JPH07112325A - Power unit for electric discharge machine - Google Patents

Abstract

PURPOSE:To apply fine finishing to a workpiece on its surface to be machined by setting electric current for charging a capacitor placed in connection between a machining electrode and the workpiece to the pulse current row of the same pulse width as that of the discharge of the capacitor. CONSTITUTION:A power unit for electric discharge machine is provided with a d.c. power source 1 for supplying d.c. pulse current to a machining gap between a machining electrode 2 and a workpiece 3 and a series curcuit composed of a switching device 4 and a resistor 5, and a capacitor 6 is connected in parallel to the machining electrode 2 and the workpiece 3. Discharge generated in the machining gap is detected by a discharge detecting means 7 and the detected signal is input in an oscillation control circuit 80. On/off control to the switching element 4, is repeated until the capacitor 6 makes it discharge and a discharge detecting means 7 detects the discharge and, after elapse of a specific off time after discharge is detected, on/off control is repeated again. Thus a precise machining can be accomplished by preventing any current of a pulse width of more than that of the discharge from the capacitor 6 from flowing into the machining gap.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for an electric discharge machine which supplies machining electric power to a machining gap between a machining electrode provided in an electric discharge machining fluid and a workpiece.

[0002]

2. Description of the Related Art Conventionally, as a prior art document relating to a power supply device for an electric discharge machine, one disclosed in Japanese Patent Laid-Open No. 3-55117 is known. In this device, a pulse train having a predetermined repetition frequency is intermittently driven at predetermined time intervals to drive a switching element, and an AC pulse current is supplied to a machining gap between a machining electrode in which a capacitor is connected in parallel and a workpiece. It is stated that the electric charge of the capacitor is completely discharged into the machining gap to prevent the arc current from continuing and the surface roughness in the electric discharge machining is improved.

[0003]

By the way, in the case of performing electric discharge machining by supplying a DC pulse current in place of the AC pulse current into the machining gap between the machining electrode and the workpiece, the above-mentioned technique is used. Can not. As a measure against this, a power supply device for an electric discharge machine as shown in FIG. 10 is known. FIG. 10 is a circuit diagram showing the configuration of a power supply device for an electric discharge machine that utilizes charging and discharging of a capacitor. In FIG. 10, 1 is a DC power supply, 2 is a processing electrode, 3 is a workpiece, 4
Is a switching element including a transistor and the like, and 5 is a resistor for limiting current. Further, 6 is a capacitor connected in parallel to the machining electrode 2 and the workpiece 3, 7 is a discharge detecting means connected to the machining electrode 2 and the workpiece 3, and 8 is connected to the switching element 4. It is a transmission control circuit. A switching element 4 is provided between the DC power source 1 and the processing electrode 2.
And the resistor 5 are connected in series. Further, the discharge detecting means 7 sends a discharge detection signal Sd to the transmission control circuit 8 when detecting the discharge between the machining electrode 2 and the workpiece 3.

Next, the operation will be described. The DC power supply 1 supplies a machining power between the machining electrode 2 and the workpiece 3 which are arranged in the machining fluid so as to face each other with a minute gap therebetween. The switching element 4 is on / off controlled by the transmission control circuit 8. The capacitor 6 is configured to be charged by a current limited by a series circuit including the DC power source 1, the switching element 4, and the resistor 5. The capacitor 6 discharges when the charging voltage reaches the dielectric breakdown voltage between the machining electrode 2 and the workpiece 3, and the workpiece 3 is machined by the discharge current. This is used when the time width is set to a very short pulse current and the processing amount for processing the workpiece by one discharge is made minute.

The pulse width of the discharge current of the capacitor 6 is its capacitance, the capacitor 6, the machining electrode 2 and the workpiece 3.
Although it is determined by the minute resistance and inductance of the line existing in the series circuit consisting of, the pulse width is extremely short, and is about a fraction of a microsecond. Further, the voltage between the machining electrode 2 and the workpiece 3 during the discharge when the discharge occurs in the machining gap is approximately constant, about 25V.

The electric discharge detecting means 7 detects that an electric discharge is generated in the machining gap between the machining electrode 2 and the workpiece 3 when the voltage between the machining electrode 2 and the workpiece 3 becomes a certain voltage or less. It is designed to detect. When the discharge detection means 7 detects a discharge, it sends a discharge detection signal Sd to the transmission control circuit 8, and the transmission control circuit 8 turns off the switching element 4 immediately upon receiving the discharge detection signal Sd, and the machining electrode 2 and the workpiece 3 It operates so as to stop the current supply to the machining gap and the capacitor 6. However, there is inevitably a time delay from when the discharge detection signal Sd is received until the switching element 4 is turned off. After this, after a certain time such that the insulation between the processing electrode 2 and the workpiece 3 is restored,
The transmission control circuit 8 turns on the switching element 4 again,
The charging of the capacitor 6 and the discharging between the machining electrode 2 and the workpiece 3 as described above are repeated.

In each waveform shown in FIG. 11, the horizontal axis is the time axis,
11 is a timing chart showing transitions of current / voltage and output signals of respective parts in the circuit of FIG. 10. The inter-electrode voltage Vp is a charging voltage waveform between the machining electrode 2 and the workpiece 3. The circuit current Es is a current waveform flowing in a series circuit composed of the DC power supply 1, the switching element 4 and the resistor 5, and is up to the discharge start point t01 where discharge is generated in the machining gap between the machining electrode 2 and the workpiece 3. It is equal to the charging current to the capacitor 6 and equal to the current flowing into the machining gap in addition to the discharge current from the capacitor 6 to the machining gap during discharging. The machining gap current Ep is a discharge current waveform flowing in the machining gap between the machining electrode 2 and the workpiece 3.

Now, a discharge occurs at the discharge start point t01, and a delay time T11 occurs until the discharge detecting means 7 detects the discharge and generates the discharge detection signal Sd. Further, there is a delay time T12 from when the transmission control circuit 8 receives the discharge detection signal Sd to when the switching element 4 is turned off. Therefore, there is a delay time (T11 + T12) from the actual discharge start at the discharge start point t01 until the switching element 4 is turned off after the discharge is detected. During this delay time (T11 + T12), the discharge continues, so the inter-electrode current E
During the time T13 after the peak current waveform in the discharge current waveform of p, not the discharge current from the capacitor 6, but the processing electrode 2 and the workpiece 3 from the DC power source 1 via the switching element 4 and the resistor 5. The discharge current will be supplied during this period.

That is, in the above-mentioned power supply device for an electric discharge machine,
In addition to the discharge current from the capacitor 6, a current with a long pulse width flows as a discharge current from the DC power supply 1 through the switching element 4 and the resistor 5 into the machining gap between the machining electrode 2 and the workpiece 3 as a pulse current. A short discharge current cannot be obtained. Therefore, the amount of machining by one discharge increases,
There was a problem that the EDM surface became rough.

Therefore, the present invention has been made in order to solve such a problem, and an object thereof is to provide a power supply device for an electric discharge machine which does not deteriorate surface roughness by using a DC pulse current.

[0011]

A power supply device for an electric discharge machine according to claim 1 is a DC power supply for supplying a DC pulse current to a machining gap between a machining electrode and a workpiece, a switching element and a resistor. A series circuit consisting of, a discharge detection means for detecting generation of discharge between the machining electrode and the workpiece by a capacitor connected in parallel to the machining electrode and the workpiece, and the serial circuit With respect to the switching element in the circuit, the capacitor discharges the ON / OFF control in which the pulse width of the discharge current of the capacitor is equal to or less than the pulse width of the capacitor and is turned off for a predetermined time. Repeat until detected,
An emission control circuit for repeating the ON / OFF control again after a predetermined OFF time after the discharge is detected by the discharge detecting means.

According to a second aspect of the present invention, in addition to the first aspect, the power supply device for an electric discharge machine is the one after the electric discharge between the machining electrode and the workpiece is detected by the electric discharge detection means. Counting means for counting the number of on / off controls until the discharge detecting means detects discharge by repeating the on / off control for the switching element after a predetermined off time, and the count And a preset value is compared, and when the value counted by the counting means is smaller, a charging current large signal indicating that the current for charging the capacitor is larger is generated, and the counting is performed. When the value counted by the means is larger, the comparator means for generating a small charging current signal indicating that the current for charging the capacitor is small.

According to a third aspect of the present invention, in addition to the first aspect, the power supply device for an electric discharge machine is the one after detecting the electric discharge between the machining electrode and the workpiece by the electric discharge detecting means. Counting means for counting the number of on / off controls until the discharge detecting means detects discharge by repeating the on / off control for the switching element after a predetermined off time, and the count Storage means for storing the stored value a predetermined number of times, computing means for computing the average value of the stored values, and the computing means for comparing the computed value with a preset value. If the value is smaller, a charging current large signal indicating that the current for charging the capacitor is larger is generated, and if the value calculated by the calculating means is larger, the capacitor is charged. Is intended to and comparator means for generating a charging current small signal indicating that flow is small.

According to a fourth aspect of the present invention, in addition to the second or third aspect of the power supply device for an electric discharge machine, when the small charging current signal is generated by the comparing means, the resistor of the series circuit is provided. There is provided a changing means for decreasing the resistance value of No. 1 by a constant value and increasing the resistance value of the resistor of the series circuit by a constant value when the charging current large signal is generated by the comparing means.

According to a fifth aspect of the present invention, in addition to the second or third aspect of the power source device for an electric discharge machine, when the charging current small signal is generated by the comparing means, the DC power source of the series circuit is provided. There is provided a changing means for increasing the voltage value of 1 by a constant value and decreasing the voltage value of the DC power source of the series circuit by a constant value when the charging current large signal is generated by the comparing means.

According to a sixth aspect of the present invention, in addition to the second or third aspect of the power supply device for an electric discharge machine, the current for charging the capacitor when the small charging current signal is generated by the comparing means. There is provided a changing means for increasing the pulse width by a fixed value and shortening the pulse width of the current for charging the capacitor by a fixed value when the charging current large signal is generated by the comparing means.

