JPH06297249A - Electrode feeder for electric discharge machine - Google Patents

Abstract

PURPOSE:To provide an electrode feeder for highly accurate electric discharge machining by which a position of an electrode for the electric discharge machining can be detected accurately. CONSTITUTION:A pulse signal generated by a pulse signal generating circuit 61 is converted into three kinds of pulse signals having a different phase from each other by a phase converting circuit 62, and is amplified by an amplifying circuit 63, and is impressed on the first axis directional piezoelectric element 7, the second diameter directional piezoelectric element 12 and the third diameter directional piezoelectric element 20. A counter circuit 65 counts the number of pulses of pulse signals impressed on the first axis directional piezoelectric element 7, and outputs it to an operation circuit 66. The operation circuit 66 finds a difference between the number of pulses impressed on the first axis directional piezoelectric element 7 to carry out feed operation of an electrode 4 and the first axis directional piezoelectric element to carry out return operation of the electrode 4. The product of a difference in this number of pulses and a feed quantity of the electrode 4 per single pulse is found, and the sum of this product and a feed and return operation starting position of the electrode 4 is found, so that a position of the electrode 4 can be found.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode-feeding device for electric discharge machining, and more particularly to an electrode-feeding device having a function of feeding only electrodes.

[0002]

2. Description of the Related Art Conventionally, as an electrode feeding device for an electric discharge machine, there has been known a device for moving an electrode by utilizing expansion and contraction of a piezoelectric element to bring the electrode close to a work for electric discharge machining. In such an electric discharge machine, the position of the electrode or the holder for fixing the electrode is measured by a displacement meter to accurately control the feed or return of the electrode, thereby making the electric discharge machining sophisticated.

[0003]

However, in the electrode feeding device capable of feeding back only the electrode, a holder for fixing the electrode is not required, and therefore the electrode must be directly measured to detect the position. When measuring the position of a thin wire of 0.5 mm or less, the displacement measurement sensor that can be measured is limited. Further, since the wire electrode has a small diameter, the measurement point is not stable even with a measurable displacement measuring sensor, and it is difficult to perform highly accurate measurement. For this reason, for example, in the through-hole machining by electric discharge, it is judged that the machining operation is completed before the hole of the same diameter is perforated, or even after the machining is completed, the electrode is further discharged and sent, and other members etc. Can be damaged.

The present invention has been made in order to solve such a problem, and provides a highly accurate electric discharge machining electrode feeding device for accurately detecting the position of the electric discharge machining electrode.

[0005]

An electrode-feeding device for electric discharge machining according to the present invention for solving the above-mentioned problems is housed in a housing, and is a laminated first shaft provided so as to be capable of expanding and contracting in parallel with the axial direction of the electrode. Direction piezoelectric element, a case fixed to the free end of the first axial direction piezoelectric element and movable in the axial direction of the electrode with respect to the housing, and a laminated type housed in the case and expandable / contractible in the radial direction of the electrode. A second radial piezoelectric element of
A first electrical insulator that is in contact with the free end of the second radial piezoelectric element and crimps and releases the electrode according to the expansion and contraction operations of the second radial piezoelectric element; Of the laminated radial third piezoelectric element and the free end of the third radial piezoelectric element are brought into contact with each other, and electrodes are formed in accordance with the expansion operation and the contraction operation of the third radial piezoelectric element. Electrode position detection for detecting the position of an electrode from the second electrical insulator that is crimped and released, and the pulse voltage applied to the first axial piezoelectric element, the second radial piezoelectric element and the third radial piezoelectric element And means.

[0006]

According to the electrode-feeding device for electric discharge machining of the present invention, the displacement of a physical object such as an electrode is measured by counting the pulse signals applied to the piezoelectric element that expands and contracts and sends back the electrode. The position of the electrode is accurately detected electrically without measuring with a sensor.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 of a first embodiment in which the electrode feeder for electric discharge machining of the present invention is applied to the electrode feeder for a hole-cutting electric discharge machine.
Shown in. As shown in FIG. 2, in the electrode feeding device 1, the electrode 4 is inserted into the electrode insertion hole 3 of the housing 2.
In FIG. 2, the hole 3 is symmetrical with respect to the center, so for convenience of description, the structure of the right half of the hole 3 will be described first.

