WO2016059689A1 - Power supply device for electrical discharge machine - Google Patents

Power supply device for electrical discharge machine Download PDF

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Publication number
WO2016059689A1
WO2016059689A1 PCT/JP2014/077460 JP2014077460W WO2016059689A1 WO 2016059689 A1 WO2016059689 A1 WO 2016059689A1 JP 2014077460 W JP2014077460 W JP 2014077460W WO 2016059689 A1 WO2016059689 A1 WO 2016059689A1
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Prior art keywords
voltage
smoothing capacitor
power supply
electrode
discharge
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PCT/JP2014/077460
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French (fr)
Japanese (ja)
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博紀 彦坂
森田　一成
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三菱電機株式会社
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Priority to PCT/JP2014/077460 priority Critical patent/WO2016059689A1/en
Priority to JP2015531395A priority patent/JPWO2016059689A1/en
Publication of WO2016059689A1 publication Critical patent/WO2016059689A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode

Definitions

  • the present invention relates to a power supply device for an electric discharge machine that applies a voltage between an electrode and a workpiece and processes the workpiece using a discharge phenomenon generated between the electrodes.
  • a DC voltage power supply is used as the power supply of the electric discharge machining apparatus, and this DC voltage power supply is configured such that a commercial AC power supply is rectified by a rectifier and smoothed by a smoothing capacitor.
  • a commercial AC power supply is rectified by a rectifier and smoothed by a smoothing capacitor.
  • Patent Document 1 As a means for suppressing the above-described output voltage fluctuation of the DC voltage power supply, there is a method of connecting a stabilized power supply to the outside of the power supply device of the electric discharge machine, Generally, it is very expensive and requires a place for installation. As another method for stabilizing the processing, there is a method disclosed in Patent Document 1 below.
  • a constant machining current is controlled by a switching system circuit at the time of rough machining that handles a large current to always supply a constant machining current pulse, and a resistance machining circuit at the time of finishing machining that handles a small current. Is operated, a constant machining current pulse is supplied with a constant DC power supply voltage maintained by pulse width modulation (PWM) control even if the commercial power supply voltage fluctuates. Thereby, stable electric discharge machining can be realized.
  • PWM pulse width modulation
  • a DC power supply is generated by disturbance such as fluctuations in commercial power supply voltage by selecting an appropriate capacity for the smoothing capacitor for pulse width modulation control used for power supply control. Even when the voltage increases or decreases, it is possible to quickly return to the predetermined voltage.
  • the peak value of the machining current becomes constant when the DC power supply voltage is kept constant, but the discharge frequency changes depending on the state of the discharge gap, and the current flowing within the unit time varies.
  • an increase in current flowing in a unit time due to temporary concentrated discharge causes deterioration of arc and flatness, and abnormal wear of electrodes.
  • the present invention has been made in view of the above, and it is possible to suppress an increase in current flowing in a unit time due to temporary concentrated discharge, and to suppress deterioration of arc and flatness, and abnormal consumption of electrodes. It aims at obtaining the power supply device of an electric discharge machine.
  • the present invention provides a DC voltage converter that rectifies an AC power source and outputs a DC voltage, and a smoothing capacitor that applies a voltage between the electrode and the workpiece.
  • a constant voltage control unit that makes the smoothing capacitor constant by performing pulse width modulation control on the basis of the DC voltage, and is connected between the smoothing capacitor and the electrode, from the smoothing capacitor to the electrode.
  • a current limiting resistor for limiting the current flowing to the capacitor, and the capacity of the smoothing capacitor is a predetermined voltage set for the smoothing capacitor to determine the amount of charge used for discharging during one discharge duration. It is characterized by being smaller than the divided value.
  • the power supply device for an electric discharge machine is capable of suppressing an increase in current flowing in a unit time due to temporary concentrated discharge and suppressing deterioration of arc and flatness and abnormal consumption of electrodes. Play.
  • FIG. 6 is a diagram illustrating an example of a variable capacitance smoothing capacitor according to the third embodiment.
  • FIG. 1 is a diagram illustrating a schematic configuration of an electric discharge machine 100 according to the first embodiment of the present invention.
  • the electric discharge machine 100 includes a power supply device 110 of an electric discharge machine connected to a commercial AC power supply 101, an electrode 1, and a workpiece 2 that is an object of electric discharge machining.
  • a power supply device 110 for an electric discharge machine includes a DC voltage conversion unit 102 that rectifies a commercial AC power supply 101 by a rectifier and outputs a DC voltage, and a constant voltage control unit that is connected to the DC voltage conversion unit 102 and converts the DC voltage to a constant voltage.
  • a smoothing capacitor 5 for constant voltage control connected to the constant voltage control unit 103, and a current limiting resistor switching unit having a current limiting resistor for limiting the current flowing from the smoothing capacitor 5 to the electrode 1 for electric discharge machining 104.
  • the current limiting resistance switching unit 104 can switch the current limiting resistance and is connected to the electrode 1.
  • One end of the smoothing capacitor 5 is connected to the current limiting resistance switching unit 104, and the other end of the smoothing capacitor 5 is connected to the workpiece 2.
  • the smoothing capacitor 5 is subjected to pulse width modulation control so as to have a predetermined voltage by the constant voltage control unit 103, and functions as a power source that generates a discharge by applying a voltage between the electrode 1 and the workpiece 2.
  • FIG. 2 is a diagram showing in detail an example of the circuit configuration of the power supply device 110 of the electric discharge machine shown in FIG. 1 according to the first embodiment.
  • components given the same reference numerals as those in FIG. 1 are the same components.
  • the DC voltage conversion unit 102 includes a rectifier 3 that rectifies the commercial AC power supply 101 and a capacitor 4 that is connected in parallel to the rectifier 3 in order to smooth the rectifier 3.
  • the constant voltage control unit 103 includes a discharge resistor 13 connected in parallel to the smoothing capacitor 5, a capacitor 6 connected in parallel to the DC voltage conversion unit 102, and a driving method connected between the smoothing capacitor 5 and the capacitor 6.
  • the smoothing capacitor 5, the discharge resistor 13, the capacitor 6, the rectifying diode 19, and the switching element 8 are all connected to the workpiece 2 through the switching element 10 described later.
  • the current limiting resistor switching unit 104 includes a current limiting resistor 14 for limiting a discharge current, a rectifying diode 17, a switching element 11 connected between the current limiting resistor 14 and the rectifying diode 17, Is provided.
  • the electric discharge machine 100 further includes a switching element 10 connected between the workpiece 2 and the switching element 8, a rectifying diode 18 connected between the workpiece 2 and the smoothing capacitor 5, and a reactor.
  • Switching element 9 and rectifying diode 16 connected in series between 12 and electrode 1, and rectifying diode 15 connected between switching element 9 and rectifying diode 16 and switching element 10.
  • the electric discharge machine 100 further includes a detection unit 30 that detects the voltage V C1 across the smoothing capacitor 5.
  • the detection unit 30 switches the ON state or the OFF state of the switching elements 7 and 8 based on the magnitude relationship between the detected both-end voltage V C1 and a predetermined set voltage V 0 .
  • This circuit operates as a first drive system that supplies constant machining current pulses by constant current control of the switching system circuit for rough machining that requires a current of several tens of amperes or more. Even if the voltage of the commercial AC power supply 101 fluctuates for finishing processing that requires a current of ampere or less, a constant DC power supply voltage is maintained by pulse width modulation control and a constant current pulse for finishing processing is supplied.
  • Two drive systems In the first embodiment, this second driving method is used.
  • FIG. 3 shows a circuit diagram in which an operation loop according to the second driving method in the circuit shown in FIG. 2 is added.
  • the electromagnetic switch 20 and the switching element 9 are in the OFF state during any of the voltage no-load period, the discharge duration period, and the rest period, and the switching element 10 Is in the ON state.
  • the voltage no-load period is a period in which a voltage is applied between the electrode 1 and the work piece 2 but in an insulated state and no discharge is generated.
  • the discharge duration is a period in which a voltage is applied between the electrode 1 and the workpiece 2 and a discharge is actually generated.
  • the rest period is a period in which no voltage is applied between the electrode 1 and the workpiece 2.
  • the switching elements 7 and 8 are turned on or off by the detection unit 30 that detects the voltage V C1 across the smoothing capacitor 5 during any of the voltage no-load period, the discharge duration period, and the rest period. The state is switched.
  • the detection unit 30 turns on both the switching elements 7 and 8, and direct current is generated along the loop (1) indicated by the broken line in FIG. A current is passed from the voltage conversion unit 102 to the reactor 12, and energy is stored in the coil of the reactor 12 as a magnetic flux.
  • the detection unit 30 turns off both the switching elements 7 and 8 and follows the loop (2) path indicated by the one-dot chain line in FIG.
  • the smoothing capacitor 5 is charged with the current from the reactor 12.
  • the voltage of the both-end voltage V C1 is increased and controlled so as to be kept close to the set voltage V 0 .
  • the carrier frequency is constant, that is, the period is constant. Then, the ratio between the ON period and the OFF period of the switching elements 7 and 8 within a certain period is changed.
  • pulse width modulation control is performed in which the duty of the ON period and OFF period of the switching elements 7 and 8 is changed.
