JPH0585286B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an electrical conductivity measuring device, and particularly to an electrical conductivity measuring device for an electric discharge machine.

"Prior Art" Conventionally, this type of device has an electrode 1a placed in a liquid to be measured 1b as shown in FIG.
An alternating current voltage was applied from c, the current was measured using an alternating current meter 1d, and the conductivity was determined based on the value of the current. However, this method requires the preparation of an alternating current power source, and since the measured value is obtained as an alternating current value, it has the drawback that it cannot be directly inputted into a control device of, for example, an electric discharge machine. Note that the measurement of electrical conductivity must be performed using alternating current in order to suppress polarization effects.

"Problems to be Solved by the Invention" The present invention has been made in view of the above problems, and is capable of measuring electrical conductivity without requiring an AC power source, and also provides a control device for an electric discharge machine. It is an object of the present invention to provide a conductivity measuring device that can obtain measured values in a form that allows the measured conductivity to be directly input into the device.

"Means for Solving the Problem" According to the present invention, there is provided a measuring electrode disposed facing each other in the machining liquid, a capacitor connected in series with the measuring electrode, and a DC power source connected to the measuring electrode. a switch means for exclusively opening and closing a first path leading to a series circuit of an electrode and a capacitor and a second path parallel to the DC power source while monitoring the voltage across the capacitor; There is provided a machining fluid conductivity measuring device for an electrical discharge machine, which includes a detection means for detecting the conductivity of the machining fluid by detecting a charging/discharging time interval of the capacitor.

"Operation" According to the above configuration, a rectangular wave voltage is applied from the DC power source to the series circuit of the measuring electrode and the capacitor via the switch means, and the area of the measuring electrode and the distance between the electrodes are applied to both ends of the capacitor. , and a charging/discharging voltage with a charging/discharging time interval that changes depending on the resistance value depending on the electrical conductivity of the machining fluid and the capacitance of the capacitor, so by detecting the charging/discharging time interval, The electrical conductivity of the machining fluid can be detected.

"Example" Next, an example of the measuring device of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing the basic configuration of a measuring device according to one embodiment of the present invention, and FIG. 2 is a circuit diagram of one embodiment.

As shown in FIG. 1, the measurement electrode 2a is used to measure the liquid to be measured 2, which is the processing liquid whose conductivity is to be determined.
b is placed opposite to the machining liquid tank 2c that stores the liquid. A charging circuit is constructed in which a DC power source 2h passes through a charging switch 2d and connects to a capacitor 2f having a required capacitance via an electrode 2a. Also,
A discharge circuit is constructed from the capacitor 2f through the electrode 2a and the discharge switch 2e.
This capacitor 2f is connected to both ends of the capacitor 2f.
A terminal 2g is provided for measuring the voltage across the terminal. Although not shown in this figure, the voltage at the terminal 2g is monitored and the switch 2d,
A control circuit for opening and closing 2e is connected. The switch 2d and the switch 2e are mutually exclusive, and when one is on, the other is turned off. still,
The liquid to be measured 2b as the machining liquid is applied to a wire electrode (not shown) and a workpiece (not shown) for performing wire cut discharge using a pump (not shown).
The machining fluid is supplied to the machining gap between the machining fluid and the machining fluid tank 2c, and is then collected into the machining fluid tank 2c.

By repeating opening and closing of the switches 2d and 2e, the DC power source 2h is connected to the electrode 2.
A and the capacitor 2f are applied with a rectangular waveform voltage having a frequency that approximately corresponds to the frequency characteristics of the liquid to be measured 2b, so a current of approximately a predetermined frequency that repeatedly reverses polarity flows through the electrode 2a, and the voltage at the electrode 2a is While suppressing the polarization effect, a substantially triangular wave-shaped voltage change appears at the terminal 2g with a time interval depending on the conductivity of the liquid to be measured 2b. Since this voltage change is obtained as a ripple current, it is easy to input it to a logic circuit, for example.

