JPH09152807A - Fixing device using induction heating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact fixing device with induction heating which can prevent the temperature rise of an induction coil, which has good fixing performance at a low cost by possessing a heating member, a pressure member, and the induction coil. SOLUTION: A coil assembly 17 generating a magnetic flux supplied to a metallic sleeve 10 is held by a holder 19 and disposed inside the pressure roller 13 in order to generate a induction current (eddy current) on the sleeve 10. The holder 19 is fixed to a fixing unit frame so as not to rotate, and is housed inside the roller 13 with an interval having a specified size between the inside peripheral surface of the roller 13 and the holder 19. Thus, the peripheral part of the coil 22 is prevented from being heated by the heat radiation of the sleeve 10 as the heating member toward the inside surface as in the conventional manner, heat energy by the heating of the coil 22 itself is absorbed by the roller 13, so that the temperature around the coil 22 can be restrained from rising.

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 image forming apparatus such as an electrophotographic copying machine, a printer and a facsimile, and more specifically, it fixes a toner image on a sheet by using induction heating. Regarding the fixing device.

[0002]

2. Description of the Related Art An electrophotographic copying machine or the like is provided with a fixing device for fixing a toner image transferred onto a sheet such as recording paper or a transfer material as a recording medium onto the sheet. This fixing device has, for example, a fixing roller also referred to as a heating roller that heat-melts the toner on the sheet, and a pressure roller that presses the fixing roller to sandwich the sheet. The fixing roller is formed in a hollow shape, and a heating element is held by a holding means on the central axis of the fixing roller. The heating element is composed of, for example, a tubular heating heater such as a halogen lamp, and generates heat when a predetermined voltage is applied. Since this halogen lamp is located on the central axis of the fixing roller, the heat emitted from the halogen lamp is radiated uniformly to the inner wall of the fixing roller,
The temperature distribution on the outer wall of the fixing roller becomes uniform in the circumferential direction. The outer wall of the fixing roller is heated until its temperature reaches a temperature suitable for fixing (for example, 150 to 200 ° C.). In this state, the fixing roller and the pressure roller rotate in opposite directions while being in pressure contact with each other to sandwich the sheet to which the toner adheres. At the pressure contact portion (hereinafter also referred to as a nip portion) between the fixing roller and the pressure roller, the toner on the sheet is melted by the heat of the fixing roller and is fixed on the sheet by the pressure applied from both rollers.

However, in the above fixing device having a heating element composed of a halogen lamp or the like, since the fixing roller is heated by utilizing the radiant heat from the halogen lamp, after the power is turned on, the temperature of the fixing roller is increased. It took a relatively long time to reach a predetermined temperature suitable for fixing (hereinafter referred to as "warm-up time"). During that time, the user cannot use the copying machine and is forced to wait for a long time. On the other hand, if a large amount of electric power is applied to the fixing roller in order to shorten the warm-up time and improve the operability for the user, the power consumption of the fixing device increases, which is against energy saving. It was Therefore, in order to increase the value of products such as copiers, it is more important and more important to achieve both energy saving (low power consumption) of the fixing device and improvement of user operability (quick print). Has been done.

An apparatus which meets such a request is disclosed in Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Publication No. 9-33787, an induction heating type fixing device utilizing high frequency induction as a heating source has been proposed. In this induction heating fixing device, a coil is concentrically arranged inside a hollow fixing roller made of a metal conductor, and an induction eddy current is generated in the fixing roller by a high frequency magnetic field generated by applying a high frequency current to the coil. The skin resistance of the fixing roller itself causes the fixing roller itself to generate Joule heat. According to this induction heating type fixing device, the electric-heat conversion efficiency is remarkably improved, so that the warm-up time can be shortened.

By the way, in such an induction heating type fixing device, the self-heating of the coil for generating magnetic flux disposed inside the fixing roller and the heat radiation to the inner surface of the fixing roller, The temperature rise around the coil is large,
Therefore, it is necessary to use a material excellent in heat resistance at high temperature as a peripheral member, which results in high cost. There is also a type in which a flexible thin metal sleeve is used as the heating member instead of the fixing roller, but the above situation is the same.

Therefore, as disclosed in, for example, Japanese Patent Laid-Open No. 54-39645, it has been proposed to provide a cooling mechanism such as a blowing means to the inside of the fixing roller in order to suppress the temperature rise of the coil. ing.

