JP2012015761

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DESCRIPTION JP2012015761
An oscillation device capable of realizing a high sound pressure level while achieving downsizing
is provided. An oscillating device includes a piezoelectric vibrator, a vibrating member for
restraining one surface of the piezoelectric vibrator, a metal member attached to the other
surface of the piezoelectric vibrator, and piezoelectricity of the metal member. The piezoelectric
element 10 is supported via the elastic member 24 attached to the surface opposite to the
surface in contact with the vibrator 10, the support member 30 supporting the edge of the
vibrating member 20, and the metal member 22 and the elastic member 24. And a supporting
member 35. [Selected figure] Figure 1
Oscillator
[0001]
The present invention relates to an oscillation device using a piezoelectric vibrator.
[0002]
An electro-acoustic transducer is known as an electro-acoustic transducer for portable devices
and the like.
Electrokinetic electroacoustic transducers generate vibrational amplitude using the action of a
magnetic circuit. However, since the magnetic circuit is constituted by a large number of
members such as permanent magnets and voice coils, there is a limit to the miniaturization of the
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electrodynamic electroacoustic transducer.
[0003]
As an electroacoustic transducer replacing electrokinetic electroacoustic transducer, there is a
piezoelectric electroacoustic transducer. The piezoelectric-type electroacoustic transducer
generates an oscillation amplitude by using an expansion and contraction motion generated by
applying an electric field to the piezoelectric vibrator. The piezoelectric electro-acoustic
transducer is advantageous for miniaturization because it does not require a large number of
members to generate vibration amplitude.
[0004]
As a technique regarding a piezoelectric type electroacoustic transducer, there exist some which
are described in patent document 1, patent document 2, and patent document 3. FIG. The
technique described in Patent Document 3 is to provide a spring material as a damping means on
one side or both sides of a piezoelectric diaphragm. The technique described in Patent Document
1 is to support the outer peripheral portion of the piezoelectric diaphragm via a thin flange and
support the central portion of the piezoelectric diaphragm via an elastic body. It is described that,
together with the improvement of the sound pressure level, an excellent frequency characteristic
with less peak dip is realized.
[0005]
The technique described in Patent Document 2 is to join a piezoelectric element and a vibrating
film via a vibration transmitting member having elasticity. It is described that it is possible to
obtain sufficient vibration amplitude by utilizing the elastic restoring action of the vibration
transfer member.
[0006]
Patent Document 1: Japanese Patent Application Laid-Open No. 2002-135893 Patent Document
1: International Publication WO 2005/094121
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[0007]
By using the piezoelectric vibrator, the electroacoustic transducer can be miniaturized.
On the other hand, the electroacoustic transducer is required to secure a certain sound pressure
level or more for enabling acoustic reproduction.
[0008]
An object of the present invention is to provide an oscillation device capable of realizing a high
sound pressure level while achieving miniaturization.
[0009]
According to the present invention, a piezoelectric vibrator, a vibrating member for restraining
one surface of the piezoelectric vibrator, a metal member attached to the other surface of the
piezoelectric vibrator, and a surface of the metal member in contact with the piezoelectric
vibrator A first elastic member attached to the opposite surface, a first support member
supporting an edge of the vibration member, the piezoelectric element through the metal
member and the first elastic member And a second support member for supporting the oscillator.
[0010]
According to the present invention, it is possible to provide an oscillation device capable of
realizing a high sound pressure level while achieving downsizing.
[0011]
FIG. 1 is a cross-sectional view showing an oscillation device according to a first embodiment.
It is sectional drawing which shows the piezoelectric vibrator shown in FIG.
FIG. 6 is a cross-sectional view showing an oscillation device according to a second embodiment.
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FIG. 7 is a cross-sectional view showing an oscillation device according to a third embodiment. It
is a perspective view showing a piezoelectric vibrator concerning a 4th embodiment. It is the
schematic which shows the structure of a mobile communication terminal.
