JPH11288190A - Image heating device, heating roller and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease wearing of a heating layer and operation resistance by separately arranging an exciting member on the outside of a heating roller and rotating the heating layer integrally with a support layer. SOLUTION: An endless belt 21 functioning as the heating layer is formed like a belt by electroforming Ni, and the surface 22 thereof is coated with PTFE in order to improve releasing property. An elastic roller 23 functioning as a low heat conduction layer is integrally molded on a rotary shaft 24 constituted of metal such as aluminum, and constituted of a silicone heat resistant rubber foamed body and has elasticity. The support layer supporting the belt 21 is constituted of the roller 23 and the shaft 24. The shaft 24, the roller 23 and the belt 21 are integrally driven to be rotated in a direction shown by an arrow A with the rotary shaft as center by a driving means. An exciting coil 25 functioning as the exciting member is wound round to core material 26 constituted of ferrite and the core material 26 is fixed and supported in the main body at the end in a depth direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image heating apparatus for heating by generating eddy current by utilizing electromagnetic induction, and more particularly to an unfixed image used for an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus. TECHNICAL FIELD The present invention relates to an image heating device suitable for a fixing device for fixing an image, a heating roller applied to the image heating device, and an image forming apparatus using the image heating device.

[0002]

2. Description of the Related Art As an image heating device represented by a heat fixing device, a contact heating system such as a heat roller system and a film heating system has been generally used.

In recent years, several proposals have been made to utilize electromagnetic induction heating in a film heating method having a small heat capacity for the purpose of shortening a warm-up time.

[0004] Japanese Patent Application Laid-Open No. 7-114276 is an example, and FIG. 8 shows the structure. An exciting coil 53 wound around an iron core 52 is installed inside an endless rotating film 51 so that an alternating magnetic field penetrates the film 51. Then, the toner image 56 on the recording material 55 passing between the pressure roller 54 and the toner image 56 is fixed by heat generated by the eddy current generated in the film 51. The film 51 has a three-layer structure, and the central layer 57 is a conductive layer, and an eddy current is generated in this portion to generate heat. The inner layer 58 is a layer having low thermal conductivity, which makes it difficult for generated heat to be transmitted to components such as an internal excitation coil, and at the same time, slides between fixed components installed inside. The outer layer 59 is a resin layer for improving the releasability from the toner.

[0005]

In general, when heat is generated using an excitation coil, the heat generation becomes unstable if the temperature of the excitation coil or the iron core itself rises excessively.

Therefore, in Japanese Patent Application Laid-Open No. Hei 7-114276, a low thermal conductive layer is formed on the inner surface of the film in order to prevent the temperature of the exciting coil and the iron core from rising.

However, since the film must be rotated while being deformed, the low thermal conductive layer cannot be made too thick, and the recording material or the pressure roller is pressed from the inside by an iron core or the like through the film. Therefore, they have to be in close contact with each other, and there is room for further improvement in the heat insulating effect in this conventional configuration.

Further, in the configuration of the above-mentioned conventional example, the components such as the film and the inner iron core always slide while being pressed against each other during operation, so that abrasion and operational resistance pose a problem. This is a major problem, especially when operating at high speeds.

Therefore, in the above-mentioned prior art, grease or oil is applied to the sliding portion of the inner surface of the film, but it is difficult to maintain the effect of these in long-time operation at a high temperature.

Further, in a general film heating method,
Since it is necessary to fix the components such as the internal heating element and rotate the film while sliding it around, there is a problem that the film is likely to meander.

[0011]

According to a first aspect of the present invention, there is provided an image heating apparatus comprising: a heating layer having conductivity; and a heating layer provided inside the heating layer to support the heating layer. A heating roller having a solid support layer, wherein the two layers are integrally rotated, and an excitation member that is disposed separately from the outside of the heating roller and generates an eddy current in the heating layer by applying an alternating magnetic field. It is characterized by having.

According to the first aspect of the present invention, the exciting member is disposed separately from the outside of the heating roller, and the heat generating layer rotates integrally with the support layer. Therefore, wear of the heat generating layer and reduction of operating resistance are reduced. It is planned. It should be noted that, by disposing the excitation member separately from the outside of the heating roller, it is possible to prevent the temperature of the excitation member from excessively rising. Further, the meandering of the heat generating layer is prevented beforehand by rotating the heat generating layer integrally with the support layer.

