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DESCRIPTION JP2007221532

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DESCRIPTION JP2007221532
PROBLEM TO BE SOLVED: To obtain an acoustic vibration generating element small in size,
satisfying a desired frequency characteristic, having a high output (a large driving force) and
having few sound leaks, and having good acoustic matching with a human body and easy
manufacturing. The challenge is to provide SOLUTION: Two piezoelectric bimorph elements 3 are
joined via an elastic plate 4, and the whole is covered with a flexible material 8. [Selected figure]
Figure 5
Acoustic vibration generating element
[0001]
The present invention relates to a piezoelectric acoustic vibration generating device suitable for
bone conduction application products.
[0002]
Conventionally, in electro-mechanical transducers used in bone conduction application products,
electromagnetic electricity is mainly used to convert the driving force generated by the
interaction between the current flowing through the coil and the magnet into mechanical
vibration on the same principle as a dynamic speaker. -Mechanical transducers are used.
Patent documents 1 and 2 disclose bone conduction application products using such an
electromagnetic type electro-mechanical transducer.
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[0003]
The generation source of the electromagnetic type electro-mechanical transducer is an
electromagnetic force. This electromagnetic force is generated by applying a current to the
winding applied to the magnetic material, but the electrical resistance of the winding causes
energy loss, and most of the energy supplied from the power source is dissipated as Joule heat.
Therefore, there is a disadvantage that the amount of energy supplied from the power source is
used as acoustic energy is only 1%. In addition, since the electromagnetic type electro-mechanical
transducer has a low impedance, the current tends to be excessive and the load on the power
source side is large. As a result, the output must be limited in the low range, and the sound
output in the low range is insufficient.
[0004]
On the other hand, although there are only a few, proposals have also been made for bone
conduction transducers using piezoelectric elements. In a bone conduction transducer using a
piezoelectric element, a piezoelectric unimorph element often used as a piezoelectric sounding
body in which a metal plate and a piezoelectric material are bonded is used as an acoustic
vibration generating element. A transducer for bone conduction using such a piezoelectric
element is disclosed in Patent Document 3 and Patent Document 4.
[0005]
However, the above-mentioned piezoelectric unimorph element has a drawback that the
reproduction of so-called bass band lower than the resonance frequency tends to be insufficient
because the resonance frequency is 1 kHz or more. In addition, the mechanical quality factor Q
of the vibration system is high, and the generation of vibration is emphasized at a specific
frequency, or the vibration is attenuated, so that natural sound can not be reproduced.
[0006]
The inventors of the present invention have already examined these problems, and acoustic
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vibration is generated in a configuration in which a plurality of piezoelectric ceramic rectangular
plates are arranged in parallel on both sides of an elastic plate and laminated, and the front and
back or the entire surface is covered with a flexible material. A device is proposed. These acoustic
vibration generating elements are disclosed in Patent Document 5.
[0007]
Patent No. 2967777 Patent No. 3358086 Japanese Patent Laid-Open No. 59-14079 Japanese
Patent Laid-open No. 59-178895 Japanese Patent Laid-Open No. 2005-311415
[0008]
However, the acoustic vibration generating element disclosed in Patent Document 5 provides a
large output as compared to the previous acoustic vibration generating element, and is an
acoustic vibration generating element with less distortion, but the vibration radiation area is long.
There is also a problem that the size is as large as 30 mm, width 24 mm, thickness 4 mm, and
there are many sound leaks.
[0009]
Therefore, an object of the present invention is to solve the problems of the prior art.
Specifically, an acoustic vibration generating element which is small and satisfies a desired
frequency characteristic and has a high output (large driving force) and little sound leakage is
obtained, and the propagation efficiency of the vibration at the contact portion with the human
body is good. It is an object of the present invention to provide an acoustic vibration generating
element that is easy to use.
[0010]
The present invention adopts the following means in order to solve the problems.
