JPH08141846A - Inter-electrode space control device - Google Patents

Abstract

PURPOSE: To precisely control a space between consumed electrodes with extremely simple structure without using a moving device of high accuracy or complicated, advanced feedback control mechanism. CONSTITUTION: An inter-electrode space control device is provided with an energizing means 6 for energizing in the direction of reducing a space between electrodes 1, 2, and a shape memory alloy 5 with shape recovery force acting in the direction of enlarging the space at the time of being heated, and it is so constituted that a current flows to the alloy 5 according to a current flowing between the electrodes 1, 2. When the current flows between the electrodes 1, 2, the current flows also to the alloy 5, so that the alloy 5 is heated to generate shape recovery force, thus enlarging the space between the electrodes. When the space is enlarged to the fixed value or more, the current ceases to flow between the electrodes 1, 2 and to the alloy 5, so that the alloy 5 is cooled to lose shape recovery force, and the space is reduced by the energizing means 6. With the repetition of this action, the space is adjusted autonomously and precisely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode (including a workpiece) that is consumed in an electric discharge machine, an electrolytic machine, or the like.
The present invention relates to a device for controlling a gap between electrodes that controls a gap between the electrodes.

[0002]

2. Description of the Related Art In an electric discharge machining apparatus, it is necessary to adjust a distance between a work piece and an electrode with high precision as the work piece and the electrode are consumed.

[0003]

Therefore, conventionally, it was necessary to control the distance between the workpiece and the electrode by using a highly accurate moving device and a complicated advanced feedback control mechanism. The manufacturing cost was very high.

The present invention has been made in view of the above circumstances, and one of the objects of the present invention is to use an electric discharge machine or the like without using a highly accurate moving device or a complicated advanced feedback control mechanism. , With an extremely simple structure, it is possible to precisely control the interval between the consumable electrodes (including the work piece etc.), which makes it possible to reduce the manufacturing cost of the device very much and to make the device very compact. Another object of the present invention is to provide a device for controlling the gap between the electrodes.

Other objects of the invention will be apparent from the following description.

[0006]

A device for controlling a gap between electrodes according to the present invention comprises a first electrode and a second electrode which are opposed to each other with a variable gap between the electrodes. In a device in which at least one of the electrodes is consumed due to discharge occurring in the device or a current flowing between these electrodes, a device for controlling the interval between the electrodes is provided. , (1) biasing means for biasing the first electrode or / and the second electrode in a direction in which the distance between the two electrodes becomes smaller, and the first electrode or ( And) mechanically linked to the first electrode or / and the second electrode so that a shape recovery force acts on the second electrode in a direction in which the distance between the two electrodes increases. And the flow between the electrodes Is made of a shape memory alloy current flows in response to that current.

As the urging means, a spring, another shape memory alloy, a means for urging the electrode by magnetic force or gravity, or the like can be used (when the electrode is urged by gravity, the electrode itself or A member that functions as a weight that is integrated with the electrode serves as a biasing means).

If the first electrode is a work piece, this apparatus can be applied to an electric machining apparatus such as an electric discharge machining apparatus or an electrolytic machining apparatus.

[0009]

In the present invention, assuming that the first electrode and the second electrode are in contact with each other at first, when a voltage is applied between both electrodes, a current flows between both electrodes. Therefore, an electric current also flows through the shape memory alloy. Then, the shape memory alloy is heated to a certain temperature range by Joule heat,
The shape memory alloy generates a shape recovery force, and this shape recovery force acts in the direction of increasing the distance between the electrodes, so that the distance between the electrodes is widened. Therefore, when the voltage applied between both electrodes is large to some extent, a discharge occurs between both electrodes, and the first electrode and / or the second electrode is consumed. When the distance between both electrodes becomes larger than a certain amount, the discharge between both electrodes is stopped and the power supply to the shape memory alloy is also stopped, so the shape memory alloy cools and the shape recovery force decreases or disappears. The spacing between the electrodes is reduced by the biasing means. Therefore, discharge again occurs between both electrodes, and
By repeating the same operation as described above, the interval between both electrodes is autonomously and precisely adjusted. Therefore, for example, if the first electrode is a workpiece, the workpiece can be electric discharge machined.

