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JP2007158911

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DESCRIPTION JP2007158911
An object of the present invention is a structure which is excellent in acoustic characteristics,
effective in preventing chipping of a giant magnetostrictive element and preventing sound
leakage, and capable of avoiding the deterioration of sound quality and the decrease in sound
pressure as much as possible even when the angle pressed against an external vibrator changes.
An electromagnetic transducer for an acoustic radiation device is provided. A coil applies a
magnetic field to a giant magnetostrictive element to drive the giant magnetostrictive element in
an axial direction. The giant magnetostrictive element 4 has one end fixed and the other end
movable. One end side of the expansion / contraction transmission member 5 is connected to the
movable end of the giant magnetostrictive element 4, and the other end side is guided to the
outside. The pressure member 6 is made of an elastic material, and urges the expansion /
contraction transmission member 5 in the direction of the giant magnetostrictive element 4. The
first permanent magnet 11 and the second permanent magnet 12 apply a magnetic bias to the
giant magnetostrictive element 4, and the first permanent magnet 11 disposed on the fixed end
side of the giant magnetostrictive element 4 And a second permanent magnet 12 disposed on the
movable end side of the magnetostrictive element 4. The first permanent magnet 11 and the
second permanent magnet 12 have different overall surface magnetic fluxes. [Selected figure]
Figure 1
Electromagnetic converter for acoustic radiation device
[0001]
The present invention relates to an electromagnetic transducer for an acoustic radiation device
using a giant magnetostrictive element.
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[0002]
An electromagnetic transducer of this type supplies an input signal to a coil to cause expansion /
contraction vibration in a giant magnetostrictive element, and a component that is in direct or
indirect contact with the stretchable end of the giant magnetostrictive element as an external
vibrator. It is used as an acoustic radiation device that transmits stretching vibration to an
external vibrating body by pressing or the like to generate sound, and is disclosed, for example,
in Patent Document 1, Patent Document 2 and the like.
[0003]
However, in the conventional electromagnetic transducer of this type represented by Patent
Document 1 and Patent Document 2 etc., there are many points to be further improved in order
to enhance its function to a practical level.
[0004]
First, the giant magnetostrictive element has the smallest size when no magnetic field is applied,
and has the property of stretching as the applied magnetic field becomes stronger.
That is, the giant magnetostrictive element can not be contracted from the state where no
magnetic field is applied, but can only be stretched.
Therefore, in order to expand and contract the giant magnetostrictive element, it is necessary to
apply a predetermined magnetic bias to the giant magnetostrictive element.
Therefore, a structure that applies such a magnetic bias efficiently must be considered.
[0005]
Next, the strain rate characteristic of the giant magnetostrictive element includes a non-linear
portion, and the magnetic bias determines which portion of the strain rate characteristic curve is
to be used. For this reason, it is extremely important to apply an appropriate magnetic bias to the
giant magnetostrictive element in order to obtain expansion and contraction vibration of the
giant magnetostrictive element that is acoustically good. Therefore, a structure that finds such an
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appropriate magnetic bias and specifically realizes it must be considered.
[0006]
In addition, the giant magnetostrictive element used in this type of electromagnetic transducer
can obtain large stretching vibration. As the giant magnetostrictive material, for example, a
material having a central composition of Tb0.34-Dy0.66-Fe1.90 can be used. However, this type
of material is extremely fragile, and in particular at the corners of the giant magnetostrictive
element, a slight impact applied from a predetermined direction may cause fine chips. When a
minute chip occurs and the piece adheres to the periphery of the giant magnetostrictive element,
it contracts with the surrounding members as the giant magnetostrictive element stretches, and
inhibits appropriate stretching vibration. Furthermore, when the fragments get in between the
end face of the giant magnetostrictive element and the other member in contact with it, the
transmission of the stretching movement of the giant magnetostrictive element is inhibited.
Therefore, means for preventing chipping of the giant magnetostrictive element are needed.
[0007]
Furthermore, since this type of electromagnetic conversion device generates sound by the
expansion and contraction operation of the giant magnetostrictive element, the portion that
should not normally be sounded receives the expansion and contraction of the giant
magnetostrictive element directly or indirectly. There is a problem of so-called sound leakage,
which generates a sound. How to solve this problem is also a problem at the practical level.
[0008]
In addition, this type of electromagnetic conversion device itself does not produce sound, but
presses a component that is in direct or indirect contact with the telescopic end of the giant
magnetostrictive element against the external vibrator, etc. Since the sound is generated on the
external vibrator, the angle to which the external vibrator is pressed changes, and a structure
that can avoid sound quality deterioration, sound pressure reduction, etc. even when the contact
area becomes small is also considered. There must be.
[0009]
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The electromagnetic conversion devices disclosed in Patent Document 1 and Patent Document 2
described above do not meet the above requirements completely, and there are many points to
be further improved in order to raise them to a practical level. Seen.
JP 10-145892 JP JP 2004-57261 A
[0010]
An object of the present invention is to provide an electromagnetic transducer for an acoustic
radiation device having good acoustic characteristics.
[0011]
Another object of the present invention is to provide an electromagnetic transducer for an
acoustic radiation device that is effective for preventing chipping of a giant magnetostrictive
element, sound leakage and the like.
