WO2004070930A1

WO2004070930A1 - Linear actuator

Info

Publication number: WO2004070930A1
Application number: PCT/JP2004/001016
Authority: WO
Inventors: Teruo Mori; Kunihiro Fukushima
Original assignee: Tdk Corporation
Priority date: 2003-02-03
Filing date: 2004-02-02
Publication date: 2004-08-19
Also published as: JP4105958B2; TW200419888A; JP2004266881A

Abstract

A compact linear actuator exhibiting a high driving force in which feeding speed of a slider is high and highly accurate positioning is ensured. The linear actuator (10) comprises a casing (12), a slider (14) supported slidably on the casing (12), magnetostrictive elements (16, 17) for shaking the casing (12), and magnetic field generating coils (32, 34) for imparting a magnetic field to the magnetostrictive elements (16, 17), wherein the slider (14) is slid back and forth by supplying a current to the magnetic field generating coils (32, 34) intermittently thereby shaking the casing (12).

Description

Specification

Reactivator

Technical field

The present invention relates to a linear actuator used in the field of AV (Audio Video) equipment and home electric appliances. Background art

2. Description of the Related Art Reactuators have been used in various fields, for example, for adjusting the focus of a lens. For example, in a digital camera, a mouth bot, and the like, a linear actuator may be used to adjust the focus of an imaging lens. Also, in optical recording devices, magneto-optical recording devices, and the like, a linear actuator may be used to adjust the focus of a laser beam irradiation lens.

As such a reactor, a device using a hydraulic (or pneumatic) cylinder and a rotary motor, a device using a vibration of a piezoelectric element, and the like are known. Incidentally, in a linear motor using the vibration of a piezoelectric element, an impact drive type in which the piezoelectric element is configured in a bimorph type so as to generate an impact (for example, see Japanese Patent Application Laid-Open No. 2001-86867). No. 8) and an ultrasonic motor which generates a traveling wave (for example, see Japanese Patent Application Laid-Open No. 2002-199753).

However, hydraulic (or pneumatic) cylinders have the problem that the expansion and contraction speed is slow, and that high-precision positioning is difficult.

Also, the linear actuator using a rotary motor has a problem that a structure for converting a rotary motion into a linear motion is required, so that the structure is complicated and it is difficult to make the linear compact. Further, since the rotation angle of the motor is controlled in units of the pitch of the stator, there is a problem in that high-precision positioning is difficult. In addition, an impact-driven linear motor using a piezoelectric element has a weak driving force, and may not be able to obtain a sufficient driving force. On the other hand, an ultrasonic motor using a piezoelectric element has a problem in that it generates a large amount of heat and is difficult to use continuously for a long time. Further, ultrasonic motors often require a booster circuit such as a transformer due to a high applied voltage, and have a problem in that the structure is complicated and compactness is difficult. Disclosure of the invention

The present invention has been made in view of the above problems, and provides a compact linear actuator that has a high slider feed speed, high-precision positioning, and a large driving force. Is the task.

The inventor of the present invention has solved the above-mentioned problem by using a magnetostrictive element, which generates a larger strain than a piezoelectric element, for a reactor.

That is, the present invention as described below solves the above problems.

(1) A casing, a slider slidably supported by the casing, a magnetostrictive element for vibrating the casing, and a magnetic field generating coil for applying a magnetic field to the magnetostrictive element. A linear actuator, wherein the slider is slid in the front-rear direction by intermittently energizing the magnetic field generating coil to vibrate the casing.

(2) The linear actuator according to (1), wherein the magnetostrictive element is a giant magnetostrictive element containing a lanthanoid and an iron element.

(3) The V-actuator according to (1) or (2), wherein at least one of the sliding surfaces of the slider and the casing is coated with a fluorine resin.

