JP2002058268A - Supermagnetostrictive actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit a suppression of a displacement of a supermagnetostrictive rod even by extending the rod in a state in which a prestress is actuated and to simultaneously enable a simple regulation of a prestress to an optimum set pressure. SOLUTION: A spring (8) having a smaller spring constant of a preset actuating deflecting range than that when its deflection is smaller than the preset range and having substantially predetermined nonlinear characteristics in which a spring force is equal to the set pressure of the prestress within the deflecting range and a pressurizing member (3T) for actuating the rod (2) in its axial direction with the spring force as the prestress are arranged at a free end side of the rod (2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a giant magnetostrictive actuator used for converting electric energy into mechanical energy.

[0002]

FIG. 3 shows a conventional giant magnetostrictive actuator 3.
0, a cylindrical permanent magnet 32 and a giant magnetostrictive rod 3
3 and a pair of upper and lower yokes 34 and 35 for connecting these upper ends and lower ends thereof to form a closed magnetic path.

In order to apply a magnetic bias to the giant magnetostrictive rod 33, an electromagnet 36 formed by winding a coil around the giant magnetostrictive rod 33 is provided in a space surrounded by the permanent magnet 32 and the yokes 34 and 35. Is arranged. Further, a spring 37 for applying a prestress to the giant magnetostrictive rod 33 is disposed between the casing 31 and the yoke 35.

According to this, a magnetic bias is applied to the giant magnetostrictive rod 33 via the yokes 34 and 35 by the permanent magnet 32, and a current is applied to the electromagnet 36 in a state where a prestress is applied by the spring 37. When supplied, the giant magnetostrictive rod 33 expands and contracts according to the magnitude of the magnetic force, and the push rod 38 provided at the tip of the giant magnetostrictive rod 33 moves, so that the displacement can be taken out as mechanical power.

[0005]

By the way, the prestress is used for the two purposes of aligning the magnetic domains in the giant magnetostrictive rod 33 in one direction to increase the displacement saturation value and to prevent the tensile stress from acting. , 7 to 10 MPa. As the spring 37 for generating the prestress, a disc spring having an advantage that a large load can be applied in a narrow space is generally used.

However, when a disc spring is used as the spring 37, the spring constant is extremely large and the slope of the load-deflection curve is large. Since a compressive load larger than the prestress acts on 33, there is a problem that displacement is suppressed.

Further, since the slope of the load-deflection curve is large, the prestress fluctuates greatly due to a slight increase or decrease in the amount of deflection of the spring 37, and a great deal of time and effort is required to adjust the prestress to an optimal set pressure. Was.

On the other hand, when driving the giant magnetostrictive actuator 30 by applying a magnetic field to the giant magnetostrictive rod 33, the main magnetic flux of the magnetic force generated by the permanent magnet 32 and the electromagnet 36 flows in the closed magnetic path, but the yoke 34, 35 There is a problem that a leakage magnetic flux φ is easily generated between them.

That is, when a magnetic force generated by the permanent magnet 32 forms a closed magnetic path extending from the yoke 35 side to the opposite yoke 34 side through the giant magnetostrictive rod 33 disposed at the center thereof, Since the giant magnetostrictive rod 33 is interposed and the yokes 34 and 35 are vertically divided, a leakage magnetic flux φ is easily generated therebetween.

When a magnetic force generated by the electromagnet 36 forms a closed magnetic path from the yoke 34 side to the opposite yoke 35 side through the permanent magnet 32 disposed around the yoke 34, a permanent magnetic path is formed in the closed magnetic path. The yoke 3 with the magnet 32 interposed
Since the portions 4 and 35 are vertically divided, a leakage magnetic flux φ is easily generated therebetween.

For this reason, a measurement error or malfunction occurs when there is a measuring instrument or equipment around the actuator 30 which is susceptible to the magnetic field, and the magnetic field leaks more easily when there is a magnetic material around the actuator 30. 30 has a problem of causing a malfunction.

Further, the yoke 35 includes an annular member 35a integrally attached to the permanent magnet 32 and a giant magnetostrictive rod 3
3, a gap G is formed between the two members so that the giant magnetostrictive rod 33 can freely expand and contract.
Is also a magnetic resistance, causing leakage magnetic flux.

Therefore, the present invention is to prevent the displacement of the giant magnetostrictive rod even when it is extended in the state where the prestress is applied, and to adjust the prestress to the optimum set pressure extremely easily. To be able to
In addition, the generation of leakage magnetic flux is suppressed as much as possible, causing measurement errors and malfunctions when there are measuring instruments and equipment in the vicinity, and malfunctioning when there is a magnetic material nearby. It is a technical object to provide a magnetostrictive actuator.

[0014]

SUMMARY OF THE INVENTION To solve this problem, the present invention applies a magnetic field in a prestressed state by axially pressing a free end of a giant magnetostrictive rod having one end fixed. Thereby, in the giant magnetostrictive actuator configured to expand and contract the giant magnetostrictive rod to output the displacement of its free end, the spring constant of the preset operating bending range is further deflected toward the free end of the giant magnetostrictive rod. A spring having a substantially constant non-linear characteristic in which the spring force is equal to the prestress set pressure within the operation deflection range, and the spring force is the prestress in the axial direction of the giant magnetostrictive rod. And a pressurizing member for acting on

According to the present invention, in order to apply a prestress to the giant magnetostrictive rod, the spring constant of the preset operation bending range is smaller than the spring constant when the deflection is smaller than the predetermined range, and the operation bending range is smaller. A spring having a non-linear characteristic with a substantially constant spring force is used.

This spring has a linear characteristic in which the spring constant is large until the deflection reaches from 0 to the lower limit of the operation deflection range, and the spring constant is close to 0 until the deflection reaches from the lower limit to the upper limit of the operation deflection range. ing. Since the spring constant is close to 0 within the operation bending range, the spring force is maintained substantially constant even when the bending changes. That is, when the spring is deformed within the elastic range, when the deflection is small, the spring force increases in proportion to the deflection, but when the spring reaches the operation bending range, the spring force is further increased. It does not increase in proportion to the deflection and is maintained at a substantially constant value.

Since the spring force in this operation bending range is equal to the magnitude of the pre-stress, if this is bent to the operation bending range, it is extremely easy to optimize the pre-stress without accurately adjusting the spring bending. A set pressure can be obtained. In addition, even if the giant magnetostrictive rod elongates and the spring bends, the displacement is not suppressed because the spring force is maintained substantially constant.

Further, if the giant magnetostrictive rod is brought into contact with the bottom surface and the top surface of the cylindrical yoke via the magnetic bias permanent magnets provided coaxially at both ends thereof, the magnetic bias permanent magnet is Since it is provided coaxially with the giant magnetostrictive rod and there is no need to arrange a cylindrical permanent magnet on the peripheral surface of the yoke, the yoke is not divided vertically. That is, since the bottom surface and the top surface of the cylindrical yoke are magnetically connected via the peripheral surface, little leakage magnetic flux is generated.

Further, the cylindrical yoke has a maximum relative magnetic permeability of 1.
If it is made of a material having a high magnetic permeability of 000 or more, it is easy to pass a magnetic field, and if the corners formed on the surface of the yoke are round-finished, there will be no sharp corners that easily cause leakage magnetic flux. Generation of the leakage magnetic flux is suppressed also in terms of shape. Therefore, when a current is applied to an electromagnet formed by winding a coil around the giant magnetostrictive rod, the magnetic force acts on the giant magnetostrictive rod without waste through the yoke, and a large displacement can be obtained with a relatively small current. .

[0020]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a sectional view showing a giant magnetostrictive actuator according to the present invention, and FIG. 2 is a graph showing characteristics of a spring used in the present invention.

The giant magnetostrictive actuator 1 of the present embodiment operates by applying a magnetic field to the free end of the giant magnetostrictive rod 2 having one end fixed in the axial direction by applying a prestress to the free end of the giant magnetostrictive rod 2. The cylindrical yoke 4 is disposed in a casing 3 made of a non-magnetic material, and the giant magnetostrictive rod 2 is disposed at the center of the casing 3. An electromagnet 5 is formed by winding a coil around the giant magnetostrictive rod 2.

As the giant magnetostrictive rod 2, a cylindrical ETR is used.
EMATERFENOL-D (trade name of Etrimer)
And permanent magnets 6B and 6T for magnetic bias, which are formed to have the same diameter as the giant magnetostrictive rod 2, are provided coaxially at both ends. As the permanent magnets 6B and 6T, neodymium / iron / boron magnets or SmCo magnets belonging to the class having the strongest magnetic force among rare earth magnets are used.
The giant magnetostrictive rod 2 is in contact with the bottom surface 4B and the top surface 4T of the cylindrical yoke 4 via the permanent magnets 6B and 6T,
A closed magnetic path is formed together with the yoke 4.

The cylindrical yoke 4 has a bottom surface 4B fixed to the cylindrical peripheral surface 4S and an upper surface 4T formed in a disk shape, and slides axially along the inside of the peripheral surface 4S. As a result, the giant magnetostrictive rod 2 has a fixed end on the bottom surface 4B side and a free end on the top surface 4T side. The entire surface of the upper surface 4T and the peripheral surface 4
On the inner surface of S, a fluororesin coating film 7 is formed to reduce the coefficient of friction when sliding with each other.

