JPH06348176A - Fixing device for electrophotography - Google Patents

Abstract

PURPOSE:To uniform the temperature distribution, reduce temperature variation, downsize, and reduce the power consumption of a fixing roller by using a heat pipe itself as a fixing roller and induction-heating a heating part installed projectedly at its end. CONSTITUTION:A fixing device for electrophotography is provided with a fixing roller 1 in which a heating part 1b of a heat pipe is installed projectedly at its side and a releasing layer is provided around a heat radiation part 1a, and a high frequency coil 6 as an induction heating means around the heating part 1b. The fixing roller 1 used for the fixing device constitutes the heat pipe by itself, and its material is desirably copper or phosphor bronze. When a high frequency current generated in a high frequency oscillator 5 is flowed through a primary high frequency coil 6, a magnetic flux is generated in the high frequency coil 6 and an eddy current is produced in the secondary side iron layer of the fixing roller 1, the heating part 1b is heated by an eddy current loss, the working liquid inside is heated to increase the temperature of the entire fixing roller rapidly. Thus uniform temperature distribution can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device such as a printer, a fax machine or a copying machine which uses an electrophotographic process.

[0002]

2. Description of the Related Art Conventionally, a heating roll system has been generally used as a fixing device for electrophotography. This type of fixing device heats the fixing roll by providing a heat source such as a halogen lamp in a cylindrical fixing roll having a release layer on the surface and applies pressure between the fixing roll and the pressure roll. While being rotated, the copy image is fixed by fusing the toner through a sheet carrying the powder toner image between the fixing roll and the pressure roll.

However, in a fixing device using a fixing roll incorporating such a halogen lamp, it is not possible to downsize the fixing roll because there is a limit to reducing the diameter of the halogen lamp, and therefore the fixing device is also downsized. There was a limit. Also, since the heat of the halogen lamp is transferred to the fixing roll by radiation, it is necessary to increase the capacity of the halogen lamp in order to shorten the warm-up time, which not only increases the power consumption but also the life of the halogen lamp. There is a problem that is shortened.

Furthermore, when the fixing roll having such a structure is used for continuous fixing, the heat of the surface of the fixing roll is removed by the passing paper, and the surface temperature of the fixing roll varies, resulting in uneven fixing. There is also a problem that is likely to occur.

As a means for solving the above-mentioned problems, conventionally, a method of lowering the reflectance of the inner surface of the fixing roll in order to improve the heat transfer between the halogen lamp and the fixing roll, and a fixing roll Various methods have been proposed in which a heat pipe is embedded in a fixing roll in order to reduce the heat capacity and make the temperature distribution uniform.

[0006]

However, even with these improvements, it has not been possible to sufficiently meet the demands for downsizing and low power consumption of the fixing device. Therefore, it is an object of the present invention to provide a fixing device which is small in size and consumes less power, in which the temperature distribution of the fixing roll is made uniform by using a heat pipe and the temperature variation is also reduced.

[0007]

In order to achieve the above object, in the present invention, a fixing roll having a heating portion of a heat pipe protruding laterally and a release layer provided around the heat radiating portion is provided. A fixing device for electrophotography is provided by surrounding the heating part and providing an induction heating means.

The fixing roll used in the fixing device of the present invention itself constitutes a heat pipe, and its material is preferably copper or phosphor bronze. Water or alcohol can be used as the working fluid of the heat pipe, but if the amount of working fluid is too small, circulation will not work well and the temperature will not be uniform, and if it is too large, it will take time for the working fluid to warm up. Since it becomes too impractical, it is preferable to fill the working fluid with about 20 to 40% of the inner volume of the fixing roll.

Since the heat radiating portion of the fixing roll constituted by such a heat pipe serves as the paper passing portion, when the paper passing speed is high and the roll itself needs a certain heat capacity, an aluminum layer is provided around the heat radiating portion. The fixing roll can be provided with a heat capacity, for example. Further, since the paper passing surface of the roll needs to be released from the toner, a release layer made of fluororesin or silicone rubber is provided.

Further, the heating portion of the heat pipe is provided so as to extend laterally from the end portion of the fixing roll, and is provided with induction heating means so as to surround it. That is, an iron layer having a thickness of, for example, about 0.1 to 3 mm is provided around the heating portion by, for example, shrink fitting an iron pipe, and a high frequency coil of copper wire is provided so as to surround the heating portion. Then, a high-frequency current from the high-frequency oscillator is passed through the high-frequency coil so that the iron layer portion can be induction-heated.

