JPH03208521A - Electric power supply for discharge machining - Google Patents

Abstract

PURPOSE:To make the building-up of electric current for machining gentle by providing a discharge detection circuit, an ON time/OFF time control circuit, a synchronous circuit, a counter, a count control circuit, and a timing pulse generator in the switching control circuit of a electric power supply for electric discharge. CONSTITUTION:A discharge detection circuit 21 detects a discharging condition derived from a gap voltage Vg to issue a signal ED during discharging. An ON time . OFF time control circuit 21 turns off a voltage signal VON after passing the ON time set since the signal ED becomes an H level, and turn on after passing the OFF time set since the signal VON is off. The signal ED and the signal VON are input to a synchronous circuit 23 and the ON output issued from this circuit 22 cleans a counter 23 and a timing pulse generator 25. The signal ED is turned on, the counter 23 counts timing pulses, switching elements SW0-SW6 are turned on.off by the output C1-C6 of each bit. As the result, when electric current for machining is increased to reach a preset value, the counting operation is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a die-sinking electric discharge machining apparatus, and more particularly to a power source for electric discharge machining.

Conventional technology Electrical discharge machining in which multiple resistors that limit current and switching elements connected to each resistor are connected in parallel, and current is passed between the electrode and the workpiece from a DC power source via the resistors and switching elements. Power supplies for this purpose are already known.

This electric discharge machining power supply selects the switching element described above according to the peak current value flowing between the electrode and the workpiece, and maintains the set on-time. Electrical discharge machining is performed by simultaneously turning on and off the selected switching element at a set on time and off time by a control circuit that outputs a switching pulse according to the off time.

Problems to be Solved by the Invention Conventional electric discharge machining power supplies that control the current flowing between the workpiece and the electrode using the above-mentioned current limiting resistor and switching element turn on selected switching elements at the same time and set current flows between the workpiece and the electrode. Flowing and controlled. However, if the current rises steeply, the electrodes are subject to rapid wear and tear. Therefore, in order to reduce wear on the electrodes, it is desirable to slow the rise of the current.

However, on the other hand, there are cases where it is desired to increase the machining speed even if the consumption of the electrodes is ignored. In such a case, it is better to make the current rise steeper.

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a power source for electrical discharge machining that can gently control the current rise during electrical discharge machining.

Furthermore, a second object of the present invention is to provide a power source for electric discharge machining that can freely set and control the current rise in electric discharge machining according to the purpose of electric discharge machining.

Means for Solving the Problem A DC power source is connected between the electrode and the workpiece through a circuit in which a plurality of circuits each consisting of a resistor that limits current and a switching element connected in series with the resistor are connected in parallel, and the switching element is connected to the workpiece. In a power source for electric discharge machining having a switching control circuit that controls on/off of the electric discharge machining device, the present invention provides a discharge detection circuit that detects a discharge state and outputs an in-discharge signal, and inputs the in-discharge signal into the switching control circuit. an on-time off-time control circuit that outputs a voltage application signal as an output, controls the voltage application signal to be turned off when the discharge time reaches a set on-time, and turned on after the set off-time elapses; a timing pulse generator that outputs timing pulses at a frequency, a counter that is cleared when the voltage application signal is turned off and counts the timing pulses when the discharging signal is turned on, and the value of the counter reaches a set value. Then, a counter control circuit is provided to stop the counting operation of the counter, and the switching element is turned on and off by the output of each bit of the counter gated with the voltage application signal.

Furthermore, a carry control circuit is added to the switching control circuit, and when the bypass signal input corresponding to each bit of the counter is off, the carry output of the corresponding bit is output, and when it is on, the carry output of the corresponding bit is output at the timing. The pulse is used as a carry input signal for the next bit, and when the bypass signal is on, the value of the corresponding bit of the set value is preset and fixed in the corresponding bit of the counter.

In addition, the above counter is used as a preset counter, and when the voltage application signal is turned off, the lower limit value of the set counter is preset, and when the discharging signal is turned on, the counter is counted from the lower limit value, and each bit output of the counter is Each gate may be gated by a voltage application signal, and the switching element may be turned on and off by each gate output.

Also, if the bypass signal input corresponding to each bit of the counter is on when the voltage application signal is turned off, the value of the corresponding bit of the set counter upper limit value is preset to the corresponding bit of the counter. However, when the bypass signal is off, a reset control circuit is provided that presets the value of the corresponding bit of the set counter lower limit value to the corresponding bit of the counter, and when the discharging signal turns on, the bypass signal is turned on. a carry control circuit that causes the counter to count the timing pulse as a carry output of the corresponding bit when it is off, and uses the timing pulse as a carry input signal for the next bit when it is on; A gate circuit is provided that gates the voltage application signal with each bit output of , and turns on and off the switching element with each gate output, so that the current that increases for each timing pulse can be selected, and the current increases from the lower limit value of the setting. The machining current may be increased gradually up to a set upper limit value.