[0017]

In the power supply device for the electric discharge machine according to claim 1,
The switching element is turned off after the capacitor is discharged, and only a discharge current from the capacitor flows between the machining electrode and the workpiece.

According to a second aspect of the present invention, in addition to the operation of the first aspect, the power supply device for an electric discharge machine has a preset value and a value obtained by counting the number of on / off control times for the switching element until the capacitor reaches the discharge state. By comparing with, the magnitude of the charging current for the capacitor is determined.

In addition to the effect of claim 1, the power supply device for an electric discharge machine according to claim 3 stores and calculates a value obtained by counting the number of on / off control times for the switching element until the capacitor reaches the discharge state, a fixed number of times. The magnitude of the charging current for the capacitor is determined by comparing the average value thus obtained with a preset value.

According to a fourth aspect of the present invention, in addition to the operation of the second or third aspect, the power supply device for an electric discharge machine changes the resistance value of the resistor based on the determination of the magnitude of the charging current to the capacitor. The capacitor charging current is optimized.

In the electric power supply device for an electric discharge machine according to a fifth aspect, in addition to the operation of the second or third aspect, the voltage value of the DC power source is changed based on the magnitude judgment of the charging current to the capacitor, The capacitor charging current is optimized.

According to a sixth aspect of the present invention, in addition to the operation of the second or third aspect, the pulse width of the charging current is changed based on the determination of the magnitude of the charging current with respect to the capacitor. The capacitor charging current is optimized.

[0023]

EXAMPLES The present invention will be described below based on specific examples. <First Embodiment> FIG. 1 is a circuit diagram showing a power supply device for an electric discharge machine according to a first embodiment of the present invention. In addition, this embodiment corresponds to the embodiment of claim 1, and those having the same configurations or corresponding portions as those of the above-described conventional apparatus are denoted by the same reference numerals and symbols. In FIG. 1, 1 is a DC power supply, 2 is a processing electrode, 3 is a workpiece, 4 is a switching element formed of a transistor or the like, and 5 is a current limiting resistor. Further, 6 is a capacitor connected in parallel to the machining electrode 2 and the workpiece 3, 7 is a discharge detecting means connected to the machining electrode 2 and the workpiece 3, and 80 is connected to the switching element 4. It is a transmission control circuit. The DC power supply 1 has a voltage sufficient to generate an electric discharge between the machining electrode 2 and the workpiece 3. A switching element 4 and a resistor 5 are connected in series between the DC power supply 1 and the processing electrode 2. Further, the discharge detecting means 7 sends a discharge detection signal Sd to the transmission control circuit 80 when detecting the discharge between the machining electrode 2 and the workpiece 3. The switching element 4 is on / off controlled by the transmission control circuit 80. As described above, the configuration of this embodiment is apparently the same as that of the conventional device described above, but the switching element 4 is turned on / off.
The operation of the transmission control circuit 80 for off control is different.

Each waveform shown in FIG. 2 has a horizontal axis on the time axis,
3 is a timing chart showing transitions of current / voltage and output signals of respective parts in the circuit of FIG. 1. In FIG. 2, the voltage between contacts Vp is a voltage waveform between the processing electrode 2 and the workpiece 3. At time t1, the inter-electrode voltage Vp is equal to the machining electrode 2
When the dielectric breakdown voltage of the machining gap between the workpiece 3 and the workpiece 3 is reached, discharge occurs and the voltage Vp between the electrodes sharply drops, but the voltage during discharge is approximately constant, about 25V.

The circuit current Es is a current waveform flowing through a series circuit composed of the DC power supply 1, the switching element 4 and the resistor 5, and the discharge start point at which discharge is generated in the machining gap between the machining electrode 2 and the workpiece 3. It is equal to the charging current to the capacitor 6 up to t1, and is equal to the current flowing into the machining gap in addition to the discharge current from the capacitor 6 to the machining gap during discharging. This circuit current Es is a DC pulse current in which the charging current to the capacitor 6 is turned on for the pulse width T1 and turned off for the predetermined time T2, and until the machining gap between the machining electrode 2 and the workpiece 3 is discharged. It is designed to be repeated. Further, the inter-electrode current Ep is a discharge current waveform flowing in the machining gap between the machining electrode 2 and the workpiece 3, and the discharge start point t at which the discharge is generated.
It is indicated by the time T4 from 1 to the discharge stop point t2 at which the discharge is stopped.

Now, a discharge occurs at the discharge start point t1, and there is a delay time T5 until the discharge detecting means 7 detects the discharge and generates the discharge detection signal Sd. Regardless of the delay time T5 of the discharge detection signal Sd, the switching element 4 is turned off after the pulse width T1 in the power supply device for an electric discharge machine of this embodiment. Therefore, in the machining gap between the machining electrode 2 and the workpiece 3, the machining gap Ep and the time T
Only the discharge current having the peak current waveform from the capacitor 6 indicated by 4 is supplied.

The pulse width T1 for turning on the switching element 4 by the on / off control of the transmission control circuit 80 is set to a time equivalent to the width T4 of the discharge current waveform of the capacitor 6 indicated by the inter-electrode current Ep. ing. Further, the predetermined time T2 during which the switching element 4 is turned off by the on / off control of the transmission control circuit 80 is longer than the delay time T5 until the discharge detection means 7 detects the discharge and generates the discharge detection signal Sd. Set to time. After the discharge is detected, after a predetermined off-time T3 sufficient to restore the insulation state to the machining gap between the machining electrode 2 and the workpiece 3, the oscillation control circuit 80 again causes the same switching element 4 to operate. Repeat ON / OFF control for.

As described above, in the power supply device for the electric discharge machine according to the first aspect of the invention, the DC power supply 1 for supplying the DC pulse current to the machining gap between the machining electrode 2 and the workpiece 3 and the switching element. 4 and a resistor 5 and a capacitor 6 connected in parallel to the machining electrode 2 and the workpiece 3.
A discharge detecting means 7 for detecting the occurrence of discharge between the machining electrode 2 and the workpiece 3 by the capacitor 6, and the capacitor 6 for the switching element 4 in the series circuit.
The discharge detecting means 7 repeats ON / OFF control for turning on for a pulse width T1 equal to or less than the pulse width of the discharge current and turning off for a predetermined time T2 until the capacitor 6 discharges and the discharge detecting means 7 detects the discharge. The transmission control circuit 80 repeats the on / off control again after a predetermined off time T3 after the discharge is detected in 7.

Therefore, only the discharge current waveform from the capacitor 6 is supplied to the machining gap between the machining electrode 2 and the workpiece 3. Therefore, as the discharge current waveform, a discharge current having a short pulse width is obtained, so that the amount of electric discharge machining by one discharge becomes appropriate and the machined surface is prevented from becoming rough.

<Second Embodiment> FIG. 3 is a circuit diagram showing a power supply device for an electric discharge machine according to a second embodiment of the present invention. It should be noted that this embodiment corresponds to the embodiment of claim 2, and those having the same configurations or corresponding portions as those of the above-mentioned embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. In FIG. 3, 1 is a DC power source, 2 is a processing electrode, and 3
Is a workpiece, 4 is a switching element, 5 is a resistor, 6 is a capacitor, 7 is a discharge detecting means, and 80 is a transmission control circuit connected to the switching element 4. Further, 9 is a counter circuit for achieving the counting means, and 10 is a comparing circuit for achieving the comparing means.

The transmission control circuit 80 drives the switching element 4 with the same signal as in the first embodiment, and at the same time sends a pulse signal having the same timing as the drive signal of the switching element 4 to the counter circuit 9. Until the transmission control circuit 80 receives the discharge detection signal Sd from the discharge detection means 7, the counter circuit 9 counts the pulse signal from the transmission control circuit 80 for turning on / off the switching element 4, and compares the count values. At the same time as sending to the circuit 10, the count value so far is reset. Comparison circuit 10
Is preset with a target value of the number of pulses of the charging current until the capacitor 6 is charged and discharge is generated. The target value is compared with the count value from the counter circuit 9, and the counter circuit 9 counts. When the value is larger, the charging current small signal Ss indicating that the current for charging the capacitor 6 is smaller is generated, and when the value counted by the counter circuit 9 is smaller, the current for charging the capacitor 6 is larger. A charging current large signal Sl indicating that is generated. The small charging current signal Ss and the large charging current signal Sl are sent to another control circuit (not shown) or the like, and are appropriately used to appropriately charge the capacitor 6.

As described above, in the power supply device for an electric discharge machine according to the second aspect of the present invention, in addition to the power supply device for an electric discharge machine according to the first aspect of the present invention, the electric discharge detecting means 7 is used for the machining electrode 2 and the workpiece On / off control for the switching element 4 is repeated after a predetermined off-time T3 after detecting the discharge with the object 3, and the on / off until the discharge is generated again and the discharge detecting means 7 detects the discharge. Counting means comprising a counter circuit 9 for counting the number of times of OFF control is compared with a value counted by the counting means and a preset value, and if the value counted by the counting means is smaller, a capacitor A large charging current signal Sl indicating that the current for charging 6 is large is generated, and when the value counted by the counting means is larger, it means that the current for charging the capacitor 6 is smaller. And a comparison means including a comparison circuit 10 for generating a small charging current signal Ss.

Therefore, the charging current large signal Sl or the charging current small signal Ss is generated by comparing the number of ON / OFF control for the switching element 4 until the capacitor 6 reaches the discharging state with a preset value. . Therefore, an appropriate charging current for the capacitor 6 can be notified to the operator and other control circuits.

<Third Embodiment> FIG. 4 is a circuit diagram showing a power supply device for an electric discharge machine according to a third embodiment of the present invention. FIG. 4 is a circuit diagram showing a configuration for displaying the number of times the small charging current signal Ss or the large charging current signal Sl output from the comparison circuit 10 in FIG. 3 is displayed. That is, the present embodiment corresponds to the other embodiment of claim 2, and those having the same configurations or corresponding portions as those of the above-described embodiment are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. . The charging current small signal Ss and the charging current large signal Sl generated in the comparison circuit 10 are input to the up / down counter circuit 11 in the number of occurrences thereof, and the counted number of pulses is displayed in the display circuit 12.