[0012]
Yet another object of the present invention is to provide an electromagnetic transducer for an
acoustic radiation device having a structure capable of avoiding the deterioration of sound
quality, the decrease in sound pressure and the like as much as possible even when the angle of
pressing on an external vibrator changes. It is.
[0013]
In order to solve the problems described above, an electromagnetic transducer for an acoustic
radiation device according to the present invention includes an exterior body, a coil, a super
magnetostrictive element, an expansion / contraction transmission member, a pressure member,
and a permanent magnet.
The exterior body has an internal space.
The coil, the giant magnetostrictive element, the expansion / contraction transmission member,
the pressure member, and the permanent magnet are accommodated in the internal space of the
exterior body.
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[0014]
The coil applies a magnetic field to the giant magnetostrictive element to stretch and drive the
giant magnetostrictive element in the axial direction of the cylinder.
The super magnetostrictive element has one end fixed and the other end movable. One end side
of the expansion / contraction transmission member is connected to the other end of the super
magnetostrictive element, and the other end side is guided to the outside through the opening of
the exterior body. The pressurizing member is made of an elastic material, and urges the
stretchable transmission member in the direction of the giant magnetostrictive element. The
permanent magnet applies a magnetic bias to the giant magnetostrictive element, and the first
permanent magnet disposed on the fixed end side of the giant magnetostrictive element and the
movable end of the giant magnetostrictive element And a second permanent magnet disposed.
[0015]
A feature of the present invention is that, in the above-described configuration, the entire surface
magnetic flux of the first permanent magnet and the second permanent magnet are made
different from each other. According to this configuration, it has been found that the acoustic
distortion is reduced and the sound quality is improved. Although the reason is not clear, it
seems that the application of the bias magnetic field to the giant magnetostrictive element may
be made appropriate.
[0016]
As a specific arrangement, the second permanent magnet preferably has an overall surface
magnetic flux smaller than that of the first permanent magnet. With such an arrangement, the
mass of the second permanent magnet positioned on the movable side can be reduced, and the
inertia weight can be reduced, so that the response to expansion and contraction of the giant
magnetostrictive element is improved, and the acoustic characteristics are improved.
[0017]
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The number of giant magnetostrictive elements may be one or plural. When a plurality of giant
magnetostrictive elements are used, a structure in which they are connected in series can be
employed. According to this structure, it is possible to avoid the breakage accident which tends
to occur when one super magnetostrictive element is used. One of the preferable modes in the
case of using a plurality of giant magnetostrictive elements is to connect a plurality of giant
magnetostrictive elements in series via a third permanent magnet. By so doing, the distribution of
the bias magnetic field inside the giant magnetostrictive element can be made uniform, and
acoustic distortion can be reduced.
[0018]
The electromagnetic conversion device according to the present invention can include a magnetic
yoke. The magnetic yoke is disposed between the first permanent magnet and the giant
magnetostrictive element. The magnetic yoke preferably has a planar area larger than that of the
first permanent magnet. It has been found that such a magnetic yoke reduces acoustic distortion.
The reason seems to be that the alternating magnetic field by the coil is made uniform inside the
giant magnetostrictive element. The magnetic yoke may be disposed between the second
permanent magnet and the giant magnetostrictive element. Also in this case, the planar area of
the magnetic yoke is made larger than that of the second permanent magnet. Furthermore, the
magnetic yoke may be disposed between the first permanent magnet and the second permanent
magnet and the giant magnetostrictive element, and the first permanent magnet or the second
permanent magnet may be used. It may also be located outside.
[0019]
As another aspect, of the first permanent magnet, the second permanent magnet, or the magnetic
yoke, the magnetic member in contact with the giant magnetostrictive element is applied to the
surface in contact with the giant magnetostrictive element in the contact region A recess may be
provided, and the super magnetostrictive element may be adhered to a magnetic member such as
the first permanent magnet, the second permanent magnet, or the magnetic yoke by an adhesive
filled in the recess. it can. According to this structure, since the giant magnetostrictive element is
integrated with the magnetic member such as the first permanent magnet, the second permanent
magnet, or the magnetic yoke, and vibrates together, the physically fragile super The
magnetostrictive element can avoid a defect such as chipping due to micro vibration caused by
the alternating magnetic field of the coil. Further, even if the alternating magnetic field of the coil
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is applied to the giant magnetostrictive element and the magnetic yoke, so-called sound leakage
is suppressed because the contact / separation operation does not occur between them.
[0020]
Another effective means for preventing chipping of the giant magnetostrictive element and
sound leakage is that the giant magnetostrictive element, the first permanent magnet, the second
permanent magnet, or the magnetic yoke are adjacent to each other. An organic buffer member
is provided between the end faces at at least one place between the mating members. According
to this structure, it is possible to avoid chipping of the giant magnetostrictive element and to
suppress sound leakage by the buffer action of the buffer member.
