Electric heating – Metal heating – Cutting or disintegrating
Patent
1989-07-03
1990-10-30
Pellinen, A. D.
Electric heating
Metal heating
Cutting or disintegrating
219 6918, 323271, B23H 102
Patent
active
049670549
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an electric-discharge-machining power source for use in an electric discharge machine, and more particularly, to a transistor type electric-discharge-machining power source which is capable of increasing a machining speed.
In order to increase a machining speed in electric discharge machining, it is desirable to use machining pulses which are large in peak value but small in pulse width. Conventionally, a capacitor type electric-discharge-machining power source is employed so as to generate machining pulses which satisfy the aforementioned requirement. Recently, a transistor type electric-discharge-machining power source has been employed which has an electric current return circuit for protecting a transistor from a surge current (which is generated attributable to energy, accumulated in a stray inductance in a discharge circuit of the electric-discharge-machining power source) when the transistor is turned off.
However, it is difficult to generate machining pulses having a large peak value and a small pulse width in the transistor type electric-discharge-machining power source since restrictions are found in increasing a power source voltage and decreasing a stray inductance.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an electric-discharge-machining power source in an electric discharge machine, which is capable of generating machining pulses having a large peak value and a small pulse width, thereby attaining an improved machining speed.
In order to achieve the above-mentioned object, an electric-discharge-machining power source of the present invention comprises: electric power source means; switching means for permitting and prohibiting an application of an electric power voltage from the electric power source means in between a workpiece and a tool electrode; a capacitor arranged to be charged up to a voltage beyond the electric power voltage; and a return circuit for returning a return electric current to the capacitor to charge the same capacitor. The return electric current is generated due to presence of a stray inductance of a discharge circuit when the application of the electric power voltage is prohibited by the switching means.
As mentioned above, according to the present invention, a return electric current (which is generated due to the presence of energy accumulated in the stray inductance of the discharge circuit of the electric-discharge-machining power source when the application of the electric power voltage in between the workpiece and the tool electrode is prohibited by the switching means) is returned to the capacitor so as to charge the same capacitor up to a voltage beyond the electric power voltage. Accordingly, it is possible to cause a return electric current to fall rapidly, and generate machining pulses having a large peak value and a small pulse width, so that an improved machining speed is attained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram of an essential part of an electric-discharge-machining power source according to an embodiment of the present invention;
FIGS. 2A to 2F are timing diagrams of a relationship among various signals appearing at various portions of FIG. 1;
FIG. 3 is a waveform diagram of an electric discharge current in the arrangement of FIG. 1 in a comparison to that of a conventional arrangement;
FIG. 4 is a circuit diagram of a conventional electric-discharge-machining power source; and
FIGS. 5A and 5B are timing diagrams of a relationship between a pulse train for ON/OFF control of a transistor and an electric discharge current in the arrangement of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Prior to an explanation of the present invention being given, a conventional transistor type electric-discharge-machining power source, having an electric current return circuit for transistor protection, will be explained with reference to FIGS. 4 and 5.
A machining power source shown in FIG. 4 comprises transistors T1 and T2 each havin
Izumiya Syunzo
Obara Haruki
Evans Geoffrey S.
Fanuc Ltd
Pellinen A. D.
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