In FIG. 2, the first output terminal of the logic circuit 3
OUT is connected to one of the measurement electrodes 2a forming the sensor, and the other of the measurement electrodes 2a arranged opposite to each other is connected to the non-grounded side of the capacitor 2f, and the trigger terminal TRIG of the logic circuit 3 and the threshold The terminal THRSH has been introduced. Further, the second output terminal DISCH of the logic circuit 3 is connected to the clock terminal CLK of the counter 4. The output signal of the counter 4 is introduced into a central processing unit (CPU) 5. Logic circuit 3 generates a voltage at the first output terminal OUT when the threshold terminal THRSH is below a certain potential, and when the potential of the trigger terminal TRIG exceeds a certain value, the voltage at the output terminal OUT becomes zero (≡0). It is a thing,
The second output terminal DISCH is a semiconductor integrated circuit forming a kind of flip-flop circuit that outputs a signal voltage reciprocal to the first output terminal OUT. still,
This semiconductor integrated circuit is manufactured by Signetics.
It is composed of NE555.

According to the above configuration, when power is supplied to the logic circuit 3, the threshold terminal
Since the potential of THRSH is zero, the first output terminal
A constant voltage is generated at OUT, and the capacitor 2f begins to be charged through the resistance of the liquid to be measured 2b between the electrodes 2a. When the voltage at the upper terminal 2g of the capacitor 2f reaches a predetermined value due to its charging, the voltage at the output terminal OUT disappears, and the charge in the capacitor 2f is discharged through the electrode 2a. When the potential of the terminal 2g decreases to a predetermined value due to the discharge of the capacitor 2f, a constant voltage is generated at the output terminal OUT again, and the voltage of the capacitor 2g is generated via the electrode 2a.
The capacitor 2f begins to be charged, and the capacitor 2f is similarly charged and discharged via the liquid to be measured 2b between the electrodes 2a. The charging/discharging waveform appearing on the terminal 2g is a substantially triangular waveform depending on the conductivity of the liquid to be measured 2b between the electrodes 2a.When the conductivity is high, the charging/discharging time is short, and when the conductivity is low, the charging/discharging time is short. The time is long. Also, the waveform of the output voltage at the output terminal OUT is
Similarly, it becomes a rectangular wave having a time interval depending on the electrical conductivity of the liquid to be measured 2b.

On the other hand, the waveform of the output signal voltage at the second output terminal DISCH becomes a rectangular wave having high and low potentials reciprocally with the waveform at the output terminal OUT, and is introduced into the clock terminal CLK of the counter 4. and,
The counter 4 counts pulses that increase or decrease depending on the level of conductivity of the liquid to be measured 2b at predetermined time intervals.
The CPU 5 reads this number of pulses, and depending on the number of pulses, that is, the electrical conductivity of the liquid to be measured 2b,
By turning on and off an ion exchanger (not shown), the conductivity of the liquid to be measured 2b can be controlled to a predetermined value, and the discharge circuit can be controlled.

"Effects" As described above, since the measuring device of the present invention has the above configuration, it is possible to measure the electrical conductivity of the machining fluid without requiring an AC power supply, and the measured electrical conductivity is It has excellent effects such as being able to be obtained in a form that can be directly input to the machine's control device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the basic configuration of a measuring device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of one embodiment, and FIG. 3 is a circuit diagram of a conventional device. 2a... Measuring electrode, 2b... Liquid to be measured, 2h... DC power supply, 2d... Charging switch, 2e... Discharging switch, 2f... Capacitor, 2g... Voltage output terminal, 3... Logic circuit, 4... Counter, 5... Central processing unit.

Claims (1)

[Claims] 1. A method in which a voltage is applied between a machining gap between a discharge electrode and a workpiece electrode that are moved relatively to generate a discharge through a machining fluid interposed between them. An electrical discharge machine that processes a workpiece using electrical discharge energy includes: a measuring electrode disposed facing each other in the machining fluid, a capacitor connected in series with the measuring electrode, and a DC power source connected to the measuring electrode and the capacitor. a switch means for exclusively opening and closing a first path leading to a series circuit with the DC power source and a second path parallel to the DC power source while monitoring the voltage across the capacitor; A machining fluid conductivity measuring device for an electric discharge machine, comprising: a detection means for detecting the conductivity of the machining fluid by detecting a discharge time interval.