A cylindrical piezoelectric element mounting hole 5 is formed in the housing 2 in parallel to the axial direction of the electrode 4. One end 7a of the first axial piezoelectric element 7 is fixed to the hole bottom 5a, and the inner peripheral wall is formed. The first axial piezoelectric element 7 is accommodated in 5b slidably in the axial direction of the electrode 4, and the other end 7b is fixed to the case 8. The first axial piezoelectric element 7 is formed by stacking disk-shaped piezoelectric elements in the plate thickness direction.

The case 8 is accommodated so that the top surface 8a and the bottom surface 8b are slidable with respect to the housing 2 in the axial direction of the electrode 4. As shown in FIG. 3, in the cylindrical hole 10 of the case 8, one end 12a of the second radial piezoelectric element 12 is formed on the hole bottom 10a.
Is fixed. The other end 12b of the piezoelectric element 12 is fixed to the electric insulator 14. The pair of electrical insulators 14 and 15 and the feeding electrode 43 housed in the case 8 are the electrodes 4
It is provided above and below with sandwiching. The power supply electrode 43 is fitted in the recess on the bottom surface of the upper electric insulator 15. The bottom surface 14a of the lower electrical insulator 14 has the second radial piezoelectric element 12
Is fixed to the other end 12b. The top surface 15 a of the upper electric insulator 15 is fixed to the case 8. Arc-shaped recesses 14b and recesses 43b are formed on the top surface of the electrical insulator 14 and the bottom surface of the power supply electrode 43 so that the electrode 4 can be sandwiched therebetween.

As shown in FIG. 2, the end surface 2 of the housing 2
The housing 18 fixed to a has a cylindrical hole 21 formed in the radial direction of the electrode 4. As shown in FIG. 4, one end 20a of the third radial piezoelectric element 20 is fixed to the hole bottom 21a of the cylindrical hole 21. Third radial piezoelectric element 20
The other end 20b of is fixed to the electrical insulator 22. The electrical insulator 22 and the feeding electrode 44 are the same as those of the electrical insulator 14 described above.
And the arc-shaped concave portion 22 having the same structure as the feeding electrode 43 and capable of gripping the electrode 4 on the top surface and the bottom surface thereof, respectively.
b and a recess 44b.

Further, as shown in FIG.
An electrode guide 25 having a guide hole 25a through which the electrode 4 can be inserted is fixed to the end surface of the. Second radial piezoelectric element 1
The 2nd and 3rd radial direction piezoelectric elements 20 are laminated, respectively, and extend in the laminating direction when energized, the electric insulator 14 and the electric insulator 22 rise respectively, and the power feeding electrode 43 and the power feeding electrode 44 respectively. The electrode 4 is sandwiched.

The electric insulator 14 and the electric insulator 22 are formed with a groove portion into which the electrode 4 is inserted, and both ends of the groove portion are widened so that the electrode 4 can be easily inserted. . As shown in FIG. 1, an electrode position detection system using an electrode feeding device in the right half of FIG. 2 is a pulse signal generation circuit 61 for generating a pulse signal, and a pulse signal generation circuit 61 is followed and the phase of the pulse signal is converted. Phase conversion circuit 6
2, an amplification circuit 63 that follows the phase conversion circuit 62 and amplifies the voltage of the phase-converted pulse signal, a counter 65 that counts the number of pulses of the pulse signal that is applied to the first axial piezoelectric element 7 before amplification, a counter Calculation for determining the position of the electrode 4 from the number of pulses counted by the circuit 65 and the number of pulse signals applied to the first axial piezoelectric element 27 before amplification counted by a counter circuit (not shown) in the left half of FIG. Circuit 6
6, a display device 67 for displaying the position of the electrode 4.