Further, for example, the first electrode is a work piece, and a liquid serving as an electrolytic solution is interposed between the work piece and the second electrode, and the work piece and the work electrode are to some extent. When a small voltage (a direct current or a pulse voltage with a small duty ratio is applied) is applied, a current flows between the work piece and the working electrode through the electrolytic solution, so that the work piece is electrolyzed. Then, by the action of the shape memory alloy, the workpiece is electrolytically machined while the interval between the workpiece and the machining electrode is autonomously and precisely adjusted in the same manner as described above.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in the drawings. FIG. 1 shows a first embodiment of the present invention, which is an embodiment in which the present invention is applied to an electric discharge machining apparatus / electrolytic machining apparatus.
In this embodiment, the first electrode is the work piece 1 and the second electrode is the work electrode (tool) 2, and the work piece 1 is set on the working table 3. An electrode support member 4 is provided above the processing table 3, and the electrode support member 4 can be moved in the vertical direction by a coarse feed device (not shown). An upper end of a linear shape memory alloy 5 made of a Ti—Ni alloy is attached to the electrode support member 4, and a machining electrode 2 is attached to a lower end of the shape memory alloy 5.

A biasing means 6 composed of a compression coil spring is attached between the electrode supporting member 4 and the machining electrode 2, and the biasing means 6 moves the machining electrode 2 downward, in other words, the workpiece 1. The bias is applied in a direction in which the distance between the processing electrode 2 and the processing electrode 2 decreases. As a result, the shape memory alloy 5 is stretched and deformed by the spring force of the urging means 6 in a state of a temperature lower than the constant temperature section, but is heated to the constant temperature section. A shape recovery force that shrinks to return to the stored length is generated, and this shape recovery force increases above the machining electrode 2, in other words, increases the distance between the workpiece 1 and the machining electrode 2. It is designed to work in any direction.

The upper end of the shape memory alloy 5 is electrically connected to one pole of the power source 7, and the other pole of the power source 7 is electrically connected to the workpiece 1. Work piece 1 from the power supply 7
The voltage applied between the machining electrode 2 and the machining electrode 2 is a DC voltage,
The AC voltage or the pulse voltage may be used, but the pulse voltage is preferable for the reason described later.

A machining liquid 8 such as water or oil is filled between the workpiece 1 and the machining electrode 2. The working fluid 8 may be one that conducts electricity or one that is electrically insulating. Further, in the present embodiment, a machining tank for containing the machining liquid 8 is not provided, but the workpiece 1 and the machining electrode 2 are accommodated in the machining tank, and the machining liquid 8 is filled in the machining tank to process the workpiece. The machining liquid 8 may be interposed between the object 1 and the machining electrode 2. Further, the machining liquid 8 may be supplied between the workpiece 1 and the machining electrode 2 by a pump. Further, in the present invention, it is possible to perform electric discharge machining without using a machining liquid.

Next, the operation of this embodiment will be described. the first,
In the state where the workpiece 1 and the machining electrode 2 are in contact with each other, when a voltage larger than a certain level is applied between them, the workpiece 7 and the machining electrode 2 have a space between them and the shape memory alloy. Current flows through 5. Then, the shape memory alloy 5 is heated to a certain temperature range by Joule heat,
Since a shape recovery force is generated and this shape recovery force acts in the direction of increasing the gap between the workpiece 1 and the machining electrode 2, the gap between the workpiece 1 and the machining electrode 2 is widened. Therefore, an electric discharge is generated between the workpiece 1 and the machining electrode 2,
The workpiece 1 is subjected to electric discharge machining (at this time, the machining electrode 2 is also consumed). When the distance between the work piece 1 and the machining electrode 2 becomes larger than a certain value, the discharge between the two is stopped and the energization of the shape memory alloy 5 is stopped, so that the shape memory alloy 5 cools and the shape recovery force. Becomes smaller or disappears, and the spring force of the biasing means 6 reduces the gap between the workpiece 1 and the machining electrode 2. Therefore, electric discharge is again generated between the workpiece 1 and the machining electrode 2. Hereinafter, the same operation as described above is repeatedly performed, so that the workpiece 1 is subjected to electric discharge machining while the interval between the workpiece 1 and the machining electrode 2 is autonomously adjusted. Such an autonomous adjusting action of the distance between the workpiece 1 and the processing electrode 2 is considered to be performed in the atomic order, and is extremely precise.

