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JP2008236662

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DESCRIPTION JP2008236662
An object of the present invention is to provide a magnetostrictive actuator which can be reduced
in size and cost and is easy to assemble. A magnetostrictive actuator (10) includes a
magnetostrictive element (11), bias magnets (12a, 12b) provided at both ends of the
magnetostrictive element (11), a bobbin (14) around which an actuator coil (13) is wound, and
these members. Outer case 15 and an inner case 16 of FIG. When the magnetostrictive element
11 is housed in the case, the magnetostrictive element 11 is sandwiched between the top plate
portions 15 a and 16 a of the outer case 15 and the inner case 16 via the bias magnet 12. An
appropriate pre-load is applied to the magnetostrictive element 11 by the leaf spring property of
the case, so that the vibration by the magnetostrictive element 11 can be accurately transmitted
to the outside. [Selected figure] Figure 1
Magnetostrictive actuator
[0001]
The present invention relates to a magnetostrictive actuator, and more particularly to a case
structure of a magnetostrictive actuator.
[0002]
Magnetostrictive actuators are known which convert acoustic signals into mechanical vibrations
using magnetostrictive elements.
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This type of actuator requires a preloading member such as a spring material for applying a
preload to the magnetostrictive element, and also uses a rod for transmitting mechanical
vibration of the magnetostrictive element to an external diaphragm (for example, Patent
Document 1). Furthermore, they are housed in a sturdy housing and securely sealed by screwing.
As a result, damage to the magnetostrictive element can be prevented, sufficient expansion and
contraction of the magnetostrictive element can be performed, and sufficient performance as an
actuator can be exhibited. Japanese Patent Application Publication No. 2004-320606
[0003]
Recently, various applications incorporated in electronic devices have been proposed for
magnetostrictive actuators, and the demand for downsizing and cost reduction has been
increasing as in other electronic components. However, since the conventional magnetostrictive
actuator has a complicated structure and is housed in a strong casing, there is a limit to
miniaturization and cost reduction.
[0004]
Therefore, an object of the present invention is to provide a magnetostrictive actuator which can
be miniaturized and reduced in cost and which is easy to assemble.
[0005]
The above object of the present invention is such that the inner case, the outer case fitted with
the inner case, and the both ends are sandwiched between the top plate portion of the inner case
and the top plate portion of the outer case directly or through other members. This is achieved
by a magnetostrictive actuator comprising a vibrating element including a magnetostrictive
element disposed, and a coil for applying a magnetic field based on an acoustic signal to the
magnetostrictive element.
[0006]
According to the present invention, since the magnetostrictive element is in direct or indirect
contact with the top plate portion of the inner case and the outer case, the inner case and the
outer case can function as a preloading member or a rod. It can be omitted.
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As a result, the number of parts can be reduced, and the size and cost of the entire apparatus can
be reduced.
[0007]
In the present invention, the inner case includes a top plate portion and a plurality of side plate
portions extending from the end of the top plate portion in a direction orthogonal to the top plate
portion, and the outer case includes a top plate portion; A fitting projection provided on a side
plate portion of either the inner case or the outer case, comprising a plurality of side plate
portions extending in a direction orthogonal to the top plate portion from an end of the top plate
portion; It is preferable to provide a fitting hole provided in the other side plate portion
corresponding to the fitting protrusion.
According to this, it is possible to easily accommodate the magnetostrictive element with an
extremely simple configuration.
[0008]
In the present invention, the other members are preferably bias magnets disposed at both ends
of the magnetostrictive element. According to this, it is possible to apply an appropriate magnetic
bias to the magnetostrictive element. In addition, since the magnetostrictive element and the bias
magnet can be handled integrally as one vibrating element, the positioning of the
magnetostrictive element and the bias magnet in the case can be facilitated.
[0009]
In the present invention, the inner case and the outer case both have a gap between adjacent side
plate portions, and the gap between the side plate portions on the inner case side is wider than
the gap between the side plate portions on the outer case side Is preferred. According to this, the
inner case can be easily covered on the outer case.
