JPH11167979A - High frequency heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the breakage of the constituting elements of a high fre quency heating power source due to voltage surge. SOLUTION: Plural arms of semiconductor switch elements 311 to 322 are connected in parallel between the positive and the negative terminals of a DC power source, respective outputs are connected to respective one side terminals of plural heating coils 51, 52. Furthermore, one more series arm of respective semiconductor switch elements 33, 34 are connected additionally in parallel, and the respective other ends of the plural heating coils 51, 52 are commonly connected to the output of the additionally connected series arm. As a result, the switching of the heating coils 51, 52 becomes possible without the use of an electromagnetic contactor, and element breakage due to a voltage surge is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating device for high-frequency heating an object to be heated.

[0002]

2. Description of the Related Art FIG. 10 shows a conventional high-frequency heating apparatus for outputting a high-frequency current from one high-frequency power supply to two heating coils. The rectifier 1 supplies a direct current to a high frequency power supply 3 composed of a thyristor via a reactor 2.
The gate drive circuit 6 receives a control signal from the control device 7,
A gate signal is applied to each semiconductor switch element of the high frequency power supply 3. Two electromagnetic contactors 81 and 82, capacitors 41 and 42, heating coil 5 are connected in parallel from the output terminal of high-frequency power supply 3.
1, 52. The loss of each heating coil due to heating energy to the object to be heated is represented here by a resistor connected in series with the heating coil.

[0003] Heating of an object to be heated by a plurality of heating coils is performed as follows. That is, the electromagnetic contactor 8
When the operation command is given to the control device 7 by closing 1 and 82, the control signal is input to the gate drive circuit 6, and the gate signal is input to each of the semiconductor switch elements 31 to 34. In the steady state, the semiconductor switch elements 31 and 34 of the high-frequency power supply 3 are controlled in such a manner that they are fired → 32 and 33 are fired → to output a high-frequency current. The rectifier 1 controls the DC voltage to control the magnitude of the DC current. As a result, the heating energy supplied to the heating coils 51 and 52 to the object to be heated can be controlled. When the operation is stopped, the control signal and the gate signal are cut off by turning off the operation command, the output of the high-frequency power supply 3 is turned off, and the heating of the object to be heated by the heating coil is stopped. Next, when heating the object to be heated only by the heating coil 51, the operation is performed with the electromagnetic contactor 82 opened when the operation is stopped. When the heating coil 52 is also added, the operation is stopped and then the electromagnetic contactor 82 is closed to operate.

[0004]

In the high frequency heating apparatus for heating an object to be heated by the plurality of heating coils, for example, when the heating by the heating coil 51 is completed before the heating by the heating coil 52, or 51
Is different from the heating energy by the heating coil 52, the electromagnetic contactor 81 cannot be opened while the high-frequency power supply 3 is outputting the high-frequency current, for example, when switching the output of the high-frequency current in a time-division manner. This is because the semiconductor switch element of the high-frequency power supply 3 is damaged by a surge voltage generated when the electromagnetic contactor 81 is opened. Therefore, an object of the present invention is to prevent the semiconductor switch element of the high-frequency power supply 3 from being damaged by a surge voltage.

[0005]

In order to solve the above-mentioned problem, according to the invention of claim 1, between the positive and negative terminals of a DC power supply, the anode side of the semiconductor switch element is defined as a positive side and the cathode side is defined as a negative side. A plurality of serial arms connected in series are connected in parallel, each middle point is connected to one terminal of each of the plurality of heating coils, and one additional serial arm is connected in parallel. The midpoint of the series arm is connected to the other terminal of each of the plurality of heating coils. In the invention of claim 2, a plurality of serial arms connected in series between the positive and negative terminals of the DC power supply, with the anode side of the semiconductor switch element being the positive side and the cathode side being the negative side, are connected in parallel. From the middle point to one terminal of each of the plurality of heating coils, and further connect a plurality of series arms in parallel, and connect the middle point of the additionally connected series arm to the other of each of the plurality of heating coils. It is connected to the terminal.

