JP3243368B2 - Power supply for electric discharge machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for an electric discharge machine, and more particularly to a power supply device for an electric discharge machine which has improved machining accuracy and a simplified structure.

[0002]

2. Description of the Related Art In a wire electric discharge machine or a die-sinking electric discharge machine, an auxiliary power supply is used to generate an electric discharge between a work and an electrode (hereinafter, referred to as an electrode gap). Is applied between the poles. Then, after detecting the occurrence of discharge, a main current is applied from a main power supply to perform rough machining,
At the time of finishing, the main power supply is disconnected and a small current for finishing is supplied from the auxiliary power supply.

FIG. 5 is a circuit diagram showing the configuration of a conventional power supply device for an electric discharge machine of this type. In FIG. 5, an auxiliary power supply Vs is connected between poles via a switching transistor Tr1, a coaxial cable W1 and a resistor R1, and a main power supply VM is connected to a switching transistor Tr2 and a resistor R1.
2. Diode D1, coaxial cable W as power supply line
It is connected between the poles via 2 and the electromagnetic switch K.

At the time of rough machining, the electromagnetic switch K is turned on, the transistor Tr1 is turned on, and the voltage of the auxiliary power supply Vs is supplied between the poles to generate a discharge between the poles. After the discharge occurs between the poles, the transistor Tr2 is turned on, and the main power supply VM is supplied between the poles to perform rough machining. At the time of finishing, the transistor Tr
2 and the electromagnetic switch K are turned off, the main power supply VM is electrically disconnected, and the finishing process is executed only with the auxiliary power supply. The occurrence of discharge between the electrodes is detected by a discharge detection unit 2, and a pulse control unit 1 receiving the detection signal outputs a signal from a transistor Tr1.
And Tr2 ON / OFF operation is controlled.

Incidentally, the main power supply VM and the auxiliary power supply Vs
Power is supplied to the gap from the power supply by the power supply lines W1 and W2, but the stray capacitance of the power supply line greatly affects the processing performance.

For example, when a power supply cable having a small stray capacitance is used during rough machining, the inductance component increases, the rise of machining current becomes gentle, and the rough machining speed decreases. Therefore, conventionally, a coaxial cable W2 having a large stray capacitance has been used. At this time, the electromagnetic switch K is in the ON state.

The current supply from the auxiliary power supply Vs at the time of finishing is performed via the power supply line W1, but if the stray capacitance of the power supply line W1 is large, the charging energy is discharged and the discharge is performed at the time of finishing. The current is superimposed on the current from the auxiliary power supply, and the finishing accuracy is reduced. Therefore, conventionally, a coaxial cable having a small stray capacitance is used as the auxiliary power supply line W1.

Here, at the time of finishing, the transistor T
Since the main power VM is not supplied because the r2 is turned off, the power supply line W2 is connected, and the large stray capacitance adversely affects the finishing accuracy.
The electromagnetic switch K is turned off to disconnect the connection.

[0009]

As described above, the power supply line suitable for each of the roughing and the finishing conditions is used, and the power supply line W2 used for the roughing is used for the electromagnetic switch during the finishing process. A device for reducing the capacitance of the current-carrying system at the time of finishing by shutting off by K and energizing through another low capacitance power supply line W1 is shown in FIGS. 1 to 5 of JP-A-59-73226. Is disclosed.

However, in this device, a large electromagnetic switch having a large current capacity and a large contact area must be installed on the output cable side of the main power supply. Is difficult to install, and there is a cost problem. Further, since the reciprocating supply line is separated by wiring around the electromagnetic switch, the impedance component of the output supply line increases. for that reason,
At the time of rough machining using the main power supply, the rise and fall of the current of the main power supply are slowed down, and the machining performance (surface roughness and machining speed) is reduced.

Therefore, as shown in FIG. 1 to FIG. 3 of Japanese Patent Publication No. 4-59092, movable energizing terminals for rough machining and energizing terminals for finishing are provided, and And the power supply for rough processing and the power supply for finish processing are connected via power supply (energization) lines suitable for the respective processing conditions at the time of finish processing. Thus, an apparatus has been proposed in which the influence of the stray capacitance of a supply line used in roughing during finishing is removed.

However, the machining current of the main power source for rough machining is usually as large as several tens of amperes to several hundreds of amperes, so that the energizing terminals are increased in size, and there is a problem in terms of practicability to adopt a movable energizing terminal structure.