[0010]
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In the present invention, preferably, the lead portion of the coil is drawn out from the gap
between the inner case and the outer case. According to this, it is possible to easily pull out the
lead portion of the coil to the outside without applying special processing to the case.
[0011]
Preferably, the magnetostrictive actuator of the present invention further comprises a bobbin
around which a coil is wound. According to this, the coil can be easily disposed around the
magnetostrictive element. Further, by inserting the magnetostrictive element into the hollow
portion of the bobbin, positioning within the case can be facilitated.
[0012]
The actuator of the present invention further includes a thermally conductive resin filled between
the coil and the inner case, and the thermal conductivity of the thermally conductive resin is
preferably higher than the thermal conductivity of the bobbin. According to this, it is possible to
quickly release the heat generated by energization of the coil to the case side.
[0013]
As described above, according to the present invention, it is possible to provide a
magnetostrictive actuator which can be reduced in size and cost and is easy to assemble.
[0014]
Hereinafter, preferred embodiments of the present invention will be described in detail with
reference to the accompanying drawings.
[0015]
FIG. 1 is an exploded perspective view showing the configuration of a magnetostrictive actuator
10 according to a preferred embodiment of the present invention, and FIG. 2 is an assembly
completed view thereof.
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FIG. 3 is a cross-sectional view taken along the line X-X of FIG.
[0016]
As shown in FIGS. 1 to 3, the magnetostrictive actuator 10 includes a magnetostrictive element
11, bias magnets 12 (12 a and 12 b) provided at both ends of the magnetostrictive element 11,
and a bobbin 14 around which an actuator coil 13 is wound. And a first case (outer case) 15 and
a second case (inner case) 16 for accommodating these members.
[0017]
The magnetostrictive element 11 is a substantially cylindrical member made of a
magnetostrictive material.
The magnetostrictive material has a characteristic that the permeability changes when an
external stress is applied, and the amount of magnetostriction changes when an external
magnetic field is applied.
In the present embodiment, the characteristics of such a magnetostrictive material are utilized to
use as an actuator. The magnetostrictive material is not particularly limited, but a material having
Tb0.34-Dy0.66-Fe1.90 as a central composition can be used. The dimensions of the
magnetostrictive element 11 may be appropriately selected in accordance with the target amount
of magnetostriction. For example, in the case where the magnetostrictive element 11 is formed
using a material capable of obtaining a magnetostriction amount of about 1000 ppm, if the
expansion and contraction of about 10 μm is desired, the magnetostrictive element 11 may have
a length of about 1 cm. If the magnetostrictive element 11 alone does not have a sufficient
overall length, an interpolation member made of a non-magnetostrictive material may be inserted
as needed.
[0018]
The bias magnet 12 is a permanent magnet for applying a magnetic bias to the magnetostrictive
element 11. The magnetostrictive element 11 has the property of being shortest when no
magnetic field is applied, and expanding as the magnetic field becomes stronger. That is, the
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magnetostrictive element 11 can not be contracted from the state where the magnetic field is not
applied, but is merely stretched. Therefore, in order to contract the magnetostrictive element 11,
it is necessary to apply a predetermined magnetic bias in a normal state (neutral state), and the
bias magnet 12 is provided for that purpose. The magnetic field generated by the bias magnet 12
penetrates the magnetostrictive element 11 in the axial direction (longitudinal direction).
[0019]
Although not particularly limited, the bias magnet 12 is preferably cylindrical (or disc-like) like
the magnetostrictive element 11, and the diameter of the bias magnet 12 is the same as the
diameter of the magnetostrictive element 11. Is preferred. In this way, the bias magnet 12 can be
integrally handled as one vibrating element together with the magnetostrictive element 11, and
can be accommodated in the bobbin 14 of the magnetostrictive element 11 and the bias magnet
12. In addition, it is preferable that the thickness of the bias magnet 12 be as thin as possible as
long as it can provide a desired magnetic bias and can ensure sufficient mechanical strength.
