JPH09197863A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten warming-up time and to restrain the thermal damage of a heating roller and its peripheral parts and the occurrence of image offset by providing the heating roller with a heat pipe roller and a resistance heating element on the outer peripheral surface of the pipe roller. SOLUTION: This fixing device is provided with the heating roller 100 and a pressure roller 200, and an image is thermally fixed on a recording material holding an unfixed image. The heating roller 100 includes the heat pipe roller 110 consisting of a heat pipe, an electric insulating layer 120 formed on the outer peripheral surface of the roller 110, the layered resistance heating element 130 which is energized to generate heat, and a mold-released layer 140. Furthermore, the circumferntial wall of the roller 110 is formed of iron, ferroalloy, copper, copper alloy, nickel, nickel alloy, titanium alloy or stainless steel, and the thickness of the circumferential wall is set to <=1/30 of the outside diameter of the roller 110. Heating is directly performed by an electromagnetic induction heating means including an induction coil arranged near the roller 110.

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 heating and fixing an unfixed image such as a toner image on a recording material in an image forming apparatus such as an electrophotographic copying machine and a printer.

[0002]

2. Description of the Related Art A fixing device in an image forming apparatus such as a copying machine, a printer or a facsimile machine, which forms a print image by an electrophotographic method, usually has a heating roller for heating an unfixed image to a recording material to fix it. The recording material, which has an unfixed image such as a toner image, usually includes this heating roller and a backup member (for example, a pressure roller, a pressure belt, a pressure plate body, etc.) arranged to face the heating roller. And is heated and fixed under pressure.

Hitherto, a heating roller having a built-in heating heater such as a halogen lamp heater and heating the roller by radiant heat from the heater has been widely used. However, in a fixing device that employs a heating roller that uses a built-in heating heater such as a halogen lamp heater as a heat source, the temperature rising rate from the start of energization of the heater until the surface of the heating roller reaches a predetermined fixing temperature is low. The preheating time (so-called warming-up time) from when the power switch of the above is turned on until the fixing device reaches the predetermined fixing temperature becomes long, and the device becomes so difficult to use.

Therefore, as a heating roller in which the temperature rising time required to reach a predetermined temperature can be shortened, for example, Japanese Patent Laid-Open No. 59-18 is used.
As disclosed in Japanese Patent No. 9381, there is proposed a heating roller formed on a core roller so that a resistance heating element made of a substance that generates heat when energized is rotated together with the core roller. This type of heating roller has high electric-heat conversion efficiency, and can quickly raise the heating roller surface temperature to a predetermined temperature after starting the energization of the resistance heating element, thereby shortening the preheating time of the fixing device. You can

On the other hand, as a problem related to the fixing device, a region on the surface of the heating roller where the recording material passes (hereinafter,
It is called "paper passing area". ), There is a problem of abnormal temperature rise in the outer area (non-sheet passing area). That is, in order to control the surface temperature of the heating roller, usually, the surface temperature of the common area through which recording materials of various sizes pass is detected by the temperature detecting means, and the surface temperature of the heating roller is adjusted to the predetermined fixing temperature based on the detected temperature. However, if many small-sized recording materials are passed through the paper passing area, the surface temperature of the heating roller in that area is lowered. The surface temperature of the heating roller is controlled so as to correct the temperature. As a result, even if the surface temperature of the heating roller in the area where the small-sized recording material passes is appropriately maintained, the heat-deprived recording material does not pass in the non-sheet passing area. Since there is not any, the surface temperature of the heating roller in that part gradually rises and becomes an abnormally high temperature. Due to this abnormal temperature rise, the heating roller and its peripheral parts are thermally damaged, and when the next large size recording material is passed through, the recording material is thermally damaged and the recording material is thermally damaged. Even if it does not, the toner forming the image is excessively melted and transferred (offset) to the heating roller side.

