JPS6029211A - Electric discharge machining power source - Google Patents

Abstract

PURPOSE:To prevent a drop and variations in discharge energy from occurring as well as to stabilize an operation in electro-discharge machining, by constitution the voltage of a condenser so as to keep it in a constant level for a period of up to a discharge start after an end of charging upon resupply for a leakage current, in case of an electro-discharge machining power source for an electric discharge machine using the discharge of the condenser. CONSTITUTION:For a period of waiting a discharge start after a condenser C0 being charged, if voltage of the condenser C0 drops and it comes below the reference voltage Vd of a comparator Cd due to a leakage current lying between gaps, an H-level signal is inputted into an AND gate Gd via an inverter Id, turning on each transistor via a preamplifier and charging the condenser C0. When the voltage of the condenser drops below the reference voltage values Va-Vc as the leakage current is large enough, each transistor is turned on via preamplifiers A1-Ac, charging the condenser likewise. With this constituion, uniformization in the condenser voltage is well promoted and, what is more, stable electro- discharge machining is thus achievable.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining power source for an electric discharge machine that performs electric discharge machining using a single electric discharge.

Figure 1 shows the basic circuit of a conventional electric discharge machining power supply that uses capacitor discharge and inserts a transistor in the discharge circuit that performs machining. A signal is input to q2 to make transistor Q2 conductive, and capacitor Co
is charged from the high-voltage DC current ME through the resistor Ro, and the capacitor Co is charged to the reference voltage, and the above 1-transistor Q
2 is turned off, and the transistor Q1 connected to the capacitor Co is turned on.
Electric discharge is generated between the electrode P and the workpiece, and electrical discharge machining is performed. However, if a conductive liquid such as water is used as the machining fluid injected between the electrode P and the workpiece W, the capacitor C.

After reaching the reference voltage and stopping charging by setting the transistor Q2 to A), the charging current of the capacitor Co may drop due to the leakage current flowing between the gaps.

Therefore, the discharge energy differs each time, making it impossible to perform stable discharge machining, which is not preferable.

Furthermore, in the electric discharge machining power supply of the type in which a capacitor C1 is inserted in the discharge circuit, when the charging voltage of the capacitor Co decreases due to leakage current, the base q1 of the transistor Q1 in the discharge circuit is reduced by the action of the control circuit. No signal is input to the transistor Q1, and after the transistor Q1 is set to A, discharge starts, which may destroy the resistor Q1. Therefore, conventionally, another transistor was installed in parallel with the transistor Q2 that charges the capacitor Co, and the transistors 1 to 1 were controlled on and off to compensate for the leakage current. If the transistor current is too large compared to the leakage current, overcharging may occur due to switching delays in the transistor.
~If the transistor current was reduced, the charging voltage could not be maintained at the reference voltage level, making control extremely difficult.

OBJECT OF THE INVENTION The object of the present invention is to improve the drawbacks of the above-mentioned prior art in an electric discharge machining power supply that performs electric discharge machining using ndenna discharge, and to supplement the leakage current between the end of charging and the start of discharge. 1. An object of the present invention is to provide an electric discharge machining power source that maintains the voltage of the capacitor within a certain level range.The present invention charges the capacitor by turning on the switching element and turning off the switching element. After that, a plurality of switching elements for current replenishment are connected in parallel with the switching element in the electric discharge machining power supply d3 that performs electric discharge machining by the discharge of content 1 no, the voltage of the capacitor is measured, and the charging voltage is A current replenishment circuit is provided () that turns on each of the plurality of current replenishment switching elements only between voltages that are higher than a set reference voltage and at different levels of the reference voltage 11 or higher. This electrical discharge machining power source is designed to supplement the leakage current between the two and maintain the above-mentioned voltage within a certain level range.

Embodiment FIG. 2 is a basic circuit diagram of an electric discharge machining power supply according to an embodiment of the present invention, and FIG. 3 is a control circuit diagram thereof.

In addition, a current detector 1 such as a Rogowski coil, which constitutes a discharge current detection circuit that detects the discharge current of the capacitor Go, is inserted into the discharge circuit to detect the group 1m current, and a resistor R3 is inserted.
, comparator C! via an integrating circuit consisting of capacitor C1. It is input to the reference voltage Vc, and if the comparison voltage is higher than the comparison voltage Vc, an output is output to the OR gate G1.

And these current detectors 1. A discharge current detection circuit 2 is composed of an integrating circuit and a comparator C2. In addition, the capacitor CoO') voltage is divided and detected through resistors R+ and R2 provided in parallel with the capacitor Co that charges and discharges, and the voltage and the reference voltage v1 are compared by a comparator Cv. A charging voltage detection circuit 3 is provided which outputs an H level output when the voltage exceeds the voltage.
] Transistor Q2 for charging battery Co. Resistance R.