When the active discharge signal is turned on, the counter counts timing pulses and turns on and off the switching elements according to the output of each bit of the counter. As a result, the machining current increases as the count value of the counter increases. When the counter value reaches the set value, the counter control circuit outputs an output and stops the counter's counting operation, so that the machining current corresponds to the set value and the voltage application signal is turned off. will be maintained until As a result, the rise of the machining current can be controlled gently. In this case, the slope of the rise of the machining current can be changed by changing the period of the timing pulse.

In addition, the bypass signal presets and fixes the lower bits of the counter to the same value as the corresponding bit of the set value, and a carry control circuit that counts timing pulses from the unfixed bits starts the timing pulses from the upper bits of the counter. Count the pulses and change the weight of the timing pulse. As a result, if the resistance connected to the switching element that turns on and off at each bit output of the counter is made smaller for the higher bits of the counter,
The value of the machining current added for each timing pulse can be changed by the bypass signal, and the slope of the rise of the machining current can be arbitrarily selected.

Furthermore, if a preset counter is used as the counter, the counter changes by counting timing pulses from a preset value, so when the discharging signal turns on, the machining current first changes to the value corresponding to the preset value. The value changes, and then increases with a slope up to the set value.

Furthermore, if a preset control circuit and a carry control circuit are used, the counter will count timing pulses from the preset value (nearby) using higher bits than the bits that are not fixed by preset, so the machining current will not be set. The counter value changes with a slope from a value corresponding to the set counter lower limit value (nearby) to a value corresponding to the set counter upper limit value. This slope can be arbitrarily adjusted by changing the bit fixed by presetting.

Example FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

Code 1 is DC power supply, RO-R6 is current limiting resistor, SWO
-SW6 is a switching element such as a transistor connected to each of the current limiting resistors RO to R6. The electrode P is connected from the DC power source 1 through the switching element-current limiting resistance circuit (SWO.RO to SW6, R6) connected in parallel.
A current ■ is applied between the workpiece W and the workpiece W.

Reference numeral 2 denotes a switching control circuit that controls on/off the switching elements SWO to S'W6, and the switching element SW is turned on/off by the switching control circuit 2.
The current flowing between the workpiece W and the electrode P is controlled by selecting O to SW6. In this embodiment, the resistance values of the current limiting resistors R1 to R6 are sequentially set to values that are in a multiple relationship.

For example, R1=80Ω, R2=40Ω, R3=20Ω.
R4=10Ω. R5 = 5Ω, R6 = 2.5Ω, the DC power supply is IOOV, the gap voltage between the workpiece W and the electrode P during electrical discharge machining is 20V1, and if the ON voltage of the switching elements is ignored, when each switching element SWI to SW6 is turned on. , the flowing current is as follows.

Switching current limiting resistance 2 current element SWI 80Ω IASW2
40Ω 2ASW3 20Ω
4ASW4 10Ω 8
ASW5 5Ω 16ASW6
2.5Ω 32A switching element SWO
In order to start the discharge, the switching element SWI~
Regardless of the state of SW6, it functions to apply a voltage to the electrode during work time, and the resistor RO is set to, for example, 800Ω to allow a minute current to flow.

FIG. 2 shows a first embodiment of the switching control circuit 2, in which a discharge detection circuit 20 detects the discharge state from the gap voltage Vg and outputs a discharging signal ED.

The on-time off-time control circuit 21 is configured so that the discharging signal ED is H.
The voltage application signal VON is turned off (L level) after the set on time has elapsed since the voltage application signal VON is turned off, and is turned on (H level) after the set off time has elapsed since VON was turned off. The voltage application signal VON is applied to the switching element S
It is input to WO and also to one terminal of each AND gate G1 to G6 of the gate circuit 26. Further, the above-mentioned discharging signal ED and voltage application signal VON are input to the synchronization circuit 22, and the synchronization circuit 22 is set and turned on (H level) when the voltage application signal falls, and is reset when the discharging signal rises. The synchronous circuit 22 outputs an off (L level) signal, and the counter 23 and timing pulse generator 25 are cleared by the on output of the synchronization circuit 22.

A count input terminal of the counter 23 receives the output of a timing pulse generator 25 that outputs a timing pulse TP of a set frequency.