Further, according to the image heating apparatus of the second aspect,
Since the excitation coil is disposed inside the pressure member, the pressure member has a heat insulating effect, which can prevent an excessive rise in temperature of the excitation coil, and the excitation coil is disposed at a pressure contact portion between the heating roller and the pressure member. Since an alternating magnetic field is applied, the image can be efficiently heated.

Further, according to the image heating apparatus of the third aspect,
The pressing member has heat resistance, so that excessive heating of the exciting coil can be further prevented.In addition, since the pressing member is a non-conductive non-magnetic material, a magnetic field directed to the heating roller of the exciting member disposed inside is used. Does not prevent the occurrence of

Further, according to the image heating apparatus of claim 5,
Since the support layer has a low thermal conductivity layer, the heat generated in the heat generating layer is hard to conduct inside, so that the heat amount of the heat generating layer can be further increased and the heating efficiency of the image is further improved. Also, the temperature of the rotating shaft is prevented from being excessively increased.
In the case where the low thermal conductive layer is formed as a foamed elastic body formed of a material having low thermal conductivity as in claim 6, the low thermal conductivity of the material itself and the space inside the foam are reduced. The amount of heat of the heat generating layer can be further increased by the synergistic effect with the low thermal conductivity shown.

On the other hand, an image heating apparatus according to a seventh aspect of the present invention has a magnetically permeable layer having a magnetic permeability and a Curie temperature of approximately the fixing temperature, and a conductive layer provided inside the magnetically permeable layer and having conductivity. A heating roller that includes a solid support layer provided on the inner side of the conductive layer, and the three layers are integrally rotated, and are disposed separately from the outside of the heating roller;
An exciting member for generating an eddy current in the heating roller by applying an alternating magnetic field.

According to a seventh aspect, the first aspect is provided.
In addition to the action of the above, the following action is exerted.

That is, when the heating temperature of the magnetically permeable layer is lower than the Curie temperature, an eddy current is generated in the magnetically permeable layer, so that the magnetically permeable layer generates heat. When the heating temperature of the magnetically permeable layer is equal to or higher than the Curie temperature, the magnetism of the magnetically permeable layer is reduced and an eddy current is generated between the magnetically permeable layer and the conductive layer. Become smaller.

That is, according to the seventh aspect, the heating amount is automatically controlled according to the heating roller temperature.

On the other hand, the heating roller according to the present invention has a heat generating layer which is conductive and generates heat by generating an eddy current by electromagnetic induction from the outside, and is provided inside the heat generating layer to support the heat generating layer. A solid support layer.

The heating roller according to the present invention has a magnetic permeability layer whose Curie temperature is approximately a fixing temperature, and a conductive roller provided inside the magnetic permeability layer and having conductivity. And a solid support layer provided inside the conductive layer.

[0022]

FIG. 3 is a sectional view of an image forming apparatus using an image heating device according to an embodiment of the present invention as a fixing device.

Reference numeral 1 denotes an electrophotographic photosensitive member (hereinafter, photosensitive drum). The surface of the photosensitive drum 1 is uniformly charged to a predetermined negative dark potential V0 by the charger 2 while being rotationally driven at a predetermined peripheral speed in the direction of the arrow.

Reference numeral 3 denotes a laser beam scanner which outputs a laser beam modulated in accordance with a time-series electric digital pixel signal of image information input from an image reading device (not shown) or a host device such as a computer. The surface of the photosensitive drum 1, which is uniformly charged as described above, is scanned and exposed by this laser beam, and the exposed portion has a small absolute value of potential and becomes a bright potential VL, and an electrostatic latent image is formed on the surface of the photosensitive drum 1. It is formed.

Next, the latent image is reversely developed with a negatively charged powder toner by a developing device 4 to be visualized.

The developing device 4 has a developing roller 4a which is driven to rotate.
And a thin layer of toner having a negative charge is formed on the outer peripheral surface of the roller and faces the surface of the photosensitive drum 1. The absolute value of the developing roller 4a is
Is applied, the toner on the developing roller 4a transfers to only the portion of the photosensitive drum 1 where the light potential VL is applied, and the latent image is visualized. Is done.

On the other hand, a recording material 15 is fed one by one from a paper supply unit 10 and passes through registration roller pairs 11 and 12 to a nip portion between the photosensitive drum 1 and a transfer roller 13 abutted against the photosensitive drum 1. Sent at an appropriate timing synchronized with the rotation of the body drum 1. Transfer roller 1 to which transfer bias is applied
By the operation of 3, the toner image on the photosensitive drum 1 is sequentially transferred to the recording material 15. The recording material 15 that has passed through the transfer section is separated from the photosensitive drum 1 and introduced into a fixing device 16, where the transfer toner image is fixed. The recording material 15 on which the image has been fixed and fixed is output to the paper discharge tray 17.