Switching elements 1 to transistors Qa to Qdd5 and resistors Ra to Rd for current replenishment are installed (blocked) in parallel with the charging voltage detection circuit 3, as shown in FIG. The output of is monostable multivibrator M1
is input to the OR gate G1, and the output of the monostable multivibrator M1 and the output of the discharge current detection circuit 2 are further input to the OR gate G1.
The output of 1 is sent from 1 to transistor Q1 via preamplifier A1.
is input to the base q1 of the transistor Q1, thereby making the 1-herald transistor Q1 conductive. In addition, the above “A Age-1-G”
The + output horn is input to the monostable multivibrator M2 and the NOR gate G2, and the output of the monostable multivibrator M2 is input to the NOR gate G2. and is input to the base q2 of the transistor Q2. Roughly speaking, the voltage Vo of the capacitor Co divided by the resistor IR1°R2 is input to the comparator Ca ""' Cd of the current replenishment circuit 4, and each comparator Ca
~Cd has operational amplifier OPa~OP dF
The generated comparison voltage J1Va-Vd is inputted and compared.Then, these comparison voltages are ``-distributed charging voltage L[base ll(r1i The voltage Vt is set to be slightly higher than the reference voltage V, for example, so as to have the following relationship.

Va −1,02XVa Vl)=1.04. XV* Vc = 1.06 XV history Vd = 1.08 , are input to AND gates Qa-Qd via inverters Ia-Id, and furthermore, the output of charging voltage detection circuit 3 and the signal from switch SW are input to AND gates Q1-Qa-Gd. , and these AND gates Ga
The output of ~Gd is sent to the base qa~ of each of the above transistors Qa-Qd via preamplifiers Aa-Ad, respectively.
It is input to Qd.

Next, the operation of this embodiment will be explained.

Now, transistor Q2 is turned on, and the transistor Q2 is turned on.
Suppose you are charging. The voltage across this capacitor C0 is detected by the charging voltage detection circuit 3, and when the divided voltage V'o across the capacitor Go exceeds the reference voltage V,
] - Outputs the output of Lulubell, sends a signal to the base 9 of transistor Q1 via A gate G+ and preamplifier A2, and turns on transistor Q1. On the other hand, since the output of the OR gate G1 is input to the NOR gate G2, the pulse that has been input to the base q2 of the transistor Q2 is increased, the transistor Q2 is turned off, and charging is stopped. Then, when the discharge of the battery Co starts, the current detector 1 of the current detection circuit 2 detects the discharge current, integrates it in the integrating circuit, and compares it with the comparison iu JfVt by the comparator C.I. , as the comparison voltage Vtl becomes higher, the comparator C■ outputs a torque of 5. Output 11 is output, and output continues to be output from OR gate G1. On the other hand, when discharging starts and the voltage of the capacitor Co decreases to below the reference voltage Vt, the output of the amparator Cv stops, but as the output falls, the monostable multivibrator M1 is turned on and a pulse of a constant width is generated. It is output and input to OR gate G1. Note that this monostable multivibrator M1 has the role of extending the output of the comparator Cv, and before the output of the charging voltage detection circuit 3, that is, the comparator C2, falls, the discharge current detection circuit 2', that is, the comparator Cr The output of (
If Figure 4 (e)) is up, it is not necessary.
The design is designed to compensate for these fluctuations in the rise so that the output from the OR gate G1 is sustained from the rise of the output of the charging voltage detection circuit 3 to the fall of the output of the discharge current detection circuit 2. It is something that

In this way, the OR gate 2 continues to output an output of 1 level, but when the discharge current from the capacitor Go decreases and the output voltage of the current detector 5 becomes lower than the comparison voltage Vt, the output of the comparator C+ becomes Falling, or gate G
The output of 1 goes high. However, due to this fall, the monostable multivibrator M2 is turned on and outputs a pulse with a constant width, so the output of the NOR gate G2 is not output.
1-Fungista Q2 is not turned on. and,
When the output of the monostable multivibrator M2)] disappears, the input of the NOR gate G2 (, 1 disappears, so
1 level output comes out from Noagu 1~G2 and preamplifier A
Turn on transistor Q2 from 1 through 1 and start charging Co again.