[0007]

However, the above-mentioned conventional induction heating type fixing device requires a heat resistant resin in order to protect the inner surfaces of the coil, core, fixing roller and the like, and When the cooling mechanism is installed, the installation space is required, which not only increases the size of the apparatus, but also causes a problem such as an increase in cost.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to prevent the temperature rise of the induction coil and to have a good fixing performance at a low cost and a compact size. Another object of the present invention is to provide an induction heating fixing device.

[0009]

The present invention for achieving the above object is specified as follows for each claim. The invention according to claim 1 is such that a heating member that generates heat by an induced current, a pressure member that is arranged in pressure contact with the heating member, and a magnetic flux that is provided inside the pressure member and that is supplied to the heating member. An induction heating fixing device having an induction coil for generating a. In the invention specified in this way,
It is possible to avoid the situation where the induction coil for generating magnetic flux is heated by the heat radiation to the inner surface of the heating member, and the heat energy due to the heat generation of the induction coil itself is absorbed by the pressurizing member, and the temperature rise of the induction coil is suppressed. Moreover, since the pressure roller is simultaneously heated due to the absorption of heat energy by the heat generation of the induction coil into the pressure roller, good fixing performance can be obtained, and even when the set temperature of the heating member is lowered, good fixing is achieved. Performance is maintained.

According to a second aspect of the present invention, in the induction heating fixing device according to the first aspect, the heating member is composed of a thin cylindrical magnetic body.
In the invention thus specified, the heat capacity of the heating member is small, and the temperature rises more quickly.

According to a third aspect of the present invention, in the induction heating fixing device according to the first aspect, the pressing member is made of a non-magnetic material. In the invention thus specified, the magnetic flux generated by the induction coil is supplied to the heating member while being hardly absorbed by the pressing member.

According to a fourth aspect of the present invention, in the induction heating fixing device according to the first aspect, the pressing member is a belt having elasticity and formed of a non-magnetic material. In the invention thus specified, the length (nip width) in the sheet conveying direction of the press contact portion between the heating member and the pressing member can be increased, so that the set temperature of the heating member can be further lowered. As a result, the temperature rise time is shortened and the temperature rise around the area is further suppressed. Moreover, since the pressure contact force can also be reduced, the load on the drive source such as the belt is reduced.

According to a fifth aspect of the present invention, in the induction heating fixing device according to the first aspect, the pressure member has an inner surface formed of a heat absorbing member having a heat absorption coefficient of a predetermined value or more. It is characterized by In the invention thus specified, the heat energy generated by the heat generation of the induction coil itself is quickly absorbed by the pressurizing member without being stored inside.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view schematically showing an induction heating fixing device according to a first embodiment of the present invention.

As shown in FIG. 1, an induction heating fixing device incorporated in a printer or the like is provided with a metal sleeve 10 as a heating member which generates heat by an induction current, and a pressurizing member arranged in pressure contact with the metal sleeve 10. It has a pressure roller 13 as a member.

The metal sleeve 10 has a heat generating portion 11 as a thin-walled cylindrical magnetic body formed of a conductive magnetic material such as nickel, and a fluororesin (for example, P
FA, PTFE, etc.) is coated to form a heat-resistant release layer 12 on the surface. The heat generating portion 11 has a wall thickness of about 20 μm to 60 μm and has flexibility.

The pressure roller 13 comprises a hollow cored bar 14 made of a non-magnetic material and an elastic layer 15 which is a surface-releasing heat-resistant rubber layer formed on the outer peripheral surface thereof. Bearings are formed at both ends of the pressure roller 13 and are rotatably attached to a fixing unit frame (not shown). Further, the pressure roller 13 has a drive gear (not shown) fixed to one end thereof, and is rotationally driven in the direction of arrow a by a drive source (not shown) such as a motor connected to the drive gear.

Inside the metal sleeve 10, there is provided a non-rotating pressure contact holder 16 fixed to the fixing unit frame. The pressure contact holder 16 is made of a non-magnetic material and has flexibility. And the pressure roller 13 are arranged so as to come into pressure contact with each other. Therefore, the metal sleeve 10 is attached to the pressure roller 13 and the pressure contact holder 16 by pressing.
It is sandwiched between and and is rotated by rotation of the pressure roller 13. In this case, the metal sleeve 10 and the pressure contact holder 16 are in contact with each other and relatively slide. Since the pressure contact holder 16 is pressed against the inner peripheral surface of the metal sleeve 10, in order to secure mechanical strength that can endure pressure contact with the pressure roller 13, when the pressure contact holder 16 is made of resin, Is 1 mm or more).