  • the duty referred to here is, for example, the ratio of the ON period to one cycle including the ON period and the OFF period. Generally, a maximum value and a minimum value are set as the duty value.
  • the smoothing capacitor 5 that is controlled so that the voltage V C1 at both ends always maintains a constant set voltage V 0 is used as a power source, and the switching element 11 is in the ON state only during the voltage no-load period and the discharge duration period.
  • a voltage is applied between the electrode 1 and the workpiece 2 when the switching element 11 is in the ON state.
  • the timing at which discharge occurs in a state where a voltage is applied is a natural phenomenon and cannot be predicted. Therefore, the period during which the switching element 11 is in the ON state is divided into a voltage no-load period and a discharge duration period.
  • a finishing current pulse having a constant current peak corresponding to the value of the current limiting resistor 14 is output.
  • the switching element 11 is controlled by control means (not shown) based on the voltage between the electrode 1 and the workpiece 2, that is, the inter-electrode voltage V.
  • control means By detecting that the inter-electrode voltage V decreases after the switching element 11 is turned on, the control means can detect that discharge has occurred. Therefore, the control means turns off the switching element 11 so that the discharge duration becomes a predetermined period each time. That is, the control means can make the discharge duration constant by switching the switching element 11 from the ON state to the OFF state in a certain period from the occurrence of the discharge.
  • the discharge duration can be set to the same length in each discharge and is usually set to 500 ⁇ sec or less.
  • the control means can control the suspension period to be constant by setting the period during which the switching element 11 is in the OFF state to a predetermined period.
  • FIG. 4 shows the operation of the switching elements 7 and 8, the operation of the switching element 11, the time of the voltage V C1 across the smoothing capacitor 5 in the comparative example in which the capacity of the smoothing capacitor 5 is several hundred ⁇ F or more in the circuit configuration of FIG. It is a figure which shows the time change of a change, the time change of the voltage V between electrodes, and the electric current between the electrode 1 and the workpiece 2, ie, the electric current I between electrodes.
  • FIG. 4 also shows in what state the interelectrode voltage V is a voltage no-load period, a discharge duration period, and a rest period.
  • the voltage V C1 across the smoothing capacitor 5 can be kept constant by the pulse width modulation control as described above. .
  • the voltage V C1 across the smoothing capacitor 5 can be kept constant even when the capacity of the smoothing capacitor 5 is 100 ⁇ F. Therefore, in FIG. 4, even if the voltage of the commercial AC power supply 101 fluctuates, the constant both-end voltage V C1 is maintained by pulse width modulation control, and a current pulse for finishing with a constant interelectrode current I is output. Therefore, the uniformity of the current pulse is maintained in any power supply environment.
  • the discharge frequency and the frequency of concentrated discharge change due to factors other than the power supply environment such as the type and state of the machining fluid, machining shape, and machining area.
  • the discharge frequency is the number of discharge durations that occur in one second, and is a value proportional to the frequency of discharge.
  • the capacity of the smoothing capacitor 5 is made smaller than the value obtained by dividing the charge amount Q used in the discharge for one discharge duration by the set voltage V 0 of the smoothing capacitor 5.
  • a predetermined set voltage V 0 with respect to the voltage V C1 across the smoothing capacitor 5 is set as a value unique to the electric discharge machine 100.
  • the capacitance of the smoothing capacitor 5 is reduced to about several thousand pF such as 1000 pF.
  • the smoothing capacitor 5 may be removed. That is, the capacity of the smoothing capacitor 5 may be zero. Even when the smoothing capacitor 5 is removed, that is, when the capacitance of the smoothing capacitor 5 is set to 0, a capacitance on the order of pF can be generated as a stray capacitance.
  • the second drive is performed by making the capacity of the smoothing capacitor 5 smaller than the value obtained by dividing the charge amount Q used in the discharge for one discharge duration by the set voltage V 0 of the smoothing capacitor 5. It has been confirmed by experiments that the circuit operation can be changed without changing the system.
  • FIG. 5 shows the operation of the switching elements 7 and 8, the operation of the switching element 11, the time change of the voltage V C1 across the smoothing capacitor 5 in the first embodiment in which the capacity of the smoothing capacitor 5 is reduced in the circuit configuration of FIG. It is a figure which shows the time change of the voltage V between electrodes, and the electric current between the electrode 1 and the workpiece 2, ie, the time change of the electric current I between electrodes.
  • the smoothing capacitor 5 has a value that is less than the value obtained by dividing the charge amount Q used in the discharge for one discharge duration by the set voltage V 0 of the smoothing capacitor 5.
  • the charge of the smoothing capacitor 5 is easily charged and discharged. Since the carrier frequency of the pulse width modulation control of the switching elements 7 and 8 is constant, the capacitance of the smoothing capacitor 5 is reduced even if the duty of the ON period and OFF period of the switching elements 7 and 8 is varied to the maximum or the minimum. Charge / discharge of the electric charge of the smoothing capacitor 5 cannot follow the change of the discharge frequency during processing. As a result, as shown in FIG. 5, the voltage V C1 across the smoothing capacitor 5 changes because the set voltage V 0 cannot be maintained, and as a result, the voltage V between the electrodes also changes.
  • the interval at which the discharge duration occurs is long and the discharge frequency f is low, but the interval at which the discharge duration occurs gradually decreases and the discharge frequency f tends to be high. Therefore, in FIG. 5, the voltage V C1 across the smoothing capacitor 5 changes from a state higher than the set voltage V 0 to a low state in accordance with a temporal trend in which the discharge frequency f changes from a low state to a high state. Accordingly, the interelectrode voltage V also changes from a high state to a low state. Since the circuit shown in FIG.
  • the 2 is a resistance processing circuit using the current limiting resistor 14, the tendency of the change in the interelectrode voltage V is reflected in the interelectrode current I as it is.
  • the interpolar current I is large when f is low, and the interpolar current I is small when the discharge frequency f is high.
  • FIG. 6 is a diagram showing the relationship between the discharge frequency f on the horizontal axis and the interelectrode voltage V on the vertical axis.
  • the capacitance of the smoothing capacitor 5 is set to several hundreds ⁇ F or more, which is sufficiently higher than the value obtained by dividing the charge amount Q used for discharge in one discharge duration by the set voltage V 0 of the smoothing capacitor 5.
  • the interelectrode voltage V is constant regardless of the discharge frequency f, as shown by the broken line in FIG.
  • the interelectrode voltage V is low when the discharge frequency f is high, and the interelectrode voltage V is high when the discharge frequency f is low.
  • the interelectrode voltage V decreases when the discharge frequency f is high, thereby reducing the interelectrode current I.
  • the discharge frequency f is low, the interelectrode voltage V is decreased. Increases the inter-electrode current I.
  • FIG. FIG. 7 is a diagram illustrating a schematic configuration of an electric discharge machine 200 according to the second embodiment of the present invention.
  • the electric discharge machine 200 has a mechanism for adjusting the relative distance between the electrode 1 and the workpiece 2 based on the interelectrode voltage V.
  • the electric discharge machine 200 further includes an axis control unit 105 that performs position control of an axis that calculates an average value of the interelectrode voltage V and adjusts a relative distance between the electrode 1 and the workpiece 2.
  • the configuration of the electric discharge machine 200 other than the axis control unit 105 is the same as that of the electric discharge machine 100 of FIG.
  • the axis control unit 105 has a function of obtaining an interelectrode voltage V between the electrode 1 and the workpiece 2 and obtaining a time average value of the interelectrode voltage V during a predetermined period.
  • the length of the time averaged period is a period depending on the speed of axis control, such as 20 to 30 msec.
  • the axis control unit 105 performs control so that the workpiece 2 and the workpiece 2 are close to each other. This stabilizes the frequency of discharge, that is, the discharge frequency f.
  • the capacity Q of the smoothing capacitor 5 is further divided by the set voltage V 0 of the smoothing capacitor 5 by the amount of charge Q used for discharging for one discharge duration. Make the value smaller than By reducing the capacity of the smoothing capacitor 5 and causing the shaft control unit 105 to function, the inter-electrode voltage V is lowered when the discharge frequency f is high, so that the average voltage is lowered to escape the shaft, and when the discharge frequency f is low, As the voltage V increases, the average voltage increases and the shaft can be driven.
  • the control effect of the axis control unit 105 can be combined with the effect of avoiding the concentrated discharge in a short time range by reducing the capacity of the smoothing capacitor 5, the control to quickly reach the desired discharge frequency f can be performed. It becomes possible. That is, according to the second embodiment, the effect of avoiding the concentrated discharge obtained in the first embodiment can be realized in a longer time range.
  • FIG. 8 is a diagram illustrating an example of a smoothing capacitor having a variable capacitance.
  • the smoothing capacitor 50 is configured by connecting capacitors 51 to 54 in parallel, and switches 61 to 64 are connected to the capacitors 51 to 54, respectively.
  • Each of the switches 61 to 64 is a switching element such as a relay or an electromagnetic switch.
  • the capacitors 51 to 54 may all have the same capacity, but they do not necessarily have to be the same.
  • the capacities of the capacitors 51 to 54 may all be smaller than the value obtained by dividing the charge amount Q due to one discharge by the set voltage V 0 of the smoothing capacitor 50, but at least one of the capacities of the capacitors 51 to 54. It suffices if the charge amount Q due to one discharge is smaller than a value obtained by dividing the charge amount Q by the set voltage V 0 of the smoothing capacitor 50.
