JP3252622B2 - Machining power supply controller for wire electric discharge machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machine, and more particularly to a machining power supply control device of a wire electric discharge machine for preventing a wire from breaking and improving a machining speed.

[0002]

2. Description of the Related Art FIG.
FIG. 4 is a block diagram showing a conventional wire electric discharge machining apparatus described in Japanese Patent Application Publication No. 4-44, in which a negative voltage and a positive voltage are alternately applied to a wire electrode by a bipolar power supply. In the figure, 1 is a wire electrode, 2 is a workpiece arranged at a predetermined distance from the wire electrode 1, 3 is a wire guide for guiding the wire electrode 1 at upper and lower portions, and 4 is a workpiece 2 mounted thereon. A table, 5a is an X-axis drive motor for moving the workpiece 2 in the X-axis direction, 5b is a Y-axis drive motor for moving the workpiece 2 in the Y-axis direction, 6 is an X-axis drive motor 5a and a Y-axis drive motor. A shaft drive control device for controlling 5b; 7 a machining power supply for supplying a discharge current pulse to a machining gap between the wire electrode 1 and the workpiece 2; 8 a machining power control for controlling a switching operation of the machining power supply 7 A circuit 9, a voltage detection circuit for detecting a machining voltage between the poles; an NC controller 10 for sending an axis movement command to the axis drive controller 6 and a machining condition parameter to the power supply control circuit 8 for machining;
Is an average voltage detection circuit for detecting an average voltage during processing;
Is an NC program representing machining path information, machining electric condition parameters, and the like input to the NC control device 10.

FIG. 14 is a connection circuit diagram showing the circuit configuration of the processing power supply 7 in detail. In the figure, reference numeral 70 denotes a first DC power supply which variably sets and supplies a relatively low output voltage E1, 71 denotes a first switch circuit which is, for example, a semiconductor switch, 72 denotes a current limiting resistor, and 73 denotes a diode. Thus, the first DC power supply 70 and the first switch circuit 7
1. A first DC circuit is formed between the wire electrode 1 and the workpiece 2 by the current limiting resistor 72 and the diode 73. 74 is a second DC power supply having a high output voltage E2, 75 is a second switch circuit composed of, for example, a semiconductor switch, 76 is a diode, and these second DC power supply 74 and second switch circuit 75 , And the diode 76 form a second DC circuit between the wire electrode 1 and the workpiece 2. 77 is a third DC power supply having a voltage of the opposite polarity of the first DC power supply 70 and the second DC power supply 74, and 78 is a third switch circuit which is a semiconductor switch, for example. , 79 are current limiting resistors, these first DC power supply 70, first switch circuit 71, current limiting resistor 72 and diode 7
3 forms a first DC circuit between the wire electrode 1 and the workpiece 2. Reference numerals 91 and 92 denote voltage-dividing resistors, respectively. One end of the voltage-dividing resistor 91 is connected to the wire electrode 1, the other end is connected to one end of the voltage-dividing resistor 92. The end is connected to the workpiece 2.

[0004] The negative electrode of the first DC power supply 70 is connected to the cathode of a diode 73, and the anode of the diode 73 is connected to the wire electrode 1. On the other hand, the positive electrode of the first DC power supply 70 is connected to the drain of the first switch circuit 71 via the current limiting resistor 72, and the source of the first switch circuit 71 is connected to the workpiece 2, The gate of one switch circuit 71 is connected to the processing power supply control circuit 8. The negative electrode of the second DC power supply 74 is connected to a diode 76.
, And the anode of the diode 76 is connected to the wire electrode 1. On the other hand, the positive electrode of the second DC power supply 74 is connected to the drain of the second switch circuit 75, the source of the second switch circuit 75 is connected to the workpiece 2, and the gate of the second switch circuit 75 is connected to the gate of the second switch circuit 75. It is connected to the power supply control circuit 8 for processing. The positive electrode of the third DC power supply 77 is connected to the wire electrode 1. On the contrary,
The negative terminal of the third DC power supply 77 is connected to the source of the second switch circuit 78 via the current limiting resistor 79,
The drain of the switch circuit 78 is connected to the workpiece 2, and the gate of the third switch circuit 78 is connected to the power supply control circuit 8 for processing.

Next, the operation of the conventional wire electric discharge machine will be described. The NC program 1 is stored in the NC control device 10.
Processing path information and processing electric condition parameters are input by a tape, a floppy disk, or an operation panel (not shown) on which 2 is recorded. The input processing electric condition parameters are output to the processing power supply control circuit 8, and based on the input processing electric condition parameters, the predetermined electric current peak, pulse width,
A drive signal having a rest time or the like is generated to control the processing power supply 7. The processing power supply 7 is driven by these drive signals, and a predetermined current pulse is supplied to the processing gap between the workpiece 2 and the wire electrode 1 held by the wire guide 3 above and below the workpiece 2. This predetermined current pulse is supplied to the machining gap between the wire electrode 1 and the workpiece 2, and generally, water or an aqueous machining fluid is supplied to the machining gap to perform wire electric discharge machining.

FIG. 15 is a timing chart showing the circuit operation of the wire electric discharge machine. In the figure, (a)
Is a voltage waveform in the machining gap, (b) is a current waveform flowing in the machining gap, and (c) is a timing T of the first switch circuit 71.
A signal waveform indicating R1; (d) is a second switch circuit 75
And (e) shows a signal waveform indicating the timing TR3 of the third switch circuit 78. Here, the signal waveforms (c), (d) and (e)
Is "1", the first switch circuit 71, the second switch circuit 75, and the third switch circuit 78 are turned on.