The structure of the electrode feeding device for the right half of FIG. 2 has been described above. However, the structure of the left half of FIG. 2 is similar to that of the right half, and therefore substantially the same components are designated by the same reference numerals. However, the description is omitted. Also, the electrode position detection system for detecting the position of the electrode 4 by the piezoelectric element group on the left half has the same configuration as the system on the right half, and is not shown. The left half of the first axial piezoelectric element 2
7, second radial direction piezoelectric element 32, third radial direction piezoelectric element 40
And the power supply electrodes 41 and 42 are respectively the first half of the right half.
It corresponds to the axial piezoelectric element 7, the second radial piezoelectric element 12, the third radial piezoelectric element 20, and the feeding electrodes 44 and 43. Also, a pulse signal generation circuit (not shown) on the left half,
The phase conversion circuit, the amplification circuit, and the counter circuit correspond to the pulse signal generation circuit 61, the phase conversion circuit 62, the amplification circuit 63, and the counter circuit 65 in the right half of FIG. The arithmetic circuit and the display device are common to the right half.

In the first embodiment, the first axial piezoelectric elements 7 and 27, the second radial piezoelectric elements 12 and 32, and the third radial piezoelectric elements 20 and 40 are paired on the right side and the left side, for a total of two sets. This piezoelectric element group is provided so that the first set of piezoelectric element groups on the right side performs the feeding operation and the second set of piezoelectric element groups on the left side performs the returning operation to share the feeding function and the returning function. Is. This is because by applying a tensile force only to the electrode 4 when the electrode is fed and returned.
This is to prevent sagging and to perform fixed-quantity feeding accurately. Also, the first set and the second set are each only in one direction,
That is, by having only the feed function or the return function only in one direction which is opposite to each other, the accuracy of the electrode fixed amount feed is improved when the piezoelectric element is energized.

Although two sets of piezoelectric element groups are provided in the first embodiment, it is a matter of course that the present invention can achieve the above-mentioned object even with one set of piezoelectric element groups. Next, the electric discharge machining operation according to the first embodiment will be described. As shown in FIG. 5, in the initial state of the electrode feeding device 1, all of the first axial piezoelectric elements 7, 27, the second radial piezoelectric elements 12, 32 and the third radial piezoelectric elements 20, 40 are turned off. is there. Next, the second radial direction piezoelectric element 12 is turned on, and the electric insulator 14 and the power feeding electrode 43 shown in FIG. 2 are closed at (a) shown in FIG. Then, the first axial piezoelectric element 7 is turned on in (b) shown in FIG. Then, the case 8 shown in FIG. 2 moves rightward in FIG. 2 due to the extension of the first axial piezoelectric element 7, and the electrode 4 moves in the feeding direction (rightward) together with the electrical insulator 14 and the feeding electrode 43. Then the third
The radial piezoelectric element 20 is turned on in (c) of FIG.
The radial piezoelectric element 12 is turned off in (d) shown in FIG.
Next, the first piezoelectric element 7 is turned off in (e) shown in FIG. Then, with the electrode 4 held at that position,
The electrical insulator 14 and the power supply electrode 43 are opened, and the case 8 returns to the initial state shown in FIG. 2 due to the contraction of the first axial piezoelectric element 7. By repeating a series of operations (a) to (e) shown in FIG. 5, the required amount of the electrode 4 is sent out.

Fine adjustment of the feed amount of the electrode 4 is performed by turning on the second radial direction piezoelectric element 12 from the initial state and then turning on the analog voltage to the first axial direction piezoelectric element 7 by this voltage adjustment. The extension amount of the piezoelectric element 7 is finely adjusted, and accordingly, the feed amount of the electrode 4 is finally finely adjusted. Further, the discharge voltage is applied to the electrode 4 in order to perform the electric discharge between the electrode 4 and the work (not shown) to perform the drilling by the electric discharge machining, when the second radial direction piezoelectric element 12 or the third radial direction piezoelectric element 20 is turned on. Done. The supply voltage generated by the original power supply (not shown) is
It is applied to the electrode 4 via the power supply electrodes 43 and 44. Further, as shown in FIG. 5, the application of voltage from the switching circuit to the power supply electrodes 43 and 44 is turned on and off when the power supply electrode 43 or the power supply electrode 44 is surely in contact with the electrode 4, and Alternatively, the electrical conduction failure that causes discharge between the power feeding electrode 44 and the electrode 4 is suppressed.