[0021]
The buffer member is preferably a laminate of a sponge-like elastic layer and a wear resistant
layer, and the wear resistant layer is preferably arranged in contact with the end face of the giant
magnetostrictive element. With such a laminated structure, when the expansion transmission
member is pressed against the external vibrator, the sponge-like elastic layer is compressed to
the limit and is substantially integrated with the first permanent magnet and the second
permanent magnet. The movement of the giant magnetostrictive element is faithfully transmitted
to the first permanent magnet, the second permanent magnet, and the stretch transmitting
member. Therefore, the sound generation operation faithfully following the expansion and
contraction of the giant magnetostrictive element is secured. Conversely, when the stretch
transmission member is separated from the external vibrator, the sponge-like elastic layer
elastically restores, and hammering and sound leakage are prevented.
[0022]
The sponge-like elastic body exerts the important functions as described above, but on the other
hand, the material is soft, so when the direct contact with the giant magnetostrictive element, the
contact part is worn away and there is a hole, eventually the sound leaks It will cause. Therefore,
in the present invention, in order to improve the abrasion resistance without impairing the
advantages of the sponge-like elastic body, the abrasion-resistant film is stuck on the sponge-like
elastic body.
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[0023]
In the electromagnetic conversion device according to the present invention, the receiving
member for receiving the fixed end of the giant magnetostrictive element has a structure having
a recess, and an assembly structure in which part or all of the first permanent magnet in the
thickness direction is in the recess. It can be taken. With such a structure, it is possible to
miniaturize the overall shape, to accurately position the giant magnetostrictive element, and to
obtain predetermined characteristics.
[0024]
Since the expansion / contraction transmission member is a portion which presses the tip to
contact with the external vibrating body, it is necessary to secure a large stable sounding
operation characteristic of the sound pressure regardless of the pressing angle to the external
vibrating body. As the means, the expansion / contraction transmission member is first brought
into contact with the second permanent magnet or the magnetic yoke in a non-bonding state.
And it is set as a structure provided with a projection and a collar, and the projection has an
outer diameter smaller than the opening, and leads to the outside through the opening. The
flange portion is at the rear end of the protrusion and faces a case partition surrounding the
opening. And an elastic body is arrange ¦ positioned between the said collar part and the said
case partition.
[0025]
According to the above-described structure, even when the pressing angle with respect to the
external vibrator changes, the stretch transmission member first contacts with the second
permanent magnet or the magnetic yoke in a non-bonded state, and hence the second permanent
magnet or The magnetic yoke can be displaced according to the pressing angle with respect to
the external vibrator.
[0026]
Since the protrusion of the expansion / contraction transmission member has an outer diameter
smaller than the opening, the displacement is made in accordance with the pressing angle with
respect to the external vibrator within the range of the gap formed between the protrusion and
the opening can do.
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[0027]
In addition, since the elastic body is disposed between the case partition and the ridge portion
facing the case partition surrounding the opening at the rear end of the protrusion, the
expansion and contraction transmission member is directed to the external vibrator. Even in the
case of displacement according to the pressing angle, the expansion and contraction action of the
elastic body can keep the pressurization constant and avoid sound quality deterioration, sound
pressure reduction and the like.
[0028]
Other objects, configurations and advantages of the present invention will be described in more
detail with reference to the attached drawings.
However, the attached drawings are merely illustrative.
[0029]
As described above, according to the present invention, the following effects can be obtained.
(A) It is possible to provide an electromagnetic transducer for an acoustic radiation device with
good acoustic characteristics.
(B) It is possible to provide an electromagnetic transducer for an acoustic radiation device that is
effective for preventing chipping of a giant magnetostrictive element, sound leakage, and the like.
(C) It is possible to provide an electromagnetic transducer for an acoustic radiation device having
a structure capable of avoiding the deterioration of sound quality, the decrease in sound pressure
and the like as much as possible even when the angle of pressing on the external vibrator
changes.
[0030]
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FIG. 1 is a front sectional view showing an example of an electromagnetic transducer for an
acoustic radiation device according to the present invention. The illustrated electromagnetic
conversion device for an acoustic radiation device includes an exterior body 2, a coil 3, a super
magnetostrictive element 4, an expansion / contraction transmission member 5, a pressure
application member 6, a first permanent magnet 11, and a second And a permanent magnet 12.
In the illustrated embodiment, the bobbin 7 is further included.
[0031]
The outer package 2 may be made of any of a magnetic material, a nonmagnetic conductive
material, a ceramic or a plastic material. When the exterior body 2 is made of a magnetic
material, the leakage flux is reduced and the magnetic efficiency is increased. In the case of a
conductive magnetic material, for example, a metallic magnetic material, although a high
shielding effect can be obtained, it may cause problems of deterioration of frequency
characteristics and heat generation due to eddy currents. When configured with nonmagnetic
conductive materials, the problem of eddy current losses still remains. When made of a ceramic
or plastic material, the problem of heat generation does not occur, but the leakage flux increases
and the magnetic efficiency decreases. Therefore, the constituent material of the exterior body 2
needs to be selected to suit the scene, taking into consideration the advantages and
disadvantages described above.
[0032]
The illustrated exterior body 2 has a cylindrical body 21 and a receiving member 22 made of a
rigid material such as iron, and forms an internal space 23. The exterior body 2, the coil 3, the
giant magnetostrictive element 4, the expansion / contraction transmission member 5, the
pressure applying member 6, the permanent magnet 1 and the bobbin 7 are accommodated
inside the internal space 23 of the exterior body 2. Therefore, the whole component can be
protected by the exterior body 2.