The counter control circuit 24 is composed of a comparison circuit, and outputs the outputs C1 to C6 of each bit of the counter 23 and the outputs of the counter 23.
compares it with a counter upper limit value signal that sets the upper limit value for counting timing pulses TP, and if they match, it is output to the count enable terminal of the counter 23, and the counter 23
Stops the counting operation.

Note that by blocking the input of the timing pulse TP to the counter 23 using the output of the counter control circuit 24,
Alternatively, the counting operation of the counter 23 may be stopped by stopping the operation of the timing pulse generator 25.

The outputs 01 to C6 of each bit of the counter 23 are input to the other terminals of the AND gates G1 to G6 of the gate circuit 26, and the AND gates G1 to G6 are respectively connected to the switching elements SW1 to SW6 in FIG. It is output and turns on/off the switching elements SW1 to SW6.

The on time after the discharging signal ED of the on time off time control circuit 21 is turned on is 50 μs, and the off time is 50 μs.
s, the timing pulse TP is output every 1 μs, and the count upper limit signal is 15. The operation of this embodiment will be explained with reference to the timing chart of FIG. 3.

When the off time of the previous cycle is completed, the voltage application signal VO
N is turned on, the switching element SWO is turned on by the signal VON, and a voltage is applied to the discharge gap. When discharge is started, the discharging signal ED is turned on, and 50 μs after the discharging signal ED is turned on, the signal VON is turned off, and as a result, the discharging signal ED is also turned off. VON
turns on again after being off for 50 μs and the above cycle repeats. Then, when the discharging signal ED turns on, the output of the synchronization circuit 22 turns off, and the clear signals of the counter 23 and timing pulse generator 25 are released.
The counter 23 starts counting timing pulses TP from the timing pulse generator 25. counter 23
When counts one timing pulse TP, output C1
is output (H level), and the AND gate Gl outputs an H level output as shown in FIG. 3, turning on the switching element SWI. As a result, a current I of 1A flows. However, the current flowing through the switching element SWO is so small that it can be ignored. next,
When the count value of the counter 23 reaches "2", the output C2 is output, and only the AND gate G2 becomes H level, turning on the switching element SW2. As a result, the current I
becomes 2A. When the count value of the counter 23 becomes "3", the outputs Cl, C2 are output, and the AND game}Gl, G
2 is turned on, and the current I becomes 3A.

Thereafter, as the count value of the counter 23 increases sequentially, the outputs of the AND gates G1 to G6 of the gate circuit 26 sequentially change as shown in FIG. ■ is inclined and OA
It will increase sequentially from

Then, the count value of the counter 23 is 15 (C1=C2
=C3=C4=H level) and matches the set counter upper limit value signal (15), the control circuit 24 outputs an output and stops the counting operation of the counter 23.

As a result, H level signals are output from the AND gates 61 to G4 until the voltage application signal VON is turned off, and the switching elements SWI to SW4 are turned on and the voltage is increased to 15A.
(=1+2+4+8) machining current flows between the workpiece W and one pole P. When the voltage application signal VON is turned off, all outputs from the gate circuit 26 become L level,
Switching elements SWO to SW6 are all turned off,
The current l becomes "0" and the counter 23 is cleared. Then, after 50 μs, when the voltage application signal VON is turned on again, the above-described operation is started again.

As described above, in this embodiment, the machining current ■ is increased sequentially from OA, and when the set time (counter upper limit value x timing pulse period) of 15 μs has elapsed, the control is performed so that the set current value (counter upper limit value) is 15 A. It is something.

That is, in this embodiment, the upper limit value of the machining current I is set by the counter upper limit value signal, and the upper limit value of the machining current I' is
The time from A to the upper limit value is determined by the set frequency of the timing pulse generator 25.

However, in the first embodiment, the timing pulse TP is one pulse, and the current does not increase unless it is IAL.

Therefore, when setting the machining current l to a large current, for example, 50 A, the timing pulse TP reaches the set value in 50 pulses, and the discharging signal ED changes from on to 50 A.
When the μs voltage application signal VON is on, the waveform of the machining current becomes a sawtooth wave.

In order to avoid a sawtooth waveform, the set frequency of the timing pulse TP may be increased, but this would result in an increase in switching of the switching elements, which is not preferable.

Therefore, a second embodiment of the switching control circuit 2 in which the current increases with one pulse of the timing pulse TP will be explained with reference to FIGS. 4 and 5.

The switching control circuit of this second embodiment is different from the switching control circuit of the first embodiment in that a carry control circuit 31 is added, and because of the addition of this carry control circuit 31, the error counter 30 The difference is that the composition of
Since the other configurations are the same as those in the first embodiment, the same reference numerals are used.

