JP4023787B2 - Power supply for high frequency heating - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency heating power supply device that can rapidly heat up a high-frequency power for heating in a short pulse and quickly and efficiently inductively heat a thin and small object to be heated in a short time when heating power is input. .
[0002]
[Prior art]
Conventionally, as a power supply device for this type of high-frequency heating, a power supply device in which the output power during heating rises as fast as possible in order to quench a thin-walled, small metal part (object to be heated) by high-frequency induction heating. It was necessary. When heated for a long time with a small electric power, heat is conducted to an undesired portion, and a good quenching pattern cannot be obtained. Further, if the heating power is too large, overheating may occur and the heated part of the part may be melted.
For this reason, in order to perform stable quenching on this type of heated object, a high-frequency heating power supply device that can quickly output power and sufficiently manage power has been conventionally required.
[0003]
FIG. 8 shows a circuit configuration of a conventional high-frequency heating power supply device.
Since high frequency is generally required for induction hardening of a small object 100 to be heated made of a metal material, a vacuum tube oscillator capable of oscillation up to 5 MHz band will be described as an example.
[0004]
The configuration of the high-frequency heating power supply device 101 shown in FIG. 8 includes two power thyristors 11a connected in parallel to each other in the opposite direction and connected to a three-phase commercial AC power supply E via, for example, an electromagnetic switch 9. 11b, a step-up transformer 12, a high-voltage rectifier diode 13, an LC smoothing circuit 14, a vacuum tube self-excited oscillation circuit 15, and a matching transformer 16, and a high-frequency heating coil 3 are connected in series, and the heating coil 3, the object to be heated 100 is heated at high frequency, and further includes an error amplifier 4, an output setting device 5, and a phase controller 6.
[0005]
The high voltage rectified diode 13 detects the high voltage output voltage after rectification by the resistors 17a and 17b for resistance voltage division and inputs them to the error amplifier 4 as feedback signals.
The feedback signal is compared with the set value (voltage) of the output setting unit 5 for setting the heating power, and the output voltage after rectification is stabilized by controlling the phase controller 6 so that the error becomes zero. ing. The set value of the output setting device 5 is turned on and off by a switch 18. When the switch is turned off, the output voltage becomes zero, and when the switch is turned on, the output voltage setting value (voltage value) is set. The switch 18 is driven by a heating ON / OFF signal of the power supply device.
The phase controller 6 adjusts the firing angles of the thyristors 11a and 11b of the main circuit unit 2 in accordance with the error voltage (error signal) from the error amplifier 4 in synchronization with the frequency of the commercial AC power supply E. Yes.
[0006]
[Problems to be solved by the invention]
By the way, in the conventional high-frequency heating power supply device 101, when the object to be heated 100 is to be heated for a short time of 1 second or less using the power supply device 101, high-frequency output power (or heating coil current) is used. ) Has a very slow rise time and it is difficult to perform good quenching.
In order to increase the rise time of the high-frequency output power (or heating coil current), an attempt was made to reduce the error integral constant of the error amplifier 4 to increase the speed, but the stable use is 100 ms (millimeters). Second) to about 200 ms.
[0007]
Further, when the error integration constant of the error amplifier 4 is reduced, the feedback is distorted. The reason for this irregularity is that the main circuit section 2 is constituted by a reactor, a capacitor, and the like, and the feedback loop is a so-called secondary delay. Further, the constants of the reactor and the capacitor cannot be reduced because the frequency of the commercial AC power source is controlled every 10 ms by the thyristor.
[0008]
The present invention has been made in view of the above points, and its object is to solve the above problems, a high-frequency output power (or heating coil current) has a fast rise time, and high-frequency heating power that does not cause turbulence in the feedback loop To provide an apparatus.
[0009]
Another object of the present invention is to provide a high-frequency heating power supply device capable of performing high-frequency heating on a thin and small object to be heated in a short pulse of 1 second or less, for example.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a configuration of the present invention includes a main circuit unit including a thyristor connected to an AC power source and an oscillator that outputs high-frequency heating power using a DC output voltage of the thyristor, and an ignition phase angle of the thyristor. In a power supply device including a phase controller that outputs a signal for controlling the power supply, the power supply device is as follows.