[0033]
The exterior body 2 has a structure in which the receiving member 22 is disposed at one end of
the cylindrical body 21 and fixed to the cylindrical body 21. The receiving member 22 is made of
a rigid material such as iron and has a flat plate shape partially cut away, and has a recess 221 in
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which the first permanent magnet 11 is embedded in the inner plate surface. Inside the recess
221, a part of the first permanent magnet 11 is embedded. This structure ensures the positioning
of the first permanent magnet 11.
[0034]
The recess 221 may have a structure in which the whole of the first permanent magnet 11 in the
thickness direction is embedded. With such a structure, it is possible to miniaturize the entire
shape, accurately position the giant magnetostrictive element 4, and obtain predetermined
characteristics. Further, when the receiving member 22 is made of a magnetic material, the
receiving member 22 functions as a yoke, so that effects such as reduction of acoustic distortion
can be obtained.
[0035]
The exterior body 2 has an opening 24 on the side facing the receiving member 22. The opening
24 has a case partition 25 with an inward flange formed at the other end of the cylinder 21.
[0036]
The bobbin 7 is a molded body of a polymer material, and has a cylindrical portion 70 and flange
portions 71, 72, 73 at both ends and the center thereof. The central flange portion 73 divides the
outer peripheral surface of the cylindrical portion 70 of the bobbin 7 into two to form two
winding spaces.
[0037]
The coil 3 applies a magnetic field to the giant magnetostrictive element 4 to extend and contract
the giant magnetostrictive element 4 in the axial direction of the cylindrical body 21, and is
wound around the winding space of the bobbin 7. The winding method may be arbitrary, but
split winding results have been obtained. As the split winding, first, it is wound to half the coil
winding thickness in the winding space between the collars 71 to 73, and then transferred to the
winding space between the collars 73 to 72, and so on to half the coil winding thickness as well.
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It is possible to adopt a method of repeating and completing the winding operation. The divided
winding method may be a method of further dividing the winding space and the winding
thickness. By dividing and winding the coil 3, the sound becomes tight and a good sound can be
obtained.
[0038]
The giant magnetostrictive element 4 is inserted into the cylindrical portion 70 of the bobbin 7.
The illustrated giant magnetostrictive element 4 is formed in a cylindrical shape using, for
example, a material having a central composition of Tb0.34-Dy0.66-Fe1.90. Among the opposite
ends of the giant magnetostrictive element 4, one end is received by the receiving member 22 via
the first permanent magnet 11, and the second permanent magnet 12 is adjacent to the other
end.
[0039]
The expansion / contraction transmission member 5 has a small diameter portion 511 and a
large diameter portion 512, the large diameter portion 512 is connected to the other end side of
the super magnetostrictive element 4 via the second permanent magnet 12, and the small
diameter portion 511 is It is led out through the opening 24. The material of the expansion /
contraction transmission member 5 is desirably hard and made of iron, brass or the like.
[0040]
Inside the case partition 25, a bearing 26 made of an organic material rich in slidability with
small frictional resistance is provided, and the small diameter portion 511 of the stretchable
member 5 contacts the bearing 6 to the outside. It is being guided. With such a structure, lateral
movement of the expansion and contraction transmission member 5 can be prevented. In
addition, the friction between the small diameter portion 511 of the expandable member 5 and
the bearing 6 can be minimized to prevent sound leakage. The small diameter portion 511 of the
expansion / contraction transmission member 5 is guided to the outside with a gap between the
opening 24 and the opening 24. Therefore, the contact between the small diameter portion 511
of the expansion / contraction transmission member 5 and the case partition 25 can be avoided. .
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[0041]
The pressure member 6 is made of an elastic material, and biases the expansion / contraction
transmission member 5 in the direction of the giant magnetostrictive element 4. The pressurizing
member 6 may be an elastic material mainly composed of a polymer material, a metal plate
spring, or a metal coil spring. The pressure member 6 is compressed between the large diameter
portion 512 of the expansion and contraction transmission member 5 and urges the expansion
and contraction transmission member 5 in the direction of the giant magnetostrictive element 4.
[0042]
The first permanent magnet 11 and the second permanent magnet 12 apply a magnetic bias to
the giant magnetostrictive element 4. One of the features of the present invention resides in that
the overall surface magnetic flux of the first permanent magnet 11 and the second permanent
magnet 12 are made different from each other. According to this configuration, it has been found
that the acoustic distortion is reduced and the sound quality is improved. Although the reason is
not clear, it seems that the application of the bias magnetic field to the giant magnetostrictive
element 4 may be made appropriate.
[0043]
As a specific arrangement, the second permanent magnet 12 preferably has an overall surface
magnetic flux smaller than that of the first permanent magnet 11. With such an arrangement, the
inertial weight of the second permanent magnet 12 located on the movable side can be reduced,
so that the response to expansion and contraction of the giant magnetostrictive element 4
becomes good, and the acoustic characteristics are improved. The specific means for giving a
difference to the entire surface magnetic flux is more than the diameter A1 of the first permanent
magnet 11, assuming that the thicknesses of the first permanent magnet 11 and the second
permanent magnet 12 are the same. , The diameter A2 of the second permanent magnet 12 is to
be reduced. It is also effective to make the materials of the first permanent magnet 11 and the
second permanent magnet 12 different from each other as another specific means for giving a
difference to the entire surface magnetic flux.
