JPH03196076A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent transfer void from occurring when humidity is high and to reduce the cost of the device by applying a fluorocarbon resin film to the end part of a bearing receiving part on the surface of a fixing roller. CONSTITUTION:Since the insulation resistance of a transfer paper is lowered because of humidification and a resistance value becomes low by actuating a copying machine, etc., when the humidity is high, output from a transfer device tries to escape from the transfer paper by earthing to the fixing roller 20. Then, the fixing roller 20 is rotatably supported to a fixing device main body and the surface of the fixing roller 20 is coated with the fluorocarbon resin film 29 excellent in electric insulation to the end part of the bearing receiving parts 30a and 30b of the fixing roller 20. Therefore, even when anodizing treatment is not performed to the fixing roller 20, the insulation resistance of the roller 20 is surely secured and the output from the transfer device is prevented from leaking. Thus, the transfer void is prevented from occurring when the humidity is high and the cost of the device is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fixing device for laser printers, copying machines, and the like.

<Prior art> In general, in a copying machine, if the conveyance distance from the transfer device for transferring the toner on the photoconductor to the transfer paper to the fixing device is short (for example, 150 mm or less), the insulation of the transfer paper may deteriorate under high humidity. As the withstand voltage decreases due to moisture absorption and the resistance value decreases,
The output of the transfer device is grounded from the transfer paper to the fixing roller of the fixing device and escapes.

For this reason, the transfer becomes insufficient and transfer white spots occur.

To cope with this, in the conventional fixing device, as shown in FIG. 3, both ends F and R of the fixing roller 1 are subjected to alumite treatment for the purpose of electrical insulation.

In the figure, 2 is a bearing, 3 is a gear, 4 is a C-ring, and 5 is a support (frame chassis).

<Problems to be Solved by the Invention> Incidentally, copying machines in which the distance from the transfer section to the fixing unit section is short are often small, low-speed machines, and there is a need to reduce manufacturing costs.

However, in order to ensure the dielectric strength between the fixing roller 1 and the seven-frame chassis 5 as in the conventional fixing device, performing alumite treatment on the fixing roller 1 requires an additional step in the assembly process of the fixing device. This is a cause of high costs.

In view of the above, it is an object of the present invention to provide a fixing device that reliably ensures the dielectric strength of the fixing roller, prevents transfer white spots at high temperatures, and leads to cost reduction.

<Means for Solving the Problems> The means for solving the problems according to the present invention, as shown in FIG. The ends of the bearing passive parts 30a and 30b are covered with a superior fluororesin film 29.

<Function> In the above problem solving means, when a copying machine or the like is operated in high humidity, the dielectric strength voltage of the transfer paper decreases due to moisture absorption, and the resistance value decreases. As a result, the output of the transfer device tends to escape from the transfer paper by being grounded to the fixing roller 20.

At this time, the bearing passive portion 30a on the surface of the fixing roller 20,
Since the fluororesin film 29 is coated up to the end of the fuser roller 30b, the dielectric strength of the fuser roller can be ensured without anodizing the fuser roller as in the conventional case, and leakage of the output of the transfer device can be prevented. It is possible to prevent transfer white spots from occurring at times of high humidity.

<Example> Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2.

FIG. 1 is a perspective view of a fixing roller of a fixing device showing an embodiment of the present invention, and FIG. 2 is an overall configuration diagram of a copying machine.

In general, a small-sized copying machine includes a photoreceptor 10 that forms an electrostatic latent image on its surface using reflected light from an optical system, and a developing device that visualizes the electrostatic latent image on the photoreceptor 10, as shown in FIG. 11, a transfer device 12 that transfers the visualized toner image on the photoreceptor 10 to a transfer paper, and a fixing device 13 that fixes the transferred toner image to the transfer paper.

In addition, in the figure, 14 is a paper feed roller, 15 is a manual feed slot, and 16 is a paper feed roller.
17 is a feed roller, 17 is a conveyance roller, 18 is a peeling roller, 19 is a fixing paper guide, T is a tray, and an insulating film is formed on the fixing paper guide 18.