[0011]
A mini-model circuit unit that is substantially equivalent in electrical characteristics to the main circuit unit and includes a thyristor having a smaller capacity than the thyristor. The mini model circuit unit is arranged in parallel with the main circuit unit and controls the output of the phase controller. The mini-model circuit unit in which the ignition phase angle of the small-capacity thyristor is controlled by a signal, an output setting unit that sets the output of the heating power of the main circuit unit, and the equivalent of the oscillator of the mini-model circuit unit An error amplifier for comparing an output voltage from both ends of the resistor with a set voltage of the output setter and sending the error voltage to the phase controller, and the mini model circuit according to an output control signal of the phase controller Based on a signal for controlling the ignition phase angle of the small-capacity thyristor so that the output voltage from both ends of the equivalent resistor of the oscillator matches the set voltage of the output setting device, the main circuit unit It is a high-frequency heating power supply device for controlling the ignition phase angle of the thyristor.
[0012]
The frequency of the high-frequency heating power output from the oscillator is a high-frequency heating power supply device having a frequency of 100 kHz to 5 MHz.
[0013]
The mini-model circuit unit is a high-frequency heating power unit that is a passive circuit including the small-capacity thyristor connected to the AC power source, a rectifier circuit, and an equivalent resistance of an oscillator of the main circuit unit.
[0014]
Furthermore, a high-frequency heating for conducting or blocking a signal for controlling the ignition phase angle of the thyristor of the main circuit unit by the phase controller by a signal for turning on / off the heating power of the main circuit unit via an AND gate circuit Power supply device.
[0015]
Since the high-frequency heating power supply device of the present invention is configured as described above, a mini-model circuit unit that approximates the main circuit unit so that the electrical characteristics are substantially equivalent to the AC power supply, The mini-model circuit unit is installed in parallel with the main circuit unit, and the feedback state is always applied to the mini-model circuit unit. The control signal of the feedback is branched to control the main circuit unit. And the output of the high frequency electric power from the said main circuit part can be started or stopped by conducting or interrupting | blocking the control signal branched to the main circuit part.
[0016]
Further, the effect of the present invention is that the high-frequency output power (or heating coil current) rises at a high speed, and can always obtain a constant output even when the connected AC power supply voltage fluctuates. A power supply can be realized.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram including a circuit diagram of a power supply device 1 showing an embodiment of the power supply device 1 for high-frequency heating according to the present invention. The same members as those in FIG. Is omitted.
[0018]
In FIG. 1, the high-frequency heating power supply device 1 is a device that uses a high-frequency heating coil 3 to inductively heat a small object to be heated 100 that is substantially in a rod shape at a frequency of about 1 MHz. The frequency of the high frequency heating power of the power supply device 1 is preferably 100 kHz to 5 MHz.
[0019]
The high-frequency heating power supply device 1 includes a main circuit unit 2, a mini model circuit unit 20, a high-frequency heating coil 3, an error amplifier 4, and an output setting unit 5 for setting the heating power output of the main circuit unit 2. And a phase controller 6 and an AND gate circuit 7.
[0020]
The main circuit unit 2 includes two power thyristors 11a and 11b connected to a three-phase commercial AC power source E via, for example, an electromagnetic switch 9 and connected in parallel and in opposite directions. Boosting transformer 12 for boosting the alternating voltage from the thyristors 11a and 11b, a high voltage rectifying diode 13 for rectifying the boosted alternating voltage, an LC smoothing circuit 14 for obtaining a direct current voltage after rectification, and the direct current voltage The vacuum tube self-excited oscillation circuit 15 that outputs high-frequency heating power by the above and a matching transformer 16 that supplies the heating coil 3 with the high-frequency power output from the self-excited oscillation circuit 15 are connected in series. The vacuum tube self-excited oscillation circuit 15 may be an oscillation circuit using other semiconductor elements.