In the processing power supply circuit 7 shown in FIG. 14, a relatively low voltage DC power supply E1 is applied to the processing gap at the timing TR1 of the first switch circuit 71. Then
After the first switch circuit 71 is turned ON, the voltage in the machining gap until the start of electric discharge increases to the DC voltage E1 of the first DC power supply 70, and with the start of discharge, the voltage in the machining gap decreases to the arc potential. I do. Simultaneously with the start of this discharge, the second
Is turned on and the machining current is supplied from the second DC power supply 74, the current waveform in the machining gap increases at a predetermined gradient as shown in FIG. 15B. Predetermined time (period "1" shown in FIG. 15 (c))
After that, when the first switch circuit 71 is turned off, the third
The switch circuit 78 is turned ON, and the voltage of the machining gap (hereinafter, referred to as machining gap voltage Vg) is reverse to the DC voltage E1 up to the DC voltage E3 of the third DC power supply 77, as shown in FIG. It rises to the polarity side. Thereafter, when the third switch circuit 78 is turned off, the first switch circuit 71
Is turned ON again, and the above-described operation is repeated, and the electric discharge machining is continued.

[0008] The average voltage detection circuit 11
An average voltage proportional to the machining gap voltage Vg generated at both ends of the voltage-dividing resistor 91 is detected, and based on this average voltage, the electrodes are maintained so that the relative position between the electrode 1 and the workpiece 2 is kept constant. The feed control of 1 or the work 2 is performed. That is, when the detected average voltage is equal to or higher than a predetermined value, the electrode 1
Alternatively, the feed speed is calculated by the NC device 12 so that the feed speed of the workpiece 2 is increased and the feed speed of the electrode 1 or the workpiece 2 is reduced when the average voltage is equal to or lower than a predetermined value. A desired shape is processed by outputting a positioning command to the drive control device 6 based on the information and controlling the positioning of the table 4 by the X-axis drive motor 5a and the Y-axis drive motor 5b.

In a conventional electric discharge machine, a large amount of machining current needs to be supplied in order to improve the electric discharge machining speed. This has been dealt with by increasing the peak value or increasing the discharge frequency. However, in such a case, direct contact between the wire electrode and the workpiece due to the presence of sludge between the wire electrode and the workpiece, which is generally referred to as continuous abnormal discharge (hereinafter, referred to as a short-circuit state), Since the gap between the poles of the wire electrode and the workpiece is abnormally narrow, electric discharge (hereinafter referred to as “immediate electric discharge”) that occurs with almost no load time is likely to occur, and machining is likely to be unstable. In the case of Die-sinker EDM, sludge is often short-circuited due to the presence of sludge, and the short-circuit current attracts the sludge. It is known to be effective in resolving. In the case of a wire electric discharge machine, on the other hand, the wire electrode vibrates violently due to the discharge repulsion force or the machining fluid, and thus the short-circuit state is considered to be the direct contact between the wire electrode and the workpiece. Can be Therefore, if an excessive current is supplied in a short-circuit state, the temperature rise of the wire electrode is particularly large and the wire is likely to be broken.On the other hand, in order to eliminate the short-circuit state, it is necessary to supply a current enough to separate the wire electrode from the workpiece. is there.

Conventionally, as one of the techniques for detecting the short-circuit state and controlling the machining current, for example, Japanese Patent Laid-Open No. 57-1385.
No. 31 and JP-A-59-19633,
There is disclosed a technique for detecting a short circuit state by detecting a voltage at the time of occurrence of discharge and comparing the voltage with a reference potential equal to or lower than an arc potential.

Further, as means for avoiding discharge concentration, for example, Japanese Patent Laid-Open Publication No. 61-88770 discloses that if a predetermined number of abnormal discharges continue, the pause time is extended until a normal discharge occurs to distribute the discharge to another place. A technique for causing this to occur is disclosed.

[0012]

In the above-mentioned conventional machining power supply for a wire electric discharge machine, when detecting a short-circuit state, a machining gap voltage at the time of occurrence of electric discharge is detected, and a reference potential which is a predetermined potential is detected. It was compared with the potential. Therefore, in order to determine a short circuit or a discharge state, generally, E0 (1−exp (−1 / (RC))) (E0: power supply voltage, R: current limiting resistance, C: floating capacitance between the electrodes) is used. It is necessary to detect the machining gap voltage value to be detected, but the voltage rises to the reference potential depending on the current limiting resistor in the circuit for applying the no-load voltage and the magnitude of the voltage of the first DC power supply. However, there is a variation in time. For example, when the current limiting resistance value is large and the voltage of the first DC power supply is low, the voltage gradient rises slowly and it takes much time to rise to the reference potential, but the current limiting resistance value is small. The high voltage of the first DC power supply has a steep voltage gradient, and rises to the reference potential in a relatively short time. As described above, in the conventional means for detecting the short circuit or the discharge state, the short circuit or the arc state is determined based on whether the machining gap voltage has risen to the reference potential.
There is a problem that takes time.

As a conventional means for avoiding abnormal discharge,
If a predetermined number of abnormal discharges continue, the pause time is extended until normal discharge occurs and the discharge is dispersed to another location, the average current supplied during abnormal discharge decreases, and further abnormal discharge occurs Therefore, there is a problem that the processing speed cannot be improved because the process waits until the problem is solved. Furthermore, in the case where the means for extending the pause time and avoiding wire breakage is adopted in a bipolar pulse power supply that applies a voltage of the opposite polarity to the no-load voltage during the pause time, the abnormal discharge state occurs during the pause time. Also, there is another problem that abnormal discharge continues because a voltage of opposite polarity is applied.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a first object of the present invention is to provide a wire capable of quickly detecting an abnormal discharge in a machining gap without causing time variation. A machining power supply control device for an electric discharge machine is obtained. A second object is to provide a machining power supply control device of a wire electric discharge machine capable of accurately detecting abnormal discharge in a machining gap. A third object of the present invention is to provide a machining power supply control device for a wire electric discharge machine capable of quickly eliminating abnormal discharge and improving machining speed. Still another object of the present invention is to provide a machining power supply control device for a wire electric discharge machine capable of quickly detecting an abnormal discharge in a machining gap, supplying an appropriate current corresponding to the abnormal discharge, and improving a machining speed. It is.

