JPH0526590Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fixing device in an electrophotographic apparatus such as a copying machine.

[Prior Art] Generally, in an electrophotographic apparatus, a web image is formed on an image bearing member such as a photosensitive drum by irradiating optical information according to the subject onto the image bearing member, and the formed web image is developed. After being converted into a toner image in the process, it is transferred onto a transfer material such as paper or resin film, and then the transfer material on which the toner image is formed is peeled off from the image carrier and introduced into a fixing device by a guide plate, etc. The toner image is fixed. This fixing device typically includes a fixing roller that has a built-in heater or is placed near its circumferential surface, and a roller or endless belt that fixes the toner image by sandwiching and conveying the transfer material between the fixing roller and the fixing roller. It consists of a pressing device and related members such as a peeling claw and a paper ejection roller that are operably arranged around these members and in association with them.

[Problems to be Solved by the Invention] Incidentally, in the apparatus using an endless belt as a pressure device for the fixing roller as described above, since the contact time of the transfer material with the fixing roller can be set to be relatively long, It has the advantage that the temperature and pressure of the rollers can be kept relatively low, but on the other hand, it has the problem that the endless belt tends to shift or meander, which can damage the belt or cause wrinkles in the transfer material. It was hot.

The present invention has been made in view of the problems of the prior art described above, and it is an object of the present invention to provide a simple and convenient fixing device that can prevent the endless belt from lateral shifting or meandering relative to the fixing roller.

[Means for Solving the Problems] In order to achieve the above object, the fixing device according to the present invention includes a heating fixing roller that fixes the toner image formed on the transfer material. In the fixing device, the endless belt has elasticity or tension, and both edges thereof protrude outward in the axial direction from both ends of the support rollers. The roller is provided wider than the support roller so as to press down the end of the support roller by its tightening force, and contacts the edge of the endless belt at the outer end of at least one of the support rollers. The present invention is characterized by providing a flange member having a flexible surface and rotatable concentrically and independently of the roller.

[Function] With the above means, the portion near the edge of the endless belt protruding from the end of the support roller presses down the end of the support roller by the belt's own tightening force, and the lateral displacement of the endless belt is somewhat suppressed. Empower. However, this restraining force is not always sufficient, and in some cases, when the endless belt exceeds this restraining force and begins to shift laterally, the edge of the endless belt comes into contact with the surface of the flange member, causing To reliably prevent the above lateral displacement. At this time, since the flange member is formed to be rotatable concentrically with the support roller, the flange member rotates in the circumferential direction due to the frictional force with the endless belt.

[Example] Next, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a preferred embodiment of the present invention. In the figure, 1 is a heat fixing roller disposed inside an electrophotographic apparatus, and is pressed against the fixing roller 1 with a transfer material, such as paper, sandwiched therebetween. An endless belt device 2 is provided as a pressurizing device. The fixing roller 1 is usually a hollow A roller whose surface is coated with an offset prevention material such as tetrafluoroethylene resin, and a rod-shaped heater is disposed within the hollow. Further, the endless belt 3 of the belt device 2 is wrapped around a plurality of support rollers, in the illustrated example, a pair of support rollers 4 and 5, and the upper running portion of the belt 3 is pressed against the fixing roller between the pair of rollers.

The fixing roller is rotatably provided with respect to a fixed side plate 6 (only one of which is shown) of the electrophotographic apparatus, and is rotated in the direction of arrow A during operation by a drive device (not shown). Around the fixing roller, there is a peeling claw 25 that prevents paper from wrapping around the roller, and an oil application device 2 that supplies offset prevention oil to the fixing roller.
6, a cleaning blade 27, a surface temperature detector 28, and the like are arranged. , 29 is a guide plate for conveying the transfer material conveyed from the photosensitive drum to the fixing device, and 30 is a discharge roller for the transfer material.