Therefore, in Japanese Utility Model Application Laid-Open No. 53-123940 and Japanese Patent Application Laid-Open No. 6-318000, even if a small-sized recording material is continuously passed through a certain area, the surface temperature of the heating roller is equal to that of the roller surface. He teaches a fixing device in which the heating roller or a member corresponding to the heating roller is composed of a heating member composed of a heat pipe so as to be uniformized in each region. In the fixing device described in Japanese Utility Model Laid-Open No. 53-123940, an endless belt is wound around a plurality of rollers, a fixing roller is brought into contact with the belt, and at least one of the rollers is a heat pipe roller. Japanese Patent Laid-Open No. 6-318000 teaches a configuration in which a heating unit is coaxially built in a pipe roller, and a heating member (for example, a heat pipe roller) made of a heat pipe and a pressure roller are opposed to each other, and the heating member is provided. A heat-resistant film, which has been subjected to a mold release treatment and is wound around, is passed through the nip portion between the heating member and the pressure roller so that the recording material is nipped and passed between the film and the pressure roller. A heating member (heater lamp, planar heating element), which is prepared separately from the heating member including a heat pipe and is supported by a supporting member in the fixing device main body or the like. It teaches a structure for heating in).

[0007]

The abnormal temperature rise in the non-sheet passing area of the heating roller and the accompanying high temperature offset, etc., are as described above.
The heat pipe roller taught by JP-A-123940, JP-A-6-318000 and the like may be adopted. In the heat pipe roller taught by JP-A-53-123940, its heating means is coaxial with the roller. Since it is built in the roller, the number of parts is large, the structure is complicated, and the roller manufacturing is extremely difficult and expensive. Also,
In the case of the heat pipe roller taught in JP-A-6-318000, the heating means is configured and arranged separately from the heat pipe roller and is supported by the support member, so that the heat capacity of the support member causes Also, the heat is taken away, the heat pipe roller cannot be heated quickly, and the warm-up time becomes longer accordingly.

Further, in terms of shortening the warming-up time, in a fixing device which employs a heating roller having a resistance heating element which heats when the core roller is energized, a built-in heating heater such as a halogen lamp heater is used as a heat source. Although the warming-up time is shortened as compared with the fixing device using the heating roller, the heating capacity is still large due to the thickness of the heating roller required for strength, and therefore there is a limit to speeding up the temperature rise.

That is, aluminum has been the main material for the core roller, which is the main body of the heating roller, but aluminum is relatively low in strength as compared with other metals. Therefore, it is thick to be used as the core roller of the heating roller. Needs to be thickened to some extent, and its heat capacity limits the rate of temperature rise. In this respect, if a relatively strong material such as iron or stainless steel is used, the thickness of the core roller can be reduced and the heat capacity can be reduced. It can be faster.

However, a material having a relatively high strength such as iron or stainless steel does not have a high thermal conductivity as compared with aluminum, and even if the wall thickness can be made thin, the thinning of the material makes it possible to transfer heat particularly in the direction of the rotation axis of the heating roller. As the heat resistance is reduced, only a heating roller with considerably poor heat transfer can be obtained as compared with the case of using an aluminum core roller. When such a heating roller is used, for example, the difference between the heating roller surface temperature in the non-sheet passing area and the heating roller surface temperature in the sheet passing area when a small-sized recording material is continuously passed becomes large, and the non-sheet passing area is The temperature rises abnormally, causing thermal damage to the heating roller and its peripheral parts and the same offset as described above.

Therefore, the present invention relates to a fixing device provided with a heating roller for heating and fixing an unfixed image on a recording material, and the conventional fixing using a heat pipe roller as the heating roller. An object of the present invention is to provide a fixing device which can shorten the warming-up time as compared with the device, can sufficiently suppress the thermal damage to the heating roller and its peripheral parts and the occurrence of image offset, and can be manufactured at a low cost with a simple structure. .

[0012]

In order to solve the above-mentioned problems, the present invention provides the following two types of fixing devices. (1) In a fixing device that heat-fixes an unfixed image on a recording material that holds the unfixed image, the heating roller is for heating and fixing the unfixed image on the recording material, the heat-pipe roller including a heat pipe; A fixing device comprising a heating roller provided on the outer peripheral surface of the heat pipe roller, the heating roller including a resistance heating element that generates heat when energized. (2) A fixing device that heat-fixes an unfixed image on a recording material that holds the unfixed image, and includes a heating roller that heat-fixes the unfixed image on the recording material, and the heating roller is a heat pipe. The fixing device is characterized in that it comprises a heat pipe roller consisting of, and the heat pipe roller is directly heated by an electromagnetic induction heating means including an induction coil arranged in the vicinity thereof.

In each of the fixing devices (1) and (2), the peripheral wall of the heat pipe roller is made of a metal having a strength higher than that of aluminum, such as iron or iron, in order to make the peripheral wall of the heat pipe roller thin and have a small heat capacity. It can be formed from one or more of alloys, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys and stainless steel.