(4) The two magnetostrictive elements are provided in the casing, and one of the magnetostrictive elements is attached to the casing at a rear end and extends in the front-rear direction. The other end of the magnetostrictive element is mounted in the casing at the front end and expands and contracts in the front-rear direction so that the rear end contacts the casing. Any one of the above (1) to (3), wherein the casing is disposed so as to be in contact with and separated from the casing, and a forward impact and a rearward impact can be selectively applied to the casing. Linear Actuator.

(5) The linear actuator according to (4), wherein the linear expansion coefficient of the magnetostrictive element and the linear expansion coefficient of the casing are substantially equal.

(6) The magnetostrictive element is attached to the case so as to be extendable and contractible in the front-rear direction, and the casing is vibrated in the front-rear direction by a reaction of inertial force due to expansion and contraction of the magnetostrictive element. The linear actuator according to any one of the above (1) to (3).

(7) The relay actuator according to (6), wherein the magnetostrictive element is attached to the casing at one of a front end and a rear end in a substantially cantilever state.

(8) A power supply is provided for increasing or decreasing the current value, and supplying a current having a different increasing speed and a decreasing speed to the magnetic field generating coil, and in a vibration mode in which the forward acceleration and the backward acceleration are different. The reactuator according to (6) or (7), wherein the magnetostrictive element vibrates the casing.

(9) Two sets of the magnetostrictive element and the magnetic field generating coil are provided, and one of the magnetostrictive elements vibrates the casing in a vibration mode in which a forward acceleration is larger than a backward acceleration, and Control means for controlling the vibration mode of the two magnetostrictive elements so that the other magnetostrictive element vibrates the casing in a vibration mode in which the acceleration of the two is greater than the acceleration in the forward direction. Means that a current having the increasing speed higher than the decreasing speed is applied to one magnetic field generating coil, and the decreasing speed is applied to the other magnetic field generating coil. Wherein the output current from the power supply to the two magnetic field generating coils is controlled so as to supply a current faster than the increasing speed. .

(10) A vibration mode in which one set of the magnetostrictive element and the magnetic field generating coil is disposed, and a vibration mode in which the forward acceleration is larger than the rear acceleration and a vibration mode in which the rear acceleration is larger than the front acceleration. Control means for controlling the vibration mode of the magnetostrictive element such that one magnetostrictive element selectively vibrates the casing in the two vibration modes; Output current from the power supply to one of the magnetic field generating coils so that a current faster than the decreasing speed and a current faster than the decreasing speed are selectively applied to one magnetic field generating coil. The linear actuator according to the above (8), wherein the linear actuator is controlled.

(11) The slider is made of a magnetic material, a detection coil is provided around the slider, and a relative position between the casing and the slider is detected based on an impedance of the detection coil. The linear actuator according to any one of (1) to (10), characterized in that: BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a side cross-sectional view including a partial block diagram schematically showing the structure of a reactor actuator according to a first embodiment of the present invention.

FIG. 2 is a graph showing a waveform of a drive current of the linear actuator.

FIG. 3 is a side cross-sectional view including a partial block diagram schematically showing a structure of a reactor actuator according to a second embodiment of the present invention.

FIG. 4 is a graph showing a waveform of a drive current of the linear actuator.

FIG. 5 shows a structure of a reactor according to a third embodiment of the present invention. It is a side sectional view including a partial block diagram schematically shown.

FIG. 6 is a side cross-sectional view including a partial block diagram schematically showing a structure of a linear actuator according to a fourth embodiment of the present invention.

FIG. 7 is a side cross-sectional view including a partial block diagram schematically illustrating a structure of a linear actuator according to a fifth embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side sectional view schematically showing the structure of the linear actuator 10 according to the present embodiment.

The relay actuator 10 includes a game sink 12, a slider 14 slidably supported on the casing 12, magnetostrictive elements 16 and 17 for exciting the casing 12, and magnetostriction. A magnetic field generating coil 32, 34 for applying a magnetic field to the elements 16, 17 is provided, and the casing 12 is vibrated by intermittently energizing the magnetic field generating coils 32, 34. Thus, the slider 14 slides in the front-rear direction. The other configuration is the same as that of the conventional linear actuator, and therefore, the description thereof will be omitted as appropriate.

