JP2011164167A - Linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin linear actuator that is suitable for driving an optical element such as a lens. <P>SOLUTION: Cylindrical supermagnetostrictive elements 31 to 34 are arranged in magnetic field having uniform intensity in a circumferential direction, and have uniform expansion and contraction amounts. Thus, the supermagnetostrictive elements 31 to 34 are expanded and contracted without inclining an axial line. The the supermagnetostrictive elements 31 to 34 which expand and contract by supply of power to a coil 50 has a cylindrical shape, thereby increasing supporting end faces of the supermagnetostrictive elements 31 to 34. Even when large pressure is received by reaction force from a driven member 20, they have almost rotationally symmetric shape, and the supermagnetostrictive elements 31 to 34 uniformly and translationally expand in an axial line direction. They linearly move with high rigidity without inclining the driven member 20 while securing linearity without using any guide mechanism. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a linear actuator, and more particularly to a linear actuator that can ensure a large amount of movement.

  Linear actuators that move small optical components and the like with high accuracy are known. In conventional linear actuators, the position detecting means of the moving element is generally externally attached, which increases the number of parts and costs, and the linear actuator mounted with the position detecting means has a relatively large volume. Therefore, the size of the apparatus equipped with such a linear actuator has been increased.

  On the other hand, as shown in Patent Document 1, there is also known a linear actuator that realizes a simpler configuration using a piezoelectric element. In such a linear actuator, a rod-shaped engaging member is fixed to one end face in the stacking direction of the piezoelectric elements, that is, the displacement direction, which generates a displacement according to the predetermined electric signal, and is driven. The sliding contact hole of the driven member is pressed against the engaging member by the elastic force of the leaf spring fixed to the member, and the engaging member and the driven member are frictionally engaged.

  By applying a high frequency current to the piezoelectric element and repeatedly expanding and contracting, the engaging member can be reciprocated minutely. Here, when the engaging member moves slowly, the driven member moves together with the engaging member by the frictional force in the friction engaging portion. On the other hand, when the engaging member moves faster than a certain degree and the inertial force becomes larger than the frictional force of the friction engaging portion, slipping occurs in the friction engaging portion, and the driven member remains engaged or remains substantially stationary. Only the member moves. Therefore, when the engagement member moves in one direction, the driven member is moved together with the engagement member and sent, while when the engagement member moves in the other direction, the driven member is made stationary or substantially stationary by sliding. The driven member can be intermittently moved in one direction by moving the engaging member while keeping it repeated.

  By the way, although the piezoelectric element used with the conventional linear actuator has the advantage that it is comparatively cheap and is easy to acquire, generally the displacement amount is about 1 micrometer, although a high voltage of several hundred volts is required for a drive. However, if it is made small, small and light, there is a problem that the insulation and displacement amount are lowered, and the reliability and function are lowered. Piezoelectric elements are difficult to use for small and light actuators because they have large capacitance components, are prone to delay during driving, and have creep characteristics that are not constant and require a position detection and feedback circuit. It can be said that. On the other hand, Patent Document 2 discloses a linear actuator using a giant magnetostrictive element.

Japanese Patent Laid-Open No. 04-69070 Japanese Patent Laid-Open No. 06-140684

  A giant magnetostrictive element as shown in Patent Document 2 has a property of expanding and contracting in a magnetic field generated by a current applied to a coil, but since it can be driven with only a few V, the circuit burden is much larger than that of a piezoelectric element. There is an advantage that it is light and easy to match with other circuits. In addition, the load can be driven at high speed due to reactance, can be driven in a non-contact manner, and the displacement and generated force are much larger than those of piezoelectric elements, etc. Further, the heat resistance is high at 380 ° C. It can also be directly put into a furnace (about 260 ° C.) and has reflow resistance, so it is excellent as a drive source for a linear actuator. By using such a giant magnetostrictive element, the drive voltage can be reduced from several hundred volts used for piezoelectric elements to several volts at a stroke, thereby preventing electric shock, electric leakage, destruction of other elements due to humidity or insulation failure. And a highly safe linear actuator can be realized.