By the way, in a wire electric discharge machine,
In order to improve the accuracy of the machined surface, there is a case where the finishing process is performed by reversing the polarity from the power supply supplied between the electrodes.

FIG. 6 is a circuit diagram of a power supply portion of this type of wire electric discharge machine. As described above, the electromagnetic switch K is turned on, and the power from the auxiliary power supply Vs is supplied to the resistor R1 by controlling the ON operation of the transistor Tr1.
And a wire electrode WE via a relay RL and a conducting terminal S
After the discharge is generated between the electrodes, the transistor Tr2 is turned ON to change the main power supply VM from the wire electrode WE to the work W through the resistor R2, the backflow prevention diode D1, and the conduction terminal S. Roughing is carried out by supplying in between. At the time of the final finishing work thereafter, the relay RL is switched and the polarity is reversed to improve the finished work surface accuracy. Such polarity reversal electric discharge machining is disclosed in FIGS. 1 and 2 of JP-B-46-24678. At this time, since the power supply has a configuration in which the auxiliary power supply Vs and the main power supply VM are connected in series, the electromagnetic switch K is turned off to disconnect both power supplies and prevent mutual interference.
FF. At the time of finishing, the stray capacitance of the power supply line is removed by turning off the electric switch K as in FIG.

The electromagnetic switch K must be installed in the vicinity of the gap, and a large-capacity switch is required as described above.
There is a problem in terms of size and cost.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply device for an electric discharge machine, which has a simple structure and has improved machining performance in finishing.

It is another object of the present invention to provide a power supply device for an electric discharge machine capable of electrically disconnecting a main power supply and an auxiliary power supply without an electromagnetic switch.

[0018]

In order to solve the above-mentioned problems, a power supply device for an electric discharge machine according to the present invention comprises an auxiliary power supply between a machining electrode and a work electrode via a first power supply line. And a main power supply is connected between the poles via a second power supply line. During roughing, after a discharge is generated between the poles by a voltage supplied from the auxiliary power supply, a main current is supplied from the main power supply. In the power supply device of the electric discharge machine, which performs the machining by supplying the electric current supplied from the auxiliary power supply during the finish machining, the second power supply line and one of the machining electrode or the work electrode And a reverse bias power supply for supplying a predetermined reverse bias voltage to the diode, the diode being configured to prevent a current from flowing from the auxiliary power supply to the main power supply.

In the power supply device for an electric discharge machine according to the present invention, the auxiliary power supply is connected between the machining electrode and the work electrode via the first power supply line, and the main power supply connects the second power supply line. Is connected between the poles, and during roughing, after a discharge is generated between the poles by a voltage supplied from the auxiliary power supply, a main current is supplied from the main power supply to perform processing, and during finishing processing, In a power supply device for an electric discharge machine that performs machining by a current supplied from the auxiliary power supply, the power supply device is connected between the second power supply line and one of the machining electrode or the work electrode, and A diode for preventing current from flowing into the main power supply, a reverse bias power supply for supplying a predetermined reverse bias voltage to the diode, a voltage from the auxiliary power supply connected between the auxiliary power supply and the pole; Constructed and a polarity switching means for supplying between the electrode and reverse polarity.

[0020]

According to the present invention, the second power supply for supplying the main power between the poles is provided.
A diode is connected between the supply line and one of the electrodes, and a predetermined reverse bias voltage is supplied to the diode from a reverse bias power supply to reduce the stray capacitance of the second supply line. Significantly reduce impact. Further, when a diode is connected between the second supply line that supplies the main power supply between the electrodes and the electrode, the polarity of the voltage from the auxiliary power supply is inverted, and the polarity is supplied between the electrodes to perform finishing processing. By supplying a predetermined reverse bias voltage to the diode from a reverse bias power supply, the effect of the stray capacitance of the second supply line is reduced, and the electric power of the main power supply and the auxiliary power supply is eliminated without an electromagnetic switch. Enables disconnection.

[0021]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration circuit diagram showing an embodiment of a power supply device for an electric discharge machine according to the present invention.

In the present embodiment, the reverse bias voltage is applied from the DC power supply Vb to the backflow preventing diode D without using the electromagnetic switch K shown in FIG. 5 to significantly reduce the effect of the stray capacitance of the power supply line W2. It is to reduce.

