JP2001210462A - Heating coil for induction heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized and inexpensive induction heater by realizing an inexpensive heating coil with simple structure without increase in the loss. SOLUTION: An inexpensive heating coil preventing the increase in the loss with simple structure, is composed of two spiral heating coils which are the lamination of more than two layers stacked in the direction to which the object to be heated 13 is loaded. Respective ending parts at the peripheral side of the first heating coil 11 and the second heating coil 12 are connected each other while upside and down side of the layers are reversed at the above connecting part to the face of the object to be heated 13 so as to make the distribution of electric current of respective layers and that of inside a layer become uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating device used in ordinary households, restaurants, factories, and the like, and more particularly, to a heating coil thereof.

[0002]

2. Description of the Related Art A heating structure of a conventional induction heating apparatus will be described with reference to FIGS. FIG. 15 is a cross-sectional view of a conventional induction heating cooker. Reference numeral 1 denotes an object to be heated which is induction-heated by a high-frequency magnetic field generated from a heating coil 2, reference numeral 2 denotes a heating coil for induction heating the object 1 to be heated, and reference numeral 3 denotes a heating coil. 2, which is connected to the heating coil 2 although not particularly shown in the figure. Reference numeral 4 denotes a plate on which the object to be heated 1 is placed on its upper surface, the material being ceramic. 5 is a housing,
Reference numeral 6 denotes a coil table on which the heating coil 2 is placed.

FIG. 16 shows a top view of the coil base 6. The coil wire of the heating coil 2 has a diameter of 0.3 mm to 0.1 mm.
It is configured by twisting about 30 strands of about 5 mm (Litz wire configuration). The twist pitch is about several centimeters, and each element wire is configured to repeat the vertical positional relationship with the lower surface of the object 1 several times during one turn.

[0004] The material of the wires is copper, and the surface thereof is covered with an insulator so that the wires are not electrically connected. Each wire is a heating coil 2
Dissolve the insulator at the beginning and end of the and electrically connect,
Not noted especially in the figure, caulking etc. have been fit in the glasses terminal. Although not shown in the figure, the crimped terminal is screwed to a terminal on a circuit board provided at a position away from the heating coil. The reason why the coil wire of the heating coil 2 is formed by twisting such wires is as follows.
Since the high-frequency current having a frequency of about 20 to 30 kHz flowing through the heating coil 2 is concentrated on the surface of the coil wire due to the skin effect, it is necessary that the high-frequency current be sufficiently small with respect to the skin depth of the high-frequency current flowing through the diameter of the coil wire. This is to prevent the current from being concentrated on a specific strand due to the proximity effect acting between the heating coil and the object to be heated.

When the diameter of the coil wire is larger than the skin depth of the flowing high-frequency current, no current flows inside the wire, so that the impedance becomes large. Even if the strand has a sufficiently small diameter, if there is no twist at all, the current will concentrate on the strand group on the side of the object to be heated 1 due to the proximity effect, and the impedance will also increase.

When the impedance of the heating coil 2 increases, the loss increases, which is a problem in terms of temperature rise and heating efficiency. Heat resistance of insulator is generally 150-180 ° C
If the coil wire temperature exceeds this heat resistance, it becomes difficult to insulate the wires and between the coil wires, and in this case, it becomes impossible to fulfill the function as a coil.

The number of turns of the coil shown in FIG. 12 is simply shown, and the actual number of turns is about 20 to 30 turns.

[0008]

However, such a conventional induction heating apparatus has the following problems.
That is, the heating coil having a configuration in which a plurality of strands are twisted and wound as described above has a complicated configuration, the manufacturing cost is extremely large, and as a result, the cost of the product is increased. Specifically, if at least one strand breaks at the stage of twisting a plurality of strands, production stops,
In order to maintain the shape of the coil, it is necessary to raise the temperature after coil winding to bring the individual wires into close contact (thermal welding), which is complicated and time-consuming.

An object of the present invention is to solve the above-mentioned conventional problems, realize a low-cost heating coil with a simple and easy construction method and the same loss as the conventional one, and provide an inexpensive induction heating apparatus as a result. Is what you do.