After the separation of the recording material, the surface of the photosensitive drum 1 is cleaned by the cleaning device 5 to remove the residual toner such as toner remaining after transfer, and is repeatedly used for the next image formation.

Next, an image heating apparatus according to an embodiment of the present invention will be described in detail. FIG. 1 is a sectional view of a fixing device as an image heating device according to a first embodiment of the present invention.

Reference numeral 21 denotes an endless belt as a heat-generating layer having a thickness of 100 μm, which is formed in a belt shape by electroforming Ni.
FE is coated. The material of the belt 21 is Fe,
Any conductive metal such as Co, Cu, and Cr may be formed alone or in combination. When a material having a high magnetic permeability is used, the magnetic flux concentrates on the belt 21 and the amount of heat generated increases. The surface coating material may be coated with a resin or rubber having good releasability, such as PFA, FEP, or silicone, alone or as a mixture.

Reference numeral 23 denotes an elastic roller as a low heat conductive layer formed of a heat-resistant rubber foam of silicone, which is integrally formed with a rotating shaft 24 formed of a metal such as aluminum. Have. The elastic roller 23 may be made of another heat-resistant resin or rubber such as melamine.

Incidentally, a support layer for supporting the belt 21 is constituted by the elastic roller 23 and the rotating shaft 24.

The belt 21 is adhered so as to cover the surface of the elastic roller 23. Elastic roller 23
Since the belt 21 has elasticity, the belt 21 may be fixed by fitting without bonding. The rotating shaft 24, the elastic roller 23, and the belt 21 are integrally and rotationally driven around the rotating shaft 24 in the direction of arrow A by a driving unit (not shown).

Numeral 25 denotes an exciting coil as an exciting member, which is wound around a core material 26 made of ferrite.
The core member 26 is fixedly supported by the image forming apparatus main body at an end portion in the depth direction of the paper. The core 26 may be made of a material having a high magnetic permeability such as iron or permalloy. An alternating current of 30 kHz is applied to the exciting coil 25 from an exciting circuit (not shown).
The magnetic flux indicated by repeats generation and extinction. Magnetic flux H is belt 2
1, the core material 26 is configured to have a cross-sectional shape of E in this embodiment. The higher the magnetic permeability of the belt 21, the higher the ratio of the magnetic flux H passing through the inside of the belt.

FIG. 2 is a perspective view of the structure of the core member 26 and the exciting coil 25, and a magnetic flux is generated as shown by an arrow.

The generation and extinction of the magnetic flux H generate an induced current in the belt 21 and the Joule heat heats the belt. The thickness of the belt 21 can be 10 to 500 μm. At this time, if the thickness of the belt 21 is too small, the electric resistance becomes too large and the energy efficiency is deteriorated. On the other hand, if the thickness is too large, the rigidity becomes too strong, and as shown in FIG. 1, deformation due to pressure contact with a pressure roller described later becomes difficult, and a large nip cannot be formed.

Referring again to FIG. 1, reference numeral 27 denotes a pressing roller as a pressing member, which is a thin-walled cylinder made of a heat-resistant member such as phenol or fluororesin.
The image forming apparatus 1 is rotatably supported by the image forming apparatus main body so as to be able to rotate at a position pressed against the belt 21 so as to deform the image forming apparatus 1 by a predetermined amount. Thus, the belt 21 rotates while forming a nip 29 with the belt 21.

The material of the pressure roller 27 is a non-magnetic material, and may be made of another heat-resistant resin such as epoxy or glass as long as it has high electric resistance. If the electric resistance is too low, the rate of generation of the induced current in this portion increases, and it becomes difficult for the magnetic field to reach the belt 21. On the other hand, heat generation may be appropriately distributed to both the belt 21 and the pressure roller 27 by using a metal whose thickness is made thinner using iron or the like having a relatively smaller conductivity than aluminum or the like. Pressing roller 2
PFA, PTF on the surface of No. 7 to enhance the release property
A resin or rubber such as E, FEP, or silicone may be coated alone or as a mixture.

Reference numeral 30 denotes a thermistor which detects the temperature of the surface of the belt 21 after passing through the nip portion 29 and controls the current flowing through the exciting coil 25 in accordance with the output of the belt 21 to maintain an appropriate fixing temperature.

