JP5050657B2 - Non-conducting pan for induction heating and induction heating cooker using the same - Google Patents

Description

  The present invention relates to a non-conducting pan for induction heating such as a clay pot and an induction heating cooker using the same.

Conventionally, as this kind of non-conductive pan for induction heating, a heating layer made of a conductive material such as metal or carbon is provided on the bottom surface of the outer wall of the pan, and the heating layer is thicker than the surrounding area at the center position. It is known that a thick layer portion having a large thickness can be cooked with an IH cooker for 100 V and 200 V power supplies (see, for example, Patent Document 1).
JP 2005-334351 A

  However, in the above-mentioned conventional configuration, cooking can be performed with an IH cooker for 100 V and 200 V power supplies. There was a risk that the body would peel off.

  This invention solves the said conventional subject, and provides a non-conduction pan for induction heating in which a heating element does not peel from a pan even if heated at high temperature, and an induction heating cooker using the same. Objective.

In order to solve the above-described conventional problems, the non-conductive pan for induction heating according to the present invention is provided with a heat generating layer that is formed of a thin film having a thickness of 100 microns or less on the bottom surface of the outer wall and is induction-heated by a heating coil. A heating element having a thickness of 0.5 mm or more is provided on the bottom of the outer wall on the inner side and outer side of the layer, and the heating element is fixed by a silicon-based adhesive .

  As a result, there is a thin heat generating layer that is difficult to peel off even at high temperatures at the most temperature rising portion of the bottom surface of the outer wall of the non-conducting pan, and the heating element having a thickness larger than that of the heat generating layer is at the other portion, so the thickness increases. The adhesive of the heating element is not peeled off. In other words, by changing the specifications of the heat generating part of the non-conductive pan between the most heated part and the other parts, there is no peeling of the heat generating part even when the non-conductive pan becomes hot, and induction heating increases the heating power. Can be realized. In addition, by providing a heating element that is easily heated by induction other than at a high temperature, the heating power in induction heating can be increased, and high heating power can be obtained even in an induction heating cooker with a low power of 100 V voltage.

Moreover, the induction heating cooker of this invention is equipped with the apparatus main body which has an annular | circular shaped heating coil, and the non-conductive pan heated by the heating coil of this apparatus main body, and is a non-conductive pan facing a heating coil. provided the heat generation layer of the small width of the annular than circular width of the heating coil is formed by a thin film of a thickness of less than 100 microns on an outer wall bottom, the outer wall bottom surface of the non-conducting pan inside and outside of the heating layer Is provided with a heating element having a thickness of 0.5 mm or more, and the heating element is fixed by a silicon-based adhesive .

  As a result, the non-conductive pan can be heated by the heat generating layer in the portion where the temperature rises the most, and other than the heat generating layer portion where the temperature becomes high, it can be heated by a heating element that is easily induction-heated, and the heating power in induction heating is increased. be able to. Further, the heat generating layer is thin and difficult to peel off even at a high temperature, and since the heat generating element is thicker than the heat generating layer but is located at a portion other than the high temperature part, the heat generating element is not peeled off.

  The non-conducting pan for induction heating and the induction heating cooker using the same according to the present invention do not peel off the heat generating portion even when the non-conducting pan becomes high temperature, and can achieve high heating power by induction heating. .

According to a first aspect of the present invention, a heat generating layer that is formed of a thin film having a thickness of 100 microns or less and is heated by induction by an opposing heating coil is provided on the bottom surface of the outer wall so as to hardly peel off even at high temperatures. A heating element is formed on the bottom of the outer wall other than the portion where the temperature rises most on the inside and outside of the layer, and a stainless steel material is formed to a thickness of 0.5 mm or more and the temperature rises easily by induction heating. The heating layer transfers silver. The heating element is bonded and baked by printing, the heating element is fixed by a silicon-based adhesive , a space is provided between the heating layer and the heating element, and the heat of the heating layer with the highest temperature rises to the heating element. The non-conducting pan for induction heating is configured to prevent the silicon adhesive having a low heat-resistant temperature from deteriorating due to high heat and peeling off the heating element . As a result, there is a thin heat generating layer that is difficult to peel off even at high temperatures at the most temperature rising portion of the bottom surface of the outer wall of the non-conducting pan, and the heating element having a thickness larger than that of the heat generating layer is at the other portion, so the thickness increases The adhesive of the heating element is not peeled off. In other words, by changing the specifications of the heat generating part of the non-conductive pan between the most heated part and the other parts, there is no peeling of the heat generating part even when the non-conductive pan becomes hot, and induction heating increases the heating power. Can be realized. Further, by providing the inductive heating is susceptible heating element other than the areas of high temperature, the induction heating power in the heating can be increased, also it is possible to obtain high heating power at a power of 100V voltage is lower induction heating cooker, the outer wall By providing a space between the bottom heating layer and the inner and outer heating elements, the heat of the heating layer where the temperature rises the most is prevented from being directly transferred to the heating element. worse by adhesive high fever which are fixed to, Ru can be prevented from peeling off from the non-conducting pot of the heating element.