[0010]

According to the present invention, there is provided a heating coil comprising at least two layers of spiral electric conductors stacked in a direction in which an object to be heated is placed. One end of the outer peripheral portion of the first heating coil and the second end
One end of the outer peripheral portion of the heating coil is connected to the surface of the object to be heated such that the position of each layer is in an upside-down relationship.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 has two heating coils made of spiral electric conductors which are stacked at least two or more layers in the direction in which the object to be heated is placed, Induction heating characterized in that one end of the outer peripheral part of the heating coil and one end of the outer peripheral part of the second heating coil are connected to the surface of the object to be heated so that the positions of the respective layers are in an upside-down relationship. A heating coil for the device.

With this configuration, it is not necessary to twist a plurality of strands, and the current flowing between the layers is not biased toward the surface of the object to be heated. A coil can be realized. Furthermore, because it has a configuration having two spiral electric conductors,
An object of the present invention is to provide an induction heating device which can flexibly cope with the shape of an object to be heated as compared with a conventional heating coil composed of a single spiral, and has excellent heating efficiency. In addition, since the two spiral electric conductors can be turned upside down, the pitch of the inverted portions can be made sufficiently large, and the production can be made extremely easily.

According to a second aspect of the present invention, the object to be heated is a rice cooker, the first heating coil induction heats a substantially central portion of the bottom of the rice cooker, and the second heating coil is formed substantially from the outer periphery of the rice cooker bottom. The heating coil for an induction heating device according to claim 1, wherein the side surface of the rice cooker is induction-heated.

According to this configuration, in particular, in an induction heating type rice cooker, a heating coil configuration for obtaining optimum convection of a rice cooking pot can be realized with a simple construction method and low loss, so that an inexpensive induction heating type rice cooker can be provided. Things.

According to a third aspect of the present invention, there is provided the heating coil for the induction heating device according to the first aspect, wherein the positions of the lead lines at one end of the outer peripheral portion of each layer are different from each other. You.

According to this configuration, twisting is not required as compared with the configuration of the first aspect, so that a simpler construction method can be obtained, and a more inexpensive induction heating device can be obtained.

According to a fourth aspect of the present invention, the induction heating device according to the first aspect is characterized in that one end of the inner peripheral portion has a shape of an eyeglass terminal and a part of the coil wire of the inner peripheral portion is used for wiring. Heating coil.

According to this configuration, since a part of the inner peripheral portion can be used as a wiring, it can be easily connected to a circuit board, and a caulking process using eyeglass terminals, which is conventionally required, is not required. Therefore, the manufacturing cost can be further reduced.

The invention according to claim 5 is characterized in that one end of the inner peripheral portion is shaped like an eyeglass terminal and is directly electrically connected to a circuit board arranged on the side opposite to the surface to be heated. A heating coil for the induction heating device described above.

According to this configuration, the circuit board is disposed immediately below the heating coil, and the eyeglass terminals can be directly connected to the circuit board.
The manufacturing cost can be further reduced.

According to a sixth aspect of the present invention, there is provided a heating coil for an induction heating device according to the first aspect, wherein the heating coil is obtained by removing a portion other than the coil wire from a state having a connection wire between the coil wires. is there.

With this configuration, it is possible to avoid an unstable state during the manufacturing process, and it is possible to further reduce the manufacturing cost.

According to a seventh aspect of the present invention, there is provided the heating coil for the induction heating device according to the sixth aspect, wherein the positions of the connection lines between the coil wires are different in each layer.

With this configuration, the interlayer insulation after removing the connection line is not required, so that the manufacturing cost can be further reduced.

The invention according to claim 8 is characterized in that the winding is performed so that the direction of the high-frequency magnetic field generated by the first heating coil and the direction of the high-frequency magnetic field generated by the second heating coil are opposite to each other. A heating coil for an induction heating device according to claim 1.

With this configuration, since the generated high-frequency magnetic fields are opposite to each other, the leakage magnetic field becomes particularly small,
The magnetic shield means can be simplified, and an inexpensive induction heating device can be realized.