Further, a bottom surface 4B, a peripheral surface 4S, and an upper surface 4
Each member of T is 45 permalloy, 50 permalloy, 78
Made of high magnetic permeability material with a maximum relative permeability of 1000 or more such as permalloy, pure iron, silicon steel, soft magnetic amorphous, directional silicon steel, permendur, alpalm, sendust, supermalloy with Mo, supermalloy with Cu, etc. ing. Further, all corners are rounded so that sharp corners such as a portion 4b where the bottom surface 4B and the peripheral surface 4S are continuous, an upper edge 4s of the peripheral surface 4S, and a periphery 4t of the upper surface 4T are not exposed. Finished.

The yoke 4 is accommodated in a casing 3 in which the upper and lower ends of a cylinder 3S are closed by a base 3B and a lid 3T, and a spring 8 is provided between the upper surface 4T and the lid 3T.
Is provided, and a push rod 10 made of a non-magnetic material for transmitting the displacement of the giant magnetostrictive rod 2 to the outside is formed integrally with the spring guide 9 and provided through the lid 3T. ing.

As shown in FIG. 2, the spring 8 has a spring constant in a preset operation bending range (for example, 5 to 35%) smaller than a spring constant when the bending is smaller (0 to 5%). In addition, the spring force has a substantially constant non-linear characteristic within the operation bending range.

In this embodiment, an obliquely wound coil spring such as a valseal (trade name of balseal) whose spring force is substantially equal to the set pressure of the prestress within the range of the operation deflection is used, and this spring 8 is mounted on the upper surface of the spring guide 9. It was inserted into the formed circumferential groove 9a and interposed between the casing 3 and the lid 3T. The lid 3T is screwed to the cylinder 3S as a pressure member for bending the spring 8, and by screwing this, the spring force can be applied in the axial direction of the giant magnetostrictive rod 2.

The above is one configuration example of the present invention, and its operation will be described below. Permanent magnets 6 at both ends of giant magnetostrictive rod 2
B and 6T are arranged and attached to the center of the cylindrical yoke 4, and the coil wound in a cylindrical shape is mounted in the gap between the giant magnetostrictive rod 2 and the yoke 4 to form the electromagnet 5.

Next, the upper surface 4T is attached to the distal end side of the giant magnetostrictive rod 2 and is fitted into the peripheral surface 4S. After being inserted into the casing 3, the spring 8 is set on the spring guide 9 and finally the casing 3 lids 3
Tighten T. The spring 8 has a spring constant in a preset operation bending range (for example, 5 to 35%) smaller than the spring constant when the bending is smaller (0 to 5%),
Further, it has a non-linear characteristic in which the spring force is set to a constant value substantially equal to the pre-stress set pressure within the operation bending range. Therefore, if the spring 8 is bent to the operating bending range by tightening the lid 3T, the prestress can be maintained at a predetermined set pressure without strictly adjusting the bending amount.

Further, since the closed magnetic path is formed by the giant magnetostrictive rod 2 and the yoke 4, the magnetic force of the permanent magnets 6B and 6T passes through the closed magnetic path and acts on the giant magnetostrictive rod 2 as a magnetic bias. At this time, since the permanent magnet for magnetic bias is provided coaxially with the giant magnetostrictive rod 2 and the cylindrical permanent magnet is not disposed on the peripheral surface 4S of the yoke 4, the yoke 4 is vertically divided. Not even.

That is, the cylindrical yoke 4 has its peripheral surface 4
Since the bottom surface 4B and the top surface 4T are magnetically connected via S, almost no leakage magnetic flux is generated. Further, since the upper surface portion 4T of the cylindrical yoke 4 is fitted slidably in the axial direction along the inside of the peripheral surface portion 4S, the upper surface portion 4T and the peripheral surface portion 4S are in close contact with each other, and there is almost no gap therebetween. The generation of leakage magnetic flux is also suppressed.

Further, the cylindrical yoke has a maximum relative magnetic permeability of 100.
Since it is formed of a material having a high magnetic permeability of 0 or more, a magnetic field easily passes therethrough, and further, a portion 4b where the bottom surface portion 4B and the peripheral surface portion 4S are continuous, an upper edge 4s of the peripheral surface portion 4S, a peripheral edge 4t of the upper surface portion 4T, and the like. Since the corners formed on the surface of the yoke are rounded and there are no sharp corners that easily generate leakage magnetic flux, generation of leakage magnetic flux is suppressed both in material and shape.