  However, the linear actuator disclosed in Patent Document 2 has a problem that it is difficult to use depending on the application because it enlarges the distortion of the giant magnetostrictive element and finally converts it into the thrust of the shaft. For example, in an imaging apparatus, when the linear actuator disclosed in Patent Document 2 is used to drive a lens or the like for focusing or zooming, it is necessary to push a flange of the lens or a point in the vicinity thereof with a shaft provided with thrust. Therefore, there is a possibility that the optical axis of the lens is tilted, which may cause coma aberration and reduce the image quality of the captured image. In recent years, mobile phones with imaging devices have been widely used, but there is also a demand for realizing an autofocus and zoom function for a thinner body.

  The present invention has been made in view of the problems of the prior art, and is intended to provide a linear actuator that is suitable for driving an optical element such as a lens and can be thinned.

  The linear actuator according to claim 1 has a cylindrical super magnetostrictive element and a coil disposed substantially coaxially with the super magnetostrictive element on the outer side in the direction perpendicular to the axis of the super magnetostrictive element, and is generated from the coil The driven member is moved relative to the fixed portion by driving the giant magnetostrictive element with a magnetic field.

  According to the present invention, since the coil is arranged substantially coaxially on the outer side in the direction orthogonal to the axis of the giant magnetostrictive element, the magnetic field generated in the coil when the coil is fed from the outside is the giant magnetostrictive on the inside. It acts on the whole element and can be expanded and contracted. At this time, if the giant magnetostrictive element is cylindrical, it is arranged in a magnetic field having a uniform strength in the circumferential direction, and the giant magnetostrictive element can be expanded and contracted without tilting the axis. Further, since the shape of the giant magnetostrictive element that expands and contracts by supplying power to the coil is made cylindrical, the support end surface of the giant magnetostrictive element increases, and a large force is received by the reaction force from the driven member. However, because it has a substantially rotating shape, it can be structured to be able to translate and expand evenly in the axial direction, and it can ensure straightness without using any guide mechanism, and it can move straightly with high rigidity without tilting the driven member. Can be made. As a result, it is possible to realize a structure that advances and retreats in one direction with high accuracy without giving tilt or twist to the driven member, so that it is highly reliable for applications such as auto focus, zoom or camera shake correction of optical elements, for example. Reliable operation can be provided. The cylindrical shape is preferably a cylindrical shape, but may be a rectangular tube shape, or may be a shape in which a part of the circumferential direction is cut away. In addition, the insulator is not necessarily used for enlarging the displacement but can also be used for reducing the displacement. In this case, the dynamic range of the displacement is reduced, but the minute movement with high accuracy and high rigidity can be performed. It can be carried out.

  A linear actuator according to a second aspect is the invention according to the first aspect, wherein the number of the giant magnetostrictive elements (N is an integer of 2 or more) is arranged, the diameters of the giant magnetostrictive elements are different, and The giant magnetostrictive element is coaxially arranged, and the displacement of the nth (n is an integer not less than 1 and not more than N−1) th of the giant magnetostrictive element from the outside in the axis orthogonal direction is the (n + 1) th from the outside in the axis orthogonal direction. It is transmitted to the giant magnetostrictive element through an insulator.

  According to the present invention, the displacement of the giant magnetostrictive element on the outer side in the direction orthogonal to the axis is doubled and enlarged by the insulator toward the giant magnetostrictive element on the inner side in the direction perpendicular to the axis, and finally transmitted to the driven member. Since the giant magnetostrictive element generally has a large generated force, even if the reaction force from the driven member is doubled and transmitted in the reverse direction by using such an insulator, the giant magnetostrictive element outside the axis orthogonal direction is used. As a result, a large displacement of the driven member can be realized.

  A linear actuator according to a third aspect of the present invention is the invention according to the second aspect, wherein one end of the super magnetostrictive element on the outermost peripheral side is connected to the fixed portion, and the super magnetostrictive element on the innermost peripheral side is One end is connected to the driven member. The displacement amount of the giant magnetostrictive element at the outermost periphery is input to the insulator and doubled, and then transmitted to the second giant magnetostrictive element from the outer periphery, and the displacement superimposed on the displacement is doubled by the insulator. Above, it is further transmitted to the third giant magnetostrictive element from the outer periphery, and so on, so that the gradual displacement amount can be increased. Thereby, the driven member can be moved with a large stroke with respect to the fixed portion.

  The linear actuator according to claim 4 is the invention according to claim 2 or 3, wherein a plurality of insulators for connecting the nth giant magnetostrictive element and the (n + 1) th giant magnetostrictive element are provided, It arrange | positions at equal intervals in the circumferential direction, It is characterized by the above-mentioned. Thereby, the displacement of the super magnetostrictive element on the outer side in the axis orthogonal direction can be transmitted to the super magnetostrictor side on the inner side in the axis orthogonal direction while maintaining coaxiality with high accuracy.