The carry control circuit 31 connects carry circuits K1 to K between the lower bit of the counter 30 and the bit one higher than that bit.
5, timing pulse TP and bypass signals BPI to BP5 are inputted to the carry circuits K1 to K5, respectively, and carryout signals Col to Co5 are inputted from the lower bits, respectively, and carryout signals Col to Co5 are inputted to the upper bits, respectively. In signals Ci2 to Ci6 are output.

Further, a counter upper limit value signal is inputted to each bit 81 to B5 of the counter 30 except for the most significant bit B6, and each bypass signal BPI to BP5 is inputted thereto. A timing pulse TP is manually input to the least significant bit B1. Further, as in the first embodiment, the output of the counter control circuit 24 is input to the count enable terminal, and when a match signal is output from the counter control circuit 24, the counting operation is stopped. , each bit B1 to B of the counter 30 is turned on by the output of the synchronous circuit 22, which is turned on at the fall of the voltage application signal VON.
6 is cleared, which is the same as in the first embodiment.

When the bypass signal BPI-BP5 is turned on, bits B1 to B5 of the counter 30 to which the turned-on bypass signal is input are preset to the value of the bit input as the counter upper limit signal, and the preset value is Retained until cleared. In addition, a carry circuit K1 to which the turned-on bypass signals BP1 to BP5 are input.
-K5 are configured to use the timing pulse TP as a carry signal, and turn on the carry-in signals Ci2 to Ci6. For example, if the setting counter upper limit signal is 5
Assuming that it is 0 (1st bit rOJ, 2nd bit “1”, 3.4th bit rOJ, 5.6th bit “1”),
When the bypass signal BPI is turned on, the least significant bit B1 of the counter 30 is reset to "0", and the carry circuit K1 uses the timing pulse TP as a carry signal and turns on the carry-in signal Ci2 to turn on the counter 30. input to the second bit B2. In addition, bypass signal BP2
When turned on, the second bit B2 of the counter 30 becomes “1”.
”, and the carry circuit K2 is configured to turn on the carry-in signal Ci3 using the timing pulse TP as a carry signal and input it to the third bit B3 of the counter 30.

Note that if the bypass signal is not on, only when the on carry-out signal is input, the on carry-in signal is sent to each carry circuit K1 to K by the timing pulse TP.
5 outputs.

Next, the operation of this second embodiment will be explained.

First, set the ON time to 50 μs. The setting value of the off time is 50 μs, and the period of the timing pulse TP is 1 μs.
shall be. An example will be explained in which the counter upper limit value signal is set to 50 and the bypass signals BPI and BP2 are turned on. Since the counter upper limit signal is 50 and the bypass signals BPI and BP2 are on, the first bit B1 of the counter 30 is "0" and the second bit B2 is "0".
1".

When the voltage application signal VON turns on, a voltage is applied to the discharge gap, and when discharge starts, the discharging signal ED turns on, and then, as shown in FIG. 5, the voltage application signal V
ON remains on for 50 μs. Since the output of the synchronization circuit 22 is turned off and the clear signal is released, the first and second bits Bl and B2 of the counter 30 are preset to "0" and "1", respectively, as described above, and the signal C2 is turned on. As a result, the output of the AND gate G2 is turned on and the switching element SW2 is turned on, so that the current I of 2A is
flows. Next, when the timing pulse TP occurs,
Since bypass signal BP2 is on, carry circuit K2
The carry-in signal Ci3 from is turned on, the third bit B3 of the counter 30 is inverted and turned on, and the output C3 is turned on, so an output is output from the AND gate G3.
Since the switching element SW3 is also turned on, a processing current I of 2A+4A=6A flows. Then, at the next timing pulse TP, the third bit B3 is inverted and turned off, and the carry-out signal Co3 is turned on, so the carry-in signal C+4 from the carry circuit K3 is turned on, and the fourth bit B4 is turned on. shall be. As a result, output is output from AND gates G2 and G4 and turns on switching elements SW2 and SW4, so the processing current is 2A.
+8A=10A will flow. At the next timing pulse TP, the third bit B is turned on, and the switching elements SW2. SW3 and SW4 are turned on, 2+4+8
A machining current I of =14A flows. Hereinafter, the machining current I is 4A every time the timing pulse TP is generated.
It will increase each time.

