JP2009159574A - Planar vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar vibrator which uses a high magnetostriction material, is capable of miniaturization and simplification, and is suitable for a speaker or an ultrasonic-wave generating source. <P>SOLUTION: The planar vibrator includes a planar magnetostriction member 2, a bias magnetic-field generating magnet 4 and a coil 6 respectively arranged at different positions in planar directions L of the magnetostriction member, and a yoke 8 arranged in a direction T perpendicular to the planar directions of the magnetostriction member from the periphery of the magnetostriction member and extending at least up to the height same as that of the bias magnetic-field generating magnet. The planar vibrator functions as a vibrator by making the magnetostriction member be expanded and contracted in the planar directions by a signal supplied to the coil 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vibrator using a magnetostrictive material, for example, a vibrator suitable for use in a speaker or an ultrasonic wave generation source.

  Conventionally, a planar speaker using a plate piezoelectric element is known (see Patent Document 1). A speaker using a magnetostrictive material instead of a piezoelectric element is also known (see Patent Documents 2 and 3).

Japanese Patent Laid-Open No. 10-117397 Japanese Patent Laid-Open No. 11-266496 Japanese Patent No. 3615883

  However, in the case of the technique described in Patent Document 1, the displacement amount is small because the displacement in the thickness direction of the piezoelectric element is used. Furthermore, since impedance conversion is necessary for high voltage driving, there is a problem that there is a limit to downsizing of the power supply. Further, the mechanical strength of the piezoelectric element itself is low, and it is weak against bending stress and impact force.

  On the other hand, in the case of the techniques described in Patent Documents 2 and 3, since the magnetostrictive material is rod-shaped and uses vibration in the length direction, a certain amount of rod length is required to obtain a large speaker volume. Therefore, there is a problem that it is difficult to manufacture a thin planar speaker because the thickness of the speaker is increased.

  Further, as a magnetostrictive material for a planar speaker, a conventional magnetostrictive material such as iron or nickel has a small magnetostriction amount, and it is difficult to obtain a large speaker volume. Furthermore, the giant magnetostrictive material Terfenol-D is brittle and difficult to process into a disk shape.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a planar vibrator that uses a plate-like magnetostrictive material and can be miniaturized and simplified and can be greatly displaced in a plane direction. And

  In order to achieve the above object, the planar vibrator of the present invention uses a magnetostrictive material made of an iron-based alloy having excellent workability.

  Accordingly, the magnetostrictive member processed into a flat plate shape, the bias magnetic field generating magnet and the coil arranged at different positions in the plane direction of the magnetostrictive member, and the direction perpendicular to the plane direction of the magnetostrictive member from the periphery of the magnetostrictive member And a yoke extending at least as high as the bias magnetic field generating magnet, and the magnetostrictive member expands and contracts in the plane direction by a signal supplied to the coil.

  With such a configuration, since the magnetostrictive member expands and contracts in the plane direction, it is possible to increase the amount of displacement compared to a conventional planar vibrator that displaces in the thickness direction using a piezoelectric element. Can be bigger.

  Furthermore, since the magnetostrictive material has higher mechanical strength than the piezoelectric element, it can be resistant to bending stress and impact force.

  Further, the thickness of the speaker can be reduced as compared with a speaker using a conventional rod-shaped magnetostrictive member, and the degree of freedom of the shape of the planar vibrator is increased. Further, the magnetostrictive member itself acts as a diaphragm.

  In order to obtain a larger volume, it is necessary to provide a diaphragm separately. However, it is possible to attract and fix the diaphragm made of a magnetic material by using the leakage magnetic flux of the bias magnetic field generating magnet disposed in the speaker. Can be reduced in size and simplified.

  Instead of the yoke, the magnetostrictive member may extend from the periphery in the perpendicular direction.

