JPH02160418A - Electric discharge machining device - Google Patents

Abstract

PURPOSE:To easily change rising slope of interelectrode pulse current at the beginning of application of interelectrode pulse by constituting direct current pulse electric source circuits out of a machining pulse generating circuit to drivingly control by its output pulse and a function generating circuit to change the pulse duration of the output pulse of the machining pulse generating circuit. CONSTITUTION:Direct current pulse electric source circuits 12, 13, supplying the current having a rising time to the maximum value of pulse current as a pulse duration and the current having the sloping down time as a pulse dura tion, are drivingly controlled by the output pulse from a machining pulse generat ing circuit 9. Further, the pulse duration of the output pulse from the machining pulse generating circuit 9 is changed by a voltage function generating circuit 14. Hereby, the rising slope of an interelecetrode pulse current can be easily changed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an electric discharge machining apparatus that moves an electrode and a workpiece in a facing state and processes the workpiece by passing a pulse current between the electrodes. In particular, it relates to the control structure of the electrical discharge machining pulse current.

[Prior Art] As a conventional electric discharge machining apparatus of this type, for example, a technique as shown in FIGS. 5 and 6 can be cited.

FIG. 5 is a circuit configuration diagram of a conventional electric discharge machining apparatus, and FIG. 6 is a circuit configuration diagram showing its DC pulse power supply circuit.

In the figure, (1) is the electrode of the electrical discharge machining device, (2) is the workpiece, (3) is the DC voltage source, (4) is the switching element that opens and closes the DC voltage source, and (5) is the switching element ( This is a switch drive circuit that controls the on/off of 4), and operates in response to a processing pulse from the processing pulse generation circuit (6) or another switch drive circuit. (7) is a flywheel diode, (8) is a reverse current blocking diode for interelectrode current connected in series between the electrode (1) and the switching element (4) together with the beam axle (1o);
A pulsed current is passed between the electrodes.

(11) is a flywheel current absorption voltage source that absorbs the pulse current flowing back through the flywheel diode (7) when the switching element (4) is turned off. Then, the absorbed pulse current is returned to the DC voltage source (3) and reused by means such as power regeneration.

Next, the operation of the conventional electrical discharge machining apparatus configured as described above will be explained.

First, we will discuss the operation of the DC pulse power supply circuit (12) that constitutes one unit of the electrical discharge machining circuit of the electrical discharge machining device.
To explain with reference to FIG. 7 and FIG. 7, in the electrical discharge machining circuit shown in FIG. 6, the machining pulse output from the machining pulse generation circuit (6) is transmitted to the switch drive circuit (5) and turns on the switching element (4). let When the switching element (4) is turned on, the voltage (Ve) of the DC voltage source (3)
is applied between the electrode (1) and the workpiece (2) through the interelectrode current blocking diode (8) and reactor (10). Thereafter, when a discharge occurs between the electrodes, the voltage (Ve) and the arc voltage (V
a) Rising slope determined by (d/d t)! A current of = (Ve-Va)/L begins to flow.

As mentioned above, the time required for the current value to reach the predetermined maximum current value (Ip) after the current starts flowing between the electrodes (
After T), the output of the machining pulses ends. When the processing pulse ends, the switching element (4) is turned off via the switch drive circuit (5). After that, the current flow path changes from the switching element (4) side to the flywheel diode (7) side, and passes through the flywheel current absorption voltage source (11) between the workpiece (2) and the electrode (1). flows. From the time (T) when the switching element (4) is turned off, the voltage (Vs) of the flywheel current absorption voltage source (11) and the interelectrode arc voltage (Va)
The current has a falling slope (d/d t)I = -(Vs+Va)/L, which is determined by , and the current becomes "0" after a lapse of time (T). As a result, a pulse current for (2T) time flows between the electrodes. FIG. 7 shows the current waveform of the pulse current.

In addition, the pulse width (T) of the processing pulse is T=I pxL
/ (Ve-Va), and the voltage (Vs) is selected as Vs=Ve-2XVa. Also, between time (T) and time (2T),
A processing pulse with a time delay of pulse width (T) is output from the switch drive circuit (5).