The casing 12 has a bottom plate 18, a front wall 20, a rear wall 22, and a tubular portion 24.

The tubular portion 24 is supported between the front wall 20 and the rear wall 22, the front end is opened outside the front wall 20, and the rear end is closed by the rear wall 22. A partition wall 24A is provided inside the cylindrical portion 24 near the center in the longitudinal direction. Further, an impact plate 24 B is provided between the partition plate 24 A and the rear wall 22.

The slider 14 is a round bar-shaped body made of a magnetic material, is slidably fitted inside the cylindrical portion 24 of the casing 12, and protrudes outside the front wall 20. The sliding surface 24 C inside the cylindrical portion 24 is, for example, Teflon (registered trademark). And the like, whereby the frictional force between the casing 12 and the slider 14 is adjusted. A detection coil 26 is provided around the slider 14 so as to surround the cylindrical portion 24 along the longitudinal direction.

Each of the magnetostrictive elements 16 and 17 is a round bar, and is made of a giant magnetostrictive element containing a lanthanide and an iron element. The linear expansion coefficients of the magnetostrictive elements 16 and 17 and the linear expansion coefficient of the casing 12 are substantially equal. The magnetostrictive element 16 is attached to the rear wall 22 of the casing 12 at the rear end 16A and expands and contracts in the front-rear direction so that the front end 16B comes into contact with and separates from the impact plate 24B. It is arranged.

On the other hand, the magnetostrictive element 17 is attached to the partition wall 24A of the casing 12 at the front end 17A, and expands and contracts in the front-rear direction, so that the rear end 17B comes into contact with and separates from the impact plate 24B. It is arranged as follows.

The magnetic field generating coil 32 is arranged so as to surround the magnetostrictive element 16, and the magnetic field generating coil 34 is arranged so as to surround the cylindrical part 24 around the magnetostrictive element 17. A power source 36 is connected to the magnetic field generating coils 32 and 34.

The power supply 36 is connected with control means 38 for controlling the oscillation mode of the magnetostrictive elements 16 and 17 by controlling the output current of the power supply 36. The control means 38 is connected to the detection coil 26, and can detect the relative position between the casing 12 and the slider 14 based on the impedance of the detection coil 26.

Next, the operation of the linear actuator 10 will be described.

The control means 38 controls the output current of the power supply 36, and when the power supply 36 supplies a current having a rectangular waveform as shown in FIG. Generates a magnetic field. As a result, the magnetostrictive element 16 elongates and the front end 16 B collides with the impact plate 24 B, and the casing An impact is applied. Due to this impact, the casing 12 swings forward, and the slider 14 also swings forward due to the frictional force with the casing 12. On the other hand, when the casing 12 returns to the rear after the collision, the slider 14 slides forward against the frictional force with the casing 12 due to inertia, and remains at the front of the original position. I do. The above operation is repeated by intermittently supplying a current having a rectangular waveform as described above to the magnetic field generating coil 32, and the slider 14 is sent forward.

Similarly, when the power supply 36 intermittently supplies a current having a rectangular waveform as described above to the magnetic field generating coil 34, the slider 14 is sent backward. When the slider 14 slides back and forth, the volume occupied by the slider 14 in the space inside the detection coil 26 changes. That is, the volume of the magnetic material occupying the space inside the detection coil 26 changes, and as a result, the impedance of the detection coil 26 changes. By detecting this impedance by the control means 38, the position of the slider 14 with respect to the casing 12 can be detected.

Since the magnetostrictive elements 16 and 17 are giant magnetostrictive elements that generate a large strain when a magnetic field is applied, a correspondingly large impact can be applied to the casing 12, and the linear actuator 10 is driven. Power is great.