The recording material 15 on which the toner image has been transferred by the image forming apparatus shown in FIG. 3 is applied to the fixing device having the above-described configuration, with the surface with the toner 28 facing upward as shown in FIG. And the toner on the recording material 15 was fixed.

According to the above-described embodiment, since the belt 21 has a very small heat capacity as compared with the conventional heat roller system, it can be quickly warmed, and the warm-up time required to reach the fixing temperature can be extremely short. . Also, since the belt itself for fixing the toner image directly generates heat, the heat efficiency is good.

The exciting coil 25 is connected to the pressing roller 2.
7, the heat is mainly generated in the belt 21, so that the temperature rise of the exciting coil 25 and the core material 26 is small and the heat generation operation is not unstable.

On the other hand, the elastic roller 23 inside the belt 21
Is made of a foam having a low thermal conductivity of the material itself.
The heat generated is very difficult to escape and more efficient.

Furthermore, since these components are integrally rotated as a whole, there are few sliding portions due to the rotation and few wear portions, so that they can withstand long-time high-speed rotation. Further, since the belt 21 rotates integrally with the rotating shaft 24 together with the elastic roller 23, the belt 21 does not meander, and stable rotation can be obtained even at high speed.

Further, in the nip portion 29, the belt 21
Is deformed along the outer peripheral surface of the pressure roller 27, and when the recording material comes out through the nip portion, the recording material is pushed out in a direction away from the belt 21 so that the releasability is reduced. Very good.

Next, a fixing device as an image heating device according to a second embodiment will be described with reference to FIG. In the second embodiment, the description of the portions having the same configuration and the same role as those of the fixing device of the first embodiment will be omitted. In this embodiment, the configuration of the elastic roller, the pressure roller and the like is the same as that of the first embodiment.

In this embodiment, the belt 31 has a thickness of 50 μm by plating on the surface of a first layer (conductive layer) 32 as a 200 μm-thick substrate having high electrical conductivity such as phosphor bronze. A second layer (magnetically permeable layer) 33 made of Ni or the like having a high magnetic permeability is formed by plating. The first layer 32 can be similarly used as long as it is another material having high electric conductivity such as Cu. The second layer may be any other metal having a high magnetic permeability, such as iron or Co. Further, a layer may be formed by vapor deposition, sputtering or the like instead of plating. Other configurations are the same as those of the first embodiment.

In this embodiment, when the Curie temperature of the second layer is close to the temperature required for fixing, for example, 220 ° C., the partial self-temperature control becomes possible. That is, in a state where the second layer has not yet been heated to the Curie temperature or lower, eddy current is almost generated on the surface of the second layer due to the magnetism of the second layer, and large heat is generated by Joule heat. When the second layer exceeds the Curie point, its magnetism decreases, so that the flow of the magnetic field spreads inside and the generated eddy current reaches the first layer. Therefore, if the first layer is made of a material having a high electric conductivity and a large thickness, the electric resistance can be made smaller than that of the second layer, so that the heat generation is reduced. The magnitude of the electric resistance of the first layer can be freely set depending on the material and the thickness. The surface of the second layer is made of PTFE,
As in the first embodiment, a resin or rubber having good releasability, such as PFA, FEP, or silicone, may be coated alone or as a mixture.

As described above, in the second embodiment, the belt having a two-layer structure of the first layer having a small electric resistance and the second layer having a high magnetic permeability and a predetermined Curie temperature substantially corresponding to the fixing temperature is used. By using, it is possible to prevent a partial excessive temperature rise of the belt. Therefore, even if a recording material having a width considerably smaller than the width of the belt is continuously passed, it is possible to prevent a portion of the belt width through which the recording material does not pass from abnormally rising in temperature.

In the above-described second embodiment, the belt is constituted by a two-layer integral belt. However, even if two independent belts having the same properties as those described above are stacked, at least at the nip portion, the pressure is increased. , The same effect as above can be obtained.

Next, a fixing device as an image heating device according to a third embodiment will be described with reference to FIG. Here, the description of the same components as before is omitted.

In this embodiment, the configuration of the belt, elastic roller, pressure roller and the like is the same as in the first embodiment. The cross section of the exciting coil 41 and the core material 42 is as shown in FIG.
As shown in the figure, the magnetic flux H is generated in the axial direction. Since the belt is made of a material having high magnetic permeability, the amount of magnetic flux passing through the belt increases.