2nd invention is equipped with the apparatus main body which has an annular | circular shaped heating coil, and the non-conducting pan of the earthenware pot container heated with the heating coil of this apparatus main body, it opposes a heating coil, and the part where temperature rises most The bottom surface of the outer wall of the non-conductive pan is provided with an annular heating layer formed of a thin film having a thickness of 100 microns or less so as not to be peeled off even at high temperatures, and having a width smaller than the annular width of the heating coil. the outer wall bottom surface of the non-conducting pan other than the portion to be the most temperature rise of the inside and outside of the heating element tends to increase in temperature provided by induction heating to form a stainless steel material to a thickness of at least 0.5 mm, wherein the heating layer Silver is pasted and fired by transfer printing, the heating element is fixed by a silicon-based adhesive , a space is provided between the heating layer and the heating element, and the heat of the heating layer with the highest temperature rises. Communicating to the heating element It is an induction heating cooker having a low allowable temperature limit the silicon adhesive the heating element deteriorated by high heat is to prevent peeling. As a result, the non-conductive pan can be heated by the heat generating layer in the portion where the temperature rises the most, and other than the heat generating layer portion where the temperature becomes high, it can be heated by a heating element that is easily induction-heated, and the heating power in induction heating is increased. be able to. Further, the heat generating layer is thin and difficult to peel off even at a high temperature, and since the heat generating element is thicker than the heat generating layer but is located at a portion other than the high temperature part, the heat generating element is not peeled off.

In a third aspect of the invention, in particular, in the second aspect of the invention, the annular heating coil has a plurality of winding configurations with a space between the conductors of the windings, and the heat generation layer of the non-conductive pan is opposed to the heating coil. The heat generating layer is divided into a plurality of heat generating layers by sequentially providing a heat generating element inside the inner heat generating layer, between the inner heat generating layer and the outer heat generating layer, and outside the outer heat generating layer. It is possible to reduce the concentration of the hot part of the non-conductive pan on the bottom of the outer wall of the non-conductive pan, and to reduce the stress concentration due to the difference in thermal expansion between the non-conductive pan and the heat generating part, thereby deforming the non-conductive pan. And damage can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIGS. 1-5 shows the non-conduction pan for induction heating in Embodiment 1 of this invention, and the induction heating cooking appliance using the same.

  As shown in FIG. 1, the apparatus main body 1 which comprises an induction heating cooking appliance has the top plate 2 made from heat-resistant tempered glass, and the upper case 3 which comprises the outline of a product. In the figure, the top plate 2 and the case 3 are rectangular, but there is no particular problem even if they are round or grooved. Further, an operation unit 4 having a liquid crystal display window on a lower surface from the top plate 2 is provided in front of the case 3.

  FIG. 2 shows the inside of the apparatus main body 1 with the upper case 3 removed, and has an annular heating coil 5. The heating coil 5 is attached to the coil base 6, and a sensor 7 is provided at the center of the heating coil 5. In general, the sensor 7 is provided at the center of the coil base 6, but is not limited to the center.

  Below the heating coil 5, an induction heating control unit 8 and a fan 9 for cooling the heating coil 5 and the induction heating control unit 8 are installed, and an operation control unit 10 is installed in front of the heating coil 5. The signal line 11 is connected to the induction heating control unit 8. A power supply control unit 12 is placed on the right rear side in the case 3. A detachable power cord 13 is connected to the power controller 12.

