JP3272680B2 - Induction heating device - Google Patents

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 having a plurality of heating coils and a plurality of power supplies for supplying high-frequency currents having different frequencies to the respective heating coils. This induction heating device, as represented by, for example, high-speed wire heating, applies a high-frequency current to a heating coil, and a high-frequency magnetic field generated at this time causes an object to be heated formed of a metal, a magnetic material, or a carbon material. Is induction-heated. The heating coil has a hollow solenoid shape,
A flat spiral made of litz wire or copper pipe is used.

[0002]

2. Description of the Related Art There is a recent induction heating apparatus in which a heating coil is independently connected to a plurality of power supplies 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 power supply connected to the heating coil is disturbed, and the output cannot be stabilized, and 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 power supply is adversely affected, and the oscillation operation itself becomes impossible, or if the transistor is arranged in the output stage, it is damaged. Sometimes. The second problem is that a very loud beat sound is generated from the heating coil and the work due to mutual interference, which is not preferable in the working environment. For example, in the case of a power supply that outputs high-frequency currents of 25 kHz and 28 kHz, no noise is generated by single heating because the frequency is higher than the audible frequency of a person, but in the case of simultaneous heating, the noise of the differential frequency of 3 kHz or a harmonic component thereof is reduced. appear.

Conventionally, to solve these problems, for example, as shown in FIG. 5, a heating coil 62 supplied from a power source A61 and a heating coil 72 supplied from a power source B71 are provided.
A method of arranging an interference prevention member 80 made of a magnetic material or a ferromagnetic metal between the heating coils 6 adjacent to each other as shown in FIG.
The two power supplies 61, 72A, 72B, 72B, 72B are arranged such that the directions of the high-frequency currents supplied thereto are opposite to each other.
A method of devising the output of the 71 has been proposed. The former method is described in detail, for example, in JP-A-9-105558, and the latter method is described in, for example, JP-A-8-18.
No. 7971 can be referred to.

According to each conventional example, mutual interference when a plurality of heating coils are simultaneously supplied with power can be suppressed. However, each conventional example has a problem that it is not possible to sufficiently cope with a change in the mutual interference level due to a change in the material of the work or the heating mode. That is, when the load state changes due to a change in the material of the work, movement of the work, or the like, the fluctuating mutual interference level cannot be reduced by adjustment, and the power sources 61 and 71 cannot be stabilized. .

Accordingly, an object of the present invention is to provide a novel induction heating apparatus which can prevent mutual interference when an object to be heated is induction-heated using a plurality of heating coils. Another object of the present invention is to provide an induction heating apparatus that can effectively avoid a situation in which the operation or control of a power supply becomes unstable due to a change in a mutual interference level.

[0007]

An induction heating apparatus according to the present invention for solving the above-mentioned problems has a plurality of high-frequency circuits including a heating coil and a power supply, and a plurality of heating circuits supplied simultaneously by the power supplies of the respective high-frequency circuits. In an induction heating device for inductively heating an object to be heated by a coil, the heating coil of one high-frequency circuit has a reverse-coupling transformer for reversely coupling high-frequency circuits including adjacent heating coils. The generated interference electromotive force is canceled by the reverse coupling transformer.

According to another aspect of the present invention, there is provided an induction heating apparatus comprising: the reverse coupling transformer; interference detecting means for detecting an interference electromotive force generated in a heating coil of the other high-frequency circuit by a heating coil of one high-frequency circuit; Visualization means for visualizing the interference electromotive force detected by the detection means, wherein the interference electromotive force is canceled by the reverse coupling transformer and the interference electromotive force after cancellation is made visible by the visualization means. .

Another induction heating apparatus of the present invention has the reverse coupling transformer, interference detecting means, and coupling degree adjusting means for changing the coupling degree of the reverse coupling transformer, and the detection is performed by the interference detecting means. The coupling degree adjusting means is controlled so as to reduce the interference electromotive force. In this case, the reverse coupling transformer includes, for example, a primary core on which wiring of one high-frequency circuit is wound and a secondary core on which wiring of the other high-frequency circuit is wound in a direction opposite to the primary core. Wherein the coupling degree adjusting means includes a driving mechanism that drives at least one of the primary iron core and the secondary iron core based on a detection result by the interference detecting means to change a gap between the iron cores. Things.