[0015]

According to a first aspect of the present invention, there is provided a machining power supply control apparatus for a wire electric discharge machine, comprising: an electrode disposed to face a workpiece at a predetermined distance from the workpiece; and an electrode disposed between the electrode and the workpiece. A first series circuit comprising a first power supply and a first switch circuit connected to the workpiece and the electrode, the first series circuit being connected in parallel to the first series circuit, and A third series circuit composed of a third power supply and a third switch circuit having charges of opposite polarities to one power supply, and both the first switch circuit and the third switch circuit are alternately turned on. A control path for controlling a discharge generated between the workpiece and the electrode, and a period from when the first switch circuit is turned off to when the first switch circuit is turned on again, And during the period in which the third switch circuit is on, It is obtained by a short circuit determination circuit for detecting a short-circuit state of the object and the electrode.

In the short-circuit determination circuit, the workpiece and the electrode are in a short-circuit state during a predetermined period of time during which the third switch circuit is on, and during a period that can be variably set within that period. Is determined.

Further, a machining power supply control device for a wire electric discharge machine according to the present invention is connected to an electrode which is opposed to a workpiece at a predetermined distance from the workpiece, and connected between the electrode and the workpiece. A first switch comprising a first power supply and a first switch circuit;
And a third power supply connected in parallel to the first series circuit between the workpiece and the electrode, and having a charge of opposite polarity to the first power supply. A control in which a third series circuit including a third switch circuit and the first switch circuit and the third switch circuit are alternately turned on to generate a discharge between the workpiece and the electrode. Circuit, a discharge state determination circuit that detects whether the discharge between the workpiece and the electrode is normal or abnormal, and when the discharge state determination circuit determines that abnormal discharge is continuously occurring, And a switch control circuit for stopping the third switch circuit after alternately turning on the first and third switch circuits for a predetermined time.

Further, a first series circuit is connected in parallel between the workpiece and the electrode, and the first series circuit is connected to the electrode.
A second power supply for applying a potential having the same polarity as that of the power supply and a second series circuit of a second switch circuit, and the workpiece and the electrode are short-circuited by the short-circuit determination circuit. When it is determined that the first and third switch circuits are alternately turned on for a predetermined time, the third switch circuit is stopped.

Further, the peak value of the machining current supplied by the second series circuit during the predetermined time is changed and controlled.

[0020]

In the machining power supply control device of the wire electric discharge machine configured as described above, the third power supply voltage rise is detected during the period in which the third switch circuit is on, so that the third power supply voltage rises. A short circuit state when the switch circuit is turned off and the first switch circuit is turned on is determined.

Further, at the point where the rising state of the third power supply voltage can be accurately recognized during the period when the third switch circuit is on, the short-circuit state is detected by detecting the rising of the third power supply voltage. Determine.

Further, the number of continuous abnormal discharges is detected, and when it is determined that the predetermined number of abnormal discharges are continuously occurring, the number of continuous abnormal discharges is detected in order to eliminate the abnormal discharge. On-off control as usual during the predetermined time,
After the elapse of the predetermined time, the third switch circuit is turned off for a predetermined time.

Further, by detecting the rise of the third power supply voltage while the third switch circuit is on, the short-circuit state is quickly detected, and a predetermined number of short-circuit states are continuously generated. If it is determined that the short circuit has occurred, the first, second, and third switch circuits are normally turned on and off for a predetermined period of time in order to eliminate the short-circuit state. The first, second and third switch circuits are turned off for a predetermined time.

Further, a short-circuit state is determined during a period in which the third switch circuit is on, and based on a result of the determination, in the short-circuit state, the processing current peak value applied to the processing gap by the second series circuit is changed. .

[0025]

【Example】

Embodiment 1 FIG. FIG. 1 is a block diagram showing a configuration of a wire electric discharge machine according to one embodiment of the present invention, and FIG. 2 is a connection circuit diagram showing a circuit configuration of a machining power source 7 in detail. In the figure, reference numerals 1 to 7, 9 to 12, 71 to 79, and 91 to 92 are the same as those of the above-described conventional device, and a description thereof will be omitted. Reference numeral 18 corresponds to the processing power supply control circuit 8 of the conventional apparatus.
A processing power supply control circuit that controls a switching operation of the processing power supply 7.

FIG. 3 is a diagram showing details of the processing power supply control circuit 18 according to the first embodiment of the present invention. In the figure, reference numeral 21 denotes a first pulse oscillator, which oscillates a pulse S1 which becomes "1" during a period T1 and "0" during a period T2 in FIG. 4 according to a command from the NC control device 10. Reference numeral 22 denotes a second pulse oscillator which oscillates a pulse S2 which becomes "1" during a period T3 from the rising of the pulse S1. Reference numeral 23 denotes a third pulse oscillator which oscillates a pulse S3 which becomes "1" during a period T3 from the rising of the pulse S1. A comparator 24 compares the machining gap voltage Vg output from the voltage detection circuit 9 with a first reference voltage V1 set to be higher than the arc potential at the time of electric discharge and lower than the potential of the first power supply 70.
Is an OR circuit, and the output of the comparator 24 and the third
The output of the oscillator 23 is connected. 26 is a current peak value setting unit.

The current peak value setting section 26 has an O
An inverter circuit 261 for inverting the output of the R circuit 25,
The output of the inverter circuit 261 is connected to the Cp input, the latch circuit 262 to which the output signal S2 of the second oscillator 22 is connected to the D input, and the output of the OR circuit 25 is connected to the input. A one-shot multivibrator 26 that oscillates to be "1" during ON1 and ON2 according to a command from the control device 10.
3, 264, an inverter circuit 265 connected to the output Q of the latch circuit 262, a one-shot multivibrator 263 as an input and an AND circuit 266 as an inverter circuit 265, and an input as a one-shot multivibrator 26
4 and an AND circuit 367 as a latch circuit 262, AN
OR circuit 26 for taking a logical sum from D circuits 266 and 267
8.

