JP3725249B2 - Induction heating device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction heating apparatus including a plurality of heating coils and a high-frequency power source that simultaneously supplies high-frequency power of different frequencies to the heating coils. This induction heating device, for example, as represented by an electromagnetic cooker, rice cooker, or high-speed filament heating, allows a high-frequency current to flow through the heating coil, and depending on the high-frequency magnetic field generated at this time, metal, magnetic material, or carbon An object to be heated formed of a material is induction-heated. As the heating coil, a flat spiral shape or a curved shape made of a litz wire or a copper pipe, a solenoid shape, or the like is used.
[0002]
[Prior art and problems to be solved by the invention]
In some recent induction heating apparatuses, one or a plurality of objects to be heated are induction-heated simultaneously by independently connecting a heating coil to a plurality of high-frequency power sources. However, when induction heating is performed by bringing a plurality of heating coils close to each other, magnetic fluxes generated between adjacent heating coils are linked to each other, causing mutual interference, resulting in the following problems.
[0003]
The first problem is that the output of the high-frequency power source connected to the heating coil is disturbed, the stabilization becomes impossible, and the heating temperature of the workpiece that is the object 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 oscillation operation itself becomes impossible, or damage is caused if a transistor is arranged in the output stage Sometimes.
[0004]
The second problem is that a very loud beat sound due to mutual interference is generated from the heating coil and the workpiece, which is not preferable in the work environment. For example, in the case of high frequency power supplies of 25 kHz and 28 kHz, no noise is generated due to a frequency higher than the human audible frequency in single heating, but in the case of simultaneous heating, noise of 3 kHz or its harmonic component which is a differential frequency is generated.
[0005]
Conventionally, in order to solve these problems, for example, a method of preventing mutual interference by providing a metal shield plate or a ring or a magnetic material around a plurality of heating coils (hereinafter referred to as a first conventional example), between heating coils There are proposed a method of separating a distance that does not interfere (hereinafter referred to as a second conventional example) and a method of preventing mutual interference by synchronously driving a plurality of high-frequency power sources to have the same output frequency (hereinafter referred to as a third conventional example). .
The contents of the first conventional example are described in detail in, for example, Japanese Patent Laid-Open Nos. 55-121297, 57-3388, and 02-301522. The contents of the second conventional example are described in, for example, JP-A-63-148588 and JP-A-08-66300, and the contents of the third conventional example are described in JP-A-01-267991. Yes.
[0006]
According to each conventional example described above, the intended purpose of preventing mutual interference can be achieved under predetermined conditions. However, the following problems to be solved remained.
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 very close. Further, in the second conventional example, a continuous heating distribution in which a plurality of heating coils are brought close cannot be obtained. In the third conventional example, in principle, mutual interference between high frequency power supplies does not occur, but the common drive circuit of each heating coil is forcibly driven at a specific frequency, so the optimum frequency of each resonance circuit is set. It cannot be optimally controlled. Therefore, the output fluctuates when there are load fluctuations, resonance circuit fluctuations, temperature characteristics, or changes with time. In particular, the output voltage and current phase of each high-frequency power supply cannot be fixed, which may cause a change in heating efficiency, or an excessive current may flow and adversely affect the heating coil. Further, in the third conventional example, since there is no viewpoint of actively using a plurality of frequencies for improving the heating distribution, a large planar area is simultaneously heated using a plurality of high-frequency power supplies that output power having different frequencies. In some cases, it may not be sufficiently applicable to applications in which the heating distribution is partially changed.
[0007]
Accordingly, an object of the present invention is to provide an improved induction heating apparatus capable of exhibiting an effect in an application for obtaining a target heating distribution by eliminating mutual interference during simultaneous induction heating by a plurality of heating coils. .
[0008]
[Means for Solving the Problems]
An induction heating apparatus of the present invention includes a plurality of heating coils that induction-heat an object to be heated, and a high-frequency power source that simultaneously supplies high-frequency power of different frequencies to each heating coil, and each heating coil is adjacent to another heating coil. In this arrangement, the induced electromotive force generated by energization of the heating coil is offset.
[0009]
Moreover, the following structure is employable as a modification of this invention.
