JP2919086B2 - 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 used in an electrophotographic printer, a copying machine and the like.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic printer or copier, a charged photosensitive drum is irradiated by a light source to form an electrostatic latent image on the surface thereof, and toner is attached to the electrostatic latent image. After the development, the toner image is transferred to a recording medium.

As a fixing roller used in the above-described electrophotographic printer or copier, a heater is built in a metal pipe made of aluminum or the like, and the heat generated by the heater causes the metal pipe to be heated to 180 ° C. to 200 ° C. The toner is heated to about ° C, and the toner is thermally fixed by passing the developed paper between the metal pipe and the pressure roller (see Japanese Utility Model Application Laid-Open No. 61-160464).

In the case of the fixing roller having the above-described structure, the surface temperature of the metal pipe is normally 180 ° C. to 200 ° C.
It takes a rise time of about 5 minutes after the heater is turned on, and 1 Kw of electric power is required. Therefore, a fixing roller has been provided in which the rise time of heat is reduced and power consumption is reduced.

FIG. 2 is a sectional view of a fixing roller having low power consumption. As shown in the figure, the fixing roller has a heating resistor layer 2 formed on the surface of a roller base material 1 made of a low thermal conductor such as glass, enamel, ceramics, etc., and the surface thereof is covered with a fluororesin layer 3. Ring-shaped electrodes 4 on both ends of body layer 2
And a voltage is applied between the electrodes 4.

In the case of the fixing roller having the above structure, the rise time of heat can be reduced to about 1/5 or less of that of the related art, and the power consumption can be reduced.

[0007]

However, in the above-mentioned conventional fixing roller, since heat is radiated from both sides of the roller at the time of heat generation, the temperature on both sides is lower than the central portion, and it is difficult to obtain a uniform temperature distribution over the entire length. However, when the present invention is applied to an electrophotographic printer or the like, the fixing state of the toner varies, and the print quality deteriorates.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device which solves the above-mentioned problems of the conventional fixing roller, makes the temperature distribution on the surface of the base material uniform, and improves print quality.

[0009]

For this purpose, in the fixing device of the present invention, electrodes are connected to both ends, and a current is caused to flow between the electrodes to cause the heat generating portion to generate heat, thereby performing fixing. . The heat generating portion includes a base made of a material having low thermal conductivity, and an amorphous heat generating resistor layer formed by coating the surface of the base.

[0010] The heating resistor layer has both ends and a central portion having different degrees of crystallinity by making different amounts of heat when heat treatment is performed.

[0011]

According to the present invention, as described above, in the fixing device, electrodes are connected to both ends, and a current is caused to flow between the electrodes to cause the heat generating portion to generate heat, thereby performing fixing.

The heat generating portion has a base made of a material having low thermal conductivity, and an amorphous heat generating resistor layer formed by coating the base on the surface of the base. Further, the heat generating resistor layer has both ends and a central portion having different degrees of crystallinity by making different amounts of heat when heat treatment is performed. In this case, since the resistance value at both ends of the heating resistor layer is higher than the resistance value at the center portion, when a current flows between the electrodes connected to both ends of the fixing device, the heat generation at both ends is smaller than the heating value at the center portion. The amount increases.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a process chart of a method of manufacturing a fixing roller according to an embodiment of the present invention. First, a material having low thermal conductivity, for example, synthetic resin such as phenol resin, ground glass, glass such as crystal glass, alumina ceramics,
Alternatively, the surface of a roller base material such as an enameled stainless steel pipe is immersed in an organic solvent such as trichlene or chlorocene or degreased by steam washing.

Next, the roller base material is immersed in a solution of tin chloride and hydrochloric acid for 1 minute and washed with water for 30 seconds, and then immersed in an aqueous solution of palladium chloride and hydrochloric acid for 1 minute and washed with water for 30 seconds. This process is repeated several times to perform pre-processing. Next, electroless Ni-P plating is performed to form a uniform film having a thickness of 0.1 to 1 μm on the surface of the roller base material to form an amorphous heating resistor layer. In this case, not only Ni-P plating but also N
If it is an i-type, for example, Ni-W plating, Ni-C
u plating may be used. Further, since the roller base material is made of a material having a high insulating property, an electroless plating process is performed. Further, the heating resistor layer may be formed by vacuum evaporation or thick film printing instead of plating as long as it is an amorphous film.