[0012]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. In all the drawings, the same components are denoted by the same reference numerals,
and the description thereof will be appropriately omitted.
[0013]
FIG. 1 is a cross-sectional view showing an oscillation device 100 according to the first
embodiment. The oscillation device 100 includes a piezoelectric vibrator 10, a vibrating member
20, a metal member 22, an elastic member 24, a support member 30, and a support member 35.
The oscillation device 100 is used, for example, as a speaker or an oscillation source of a sound
wave sensor. Moreover, it can also function as a temperature sensor by utilizing the pyroelectric
effect of a piezoelectric material. When the oscillation device 100 is used as a speaker, it is used,
for example, as a sound source of an electronic device (mobile phone, laptop computer, small
game machine, etc.).
[0014]
The vibrating member 20 restrains one surface of the piezoelectric vibrator 10. The metal
member 22 is attached to the other surface of the piezoelectric vibrator 10. The elastic member
24 is attached to the surface of the metal member 22 opposite to the surface in contact with the
piezoelectric vibrator 10. The support member 30 supports the edge of the vibrating member 20.
The support member 35 supports the piezoelectric vibrator 10 via the metal member 22 and the
elastic member 24. The configuration of the oscillation device 100 will be described in detail
below with reference to FIGS. 1 and 2.
[0015]
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As shown in FIG. 1, the oscillation device 100 further includes lead wires 26 and an external
terminal 28. The external terminal 28 is embedded in the metal member 22. Further, the external
terminal 28 is connected to the piezoelectric vibrator 10. The lead wire 26 is connected to the
external terminal 28 at one end, and extends to the outside of the oscillation device 100 at the
other end.
[0016]
As shown in FIG. 1, the oscillation device 100 further includes a control unit 90 and a signal
generation unit 95. The signal generation unit 95 generates an electrical signal to be input to the
piezoelectric vibrator 10. The control unit 90 controls the signal generation unit 95 based on the
information input from the outside. When the oscillation device 100 is used as a speaker, the
information input to the control unit 90 is an audio signal. Moreover, when using the oscillation
apparatus 100 as a sound wave sensor, the signal input into the control part 90 is a command
signal to the effect of oscillating a sound wave. Then, when the oscillation device 100 is used as a
sound wave sensor, the signal generation unit 95 causes the piezoelectric vibrator 10 to generate
a sound wave of the resonance frequency of the piezoelectric vibrator 10.
[0017]
FIG. 2 is a cross-sectional view showing the piezoelectric vibrator 10 shown in FIG. As shown in
FIG. 2, the piezoelectric vibrator 10 includes an upper electrode 40, a lower electrode 45, and a
piezoelectric body 50. The piezoelectric vibrator 10 has, for example, a circular shape, an
elliptical shape, or a rectangular shape. The piezoelectric body 50 is sandwiched between the
upper electrode 40 and the lower electrode 45. The piezoelectric body 50 is made of a material
having a piezoelectric effect, and is made of, for example, lead zirconate titanate (PZT), barium
titanate (BaTiO3) or the like. The thickness of the piezoelectric body 50 is preferably 10 um to 1
mm. If the thickness is less than 10 um, the piezoelectric body 50 is made of a brittle material,
and thus breakage or the like is likely to occur. On the other hand, when the thickness exceeds 1
mm, the electric field strength of the piezoelectric body 50 is reduced. Therefore, the energy
conversion efficiency is reduced.
[0018]
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The upper electrode 40 and the lower electrode 45 are made of, for example, silver or a silver /
palladium alloy. The thickness of the upper electrode 40 and the lower electrode 45 is preferably
1 to 50 μm. If the thickness is less than 1 um, uniform molding becomes difficult. On the other
hand, when it exceeds 50 um, the upper electrode 40 or the lower electrode 45 becomes a
constraining surface with respect to the piezoelectric body 50, and the energy conversion
efficiency is lowered.
