JPH1027681A - Induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating device which can display an effect in use capable of obtaining objective heating distribution by removing mutual interference in the case of simultaneous induction heating by a plurality of heating coils. SOLUTION: A device is provided with first/second heating coils 1, 2A, 2B directing a coil surface to a heating location respectively of a heated object 10 and first/second power sources D1, D2 outputting high frequency power of respectively different frequency. In the first heating coil 1, power is fed by the first power source D1. The second heating coils 2A, 2B, with power fed by the second power source D2, are a heating coil of the same dimension, to be positioned in a location symmetrical relating to the center of the first heating coil 1, the second heating coils are connected in series in a direction mutually canceling induction electromotive force generated between the second heating coil and the first heating coil 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating apparatus provided with a plurality of heating coils and a high-frequency power supply for simultaneously supplying high-frequency powers of different frequencies to the respective heating coils. This induction heating device is, for example, an electromagnetic cooker, a rice cooker, or a high-speed linear heating, as represented by a high-frequency current flowing through a heating coil, and a high-frequency magnetic field generated at this time causes metal, magnetic material, or carbon. The object to be heated formed by the material is induction-heated. As the heating coil, a flat spiral or curved coil made of a litz wire or a copper pipe, a solenoid coil, or the like is used.

[0002]

2. Description of the Related Art A recent induction heating apparatus is of a type in which a heating coil is independently connected to a plurality of high-frequency power sources to simultaneously heat one or a plurality of objects to be heated. . However, when induction heating is performed by bringing a plurality of heating coils close to each other, magnetic fluxes generated between adjacent heating coils interlink with each other, causing mutual interference, and the following problems occur.

The first problem is that the output of the high-frequency power supply connected to the heating coil is disturbed and cannot be stabilized.
The point is that the heating temperature of the work to be heated changes. When the degree of mutual interference is large, the circuit that controls the phase and level of the output in the high-frequency power supply is adversely affected, and the oscillation operation itself becomes impossible, or if a transistor is provided in the output stage, it is damaged. Sometimes.

[0004] The second problem is that a very loud beat sound due to mutual interference is generated from the heating coil and the work, which is not preferable in the work environment. For example, 25kHz and 28k
In the case of a high-frequency power supply of 1 Hz, no noise is generated by single heating because it is higher than the audible frequency of a person, but in the case of simultaneous heating, noise of a differential frequency of 3 kHz or a harmonic component thereof is generated.

Conventionally, in order to solve these problems, for example, a method of providing a metal shield plate or a ring or a magnetic material around a plurality of heating coils to prevent mutual interference (hereinafter referred to as a first conventional example), A method of separating the coils by a distance that does not cause interference (hereinafter referred to as a second conventional example) and a method of synchronously driving a plurality of high-frequency power supplies to have the same output frequency to prevent mutual interference (hereinafter referred to as a third conventional example) are proposed. Have been. The contents of the first conventional example are described in, for example, JP-A-55-121297, JP-A-57-3388, and JP-A-02-30.
No. 1522 describes this in detail. The contents of the second conventional example are described in, for example, JP-A-63-148588,
It is described in Japanese Patent Application Laid-Open No. 08-66300,
The contents of the conventional example are described in JP-A-01-267991.

According to each of the above-mentioned conventional examples, the desired object of preventing mutual interference can be achieved under predetermined conditions. However, the following problems were left to be solved. For example, in the first conventional example, the mutual interference between the high-frequency power sources cannot be completely removed, and the effect is not exhibited when the gap between the heating coils is extremely close. Further, in the second conventional example, a continuous heating distribution in which a plurality of heating coils are approached cannot be obtained. In the third conventional example, mutual interference between high-frequency power sources does not occur in principle,
Since the common drive circuit of each heating coil is forcibly driven at one specific frequency, the optimum frequency of each resonance circuit cannot be optimally controlled. Therefore, the output fluctuates when there is a load fluctuation, a fluctuation in the resonance circuit, or a temperature characteristic or a change with time. In particular, the phase of the voltage or current of the output of each high-frequency power supply cannot be fixed, causing a change in heating efficiency, or an excessive current flowing to adversely affect the heating coil. Further, in the third conventional example, since there is no viewpoint of actively using a plurality of frequencies to improve the heating distribution, a wide flat area can be simultaneously heated using a plurality of high-frequency power sources that output powers having different frequencies. In some cases, it is not possible to sufficiently adapt to applications in which the heating distribution is partially changed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved induction heating apparatus which can be used effectively to obtain a desired heating distribution by eliminating mutual interference during simultaneous induction heating by a plurality of heating coils. It is in.