Reference numeral 27 denotes a NOR circuit, whose input is connected to the output of the OR circuit 268 and the output signal S 1 of the first pulse oscillator 21. 28 is a third switch circuit 78
A short-circuit state detection unit that is a short-circuit determination circuit that detects a short-circuit state between the workpiece 2 and the wire electrode 1 during a period from when the first switch circuit 70 is turned on to when the first switch circuit 70 is turned on.
Reference numeral 29 denotes a short-circuit counting unit that counts the number of times of the short-circuit state detected by the short-circuit state detection unit 28 to generate a first predetermined time. Reference numeral 30 denotes a second predetermined time by counting the pulse time of the reference clock. During this period, the first switch circuit 71, the second switch circuit 74, and the third switch circuit 78 are commanded to turn off.

The short-circuit state detecting section 28 includes a comparator 281 for comparing the machining gap voltage Vg output from the voltage detecting circuit 9 with a second reference voltage V2 set lower than the arc potential at the time of discharge, and a NAND circuit. A one-shot multivibrator 282 that generates a pulse signal that becomes “1” during the smile time T5 at the rising timing of the output signal 27;
A flip-flop 283 connected to the output of the comparator 281 at the set (S) terminal and the output of the one-shot multivibrator 282 to the reset (R) terminal, and an inverter circuit 28 for inverting the output signal of the flip-flop 283.
4. An AND circuit 2 that takes the logical product of the output signal from the inverter circuit 284 and the output signal S1 of the first pulse oscillator
85, an AND circuit 2 that takes the logical product of the output signal of the flip-flop 283 and the output signal S1 of the first pulse oscillator
86, signal from AND circuit 286 and short circuit counting section 2
9 is composed of an OR circuit 287 for taking a logical sum with the output from the coincidence comparison circuit 292 in FIG.

The short-circuit counting section 29 includes a continuous-number setting device 291 for presetting the number of continuous short circuits corresponding to the first predetermined time.
A counter 293 connected from the AND circuit 285 to the data input terminal and connected from the OR circuit 287 to the reset input.
91 (M1 to Mn) and the other input (A1 to A
The output (P1 to Pn) from the counter 293 is connected to n), and is constituted by a match comparison circuit 292 for comparing whether or not both values match.

Next, the pulse stop command section 30 has a data input connected to a reference clock (for example, several KHz to several hundred KHz), a counter 301 connected to a reset input and a coincidence comparison circuit, and one input (A1). To An) are connected to outputs (P1 to Pn) of a counter 1833, and the other inputs (B1 to Bn) are pulse stop time setting units 303 for setting pulse values of a reference clock corresponding to a third predetermined time.
Comparator 30 to which the outputs (M1 to Mn) are connected
2. The flip-flop 304 is connected to the coincidence output of the coincidence comparison circuit 302 at the S terminal and connected to the coincidence output of the coincidence comparison circuit 302 at the R terminal.

The output of the flip-flop 304 in the pulse stop command unit 30 takes the logical product of the output signal S1 from the first pulse oscillator 21 and the signal TR1 for driving the first switch circuit 71 by the AND circuit 31. Becomes Similarly,
The output of the flip-flop 304 is the current peak setting unit 2
6 and the signal from the OR circuit 268 in the
Signal TR2 for driving the switch circuit of FIG. further,
The output of the flip-flop 304 is ANDed with the NOR circuit 27 and the signal TR for driving the third switch circuit is obtained.
It becomes 3.

FIG. 4 is an operation timing chart showing the circuit operation of the processing power supply control circuit 18. In the figure,
S1 is a pulse signal oscillated by the first pulse oscillator 21 so as to be "1" during a period T1 and "0" during a period T2, and S2 is a signal S1 generated by a second pulse oscillator 22.
S3 is a signal oscillated to be “1” during a period T3 from the rise of the signal S3.
This signal is oscillated so as to be “1” during a period T4 from the rise of “1”. S4 is a signal output from the comparator 24 when the divided value Vg of the voltage value of the machining gap detected by the voltage detection circuit 9 is equal to or higher than the reference voltage V1. S3 is a signal obtained by taking the logical sum with S3, and S6 is the timing of the discharge start, that is,
At the falling timing of the signal, latches whether the signal S2 is "1" or "0", outputs "1" if the signal S2 is "1", and outputs "0" if the signal S2 is "0" Signal.

In step S7, the logical product of the signal oscillated to be "1" during the ON1 period in accordance with the command of the NC controller 10 and the signal of the signal 6 via the inverter circuit 265 is obtained at the rising timing of the signal S5. At the rising timing of the signal S5
A signal obtained by taking the logical sum of the signal oscillated to be "1" during the ON2 period and the signal obtained by taking the logical product of the signal 6 under the command of the control device 10, and S8 is the signal S1 and the signal S
7 is a signal that outputs “1” when the output of the OR is not “1”. S9 is the signal waveform of the output signal of the flip-flop 304.

3 and 4, the operation of the machining power supply control circuit 18 when the electric discharge machining is performed normally and no short circuit occurs will be described. The first pulse oscillator 21 outputs a signal S1 and the second pulse oscillator 22 outputs a signal S1.
Second and third pulse oscillators 23 oscillate the signal S3. If the relationship between the machining gap voltage Vg and the predetermined reference voltage V1 is V1 ≧ Vg, the comparator 24 outputs a signal S4 of “1” to the OR circuit 25. The OR circuit 25 outputs a signal S5 obtained by calculating the logical sum of the signal S4 and the signal S3 to the current peak value setting unit 26.

In the current peak value setting section 26, the signal S5
Is input to the latch circuit 262 via the inverter 261 to latch whether the signal S2 is “1” or “0” at the falling timing of the signal S5,
Is "1", a signal S6 is output which outputs "1", and if the signal S2 is "0", a signal S6 which outputs "0" is generated. Also, the signal S
5 is a one-shot multivibrator 263 and 26
4, a signal (not shown) oscillated to become “1” during the ON1 period or the ON2 period according to the command of the NC control device 10 at the rising timing of the signal S5. A signal obtained by ANDing the signal from the one-shot multivibrator 263 with the signal of the signal 6 through the inverter circuit 256 (not shown) and a signal obtained by ANDing the signal from the one-shot multivibrator 264 with the signal 6 The OR circuit 268 takes a logical sum with the signal (not shown) to generate a signal S7.