Therefore, it is possible to know which of the small charging current signal Ss and the large charging current signal Sl is output from the display of the display circuit 12. Therefore, the operator or the like can make the charging current appropriate by setting the peak value of the charging current or the pulse width so that the change in the display value of the display circuit 12 is reduced.

<Fourth Embodiment> FIG. 5 is a circuit diagram showing a power supply device for an electric discharge machine according to a fourth embodiment of the present invention. The present embodiment corresponds to the embodiment of claim 3, and those having the same configurations or corresponding portions as those of the above-described embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. In FIG. 5, 1 is a DC power source, 2 is a processing electrode, and 3
Is a workpiece, 4 is a switching element, 5 is a resistor, 6 is a capacitor, 7 is a discharge detecting means, 80 is a transmission control circuit,
Reference numeral 9 is a counter circuit, and 10 is a comparison circuit. These configurations are exactly the same as the configurations described in FIG. Thirteen
Is a storage operation circuit that realizes storage means and operation means arranged between the counter circuit 9 and the comparison circuit 10.

The storage operation circuit 13 is composed of a transmission control circuit 8
The value counted by the counter circuit 9 is temporarily stored every time until discharge occurs as the pulse number of the charging current for turning on the switching element 4 and charging the capacitor 6 by 0,
For example, when the number of stored values reaches 10, the average value of those values is calculated. At the same time as the result of this operation is sent to the comparison circuit 10, the stored value of the storage operation circuit 13 is reset and the value newly sent from the counter circuit 9 is stored.

In the comparison circuit 10, the value sent from the storage operation circuit 13 is compared with the reference value stored in advance, and when the result of counting the number of pulses of the charging current and calculating the average value is larger, Generates a small charging current signal Ss and generates a large charging current signal Sl when the result of counting the number of pulses of the charging current and calculating the average value is smaller. These small charging current signal Ss and large charging current signal Sl
Is appropriately used to appropriately charge the capacitor 6 by using it in another control circuit (not shown) or the like. That is, as in the case of FIG. 4, the up-down counter circuit 11 and the display circuit 12 are connected to the subsequent stage of the comparison circuit 10, and the charging current small signal Ss and the charging current large signal Sl are input, so that the charging current of the capacitor 6 is reduced. Can be set appropriately.

As described above, in the power supply device for an electric discharge machine according to the third aspect of the present invention, in addition to the power supply device for an electric discharge machine according to the first aspect of the present invention, the electric discharge detecting means 7 and the machining electrode 2 and the workpiece are used. On / off control for the switching element 4 is repeated after a predetermined off-time T3 after detecting the discharge with the object 3, and the on / off until the discharge is generated again and the discharge detecting means 7 detects the discharge. Counting means composed of a counter circuit 9 for counting the number of times of OFF control, and a storage operation circuit 1 for storing the value counted by the counting means a predetermined number of times.
3, a storage means for calculating the average value of the values stored in the storage means, and a storage means for calculating an average value of the values stored in the storage means; When the value calculated by the calculating means is smaller, the charging current large signal Sl indicating that the current for charging the capacitor 6 is larger is generated, and when the value calculated by the calculating means is larger, the capacitor is generated. And a comparison means including a comparison circuit 10 for generating a small charging current signal Ss indicating that the current for charging 6 is small.

Therefore, the number of on / off controls for the switching element 4 until the capacitor 6 reaches the discharging state is stored a fixed number of times, and the charging current large signal Sl or charging is calculated by comparing the average value with a preset value. A small current signal Ss is generated. Therefore, an appropriate charging current for the capacitor 6 can be notified to the operator and other control circuits.

<Fifth Embodiment> FIG. 6 is a circuit diagram showing a power supply device for an electric discharge machine according to a fifth embodiment of the present invention. In addition, this embodiment corresponds to the embodiment of claim 4, and those having the same configurations or corresponding parts as those of the above-mentioned embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. In FIG. 6, 1 is a DC power supply, 2 is a processing electrode, 3
Is a work piece, 6 is a capacitor, 7 is a discharge detecting means, 9 is a counter circuit, 10 is a comparison circuit, and 13 is a storage operation circuit. These configurations are exactly the same as the configurations described in FIG. .

4A, 4B and 4C are switching elements,
The resistors 5A, 5B and 5C for limiting current are connected in series. In addition, the switching element 4A and the resistor 5
A is connected in series, both ends of which switching element 4B and resistor 5B are connected in series, switching element 4
Both ends where C and the resistor 5C are connected in series are connected in parallel, and these are connected in series with the DC power supply 1.
80A is a transmission control circuit, which is a switching element 4A,
4B and 4C are turned on / off by the transmission control circuit 80A.
Controlled off.

When the charging circuit small signal Ss or the charging current large signal Sl is generated in the comparison circuit 10, those output signals are sent to the transmission control circuit 80A. When the transmission control circuit 80A receives the charging current small signal Ss from the comparison circuit 10, the current value of the pulse current for charging the capacitor 6 is smaller than the proper value at the currently set value.
Therefore, the transmission control circuit 80A switches the switching elements 4A and 4B so that the current value of the pulse current becomes larger than the current value, that is, the resistance value of the current limiting resistor becomes small when the pulse current flows. , 4C are turned on / off.

Here, for example, the current limiting resistor 5
It is assumed that the resistance values of A, 5B, and 5C are the same, the switching elements 4A and 4B are on / off controlled, and the pulse current is performing electric discharge machining while charging the capacitor 6. At this time, when the small charging current signal Ss is generated, the number of pulses of the charging current until the capacitor 6 is charged and discharged is reduced. Therefore, the switching element 4A is configured to increase the charging current from the time when the pulse current for the next charging is passed. , 4B as well as the switching element 4C are simultaneously ON / OFF controlled.

On the contrary, when the transmission control circuit 80A receives the large charging current signal Sl from the comparison circuit 10, the number of pulses of the charging current until the capacitor 6 is charged and discharged is increased. Switching elements 4A and 4B to reduce the charging current from when the pulse current flows
Among them, for example, only the switching element 4A is controlled to be turned on / off.

As described above, the power supply device for an electric discharge machine according to the embodiment of claim 4 is the power supply device for an electric discharge machine according to the embodiment of claim 2 or 3, and is a comparison means including a comparison circuit 10. When the charging current small signal Ss is generated, the DC power source 1, the switching elements 4A, 4B and 4C and the resistors 5A and 5
The resistance value of the resistor of the series circuit composed of B and 5C is reduced by a constant value, and when the charging current large signal Sl is generated by the comparison means, the resistance value of the resistor of the series circuit is increased by a constant value. The transmission control circuit 80A is provided with a changing unit.

Therefore, the charging current large signal Sl or the charging current small signal Ss can be determined by comparing the number of ON / OFF control for the switching elements 4A, 4B, 4C until the capacitor 6 reaches the discharging state with a preset value. Is generated. Signals based on the determination of the magnitude of the charging current for the capacitor 6 are switching elements 4A, 4B, 4C.
Is selectively turned on / off to change the resistance value of the resistor. Therefore, an appropriate charging current for the capacitor 6 can be automatically supplied.

By the way, in the above-mentioned embodiment corresponding to claim 4, an example in which the resistance values of the current limiting resistors 5A, 5B and 5C are set to the same value is shown, but resistors having different resistance values are used. When the switching elements 4A, 4B, and 4C are controlled to be turned on / off in combination, a maximum of seven resistance values can be obtained, and fine control is possible. Further, finer control becomes possible by increasing the number of current limiting resistors and switching elements.

<Sixth Embodiment> FIG. 7 is a circuit diagram showing a power supply device for an electric discharge machine according to a sixth embodiment of the present invention. It should be noted that this embodiment corresponds to another embodiment of claim 4, and those having the same configurations or corresponding portions as those of the above-mentioned embodiment are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. . In FIG. 7, 1 is a DC power supply, 2 is a processing electrode, 3 is a workpiece, 4 is a switching element, 6 is a capacitor, 7 is a discharge detecting means, 80 is a transmission control circuit, 9 is a counter circuit, and 13 is a memory. The arithmetic circuit 10 is a comparison circuit, and the configuration thereof is exactly the same as the configuration described in FIG. 5 above.

In FIG. 6 showing the fifth embodiment, a plurality of switching elements and resistors are combined to obtain multi-stage resistance values, and the current value of the pulse current for charging is controlled. On the other hand, in FIG. 7 of the present embodiment, 5D is a variable resistance variable resistor for resistance limitation, 14 is resistance control means, and the resistance control means 14 variably controls the resistance value of the variable resistor 5D itself. I am trying. The resistance control means 14 receives the small charging current signal Ss or the large charging current signal Sl generated by the comparison circuit 10. Here, when the small charging current signal Ss is received, the resistance value of the variable resistor 5D is reduced by a fixed value in order to increase the charging current of the capacitor 6, and conversely, when the large charging current signal Sl is received, the variable resistance is reduced. The resistance value of the device 5D is controlled to be increased by a constant value.

As described above, the power supply device for an electric discharge machine according to another embodiment of the fourth aspect is a comparison circuit including a comparison circuit 10 in addition to the power supply device for an electric discharge machine according to the second or third embodiment. When the charging current small signal Ss is generated by the means, the resistance value of the variable resistor 5D in the series circuit including the DC power source 1, the switching element 4 and the variable resistor 5D is reduced by a certain value,
The control means comprises a resistance control means 14 for increasing the resistance value of the variable resistor 5D of the series circuit by a certain value when the charging current large signal Sl is generated by the comparison means.

