JPH01153220A - Power source for electrospark machining - Google Patents

Abstract

PURPOSE:To reduce electric power consumption by accumulating temporarily working current energy accumulated in wiring inductance in a capacitor when a first switching circuit is turned off and regenerated it in DC power supply when a second switching circuit is turned on. CONSTITUTION:When a switching element Q1 is turned on by a pulse signal from a pulse generator PG, voltage of a DC power source E1 is applied across a gap between a wire N and a workpiece P to generate discharge. When next said element is turned off, working current is sent through a diode D2 to capacitors C1, C2 by the inertia of wiring inductance L to increase voltage so that the working current is attenuated to zero, while the diode D2 is turned off. The increase of voltage of capacitor C2 elevates the duty ratio of a pulse width modulating circuit PWN, elongates timing of turning on a switching transistor Q3 and regenerates working current energy in said power source E1 through DC reactor L1. Thus, the electric power consumption of DC power source can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply device for electrical discharge machining, and particularly to a power supply device for wire-cut electrical discharge machining that cuts a material using a wire as an electrode.

[Prior art] As a conventional technology of this type of electric discharge machining power supply device, the fourth
The technique shown in the circuit diagram of a conventional electric discharge machining power supply device shown in FIG.

In the figure, (El) is the workpiece (
(R2) is a DC power source that serves as an auxiliary power source, (R1) and (R2) are resistors, (C1) and (C2) are capacitors, (Dl) and (D2) and (D3) are diodes, (
GAI) and (GA2) are drive circuits that switch output side transistors according to input signals, (Ql) and (C2) are switching transistors,
(PG) is a pulse generator that outputs a pulse signal at a predetermined period, (L) is a wiring inductance, (N) is a wire serving as a negative discharge electrode, and (CP) is a comparator.

The conventional electrical discharge machining power supply device configured as above is
It works like this:

The pulse signal generated by the pulse generator (PG) is passed through the drive circuit (GAI) to the switching transistor (
Ql) is turned on. Switching transistor (Ql)
When turned on, the voltage of the DC power supply (El) is applied to the interval between the wire (N) and the workpiece (P) via the diode (Dl) and the wiring inductance (1-), and arc discharge occurs in the interval. is generated and the machining current flows. At this point, the diode (D2) becomes reverse biased, and during this time, the capacitor (C1) is connected to the resistor (R
1) and is precharged via the capacitor (C1).
The voltage (Vcl) becomes the preliminary charging voltage (Vc).

When the switching transistor (Ql) is turned off, this processing current flows into the capacitor (C1) and the capacitor (C2) via the diode (D?) due to the inertia of the wiring inductance (L).

Therefore, the machining current attenuates and becomes zero, and at the same time, the diode (D2) becomes reverse biased and turns off. When the machining current flows into the capacitor +1 (cl), the voltage of the capacitor (C1) rises above the pre-charge voltage (Vc), as shown in the waveform diagram of FIG. 5(a). When the voltage (Vcl) of the capacitor (C1) increases by a predetermined value (ΔV), the output of the comparator (CP>) is inverted and the switching transistor (C2) is turned on via the drive circuit (GA2).At this time, , as shown in FIG. 5(b), a discharge current (i>) limited by the resistor (R2) flows, lowering the voltage (VCl) of the capacitor (C1) to the precharge voltage (VC).

The above operation is performed at every interval of a pulse signal generated from a pulse generator (PG). This operation consumes the energy of the machining current accumulated in the wiring inductance (L), and the voltage of the DC power supply (El) is repeatedly applied to the gap between the wire (N) and the workpiece (P), and the Intermittent arc discharge is generated at intervals, and a machining current flows due to the intermittent arc discharge, thereby machining the workpiece (P).

[Problems to be Solved by the Invention] Since the conventional electric discharge machining power supply device is configured as described above, the machining current flows into the capacitor (C1), and the voltage (Vcl) of the capacitor (C1) decreases. As the discharge current (i>) increases, the switching transistor (
Since the machining current flows through the resistor (R2) when C2) is turned on, the energy of the machining current accumulated in the wiring inductance (L) while the switching transistor (Ql) is on is consumed as heat by the resistor (R2). Therefore, the DC power supply (El) is equal to the power required for machining, and this resistance (El) is equal to the power required for processing.
The power consumed by R2) must also be supplied,
There was a problem that the DC power supply capacity became large. Also,
In order to prevent heat generation in the resistor (R2), a powerful cooling fan was required, and its noise was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a power supply device for electric discharge machining that does not consume energy due to machining current accumulated in wiring inductance as Joule heat.