[0006]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. The rectifier 1 supplies a direct current to a high frequency power supply 3 composed of, for example, a thyristor via a reactor 2. The gate drive circuit 6 receives a control signal from the control device 7 and supplies a gate signal to each semiconductor switch element of the high-frequency power supply 3. One of the capacitor 41 and the heating coil 51 is connected to the output terminal of the arm composed of the semiconductor switch elements 311 and 312 of the high frequency power supply 3, and the condenser 42 is connected to the output terminal of the arm composed of the semiconductor switch elements 321 and 322. , One of the heating coils 52 is connected. Capacitors 41, 4 are connected to the output terminals of the arm composed of the semiconductor switch elements 33, 34.
2. The other of the heating coils 51 and 52 is commonly connected.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. The rectifier 1 supplies a direct current to a high frequency power supply 3 composed of, for example, a thyristor via a reactor 2. The gate drive circuit 6 receives a control signal from the control device 7 and supplies a gate signal to each semiconductor switch element of the high-frequency power supply 3. Semiconductor switch element 31 of high frequency power supply 3
The capacitor 41 and the heating coil 51 are connected in parallel between the output terminal of the arm composed of the semiconductor switch elements 313 and 314 and the output terminal of the arm composed of the semiconductor switch elements 313 and 314. 322, the output terminal of the arm composed of
A condenser 42 and a heating coil 52 are connected in parallel between the output terminal of the arm constituted by 23 and 324.

Here, the circuit operation of FIG. 1 will be described with reference to FIGS.
This will be described with reference to FIGS. As shown in FIG. 3, the semiconductor switch elements 311 and 34 of the high-frequency power supply 3 are fired (（).
(See the mark), the current from the high-frequency power supply 3 flows through the capacitor 41 and the heating coil 51 as shown by arrows. FIG. 9 shows the voltage and current waveforms of each part in the steady state. 2A shows the output current, FIG. 2B shows the output voltage, FIG. 2C shows the current flowing through the capacitor, and FIG. 2D shows the current flowing through the heating coil.

When the output voltage Vo of the high frequency power supply 3 is positive and the current flowing through the heating coil is ≒ 0, the semiconductor switching element 3
When a gate signal is given to 21, the voltage Vo is applied to a circuit in which the capacitor 42 is connected in series between the anode and the cathode of the semiconductor switch element 321, so that the value obtained by subtracting the voltage of the capacitor 42 from the output voltage Vo is the semiconductor voltage. The voltage is applied to the switch element 321, and when the value is positive, the ignition occurs. The state at that time is shown in FIG. The semiconductor switch element 321 is marked with a circle to indicate that it has been fired.

At this time, the electric charge of the capacitor 41 moves to the capacitor 42, thereby causing the semiconductor switch element 3
The current flowing through the capacitor 41 through 11 decreases,
The current flowing through the capacitor 42 through the semiconductor switch element 321 increases. Then, the semiconductor switch element 3
The current flowing through the capacitor 41 through the capacitor 11 is inverted in polarity by a wiring inductance (not shown), and the semiconductor switch element 311 is extinguished. Thereby, as shown in FIG. 5, the semiconductor switch elements 321 and 34 are ignited, and the high-frequency power supply 3
High frequency current will flow. The above heating coil 51
The switching of the high-frequency current from the heating coil 52 to the heating coil 51 is also possible in the same manner as the switching of the high-frequency current from
Switching from the semiconductor switching element 321 to the semiconductor switching element 311 is possible in the same manner as switching from 1 to the semiconductor switching element 321.

Next, the operation of FIG. 2 will be described with reference to FIGS.
This will be described with reference to FIG. Now, as shown in FIG. 6, assuming that the semiconductor switch element 311 and the semiconductor switch element 314 of the high-frequency power supply 3 are ignited (see a circle), the current from the high-frequency power supply 3 is supplied to the capacitor 41 and the heating coil 5.
1 flows as indicated by the arrow. The voltage and current waveforms of the respective parts in the steady state are the same as in FIG. 9; FIG. 9A shows the output current, FIG. 9B shows the output voltage, FIG. 9C shows the current flowing through the capacitor, and FIG. The current flowing through the heating coil is shown.