After the boring process, the electrode 4 is returned by the operation of the second set of the first axial piezoelectric element 27, the second radial piezoelectric element 32 and the third radial piezoelectric element 40. When the electrode 4 is returned, the first set of the first axial piezoelectric element 7, the second radial piezoelectric element 12 and the third radial piezoelectric element 20 in the right half shown in FIG. 2 are turned off. The return operation by the second set of the left half shown in FIG. 2 is required by repeating the series of operations from the initial state to (e) as shown in FIG. 5 with the piezoelectric elements 27, 32 and 40 of the second set. These series of operations are repeated by the amount. This completes the one-hole machining on the work.

Next, the electrode position detecting operation will be described below. The pulse signal generated by the pulse signal generation circuit 61 is converted into three types of pulse signals having different phases by the phase conversion circuit 62, as shown in FIG. The frequency of the pulse signal determines the feed rate of the electrode 4. The higher the frequency, the faster the speed, and the lower the frequency, the slower the speed.
The frequency of the pulse signal generated by the pulse signal generation circuit 61 can be changed by the instruction of the program stored in the arithmetic circuit 66 described later. FIG. 6 extends the time axis of the time chart shown in FIG.
With reference to the pulse signal applied to the radial piezoelectric element 20, a phase shift of the pulse signal (2) applied to the second radial piezoelectric element 12 is applied to the first axial piezoelectric element 7 by -180 °. The phase shift of the pulse signal (3)
It is set at 70 °. Each pulse signal with a different phase is
The amplifying circuit 63 is applied to the voltage required for the expansion / contraction operation of the axial piezoelectric element 7, the second radial piezoelectric element 12, and the third radial piezoelectric element 20.
And is applied to the first axial piezoelectric element 7, the second radial piezoelectric element 12, and the third radial piezoelectric element 20. The amount of amplification in the amplifier circuit 63 can be changed by a dial (not shown) of the amplifier circuit.

When the pulse signal 203 is applied to the first axial piezoelectric element 7 of FIG. 6 by the first axial piezoelectric element 7 of the electrode 4, the electrodes 4 are shown in each cycle of (a), (c) and (e). The sheet is fed in the feeding direction (rightward) shown in 2. The feed amount of the electrode 4 per cycle depends on the voltage value of the pulse signal 203 applied to the first axial piezoelectric element. If the voltage value is high, the feed amount per cycle is large, and if the voltage value is low, it is 1
The feed amount per cycle becomes smaller.

The counter circuit 65 counts the number of pulses of the pulse signal applied to the first piezoelectric element 7 and outputs it to the arithmetic circuit 66. When performing the electrode return operation,
Since the piezoelectric element in the right half of is turned off, the number of pulses counted by the counter circuit 65 becomes zero. During the return operation of the electrode 4, the number of pulses of the pulse signal applied to the first axial piezoelectric element 27 from the counter circuit on the left half of FIG. 2 is counted and input to the arithmetic circuit 66.

In the arithmetic circuit 66, the difference between the numbers of pulses applied to the first axial direction piezoelectric elements 7 and 27 is obtained during the machining of one workpiece, and the difference between the number of pulses and the electrode 4 per pulse is calculated.
Calculate the product with the feed amount. This is the relative position from the feed-back operation start position of the electrode 4. If the position of the electrode 4 before the start of the feeding back operation of the electrode 4 is measured, the position of the electrode 4 can be calculated by calculating the sum with the relative position. The calculated position of the electrode 4 is sent from the arithmetic circuit 66 to the display device 67, and the position of the electrode 4 can be known in real time.

The control of the returning operation of the electrode 4 by the left half of FIG. 2 is the same except that the moving direction of the electrode 4 is opposite to that of the right half. The pulse signal 201 applied to the third radial piezoelectric element shown in FIG. 6 is applied to the third radial piezoelectric element 40, and the pulse signal 202 applied to the second radial piezoelectric element is applied to the second radial piezoelectric element 40.
The pulse signal 203 applied to the first piezoelectric element 32 is applied to the first piezoelectric element 32 in the radial direction.

In the present invention, the portion shown by the dotted line 100 in FIG. 1 can be replaced with an electronic control unit such as a personal computer. According to the first embodiment, it is possible to feed the piezoelectric element 7 in the right direction in FIG. 2 by the extension amount of the piezoelectric element 7 by the on / off combination operation of the three piezoelectric elements 7, 12, 20. The required amount can be sent out by repeating this. The precision of the position adjustment of the electrode 4 can be improved by analogly controlling the voltage applied to the piezoelectric element 7 during the energization processing.