[Means for Solving the Problems] The electric discharge machining power supply device according to the present invention provides a direct current that is applied to the machining interval formed between the electrode and the workpiece and supplies energy for machining the workpiece. a first switching circuit that intermittently controls opening and closing of the output of the power supply; a capacitor that temporarily absorbs energy accumulated in the wiring inductance due to the processing current of the DC power supply when the first switching circuit is turned off; and a terminal of the capacitor. It consists of a second switching circuit that is controlled on and off depending on the magnitude of the voltage and regenerates the energy stored in the capacitor into the DC power supply.

[Function] In the present invention, the first switching circuit is controlled to open and close intermittently to generate an arc discharge intermittently in the machining gap formed between the electrode and the workpiece. Energy for processing objects is supplied from a DC power source. The processing current of the DC power supply causes the energy accumulated in the wiring inductance to be temporarily absorbed by the capacitor when the first switching circuit is turned off. Then, a second switching circuit connected to the connection point between the capacitor, the DC reactor, and the diode, which has once absorbed the energy accumulated in the wiring inductance, is turned on and off according to the magnitude of the terminal voltage of the capacitor. The energy stored in the capacitor is then regenerated into the DC power supply.

Therefore, the second switching circuit is controlled on and off in accordance with the magnitude of the terminal voltage of the content 1 which has once absorbed the energy accumulated in the wiring inductance, and the energy accumulated in the capacitor is converted into direct current. Since the energy is regenerated into the power supply, the energy accumulated in the wiring inductance of the DC power supply can be regenerated with almost no loss, and as a result, the output current of the DC power supply is reduced.

[Example] Next, a power supply device for electrical discharge machining according to an example of the present invention will be described.

FIG. 1 is a circuit diagram of the overall configuration of a power supply device for electric discharge machining according to an embodiment of the present invention.

In the figure, (El) is a DC power supply that supplies energy to machine the workpiece (P) by intermittently generating arc discharge in the machining gap, and the workpiece (P) that becomes the positive discharge electrode.
P), wire (N) that becomes the discharge electrode on the negative electrode side, wiring inductance (L), diode for backflow prevention (Dl),
It is connected to a series circuit consisting of a switching transistor (Ql). Further, the DC power supply (El) is connected to a series circuit consisting of a capacitor (C1) and a capacitor (C2). The capacitor (C1) is connected in series with a resistor (R1) to both poles of another DC power source (R2). The switching transistors 1 and 2 (Ql) are controlled on and off by a pulse generator (PG) which outputs a pulse signal at a predetermined period via a drive circuit (GAI). The connection point between the capacitor (C1) and the capacitor (C2) and the cathode side of the diode (Dl) are a switching diode (D2), whose anode side is connected to the cathode side of the diode (Dl), and its cathode side is connected to the capacitor (C1). ) side. A DC reactor (
Ll) and a diode (D4) that is reverse biased with respect to the DC power supply (El) are connected in series, and the capacitor (C1) has a series circuit consisting of the DC reactor (Ll) and a switching transistor (C3). connected in parallel. The switching transistor (C3) is connected to a capacitor (C2) via a drive circuit (GA3).
) Pulse width modulation circuit (PWM) that uses the voltage value of
On/off is controlled by the output.

FIG. 2 is an overall block diagram of a pulse width modulation circuit (PWM) used in the electric discharge machining power supply device of this embodiment.

In the figure, the voltage (VC2) across both terminals of the capacitor (C2) is input to the input of the isolation amplifier (OPI). The voltage (Vc2) across both terminals of the capacitor (C2) is input to the differential amplifier (OF2) via the isolation amplifier (OPI), where it is connected to the output voltage (Vth) of the potentiometer (PM) through the threshold setting device. and inputs it to the comparator (CPI) via the amplifier (OF2).Since the output of the triangular wave generator (PGI) is received as the other input of the comparator (CPI), the comparator (CPI) The output of CPI ) is connected to a capacitor (C
2) is a pulse width modulated output with a duty ratio proportional to the both terminal voltage (Vc2).

The electrical discharge machining power supply device of this embodiment configured as described above operates as follows.