Also, since the magnetostrictive elements 16 and 17 are giant magnetostrictive elements, the response speed at which distortion occurs with respect to the input current is fast, and the linear actuator 10 can send the slider 14 in the front-rear direction at high speed. it can.

Since the linear expansion coefficients of the magnetostrictive elements 16 and 17 and the linear expansion coefficient of the casing 12 are substantially equal, even if the temperature changes due to heat generation of the magnetic field generating coils 32 and 34, etc. The change in the gap between the free ends of the magnetostrictive elements 16 and 17 and the casing 12 is limited to a small range, and the impact can be reliably applied to the casing 12.

Also, fluorine resin is coated on the sliding surface of the cylindrical part 24 of the casing 12. Since the friction coefficient between the casing 12 and the slider 14 is adjusted, the slider 14 can be reliably driven by vibrating the case 12. '

Further, the control means 38 detects the position of the slider 14 based on the impedance of the detection coil 26, and energizes the magnetic field generating coils 32, 34 as appropriate. The relative position of 14 can be controlled with high accuracy.

Further, the slider 14 and the magnetostrictive elements 16 and 17 are accommodated in the cylindrical portion 24, and the detection coil 26, the first magnetic field generating coil 32 and the second magnetic field are generated around the cylindrical portion 24. Since the coil 34 is provided, the linear actuator 10 has a simple structure and is compact.

Next, a second embodiment of the present invention will be described.

FIG. 3 is a side sectional view schematically showing the structure of the linear actuator 40 according to the second embodiment.

The linear actuator 40 is attached to the casing 46 so that the magnetostrictive elements 42 and 44 can expand and contract in the front-rear direction with respect to the linear actuator 10, and the magnetostrictive elements 42 and 4 It is characterized in that the casing 46 is vibrated in the front-rear direction by the reaction of inertia force due to the expansion and contraction of 4. The other configuration is the same as that of the reactor 10, so that the same reference numerals as in FIG.

Each of the magnetostrictive elements 42 and 44 is a round bar like the magnetostrictive elements 16 and 17 and is made of a giant magnetostrictive element containing a lanthanide and an iron element. The magnetostrictive elements 42 and 44 are housed in series in a cylindrical housing member 50 arranged in the front-back direction. The housing member 50 is attached to the casing 46 at its front end in a cantilever manner, and a partition plate 5OA is provided inside near the center in the longitudinal direction. The rear end of the housing member 50 is closed by a rear wall 50B. The housing member 50 is flexible and can be expanded and contracted. Magnetic The distortion element 42 is cantileverly attached to the rear wall 62 of the casing 46 at the front end 42A, and the rear end 42B is connected to the partition plate 5OA. On the other hand, the magnetostrictive element 44 is supported by a partition plate 50A at a front end 44A, and a rear end 44B is connected to a rear wall 50B of the housing member 50. That is, the magnetostrictive element 44 is attached to the casing 46 substantially in a cantilever state via the partition plate 50A and the magnetostrictive element 42.

A magnetic field generating coil 54 for applying a magnetic field to the magnetostrictive element 42 is provided around the magnetostrictive element 42, and a magnetic field for applying a magnetic field to the magnetostrictive element 44 is provided around the magnetostrictive element 44. All of the generating coils 56 are arranged so as to surround the housing member 50.

A power supply 36 is connected to the magnetic field generating coils 54 and 56, and a control means 38 for controlling the vibration mode of the magnetostrictive elements 42 and 44 is connected to the power supply 36. The control means 38 controls the power supply 36 to supply a current having a triangular waveform whose increasing speed is faster than the decreasing speed to the magnetic field generating coil 54 to the magnetic field generating coil 54 as shown in FIG. The power supply 36 is controlled so that the generator coil 56 has a triangular waveform shown in FIG. 4 and a symmetrical triangular waveform as shown in FIG.