When the electrode is attached or detached, the electrode 4 is crimped or released by the axial expansion or contraction of the piezoelectric element, not the radial expansion or contraction of the piezoelectric element. Therefore, a large amount of expansion or contraction can be secured in the axial direction, so that the electrode having a small diameter can be accurately applied. You can grab and release. Moreover, since the electrodes are pressure-bonded or separated by the axial expansion / contraction operation of the laminated piezoelectric elements, it is possible to accurately grasp and separate the electrodes having a small diameter.

Since a large amount of expansion or contraction of the laminated piezoelectric elements in the axial direction can be secured when the electrodes are fed, the electrodes can be fed accurately. By repeating the feeding operation, the feeding amount of the electrode can be adjusted appropriately. In addition, the piezoelectric element groups 7, 12, 20 and 27, 32, 4 which are separate at the time of feeding and at the time of returning
With 0, individual control at the time of feeding and returning is possible, and precise control of the feeding amount and the returning amount is possible. Further, during analog control of the piezoelectric element in the axial direction, it is not necessary to re-hold the electrodes by the two radial piezoelectric elements, so that dead time can be reduced and the responsiveness of the electrode can be improved.

Further, as an electrode feed drive system using this apparatus, the drive frequency is in a region other than a general control region, in which the drive frequency is matched with a higher-order resonance frequency exceeding the break point frequency (cutoff frequency) of the system. It is possible to control the feed of the electrodes with. Therefore, in electrode feeding using the resonance frequency of the first axial piezoelectric element, the amount of displacement per electrode step increases, and high-frequency vibration can be applied to the electrode. At the resonance frequency, control has generally been impossible because a phase delay occurs with respect to the control signal. However, in the case of this device, since the response delay (-90 °) of the piezoelectric element is added to the delay of the secondary system (-90 °) at the resonance frequency, the system delay is delayed by -180 ° as a whole. Therefore, the phase of the control signal with respect to the fluctuation of the gap voltage between the electrode and the work should be -18.
By reversing it by 0 °, the same control as the conventional one is possible.

Further, since the electrode 4 is linear, the electrode is continuously replenished and fed even if the electrode is worn, so that the frequency of replacement work when the electrode is worn out can be reduced, and frequent replacement work of the electrode is possible. Is unnecessary, and maintenance and inspection work is easy. Next, an electrode position detection system of an electrode feeder for electric discharge machining according to a second embodiment of the present invention will be described with reference to FIGS.
It will be described with reference to FIG. The second embodiment realizes an electrode feeding device only with the right half of the first embodiment, and the configuration of the electrode feeding device is the same as that of the right half of the first embodiment, so a description thereof will be omitted. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the second embodiment, as shown in FIG. 7, the feed operation and the return operation of the electrode 4 are performed by one set of piezoelectric element groups, so that the first axial piezoelectric element 7 has two kinds of phases. A pulse signal is needed. Pulse signals of the same phase are applied to the second radial direction piezoelectric element 12 and the third radial direction piezoelectric element 20 as shown in FIGS. 6 and 8 for both the feeding operation and the returning operation of the electrode 4. In the phase conversion circuit 82 shown in FIG. 7, pulse signals having a phase difference of 180 degrees applied to the first axial piezoelectric element 7 are supplied to the amplification circuit 63 via the signal line 91 depending on the position of the electrode 4.

In the electrode feed direction discriminating circuit 84, there is a phase shift between the pulse signal applied to the first axial piezoelectric element 7 and the pulse signal applied to the third radial piezoelectric element 20.
Since the feeding operation and the returning operation of the electrode 4 are different, the feeding back direction of the electrode 4 is detected and sent to the counter circuit 85.
The counter circuit 85 counts the pulse number of the pulse signal applied to the first axial direction piezoelectric element 7 for each of the feeding operation and the returning operation of the electrode 4, and sends it to the arithmetic circuit 86. In the arithmetic circuit 86, the difference between the counted values of the number of pulses counted for each of the feeding operation and the returning operation is obtained, and the product of the difference between the number of pulses and the movement amount of the electrode per pulse which is measured in advance is obtained. The position of the electrode 4 is detected. The detected position of the electrode 4 is displayed on the display device 67.

