JP2009159574

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DESCRIPTION JP2009159574
The present invention provides a planar vibrator suitable as a speaker and an ultrasonic wave
generation source, which can be miniaturized and simplified by using a high magnetostrictive
material. A flat magnetostrictive member 2, bias magnetic field generating magnets 4 and coils 6
disposed at different positions in the planar direction L of the magnetostrictive member, and a
direction perpendicular to the planar direction of the magnetostrictive member from the
periphery of the magnetostrictive member A yoke 8 disposed at T and extending to at least the
same height as the bias magnetic field generating magnet is provided, and the magnetostrictive
member expands and contracts in a planar direction by a signal supplied to the coil 6 to function
as a vibrator. [Selected figure] Figure 1
Planar oscillator
[0001]
The present invention relates to a vibrator using a magnetostrictive material, for example, to a
vibrator suitable for use as a speaker or an ultrasonic wave generation source.
[0002]
Conventionally, a planar speaker using a flat plate piezoelectric element is known (see Patent
Document 1).
There is also known a speaker using a magnetostrictive material instead of a piezoelectric
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element (see Patent Documents 2 and 3).
[0003]
Patent Document 1: Japanese Patent Application Laid-Open No. 10-117397 Patent Document No.
11-266496 Patent No. 3615883
[0004]
However, in the case of the technology described in Patent Document 1 described above, the
displacement amount is small because displacement in the thickness direction of the piezoelectric
element is used.
Furthermore, there is a problem that there is a limit to the miniaturization of the power supply
because impedance conversion is required by high voltage driving. In addition, the mechanical
strength of the piezoelectric element itself is low and it is weak to bending stress and impact
force.
[0005]
On the other hand, in the case of the techniques described in Patent Documents 2 and 3
described above, since the magnetostrictive material is in the shape of a rod and vibration in the
length direction is used, a certain rod length is necessary to obtain a large speaker volume. Since
the thickness of the speaker is increased, there is a problem that it is difficult to manufacture a
thin planar speaker.
[0006]
Further, as a magnetostrictive material of the planar speaker, the magnetostriction amount is
small with a conventional magnetostrictive material such as iron or nickel, and it is difficult to
obtain a large speaker volume.
Furthermore, since the giant magnetostrictive material Terfenol-D is brittle, it is difficult to
process it into a disk shape.
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[0007]
The present invention has been made to solve the above-mentioned problems, and it is an object
of the present invention to provide a planar vibrator which can be miniaturized or simplified and
which can be largely displaced in a plane direction by using a flat magnetostrictive material. I
assume.
[0008]
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.
[0009]
Thus, the magnetostrictive member processed into a flat plate shape, the bias magnetic field
generating magnet and the coil respectively disposed at different positions in the plane direction
of the magnetostrictive member, and the periphery of the magnetostrictive member in the
direction perpendicular to the plane direction of the magnetostrictive member The yoke is
disposed and extended to at least the same height as the bias magnetic field generating magnet,
and the magnetostrictive member is expanded and contracted in the planar direction by a signal
supplied to the coil.
[0010]
With such a configuration, the magnetostrictive member expands and contracts in the planar
direction, so the displacement amount can be increased compared to a planar vibrator that
displaces in the thickness direction using a conventional piezoelectric element. It can be
enlarged.
[0011]
Furthermore, since the magnetostrictive material has higher mechanical strength compared to
the piezoelectric element, it can be made resistant to bending stress and impact force.
[0012]
In addition, the thickness of the speaker can be reduced as compared with the conventional
speaker using a rod-shaped magnetostrictive member, and the degree of freedom of the shape of
the planar vibrator becomes high.
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Furthermore, the magnetostrictive member itself acts as a diaphragm.
[0013]
In order to obtain a higher volume, it is necessary to separately provide the diaphragm, but
suction and fixation to the diaphragm made of a magnetic material using the leakage flux of the
bias magnetic field generating magnet disposed in the speaker And can be miniaturized and
simplified.
[0014]
Instead of the yoke, the magnetostrictive member may be extended from the peripheral edge in
the perpendicular direction.
[0015]
The magnetostrictive member is a bimorph formed by laminating a flat plate-like positive
magnetostrictive material and a flat plate-like negative magnetostrictive material, the positive
magnetostrictive material is positioned on the surface side, and a magnetic flux is applied by a
signal supplied to the coil. The displacement in which the magnetostrictive member bulges to the
surface side may be superimposed.
[0016]
With such a configuration, the magnetostrictive member is expanded and contracted in the plane
direction by the signal supplied to the coil, and the displacement that bulges on the surface side
(the positive magnetostrictive material side) is superimposed, so the displacement amount is
further increased. For example, the volume of the speaker can be further increased.
[0017]
At least a portion of the magnetostrictive member and / or the yoke may be formed with a slit for
reducing eddy current loss.
[0018]
According to the present invention, a planar magnetostrictive material can be used to miniaturize
and simplify a planar vibrator and can be largely displaced in the planar direction.