Therefore, the comparison circuit 10 compares the number of ON / OFF control for the switching element 4 until the capacitor 6 reaches the discharge state with a preset value,
The large charging current signal Sl or the small charging current signal Ss is generated. The signal based on the determination of the magnitude of the charging current for the capacitor 6 is input to the resistance control means 14 to change the resistance value of the variable resistor 5D. Therefore, an appropriate charging current for the capacitor 6 can be automatically supplied.

By the way, in the above-mentioned embodiment corresponding to claim 4, the pulse signal from the transmission control circuit 80 is obtained through the counter circuit 9, the storage operation circuit 13 and the comparison circuit 10, and the charging current small signal Ss and Although the example of controlling the current value of the pulse current to be charged by using the large charging current signal Sl has been described, the counter circuit 9 and the comparison circuit 1 as shown in FIG.
The current value of the pulse current for charging may be controlled by using the small charging current signal Ss and the large charging current signal Sl obtained through 0.

<Seventh Embodiment> FIG. 8 is a circuit diagram showing a power supply device for an electric discharge machine according to a seventh embodiment of the present invention. The present embodiment corresponds to the embodiment of claim 5, and those having the same configurations or corresponding portions as those of the above-described embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. Processing electrode 2, workpiece 3, switching element 4,
The resistor 5, the capacitor 6, the discharge detecting means 7, the oscillation control circuit 80, the counter circuit 9, the storage operation circuit 13 and the comparison circuit 10 are exactly the same as those described in the embodiment of FIG. 5 corresponding to claim 3. .

Reference numeral 1A is a variable DC power supply whose voltage is variable, 15 is a power supply voltage changing means, and the power supply voltage changing means 15 can change the output voltage of the variable DC power supply 1A. The power supply voltage changing means 15 receives the charging current small signal Ss or the charging current large signal Sl generated by the comparison circuit 10. Here, when the charging current small signal Ss is received, the capacitor 6
In order to increase the charging current of the variable DC power supply 1A, the voltage of the variable DC power supply 1A is increased by a constant value, and conversely, when the large charging current signal Sl is received, the voltage of the variable DC power supply 1A is decreased by a constant value. is there.

As described above, the power supply device for an electric discharge machine according to the fifth aspect of the present invention is a comparison means including the comparison circuit 10 in addition to the power supply device for an electric discharge machine according to the second or third embodiment. When the charging current small signal Ss is generated, the voltage value of the variable DC power supply 1A in the series circuit including the variable DC power supply 1A, the switch element 4 and the resistor 5 is increased by a constant value, and the charging current large signal Sl is generated by the comparison means. Is generated, the power supply voltage changing means 15 is provided to change the voltage value of the variable DC power supply 1A of the series circuit by a fixed value.

Therefore, the comparison circuit 10 compares the number of ON / OFF control for the switching element 4 until the capacitor 6 reaches the discharge state with a preset value,
The large charging current signal Sl or the small charging current signal Ss is generated. A signal based on the determination of the magnitude of the charging current for the capacitor 6 is input to the power supply voltage changing means 15 to change the voltage value of the variable DC power supply 1A. Therefore, an appropriate charging current for the capacitor 6 can be automatically supplied.

By the way, in the above-mentioned embodiment corresponding to claim 5, the pulse signal from the transmission control circuit 80 is obtained through the counter circuit 9, the storage operation circuit 13 and the comparison circuit 10, and the charging current small signal Ss and An example in which the current value of the pulse current to be charged is controlled by varying the voltage of the variable DC power supply using the charging current large signal Sl has been shown. However, as shown in FIG. The charging current small signal Ss and the charging current large signal Sl obtained as described above may be used to control the current value of the pulse current for charging by varying the voltage of the variable DC power supply.

<Eighth Embodiment> FIG. 9 is a circuit diagram showing a power supply device for an electric discharge machine according to an eighth embodiment of the present invention. The present embodiment corresponds to the embodiment of claim 6, and those having the same configurations or corresponding portions as those of the above-described embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. In FIG. 9, 1 is a DC power source, 2 is a processing electrode, and 3
Is a workpiece, 4 is a switching element, 5 is a resistor, 6 is a capacitor, 7 is a discharge detecting means, 9 is a counter circuit, 1
Reference numeral 3 is a storage operation circuit, and 10 is a comparison circuit, and these configurations are exactly the same as the configurations described in FIG.

Reference numeral 80B is a transmission control circuit, which is a circuit for controlling ON / OFF of the switching element 4, and it is possible to change the pulse width T1 of the charging current by varying the ON time. The transmission control circuit 80B is the comparison circuit 10.
When the charging current small signal Ss or the charging current large signal Sl generated by the above is received, and when the charging current small signal Ss is received, the pulse width T1 of the charging current is lengthened by a constant value and the amount of charge charged by the capacitor per pulse. The charging current large signal S
When it receives l, the pulse width T1 of the charging current is shortened by a constant value to reduce the amount of charge charged in the capacitor per pulse.

As described above, the electric power supply device for an electric discharge machine according to the sixth aspect of the present invention is a comparison means including the comparison circuit 10 in addition to the electric power supply device for an electric discharge machine according to the second or third embodiment. When the charging current small signal Ss is generated, the capacitor 6
From the transmission control circuit 80B, the pulse width T1 of the current for charging the capacitor 6 is lengthened by a fixed value, and when the charging current large signal Sl is generated by the comparison means, the pulse width T1 of the current for charging the capacitor 6 is shortened by a fixed value. It is provided with a changing means.

Therefore, the comparison circuit 10 compares the number of on / off controls for the switching element 4 until the capacitor 6 reaches the discharge state with a preset value,
The large charging current signal Sl or the small charging current signal Ss is generated. The signal based on the determination of the magnitude of the charging current for the capacitor 6 changes the pulse width of the current that is input to the transmission control circuit 80B and charges the capacitor 6. Therefore, an appropriate charging current for the capacitor 6 can be automatically supplied.

By the way, in the above-mentioned embodiment corresponding to claim 6, the pulse signal from the transmission control circuit 80B is obtained through the counter circuit 9, the storage operation circuit 13 and the comparison circuit 10, and the charging current small signal Ss and An example has been described in which the charge current charge amount per pulse is controlled by varying the pulse width of the charge current using the charge current large signal Sl.
As shown in FIG. 3, the charging current small signal Ss and the charging current large signal Sl obtained through the counter circuit 9 and the comparison circuit 10 are used to change the pulse width of the charging current to change the charging current charge per pulse. The amount may be controlled. Although a transistor is shown and used as the switching element in the above-described embodiments for description, any element that can be electrically turned on / off can be used, such as a MOSFET or an I / O element.
Even if GBT or the like is used, the same effect can be obtained.

[0064]

The present invention is constructed as described above and has the following effects.

According to another aspect of the power source device for an electric discharge machine of the present invention, the current for charging the capacitor connected between the machining electrode and the workpiece is a pulse current train having a pulse width equivalent to the pulse width of the discharge of the capacitor. Therefore, the current flowing in the machining gap between the machining electrode and the work piece can be only the discharge current from the capacitor, and the work surface of the work piece can be finely finished.

In addition to the effect of claim 1, the power supply device for an electric discharge machine according to claim 2 and claim 3 determines whether the current value and pulse width of the pulse current for charging the capacitor are optimum. Or other control circuits can be notified.

In addition to the effect of claim 2 or claim 3, the power supply device for an electric discharge machine according to claim 4, claim 5 or claim 6 can optimize the current value for charging the capacitor. It can be expected that the processing efficiency per unit time will be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a power supply device for an electric discharge machine according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing respective output states of a machining gap voltage, a circuit current, a machining gap current, a discharge detection signal, and a switching element in the power supply device for an electric discharge machine according to the first embodiment of the present invention. .

FIG. 3 is a circuit diagram showing a power supply device for an electric discharge machine according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a power supply device for an electric discharge machine according to a third embodiment of the present invention.

FIG. 5 is a circuit diagram showing a power supply device for an electric discharge machine according to a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram showing a power supply device for an electric discharge machine according to a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a power supply device for an electric discharge machine according to a sixth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a power supply device for an electric discharge machine according to a seventh embodiment of the present invention.

FIG. 9 is a circuit diagram showing a power supply device for an electric discharge machine according to an eighth embodiment of the present invention.

FIG. 10 is a circuit diagram showing a conventional power supply device for an electric discharge machine.

FIG. 11 is a timing chart showing respective output states of a voltage between contacts, a circuit current, a current between contacts, a discharge detection signal, and a switching element in a conventional power supply device for an electric discharge machine.

[Explanation of symbols]

 1 DC Power Supply 1A Variable DC Power Supply 2 Processing Electrode 3 Workpiece 4, 4A, 4B, 4C Switching Element 5, 5A, 5B, 5C Resistor 5D Variable Resistor 6 Capacitor 7 Discharge Detection Means 9 Counter Circuit 10 Comparison Circuit 13 Storage arithmetic circuit 14 Resistance control means 15 Power supply voltage changing means 80, 80A, 80B Transmission control circuit Sd Discharge detection signal Sl Charging current large signal Ss Charging current small signal

[Procedure amendment]

[Submission date] March 24, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

[Title of Invention] Power supply device for electric discharge machine

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for an electric discharge machine which supplies machining electric power to a machining gap between a machining electrode provided in an electric discharge machining fluid and a workpiece.

[0002]

2. Description of the Related Art Conventionally, as a prior art document relating to a power supply device for an electric discharge machine, one disclosed in Japanese Patent Laid-Open No. 3-55117 is known. In this device, a pulse train having a predetermined repetition frequency is intermittently driven at predetermined time intervals to drive a switching element, and an AC pulse current is supplied to a machining gap between a machining electrode in which a capacitor is connected in parallel and a workpiece. It is stated that the electric charge of the capacitor is completely discharged into the machining gap to prevent the arc current from continuing and the surface roughness in the electric discharge machining is improved.