The casing 46 has a bottom plate 58, a front wall 60, a rear wall 62, and a tubular portion 64.

The cylindrical portion 64 is supported between the front wall 60 and the rear wall 62, and has a front end opened outside the front wall 60 and a rear end closed by the rear wall 62. Further, the sliding surface 64 A inside the cylindrical portion 64 is coated with a fluorine resin, and the frictional force with the slider 14 is adjusted. Note that no partition wall is provided inside the cylindrical portion 64.

Next, the operation of the linear actuator 40 will be described.

When the power supply 36 supplies a triangular waveform current as shown in FIG. 4 to the magnetic field generating coil 54, a magnetic field is generated temporarily near the magnetostrictive element 42, and The material 50 rapidly expands in the backward direction together with the magnetostrictive element 42, and then gradually contracts. At this time, the magnetostrictive element 44 also moves back and forth in the front-back direction, but does not expand or contract. Due to the reaction of the inertial force of the magnetostrictive elements 42, 44 and the housing member 50, the casing 46 is vibrated after a vibration state in which the forward acceleration is larger than the backward acceleration. When the casing 46 is urged forward, the acceleration is large, and the slider 14 slides rearward relative to the casing 12. On the other hand, when the casing 46 is urged rearward, the acceleration is small, so that the slider 14 gently finely moves rearward integrally with the casing 12 and does not slide with respect to the casing 12. That is, the slider 14 moves backward from the original position. By repeating the above operation by intermittently supplying a triangular waveform current to the magnetic field generating coil 54, the slider 14 is sent backward. Similarly, the power supply 36 intermittently supplies a current having a triangular waveform symmetrical to that of FIG. 4 to the magnetic field generating coil 56, so that the slider 14 is sent forward.

Since the magnetostrictive element 42 and the magnetostrictive element 44 are giant magnetostrictive elements, the amplitude of expansion and contraction is large and the reaction of the inertial force is correspondingly large. Therefore, the casing 46 can be vibrated strongly, and the linear actuator 40 has a large driving force. In addition, since the amplitude is large, the feed amount by one vibration is correspondingly large, and the slider 14 can be moved in the front-rear direction at a high speed.

In the second embodiment, two magnetostrictive elements 42 and 44 are arranged in series, and the magnetostrictive element 42 applies the casing 46 in a vibration mode in which the acceleration in the forward direction is larger than the acceleration in the backward direction. A symmetrical triangular waveform current is input to the magnetic field generating coils 54 and 56 so that the magnetostrictive element 44 vibrates the casing 46 in a vibration mode in which the rearward acceleration is greater than the forward acceleration. However, the present invention is not limited to this, and a magnetostrictive element such as a linear actuator 50 according to a third embodiment of the present invention as shown in FIG. And one set of magnetic field generating coils, and selectively apply a symmetrical triangular waveform current to one magnetic field generating coil 54, so that the forward acceleration is greater than the backward acceleration. One magnetostrictive element 42 may vibrate the casing 46 in two vibration modes, a vibration mode and a vibration mode in which the rearward acceleration is larger than the forward acceleration. By doing so, the compactness of the relay actuator can be further increased.