A large movement of the machining electrode 2 can be performed by the rough feed device, but the movable range of the machining electrode 2 by the shape memory alloy 5 is very large.
No feedback mechanism or precise feed mechanism is required in the coarse feed device. Further, it is also possible to manually move the electrode support member 4 without providing the rough feed device.

As described above, according to the present invention, since the electric discharge machining apparatus can be constructed without using a highly precise moving device or a complicated and sophisticated feedback control mechanism, the manufacturing cost of the electric discharge machining apparatus can be made very low. As well as
The device can be made extremely small, and a hand-held pen-type electric discharge machining device, which has never been considered before, can be realized.

In the case of an electromagnetic actuator, the force at the beginning of movement is small. However, in the case of the shape memory alloy actuator as in the present invention, the deformed shape memory alloy is heated to generate the maximum force at the first position where the shape memory alloy starts to move to recover the shape, and the shape recovery force is increased as the deformation is recovered. Has the excellent property of gradually decreasing. Moreover, the inertia of the shape memory alloy actuator is very small. These facts also have an extremely advantageous effect on the above-described autonomous adjustment action of the distance between the workpiece 1 and the machining electrode 2, and the workpiece 1 in the air without the machining liquid 8
It is also possible to continuously generate electric discharge between the machining electrode 2 and the machining electrode 2 to perform electric discharge machining of the workpiece 1.

Further, as described above, the power source 7 is connected to the workpiece 1
The voltage applied between the machining electrode 2 and the machining electrode 2 is a DC voltage,
The AC voltage or the pulse voltage may be used, but the pulse voltage is the most stable processing state, and the processing state can be easily adjusted. When a pulse voltage is used, polarization is less likely to occur and a stable state can be maintained even for long-term energization.
The pulse frequency is usually a frequency sufficiently higher than the natural frequency of the machining electrode 2. Vibration may occur when the pulse frequency is low. The processing conditions can be changed by changing the pulse voltage and the duty ratio.

If the shape memory alloy 5 is water-cooled, forcedly cooled by a fan, or a heat sink is used,
It is possible to increase the response speed of the shape memory alloy 5 and increase the electric discharge machining speed.

The present apparatus can also be used as an electrolytic processing apparatus as follows. In this case, a liquid that acts as an electrolytic solution is used as the working liquid 8. As such a liquid, of course, a liquid that is generally used for electrolytic processing,
Other than that, for example, tap water,
Since it contains chlorine and the like, it can be practically used as an electrolytic solution. Then, a liquid such as tap water can be commonly used for both the electric discharge machining and the electrolytic machining as described above.

When used as an electrolytic processing apparatus as described above, the voltage applied between the workpiece 1 and the processing electrode 2 is a complete DC or a pulse with a large duty ratio, and the voltage is reduced to some extent. Then, the working fluid 8
When a current flows between the workpiece 1 and the machining electrode 2 via the (electrolytic solution), the surface of the workpiece 1 is electrolyzed and a current also flows through the shape memory alloy 5. Therefore, the shape memory alloy 5 is heated to a certain temperature range by Joule heat, and the shape memory alloy 5 generates a shape recovery force,
Since this shape recovery force acts in the direction of increasing the gap between the workpiece 1 and the machining electrode 2, the gap between the workpiece 1 and the machining electrode 2 is widened. As a result, the current flowing between the work piece 1 and the machining electrode 2, and hence the current flowing through the shape memory alloy 5, is reduced, so that the temperature of the shape memory alloy 5 is reduced and the shape recovery force is reduced or disappears. However, the spring force of the biasing means 6 reduces the distance between the workpiece 1 and the machining electrode 2. Therefore, the current flowing between the workpiece 1 and the machining electrode 2 again, and thus the shape memory alloy 5
The current flowing through it increases. Thereafter, the same operation as described above is repeatedly performed, and the workpiece 1 is electrolytically machined while the interval between the workpiece 1 and the machining electrode 2 is autonomously and precisely adjusted.

As described above, according to this apparatus, it is possible to perform both electric discharge machining and electrolytic machining with the same apparatus. During electrical discharge machining, a large amount of energy is intermittently applied to the machined part, so the machined surface becomes relatively rough, but if the electrolytic machining (electrolytic polishing) state is set as described above, the machined surface is finished extremely smooth. be able to. FIG. 2 shows an example of applied pulses in such an electric discharge machining state and an electrolytic machining state (in FIG. 2, the vertical axis represents voltage or current,
Time is taken on the horizontal axis).