[0019]
The vibrating member 20 is fixed by the support member 30. Therefore, the vibration generated
from the piezoelectric vibrator 10 has a function of causing the oscillation device 100 to
generate a vibration. The vibrating member 20 also has a function of improving the mechanical
strength of the oscillation device 100. The vibrating member 20 is made of a material having a
high elastic modulus with respect to the ceramic material, and is made of, for example, phosphor
bronze or stainless steel. The thickness of the vibrating member 20 is preferably 5 to 500 μm.
The longitudinal elastic modulus of the vibrating member 20 is preferably 1 to 500 GPa. If the
longitudinal elastic modulus of the vibrating member 20 is excessively low or high, the
characteristics and reliability as a mechanical vibrator may be impaired. The support member 30
is made of, for example, a metal film such as stainless steel.
[0020]
The metal member 22 is attached to, for example, the other surface of the piezoelectric vibrator
10 at a position where the displacement amount of vibration is maximum. The elastic member 24
is made of, for example, a resin material. The Young's modulus of the metal member 22 is
preferably 20 times or more that of the elastic member 24. When vibration occurs in the
oscillation device 100, the elastic member 24 produces an absorption / repulsion effect due to
the restoring force. The absorption and repulsion effect is transmitted to the piezoelectric
vibrator 10 and the vibrating member 20 through the metal member 22. Thereby, the amplitude
of the oscillation device 100 is increased. The support member 30 and the support member 35
are provided integrally, for example.
[0021]
Next, a method of manufacturing the oscillation device 100 according to the present embodiment
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will be described. First, the piezoelectric body 50 is manufactured. The piezoelectric body 50 is
manufactured by a green sheet method, and is fired at 1100 ° C. for 2 hours in the air. Next, the
upper electrode 40 and the lower electrode 45 are formed on the piezoelectric body 50. Then,
polarization treatment is applied to the piezoelectric body 50 in the thickness direction. The
piezoelectric vibrator 10 thus obtained is bonded to the vibrating member 20 using an epoxy
resin or the like. Thereafter, the edge of the vibrating member 20 is supported by the support
member 30. In addition, the piezoelectric vibrator 10 is supported by the support member 35 via
the metal member 22 and the elastic member 24. Thus, the oscillation device 100 is formed.
[0022]
The piezoelectric body 50 can have an outer diameter of 15 mm and a thickness of 100 um. The
piezoelectric body 50 can use lead zirconate titanate ceramic. The upper electrode 40 and the
lower electrode 45 can have a thickness of 8 um. The upper electrode 40 and the lower electrode
45 can use a silver / palladium alloy (70% by weight ratio: 30%). The vibrating member 20 can
have an outer diameter of φ 17 mm and a thickness of 300 um. The vibrating member 20 can
use phosphor bronze. The supporting member 30 and the supporting member 35 can constitute
a bathtub-like case having an outer diameter of 19 mm and an inner diameter of 18 mm. The
support member 30 and the support member 35 can use SUS304. The metal member 22 and the
elastic member 24 can have an outer diameter of φ3 mm. The metal member 22 can be made of
stainless steel. The elastic member 24 can be made of a PET material.
[0023]
Next, a sound reproduction method by the piezoelectric type electroacoustic transducer using the
oscillation device 100 according to the present embodiment will be described. In the present
embodiment, for example, sound can be reproduced using the operation principle of the
parametric speaker. In this case, the control unit 90 inputs a modulation signal as a parametric
speaker to the piezoelectric vibrator 10 via the signal generation unit 95. When used as a
parametric speaker, the piezoelectric vibrator 10 uses a sound wave of 20 kHz or more, for
example, 100 kHz as a transport wave of a signal.
