JP2001258095

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DESCRIPTION JP2001258095
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
magnetostrictive vibrator using a giant magnetostrictive element which vibrates in a
predetermined direction by a magnetic field corresponding to an electric signal, and more
particularly to an acoustic instrument using the same.
[0002]
2. Description of the Related Art A giant magnetostrictive element is an element having a
characteristic of being largely displaced in the direction of the magnetic field when a magnetic
field is applied. In addition, it is expected to be used for various applications because it has
advantages such as high stress generation, high response speed, and low voltage driving.
[0003]
Conventionally, using the characteristics of this giant magnetostrictive element, for example,
giant magnetostrictive elements have been used in general-purpose audio instruments such as
speakers. In such an acoustic instrument, when an electric signal as an audio signal is input, a
magnetic field corresponding to it is generated, and further, the super magnetostrictive element
is expanded and contracted by the magnetic field, thereby vibrating the diaphragm, It shakes the
air and outputs a sound.
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[0004]
Examples of this type of acoustic instrument include those disclosed in Japanese Patent
Application Laid-Open No. 10-145892.
[0005]
However, since it has been considered that high conversion efficiency can not be obtained if the
super magnetostrictive device is miniaturized in the past, a large-sized acoustic instrument using
the giant magnetostrictive device has been proposed. There were many.
Therefore, its use has also been limited.
[0006]
Then, this invention aims at achieving size reduction of the acoustic instrument using a supermagnetostrictive element, and expanding the application of the acoustic instrument using a
super-magnetostrictive element by it.
[0007]
[Means for Solving the Problems] As a result of conducting various experiments to solve the
above-mentioned problems, the inventors of the present invention have applied pressure
(prestress) to the giant magnetostrictive element in advance. I realized that I could get high
conversion efficiency.
It has also been found that the conversion efficiency is further improved by selecting an
appropriate bias magnetic field.
[0008]
Moreover, in the conventional general form, the diaphragm is vibrated according to the change
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of the audio signal, and is once output as a wave of air, but according to this configuration, the
diaphragm becomes an essential component I will. However, the generated stress in the giant
magnetostrictive element adjusted as described above is quite large, and if it has a certain degree
of hardness, it directly vibrates by transmitting the generated stress directly. It is possible.
Therefore, the inventor of the present invention omits the diaphragm in a general sound
instrument, converts an electric signal into vibration, and directly supplies the vibration to the
outside, thereby miniaturizing the sound instrument itself. I thought that I could
[0009]
The present invention provides the following acoustic device based on such an eye as a specific
means for solving the above-mentioned problems.
[0010]
That is, according to the present invention, magnetic field generating means for generating a
magnetic field corresponding to an audio signal input as an electrical signal, a giant
magnetostrictive element that expands and contracts according to the magnetic field, the giant
magnetostrictive element and the magnetic field generating means A magnetostrictive vibration
unit having a case to be accommodated and a lid for sealing the case so as to be in direct contact
with the super magnetostrictive element, and the voice signal is converted by pressing the lid
against an object The obtained vibration is transmitted to the object, and the object is vibrated to
obtain an acoustic effect.
[0011]
Here, the giant magnetostrictive element is provided in the case so as to be expandable and
contractible in the depth direction of the case and to be prestressed in the depth direction.
Further, the magnetic field generating means includes a coil for generating a magnetic field
corresponding to the electric signal, and a bias magnet for adjusting the magnetic field generated
by the coil.
[0012]
The acoustic instrument thus obtained can be used in various applications because it is compact
and lightweight since the diaphragm in the conventional configuration is omitted.
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[0013]
For example, assuming the peripheral portion of an ear in the head of a human body as the
object, design the shape or the like of the magnetostrictive vibrator, and further, hold the
magnetostrictive vibrator in contact with the peripheral portion of the ear By further providing a
holding unit for the purpose, an acoustic instrument in the form of a so-called headphoneearphone can be configured.
[0014]
Moreover, according to such an audio instrument, even a person with weak hearing or a person
who has lost hearing may be able to easily listen to music in the same manner as a healthy
person.
[0015]
Deafness, that is, deafness, can be roughly classified into conductive deafness and sensorineural
deafness according to the cause and mechanism.
Of these, conductive hearing loss occurs because the tympanic membrane and the like do not
function well, and bone conduction hearing ability is not lost.
In view of this point, in the past, acoustic instruments using the bone conduction method have
been provided for persons with conductive hearing loss, but due to the configuration, the size of
the instrument has to be increased.
Moreover, when trying to reduce the size of the audio equipment so that the deaf person can use
it daily, the performance could not but be lowered and it can be said that the deaf person could
casually use it on a daily basis. I wanted.
[0016]
However, according to the present invention, the acoustic instrument can be made smaller and
lighter, and can have a simple configuration, so it can be used for such a person with weak
hearing or who has lost hearing.