This is because thinning of the bias magnet 12 contributes to reducing the overall height of the
magnetostrictive actuator 10.
[0020]
The actuation coil 13 is provided to drive the magnetostrictive element 11. Thus, the actuator
coil 13 is disposed on the outer periphery of the magnetostrictive element 11 in a state of being
wound around the bobbin 14. When a current is supplied to the actuator coil 13, a magnetic field
penetrating the axial direction (longitudinal direction) of the magnetostrictive element 11 is
generated, whereby the magnetostrictive element 11 can be expanded and contracted. When the
direction of the magnetic field by the actuating coil 13 is the same as the direction of the
magnetic field by the bias magnet, it is expanded, and in the opposite case it is contracted. Thus,
for example, when a magnetic field change modulated by an acoustic signal is provided, it can be
used as an electroacoustic transducer.
[0021]
The bobbin 14 is a substantially cylindrical member around which the actuator coil 13 is wound.
The magnetostrictive element 11 and the bias magnet 12 are inserted into the hollow portion of
the bobbin 14. Therefore, the bobbin 14 also functions as a positioning member (sub-case) for
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housing the magnetostrictive element 11 and the bias magnet 12. Circular flanges 14 a are
provided at both ends of the bobbin 14, and the diameter of the flanges 14 a is set to be equal to
the width of the inner case 15 so as to be fitted into the inner case 15. Therefore, the
magnetostrictive element 11 and the bias magnet 12 accommodated in the bobbin 14 can be
disposed at the central portion in the case. The flange portion 14a is not limited to a circular
shape, and may be a rectangular shape (square shape). If it is a rectangular shape, it is possible to
fit in the inner case more precisely.
[0022]
FIG. 4 is a development view of the outer case 15.
[0023]
The outer case 15 is a member for housing the magnetostrictive element 11 and the like together
with the inner case 16 and, as shown in FIG. 4, from the end of the substantially square top plate
portion 15a having a leaf spring property and the top plate portion 15a. It is comprised by four
side plate parts 15b extended in the direction which intersects perpendicularly with top plate
part 15a.
As a material of the outer case 15, a nonmagnetic metal material is preferably used, and for
example, a stainless steel material such as SUS303 can be used.
[0024]
A fitting hole 17 is provided substantially at the center of each side plate portion 15b. The fitting
holes are for fitting the fitting projections of the inner case 16. In addition, a gap 15c is present
between two side plate portions 15b and 15b adjacent to each other. The gap 15c is used as an
outlet for drawing out the lead portion 14a of the coil 14 to the outside. The outer case 15 can
be formed by bending a metal plate punched into a substantially cross shape.
[0025]
FIG. 5 is a development view of the inner case 16.
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[0026]
The inner case 16 is a member for housing the magnetostrictive element 11 and the like together
with the outer case 15, and as shown in FIG. 5, from the end of the substantially square top plate
portion 16a having a leaf spring property and the top plate portion 16a. It comprises four side
plate portions 16b extended in a direction orthogonal to the top plate portion 16a.
Since the inner case 16 enters the inside of the outer case 15, the planar size thereof is slightly
smaller than that of the outer case 15. It is preferable to use the same material as the outer case
15 as the material of the inner case 16. That is, it is preferable to use a nonmagnetic metal
material, and for example, a stainless steel material such as SUS303 can be used.
[0027]
At substantially the center of each side plate portion 16b, a fitting projection 18 corresponding
to the above-mentioned fitting hole 17 is provided. Although not particularly limited, the fitting
projection 18 can be formed by punching out a metal plate. The inner case 16 is fixed to the
outer case 15 by fitting the fitting projection 18 into the fitting hole of the outer case 15. As
described above, the case of the present embodiment does not require screwing or the like, and
has an extremely simple structure of merely fitting. Therefore, the case itself can be easily
manufactured, and a simple and low cost case can be provided.
