JPS60180719A - Discharge voltage detector - Google Patents

Abstract

PURPOSE:To precisely measure the gap voltage even when discharge-machining at a large current by inputting the voltage generated across a detection coil at the rise and fall of a discharge current into a voltage dividing circuit and eliminating the effect on the measured voltage by stray inductance. CONSTITUTION:When voltage is applied across a work W and an electrode P, high voltage due to the gap voltage is generated across terminals T1, T2 before a discharge occurs, the gap voltage drops after a discharge current I1 flows, and the voltage across the terminals T1, T2 drops. In this case, the voltage proportional to the differential of the discharge current I1 is generated across a coil C, this voltage is divided by resistors R3, R2 and is reversely applied across the terminal T1, T2 so as to eliminate the effect of stray inductance L. As a result, the voltage generated by the stray inductance L is offset by the voltage generated by the coil C at the rise and fall of the discharge current, thus the precise gap voltage can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application and Prior Art The present invention relates to a discharge voltage detection method for measuring and detecting the voltage between an electrode and a workpiece in electrical discharge machining.

To measure the gap voltage between the electrode and workpiece of an electric discharge machine, it is sufficient to directly measure the voltage between The lead wires for this purpose become long, and as a result, stray inductance inevitably occurs. For this reason, when performing electric discharge machining by passing a large current,
When the rise and fall of this current becomes large and the influence of the above-mentioned floating inductance appears, a phenomenon occurs when the gap voltage between the electrode and the workpiece cannot be determined accurately.

For example, Fig. 1 shows a conventional detection device that detects and measures the gap voltage between an electrode and a workpiece in electrical discharge machining.
E is the power supply section, P is the electrode, W is the workpiece, Ri and R2 are the resistances, and . The voltage is divided by resistors R1 and R2 of a voltage dividing circuit, and the voltage is applied to the terminal T I .

The gap voltage measurement voltage Va-t- is obtained from T2.

When attempting to detect and measure the gap voltage during electrical discharge machining by flowing a large discharge current 11 through the electrode P and the workpiece Wfli using such a device, the rise and fall of the discharge current I are large, so floating Due to the influence of the inductance L, an accurate measurement voltage waveform Vc of the gap voltage cannot be obtained. Figure 2 shows an explanatory diagram of gap voltage measurement when a large current is passed through the
FIG. 2 (2) shows the waveform of the discharge current 11, and in FIG. 21 (3), a is the measured voltage waveform V of the gap voltage generated between the terminals T1 and 12.
Indicates o. Therefore, as shown in FIG. 2 (1), a voltage is applied between the work W and the electrode 1, and as shown in FIG. 2 (2), a discharge current 11 flows between the work W and the electrode 1. , the measured voltage waveform Vo between the terminals T1 and T12 is as shown by a in FIG. 2 (3). However, work W
A voltage is applied to the gap between the electrode P and the electrode P, and the gap voltage is high before the discharge starts, and when the discharge starts, the gap voltage decreases. Therefore, the waveform of the actual gap voltage is as shown in FIG. 2 (3). The waveform must be as shown in b. However, as mentioned above, the influence of stray inductance appears at the rise and fall of the discharge current, and the terminals T, 1. T
The gap voltage waveform measured between the two ends up being a waveform like a in FIG. 2 (3), making it impossible to obtain an accurate gap voltage.

As described above, the conventional discharge voltage detection device has a drawback in that it cannot accurately detect and measure the gap voltage, especially when the discharge current becomes large.

OBJECTS OF THE INVENTION An object of the present invention is to improve the drawbacks of the prior art and to provide a discharge voltage detection device that can accurately detect and measure a gap voltage even when a large current is applied and electrical discharge machining is performed.

Structure of the Invention The present invention provides a group N voltage detection device for measuring the voltage of an electrical discharge machining device via a voltage dividing circuit, in which a coil for detecting a discharge current is provided in the discharge circuit, and a coil for detecting the discharge current is detected at the rise and fall of the discharge current. The voltage generated in the coil is input to the voltage divider circuit, and a stray inductance in the discharge circuit eliminates the influence of the voltage generated by the rise and fall of the discharge current on the measured voltage. This is a discharge voltage detection device.

Embodiment FIG. 3 shows an embodiment of the present invention. Components having the same configuration as the conventional example shown in FIG. A coil C is provided to detect the discharge current 11, and the voltage generated when the coil C detects the discharge current 11 is divided by a resistor R3 and a resistor R2 of a voltage divider circuit that divides the gap voltage, thereby eliminating the influence of the stray inductance L. Connect to eliminate.

Discharge voltage detection in such a discharge voltage detection device will be explained with reference to the discharge voltage detection explanatory diagram of FIG. 4.

Figure 4 (1) shows the workpiece W and electrode 1 as in Figure 2 (1).
This shows the R1 question where a voltage is applied between. (2) shows the discharge current 11, (3) shows the measured voltage waveform of the gap voltage measured between terminals TI and T2, and (4) shows the voltage waveform of the coil C generated by the discharge current 11. , First, when a voltage is applied between the workpiece W and the electrode 1 as shown in FIG. 4 (1), there is a gap between the terminals T1 and T12 as shown in FIG. 4 (3) before discharge occurs. A high voltage is generated due to the voltage. Then, as shown in Figure 3 (2), when discharge occurs and discharge current ■1 flows, the gap voltage resists, and the voltage between terminals T1 and T12 begins to decrease as shown in Figure 4 (3). . At this time, the differential (dot/
dt) is generated, and this voltage is connected to the resistor R
3 and R2, and the polarity is reversed so that the influence of the stray inductance 1- disappears, and the voltage is generated between the terminals T1 and T12 as shown in FIG. 4 (4). As a result, the voltage generated by the floating inductor lath L (a in Figure 2 (3)
and b) is erased by the voltage generated by the coil C at the rise and fall of the discharge current, making it possible to obtain an accurate gap voltage as shown in FIG. 4 (3). Note that by making the value of resistor R3 sufficiently large, it can be made so that it does not affect the voltage division ratio of resistors R1 and R2 in the voltage divider circuit. This is the value determined by

Effects of the Invention The present invention has a simple configuration that eliminates the influence of the stray inductance of the discharge circuit on the measurement voltage of the gap voltage. Therefore, even in electrical discharge machining using a large current, the gap voltage can be detected accurately and the electrical discharge machining process is improved. This can improve accuracy and cutting speed.

[Brief explanation of drawings]

Fig. 1 is a conventional discharge-voltage detection device, Fig. 2 is an explanatory diagram of gap voltage measurement related to the same discharge voltage detection device, Fig. 3 is an embodiment of the present invention, and Fig. 4 is FIG. 2 is an explanatory diagram of gap voltage measurement in the same example. P...electrode, W...work, D...segment circuit, C
... Coil, L... Stray inductance, E...
Power supply section, R'l, R2, R3...resistance. (1 idiot) Figure 1 Figure 2

Claims (1)

[Claims] In a discharge voltage detection device that measures the voltage of an electrical discharge machining device via a voltage dividing circuit, a coil for detecting a discharge current is provided in the discharge circuit, and the voltage generated in the coil at the rise and fall of the discharge current is detected as described above. A discharge voltage detection device, characterized in that the influence of the voltage generated by the rise and fall of the discharge current on the measured voltage is erased by inputting it into a voltage dividing circuit and caused by a stray inductance in the discharge circuit.