When the no-load time from the application of the voltage E1 to the occurrence of discharge is shorter than the period of T3 (short-circuit state or immediate discharge), the signal S7 selects the pulse width ON2, and conversely, If the time is longer than the period of T3 (normal discharge), the pulse width ON1 is selected and the power supply 7 for machining is selected.
, And a processing current is supplied by a high-current second DC power supply 74. Here, generally, in order to improve the processing speed, the pulse width ON2 is set to a shorter time than the pulse width ON1. Such a triangular waveform having different peaks is often used particularly in a wire electric discharge machine, and by controlling a current waveform (such as a peak value) according to a state of electric discharge, disconnection of the wire electrode 1 can be prevented. Processing speed is greatly improved.

The signal S7 output from the current peak value setting section 26 is input to the NOR circuit 27, and the logical OR of the signal S7 with the signal S1 from the first pulse oscillator 21 is generated to generate a signal S8. It is input to the short-circuit state detector 28. Thereafter, the short-circuit state detecting unit 28 detects whether or not short-circuits have continuously occurred between the workpiece 2 and the wire electrode 1 in the wire electric discharge machining.

At this time, assuming that the short circuit does not occur continuously, the one-shot multivibrator 282, to which the signal S8 is input, sets "1" to the R terminal of the flip-flop 283 for T5 from the rising of the signal S8. Output. The comparator 281 also compares the machining gap voltage Vg with the second reference voltage V2, and as a result,
Is output when the potential is lower than the reference voltage V2, and is output to the S terminal of the flip-flop 283. The flip-flop 283 always outputs the output “1” as a result of the input signals of the R terminal and the S terminal, and holds the data until the timing when the next reverse polarity voltage E3 is applied. Since the output of the flip-flop 283 is always “1”, the signal output from the AND circuit 285 via the inverter 284 is always “0”, and the counter 293 does not count up. Therefore, the output from the match comparison circuit 292 is always “0”, and the S
The signal is output to the terminal, and the flip-flop 304 always outputs “1” indicated by the signal S9.

In the AND circuit 31, the signal S1 and the signal S9
And a signal TR1 for driving the first switch circuit 71 is generated. Similarly, the AND circuit 32 generates a signal TR2 for driving the second switch circuit 75 based on the signals S7 and S9, and the AND circuit 33 generates the signal TR2.
The signal TR3 for driving the third switch circuit 78 is generated based on the signal 8 and the signal S9.

Next, the operation of the machining power supply control circuit 18 in a state in which short-circuits occur continuously during electric discharge machining will be described with reference to an operation timing chart showing the circuit operation of FIG. The circuit operation in the current peak value setting unit 26 is the same as that of the above-described embodiment, and therefore the description thereof will be omitted.
8. The circuit operations of the short circuit counting section 29 and the pulse stop command section 30 will be mainly described. In the figure, the reverse polarity voltage E
The one-shot multivibrator 282 generates a signal S10 that is “1” during a period T5, which is a very short time from the rise of the signal S8, which is the timing to apply 3, and outputs the signal S10 to the R terminal of the flip-flop 283. At the same time, the comparator 281 compares the machining gap voltage Vg with the second reference voltage V2 during a period from when the third switch circuit 78 is turned on to when the first switch circuit 71 is next turned on. Only when the reverse polarity voltage E3, which is the machining gap voltage Vg, becomes lower than the second reference voltage V2, the machining gap voltage Vg
Rises, that is, is not in a short circuit or arc state, and outputs “1” to the S terminal of the flip-flop 283. In this description, since the short circuit occurs continuously during the electric discharge machining, the output signal from the comparator 281 has a waveform like the signal S11 in FIG. Here, in the waveform of the signal S11, since the voltage E3 of the opposite polarity is applied during the period of "1", it can be said that no short circuit has occurred.

In the flip-flop 283, the signal S10
Is input to the R terminal and the signal S11 is input to the S terminal, so that the data of “1” or “0” of the signal S11 output during the period in which the third switch circuit is turned on is then transmitted to the first switch. Until the circuit 71 is on, the signal waveform indicated by the held signal S12 is output. Next, A
The ND circuit 285 outputs the signal S12 from the inverter 284.
Is obtained by calculating the logical product of the inverted output of the pulse signal S1 and the pulse signal S1 so that the signal S becomes "1" only in a short circuit or arc state.
A pulse output indicated by 14 can be obtained. As described above, the state of the machining gap is a short circuit or an arc during a period from when the third switch circuit is turned on to when the first switch circuit is next turned on, that is, during a period when the reverse polarity voltage E3 is applied. Can be accurately detected without being affected by the delay of the rise time of the no-load voltage.

Next, the pulse output of the signal S14 is counted by the counter 293. Here, the counter 293
Is a signal S13 which is the logical product of the signal S12 and the signal S1.
Is reset, or when the output of the counter 293 matches the output of the value corresponding to the first predetermined time preset in the continuous number setting unit 291, the counter 293 is reset. The counter 293 outputs the output values (A1 to An) of the count values (P1 to Pn) obtained by counting the pulses of the signal S14 to the coincidence comparison circuit 292 and the continuous number setting unit 29.
1 is compared with the output value (B1 to Bn) output to the coincidence comparison circuit 292 of a value (M1 to Mn corresponding to the first predetermined time) which is predetermined in advance, and only when the values match, is shorter than the time of T2. The coincidence output signal S15 having the time "1" is output. Based on the coincidence output signal S15, the counter 293
Reset.