When the output voltage Vo of the high frequency power supply 3 is positive and the current flowing through the heating coil is ≒ 0, the semiconductor switch element 3
When a gate signal is applied to the gates 21 and 324, the anode and cathode of the semiconductor switch element 321 and the capacitor 4
Since Vo is applied to a circuit connected in series with the semiconductor switch element 324 and the semiconductor switch element 324, the value obtained by subtracting the voltage of the capacitor 42 from the output voltage Vo is the semiconductor switch element 32
1,324, and when the value is positive, it fires.
FIG. 7 shows the state at that time. Semiconductor switch element 32
A circle mark is added to 1,324 to indicate that firing has occurred.

At this time, the electric charge of the capacitor 41 moves to the capacitor 42, and the semiconductor switch element 3
11, the capacitor 41, the semiconductor switch element 314
Current flowing through the semiconductor switching element 321 decreases.
, The current flowing through the capacitor 42 and the semiconductor switch element 324 increases. After that, the capacitor 41 and the semiconductor switch element 31 pass through the semiconductor switch element 311.
4, the polarity of the current flowing through the semiconductor switch element 311,
314 extinguishes the arc. As a result, as shown in FIG. 8, the semiconductor switch elements 321 and 324 are fired, and a high-frequency current flows from the high-frequency power supply 3 to the capacitor 42 and the heating coil 52.

In the same manner as the switching of the high-frequency current from the heating coils 51 to 52, the switching of the output of the high-frequency current from the heating coil 52 to the heating coil 51 is also possible. Switching from the semiconductor switching elements 312 and 313 to the semiconductor switching elements 322 and 323 and switching from the semiconductor switching elements 311 and 314 to the semiconductor switching elements 32
Switching to 2,323 is also possible. Needless to say, it is possible to switch to high-frequency current output to one heating coil when outputting high-frequency current to two heating coils.

[0015]

According to the present invention, a high frequency current is output to one heating coil only by adding at least one series arm of a semiconductor switch element without using an electromagnetic contactor or the like.
The advantage is obtained that the output of the high-frequency current can be switched to another heating coil. As a result, each object to be heated is heated in a time-division manner, and by arbitrarily adjusting the output time of the high-frequency current to each heating coil, each object to be heated requiring different heating energy is heated. When the heating is completed, the output of the high-frequency current to the heating coil of the object to be heated can be stopped.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a first operation of FIG. 1;

FIG. 4 is a diagram illustrating a second operation of FIG. 1;

FIG. 5 is a diagram illustrating a third operation of FIG. 1;

FIG. 6 is a first operation explanatory diagram of FIG. 2;

FIG. 7 is a diagram illustrating a second operation of FIG. 2;

FIG. 8 is a diagram illustrating a third operation of FIG. 2;

FIG. 9 is a current and voltage waveform diagram of each part in the steady state of FIGS. 1 and 2;

FIG. 10 is a circuit diagram showing a conventional example of a high-frequency heating device.

[Explanation of symbols]

1. Rectifier. 2 ... reactor, 3 ... high frequency power supply, 41,
42: condenser, 51, 52: heating coil, 6: gate drive circuit, 7: control device.

Claims (2)

[Claims] 1. A semiconductor switching device comprising a positive terminal and a negative terminal connected between a positive terminal and a negative terminal of a DC power supply.
A plurality of serial arms connected in series are connected in parallel, each middle point is connected to one terminal of each of the plurality of heating coils, and one additional serial arm is connected in parallel. A high-frequency heating device, wherein a middle point of the series arm is connected to each of the other terminals of the plurality of heating coils. 2. A semiconductor switching device according to claim 1, wherein an anode side is a positive side and a cathode side is a negative side between positive and negative terminals of a DC power supply.
A plurality of serial arms connected in series are connected in parallel, each middle point is connected to one terminal of each of the plurality of heating coils, and further a plurality of serial arms are connected in parallel, and this additional connection is made. A high-frequency heating device, wherein a middle point of the series arm is connected to each of the other terminals of the plurality of heating coils.