[0011]

In the fixing device of the present invention, when the high frequency current generated in the high frequency oscillating section is passed through the high frequency coil on the primary side, a magnetic flux is generated in the high frequency coil to cause the iron on the secondary side of the fixing roll. An eddy current is generated in the layer, heat is generated by the eddy current loss, the heating portion is heated, the internal working fluid is heated, and the temperature of the entire fixing roll is rapidly raised, and a uniform temperature distribution is obtained.

[0012]

【Example】

(Example of the present invention) FIG. 1 is a sectional view of a fixing device of the present invention.
1 is a fixing roll, 2 is a pressure roll, 3 is a thermistor for temperature control means, 4 is an AC power supply, 5 is a harmonic oscillator for temperature adjustment at the same time as high frequency oscillation, 6 is a high frequency coil, and 7 is an iron pipe. , 8 is a drive gear, 9 is a fixing roll bearing, 10
Is a pressure roll bearing, and 11 is a thermal fuse.

Here, the fixing roll 1 is composed of a straight copper heat pipe having an outer diameter of 9.5 mm, a thickness of 0.9 mm and a length of 345 mm, and contains 35% of the inner volume of water as a working fluid. ing. A PFA tube with a thickness of 50 μm is applied as a release layer at the paper passing surface position of 220 mm in length corresponding to the central portion of the heat radiating portion 1a of the heat pipe, and the heating portion 1b has an outer diameter of 10.5 mm and a thickness of 0.5mm, length 50mm
The iron pipe 7 is shrink-fitted.

The high frequency coil 6 is formed by winding a copper wire having a wire diameter of 3 mm so as to have an outer diameter of 32 mm and a pitch of 6 mm and a length of 50 mm, and is configured to pass a high frequency current. The pressure roll 2 has a surface hardness of ASKER C which is obtained by coating a core metal having a diameter of 8 mm with a silicone sponge layer having a thickness of 4 mm.
It is a roll having a hardness of 36 °.

In the fixing device shown in FIG. 1, the surface temperature of the fixing roll was set to 160 ° C., a high frequency current of 100 KHz and an output of 190 W was passed through the high frequency coil, and the warm-up time was measured. The warm-up time was 57 seconds, and the temperature was raised in a short time despite the low output of 190W.

(Comparative Example) FIG. 2 shows the structure of a fixing device of a comparative example. 1 is a fixing roll, 2 is a pressure roll, 3 is a thermistor for temperature control means, 8 is a drive gear, 9 is a bearing for the fixing roll, 10 is a pressure roll bearing, 11 is a thermal fuse, 1
Reference numeral 2 is a heating unit cover, 13 is a halogen lamp, 14 is a reflector of the halogen lamp, and 15 is a temperature control unit.

The fixing roll 1 incorporated in this fixing device
Has the same structure as that used in the fixing device of the present invention except that an iron pipe is not fitted in the heating portion. A 250 W halogen lamp 13 is used to heat this heating unit, and a reflector 14 and a heating unit cover 12 are provided for efficient heating. The pressure roll 2 and other members have the same structure as that used in the fixing device of the present invention.

In the fixing device of FIG. 2, the surface temperature of the fixing roll is set to 160 as in the fixing device of the present invention.
After setting the temperature to ℃ and measuring the warm-up time,
The warm-up time up to 160 ° C. with a 250 W halogen lamp was 210 seconds, which was three times longer than that of the fixing device of the present invention.

[0019]

In the fixing device of the present invention, the heat pipe itself is used as the fixing roll, and the heating portion projecting at the end of the fixing pipe is induction-heated. Therefore, the diameter of the fixing roll is reduced and the fixing device is miniaturized. In addition, the induction heating provides better heat transfer efficiency than using a halogen lamp, which not only consumes less power but also significantly shortens the warm-up time, and the temperature distribution of the fixing roll is more uniform. Has the effect of being converted. In addition, since there is no damage to parts such as halogen lamps, there is an advantage that maintenance labor and cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a structure of a fixing device according to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of an essential part showing the structure of a fixing device of a comparative example of the present invention.

[Explanation of symbols]

 1 Fixing Roll 1a Heat Dissipating Section 1b Heating Section 2 Pressurizing Roll 3 Thermistor 4 AC Power Supply 5 High Frequency Oscillating Section 6 High Frequency Coil 7 Iron Pipe 8 Driving Gear 9 Fixing Roll Bearing 10 Pressurizing Roll Bearing 11 Temperature Fuse 12 Cover 13 Halogen Lamp 14 Reflector 15 Temperature controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masakuni Shimoyama 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industry Co., Ltd.

Claims (1)

[Claims] 1. A fixing roll provided with a heating portion of a heat pipe projecting laterally and a release layer around the heat radiating portion, and induction heating means provided around the heating portion. Fixing device for electrophotography.