[0003]

By the way, in the case of performing electric discharge machining by supplying a DC pulse current in place of the AC pulse current into the machining gap between the machining electrode and the workpiece, the above-mentioned technique is used. Can not. As a measure against this, a power supply device for an electric discharge machine as shown in FIG. 10 is known. FIG. 10 is a circuit diagram showing the configuration of a power supply device for an electric discharge machine that utilizes charging and discharging of a capacitor. In FIG. 10, 1 is a DC power supply, 2 is a processing electrode, 3 is a workpiece, 4
Is a switching element including a transistor and the like, and 5 is a resistor for limiting current. Further, 6 is a capacitor connected in parallel to the machining electrode 2 and the workpiece 3, 7 is a discharge detecting means connected to the machining electrode 2 and the workpiece 3, and 8 is connected to the switching element 4. Oscillation control circuit. A switching element 4 is provided between the DC power source 1 and the processing electrode 2.
And the resistor 5 are connected in series. The discharge detecting means 7 sends a discharge detection signal Sd to the oscillation control circuit 8 when detecting the discharge between the machining electrode 2 and the workpiece 3.

Next, the operation will be described. The DC power supply 1 supplies a machining power between the machining electrode 2 and the workpiece 3 which are arranged in the machining fluid so as to face each other with a minute gap therebetween. The switching element 4 is on / off controlled by an oscillation control circuit 8. The capacitor 6 is configured to be charged by a current limited by a series circuit including the DC power source 1, the switching element 4, and the resistor 5. The capacitor 6 discharges when the charging voltage reaches the dielectric breakdown voltage between the machining electrode 2 and the workpiece 3, and the workpiece 3 is machined by the discharge current. This is used when the time width is set to a very short pulse current and the processing amount for processing the workpiece by one discharge is made minute.

The pulse width of the discharge current of the capacitor 6 is its capacitance, the capacitor 6, the machining electrode 2 and the workpiece 3.
Although it is determined by the minute resistance and inductance of the line existing in the series circuit consisting of, the pulse width is extremely short, and is about a fraction of a microsecond. Further, the voltage between the machining electrode 2 and the workpiece 3 during the discharge when the discharge occurs in the machining gap is approximately constant, about 25V.

The electric discharge detecting means 7 detects that an electric discharge is generated in the machining gap between the machining electrode 2 and the workpiece 3 when the voltage between the machining electrode 2 and the workpiece 3 becomes a certain voltage or less. It is designed to detect. When the discharge detection means 7 detects a discharge, it sends a discharge detection signal Sd to the oscillation control circuit 8, and the oscillation control circuit 8 turns off the switching element 4 immediately after receiving the discharge detection signal Sd, and the machining electrode 2 and the workpiece 3 It operates so as to stop the current supply to the machining gap and the capacitor 6. However, there is inevitably a time delay from when the discharge detection signal Sd is received until the switching element 4 is turned off. After this, after a certain time such that the insulation between the processing electrode 2 and the workpiece 3 is restored,
The oscillation control circuit 8 turns on the switching element 4 again,
The charging of the capacitor 6 and the discharging between the machining electrode 2 and the workpiece 3 as described above are repeated.

In each waveform shown in FIG. 11, the horizontal axis is the time axis,
11 is a timing chart showing transitions of current / voltage and output signals of respective parts in the circuit of FIG. 10. The inter-electrode voltage Vp is a charging voltage waveform between the machining electrode 2 and the workpiece 3. The circuit current Es is a current waveform flowing in a series circuit composed of the DC power supply 1, the switching element 4 and the resistor 5, and is up to the discharge start point t01 where discharge is generated in the machining gap between the machining electrode 2 and the workpiece 3. It is equal to the charging current to the capacitor 6 and equal to the current flowing into the machining gap in addition to the discharge current from the capacitor 6 to the machining gap during discharging. The machining gap current Ep is a discharge current waveform flowing in the machining gap between the machining electrode 2 and the workpiece 3.

Now, a discharge occurs at the discharge start point t01, and a delay time T11 occurs until the discharge detecting means 7 detects the discharge and generates the discharge detection signal Sd. Further, there is a delay time T12 from when the oscillation control circuit 8 receives the discharge detection signal Sd to when the switching element 4 is turned off. Therefore, there is a delay time (T11 + T12) from the actual discharge start at the discharge start point t01 until the switching element 4 is turned off after the discharge is detected. During this delay time (T11 + T12), the discharge continues, so the inter-electrode current E
During the time T13 after the peak current waveform in the discharge current waveform of p, not the discharge current from the capacitor 6, but the processing electrode 2 and the workpiece 3 from the DC power source 1 via the switching element 4 and the resistor 5. The discharge current will be supplied during this period.

That is, in the above-mentioned power supply device for an electric discharge machine,
In addition to the discharge current from the capacitor 6, a current with a long pulse width flows as a discharge current from the DC power supply 1 through the switching element 4 and the resistor 5 into the machining gap between the machining electrode 2 and the workpiece 3 as a pulse current. A short discharge current cannot be obtained. Therefore, the amount of machining by one discharge increases,
There was a problem that the EDM surface became rough.

Therefore, the present invention has been made in order to solve such a problem, and an object thereof is to provide a power supply device for an electric discharge machine which does not deteriorate surface roughness by using a DC pulse current.

[0011]

A power supply device for an electric discharge machine according to claim 1 is a DC power supply for supplying a DC pulse current to a machining gap between a machining electrode and a workpiece, a switching element and a resistor. A series circuit consisting of, a capacitor connected in parallel to the machining electrode and the workpiece, a discharge detection means for detecting the occurrence of discharge between the machining electrode and the workpiece, and For the switching element in the series circuit, the capacitor discharges the on / off control in which the pulse width of the discharge current of the capacitor is equal to or less than the pulse width of the capacitor, and is turned off for a predetermined time. And an oscillation control circuit that repeats the on / off control again after a predetermined off time after the discharge is detected by the discharge detection means. It is.

According to a second aspect of the present invention, in addition to the first aspect, the power supply device for an electric discharge machine is the one after the electric discharge between the machining electrode and the workpiece is detected by the electric discharge detection means. Counting means for counting the number of on / off controls until the discharge detecting means detects discharge by repeating the on / off control for the switching element after a predetermined off time, and the count And a preset value is compared, and when the value counted by the counting means is smaller, a charging current large signal indicating that the current for charging the capacitor is larger is generated, and the counting is performed. When the value counted by the means is larger, the comparator means for generating a small charging current signal indicating that the current for charging the capacitor is small.

According to a third aspect of the present invention, in addition to the first aspect, the power supply device for an electric discharge machine is the one after detecting the electric discharge between the machining electrode and the workpiece by the electric discharge detecting means. Counting means for counting the number of on / off controls until the discharge detecting means detects discharge by repeating the on / off control for the switching element after a predetermined off time, and the count Storage means for storing the stored value a predetermined number of times, computing means for computing the average value of the stored values, and the computing means for comparing the computed value with a preset value. If the value is smaller, a charging current large signal indicating that the current for charging the capacitor is larger is generated, and if the value calculated by the calculating means is larger, the capacitor is charged. Is intended to and comparator means for generating a charging current small signal indicating that flow is small.

According to a fourth aspect of the present invention, in addition to the second or third aspect of the power supply device for an electric discharge machine, when the small charging current signal is generated by the comparing means, the resistor of the series circuit is provided. There is provided a changing means for decreasing the resistance value of No. 1 by a constant value and increasing the resistance value of the resistor of the series circuit by a constant value when the charging current large signal is generated by the comparing means.

According to a fifth aspect of the present invention, in addition to the second or third aspect of the power source device for an electric discharge machine, when the charging current small signal is generated by the comparing means, the DC power source of the series circuit is provided. There is provided a changing means for increasing the voltage value of 1 by a constant value and decreasing the voltage value of the DC power source of the series circuit by a constant value when the charging current large signal is generated by the comparing means.

According to a sixth aspect of the present invention, in addition to the second or third aspect of the power supply device for an electric discharge machine, the current for charging the capacitor when the small charging current signal is generated by the comparing means. There is provided a changing means for increasing the pulse width by a fixed value and shortening the pulse width of the current for charging the capacitor by a fixed value when the charging current large signal is generated by the comparing means.

[0017]

In the power supply device for the electric discharge machine according to claim 1,
The switching element is turned off after the capacitor is discharged, and only a discharge current from the capacitor flows between the machining electrode and the workpiece.

According to a second aspect of the present invention, in addition to the operation of the first aspect, the power supply device for an electric discharge machine has a preset value and a value obtained by counting the number of on / off control times for the switching element until the capacitor reaches the discharge state. By comparing with, the magnitude of the charging current for the capacitor is determined.

In addition to the effect of claim 1, the power supply device for an electric discharge machine according to claim 3 stores and calculates a value obtained by counting the number of on / off control times for the switching element until the capacitor reaches the discharge state, a fixed number of times. The magnitude of the charging current for the capacitor is determined by comparing the average value thus obtained with a preset value.

According to a fourth aspect of the present invention, in addition to the operation of the second or third aspect, the power supply device for an electric discharge machine changes the resistance value of the resistor based on the determination of the magnitude of the charging current to the capacitor. The capacitor charging current is optimized.

In the electric power supply device for an electric discharge machine according to a fifth aspect, in addition to the operation of the second or third aspect, the voltage value of the DC power source is changed based on the magnitude judgment of the charging current to the capacitor, The capacitor charging current is optimized.

According to a sixth aspect of the present invention, in addition to the operation of the second or third aspect, the pulse width of the charging current is changed based on the determination of the magnitude of the charging current with respect to the capacitor. The capacitor charging current is optimized.