In FIG. 5, a second DC pulse power supply circuit (13) having the same function as the first DC pulse power supply circuit (12) is connected in parallel between the electrodes.
This figure shows an electric discharge machining apparatus in which the machining pulse output delayed by the time (T) of the switch drive circuit (5) of FIG.

An example of the pulse current in the electric discharge machining apparatus shown in FIG. 5 will be explained with reference to FIG. 8.

First, at time "0", a machining pulse is sent from the machining pulse generation circuit (6) to the first DC pulse power supply circuit (12), and the maximum current value (Ip) is sent from the first DC pulse power supply circuit (12). , ill upstream time (T) is supplied between the electrodes. After the time (T) has elapsed, the second processing pulse delayed by the time (T) is supplied from the first DC pulse power supply circuit (12) to the second DC pulse power supply circuit (13), and the second processing pulse is delayed by the time (T). DC pulse power supply circuit (13
), the triangular current is simultaneously supplied between the electrodes. Therefore, during the period from time (T) to time (2T), the pulse current actually passed between the electrodes is at the maximum current value (Ip
) will be maintained.

As a result, the pulse current has a rising period up to the maximum current value (Ip) until time (T), and a rise period from time (T) to time (2T).
) for a certain period of maximum current value (Ip), time (2
T) to time (3T), the maximum current value (Ip)
It becomes a trapezoidal waveform with a falling period up to 0''.

The pulse current in Fig. 9 is the same as the pulse current in Fig. 8 mentioned above (
The waveform is continuous N) times, and the pulse width is (2N+1)X
There is a waiting time. At this time, the processing pulse generation circuit (6) sends the processing pulse to the first DC pulse power supply circuit (12) for the first time, and then sends the processing pulse to the second DC pulse power supply circuit (13).
The processing pulses are repeatedly sent to the first DC pulse power supply circuit (12) until the time-delayed processing pulses are received (N) times. This processing pulse (21
) and (22) are output from the machining pulse generation circuit (6) illustrated in FIG. That is, AND gates (19a) and (19b) are generated from a clock with a period (2T) generated from the clock generator (16) and a processing pulse signal generated from the processing pulse signal generator (15).
This is the processing pulse created by taking the logical product.

In addition, (17) in FIG. 11 is a buffer gate, (18)
is an inverter gate.

[Problems to be Solved by the Invention] By the way, the electrode wear ratio, which is one of the indicators representing the machining performance of an electrical discharge machining device, is as shown in the characteristic diagram of FIG.
It depends on the magnitude of the initial rising slope of the interelectrode pulse current. However, in the conventional electric discharge machining apparatus shown in Fig. 5, when trying to improve the electrode wear ratio by changing the rising slope of the pulse current between the electrodes, the voltage (Ve) of the DC voltage source (3) or the glue of the accelerator (10) It is difficult to improve the electrode consumption ratio because it is necessary to change the processing circuit constant of the actance value (L), which makes the entire device expensive.

Therefore, it is an object of the present invention to provide an electric discharge machining apparatus that can easily change the rising slope of the inter-electrode pulse current and improve the electrode wear ratio among machining characteristics.

[Means for Solving the Problems] The electric discharge machining apparatus according to the present invention uses a DC pulse power supply circuit that supplies a current whose pulse width is the rise time and fall time to the maximum current value of the pulse current to generate machining pulses. The drive is controlled by the output pulse of the circuit, and the pulse width of the output pulse of the machining pulse generation circuit is changed by the function generation circuit.

[Function] In this invention, the pulse width of the inter-electrode pulse current applied by the DC pulse power supply circuit can be changed in the function generating circuit at the initial stage of application of the inter-electrode pulse, and the pulse width of the pulse current applied alternately can be changed over time. It can change over time. Thereby, the rising slope of the interelectrode pulse current can be easily changed.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a circuit configuration diagram of an electric discharge machining apparatus according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing details of the machining pulse generation circuit, and FIG. 3 is a circuit configuration diagram showing details of the voltage function generation circuit. It is a diagram. Note that in the drawings, the same reference numerals and symbols as those in the conventional example shown in FIG. 5 indicate parts that are the same as or correspond to the components in the conventional example described above, and thus redundant explanation will be omitted here.