In the first embodiment, particularly, the pressure roller 1
In order to generate an induced current (eddy current) in the metal sleeve 10, a coil assembly 17 that generates a magnetic flux to be supplied to the metal sleeve 10 is provided inside the holder 3 while being held by a holder 19. The holder 19 is fixed to the fixing unit frame and is non-rotating, and is housed inside the roller 13 with a gap of a predetermined dimension between the holder 19 and the inner peripheral surface of the pressure roller 13. Therefore, it is possible to prevent the surroundings of the induction coil 22 from being heated by heat radiation to the inner surface of the metal sleeve 10 as a heating member as in the conventional case, and the thermal energy generated by the heat generation of the induction coil 22 itself is applied. Induction coil 2 absorbed by roller 13
2 It is possible to suppress the temperature rise around the area. Moreover, in the present embodiment, the inner surface of the hollow core metal 14 of the pressure roller 13 is formed of, for example, a black-painted heat-absorbing member having a high heat-absorption rate, and the heat generated by the heat generation of the induction coil 22 itself. Energy is quickly absorbed by the pressure roller 13 without being trapped inside.

The coil assembly 17 has a core 23 made of a magnetic material, and an induction coil 22 formed by winding a copper wire around the core 23 a plurality of times in one direction via an insulating member (not shown). Here, the core 23 is arranged so as to be orthogonal to the copper wire of the induction coil 22 and forms a magnetic path. As the coil 22, it is preferable to use a single or litz copper wire having a fusion layer and an insulating layer on the surface. The core 23 is made of a magnetic material, for example, a ferrite core or a laminated core.

The coil assembly 17 is housed in a holder 19 so as not to be exposed to the outside, as shown in the drawing. Thus, the coil assembly 17 includes the holder 1
It is held so as to be surrounded by 9, and constitutes a holder unit 18 as a whole.

The toner carrier, that is, the sheet on which the unfixed toner image has been transferred is conveyed from the left direction as shown by an arrow b in the figure, and enters the nip portion n between the metal sleeve 10 and the pressure roller 13. Sent to you. The sheet is conveyed through the nip portion n while being heated by the heated metal sleeve 10 and the pressure applied from the metal sleeve 10 and the pressure roller 13. As a result, the unfixed toner is finally fixed, and a fixed toner image is formed on the sheet. The sheet that has passed through the nip portion n is naturally separated from the metal sleeve 10 due to the curvature of the metal sleeve 10, or the metal sleeve 10 is separated by a separation claw (not shown) provided so that the leading end of the sheet slides on the surface of the metal sleeve 10. The paper is forcibly separated from and is transported to the right in the figure. Then, this sheet is conveyed by a paper ejection roller (not shown) and ejected onto the paper ejection tray.

A temperature sensor (not shown) for detecting the temperature of the metal sleeve 10 is provided substantially above the metal sleeve 10.
Is pressed against the surface of. The temperature sensor is composed of, for example, a thermistor, and while detecting the temperature of the metal sleeve 10, energization of the induction coil 22 is controlled so that the temperature of the metal sleeve 10 becomes the optimum temperature.

The holder 19 is made of heat resistant insulating engineering plastic, and the pressure contact holder 16, the bearing portion and the separating claw are made of heat resistant sliding engineering plastic.

Further, as shown in the figure, a preheating member 30 is provided on the upstream side (left side in the drawing) of the nip portion n between the metal sleeve 10 and the pressure roller 13 in the sheet conveying direction. The preheating member 30 is separated from the surface of the pressure roller 13 by a predetermined distance and is arranged so as to cover a part of the preheating member 30, and the preheating member 30 is connected to the arc surface portion 31 and also functions as a guide plate during sheet conveyance. It is composed of a plate-shaped portion 32, and is made of a metal plate that generates heat due to eddy current loss and hysteresis loss, like the metal sleeve 10 when receiving the magnetic flux generated by the induction coil 22. Plate-shaped portion 32 of the preheating member 30
Is mainly heated by transferring heat from the arcuate surface portion 31 that self-heats. Thereby, it is possible to uniformly preheat the entire area of the sheet to 100 to 130 ° C. for softening the toner by utilizing the small space.