In the second embodiment, the two magnetostrictive elements bias the casing in the front-rear direction by virtue of the reaction of the inertial force to vibrate the casing, and in the first embodiment, the two magnetostrictive elements move in the forward Although the casing is vibrated by selectively applying the shock of the rearward direction and the shock of the rearward direction, a configuration in which these are combined may be employed. For example, as in the linear actuator 50 according to the fourth embodiment of the present invention shown in FIG. 6, the casing is applied by the reaction of the inertial force so that the acceleration in the forward direction becomes larger than the acceleration in the backward direction. One magnetostrictive element for vibrating and one magnetostrictive element for applying a rearward impact to the casing may be provided. Also, one magnetostrictive element for vibrating the casing by the reaction of the inertial force so that the rearward acceleration becomes larger than the forward acceleration, and one magnetostrictive element for applying a forward impact to the casing. It may be provided. Further, in the first to fourth embodiments, the magnetostrictive element and the slider are disposed apart from each other in the axial direction. However, the present invention is not limited to this. Like the reactor 7 according to the fifth embodiment, a void 74 is formed in the slider 72 to form a hollow structure, and the giant magnetostrictive element 42 and the magnetic field generating coil are provided in the void 74. May accommodate 4 4. By doing so, it is possible to achieve a significant compaction in the axial direction. The structure of the linear actuator 70 will be briefly described. The gap 74 is provided on the rear end side of the slider 72, and the slider 72 is formed on the inner peripheral surface of the gap 74. The outer peripheral surface of the housing member 76 is slidably fitted in the axial direction. The housing member 76 has a structure in which the front end and the rear end of the cylindrical side wall 76 A are closed by the front wall 76 B and the rear wall 76 C, and is fixed to the casing 78 at the rear wall 76 C. Have been.

The magnetostrictive element 42 and the magnetic field generating coil 54 are housed in a housing member 76, and the magnetostrictive element 42 is cantilevered on a rear wall 76C of the housing member 76 at a rear end 42B. ing. Note that a gap is formed between the front end 42 A of the magnetostrictive element 42 and the front wall 76 B of the housing member 76.

If a gap is formed so that the front end 42A does not abut on the front wall 76B even if the magnetostrictive element 42 extends, the linear actuators 40, 50 according to the second and third embodiments are formed. Similarly, a rear actuator that vibrates the casing 78 by the reaction of the inertial force of the magnetostrictive element 42 can be configured. On the other hand, if a gap is formed so that the front end 42 A and the front wall 76 B are in contact with each other by the extension of the magnetostrictive element, the casing 78 is vibrated by impact similarly to the linear actuator according to the first embodiment. Can be configured.

The reactor 70 has only one magnetostrictive element. However, as in the first, second, and fourth embodiments, the reactor has two magnetostrictive elements. Of course, it is also possible to accommodate in the slider 72. Also, when only one of the two magnetostrictive elements is housed in the slider 27, compactness in the axial direction can be achieved.

In the first to fifth embodiments, the slider is made of a magnetic material, and the detection coil directly detects the position of the slider. However, the present invention is not limited to this. For example, a magnetic object may be attached to a non-magnetic slider, and the position of the slider may be indirectly detected via the object. Further, a position detection sensor having another configuration may be provided. Also in this case, by appropriately applying a magnetic field to the two magnetostrictive elements, the slider can be slid with high driving force and at high speed to achieve high precision. Can be positioned.

In the first to fifth embodiments, the sliding surface of the casing is coated with fluororesin. However, the present invention is not limited to this. May be coated. Further, the sliding surfaces of both the casing and the slider may be coated with a fluororesin.

If an appropriate coefficient of friction cannot be obtained with fluororesin, a coating of another material may be formed on at least one of the sliding surfaces of the casing and the slider. On the other hand, if the friction coefficient between the casing and the material for the slider is appropriate, the coating may not be formed on the sliding surfaces of both the casing and the slider.

In the first to fifth embodiments, the magnetostrictive element is a giant magnetostrictive element containing a lanthanide and an iron group element. However, the present invention is not limited to this. The material is not particularly limited as long as it has an effect. In order to increase the sliding speed of the slider and increase the driving force, it is preferable to use a giant magnetostrictive element in which a large strain is quickly generated by applying a magnetic field.