[0044]
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FIG. 2 is a view showing an acoustic radiation device in which the acoustic drive unit 100 is
added to the electromagnetic conversion device according to the present invention. The sound
drive unit 100 is configured to include an AMP 101, a sound source 102, a battery 103, and the
like, amplifies the audio signal (mainly, a music signal) supplied from the sound source 102 with
the AMP 101, and amplifies the amplified sound output from the AMP 101 The signal excites the
coil 9 of the electromagnetic transducer.
[0045]
FIG. 3 shows the use of the acoustic radiation device shown in FIG. 2, and in particular shows a
portion of the electromagnetic transducer which is the subject of the present invention. As
illustrated, the acoustic radiation device in which the electromagnetic conversion device is added
to the present invention is used by bringing the small diameter portion 511 of the expansion and
contraction transmission member 5 into contact with the external vibrating body P. Thereby, the
expansion and contraction vibration of the giant magnetostrictive element 4 based on the
excitation by the coil 3 can be transmitted from the expansion and contraction transmission
member 5 to the external vibrator P, and the sound due to the vibration of the external vibrator P
can be radiated. There is no restriction ¦ limiting in particular in the external vibrating body P, It
can comprise using metal, glass, wood, a synthetic resin, or those combination materials. Also,
the shape thereof may be any shape such as a flat plate shape, a block shape and the like. As a
specific example of usable external vibrating body P, outdoor advertising boards, indoor
advertising boards, glass windows of cars, tables, TV boxes, etc. have no spare time.
[0046]
The electromagnetic conversion device according to the present invention can adopt various
aspects. The example is demonstrated with reference to FIGS. 4-21. In these drawings, parts
corresponding to the constituent parts shown in FIGS. 1 to 3 are given the same reference
numerals, and repeated descriptions may be omitted.
[0047]
First, FIG. 4 is a front sectional view showing another embodiment of the electromagnetic
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transducer according to the present invention. The feature of this embodiment is that a plurality
of super magnetostrictive elements 41 and 42 are used and arranged in series. According to this
structure, it is possible to avoid the breakage accident which tends to occur when one super
magnetostrictive element is used.
[0048]
Another feature of the embodiment illustrated in FIG. 4 is that a plurality of super
magnetostrictive elements 41 and 42 are connected in series via the third permanent magnet 13.
By so doing, the distribution of the bias magnetic field inside the giant magnetostrictive elements
41 and 42 can be made uniform, and acoustic distortion can be reduced. The third permanent
magnet 13 preferably has an outer diameter smaller than that of the giant magnetostrictive
elements 41 and 42, but may have the same diameter.
[0049]
FIG. 5 is a front sectional view showing still another embodiment of the electromagnetic
transducer according to the present invention. The feature of this embodiment is that the
connection structure between the first permanent magnet 11 and the second permanent magnet
12 and the giant magnetostrictive element 4 is devised.
[0050]
First, regarding the connection structure of the first permanent magnet 11 and the giant
magnetostrictive element 4, referring to FIGS. 6 and 7 together with FIG. 5, the first permanent
magnet 11 is in contact with the giant magnetostrictive element 4. The first permanent magnet
11 and the giant magnetostrictive element 4 are fixed by an adhesive 85 filled in the recess 86.
[0051]
According to such a structure, since the giant magnetostrictive element 4 is integrated with the
first permanent magnet 11, the giant magnetostrictive element 4 performs expansion and
contraction together with the first permanent magnet 11.
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For this reason, even if an alternating magnetic field of the coil 3 is applied, no separation
operation occurs between the giant magnetostrictive element 4 and the first permanent magnet
11, so that the giant magnetostrictive element 4 is a first permanent magnet. Hammering that
repeatedly collides with 11 does not occur, so that chipping of the giant magnetostrictive
element 4 due to hammering can be avoided and sound leakage is prevented.
[0052]
In the embodiment shown in FIGS. 6 and 7, the recess 86 is ring-shaped, but the embodiment is
not limited to this, and various aspects can be adopted. An example is shown in FIGS. First, in the
examples of FIGS. 8 and 9, circular recesses 86 are equally spaced apart. In the example of FIG.
10, not circular but fan-shaped concave portions 86 are equally spaced apart. However, it is not
necessary to equally arrange, to limit to four, and to be circular or fan-shaped.
[0053]
Next, the connection structure of the second permanent magnet 12 and the giant
magnetostrictive element 4 will be described with reference to FIG. 11 together with FIG. 5. A
sponge-like structure is provided between the giant magnetostrictive element 4 and the second
permanent magnet 12. An organic buffer member 9 in which the elastic body 91 and the
abrasion resistant film 92 are laminated is sandwiched. According to this structure, it is possible
to suppress chipping and sound leakage due to hammering.
[0054]
That is, since the sponge-like elastic body 91 is highly elastic, when the expansion transmission
member 5 is pressed against the external vibrator, the sponge-like elastic layer 91 is compressed
to the limit and the second permanent magnet 12 is substantially compressed. The movement is
integrated and the movement of the giant magnetostrictive element 4 is faithfully transmitted to
the second permanent magnet 12 and the extension transmission member 5. Therefore, the
sound generation operation faithfully following the expansion and contraction of the giant
magnetostrictive element 4 is secured. Conversely, when the stretchable transmission member 5
is separated from the external vibrator, the sponge-like elastic layer 91 elastically restores, and
hammering and sound leakage are prevented.