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[0017]
BEST MODE FOR CARRYING OUT THE INVENTION An acoustic instrument according to an
embodiment of the present invention will be described below with reference to the drawings.
Referring to FIG. 1, the acoustic instrument according to the present embodiment is of the socalled headphone type.
[0018]
The acoustic device includes a pair of magnetostrictive vibration units 1 and a holding unit 2, and
a bridge unit 3 connecting the pair of holding units 2.
[0019]
The magnetostrictive vibration unit 1 vibrates in response to an audio signal (electric signal)
input from an audio device or the like through the input signal line 4, and the details thereof will
be described later.
As shown in FIG. 1, the magnetostrictive vibration unit 1 is fitted in the corresponding holding
unit 2 and held and fixed.
[0020]
The holding portion 2 has the plate-like main portion 21 into which the magnetostrictive
vibration portion 1 is fitted as described above, and the arm portion 21 having a substantially arc
shape.
In the present embodiment, the holding portion 2 is formed of a light member which is hard and
low in elasticity. In addition, the magnetostrictive vibration unit 1 is fitted so as to protrude
inward from the inner side surface of the main portion 21 formed of such members, and the arm
unit 22 is directed to the side opposite to the bridge 3 side. It is formed to extend from the upper
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side of the main portion 21.
[0021]
The bridge portion 3 is made of a member having a substantially arc-like elasticity, such as a
synthetic resin. The lower end side of the holding portion 2 (main portion 21) is fixed to both
ends of the bridge portion 3. Therefore, when a force is applied in a direction to widen the
distance between both ends of the bridge portion 3, the bridge portion 3 tries to narrow the
distance by its elasticity, whereby the holding portions 2 force the forces toward each other. It
will be received. The distance between both ends of the bridge portion 3 is selected to be slightly
smaller than the distance between the average human ear.
[0022]
In the headphone having such a configuration, as shown in FIG. 2, the bridge portion 3 is
inserted from the lower rear side of the head with the bridge portion 3 slightly expanded, and the
arm portion 22 of the holding portion 2 extends from the rear side to the front side of the ear
Attached by hooking. At this time, the magnetostrictive vibration unit 1 held by the main portion
21 is positioned behind the ear due to the shape relationship between the arm portion 22 and
the main portion 21 of the holding portion 2. In other words, when the arm portion 22 is hooked
to the ear, the main portion 21 and the arm portion 22 are arranged such that the
magnetostrictive vibration portion 1 held by the main portion 21 is disposed behind the ear The
shape is determined. From the geometrical relationship between the main portion 21 and the
arm portion 22 as described above, the magnetostrictive vibration portion 1 disposed on the rear
side of the ear further has an elastic force for narrowing the distance between both ends of the
bridge portion 3. It is received via the main part 21 to be held and pressed against the back of
the corresponding ear. As a result, the magnetostrictive vibration unit 1 is brought into pressure
contact with the back side of the ear, and by vibrating according to the audio signal, the vibration
can be directly transmitted to the head.
[0023]
Hereinafter, the structure and the like of the magnetostrictive vibration unit 1 will be described
in detail with further reference to FIG.
[0024]
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As shown in FIG. 3, the magnetostrictive vibration unit 1 includes a giant magnetostrictive
element 11, a coil 12, a bias magnet 13, a cap 14 and a case 15.
[0025]
The giant magnetostrictive element 11 has a substantially cylindrical shape, and is disposed at
the central portion of the case 15 so as to stand (extend) in the depth direction of the case 15.
In particular, in the present embodiment, 3 mm is selected as the diameter of the giant
magnetostrictive element 11.
A coil 12 is disposed around the giant magnetostrictive element 11, and a biasing magnet 13 is
disposed around the coil 12. The positional relationship of the super magnetostrictive element
11, the coil 12 and the bias magnet 13 in the case 15 is fixed, and the side wall of the case 15
which surrounds the bias magnet 13 has a constant thickness. It is formed to have. As
understood from this description, in the present embodiment, the outer shape of the case 15 is
substantially cylindrical, and the cavity formed by the case 15 is also substantially cylindrical.
Further, since the cap 14 seals the case, it has a substantially disc shape. In particular, in the
present embodiment, the engagement groove 151 is formed in the upper portion of the side wall
portion of the case 15, the locking portion 141 of the cap 14 is locked there, and the cap 14 and
the case 15 are fixed to each other. However, they may be fixed by screws or other means.
[0026]
The cap 14 is a portion facing the inner side of the headphone in FIG. 1, and in the present
embodiment, is a portion directly in contact with the back side of an ear as an object of vibration
transmission. The cap 14 is formed to have a greater elasticity than the bottom of the case 15
opposed thereto. In the present embodiment, both the cap 14 and the case 15 are made of
plastic, and by making the bottom of the case 15 thicker than the cap 14, the elasticity of the cap
14 is made relatively larger than that of the case bottom. Was configured. The cap 14 and the
case 15 may be made of, for example, other nonmagnetic materials, or they may be made of
different materials.