Then, the object to be heated 100 is heated at high frequency via the matching transformer 16 and the heating coil 3 by the high frequency power output from the self-excited oscillation circuit 15.
[0021]
The mini model circuit unit 20 is composed of a passive circuit whose electric characteristics are substantially equivalent to those of the main circuit unit 2. However, the same parts are not used just to make the electrical characteristics equivalent. The thyristors 21a and 21b correspond to the thyristors 11a and 11b of the main circuit section 2. The current capacity of the thyristors 21a and 21b is a small capacity thyristor such as 1A to 0.1A. The transformer 22 is not a step-up transformer but a small step-down transformer of several watts, and its secondary output voltage is about 0V to 10V. A resistor 25 connected in series with the rectifier diode 23 and the series reactor 24 is an equivalent parallel resistor in a portion corresponding to the self-excited oscillation circuit 15 of the main circuit unit 2.
[0022]
That is, the configuration of the mini-model circuit unit 20 is smaller than that of the two power thyristors 11a and 11b connected to the three-phase commercial AC power source E and connected in parallel and in opposite directions. Capacitor thyristors 21a and 21b, a step-down transformer 22 that steps down the AC voltage from the thyristors 21a and 21b, a low-voltage rectifier diode 23 that rectifies the stepped-down AC voltage, and a series for obtaining a DC voltage after rectification. An equivalent parallel resistance 25 of the vacuum tube self-oscillation circuit 15 including a reactor 24 and a load side (including the matching transformer 16 and the heating coil 3 heating the object to be heated 100) to output the DC voltage. Each of which is connected in series.
The mini model circuit unit 20 is arranged and connected in parallel with the main circuit unit 2 with respect to the three-phase commercial AC power source E.
[0023]
The output voltage across the equivalent parallel resistor 25 of the self-excited oscillation circuit 15 of the mini model circuit unit 20 is input to the error amplifier 4 as a feedback signal.
In the error amplifier 4, the output voltage fed back from the mini-model circuit unit 20 is compared with a set voltage as a set value of the output setting unit 5, and the error voltage is sent to the phase controller 6. .
The phase controller 6 is synchronized with the frequency of the three-phase commercial AC power supply E.
[0024]
Then, the phase controller 6 uses the output signal so that the output voltage from both ends of the equivalent parallel resistor 25 of the mini-model circuit unit 20 matches the set voltage of the output setter 5. The ignition phase angle of the thyristors 21a and 21b of the model circuit unit 20 is controlled. When the output voltage from both ends of the equivalent parallel resistor 25 is 0V, the thyristors 21a and 21b are in a non-conductive state at all angles, and at a full voltage of 10V, they are in a full-angle conductive state (completely conductive state).
[0025]
Here, in FIG. 2, the DC error voltage (vertical axis) output from both ends of the equivalent parallel resistor 25 of the mini-model circuit unit 20 with respect to the control error voltage (horizontal axis) sent from the error amplifier 4 is shown. Show the relationship. The output DC voltage of the mini-model circuit 20 shown on the vertical axis corresponds to the rectified voltage in the smoothing circuit 14 in the main circuit 2 or the coil current of the heating coil 3.
[0026]
In FIG. 2, the relationship between the control error voltage on the horizontal axis and the output DC voltage on the vertical axis changes the slope of the curve in proportion to the voltage of the commercial AC power supply E. When the AC power supply voltage is 200V, for example, the curve I is shown. When the AC power supply voltage is 220V, the curve II is shown. When the AC power supply voltage decreases to 180V, the curve III is shown.
[0027]
The relationship between the control error voltage and the output DC voltage when the AC power supply voltage changes will be described with reference to FIG.
Now, when the AC power supply voltage is 200 V, the control error voltage is set to the value of v1, and the output DC voltage V from the curve I is obtained. Next, when the AC power supply voltage rises to 220V, the control error voltage is lowered to v2 to obtain an output DC voltage of V from curve II. When the AC power supply voltage drops to 180V, the control error voltage is increased to v3, and an output DC voltage of V is obtained from curve III.