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[0055]
The sponge-like elastic body 91 exerts the important function as described above, but on the
other hand, since the material is soft, when the direct contact with the giant magnetostrictive
element 4, the contact portion is abraded and there is a hole, eventually the sound It will cause a
leak. Therefore, in the present invention, in order to improve the wear resistance without
impairing the advantages of the sponge-like elastic body 91, the wear-resistant film 92 is
attached on the sponge-like elastic body 91.
[0056]
As the sponge-like elastic body 91, in addition to a sponge, elastic foam silicone, urethane foam,
etc. can be used, and as the abrasion resistant film 92, a polyethylene film, a polyimide film, etc.
can be used. The abrasion resistant film 92 may have a thickness of about 25 μm to 50 μm,
and the sponge-like elastic body 87 may have a thickness several times to several tens of that of
the abrasion resistant film 92.
[0057]
The buffer member 9 may be disposed in at least one place between the end faces of the giant
magnetostrictive element 4, the first permanent magnet 11 and the second permanent magnet
12 which are adjacent to each other. The illustrated embodiment is merely an example.
[0058]
Although it is conceivable to use, for example, a sheet of Teflon (registered trademark) as a
chipping preventing means of the giant magnetostrictive element 4, since the sheet is hard, the
sound leaks even if it is effective for chipping prevention. The effectiveness for prevention is low.
[0059]
FIG. 5 shows an example in which the side of the first permanent magnet 11 is adhered and the
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buffer member 9 is disposed on the side of the second permanent magnet 12, but the side of the
second permanent magnet 12 is adhered. The buffer member 9 may be disposed on the side of
the first permanent magnet 11 or, as illustrated in FIG. 12, on both the side of the first
permanent magnet 11 and the side of the second permanent magnet 12. , And the buffer
member 9 may be disposed.
That is, the bonding structure and the buffer member sandwiching structure described above can
be used properly in the same electromagnetic conversion device. Further, in FIG. 12, the buffer
member 9 adjacent to the first permanent magnet 11 may be omitted.
[0060]
FIG. 13 is a front sectional view showing another embodiment of the electromagnetic transducer
according to the present invention. The feature of this embodiment is that two giant
magnetostrictive elements 41 and 42 are connected in series and that the third permanent
magnet 13 is disposed between the giant magnetostrictive elements 41 and 42. . The first
permanent magnet 11 is bonded (85, 86) to the end face of the giant magnetostrictive element
41, and the second permanent magnet 12 is bonded (85, 86) to the end face of the giant
magnetostrictive element. The details of the adhesive structure are as shown in FIGS.
[0061]
As described above, according to the structure in which two super magnetostrictive elements 41
and 42 are connected in series, it is possible to avoid a breakage accident which tends to occur
when one super magnetostrictive element is used. Further, since the giant magnetostrictive
elements 41 and 42 are connected in series via the third permanent magnet 13, the distribution
of the bias magnetic field inside the giant magnetostrictive elements 41 and 42 can be made
uniform to reduce the acoustic distortion. it can.
[0062]
FIG. 14 is a front sectional view showing still another embodiment of the electromagnetic
transducer according to the present invention. This embodiment is the same as the embodiment
of FIG. 13 in that the third permanent magnet 13 is disposed between the giant magnetostrictive
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elements 41 and 42 connected in series, but the second permanent magnet 12 and the giant
magnetostrictive The difference is that the buffer member 9 is disposed between the element 42
and the element 42. The details of the buffer member 9 are as described with reference to FIG.
[0063]
FIG. 15 is a front sectional view showing still another embodiment of the electromagnetic
transducer according to the present invention. This embodiment is the same as the embodiment
of FIGS. 13 and 14 in that the third permanent magnet 13 is disposed between the giant
magnetostrictive elements 41 and 42 connected in series, but the first permanent magnet 11 is
the same. And the giant magnetostrictive element 41, and between the second permanent
magnet 12 and the giant magnetostrictive element 42 in that buffer members 9, 9 are disposed.
[0064]
As the embodiment of FIGS. 13 to 15 suggests, the bonding structure and the elastic body
sandwiching structure can be properly used even when a plurality of giant magnetostrictive
elements 41 and 42 are used.
[0065]
FIG. 16 is a front sectional view showing still another embodiment of the electromagnetic
transducer according to the present invention.
The feature of this embodiment is to provide a first magnetic yoke 81 and a second magnetic
yoke 82. The first magnetic yoke 81 is bonded to one end side of the giant magnetostrictive
element 4, and the first permanent magnet 11 is adjacent to the first magnetic yoke 81. The
second magnetic yoke 82 is bonded to the other end side of the giant magnetostrictive element
4, and the second permanent magnet 12 is adjacent to the second magnetic yoke 82. The first
magnetic yoke 81 and the second magnetic yoke 82 are made of ferrite, iron or the like.