According to a ninth aspect of the present invention, the outer shape of the first heating coil and the outer shape of the second heating coil are formed in a semicircular dual shape. Heating coil.

With this configuration, since the first heating coil outer shape and the second heating coil outer shape have a semicircular and dual relationship, it is possible to efficiently perform induction heating on a circular object to be heated. .

[0029]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a first embodiment of the invention.
FIG. 4 is a diagram showing the example of the first embodiment, showing the positional relationship between the first heating coil 11, the second heating coil 12, and the object to be heated 13, and the first heating coil 11 and the second heating coil 12 viewed from above. 2 is an enlarged view of a cross section of the first heating coil 11 and the second heating coil 12. Hereinafter, the first heating coil 11 and the second heating coil 12 may be collectively referred to as a heating coil.

In FIG. 1, reference numeral 11 denotes a spiral first heating coil. In this embodiment, a first layer 14 and a second layer 15 are provided.
Of two layers of rectangular spiral electric conductor (copper). The thickness of the layer is set to a value sufficiently smaller than the skin depth determined by the high-frequency current flowing through the first heating coil 11 and the conductor material. Reference numeral 12 denotes a second heating coil, the configuration of which is the same as that of the first heating coil 11;
Is electrically connected to the end of the outer peripheral portion of the second heating coil 12. Reference numeral 13 denotes an object to be heated, which is induction-heated by a high-frequency magnetic field generated by a high-frequency current flowing through the first heating coil 11 and the second heating coil 12.
Each layer of the first heating coil 11 and the second heating coil 12 is stacked in parallel with the surface of the object 13 to be heated. Each layer is electrically insulated by an insulator 16.
As shown in the drawing, the first heating coil 11 and the second heating coil 12 are arranged such that the first layer 14 is placed on the upper surface (when the surface of the heating object 13
The third layer 15 has a structure in which the second layer 15 is turned upside down from bottom to top.

FIG. 2 is a view of the object to be heated 13 viewed from above. The object to be heated 13 has a rectangular shape as shown in FIG. The outer shape is almost the same, and induction heating can be performed over the entire surface.

FIG. 3 a) shows a first layer 14 and a second layer 1.
5B is a diagram showing a current flowing in the case 5, in the case where the upside down is not performed in the inverting unit 17 (that is, the first layer 14 is always on the object to be heated 13, and the second layer 15 is always upside down). The same current distribution.

FIG. 4 is a diagram illustrating a method for manufacturing the first heating coil 11 and the second heating coil 12, and the inversion section 17 as shown in a) obtained by the etching method or the press method is used. First heating coil 11 as boundary
The spiral conductor in which the winding direction of the second heating coil 12 and the second heating coil 12 is reversed is turned upside down by a method such as twisting in the reversing section 17 so that the first layer 14 and the second layer 15 are turned upside down. It is manufactured in.

The operation of this embodiment will be described below. When a high-frequency current (20 kHz or more in this embodiment) flows through the first heating coil 11 and the second heating coil 12, the current first flows intensively on the surface portion of each layer due to the skin effect. In the case of, since the thickness of each layer is sufficiently thin with respect to the skin depth (for example, about 0.3 mm at 20 kHz)
Non-uniformity of the current distribution due to the skin effect does not occur. Furthermore, since the reversing unit 17 has a vertically inverted structure, the current distribution in the upper and lower layers is uneven due to the proximity effect generated between the object to be heated 13 and the first heating coil 11 and the second heating coil 12. Is significantly improved compared to the distribution without inversion. According to the experiments by the inventors, the input power was about 1
2A), the current of the first layer 14 is 12 A, the current of the second layer 15 is 10 A, and in the case of FIG. 2B), the current of the first layer 14 is 15 A, and the current of the second layer 15 is 200 W. Was 7 A.

As described above, in the present embodiment, a plurality of thin coils stacked on the surface of the object to be heated 13 are turned upside down during winding, thereby achieving a very simple configuration as compared with the conventional litz configuration. Therefore, the manufacturing cost can be reduced, and the current distribution in each layer can be made uniform, so that an increase in loss can be prevented. As described above, it is possible to realize an inexpensive induction heating device.