[0010] The plurality of heating coils are preferably pairs of heating coils having the same shape and dimensions. The coils may be wound in the same direction around the cylindrical body that accommodates the object to be heated, and may be arranged so that each coil surface is along the outer bottom surface of the bottomed container. .

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an induction heating device using two heating coils. The induction heating apparatus 1 includes a first high-frequency circuit including a power supply A11 and a heating coil A12, and a second high-frequency circuit including a power supply B21 and a heating coil B22.
And a high-frequency circuit. Each high-frequency circuit is reverse-coupled by a reverse-coupling transformer 30. Power supply A11 and power supply B
21 includes an oscillator for oscillating signals of different frequencies, and a current generating circuit for generating a high-frequency current based on the signal oscillated by the oscillator. The generated high-frequency current is supplied to the heating coil 12 of the high-frequency circuit. , 22.

Each of the heating coils 12 and 22 is a hollow solenoid coil having the same shape and diameter, and the workpiece 10 to be heated can move freely in the hollow portions of the heating coils 12 and 22. ing.

The second high-frequency circuit further includes a detection coil 4
0 is inserted and connected. The detection coil 40 detects an interference current flowing in the second high-frequency circuit based on an interference electromotive force generated in the heating coil B22 by the heating coil A12. The detected interference current is amplified by the high-frequency amplifier circuit 41, synchronously detected at the oscillation frequency of the power supply A11, and sent to the meter circuit 42. Meter circuit 42
Displays this interference current on a predetermined scale.

As shown in FIG. 2, for example, the reverse coupling transformer 30 has a primary iron core 31 in which the wiring of the first high-frequency circuit is wound in the forward direction, and a wiring in which the wiring of the second high-frequency circuit is wound in the reverse direction. The secondary iron core 32 is opposed to the secondary iron core 32 at a constant gap. With such a configuration, the above-described interference electromotive force is canceled out, so that abnormal oscillation of the power supply A11 and the power supply 21 can be prevented. The amount of cancellation of the interference electromotive force, that is, the degree of coupling of the reverse coupling transformer 30 is determined by the
It is determined by the gap between them. The interference current displayed by the meter circuit 42 is based on the interference electromotive force after the cancellation.

If the workpiece 10 to be heated is of a variety of materials and shapes, or the workpiece 10 moves during induction heating or is in a no-load state during induction heating, the level of mutual interference is reduced. Therefore, it is preferable to change the degree of coupling of the reverse coupling transformer 30 as needed.

In order to cope with such a situation, in this embodiment, a coupling degree adjusting means is provided. The coupling degree adjusting means includes:
Specifically, the displacement mechanism 43 of the secondary core 32 shown in FIG.
And a motor circuit 44 for controlling the displacement mechanism 43 to adjust the gap between the primary iron core 31 and the secondary iron core 32. The motor circuit 44 includes the high-frequency amplification circuit 41
On the basis of the output of (1), the interference current approaches the zero value. By using the above-described meter circuit 42 together, the current coupling degree can be visually recognized. As described above, in the induction heating apparatus 1 of the present embodiment, the degree of coupling of the reverse coupling transformer 30 automatically changes in response to the change in the level of mutual interference.
11. The operation of the power supply B21 is always stabilized.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The induction heating apparatus 1 of the above embodiment can be applied to high-speed linear heating, beverage can heating in a vending machine, electromagnetic cooking, and the like. When heating a linear work or a beverage can, a litz wire or the like is wound around the cylindrical body accommodating them in the same direction, and the heating coils A12 and B22 are heated.
And

When heating the electromagnetic cooking container,
A heating coil A is formed by winding a litz wire along the outer bottom surface of the container, and a heating coil B is formed by winding a litz wire along the outer surface of the container. For example, FIG. 4 is a schematic configuration diagram of an induction heating device when heating an electromagnetic cooking container. For convenience, elements having the same functions as those in FIG. 1 are denoted by the same reference numerals. A flat spiral heating coil A12 is arranged near the center of the bottom surface of the container 50, and the heating coil A12 and the power supply A11 form a first high-frequency circuit. A hollow spiral heating coil B22 along the side surface of the container 50 is disposed on the side surface of the container 50, and the heating coil B22 and the power supply B21 form a second high-frequency circuit. Each high frequency circuit is reverse-coupled by a reverse coupling transformer 30.