Then, when 12 timing pulses TP are generated, B2, B5, and B6 of the counter 30 are turned on, and the output signals C2 (=2) and C5 (=16) are turned on.
．． C6 (=32) turns on and matches the set counter upper limit value signal 50 (2+16+32=50)L, the count control circuit 24 outputs an output and stops the counting operation of the counter 30, so the AND gate G2, G5,G
From 6 onwards, the machine stops with the output being output, and the switching elements SW2, SW5, 3W6 continue to be on, and a machining current of 50 A flows. Then, when the voltage application signal VON turns off after 50 μs, the counter 30 is cleared, all bits 81 to B6 are turned off, their outputs 01 to C6 are also turned off, and the outputs of the AND gates G1 to G6 are also turned off. The switching elements SWO to SW6 are also turned off, and the processing current I becomes rOJ.

When the 50 μs off time of the voltage application signal VON has elapsed and the voltage application signal VON is turned on again, the above-described operation will be started again.

In this way, when the discharging signal ED is turned on, the machining current I initially flows at 2 A, and thereafter increases by 4 A each time a timing pulse TP occurs, until the timing pulse TP reaches 12 A.
With pulse (12μs), 2+12X4=50A,
Thereafter, a processing current of 50 A flows until the voltage application signal VON is turned off.

Also, in this second embodiment, the timing pulse T
If the processing current value incremented every P periods is 2A, the bypass signal BPI is turned on and the least significant bit of the counter is preset to the value of the corresponding bit of the set counter upper limit value.

For example, if the counter upper limit is 50, B1=0, and if the upper limit is 51, B1=1. Then, every time the timing pulse TP is output, bit B2 of the counter 30
Since the timing pulse TP is counted as the lowest value, the weight of the timing pulse is "2", the processing current increases every 2A, and when 25 timing pulses TP are counted, the upper limit of the count is 50 and the bit is set. B1=
If it is set to O, the output of the counter 30 will be 50, the counting operation will be stopped, and a machining current I of 50 A will flow. Also, if the counter upper limit value is 51, B1=1, so when the timing pulse TP is counted 25, the output of the counter 30 becomes 51, and 5
1A will flow.

Furthermore, if the machining current is increased by 4A for each timing pulse TP, the bypass signal B
P.I. BP2 is turned on, timing pulse TP is counted by bits B3 to B6, the weight of timing pulse TP is set to 4, and bits }B1 and B2 are preset to the value of the corresponding bit of the set upper limit value. Similarly, if the increment of the machining current is 8A, the bypass signals BPI, BP
2, BP3 is turned on, the counter 30 counts the timing pulse TP from bit B4, the weight of the timing pulse is set to 8, and bits B1, B2, and B3 are preset to the values of the corresponding bits of the set upper limit value.

FIG. 6 shows a third embodiment of the switching control circuit 2,
The difference from the switching control circuit in the first embodiment shown in FIG.
This is the point set to 0. Since the other configurations are the same as those of the first embodiment, the same reference numerals are given.

That is, the preset counter 40 receives the voltage application signal VO.
When N is turned off and the synchronization circuit 22 is turned on, it is preset to the value set by the counter lower limit value signal.

Therefore, when the on time is 50 μs and the off time is 50 μs,
An example in which the timing pulse TP is output every 1 μs, the counter upper limit value signal is set to 20, and the counter lower limit value signal is set to 10 will be explained with reference to the timing chart of FIG.

When the voltage application signal VON is turned on, a voltage is applied to the discharge gap, and when discharge is started, the discharging signal ED is turned on, and thereafter the voltage application signal VON remains on for 50 μs. Note that the counter 40 receives the discharging signal ED.
The output of the synchronizing circuit 22, which is turned on when the counter is off, is preset to 10, which is the value set by the counter lower limit signal. Therefore, the output signal C2. C4 is turned on, output is output from AND gates G2 and G4, and switching elements SW2 and
SW4 is turned on and the machining current I is IOA.

Then, the counter 40 will count the timing pulses TP from the count value 10, and each time the timing pulse TP is inputted, it will be 11, 12, 13...
The processing current l increases by IA each time a timing pulse TP is generated from IOA. . Then, when the count value reaches 20, it matches the value 20 set in the count upper limit value signal, so an output is output from the count control circuit 24, and the counting operation of the counter 40 is stopped. From then on, the voltage application signal VON is turned off. A machining current I of 20 A flows until the current I.

That is, the machining current I of IOA initially flows for 10 μs.
As time passes, the machining current I becomes 20 A, and thereafter, the machining current I of 20 A flows until the voltage application signal VON is turned off (50 μS). The above operation is repeated every time the voltage application signal VON is turned on.

FIG. 8 is a block diagram of a switching control circuit in a fourth embodiment of the present invention. In this fourth embodiment, the machining current l is set to the set lower limit value (nearly) immediately after the discharging signal ED is turned on, and is then increased by a set unit amount for each timing pulse TP to the set upper limit value. .