As an alternative to the litz configuration, a plurality of thin coils as in this embodiment are stacked and arranged and wound, for example, perpendicularly to the surface of the object to be heated 13 in order to prevent current unevenness due to the skin effect. However, in this case, a current bias occurs in the vertical direction due to the proximity effect as described above, so that the loss is larger than in the conventional case, which is not practical. From this point of view, it can be said that a configuration in which the surface of the object to be heated 13 is turned upside down during winding is extremely effective. Also the first
Is reversed between the heating coil 11 and the second heating coil 12, the twist pitch of this portion can be increased, and this can be realized by an easy construction method. Further, since two heating coils are used, it is possible to flexibly conform to the shape of the object to be heated. For example, even if a triangular load such as an iron base is used, the first coil is formed as a round spiral.
By making the diameter of the heating coil 11 smaller than the diameter of the second heating coil 12, heating can be performed efficiently.

In the case of the present embodiment, the object to be heated 13 having a square bottom surface
In order to heat the wire, two rectangular spiral heating coils are used. However, for example, in the conventional method of winding a litz wire, it is extremely complicated to wind the wire into such a square shape. (It is necessary to insert a shape-regulating jig in the middle of the winding to adjust the shape, because the outer shape is almost circular even if the coil is wound as a square at the center.) However, the method and configuration of the present embodiment are extremely effective.

Also, conventionally, it has been difficult to provide a gap between each coil wire (a wire in a form in which a plurality of strands are twisted).
In the configuration as in the present embodiment, a gap can be easily provided between the coil wires, and as a result, the cooling of the heating coil becomes extremely easy. Therefore, the cooling configuration can be simplified, and in this respect, the device as the device is also used. The cost can be further reduced.

In this embodiment, the number of layers is two.
If the number of layers is increased to three or four, the loss can be further reduced. The number of turns in FIG. 1 is a simplified one, and actually has a configuration of several tens of turns in total. Although the number of the reversing unit 17 is one, when the reversing unit 17 is implemented at a plurality of locations, the greater the number of locations is, the closer to the same as the conventional litz configuration, the more uniform the process is. The insulator 16 is necessary for insulation between the first layer 14 and the second layer 15 and for insulation between coil wires, and may insulate the entire layer.

In this embodiment, two heating coils are used. However, by increasing the number of heating coils to three, four, and appropriately setting the upper and lower relations, it is possible to cope with a more complicated shape of the object to be heated. .

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a view showing the present embodiment, in which the object to be heated 13 is a rice cooker, and the first heating coil 11 is arranged to heat the bottom center of the object to be heated 13. In addition, the second heating coil 12 is disposed so as to induction heat the side portion from the outer peripheral portion of the pot bottom. The first heating coil 11 and the second heating coil 12 are connected in series similarly to the first embodiment, and are turned upside down in the middle of the wiring to be connected. Due to the induction heating from the first heating coil 11, in the rice cooker, convection occurs from the center of the pot bottom to the top (the pot lid surface) and from the upper side to the lower part of the pot, but the induction of the second heating coil 12. Heating causes convection in a direction opposite to this direction, so that the two become close to each other (making the convection generated by the second heating coil 12 slightly stronger), thereby obtaining optimal convection for rice cooking. Can be.

As described above, in this embodiment, particularly in the induction heating type rice cooker, the heating coil configured to obtain the optimal convection in the rice cooking pot can be configured at low cost without using a litz wire. In addition, since two heating coils are used in particular, it is extremely significant that a flexible heating distribution can be obtained under such a load of a rice cooker, and since the connection portion is inverted, it can be realized by an easy method. .

(Embodiment 3) Hereinafter, a third embodiment of the present invention will be described with reference to FIG. In FIG. 6, a)
Shows the first heating coil 11 and the second heating coil 12 of the present embodiment. b) shows only the first layer 14 and c) shows only the second layer. As shown in the figure, the position of the lead line at the outer peripheral end forming the first layer 14 is different from that of the lead line forming the second layer 15. a)
In the state (1), the layers (b) and (c) are inserted so as to be turned upside down as shown in FIG. 1, and therefore the positions of the lead lines are different. That is, if the positions of the lead lines are the same, the lead lines of the first layer 14 and the second layer 15 contact each other at the time of insertion, so that such a configuration becomes impossible.

