JPH06282187A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To improve the rigidity of a film by increasing the thickness thereof without decreasing fixing efficiency in a thermal fixing device heating a transfer material by using a heat-resistant film. CONSTITUTION:In the film thermal fixing device composed of a rotational heat-resistant film 1 including a fixing support and a pressure roller 3 rotating confronted with the heat-resistant film 1, a heater 5 heating the film 1 is arranged closely to or in contact with the surface of the film on the upstream of the close contact part of the film and the pressure roller 3, so that the film 1 is directly heated from the outside by the heater 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device for fixing an unfixed toner image on a transfer material by pressing a heated heat resistant film.

[0002]

2. Description of the Related Art In recent years, in consideration of energy saving of OA equipment and user's ease of use, development and practical application of a quick-fixing heat fixing device for electrophotographic copying machines and printers have been actively conducted. Has become.

Under such circumstances, the present applicant has previously proposed a quick start fixing device using a heat-resistant film as disclosed in, for example, Japanese Patent Laid-Open No. 63-313182.

In this system, as shown in FIG. 5, a thin heat resistant film 1 made of polyimide or the like, a heater 5 fixedly supported by a stay 2 on one surface side of the film, and a heater on the other surface side facing the heater. And a pressurizing member 3 which is placed in close contact with the heater to fix the transfer material to be fixed via a film.

Since a heater having a low heat capacity can be used in such a film heating type fixing device, the wait time can be shortened as compared with the heat roller type which has been widely used conventionally.

Further, since the quick start can be performed, preheating at the time of non-operation is not required, and power saving can be achieved in a comprehensive sense.

[0007]

However, the heat-resistant film used in the fixing device of the above-mentioned film heating type has a polyimide base material having a thickness of 20 to 50 .mu.m and a PTFE or PFA having a thickness of 5 to 20 .mu.m. Since the mold layers are laminated and the thermal conductivity of the polyimide and the mold release layer is extremely low, it has been difficult to cope with long life or high speed.

That is, when the thickness of the polyimide layer is increased to increase the rigidity of the film in order to extend the life, the heat conduction from the heater to the film surface is reduced. In order to guarantee the deterioration of the fixing property due to this, the control temperature of the heater must be raised, and high heat resistance characteristics are required for the fixing device constituent parts, which inevitably results in a complicated and expensive device structure.

[0009]

According to the present invention, a heat-resistant film which encloses and rotates a fixed support,
In a film heating and fixing device composed of a pressure roller rotating facing a heat-resistant film, a heater for heating the film should be arranged close to or in contact with the film surface upstream of the close contact portion between the film and the pressure roller. Thus, since the surface of the film that comes into contact with the transfer material having the unfixed toner image is directly heated, it is possible to increase the rigidity of the film while maintaining the fixing efficiency without raising the heating heater control temperature.

[0010]

The present invention will be described below with reference to the drawings.

FIG. 1 shows a sectional view of a film heating and fixing apparatus using the present invention.

The endless belt-shaped fixing film 1 is
A polyimide release layer having a thickness of 50 μm is used as a base layer, and a release layer made of PFA or PTFE or the like for preventing toner adhesion to the outer surface of the film is laminated by about 10 μm.

A support stay 2 made of a highly heat-resistant resin such as PPS (polyphenylene sulfide) is provided inside the film cylinder 1 to support the rotation of the film.
And the fixing film 1 is pressed against the support stay 2 by the pressure roller 3 having a rubber elastic layer having a good releasability such as silicon rubber.

The pressure roller 3 rotates in the direction of arrow a, and the friction causes the fixing film 1 to rotate with respect to the support stay 2 in the direction of arrow b at the same speed as the surface speed of the pressure roller 3.

In order to smooth the rotation of the fixing film 1, an uneven rib is provided in the fixing film contact area on the side surface of the supporting stay, and heat resistant silicon grease or the like is applied between the film and the supporting stay. You can

The recording material guide 4 guides and fixes the transfer material having the unfixed toner image on the contact portion between the fixing film and the pressure roller.

Reference numeral 5 denotes a heater for heating the surface of the fixing film 1, which is located outside the heat-resistant film 1 on the upstream side of the nip portion between the heat-resistant film 1 and the pressure roller 3, that is, the nip portion for nipping the transfer material. It is provided in. Preferably, the heater 5 is selected near or in contact with the heat resistant film 1. The heater 5 is made of an electrically resistive material such as Ag / Pd (silver palladium) along one side of a substrate made of heat-resistant ceramics and has a thickness of about 10 μm and a width of 1 μm.
A ceramic heater coated by screen printing or the like on 3 mm is used.

The temperature detecting element 6 is arranged in contact with the surface of the fixing film 1 located between the heater 5 and the pressure roller, detects the surface temperature of the fixing film, and maintains it at a predetermined temperature. Thus, the electric circuit 7 controls the input voltage of the heater.