This embodiment basically operates as described above.
After capacitor Co is charged to reference voltage Vn and transistor 01 is turned off /i5! Until the charging starts, when a leakage current occurs between the gap between the electrode P and the workpiece W and the voltage of the capacitor C1 drops below the reference voltage Ve, the charging voltage detection circuit 3 outputs 1-Level. No more output and 111 stable multivibrator output horn pulse b #! Moreover, the comparator Cr of the discharge current detection circuit 2 is configured so that the signal from the current detector 1 is the comparison voltage V.
When the output of less than 1 level is not output, transistors 1 to 1 are turned off via Agate G+ and preamplifier A1, but (8) When the discharge starts, the transistor Q1 may be destroyed.Furthermore, the voltage of the capacitor CO may be lower than the reference voltage Vt.
If the monostable multivibrator M1 outputs an output and starts its intermittent discharge under the following conditions, the transistor Q
1 is never turned off, but the discharge energy is less than the reference voltage, which is not preferable for electrical discharge machining.

To this end, one embodiment of the present invention is the comparators Ca to Cd, which are current supplementary circuits 4 as described above.

Configurations such as AND gates Qa to Gd and l-transistors Qa to Qd are added. Now, as shown in FIG. 4, the capacitor Go is charged and exceeds the reference voltage VA, causing some overshoot. Then, the discharge starts, but during that time, the voltage of the capacitor CO decreases due to the leakage current between the gaps, and when it becomes lower than the comparison voltage Vd (=1.08Va) of the comparator Cd, the output of the comparator Cd stops. level, and a signal of 1 level is input to the controller 1-Gd via the inverter Id. Since the 1 level signal from the charging voltage detection circuit 3 and the 1 level signal from the switch SW input when performing leakage current control are input to the AND gate Ga-Gd, the output of the AND gate Ga-Gd becomes H level,
Turn on the transistor Qd via the preamplifier Δd,
Capacitor GO via resistor Rd, 1 to transistor Qd
will be charged. Then, if the voltage of the capacitor Co exceeds the comparison voltage Vd of the comparator Cd, 1
~The transistor Qd turns off and stops charging, but the leakage current is large and the voltage of the capacitor Co further decreases.
Comparison voltage vc (-1,06Vn).

Vl+ (=1.04Vn), Va (=1.02V
t ) or less, the transistor Qc
.

Qb and Qa turn on and start charging, so the larger the leakage current, the more the transistor Qa-
When Qd turns on a lot, -C starts charging quickly, compensates for the drop in the charging voltage J1: of capacitor Co due to the leakage current, and stops charging when the comparison voltages Va, Vb, Vc, and Vd are exceeded, respectively. Between the reference voltage Vn set above and the comparison voltage Vd, that is, the reference voltage Vi~1.
The charging voltage of the capacitor Co is maintained during '08Vj.

In the above embodiment, a discharge machining power supply in which a transistor Q1 is inserted in the discharge circuit of the discharge machining power supply is described, but the present invention can also be implemented in a conventional discharge machining power supply of a type in which this transistor Q1 is not inserted. Of course it is possible.

Effects of the Invention As described above, the present invention provides an electric discharge machining power supply that performs machining by capacitor discharge, even if the charging voltage of the capacitor decreases due to gap leakage current between the electrode and the workpiece.
Since the voltage of the capacitor is detected and the capacitor 1 is charged in stages according to the voltage level of the voltage level, the charging voltage of the capacitor is maintained within a constant voltage range. IIi There is no drop or variation in electrical energy, allowing stable electrical discharge machining.

In addition, in the type of electrical discharge machining Ti source that is controlled by inserting a transistor into the discharge circuit, the charging voltage of the capacitor is maintained above the reference voltage, so the transistor is not turned off before the start of molding. Therefore, the transistor will not be destroyed by discharge.

[Brief explanation of drawings]

Fig. 1 is a basic circuit diagram of a conventional electric discharge machining power supply in which 1 to 1 transistors are inserted in the discharge circuit, Fig. 2 is a basic circuit diagram of an embodiment of the present invention, and Fig. 3 is a basic circuit diagram of the same embodiment. An example control circuit diagram, FIG. 4, is a diagram illustrating the charging state of a capacitor that performs discharging. 1... Current detector, 2... Discharge current detection circuit, 3.
...Charging voltage detection circuit, 4...Current replenishment circuit, Q+
, G2. Qa~Qd...transistor, co...capacitor, Or, Cv, Ca~Ccl +++] amplifier, A+, △2, Aa-Ad- preamplifier,
G1-A Agate, G2... Noagu 1-, Ga~G
(1...and gate. (I or 1 person)

Claims (1)

[Claims] In an electrical discharge machining power supply that turns on a switching element to charge a capacitor, turns off the switching element, and then performs electrical discharge machining by discharging the capacitor, a plurality of switching elements for current replenishment are connected in parallel with the switching element, A current replenishment circuit is provided that measures the voltage of the capacitor and turns on each of the plurality of current replenishment switching elements only when the charging voltage is equal to or higher than a set reference voltage and is at a different level than the reference voltage. (An electric discharge machining power supply that replenishes leakage current between the end of charging and the start of discharge to maintain the capacitor voltage within a certain level range.