[0023]

EXAMPLES The present invention will be described below based on specific examples. <First Embodiment> FIG. 1 is a circuit diagram showing a power supply device for an electric discharge machine according to a first embodiment of the present invention. In addition, this embodiment corresponds to the embodiment of claim 1, and those having the same configurations or corresponding portions as those of the above-described conventional apparatus are denoted by the same reference numerals and symbols. In FIG. 1, 1 is a DC power supply, 2 is a processing electrode, 3 is a workpiece, 4 is a switching element formed of a transistor or the like, and 5 is a current limiting resistor. Further, 6 is a capacitor connected in parallel to the machining electrode 2 and the workpiece 3, 7 is a discharge detecting means connected to the machining electrode 2 and the workpiece 3, and 80 is connected to the switching element 4. Oscillation control circuit. The DC power supply 1 has a voltage sufficient to generate an electric discharge between the machining electrode 2 and the workpiece 3. A switching element 4 and a resistor 5 are connected in series between the DC power supply 1 and the processing electrode 2. Further, the discharge detecting means 7 sends a discharge detection signal Sd to the oscillation control circuit 80 when detecting the discharge between the machining electrode 2 and the workpiece 3. The oscillation control circuit 80 controls ON / OFF of the switching element 4. As described above, the configuration of this embodiment is apparently the same as that of the conventional device described above, but the switching element 4 is turned on / off.
The operation of the oscillation control circuit 80 for turning off is different.

Each waveform shown in FIG. 2 has a horizontal axis on the time axis,
3 is a timing chart showing transitions of current / voltage and output signals of respective parts in the circuit of FIG. 1. In FIG. 2, the voltage between contacts Vp is a voltage waveform between the processing electrode 2 and the workpiece 3. At time t1, the inter-electrode voltage Vp is equal to the machining electrode 2
When the dielectric breakdown voltage of the machining gap between the workpiece 3 and the workpiece 3 is reached, discharge occurs and the voltage Vp between the electrodes sharply drops, but the voltage during discharge is approximately constant, about 25V.

The circuit current Es is a current waveform flowing through a series circuit composed of the DC power supply 1, the switching element 4 and the resistor 5, and the discharge start point at which discharge is generated in the machining gap between the machining electrode 2 and the workpiece 3. It is equal to the charging current to the capacitor 6 up to t1, and equal to the current flowing into the machining gap in addition to the discharge current from the capacitor 6 to the machining gap during discharging. This circuit current Es is a DC pulse current in which the charging current to the capacitor 6 is turned on for the pulse width T1 and turned off for the predetermined time T2, and until the machining gap between the machining electrode 2 and the workpiece 3 is discharged. It is designed to be repeated. Further, the inter-electrode current Ep is a discharge current waveform flowing in the machining gap between the machining electrode 2 and the workpiece 3, and the discharge start point t at which the discharge is generated.
It is indicated by the time T4 from 1 to the discharge stop point t2 at which the discharge is stopped.

Now, a discharge occurs at the discharge start point t1, and there is a delay time T5 until the discharge detection means 7 detects the discharge and generates the discharge detection signal Sd. Regardless of the delay time T5 of the discharge detection signal Sd, the switching element 4 is turned off after the pulse width T1 in the power supply device for an electric discharge machine of this embodiment. Therefore, in the machining gap between the machining electrode 2 and the workpiece 3, the machining gap Ep and the time T
Only the discharge current having the peak current waveform from the capacitor 6 indicated by 4 is supplied.

The pulse width T1 for turning on the switching element 4 by the on / off control of the oscillation control circuit 80 is set to a time equivalent to the width T4 of the discharge current waveform of the capacitor 6 indicated by the inter-electrode current Ep. ing. Further, the predetermined time T2 during which the switching element 4 is turned off by the on / off control of the oscillation control circuit 80 is longer than the delay time T5 until the discharge detection means 7 detects the discharge and generates the discharge detection signal Sd. Set to time. After the discharge is detected, after a predetermined off-time T3 sufficient to restore the insulation state to the machining gap between the machining electrode 2 and the workpiece 3, the oscillation control circuit 80 again causes the same switching element 4 to operate. Repeat ON / OFF control for.

As described above, in the power supply device for the electric discharge machine according to the first aspect of the invention, the DC power supply 1 for supplying the DC pulse current to the machining gap between the machining electrode 2 and the workpiece 3 and the switching element. 4 and a resistor 5 and a capacitor 6 connected in parallel to the machining electrode 2 and the workpiece 3.
A discharge detection means 7 for detecting the occurrence of discharge between the machining electrode 2 and the workpiece 3, and a pulse width of the discharge current of the capacitor 6 for the switching element 4 in the series circuit, which is equal to or less than that. The ON / OFF control of turning on for the pulse width T1 and turning off for the predetermined time T2 is repeated until the capacitor 6 discharges and the discharge detecting means 7 detects the discharge, and the predetermined off time after the discharge detecting means 7 detects the discharge. The oscillation control circuit 80 repeats the ON / OFF control again after T3.

Therefore, only the discharge current waveform from the capacitor 6 is supplied to the machining gap between the machining electrode 2 and the workpiece 3. Therefore, as the discharge current waveform, a discharge current having a short pulse width is obtained, so that the amount of electric discharge machining by one discharge becomes appropriate and the machined surface is prevented from becoming rough.

<Second Embodiment> FIG. 3 is a circuit diagram showing a power supply device for an electric discharge machine according to a second embodiment of the present invention. It should be noted that this embodiment corresponds to the embodiment of claim 2, and those having the same configurations or corresponding portions as those of the above-mentioned embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. In FIG. 3, 1 is a DC power source, 2 is a processing electrode, and 3
Is a workpiece, 4 is a switching element, 5 is a resistor, 6 is a capacitor, 7 is a discharge detecting means, and 80 is an oscillation control circuit connected to the switching element 4. Further, 9 is a counter circuit for achieving the counting means, and 10 is a comparing circuit for achieving the comparing means.

The oscillation control circuit 80 drives the switching element 4 with the same signal as in the first embodiment, and at the same time sends a pulse signal to the counter circuit 9 at the same timing as the drive signal of the switching element 4. Until the oscillation control circuit 80 receives the discharge detection signal Sd from the discharge detection means 7, the counter circuit 9 counts the pulse signal for turning on / off the switching element 4 from the oscillation control circuit 80 and compares the count values. At the same time as sending to the circuit 10, the count value so far is reset. Comparison circuit 10
Is preset with a target value of the number of pulses of the charging current until the capacitor 6 is charged and discharge is generated. The target value is compared with the count value from the counter circuit 9, and the counter circuit 9 counts. When the value is larger, the charging current small signal Ss indicating that the current for charging the capacitor 6 is smaller is generated, and when the value counted by the counter circuit 9 is smaller, the current for charging the capacitor 6 is larger. A charging current large signal Sl indicating that is generated. The small charging current signal Ss and the large charging current signal Sl are sent to another control circuit (not shown) or the like, and are appropriately used to appropriately charge the capacitor 6.

As described above, in the power supply device for an electric discharge machine according to the second aspect of the present invention, in addition to the power supply device for an electric discharge machine according to the first aspect of the present invention, the electric discharge detecting means 7 is used to form the machining electrode 2 and the workpiece. On / off control for the switching element 4 is repeated after a predetermined off-time T3 after detecting the discharge with the object 3, and the on / off until the discharge is generated again and the discharge detecting means 7 detects the discharge. Counting means comprising a counter circuit 9 for counting the number of times of OFF control is compared with a value counted by the counting means and a preset value, and if the value counted by the counting means is smaller, a capacitor A large charging current signal Sl indicating that the current for charging 6 is large is generated, and when the value counted by the counting means is larger, it means that the current for charging the capacitor 6 is smaller. And a comparison means including a comparison circuit 10 for generating a small charging current signal Ss.

Therefore, the charging current large signal Sl or the charging current small signal Ss is generated by comparing the number of ON / OFF control for the switching element 4 until the capacitor 6 reaches the discharging state with a preset value. . Therefore, an appropriate charging current for the capacitor 6 can be notified to the operator and other control circuits.

<Third Embodiment> FIG. 4 is a circuit diagram showing a power supply device for an electric discharge machine according to a third embodiment of the present invention. FIG. 4 is a circuit diagram showing a configuration for displaying the number of times the small charging current signal Ss or the large charging current signal Sl output from the comparison circuit 10 in FIG. 3 is displayed. That is, the present embodiment corresponds to the other embodiment of claim 2, and those having the same configurations or corresponding portions as those of the above-described embodiment are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. . The charging current small signal Ss and the charging current large signal Sl generated in the comparison circuit 10 are input to the up / down counter circuit 11 in the number of occurrences thereof, and the counted number of pulses is displayed in the display circuit 12.

Therefore, it is possible to know which of the small charging current signal Ss and the large charging current signal Sl is output from the display of the display circuit 12. Therefore, the operator or the like can make the charging current appropriate by setting the peak value of the charging current or the pulse width so that the change in the display value of the display circuit 12 is reduced.

<Fourth Embodiment> FIG. 5 is a circuit diagram showing a power supply device for an electric discharge machine according to a fourth embodiment of the present invention. The present embodiment corresponds to the embodiment of claim 3, and those having the same configurations or corresponding portions as those of the above-described embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. In FIG. 5, 1 is a DC power source, 2 is a processing electrode, and 3
Is a workpiece, 4 is a switching element, 5 is a resistor, 6 is a capacitor, 7 is discharge detection means, 80 is an oscillation control circuit,
Reference numeral 9 is a counter circuit, and 10 is a comparison circuit. These configurations are exactly the same as the configurations described in FIG. Thirteen
Is a storage operation circuit that realizes storage means and operation means arranged between the counter circuit 9 and the comparison circuit 10.

This memory operation circuit 13 is composed of an oscillation control circuit 8
The value counted by the counter circuit 9 is temporarily stored every time until discharge occurs as the pulse number of the charging current for turning on the switching element 4 and charging the capacitor 6 by 0,
For example, when the number of stored values reaches 10, the average value of those values is calculated. At the same time as the result of this operation is sent to the comparison circuit 10, the stored value of the storage operation circuit 13 is reset and the value newly sent from the counter circuit 9 is stored.