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[0019]
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 and the target
object of a vibration which concern on the 1st Embodiment of this invention, FIG.1 (b) is an A- of
FIG. 1 (a). It is a perspective view of the cross section in A '.
In this figure, the planar vibrator 20 includes a disc-shaped magnetostrictive member 2, a bias
magnetic field generating magnet 4, a coil 6, and a yoke 8 disposed on the upper surface of the
magnetostrictive member 2. ) Is adsorbed to 10).
[0020]
The bias magnetic field generating magnet 4 has a ring shape, and is disposed on the lower
surface of the yoke 8 concentrically with the center 2 c 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 2 c of the
magnetostrictive member 2.
Thus, the bias magnetic field generating magnet 4 and the coil 6 are respectively disposed at
different positions in the planar direction L of the magnetostrictive member 2.
[0021]
The yoke 8 is a disc having the same size as the magnetostrictive member 2, and is concentrically
stacked on the lower surface of the magnetostrictive member 2.
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The yoke 8 is disposed from the periphery in a direction T perpendicular to the planar direction
L of the magnetostrictive member, and extends to at least the same thickness (height) as the bias
magnetic field generating magnet 4.
The outer edge of the coil 6 is located inside the extension of the yoke 8.
[0022]
In this embodiment, the second yoke 8b is disposed in the air gap of the central portion of the
bias magnetic field generating magnet 4, but the second yoke 8b may not necessarily be
provided.
On the other hand, in order to apply a sufficient bias magnetic field in the planar direction of the
magnetostrictive member 2, the yoke 8 is an essential configuration in the first embodiment.
[0023]
As the magnetostrictive member 2, it is preferable to use a high magnetostrictive material that
can be processed into a thin disk shape and has a large amount of magnetostriction.
Examples of the high magnetostrictive material include an Fe-Ga alloy, an Fe-Co alloy, and an FeAl alloy.
[0024]
Next, an aspect in which the magnetostrictive member 2 is displaced by the magnetic field will be
described with reference to FIG.
From the bias magnetic field generating magnet 4, a bias magnetic field Hm is applied from the
center 2 c side to the peripheral side in the surface (planar direction L) of the magnetostrictive
member 2.
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[0025]
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 planar direction L, the magnetostrictive member 2 generally
proceeds from the center 2c to the peripheral side as a whole. A magnetic field of Hm + Hc is
applied.
Therefore, the magnetostrictive member 2 is displaced so as to extend in the planar direction L
from the center 2c toward the peripheral edge.
[0026]
On the other hand, when the magnetic field -Hc of opposite phase is applied to the coil 6, a
magnetic field of Hm-Hc from the center 2c side toward the peripheral side as a whole is applied
in the planar direction L of the magnetostrictive member 2. Therefore, the magnetostrictive
member 2 contracts in the planar direction L (compared to when a magnetic field of Hm + Hc is
applied). Thus, the magnetostrictive member 2 contracts periodically in the planar direction L at
the frequency of the AC magnetic field.
[0027]
The relationship between the AC magnetic field applied to the coil 6 and the displacement of the
magnetostrictive member 2 is described in, for example, the specification of Japanese Patent No.
2652644 and FIG.
[0028]
As described above, since the magnetostrictive member 2 expands and contracts in the planar
direction L, the amount of displacement can be increased compared to a planar vibrator that is
displaced in the thickness direction using a conventional piezoelectric element. For example, the
volume of the speaker is increased. be able to.
[0029]
In addition, although the magnetostrictive material has large anisotropy and it is difficult to make
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the displacement in the thickness direction constant in the case of a flat plate, in the present
invention, this is because the flat magnetostrictive material is displaced in the planar direction.
You can avoid the problem.
[0030]
The displacement of the magnetostrictive member 2 is transmitted to the target object 10 having
adsorbed the planar vibrator 20, and the target object 10 vibrates to generate a sound wave.
[0031]
Further, in the present invention, the thickness of the speaker can be reduced as compared with
the conventional speaker using a rod-shaped magnetostrictive member, and the degree of
freedom of the shape of the planar vibrator becomes high.
[0032]
Furthermore, since the magnetostrictive member itself acts as a diaphragm, miniaturization and
simplification can be achieved as compared with a speaker using a magnetostrictive member
provided separately with a diaphragm.
[0033]
In addition to these, since the yoke extends from the peripheral edge in a direction perpendicular
to the planar direction of the magnetostrictive member and extends at least to the same
thickness (position) as the bias magnetic field generating magnet, the magnetic flux wraps
around the back surface of the planar vibrator. The planar vibrator can be attracted and fixed to
the target (magnetic body) 10 placed on the back of the planar vibrator by magnetic force.
[0034]
When the target 10 placed on the back of the planar vibrator is a nonmagnetic material, the
planar vibrator can be fixed to the target 10 by placing a magnetic body on the back.
[0035]
The size of the planar vibrator according to the first embodiment of the present invention is not
particularly limited, but can be, for example, about 2 to 10 mm in diameter of the
magnetostrictive member 2 and about 1 to 5 mm in thickness of the planar vibrator.