In the first embodiment, the linear expansion coefficients of the magnetostrictive elements 16 and 17 and the linear expansion coefficient of the casing 12 are substantially equal. However, the present invention is not limited to this. Even when the temperature change around the element is small, or even when the temperature change around the magnetostrictive element is large, if the deformation of the magnetostrictive element and the casing is sufficiently small, the linear expansion coefficient of the magnetostrictive elements 16 and 17 is not necessarily required. It is not necessary to make the linear expansion coefficient of the casing 12 substantially equal to that of the casing 12. Industrial potential

As described above, according to the present invention, by using the magnetostrictive element, the slider can be moved at a high speed, high-precision positioning is possible, and the driving force is large. 30

PCT / JP2004 / 001016

14 linear actuators can be realized

Claims

The scope of the claims

1. A casing, a slider slidably supported by the casing, a magnetostrictive element for exciting the casing, and a magnetic field generating coil for applying a magnetic field to the magnetostrictive element. A linear actuator, wherein the slider is slid in the front-rear direction by exciting the casing by intermittently energizing the magnetic field generating coil.

2. The linear actuator according to claim 1, wherein the magnetostrictive element is a giant magnetostrictive element containing a lanthanoid and an iron group element.

3. The linear actuator according to claim 1, wherein at least one sliding surface of the slider and the casing is coated with a fluorine resin.

4. Two of the magnetostrictive elements are provided in the casing, and one of the magnetostrictive elements is attached to the casing at a rear end and expands and contracts in the front-rear direction so that the front end contacts and separates from the casing. The other magnetostrictive element is mounted in the casing at the front end, and is arranged so that the rear end contacts and separates from the casing by expanding and contracting in the fore-and-aft direction. 4. The reactuator according to claim 1, wherein a forward impact and a rearward impact can be selectively applied to the casing.

5. The linear actuator according to claim 4, wherein a linear expansion coefficient of the magnetostrictive element and a linear expansion coefficient of the casing are substantially equal.

6. The magnetostrictive element is attached to the casing so as to be able to expand and contract in the front-rear direction, and the casing is vibrated in the front-rear direction by a reaction of inertial force due to expansion and contraction of the magnetostrictive element. The linear actuator according to any one of claims 1 to 3, characterized in that:

Five

,

7. The linear actuator according to claim 6, wherein the magnetostrictive element is attached to the casing substantially at one of a front end and a rear end in a cantilever state.

108. A vibration mode in which a current value increases and decreases, and a power supply for supplying a current having a different increasing speed and a decreasing speed to the magnetic field generating coil is provided, and the forward acceleration and the backward acceleration are different. 8. The linear actuator according to claim 6, wherein the magnetostrictive element vibrates the casing.

1 5

9. Two sets of the magnetostrictive element and the magnetic field generating coil are provided, and one of the magnetostrictive elements vibrates the casing in a vibration mode in which a forward acceleration is larger than a backward acceleration, and a rearward acceleration is provided. Is provided with control means for controlling the vibration mode of the two magnetostrictive elements so that the other magnetostrictive element vibrates the casing in a vibration mode larger than the acceleration in the forward direction. However, the power source supplies current to the one magnetic field generating coil such that the increasing speed is faster than the decreasing speed, and supplies current to the other magnetic field generating coil so that the decreasing speed is faster than the increasing speed. An output current to two of said magnetic field generating coils is controlled.

25. The linear actuator according to item 8.

0. One set of the magnetostrictive element and the magnetic field generating coil is provided, and One front magnetostrictive element selectively vibrates the casing in two vibration modes, a vibration mode in which the forward acceleration is greater than the backward acceleration, and a vibration mode in which the backward acceleration is higher than the forward acceleration. Control means for controlling the oscillation mode of the magnetostrictive element so that the current increases at a rate higher than the decreasing speed and the current increases at a rate higher than the decreasing rate. 9.The power supply according to claim 8, wherein an output current from the power supply to one of the magnetic field generating coils is controlled so as to selectively energize the magnetic field generating coils. Linear Actuator.

11. The slider is made of a magnetic material, a detection coil is provided around the slider, and a relative position between the casing and the slider is detected based on an impedance of the detection coil. The reactuator according to any one of claims 1 to 10, characterized in that: