JPH055604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an electric discharge machine in which a large number of unit parallel conducting wires adjacent to each other are used as lead wires for a capacitor discharge circuit when machining a workpiece by capacitor discharge controlled by a transistor. The present invention relates to a power supply device for electrical discharge machining that reduces the inductance of a discharge circuit by using a parallel conductive wire assembly that is made up of a set of parallel conductive wires and allows current to flow in opposite directions to the adjacent parallel conductive wires.

In a capacitor discharge circuit with transistor control, which takes advantage of the ease of control over a wide range of transistors as switching elements,
It is assumed that reducing the self-inductance value of the discharge circuit as much as possible will increase the machining speed.
Several inventions have been made. For example, JP-A-56
As shown in Japanese Patent No. 119316, various efforts have been made to reduce the inductance value of a discharge circuit using a coaxial cable, a flat or ring-shaped braided copper wire, or a flexible printed wiring board.

Furthermore, Japanese Patent Laid-Open No. 57-1617 discloses a structure in which adjacent flat electric wires are configured so that currents flow in opposite directions, and the inductance of the discharge circuit is reduced by canceling out the magnetic flux generated by the currents. It describes the inventions that were made. However, this JP-A-57-
In the invention described in Publication No. 1617, for each flat electric wire located at both ends of the laminate, since the adjacent electric wire exists only on one side, the magnetic flux generated by the current cannot be canceled out, and the magnetic flux The inductance reduction effect due to the cancellation of
Furthermore, the structure in which flat electric wires are laminated in multiple layers has a drawback that the heat dissipation effect generated by energization is poor and impedance increases as the temperature rises.

The present invention overcomes the drawbacks of the prior art mentioned above,
The object of the present invention is to provide a power supply device that has an excellent inductance reduction effect by canceling magnetic flux and also has an excellent heat dissipation effect.

In order to achieve this object, the electric discharge machining power supply device of the present invention includes a capacitor charged by a DC power source, a switching element that turns on and off the output of the capacitor to generate a voltage pulse, and a In a power supply device for electrical discharge machining, the lead wire is provided with a lead wire that applies a voltage pulse between an electrode and a workpiece, and the lead wire connects a plurality of unit conductive wires each having an insulating coating in parallel with each other and It consists of an aggregate in which the cross sections perpendicular to the axis of the conductor wires are assembled to form a closed curve shape, and a large number of unit conductors in the aggregate are divided into two groups of every other conductor, and the plurality of unit conductors belonging to each group are divided into two groups of every other conductor. Each unit conductor wire is tied at both ends of the unit conductor wire, and each bundled end is used as a connection end, and the connection end of each set on one end side of the lead wire is connected to each of the electrodes and the workpiece. The capacitor and the switching element are respectively connected to the current-carrying connection portion, and the connecting ends of each pair on the other end are connected to the terminals of the capacitor and the terminal of the switching element that are not provided for interconnection between the capacitor and the switching element. It is characterized by

Hereinafter, the present invention will be specifically explained based on the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of the device according to the present invention, FIG. 2 is an enlarged view of a part of FIG. 1,
FIG. 3 is a sectional view showing an embodiment of the lead wire according to the present invention, and FIG. 4 is a sectional view taken along the line A--A in FIG. 2.

In FIG. 1, a column 2 provided on a bed 1 is provided with an upper arm 4 and a lower arm 5 that support a wire electrode 3 and extend toward a table 9, which will be described later. A head 6 is supported at the tip of the upper arm 4 so as to be able to move up and down, and a block 7 at the bottom of the head 6 is operated by a numerical control device (not shown) to control X and Y at right angles to each other on a horizontal plane. It is supported so that it can be driven in the direction. The workpiece 8 is mounted on a clamp plate 1 on a stand 10 fixed to a table 9.
Fixed by 1. The table 9 is supported by the bed 1, and is moved on a horizontal plane in X and Y directions perpendicular to each other by a numerical control device (not shown). The wire electrode 3 passes from the feed drum 13 to the guide roller 14, and then to the pinch roller 15 and the brake roller 1, which apply brakes to give a predetermined tension to the wire electrode 3.
It is caught in 6. Then, it changes direction through a guide roller 17, contacts an energizing pin 18, and faces the workpiece 8 through a boat-shaped guide such as sapphire or a die guide 19. A switching element 30 turns on and off the output of a capacitor 29 that is charged by a DC power supply 20 between the current-carrying pin 18 and the workpiece 8.
A voltage pulse formed with off-control is applied,
Machining is performed under the injection of machining fluid 21. Used wire electrode 3 with unevenness caused by processing
is the other boat-shaped guide or die guide 22, a plurality of guide rollers 23, 24, and the guide roller 2.
The wire electrode 3 is wound around the winding drum 27 through the portion sandwiched between the update driving pinch roller 25 and the capstan 26 provided between the wire electrodes 3 and 24. A capacitor 29 as a pseudo DC power source and a transistor 30 constituting the switching element are placed on the installation part 28 of the capacitor and switching element installed close to the table 9 at a position closest to the machining gap.
A control circuit 31 is installed, which includes an oscillation circuit for controlling the pulse width, a processing condition setting circuit for setting the pulse width, rest time, peak current, etc. Among the terminals 32 and 33 of this capacitor 29, the terminal 34 connected to the terminal 32 and the current-carrying pin 18 is connected to the lead wire 3.
6 and connected to the workpiece 8 and the transistor 30 are connected by a lead wire 37. The lead wires 36 and 37 are integrally constructed by a collection of a large number of unit conducting wires, and the lead wire 38 that integrally constitutes the lead wires 36 and 37 is a cross section taken along the line A-A in FIG. As shown in FIG. 4, it consists of a large number of unit conducting wires C each consisting of a core wire A and an insulating coating B, and these many unit conducting wires are arranged parallel to each other and with the axis of the unit conducting wire as shown in FIG. A set of 36a, 36b, 36c, etc. belonging to the lead wire 36 is assembled such that the orthogonal cross sections form a closed curve shape such as an annular shape, and every other unit conductor wire has a large number of unit wires.
37a, 37b, 37c... belonging to the lead wire 37
The device is divided into two groups, a group of The lead wire 37 is connected to the terminal 32 of the capacitor 29 via the terminal 34 of the workpiece 8 and the current limiting resistor 39, and the lead wire 37 is connected to the terminal 35 of the workpiece 8 and the transistor 30.
are connected to each other.

The connecting end of the lead wire 37 on the side of the plurality of transistors 30 connects a desired number of nearby unit conductors, such as one or more unit conductors, depending on the allowable current of one unit conductor and the current flowing through one transistor 30. The items are tied together and connected to the emitter electrode of each nearby transistor 30. In this way, the collector electrodes of the transistors 30, in which the necessary number of transistors are arranged in parallel, are connected to the conductive wire 40.
is connected to the terminal 33 of the capacitor 29 via the terminal 33 of the capacitor 29.
Then, the base electrode of the transistor 30 and the control circuit 31 are connected by a conductive wire 41. capacitor 2
Coaxial cable 42 connected to terminals 32 and 33 of 9
is connected to a DC power supply 20 in the bed 1 or in a power supply box or the like provided separately from the bed 1 and column 2.

In this invention, the capacitor 29 is charged by the DC power supply 20 through the coaxial cable 42, and acts as a pseudo DC power supply provided near the processing section. This charging voltage is turned on and off by the control circuit 31.
The switching element consisting of the transistor 30 which turns off generates intermittent voltage pulses that connect the terminal 34 connected to the current-carrying pin 18 in contact with the wire electrode 3 and the workpiece 8 via the lead wires 36 and 37. The voltage is applied to the terminal 35 connected to the terminal 35. The cross-sectional shape of the lead wire 38, in which the unit conductors belonging to the two sets of lead wires 36 and 37, each consisting of a plurality of unit conductors, are arranged adjacent to each other alternately in parallel and brought together, is annular or the like as shown in FIG. By forming the closed curve shape, for example, a unit conducting wire 37a belonging to the lead wire 37 becomes a unit conducting wire 36a belonging to the lead wire 36 through which current flows in the opposite direction to the lead wire 37.
and 36b, all unit conductors are sandwiched from both sides by unit conductors through which current flows in the opposite direction to the unit conductor. In response to the magnetic flux generated by the current flowing through the conductor, a magnetic flux is generated in a direction that cancels it, and as a result, the magnetic flux generated by the current flowing through all unit conductors is canceled out, and the inductance of the discharge circuit increases. is reduced. Further, since the lead wire 38 of the present invention has a hollow tubular shape, it has an excellent heat dissipation effect and can prevent an increase in impedance due to a rise in temperature.