In each of the fixing devices (1) and (2), or in each of the fixing devices (1) and (2), the peripheral wall of the heat pipe roller is made of iron, iron alloy, copper, Copper alloy, nickel, nickel alloy, titanium,
In a fixing device formed of one or more of titanium alloy and stainless steel, it is conceivable that the wall thickness of the circumferential wall of the heat pipe roller is 1/30 or less of the outer diameter of the heat pipe roller.

In any of the fixing devices according to the present invention, the heating roller is heated from the non-operating state, and after the fixing device reaches a predetermined fixing temperature, the recording material holding the unfixed image is passed through the heating roller. While the unfixed image is heated by the roller, the unfixed image is heated and fixed on the recording material. At this time, according to the fixing device of the type (1) according to the present invention, the heating roller is energized to the resistance heating element on the outer peripheral surface of the heat pipe roller, so that the heating roller surface temperature is directed to a predetermined temperature, Rises quickly. Further, almost all of the heat from the resistance heating element is directly absorbed without being taken away by other members,
It is efficiently transmitted to the heat pipe roller, so that the temperature of the heat pipe roller also rises accordingly. By these, the surface temperature of the heating roller as a whole can be quickly raised to a predetermined temperature, and the warming-up time is shortened as compared with the conventional fixing device using a heat pipe roller as the heating roller.

In the fixing device of the type (2) according to the present invention, the heat roller is directly and efficiently heated by electromagnetic induction by energizing the induction coil in the electromagnetic induction heating means. The surface temperature of the heating roller rises rapidly, and in this case as well, the warming-up time is shortened as compared with the conventional fixing device using the heat pipe roller.

In any fixing device, the temperature of each part of the heat pipe roller is made uniform by the heat pipe function, so that the surface temperature of each part of the heating roller is made uniform. For example, even when many sheets of small-sized recording material are passed through the sheet-passing area for that purpose, the temperature of the heating roller surface is kept uniform, so that the non-sheet-passing area is abnormally heated and the heating roller and its periphery are heated. Occurrence of a situation in which a component is thermally damaged is sufficiently suppressed, and image offset or the like is sufficiently suppressed even when a large number of recording materials are passed after passing a small number of recording materials.

In the fixing device according to the present invention, as described above, the peripheral wall of the heat pipe roller is made of a metal having a higher strength than aluminum, such as iron, iron alloy, copper, copper alloy, nickel, nickel alloy, titanium, When it is formed of one or more of titanium alloy and stainless steel, the peripheral wall of the heat pipe roller can be made considerably thinner and the heat capacity can be made smaller than that of aluminum which has been the mainstream as the core roller material of the conventional heating roller. Therefore, the warm-up time can be further shortened.

Further, in the fixing device according to the present invention, when the wall thickness of the circumferential wall of the heat pipe roller is set to 1/30 or less of the outer diameter of the heat pipe roller as described above, the heat capacity can be reduced accordingly. The warming up time can be further shortened. Thus, the thickness of the circumferential wall of the heat pipe roller is set to 1/3 of the outer diameter of the heat pipe roller.
When it is set to 0 or less, the peripheral wall of the heat pipe roller is made of a metal having a higher strength than aluminum, such as iron or iron alloy,
If it is formed from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, and stainless steel, it is easy to reduce the thickness to 1/30 or less, the degree of thinning can be increased, and warming up is possible. The time can be surely shortened.

For example, in the conventional heat pipe roller made of aluminum, when the outer diameter φ = 20 mm, the wall thickness of the circumferential wall is usually 1 mm (outer diameter) in order to make the strength of the heat pipe roller sufficient. 1/20 of)
As described above, when the peripheral wall of the heat pipe roller in the fixing device of the present invention is made of the above-mentioned material having higher strength than aluminum, for example, when the outer diameter φ = 20 mm, the wall thickness of the peripheral wall is 0. It can be made as thin as 3 to 0.5 mm (about 1/60 to 1/40 of the outer diameter), and as a result, the heat pipe roller 110 has a small heat capacity, which further shortens the warm-up time.