FIG. 2 is a diagram for explaining the magnetic flux generated by the induction coil of the induction heating and fixing device according to the first embodiment, and FIG. 3 is a diagram for explaining the heating principle of the induction heating and fixing device according to the first embodiment. Is.

When the fixing device is configured as described above and the induction coil 22 is supplied with a high frequency current of, for example, 20 to 40 KHz from the commercial AC power source 25 through the rectifier circuit 26 and the inverter circuit 27 as shown in FIG. , The magnetic flux shown by the arrow in the figure is generated. As shown in FIG. 3, the magnetic flux generated by the induction coil 22 is supplied to the metal sleeve 10 without being absorbed by the pressure roller 13 made of a non-magnetic material, and an induction current is generated. Generate heat. Since the metal sleeve 10 is a thin-walled cylindrical magnetic body, it has a small heat capacity and can heat up more quickly. At the same time, a part of the magnetic flux generated by the induction coil 22 is supplied to the circular arc surface portion 31 of the preheating member 30,
Similarly, an induced current is generated and heat is generated. This heat is generated by the plate-shaped portion 32.
The sheet S that has been transferred to the nip portion n is preheated. On the other hand, the heat energy of the induction coil 22 itself is absorbed by the pressure roller 13, so that the pressure roller 13 is also heated. The sheet S on which the toner image is formed is conveyed from the left side in the state of being preheated as shown by an arrow b in the figure, and the heat of the metal sleeve 10 and the pressure roller 13 and the heat of the metal sleeve 10 and the pressure roller 13 are conveyed. 1
By applying the pressure acting from 3, the unfixed toner is finally fixed and a fixed toner image is formed on the sheet S.

FIG. 4 is a graph showing changes in coil assembly temperature, FIG. 5 is a graph showing changes in pressure roller temperature, FIG. 6 is a graph showing the relationship between the number of copies and fixing strength, and FIG. 6 is a graph showing the relationship between the metal sleeve setting temperature and the fixing strength. In FIG. 4, 1 is a conventional case in which the coil assembly is arranged inside a metal sleeve, and 2 is
Shows the case of the present invention in which the coil assembly is arranged inside the pressure roller (same in subsequent FIGS. 5 to 7).
In addition, 3 shows the actual set temperature of the metal sleeve.

As shown in FIG. 4, conventionally, the periphery of the induction coil 22 is heated by heat radiation to the inner surface of the metal sleeve 10 as a heating member, and the coil itself gradually rises above a set temperature. In the embodiment, since the coil assembly 17 is arranged inside the pressure roller 13, the thermal energy generated by the heat generation of the induction coil 22 itself is
Since it is absorbed by the pressure roller 13, the temperature rise around the induction coil 22 and the temperature of the coil itself can be suppressed.

Further, from FIG. 5, in the present embodiment, the pressure roller 13 is also heated at the same time because the heat energy of the induction coil 22 itself is absorbed by the pressure roller 13, so that the pressure roller 13 is heated more than the conventional case. It can be seen that the temperature rises. Therefore, as shown in FIG. 6, in the present embodiment, good fixing performance can be obtained from the initial stage after the printer is turned on, and as shown in FIG. 7, the set temperature of the metal sleeve is lowered. Even in this case, good fixing performance can be maintained.

FIG. 8 is a sectional view schematically showing an induction heating fixing device according to the second embodiment of the present invention, and FIG. 9 is a sectional view schematically showing an induction heating fixing device according to the third embodiment of the present invention. The same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the second embodiment, the pressing member 35 is used instead of the pressure contact holder 16 of the first embodiment, and the other points are the same as those of the first embodiment. An arcuate surface is formed at a portion of the pressing member 35 pressed against the inner peripheral surface of the metal sleeve 10.

The third embodiment differs from the first embodiment in that the metal sleeve 10 and the pressure roller 13 of the first embodiment are replaced by a fixing roller 50 and a pressure member 53, which are also called heating rollers. doing. In the induction heating fixing device according to the third embodiment, the fixing roller 50 as a heating member that is rotatably driven in the direction of arrow c, and the fixing roller 50 that is provided so as to be in pressure contact with the fixing roller 50 are rotated. And a pressure member 53 that is driven to rotate. The pressure member 53 is made of an elastic member having surface releasability and heat resistance. In the present embodiment, the pressure member 53 is sandwiched between the fixing roller 50 and the holder unit 18, and the fixing roller 50 rotates. It is designed to be driven to rotate with. The fixing roller 50 has a non-magnetic core member 51, which is a hollow conductor pipe, and has a heat generating portion and a release layer 52 on the outer peripheral surface thereof.
Are formed. The same effects as those of the first embodiment can be obtained by the second and third embodiments.