That is, the gist of the present invention is a structure in which the piezoelectric bimorph
elements are overlapped in the thickness direction so that the output can be maintained even if
the size and the vibration radiation area are reduced.
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[0011]
According to the present invention, there is provided an acoustic vibration generating element
characterized in that a plurality of piezoelectric bimorph elements are laminated and joined in
the thickness direction via an elastic plate.
[0012]
The acoustic vibration generating element according to the present invention has a laminated
structure in which a plurality of piezoelectric bimorph elements are stacked and joined while
sandwiching an elastic plate in the direction forming the thickness.
As the elastic body, a soft elastic body having a Young's modulus of 20 GPa or less, such as
urethane rubber, foamed urethane rubber, silicone resin, epoxy resin, etc., is suitable. Further, the
soft elastic body may be formed into a plate shape to be a soft elastic plate, and the size,
thickness, position and number of arrangement may be appropriately designed, and an adhesive
may be used for bonding. With such a laminated structure, the area to which acoustic vibration is
emitted is an area corresponding to one piezoelectric bimorph element, and is smaller than the
area in which the conventional piezoelectric bimorph elements are arranged side by side.
Furthermore, even if the area is small, a desired sound pressure can be obtained, and the acoustic
vibration generating element is small and has little sound leakage.
[0013]
According to the present invention, there is provided an acoustic vibration generating element
characterized in that an insulating sheet having a conductor wiring on its surface is sandwiched
between the piezoelectric bimorph element and the elastic plate.
[0014]
The acoustic vibration generating element according to the present invention may take out the
electrode from each electrode layer after laminating and bonding, but when the piezoelectric
bimorph element is stacked in the thickness direction, while sandwiching an insulating sheet
provided with conductor wiring on the surface It is preferable that the conductor wiring be taken
out of the electrode by laminating and bonding.
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[0015]
According to the present invention, there is provided an acoustic vibration generating element
characterized in that the conductor wiring is electrically connected to the piezoelectric bimorph
element, the insulating sheet is in a zigzag state, and is sandwiched by the piezoelectric bimorph
element. .
[0016]
The insulating sheet having the conductor wiring used for the acoustic vibration generating
element according to the present invention is laminated and joined so that the piezoelectric
bimorph element and the elastic plate are disposed between the single sheet in a zigzag state. .
With this configuration, it is sufficient to use one insulating sheet having the conductor wiring to
be used on the surface, and the manufacturing of the acoustic vibration generating element is
simplified.
[0017]
According to the present invention, there is provided an acoustic vibration generating element
characterized in that the insulating sheet having the conductor wiring on the surface is a flexible
substrate.
[0018]
As an insulating sheet having on its surface a conductor wiring used for an acoustic vibration
generating element according to the present invention, for example, it was made of a flexible
material called a so-called flexible substrate in which a copper resin pattern wiring is applied to a
copper foil substrate It is preferred to use a substrate.
[0019]
According to the present invention, there is provided an acoustic vibration generating element
characterized in that the acoustic vibration generating element is coated with a flexible material.
[0020]
The acoustic vibration generating device according to the present invention is coated with a
flexible substance such as urethane or silicone resin, in whole or in part, to improve not only the
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weather resistance but also to control the acoustic characteristics such as frequency
characteristics and sound pressure. It is possible to
[0021]
According to the present invention, there is provided an acoustic vibration generating element
characterized in that the piezoelectric bimorph element is formed of a rectangular piezoelectric
ceramic single plate.
[0022]
Further, according to the present invention, the piezoelectric bimorph element is formed of a
rectangular laminated piezoelectric ceramic plate in which a plurality of internal electrode layers
and a piezoelectric ceramic layer are laminated in the thickness direction and connected to a
common external electrode every other layer. An acoustic vibration generating element
characterized by
[0023]
The piezoelectric bimorph element used for the acoustic vibration generating element according
to the present invention may use a disk-shaped piezoelectric bimorph element, but it is
preferable to use a rectangular shape with little loss of material in manufacturing and easy
processing.