[0008]

An induction heating apparatus according to the present invention includes a plurality of heating coils for inductively heating an object to be heated, and a high-frequency power supply for simultaneously supplying high-frequency powers of different frequencies to the respective heating coils, Each heating coil is arranged such that induced electromotive force generated by energization of another adjacent heating coil is canceled.

Further, as a modified example of the present invention, the following configuration can be adopted. The induction heating device of the first configuration includes:
A plurality of heating coils, each of which has a coil surface directed to a heating portion of the object to be heated, and a plurality of high-frequency power supplies that output high-frequency power of different frequencies, respectively. The plurality of heating coils comprise a combination of an inner heating coil powered by one high frequency power supply and a plurality of outer heating coils powered by another high frequency power supply. The plurality of outer heating coils are, for example, composed of a pair of heating coils having the same shape and dimensions. Each of the plurality of outer heating coils is located at a position equidistant from the inner heating coil and generates induced electromotive force generated between the inner heating coil and each other. They are connected in series to cancel each other. Note that the inner heating coil is a heating coil provided from the center of the heating portion, and the outer heating coil is a heating coil provided adjacently along the outer periphery of the inner heating coil. It does not mean that it consists of a heating coil. For example, when five sets of heating coils are provided in a row or concentric manner, the fourth set of heating coils is an inner side heating coil with respect to the fifth set of heating coils in the outer circumferential direction, but is located inside the fifth set of heating coils. The outer heating coil is used for the third heating coil set.

In the induction heating apparatus having the above structure, the arrangement of each heating coil is changed according to the shape of the object to be heated.
Application can be expanded. For example, when the object to be heated is a curved or cylindrical bottomed container, the plurality of heating coils are arranged so that each coil surface is along the outer bottom surface of the bottomed container.

The induction heating device of the second configuration is suitable for use in induction heating while moving the object to be heated at a high speed, and is wound around a rod-shaped or linear object to be heated in a non-contact manner and arranged. A plurality of solenoid-shaped heating coils and a plurality of high-frequency power supplies that output high-frequency power of different frequencies are provided. The plurality of heating coils comprise a combination of a central heating coil powered by one high frequency power supply and a plurality of end heating coils powered by another high frequency power supply. The plurality of end-side heating coils are connected in series at positions equidistant from the center-side heating coil so as to cancel out induced electromotive forces generated between the heating coil and the center-side heating coil. In addition, the center side heating coil means a heating coil provided from the center of the array, and the end side heating coil means a heating coil provided adjacent to the end side of the center side heating coil. It is the same as the case of the first configuration that the purpose is not limited to two sets of heating coils.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1A is a front view of an induction heating apparatus according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA. The induction heating apparatus includes a first heating coil 1 having a flat elliptical spiral shape, and the first heating coil 1
It is arranged at a symmetrical position on the same plane with respect to the center of
The second heating coils 2A and 2B are connected in series and have a flat elliptical spiral shape and the same dimensions. Each heating coil 1, 2
A plate-like object to be heated 10 made of a material such as iron, stainless steel, or carbon is arranged at predetermined intervals on the coil surface side of A and 2B. A first power supply D1 for supplying a high-frequency current to the heating coil 1 and a second power supply D2 for supplying a high-frequency current to each of the second heating coils 2A and 2B are provided. Each power supply D1, D
2 supplies currents of different frequencies to the respective heating coils 1
These are supplied to 2A and 2B, and are used, for example, for heating steel plates, billet heaters, electromagnetic cookers, and quenching.