When the electromagnetic induction heating means is used as the heat pipe roller heating means, the heat pipe roller peripheral wall material is a conductive metal material.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of an example of a fixing device according to the present invention. This fixing device includes a heating roller 100 and a pressure roller 200 that is pressed against the heating roller 100. The heating roller 100 includes a heat pipe roller 110, and the end portion of the heating roller 100 is fitted in the bearing portion 150 fitted in the circular through hole 310 provided in the side plate member 300 of the fixing device housing in advance. It is rotatably supported by. Further, the pressure roller 200 has a support shaft 210 of the roller 200 rotatably supported by a side plate member 300 via a bearing portion (not shown) and is pressed toward the heating roller 100 by a pressing means (not shown). Has been done. Heating roller 10
0 and the pressure roller 200 are rotationally driven in the recording paper feeding direction by a driving unit (not shown).

The heating roller 100 has a heat pipe roller 110 having a hollow cylindrical shape with both ends sealed. The peripheral wall of the roller 110 is made thin to have a small heat capacity, and thus iron, iron alloy, copper, copper alloy, nickel,
It is recommended to be made of one or more of nickel alloy, titanium, titanium alloy and stainless steel, but here, it is made of stainless steel (SUS430), and the wall thickness of the circumferential wall is 1 of the outer diameter of the roller 110. / 30
It is formed below (here, 1/40 of the outer diameter of the roller 110 and 0.5 mm). Both ends of the heat pipe roller 110 are hermetically sealed to reduce the pressure, and water is sealed inside as a working fluid. In addition to water, naphthalene or diphenyl [(C ₆ H
₅ ) ₂ ] and an organic heat medium such as a eutectic mixture of diphenyl ether [(C ₆ H ₅ ) ₂ O]. On the outer peripheral surface of the heat pipe roller 110, an electric insulating layer 120, a layered resistance heating element 130, and a release layer 140 are formed in this order.

The electric insulating layer 120 is made of polyimide which is a heat resistant insulating resin, the resistance heating layer 130 is made of barium titanate ceramic, and the release layer 140 is made of polytetrafluoroethylene (PTFE) which is a heat resistant resin. Has been formed. The materials of the electric insulation layer 120, the resistance heating layer 130, and the release layer 140 are not limited to these.
The electrically insulating layer 120 may be made of polyamide or the like, and the release layer 140 may be made of a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene (PFA) or the like. The electrical insulating layer 120, the resistance heating element layer 130, and the release layer 140 rotate integrally with the heat pipe roller 110. The width of the release layer 140 is the heating roller 100.
The width of the recording paper is larger than the maximum width of the recording paper holding the toner image to be passed between the pressure roller 200 and the pressure roller 200. Resistance heating element layer 1
The width of 30 is wider than that of the release layer 140, and the width of the electrically insulating layer 120 is equal to that of the heat pipe roller 11
In order to maintain electrical insulation between 0 and the resistance heating element layer 130, it is formed wider than the resistance heating element layer 130, but in this example, narrower than the width in the rotation axis direction of the heat pipe roller 110.

On both outer peripheral surfaces of the resistance heating element layer 130,
A ring-shaped power receiving member 161 made of a pair of conductive copper alloys
a, 161b are provided, and the power receiving members 161a, 1 are provided.
61b and the resistance heating layer 130 are electrically connected. The power receiving members 161a and 161b are also electrically insulating layers 120,
The resistance heating element layer 130 and the release layer 140 rotate integrally with the heat pipe roller 110. This power receiving member 16
1a and 161b are provided with a pair of conductive carbon-made power supply members 162a and 162b, respectively, as springs 163a and 1a.
It is pressed by 63b. Then, the power receiving member 161
a (161b) and the power feeding member 162a (162b), the power receiving member 161a (161b) is the heat pipe roller 11
Even if it rotates together with 0, the electrical connection is maintained at the contact surfaces of both.

The power feeding member 162a is connected to one end of the power source 400 via the safety switch 410, and the power feeding member 162b is connected to the other end of the power source 400 via the safety switch 420 and the relay RY. The safety switches 410 and 420 are heat-sensitive safety switches such as thermal fuses, and are placed in contact with or close to the heating roller 100. Further, a thermistor TM, which is a temperature detecting means, is arranged in contact with the resistance heating element layer 130 via the release layer 140. The detected temperature information output by the thermistor TM is the heating roller temperature control unit 5
00 is input. Further, the relay RY is opened / closed according to an instruction from the control unit 500. The controller 500 outputs a contact opening / closing signal to the relay RY according to the temperature detected by the thermistor TM, and thereby controls the temperature of the heating roller 100.