The difference between this fourth embodiment and the first embodiment shown in FIG. 2 is that a counter 50, a carry control circuit 51, and a preset control circuit 52 are provided in place of the counter 23. The other configurations are the same as those of the first embodiment shown in FIG. 2, and are given the same reference numerals.

The preset control circuit 52 controls each bit Bl of the counter 50.
-86, each preset circuit PS1 to PS6 has a signal of a corresponding bit (bit of a corresponding digit in binary value) of a counter upper limit value signal and a counter lower limit value signal. It has been entered. In addition, the preset circuits PS1 to PS5 have a bypass signal B.
PI to BP5 are respectively input, and when the bypass signals BPI to BP5 are on, each preset circuit PS
1 to PS5 select each output of the counter upper limit value signal and preset it to each corresponding bit 81 to B5 of the counter 50, and when the bypass signals BPI to BP5 are off, each preset circuit PS1 to PS5 selects the counter lower limit value signal. , and when the output of the synchronization circuit 22 is on, the corresponding bits 81 to B5 are preset. When the bypass signals BPI to BP5 are turned on and the values of the corresponding bits of the counter upper limit value signal are preset to the bits B1 to B5 of the corresponding counter 50, the preset values of the bits 81 to B5 do not change. First, it maintains the preset value.

Further, the carry control circuit 51 has carry circuits K1 to K5 between the lower bit of the counter 50 and the bit one higher than the lower bit, similarly to the carry control circuit 31 of the embodiment shown in FIG. A timing pulse TP is input to each carry circuit K1 to K5, and a corresponding bypass signal BPI is input to each carry circuit K1 to K5.
~BP5 and carry-out signal Cok from lower bit
(k=1 to 5) is input, and a carry-in signal Cik (k=2 to 6) is output to the upper bit. When the bypass signals BPI to BP5 are on, the timing pulse TP turns on the carry-in signal Cik as a carry signal, and the bypass signal BPI
~ When BP5 is off, a carry-in signal that is on is output to the next bit using the timing pulse TP only when the carry-out signal Cok is input.

Next, the on time is set to 50 μs, the off time is set to 50 μs, the set frequency of the timing pulse is set to 1 μs, and the set counter lower limit value is set to 10. The setting counter upper limit value is 50.
An example will be explained in which the bypass signals BPI and BP2 are turned on.

FIG. 9 is a timing chart in this example.

When the setting counter lower limit value is "10", the data of the lower limit value corresponding to bits B1 to B5 of the counter 50 is B1.
=O. B2=1.83=0.84=1. B5=0. B6
=0. Furthermore, the data corresponding to the set counter upper limit value "50" is BO=0, B2=1. B3=O, B4=
0. B5=1.86=1. As a result, when bypass signals BPI and BP2 are on and BP3 to BP5 are off, bits Bl. B2 has the setting counter upper limit value “50”.
", and bits 83 to B6 contain the value corresponding to the set counter lower limit value "10" when the output of the synchronous circuit 22 is turned on (when the voltage application signal VON is turned off) Therefore, the counter 50 has B1=O. B2=1.83=O. B4=1. B5=0.
B6=O will be preset (as a result, the same value as the set counter lower limit value "10" will be preset).

Therefore, when the voltage application signal VON is turned on and a voltage is applied to the discharge gap to start discharge, the counter 50
AND gate G by the preset value "10"
2. By the output of G4, switching elements SW2, SW
4 is on, so the IOA machining current l corresponding to "10" preset as the counter lower limit value
will flow. And bypass signal BPI,
Since BP2 is on, bit B3 of the counter 50 is repeatedly inverted every time the timing pulse TP is output, and the counter 50 counts the timing pulse TP using bits B3 to B6. That is, bit B3 of the counter 50 is turned on by the first timing pulse TP, and the output of the counter 50 is B1=0.
．． B2=1, B3=1, B4=1, B5=O. B6=0
Therefore, the switching elements SW2, SW3, and SW4 are turned on, and a current l of 2+4+8=14 A flows. When the next timing pulse TS is input, bit B
3 becomes "0" and outputs the carry-out signal Co3, so the carry-in signal Cj4 is output from the carry circuit K3.
is turned on, bit B4 is also inverted and becomes 0,
Outputs carry-out signal Co4. As a result, the carry-in signal Ci5 is turned on from the carry circuit K4,
Bit B5 is set to "1". As a result, the counter 50 has B1=0, B2=1. B3=0. B4=O, B5=1,
Since B6=0, outputs are output from the AND gates G2 and G5 and turn on the switching elements sw2 and SW5, so a machining current (2) of 2+16=18A flows.