10 to 12 are sectional views schematically showing an induction heating fixing device according to Embodiments 4 to 6 of the present invention, and members common to those of Embodiments 1 to 3 are The same reference numerals are given and the description thereof is omitted.

In the fourth to sixth embodiments, instead of the pressure roller 13 or the pressure member 53 of the first to third embodiments,
The difference is that the belt 60 is used as the pressing member. The belt 60 is made of a non-magnetic elastic member having surface releasability and heat resistance, and is driven by rotating the drive roller 62 in the direction of arrow d in the figure. In these embodiments, the holder unit 18 uses the belt 60.
The metal sleeve 10 and the fixing roller 80 are driven and rotated by driving the belt 60. The same effects as those of the first embodiment can be obtained by the fourth to sixth embodiments. In addition, when the belt 60 is used as the pressing member in this manner, there is an advantage that the distance in the sheet conveyance direction of the nip portion n (hereinafter, referred to as nip width) can be increased. The fixing roller 80
Need not be driven to rotate.

13 to 15 are sectional views schematically showing an induction heating fixing device according to Embodiments 7 to 9 of the present invention, and members common to those of Embodiments 4 to 6 are shown. The same reference numerals are given and the description thereof is omitted.

The seventh to ninth embodiments are different in that the drive roller 62 of the fourth to sixth embodiments is brought closer to the metal sleeve 10 side. In addition, reference numeral "63" in the drawing denotes a driven roller. Further, with such a configuration, the shape of the core 73 of the coil assembly 70 is
It has a shape that makes it easy to supply magnetic flux to the heating member.

Now, a ninth embodiment shown in FIG. 15 will be described. The nip width of this induction heating fixing device is further increased as compared with that of the above-described embodiment.
By doing so, not only the same effects as those of the first embodiment can be obtained, but also the nip width can be made extremely long as compared with the system in which the upper and lower rollers are used as the heating member and the pressing member, so that the toner image is formed. The heating time for the formed sheet S also becomes longer, the fixing temperature can be set lower, and the pressure contact force can be lowered.

That is, since the fixing temperature can be set low, the temperature rising time can be shortened and wasteful heat dissipation can be reduced. This is because the higher the fixing temperature, the larger the heat radiation amount. Further, it is possible to suppress the temperature rise inside the entire printer. Moreover, since the pressure contact force can be reduced,
The driving torque for the fixing roller 80 and the belt 65 can be small, and the load on the drive motor (not shown) can be reduced.

In addition to these advantages, by arranging the coil assembly 70 inside the belt 65 as shown in the drawing, it is possible to heat only the nip portion n of the fixing roller 80, and it is not necessary to heat unnecessary portions. Therefore, wasteful heat dissipation can be reduced. That is, the generated heat can be efficiently transferred to the sheet S. Further, the heat-generating metal part of the fixing roller 80 and the core 73 of the coil assembly 70 can be brought closer to each other, and the energy transfer efficiency is improved.

In the conventional method using the upper and lower rollers as the heating member and the pressing member, particularly in a high-speed machine, it is necessary to increase the roller diameter in order to make the nip width long, so that not only the apparatus becomes large, but also the fixing roller. In general, the heat capacity is increased and the warm-up time is increased. However, as described above, in the present embodiment, a small and efficient fixing device can be realized.

In the ninth embodiment, the fixing roller 80 has a heat generating portion 81 which is a hollow conductor pipe having a release layer on the outer surface, and the inner surface thereof is made of ceramic, engineering plastic or the like. A heat insulating material layer 82 is formed. The heat insulating material layer is provided on the inner side in order to reduce the radiation loss to the inside of the generated heat, and also when the heat capacity is low, the heat generating portion 81, which is a thin metal portion, is reinforced.

16 to 18 are sectional views schematically showing an induction heating fixing device according to the tenth to twelfth embodiments of the present invention. Members common to the seventh to ninth embodiments are the same. The same reference numerals are given and the description thereof is omitted.