Next, when a DC or AC current is applied to the coil of the electromagnet 5, the electromagnet 5 forms a magnetic field that passes through a closed magnetic path composed of the giant magnetostrictive rod 2 and the cylindrical yoke 4, and the magnetic field varies depending on the magnetic field strength. The giant magnetostrictive rod 2 expands and contracts.
In the experiment, when a current of ± 1.7 (A) was supplied to the coil of the electromagnet 5, a magnetic force having a magnetic field strength of 450 (Oe) acted on the giant magnetostrictive rod 2 and the tip of the push rod 9 ±± 1.
A displacement of 3 μm was generated, and it was confirmed that it could be used in the range of DC to 3 kHz.

Also in this case, the spring 8 is maintained at a substantially constant value in which the spring force within the range of the operation deflection is equal to the prestress. Therefore, the giant magnetostrictive rod 2
Even if the amount of flexure of the spring 8 increases due to the extension of the extension, the load acting on the giant magnetostrictive rod 2 is maintained substantially constant and does not fluctuate greatly, and the displacement of the giant magnetostrictive rod is suppressed because no excessive compressive force acts. It will not be done. Further, even if the bending amount of the spring 8 is reduced by the contraction of the giant magnetostrictive rod 2, the load acting on the giant magnetostrictive rod 2 is maintained substantially constant and does not fluctuate greatly. Regardless, a certain prestress can be continuously applied.

Further, even when the magnetic field is applied by the electromagnet 5, the generation of the leakage magnetic flux is suppressed in the same manner as described above, so that the energy loss is small and the measuring instruments and equipment around the actuator 1 are susceptible to the magnetic field. If there is, no measurement error or malfunction occurs. Furthermore, even if there is a magnetic material around the actuator 1, there is no possibility that the magnetic flux leaks due to the influence of the magnetic substance or the actuator 1 does not malfunction. Therefore, it can be used as a positioning actuator or a high-frequency actuator in equipment that is easily affected by minute magnetic fields, such as semiconductor manufacturing equipment and liquid crystal-related equipment.

[0036]

As described above, according to the present invention, even if the giant magnetostrictive rod is extended while prestress is applied by the spring, the displacement is not suppressed by the spring force and the displacement is as rated. Output characteristics,
Also, there is an extremely excellent effect that the prestress can be adjusted to the optimum set pressure extremely easily. Furthermore, if the permanent magnet is arranged coaxially with the giant magnetostrictive rod, the yoke is not divided vertically so that the occurrence of magnetic flux leakage can be suppressed as much as possible. An extremely excellent effect is obtained in that no output failure is caused, and even when a magnetic substance is present nearby, output characteristics as rated can be obtained without occurrence of operation failure.

[Brief description of the drawings]

FIG. 1 is a sectional view of a giant magnetostrictive actuator according to the present invention.

FIG. 2 is a characteristic graph of a spring.

FIG. 3 is a sectional view showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Giant magnetostrictive actuator 2 ... Giant magnetostrictive rod 3 ... Casing 3S ... Cylinder 3B ... Base 3T ... Lid 4 ... Cylindrical yoke 4B ... Bottom part 4T ... Top part 4S ... Peripheral surface part 5 ... Electromagnet 6B, 6T ... Permanent magnet 7 ... Coating film 8 ... Spring

Continued on the front page (72) Inventor Masayoshi Tatsu 1-3-3 Minami Azamino Minami, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Inside Moritex Yokohama Technical Center Co., Ltd.

Claims (2)

[Claims] 1. A free end of a giant magnetostrictive rod (2), one end of which is fixed, is axially pressed to apply a magnetic field in a prestressed state, thereby expanding and contracting the giant magnetostrictive rod (2). In the giant magnetostrictive actuator configured to output the displacement of the free end, the spring constant of the preset operation bending range is set at the free end side of the giant magnetostrictive rod (2) from the spring constant when the bending is smaller than that. A spring (8) which is small and has a substantially constant non-linear characteristic in which the spring force is equal to the set pressure of the prestress within the operation bending range, and the spring force is used as the prestress in the axial direction of the giant magnetostrictive rod (2). A giant magnetostrictive actuator comprising a pressure member (3T) to act on. 2. A magnetic biasing permanent magnet (6B, 6B) provided coaxially at both ends thereof with said giant magnetostrictive rod (2).
T), the bottom surface (4B) and the top surface (4T) of the cylindrical yoke (4) are brought into contact with each other, and a coil is wound around the giant magnetostrictive rod (2) to form an electromagnet (5). A bottom surface (4B) of the cylindrical yoke (4) has a peripheral surface (4).
S), the upper surface (4T) is fitted slidably in the axial direction along the inside of the peripheral surface (4S), and is formed of a high magnetic permeability material having a maximum relative magnetic permeability of 1000 or more. 2. The giant magnetostrictive actuator according to claim 1, wherein corner portions (4b, 4s, 4t) formed on the surface of the yoke (4) are rounded.