The coincidence output signal S15 is input to the pulse stop command section 30, resets the internal counter 301, counts the reference clock pulse, and outputs the count value (P1 to Pn) to the coincidence comparison circuit 302. I do. On the other hand, the pulse stop time setting unit 303 outputs to the coincidence comparison circuit 302 the pulse values (M1 to Mn) of the reference clock corresponding to the predetermined pulse stop time (third predetermined time). In the coincidence comparison circuit 302, values (A1 to An) based on the count value from the counter 301 and values (B1 to Bn) based on the pulse value from the pulse stop time setting unit 303 are used.
And outputs a second coincidence output signal to the flip-flop 304 which becomes "1" for a time shorter than the time of T2 if they coincide with each other. The flip-flop 304 performs set / reset based on the coincidence output signal S15 and the second coincidence output signal, and generates a signal indicated by a signal S9a. The signal S9a is inverted via an inverter circuit, input to the AND circuits 31, 32, and 33, and when the output of the flip-flop 304 is "1", that is, the predetermined time T set in the pulse stop time setting unit 303. Period T
The outputs of R1, TR2, and TR3 are set to “0”, and the driving of each of the first switch circuit 71, the second switch circuit 75, and the third switch circuit 78 is stopped.

In the above embodiment, the first to third switch circuits are turned off for the third predetermined time after the first predetermined time has elapsed.
By doing so, the abnormal electric discharge is effectively eliminated, and the wire breakage due to the excessive electric current continuing to flow due to the abnormal electric discharge is prevented.
Only the switch circuit may be turned off. Further, in the above embodiment, an example has been described in which the first switch circuit and the third switch circuit are alternately turned on so that either one of the first switch circuit and the third switch circuit is always on. The third switch circuit is turned on during the entire period until the first switch circuit is turned on again, and a short-circuit state between the workpiece and the wire electrode is detected during this period. The ON period of the third switch circuit in the invention is not limited to the entire period described above, but is a part of the period after the first switch circuit is turned off and before the first switch circuit is turned on again. A short-circuit state between the workpiece and the wire electrode may be detected.

FIG. 6 shows a current waveform when the above operation is performed while the short circuit continues.
After the voltage application between the poles is stopped, a predetermined number of short-circuit currents of a predetermined peak value will flow, and again, when a predetermined number of short-circuits continue, the voltage application between the poles is stopped again. Repeat the operation. Therefore, the short-circuit state can be effectively eliminated by determining the allowable number of short-circuit currents and the peak value within a range in which no disconnection occurs.
In addition, the processing power supply control device 18 described above includes the voltages E1, E
2, or by controlling the time for applying the voltage E3, the average processing voltage can be reduced to 0 V, which has the effect of preventing electrolytic corrosion of the workpiece. , Switch elements TR1, TR2,
Since all of the TR3 are turned off and the application of the voltage to the gap is stopped, the average processing voltage can be kept at 0 V also during this period, and the average processing voltage can be maintained at 0 V even during the control. There is no reduction in the processing quality of the workpiece.

Embodiment 2 FIG. In the first embodiment, the pulse stop command unit 30 of the power supply control circuit 18 sets the pulse stop time based on the reference clock.
The number of pulses to be stopped may be set. FIG. 5 is a block diagram of a wire electric discharge machine according to a second embodiment of the present invention, and FIG. 8 shows a machining power supply control circuit 19 in the present embodiment. In the figure, except for the pulse stop command unit 30a, it is completely the same as that of the first embodiment, so that the description is omitted, and only the pulse stop command unit 30a where a difference occurs will be described. The pulse stop command section 30a counts the pulses of the reference clock shown in the first embodiment, and thereby, the first switch circuit 71 and the second switch circuit 75.
The second predetermined period is generated by counting the pulse S1 instead of generating the second predetermined time for turning off all the third switch circuits 78.

The counter 301a does not count the pulse of the reference clock shown in the first embodiment, but counts the number of pulses of the pulse signal S1. Further, the pulse stop number setting unit 303a does not set the second predetermined time which is the stop time based on the number of pulses of the reference clock described in the first embodiment, but performs the first stop based on the number of pulses of the pulse signal S1. The second predetermined period is set. Match comparison circuit 302
a compares the output from the counter 301a with the output from the pulse stop count setting unit 303a, as in the first embodiment.
If they match, “1” is set in R of the flip-flop 304.
Output to terminal. The circuit operation is substantially the same as that of the first embodiment, and a description thereof will be omitted. However, in the case of the present embodiment, it is possible to stop the voltage application to the machining gap by a constant number of pulses regardless of the discharge cycle.

Embodiment 3 FIG. FIG. 9 is a timing chart illustrating the circuit operation of the processing power supply control device according to the third embodiment. In the first embodiment, the timing for detecting the short circuit or the arc state is set to the period of the minute time T3 in which the output of the one-shot multivibrator 282 in FIG. 3 becomes “1”. As shown in FIG. 9, T5 is set so that T6 = T2-T5 = constant. For example, when processing conditions are set by the first pulse oscillator 21 so as to lengthen the pause period T2 in the output of the pulse signal S1, the time for applying the reverse polarity voltage E3 increases. If the time for applying the reverse polarity voltage E3 becomes long, the state between the workpiece and the wire electrode may shift from the non-short circuit state to the short circuit state during the period of T2. Therefore, the detection accuracy can be improved by setting a time sufficient to detect the machining gap voltage Vg immediately before the application of the no-load voltage E1 to detect the short-circuit state.