The pulse signal generated by the pulse generator (PG) is passed through the drive circuit (GAI) to the switching transistor (
Ql) is turned on. Switching transistor (Ql)
When turned on, the voltage of the DC power supply (El) is applied to the interval between the wire (N> and the workpiece (P)) via the diode (Dl) and the wiring inductance (L), causing an arc discharge in that interval. At this time, the diode (D2) becomes reverse biased, and during this time, the capacitor (C1) is connected to the DC power supply (Mi2) so that it has a higher potential than the DC power supply (El). Resistance (R1
), and the voltage (MCI) of the capacitor (C1) becomes the pre-charge voltage (Vc).

When the switching transistor (Ql) is turned off, the processing current flows into the capacitor (C1) and the capacitor υ(C2)' via the diode (D2) due to the membership of the wiring inductance (L). Therefore, the machining current is attenuated and becomes zero, and at the same time the diode (D2) is turned off. When the processing current flows into the capacitor (C1),
The voltage of the capacitor (C1) is the precharge voltage (Vc)
More Ueno. In addition, the processing current is applied to a capacitor (C2
) voltage (Vc2) also increases. The rise in the voltage (Vc2) of the capacitor (C2) is due to the pulse width modulation circuit (PWM)
This will increase the duty ratio of When the duty ratio of the pulse width modulation circuit (PWM) increases, the drive circuit (GA3) inputting the duty ratio lengthens the timing at which the switching transistor (C3) is turned on. Therefore, the switching transistor (C
3) and the DC power supply (E) via the DC reactor (Ll).
The DC current regenerated in l) increases, and the capacitor (C2)
The voltage (Vc2) decreases.

The regenerative operation will be explained using the waveform diagram of the electrical discharge machining power supply device of this embodiment shown in FIG.

FIG. 3 shows that the machining current is applied to a capacitor (C2
) and shows a steady state in which a constant DC current flows from the DC reactor (Ll) to the DC power supply (El).

The switching transistor (C3) is turned on and off at a constant duty ratio, and its current and voltage waveforms are shown in Figure 3 (C
) and as shown in Figure 3(d).

Further, the diode (D4) is turned on and off in the opposite manner to the switching transistor (C3), and its current and voltage waveforms are as shown in FIGS. 3(e) and 3(f). DC react]~
As shown in FIG. 3(b), a positive voltage is applied to the switching transistor (Ll) when the switching transistor (C3) is on, and a negative voltage is applied when the switching transistor (C3) is off, and the current (11) is C
) and FIG. 3(e) are combined to form the waveform shown in FIG. 3(a>).

In this way, in steady state, the DC current (11) of the DC reactor (Ll) increases, and the switching transistor (C3
) increases, the current (1) flowing through the switching transistor (C3) increases as shown in FIG.
The width of the current waveform of 2) widens, as shown in Figure 3(e), and the width of the current waveform of the current (i3) flowing through the diode (D4) narrows, as shown in Figure 3(a). , the DC current (11) increases. This situation is shown by the broken line waveform in FIG. 3(a). In this way, the DC current (1
1) is regenerated into the DC power supply (1). In other words, it operates in the same way as a high-voltage chopper circuit, and (DC power supply voltage)
The power of x (DC current component of the DC reactor) is regenerated to the DC power supply almost without loss, and as a result, the output current of the DC power supply is reduced.

In addition, in the above embodiment, a diode (Dl) for backflow prevention is used.
However, when implementing the present invention, it is not necessarily required. Furthermore, in the above embodiment, the voltage between the terminals (Vc2) of the capacitor (C2) is controlled to be constant, but when implementing the present invention, the precharge voltage (VC) of the capacitor (C1) The voltage may be controlled to be constant.Of course, in this case, the input of the pulse width modulation circuit (P'vVM) is
The pre-charging voltage (Vc) is I>.

In the above embodiment, the output frequency of the pulse width modulation circuit (PWM) and the triangular wave generation circuit (PGI) is preferably higher than the audible frequency, but when implementing the present invention, the inductance of the DC reactor (Ll) There is no particular limitation as long as the value, ripple current value, etc. are appropriately selected.

By the way, the electric discharge machining power supply device of the above embodiment intermittently outputs the DC power (El) applied to the machining gap formed between the electrode made of the wire (N) and the workpiece (P). As the first switching circuit, which consists of a semiconductor switch element that controls opening and closing, a circuit is used that turns on and off a switching transistor (Ql) using a pulse signal generated by a pulse generator (PG) via a drive circuit (GAI). However, when implementing the present invention, the switching transistor (Ql), the drive circuit (GAl
), the first switching circuit is not limited to the configuration of a pulse generator (PG), and the first switching circuit may be configured with a semiconductor switching element that can be turned on and turned off.