  As shown in FIGS. 3 and 4, the induction heating non-conductive pan 14 that is induction-heated by the heating coil 5 of the device body 1 is an earthenware pot or the like, and the outer wall bottom surface 15 has a circle of the heating coil 5. An annular heat generating layer 16 having a smaller width than the annular width is provided. The heat generating layer 16 is provided by affixing and baking silver onto the non-conductive pan 14 by transfer printing. The heat generating layer 16 is formed with a thickness of 100 microns or less.

  Further, heating elements 17 and 18 having a thickness larger than that of the heat generating layer 16 are fixedly provided by an adhesive 19 on the outer wall bottom surface 15 of the non-conductive pan 14 inside and outside the heat generating layer 16. The heating elements 17 and 18 have a thickness of 0.5 mm or more, and are made of a material that easily rises in temperature by induction heating, such as stainless steel or carbon.

  In addition, on the outer wall bottom surface 15 outside the heating element 18 of the non-conductive pan 14, three convex-shaped legs 20 are provided. For example, the leg 20 may have a circumferential shape.

  As shown in FIG. 5, when the non-conductive pan 14 is placed on the top plate 2 of the apparatus main body 1, the heat generating layer 16 of the non-conductive pan 14 has an annular width center of the heating coil 5. It is provided so as to face the upper part. In addition, since the annular width of the heat generating layer 16 is smaller than the annular width of the heating coil 5, a part of the heating elements 17 and 18 is located above the heating coil 5. The heating element 17 is provided on the inner side of the heating layer 16 and has a disk shape. However, there is no problem even if the annular shape is formed by removing the central portion.

  Here, when the non-conductive pan 14 is placed on the top plate 2 of the apparatus body 1, only the legs 20 of the non-conductive pan 14 come into contact with the top plate 2, and the heat generating layer 16 and the heat generating members 17 and 18 are The top plate 2 is not touched, and a gap is provided therebetween.

  The operation and action of the non-conduction pan for induction heating and the induction heating cooker using the same will be described below.

  When the power cord 13 is connected to the apparatus main body 1 and the operation control unit 10 is instructed to start the induction heating operation, a signal is transmitted through the signal line 11, and the induction heating control unit 8 sends an induction current to the heating coil 5. Shed. Thereby, a magnetic field is generated, and the heat generating layer 16 and the heat generating elements 17 and 18 provided in the non-conductive pan 14 are induction-heated.

  At this time, the annular heating coil 5 has the highest magnetic flux density above the center of the winding width and the highest temperature at the metal portion above it, but the non-conductivity placed on the top plate 2. In the pan 14, the heat generating layer 16 made of a thin film receives a magnetic flux stronger than the heat generating elements 17 and 18 and becomes high temperature. However, if moisture is contained in the non-conducting pan 14, heat is taken away by the boiling of the moisture, so the temperature rise of the heat generating layer 16 is not relatively high, and is 300 ° C. or less in the experiment.

  However, when the moisture is not evaporated and it is baked or when high power is output at a voltage of 200 V, the central portion of the winding width of the heating coil 5 becomes high temperature, and the heating layer 16 of the non-conductive pan 14 is heated. The temperature becomes 300 ° C or higher. However, since the heat generating layer 16 is formed of a thin film, there is little elongation due to thermal expansion, and since it is bonded to the non-conductive pan 14 with high strength, it does not peel off even at high temperatures.

  On the other hand, the heating elements 17 and 18 are bonded to the non-conductive pan 14 with an adhesive 19, and when the adhesive 19 is made of a very hard material such as cement, the heating elements 17 and 18 are heated. When the non-conductive pan 14 is thermally expanded, the non-conductive pan 14 is subjected to a tensile stress that is longer than the length of the non-conductive pan itself, and the non-conductive pan itself is damaged. Soft material is used.

  In the case of a silicon-based adhesive, the stress due to thermal expansion is relaxed by the adhesive 19, so that it does not peel off from the non-conductive pan 14, but the heat-resistant temperature is not so high, and the adhesive 19 is It will deteriorate. However, although the heating elements 17 and 18 are thicker than the heating layer 16 and are easily induction-heated, the heating elements 17 and 18 are located at a portion other than the high temperature portion, so that the phenomenon of exfoliation of the heating elements can be prevented.