  The magnetostrictive member is a bimorph formed by laminating a flat positive magnetostrictive material and a flat negative magnetostrictive material, the positive magnetostrictive material is located on the surface side, and a magnetic flux is applied by a signal supplied to the coil. Then, the displacement of the magnetostrictive member rising on the surface side may be superimposed.

  In such a configuration, the magnetostrictive member is expanded and contracted in the plane direction by the signal supplied to the coil, and the displacement rising on the surface side (positive magnetostrictive material side) is superimposed. For example, the volume of the speaker can be further increased.

  A slit for reducing eddy current loss may be formed in at least a part of the magnetostrictive member and / or the yoke.

  According to the present invention, a planar magnetostrictive material is used, and the planar vibrator can be miniaturized and simplified and can be greatly displaced in the plane direction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig.1 (a) is a perspective view which shows the structure of the planar vibrator | oscillator which concerns on the 1st Embodiment of this invention, and the target object of a vibration, FIG.1 (b) is A- of Fig.1 (a). It is a perspective view of the section in A '. In this figure, a planar vibrator 20 includes a disk-shaped magnetostrictive member 2, a bias magnetic field generating magnet 4, a coil 6, and a yoke 8 arranged on the upper surface of the magnetostrictive member 2. ) 10 is adsorbed.

  The bias magnetic field generating magnet 4 has a ring shape and is disposed on the lower surface of the yoke 8 so as to be concentric with the center 2c of the magnetostrictive member 2. The coil 6 also has a ring shape, and is disposed on the lower surface of the yoke 8 outside the bias magnetic field generating magnet 4 and concentric with the center 2c of the magnetostrictive member 2. As described above, the bias magnetic field generating magnet 4 and the coil 6 are respectively arranged at different positions in the plane direction L of the magnetostrictive member 2.

  The yoke 8 is a disk having the same size as the magnetostrictive member 2 and is concentrically laminated on the lower surface of the magnetostrictive member 2. Further, the yoke 8 is disposed in the direction T perpendicular to the planar direction L of the magnetostrictive member from the periphery thereof and extends at least to the same thickness (height) as the bias magnetic field generating magnet 4. The outer edge of the coil 6 is located inside the extending portion of the yoke 8.

  In this embodiment, the second yoke 8b is disposed in the gap in the center of the bias magnetic field generating magnet 4, but the second yoke 8b is not necessarily provided. On the other hand, in order to apply a sufficient bias magnetic field in the plane direction of the magnetostrictive member 2, the yoke 8 is an essential configuration in the first embodiment.

  As the magnetostrictive member 2, it is preferable to use a high magnetostrictive material which can be processed into a thin disk shape and has a large magnetostriction amount. Examples of the high magnetostrictive material include Fe—Ga alloy, Fe—Co alloy, and Fe—Al alloy.

  Next, a mode in which the magnetostrictive member 2 is displaced by a magnetic field will be described with reference to FIG. A bias magnetic field Hm from the center 2c side to the peripheral side is applied from the bias magnetic field generating magnet 4 on the surface (plane direction L) of the magnetostrictive member 2.

  Here, when a current is applied to the coil 6 to generate a magnetic field Hc from the center 2c side to the peripheral side in the plane direction L, the entire plane direction L of the magnetostrictive member 2 is from the center 2c side to the peripheral side. A magnetic field of Hm + Hc is applied. Accordingly, the magnetostrictive member 2 is displaced so as to extend in the plane direction L from the center 2c toward the periphery.

  On the other hand, if a magnetic field −Hc having an opposite phase is applied to the coil 6, a magnetic field of Hm−Hc from the center 2 c side to the peripheral side as a whole is applied in the plane direction L of the magnetostrictive member 2. Accordingly, the magnetostrictive member 2 contracts in the plane direction L (compared to when a magnetic field of Hm + Hc is applied). In this way, the magnetostrictive member 2 periodically contracts in the plane direction L at the frequency of the alternating magnetic field.