In the tenth to twelfth embodiments, as in the seventh to ninth embodiments, the nip width can be increased, but the belt 70 uses the drive roller 66,
Further, they are different in that they are attached to three small rollers of the driven rollers 67 and 68. By doing so, not only the same effects as in Embodiments 1 and 7 to 9 above can be obtained, but also the nip width can be easily increased / decreased, and the length of the fixing device in the horizontal direction in the drawing can be increased. Can be reduced.

[0045]

As described above, according to the present invention, the induction coil for generating the magnetic flux for causing the heating member to generate heat by the induction current is provided inside the pressure member arranged in pressure contact with the heating member. Since it is installed, it is possible to avoid the situation where the induction coil for magnetic flux generation is heated by heat radiation to the inner surface of the heating member, and the heat energy of the induction coil itself is absorbed by the pressurizing member and the temperature of the induction coil rises. Can be suppressed.

Therefore, the temperature rise of the induction coil can be prevented without separately providing a cooling mechanism, and since it is not necessary to use a resin or the like having an excellent heat resistance at a higher temperature than necessary, the apparatus can be downsized. The cost can be reduced.

Moreover, since the pressure roller is simultaneously heated by the absorption of heat energy by the heat generation of the induction coil into the pressure roller, good fixing performance can be obtained.
Good fixing performance can be maintained even when the set temperature of the heating member is lowered.

If the pressing member is a belt made of a non-magnetic material and having elasticity, the length of the pressing contact portion between the heating member and the pressing member in the sheet conveying direction can be increased, so that the heating member is set. Since the temperature can be further lowered, the temperature rising time can be shortened, wasteful heat dissipation can be reduced, and the temperature rise in the surrounding area can be further suppressed. Moreover, since the pressure contact force can also be reduced, the driving torque for the belt or the like can be small, and the load on the driving source can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an induction heating fixing device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating magnetic flux generated by an induction coil of the induction heating fixing device according to the first embodiment.

FIG. 3 is a diagram illustrating a heating principle of the induction heating fixing device according to the first embodiment.

FIG. 4 is a graph showing changes in the temperature of the metal sleeve.

FIG. 5 is a graph showing a transition of pressure roller temperature.

FIG. 6 is a graph showing the relationship between the number of copies and fixing strength.

FIG. 7 is a graph showing a relationship between a metal sleeve set temperature and a fixing strength.

FIG. 8 is a cross-sectional view showing an induction heating fixing device according to a second embodiment.

FIG. 9 is a sectional view showing an induction heating fixing device according to a third embodiment.

FIG. 10 is a cross-sectional view showing an induction heating fixing device according to a fourth embodiment.

FIG. 11 is a cross-sectional view showing an induction heating fixing device according to a fifth embodiment.

FIG. 12 is a cross-sectional view showing an induction heating fixing device according to a sixth embodiment.

FIG. 13 is a cross-sectional view showing an induction heating fixing device according to a seventh embodiment.

FIG. 14 is a cross-sectional view showing an induction heating fixing device according to an eighth embodiment.

FIG. 15 is a cross-sectional view showing an induction heating fixing device according to a ninth embodiment.

FIG. 16 is a sectional view showing an induction heating fixing device according to a tenth embodiment.

FIG. 17 is a sectional view showing an induction heating fixing device according to an eleventh embodiment.

FIG. 18 is a sectional view showing an induction heating fixing device according to a twelfth embodiment.

[Explanation of symbols]

 10 ... Metal sleeve (heating member) 13 ... Pressing roller (pressing member) 16 ... Pressing holder 17, 70 ... Coil assembly 18 ... Holder unit 19 ... Holder 22 ... Induction coil 23, 73 ... Core 30 ... Spare Heating member 50, 80 ... Fixing roller (heating member) 53 ... Pressing member 60, 65, 70 ... Belt (pressing member)

Claims (5)

[Claims] 1. A heating member that generates heat by an induced current, a pressure member that is arranged in pressure contact with the heating member, and an induction member that is internally provided in the pressure member and that generates a magnetic flux that is supplied to the heating member. An induction heating fixing device having a coil. 2. The induction heating fixing device according to claim 1, wherein the heating member is made of a thin cylindrical magnetic body. 3. The induction heating fixing device according to claim 1, wherein the pressing member is made of a non-magnetic material. 4. The induction heating fixing device according to claim 1, wherein the pressurizing member is a belt made of a non-magnetic material and having elasticity. 5. The induction heating fixing device according to claim 1, wherein an inner surface of the pressing member is formed of a heat absorbing member having a heat absorption coefficient of a predetermined value or more.