  • FIG. 9 is a diagram showing the relationship between the discharge frequency f and the interelectrode voltage V in the third embodiment.
  • the capacity of the smoothing capacitor 50 becomes smaller from A to D in FIG. An example of realizing such a situation is shown below.
  • A is a state in which all the switches 61 to 64 are in the ON state, and the capacity of the smoothing capacitor 50 is the sum of the respective capacities of the capacitors 51 to 54.
  • B is a state in which the switch 64 is turned off and the switches 61 to 63 are all turned on, and the capacitance of the smoothing capacitor 50 is the sum of the capacitances of the capacitors 51 to 53.
  • C is a state in which the switches 63 and 64 are turned off and the switches 61 and 62 are turned on, and the capacitance of the smoothing capacitor 50 is the sum of the capacitances of the capacitors 51 and 52.
  • D is a state in which the switches 62 to 64 are turned off and only the switch 61 is turned on, and the capacity of the smoothing capacitor 50 becomes the capacity of the capacitor 51.
  • the capacitance of the smoothing capacitor 50 at A is larger than the value obtained by dividing the charge amount Q due to one discharge by the set voltage V 0 of the smoothing capacitor 50, but the capacitance of the smoothing capacitor 50 at D is the charge amount Q due to one discharge. Is smaller than the value obtained by dividing by the set voltage V 0 of the smoothing capacitor 50.
  • the smoothing capacitor 5 is replaced with the variable capacitance smoothing capacitor 50 shown in FIG. 8, and the capacitance is changed using means such as the switches 61 to 64.
  • the change width of the interelectrode voltage V depending on the discharge frequency f. That is, according to the third embodiment, in addition to obtaining the effects obtained in the first and second embodiments, the degree of the effects can be controlled.
  • the configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

Abstract

A power supply device (110) for an electrical discharge machine is provided with a DC voltage conversion unit (102) for rectifying an AC power supply and outputting a DC voltage, a smoothing capacitor (5) for applying a voltage between an electrode (1) and a workpiece (2), a constant voltage control unit (103) for stabilizing the voltage of the smoothing capacitor on the basis of the DC voltage through the use of pulse-width modulation control, and a current limiting resistance switching unit (104) that is connected between the smoothing capacitor and electrode and limits the current flowing from the smoothing capacitor to the electrode. The capacity of the smoothing capacitor is smaller than the value obtained by dividing the charge amount used for discharging in the duration of a single discharge by a set voltage set beforehand for the smoothing capacitor. The power supply device (110) for an electrical discharge machine makes it possible to suppress increasing of the current flowing in a unit of time resulting from transient concentrated discharge and suppress arcing, flatness deterioration, and abnormal electrode wear.

Description

放電加工機の電源装置Electric discharge machine power supply
　本発明は、電極と被加工物との間に電圧をかけて、両者の極間に発生する放電現象を利用して被加工物を加工する放電加工機の電源装置に関する。 The present invention relates to a power supply device for an electric discharge machine that applies a voltage between an electrode and a workpiece and processes the workpiece using a discharge phenomenon generated between the electrodes.
　放電加工装置の電源は直流電圧電源を用いるのが一般的であり、この直流電圧電源は、商用交流電源を整流器によって整流し、平滑コンデンサによって平滑化するという構成になっている。このような構成の直流電圧電源を用いた場合、直流電圧電源の出力電圧は商用交流電源の電圧変動の影響を受け、結果として安定した加工結果を得られなくなってしまうという問題があった。 Generally, a DC voltage power supply is used as the power supply of the electric discharge machining apparatus, and this DC voltage power supply is configured such that a commercial AC power supply is rectified by a rectifier and smoothed by a smoothing capacitor. When the DC voltage power supply having such a configuration is used, there is a problem that the output voltage of the DC voltage power supply is affected by the voltage fluctuation of the commercial AC power supply, and as a result, a stable processing result cannot be obtained.
　直流電圧電源の上述したような出力電圧変動を抑制する手段としては、安定化電源を放電加工機の電源装置の外部に接続する方法があるが、電源容量の大きい放電加工装置の安定化電源は一般に非常に高価な上、設置場所も必要となる。加工を安定化させる別の方法として、以下の特許文献１に示される方法がある。特許文献１に示される放電加工装置においては、大電流を扱う荒加工時にはスイッチング方式回路を定電流制御して常に一定の加工電流パルスを供給し、小電流を扱う仕上げ加工時において抵抗式加工回路が動作する場合には、商用電源電圧が変動してもパルス幅変調（ＰＷＭ：Ｐｕｌｓｅ　Ｗｉｄｔｈ　Ｍｏｄｕｌａｔｉｏｎ）制御により一定の直流電源電圧を保って一定の加工電流パルスを供給する。これにより安定した放電加工を実現することができる。 As a means for suppressing the above-described output voltage fluctuation of the DC voltage power supply, there is a method of connecting a stabilized power supply to the outside of the power supply device of the electric discharge machine, Generally, it is very expensive and requires a place for installation. As another method for stabilizing the processing, there is a method disclosed in Patent Document 1 below. In the electric discharge machining apparatus disclosed in Patent Document 1, a constant machining current is controlled by a switching system circuit at the time of rough machining that handles a large current to always supply a constant machining current pulse, and a resistance machining circuit at the time of finishing machining that handles a small current. Is operated, a constant machining current pulse is supplied with a constant DC power supply voltage maintained by pulse width modulation (PWM) control even if the commercial power supply voltage fluctuates. Thereby, stable electric discharge machining can be realized.
国際公開第２００５／１０２５７８号International Publication No. 2005/102578
　特許文献１に示される電源装置の制御回路においては、電源制御に使用されているパルス幅変調制御用の平滑コンデンサに適切な容量を選定することで、商用電源電圧の変動などの外乱により直流電源電圧が増減した場合においても速やかに既定の電圧に戻すことが可能となる。 In the control circuit of the power supply device shown in Patent Document 1, a DC power supply is generated by disturbance such as fluctuations in commercial power supply voltage by selecting an appropriate capacity for the smoothing capacitor for pulse width modulation control used for power supply control. Even when the voltage increases or decreases, it is possible to quickly return to the predetermined voltage.
　直流電源電圧が一定に保たれることで加工電流のピーク値は一定となるが、放電間隙の状態により放電周波数が変化し、単位時間内に流れる電流は変動する。特に、仕上げ加工時には、一時的な集中放電による単位時間内に流れる電流の増加によってアークおよび平坦度の悪化、電極の異常消耗が発生してしまう。 ピ ー ク The peak value of the machining current becomes constant when the DC power supply voltage is kept constant, but the discharge frequency changes depending on the state of the discharge gap, and the current flowing within the unit time varies. In particular, during finishing, an increase in current flowing in a unit time due to temporary concentrated discharge causes deterioration of arc and flatness, and abnormal wear of electrodes.
　本発明は、上記に鑑みてなされたものであって、一時的な集中放電による単位時間内に流れる電流増加を抑制し、アークおよび平坦度の悪化、電極の異常消耗を抑制することが可能な放電加工機の電源装置を得ることを目的とする。 The present invention has been made in view of the above, and it is possible to suppress an increase in current flowing in a unit time due to temporary concentrated discharge, and to suppress deterioration of arc and flatness, and abnormal consumption of electrodes. It aims at obtaining the power supply device of an electric discharge machine.
　上述した課題を解決し、目的を達成するために、本発明は、交流電源を整流して直流電圧を出力する直流電圧変換部と、電極と被加工物との間に電圧を印加する平滑コンデンサと、前記直流電圧に基づいて、前記平滑コンデンサをパルス幅変調制御することにより定電圧化する定電圧制御部と、前記平滑コンデンサと前記電極との間に接続されて、前記平滑コンデンサから前記電極へ流れる電流を制限する電流制限用抵抗と、を備え、前記平滑コンデンサの容量は、１回の放電持続期間の放電で使用される電荷量を前記平滑コンデンサに対して予め定められた設定電圧で除算した値よりも小さいことを特徴とする。 In order to solve the above-described problems and achieve the object, the present invention provides a DC voltage converter that rectifies an AC power source and outputs a DC voltage, and a smoothing capacitor that applies a voltage between the electrode and the workpiece. A constant voltage control unit that makes the smoothing capacitor constant by performing pulse width modulation control on the basis of the DC voltage, and is connected between the smoothing capacitor and the electrode, from the smoothing capacitor to the electrode A current limiting resistor for limiting the current flowing to the capacitor, and the capacity of the smoothing capacitor is a predetermined voltage set for the smoothing capacitor to determine the amount of charge used for discharging during one discharge duration. It is characterized by being smaller than the divided value.
　本発明にかかる放電加工機の電源装置は、一時的な集中放電による単位時間内に流れる電流増加を抑制し、アークおよび平坦度の悪化、電極の異常消耗を抑制することが可能になるという効果を奏する。 The power supply device for an electric discharge machine according to the present invention is capable of suppressing an increase in current flowing in a unit time due to temporary concentrated discharge and suppressing deterioration of arc and flatness and abnormal consumption of electrodes. Play.