The piezoelectric bimorph element may be a piezoelectric ceramic plate which may be a single
plate, but a plurality of internal electrode layers and a piezoelectric ceramic layer manufactured
in a lamination process are laminated in the thickness direction, and an external electrode
common to every other layer It may be a laminated piezoelectric ceramic plate connected to
By using the laminated piezoelectric ceramic plate, the effect of being able to lower the driving
voltage can be obtained.
[0024]
As described above, according to the present invention, the configuration is such that the flexible
material is coated with a plurality of piezoelectric bimorph elements via an elastic plate, so the
dimension in the width direction is reduced, and high output is maintained. Also, it is possible to
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reduce the size and the sound leakage.
[0025]
Furthermore, since the distance between the internal electrodes can be narrowed by forming the
piezoelectric ceramic rectangular plate as a laminate of a plurality of internal electrodes and a
piezoelectric ceramic layer, the acoustic vibration generating element is driven with the same
electric field strength as the piezoelectric ceramic rectangular plate. In this case, the drive voltage
can be reduced.
[0026]
In addition, with the configuration in which the front and back surfaces or the entire surface is
covered with a flexible material, the acoustic impedance of the human body can be approached,
and the Q of the vibrator can be reduced to flatten the frequency characteristics.
The use of the flexible substrate facilitates the connection of the piezoelectric bimorph element,
and a product with high mass productivity can be obtained.
[0027]
Therefore, according to the present invention, it is possible to obtain an acoustic vibration
generating element which is small and satisfies a desired frequency characteristic and has high
output (large driving force) and little sound leakage, as well as good acoustic matching with the
human body and easy manufacturing. It is possible to provide an acoustic vibration generating
element.
[0028]
The acoustic vibration generating element according to the present invention is formed by
stacking and joining a plurality of piezoelectric bimorph elements sandwiching an elastic plate in
the direction forming the thickness thereof to form a laminated structure.
Further, the flexible substrate is disposed in a zigzag state between the piezoelectric bimorph
element and the elastic plate.
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Furthermore, the whole is coated with a flexible material.
[0029]
Hereinafter, the acoustic vibration generating element of the present invention will be described
in detail with reference to the drawings, using specific examples.
[0030]
FIG. 1 is a perspective view of an acoustic vibration generating element according to a first
embodiment.
In this embodiment, two piezoelectric bimorph elements 3 in which two piezoelectric ceramic
single plates 2 are joined via an elastic plate 1 are used, and as shown in FIG. The acoustic
vibration generating element 11 was produced.
[0031]
Piezoelectric ceramic single plate 2 is made of NEC TOKIN Corporation piezoelectric ceramic
(trade name NEPEC 10), and its shape is 30 mm, width 8 mm, thickness 0.15 mm, and silver
electrodes are baked on the front and back surfaces, and the temperature is 100 ° C.
Polarization was performed by applying a DC voltage of 150 V in silicone oil.
[0032]
The elastic plate 1 was a brass plate, and the dimensions were 30 mm in length, 10 mm in width,
and 0.1 mm in thickness.
A piezoelectric ceramic single plate 2 was bonded to both surfaces of the elastic plate 1 with an
epoxy adhesive to form a piezoelectric bimorph element 3.
[0033]
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The elastic plate 4 was made of foam urethane sheet, and the dimensions were 30 mm in length,
10 mm in width, and 1 mm in thickness.
The piezoelectric bimorph element 3 is bonded to both surfaces of the elastic plate 4 with a
double-sided tape to form an acoustic vibration generating element 11.
[0034]
FIG. 2 is a cross-sectional view of an acoustic vibration generating element according to a second
embodiment.