Embodiment 4 FIG. In the present embodiment, in the machining power supply control device 18 of the first embodiment, in the case of a short circuit or an arc state, another current peak value is supplied to the gap between immediately after discharge and immediately. FIG. 10 is a block diagram showing a wire electric discharge machine according to a fourth embodiment of the present invention, and FIG. 11 shows a machining power supply controller 20 according to the present embodiment. In the figure, except for the current peak setting unit 26a, which is the same as the first embodiment, the description is omitted, and only the current peak setting unit 26a where a difference occurs will be described. In the circuit configuration in the current peak setting unit 26a, 261 to 26
2 and 265 are exactly the same as those in the first embodiment described above.
3a is 263 in the first embodiment, and 264a is the first embodiment.
The one-shot multivibrator 266a corresponding to 264 in Example 2
Is a three-input AND circuit corresponding to 267 in the first embodiment, and 268a is a three-input OR circuit corresponding to 268 in the first embodiment. 265a is an inverter for inverting the signal from the short-circuit state detection unit 28, and 269 is an OR circuit 2
A one-shot multivibrator 269 for generating a falling pulse width ON3 of the signal S5 from signal No. 5 and an AND circuit 269 for taking the logical product of the signal from the short-circuit state detector 28 and the signal from the one-shot multivibrator 269. Here, the output of the one-shot multivibrator 263a, the output of the inverter 265, and the output of the inverter 265a are connected to the input of the AND circuit 266a, and the output of the one-shot multivibrator 264a and the output of the latch circuit 262 are connected to the input of the AND circuit 267a. The output Q and the output of the inverter 265a are connected.
AND circuits 266a and 267 are input to the input of the R circuit 268a.
Three inputs a and 260 are input.

FIG. 12 is a timing chart showing the circuit operation of the machining power supply control device 20 in this embodiment.
The operation of the current peak setting unit 26a in FIG. 11 will be described. At the timing of the start of discharge by the no-load voltage E1, that is, at the timing of the fall of the logical sum of the signal S4 output from the comparator 24 and the signal S3 from the third pulse oscillator 23 (signal S5), the signal S2 changes to " A pulse signal (not shown) for latching "1" or "0" (signal S6) and for controlling the driving of the second switch circuit 75 of the second DC power supply 74 by the one-shot multivibrators 263a, 264a and 269. Oscillation). The signal 6 is generated by the latch circuit 262, and the no-load time from the application of the no-load voltage E1 to the start of the discharge is equal to the pulse T oscillated by the second pulse oscillator 22.
If it is smaller than 3, the output (Q) becomes "1", and if the no-load time is longer than the pulse T3, the output (Q) becomes "0".

On the other hand, in the short-circuit detecting section 28, as described in the above-described embodiment, the voltage E of the opposite polarity one cycle before the short-circuit is detected.
The gap state by 3 is held by the flip-flop 283 so as to be “0” if short-circuited and “1” otherwise, and the signal S12 is generated. Signal S
12 is inverted by the inverter 284 in the short-circuit detection unit 28 and is input to the current peak setting unit 26a. Signal S
12 inverted output signal, output signal S6 from latch release 262 and one-shot multivibrator 263a,
By combining the pulse signals from 64a and 269,
The signal S7a is generated. This signal S7a and the pulse signal S
1 and the signal S9, in the case of a short-circuit state, the output of the pulse width ON3 is selected to drive the second switch circuit 75 of the machining power supply 7, and from the application of the no-load voltage E1 to the occurrence of discharge. If the no-load time is equal to or less than the T3 period and is not in the short-circuit state (immediate discharge), the output of the pulse width ON2 is selected to drive the second switch circuit 75 of the machining power supply 7, and the no-load time is the T3 period. If it is larger and not in a short-circuit state (normal discharge), the output of the pulse width ON1 is selected to drive the second switch circuit 75 of the machining power supply 7,
A processing current is supplied by a power supply E2 having a relatively high current. Generally, by setting the pulse width ON1 <ON2 <ON3, wire breakage can be prevented and the processing speed can be improved. Furthermore, since the processing current peak value at the time of short circuit can be set independently, the minimum current peak value required for eliminating the short circuit is set, and the current peak value at the time of immediate discharge is set to a value larger than that at the time of short circuit. Disconnection can be efficiently prevented, and the processing speed can be improved.

Embodiment 5 FIG. In the first to fourth embodiments, the no-load voltage side is the DC power supply E1, and the opposite polarity voltage side is the DC power supply E3.
In the processing power supply having a configuration in which the no-load voltage side is connected to the DC power supply E3 and the opposite polarity voltage side is connected to the DC power supply E1, the DC power supply E2 is also positively connected as in the embodiment. The same effect can be obtained by connecting them in such a manner. In this case, for example, in FIG. 3, the reference voltage V2 is connected to the input (+) of the comparator 24, and the output Vg of the voltage detection circuit 9 is connected to the input (-). The output Vg of the voltage detection circuit 9 is connected to the input (+) of the comparator 281 and the reference voltage V2 is connected to the input (-). Also, the AND circuit 3
The first switch circuit 78 of the processing power supply 7 may be connected to the output of the processing power supply 7 and the output of the AND circuit 33.

[0054]

Since the present invention is configured as described above, it has the following effects. In the first invention, a first electrode includes a first electrode and a first switch circuit connected between the electrode and the workpiece, the electrode being opposed to the workpiece with a predetermined distance therebetween. A third power supply and a third power supply connected in parallel to the first series circuit and connected in reverse polarity to the first power supply, between the series circuit and the workpiece and the electrode. A third series circuit including a switch circuit, a control circuit that alternately turns on both the first switch circuit and the third switch circuit, and controls a discharge generated between the workpiece and the electrode; After the first switch circuit is turned off, a short-circuit state between the workpiece and the electrode is detected until the first switch circuit is turned on again and while the third switch circuit is turned on. And a short-circuit determination circuit that performs If the variation between also occurs, it is possible to quickly detect a short circuit state of the machining gap.

Further, in the second invention, the short-circuit discriminating circuit is configured to connect the workpiece and the electrode to a variable time within a predetermined period of time during which the third switch circuit is on. Is determined to be in a short-circuit state, so that when the third switch circuit is on for a long time, a predetermined time is optimally selected even if the gap state changes from a non-short-circuit state to a short-circuit state during this time. Thus, the short-circuit state can be detected, and the detection accuracy can be further improved.