According to this fixing device, the heat-fixing of the unfixed toner image on the recording paper is performed as follows. First, in the operation of the fixing device, in order to set the temperature of the heating roller 100 to a predetermined temperature required for heat fixing, the contact of the relay RY is closed by the control unit 500, and the power supply member 162a and the power receiving member 161a are connected from the power supply 400. And power supply member 16
2b and the power receiving member 161b through the resistance heating layer 130
Is applied with a voltage. The resistance heating element layer 130 generates heat due to its own Joule loss to raise the temperature of the heating roller 100. During operation of the heating roller 100, the temperature of the heating roller 100 is detected by the thermistor TM, and this is detected by the controller 5
00, the temperature is compared with a predetermined fixing temperature, and the contact opening / closing signal of the relay RY is output from the control unit 500 to the relay RY accordingly. The contact opening / closing signal opens / closes the contact of the relay RY to control the voltage application to the resistance heating layer 130 by the power supply 400, and the temperature of the heating roller 100 is maintained at a predetermined temperature.

Then, the recording paper holding the toner image is conveyed to a nip portion between the heating roller 100 and the pressure roller 200, where one end of the recording paper is heated to a predetermined fixing temperature by a conveying means (not shown). Both rollers are rotated by a driving means (not shown), and the conveyed recording paper passes between both rollers while being sandwiched by both rollers, and the toner image is heated and fixed on the recording paper.

According to the fixing device of the present invention described above,
The heating roller 100 includes a heat pipe roller 110, an insulating layer 120, a layered resistance heating element 130, and a release layer 140.
Are closely contacted with each other, the surface temperature of the heating roller 100 rapidly rises toward a predetermined fixing temperature when the resistance heating element 130 is energized. In addition, the resistance heating element layer 13
Almost all the heat from 0 is efficiently transferred to the heat pipe roller 110 without being taken away by other members, and the wall thickness of the circumferential wall of the roller 110 is 1/3 of the roller outer diameter.
Since the thickness is 0 or less, the heat pipe roller 110 also rises in temperature quickly. As a result, the surface temperature of the heating roller 100 as a whole can be quickly raised to a predetermined temperature, and compared with a conventional fixing device using a heat pipe roller such as heating the heat pipe roller by a separate heating means. The warm-up time is shortened. Further, from this, even if a part of the electric power is cut off during standby, warming up can be immediately performed at the time of the next fixing and operability is not impaired.

Further, since the heat pipe roller 110 makes its temperature uniform in each part by its own heat pipe function, the surface temperature of the heat roller 100 becomes uniform in each part, and for example, a small size recording paper is used for it. Even when many sheets are passed through the paper passing area, not only the paper passing area,
Even in the non-sheet passing area at that time, a uniform temperature state is maintained over the entire area. Therefore, heat damage to the heating roller itself and its peripheral parts due to an abnormal temperature rise in the non-sheet passing area is sufficiently suppressed, and a large number of sheets are provided. Even when the small size recording paper is passed and then the large size recording paper is passed, the thermal damage to the recording paper itself and the image offset are sufficiently suppressed. Further, from this, it is possible to select a material having a low heat resistant temperature as the material of the heating roller and the peripheral parts, and the cost of the parts can be reduced accordingly. Further, since the abnormal temperature rise can be prevented and the heat stored in the heat pipe roller 110 can be effectively utilized, the heat can be efficiently utilized.

Further, since the heat pipe roller 110 and the resistance heating element layer 130 are integrally formed in the fixing device of the present invention, the fixing device has a small number of parts, a small size and a simple structure, and the cost can be reduced accordingly. Next, FIG. 2A is a schematic plan view of another example of the fixing device according to the present invention.
(B) is a sectional view taken along the line XX.

This device is different from the device of FIG. 1 in that the insulating layer 120, the resistance heating layer 130, and the resistance heating layer 1
Power receiving members 161a, 161b, power feeding members 162a, 162b, and springs 163a, 163b for energizing 30.
Instead, the heating roller 100 ′ is formed by covering the outer peripheral surface of the heat pipe roller 110 with a release layer 140 ′.
The heating roller 10 is provided outside the heating roller 100 '.
An induction coil 600 is provided so as to cover approximately half of the outer periphery of 0 '. Further, the coil 6 is provided outside the induction coil 600.
A heat insulating material 610 having a size enough to cover 00 is provided. One end of the induction coil 600 has a safety switch 41.
0 to one end of the power supply 400 and the other end of the induction coil 600 to the power supply 4 via the safety switch 420 and the relay RY.
00 is connected to the other end. Other configurations are similar to those of the apparatus shown in FIG.