[0066]
The presence of the first magnetic yoke 81 and the second magnetic yoke 82 makes it possible
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to reduce the leakage of the coil magnetic flux, to increase the volume, and to reduce the acoustic
distortion. From this point of view, it is preferable that the first magnetic yoke 81 has an outer
diameter larger than that of the first permanent magnet 11, and the second magnetic yoke 82
has an outer diameter larger than that of the second permanent magnet 12.
[0067]
In the case of the embodiment shown in FIG. 16, since the first magnetic yoke 81 and the second
magnetic yoke 82 are adjacent to the giant magnetostrictive element 4, the connections shown in
FIGS. The structure applies. Referring to FIG. 16 with reference to FIGS. 4 to 11, the first
magnetic yoke 81 has a recess 86 covering the contact region on the surface in contact with the
giant magnetostrictive element 4 and the first magnetic yoke 81. The giant magnetostrictive
element 4 is fixed by the adhesive 85 filled in the recess 86. A buffer member 9 is disposed
between the second magnetic yoke 82 and the giant magnetostrictive element 4.
[0068]
According to this structure, since the giant magnetostrictive element 4 is integrated with the first
magnetic yoke 81, the physically fragile giant magnetostrictive element 4 receives hammering by
the alternating magnetic field of the coil 3 to cause chipping, etc. As described above, the failure
can be avoided and the sound leakage can be suppressed.
[0069]
The buffer member 9 is disposed at least at one place between the end faces of the giant
magnetostrictive element 4, the first permanent magnet 11, the second permanent magnet 12
and the magnetic yoke 82 which are adjacent to each other. Good.
The illustrated embodiment is merely an example.
[0070]
FIG. 17 is a front sectional view showing still another embodiment of the electromagnetic
transducer according to the present invention. In this embodiment, buffer members 9 are
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disposed between the first magnetic yoke 81 and the giant magnetostrictive element 4 and
between the second magnetic yoke 82 and the giant magnetostrictive element 4. Other
configurations do not differ from those of FIG.
[0071]
FIG. 18 is a front sectional view showing still another embodiment of the electromagnetic
transducer according to the present invention. The feature of this embodiment is that two giant
magnetostrictive elements 41 and 42 are connected in series and that the third permanent
magnet 13 is disposed between the giant magnetostrictive elements 41 and 42. . The first
magnetic yoke 81 is bonded (85, 86) to the end face of the giant magnetostrictive element 41,
and the second magnetic yoke 82 faces the end face of the giant magnetostrictive element 42 via
the organic elastic layer 9. The details of the connection structure are as shown in FIGS. However,
in consideration of FIGS. 4 to 11, it is necessary to replace the first permanent magnet 11 with
the first magnetic yoke 81 and replace the second permanent magnet 12 with the second
magnetic yoke 82, respectively.
[0072]
FIG. 19 is a front sectional view showing still another embodiment of the electromagnetic
transducer according to the present invention. The feature of this embodiment is the structure of
the expansion and contraction transmission member 5. Since the expansion / contraction
transmission member 5 is a portion for pressing the tip against the external vibrating body to
make contact, even if the pressing angle against the external vibrating body changes, the contact
area is fixed in a certain angle range and stable sounding operation characteristics, particularly It
is necessary to ensure a constant sound pressure.
[0073]
As means therefor, in this embodiment, the stretch transmission member 5 is first brought into
contact with the second permanent magnet 12 or the second magnetic yoke 82 in a non-bonded
state. And it is set as the structure provided with the protrusion part 51 and the outward flange
part 52 in the contact end side. The protrusion 51 has an outer diameter smaller than that of the
opening 24 and secures a gap G1 with the inner wall surface of the opening 24 and leads it from
the opening 24 to the outside. The outward flange 52 is at the rear end of the protrusion 51 and
04-05-2019
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faces the case partition surrounding the opening 24. Then, the elastic body 61 is disposed
between the outward flange 52 and the case partition 25.
[0074]
The coil 3 is thickly wound using a wire with a large wire diameter as compared with the abovedescribed embodiments, thereby optimizing the impedance with respect to the coil excitation
current, and in particular, reducing the frequency characteristics, particularly the low frequency.
The frequency characteristics in the region can be improved to improve the sound quality.
[0075]
According to the above structure, as shown in FIG. 20, when the pressing angle with respect to
the external vibrating body P is changed, the expansion / contraction transmission member 5 is
in contact with the second permanent magnet 12 in a non-bonded state. The permanent magnet
12 can be displaced corresponding to the pressing angle with respect to the external vibrator P.
For this reason, since the whole tip surface of the expansion-contraction transmission member 5
comes in contact with the external vibrating body P, the sound similar to that in the case of being
perpendicularly pressed against the external vibrating body P despite being angled The pressure
level can be secured.
[0076]
The protrusion 51 of the expansion / contraction transmission member 5 has an outer diameter
smaller than that of the opening 24, and therefore, pressing against the external vibrating body P
is within the range of the gap G1 generated between the protrusion 51 and the opening 24. It
can be displaced corresponding to the angle.
[0077]
Moreover, since the elastic body 61 is disposed between the case partition 25 surrounding the
opening 24 and the outward flange 52, the expansion / contraction transmission member 5 is
displaced according to the pressing angle with respect to the external vibrator P. Also in this
case, by the expansion and contraction action of the elastic body 61, the pressurization can be
kept constant, and the sound quality deterioration, the sound pressure reduction and the like can
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be avoided as much as possible.