When the transistor Tr1 is turned on, power from the auxiliary power supply Vs is supplied between the electrode E and the work W via the power supply line (cable) W1 and the resistor R1, and discharge occurs between the electrodes. Thereafter, the transistor Tr2 is turned on to supply power from the main power supply VM to the gap between the poles via the resistor R2, the power supply line W2, and the diode D, thereby performing rough machining. ON / OF of transistors Tr1 and Tr2
The F control is performed by a pulse control sequence output from the pulse control unit 1. The occurrence of discharge between the electrodes is detected by the discharge detection unit 2 based on a voltage drop between the electrodes supplied via the detection resistor Rd. A detection signal of the occurrence of discharge by the discharge detection unit 2 is sent to the pulse control unit 1, and the transistor T
The above-described switching sequence control of r1 and Tr2 is performed.

The diode D is connected between the power supply line and the electrode, and prevents a flow from the auxiliary power supply Vs to the main power supply.

In this embodiment, a series circuit of an interference preventing diode Db, a resistor Rb and a variable power supply Vb is connected in parallel with the diode D, and the diode D is reverse-biased by the power supply Vb.

The power from the main power supply VM is not supplied, and only the power from the auxiliary power supply Vs is supplied between the poles.
When finishing using only the current from the auxiliary power supply without using the current from the main power supply, the diode D
To apply a reverse bias voltage. At this time, the reverse bias voltage to be supplied is set to be equal to or higher than the voltage of the auxiliary power supply Vs. By doing so, the junction capacitance of the diode D can be reduced, and the effect of the stray capacitance of the power supply line W2 can be significantly reduced.

FIG. 2 shows the relationship between the junction capacitance CJ of a general diode and the reverse bias voltage VR applied to the diode. As the reverse bias voltage VR increases, the junction capacitance significantly decreases. Understand.

In the circuit of FIG. 1, since the stray capacitance C2 of the power supply line W2 and the junction capacitance CJ of the diode D are connected in series, the combined series capacitance is (C2.CJ) / (C2 + CJ). ) = CJ / (1 + CJ / C2), and if the junction capacitance CJ of the diode D is sufficiently smaller than the stray capacitance C2 of the power supply line W2, the combined capacitance becomes substantially equal to the junction capacitance CJ of the diode. The effect of the stray capacitance C2 of the supply line can be almost eliminated. In fact, C2
With respect to several thousand picofarads, the junction capacitance CJ can be reduced to about one hundred picofarads by appropriately reverse-biasing the diode D, and the effect of the stray capacitance C2 can be significantly reduced. In FIG. 1, C1 is a power supply line W1.
Shows the stray capacitance of

FIG. 3 is a circuit diagram showing another embodiment of the power supply device for the electric discharge machine according to the present invention. In the present embodiment, FIG.
Although the basic principle is the same as that of the embodiment shown in FIG. 1, a power supply Vb for applying a reverse bias voltage to the diode D is provided between the electrode E and the work W and a detection resistor in the discharge detection unit 2. Supply. That is, the + side of the power supply Vb is connected to the cathode of the diode D via the resistor R2, the-side of the power supply Vb is connected to the work W, and the diode D is reverse biased to set the junction capacitance to a small value. In addition, the effect of the stray capacitance of the power supply line W2 is reduced.

In the above embodiment, the power supply Vb for reverse-biasing the diode D may be a fixed voltage power supply in which a voltage for obtaining a necessary junction capacitance is set in advance, or a usage environment such as the characteristics of the diode D. It is also possible to use a variable voltage power supply so as to supply a reverse bias voltage optimal for the condition.

According to the above-described embodiment, the influence of the stray capacitance of the power supply line for supplying the main power can be extremely reduced, so that the finished surface roughness of 0.5 μm Rmax or less can be processed. In addition, since the power supply Vb for reverse-biasing the diode D does not require a current to flow, a small-capacity power supply may be used, and the cost is much lower than using a conventional electromagnetic switch. Further, since the impedance of the output cable of the main power supply can be reduced, there is an effect that the roughing performance is not impaired.

Next, another embodiment of the present invention will be described. In this embodiment, when performing finishing by polarity reversal,
A power supply device for a wire electric discharge machine that enables electrical disconnection between a main power supply and an auxiliary power supply without an electromagnetic switch.