FIG. 3 shows an RLC circuit as a voltage application circuit using a resistor 9, a coil 10 and a capacitor 11 in order to make up for a temporary large current. The other structure is the same as that of the first embodiment. Of course,
The voltage application circuit may be an RL circuit or an RC circuit.

FIG. 4 shows a third embodiment of the present invention. A large electric current is required for electric discharge machining, and if the electric current is passed through the shape memory alloy 5 as it is, the shape memory alloy 5 is overheated or burned out. This is an example of the case. In this embodiment, the shunt resistor 12 is connected in parallel to the shape memory alloy 5, and the workpiece 1
Only part of the current flowing between the machining electrode 2 and the machining electrode 2 is made to flow to the shape memory alloy 5. The other structure is the same as that of the first embodiment.

FIG. 5 shows a fourth embodiment of the present invention. In contrast to the case of the third embodiment, when the discharge current needs to be smaller than the current for operating the shape memory alloy 5. Is an example of. In this embodiment, one pole of the power supply 7 is connected to the upper end side of the shape memory alloy 5 and is also connected to the processing electrode 2 via the resistor 13. The other pole of the power supply 7 is connected to the workpiece 1 and the switching means 14
It is connected to the processing electrode 2 via. The control terminal of the switching means 14 is connected to the processing electrode 2,
When the voltage of this control terminal rises (or falls), the switching means 14 is turned on. The other structure is the same as that of the first embodiment.

In this embodiment, when a current flows through the path of the power source 7-workpiece 1-processing electrode 2-resistor 13 (or the reverse path), the voltage of the processing electrode 2, and thus the control terminal of the switching means 14, is changed. The temperature rises (or decreases), the switching means 14 turns on, and a current also flows in the shape memory alloy 5.
As a result, it is possible to perform electric discharge machining and electrolytic machining in the same manner as in the above-mentioned respective embodiments, and moreover, the work piece 1 and the machining electrode 2 are processed.
The electric current flowing between and can be made smaller than the electric current flowing in the shape memory alloy 5. The switching means 1
4 may have an amplification function.

Although each of the above-described embodiments is an example in which the present invention is applied to a so-called die-cutting type electric discharge machining device (also an electrolytic machining device) in the vertical direction, the present invention is also applied to other kinds of electric discharge machining devices. It is possible. FIG. 6 shows a fifth embodiment of the present invention, which is an example in which the present invention is applied to a wire cut electric discharge machine.

In this embodiment, the first electrode is the work piece 1 and the second electrode is the wire electrode 15. The workpiece 1 is set on a processing table (not shown). A wire support member 16 is provided on the side of the processing table, and the wire support member 16 can be moved in the horizontal direction by a coarse feed device (not shown). Two upper and lower pulley support members 17 are horizontally movably supported on the wire support member 16, and pulleys 18 are rotatably supported on the pulley support members 17.

The wire supporting member 16 and the pulley supporting member 1
A linear shape memory alloy 5 made of a Ti—Ni alloy is passed between 7 and 7. An urging means 6 composed of a compression coil spring is interposed between the wire supporting member 16 and the pulley supporting member 17, and the urging means 6 separates the pulley supporting member 17 from the wire supporting member 16. The direction (the left side of the drawing), in other words, the direction in which the distance between the wire electrode 15 and the workpiece 1 becomes smaller, is urged. As a result, the shape memory alloy 5 is stretched and deformed as compared with the stored length by the urging force (spring force) of the urging means 6 in a state where the temperature is lower than the constant temperature section, but up to the constant temperature section. When heated, a shape-recovering force is generated that shrinks in an attempt to return to the memorized length, and this shape-recovering force is in the direction of bringing the pulley supporting member 17 closer to the wire supporting member 16 (right side of the drawing), in other words, For example, it acts in the direction of increasing the distance between the wire electrode 15 and the workpiece 1.

The wire electrode 15 is fed from a feed reel (not shown) via two pulleys 18 to a take-up reel (not shown) under tension. The circuit for applying a voltage between the wire electrode 15 and the workpiece 1 is the same as that in each of the above embodiments.
Also in this embodiment, it is assumed that a suitable working liquid 8 can be supplied between the wire electrode 15 and the workpiece 1 by a suitable means.

