Discharge pulse generator

Details Discharge pulse generator Discharge pulse generator

2001-12-27

2003-05-20

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Pulsating or a.c. supply

C315S248000, C219S069130

Reexamination Certificate

active

06566823

ABSTRACT:

TECHNICAL FIELD
This invention relates to improvement in a discharge pulse generator used with an electric discharge machine, a laser oscillator, a particle accelerator, etc., for example, for supplying power between a pair of electrodes.
BACKGROUND OF THE INVENTION
FIG. 17
is a circuit diagram to show the configuration of a discharge pulse generator in a related art and shows an example of a discharge pulse generator of an electric discharge machine. In
FIG. 17
, numeral
1
denotes an electrode, numeral
2
denotes a workpiece, numeral
3
denotes a DC power supply, numeral
4
denotes a resistor, numeral
5
denotes a capacitor (capacitance C), and L denotes an inductance existing in wiring. A charging circuit made up of the DC power supply
3
and the resistor
4
is connected to the capacitor
5
. The electrode
1
and the workpiece
2
are immersed in a work liquid such as water or oil (not shown).
When the voltage of the capacitor
5
is raised by the above-mentioned charging circuit and the work liquid in the gap between poles of the electrode
1
and the workpiece
2
electrically break down, energy stored in the capacitor
5
flows into between the poles of the electrode
1
and the workpiece
2
. Discharge current Ig at this time becomes a damped vibration waveform caused by LC oscillation, as shown in FIG.
18
.
In
FIG. 18
, t denotes a time, first current i
1
is a current of a half cycle of the resonance frequency of LC oscillation, next current i
2
is a current of the opposite polarity to that of the current i
1
, and current i
3
is a current of the opposite polarity to that of the current i
2
; such several vibration currents flow into between the above-mentioned poles. The pulse width of the first current i
1
is a short pulse (T
1
), but the pulse width where the several vibration currents stop becomes considerably long (T) and discharge continues to occur meanwhile, forming one discharge pulse as a whole. If electric discharge machining is executed using such a discharge pulse generator in the related art, machining based on the pulse T having the comparatively long pulse width rather than machining based on the short pulse T
1
is executed and thus it is difficult to finely work on the workpiece
2
; this is a problem.
In the discharge pulse generator in the related art as in
FIG. 17
, bipolar discharge current flows as in FIG.
18
. Thus, if setting is made so that electrode consumption lessens in one of the polarities, current always flows also into the direction in which electrode consumption is much, and the electrode consumption grows and thus it becomes difficult to work with high accuracy; this is a problem.
FIG. 19
is a circuit diagram to show the configuration of another discharge pulse generator in a related art disclosed in Japanese Patent Laid-Open No.266133/1995. In the figure, numeral
1
denotes an electrode, numeral
2
denotes a workpiece, numeral
3
denotes a DC power supply, numeral
4
denotes a resistor, numeral
6
denotes a transistor, numeral
7
denotes control means, numerals
8
a
and
8
b
denote coaxial cables each with one end side open (characteristic impedances are Z
0
a
and Z
0
b
respectively), and numerals
9
a
and
9
b
denote matching impedances connected to the coaxial cables
8
a
and
8
b
(impedances are Za and Zb respectively).
FIG. 20
shows an example of discharge current Ig between poles of the electrode
1
and the workpiece
2
in the discharge pulse generator in the related art in FIG.
19
. FIG.
20
(
a
) shows the discharge current Ig when the impedances Za and Zb are equal to the characteristic impedances Z
0
a
and Z
0
b,
and FIG.
20
(
b
) shows the discharge current Ig when the impedances Za and Zb are halves the characteristic impedances Z
0
a
and Z
0
b
respectively. In the figure, t denotes a time. If the matching impedances are equal to the characteristic impedances as in FIG.
20
(
a
), the discharge current Ig becomes a pulse-like current waveform with no vibration, but if the matching impedances differ from the characteristic impedances as in FIG.
20
(
b
), the discharge current becomes a vibration-like current waveform as the discharge current in the discharge pulse generator in FIG.
18
.
That is, the discharge pulse generator in the related art in
FIG. 19
can provide a pulse-like discharge current waveform with no vibration only if the matching impedances are equal to the characteristic impedances of the coaxial cables, and therefore the peak value of the discharge current lowers to a half as the matching impedances are connected; this is a problem.
Since the matching impedances are fixed, if the voltage of the DC power supply
3
is constant, the peak value of the discharge current pulse cannot be changed; this is a problem.
DISCLOSURE OF THE INVENTION
The invention is intended for solving the problems as described above and it is an object of the invention to provide a discharge pulse generator that can raise the peak value of a discharge current pulse.
It is an object of the invention to provide a discharge pulse generator for making it possible to set the peak value of a discharge current pulse to any desired value.
It is an object of the invention to provide a discharge pulse generator fitted for micromachining and capable of decreasing electrode consumption if the discharge pulse generator is used for electric discharge machining.
According to the invention, there is provided a discharge pulse generator for supplying power between a pair of electrodes, comprising at least one distribution constant line of a predetermined length being connected at one termination to the electrodes, charging means being connected to the above-mentioned distribution constant line for charging the capacitance of the above-mentioned distribution constant line, rectification means being connected to an opposite termination of the above-mentioned distribution constant line in a direction in which no current flows relative to voltage of the above-mentioned charging means, and a resistor being connected in series to the above-mentioned rectification means and having a resistance value equal to the characteristic impedance of the above-mentioned distribution constant line.
According to the invention, there is provided a discharge pulse generator for supplying power between a pair of electrodes, comprising at least one distribution constant line of a predetermined length being connected at one termination to the electrode, charging means being connected to the above-mentioned distribution constant line for charging the capacitance of the above-mentioned distribution constant line, rectification means being connected to an opposite termination of the above-mentioned distribution constant line in a direction in which no current flows relative to voltage of the above-mentioned charging means, a resistor being connected in series to the above-mentioned rectification means and having a resistance value equal to the characteristic impedance of the above-mentioned distribution constant line, and a constant voltage source being connected in series to the above-mentioned rectification means.
According to the invention, there is provided a discharge pulse generator for supplying power between a pair of electrodes, comprising at least one distribution constant line of a predetermined length being connected at one termination to the electrode, charging means being connected to the above-mentioned distribution constant line for charging the capacitance of the above-mentioned distribution constant line, rectification means being connected to an opposite termination of the above-mentioned distribution constant line in a direction in which no current flows relative to voltage of the above-mentioned charging means, a resistor being connected in series to the above-mentioned rectification means and having a resistance value equal to the characteristic impedance of the above-mentioned distribution constant line, voltage detection means for detecting voltage of the above-mentioned resistor, voltage polarity determinatio

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