[0028]
Further, a gap 16c is present between two side plate portions 16b and 16b adjacent to each
other. In the present embodiment, it is preferable that the gap 16c between the side plate
portions 16b and 16b adjacent to each other on the inner case 16 side is wider than the gap 15f
between the side plate portions adjacent to each other on the outer case 15 side. According to
this, not only can the inner case 16 be easily fitted to the outer case 15, but also the drawing
operation of the lead portion 14 a of the coil 14 becomes easy. The inner case 16 can be formed
by bending a metal plate punched into a substantially cross shape.
[0029]
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As shown in FIG. 3, there is a space between the coil 14 wound around the bobbin 14 and the
side plate portion 16b of the inner case 16, but this space is filled with the heat conductive resin
19 Is preferred. When the coil 14 is energized, a large amount of heat is generated, but heat is
stored if the space between the coil 14 and the inner case remains hollow, which adversely
affects the characteristics of the magnetostrictive element 11. By being released to the case side,
heat storage in the case can be prevented. The heat conductivity of the heat conductive resin 19
is preferably higher than the heat conductivity of the bobbin. According to this, the heat
generated in the coil 14 is dissipated through the heat conductive resin 19, the side plate portion
16b of the inner case 16 and the side plate portion 15b of the outer case 15, and the heat
conductivity smaller than the heat conductivity of the bobbin As in the case of interposing resin
or air, a higher heat radiation effect can be obtained than in the case of heat radiation via a
bobbin.
[0030]
When assembling the magnetostrictive actuator 10, as shown in FIG. 1, first, the bobbin 14
around which the actuator coil 13 is wound is prepared, and after this bobbin 14 is
accommodated in the outer case 15, the hollow of the bobbin 14 is formed. The bias magnet 12a,
the magnetostrictive element 11, and the bias magnet 12b are sequentially inserted into the
portion. Alternatively, the bobbin 14 in a state in which the coil 13 is wound and the bias
magnets 12 a and 12 b and the magnetostrictive element 11 are accommodated may be
accommodated in the outer case 15. In addition, as long as the bias magnet 12 is disposed at
both ends of the magnetostrictive element 11, any one of the two openings of the hollow portion
of the bobbin 14 may be inserted. Thereafter, after the heat conductive resin 19 is filled, the
inner case 16 is covered to complete the magnetostrictive actuator 10 of the present
embodiment.
[0031]
In a state where the magnetostrictive element 11 is accommodated in the case formed of the
outer case 15 and the inner case 16, one end face of the magnetostrictive element 11 is in
contact with the top plate portion 15a of the outer case 15 via the bias magnet 12a. The end face
of the upper case abuts on the top plate portion 16a of the inner case 16 via the bias magnet
12b. That is, the magnetostrictive element 11 is sandwiched between top plates 15 a and 16 a of
the outer case 15 and the inner case 16 via the bias magnet 12. The outer case 15 and the inner
case 16 are both formed by bending a metal plate and have a leaf spring property. Also, the
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combined length of the magnetostrictive element 11 and the bias magnets 12a and 12b is
designed to be slightly longer than the length between the top plate portion 15a of the outer case
15 and the top plate portion 16a of the inner case 16 Therefore, the magnetostrictive element 11
is in a state in which a preload is applied in the axial direction. Thus, according to the present
embodiment, since the combination of the inner case 16 and the outer case 15 plays a role as a
preloading member, a dedicated preloading member such as a spring can be omitted.
[0032]
In the above configuration, the magnetostrictive element 11 is expanded when a current is
supplied to the actuator coil 13 to apply a magnetic field in the same direction as the magnetic
bias, and the magnetostrictive element 11 is contracted when a reverse magnetic field is applied.
Therefore, when a current modulated with an acoustic signal is applied to the coil, the acoustic
signal can be converted into mechanical vibration.
[0033]
Further, the vibrating element constituted by the magnetostrictive element 11 and the bias
magnet 12 is in contact with the outer case 15 and the inner case 16, and the magnetostrictive
element 11 is given an appropriate preload by the plate spring property of the case. The
vibration due to the magnetostrictive element 11 can be accurately transmitted to the outside.
That is, since the vibration of the magnetostrictive element 11 is directly transmitted to the
outside as the vibration of the entire case, the actuator can be configured without using a
member such as a rod.