実施の形態１にかかる放電加工機の概略構成を示す図The figure which shows schematic structure of the electric discharge machine concerning Embodiment 1. FIG. 実施の形態１にかかる放電加工機の電源装置の回路構成の一例を詳細に示した図The figure which showed in detail the example of the circuit structure of the power supply device of the electric discharge machine concerning Embodiment 1. 実施の形態１にかかる放電加工機の電源装置の回路構成の一例に動作ループを追記した図The figure which added the operation loop to an example of the circuit composition of the power supply device of the electric discharge machine concerning Embodiment 1 比較例にかかる放電加工機の電源装置の動作の時間変化の様子を示す図The figure which shows the mode of the time change of operation | movement of the power supply device of the electric discharge machine concerning a comparative example 実施の形態１にかかる放電加工機の電源装置の動作の時間変化の様子を示す図The figure which shows the mode of the time change of operation | movement of the power supply device of the electric discharge machine concerning Embodiment 1. FIG. 実施の形態１における放電周波数ｆと極間電圧Ｖとの関係を示す図The figure which shows the relationship between the discharge frequency f in Embodiment 1, and the electrode voltage V 実施の形態２にかかる放電加工機の概略構成を示す図The figure which shows schematic structure of the electric discharge machine concerning Embodiment 2. FIG. 実施の形態３にかかる容量可変な平滑コンデンサの一例を示す図FIG. 6 is a diagram illustrating an example of a variable capacitance smoothing capacitor according to the third embodiment. 実施の形態３における放電周波数ｆと極間電圧Ｖとの関係を示す図The figure which shows the relationship between the discharge frequency f in Embodiment 3, and the electrode voltage V
　以下に、本発明の実施の形態にかかる放電加工機の電源装置を図面に基づいて詳細に説明する。なお、この実施の形態によりこの発明が限定されるものではない。 Hereinafter, a power supply device for an electric discharge machine according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.
実施の形態１．
　図１は、本発明の実施の形態１にかかる放電加工機１００の概略構成を示す図である。放電加工機１００は、商用交流電源１０１に接続された放電加工機の電源装置１１０と、電極１と、放電加工の対象である被加工物２とを備える。 Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a schematic configuration of an electric discharge machine 100 according to the first embodiment of the present invention. The electric discharge machine 100 includes a power supply device 110 of an electric discharge machine connected to a commercial AC power supply 101, an electrode 1, and a workpiece 2 that is an object of electric discharge machining.
　放電加工機の電源装置１１０は、商用交流電源１０１を整流器によって整流して直流電圧を出力する直流電圧変換部１０２と、直流電圧変換部１０２に接続され直流電圧を定電圧化する定電圧制御部１０３と、定電圧制御部１０３に接続される定電圧制御用の平滑コンデンサ５と、放電加工のために平滑コンデンサ５から電極１へ流れる電流を制限する電流制限用抵抗を有する電流制限抵抗切換部１０４と、を備える。 A power supply device 110 for an electric discharge machine includes a DC voltage conversion unit 102 that rectifies a commercial AC power supply 101 by a rectifier and outputs a DC voltage, and a constant voltage control unit that is connected to the DC voltage conversion unit 102 and converts the DC voltage to a constant voltage. 103, a smoothing capacitor 5 for constant voltage control connected to the constant voltage control unit 103, and a current limiting resistor switching unit having a current limiting resistor for limiting the current flowing from the smoothing capacitor 5 to the electrode 1 for electric discharge machining 104.
　電流制限抵抗切換部１０４は、電流制限用抵抗を切り替えることが可能であり、電極１に接続されている。平滑コンデンサ５の一端は電流制限抵抗切換部１０４に接続され、平滑コンデンサ５の他端は被加工物２に接続されている。平滑コンデンサ５は、定電圧制御部１０３によって予め定めた電圧を有するようにパルス幅変調制御され、電極１と被加工物２との間に電圧を印加して放電を発生させる電源として機能する。 The current limiting resistance switching unit 104 can switch the current limiting resistance and is connected to the electrode 1. One end of the smoothing capacitor 5 is connected to the current limiting resistance switching unit 104, and the other end of the smoothing capacitor 5 is connected to the workpiece 2. The smoothing capacitor 5 is subjected to pulse width modulation control so as to have a predetermined voltage by the constant voltage control unit 103, and functions as a power source that generates a discharge by applying a voltage between the electrode 1 and the workpiece 2.
　図２は、実施の形態１にかかる図１に示した放電加工機の電源装置１１０の回路構成の一例を詳細に示した図である。図２において、図１と同一符号を付した構成要素は同じ構成要素である。 FIG. 2 is a diagram showing in detail an example of the circuit configuration of the power supply device 110 of the electric discharge machine shown in FIG. 1 according to the first embodiment. In FIG. 2, components given the same reference numerals as those in FIG. 1 are the same components.
　直流電圧変換部１０２は、商用交流電源１０１を整流する整流器３と、整流器３を平滑化するため整流器３に並列接続されたコンデンサ４と、を備える。 The DC voltage conversion unit 102 includes a rectifier 3 that rectifies the commercial AC power supply 101 and a capacitor 4 that is connected in parallel to the rectifier 3 in order to smooth the rectifier 3.
　定電圧制御部１０３は、平滑コンデンサ５に並列接続された放電抵抗１３と、直流電圧変換部１０２に並列接続されたコンデンサ６と、平滑コンデンサ５とコンデンサ６との間に接続された駆動方式を切り換えるための電磁開閉器２０と、整流用ダイオード１９と、コンデンサ６と整流用ダイオード１９との間に接続されたスイッチング素子７と、スイッチング素子７および整流用ダイオード１９に接続されたリアクトル１２と、リアクトル１２と整流用ダイオード１９との間に接続されたスイッチング素子８と、平滑コンデンサ５とリアクトル１２との間に接続された整流用ダイオード２１と、を備える。また、平滑コンデンサ５、放電抵抗１３、コンデンサ６、整流用ダイオード１９、およびスイッチング素子８はそれぞれの一端が全て、後述するスイッチング素子１０を介して被加工物２へと接続されている。 The constant voltage control unit 103 includes a discharge resistor 13 connected in parallel to the smoothing capacitor 5, a capacitor 6 connected in parallel to the DC voltage conversion unit 102, and a driving method connected between the smoothing capacitor 5 and the capacitor 6. An electromagnetic switch 20 for switching, a rectifying diode 19, a switching element 7 connected between the capacitor 6 and the rectifying diode 19, a reactor 12 connected to the switching element 7 and the rectifying diode 19, The switching element 8 is connected between the reactor 12 and the rectifying diode 19, and the rectifying diode 21 is connected between the smoothing capacitor 5 and the reactor 12. The smoothing capacitor 5, the discharge resistor 13, the capacitor 6, the rectifying diode 19, and the switching element 8 are all connected to the workpiece 2 through the switching element 10 described later.
　電流制限抵抗切換部１０４は、放電電流を制限するための電流制限用抵抗１４と、整流用ダイオード１７と、電流制限用抵抗１４と整流用ダイオード１７との間に接続されたスイッチング素子１１と、を備える。 The current limiting resistor switching unit 104 includes a current limiting resistor 14 for limiting a discharge current, a rectifying diode 17, a switching element 11 connected between the current limiting resistor 14 and the rectifying diode 17, Is provided.
　放電加工機１００は、さらに、被加工物２とスイッチング素子８との間に接続されたスイッチング素子１０と、被加工物２と平滑コンデンサ５との間に接続された整流用ダイオード１８と、リアクトル１２と電極１との間に直列に接続されたスイッチング素子９および整流用ダイオード１６と、スイッチング素子９および整流用ダイオード１６とスイッチング素子１０の間に接続された整流用ダイオード１５と、を備える。放電加工機１００は、さらに、平滑コンデンサ５の両端電圧ＶC1を検出する検出部３０を備える。検出部３０は、検出した両端電圧ＶC1と予め定められた設定電圧Ｖ0との大小関係に基づいて、スイッチング素子７および８のＯＮ状態またはＯＦＦ状態を切り替える。 The electric discharge machine 100 further includes a switching element 10 connected between the workpiece 2 and the switching element 8, a rectifying diode 18 connected between the workpiece 2 and the smoothing capacitor 5, and a reactor. Switching element 9 and rectifying diode 16 connected in series between 12 and electrode 1, and rectifying diode 15 connected between switching element 9 and rectifying diode 16 and switching element 10. The electric discharge machine 100 further includes a detection unit 30 that detects the voltage V C1 across the smoothing capacitor 5. The detection unit 30 switches the ON state or the OFF state of the switching elements 7 and 8 based on the magnitude relationship between the detected both-end voltage V C1 and a predetermined set voltage V 0 .
　図２に示した回路の動作を以下に説明する。この回路は動作方式として、数十アンペア、またはそれ以上の電流を必要とする荒加工用にスイッチング方式回路を定電流制御して常に一定の加工電流パルスを供給する第一の駆動方式と、数アンペアあるいはそれ以下の電流を必要とする仕上げ加工用に商用交流電源１０１の電圧が変動してもパルス幅変調制御により一定の直流電源電圧を保ち、一定の仕上げ加工用の電流パルスを供給する第二の駆動方式と、を有する。実施の形態１ではこの第二の駆動方式を使用する。 The operation of the circuit shown in FIG. 2 will be described below. This circuit operates as a first drive system that supplies constant machining current pulses by constant current control of the switching system circuit for rough machining that requires a current of several tens of amperes or more. Even if the voltage of the commercial AC power supply 101 fluctuates for finishing processing that requires a current of ampere or less, a constant DC power supply voltage is maintained by pulse width modulation control and a constant current pulse for finishing processing is supplied. Two drive systems. In the first embodiment, this second driving method is used.