[0027]
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In particular, in the present embodiment, the cap 14 is provided with a notch. This notch portion
constitutes a hole for introducing the input signal line 4 from the outside of the magnetostrictive
vibration unit 1 to the inside when the cap 14 seals the case 15. The input signal line 4 led to the
inside through the hole is electrically connected to the coil 12 as described later. The notch may
be formed so that the input signal line 4 finally passes through, for example, may be provided on
the case 15 side instead of the cap 14 side, or may be provided on both sides. good. Further,
instead of the cutout portion, a hole itself for the input signal line 4 may be formed.
[0028]
Further, in the present embodiment, the length of the giant magnetostrictive element 11 in the
depth direction is slightly longer than the length of the case 15 in the depth direction, and the
giant magnetostrictive element 11 is directly attached to the cap 14. It contacts and is
accommodated in case 15. Specifically, in the present embodiment, the length of the giant
magnetostrictive element 11 is configured to be about 10% longer than the depth of the case 15.
That is, for example, if the depth of the case 15 is 8 mm, the length of the giant magnetostrictive
element 11 is 8.8 mm. By doing this, the giant magnetostrictive element 11 is provided in the
case 15 with the cap 14 applied pressure (prestress) in the depth direction of the case 15.
[0029]
The prestress is preferably in the range of 5 MPa to 15 MPa, and more preferably in the range of
8 MPa to 10 MPa. By applying prestress in this range, it is possible to enhance the conversion
efficiency of converting an electrical signal into vibration. In particular, in the present
embodiment, 9.8 MPa was selected as the prestress. That is, as described above, since the
diameter of the giant magnetostrictive element 11 is 3 mm, its cylindrical cross section is about
0.07 cm 2, and hence the force applied in the longitudinal direction of the giant magnetostrictive
element 11 is about 68. It will be 6N.
[0030]
The coil 12 receives an audio signal (electric signal) from an audio device or the like through the
input signal line 4 and generates a magnetic field according to the signal. The giant
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magnetostrictive element 11 expands and contracts in accordance with the change in the
generated magnetic field. The biasing magnet 13 is selected to have its magnetic field strength
such that the expansion and contraction according to the electrical signal is transmitted to the
outside as a large vibration. In other words, the giant magnetostrictive element 11 is supplied
with a magnetic field by the coil 12 and the bias magnet 13 and expands and contracts
accordingly to generate vibration. In this sense, the coil 12 and the bias magnet play a role as a
magnetic field generating means for the giant magnetostrictive element 11.
[0031]
The bias magnet 13 is selected so that the resulting magnetic field is in the range of 7900 A / m
to 63200 A / m, and more preferably a magnetic field in the range of 23700 A / m to 47400 A /
m. It is selected as supplied to 11. In the present embodiment, a magnet made of a rare earth
magnet and a magnet made of an iron-chromium-cobalt magnet were prepared as the bias
magnet 13 and experiments were conducted to obtain favorable vibration characteristics. Under
the present circumstances, the magnetic field by the bias magnet 13 which consists of rare earth
magnets was 23700 A / m, and the magnetic field by the bias magnet 13 which consists of iron
chromium cobalt magnets was 47400 A / m. The bias magnet 13 may be formed by using a
machinable material and using the case 15 as well.
[0032]
According to the headphone-type acoustic instrument having such a configuration, by
transmitting the vibration corresponding to the audio signal to the person wearing the
headphone, the sound can be generated using the bone conduction of the person. It can make
you feel.
[0033]
In the above example, the acoustic instrument is of the headphone type, but the application to
which the magnetostrictive vibrator obtained by the present invention can be applied is not
limited to this.
For example, when vibration is transmitted to the object by bringing a magnetostrictive vibrator
into contact with the object with a plate-like object such as a table or a door as an object, the
object is a diaphragm in a conventional acoustic speaker or the like Plays the role of shaking the
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air and can output sound. As described above, when the magnetostrictive vibrator according to
the present invention is formed so as to be able to propagate vibrations to the object by
contacting the object, the acoustic instrument is realized if formed. The acoustic device according
to the invention is not limited to the headphones shown in the embodiment.
[0034]
As described above, according to the present invention, the super magnetostrictive element is
prestressed by the cap, whereby high conversion efficiency can be obtained. By directly
transmitting the vibration by the giant magnetostrictive element to the object, the acoustic effect
is exhibited, so that the miniaturization of the acoustic instrument using the giant
magnetostrictive element can be achieved, and the application of the acoustic instrument can be
expanded. it can.
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