In the comparison circuit 10, the value sent from the storage operation circuit 13 is compared with the reference value stored in advance, and when the result of counting the number of pulses of the charging current and calculating the average value is larger, Generates a small charging current signal Ss and generates a large charging current signal Sl when the result of counting the number of pulses of the charging current and calculating the average value is smaller. These small charging current signal Ss and large charging current signal Sl
Is appropriately used to appropriately charge the capacitor 6 by using it in another control circuit (not shown) or the like. That is, as in the case of FIG. 4, the up-down counter circuit 11 and the display circuit 12 are connected to the subsequent stage of the comparison circuit 10, and the charging current small signal Ss and the charging current large signal Sl are input, so that the charging current of the capacitor 6 is reduced. Can be set appropriately.

As described above, in the power supply device for an electric discharge machine according to the third aspect of the present invention, in addition to the power supply device for an electric discharge machine according to the first aspect of the present invention, the electric discharge detecting means 7 and the machining electrode 2 and the workpiece are used. On / off control for the switching element 4 is repeated after a predetermined off-time T3 after detecting the discharge with the object 3, and the on / off until the discharge is generated again and the discharge detecting means 7 detects the discharge. Counting means composed of a counter circuit 9 for counting the number of times of OFF control, and a storage operation circuit 1 for storing the value counted by the counting means a predetermined number of times.
3, a storage means for calculating the average value of the values stored in the storage means, and a storage means for calculating an average value of the values stored in the storage means; When the value calculated by the calculating means is smaller, the charging current large signal Sl indicating that the current for charging the capacitor 6 is larger is generated, and when the value calculated by the calculating means is larger, the capacitor is generated. And a comparison means including a comparison circuit 10 for generating a small charging current signal Ss indicating that the current for charging 6 is small.

Therefore, the number of on / off controls for the switching element 4 until the capacitor 6 reaches the discharging state is stored a fixed number of times, and the charging current large signal Sl or charging is calculated by comparing the average value with a preset value. A small current signal Ss is generated. Therefore, an appropriate charging current for the capacitor 6 can be notified to the operator and other control circuits.

<Fifth Embodiment> FIG. 6 is a circuit diagram showing a power supply device for an electric discharge machine according to a fifth embodiment of the present invention. In addition, this embodiment corresponds to the embodiment of claim 4, and those having the same configurations or corresponding parts as those of the above-mentioned embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. In FIG. 6, 1 is a DC power supply, 2 is a processing electrode, 3
Is a work piece, 6 is a capacitor, 7 is a discharge detecting means, 9 is a counter circuit, 10 is a comparison circuit, and 13 is a storage operation circuit. These configurations are exactly the same as the configurations described in FIG. .

4A, 4B and 4C are switching elements,
The resistors 5A, 5B and 5C for limiting current are connected in series. In addition, the switching element 4A and the resistor 5
A is connected in series, both ends of which switching element 4B and resistor 5B are connected in series, switching element 4
Both ends where C and the resistor 5C are connected in series are connected in parallel, and these are connected in series with the DC power supply 1.
80A is an oscillation control circuit, which is a switching element 4A,
4B and 4C are turned on / off by the oscillation control circuit 80A.
Controlled off.

When the charging circuit small signal Ss or the charging current large signal Sl is generated in the comparison circuit 10, those output signals are sent to the oscillation control circuit 80A. When the oscillation control circuit 80A receives the charging current small signal Ss from the comparison circuit 10, the current value of the pulse current for charging the capacitor 6 is smaller than the proper value at the currently set value.
Therefore, the oscillation control circuit 80A switches the switching elements 4A and 4B so that the current value of the pulse current becomes larger than the current value, that is, the resistance value of the current limiting resistor becomes smaller when the pulse current flows. , 4C are turned on / off.

Here, for example, the current limiting resistor 5
It is assumed that the resistance values of A, 5B, and 5C are the same, the switching elements 4A and 4B are on / off controlled, and the pulse current is performing electric discharge machining while charging the capacitor 6. At this time, when the small charging current signal Ss is generated, the number of pulses of the charging current until the capacitor 6 is charged and discharged is reduced. Therefore, the switching element 4A is configured to increase the charging current from the time when the pulse current for the next charging is passed. , 4B as well as the switching element 4C are simultaneously ON / OFF controlled.

On the contrary, when the oscillation control circuit 80A receives the large charging current signal Sl from the comparison circuit 10, the number of pulses of the charging current until the capacitor 6 is charged and discharged is increased. Switching elements 4A and 4B to reduce the charging current from when the pulse current flows
Among them, for example, only the switching element 4A is controlled to be turned on / off.

As described above, the power supply device for an electric discharge machine according to the embodiment of claim 4 is the power supply device for an electric discharge machine according to the embodiment of claim 2 or 3, and is a comparison means including a comparison circuit 10. When the charging current small signal Ss is generated, the DC power source 1, the switching elements 4A, 4B and 4C and the resistors 5A and 5
The resistance value of the resistor of the series circuit composed of B and 5C is reduced by a constant value, and when the charging current large signal Sl is generated by the comparison means, the resistance value of the resistor of the series circuit is increased by a constant value. The oscillation control circuit 80A includes a changing unit.

Therefore, the charging current large signal Sl or the charging current small signal Ss can be determined by comparing the number of ON / OFF control for the switching elements 4A, 4B, 4C until the capacitor 6 reaches the discharging state with a preset value. Is generated. Signals based on the determination of the magnitude of the charging current for the capacitor 6 are switching elements 4A, 4B, 4C.
Is selectively turned on / off to change the resistance value of the resistor. Therefore, an appropriate charging current for the capacitor 6 can be automatically supplied.

By the way, in the above-mentioned embodiment corresponding to claim 4, an example in which the resistance values of the current limiting resistors 5A, 5B and 5C are set to the same value is shown, but resistors having different resistance values are used. When the switching elements 4A, 4B, and 4C are controlled to be turned on / off in combination, a maximum of seven resistance values can be obtained, and fine control is possible. Further, finer control becomes possible by increasing the number of current limiting resistors and switching elements.

<Sixth Embodiment> FIG. 7 is a circuit diagram showing a power supply device for an electric discharge machine according to a sixth embodiment of the present invention. It should be noted that this embodiment corresponds to another embodiment of claim 4, and those having the same configurations or corresponding portions as those of the above-mentioned embodiment are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. . In FIG. 7, 1 is a DC power supply, 2 is a processing electrode, 3 is a workpiece, 4 is a switching element, 6 is a capacitor, 7 is a discharge detecting means, 80 is an oscillation control circuit, 9 is a counter circuit, and 13 is a memory. The arithmetic circuit 10 is a comparison circuit, and the configuration thereof is exactly the same as the configuration described in FIG. 5 above.

In FIG. 6 showing the fifth embodiment, a plurality of switching elements and resistors are combined to obtain multi-stage resistance values, and the current value of the pulse current for charging is controlled. On the other hand, in FIG. 7 of the present embodiment, 5D is a variable resistance variable resistor for resistance limitation, 14 is resistance control means, and the resistance control means 14 variably controls the resistance value of the variable resistor 5D itself. I am trying. The resistance control means 14 receives the small charging current signal Ss or the large charging current signal Sl generated by the comparison circuit 10. Here, when the small charging current signal Ss is received, the resistance value of the variable resistor 5D is reduced by a fixed value in order to increase the charging current of the capacitor 6, and conversely, when the large charging current signal Sl is received, the variable resistance is reduced. The resistance value of the device 5D is controlled to be increased by a constant value.

As described above, the power supply device for an electric discharge machine according to another embodiment of the fourth aspect is a comparison circuit including a comparison circuit 10 in addition to the power supply device for an electric discharge machine according to the second or third embodiment. When the charging current small signal Ss is generated by the means, the resistance value of the variable resistor 5D in the series circuit including the DC power source 1, the switching element 4 and the variable resistor 5D is reduced by a certain value,
The control means comprises a resistance control means 14 for increasing the resistance value of the variable resistor 5D of the series circuit by a certain value when the charging current large signal Sl is generated by the comparison means.

Therefore, the comparison circuit 10 compares the number of ON / OFF control for the switching element 4 until the capacitor 6 reaches the discharge state with a preset value,
The large charging current signal Sl or the small charging current signal Ss is generated. The signal based on the determination of the magnitude of the charging current for the capacitor 6 is input to the resistance control means 14 to change the resistance value of the variable resistor 5D. Therefore, an appropriate charging current for the capacitor 6 can be automatically supplied.

By the way, in the above-mentioned embodiment corresponding to claim 4, the pulse signal from the oscillation control circuit 80 is obtained through the counter circuit 9, the storage operation circuit 13 and the comparison circuit 10, and the charging current small signal Ss and Although the example of controlling the current value of the pulse current to be charged by using the large charging current signal Sl has been described, the counter circuit 9 and the comparison circuit 1 as shown in FIG.
The current value of the pulse current for charging may be controlled by using the small charging current signal Ss and the large charging current signal Sl obtained through 0.

<Seventh Embodiment> FIG. 8 is a circuit diagram showing a power supply device for an electric discharge machine according to a seventh embodiment of the present invention. The present embodiment corresponds to the embodiment of claim 5, and those having the same configurations or corresponding portions as those of the above-described embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. Processing electrode 2, workpiece 3, switching element 4,
The resistor 5, the capacitor 6, the discharge detecting means 7, the oscillation control circuit 80, the counter circuit 9, the storage operation circuit 13 and the comparison circuit 10 are exactly the same as those described in the embodiment of FIG. 5 corresponding to claim 3. .

Reference numeral 1A is a variable DC power supply whose voltage is variable, 15 is a power supply voltage changing means, and the power supply voltage changing means 15 can change the output voltage of the variable DC power supply 1A. The power supply voltage changing means 15 receives the charging current small signal Ss or the charging current large signal Sl generated by the comparison circuit 10. Here, when the charging current small signal Ss is received, the capacitor 6
In order to increase the charging current of the variable DC power supply 1A, the voltage of the variable DC power supply 1A is increased by a constant value, and conversely, when the large charging current signal Sl is received, the voltage of the variable DC power supply 1A is decreased by a constant value. is there.