FIG. 2 shows the surface temperature of the fixing film 1 measured by a far-infrared non-contact thermometer at the arrow A portion in the configuration diagram of FIG. 1 immediately downstream from the pressure roller contact portion.

The solid line shows the temperature rise of the fixing film from room temperature when the ceramic heater is subjected to the constant power control of 300 W in the fixing device according to the present invention. This is due to the rotation cycle.

On the other hand, the broken line shows the same Watt when the same ceramic heater is attached to the lower surface of the support stay 2 so as to contact the inner surface of the film (described in the conventional example).
It shows the temperature rising state of the surface of the fixing film in the stage.

As shown in the figure, even if the heater of the same Wattage is used, in the case of the heater provided on the inner surface side of the fixing film, the surface temperature of the fixing film which contributes to fixing of the recording material is higher than that of the fixing device of the present invention. Become slow. This is because the fixing film made of polyimide and fluororesin has poor heat conduction in the layer direction and heat is taken from the heater to the supporting stay of the film.

Therefore, in the method of directly heating the film surface from the outside according to the present invention, the temperature can be rapidly raised with the same Wattage, a high temperature is required for fixing, and recording is performed from the paper feeding unit to the fixing device. It is possible to cope with speeding up that the material arrives in a short time.

FIG. 3 shows a system in which the outer surface of the film is directly heated according to the present invention by changing the thickness of the fixing film in the same manner as the temperature rising condition of the surface of the fixing film in the portion A (FIG. 3).
-A) and the inner surface heating method (Fig. 3-b) are compared.

As shown in FIG. 3B, in the inner surface heating method, as the thickness of the fixing film increases, the thermal resistance of the film influences the heating rate of the fixing film surface.

On the other hand, in the method of directly heating the outer surface of the fixing film (FIG. 3-a), the temperature rise condition of the fixing film in the portion A is not so much influenced by the film thickness due to the heat insulating effect in the fixing film layer direction. .

Therefore, in the method of heating the outer surface of the fixing film according to the present invention, the rigidity can be increased by increasing the thickness of the fixing film without impairing the fixing efficiency in order to prolong the service life.

Further, the ceramic heater generally has a flat shape because a resistor is formed on a ceramic flat plate by means of screen printing or the like, but the shape of the fixing film and the pressure roller is inevitable. Since the heater is not placed in the close contact part, the shape of the film close contact part of the support stay in the fixing film can be freely selected, for example, upward convex or downward convex, and in consideration of curl correction of the transfer material. Design is possible.

Further, since the outer surface of the fixing film is heated, the temperature rise of grease for smoothing the rotation of the supporting stay and the fixing film is also reduced, so that it is not easily affected by thermal deterioration and the life is simple and the life is long.・ High reliability can be achieved.

<Second Embodiment> FIG. 4 shows the second embodiment of the film fixing device according to the present invention.
The difference from the embodiment is that the heater for heating the fixing film is composed of a halogen lamp.

The halogen lamp 8 is constructed so that it is focused on the film surface by the reflection shade 9 and black powder such as carbon having a high radiation absorption rate is filled in the outermost release layer in order to increase the temperature rising efficiency of the film. It is also possible.

[0032]

As described above, according to the present invention, a film comprising a heat-resistant film which encloses and rotates a fixed support, a pressure roller which rotates in opposition to the heat-resistant film, and a heater. In the heat fixing device, the heater is placed close to or in contact with the film surface on the upstream side of the close contact portion between the film and the pressure roller, so that the film surface in contact with the transfer material is directly heated and the toner on the transfer material is heated. To fix an image, the fixing efficiency does not depend on the thickness of the film, and the rigidity of the film can be improved by increasing the thickness of the film. Is.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a film heating and fixing device according to the present invention.

FIG. 2 is a diagram showing a film heating state in a surface heating method according to the present invention and a conventional inner surface heating method.

FIG. 3 is a diagram showing a relationship between a film temperature increase and a film thickness in each of the systems shown in FIG.

FIG. 4 is a view showing a second embodiment of the present invention, showing an example of a halogen heater as a means for heating the surface of a fixing film.

FIG. 5 is a cross-sectional view of a conventional film fixing device that heats the inner surface of the film.

[Explanation of symbols]

1 ... Fixing film 2 ... Support stay 3 ... Pressure roller 4 ... Recording material guide 5 ... Heating heater 6 ... Temperature detection element 7 ... Temperature control circuit 8 ... Halogen heater 9 ... Reflecting shade

Claims (1)

[Claims] 1. A transfer comprising a heat-resistant film which encloses and rotates a fixed support, a pressure roller which rotates in opposition to the heat-resistant film, and a heating element, and which is transferred to a contact portion between the film and the pressure roller. In a heat fixing device for fixing by guiding a material, the heating body is arranged in proximity to or in contact with a surface of the heat resistant film upstream of a contact portion with a pressure roller. apparatus.