When the pulse signals 203 (a), (c) and (e) of the pulse signal 203 to the first axial direction piezoelectric element shown in FIG. 6 are turned on, the electrode 4 is sent and the first axial direction shown in FIG. The electrode 4 is returned when the pulse signals 303 (a), (c), and (e) of the pulse signal 303 to the piezoelectric element 7 are turned off. In the present invention, the portion surrounded by the dotted line 110 shown in FIG.
For example, it may be replaced with a personal computer.

In the first and second embodiments described above, 2
Although an example using a set of piezoelectric element groups has been shown, it goes without saying that the present invention can be realized even with only one set of piezoelectric element groups.

[0032]

As described above, according to the electric-discharge machining electrode feeder of the present invention, the position of the electrode is detected by counting the pulse signals applied to the piezoelectric element.
There is an effect that an accurate position of the electrode can be measured regardless of a physical formation factor of the electrode, for example, the size of the diameter, and a fine electric discharge machining can be performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an electrode position detection system of an electric-discharge machining electrode feeder according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a first embodiment in which the electric-discharge machining electrode feed device of the present invention is applied to an electrode-feed device for a hole-cutting electric discharge machine.

FIG. 3 is a view on arrow III in FIG.

FIG. 4 is a view on arrow IV in FIG.

FIG. 5 is an explanatory diagram showing an electrode feeding operation and an on / off state of each piezoelectric element according to the first embodiment of the present invention.

FIG. 6 is a pulse signal applied to the radial piezoelectric element and the axial piezoelectric element on the right half according to the first embodiment of the present invention to perform electrode feeding operation.

FIG. 7 is a schematic configuration diagram showing an electrode position detection system of an electric-discharge machining electrode feeder according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a pulse signal applied to the radial direction piezoelectric element and the axial direction pressure transmitting element according to the second embodiment of the present invention to perform the electrode returning operation.

[Explanation of symbols]

2 Housing 4 Electrode 7 First Axial Piezoelectric Element 8 Case 12 Second Radial Piezoelectric Element 14, 15 Electrical Insulator (First Electrical Insulator) 18 Housing 20 Third Radial Piezoelectric Element 22, 23 Electrical Insulator (No. 2 electrical insulator) 27 first axial piezoelectric element 32 second radial piezoelectric element 40 third radial piezoelectric element 42, 43 feeding electrode (first feeding electrode) 41, 44 feeding electrode (second feeding electrode) 65 counter (Electrode position detection means) 66 Calculation circuit (electrode position detection means) 67 Display device (electrode position detection means) 84 Electrode feed direction determination circuit (electrode position detection means) 85 Counter (electrode position detection means) 86 Calculation circuit (electrode position) Detection means)

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tetsuji Sanada 1-1, Showa-cho, Kariya City, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Eiichi Kurokawa 1-1-1, Showa-cho, Kariya City, Aichi Prefecture Co., Ltd. (72) Inventor Naotake Mori 2-12-1, Kukata, Tenpaku-ku, Nagoya-shi, Aichi Toyota Institute of Technology

Claims (1)

[Claims] 1. A laminated first axial-direction piezoelectric element housed in a housing and provided so as to be capable of expanding and contracting in parallel with an axial direction of an electrode, and fixed to a free end of the first axial-direction piezoelectric element, and attached to the housing. On the other hand, a case that is movable in the axial direction of the electrode, a laminated second radial piezoelectric element that is housed in the case and that can expand and contract in the radial direction of the electrode, and abuts on the free end of the second radial piezoelectric element. A first electrical insulator that crimps and separates electrodes in accordance with expansion and contraction operations of the second radial piezoelectric element; and a stacked third diameter housed in the housing and expandable and contractible in the radial direction of the electrodes. A directional piezoelectric element, a second electrical insulator that abuts on a free end of the third radial piezoelectric element, and crimps and separates an electrode in accordance with expansion and contraction operations of the third radial piezoelectric element; Uniaxial piezoelectric element, the second diameter An electric discharge machining electrode feed device comprising: a directional piezoelectric element; and an electrode position detecting means for detecting the position of an electrode from a pulse voltage applied to the third radial piezoelectric element.