As described above, according to the present invention, it is possible to reduce the inductance by canceling out the magnetic flux generated by the current flowing through all the unit conductors, and it is also possible to prevent an increase in impedance due to a rise in temperature of the lead wires. By supplying machining pulses with a short discharge time and a large discharge peak current to the machining gap, machining with small machined surface roughness can be performed at high speed, and the occurrence of abnormal discharge can be prevented in wire cut electric discharge machining. This also has the effect of preventing disconnection of the wire electrode.

Also, as in the embodiment described above, the capacitor 29
By arranging the switching element 30 and the switching element 30 at a position close to the machining gap, the length of the required lead wire can be shortened, and the inductance and impedance of the discharge circuit can be further reduced. In this case, the capacitor 29 and the switching element 30
The installation position is on the side of the table 9 above the bed 1,
Any position that is always close to the machining gap, such as outside the front or rear part, on the table 9, inside the bed 1, or inside the upper arm 4, may be used.

In addition to the above-described embodiments, the present invention can be implemented with various modifications made to each part. For example, the cross-sectional shape of the lead wire 38 may be not only circular as shown in FIG. 3 but also oval or square. Any closed curved shape such as a rectangular shape with rounded portions may be used. Moreover, not only the transistor 30 but also a plurality of capacitors 29 may be used in parallel. In that case, the connection end of the lead wire 36 on the capacitor side is connected to each capacitor of each unit conducting wire belonging to the lead wire 36. A predetermined number of unit conductors located near the terminal are bundled and connected.
Also, the conductive wires 40 are connected appropriately between transistors and capacitors that are located close to each other. In addition, since the energizing pins 18 for the wire electrode 3 are usually provided on both sides of the workpiece 8 (if necessary, as energizing rollers on the side that energizes the processed wire electrode), in such a case, the terminal 3
The connecting end of the lead wire 36 connected to the terminal 4 is divided into two parts.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of this invention, and Figure 2 is the first
FIG. 3 is a cross-sectional view showing an embodiment of the lead wire according to the present invention; FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 2. . 3... Wire electrode, 8... Workpiece, 20...
DC power supply, 21... Processing fluid, 28... Capacitor, switching element installation part, 29... Capacitor, 30... Transistor, 31... Control circuit, 36, 37... Lead wire, 38... Lead wire, 40, 41...Conducting wire.

Claims (1)

[Claims] 1. A capacitor charged by a DC power source, a switching element that turns on and off the output of the capacitor to generate a voltage pulse, and applies the generated voltage pulse between an electrode and a workpiece. In the electric discharge machining power supply device comprising a lead wire, the lead wire includes a plurality of unit conductive wires each having an insulating coating, which are parallel to each other and whose cross section perpendicular to the axis of the unit conductive wire forms a closed curve shape. The unit conductor wires of the assembly are divided into two groups of every other wire, and the plurality of unit conductor wires belonging to each group are placed at both ends of the unit conductor wires. Each bundled end of the lead wire is used as a connection end, and the connection end of each pair on one end of the lead wire is connected to each current-carrying connection part of the electrode and the workpiece, and the other end A power supply device for electric discharge machining, characterized in that the connecting ends of each set of the capacitor and the switching element are respectively connected to terminals of the capacitor and terminals of the switching element that are not provided for interconnection between the capacitor and the switching element. 2. The switching element is composed of a set of a plurality of transistors, and the connecting end of the lead wire connected to each transistor terminal is a terminal of each transistor of each unit conductor wire belonging to either of the two sets. 2. The electric discharge machining power supply device according to claim 1, wherein each bundle end is a bundle of a predetermined number of unit conductive wires located near the. 3. The capacitor consists of a set of a plurality of capacitors, and the connection end of the lead wire connected to each capacitor terminal is connected to the terminal of each capacitor of each unit conductor wire belonging to either of the two sets. 2. The electric discharge machining power supply device according to claim 1, wherein each bundle end is a bundle of a predetermined number of unit conducting wires located nearby.