In addition, the capacitors that temporarily absorb the energy accumulated in the wiring inductance (L) due to the processing current of the DC power supply (El) in the above embodiment when the first switching circuit is turned off are the capacitor (C1) and the capacitor (C2). However, when carrying out the present invention, any capacitor may be used as long as it has the ability to accumulate the current flowing in the forward bias state of the diode (D2) when the first switching circuit is off.

Then, the capacitor (C1) and capacitor (C2) of the above embodiment and the DC licks 1 to 1 (Ll) of the regeneration circuit
and the diode (D4), and is controlled on/off according to the magnitude of the terminal voltage of the capacitor (C1) and the capacitor (C2),
A second switching circuit consisting of a semiconductor switching element that regenerates the energy accumulated in 01) and Conan'J (C2) to a DC power supply (El) includes a switching transistor (C3), a drive circuit (GA3), and a capacitor (C2). Pulse width modulation circuit (
However, when implementing the present invention, the voltage value of the capacitor (C1) may be used as an input to the pulse width modulation circuit (PWM). and the switching transistor (C3), the drive circuit (GA3),
It is not limited to the configuration of a pulse width modulation circuit (PWM), and the wiring inductance accumulated in the capacitor (
The second switching circuit may be configured with a semiconductor switching element that can be turned on and turned off depending on the energy of L).

[Effects of the Invention] As described above, the electric discharge machining power supply device of the present invention generates an arc discharge intermittently in the machining interval formed between the electrode and the workpiece, and generates arc discharge on the workpiece. a first switching circuit that intermittently controls the opening and closing of the output of a DC power supply that supplies energy for processing; a capacitor connected to both poles of the capacitor and the DC power supply,
It is connected to the connection point between the DC reactor and the diode of a regeneration circuit formed by connecting a DC reactor and a diode that is reverse biased with respect to the DC Na in series, and is turned on and off depending on the magnitude of the terminal voltage of the capacitor. The second switching circuit is controlled to regenerate the energy stored in the capacitor into the DC power supply.

Therefore, when the first switching circuit turns off the energy of the machining current accumulated in the wiring inductance,
- When the second switching circuit is turned on, this is stored in the capacitor and regenerated to the DC power supply via a regeneration circuit composed of a DC reactor and a diode, reducing the power consumption of the DC power supply. can be done. Also,
There is no need for a circuit to consume the energy of the machining current accumulated in the wiring inductance as Joule heat.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration circuit diagram of an electric discharge machining device according to an embodiment of the present invention, FIG.
1, FIG. 4 is a circuit diagram of a conventional electrical discharge machining power supply, and FIG. 5 is a waveform diagram of a conventional electrical discharge machining power supply. In the figure, El: DC power supply, P: workpiece, N: wire,
L: Wiring inductance, Ql, Q3
Niswitching transistor, CI, C2: capacitor, 01, D2. D4: Diode, Ll: DC reactor, PWM: Pulse width modulation circuit, PG: Pulse generator. In addition, in the figures, the same reference numerals and the same symbols indicate the same or equivalent parts.

Claims (2)

[Claims] (1) In the machining gap formed between the electrode and the workpiece,
A first component comprising a DC power source that intermittently generates arc discharge to supply energy for machining a workpiece, and a semiconductor switching element that intermittently controls opening and closing of the output of the DC power source given during the machining interval. a switching circuit, a capacitor that temporarily absorbs the energy accumulated in the wiring inductance due to the processing current of the DC power source when the first switching circuit is turned off, a DC reactor connected to both poles of the DC power source, and the DC power source. A regeneration circuit formed by connecting a diode in series with a reverse bias, and a regeneration circuit connected to the connection point between the capacitor and the DC reactor of the regeneration circuit and the diode, and controlled on/off according to the magnitude of the terminal voltage of the capacitor. and a second switching circuit including a semiconductor switching element that regenerates the energy stored in the capacitor into a DC power source. (2) A second switching circuit consisting of a semiconductor switching element that is controlled on and off depending on the magnitude of the terminal voltage of the capacitor and regenerates the energy stored in the capacitor into a DC power supply, keeps the voltage of the capacitor constant or 2. The electric discharge machining power supply device according to claim 1, wherein the second switching circuit is controlled to be on/off so as to fall within a substantially constant range.