  The relationship between the AC magnetic field applied to the coil 6 and the displacement of the magnetostrictive member 2 is described, for example, in the specification of Japanese Patent No. 22652644 and FIG.

  Since the magnetostrictive member 2 expands and contracts in the plane direction L in this way, the amount of displacement can be increased as compared with a planar vibrator that displaces in the thickness direction using a conventional piezoelectric element. For example, the volume of the speaker is increased. be able to.

  In addition, the magnetostrictive material has a large anisotropy, and it is difficult to make the displacement in the thickness direction constant when it is a flat plate. However, in the present invention, the plate-like magnetostrictive material is displaced in the plane direction. The problem can be avoided.

  The displacement of the magnetostrictive member 2 is transmitted to the target body 10 that has attracted the planar vibrator 20, and a sound wave is generated when the target body 10 vibrates.

  Further, in the present invention, the thickness of the speaker can be reduced compared to a conventional speaker using a rod-shaped magnetostrictive member, and the degree of freedom of the shape of the planar vibrator is increased.

  Furthermore, since the magnetostrictive member itself acts as a diaphragm, the size and simplification can be achieved as compared with a speaker using a conventional magnetostrictive member in which a diaphragm is provided separately.

  In addition to this, the yoke extends in the direction perpendicular to the plane direction of the magnetostrictive member from its periphery and extends at least to the same thickness (position) as the bias magnetic field generating magnet, so that the magnetic flux wraps around the back surface of the planar vibrator. The planar vibrator can be attracted and fixed by magnetic force to the object (magnetic body) 10 placed on the back surface of the planar vibrator.

  When the object 10 placed on the back surface of the planar vibrator is a non-magnetic material, the planar vibrator can be fixed to the object 10 by installing a magnetic material on the back surface.

  The size of the planar vibrator according to the first embodiment of the present invention is not particularly limited. For example, the diameter of the magnetostrictive member 2 may be 2 to 10 mm, and the thickness of the planar vibrator may be about 1 to 5 mm.

  In the first embodiment, an effect of reducing eddy current loss can be obtained by providing slits in both or either of the peripheral edge of the magnetostrictive member 2 and the side surface of the yoke 8.

  Next, a planar vibrator according to a second embodiment of the present invention will be described with reference to FIG. 3 which is a cross-sectional perspective view showing the configuration. In this figure, the planar vibrator 21 includes a disk-shaped magnetostrictive member 3, a bias magnetic field generating magnet 4b, and a coil 6, but does not include a yoke.

  In the second embodiment, the magnetostrictive member 3 is bimorph, the bias magnetic field generating magnet 4b is not in a ring shape but in a disk shape (solid), and no yoke is provided. Since there is no difference from the first embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The magnetostrictive member 3 is a bimorph in which a disc-like positive magnetostrictive material 3x and a negative magnetostrictive material 3y having the same size are laminated concentrically, and the positive magnetostrictive material 3x is located on the surface side. When a magnetic field is applied to the bimorph, the negative magnetostrictive material 3y contracts, the positive magnetostrictive material 3x expands, and the surface of the bimorph is displaced (raised) toward the positive magnetostrictive material 3x (upper side in FIG. 4).

  On the other hand, the positive magnetostrictive material 3x itself constituting the magnetostrictive member 3 expands and contracts in the plane direction L by a signal supplied to the coil 6 in the same manner as in the first embodiment.

  Accordingly, the magnetostrictive member 3 is superposed on the surface side (positive magnetostrictive material 3x side) in addition to the expansion and contraction in the plane direction L by the signal supplied to the coil 6, so that the displacement amount is further increased. The volume of the speaker can be further increased.

  Examples of the negative magnetostrictive material 3y include Ni-based alloys. Moreover, these can be laminated | stacked by adhere | attaching or welding (spot welding etc.) the negative magnetostrictive material 3x and the positive magnetostrictive material 3y.