The operation of the induction heating device having the above configuration when the heating coils 1, 2A, and 2B are simultaneously supplied with power will be described with reference to FIGS. 2 (a) and 2 (b). In FIG. 2A, a current 2AI is supplied to the second heating coil 2A on the left side of the drawing.
Flows, a magnetic flux 2AX is generated at the portion. When the magnetic flux 2AX interlinks the left side of the first heating coil 1, an induced electromotive force is generated on the left side of the first heating coil 1, and an induced current 2 for generating a magnetic flux 2AXa in the opposite direction to the magnetic flux 2AX.
AIa flows. On the other hand, the current 2BI is supplied to the right coil 2B.
Flows, a magnetic flux 2BX is generated in the relevant portion. When the magnetic flux 2BX links the right side of the first heating coil 1, the first
An induced electromotive force is generated on the right side of the heating coil 1 and the magnetic flux 2BX
An induced current 2BIa flows to generate a magnetic flux 2BXa in the opposite direction. The second power source D2 is the second heating coil 2
A, 2B, the induced current 2BI
a and 2AIa flow in the direction to cancel each other at the same level. Therefore, the first heating coil 1 is connected to the second heating coil 2
No mutual interference by A and 2B.

Similarly, the first heating coil 1 is connected to the first power source D1.
, The induced currents generated in the second heating coils 2A and 2B located on both sides thereof are canceled.
FIG. 2 (b) is a diagram showing this fact. The second heating coil 2 is controlled by the high-frequency currents 1AI and 1BI of the first heating coil 1.
The induced currents 1AIa and 1BIa generated in A and 2B are
Flow at the same level to offset each other. Therefore, the second heating coils 2A and 2B do not receive any mutual interference by the first heating coil 1.

As described above, since the mutual interference between the first heating coil 1 and the second heating coils 2A and 2B on the left and right sides thereof is canceled out, it is possible to solve the conventional problem of simultaneous power supply. Can be. Further, the intended heating distribution can be obtained in the object to be heated 10 by the heating coils 1, 2A, and 2B.

(Second Embodiment) Next, an embodiment in which a disk-shaped object to be heated is induction-heated will be described with reference to FIG. In this embodiment, a flat spiral first heating coil and two elongated flat elliptical spiral second heating coils are arranged, and a high-frequency current flows independently of each other. FIG. 3 (a)
FIG. 3 is a plan view of each heating coil, and FIG.

Referring to FIG. 3A, a first heating coil 21 is disposed at a predetermined distance from a central portion of a bottom surface of a heated object 20 made of a magnetic material. Second coils 22A and 22B connected in series are arranged in a symmetrical manner on the plane. A first power supply D1 and a second power supply D2 are connected to the heating coils 21, 22A, 22B in the directions shown in FIG. 2B, respectively. Each of the power supplies D1 and D2 supplies a current having a different frequency to each of the heating coils 21, 22A and 22B.

The operation when power is simultaneously supplied to the heating coils 21, 22A and 22B in such a coil arrangement and connection mode is the same as that of the first embodiment.
Mutual interference between 1, 22, A and 22B is cancelled. Therefore, the conventional problems at the time of simultaneous power supply are solved, and the heating coils 21, 22 A, 22 B
As a result, an intended heating distribution can be obtained.

(Third Embodiment) Next, an embodiment in which a rod-shaped or linear object moves at a high speed will be described with reference to FIG. In FIG. 4, reference numeral 30 denotes a rod-shaped or linear object to be heated made of a magnetic material such as iron or a non-magnetic stainless steel, and 31 denotes a solenoid-shaped first heating member wound around the center of the object to be heated 30 in a non-contact manner. The coils 32A and 32B are solenoid-shaped second heating coils of the same dimensions which are wound symmetrically from both ends of the first heating coil 31 from the center. Each of the second heating coils 32 </ b> A and 32 </ b> B has the same distance from the first heating coil 31. A first power supply D1 is connected in series to the first heating coil 31, and the direction of the high-frequency current to each of the second heating coils 32A and 32B is relatively opposite to that of the first heating coil 31. The second power supply D2 is connected in series so that Each power supply D1,
D2 supplies currents of different frequencies to the respective heating coils 3
1, 32A and 32B.