[0024]
Here, the operation principle of the parametric speaker will be described. The principle of
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operation of the parametric speaker is that ultrasonic waves with AM modulation, DSB
modulation, SSB modulation, FM modulation are emitted into the air, and the audible sound
appears due to non-linear characteristics when the ultrasonic waves propagate in the air Sound
reproduction. The term "nonlinear" as used herein means transition from laminar flow to
turbulent flow when the Reynolds number represented by the ratio of the inertial action of the
flow to the viscous action increases. That is, since the sound wave is finely disturbed in the fluid,
the sound wave is non-linearly propagating. In particular, when ultrasonic waves are emitted into
the air, harmonics associated with the non-linearity are significantly generated. In addition,
sound waves are in a dense / dense state in which molecular groups in the air are mixed in
density. If it takes time for air molecules to recover more than compression, air that can not be
recovered after compression will collide with continuously propagating air molecules, producing
shock waves and producing audible sounds.
[0025]
Next, the effects of the present embodiment will be described. The inventor has found that the
amplitude is significantly increased in the oscillation device 100 having the configuration in the
present embodiment. It is assumed that the absorption / repulsion effect due to the restoring
force generated by the elastic member 24 when vibration is generated in the oscillation device
100 is easily transmitted to the piezoelectric vibrator 10 and the vibrating member 20 through
the metal member 22. Be done. Therefore, according to the present embodiment, a high sound
pressure level can be realized while achieving downsizing.
[0026]
The inventor has also found that when the Young's modulus of the metal material 22 is equal to
or greater than 20 times the Young's modulus of the elastic member 24, the amplitude of the
oscillation device is further increased. Thus, the sound pressure level can be further improved.
Furthermore, the piezoelectric vibrator 10 is supported by the support member 35 via the elastic
member 24. For this reason, impact energy is absorbed by the elastic member 24 when it is
dropped or the like. Therefore, the mechanical strength of the oscillator can be improved.
[0027]
The piezoelectric vibrator 10 is in contact with the metal member 22 in which the external
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terminal 28 is embedded. Therefore, the piezoelectric vibrator 10 can be connected to the
outside through the external terminal 28 embedded in the metal member 22 without directly
providing the external terminal to the piezoelectric vibrator 10. Therefore, the manufacture of
the oscillator becomes easy.
[0028]
FIG. 3 is a cross-sectional view showing the oscillation device 102 according to the second
embodiment, and corresponds to FIG. 1 according to the first embodiment. The oscillation device
102 according to the present embodiment is the same as the oscillation device 100 according to
the first embodiment except that the lead wire 26 is connected to the piezoelectric vibrator 10
through the metal member 22.
[0029]
The lead wire 26 is connected to the piezoelectric vibrator 10 through the metal member 22. A
voltage is applied to the piezoelectric vibrator 10 via the metal member 22 and the lead wire 26.
Therefore, it is not necessary to provide the piezoelectric vibrator 10 with an external terminal
directly. Therefore, also in this embodiment, the same effect as that of the first embodiment can
be obtained.
[0030]
FIG. 4 is a cross-sectional view showing an oscillation device 104 according to the third
embodiment, which corresponds to FIG. 1 according to the first embodiment. The oscillation
device 104 according to the present embodiment is the same as the oscillation device 100
according to the first embodiment except that the elastic member 32 is provided.
[0031]
The elastic member 32 is provided on the outer peripheral portion of the vibrating member 20.
The vibrating member 20 is supported by the support member 30 via the elastic member 32.
The elastic member 32 is made of, for example, a resin material such as urethane, PET, or
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polyethylene, and has lower rigidity than the vibrating member 20. The thickness of the elastic
member 32 is not particularly limited, but the value is determined so that the ease of movement
of the end of the vibrating member 20 can be ensured, and the durability satisfies the standard.
[0032]
Also in this embodiment, the same effect as that of the first embodiment can be obtained. The
vibrating member 20 is supported by the support member 30 via an elastic member 32 provided
at the edge of the outer peripheral portion. Therefore, the end of the vibrating member 20 can be
brought close to the free end. Therefore, the sweep volume of the vibration by the vibration
member 20 is increased, and the sound pressure level of the oscillation device can be further
improved. In addition, impact energy is absorbed by the elastic member 32 when falling or the
like. Therefore, the mechanical strength of the oscillator can be further improved.