　図２に示した回路における第二の駆動方式による動作ループを追記した回路図を図３に示す。第二の駆動方式においては、電圧無負荷期間中、放電持続期間中、および休止期間中のいずれの期間中においても、電磁開閉器２０およびスイッチング素子９はＯＦＦ状態になっており、スイッチング素子１０はＯＮ状態になっている。電圧無負荷期間は、電極１と被加工物２との間に電圧が印加されているものの絶縁状態にあって放電が発生していない期間である。放電持続期間は、電極１と被加工物２との間に電圧が印加されていて実際に放電が発生している期間である。休止期間は、電極１と被加工物２との間に電圧が印加されていない期間である。 FIG. 3 shows a circuit diagram in which an operation loop according to the second driving method in the circuit shown in FIG. 2 is added. In the second driving method, the electromagnetic switch 20 and the switching element 9 are in the OFF state during any of the voltage no-load period, the discharge duration period, and the rest period, and the switching element 10 Is in the ON state. The voltage no-load period is a period in which a voltage is applied between the electrode 1 and the work piece 2 but in an insulated state and no discharge is generated. The discharge duration is a period in which a voltage is applied between the electrode 1 and the workpiece 2 and a discharge is actually generated. The rest period is a period in which no voltage is applied between the electrode 1 and the workpiece 2.
　また、スイッチング素子７および８は、電圧無負荷期間中、放電持続期間中および休止期間中のいずれの期間中においても、平滑コンデンサ５の両端電圧ＶC1を検出する検出部３０によりＯＮ状態またはＯＦＦ状態が切り替えられる。 Further, the switching elements 7 and 8 are turned on or off by the detection unit 30 that detects the voltage V C1 across the smoothing capacitor 5 during any of the voltage no-load period, the discharge duration period, and the rest period. The state is switched.
　平滑コンデンサ５の両端電圧ＶC1が設定電圧Ｖ0を上回っている場合は、検出部３０はスイッチング素子７および８を共にＯＮ状態とし、図３において破線で示したループ（１）の経路で直流電圧変換部１０２からリアクトル１２に電流を流し、リアクトル１２のコイルに磁束としてエネルギーが蓄えられる。 When the voltage V C1 across the smoothing capacitor 5 exceeds the set voltage V 0 , the detection unit 30 turns on both the switching elements 7 and 8, and direct current is generated along the loop (1) indicated by the broken line in FIG. A current is passed from the voltage conversion unit 102 to the reactor 12, and energy is stored in the coil of the reactor 12 as a magnetic flux.
　平滑コンデンサ５の両端電圧ＶC1が設定電圧Ｖ0を下回っている場合は、検出部３０はスイッチング素子７および８を共にＯＦＦ状態とし、図３において一点鎖線で示したループ（２）の経路でリアクトル１２からの電流で平滑コンデンサ５を充電する。これにより両端電圧ＶC1の電圧を上昇させて設定電圧Ｖ0に近づけ一定に保つように制御している。 When the voltage V C1 across the smoothing capacitor 5 is lower than the set voltage V 0 , the detection unit 30 turns off both the switching elements 7 and 8 and follows the loop (2) path indicated by the one-dot chain line in FIG. The smoothing capacitor 5 is charged with the current from the reactor 12. As a result, the voltage of the both-end voltage V C1 is increased and controlled so as to be kept close to the set voltage V 0 .
　このパルス幅変調制御ではキャリア周波数は一定、即ち、周期は一定である。そして、一定の周期内のスイッチング素子７および８のＯＮ期間とＯＦＦ期間の比を変化させる。即ち、スイッチング素子７および８のＯＮ期間とＯＦＦ期間のデューティを変化させて動作するパルス幅変調制御が実行される。ちなみに、ここで言うデューティは、例えば、ＯＮ期間とＯＦＦ期間とを合わせた１周期に対するＯＮ期間の比である。一般に、デューティの値には最大値および最小値が設定されている。従って、両端電圧ＶC1が設定電圧Ｖ0を上回っている場合にスイッチング素子７および８を常時ＯＮ状態にし続けること、或いは両端電圧ＶC1が設定電圧Ｖ0を下回っている場合にスイッチング素子７および８を常時ＯＦＦ状態にし続けることは出来ない。 In this pulse width modulation control, the carrier frequency is constant, that is, the period is constant. Then, the ratio between the ON period and the OFF period of the switching elements 7 and 8 within a certain period is changed. In other words, pulse width modulation control is performed in which the duty of the ON period and OFF period of the switching elements 7 and 8 is changed. Incidentally, the duty referred to here is, for example, the ratio of the ON period to one cycle including the ON period and the OFF period. Generally, a maximum value and a minimum value are set as the duty value. Therefore, to continue to the switching element 7 and 8 always ON state when the voltage across V C1 is higher than the set voltage V 0, or the switching element 7 and, if the voltage across V C1 is below the set voltage V 0 8 cannot be kept in the OFF state at all times.
　上記のように両端電圧ＶC1が常に一定の設定電圧Ｖ0を保つような制御が行われている平滑コンデンサ５を電源とし、電圧無負荷期間中および放電持続期間中だけスイッチング素子１１をＯＮ状態にする。上述したように第二の駆動方式においてスイッチング素子１０はＯＮ状態になっているので、スイッチング素子１１がＯＮ状態になることにより、電極１と被加工物２との間に電圧が印加されるが、電圧が印加された状態での放電が発生するタイミングは自然現象なので予測出来ない。従って、スイッチング素子１１がＯＮ状態である期間は、電圧無負荷期間中と放電持続期間中とに分けられる。そして、放電持続期間中は、電流制限用抵抗１４の値に応じた一定電流ピークの仕上げ加工用電流パルスが出力される。 As described above, the smoothing capacitor 5 that is controlled so that the voltage V C1 at both ends always maintains a constant set voltage V 0 is used as a power source, and the switching element 11 is in the ON state only during the voltage no-load period and the discharge duration period. To. As described above, since the switching element 10 is in the ON state in the second driving method, a voltage is applied between the electrode 1 and the workpiece 2 when the switching element 11 is in the ON state. The timing at which discharge occurs in a state where a voltage is applied is a natural phenomenon and cannot be predicted. Therefore, the period during which the switching element 11 is in the ON state is divided into a voltage no-load period and a discharge duration period. During the discharge duration period, a finishing current pulse having a constant current peak corresponding to the value of the current limiting resistor 14 is output.
　電極１と被加工物２との間の電圧、即ち極間電圧Ｖに基づいて図示せぬ制御手段によりスイッチング素子１１は制御されている。スイッチング素子１１がＯＮ状態になった後に極間電圧Ｖが低下することを検出することにより、制御手段は放電が発生したことを検知できる。従って、制御手段は、放電持続期間が毎回予め定めた期間になるようにスイッチング素子１１をＯＦＦ状態にする。即ち、制御手段は、放電の発生から一定の期間でスイッチング素子１１をＯＮ状態からＯＦＦ状態に切り替えることにより放電持続期間を一定にすることができる。放電持続期間は、毎回の放電において同じ長さの期間に設定することが可能であり、通常５００μｓｅｃ以下に設定される。さらに、制御手段はスイッチング素子１１がＯＦＦ状態である期間を予め定めた期間とすることにより休止期間も一定に制御することができる。 The switching element 11 is controlled by control means (not shown) based on the voltage between the electrode 1 and the workpiece 2, that is, the inter-electrode voltage V. By detecting that the inter-electrode voltage V decreases after the switching element 11 is turned on, the control means can detect that discharge has occurred. Therefore, the control means turns off the switching element 11 so that the discharge duration becomes a predetermined period each time. That is, the control means can make the discharge duration constant by switching the switching element 11 from the ON state to the OFF state in a certain period from the occurrence of the discharge. The discharge duration can be set to the same length in each discharge and is usually set to 500 μsec or less. Furthermore, the control means can control the suspension period to be constant by setting the period during which the switching element 11 is in the OFF state to a predetermined period.
　図４は、図２の回路構成において平滑コンデンサ５の容量を数百μＦ以上にした比較例における、スイッチング素子７および８の動作、スイッチング素子１１の動作、平滑コンデンサ５の両端電圧ＶC1の時間変化、極間電圧Ｖの時間変化、および電極１と被加工物２との間の電流、即ち極間電流Ｉの時間変化を示す図である。図４には、極間電圧Ｖがどのような状態のときが、電圧無負荷期間、放電持続期間、および休止期間であるかも示してある。 4 shows the operation of the switching elements 7 and 8, the operation of the switching element 11, the time of the voltage V C1 across the smoothing capacitor 5 in the comparative example in which the capacity of the smoothing capacitor 5 is several hundred μF or more in the circuit configuration of FIG. It is a figure which shows the time change of a change, the time change of the voltage V between electrodes, and the electric current between the electrode 1 and the workpiece 2, ie, the electric current I between electrodes. FIG. 4 also shows in what state the interelectrode voltage V is a voltage no-load period, a discharge duration period, and a rest period.