  In order to transmit the displacement of the nth giant magnetostrictive element to the (n + 1) th, the insulator arm part needs to have high rigidity without bending, but the fulcrum part that supports this is flexible and repeatedly bent. Since it is necessary to increase the resistance to the resistance, it is necessary to reduce the rigidity. As shown in FIGS. 2 and 3, the bridging member between the nth giant magnetostrictive element and the (n + 1) th giant magnetostrictive element is made wide and thick so as to function as a rigid body. Thin and bend easily. That is, an elastic hinge, which will be described later, corresponds to a fulcrum portion of the lever, and is a portion that connects the bridge portion of the lever to the fixed portion and has a rigidity lower than at least the bridge portion. The fulcrum part may be a knife edge.

  If the outer shape of the insulator is formed in a ring shape around the entire circumference so that the end face of each giant magnetostrictive element is bonded to the insulator over the entire surface, the rigidity of the insulator becomes higher. Since a twisting force is generated on the outside, there is an increased risk that the giant magnetostrictive element will be damaged, and the rigidity of the fulcrum part of the insulator will also increase. The sex will be reduced.

  For this reason, as shown in FIG. 3, when four places are arranged at equal intervals with respect to the circumference, the twisting force against the displacement of the giant magnetostrictive element and the rigidity of the fulcrum do not increase. Good. The number of insulators arranged around the circumference may be six or eight instead of the four in the present embodiment, and even if an odd number such as three or five, the displacement can be surely increased and transmitted, and high linearity can be achieved. And long life can be secured.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the linear actuator is used for driving an optical element. The linear actuator of the present invention is particularly suitable for driving an optical member, but can be applied to any application where it is desired to suppress the tilt of a driven member to be driven.

  ADVANTAGE OF THE INVENTION According to this invention, it is suitable for the drive of optical elements, such as a lens, and can provide the linear actuator which can attain thickness reduction.

It is a perspective view of the linear actuator concerning this Embodiment. It is sectional drawing of the linear actuator concerning this Embodiment. It is a perspective view which shows the relationship between a giant magnetostrictive element and an insulator.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a linear actuator according to this embodiment, and FIG. 2 is a cross-sectional view of the linear actuator according to this embodiment. FIG. 3 is a perspective view showing the relationship between the giant magnetostrictive element and the insulator.

  In FIG. 2, the linear actuator of the present embodiment includes a nonmagnetic casing 10 that is a fixed portion fixed to a frame or the like, a driven member 20, giant magnetostrictive elements 31 to 34, and insulators 41 to 43. And a coil 50. The housing 10 includes a rectangular plate-shaped top plate 11 and a bottom plate 12, and a rectangular tube-shaped side plate 13 that connects the top plate 11 and the bottom plate 12 on the outside. The top plate 11 and the bottom plate 12 are provided with openings 11a and 12a in the center, respectively, and a lens LS2 is fixed to the inner periphery of the opening 12a. A coil 50 is wound around the outer periphery of the side plate 13, and the coil 50 receives power from an external power source DC as shown in FIG. The top plate 11 and the bottom plate 12 may have a cylindrical shape, and the side plate 13 may have a cylindrical shape.

  The four giant magnetostrictive elements 31 to 34 have cylindrical shapes with different diameters, and are arranged coaxially so that each axis coincides with the axis of the side plate 13. In the giant magnetostrictive elements 31 to 34, it is preferable that the thickness of the radially outer giant magnetostrictive element is larger than the thickness of the radially inner giant magnetostrictive element, but may be equal.

  The upper end of the outermost magnetostrictive element 31 is fixed to the lower surface of the top plate 11 of the housing 10, and the lower end is connected to the outer end of the insulator 41. The inner end of the insulator 41 is connected to the lower end of the second giant magnetostrictive element 32 from the outside, and the upper end is connected to the outer end of the insulator 42. The inner end of the insulator 42 is connected to the upper end of the third giant magnetostrictive element 33 from the outside, and the lower end is connected to the outer end of the insulator 43. The inner end of the insulator 43 is connected to the lower end of the innermost magnetostrictive element 34 in the radial direction, and the upper end thereof is connected to the lower end of the substantially cylindrical driven member 20.