In such a coil arrangement and connection form,
Since the magnetic fluxes AX and BX generated when the second heating coils 32A and 32B are energized are opposite to each other, the induced current generated in the first heating coil 31 is canceled. Also, the first
A part of the magnetic flux 31X generated by the high-frequency current flowing through the heating coil 31 becomes a leakage magnetic flux and
A and 32B are linked to each other, but since the leakage magnetic flux has the same magnitude, the induced current generated in the second heating coils 32A and 32B is canceled. Therefore, the mutual interference between the first heating coil 31 and each of the second heating coils 32A and 32B at the time of the simultaneous power supply is canceled out, and the original target of the object 30 to be heated is determined by the respective heating coils 31, 32A and 32B. Can be obtained. In particular, the first heating coil 31 and the second heating coils 32A and 32B separate the object to be heated 3 by separating the frequencies of the first and second power supplies D1 and D2 by 10 times or more.
Induction heating by changing the penetration depth of the eddy current in the cross-sectional direction of 0,
By feeding the object to be heated 30 at a high speed, a desired heating distribution can be obtained.

(Fourth Embodiment) FIG. 5 shows that the number of heating coils wound and arranged on a rod-shaped or linear heating object and the number of high-frequency power supplies for supplying high-frequency current to each heating coil are further increased. It shows an example in the case of performing simultaneous heating.
In this case, the first heating coil 41 located at the center of the object to be heated 40 and the second heating coil 41 disposed at symmetrical positions at both ends thereof.
Mutual interference between the heating coils 42A and 42B is canceled out as in the third embodiment. In this embodiment, the third heating coils 43A and 43B are further disposed on both end sides of the second heating coils 42A and 42B, and the induced electromotive forces generated between the second heating coils 42A and 42B cancel each other. The third power supply D3 is connected in series in the direction in which the third heating coils 43A, 43B are arranged at both ends of the third heating coils 43A, 43B. The fourth power supply D4 is connected in series in such a direction as to cancel out the induced electromotive force. Each of the power supplies D1, D2, D3, and D4 supplies a current having a different frequency to each of the heating coils 41, 42A, 42B, 43A, and 4 respectively.
3B, 44A, and 44B.

In such a coil arrangement and connection form,
In any of the heating coils, mutual interference with other adjacent heating coils is canceled. Accordingly, the heating coils 41, 42A, 42B, 43A, 43B, 4
4A and 44B, it is possible to easily obtain the intended heating distribution, for example, the heating distribution in consideration of the penetration depth of the eddy current. Although FIG. 5 shows an example in which up to four sets of heating coils are wound, a plurality of heating coils can be further increased in the same manner.

(Fifth Embodiment) Next, an embodiment in which a bottomed container is induction-heated will be described with reference to FIG. In the figure, reference numeral 50 indicates an example of the container, and its material is the same as that of each of the above embodiments. In this embodiment, a flat spiral first heating coil 51 is arranged near the center of the bottom of the container 50, and the first heating coil 51
A pair of flat elliptical spiral second heating coils 52A and 52B having the same dimensions are arranged on both sides on the same plane as the above. Further, flat elliptical spiral third heating coils 53A and 53B are arranged on both side surfaces of the container 50. First heating coil 51
Are connected in series, a second power supply D2 is connected to the second heating coils 52A and 52B, and a third power supply 3D is connected to the third heating coils 53A and 53B, respectively. Each of the power supplies D1, D2, and D3 supplies a current having a different frequency to each of the heating coils 51, 52A, 52B,
53A and 53B.

The mutual interference between the first heating coil 51 and the second heating coils 52A and 52B during energization is canceled out as described in each of the above embodiments. According to the same principle, mutual interference between the second heating coils 52A and 52B and the third heating coils 53A and 53B is canceled. Accordingly, the heating coils 51 and 52 in the object 50 to be heated are
A, 52B, 53A and 53B make it possible to obtain the intended heating distribution. In addition, the container is not limited to the example of FIG. 6, and various shapes are applicable. For example, when the outer bottom surface is curved and mortar-shaped like a wok, each heating coil 51, 52A, 52B, 53A, 53B is
What is necessary is just to arrange so that the coil surface may be along the outer bottom surface. Alternatively, the coil surface itself may be formed.