As described above, in this embodiment, since the positions of the lead lines are shifted, it is not necessary to apply a mechanical stress such as twisting at the reversing portion as in the first embodiment, which is extremely easy. Thus, a heating coil can be realized.

(Embodiment 4) Hereinafter, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 7 shows a state during processing of the present embodiment. Reference numeral 18 denotes an eyeglass terminal having a shape of an inner peripheral end, which is manufactured similarly to other coil wires at the time of etching or pressing. FIG.
Is a view showing a state of being connected to the circuit board 19, and as shown in the figure, part of the coil wires of the first heating coil 11 and the second heating coil 12 are used as wiring to the circuit board 19; Have been. In the present embodiment, the inductances of the first heating coil 11 and the second heating coil 12 are designed such that sufficient performance can be obtained in a state where a part as shown in the figure is used as a wiring. When a part is taken out as shown in the figure, the inductance generally becomes small, so the design is made in consideration of that. FIG.
8 is a sectional view from the left side in FIG.
It is a positional relationship with. As shown in the figure, the wires coming out of the first heating coil 11 pass through the coil mount 21, pass through the bottom surface of the coil, and are fixed to the circuit board 19 using fixing screws 20.

As described above, in this embodiment, since the coil end portion is formed in advance into the shape of eyeglass terminals for screwing at the stage of etching or pressing, a conventional terminal caulking step is unnecessary, and the cost is reduced. Because it can provide a heating coil for an induction heating device, and is designed so that part of the coil wire can be used as wiring in advance,
Wiring to the circuit board 19 is also unnecessary, and a more inexpensive induction heating device can be realized.

If the terminal portion is masked in advance so as not to add an insulator, the step of melting the insulator becomes unnecessary. Although the eyeglass terminal shape is used in the present embodiment, any configuration may be used as long as it can be easily electrically connected. Needless to say, the shape may be U-shaped. This configuration may be applied to the second or third embodiment.

(Embodiment 5) Hereinafter, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a diagram showing the heating coil and the circuit board 19 in the present embodiment. As shown in the drawing, the circuit board 19 is disposed immediately below the heating coil. Similarly to the fourth embodiment, the inner end of the heating coil is shaped like an eyeglass terminal. Although not particularly shown in the figure, the eyeglass terminals 18 are directly electrically connected to the circuit board 19 disposed immediately below by using fixing screws.

According to the above configuration, the circuit board 19 is sometimes arranged immediately below the heating coil, and the terminals of the heating coil are formed in the shape of eyeglass terminals. It is possible to obtain an easy induction heating device.

(Embodiment 6) Hereinafter, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 11 is a diagram showing a heating coil during processing according to the present embodiment, and connection lines connecting the coil wires are arranged in a cross shape during etching or pressing. This connection wire is used to maintain the shape of the coil at the time of fabrication, and is cut and deleted after being layered. As described above, in the present configuration, by using the connection wire, it is possible to obtain a stable spiral shape during the manufacturing process, and it is possible to obtain a heating coil for an induction heating device that is easier to construct. . This embodiment may be used in the second to fifth embodiments.

(Embodiment 7) Hereinafter, a seventh embodiment of the present invention will be described with reference to FIG. FIG. 12 shows the first layer 14 and the second layer 1 during fabrication in the third embodiment.
FIG. As shown in the figure, connection lines similar to those in the sixth embodiment are provided between the coil wires, but the connection lines of the first layer 14 and the second layer 15 do not overlap each other. It has become. When the connection line is cut or removed, the insulating layer may be broken and the upper and lower layers may be electrically connected to each other. No short circuit occurs. Further, in the case of the present embodiment, since the shapes of the respective layers are different, it is more effective especially when used in the third embodiment. As described above, by arranging the arrangement of the connection lines of each layer, no countermeasure is required for the correlated insulation after cutting or deletion, and the construction method can be simplified.