[0034]
As described above, according to the present embodiment, since the outer case 15 and the inner
case 16 are used as the case members of the magnetostrictive element 11 and both are fitted, a
screw for sealing the case, etc. This eliminates the need for a fastening member, thereby
achieving downsizing and cost reduction. Further, according to the present embodiment, since
the case itself has a function as a plate spring material and sandwiches the magnetostrictive
element 11 and the bias magnet 12, the number of parts is reduced by omitting the conventional
preloading spring or rod. Can be reduced, and a very simplified magnetostrictive actuator can be
realized.
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[0035]
Further, according to the present embodiment, the outer case 15 and the inner case 16 are
formed by bending the metal plate, and a gap is provided between the adjacent side plate
portions, so that a wiring space can be secured. The 14 lead portions 14a can be easily pulled
out. In particular, since the gap of the inner case 16 is wider than the gap of the outer case 15,
the tip of the side plate portion 16 b of the inner case 16 is made by the fitting projection 18
when the inner case 16 is inserted into the outer case 15. Can be easily sealed in a state where
the lead portion 14a of the coil 14 is pulled out to the outside of the case.
[0036]
Although the present invention has been described above based on its preferred embodiments,
the present invention is not limited to the above embodiments, and various modifications can be
made without departing from the scope of the present invention. Needless to say, they are also
included in the scope of the present invention.
[0037]
For example, in the above embodiment, the outer case 15 and the inner case 16 are fixed by
fitting the fitting hole 17 on the outer case 15 side and the fitting protrusion 18 on the inner
case 16 side. The invention is not limited to such a structure, and any structure may be used as
long as the both fit without rattling.
[0038]
Further, in the above embodiment, the fitting hole 17 is provided on the outer case 15 side and
the fitting projection 18 is provided on the inner case 16 side, but the present invention is
limited to such a configuration. Instead, the fitting projections 18 may be provided on the outer
case 15 side, and the fitting holes 17 may be provided on the inner case 16 side.
Furthermore, although only one fitting means such as the fitting hole 17 and the fitting
protrusion 18 is provided in each side surface portion, a plurality of fitting means may be
provided.
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[0039]
Further, in the above embodiment, although the lead portion of the coil is drawn out from the
gap between the side plate portions, it is not essential in the present invention to do so, for
example, a lead in a dedicated hole provided in the side plate portion It is also possible to pass
the part.
[0040]
Moreover, in the said embodiment, although the coil is wound by the bobbin, it is not limited to
such a structure, It is also possible to use a bobbin-less coil.
In that case, it is preferable to separately use a dedicated member for positioning the coil and the
magnetostrictive element to accommodate them.
[0041]
In the above embodiment, although the case where the bias magnets 12a and 12b are disposed
at both ends of the magnetostrictive element 11 has been described, the present invention is not
limited thereto, for example, a cylindrical bias magnet using a cylindrical bias magnet. A
magnetostrictive element may be disposed in the hollow portion of the magnet to apply a bias
magnetic field.
[0042]
FIG. 1 is an exploded perspective view showing the configuration of a magnetostrictive actuator
10 according to a preferred embodiment of the present invention.
FIG. 2 is a schematic perspective view showing a completed state of the magnetostrictive
actuator 10 shown in FIG.
FIG. 3 is a cross-sectional view of the magnetostrictive actuator 10 taken along line X-X of FIG.
FIG. 4 is a development view of the outer case 15. FIG. 5 is a development view of the inner case
16.
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Explanation of sign
[0043]
DESCRIPTION OF SYMBOLS 10 Magnetostrictive actuator 11 Magnetostrictive element 12 Bias
magnet 13 Actuate coil 14 Bobbin 15 Outer case 15a Outer plate top plate portion 15b Outer
case side plate portion 15c Gap 16 Inner case 16a Inner case top plate portion 16b Inner case
side plate portion 16c Clearance 17 Fitting hole 18 Fitting protrusion 19 Thermal conductive
resin
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