JP3034317B2 - 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 for an electrophotographic apparatus.

[0002]

2. Description of the Related Art As a fixing device of an electrophotographic apparatus such as an electrophotographic copying machine, a printer, and a facsimile, an unfixed toner image is carried in a nip portion between a fixing roller having a built-in heat source and a pressing roller pressed against the fixing roller. A heat roller fixing device that fuses and fixes a toner image to the transfer paper surface by heat and pressure by passing the transfer paper, and a halogen lamp that is not in contact with the toner image bearing surface of the transferred transfer paper. 2. Description of the Related Art An infrared lamp irradiation fixing device that irradiates an infrared ray onto a toner image bearing surface of a transfer paper directly and via a reflector to heat and fuse a toner image is widely used.

[0003] The former is excellent in terms of fixability, image density and the like, but has a large heat capacity of the roller, requires energy for rising and a rising time, and has a contact area (nip width) between the roller and the transfer paper. In order to increase the temperature, it is necessary to apply an excessive pressure, and to increase the heat transfer, the temperature of the roller must be increased. Further, there is a drawback that wrinkles are generated in the case of transfer paper, especially in the case of envelopes, due to the large pressure.

In the latter case, since the non-contact type is used, the toner softened by heat is not pressed against the transfer paper surface, the contact area is small, and the toner is easily dropped. Further, although the toner is not spread, the image is sharp, but the uniformity of the solid black portion and the image density are inferior, and the heat rays of the light source are absorbed only by the black toner portion, and the transfer paper has wavy. .

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of a fixing device generally used in the prior art, the present invention has a good press-fitting property of a toner to a transfer paper surface and a uniform solid portion.
It is an object of the present invention to provide a fixing device capable of improving image density and shortening a rise time.

[0006]

In order to solve the above-mentioned problems, in order to solve the above-mentioned problems, the circumferential pressing member includes a light transmitting endless belt and a transparent rigid plate provided in a loop of the light transmitting endless belt. A fixing device, wherein the transparent rigid plate is pressed against the opposed member via the endless belt.

[0007]

According to the above construction, the transfer paper carrying the toner image is directly irradiated by infrared rays, and only the black toner is heated intensively, so that the energy efficiency is high and the rise is quick. Moreover, since the transfer paper is pressed against the opposing member by the pressure circulating member, the transfer paper is excellent in fixing property and image density.
In addition, the transfer paper can be reliably pressed even if the peripheral pressing member is a light transmissive endless belt.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. In the embodiment shown in FIG. 1, the transfer paper 1 carrying the unfixed toner image is a transparent endless fixing belt 9 wrapped around a belt wheel, and an opposing member pressed against a part of its lower surface by a pressing spring 12. The paper is passed between the pressure plate 11.
A glass plate 10 as a transparent rigid plate is provided on the back surface of the fixing belt 9 so as to face the pressure plate 11, and a halogen lamp 3 and a reflecting plate 5 are provided in a loop of the fixing belt 9 above the glass plate 10. I have.

With the above structure, the infrared light reflected directly from the halogen lamp 3 or reflected by the reflector 5a passes through the transparent glass plate 10 and the fixing belt 9 and passes through the transfer paper 1 passed therethrough.
Is irradiated. Since the transfer sheet 1 is pressed against the fixing belt 9 by the pressing plate 11 from below, the transfer sheet 1 is conveyed by frictional force with the fixing belt 9 and is heated and pressed to fix the toner image on the transfer sheet. You. In this case, the friction coefficient between the upper surface of the pressure plate 11 and the back surface of the transfer paper is set smaller than the friction coefficient between the glass plate 10 and the surface of the transfer paper so that the upper surface and the back surface of the transfer paper slide.

According to this configuration, the toner preheated by the irradiation of the infrared rays is softened, and is heated simultaneously with pressurization at the nip portion between the fixing belt 9 and the pressurizing plate 11, so that the toner is efficiently transferred onto the transfer paper surface. We fuse. Therefore, the capacity of the halogen lamp can be made smaller than that of the conventional heat fixing device, and the life is improved.

The above embodiment is excellent in terms of shortening of the rise time, improvement of thermal efficiency, fixability and image density, but one of the few disadvantages is the undulation of the transfer paper. This is based on the difference in the amount of thermal expansion caused by the difference in the amount of heat absorbed by the infrared light emitted from the halogen lamp between the toner image portion and the background portion on the transfer paper. However, the undulation of the transfer paper is also smaller than that of a conventional non-contact infrared lamp irradiation type fixing device.
The degree has improved considerably.

To further improve this point, the fixing belt 9
Is uniformly coated with a light-absorbing thin film 4b formed by dispersing carbon powder in a heat-resistant fluororesin such as PFA or 4-fluoroethylene.

With this configuration, the light beam emitted from the halogen lamp 3 is reflected directly or on the reflecting plate 5, passes through the glass plate 10, irradiates the light absorbing thin film, and is absorbed by the carbon powder therein. The temperature rises rapidly.

Therefore, the rise time until the fixing temperature is reached after the power is turned on is shortened, and the surface temperature of the fixing belt is uniform, so that the transfer paper has both a toner image portion and a background portion. The transfer paper is heated uniformly, and the transfer paper does not undulate.

The light-absorbing thin film can be formed of a metal plating layer. Although not shown, it is desirable to provide a temperature sensor and a scraper around the fixing belt 9.

【The invention's effect】

As described above, according to the present invention, the effect of shortening the fixing rise time, improving the thermal efficiency, improving the fixability and the image density is obtained, and furthermore, the surface of the translucent fixing roller is coated with the light absorbing thin film. By doing so, the waving of the transfer paper is also reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transfer paper 3 Halogen lamp (infrared light source) 9 Fixing belt (circumferential pressure member) 10 Glass plate 11 Pressure plate (opposite member) 12 Pressure spring

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (3)

(57) [Claims] A light-transmitting peripheral pressurizing member for pressing a transfer paper carrying a toner image against an opposing member; an infrared light source transmitting through the peripheral pressurizing member and irradiating the transfer paper; Wherein the circumferentially pressing member has a light-transmitting endless belt and a transparent rigid plate provided in a loop of the light-transmitting endless belt, and the transparent rigid plate has the endless belt. A fixing device, which is pressed against the opposed member via a belt. 2. The fixing device according to claim 1, wherein said opposed member is pressed against said transparent rigid plate via said endless belt by elastic force. 3. The fixing device according to claim 1, wherein a light absorbing thin film is provided on an outer peripheral surface of the light transmitting endless belt.