According to the third aspect of the present invention, there is provided an electrode opposed to a workpiece with a predetermined distance therebetween, and a first power supply and a first switch circuit connected between the electrode and the workpiece. And a first series circuit, which is connected between the workpiece and the electrode in parallel with the first series circuit and connected in reverse polarity to the first power supply. 3
A third series circuit comprising a power supply and a third switch circuit, and both the first switch circuit and the third switch circuit are alternately turned on, and a discharge is generated between the workpiece and the electrode. A control circuit to generate, a discharge state determination circuit for detecting whether the discharge between the workpiece and the electrode is normal or abnormal, and a discharge state determination circuit that determines that abnormal discharge is continuously occurring. And a switch control circuit for stopping the third switch circuit after alternately turning on both the first and third switch circuits for a predetermined time, so that abnormal discharge can be continued for a long time. Even if the first
For a predetermined period of time, the short circuit current of the peak value will flow,
By finding the peak value of the supply current within a range where disconnection does not occur, the abnormal discharge state can be effectively eliminated, and the machining speed is improved.

Further, in the fourth invention, a potential is connected between the workpiece and the electrode in parallel with the first series circuit, and a potential of the same polarity as that of the first electrode is applied to the electrode. A second series circuit of a second power supply and a second switch circuit, wherein when the short-circuit determination circuit determines that the workpiece and the electrode are in a short-circuit state, Since the third switch circuit is stopped after the first and third switch circuits are alternately turned on, the short-circuit current having the peak value flows for the first predetermined time even when the short-circuit state continues for a long time. That is, by finding the peak value of the supply current within a range in which no disconnection occurs, the short-circuit state can be effectively eliminated, and the processing speed is improved.

In the fifth aspect of the present invention, the peak value of the machining current supplied by the second series circuit is changed and controlled during the predetermined time, so that the short-circuit state can be quickly detected and the minimum necessary for eliminating the short-circuit. By independently setting the maximum current peak value, the short-circuit state can be efficiently eliminated without breaking the wire electrode, and the processing speed can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a wire electric discharge machine according to an embodiment of the present invention.

FIG. 2 is a circuit connection diagram of a processing power supply according to the present invention.

FIG. 3 is a circuit diagram of a processing power supply control circuit according to the present invention.

FIG. 4 is a timing chart showing a circuit operation of the processing power supply control device of the present invention.

FIG. 5 is a timing chart showing a circuit operation of the processing power supply control device of the present invention.

FIG. 6 is a current waveform diagram showing a current waveform of the present invention.

FIG. 7 is a block diagram showing a wire electric discharge machine according to another embodiment of the present invention.

FIG. 8 is a circuit diagram of a processing power supply control device according to another embodiment of the present invention.

FIG. 9 is a timing chart showing a circuit operation of a processing power supply control device according to Embodiment 3 of the present invention.

FIG. 10 is a block diagram showing a wire electric discharge machine according to a fourth embodiment of the present invention.

FIG. 11 is a circuit diagram of a processing power supply control device according to a fourth embodiment of the present invention.

FIG. 12 is a timing chart showing a circuit operation of a processing power supply control device according to Embodiment 4 of the present invention.

FIG. 13 is a block diagram showing a conventional wire electric discharge machine.

FIG. 14 is a circuit connection diagram of a conventional processing power supply.

FIG. 15 is a diagram showing a waveform between the poles of a conventional wire electric discharge machine.

[Explanation of symbols]

Reference Signs List 1 wire electrode 2 workpiece 7 processing power supply 18, 19, 20 processing power supply control circuit 70 first DC power supply 71 first switch circuit 74 second DC power supply 75 second switch circuit 77 third DC Power supply 78 Third switch circuit 26, 26a Current peak value setting unit 28 Short circuit state detecting unit 29 Short circuit counting unit 30, 30a Pulse stop command unit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23H 1/02 B23H 7/04

Claims (5)

(57) [Claims] 1. A first series comprising: an electrode disposed to face a workpiece separated by a predetermined distance, and a first power supply and a first switch circuit connected between the electrode and the workpiece. A third power supply and a third power supply connected in parallel to the first series circuit and connected in reverse polarity to the first power supply between the circuit and the workpiece and the electrode; A third series circuit composed of the switch circuit of the above, and a control of alternately turning on both the first switch circuit and the third switch circuit to control a discharge generated between the workpiece and the electrode. And a circuit, after the first switch circuit is turned off, before the first switch circuit is turned on again, and during the period when the third switch circuit is turned on, A short-circuit determination circuit for detecting a short-circuit state of the electrode. Machining power supply control device of a wire electric discharge machine according to symptoms. 2. The short-circuit determination circuit according to claim 1, wherein the workpiece and the electrode are in a short-circuit state during a predetermined period of time during which the third switch circuit is on, during a time period variably set within that period. The machining power supply control device for a wire electric discharge machine according to claim 1, wherein it is determined whether the electric power is supplied to the electric discharge machine. 3. A first series comprising an electrode disposed to face a workpiece and separated by a predetermined distance, and a first power supply and a first switch circuit connected between the electrode and the workpiece. A third power supply and a third power supply connected in parallel to the first series circuit and connected in reverse polarity to the first power supply between the circuit and the workpiece and the electrode; And a control circuit that alternately turns on both the first switch circuit and the third switch circuit to generate a discharge between the workpiece and the electrode. A discharge state determination circuit that detects whether the discharge between the workpiece and the electrode is normal or abnormal; and a predetermined state when the discharge state determination circuit determines that abnormal discharge is continuously occurring. Time above first and third
After the two switch circuits are alternately turned on, the third
And a switch control circuit for stopping the switch circuit. 4. A second power supply connected between the workpiece and the electrode in parallel with the first series circuit and applying a potential having the same polarity as the first power supply to the electrode. A second series circuit with a second switch circuit. When the short-circuit determination circuit determines that the workpiece and the electrode are in a short-circuit state, the switch control circuit causes the first control circuit to perform the first-time control for the first time. 3. The machining power supply control device for a wire electric discharge machine according to claim 1, wherein the third switch circuit is stopped after both the first switch circuit and the third switch circuit are turned on alternately. 5. A machining power supply control device for a wire electric discharge machine according to claim 4, wherein a peak value of a machining current supplied to the second series circuit during a predetermined time is changed and controlled.