　平滑コンデンサ５の容量を数百μＦ以上にした場合、前述したようにパルス幅変調制御によって平滑コンデンサ５の両端電圧ＶC1を一定に保つことが可能であることが実験的に明らかとなっている。平滑コンデンサ５の両端電圧ＶC1を一定に保つことは、平滑コンデンサ５の容量が１００μＦでも可能である。従って、図４においては、商用交流電源１０１の電圧が変動してもパルス幅変調制御により一定の両端電圧ＶC1が保たれ、一定の極間電流Ｉの仕上げ加工用の電流パルスが出力されるため、あらゆる電源環境において電流パルスの均一性は保たれる。 When the capacity of the smoothing capacitor 5 is several hundred μF or more, it has been experimentally revealed that the voltage V C1 across the smoothing capacitor 5 can be kept constant by the pulse width modulation control as described above. . The voltage V C1 across the smoothing capacitor 5 can be kept constant even when the capacity of the smoothing capacitor 5 is 100 μF. Therefore, in FIG. 4, even if the voltage of the commercial AC power supply 101 fluctuates, the constant both-end voltage V C1 is maintained by pulse width modulation control, and a current pulse for finishing with a constant interelectrode current I is output. Therefore, the uniformity of the current pulse is maintained in any power supply environment.
　しかし、一方で実際の加工においてはその他に加工液の種類および状態、加工形状および加工面積など電源環境以外の要因により放電周波数および集中放電の発生頻度は変化してしまうため、加工結果の均一性を保つこと或いは異常放電を回避することは、電流パルスにおける極間電流Ｉの均一性だけでは困難であるという問題がある。ここで放電周波数とは、一秒間に発生する放電持続期間の回数であり、放電の頻度に比例する値である。 However, in actual machining, the discharge frequency and the frequency of concentrated discharge change due to factors other than the power supply environment such as the type and state of the machining fluid, machining shape, and machining area. There is a problem that it is difficult to maintain the current or to avoid abnormal discharge only by the uniformity of the interelectrode current I in the current pulse. Here, the discharge frequency is the number of discharge durations that occur in one second, and is a value proportional to the frequency of discharge.
　そこで、実施の形態１においては、１回の放電持続期間の放電で使用される電荷量Ｑを平滑コンデンサ５の設定電圧Ｖ0で除算した値よりも平滑コンデンサ５の容量を小さくする。平滑コンデンサ５の両端電圧ＶC1に対して予め定められた設定電圧Ｖ0は、放電加工機１００に固有の値として設定される。具体的には、平滑コンデンサ５の容量を１０００ｐＦといった数千ｐＦ程度まで小さくする。さらに言えば、平滑コンデンサ５を除去してもよい。即ち、平滑コンデンサ５の容量を０にしてもよい。平滑コンデンサ５を除去した場合、即ち平滑コンデンサ５の容量を０にした場合であっても、浮遊容量としてｐＦオーダーの容量は生じ得る。 Therefore, in the first embodiment, the capacity of the smoothing capacitor 5 is made smaller than the value obtained by dividing the charge amount Q used in the discharge for one discharge duration by the set voltage V 0 of the smoothing capacitor 5. A predetermined set voltage V 0 with respect to the voltage V C1 across the smoothing capacitor 5 is set as a value unique to the electric discharge machine 100. Specifically, the capacitance of the smoothing capacitor 5 is reduced to about several thousand pF such as 1000 pF. Furthermore, the smoothing capacitor 5 may be removed. That is, the capacity of the smoothing capacitor 5 may be zero. Even when the smoothing capacitor 5 is removed, that is, when the capacitance of the smoothing capacitor 5 is set to 0, a capacitance on the order of pF can be generated as a stray capacitance.
　上述のように、平滑コンデンサ５の容量を１回の放電持続期間の放電で使用される電荷量Ｑを平滑コンデンサ５の設定電圧Ｖ0で除算した値よりも小さくすることにより、第二の駆動方式のままで回路動作を変えることが可能となることが実験により確認できた。 As described above, the second drive is performed by making the capacity of the smoothing capacitor 5 smaller than the value obtained by dividing the charge amount Q used in the discharge for one discharge duration by the set voltage V 0 of the smoothing capacitor 5. It has been confirmed by experiments that the circuit operation can be changed without changing the system.
　図５は、図２の回路構成において平滑コンデンサ５の容量を小さくした実施の形態１における、スイッチング素子７および８の動作、スイッチング素子１１の動作、平滑コンデンサ５の両端電圧ＶC1の時間変化、極間電圧Ｖの時間変化、および電極１と被加工物２との間の電流、即ち極間電流Ｉの時間変化を示す図である。 5 shows the operation of the switching elements 7 and 8, the operation of the switching element 11, the time change of the voltage V C1 across the smoothing capacitor 5 in the first embodiment in which the capacity of the smoothing capacitor 5 is reduced in the circuit configuration of FIG. It is a figure which shows the time change of the voltage V between electrodes, and the electric current between the electrode 1 and the workpiece 2, ie, the time change of the electric current I between electrodes.
　実施の形態１にかかる放電加工機１００の電源装置においては、１回の放電持続期間の放電で使用される電荷量Ｑを平滑コンデンサ５の設定電圧Ｖ0で除算した値よりも平滑コンデンサ５の容量を小さくしたことにより、平滑コンデンサ５の電荷が充放電しやすくなる。スイッチング素子７および８のパルス幅変調制御のキャリア周波数は一定なので、スイッチング素子７および８のＯＮ期間とＯＦＦ期間のデューティを最大あるいは最小に可変しても、平滑コンデンサ５の容量を小さくしたことにより加工中の放電周波数の変化に平滑コンデンサ５の電荷の充放電が追従できなくなる。その結果、図５に示すように平滑コンデンサ５の両端電圧ＶC1は設定電圧Ｖ0を維持出来なくなって変化し、結果として極間電圧Ｖも変化する。 In the power supply device of the electric discharge machine 100 according to the first embodiment, the smoothing capacitor 5 has a value that is less than the value obtained by dividing the charge amount Q used in the discharge for one discharge duration by the set voltage V 0 of the smoothing capacitor 5. By reducing the capacity, the charge of the smoothing capacitor 5 is easily charged and discharged. Since the carrier frequency of the pulse width modulation control of the switching elements 7 and 8 is constant, the capacitance of the smoothing capacitor 5 is reduced even if the duty of the ON period and OFF period of the switching elements 7 and 8 is varied to the maximum or the minimum. Charge / discharge of the electric charge of the smoothing capacitor 5 cannot follow the change of the discharge frequency during processing. As a result, as shown in FIG. 5, the voltage V C1 across the smoothing capacitor 5 changes because the set voltage V 0 cannot be maintained, and as a result, the voltage V between the electrodes also changes.
　図５において、当初は放電持続期間が発生する間隔が長く放電周波数ｆが低い状態であるが、次第に放電持続期間が発生する間隔が短くなり放電周波数ｆが高い状態になる傾向がみられる。従って、図５においては、放電周波数ｆが低い状態から高い状態へと変化する時間的な傾向に従って、平滑コンデンサ５の両端電圧ＶC1が設定電圧Ｖ0より高い状態から低い状態へと変化しており、それに伴い極間電圧Ｖも高い状態から低い状態へと変化している。実施の形態１にかかる図２に示した回路は、電流制限用抵抗１４による抵抗式加工回路であるため、極間電圧Ｖの変化の傾向はそのまま極間電流Ｉに反映されるので、放電周波数ｆが低い状態では極間電流Ｉは大きく、放電周波数ｆが高い状態では極間電流Ｉは小さくなる。 In FIG. 5, initially, the interval at which the discharge duration occurs is long and the discharge frequency f is low, but the interval at which the discharge duration occurs gradually decreases and the discharge frequency f tends to be high. Therefore, in FIG. 5, the voltage V C1 across the smoothing capacitor 5 changes from a state higher than the set voltage V 0 to a low state in accordance with a temporal trend in which the discharge frequency f changes from a low state to a high state. Accordingly, the interelectrode voltage V also changes from a high state to a low state. Since the circuit shown in FIG. 2 according to the first embodiment is a resistance processing circuit using the current limiting resistor 14, the tendency of the change in the interelectrode voltage V is reflected in the interelectrode current I as it is. The interpolar current I is large when f is low, and the interpolar current I is small when the discharge frequency f is high.
　図６は、横軸を放電周波数ｆ、縦軸を極間電圧Ｖとして両者の関係を示す図である。比較例のように平滑コンデンサ５の容量を数百μＦ以上にして、１回の放電持続期間の放電で使用される電荷量Ｑを平滑コンデンサ５の設定電圧Ｖ0で除算した値よりも十分に大きくした場合は、図６の破線に示すように、放電周波数ｆによらず極間電圧Ｖは一定である。しかし、実施の形態１のように平滑コンデンサ５の容量を１回の放電持続期間の放電で使用される電荷量Ｑを平滑コンデンサ５の設定電圧Ｖ0で除算した値よりも小さくした場合は、図６の実線に示すように、放電周波数ｆが高い時には極間電圧Ｖが低くなり、放電周波数ｆが低い時には極間電圧Ｖが高くなる。 FIG. 6 is a diagram showing the relationship between the discharge frequency f on the horizontal axis and the interelectrode voltage V on the vertical axis. As in the comparative example, the capacitance of the smoothing capacitor 5 is set to several hundreds μF or more, which is sufficiently higher than the value obtained by dividing the charge amount Q used for discharge in one discharge duration by the set voltage V 0 of the smoothing capacitor 5. When it is increased, the interelectrode voltage V is constant regardless of the discharge frequency f, as shown by the broken line in FIG. However, when the capacity of the smoothing capacitor 5 is made smaller than the value obtained by dividing the charge amount Q used in the discharge for one discharge duration by the set voltage V 0 of the smoothing capacitor 5 as in the first embodiment, As shown by the solid line in FIG. 6, the interelectrode voltage V is low when the discharge frequency f is high, and the interelectrode voltage V is high when the discharge frequency f is low.
　実施の形態１にかかる放電加工機の電源装置１１０によれば、放電周波数ｆが高い時には極間電圧Ｖが低くなることで極間電流Ｉが減少し、放電周波数ｆが低い時には極間電圧Ｖが高くなることで極間電流Ｉを増大させる。これにより、一時的な集中放電によって放電周波数ｆが高くなった場合であっても、極間電流Ｉの時間平均値の増加を抑制することが可能となる。即ち、一時的な集中放電による極間電流Ｉの時間平均値の増加を抑制することで加工エネルギーの均一化が図れ、アークおよび平坦度の悪化、電極１の異常消耗を抑制することが可能となる。 According to the power supply device 110 for the electric discharge machine according to the first embodiment, the interelectrode voltage V decreases when the discharge frequency f is high, thereby reducing the interelectrode current I. When the discharge frequency f is low, the interelectrode voltage V is decreased. Increases the inter-electrode current I. Thereby, even if it is a case where the discharge frequency f becomes high by temporary concentrated discharge, it becomes possible to suppress the increase in the time average value of the electric current I between poles. That is, by suppressing the increase in the time average value of the interelectrode current I due to temporary concentrated discharge, the processing energy can be made uniform, and the deterioration of the arc and flatness and the abnormal wear of the electrode 1 can be suppressed. Become.
実施の形態２．
　図７は、本発明の実施の形態２にかかる放電加工機２００の概略構成を示す図である。放電加工機２００は実施の形態１の図１の放電加工機１００と異なり、極間電圧Ｖに基づいて電極１と被加工物２との間の相対距離を調節する機構を有している。具体的には、放電加工機２００は、極間電圧Ｖの平均値を求めて電極１と被加工物２との間の相対距離を調節する軸の位置制御を行う軸制御部１０５をさらに備える。放電加工機２００の軸制御部１０５以外の構成は実施の形態１の図１の放電加工機１００と同様である。 Embodiment 2. FIG.
FIG. 7 is a diagram illustrating a schematic configuration of an electric discharge machine 200 according to the second embodiment of the present invention. Unlike the electric discharge machine 100 of FIG. 1 of the first embodiment, the electric discharge machine 200 has a mechanism for adjusting the relative distance between the electrode 1 and the workpiece 2 based on the interelectrode voltage V. Specifically, the electric discharge machine 200 further includes an axis control unit 105 that performs position control of an axis that calculates an average value of the interelectrode voltage V and adjusts a relative distance between the electrode 1 and the workpiece 2. . The configuration of the electric discharge machine 200 other than the axis control unit 105 is the same as that of the electric discharge machine 100 of FIG.
　軸制御部１０５は、電極１と被加工物２との間の極間電圧Ｖを取得して、予め定めた期間の極間電圧Ｖの時間平均値を求める機能を有する。時間平均をとる期間の長さは、２０～３０ｍｓｅｃといった軸制御のスピードの依存した期間となる。そして、求めた時間平均値が予め定めた基準値より低い場合、即ち放電が発生し易い場合は、電極１と被加工物２との間の距離が近くなっているので軸を逃がす、即ち電極１と被加工物２とを離すように軸制御部１０５は制御を行う。他方、求めた時間平均値が予め定めた基準値より高い場合、即ち放電が発生し難い場合は、電極１と被加工物２との間の距離が離れているので軸を追い込む、即ち電極１と被加工物２とを近づけるように軸制御部１０５は制御を行う。これにより放電の発生頻度、即ち放電周波数ｆの安定化を図っている。 The axis control unit 105 has a function of obtaining an interelectrode voltage V between the electrode 1 and the workpiece 2 and obtaining a time average value of the interelectrode voltage V during a predetermined period. The length of the time averaged period is a period depending on the speed of axis control, such as 20 to 30 msec. When the obtained time average value is lower than a predetermined reference value, that is, when electric discharge is likely to occur, the distance between the electrode 1 and the workpiece 2 is close, so that the axis is escaped, that is, the electrode The axis control unit 105 performs control so that 1 and the workpiece 2 are separated from each other. On the other hand, when the obtained time average value is higher than a predetermined reference value, that is, when it is difficult for discharge to occur, the distance between the electrode 1 and the workpiece 2 is long, so that the axis is driven, that is, the electrode 1 The axis control unit 105 performs control so that the workpiece 2 and the workpiece 2 are close to each other. This stabilizes the frequency of discharge, that is, the discharge frequency f.
　実施の形態２にかかる放電加工機２００の電源装置においては、さらに、平滑コンデンサ５の容量を１回の放電持続期間の放電で使用される電荷量Ｑを平滑コンデンサ５の設定電圧Ｖ0で除算した値よりも小さくする。平滑コンデンサ５の容量を小さくして軸制御部１０５を機能させることにより、放電周波数ｆが高い時には極間電圧Ｖが低くなることで平均電圧が下がって軸を逃がし、放電周波数ｆが低い時には極間電圧Ｖが高くなることで平均電圧が上がって軸を追い込むことが可能となる。 In the power supply device of the electric discharge machine 200 according to the second embodiment, the capacity Q of the smoothing capacitor 5 is further divided by the set voltage V 0 of the smoothing capacitor 5 by the amount of charge Q used for discharging for one discharge duration. Make the value smaller than By reducing the capacity of the smoothing capacitor 5 and causing the shaft control unit 105 to function, the inter-electrode voltage V is lowered when the discharge frequency f is high, so that the average voltage is lowered to escape the shaft, and when the discharge frequency f is low, As the voltage V increases, the average voltage increases and the shaft can be driven.
　即ち、平滑コンデンサ５の容量を小さくしたことによる短い時間レンジでの集中放電の回避効果に、軸制御部１０５の制御効果を組み合わせることができるので、素早く所望の放電周波数ｆになるような制御が可能となる。即ち、実施の形態２によれば、実施の形態１で得られた集中放電の回避効果をより長い時間レンジで実現することが可能となる。 That is, since the control effect of the axis control unit 105 can be combined with the effect of avoiding the concentrated discharge in a short time range by reducing the capacity of the smoothing capacitor 5, the control to quickly reach the desired discharge frequency f can be performed. It becomes possible. That is, according to the second embodiment, the effect of avoiding the concentrated discharge obtained in the first embodiment can be realized in a longer time range.
実施の形態３．
　実施の形態３においては、実施の形態１および２にかかる放電加工機１００および２００において、平滑コンデンサ５を図８に示すような容量可変な平滑コンデンサ５０に置き換える。即ち、平滑コンデンサの容量を可変にする。図８は、容量が可変な平滑コンデンサの一例を示す図である。平滑コンデンサ５０は、コンデンサ５１～５４を並列接続して構成されており、コンデンサ５１～５４のそれぞれにスイッチ６１～６４が接続されている。スイッチ６１～６４のそれぞれは、リレー或いは電磁開閉器といったスイッチング素子である。 Embodiment 3 FIG.
In the third embodiment, in the electric discharge machines 100 and 200 according to the first and second embodiments, the smoothing capacitor 5 is replaced with a variable capacitance smoothing capacitor 50 as shown in FIG. That is, the capacity of the smoothing capacitor is made variable. FIG. 8 is a diagram illustrating an example of a smoothing capacitor having a variable capacitance. The smoothing capacitor 50 is configured by connecting capacitors 51 to 54 in parallel, and switches 61 to 64 are connected to the capacitors 51 to 54, respectively. Each of the switches 61 to 64 is a switching element such as a relay or an electromagnetic switch.
　コンデンサ５１～５４の容量は全て同一であってもよいが、必ずしも全て同一でなくても構わない。コンデンサ５１～５４のそれぞれの容量は全て１回の放電による電荷量Ｑを平滑コンデンサ５０の設定電圧Ｖ0で除算した値よりも小さくてもよいが、コンデンサ５１～５４の容量の少なくともいずれか１つが１回の放電による電荷量Ｑを平滑コンデンサ５０の設定電圧Ｖ0で除算した値よりも小さければ構わない。 The capacitors 51 to 54 may all have the same capacity, but they do not necessarily have to be the same. The capacities of the capacitors 51 to 54 may all be smaller than the value obtained by dividing the charge amount Q due to one discharge by the set voltage V 0 of the smoothing capacitor 50, but at least one of the capacities of the capacitors 51 to 54. It suffices if the charge amount Q due to one discharge is smaller than a value obtained by dividing the charge amount Q by the set voltage V 0 of the smoothing capacitor 50.