  In addition, since the efficiency of induction heating of the heat generating layer 16 and the heat generating elements 17 and 18 is different, the thermal power changes when the non-conductive pan 14 is placed out of a predetermined position of the device main body 1, so that non-conductive It is possible to detect the shift of the sex pan. As a result, it can be detected that the heating layer 16 does not face the center of the winding width of the heating coil 5, and the temperature rises when the heating elements 17 and 18 face each other. By suppressing the heating power from the beginning, failure of the non-conductive pan 14 and the device main body 1 can be prevented.

  Thus, the non-conductive pan for induction heating in the present embodiment is provided with the heat generating layer 16 that is induction-heated by the heating coil 5 on the outer wall bottom surface 15, and the outer wall bottom surface 15 on the inside and outside of the heat generating layer 16. Is provided with the heating elements 17 and 18 having a thickness larger than that of the heat generating layer 16, so that the thin heat generating layer 16 which is difficult to peel off even at a high temperature is present at the most temperature rising portion of the bottom surface 15 of the outer wall of the non-conductive pan 14, Since the heating elements 17 and 18 having a thickness larger than that of the layer 16 are present in the other portions, the adhesion of the heating elements 17 and 18 having a larger thickness is not peeled off. That is, by changing the specifications of the heat generating part of the non-conductive pan 14 between the most heated part and the other parts, there is no peeling of the heat generating part even when the non-conductive pan 14 becomes hot, and induction heating High thermal power can be realized. Moreover, by providing the heating elements 17 and 18 that are easily induction-heated in addition to the high temperature portion, the heating power in induction heating can be increased, and high heating power can be obtained even in an induction heating cooker with a low power of 100V voltage. it can.

  Moreover, the induction heating cooker in this Embodiment is provided with the apparatus main body 1 which has the annular | circular shaped heating coil 5, and the non-conduction pan 14 heated by the heating coil 5 of this apparatus main body 1, The heating coil 5 An annular heat generating layer 16 having a width smaller than the annular width of the heating coil 5 is provided on the bottom 15 of the outer wall of the non-conductive pan 14 facing the non-conductive pan 14. 14 is provided with heating elements 17 and 18 having a thickness greater than that of the heat generating layer 16, so that the non-conductive pan 14 is heated by the heat generating layer 16 in the portion where the temperature rises the most, and the temperature is increased. Except for the heat generating layer portion, it can be heated by the heating elements 17 and 18 that are easily induction-heated, and the heating power by induction heating can be increased. Further, the heat generating layer 16 is thin and difficult to peel off even at a high temperature, and the heat generating members 17 and 18 are thicker than the heat generating layer 16 but are located at portions other than the high temperature portion, so that the heat generating member is not peeled off.

(Embodiment 2)
6 to 8 show a non-conduction pan for induction heating and an induction heating cooker using the same in Embodiment 2 of the present invention. Since the configuration of the device main body 1 is the same as that of the first embodiment, the description thereof is omitted.

  As shown in the figure, the outer wall bottom surface 22 facing the heating coil 5 of the non-conductive pan 21 heated by the heating coil 5 of the device body 1 has an annular shape with a width smaller than the annular width of the heating coil 5. The heat generating layer 25 is provided on the outer wall bottom surface 22 of the non-conductive pan 21 inside and outside the heat generating layer 25, and the heat generating layer 25 is provided with a ring-shaped space 28 and 29, respectively, so that the thickness is larger than that of the heat generating layer 25. The heating elements 26 and 27 are provided. A leg 23 is provided on the bottom 22 of the outer wall of the non-conductive pan 21.

  Here, the heat generating layer 25 and the heat generating elements 26 and 27 are the same as the heat generating layer 16 and the heat generating elements 17 and 18 in the first embodiment, and a description thereof will be omitted.

  Further, as shown in FIG. 8, the non-conductive pan 21 is placed on the top plate 2 of the device main body 1 and used. Is omitted.

  Thus, in this Embodiment, since the space | intervals 28 and 29 were provided between the heat generating layer 25 of the non-conduction pan 21, and the inner side and the outer heat generating bodies 26 and 27, temperature is the most. The heat of the heating layer 25 that rises is prevented from being directly transmitted to the heating elements 26, 27, and the adhesive that fixes the heating elements 26, 27 to the non-conductive pan 21 is deteriorated by high heat, and the heating elements 26, 27 The peeling from the non-conductive pan 21 can be prevented.