  The driven member 20 is disposed in the opening 11a of the top plate 11 of the housing 10, and a lens LS1 is attached to the inner periphery. The optical axis of the lens LS1 coincides with the optical axis of the lens LS2. A step portion 11b is formed around the opening 11a on the lower surface of the top plate 11, and a coil spring 70 disposed therein urges the driven member 20 downward in FIG.

  As shown in FIG. 3 (however, the insulator 42 is not shown in FIG. 3), the rectangular plate-like insulators 41 to 43 are connected to the ends of the adjacent giant magnetostrictive elements 31 to 34, respectively. They are arranged at equal intervals in the circumferential direction. As shown in FIG. 2, the insulator 41 is swingably attached to the upper surface of the bottom plate 12 by an elastic hinge 41a, and the insulator 42 is swingably attached to the lower surface of the top plate 11 by an elastic hinge 42a. Is swingably attached to the upper surface of the bottom plate 12 by an elastic hinge 43a. Here, each of the insulators 41 to 43 has a length (A) from the elastic hinges 41a to 43a to the attaching portion of the super magnetostrictive element on the radially outer side to the attaching portion of the super magnetostrictive element on the radially inner side. The lever ratio is set so as to be shorter than (B).

  The operation of the linear actuator according to this embodiment will be described. The linear actuator according to the present embodiment can be used for driving a lens that exhibits an autofocus and zoom function in an imaging device mounted on a digital camera or a mobile phone. When a signal for moving the lens LS1 in the optical axis direction is output from a control device (not shown), power is supplied to the coil 50 from the external power source DC, and thereby the four giant magnetostrictive elements 31 to 34 expand.

  Here, in FIG. 2, since the upper end of the outermost magnetostrictive element 31 in the radial direction is fixed to the lower surface of the top plate 11 of the casing 10, all the displacement is transmitted to the insulator 41 via the lower end. The lower end of the second giant magnetostrictive element 32 from the outside is pushed up by the displacement amount enlarged by the lever ratio. The amount of displacement of the giant magnetostrictive element 32 is superimposed on this, transmitted from the upper end to the insulator 42, and further pushed down the upper end of the third giant magnetostrictive element 33 from the outside with the amount of displacement enlarged by the lever ratio. The amount of displacement of the giant magnetostrictive element 33 is superimposed on this, transmitted from the lower end to the insulator 43, and further pushed up the lower end of the innermost giant magnetostrictive element 34 with the amount of displacement enlarged by the lever ratio. Since the displacement amount of the giant magnetostrictive element 33 is superimposed on this and the driven member 20 is pushed up against the urging force of the coil spring 70 via its upper end, the lens LS1 can move in the optical axis direction. By controlling the magnitude of the current supplied to the coil 50, the strength of the magnetic field generated inside the coil can be changed, so that the amount of movement of the lens LS1 in the optical axis direction can be adjusted and controlled.

  On the other hand, when the power supply from the external power source DC to the coil 50 is interrupted, the four giant magnetostrictive elements 31 to 34 contract to the original state, so that the driven member 20 together with the lens LS1 follows the biasing force of the coil spring 70. To come back.

  According to the present embodiment, since the coil 50 is arranged substantially coaxially on the outer side in the direction orthogonal to the axis of the giant magnetostrictive elements 31 to 34, the magnetic field generated in the coil 50 when the coil 50 is fed from the external power source DC is It acts on all the giant magnetostrictive elements 31 to 34 on the inner side and can be expanded and contracted. Since the giant magnetostrictive elements 31 to 34 are cylindrical, they are arranged in a magnetic field having a uniform strength both in the circumferential direction and in the radial direction, and the amount of expansion / contraction is uniform. Thereby, the giant magnetostrictive elements 31 to 34 can be expanded and contracted without tilting the axis. In addition, since the shape of the giant magnetostrictive elements 31 to 34 that expand and contract by supplying power to the coil 50 is cylindrical, the support end surfaces of the giant magnetostrictive elements 31 to 34 are increased, and the reaction force from the driven member 20 Even if it receives a large force, it can be made into a structure that can be translated and expanded uniformly in the axial direction because of its substantially rotational shape, and it can tilt the driven member 20 without using any guide mechanism to ensure straightness. High rigidity and straight movement. As a result, it is possible to realize a structure that advances and retreats in one direction with high accuracy without giving tilt or twist to the driven member 20, so that reliable and reliable operation is possible for applications such as autofocus, zoom, or camera shake correction. Can provide.