As described above, the power supply device for an electric discharge machine according to the fifth aspect of the present invention is a comparison means including the comparison circuit 10 in addition to the power supply device for an electric discharge machine according to the second or third embodiment. When the charging current small signal Ss is generated, the voltage value of the variable DC power supply 1A in the series circuit including the variable DC power supply 1A, the switching element 4 and the resistor 5 is increased by a constant value, and the charging current large signal Sl is generated by the comparison means. Is generated, the power supply voltage changing means 15 is provided to change the voltage value of the variable DC power supply 1A of the series circuit by a fixed value.

Therefore, the comparison circuit 10 compares the number of ON / OFF control for the switching element 4 until the capacitor 6 reaches the discharge state with a preset value,
The large charging current signal Sl or the small charging current signal Ss is generated. A signal based on the determination of the magnitude of the charging current for the capacitor 6 is input to the power supply voltage changing means 15 to change the voltage value of the variable DC power supply 1A. Therefore, an appropriate charging current for the capacitor 6 can be automatically supplied.

By the way, in the above-mentioned embodiment corresponding to claim 5, the pulse signal from the oscillation control circuit 80 is obtained through the counter circuit 9, the storage operation circuit 13 and the comparison circuit 10, and the charging current small signal Ss and An example in which the current value of the pulse current to be charged is controlled by varying the voltage of the variable DC power supply using the charging current large signal Sl has been shown. However, as shown in FIG. The charging current small signal Ss and the charging current large signal Sl obtained as described above may be used to control the current value of the pulse current for charging by varying the voltage of the variable DC power supply.

<Eighth Embodiment> FIG. 9 is a circuit diagram showing a power supply device for an electric discharge machine according to an eighth embodiment of the present invention. The present embodiment corresponds to the embodiment of claim 6, and those having the same configurations or corresponding portions as those of the above-described embodiments are designated by the same reference numerals and symbols, and detailed description thereof will be omitted. In FIG. 9, 1 is a DC power source, 2 is a processing electrode, and 3
Is a workpiece, 4 is a switching element, 5 is a resistor, 6 is a capacitor, 7 is a discharge detecting means, 9 is a counter circuit, 1
Reference numeral 3 is a storage operation circuit, and 10 is a comparison circuit, and these configurations are exactly the same as the configurations described in FIG.

Reference numeral 80B is an oscillation control circuit, which is a circuit for controlling ON / OFF of the switching element 4, and it is possible to change the pulse width T1 of the charging current by varying the ON time. The oscillation control circuit 80B is the comparison circuit 10.
When the charging current small signal Ss or the charging current large signal Sl generated by the above is received, and when the charging current small signal Ss is received, the pulse width T1 of the charging current is lengthened by a constant value and the amount of charge charged by the capacitor per pulse. The charging current large signal S
When it receives l, the pulse width T1 of the charging current is shortened by a constant value to reduce the amount of charge charged in the capacitor per pulse.

As described above, the electric power supply device for an electric discharge machine according to the sixth aspect of the present invention is a comparison means including the comparison circuit 10 in addition to the electric power supply device for an electric discharge machine according to the second or third embodiment. When the charging current small signal Ss is generated, the capacitor 6
From the oscillation control circuit 80B, the pulse width T1 of the current for charging the capacitor 6 is lengthened by a constant value, and when the charging current large signal Sl is generated by the comparison means, the pulse width T1 of the current charging the capacitor 6 is shortened by a constant value. It is provided with a changing means.

Therefore, the comparison circuit 10 compares the number of on / off controls for the switching element 4 until the capacitor 6 reaches the discharge state with a preset value,
The large charging current signal Sl or the small charging current signal Ss is generated. A signal based on the determination of the magnitude of the charging current for the capacitor 6 changes the pulse width of the current input to the oscillation control circuit 80B to charge the capacitor 6. Therefore, an appropriate charging current for the capacitor 6 can be automatically supplied.

By the way, in the above-mentioned embodiment corresponding to claim 6, the pulse signal from the oscillation control circuit 80B is obtained through the counter circuit 9, the storage operation circuit 13 and the comparison circuit 10, and the charging current small signal Ss and An example has been described in which the charge current charge amount per pulse is controlled by varying the pulse width of the charge current using the charge current large signal Sl.
As shown in FIG. 3, the charging current small signal Ss and the charging current large signal Sl obtained through the counter circuit 9 and the comparison circuit 10 are used to change the pulse width of the charging current to change the charging current charge per pulse. The amount may be controlled. Although a transistor is shown and used as the switching element in the above-described embodiments for description, any element that can be electrically turned on / off can be used, such as a MOSFET or an I / O element.
Even if GBT or the like is used, the same effect can be obtained.

[0064]

The present invention is constructed as described above and has the following effects.

According to another aspect of the power source device for an electric discharge machine of the present invention, the current for charging the capacitor connected between the machining electrode and the workpiece is a pulse current train having a pulse width equivalent to the pulse width of the discharge of the capacitor. Therefore, the current flowing in the machining gap between the machining electrode and the work piece can be only the discharge current from the capacitor, and the work surface of the work piece can be finely finished.

In addition to the effect of claim 1, the power supply device for an electric discharge machine according to claims 2 and 3 determines whether the current value and pulse width of the pulse current for charging the capacitor are optimum or not. It becomes possible to inform the control circuit of.

In addition to the effect of claim 2 or claim 3, the power supply device for an electric discharge machine according to claim 4, claim 5 or claim 6 can optimize the current value for charging the capacitor. It can be expected that the processing efficiency per unit time will be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a power supply device for an electric discharge machine according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing respective output states of a machining gap voltage, a circuit current, a machining gap current, a discharge detection signal, and a switching element in the power supply device for an electric discharge machine according to the first embodiment of the present invention. .

FIG. 3 is a circuit diagram showing a power supply device for an electric discharge machine according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a power supply device for an electric discharge machine according to a third embodiment of the present invention.

FIG. 5 is a circuit diagram showing a power supply device for an electric discharge machine according to a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram showing a power supply device for an electric discharge machine according to a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a power supply device for an electric discharge machine according to a sixth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a power supply device for an electric discharge machine according to a seventh embodiment of the present invention.

FIG. 9 is a circuit diagram showing a power supply device for an electric discharge machine according to an eighth embodiment of the present invention.

FIG. 10 is a circuit diagram showing a conventional power supply device for an electric discharge machine.

FIG. 11 is a timing chart showing respective output states of a voltage between contacts, a circuit current, a current between contacts, a discharge detection signal, and a switching element in a conventional power supply device for an electric discharge machine.

[Explanation of Codes] 1 DC power supply 1A Variable DC power supply 2 Processing electrode 3 Work piece 4, 4A, 4B, 4C Switching element 5, 5A, 5B, 5C Resistor 5D Variable resistor 6 Capacitor 7 Discharge detecting means 9 Counter Circuit 10 Comparison circuit 13 Storage arithmetic circuit 14 Resistance control means 15 Power supply voltage changing means 80, 80A, 80B Oscillation control circuit Sd Discharge detection signal Sl Charging current large signal Ss Charging current small signal

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Claims (6)

[Claims] 1. A series circuit including a DC power supply for supplying a DC pulse current to a machining gap between a machining electrode and a workpiece, a switching element and a resistor, the machining electrode and the workpiece. A capacitor connected in parallel to the discharge electrode, discharge detecting means for detecting generation of discharge between the processing electrode and the workpiece by the capacitor, discharge current of the capacitor with respect to the switching element in the series circuit. ON for a pulse width equal to or less than the pulse width of
The off control is repeated until the capacitor is discharged and the discharge detecting means detects the discharge, and the on / off control is repeated after a predetermined off time after the discharge is detected by the discharge detecting means. A power supply device for an electric discharge machine, comprising: a circuit. 2. The discharge detecting means detects a discharge between the machining electrode and the workpiece, and after the predetermined off time, the on / off control for the switching element is repeated, and again. Counting means for counting the number of ON / OFF control times until the discharge is generated and the discharge detecting means detects the discharge is compared with a value counted by the counting means and a preset value, and the counting means When the value counted by is smaller, a charging current large signal indicating that the current for charging the capacitor is larger is generated, and when the value counted by the counting means is larger, the capacitor is charged. 2. The power supply device for an electric discharge machine according to claim 1, further comprising: a comparison unit that generates a small charging current signal indicating that the current to be discharged is small. 3. The discharge detecting means detects a discharge between the machining electrode and the workpiece, and after the predetermined off time, the on / off control for the switching element is repeated, and again. Counting means for counting the number of times on / off control is performed until a discharge is generated and the discharge detecting means detects the discharge; storage means for storing the value counted by the counting means a predetermined number of times; and the storage means. Computation means for calculating the average value of the values stored in, and the value calculated by the computation means and a preset value are compared, and if the value calculated by the computation means is smaller, A large charging current signal indicating that the current for charging the capacitor is large is generated, and if the value calculated by the calculation means is larger, the charging that indicates that the current for charging the capacitor is smaller. The power supply device for an electric discharge machine according to claim 1, further comprising a comparison unit that generates a small current signal. 4. When the small charging current signal is generated by the comparing means, the resistance value of the resistor in the series circuit is reduced by a constant value, and when the large charging current signal is generated by the comparing means. The power supply device for an electric discharge machine according to claim 2 or 3, further comprising: a changing unit that increases a resistance value of the resistor of the series circuit by a constant value. 5. When the small charging current signal is generated by the comparison means, the voltage value of the DC power source of the series circuit is increased by a constant value, and when the large charging current signal is generated by the comparison means. The power supply device for an electric discharge machine according to claim 2 or 3, further comprising a changing unit that reduces a voltage value of the DC power supply of the series circuit by a constant value. 6. The pulse width of the current for charging the capacitor is lengthened by a constant value when the small charging current signal is generated by the comparison means, and the charging current large signal is generated by the comparison means. The power supply device for an electric discharge machine according to claim 2 or 3, further comprising changing means for shortening a pulse width of a current for charging the capacitor by a constant value.