[0033]
FIG. 5 is a perspective view showing a piezoelectric vibrator 110 according to the fourth
embodiment. The oscillator according to the present embodiment is the same as the oscillator
100 according to the first embodiment except for the configuration of the piezoelectric vibrator.
Further, the piezoelectric vibrator 110 according to the present embodiment is the same as the
piezoelectric vibrator 10 according to the first embodiment except that it has a laminated
structure.
[0034]
As shown in FIG. 5, the piezoelectric vibrator 110 is configured by alternately laminating a
plurality of piezoelectric members and a plurality of electrodes. The electrodes 70, 71, 72, 73 are
formed between the piezoelectric members 60, 61, 62, 63, 64 one by one. The electrode 70 and
the electrode 72, and the electrode 71 and the electrode 73 are connected to each other. The
polarization direction of each piezoelectric body is reverse to each other. Also, the direction of
the electric field generated between the electrodes is alternately reversed.
[0035]
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Also in this embodiment, the same effect as that of the first embodiment can be obtained.
Further, since the piezoelectric vibrator 110 has a laminated structure, the electric field strength
generated between the electrode layers is high. Thereby, the driving force of the piezoelectric
vibrator 110 can be improved. The number of stacked piezoelectric vibrators 110 can be
arbitrarily increased or decreased.
[0036]
(Example) The oscillation device shown in Drawing 1, Drawing 4, and Drawing 5 was created, and
the characteristic of each oscillation device was investigated (examples 1-3). In the present
embodiment, the oscillation device functions as a parametric speaker. Further, as Comparative
Example 1, an electrodynamic oscillation device having the same planar area as in Examples 1 to
3 was produced, and the characteristics were examined. The results are shown in Table 1. In the
measurement of the sound pressure level frequency characteristics, the sound pressure level at
the time of AC voltage 1 V input was measured by a microphone disposed at a position 10 cm
away from the piezoelectric vibrator. The measurement range of the frequency was 10 Hz to 10
kHz. Moreover, in the measurement of drop impact stability, a portable communication terminal
equipped with an electroacoustic transducer equipped with an oscillating device was allowed to
naturally drop 5 times from a height of 50 cm. After that, damage or the like of the mobile
communication terminal was visually confirmed. Furthermore, the sound pressure characteristics
were measured, and when the sound pressure level difference was within 3 dB before and after
the test, it was rated as ○.
[0037]
[0038]
From this table, it was shown that the oscillation device according to each example had a high
sound pressure level and flat frequency characteristics as compared with the comparative
example.
It was also shown that the drop impact stability is higher than that of the comparative example.
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[0039]
Further, as shown in FIG. 6, as the speaker 122 of the mobile communication terminal 120, the
oscillation device according to Examples 1 to 3 was used. The speaker 122 was attached to the
inner surface of the housing of the mobile communication terminal 120. Table 2 shows the
characteristics of the speaker 122 when each embodiment is used. The measurement conditions
are the same as in Table 1.
[0040]
[0041]
From this table, it was shown that the mobile communication terminal 120 according to each
example has a flat frequency characteristic.
It was also shown that the drop impact stability was high.
[0042]
Although the embodiments of the present invention have been described above with reference to
the drawings, these are merely examples of the present invention, and various configurations
other than the above can also be adopted.
[0043]
DESCRIPTION OF SYMBOLS 10 piezoelectric vibrator 20 vibration member 22 metal member 24
elastic member 26 lead terminal 28 external terminal 30 support member 32 elastic member 35
support member 40 upper electrode 45 lower electrode 50 piezoelectric body 60 to 64
piezoelectric body 70 to 73 electrode 90 control part 95 Signal generation unit 100 oscillator
102 oscillator 104 oscillator 110 piezoelectric vibrator 120 mobile communication terminal 122
speaker
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