The induction heating device of the first configuration includes a plurality of heating coils whose coil surfaces are each directed to a heated portion of an object to be heated, and a plurality of high-frequency power sources that output high-frequency power of different frequencies. The plurality of heating coils include a combination of an inner heating coil fed by one high frequency power source and a plurality of outer heating coils fed by another high frequency power source. The plurality of outer heating coils are composed of, for example, pairs of heating coils having the same shape and size, and the induced electromotive forces generated between the inner heating coils and the inner heating coils that are located at equal intervals from the inner heating coils are mutually connected. It is connected in series in the direction to cancel.
The inner heating coil is a heating coil provided from the center of the heating part, and the outer heating coil is a heating coil adjacently provided along the outer periphery of the inner heating coil. Only two sets of this induction heating device are always provided. 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 heating coil with respect to the fifth set of heating coils in the outer circumferential direction. The third set of heating coils is an outer heating coil.
[0010]
The induction heating apparatus having the above-described configuration can be used for a wider range of applications by changing the arrangement of the heating coils in accordance with the shape of the object to be heated. For example, when the object to be heated is a curved or cylindrical bottomed container, the plurality of heating coils are arranged such that each coil surface is along the outer bottom surface of the bottomed container.
[0011]
The induction heating device of the second configuration is suitable for the purpose of induction heating while moving the object to be heated at high speed, and is a plurality of solenoids wound and arranged in a non-contact manner on a rod-like or linear object to be heated. And a plurality of high-frequency power supplies that output high-frequency power having different frequencies. The plurality of heating coils includes a combination of a center side heating coil fed by one high frequency power source and a plurality of end side heating coils fed by another high frequency power source. The plurality of end-side heating coils are connected in series so as to cancel each other the induced electromotive force generated between the center-side heating coil and the center-side heating coil that are located at equal intervals from the center-side heating coil. 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 in the case of the first configuration that it is not intended to limit to two sets of heating coils.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
(First embodiment)
Fig.1 (a) is a front view of the induction heating apparatus which concerns on 1st Embodiment of this invention, (b) is the AA sectional view taken on the line.
The induction heating device includes a flat elliptical spiral first heating coil 1 and a flat plane of the same dimensions arranged in a symmetrical manner on the same plane with respect to the center of the first heating coil 1 and connected in series. And a second heating coil 2A, 2B having an elliptical spiral shape. On the coil surface side of each of the heating coils 1, 2 </ b> A, 2 </ b> B, a plate-like object to be heated 10 made of a material such as iron, stainless steel, or carbon is disposed at a predetermined interval. Are provided with a first power supply D1 for supplying a high-frequency current to the first 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. Each power source D1, D2 supplies currents having different frequencies to the respective heating coils 1, 2A, 2B, and is used for, for example, steel plate heating, billet heater, electromagnetic cooker, quenching and the like.
[0014]
In the induction heating apparatus having the above configuration, the operation when the heating coils 1, 2 </ b> A, and 2 </ b> B are simultaneously fed will be described with reference to FIGS. 2 (a) and 2 (b).
In FIG. 2A, when a current 2AI flows through the second heating coil 2A on the left side of the drawing, a magnetic flux 2AX is generated at the portion. When this magnetic flux 2AX is linked to 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 2AIa for generating a magnetic flux 2AXa in the opposite direction to the magnetic flux 2AX flows. . On the other hand, when a current 2BI flows through the right coil 2B, a magnetic flux 2BX is generated at that portion. When this magnetic flux 2BX is linked to the right side of the first heating coil 1, an induced electromotive force is generated on the right side of the first heating coil 1, and an induced current 2BIa for generating a magnetic flux 2BXa opposite to the magnetic flux 2BX flows. Since the second power supply D2 is connected in series to the second heating coils 2A and 2B, the induced currents 2BIa and 2AIa flow in the direction of canceling each other at the same level. Therefore, the 1st heating coil 1 does not receive the mutual interference by 2nd heating coil 2A, 2B at all.
[0015]
Similarly, when the first heating coil 1 is supplied with power from the first power supply D1, the induced currents generated in the second heating coils 2A and 2B located on both sides thereof are canceled out. FIG. 2B is a diagram showing this, and the induction currents 1AIa and 1BIa generated in the second heating coils 2A and 2B by the high-frequency currents 1AI and 1BI of the first heating coil 1 cancel each other out at the same level. Flow in the direction. Therefore, the second heating coils 2 </ b> A and 2 </ b> B do not receive any mutual interference from the first heating coil 1.