Furthermore, in small-sized copying machines, there is a strong demand for postcards and A6 size transfer paper, so the distance from the transfer device 12 to the fixing device 13 is within 140+ m.

The fixing device of this embodiment includes an upper fixing roller 20 that heats the transfer paper, and a lower fixing roller 21 that presses the transfer paper.

As shown in FIG. 1, the upper fixing roller 20 is rotatably supported by metal supports (frame chassis) 22 and 23 of the main body of the fixing device, and one end thereof is fitted into a bearing 24 and a C ring 25. , the other end is fitted into a bearing 26, a drive gear 27 and a C ring 28. The surface of the upper fixing roller 20 is covered with a fluororesin film 29 up to the ends of the bearing passive parts 30a and 3ob.

The fluororesin membrane 29 is made of a synthetic resin obtained by polymerizing olefin containing fluorine, and is made of polytetrafluoroethylene (PTFE) JtcF2cF2+ obtained mainly by milk polymerization from tetrafluoroethylene.
n is used. This PTFE has excellent electrical insulation properties and is stable even at high temperatures. The film thickness of PTFE is 15 Ω or more so that it is IMΩ or more at an applied voltage of 110 V or more.
It is set to μ− or more.

In the above configuration, the transfer paper is conveyed from the paper feed roller 14 or the manual feed slot 15 to the feed roller 16, the feed roller 16 sends it to the conveyance roller 17, and the transfer paper is conveyed from the conveyance roller 17 to the photoreceptor 11 side.

Then, the toner image on the photoreceptor 11 is transferred onto a transfer paper by the transfer device 12, and sent to the fixing device 13 via a fixing paper guide 19 by a peeling roller 18.

Next, in the fixing device 13, the toner is fixed by the upper fixing roller 20 and the lower foot fixing roller 21, and is discharged onto the tray T.

At this time, if the room is in a high humidity state, the dielectric strength of the transfer paper decreases due to moisture absorption, and the resistance value decreases. As a result, the output of the transfer device 11 is grounded from the transfer paper to the upper fixing roller 20 of the fixing device 13 and escapes, causing white spots on the transfer.

However, in this embodiment, by coating the fluororesin film 29 having a high dielectric strength up to the ends of the bearing driven parts 30a and 30b on the surface of the upper fixing roller 20, the bearing driven parts of the upper fixing roller are Since the dielectric strength of the upper fixing roller can be ensured without alumite treatment, leakage of the output of the transfer device 11 can be prevented.

Therefore, it is possible to provide a fixing device that prevents transfer white spots during high humidity and also leads to cost reduction.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, in the above embodiment, an example was described in which PTFE was used as the fluororesin film, but another type of fluororesin film (Teflon) may be used instead.

<Effects of the Invention> As is clear from the above explanation, according to the present invention, the fluororesin film is coated on the surface of the fixing roller up to the end of the bearing passive part, so it is no longer necessary to anodize the fixing roller as in the conventional case. Even without this, the dielectric strength of the fixing roller can be ensured and leakage of the output of the transfer device can be prevented.

Therefore, there is an excellent effect that it is possible to provide a fixing device that prevents the occurrence of transfer white spots at high humidity and leads to cost reduction.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a fixing roller of a fixing device showing an embodiment of the present invention, FIG. 2 is an overall configuration diagram of a copying machine, and FIG. 3 is a perspective view of a fixing roller of a conventional fixing device. 20: Fixing roller, 22.23: Support body (frame chassis), 24.26: Bearing, 25, 28: C ring, 2
7: Drive gear, 29: Fluororesin film, 30a. 30b Two pongee receiving parts. Applicant Sharp Corporation

Claims (1)

[Claims] A fixing device characterized in that a fixing roller is rotatably supported by a fixing device main body, and the surface of the fixing roller is covered with a fluororesin film having excellent electrical insulation properties up to the end of the bearing passive part.