In FIG. 1, (9) is a processing pulse generation circuit,
A voltage signal (24) is received from a voltage function generation circuit (14) used as a function generation circuit in this embodiment, and a machining pulse (21) is sent to the first electric discharge machining circuit and a machining pulse is applied to the second electric discharge machining circuit. It outputs a pulse (22) and also outputs a processing pulse signal (23) that notifies the voltage function generation circuit (14) of the output timing of the voltage signal (24). In the figure, the DC pulse power supply circuits (12) and (13) are constructed in the same manner as the conventional electric discharge machining apparatus shown in FIG. 5 described above, so their explanation will be omitted here.

Next, the processing pulse generation circuit (9) will be described in detail.

In FIG. 2, (15) is a generator for processing pulse signals (23), and (20) is a voltage/frequency converter such as a voltage controlled oscillator (VCO). The voltage signal (24) is the voltage/
The frequency is converted by the frequency converter (20) as a clock, and the buffer gate (17) and the AND gate (1
9a) to the first electrical discharge machining circuit (2).
1), which passes through the inverter gate (18) and the AND gate (19b) and becomes a machining pulse (22) to the second electrical discharge machining circuit.

Furthermore, to explain the voltage function generation circuit (14) in detail, in FIG. 3, (23) is a processing pulse signal, and the buffer gate (26) and the inverter gate (
27) via the analog switch (25a) and (2
5b). (28a), (28b
) and (28c) are resistors, (29) are capacitors,
(30) is a diode, which is an element that generates a voltage signal (24) from a reference voltage source (31).

Next, the operation of the electrical discharge machining apparatus of this embodiment configured as described above will be explained.

First, in the voltage function generation circuit (14) shown in FIG. 3, when the processing pulse signal (23) is at "L" level,
One analog switch (25a) is off, and the other analog switch (25b) is on. The output voltage of the voltage signal (24) at this time is a constant set value (Vp) obtained by dividing the voltage (Vr) of the reference voltage source (31) by the resistors (28b) and (28c). . After this,
Electric discharge occurs between the electrodes, and the machining pulse signal (23) becomes 'L'.
” level to “H# level,” one analog switch (25a) is turned on, the other analog switch (25b) is turned off, and the reference voltage source (31
) voltage (Vr) is the voltage (Vr) of the resistor (28a) and capacitor (29
) and a diode (30) to the voltage signal (24).

Therefore, immediately after the processing pulse signal (23) changes from the "L" level to the "H" level, the voltage signal (24) becomes higher than the set value (Vp), and the capacitor (29)
The set value (Vp
). This situation is illustrated in FIG. 4 as a waveform of a voltage signal.

The voltage signal (24) is frequency-converted as a clock through the voltage/frequency converter (20) in the processing pulse generation circuit (9) in FIG. The machining pulses (21) and (22) are transmitted as a function of the frequency to the two electrical discharge machining circuits. The waveforms of the machining pulses (21) and (22) to the first and second electrical discharge machining circuits are illustrated in FIG.

The processing pulse is applied to the DC pulse power supply circuit (12) and (
13) The operation after being transmitted is similar to the operation of the conventional electric discharge machining apparatus shown in Fig. 5, but since the pulse width of the machining pulse is short at the initial stage of the inter-electrode pulse current, the current of the inter-electrode pulse current The value starts small and approaches the maximum current value (Ip) as time passes, and the rising slope changes gradually.

As described above, the electric discharge machining apparatus of the above embodiment includes a DC pulse power supply circuit (12) that supplies a current whose pulse width is the rise time and fall time of the pulse current to the maximum current value;
(13) and this DC pulse power supply circuit (12), (1
3) is connected in parallel between the electrode (1) and the workpiece (2), and a machining pulse generation circuit (9).
), means for passing a trapezoidal pulsed current between the electrodes,
and means for changing the initial rising slope of the trapezoidal pulse current between the electrodes.

Therefore, according to the electrical discharge machining apparatus of this embodiment, the rising slope of the inter-electrode pulse current can be easily changed by changing the pulse width of the pulse current at the initial stage of the inter-electrode pulse current.

Therefore, the electrode consumption ratio among machining characteristics can be improved, and the entire electrical discharge machining apparatus can be manufactured at low cost.