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[0036]
Further, in the first embodiment, the effect of reducing the eddy current loss can be obtained by
providing a slit in both of the peripheral edge of the magnetostrictive member 2 and the side
surface of the yoke 8 or one of them.
[0037]
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 its
configuration.
In this figure, the planar vibrator 21 includes the disc-shaped magnetostrictive member 3, the
bias magnetic field generating magnet 4b, and the coil 6, but does not include the yoke.
[0038]
In the second embodiment, the second embodiment is the same as the second embodiment
except that the magnetostrictive member 3 is a bimorph, the bias magnetic field generating
magnet 4b is not a ring but a disk (solid), and the yoke is not provided. There is no difference
from the first embodiment, so the same components as in the first embodiment will be assigned
the same reference numerals and descriptions thereof will be omitted.
[0039]
The magnetostrictive member 3 is a bimorph in which a disc-shaped positive magnetostrictive
material 3x and a negative magnetostrictive material 3y having the same size as that of the
magnetostrictive member 3 are concentrically stacked, and the positive magnetostrictive material
3x is positioned on the surface side.
When a magnetic field is applied to the bimorph, the negative magnetostrictive material 3y
shrinks, the positive magnetostrictive material 3x expands, and the surface of the bimorph
displaces (raises) to the positive magnetostrictive material 3x side (upper side in FIG. 4).
[0040]
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On the other hand, the positive magnetostrictive material 3x itself constituting the
magnetostrictive member 3 expands and contracts in the planar direction L by the signal
supplied to the coil 6 in the same manner as in the first embodiment.
[0041]
Therefore, in addition to the expansion and contraction in the planar direction L by the signal
supplied to the coil 6, the displacement that bulges on the surface side (the positive
magnetostrictive material 3x side) is superimposed, and the displacement amount further
increases. The volume of the speaker can be further increased.
[0042]
An example of the negative magnetostrictive material 3y is a Ni-based alloy.
Moreover, these can be laminated ¦ stacked by adhere ¦ attaching or welding (spot welding etc.)
the negative magnetostriction material 3x and the positive magnetostriction material 3y.
[0043]
When the negative magnetostrictive material 3y side is located on the surface, the
magnetostrictive member 3 is not raised to the surface side by the signal to the coil 6, and the
displacement amount is not increased, which is not suitable.
[0044]
In the second embodiment, instead of the yoke, the positive magnetostrictive material 3x
constituting the magnetostrictive member 3 is extended from the peripheral edge in the direction
T perpendicular thereto, and the outer edge of the negative magnetostrictive material 3y inside
the extended portion And the outer edge of the coil 6 is located.
[0045]
Then, the extended portion of the positive magnetostrictive material 3x acts as a yoke, and the
magnetic flux density of the bias magnetic field generating magnet 4b can be increased to
effectively utilize the magnetic force.
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[0046]
The present invention is not limited to the above embodiment.
For example, the planar shape of the magnetostrictive member is not limited, and may be, for
example, a rectangular plate other than the disk.
[0047]
In the first embodiment, the shape of the yoke is not limited as long as it extends from the
peripheral edge of the magnetostrictive member in the vertical direction, for example, a ringshaped yoke or a ring having a central portion opened in a donut shape. Can be used.
[0048]
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, and in this case as
well, it can function as a vibrator.
[0049]
In the first embodiment, a negative magnetostrictive member may be interposed between the
magnetostrictive member and the yoke, the magnetostrictive member may be configured as a
bimorph, and the same function as that of the second embodiment may be added.
[0050]
Further, in the second embodiment, the positive magnetostrictive material 3x extended toward
the object 10 in the direction T perpendicular to the peripheral edge from the peripheral edge is
diverged toward the object 10 instead of the direction perpendicular to the peripheral edge. It
may be extended at an angle so that
[0051]
In the second embodiment, the negative magnetostrictive member is eliminated, that is, in the
first embodiment, the peripheral edge of the magnetostrictive member in the direction
perpendicular to the object 10 or in the diverging direction instead of the yoke. It can be
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extended.
Furthermore, in the second embodiment, the peripheral edge of the negative magnetostrictive
member instead of the positive magnetostrictive member may be extended toward the object 10.
[0052]
The present invention is advantageous in that it can be applied to any application that stretches
the magnetostrictive member in its plane, and in particular, the thickness can be reduced.
In particular, the present invention is effective as a speaker or an ultrasonic wave source.
[0053]
They are a perspective view (a) and a cross-sectional perspective view (b) which show the
structure of the planar vibrator which concerns on the 1st Embodiment of this invention.
It is sectional drawing which shows the aspect which a magnetostriction member displaces by
magnetic flux.
It is a cross-sectional perspective view which shows the structure of the planar vibrator which
concerns on the 2nd Embodiment of this invention.
Explanation of sign
[0054]
Reference Signs List 2, 3 magnetostrictive member 2c (of 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 Magnetostrictive member in plane direction T Direction perpendicular to plane
direction
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