roller for the transfer material.

The plurality of support rollers which stretch the endless belt 3 have a minimum diameter at the center and gradually increase in diameter toward both ends, and a so-called crown-shaped roller having a maximum diameter at the center. And a so-called inverted crown-shaped roller whose diameter gradually decreases toward both ends. In the illustrated example, the roller 4 on the entrance side of the transfer material is a straight roller, the roller 5 on the exit side is a crown-shaped roller, and the intermediate roller 6 is an inverted crown-shaped roller. The surfaces of the rollers 4, 5, and 6 are provided with a friction reducing means such as a Teflon coat to reduce a coefficient of friction with the belt 3, and when the belt thermally expands, the amount of elongation in the width direction is applied to the rollers. It is slidable relative to it. The roller 4 is disposed so as to press the belt 3 against the fixing roller, and transfers the transfer material conveyed between the fixing roller 1 and the belt 3 to the fixing roller 1.
Is pressed against the peripheral surface of. The fixing roller 1 may have an inverted crown shape that is complementary to the shape of the support roller 5 in addition to the straight shape.

The belt 2 has a thickness such that its central portion in the width direction swells according to the shape of the roller 5 on the side of the crown-shaped roller 5, and dents according to the shape of the roller 6 on the side of the inverted crown-shaped roller 6. The force in the opposite direction is sequentially and repeatedly received. These forces act to correct the belt offset,
Since both of them act to attract toward the center in the width direction of the belt, lateral displacement and meandering of the belt with respect to the rollers are suppressed.

In order to more reliably prevent the lateral displacement of the belt, the endless belt 3 has a wider width than the supporting rollers 4 and 5, and both ends of the endless belt 3 are supported as shown in FIG. , 6 have a width protruding axially outward by several mm to several tens mm from the edge E. The endless belt 3 is obtained by applying a toner offset preventing means such as a Teflon coat to the surface of a heat-resistant belt such as a silicone rubber, and preferably has an appropriate elasticity and contraction force. A portion 30 (FIG. 2) near the edge protruding from the edge E of the support rollers 4, 5, and 6 presses the edge E of the support roller with an appropriate pressure to prevent the belt from laterally shifting with respect to the support roller.

[0012]

[0013]

As described above, according to the present invention, the belt is supported by including a crown-shaped roller and an inverted crown-shaped roller to prevent lateral displacement of the belt. Also, by setting the belt width large and pressing down the roller end portion by the belt contracting force, the lateral displacement of the belt can be more reliably prevented.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an 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 in FIG. 1;

FIG. 3 is a front view showing a belt portion of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Endless belt device 3 Endless belt 4 Support roller 5 Support roller 6 Support roller

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) G03G 13/20 G03G 15/20 B65G 15/64 B65H 5/02

Claims (1)

(57) [Scope of request for utility model registration] A fixing roller heated by a heater;
In a fixing device including an endless belt hung between a plurality of rollers that convey the transfer material between the fixing roller and the fixing roller to fix a toner image formed on the transfer material, the plurality of rollers that hang the endless belt include: , Located on the entrance side of the transfer material
And press-contact the endless belt between the pre-fixing roller and the endless belt.
Roller and the transfer material
A roller located on the exit side, having a maximum diameter at the center and gradually decreasing in diameter toward both ends, and a roller located on the entrance side
A roller located between the roller and the roller located on the exit side, a roller having a central portion having a minimum diameter and gradually increasing in diameter toward both ends, and the endless belt further comprises: A fixing device having a width wider than each of the rollers on which the belt is hung, and arranged so that an endless belt presses an edge of each of the rollers.