By the way, the DC pulse power supply circuit that supplies a current whose pulse width is the rise time and fall time to the maximum current value of the pulse current connected in parallel between the electrode and the workpiece in the above embodiment has two Although it is composed of a first DC pulse power supply circuit (12) and a second DC pulse power supply circuit (13), when implementing the present invention, more DC pulse power supply circuits are connected in parallel. It can also be applied to However, in terms of circuitry, the simplest configuration can be achieved by using the two DC pulse power supply circuits of the above embodiment.Furthermore, the DC pulse power supply circuit of the above embodiment can be driven and controlled by its output pulses. The machining pulse generation circuit operates one of the DC pulse power supply circuits using the output of the voltage/frequency converter (20) such as a voltage controlled oscillator while the generator (15) of the machining pulse signal (23) is generating the machining pulse signal (23). However, when implementing the present invention, in addition to a function generation circuit that changes the pulse width of the output pulse of the processing pulse generation circuit, the pulse width of the output pulse of the processing pulse generation circuit is changed as a result. Therefore, any processing pulse generation circuit that can output a time-division control signal may be used.

As in the above embodiment, while the generator (15) of the processing pulse signal (23) is generating, the output of the voltage/frequency converter (20) such as a voltage controlled oscillator is used to control any DC pulse power supply circuit. The circuit configuration can be simple if a voltage function generation circuit is used as a function generation circuit for changing the pulse width of the output pulse of the processing pulse generation circuit. Of course, the function generation circuit used to implement the present invention is not limited to the voltage function generation circuit.

[Effects of the Invention] As described above, in the electric discharge machining apparatus of the present invention, the pulse width is the rise time and fall time to the maximum current value of a plurality of pulse currents connected in parallel between the electrode and the workpiece. A DC pulse power supply circuit that supplies current is composed of a machining pulse generation circuit that drives and controls its output pulse, and a function generation circuit that changes the pulse width of the output pulse of the machining pulse generation circuit. The circuit can time-divisionally control the inter-electrode pulse current applied by the DC pulse power supply circuit with a predetermined pulse width, and the rising slope of the inter-electrode pulse current can be easily changed at the beginning of the inter-electrode pulse application, thereby improving the machining characteristics. The electrode consumption ratio within can be improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of an electrical discharge machining apparatus according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing details of a machining pulse generation circuit of an electrical discharge machining apparatus according to an embodiment of the invention, and FIG.
The figure is a circuit configuration diagram showing details of a voltage function generation circuit of an electric discharge machining apparatus according to an embodiment of the present invention, and FIG. 4 shows the relationship between the machining pulse and the pulse current flowing between the electrodes in the electric discharge machining apparatus of FIG. 5 is a circuit configuration diagram of a conventional electrical discharge machining device, FIG. 6 is a circuit diagram showing the DC pulse power supply circuit of a conventional electrical discharge machining device, and FIG. FIGS. 8 and 9 are waveform diagrams showing the pulse current waveform of the power supply circuit. FIGS. FIG. 11 is a characteristic diagram showing the characteristics of the electrode wear ratio, and is a circuit configuration diagram illustrating details of the machining pulse generation circuit in the electrical discharge machining apparatus of FIG. 5. In the figure, 1: electrode 2: workpiece 9: machining pulse generation circuit 12: first DC pulse power supply circuit 13: second DC pulse power supply circuit 14: voltage function generation circuit. In the drawings, the same reference numerals and the same symbols indicate the same or equivalent parts. Agent Patent attorney Masuo Daikichi and 2 others 1: Electrode Figure 2 Figure 3 Figure 8 Figure 1 Closed Figure 6 Figure 7 Figure 9 T T Haruma Jimon

Claims (1)

[Scope of Claims] A DC pulse power supply circuit that supplies a current whose pulse width is the rise time and fall time to the maximum current value of a plurality of pulse currents connected in parallel between an electrode and a workpiece; An electric discharge machining apparatus comprising: a machining pulse generation circuit that drives and controls a pulse power supply circuit using its output pulse; and a function generation circuit that changes the pulse width of the output pulse of the machining pulse generation circuit.