  In addition, when the negative magnetostrictive material 3y side is located on the surface, the magnetostrictive member 3 does not rise to the surface side due to a signal to the coil 6 and is not suitable because the displacement amount is not increased.

  In the second embodiment, instead of the yoke, the positive magnetostrictive material 3x constituting the magnetostrictive member 3 is extended in the direction T perpendicular to the periphery thereof, and the outer edge of the negative magnetostrictive material 3y is provided inside the extended portion. And the outer edge of the coil 6 is located.

  The extending portion of the positive magnetostrictive material 3x acts as a yoke, and the magnetic flux can be effectively utilized by increasing the magnetic flux density of the bias magnetic field generating magnet 4b.

  The present invention is not limited to the above embodiment. For example, the planar shape of the magnetostrictive member is not limited and can be, for example, a rectangular plate shape in addition to a disk shape.

  In the first embodiment, the shape of the yoke is not limited, and any shape may be used as long as it extends in the perpendicular direction from the periphery of the magnetostrictive member. For example, a ring-shaped yoke or a ring having a central portion opened in a donut shape. Can be used.

  In the first embodiment, the yoke may be disposed on the lower surface of the magnetostrictive member, and the lower surface of the yoke may be attracted to the object. In this case as well, it can function as a vibrator.

  Further, in the first embodiment, a negative magnetostrictive member may be interposed between the magnetostrictive member and the yoke, and the magnetostrictive member may be configured as a bimorph so that the same action as in the second embodiment is added.

  In the second embodiment, the positive magnetostrictive material 3x extending toward the object 10 in the direction T perpendicular to the periphery of the positive magnetostrictive material 3x extends toward the object 10 instead of the direction perpendicular to the periphery. You may make it extend at an angle so that it may become.

  Further, in the second embodiment, the negative magnetostrictive member is eliminated, that is, in the first embodiment, the periphery of the magnetostrictive member instead of the yoke is in a direction perpendicular to the object 10 or in a direction of spreading toward the end. It can be extended. Furthermore, in the second embodiment, the periphery of the negative magnetostrictive member may be extended toward the object 10 instead of the positive magnetostrictive member.

  The present invention can be applied to all uses for expanding and contracting the magnetostrictive member in its plane, and is particularly advantageous in that the thickness can be reduced. In particular, the present invention is effective as a speaker or an ultrasonic wave transmission source.

1A and 1B are a perspective view and a cross-sectional perspective view showing a configuration of a planar vibrator according to a first embodiment of the present invention. It is sectional drawing which shows the aspect which a magnetostriction member displaces with magnetic flux. It is a cross-sectional perspective view which shows the structure of the planar vibrator | oscillator based on the 2nd Embodiment of this invention.

Explanation of symbols

2, 3 magnetostrictive member 2c (magnetostrictive member 2) center 3x positive magnetostrictive material 3y negative magnetostrictive material 4, 4b bias magnetic field generating magnet 6 coil 8, 8b yoke 10 object (iron plate)
20, 21 Planar vibrator Hm, Hc Magnetic field L Planar direction of magnetostrictive member T Direction perpendicular to plane direction

Claims (3)

A plate-like magnetostrictive member;
Bias magnetic field generating magnets and coils respectively disposed at different positions in the plane direction of the magnetostrictive member;
A yoke extending from a peripheral edge of the magnetostrictive member in a direction perpendicular to the planar direction of the magnetostrictive member, and having at least the same height as the bias magnetic field generating magnet,
A planar vibrator in which the magnetostrictive member expands and contracts in the planar direction by a signal supplied to the coil.   The planar vibrator according to claim 1, wherein the magnetostrictive member is extended from the peripheral edge in the perpendicular direction instead of the yoke.   3. The planar vibrator according to claim 1, wherein the magnetostrictive member is a bimorph formed by laminating a flat positive magnetostrictive material and a flat negative magnetostrictive material.

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