Further, a structure in which the end of the core material 42 is located in the vicinity of the belt, for example, only the end of the core material may have a fan shape. This reduces the gap between the core material and the belt, so that the magnetic flux diverging from the core material to parts other than the belt can be reduced, and more magnetic flux can be concentrated on the belt. Furthermore, the coil is divided into a plurality in the axial direction,
The temperature distribution in the axial direction may be controlled by controlling each of them independently.

In the first to third embodiments, the configuration in which the excitation coil is disposed inside the pressure roller is adopted. However, the present invention is not limited to this, and the configuration in which the excitation coil is disposed outside the pressure roller may be employed. good.

Specifically, a fixing device as an image heating device of the fourth embodiment will be described with reference to FIG. Here, the description of the same components as before is omitted.

In this embodiment, the structure of the belt, the elastic roller and the like are the same as in the first embodiment. The excitation coil 43 and the core member 44 are installed near the surface of the belt 21 and upstream of the nip 29 formed by the belt 21 and a pressure roller described later in the rotational direction.

In this embodiment, the pressure roller 45 is made of silicone rubber molded integrally with the metal shaft 46.
As shown in FIG. 1, the belt 21 can be rotated at that position while being pressed against the belt 21 so as to deform the belt 21 by a fixed amount.
It is rotatably supported by the image forming apparatus main body. Accordingly, the belt rotates while forming a nip portion 29 with the belt 21.

The material of the pressure roller 45 may be made of another heat-resistant resin such as fluorine rubber or fluorine resin, rubber or metal such as aluminum. Pressing roller 45
The surface of PFA, in order to increase the wear resistance and release properties,
A resin such as PTFE and FEP or a rubber may be coated alone or in a mixture.

In this embodiment, since the exciting coil 43 and the core member 44 can be brought close to the surface of the belt 21 at the minimum interval, the magnetic flux concentrates on the belt more efficiently. Also, the presence of the pressure roller 45
Since there is almost no effect on the magnetic flux generated by the belt, even if a metal or the like is used as the material of the pressure roller, there is no problem in heat generation of the belt.

In the first to fourth embodiments, an exciting coil having a coil structure is used as the exciting member. However, the present invention is not limited to this, and any mode may be used as long as an alternating magnetic field is generated. Further, a cylindrical rotatable pressure roller is used as the pressure member, but the invention is not limited to this. For example, a fixed pressure guide may be applied. in this case,
The belt, the elastic roller, the coil, and the like have the same configuration as that of the embodiment, and a nip can be formed between a fixed thin glass plate or the like and the belt, and the recording material can be fixed during this time. Thus, application to a low-speed image forming apparatus can be achieved.

Further, in the above embodiment, the support layer is constituted by the rotating shaft and the low heat conductive layer. However, other layers may be provided as appropriate depending on the fixing characteristics and the like. A non-foamed body can also be applied.

[0062]

As described above, according to the present invention, since the exciting member is spaced apart from the heating roller and the heat generating layer rotates integrally with the support layer, the wear of the heat generating layer and the reduction of the operating resistance are reduced. Is achieved. It should be noted that, by disposing the excitation member separately from the outside of the heating roller, it is possible to prevent the temperature of the excitation member from excessively rising. Further, the meandering of the heat generating layer is prevented beforehand by rotating the heat generating layer integrally with the support layer.

Further, in the present invention, the heating roller has a magnetic permeability and a Curie temperature of which is substantially equal to the fixing temperature, and a conductive layer provided inside the magnetic permeability layer and having conductivity. Since the layer and the solid support layer provided inside the conductive layer are provided, the heating amount is automatically controlled according to the temperature of the heating roller. As a result, even when a recording material having a small width is continuously passed, partial excessive temperature rise does not occur.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image heating apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view of an excitation coil and a core material used in the image heating apparatus according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of the image forming apparatus according to the embodiment of the present invention.

FIG. 4 is a sectional view of an image heating apparatus according to a second embodiment of the present invention.

FIG. 5 is a sectional view of an image heating apparatus according to a third embodiment of the present invention.

FIG. 6 is a perspective view of an excitation coil and a core material used in an image heating apparatus according to a third embodiment of the present invention.

FIG. 7 is a sectional view of an image heating apparatus according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of a conventional image heating apparatus.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 16 fixing device 21 belt 23 elastic roller 25 excitation coil 26 core material 27 pressure roller

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Nobuo Motoji 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (22)

[Claims] 1. A heating roller comprising: a heat generating layer having conductivity; and a solid support layer provided inside the heat generating layer and supporting the heat generating layer, wherein the two layers rotate integrally. An image heating apparatus, comprising: an excitation member that is disposed outside the heating roller and is spaced apart from the heating roller to generate an eddy current in the heating layer by applying an alternating magnetic field. 2. An exciter coil disposed in a pressurizing member that presses against the heating roller, wherein the exciter coil applies an alternating magnetic field to a press contact portion between the heating roller and the pressurizing member. 2. The image heating apparatus according to claim 1, wherein the recording material is heated by passing the recording material through the recording medium. 3. An image heating apparatus according to claim 2, wherein said pressure member is made of a non-magnetic material having heat resistance and low conductivity. 4. An image heating apparatus according to claim 3, wherein said pressure member is a pressure roller having a roller shape. 5. The image heating apparatus according to claim 1, wherein said support layer has a rotating shaft and a low thermal conductive layer provided outside said rotating shaft and having low thermal conductivity. 6. An image heating apparatus according to claim 5, wherein said low thermal conductive layer is a foamed elastic body formed of a material having low thermal conductivity. 7. A magnetically permeable layer having a magnetic permeability and a Curie temperature of about a fixing temperature, a conductive layer provided inside the magnetically permeable layer and having conductivity, and A heating roller provided with a solid support layer provided on the inside thereof, wherein the three layers are integrally rotated, and are arranged separately from the outside of the heating roller, and an eddy current is applied to the heating roller by applying an alternating magnetic field. An image heating device comprising: an exciting member for generating the image. 8. An eddy current is generated in the magnetically permeable layer when the temperature of the magnetically permeable layer is lower than the Curie temperature, and an eddy current is generated in the magnetically permeable layer and the conductive layer when the temperature of the magnetically permeable layer is higher than the Curie temperature. The image heating apparatus according to claim 7, wherein the apparatus generates an electric current. 9. The excitation coil is disposed inside a pressure member that is in pressure contact with the heating roller, and is an excitation coil that applies an alternating magnetic field to a pressure contact portion between the heating roller and the pressure member. 7. The image heating apparatus according to claim 6, wherein an image on the recording material is heated by passing the recording material through the recording medium. 10. An image heating apparatus according to claim 9, wherein said pressure member is made of a nonmagnetic material having heat resistance and low conductivity. 11. An image heating apparatus according to claim 10, wherein said pressure member is a pressure roller having a roller shape. 12. The image heating apparatus according to claim 7, wherein said support layer has a rotating shaft and a low heat conductive layer having low thermal conductivity provided outside said rotating shaft. 13. An image heating apparatus according to claim 12, wherein said low thermal conductive layer is a foamed elastic body formed of a material having low thermal conductivity. 14. A heat generating layer having conductivity and generating heat by generating an eddy current by electromagnetic induction from the outside, and a solid support layer provided inside the heat generating layer and supporting the heat generating layer. A heating roller, comprising: 15. The heating roller according to claim 14, wherein the support layer has a rotating shaft and a low heat conductive layer provided on the outside of the rotating shaft and having low thermal conductivity. 16. The heating roller according to claim 15, wherein said low thermal conductive layer is a foamed elastic body formed of a material having low thermal conductivity. 17. The support layer has a rotating shaft and a foamed elastic body formed of a material having low thermal conductivity attached to the rotating shaft, and the heating layer is attached to the elastic body. 15. The heating roller according to claim 14, wherein the heating roller is constituted by an endless belt having conductivity. 18. A magnetically permeable layer having a magnetic permeability and a Curie temperature of about the fixing temperature, a conductive layer provided inside the magnetically permeable layer and having conductivity, A heating roller, further comprising a solid support layer provided inside. 19. The heating roller according to claim 17, wherein the support layer has a rotating shaft and a low thermal conductive layer provided outside the rotating shaft and having low thermal conductivity. 20. The heating roller according to claim 19, wherein said low thermal conductive layer is a foamed elastic body formed of a material having low thermal conductivity. 21. A heating roller, comprising: a rotating shaft; a foamed elastic member formed of a material having low thermal conductivity attached to the rotating shaft; and a conductive layer attached to the elastic member. 19. The heating roller according to claim 18, which is constituted by an endless belt having a layer. 22. An image forming apparatus comprising: an image forming means for forming and carrying an unfixed image on a recording material; and a heat fixing device for thermally fixing the unfixed image to the recording material, wherein the heat fixing device is provided. 14. An image forming apparatus, which is the image heating apparatus according to any one of 1 to 13.