Although the present invention has been described with reference to a plurality of embodiments, the present invention is characterized in that a plurality of heating coils are arranged such that induced electromotive force generated by energization of another adjacent heating coil is offset. Since there is a focus, the present invention is not necessarily limited to the example of the above embodiment, and various design changes are possible.

[0027]

As is clear from the above description,
ADVANTAGE OF THE INVENTION According to this invention, mutual interference at the same time when a plurality of heating coils are brought close to each other is eliminated, and adverse effects on a high-frequency power supply and generation of beat sound can be reliably prevented. In addition, since the number of heating coils and high-frequency power supplies can be arbitrarily increased, a wide planar area can be simultaneously heated using electric power of a plurality of frequencies over the entire surface, and partial heating can be performed in consideration of the eddy current penetration depth. It is possible to flexibly respond to applications.

[Brief description of the drawings]

FIG. 1A is a plan view of a first embodiment of the present invention,
(B) is a sectional view taken along line AA.

FIG. 2A is an explanatory diagram showing that a second heating coil does not interfere with a first heating coil, and FIG. 2B is a diagram showing that the first heating coil does not interfere with a second heating coil. FIG.

FIG. 3A is a plan view of a second embodiment of the present invention,
(B) is a sectional view taken along line AA.

FIG. 4 is a configuration diagram of a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a fourth embodiment of the present invention.

FIG. 6 is an explanatory diagram of a fifth embodiment of the present invention.

[Explanation of symbols]

1,21,31,41,51 1st heating coil 2A, 2B, 22A, 22B, 32A, 32B, 42A, 42B, 52A, 52B 2nd heating coil 43A, 43B, 53A, 53B 3rd heating coil 44A, 44B 4th heating coil D1, D2, D3, D4 High frequency power supply 10,20,30,40,50 Heated object 1AI, 1BI, 2AI, 2BI High frequency current flowing through heating coil 1AX, 1BX, 2AX, 2BX When high frequency current is applied Generated magnetic flux 1AXa, 1BXa, 2AXa, 2BXa Induced magnetic flux 1AIa, 1BIa, 2AIa, 2BIa Induced current

Claims (5)

[Claims] 1. A heating coil for inductively heating an object to be heated, and a high-frequency power supply for simultaneously supplying high-frequency power of a different frequency to each heating coil, wherein each heating coil is provided with a heating coil of another adjacent heating coil. An induction heating device, wherein an induction electromotive force generated by energization is arranged to be offset. 2. A heating device comprising: a plurality of heating coils, each of which has a coil surface directed to a heating portion of an object to be heated; and a plurality of high-frequency power supplies for outputting high-frequency power having different frequencies. Combination of an inner heating coil provided from the center of the portion and supplied by one high-frequency power supply, and a plurality of outer heating coils provided adjacently along the outer periphery of the inner heating coil and supplied by another high-frequency power supply Wherein the plurality of outer heating coils are connected in series in directions in which induced electromotive forces generated between the inner heating coil and the inner heating coil are offset from each other at positions equidistant from the inner heating coil. An induction heating device, characterized in that: 3. The induction heating apparatus according to claim 2, wherein said plurality of outer heating coils comprise pairs of heating coils having the same shape and dimensions. 4. The heating object is a bottomed container, and the plurality of heating coils are arranged so that each coil surface is along an outer bottom surface of the bottomed container. 4. The induction heating device according to 2 or 3. 5. A plurality of solenoidal heating coils arranged in a non-contact manner wound around a rod-shaped or linear object to be heated, and a plurality of high-frequency power supplies for outputting high-frequency powers of different frequencies, respectively. The plurality of heating coils are provided from the center of the array, and are provided with a center-side heating coil that is supplied with power by one high-frequency power supply, and are provided adjacent to the end of the center-side heating coil and supplied with power from another high-frequency power supply. And a plurality of end-side heating coils, wherein the plurality of end-side heating coils are located at positions equidistant from the center-side heating coil and between the center-side heating coil and the center-side heating coil. An induction heating device, which is connected in series in such a direction as to cancel generated induced electromotive forces.