Embodiment 8 Hereinafter, an eighth embodiment of the present invention will be described with reference to FIG. FIG. 13 is a diagram showing the heating coil of the present embodiment. As shown in the drawing, the rotating directions of the currents flowing through the first heating coil 11 and the second heating coil 12 are opposite to each other. . Other configurations are the same as those of the first embodiment. As described above, the direction of the high-frequency magnetic field generated from the first heating coil 11 and the direction of the high-frequency magnetic field generated from the second heating coil 12 are opposite to each other.
Two eddy current loops are formed and induction heated. In the leakage magnetic field generated mainly between the heating coil and the object to be heated 13, the high-frequency magnetic field is canceled particularly at a distant position. And it can be easily realized. In general, this type of induction heating device is provided with, for example, a magnetic shield using a loop-shaped aluminum plate in order to reduce a leakage magnetic field. However, according to the configuration of the present embodiment, such a magnetic shield structure is abolished or simplified. Therefore, the cost can be further reduced.

Embodiment 9 Hereinafter, a ninth embodiment of the present invention will be described with reference to FIG. FIG. 14 is a diagram showing the heating coil of the present embodiment, in which the first heating coil 11 and the second heating coil 12 are each semicircular and dual. With the above configuration, it is possible to efficiently perform induction heating, particularly for a circular object to be heated, and to easily obtain an induction heating device that does not result in unnecessary leakage magnetic field or reduced efficiency. is there.

[0054]

As described above, according to the first aspect of the present invention, a plurality of thin coils stacked on the surface of the object to be heated are turned upside down in the middle of winding, thereby achieving a conventional litz configuration. Since the configuration is extremely simple as compared with the above, the manufacturing cost can be reduced. In addition, since the current distribution in each layer can be made uniform, an increase in loss can be prevented. As described above, it is possible to realize an inexpensive induction heating device. Further, since two heating coils are used, the shape of the object to be heated can be flexibly adjusted. Also, since the first heating coil and the second heating coil are inverted, the twist pitch at this portion can be increased, and this can be realized by an easy construction method.

According to the second aspect of the present invention, particularly in an induction heating type rice cooker, a heating coil configured to obtain an optimum convection in a rice cooker can be simplified without using a litz wire. It can be realized at a low cost with a construction method.

According to the third aspect of the present invention, since the positions of the lead lines are shifted from each other, each layer can be obtained by being inserted upside down and twisted at the inverted portion. This eliminates the need for applying a thermal stress and makes it possible to realize a heating coil very easily. That is, when the number of layers is increased as described in the first embodiment, bending,
Or the twisting method is more difficult (due to the large thickness), but with this configuration, there is almost no such mechanical stress and it can be easily realized. It is also easier to reduce the loss than that.

According to the fourth aspect of the present invention, since the coil end portion is formed into an eyeglass terminal shape for screwing, the conventional terminal crimping step is not required, so that the inexpensive induction heating device can be used. Since a heating coil can be provided and a part of the coil wire can be used as a wiring in advance, wiring to a circuit board is not required, and a more inexpensive induction heating device can be realized.

According to the fifth aspect of the present invention, since the circuit board is sometimes arranged immediately below the heating coil and the terminals of the heating coil are formed in the shape of eyeglass terminals, no wiring is required. It is possible to obtain an induction heating device that is easier in terms of construction than in the case of the above.

Generally, in the wiring between the heating coil and the circuit board, an insulating tube for electric protection may be used in order to prevent a short circuit with other components. No insulation is required.

According to the sixth aspect of the present invention, the use of the connecting wire makes it possible to obtain a stable spiral shape in the middle of the manufacturing process, and it is not necessary to use a shape holder or the like. It is possible to obtain a heating coil for an induction heating device that is easy to use.

According to the seventh aspect of the present invention, by shifting the positions of the connection lines, the insulating layer is broken when the connection lines are cut or deleted, and the upper and lower layers are electrically connected. This eliminates the need for insulation treatment after cutting, so that a heating coil for an induction heating device with a simpler construction method can be obtained.