[0016]
Thus, since the mutual interference between the 1st heating coil 1 and the 2nd heating coils 2A and 2B of the right and left sides is canceled, the conventional problem in simultaneous power feeding can be solved. In addition, the original heating distribution scheduled by the heating coils 1, 2 </ b> A, 2 </ b> B can be obtained in the article to be heated 10.
[0017]
(Second Embodiment)
Next, an embodiment in the case of induction heating a disk-shaped object to be 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 is allowed to flow independently of each other. FIG. 3A is a plan view of each heating coil, and FIG. 3B is a cross-sectional view taken along line AA.
[0018]
Referring to FIG. 3A, the first heating coil 21 is disposed at a predetermined distance from the central portion of the bottom of the bottom surface of the object to be heated 20 made of a magnetic material, and the first heating coil 21 is arranged on the same surface. The second coils 22A and 22B connected in series are arranged so as to be symmetrically enclosed. A first power supply D1 and a second power supply D2 are connected to the heating coils 21, 22A, 22B in the direction shown in FIG. Each of the power sources D1 and D2 supplies currents having different frequencies to the heating coils 21, 22A and 22B.
[0019]
The operation when power is simultaneously supplied to the heating coils 21, 22A and 22B in such a coil arrangement and connection form is the same as that in the first embodiment, and mutual interference between the heating coils 21, 22A and 22B is caused. Offset. Therefore, the conventional problem at the time of simultaneous power feeding is solved, and the original heating distribution scheduled by the heating coils 21, 22A, 22B in the article to be heated 20 can be obtained.
[0020]
(Third embodiment)
Next, an embodiment in which a rod-like or linear object to be heated moves at high speed will be described with reference to FIG. In FIG. 4, 30 is a rod-like or linear object to be heated of a magnetic material such as iron or a non-magnetic stainless steel, and 31 is a solenoid-like first heating wound in a non-contact manner around the center of the object to be heated 30. Coils 32 </ b> A and 32 </ b> B are solenoid-like second heating coils of the same dimensions wound symmetrically from the center on both ends of the first heating coil 31. Each 2nd heating coil 32A, 32B has the same opposing space | interval with the 1st heating coil 31. FIG. A first power supply D1 is connected in series to the first heating coil 31, and the direction of the high-frequency current is relatively opposite to the first heating coil 31 in each of the second heating coils 32A and 32B. The 2nd power supply D2 is connected in series so that it may become. Each power source D1, D2 supplies currents having different frequencies to the heating coils 31, 32A, 32B.
[0021]
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 out. . In addition, a part of the magnetic flux 31X generated by the high-frequency current flowing in the first heating coil 31 becomes a leakage magnetic flux, and links each of the second heating coils 32A and 32B. The induced current generated in the heating coils 32A and 32B is canceled out. Therefore, the mutual interference between the first heating coil 31 and the second heating coils 32A and 32B at the time of simultaneous power feeding is canceled, respectively, and the original intended by the heating coils 31, 32A and 32B in the object to be heated 30. Can be obtained.
In particular, the penetration depth of the eddy current in the cross-sectional direction of the object to be heated 30 is changed by the first heating coil 31 and the second heating coils 32A and 32B by separating the frequency of the first and second power sources D1 and D2 by 10 times or more. The target heating distribution can be obtained by induction heating and feeding the article 30 to be heated at a high speed.
[0022]
(Fourth embodiment)
FIG. 5 shows an example in which simultaneous heating is performed by further increasing the number of high-frequency power sources that supply a high-frequency current to each heating coil and a heating coil that is wound around a rod-shaped or linear object to be heated. Is. In this case, the mutual interference between the first heating coil 41 located on the center side of the object to be heated 40 and the second heating coils 42A and 42B arranged at the symmetrical positions on the both end sides is offset. Is the same as in the third embodiment. In this embodiment, the third heating coils 43A and 43B are further arranged 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 source D3 is connected in series in the direction to be connected, and the fourth heating coils 44A and 44B are arranged on both end sides of the third heating coils 43A and 43B, and this occurs between the third heating coils 43A and 43B. A fourth power supply D4 is connected in series in such a direction that the induced electromotive forces cancel each other. The power sources D1, D2, D3, and D4 supply currents having different frequencies to the heating coils 41, 42A, 42B, 43A, 43B, 44A, and 44B, respectively.