[0028]
When the AC power supply voltage changes from 220V → 200V → 180V, the control error voltage is changed from v2 → v1 → v3 to always maintain a constant output DC voltage of V.
When the thyristors 11a and 11b of the main circuit section 2 are controlled by the output signal of the phase controller 6 in response to such fluctuations in the AC power supply voltage, the heating coil of the main circuit section 2 is controlled. The coil current 3 can always be maintained at a constant coil current even if the AC power supply voltage fluctuates from 220 V to 200 V to 180 V.
[0029]
In FIG. 1, the phase controller 6 controls the firing phase angle of the thyristors 21 a and 21 b of the mini-model circuit unit 20 according to the output signal, and at the same time inputs it to one input terminal of the AND gate circuit 7. The firing phase angle of the thyristors 11a and 11b of the main circuit section 2 is controlled through the AND gate circuit 7.
Then, a signal for turning on / off the heating power of the main circuit unit 2 is input to the other input terminal of the AND gate circuit 7, and the main signal by the phase controller 6 is passed through the AND gate circuit 7 by the on / off signal. A signal for controlling the ignition phase angle of the thyristors 11a and 11b of the circuit unit 2 is made conductive or interrupted.
[0030]
That is, in the AND gate circuit 7, when the heating power is off, the gate is cut off, the control signal to the thyristors 11a and 11b of the main circuit section 2 is cut off, and when the heating power is on, the mini model is turned on. The same control signal as the firing angle control signal of the thyristors 21 a and 21 b of the circuit unit 20 is conducted to the gates of the thyristors 11 a and 11 b of the main circuit unit 2 through the AND gate circuit 7 and set in the output setting unit 5. The same high frequency power as the set value is output from the main circuit unit 2.
[0031]
The heating power on / off switching is performed at a high speed of several μs or less because a semiconductor switch such as a photocoupler is used. Therefore, the main circuit unit 2 can always be turned on / off in a state in which the fluctuation of the voltage of the commercial AC power supply is corrected, so that it is possible to generate a high-speed high-frequency current in which the coil current of the heating coil 3 rises quickly.
[0032]
Next, the relationship between the coil current waveform of the heating coil 3 and the heating temperature in the circuit diagram of FIG. 1 will be described.
FIG. 3 shows an example of a current waveform of the heating coil 3 in FIG. 1 (the horizontal axis is a time axis, the frequency is conceptually shown, and the vertical axis is the heating coil current value). The waveform shows a high frequency envelope. The reason why it is oscillating when the heating coil current rises is that there are LC components of the smoothing reactor L and the smoothing capacitor C in the main circuit section 2.
[0033]
FIG. 4 shows the relationship between the amount of energy input to the heated object 100 and time. The input energy indicates a time integral value of the square of the heating coil current. The instantaneous energy intensity is proportional to the square of the heating coil current. Further, the temperature rise of the object to be heated 100 is time accumulation (time integration) of the instantaneous energy. The vertical axis in FIG. 4 is proportional to the heating temperature.
Considering from FIG. 4, it can be seen that the vibration component at the rise of the coil current in FIG. 3 does not significantly affect the quenching characteristics.
[0034]
The effect on the quenching characteristics of the object to be heated 100 when the rise of the heating coil current from the power supply device 1 is accelerated will be described.
FIG. 5 shows the rise of the heating coil current with respect to time from the power supply device 1 (the vertical axis is the effective value of the coil current).
In the figure, the rise of the heating coil current by the conventional power supply apparatus 101 is indicated by 101, and the rise of the heating coil current by the power supply apparatus 1 in the present embodiment is indicated by 1.
[0035]
FIG. 6 shows changes in the input energy, that is, the heating temperature, of the conventional power supply device 101 shown in FIG. 5 and the power supply device 1 of the present embodiment to the object to be heated 100, and the power supply of the present embodiment The case of the device 1 is indicated by curve 1 and the case of the conventional power supply device 101 is indicated by curve 101. In the case of the conventional power supply device 101, the temperature of the object to be heated 100 gradually rises when the coil current rises.