According to the eighth aspect of the present invention, the first
Since the directions of the high-frequency magnetic fields generated by the heating coil and the second heating coil are opposite to each other, simplification or elimination of the magnetic shield device is possible, and a more inexpensive induction heating device becomes possible. is there.

According to the ninth aspect of the present invention, the first
Since the heating coil and the second heating coil each have a semicircular and dual shape, efficient induction heating can be performed particularly on a circular object to be heated, resulting in unnecessary leakage magnetic field and reduced efficiency. Thus, it is possible to easily obtain an induction heating device without any.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a heating coil for an induction heating device according to a first embodiment of the present invention.

FIG. 2 is a top view of the same.

FIG. 3 is a diagram showing a current component of each layer.

FIG. 4 is a diagram showing a method of manufacturing a heating coil.

FIG. 5 is a diagram showing a configuration of a heating coil for an induction heating device according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a heating coil for an induction heating device according to a third embodiment of the present invention.

FIG. 7 is a view showing a configuration of a heating coil for an induction heating device according to a fourth embodiment of the present invention, which is being processed;

FIG. 8 is a diagram showing a state at the time of connection with a circuit board.

FIG. 9 is a sectional view of FIG. 8 and a diagram showing a positional relationship with an object to be heated;

FIG. 10 is a diagram showing a configuration of a heating coil for an induction heating device according to a fifth embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a heating coil for an induction heating device according to a sixth embodiment of the present invention, which is being processed;

FIG. 12 is a view showing a configuration of a heating coil for an induction heating device according to a seventh embodiment of the present invention, which is being processed;

FIG. 13 is a diagram showing a configuration of a heating coil for an induction heating device according to an eighth embodiment of the present invention.

FIG. 14 is a diagram showing a configuration of a heating coil for an induction heating device according to an eighth embodiment of the present invention.

FIG. 15 is a cross-sectional view showing a component configuration of a conventional induction heating device.

FIG. 16 is a view of the heating coil as viewed from above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 1st heating coil 12 2nd heating coil 13 Heated object 18 Eyeglass terminal 19 Circuit board 22 Connection line

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tomoya Toto 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Hideki Omori 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Tetsuo Obata 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (reference) CD73 CD77

Claims (9)

[Claims] 1. A heating coil comprising at least two layers of spiral electric conductors stacked in a direction in which an object to be heated is placed, wherein one end of an outer peripheral portion of a first heating coil and a second end of a second heating coil are provided.
One end of the outer peripheral portion of the heating coil is connected to the surface of the object to be heated so that the positions of the respective layers are in an upside-down relationship. 2. A rice cooker is used as an object to be heated, a first heating coil inductively heats a substantially central portion of the bottom of the rice cooker, and a second heating coil guides the side of the rice cooker from substantially the outer periphery of the rice cooker bottom. The heating coil for an induction heating device according to claim 1, wherein the heating coil is arranged to be heated. 3. The heating coil for an induction heating device according to claim 1, wherein the positions of the lead lines at one end of the outer peripheral portion of each layer are different from each other. 4. The heating coil for an induction heating device according to claim 1, wherein one end of the inner peripheral portion is shaped like an eyeglass terminal, and a part of the coil wire of the inner peripheral portion is used for wiring. 5. The induction heating device according to claim 1, wherein one end of the inner peripheral portion has a shape of an eyeglass terminal and is directly electrically connected to a circuit board disposed on a side opposite to a surface to be heated. Heating coil. 6. The heating coil for an induction heating device according to claim 1, wherein the portion other than the coil wire is removed from a state having a connection wire between the coil wires. 7. The heating coil for an induction heating device according to claim 6, wherein the positions of connection lines between the coil wires are different in each layer. 8. The induction according to claim 1, wherein the direction of the high-frequency magnetic field generated by the first heating coil and the direction of the high-frequency magnetic field generated by the second heating coil are opposite to each other. Heating coil for heating device. 9. The heating coil for an induction heating device according to claim 1, wherein the outer shape of the first heating coil and the outer shape of the second heating coil are formed in a semicircular dual shape.