Similarly, the machining current I increases by 4 A for each timing pulse TP, and when 10 timing pulses TP are output, the values of the counter 50 are B1=0, B2=1,
B3=0, B4=0. Since B5=1 and B6=1, which match the set counter upper limit value "50", the counter control circuit 24 outputs an output and stops the counting operation of the counter 50. As a result, switching elements SW2,
With SW5 and SW6 turned on, the machining current I is 50A.
The state of (2+16+32=50) is maintained. Then, when the voltage application signal VON is turned off, the output of the AND gates GO~6 becomes "0", so the switching elements SWO-SW6 are turned off, and the processing current IrOJ becomes.

Thereafter, the above operation is repeated every time the voltage application signal VON is turned on, and the machining current I increases by 4A from IOA with the timing pulse TPI pulse, and 10 μs after the 10 timing pulse TP is output, the machining current I becomes 50A and lasts until the on-time ends.

Note that in this embodiment, bypass signals BP1 to BP
5 is turned on, the value of the corresponding bit of the counter upper limit value is preset to each bit of the counter 5o.
When the machining current I starts flowing, the current corresponding to the value set as the counter lower limit value does not necessarily flow. For example, set the counter lower limit value to rl OJ . If the counter upper limit value is "51", the counter lower limit value is "1o"
The preset value corresponding to B1=O. B2=1, B3=
O. B4=1, B5=O, B6=O, and the preset values corresponding to the counter upper limit values are B1=1, B2=1, B
3=0, B4=O, B5=1, and B6=1. Therefore, when bypass signals BP1 and BP2 are turned on, bits Bl and B2 of the counter 5o are preset to a value "1" corresponding to the counter upper limit value, and bits 83 to B6 are preset to a value corresponding to the counter lower limit value. Therefore, the counter 501m is B1=1.82=1, B3=0, B4=
1, B5=0, and B6=0 are preset, and the machining current starts flowing from 11A (1+2+8=11). Similarly, even if bypass signals BP1 and BP2 are turned on and the counter lower limit value is set to "10", if the counter upper limit value is "52", the machining current will start from 8A, and if the counter upper limit value is "53" If the counter upper limit is ``54'', the flow will start from 9A, if the counter upper limit is ``55'', the flow will start from IIA, and the counter will start flowing according to the counter upper limit setting value. Processing current I that differs from 0 to 3 A with respect to the lower limit setting value
The flow begins.

Furthermore, by turning on the bypass signals BPI, BP2, and BP3, it is possible to increase the machining current I by 8A for each timing pulse TP. , the machining current will start flowing from a machining current that is 0 to 7 A different from the machining current that corresponds to the set counter lower limit value.

In addition, the above-mentioned Fig. 4. The second embodiment shown in FIG. 5, FIG. In the fourth embodiment shown in FIG. 9, the increment unit for each timing pulse can be changed. For example, to increase every 4A, the bypass signal BPI,
Bypass signal B to turn on BP2 and increase every 8A
Changed to turn on PI, BP2, and BP3. However, it is also conceivable to turn on the upper bypass signal and turn off the lower bypass signal. For example, Figures 4 and 8
In the figure, when the bypass signal BP2 is turned on and the lower bypass signal BPI is not turned on, the counter 30.50 converts the timing pulse TP from bit B3 to
B6 counts and bit B1 is inverted every time the timing pulse TP occurs, so the machining current value increased by the timing pulse TP is 3A.
．． It will change alternately with 5A. In this case, since the value corresponding to the set counter upper limit value will not be preset to bit B1, there will be cases where the values of the counters 30 and 50 do not match the set counter upper limit value. Therefore, the above method can be employed when the counter values are employed as set values only for the values taken by the counters 30 and 50.

Effects of the Invention In the present invention, since the rise of the machining current is made gentle, it is possible to reduce electrode wear. In addition, the slope of this rise can be adjusted arbitrarily, or it can be made to rise rapidly to the set value at the rise of the machining current, and then be raised with a slope to the set machining current (peak current). The machining current can be controlled accordingly.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a first embodiment of the switching control circuit in the same embodiment, and FIG. 3 is a timing chart of the first embodiment. 4 is a block diagram of the second embodiment of the switching control circuit, FIG. 5 is a timing chart of the second embodiment,
FIG. 6 is a block diagram of the third embodiment of the switching control circuit, FIG. 7 is a timing chart of the third embodiment, FIG. 8 is a block diagram of the fourth embodiment of the switching control circuit, and FIG. is a timing chart of the third embodiment. 1... DC power supply, 2... Switching control circuit, S
WO to SW6... switching element, P... electrode,
W...Work, 20...Discharge detection circuit, 21...
On-time off-time control circuit, 22...Synchronization circuit, 23
, 30, 40.50... Counter, 24... Count control circuit, 25... Timing pulse generator, 26
...Gate circuit, 01-G6...AND gate, 31.51...Carry control circuit, 81-B6...Bit, K1-K5...
・Carry circuit, 52...Preset control circuit, PS1
~PS6...Preset circuit.