In the acoustic vibration generating element 12 according to the present embodiment, two
piezoelectric bimorph elements 3 in which two piezoelectric ceramic single plates 2 are joined
via the elastic plate 1 as in the first embodiment are used. The structure is such that the
piezoelectric bimorph element 3 is bonded with a double-sided tape, but when bonding the
piezoelectric bimorph element 3 to both sides of the elastic plate 4 with a double-sided tape, the
flexible substrate 5 is folded as shown in FIG. In this structure, the elastic plate 4 and the
piezoelectric bimorph element 3 are disposed.
[0035]
FIG. 3 is a front view of a flexible substrate according to a second embodiment.
The flexible substrate 5 used in this example is, as shown in FIG. 3, a 150 μm thick sheet
obtained by applying a copper foil wiring pattern 32 to a polyimide resin base material 31 and
processed into a U-shape. used.
In addition, the notch 33 was provided in the flexible substrate 5 so that the serpentine-folding
process was easy.
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The piezoelectric bimorph elements 3 are pasted one by one on the front and back of the elastic
plate while sandwiching the flexible substrate 5 with a double-sided tape, and the flexible
substrate 5 is wired with a conductive adhesive so that the two piezoelectric bimorph elements
vibrate in the same direction. The acoustic vibration generating element 12 was used.
The wiring may be a method of soldering a lead wire, but the use of the flexible substrate 5
facilitates the connection and makes an acoustic vibration generating element rich in mass
productivity.
[0036]
In this example, the piezoelectric ceramic single plate 2 used in Example 1 and Example 2 was
replaced with a laminated piezoelectric ceramic plate to produce an acoustic vibration generating
element. FIG. 4 is a perspective view of an acoustic vibration generating element according to a
third embodiment. FIG. 4 (a) is a perspective view of the acoustic vibration generating element,
and FIG. 4 (b) is a perspective view of the laminated piezoelectric ceramic plate. The structure of
the acoustic vibration generating device 13 according to the present embodiment is the same as
that of the second embodiment, but the acoustic vibration generating device 13 and the
piezoelectric ceramic plate 9 shown in FIG. did.
[0037]
The laminated piezoelectric ceramic plate 9 used in the present embodiment has a laminated
structure including two internal electrodes 6 between the piezoelectric ceramic layers 7. The
laminated piezoelectric ceramic plate 9 shown in FIG. 4B is a perspective view before the silver
electrode is baked on the side surface. The laminated piezoelectric ceramic plate 9 used the same
material as the above-mentioned piezoelectric ceramic single plate as a starting material. A green
sheet of 35 μm thickness is prepared, and a predetermined shape is printed as an internal
electrode pattern with an electrode paste consisting of silver and palladium on this green sheet,
and four green sheets on which the internal electrode 6 is printed are printed. The green sheets
are alternately laminated, thermocompression bonded, and sintered at 1200.degree. After that,
silver electrodes for connecting the internal electrodes 6 exposed to the two opposing side
surfaces were baked.
[0038]
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FIG. 5 is a transparent perspective view of the acoustic vibration generating element according to
the fourth embodiment. In the present embodiment, the entire surface of the acoustic vibration
generating element 13 obtained in the third embodiment is covered with the flexible material 8
to form the covered acoustic vibration generating element 14. However, the flexible substrate 5
is not shown in FIG. Urethane rubber was used as the flexible material 8. FIG. 6 is a crosssectional view of an acoustic vibration generating element according to a fourth embodiment. In
the present embodiment, urethane rubber is coated on the entire acoustic vibration generating
element 13 so as to have a thickness of 1 to 2 mm, and the coated acoustic vibration generating
element 14 is used.
[0039]
Here, for comparison, an acoustic vibration generating element disclosed in Patent Document 5
was also produced. FIG. 7 is a transparent perspective view of the conventional acoustic vibration
generating element, and FIG. 8 is a cross-sectional view of the conventional acoustic vibration
generating element. The conventional acoustic vibration generating element 15 has a
configuration in which three laminated piezoelectric ceramic plates 22 are arranged in parallel
on the front and back surfaces of the metal elastic plate 21 so as to cover the entire surface with
the same flexible material 23 as that of the first embodiment. The same laminated piezoelectric
ceramic plate 22 as that used in Example 3 was used.