(Embodiment 3)
9 and 10 show a non-conduction pan for induction heating and an induction heating cooker using the same in Embodiment 3 of the present invention. Since the configuration of the device main body 1 is the same as that of the first embodiment, the description thereof is omitted.

  As shown in the figure, an outer wall bottom surface 32 facing the heating coil 5 of the non-conductive pan 31 heated by the heating coil 5 of the device body 1 has an annular shape smaller than the annular width of the heating coil 5. The heat generating layer 36 is provided, and heat generating members 34 and 35 having a thickness larger than that of the heat generating layer 25 are provided on the inner wall bottom surface 32 of the non-conductive pan 31 inside and outside the heat generating layer 36.

  And the outer wall bottom face 32 part of the non-conduction pan 31 in which the annular heat generating layer 36 is provided protrudes into the convex shape 33 below the other parts, and the surface of the heat generating layer 36 and the heat generating layer 36 The surfaces of the inner and outer heating elements 34 and 35 are coplanar.

  Here, the heat generating layer 36 and the heat generating elements 34 and 35 are the same as the heat generating layer 16 and the heat generating elements 17 and 18 in the first embodiment, and a description thereof will be omitted.

  Moreover, as shown in FIG. 10, although the non-conductive pan 31 is mounted and used on the top plate 2 of the apparatus main body 1, since the operation | movement and an effect | action are the same as Embodiment 1, it demonstrates. Is omitted.

  Thus, in the present embodiment, the outer wall bottom surface 32 portion of the non-conductive pan 31 provided with the annular heat generating layer 36 protrudes downward in an annular shape from the other portions, and the surface of the heat generating layer 36 and the heat generating layer By making the surfaces of the inner and outer heating elements 34, 35 of 36 the same plane, the thermal efficiency of induction heating from the heating coil 5 to the heating layer 36 and the heating elements 34, 35 can be increased. Moreover, the load of the induction heating control unit 8 for induction heating is reduced, and the durability of the control unit can be increased.

  Further, no matter where the position of the sensor 7 in the apparatus body 1 is set, the temperature of the outer wall bottom surface 32 of the non-conductive pan 31 can be accurately grasped, and the abnormal temperature rise of the non-conductive pan 31 is detected by the sensor 7. Is easy to detect and can ensure safety.

(Embodiment 4)
11 and 12 show a non-conduction pan for induction heating and an induction heating cooker using the same in Embodiment 4 of the present invention. In the configuration of the device main body 1, the same elements as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in the figure, the annular heating coil is provided with a space 44 between the conductors of the windings to form a double winding configuration of the inner and outer heating coils 42 and 43, and the heat generation of the outer wall bottom surface 51 of the non-conductive pan 50. The layers 52 and 53 are opposed to the inner and outer heating coils 42 and 43 to form a double annular shape, inside the inner heating layer 52, between the inner heating layer 52 and the outer heating layer 53, and outside Heating elements 54, 55, and 56 are provided outside the heat generating layer 53, respectively.

  That is, the heating coil is configured to be wound so as to form an interval 44 on the outer side of the inner heating coil 42 and integrally wound up from the connecting portion 45 to the outer heating coil 43. The heating coil is mounted on the coil base 41 and sandwiched between the coil holders 46 from above. The coil base 41 is provided with a central sensor 47 at the center of the heating coil inside the inner coil 42. A sensor 48 between the coils is provided between the heating coils 42 and 43.

  Here, the heat generating layers 52 and 53 and the heat generating elements 54, 55, and 56 are the same as the heat generating layer 16 and the heat generating elements 17 and 18 in the first embodiment, and the description thereof is omitted.

  Further, as shown in FIG. 12, a non-conductive pan 50 is placed on the top plate 2 of the device body 1 and used. Is omitted.