Claims (4)

[Claims] (1) A DC power source is connected between the electrode and the workpiece through a circuit in which multiple circuits each consisting of a current-limiting resistor and a switching element connected in series with the resistor are connected in parallel, and the switching element is turned on and off. In a power source for electrical discharge machining, the switching control circuit includes a discharge detection circuit that detects a discharge state and outputs a discharge signal, and a discharge detection circuit that receives the discharge signal as input and outputs a voltage application signal. an on-time off-time control circuit that controls the applied signal to be turned off when the discharge time reaches a set on-time and turned on after the set off-time elapses; a timing pulse generator that outputs timing pulses at a frequency and is reset when the voltage application signal turns off; and a timing pulse generator that is cleared when the voltage application signal turns off and counts the timing pulses when the discharging signal turns on. a counter; a counter control circuit that stops the counting operation of the counter when the value of the counter reaches a set value;
A power source for electric discharge machining, comprising a gate circuit that gates the voltage application signal with each bit output of the counter, and turns on and off the switching element with each gate output. (2) By the bypass signal input corresponding to each bit of the counter, the value of the corresponding bit of the set value is preset and fixed to the corresponding bit of the counter by the discharging signal, and the bits that are not fixed are fixed. 2. The electric discharge machining power source according to claim 1, further comprising a carry control circuit configured to count the timing pulses from the .times..times..times..times..times. (3) A DC power source is connected between the electrode and the workpiece through a circuit in which multiple circuits each consisting of a current-limiting resistor and a switching element connected in series with the resistor are connected in parallel, and the switching element is turned on and off. In a power source for electrical discharge machining, the switching control circuit includes a discharge detection circuit that detects a discharge state and outputs a discharge signal, and a discharge detection circuit that receives the discharge signal as input and outputs a voltage application signal. an on-time off-time control circuit that controls the applied signal to be turned off when the discharge time reaches a set on-time and turned on after the set off-time elapses; A timing pulse generator that outputs a timing pulse at a frequency and is reset when the voltage application signal turns off, and a counter lower limit value is preset when the voltage application signal turns off, and the discharging signal turns on. a counter that counts timing pulses, a counter control circuit that stops the counting operation of the counter when the value of the counter reaches a set upper limit value, and a voltage application signal that is applied to each bit output of each of the counters. 1. A power source for electric discharge machining, comprising: a gate circuit that turns on and off the switching element according to each gate output. (4) A DC power source is connected between the electrode and the workpiece through a circuit in which multiple circuits each consisting of a current-limiting resistor and a switching element connected in series with the resistor are connected in parallel, and the switching element is turned on and off. In a power source for electrical discharge machining, the switching control circuit includes a discharge detection circuit that detects a discharge state and outputs a discharge signal, and a discharge detection circuit that receives the discharge signal as input and outputs a voltage application signal. An on-time off-time control circuit that controls the applied signal to turn off when the discharge time reaches a set on-time and turn on after the set off-time elapses, and a frequency set by the output of the above-mentioned discharging signal. A timing pulse generator that outputs a timing pulse and is reset when the voltage application signal turns off, a counter that counts the timing pulses, and an input that corresponds to each bit of the counter when the voltage application signal turns off. When the bypass signal to be set is on, the value of the corresponding bit of the set counter upper limit is preset and fixed to the corresponding bit of the counter, and when the bypass signal is off, the value of the corresponding bit of the set counter upper limit is preset and fixed. A preset control circuit that presets the value of the corresponding bit of the value to the corresponding bit of the counter, and when the above-mentioned discharging signal is turned on, a carry output of the corresponding bit is output when the bypass signal is off, and a carry output of the corresponding bit when it is on. a carry control circuit that causes the counter to count the timing pulse by using the timing pulse as a carry input signal for the next bit;
A counter control circuit that stops the counting operation of the counter when the value of the counter reaches a set counter upper limit value; and a counter control circuit that gates a voltage application signal with each bit output of each of the counters, and controls the switching element with each gate output. A power source for electrical discharge machining, characterized in that it has a gate circuit that turns on and off.