As described in the above embodiment, the mutual interference between the heating coils A12 and B22 is canceled by the reverse coupling transformer 30 when the power is supplied. Therefore, in the container 50, it is possible to obtain the intended heating distribution by the heating coils A12 and B22.

The shape of the container 50 is not limited to the shape shown in FIG. 4, but various shapes are applicable. For example, when the outer surface is curved and mortar-shaped, such as a wok, the heating coils A12 and B22 may be arranged so that the coil surfaces are along the outer surface of the container. Alternatively, the coil surface itself may be formed.

[0021]

As is clear from the above description,
In the present invention, the mutual interference between the plurality of high-frequency circuits including the heating coil and the power supply is canceled by the reverse coupling transformer, so that the adverse effect on the power supply when the plurality of heating coils are brought close to and simultaneously supplied with power is simplified. Can be prevented. Further, when the mutual interference level fluctuates, the degree of coupling of the reverse coupling transformer is automatically adjusted correspondingly, so that the operation of the induction heating device is stabilized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an induction heating device according to an embodiment of the present invention.

FIG. 2 is a structural explanatory view of the reverse coupling transformer according to the present embodiment.

FIG. 3 is a structural explanatory view showing a specific example of a coupling degree adjusting unit according to the embodiment;

FIG. 4 is a schematic configuration diagram when the present invention is applied to heating of an electromagnetic cooking container.

FIG. 5 is a schematic configuration diagram of a conventional induction heating device.

FIG. 6 is a schematic configuration diagram of another conventional induction heating device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Induction heating apparatus 10 Heated object (work) 11, 21, 61, 71 Power supply 12, 22, 62, 62A, 62B, 72, 72A, 7
2B Heating coil 30 Reverse coupling transformer 31, 32 Transformer core 40 Interference current detection coil 41 High frequency amplifier circuit 42 Meter circuit 43 Motor circuit 50 Container for electromagnetic cooking

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05B 6/10 H05B 6/44 H05B 6/06 H05B 6/12

Claims (6)

(57) [Claims] 1. An induction heating apparatus comprising: a plurality of high-frequency circuits including a heating coil and a power supply, wherein the plurality of heating coils supplied with power by the respective high-frequency circuits simultaneously heat the object to be heated. A reverse-coupling transformer for reverse-coupling high-frequency circuits including coils, interference detection means for detecting an interference electromotive force generated in a heating coil of the other high-frequency circuit by a heating coil of one high-frequency circuit, and detection by the interference detection means Visualizing means for visualizing the generated interference electromotive force, wherein the interference electromotive force is canceled by the reverse coupling transformer and the interference electromotive force after cancellation is made visible by the visualization means. Induction heating device. 2. An induction heating apparatus comprising: a plurality of high-frequency circuits each including a heating coil and a power supply; wherein the plurality of heating coils simultaneously supplied with power from the respective high-frequency circuits inductively heat an object to be heated; A reverse-coupling transformer for reverse-coupling high-frequency circuits including coils; an interference detection unit for detecting an interference electromotive force generated in a heating coil of the other high-frequency circuit by a heating coil of one high-frequency circuit; and a coupling of the reverse-coupling transformer And a coupling degree adjusting means for changing the degree of coupling, wherein the coupling degree adjusting means is controlled in a direction to reduce the interference electromotive force detected by the interference detecting means. 3. The reverse-coupled transformer includes a primary core on which wiring of one high-frequency circuit is wound and a secondary core on which wiring of the other high-frequency circuit is wound in a direction opposite to the primary core. Wherein the coupling degree adjusting means is configured to include a drive mechanism that drives at least one of the primary iron core and the secondary iron core based on a detection result of the interference detection means to change a gap between the iron cores. The induction heating device according to claim 2, wherein 4. The heating coil of claim 2, wherein said plurality of heating coils comprise pairs of heating coils of the same shape and size.
The induction heating device according to any one of claims 1 to 3 . Wherein said plurality of heating coils, characterized in that they are respectively wound in the same direction to the tubular body for accommodating the object to be heated, of according to one of claims 1 to 3 Induction heating device. 6. The heating object is a bottomed container, and the plurality of heating coils are arranged so that respective coil surfaces are along an outer bottom surface and an outer surface of the bottomed container. to, the induction heating apparatus according to one of claims 1 to 3.