In this embodiment, a voltage is applied between the wire electrode 15 and the workpiece 1 to perform electric discharge machining in the same manner as in the above embodiments. Reference numeral 1a indicates a processed portion of the workpiece, and 1b indicates an unprocessed portion. In order to bend the processing portion for the work piece 1, the wire support member 16 may be moved with respect to the processing table so that the movement trajectory of the wire support material 16 draws a curve.

In this embodiment, since the wire electrode 15 is driven by the shape memory alloy 5 in only one direction, the wire support member 1 is driven in the direction perpendicular to the driving direction.
Although it is impossible to move 6 in the moving direction, for example, two sets of shape memory alloy and biasing means are provided, and the two sets of shape memory alloy drive the wire electrodes 15 in directions (X, Y directions) orthogonal to each other. By doing so, there is no restriction on the moving direction of the wire support member 16, and the same operation as a normal wire electric discharge machine can be performed.

Although the electrodes 2 and 15 are driven by the shape memory alloy 5 in each of the above-described embodiments, the workpiece 1 may be driven by the shape memory alloy 5 via the machining table 3. Good.

In each of the above embodiments, the spring is used as the biasing means 6 for biasing the shape memory alloy.
In the present invention, as the biasing means, another shape memory alloy, a means for biasing the electrode by magnetic force or gravity, or the like other than the spring can be used.

Further, in each of the above-described embodiments, the space between the electrodes (the space between the workpiece and the electrode) is changed by utilizing the shape recovery force from the elongation deformation of the linear shape memory alloy. However, in the present invention, a shape memory alloy having a shape other than the linear shape may be used, or the space between the electrodes may be changed by utilizing the shape recovery force of the shape memory alloy from deformation other than elongation deformation.

Further, in each of the above-mentioned embodiments, the Ti-Ni alloy is used as the shape memory alloy 5, but it is also possible to use a shape memory alloy other than the Ti-Ni alloy in the present invention.

Further, in each of the above-mentioned embodiments, the shape memory alloy 5 and the biasing means 6 drive only one electrode respectively, but both the shape memory alloy and / or the biasing means act. The electrodes may be driven together to change the distance between the electrodes.

Further, although each of the above-mentioned embodiments is an example in which the present invention is applied to an electric discharge machining apparatus or an electrolytic machining apparatus, the present invention is an apparatus other than an electric discharge machining apparatus or an electrolytic machining apparatus, in which electrodes are consumed by electric discharge or current. It can also be applied to devices such as arc welding devices, lighting devices by arc discharge, ignition devices by discharge, devices that cause a chemical reaction by using discharge, STM (scanning tunnel effect micrography), etc. is there.

[0040]

As described above, according to the present invention, it is possible to precisely control the interval between consumable electrodes with an extremely simple structure without using a highly precise moving device or a complicated and sophisticated feedback control mechanism. Therefore, the manufacturing cost of the device can be made very low, and the device can be made extremely small.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 shows an example of a pulse applied between a workpiece (first electrode) and a machining electrode (second electrode) in the above-mentioned embodiment.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a sectional view showing a third embodiment of the present invention.

FIG. 5 is a sectional view showing a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing a fifth embodiment of the present invention.

[Explanation of symbols]

 1 Workpiece (first electrode) 2 Processing electrode (second electrode) 6 Energizing means 8 Processing liquid

Claims (3)

[Claims] 1. A first electrode and a second electrode, which are opposed to each other with a variable distance between them, are provided, and a discharge is generated between these electrodes or a current is passed between these electrodes. As a result, in at least one of the electrodes, the gap control device for controlling the gap between the electrodes in a device in which at least one of the electrodes is consumed, the first electrode or / and the second electrode. When heated to a constant temperature section and a biasing means that biases the electrode in a direction in which the distance between both electrodes becomes smaller, the first electrode or (and) the second electrode causes It is mechanically linked to the first electrode and / or the second electrode so as to exert a shape recovery force in the increasing direction, and a current is applied depending on the current flowing between the electrodes. With flowed shape memory alloy Interval control device between the made electrode. 2. The work piece according to claim 1, wherein the first electrode is a work piece, and an electric discharge is generated between the work piece and the second electrode to cause the work piece to be electric discharge machined. Device for controlling the gap between electrodes. 3. The first electrode is a workpiece, and an electrolytic solution is interposed between the workpiece and the second electrode,
The device for controlling the gap between electrodes according to claim 1, wherein an electric current is passed between the workpiece and the second electrode via the electrolytic solution to electrolytically process the workpiece.