In order to raise the to-be-heated body 100 to the quenching temperature T, the power supply device 1 of the present embodiment only needs to t1, whereas the conventional power supply device 101 takes more than t1 to t2, and takes time. It is getting longer.
[0036]
The influence on the quenching of the object to be heated 100 when the rise of the coil current of the heating coil 3 is slow and the heating time is long will be described with reference to FIG.
FIG. 7 shows the power source of the present embodiment when the heating coil 3 is arranged on a cylindrical circumference made of a metal material as a model of the heated body 100 and the circumferential surface of the heated body 100 is quenched. FIG. 7A shows a case where the rise of the heating coil current of the apparatus 1 is fast, and FIG. 7B shows a case where the rise of the heating coil current of the conventional power supply apparatus 101 is slow.
[0037]
7 (a) and 7 (b), the vertical axis is the time axis, and moves downward as time passes, and the temperature pattern in the depth direction from the circumferential surface of the heated body 100 with respect to time, The relationship with a heating coil current is shown. The temperature patterns 30 and 130 in the depth direction of the heated object 100 at each time should be three-dimensionally originally, but are inevitably two-dimensionally shown in the drawing (the starting point indicates the time).
In the conventional power supply device 101 in which the heating coil current rises slowly, the temperature pattern 130 in the depth direction of the object to be heated 100 is more gradual than the temperature pattern 30 in the depth direction by the power supply device 1. As the temperature rises, heat is transferred to the inside by heat conduction, and when the surface is the same temperature, it can be seen that the depth of the temperature rising portion is deep.
[0038]
On the other hand, the quenching portion 10 indicated by the oblique lines of the heated object 100 by the power supply device 1 having a fast rise of the heating coil current as in the present embodiment has a slow rise of the heating coil current. The depth from the circumferential surface of the object to be heated 100 is considerably shallower than that of the quenching portion 110 indicated by hatching by the power source 101.
[0039]
In the comparison of the quenching quality between the quenching portion 10 by the power supply device 1 having the fast rise of the heating coil current and the quenching portion 110 by the power supply device 101 having the slow rise of the heating coil current, the circumferential surface is required. However, when the inside is heated, the heated object 100 itself is distorted by the temperature. Since it is preferable that there is no unnecessary heating to other than the necessary quenching portion, the quenching portion 10 is superior to the quenching portion 110.
[0040]
Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications and changes can be made based on the technical idea of the present invention.
[0041]
【The invention's effect】
As is clear from the above description, according to the power supply device for high frequency heating of the present invention, in the power supply device that outputs the high frequency heating power by the DC output voltage of the thyristor, the main circuit portion and the electrical characteristics are substantially equivalent and small. A mini-model circuit unit comprising a passive circuit including a capacitive thyristor, which is arranged in parallel with the main circuit unit, and the ignition phase angle of the small-capacity thyristor is controlled by an output control signal of a phase controller. Compare the output voltage from the equivalent resistance terminal of the oscillator of the mini-model circuit unit with the set voltage of the output setting unit, the model circuit unit, the output setting unit that sets the heating power output of the main circuit unit An error amplifier that sends the error voltage to the phase controller, and an output voltage from both ends of the equivalent resistor of the oscillator of the mini-model circuit unit according to an output control signal of the phase controller. Since the ignition phase angle of the thyristor of the main circuit unit is controlled based on a signal for controlling the ignition phase angle of the small-capacity thyristor that matches the set voltage of the output setting device, a high-frequency output The power (or heating coil current) rise time is fast, and an excellent effect is achieved that no turbulence occurs in the feedback loop.
[0042]
At the same time, high-frequency heating can be performed on a thin and small object to be heated in a short time of, for example, a short pulse of 1 second or less, so that precise heating is possible and fine quenching can be adjusted.
[0043]
The high-frequency heating power supply device of the present invention enables a high-frequency power supply device that can respond at high speed and can be heated in a short time without greatly changing the conventional equipment. In addition, variations in products due to fluctuations in power supply voltage could be suppressed. Since high-speed response and short-time heating are possible, it has become possible to perform good quenching on thin plates and small parts that have been considered difficult in the past.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a power supply device for high-frequency heating according to the present invention, including a circuit diagram of the device.
FIG. 2 is a diagram showing a relationship between a control error voltage (horizontal axis) sent from an error amplifier and a DC voltage (vertical axis) outputted from a mini-model circuit when the AC power supply voltage fluctuates.
3 is a high-frequency envelope diagram showing an example of a waveform of a current flowing through the heating coil of FIG. 1. FIG.
FIG. 4 is a diagram showing the relationship of the amount of heating energy input to the object to be heated with respect to time.
FIG. 5 is a diagram showing a rise change with respect to time of a heating coil current from a high-frequency heating power supply device, and showing a comparison between a power supply device according to the present embodiment and a conventional power supply device.
FIG. 6 is a diagram showing changes in energy (that is, heating temperature) applied to an object to be heated between the power supply device of the present embodiment and the conventional power supply device shown in FIG. 5;
FIG. 7 is a diagram showing the influence of the heating time due to the rise of the heating coil current on the quenching of the heated object, and when quenching the circumferential surface of a cylindrical material made of a metal material as a model of the heated object 7A is a diagram showing a case where the rise of the heating coil current of the power supply device of this embodiment is fast, and FIG. 7B is a diagram showing a case where the rise of the heating coil current of the conventional power supply device is slow. .
FIG. 8 is a configuration diagram including a circuit diagram of a conventional power supply device for high-frequency heating.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,101 Power supply device 2 for high frequency heating Main circuit part 3 High frequency heating coil 4 Error amplifier 5 Output setting device 6 Phase controller 7 AND gate circuit 10, 110 Hardened part 11a, 11b, 21a, 21b Thyristor 15 Vacuum tube self-excited oscillation circuit 20 Mini-model circuit part 25 Resistor (Equivalent parallel resistor)
30,130 Temperature pattern E Commercial AC power supply

Claims (4)

A main circuit unit including a thyristor connected to an AC power source, an oscillator that outputs high-frequency heating power using a DC output voltage of the thyristor, and a phase controller that outputs a signal for controlling an ignition phase angle of the thyristor. In power supply,
A mini-model circuit unit that is substantially equivalent in electrical characteristics to the main circuit unit and includes a thyristor having a smaller capacity than the thyristor. The mini model circuit unit is arranged in parallel with the main circuit unit and controls the output of the phase controller. The mini-model circuit unit in which the ignition phase angle of the small-capacity thyristor is controlled by a signal;
An output setting device for setting the output of the heating power of the main circuit section;
The output voltage from both ends of the equivalent resistor of the oscillator of the mini-model circuit unit is compared with a setting voltage of the output setting device, and an error amplifier that sends the error voltage to the phase controller,
The ignition phase of the small-capacity thyristor so that the output voltage from both ends of the equivalent resistor of the oscillator of the mini-model circuit unit matches the set voltage of the output setting device by the output control signal of the phase controller. A power supply apparatus for high-frequency heating, characterized by controlling an ignition phase angle of the thyristor of the main circuit section based on a signal for controlling the angle. 2. The high frequency heating power supply device according to claim 1, wherein the frequency of the high frequency heating power output from the oscillator is 100 kHz to 5 MHz. 2. The mini-model circuit unit is a passive circuit including the small-capacity thyristor connected to the AC power source, a rectifier circuit, and an equivalent resistance of an oscillator of the main circuit unit. The power supply device for high frequency heating described. Furthermore, a signal for controlling the ignition phase angle of the thyristor of the main circuit unit by the phase controller is turned on or off by a signal for turning on / off the heating power of the main circuit unit via an AND gate circuit. The power supply device for high frequency heating according to claim 1, wherein the power supply device is high frequency heating.

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