FIG. 4 is a configuration circuit diagram of the present embodiment. In the present embodiment, the auxiliary power supply Vs is
Is supplied between the wire electrode WE and the work W via the relay RL, and after reaching a discharge state, the power from the main power supply VM is supplied between the work W and the pole of the wire electrode WE, and rough machining is performed. Done. The power supply sequence is controlled by pulses supplied from the pulse control unit 1 to the transistors Tr1 and Tr2. Further, similarly to the above, the discharge state between the gaps is detected by the gap detection section 2, and a detection signal is supplied to the pulse control section 1.

At the time of final finishing, the polarity is reversed by switching the relay RL. At this time, a power supply Vb for reversely biasing the diode D is provided to disconnect the main power supply VM from the auxiliary power supply Vs. That is, the anode of the reverse current blocking diode D is connected to the power supply terminal S, the cathode is connected to the + side of the power supply Vb via the resistor Rb, and the-side is connected to the work. Here, when the power supply voltage Vb is set higher than Vs, the diode D is reverse-biased, so that both power supplies can be electrically disconnected. As described with reference to FIGS. 1 and 2, when the reverse bias voltage is increased, the junction capacitance of the diode D is reduced, so that the influence of the large stray capacitance of the supply cable of the main power supply VM can be significantly reduced. At this time, Vb
It is clear that interference between the two power supplies is prevented even when is equal to Vs.

According to the present embodiment, similarly to the embodiment shown in FIGS. 1 and 2, the effect of the stray capacitance of the main power supply line is reduced, and the polarity is inverted so that the auxiliary power is supplied between the poles. Therefore, there is no need to install a large relay, and the main power supply and the auxiliary power supply can be electrically separated.

[0036]

As described above, according to the power supply device for an electric discharge machine according to the present invention, the influence of the stray capacitance of the power supply line for supplying the main power between the poles can be significantly reduced with a simple configuration. In addition, the processing accuracy can be greatly improved.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining the operation of the embodiment of FIG. 1;

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

FIG. 4 is a configuration circuit diagram showing one embodiment of a power supply device of the wire electric discharge machine according to the present invention.

FIG. 5 is a configuration circuit diagram of a power supply device of a conventional electric discharge machine.

FIG. 6 is a configuration circuit diagram of a power supply device of a conventional wire electric discharge machine.

[Explanation of symbols]

 Reference Signs List 1 pulse control unit 2 pole detection unit D diode VM main power supply VS auxiliary power supply Vb reverse bias power supply W1 first power supply line W2 second power supply line

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23H 1/02

Claims (5)

(57) [Claims] An auxiliary power supply is connected between a pole between a machining electrode and a work electrode via a first power supply line, and a main power supply is connected between the poles via a second power supply line. At the time, after the discharge occurs between the poles by the voltage supplied from the auxiliary power supply, the main power is supplied from the main power supply to perform the processing, and at the time of finishing processing, the processing is performed by the current supplied from the auxiliary power supply. A power supply device for an electric discharge machine, wherein the diode is connected between the second power supply line and one of the machining electrode or the work electrode, and prevents a current from flowing from the auxiliary power supply to the main power supply. And a reverse bias power supply for supplying a predetermined reverse bias voltage to the diode. 2. A power supply device for an electric discharge machine according to claim 1, wherein a voltage of said reverse bias power supply is higher than a voltage of said auxiliary power supply. 3. The power supply device for an electric discharge machine according to claim 1, wherein said reverse bias power supply is a variable voltage power supply. 4. An auxiliary power supply is connected between the working electrode and the work electrode via a first power supply line, and a main power supply is connected between the working electrode and the work electrode via a second power supply line. At the time, after the discharge occurs between the poles by the voltage supplied from the auxiliary power supply, the main power is supplied from the main power supply to perform the processing, and at the time of finishing processing, the processing is performed by the current supplied from the auxiliary power supply. A power supply device for an electric discharge machine, wherein the diode is connected between the second power supply line and one of the machining electrode or the work electrode, and prevents a current from flowing from the auxiliary power supply to the main power supply. A reverse bias power supply for supplying a predetermined reverse bias voltage to the diode; a polarity switch connected between the auxiliary power supply and the pole, for inverting the polarity of the voltage from the auxiliary power supply and supplying the polarity between the poles; Discharge machine of a power supply device and characterized in that it comprises a recombinant means. 5. The power supply device for a wire electric discharge machine according to claim 4, wherein a voltage of the reverse bias power supply is higher than a voltage of the auxiliary power supply.