  As described above, in the present embodiment, the annular heating coil is provided with a space 44 between the conductors of the windings to form a double winding structure of the inner and outer heating coils 42, 43, and the non-conductive pan 50. The heat generation layers 52 and 53 are opposed to the inner and outer heating coils 42 and 43 to form a double annular shape, inside the inner heat generation layer 52, between the inner heat generation layer 52 and the outer heat generation layer 53, and outside. By providing the heating elements 54, 55, and 56 on the outside of the heating layer 53, the heating layer is divided into the heating layers 52 and 53, and the high temperature portion of the heating layer is a part of the bottom surface of the outer wall of the non-conductive pan 50. Can be less concentrated on Therefore, the stress concentration due to the difference in thermal expansion between the non-conductive pan 50 and the heat generating portion can be reduced, and deformation or breakage of the non-conductive pan 50 can be prevented. At the same time, the temperature rise of the heat generating layers 52 and 53 can be suppressed, the exfoliation of the heat generating layers 52 and 53 from the non-conductive pan 50, and the heating coils 42 and 43 burnt by the radiant heat from the heat generating layers 52 and 53. Can be prevented.

  The division of the heating coil and the heat generation layer is appropriately divided as necessary, and is not limited to two divisions as in the present embodiment.

  As described above, the induction heating cooker according to the present invention does not peel off the heat generating portion even when the non-conductive pan becomes high temperature, and can realize high heating power by induction heating, regardless of the form. It can be applied to all induction heating cookers.

The perspective view of the induction heating cooking appliance in Embodiment 1 of this invention Front view of the inside of the induction heating cooker The perspective view which looked at the non-conduction pan heated by the induction heating cooking appliance from the bottom side Side sectional view showing a part of the non-conductive pan in an enlarged manner Side sectional view showing the usage state of the induction heating cooker The perspective view which looked at the non-conduction pan heated by the induction heating cooking appliance in Embodiment 2 of this invention from the bottom face side Side sectional view showing a part of the non-conductive pan in an enlarged manner Side sectional view showing the usage state of the induction heating cooker The perspective view which looked at the non-conduction pan heated by the induction heating cooking appliance in Embodiment 3 of this invention from the bottom face side Side sectional view showing the usage state of the induction heating cooker The front view inside the induction heating cooking appliance in Embodiment 4 of this invention Side sectional view showing the usage state of the induction heating cooker

Explanation of symbols

1 Device body 5, 42, 43 Heating coil 14, 21, 31, 50 Non-conductive pan 15, 22, 32, 51 Bottom of outer wall 16, 25, 36, 52, 53 Heat generation layer 17, 18, 26, 27, 34 , 35, 54, 55, 56 Heating element 28, 29, 44 Spacing 33 Convex shape

Claims (3)

A heat generating layer that is formed of a thin film having a thickness of 100 microns or less and that is heated by induction by opposed heating coils is provided on the bottom surface of the outer wall so that the temperature rises most . most temperature on an outer wall bottom other than the portion which rises provided a heating element which is liable to increase in temperature by induction heating to form a stainless steel material to a thickness of at least 0.5 mm, wherein the heating layer is baked paste by transfer printing silver The heating element is fixed by a silicon-based adhesive, and a space is provided between the heating layer and the heating element, so that the heat of the heating layer that rises the most is transmitted to the heating element, so A non-conductive pan for induction heating in which the low silicon adhesive is prevented from deteriorating due to high heat and peeling off the heating element . A device body having an annular heating coil and a non-conducting pan of a clay pot heated by the heating coil of the device body, facing the heating coil, and the outer wall of the non-conducting pan in the portion where the temperature rises most An annular heat generating layer having a width smaller than the annular width of the heating coil is provided on the bottom surface so as not to be peeled off even at high temperatures, and the innermost and outermost temperatures of the heating layer are provided. the outer wall bottom surface of the non-conducting pan other than the portion which rises provided a heating element which is liable to increase in temperature by induction heating to form a stainless steel material to a thickness of at least 0.5 mm, the heating layer is bonded by transfer printing silver The heating element is fixed by a silicon-based adhesive, an interval is provided between the heating layer and the heating element, and the heat of the heating layer that rises the most is transmitted to the heating element. Low heat resistance temperature Induction heating cooker wherein the silicone adhesive is a heat-generating body is deteriorated by high heat is to prevent peeling. The annular heating coil has a multi-winding configuration with a gap between the conductors of the windings, and the heat generation layer of the non-conductive pan has a plurality of annular shapes facing the heating coil, inside and inside the heat generation layer. The induction heating cooker according to claim 2 , wherein a heating element is provided between the heat generating layer and the outer heat generating layer and between the outer heat generating layer and the outer heat generating layer in order.

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