[0023]
In such a coil arrangement and connection form, any heating coil cancels out mutual interference with other adjacent heating coils. Therefore, it is possible to easily obtain the original heating distribution planned by the heating coils 41, 42A, 42B, 43A, 43B, 44A, 44B, for example, the heating distribution in consideration of the penetration depth of the eddy current in the article 40 to be heated. it can. In addition, although the example at the time of winding up to 4 sets of heating coils was shown in FIG. 5, a several heating coil can be increased similarly.
[0024]
(Fifth embodiment)
Next, an embodiment in the case of induction heating the bottomed container will be described with reference to FIG. In the figure, reference numeral 50 denotes an example of the container, and the material thereof is the same as that of each of the above-described embodiments. In this embodiment, a flat spiral first heating coil 51 is disposed near the center of the bottom surface of the container 50, and a pair of flat elliptical spirals having the same dimensions are provided on both sides on the same plane as the first heating coil 51. Shaped second heating coils 52A, 52B are arranged. Further, third elliptical spiral coils 53 </ b> A and 53 </ b> B are arranged on both side surfaces of the container 50. A first power supply D1 is connected in series to the first heating coil 51, a second power supply D2 is connected in series to the second heating coils 52A and 52B, and a third power supply 3D is connected in series to the third heating coils 53A and 53B. Has been. Each power source D1, D2, D3 supplies currents having different frequencies to the heating coils 51, 52A, 52B, 53A, 53B.
[0025]
As described in the above embodiments, the mutual interference between the first heating coil 51 and the second heating coils 52A and 52B during energization is canceled out. By the same principle, the mutual interference between the second heating coils 52A and 52B and the third heating coils 53A and 53B is canceled. Therefore, it is possible to obtain the original heating distribution scheduled by the heating coils 51, 52A, 52B, 53A, 53B in the object to be heated 50.
In addition, a container is not limited to the example of FIG. 6, The thing of various shapes is applicable. For example, when the outer bottom surface is in a curved filed bowl shape like a wok, each heating coil 51, 52A, 52B, 53A, 53B may be arranged so that the coil surface is along the outer bottom surface. Or you may shape | mold the coil surface itself.
[0026]
As mentioned above, although this invention was demonstrated by several embodiment, this invention has a main point at the point which arrange | positions several heating coils so that the induced electromotive force generate | occur | produced by electricity supply of the other heating coil which adjoins may be offset. Therefore, it is not necessarily limited to the example of the above embodiment, and various design changes are possible.
[0027]
【The invention's effect】
As is clear from the above description, according to the present invention, there is no mutual interference when a plurality of heating coils are brought close to each other and power is supplied simultaneously, and it is possible to reliably prevent adverse effects on the high-frequency power source and occurrence of beat sounds. be able to. In addition, since the number of heating coils and high-frequency power supplies can be increased arbitrarily, partial heating is performed in consideration of the use of multiple frequency power to simultaneously heat a wide planar area entirely, and the penetration depth of eddy currents. It is possible to respond flexibly to usages.
[Brief description of the drawings]
1A is a plan view of a first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA.
2A is an explanatory view showing that the second heating coil does not interfere with the first heating coil, and FIG. 2B shows that the first heating coil does not interfere with the second heating coil. FIG.
3A is a plan view of a second embodiment of the present invention, and FIG. 3B is a cross-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 Second 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 Object to be heated
1AI, 1BI, 2AI, 2BI High-frequency current flowing through the heating coil
1AX, 1BX, 2AX, 2BX Magnetic flux generated when high-frequency current is applied
1AXa, 1BXa, 2AXa, 2BXa induced magnetic flux
1AIa, 1BIa, 2AIa, 2BIa induced current

Claims (1)

A plurality of solenoidal heating coils arranged in a non-contact manner around a rod-shaped or linear object to be heated, and a plurality of high-frequency power sources that output high-frequency power of different frequencies, respectively.
The plurality of heating coils are:
A central heating coil provided from the center of the array and fed by one high frequency power source;
Next to the end side of this center side heating coil, comprising a combination with a plurality of end side heating coils fed by other high frequency power supply,
The plurality of end-side heating coils are connected in series so that the induced electromotive forces generated between the plurality of end-side heating coils and the center-side heating coil are offset from each other at positions that are equidistant from the center-side heating coil. Characteristic induction heating device.

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