On the other hand, a support roller 4 that stretches the endless belt 3,
The belt 5 is arranged such that its upper end is located above the lower end of the fixing roller so that the belt can be brought into pressure contact with the fixing roller. Both ends of the support rollers 4 and 5 are connected to a pair of spaced apart swinging members 8 (only one is shown).
The swinging member 8 is rotatably supported by a support shaft 7 relative to the side plate 6 of the main body of the device. As a result, roller 4,
5 can move in the vertical direction around the axis 7. FIG. 2 shows an example of a roller support means. In this example, a disc-shaped side wall member 11 is fixed to a support shaft 9 whose both ends are fixed to a swinging member 8. On the other hand, for example, a cylindrical roller 4 made by A
is attached via a bearing device 12, so that the roller is rotatably provided around the axis.
The roller 5 can also have a similar configuration. The support rollers 4 and 5 may have a straight cylindrical shape, or may have a drum shape that has a maximum diameter at the center in the axial direction and gradually decreases in diameter toward both ends. In the latter case, the fixing roller 1 Complementary to this, the cross section has an inverted crown shape, with the minimum diameter at the center and gradually increasing diameter toward both ends.

The endless belt 3 has a wider width than the support rollers 4 and 5, and as shown in FIG. It protrudes from mm to tens of mm. The endless belt 3 is preferably made of a heat-resistant material such as silicone rubber and has appropriate elasticity and tightness.
Due to the tightening force of the belt, the portion of the belt near the edge protruding from the end of the support roller presses the end of the support roller with appropriate pressure.

On the other hand, a tension spring 14 is installed at an appropriate position of the swinging member, for example, between the support shaft 9 of one roller 4 and a pin 13 fixed to the outer surface of the side plate 6, The swinging range of the swinging member is restricted by contact with the regulating windows 16 and 17 formed in the side plate 6 through which the shaft passes, and the endless belt 3 is moved against the surface of the fixing roller 1 by the spring force of the spring 14. Press them together. Usually, the spring 14 is connected to the side plate 6
mounted on the outside of the Note that the rollers 4 and 5 may be brought into direct pressure contact with the fixing roller 1 with the belt 3 interposed therebetween.

In order to reliably prevent the endless belt from shifting laterally,
At least one roller of the support rollers, for example, a flange member 21 is provided on the support shaft 9 at a position between the side wall 11 and the swinging member 8 on the outer side of the roller 4, for example, on the support shaft 9, and is fixed in the axial direction and supported by a bearing 22. The roller 4 is provided concentrically with and rotatably independently of the roller 4. The flange member 21 has a larger diameter than the roller 4,
It has a surface 23 that can come into contact with the edge of the endless belt when a lateral shift of the endless belt occurs. The distance between the surface 23 and the end of the belt under normal conditions (no lateral deviation) is set to, for example, several mm. This flange member may be provided at both ends of the roller 4 and/or at the ends of all rollers. Note that the belt has an appropriate thickness so that it does not roll up or roll up due to contact with the flange member.

[Effects of the invention] As described above, according to the invention, lateral deviation of the belt is suppressed by engagement with the roller end due to the tightening force of the belt, and such lateral deviation is reliably prevented by the installation of the flange member. Ru. Further, since the flange member is rotatably provided concentrically with the support member, even when it comes into contact with the flange member, resistance such as winding up the belt does not occur, and lateral slippage is smoothly prevented.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing the internal structure of a fixing device according to an example of the present invention, and FIG. 2 is a side view of the portion shown in FIG. 1. 1... Fixing device, 3... Endless belt, 4, 5...
...Support roller, 9, 15... Support shaft, 21... Flange member.

Claims (1)

[Scope of utility model registration request] In a fixing device having an endless belt that is hung between a heating fixing roller and a plurality of support rollers for sandwiching and conveying the transfer material in order to fix the toner image formed on the transfer material, the endless belt is It has elasticity or elasticity and is wider than the support roller so that both edges protrude outward in the axial direction from both ends of the support roller and press down the ends of the support roller by the tightening force. A flange member is provided outside the end of at least one of the support rollers, the flange member having a surface capable of contacting the edge of the endless belt and rotatable concentrically and independently of the roller. A fixing device characterized by: