JP5253441B2 - Power supply for electric discharge machining - Google Patents

Description

  The present invention relates to a power supply device for electric discharge machining, and more particularly, to a power supply device for electric discharge machining that can control a voltage applied between electrodes using resonance.

  The wire electric discharge machining apparatus is an apparatus for machining using an arc discharge between a wire electrode and a workpiece. Finishing conditions that gradually reduce the machining current from the rough machining conditions that have a relatively large machining current (for example, a pulse width of about several microseconds), and finally the current pulse width is about several tens of nanoseconds. To improve surface roughness.

  A finishing power source used for finishing processing conditions is disclosed in Patent Document 1, for example. In the configuration disclosed in Patent Document 1, a capacitor is provided in parallel between the electrodes formed by the electrodes and the workpiece, and a reactor is connected in series with the electrodes. By using an AC sine wave, series resonance is induced in the stray capacitance and the reactor existing between the electrodes, and a high-frequency current pulse is generated between the electrodes to improve the surface roughness.

  However, the value of the stray capacitance in the electrode gap changes depending on the open (non-discharge), discharge, and short circuit states, making it difficult to obtain series resonance. When it is out of resonance, the voltage between the electrodes decreases, and stable discharge cannot be obtained.

  Patent Document 2 discloses a configuration in which a DC power source that outputs a DC voltage, a bridge circuit including semiconductor switching elements on each side, and an inductance element connected in parallel to an electrode gap are disclosed. When an AC pulse is applied by the inverter, energy stored in the inductance element is released between the electrodes, and parallel resonance occurs between the inductance element and the floating capacitance in the electrode gap.

  Since parallel resonance is obtained by the inductance element and the stray capacitance, the output of the inverter is directly transmitted to the electrode gap without being affected by the stray component. That is, a voltage substantially equal to the power supply voltage can be generated in the electrode gap. Also, by inserting an inductance element in parallel with the electrode gap, the average voltage between the electrodes can be made 0V. When the polarity of the voltage generated between the electrodes is biased, it is known that when water is used as the machining liquid, electrolytic corrosion occurs and the machining is adversely affected.

  Furthermore, for the purpose of improving the surface roughness of the workpiece, Patent Document 1 discloses a technique in which an applied voltage and a machining current are different between when the workpiece functions as a cathode and when it functions as an anode. In Patent Document 1, the current limiting resistance value is asymmetrical for the above purpose.

  In any of the methods disclosed in Patent Documents 1 and 2, a high frequency pulse is applied to the electrode gap using resonance to improve the finished surface accuracy. This resonance may be a series resonance or a parallel resonance.

Japanese Patent Laid-Open No. 3-49824 Japanese Patent Laid-Open No. 11-347842

  However, the methods disclosed in Patent Documents 1 and 2 have a problem that a sufficient voltage cannot be applied to the electrode gap because the impedance value between the electrodes changes when using series resonance. In addition, many high-frequency power supplies that operate at 10 MHz to several tens of MHz amplify the oscillation of the crystal oscillator in multiple stages to increase the output. Therefore, there has been a problem that the operation of the power supply itself becomes unstable.

  On the other hand, when using parallel resonance, in the configuration disclosed in Patent Document 2, an inductance element is inserted into the inverter output, and energy is injected into the inductance element according to the ON time of the switching element and the DC power supply voltage. For this reason, the inductance element has restrictions depending on the power supply configuration, and thus there is a possibility that the value calculated from the stray capacitance between the electrodes cannot be used as it is.

  In the electric discharge machining apparatus, a servo feed mechanism is generally used. This is set so that the distance between the electrodes is kept constant by moving the wire electrode closer to or away from the workpiece in accordance with the state between the electrodes. The average value of the interelectrode voltage is often used as this index, but if parallel resonance is used, fluctuations in the interelectrode voltage value will be small, making it difficult to distinguish between open, discharge, and short-circuit states. There was a problem that the mechanism could not operate sufficiently.

  The present invention has been made in view of the above, and can independently control the injection of energy between the electrodes and the voltage adjustment between the electrodes in accordance with the interelectrode state, while obtaining a stable processing state. An object of the present invention is to obtain a power supply device for electric discharge machining that can monitor a gap state.

  In order to solve the above-described problems and achieve the object, the power supply device for electric discharge machining according to the present invention is a power supply device for electric discharge machining that applies a pulse voltage between the electrodes and the workpiece, A DC power source, a bridge circuit in which a semiconductor switching element is provided on each side, a first inductance element connected between the output ends of the bridge circuit without the gap between the poles, and the gap between the poles And a second inductance element connected between the output ends of the bridge circuit.

  According to this invention, it is possible to independently control the injection of energy between the electrodes and the voltage adjustment between the electrodes according to the interelectrode state, and it is possible to monitor the interelectrode state while obtaining a stable processing state There is an effect.

FIG. 1 is a circuit diagram showing a schematic configuration of a first embodiment of a power supply device for electric discharge machining according to the present invention. FIG. 2 is a diagram illustrating an example of waveforms of the control signals SC1 to SC4 and the interelectrode voltage Vg of the switching elements SW1 to SW4 in FIG. FIG. 3 is a circuit diagram showing another example of a schematic configuration of the power supply device for electric discharge machining according to the first embodiment of the present invention. FIG. 4 is a diagram showing the waveforms of the control signals SC1 to SC4, the voltage between the electrodes, and the current between the electrodes at the time of short circuit, discharge, and open compared with the waveform when there is no energy regulating reactor L1. FIG. 5 is a diagram showing an example of waveforms of the control signals SC1 to SC4 and the interelectrode voltage Vg in the second embodiment of the power supply device for electric discharge machining according to the present invention. FIG. 6 is a diagram showing an example of waveforms of the control signals SC1 to SC4 and the interelectrode voltage Vg in the third embodiment of the power supply device for electric discharge machining according to the present invention. FIG. 7 is a circuit diagram showing a schematic configuration of the power supply device for electric discharge machining according to the fourth embodiment of the present invention.

  Hereinafter, an embodiment of a power supply device for electric discharge machining according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing a schematic configuration of a first embodiment of a power supply device for electric discharge machining according to the present invention. In FIG. 1, a power supply device 1 for electric discharge machining supplies a machining pulse between electrodes 2 and a workpiece 3 to machine the workpiece 3. The power supply device 1 for electric discharge machining and the electrodes can be connected with a cable.

  The electric discharge machining power supply device 1 is provided with a DC power supply V1, switching elements SW1 to SW4, an energy regulating reactor L1, and a series resonance reactor L2. The series resonance reactor L2 operates so as to increase the voltage between the electrodes 2 and the workpiece 3, and the energy regulating reactor L1 is between the electrodes 2 and the workpiece 3. Can be operated to inject energy.

  The inter-electrode gap between the electrode 2 and the workpiece 3 can be equivalently simulated by the stray capacitance Cg and the inter-electrode resistance Rg. In the non-processed (open) state, when water is used as the working fluid, the water has a dominant interelectrode resistance, and a typical value is 1 kΩ to several MΩ. Since an arc voltage is generated between the electrodes in the discharge state, the resistance between the electrodes changes from several mΩ to several hundred Ω. If the electrode 2 and the workpiece 3 are in a short-circuited state, it may be considered as several mΩ to several Ω depending on the contact resistance between the electrode 2 and the workpiece 3. On the other hand, the stray capacitance Cg depends on the facing area between the wire electrode 2 and the workpiece 3 and the distance between the electrodes, and is about several hundred pF to several nF.

  For example, FETs (field effect transistors) or IGBTs (insulated gate bipolar transistors) can be used as the switching elements SW1 to SW4, and a full-bridge inverter having the switching elements SW1 to SW4 as respective sides is configured. Here, the switching elements SW1 and SW4 can constitute one diagonal arm of the full bridge, and the switching elements SW2 and SW3 can constitute the other diagonal arm of the full bridge.

  The energy regulating reactor L1 is provided at the output end of the full bridge. Specifically, the source terminal of the switching element SW1 (and the drain terminal of the switching element SW2) is used as one end, and the source terminal (and the switching element of the switching element SW3). The drain terminal of SW4 is connected to the other end.

  Furthermore, one end of the energy regulating reactor L1 is connected to the electrode 2 via the series resonance reactor L2, and the other end of the energy regulating reactor L1 is connected to the workpiece 3. The insertion position of the series resonance reactor L2 does not have to be between the electrode 2 and the energy regulating reactor L1, but may be between the workpiece 3 and the energy regulating reactor L1. The insertion position of the series resonance reactor L2 is connected between the source terminal of the switching element SW1 and one end of the energy regulating reactor L1 or between the source terminal of the switching element SW3 and the other end of the energy regulating reactor L1. May be.

  The switching elements SW1 to SW4 can be turned on / off according to the control signals SC1 to SC4 when the control signals SC1 to SC4 output from the control circuit (not shown) are input to the gates.

  FIG. 2 is a diagram illustrating an example of waveforms of the control signals SC1 to SC4 and the interelectrode voltage Vg of the switching elements SW1 to SW4 in FIG. In FIG. 2, at the on time t1, the switching elements SW1 and SW4 are turned on, and a current flows from the DC power supply V1 to the energy regulating reactor L1. The energy stored in the energy regulating reactor L1 at the moment when the switching element SW1 is turned off is output between the electrodes.

  The energy at this time is defined by the inductance value L of the energy regulating reactor L1, the on time t1, and the voltage value of the DC power supply V1, and may be considered to be the same as that of a normal non-insulated boost chopper. However, since the machined surface roughness depends on the discharge frequency, it is desirable to shorten the on time t1 and the off time s1 as much as possible, and the voltage value of the DC power supply V1 is increased in consideration of the breakdown voltage of the switching elements SW1 to SW4. I can't pass it. That is, when the frequency and the voltage value of the DC power supply V1 are determined, the shape of the output voltage pulse is performed by adjusting the inductance value L of the energy regulating reactor L1.

  In the example of FIG. 2, the waveforms of the control signals SC1 to SC4 are set so that the diagonal arms of the inverter are synchronized. Here, the control signals SC1 to SC4 are controlled so that the switching elements SW1 to SW4 are repeatedly turned on and off continuously (multiple times in the example of FIG. 2) for each diagonal arm of the inverter. Is applied to the gates of the switching elements SW1 to SW4. That is, after the switching elements SW1 and SW4 are repeatedly turned on / off repeatedly a plurality of times, the switching elements SW2 and SW3 are repeatedly turned on / off repeatedly a plurality of times.

  By performing such an operation, it is possible to make it difficult for a current that causes an arm short circuit between the switching elements connected in series to flow, and to suppress heat generation of the switching elements. Even when such an operation is performed, since the energy regulating reactor L1 is connected in parallel with the poles, an AC pulse is generated between the poles, and the average pole voltage is maintained at 0V. .

  Each time the switching element is turned on once for each diagonal arm, the diagonal arm that is turned on may be alternately replaced. However, if the diagonal arms are alternately switched at a high frequency, a current that causes a short circuit between the switching elements connected in series easily flows, but the average inter-electrode voltage instantaneously becomes 0 V. It becomes easy to control the average voltage between.

  Further, when the switching elements SW2 and SW3 are operated, the ON time t2 and the OFF time s2 of the switching elements SW2 and SW3 may be different from the ON time t1 and the OFF time s1 of the switching elements SW1 and SW4. Alternatively, the switching elements SW2 and SW3 are not necessarily operated.

  That is, in the example of FIG. 1, the switching elements SW <b> 1 to SW <b> 4 are arranged on each side, but a configuration using only the diagonal may be used. As shown in FIG. 3, the switching elements SW2 and SW3 may be removed and only the switching elements SW1 and SW4 may be operated. Moreover, you may make it comprise the power supply device 1 for electrical discharge machining only by one switching element. However, in order to quickly and reliably separate the circuit output and the electrode gap, it is desirable to simultaneously turn on / off both switching elements connected to the electrode 2 side and the workpiece 3 side of the electrode gap.

  In FIG. 1, the voltage generated at both ends of the energy regulating reactor L1 is applied to the electrode gap via the series resonance reactor L2, and between the energy regulating reactor L1 and the series resonance reactor L2 and the stray capacitance Cg. Resonance state is entered.

  FIG. 4 is a diagram showing the waveforms of the control signals SC1 to SC4, the voltage between the electrodes, and the current between the electrodes at the time of short circuit, discharge, and open compared with the waveform when there is no energy regulating reactor L1. 4A shows an operation waveform when the value of the series resonance reactor L2 is 2 μH, and FIG. 4B shows an operation waveform when the value of the series resonance reactor L2 is 0 μH. 0 μH is assumed to be when no series resonance reactor is inserted. The calculation of this waveform was performed assuming that the stray capacitance Cg was 2 nF and that the interelectrode resistance Rg appropriately changed according to the discharge state.

  Specifically, in the open state, the resistance of water as a working fluid is taken into consideration, 1 kΩ, 20 Ω during discharge, and 5 Ω during short-circuiting, and each is switched at intervals of 4 μs. Since the inter-electrode voltage at the time of opening needs to exceed the discharge start voltage, the voltage value of the DC power supply V1 was adjusted to be around 100V. Further, the on time t1 and the off time s1 are set to 200 ns, respectively, and a 2.5 MHz pulse is continuously applied.

  In FIG. 4 (a), the inter-electrode voltage increases at the time of opening, and the inter-electrode voltage decreases at the time of discharging and short-circuiting. The ideal processing from the viewpoint of improving the surface roughness is a state in which the voltage between the electrodes decreases at the moment of discharge and the discharge current is small. Since it is in a series resonance state when open, the interelectrode voltage becomes high, and in the discharge state or short-circuit state, series resonance cannot be obtained, so that the interelectrode voltage decreases and the interelectrode current also decreases. For this reason, the workpiece 3 can be expected to have good surface roughness.

  Further, when switching from the discharge state to the open state, several cycles are required until the interelectrode voltage reaches a steady state. This is a series resonance growth period, and can be adjusted by the value of the series resonance reactor L2. Although electric discharge machining is an accumulation of single discharge phenomena, it is desirable that each discharge phenomenon is independent for each shot. If arc discharge continues without interruption even when a high frequency is applied, it is apparently equivalent to applying a low frequency pulse. This leads to deterioration of surface roughness. Therefore, it is necessary to reliably generate or terminate a single discharge. By designing for a period of several cycles until the open-circuit voltage from the discharge state or the short-circuit state reaches a steady state, it becomes difficult for the discharge to continue, so that a good machining state can be obtained.

  In the present embodiment, the crystal oscillation is not amplified as a high-frequency pulse generation method, but a switching operation by an inverter circuit is used. In an analog amplifier based on crystal oscillation, fluctuations in the impedance of the electrode gap affects the matching state of each amplification stage, resulting in large output fluctuations. Even if it becomes stable, the value of the DC power supply V1, the switching timing, and the value of the energy regulating reactor L1 are regulated, so that it is relatively stable.

  The inductance value, which is an element in the resonance state, is determined by the combination of the energy regulating reactor L1 and the series resonance reactor L2. For this reason, the influence when the inter-pole state fluctuates is distributed to the series resonance reactor L2 and the energy regulating reactor L1, and the fluctuation caused by the inter-pole state of the voltage (current) generated at both ends of the energy regulating reactor L1. Can be small.

  On the other hand, in FIG. 4B, when the value of the series resonance reactor L2 is 0 μH, parallel resonance occurs between the energy regulating reactor L1 and the stray capacitance Cg between the electrodes. The voltage between the electrodes is not easily affected by the impedance between the electrodes, and the voltage fluctuation range is small. This is disadvantageous from the standpoint of sensing the inter-pole state for the servo feed mechanism. The servo feed mechanism operates so as to reduce the distance between the poles when the distance between the poles is open, and operates to increase the distance between the poles when the distance between the poles is short-circuited. The configuration can be simplified by using a value obtained by averaging the inter-electrode voltage as an index of the inter-electrode state. Therefore, by using the series resonance in FIG. 4A, the voltage fluctuation width in the discharge state is made larger than the voltage fluctuation width in the short-circuit state compared to the method not using the series resonance in FIG. The voltage fluctuation width in the open state can be made larger than the voltage fluctuation width in the discharge state.

  In parallel resonance, the current changes as the resonance state while the voltage remains constant. FIG. 4B shows this state, and the current that flows during a short circuit is large. In this state, the processing surface is roughened, leading to deterioration in processing quality. For example, when the electrode gap is short-circuited through sludge, the sludge in the electrode gap is Joule-heated by a large short-circuit current to be turned into plasma, and the surface of the workpiece 3 may be unnecessarily roughened. Therefore, it is desirable that the short circuit current is equal to or less than the discharge current. By using the series resonance in FIG. 4A, the short-circuit current value can be reduced and the processing quality can be improved as compared with the method not using the series resonance in FIG. 4B.

  The start of discharge is determined by the voltage between the electrodes, and the machining energy is determined by the discharge current. For this reason, the voltage is large in the open state and the current is small in the discharge (short-circuit) state, which is a condition that the surface roughness is improved and the discharge is stably generated. In view of the above, it is an element of a machining power source to obtain good machining quality to include at least a series resonance element. As shown in the present embodiment, the energy regulating reactor L1 for regulating the processing energy and the series resonance reactor L2 for inducing series resonance are separated, and the energy regulating reactor L1 is separated from the power supply configuration and the applied frequency. If the value of the reactor for series resonance L2 is selected from the viewpoint of the occurrence of electric discharge, the stability of the interelectrode state, and the monitoring of the interelectrode state, the stability of the machining power source for the parallel resonance and the machining state of the series resonance are determined. Both stability can be achieved.

Embodiment 2. FIG.
FIG. 5 is a diagram showing an example of waveforms of the control signals SC1 to SC4 and the interelectrode voltage Vg in the second embodiment of the power supply device for electric discharge machining according to the present invention. In the following description, the case where the configuration of FIG. 1 is used as the power supply device for electric discharge machining is taken as an example.

5, the power adjustment to the electrode gap can be carried out by a voltage value of the DC power supply V1, input of energy to the energy defined reactor L1 is determined by ^{1/2 * L * I 2} . The current I can be defined by V * t / L if the resistance component is ignored. Here, L is the inductance value of the energy regulating reactor L1, I is the current flowing through the energy regulating reactor L1, t is the ON time of the switching elements SW1 to SW4, and V is the voltage value of the DC power supply V1.

  Thus, if the on-time of the switching elements SW1 to SW4 is changed, the energy released from the energy regulating reactor L1 can be adjusted. For this reason, if the state detection speed between electrodes is sufficiently high, the energy can be adjusted according to the inter-electrode state for each discharge.

  In the present embodiment, a method for reducing the voltage between the electrodes by shortening the on-time of the switching elements SW1 to SW4 when the open state continues for a long time will be described. However, the on-time of the switching elements SW1 to SW4 is controlled. It can be applied to other methods. For example, the open-circuit voltage may be increased when the open state continues for a long time according to the processing environment, or the on-time of the switching elements SW1 to SW4 may be controlled by detecting a short circuit state or a discharge state.

  For example, when a high voltage is applied during non-discharge during finishing, the wire electrode may be pulled on the side surface of the workpiece 3 by electrostatic attraction, and the machining shape may deteriorate. If discharge is not performed in the direction of travel of the wire electrode, high voltage is not applied unnecessarily, the interelectrode voltage is lowered, and the effective discharge in the direction of travel of the wire electrode is achieved by returning to the original interelectrode voltage as discharge starts. The rate can be increased.

  In the example of FIG. 5, the method of alternately switching the diagonal arm on operation every half cycle is shown. Here, the period A is when the open state continues. It is possible to detect that the open state is continuous by detecting the average value of the voltage between the electrodes at this time or the differential value thereof. In the period B, the on-time of the switching elements SW1 to SW4 is shifted from t1 to t2 in response to the detection result. Note that the change in the ON time of the switching elements SW1 to SW4 may pass through several stages. Since the frequency is determined by the series resonance frequency, only the on-pulse width is changed while the period is constant.

  As a result, the inter-electrode voltage Vg in the period B is lower than that in the period A. Here, the discharge is detected in the period B ′. In the discharge detection, a discharge current may be detected, or a differential change in the interelectrode voltage may be detected. When the discharge starts, in order to increase the interelectrode voltage Vg, the period shifts to the period A ', and the on-time returns from t2 to t1. In the period A ′, the discharge continues.

  The on-time control of the switching elements SW1 to SW4 may be performed at the time of a short circuit between the electrodes. For example, if an excessive short-circuit current is detected at the on-time t1 in the period A, the on-pulse width is narrowed by changing the on-time from t1 to t2 in the period B, and the input power to the energy regulating reactor L1 is reduced. Short circuit current can be avoided and unnecessary surface roughness deterioration can be prevented.

  As described above, the optimum machining control operation required varies depending on the machining environment and machining state such as the wire material and wire diameter, the material and plate thickness of the workpiece 3, and the machining shape. By using the circuit configuration, as described in the second embodiment, the pulse width of the switching elements SW1 to SW4 can be controlled while maintaining the voltage value of the DC power supply V1 constant, thereby improving the processing quality. Can be made.

Embodiment 3 FIG.
FIG. 6 is a diagram showing an example of waveforms of the control signals SC1 to SC4 and the interelectrode voltage Vg in the third embodiment of the power supply device for electric discharge machining according to the present invention. In the following description, a case where the configuration of FIG.

  In FIG. 6, since arc heat is different between the cathode and the anode in the electric discharge machining, it is known that the consumption of the anode is large and the consumption of the cathode is small if the electrodes are made of the same material. That is, the anode is easier to process than the cathode. For this reason, in an electric discharge machine that applies an AC pulse, in order to improve the surface roughness of the workpiece 3, the voltage value when the workpiece 3 functions as an anode is increased, and the voltage value when the workpiece 3 functions as a cathode. Should be set low. However, these are only cases where the cathode and the anode are made of the same material, and the same material is rarely used in practice. That is, it is desirable that the voltage when acting as the cathode and the voltage when acting as the anode are appropriately different according to the actual processing environment.

  In the fourth embodiment, an operation is performed in which the on-pulse width is different between the diagonal arms of the switching elements SW1 and SW4 and the diagonal arms of the switching elements SW2 and SW3. For example, when the on period of the switching elements SW1 and SW4 is t1, and the on period of the switching elements SW2 and SW3 is t2, it can be set to satisfy t1> t2. Since the energy stored in the energy regulating reactor L1 is different between the on period t1 and the on period t2, the output waveform is also asymmetric.

  However, since the energy regulating reactor L1 is connected in parallel to the stray capacitance Cg between the electrodes, the average voltage between the electrodes is 0V. FIG. 6 shows an example in which the positive and negative areas are adjusted to be the same as the waveforms of the low voltage long pulse and the high voltage short pulse, but the average period of 0 V is the energy regulating reactor L1. It depends on the inductance value of the series resonance reactor L2.

  In this way, by making the on-pulse width different between the diagonal arms of the switching elements SW1 and SW4 and the diagonal arms of the switching elements SW2 and SW3, the interelectrode voltage Vg can be made asymmetric without using a current limiting resistor. The electrical discharge machining characteristics can be improved with a simple configuration.

Embodiment 4 FIG.
FIG. 7 is a circuit diagram showing a schematic configuration of the power supply device for electric discharge machining according to the fourth embodiment of the present invention. In FIG. 7, the electric discharge machining power supply device 11 is provided with only one switching element SW11 for converting direct current into alternating current. The energy regulating reactor L11 has one end connected to the source terminal of the switching element SW11, the other end connected to the low voltage side of the DC power supply V11, and is connected in parallel with the poles via the series resonance reactor L12. . The series resonance reactor L12 has one end connected to one end of the energy regulating reactor L11 and the other end connected to the electrode 2. Note that the series resonance reactor L12 may be connected to the workpiece 3 side.

  By adopting such a circuit configuration, the processing energy is determined by the energy regulating reactor L11 while reducing the number of the switching elements SW11, and the series resonance reactor L12 determines the stability of discharge and the ease of monitoring the inter-electrode state. Therefore, both the stability of the machining power source and the stability of the machining state can be achieved.

  In the fourth embodiment, the drain terminal of the switching element SW11 is connected to the plus terminal of the DC power supply V11. However, the source terminal of the switching element SW11 is connected to the minus terminal of the DC power supply V11. You may do it. In this case, the drain terminal of the switching element SW11 is connected to one end of the energy regulating reactor L11. With this circuit configuration, the gate circuit for controlling the gate of the switching element can be designed based on the GND potential (the same potential as the DC power supply V11), and the cost of the circuit can be reduced.

  Moreover, as long as the energy regulation reactors L1 and L11 and the series resonance reactors L2 and L12 of the first to fourth embodiments described above have specific inductance values, any elements may be used. It may be used.

  As described above, the power supply device for electric discharge machining according to the present invention can independently control the injection of energy between the electrodes and the voltage adjustment between the electrodes in accordance with the inter-electrode state, and processing with good surface roughness. It is suitable for the method of performing the process stably.

DESCRIPTION OF SYMBOLS 1,11 Power supply apparatus for electrical discharge machining 2 Electrode 3 Workpiece V1, V11 DC power supply SW1-SW4, SW11 Switching element L1, L11 Reactor for energy regulation L2, L12 Reactor for series resonance Cg Floating capacitance Rg Polar resistance

Claims (5)

A power supply device for electric discharge machining that applies a pulse voltage between electrodes between an electrode and a workpiece,
DC power supply,
A full bridge circuit switching element is provided on each side,
To so that is connected between the output terminal of the full bridge circuit without via the interpolar, a first inductance element connected in parallel between the output end of the the between the pole full bridge circuit,
To so that is connected through the machining gap between the output terminal of the full bridge circuit, and a second inductance element connected in series between between the said first inductance element electrode,
The pulse on time of the switching element is different for each diagonal arm of the full bridge circuit,
The on operation of the switching element is alternately performed for each diagonal arm of the full bridge circuit,
The power supply device for electric discharge machining performs an energy storage operation for supplying energy from the DC power source to the first inductance element by turning on the switching element during the pulse on time, and a pulse off time following the pulse on time. Then, by turning off the switching element, a series resonance operation is performed between the first inductance element, the second inductance element, and the pole according to a discharge state between the poles,
The electric discharge machining power supply apparatus alternately performs the energy storage operation and the series resonance operation to generate an alternating voltage between them to process the workpiece. .   The power supply device for electric discharge machining performs the series resonance operation between the first inductance element, the second inductance element, and the pole when the gap is in an open state during the pulse-off time. And controlling so that the series resonance operation is not performed between the first inductance element, the second inductance element, and the pole when the gap is in a discharge state or a short-circuit state.
  2. The power supply device for electric discharge machining according to claim 1, wherein:   The electric discharge machining power supply device performs an on / off operation of the switching element according to a pulse having a frequency determined in accordance with a resonance frequency at the time of the series resonance operation.
  The power supply device for electric discharge machining according to claim 1, wherein the power supply device is for electric discharge machining.   The power supply device for electric discharge machining changes the length of the pulse-on time according to the discharge state between the electrodes.
  The power supply device for electric discharge machining according to claim 3.   The power supply device for electric discharge machining changes the length of the pulse-on time according to the polarity of discharge between the electrodes.
  The power supply device for electric discharge machining according to claim 3.

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