[0040]
Further, in consideration of the influence of the flexible substrate, the flexible substrate is
adopted as the conventional acoustic vibration generating element 15 as a comparative example.
FIG. 9 is a front view of a conventional flexible substrate for an acoustic vibration generating
element. The material was the same as that used in Examples 2 to 3, and the shape was adjusted
to the conventional acoustic vibration generating element 15 as shown in FIG.
[0041]
Next, in order to quantitatively confirm the acoustic output of the acoustic vibration generating
element 14 coated according to the fourth embodiment and the conventional acoustic vibration
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generating element 15 manufactured as a comparative example, a cochlear implant (Artificial
Mastoid Type 4930 manufactured by B & K Co., Ltd. The vibration generating force was
measured using. FIG. 10 is a graph showing the measurement results of the vibration generating
force.
[0042]
As apparent from the graph of FIG. 10, it can be confirmed that even if the size of the covered
acoustic vibration generating element 14 according to the fourth embodiment is reduced, an
output equivalent to that of the conventional acoustic vibration generating element 15 can be
obtained. The
[0043]
In addition, in order to confirm the sound leakage of the acoustic vibration generating element
14 coated according to the fourth embodiment and the conventional acoustic vibration
generating element 15 manufactured as a comparative example, a sine wave of 1 Vrms is input
to the acoustic vibration generating element, 10 cm A microphone (B & K 2665) was installed at
a remote place, and sound leakage was measured.
FIG. 11 is a graph showing measurement results of sound leakage.
[0044]
As apparent from the graph shown in FIG. 11, it can be confirmed that the vibration radiation
area of the coated acoustic vibration generating element 14 according to Example 4 is reduced,
and the sound leakage particularly in the high frequency band of 3 kHz or more is reduced The
[0045]
As described above, according to the present invention, it is possible to obtain an acoustic
vibration generating element which is small, satisfies a desired frequency characteristic, has a
high output (large driving force) and has little sound leakage, and has good acoustic matching
with the human body. It is possible to provide an acoustic vibration generating element that is
easy to use.
[0046]
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The receiving device according to the present invention can be used as a receiving device for
receiving an audio signal particularly in a noisy environment, and can be used for receiving audio
of an audio device, a portable terminal device, and the like.
[0047]
FIG. 1 is a perspective view of an acoustic vibration generating element according to a first
embodiment.
FIG. 7 is a cross-sectional view of an acoustic vibration generating element according to a second
embodiment.
FIG. 7 is a front view of a flexible substrate according to a second embodiment.
FIG. 4A is a perspective view of an acoustic vibration generating element according to a third
embodiment. FIG. 4B is a perspective view of a laminated piezoelectric ceramic plate. FIG. 16 is a
transparent perspective view of an acoustic vibration generating element according to a fourth
embodiment. FIG. 14 is a cross-sectional view of an acoustic vibration generating element
according to a fourth embodiment. The transparent perspective view of the conventional acoustic
vibration generating element. Sectional drawing of the conventional acoustic vibration generating
element. The front view of the flexible substrate for the conventional acoustic vibration
generating elements. The graph which shows the measurement result of vibration generating
force. The graph which shows the measurement result of a sound leak.
Explanation of sign
[0048]
Reference Signs List 1 elastic plate 2 piezoelectric ceramic single plate 3 piezoelectric bimorph
element 4 elastic plate 5 30, flexible substrate 6 internal electrode 7 piezoelectric ceramic layer
8, 23 flexible substance 9, 22 laminated piezoelectric ceramic plate 11, 12, 13, 14 acoustic
vibration Generating element 15 Conventional acoustic vibration generating element 21 Metal
elastic plate 31 Base material 32 Wiring pattern 33 Notch
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