　図９は、実施の形態３における放電周波数ｆと極間電圧Ｖとの関係を示す図である。図９のＡからＤになるに従って平滑コンデンサ５０の容量は小さくなってゆく。このような状況を実現する一例を以下に示す。 FIG. 9 is a diagram showing the relationship between the discharge frequency f and the interelectrode voltage V in the third embodiment. The capacity of the smoothing capacitor 50 becomes smaller from A to D in FIG. An example of realizing such a situation is shown below.
　Ａはスイッチ６１～６４を全てＯＮ状態にした状態であり、平滑コンデンサ５０の容量はコンデンサ５１～５４のそれぞれの容量を合計した値になる。Ｂはスイッチ６４をＯＦＦ状態にして、スイッチ６１～６３を全てＯＮ状態にした状態であり、平滑コンデンサ５０の容量はコンデンサ５１～５３のそれぞれの容量を合計した値になる。Ｃはスイッチ６３および６４をＯＦＦ状態にして、スイッチ６１および６２をＯＮ状態にした状態であり、平滑コンデンサ５０の容量はコンデンサ５１および５２のそれぞれの容量を合計した値になる。Ｄはスイッチ６２～６４をＯＦＦ状態にして、スイッチ６１のみをＯＮ状態にした状態であり、平滑コンデンサ５０の容量はコンデンサ５１の容量になる。 A is a state in which all the switches 61 to 64 are in the ON state, and the capacity of the smoothing capacitor 50 is the sum of the respective capacities of the capacitors 51 to 54. B is a state in which the switch 64 is turned off and the switches 61 to 63 are all turned on, and the capacitance of the smoothing capacitor 50 is the sum of the capacitances of the capacitors 51 to 53. C is a state in which the switches 63 and 64 are turned off and the switches 61 and 62 are turned on, and the capacitance of the smoothing capacitor 50 is the sum of the capacitances of the capacitors 51 and 52. D is a state in which the switches 62 to 64 are turned off and only the switch 61 is turned on, and the capacity of the smoothing capacitor 50 becomes the capacity of the capacitor 51.
　Ａにおける平滑コンデンサ５０の容量は１回の放電による電荷量Ｑを平滑コンデンサ５０の設定電圧Ｖ0で除算した値よりも大きいが、Ｄにおける平滑コンデンサ５０の容量は１回の放電による電荷量Ｑを平滑コンデンサ５０の設定電圧Ｖ0で除算した値よりも小さくなっている。 The capacitance of the smoothing capacitor 50 at A is larger than the value obtained by dividing the charge amount Q due to one discharge by the set voltage V 0 of the smoothing capacitor 50, but the capacitance of the smoothing capacitor 50 at D is the charge amount Q due to one discharge. Is smaller than the value obtained by dividing by the set voltage V 0 of the smoothing capacitor 50.
　上述したように実施の形態１および２にかかる放電加工機の電源装置１１０において、平滑コンデンサ５を図８の容量可変な平滑コンデンサ５０に置き換えてスイッチ６１～６４といった手段を用いて容量を変化させることにより、放電周波数ｆに依存した極間電圧Ｖの変化幅を制御することが可能になる。即ち、実施の形態３によれば、実施の形態１および２で得られる効果が得られることに加えて、当該効果の程度を制御することも可能になる。 As described above, in the power supply device 110 for the electric discharge machine according to the first and second embodiments, the smoothing capacitor 5 is replaced with the variable capacitance smoothing capacitor 50 shown in FIG. 8, and the capacitance is changed using means such as the switches 61 to 64. Thus, it is possible to control the change width of the interelectrode voltage V depending on the discharge frequency f. That is, according to the third embodiment, in addition to obtaining the effects obtained in the first and second embodiments, the degree of the effects can be controlled.
　以上の実施の形態に示した構成は、本発明の内容の一例を示すものであり、別の公知の技術と組み合わせることも可能であるし、本発明の要旨を逸脱しない範囲で、構成の一部を省略、変更することも可能である。 The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.
　１　電極、２　被加工物、３　整流器、４，６　コンデンサ、５　平滑コンデンサ、７，８，９，１０，１１　スイッチング素子、１２　リアクトル、１３　放電抵抗、１４　電流制限用抵抗、１５，１６，１７，１８，１９，２１　整流用ダイオード、２０　電磁開閉器、３０　検出部、１００，２００　放電加工機、１０１　商用交流電源、１０２　直流電圧変換部、１０３　定電圧制御部、１０４　電流制限抵抗切換部、１０５　軸制御部、１１０　放電加工機の電源装置。 1 electrode, 2 workpiece, 3 rectifier, 4, 6 capacitor, 5 smoothing capacitor, 7, 8, 9, 10, 11 switching element, 12 reactor, 13 discharge resistance, 14 current limiting resistance, 15, 16, 17 , 18, 19, 21 Rectifier diode, 20 electromagnetic switch, 30 detector, 100, 200 electric discharge machine, 101 commercial AC power supply, 102 DC voltage converter, 103 constant voltage controller, 104 current limiting resistor switching unit, 105 Axis control unit, 110 Power supply device for EDM.

Claims (4)

  1. 　交流電源を整流して直流電圧を出力する直流電圧変換部と、
    　電極と被加工物との間に電圧を印加する平滑コンデンサと、
    　前記直流電圧に基づいて、前記平滑コンデンサをパルス幅変調制御することにより定電圧化する定電圧制御部と、
    　前記平滑コンデンサと前記電極との間に接続されて、前記平滑コンデンサから前記電極へ流れる電流を制限する電流制限用抵抗と、
    　を備え、
    　前記平滑コンデンサの容量は、１回の放電持続期間の放電で使用される電荷量を前記平滑コンデンサに対して予め定められた設定電圧で除算した値よりも小さい
    　ことを特徴とする放電加工機の電源装置。     A DC voltage converter that rectifies an AC power supply and outputs a DC voltage;
    A smoothing capacitor for applying a voltage between the electrode and the workpiece;
    A constant voltage control unit configured to make a constant voltage by performing pulse width modulation control on the smoothing capacitor based on the DC voltage;
    A current limiting resistor connected between the smoothing capacitor and the electrode to limit a current flowing from the smoothing capacitor to the electrode;
    With
    The capacity of the smoothing capacitor is smaller than a value obtained by dividing the amount of electric charge used in discharging for one discharge duration by a preset voltage for the smoothing capacitor. Power supply.
  2. 　前記電極と前記被加工物との間の極間電圧に基づいて、前記電極と前記被加工物との間の相対距離を調節する軸の制御を行う軸制御部をさらに備える
    　ことを特徴とする請求項１に記載の放電加工機の電源装置。     An axis control unit that controls an axis that adjusts a relative distance between the electrode and the workpiece based on a voltage between the electrodes and the workpiece is further provided. The power supply device for an electric discharge machine according to claim 1.
  3. 　前記平滑コンデンサの容量は可変である
    　ことを特徴とする請求項１または２に記載の放電加工機の電源装置。     The power supply apparatus for an electric discharge machine according to claim 1 or 2, wherein the smoothing capacitor has a variable capacity.
  4. 　前記平滑コンデンサの容量は０である
    　ことを特徴とする請求項１または２に記載の放電加工機の電源装置。     The electric capacity of the electric discharge machine according to claim 1 or 2, wherein the smoothing capacitor has a capacity of 0.
PCT/JP2014/077460 2014-10-15 2014-10-15 Power supply device for electrical discharge machine WO2016059689A1 (en)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57194823A (en) * 1981-05-26 1982-11-30 Mitsubishi Electric Corp Electrospark machining device
JPS6138819A (en) * 1984-07-31 1986-02-24 Hitachi Seiko Ltd Power supply device for wire cut electric discharge machining
JPS61188021A (en) * 1985-02-18 1986-08-21 Techno Fine Houden Gijutsu Kenkyusho:Kk Servoing method and device of discharge gap distance in electric discharge machining
JPH01164520A (en) * 1987-12-17 1989-06-28 Stanley Electric Co Ltd Work aligning method in electrolytic finishing device
JP2005153078A (en) * 2003-11-26 2005-06-16 Mitsutoyo Corp Discharge pulse power circuit
WO2005102578A1 (en) * 2004-04-19 2005-11-03 Mitsubishi Denki Kabushiki Kaisha Discharge processing machine power supply apparatus and power supply control method
JP2006263871A (en) * 2005-03-24 2006-10-05 Tochigi Prefecture Micro-boring method of disk for generating microplasma

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57194823A (en) * 1981-05-26 1982-11-30 Mitsubishi Electric Corp Electrospark machining device
JPS6138819A (en) * 1984-07-31 1986-02-24 Hitachi Seiko Ltd Power supply device for wire cut electric discharge machining
JPS61188021A (en) * 1985-02-18 1986-08-21 Techno Fine Houden Gijutsu Kenkyusho:Kk Servoing method and device of discharge gap distance in electric discharge machining
JPH01164520A (en) * 1987-12-17 1989-06-28 Stanley Electric Co Ltd Work aligning method in electrolytic finishing device
JP2005153078A (en) * 2003-11-26 2005-06-16 Mitsutoyo Corp Discharge pulse power circuit
WO2005102578A1 (en) * 2004-04-19 2005-11-03 Mitsubishi Denki Kabushiki Kaisha Discharge processing machine power supply apparatus and power supply control method
JP2006263871A (en) * 2005-03-24 2006-10-05 Tochigi Prefecture Micro-boring method of disk for generating microplasma

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