Next, the roller on which the heating resistor layer is formed is heat-treated at a high temperature. By this heat treatment, the film of the electroless Ni-P plating is crystallized, and at this time, the resistance value is lowered and stabilized. FIG. 3 is a heat treatment state diagram in the fixing roller manufacturing method of the present invention. In the figure, 11 is a roller having a heating resistor layer formed on the surface, and 12 is an auxiliary heater.

In the heat treatment step, an auxiliary heater 12 is provided so as to surround the roller 11, and firing is performed in that state. That is, the baking is performed in a vacuum or in an oxygen-free atmosphere such as a nitrogen atmosphere with the center of the roller 11 at a high temperature and the ends at a low temperature. The firing conditions are a firing temperature of 400 ° C. and a firing time of 1 hour. As a result, the heating resistor layer is fired,
The temperature of the center is 400 ° C. + α (the amount heated by the heater), while the temperature of the ends is
00 ° C.

FIG. 4 is a graph showing the relationship between the heat treatment temperature and the rate of change in resistance. As shown in the figure, the resistance tends to decrease when the heat treatment temperature is high. Therefore, the resistance of the fixing roller increases at both ends and the amount of generated heat increases, and the resistance decreases at the center and the amount of generated heat decreases. When the fixing roller having the above-described configuration is used, the temperature distribution becomes uniform because of the influence of heat radiation from both sides.

Further, a fluorine resin layer such as a PFA resin is formed to a thickness of 10 to 40 μm so as to cover the surface of the heating resistor layer. Then, ring-shaped electrodes are attached to both ends in close contact with the heating resistor layer. In the above embodiment,
Although the heating temperature of the heating resistor layer is made different at the center and both ends, the heating time may be made different. That is, the heating time of the central portion of the heating resistor layer may be made longer than the heating time of both end portions, and the heating amount may be made different.

When a current flows between the electrodes of the fixing roller manufactured by the above method, Joule heat is generated by the current flowing through the heating resistor layer. The toner image transferred onto the paper can be fixed using the fixing roller whose temperature has been increased by the Joule heat. In this case, the resistance value of the heating resistor layer is high at both ends of the fixing roller,
Since it is low at the center, the current density at both ends becomes high when current is supplied, and the amount of generated heat increases. Therefore,
Even if the amount of heat radiated at both ends of the fixing roller is large, the temperature does not decrease, and a uniform temperature can be obtained over the entire length of the fixing roller.

It should be noted that the present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0021]

As described above in detail, according to the present invention, in a fixing device, electrodes are connected to both ends, and a current is caused to flow between the electrodes to cause the heat generating portion to generate heat, thereby performing fixing. It has become. The heat generating portion includes a base made of a material having low thermal conductivity, and an amorphous heat generating resistor layer formed by coating the surface of the base. Further, the heat generating resistor layer has both ends and a central portion having different degrees of crystallinity by making different amounts of heat when heat treatment is performed.

In this case, when a current is passed between the electrodes connected to both ends of the fixing device, the crystallinity at both ends of the heating resistor layer and the crystallinity at the center are different. And the amount of heat generated can be different. Therefore, for example, when the amount of heat radiation at both ends of the fixing device is large, the amount of heat generated at both ends can be increased, and the temperature distribution can be made uniform between the center and both ends. As a result, print quality can be improved.

[Brief description of the drawings]

FIG. 1 is a process diagram of a method of manufacturing a fixing roller according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a fixing roller with low power consumption.

FIG. 3 is a heat treatment state diagram in the method for manufacturing a fixing roller of the present invention.

FIG. 4 is a relationship diagram between a heat treatment temperature and a resistance change rate.

[Explanation of symbols]

 11 roller 12 auxiliary heater

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kenji Hatsuzawa 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (56) Reference JP-A-2-1411783 (JP, A) JP-A 63-78188 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/20 G03G 15/20 H03B 3/00 335 H03B 3/12

Claims (1)

(57) [Claims] 1. A fixing device in which electrodes are connected to both ends, and a current is caused to flow between the electrodes to cause a heat generating portion to generate heat and perform fixing.
In location, (a) the heating unit, group consisting of low thermal conductivity material
Wood, and it is formed by coating the surface of said substrate
The Rutotomoni that having a heat generating resistor layer of amorphous, (b) the heat generating resistor layer, the amount of heat when the heat treatment is performed
Different degrees of crystallinity by making
The fixing device according to claim Rukoto provided with both end portions and a central portion.