According to this fixing device, the induction coil 600
In addition to the electromagnetic induction heating of the heat pipe roller 110 by energizing the sheet, the unfixed toner image is heat-fixed on the recording paper in the same manner as the apparatus of FIG. According to this fixing device, the heat conduction to the induction coil 600 directly and efficiently heats the heat pipe roller 110 by electromagnetic induction, so that the surface temperature of the heating roller 100 'as a whole rapidly rises to a predetermined temperature. Warming-up time is shortened as compared with a conventional fixing device using rollers. Other advantages are similar to those of the fixing device shown in FIG.

Next, one experiment will be described. That is, for each of the fixing device of FIG. 1 and the conventional fixing device that employs a hollow roller made of the same material in place of the heat pipe roller 110 in the device of FIG. The temperature distribution of the surface temperature of the heating roller in the roller rotation axis direction was measured after 100 sheets were continuously passed. In each of the devices, stainless steel (SUS430) was used as the material of the heat pipe roller or the roller replacing it.

The results are shown in FIG. As can be seen from FIG. 3, in the conventional fixing device B in which a simple hollow roller is used as the heating roller instead of the heat pipe roller, the temperature of the non-sheet passing portion is 100% after passing the sheet.
The maximum fixing temperature of 180 ° C. was increased by 70 ° C., but in the apparatus A of FIG. 1 according to the present invention, the maximum increase of 5 ° C. was suppressed.

[0036]

As described above, according to the present invention, there is provided a fixing device equipped with a heating roller for heating and fixing an unfixed image on a recording material, the heating roller being a heat pipe roller. A fixing device that can shorten the warming-up time compared to a conventional fixing device that uses a heat roller, can sufficiently suppress thermal damage to the heating roller and its peripheral parts and the occurrence of image offset, and can be manufactured at a low cost with a simple structure. can do.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an example of a fixing device according to the present invention.

FIG. 2A is a schematic plan view of another example of the fixing device according to the present invention, and FIG. 2B is a cross-sectional view taken along line XX of FIG.

FIG. 3 is a diagram showing a surface temperature distribution of a heating roller in each of the fixing device A and the conventional fixing device B shown in FIG.

[Explanation of symbols]

 100, 100 'Heating roller 110 Heat pipe roller 120 Electric insulating layer 130 Resistance heating element layer 140 Release layer 150 Bearing part 161a, 161b Power receiving member 162a, 162b Power feeding member 163a, 163b Spring 200 Pressure roller 210 Pressure roller 200 Support shaft 300 Side plate member 310 Through hole 400 Power supply 410, 420 Safety switch 500 Control unit 600 Induction coil 610 Insulation material RY relay TM Thermistor

Claims (6)

[Claims] 1. A fixing device that heat-fixes an unfixed image on a recording material that holds the unfixed image, and a heating roller that heat-fixes the unfixed image on the recording material, the heat comprising a heat pipe. A fixing device comprising a pipe roller and a heating roller provided on the outer peripheral surface of the heat pipe roller and including a resistance heating element that generates heat when energized. 2. The peripheral wall of the heat pipe roller is made of iron,
1 or 2 of iron alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy and stainless steel
The fixing device according to claim 1, which is formed from the above. 3. The fixing device according to claim 1, wherein the thickness of the circumferential wall of the heat pipe roller is 1/30 or less of the outer diameter of the heat pipe roller. 4. A fixing device for heating and fixing an image on a recording material carrying an unfixed image, comprising a heating roller for heating and fixing the unfixed image on the recording material. A fixing device comprising a heat pipe roller made of a heat pipe, wherein the heat pipe roller is directly heated by an electromagnetic induction heating means including an induction coil arranged in the vicinity thereof. 5. The heat pipe roller has a peripheral wall made of iron,
1 or 2 of iron alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy and stainless steel
The fixing device according to claim 4, which is formed from the above. 6. The fixing device according to claim 4, wherein the thickness of the circumferential wall of the heat pipe roller is 1/30 or less of the outer diameter of the heat pipe roller.