Furthermore, in the embodiment of FIG. 19, since the elastic body 62 is disposed between the
receiving member 22 and the lid 26, the whole is also subjected to the spring pressure by the
elastic body 62.
[0078]
Further, the entire first permanent magnet 11 is disposed inside the recess 221 of the receiving
member 22 made of a magnetic body, and the recess 221 is closed by the first magnetic yoke 81.
This structure is a means of minimizing axial length. At first glance, a closed magnetic path is
formed by the receiving member 22 made of magnetic material and the first magnetic yoke 81
for the first permanent magnet 11, and the magnetic flux of the first permanent magnet 11 acts
on the giant magnetostrictive element 4. Also, it seems that certain characteristics can not be
obtained. However, in fact, in spite of the closed magnetic circuit, no significant difference is
observed in the leakage flux seen on the center line of the first magnetic yoke 81 in contrast to
the open magnetic circuit, and the leakage magnetic flux is maintained substantially constant. It
has been confirmed that there is no problem in operation.
[0079]
FIG. 21 is a front sectional view showing still another embodiment of the electromagnetic
transducer according to the present invention. This embodiment is the same as the embodiment
shown in FIG. 20 except that the plurality of giant magnetostrictive elements 41 and 42 are
arranged in series via the third permanent magnet 13.
[0080]
FIG. 22 is a front sectional view showing still another embodiment of the electromagnetic
transducer according to the present invention. In this embodiment, the relationship between the
second permanent magnet 12 and the second magnetic yoke 82 with respect to the giant
magnetostrictive element 4 is reversed to that of the previously described embodiment. That is,
the second permanent magnet 12 is adjacent to one end surface of the giant magnetostrictive
element 4, and the second magnetic yoke 82 is adjacent to the second permanent magnet 12.
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Then, an organic buffer member 9 is provided between the second permanent magnet 12 and
the second magnetic yoke 82. Also in this embodiment, the same effects as those of the other
embodiments can be obtained. Although illustration is omitted, the organic buffer member 9 may
be provided between the second permanent magnet 12 and the giant magnetostrictive element 4.
[0081]
Although the present invention has been described in detail with reference to the preferred
embodiments, the present invention is not limited thereto, and various modifications can be
made by those skilled in the art based on the basic technical concept and teaching thereof. It is
self-evident that For example, the structure of the expansion / contraction transmission member
5 disclosed in FIGS. 19 to 21 may be diverted to the embodiments illustrated in FIGS. 1 to 18, the
permanent magnet or the magnetic yoke disclosed in FIGS. It is free to divert the connection
structure to the giant magnetostrictive element to the embodiment shown in FIGS.
[0082]
It is front sectional drawing which shows an example of the electromagnetic conversion
apparatus for acoustic radiation apparatuses which concerns on this invention. It is a circuit
diagram of an acoustic radiation device which added an acoustic drive part to an electromagnetic
conversion device concerning the present invention. It is a figure which shows the state which
used the electromagnetic conversion apparatus shown in FIG. 1 as an acoustic radiation
apparatus as shown in FIG. It is front sectional drawing which shows another Example of the
electromagnetic conversion apparatus based on this invention. It is front sectional drawing which
shows another Example of the electromagnetic conversion apparatus based on this invention. It
is a top view which shows the bonding structure of a super-magnetostrictive element and a
magnetic yoke. It is sectional drawing which shows the adhesion structure shown in FIG. It is a
top view which shows another bonding structure of a super-magnetostrictive element and a
magnetic yoke. It is sectional drawing which shows the adhesion structure shown in FIG. It is a
top view which shows another bonding structure of a super-magnetostrictive element and a
magnetic yoke. It is sectional drawing which shows the state which inserted ¦ pinched the buffer
member arrange ¦ positioned between the giant-magnetostrictive element and the permanent
magnet. It is front sectional drawing which shows another Example of the electromagnetic
conversion apparatus based on this invention. It is front sectional drawing which shows another
Example of the electromagnetic conversion apparatus based on this invention. It is front sectional
drawing which shows another Example of the electromagnetic conversion apparatus based on
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this invention. It is front sectional drawing which shows another Example of the electromagnetic
conversion apparatus based on this invention. It is front sectional drawing which shows another
Example of the electromagnetic conversion apparatus based on this invention. It is front sectional
drawing which shows another Example of the electromagnetic conversion apparatus based on
this invention. It is front sectional drawing which shows another Example of the electromagnetic
conversion apparatus based on this invention. It is front sectional drawing which shows another
Example of the electromagnetic conversion apparatus based on this invention. It is a figure which
shows the state which used the electromagnetic conversion apparatus shown in FIG. 19 as an
acoustic radiation apparatus. It is front sectional drawing which shows another Example of the
electromagnetic conversion apparatus based on this invention. It is front sectional drawing which
shows another Example of the electromagnetic conversion apparatus based on this invention.
Explanation of sign
[0083]
11, 12, 13 Permanent magnet 2 Outer package 22 Receiving member 23 Internal space 3 Coil 4,
41, 42 Super magnetostrictive element 5 Stretching transmission member 6 Pressure member 7
Bobbin 81, 82 Magnetic yoke
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