  Furthermore, according to the present embodiment, since the four insulators 41 to 43 are arranged at equal intervals in the circumferential direction, the coaxiality at the time of expansion / contraction of the giant magnetostrictive elements 31 to 34 can be maintained. The number of giant magnetostrictive elements is not limited to four, and may be three or five or more.

  In addition, since the fixed portion between the driven member 20 and the giant magnetostrictive element 31 is a ring-shaped end surface that has a spread, reliable abutment can be ensured even in connection with the driven member, and the feed by expansion and contraction can be ensured. It can be fixed with high accuracy in the axial direction. As described above, according to the present embodiment, it is possible to realize a linear actuator that has good straightness, high accuracy, and high displacement.

Hereinafter, the examination results of the present inventors will be described. 1 to 3, the number of substantially cylindrical super magnetostrictive elements is N, one end of the super magnetostrictive element arranged on the outermost periphery is fixed, and one end of the innermost super magnetostrictive element is Consider the case where it is fixed to a driven member. The end face of the other giant magnetostrictive element is attached to an insulator by an elastic hinge. When the enlargement ratio of this insulator is set to n times, the final displacement enlargement ratio M is
M = n · exp (N−1) + n · exp (N−2) +... + N + 1 (1)
It is expressed as a geometric series. Accordingly, the final displacement enlargement ratio M is rewritten as follows.
M = (1-n · exp (N)) / (1-n) (2)

For example, if the number of giant magnetostrictive elements N is 4 and the enlargement factor n of the insulator is 2, the final enlargement factor M is 15 times according to the equation (2). The amount of displacement due to the magnetic field of the giant magnetostrictive element is approximately 1000 ppm / kOe, and the magnetic field generated by flowing a current of 80 mA through a 330-turn coil having a diameter of 10 mm corresponds to 1 kOe. When the final displacement D is calculated with a thickness of 1 mm,
D = 1 mm × 1000 ppm / kOe × 1 kOe × 15 times = 15 μm (3)
Thus, a displacement of 15 μm can be created with a thickness of only 1 mm. Further, when the enlargement factor n of the insulator is 3 and the drive current is 150 mA, the final enlargement factor M is 40 times and the final displacement amount D is 75 μm, and an extremely large displacement amount can be obtained.

  However, even if such a large displacement is generated, if the trajectory of expansion or contraction is inclined or twisted, it is not possible to obtain the straight movement accuracy of the driven member. On the other hand, if the giant magnetostrictive element has a cylindrical shape (or may be a rectangular tube shape) and has a good rotational symmetry, expansion and contraction are uniformly performed in the axial direction, and the moved member is inclined. There is no turning.

The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate.

DESCRIPTION OF SYMBOLS 10 Case 11 Top plate 11a Opening 11b Step part 12 Bottom plate 12a Opening 13 Side plate 20 Driven member 31-34 Giant magnetostrictive element 41-43 Insulator 41a-43a Elastic hinge 50 Coil 70 Coil spring LS1 Lens LS2 Lens

Claims (5)

  A cylindrical super magnetostrictive element; and a coil disposed substantially coaxially with the super magnetostrictive element on the outer side in the direction orthogonal to the axis of the super magnetostrictive element, and driving the super magnetostrictive element by a magnetic field generated from the coil. To move the driven member with respect to the fixed portion.   The number of the giant magnetostrictive elements is N (N is an integer of 2 or more), the diameters of the giant magnetostrictive elements are different, and the giant magnetostrictive elements are coaxially arranged, and n (n The displacement of the first giant magnetostrictive element is transmitted from the outer side in the direction perpendicular to the axis to the (n + 1) th giant magnetostrictive element via an insulator. The linear actuator according to claim 1.   The one end of the giant magnetostrictive element on the outermost peripheral side is connected to the fixed portion, and the one end of the giant magnetostrictive element on the innermost peripheral side is connected to the driven member. 2. The linear actuator according to 2.   4. The insulator according to claim 2, wherein a plurality of insulators connecting the n-th giant magnetostrictive element and the (n + 1) -th giant magnetostrictive element are provided and arranged at equal intervals in the circumferential direction. The linear actuator described.   The linear actuator according to claim 1, wherein the linear actuator is used for driving an optical element.

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