DESCRIPTION JP2012217033

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DESCRIPTION JP2012217033
An object of the present invention is to improve the reliability of an oscillation device by
suppressing the growth of a crack generated in a piezoelectric vibrator. An oscillating device
(100) includes a piezoelectric vibrator (10) made of ceramic, a gel material (12) provided on one
surface of the piezoelectric vibrator (10), and a vibrating member for restraining the piezoelectric
vibrator (10) through the gel material 20 and a support member 30 for supporting the edge of
the vibrating member 20. Thereby, the growth of the crack generated in the piezoelectric
vibrator can be suppressed, and the reliability of the oscillation device can be improved. [Selected
figure] Figure 1
Oscillator and portable terminal device
[0001]
The present invention relates to an oscillation device having a piezoelectric vibrator, and a
portable terminal device.
[0002]
As an electroacoustic transducer used for an electronic device, there is a piezoelectric
electroacoustic transducer using a piezoelectric vibrator.
The piezoelectric type electroacoustic transducer generates vibration amplitude by using the
expansion and contraction motion of the piezoelectric vibrator. For this reason, it becomes
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advantageous to thickness reduction compared with the electrodynamic electroacoustic
transducer comprised from a magnet, a voice coil, etc.
[0003]
As a technique regarding the electroacoustic transducer which used the piezoelectric vibrator,
there exist a thing of patent documents 1-3, for example. The technique described in Patent
Document 1 is to transmit the vibration of the drive plate portion generated by the drive of the
piezoelectric element to the diaphragm portion through the medium. Further, in the technology
described in Patent Document 2, the outer edge of the piezoelectric diaphragm is held by a
polymer gel material and mounted in a housing. The technique described in Patent Document 3
is that the vibrating membrane is made of a polymer gel.
[0004]
JP 2007-104650 JP JP 2004-80198 JP JP 2003-219499 JP
[0005]
The piezoelectric vibrator is made of, for example, a brittle material such as ceramic.
For this reason, a crack may occur in the piezoelectric vibrator due to a stress load or the like
generated at the time of bonding to another member or at the time of terminal connection to the
electrode layer. The cracks generated in the piezoelectric vibrator grow when the oscillation
device is driven, causing an electrical connection failure, attenuation of piezoelectric
characteristics, and the like. Therefore, it is required to suppress the growth of the crack
generated in the piezoelectric vibrator to improve the reliability of the oscillation device.
[0006]
According to the present invention, a piezoelectric vibrator made of ceramic, a gel material
provided on one surface of the piezoelectric vibrator, a vibrating member for restraining the
piezoelectric vibrator through the gel material, the vibrating member And a support member for
supporting an edge of the oscillator.
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[0007]
According to the present invention, there is provided a portable terminal device equipped with
the above-described oscillation device.
[0008]
According to the present invention, the growth of the crack generated in the piezoelectric
vibrator can be suppressed, and the reliability of the oscillation device can be improved.
[0009]
FIG. 2 is a cross-sectional view showing an oscillation device according to the present
embodiment.
It is sectional drawing which shows the piezoelectric vibrator shown in FIG.
It is sectional drawing explaining the effect of the oscillation apparatus shown in FIG.
It is sectional drawing which shows the oscillation apparatus which concerns on a comparative
example. It is a graph which shows the relationship between a drive voltage and vibration
displacement in the oscillation apparatus which concerns on this embodiment and a comparative
example. It is sectional drawing which shows the modification of the oscillation apparatus shown
in FIG.
[0010]
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.
[0011]
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FIG. 1 is a cross-sectional view showing an oscillation device 100 according to the first
embodiment. The oscillation device 100 according to the present embodiment includes the
piezoelectric vibrator 10, the gel material 12, the vibration member 20, and the support member
30. The oscillation device 100 is mounted on, for example, a mobile terminal device such as a
mobile phone.
[0012]
The piezoelectric vibrator 10 is made of ceramic. The gel material 12 is provided on one surface
of the piezoelectric vibrator 10. The vibrating member 20 restrains the piezoelectric vibrator 10
via the gel material 12. The support member 30 supports the edge of the vibrating member 20.
Hereinafter, the configuration of oscillation device 100 will be described in detail.
[0013]
The vibrating member 20 has, for example, a flat plate shape. The vibrating member 20 is made
of a material such as metal or resin having a high elastic modulus with respect to a ceramic
which is a brittle material, and is made of a general-purpose material such as phosphor bronze or
stainless steel. The thickness of the vibrating member 20 is preferably 5 to 500 μm. Moreover,
it is preferable that the longitudinal elasticity coefficient of the vibration member 20 is 1-500
GPa. If the longitudinal elastic modulus of the vibrating member 20 is excessively low or high,
the vibration characteristics and reliability of the oscillator may be impaired.
[0014]
As shown in FIG. 1, the oscillation device 100 includes an elastic member 22. The elastic member
22 is provided at the edge of the vibrating member 20. The elastic member 22 is provided, for
example, on the entire circumference of the vibrating member 20. The elastic member 22 is
made of, for example, a resin material such as urethane, PET, or polyethylene. The support
member 30 supports the vibrating member 20 via the elastic member 22.
[0015]
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The gel material 12 is made of, for example, a synthetic gel such as PVA (polyvinyl alcohol) or
polyacrylic acid. The gel material 12 is heated and solidified by the heat generated in the
piezoelectric vibrator 10 when the oscillation device 100 is driven. This makes it possible to
suppress the growth of the crack generated in the piezoelectric vibrator 10 as described later.
The heat generated in the piezoelectric vibrator 10 when the oscillation device 100 is driven is,
for example, 40 ° C. or more and 150 ° C. or less. Further, as the gel material 12, for example,
a gel-based adhesive such as a synthetic gel such as PVA or polyacrylic acid can be used. In this
case, adhesion between the piezoelectric vibrator 10 and the vibrating member 20 can be
performed using the gel material 12, and it is not necessary to use another adhesive. Therefore,
the manufacturing cost of the oscillator can be reduced.
[0016]
The film thickness of the gel material 12 is, for example, 20 μm or more and 100 μm or less.
When the film thickness of the gel material 12 is 20 μm or more, the growth of the crack
generated in the piezoelectric vibrator 10 can be sufficiently suppressed. In addition, when the
film thickness of the gel material 12 is 100 μm or less, the restraint force from the gel material
12 can be prevented from applying a load to the vibration of the vibrating member 20. The gel
material 12 is provided between the piezoelectric vibrator 10 and the vibrating member 20.
Therefore, the piezoelectric vibrator 10 is not in direct contact with the vibrating member 20.
[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 has a piezoelectric body 70, an upper electrode 72 and a
lower electrode 74. The piezoelectric body 70 is sandwiched between the upper electrode 72 and
the lower electrode 74. The piezoelectric body 70 is polarized in the thickness direction (vertical
direction in FIG. 2). The piezoelectric vibrator 10 has, for example, a circular shape or an
elliptical shape in a plane direction parallel to one surface of the vibrating member 20.
[0018]
The piezoelectric body 70 is made of a material having a piezoelectric effect, and is made of, for
example, lead zirconate titanate (PZT) or barium titanate (BaTiO 3) as a material having high
electromechanical conversion efficiency. The thickness of the piezoelectric body 70 is preferably
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10 μm to 1 mm. When the thickness is less than 10 μm, since the piezoelectric body 70 is
made of a brittle material, breakage or the like is likely to occur during handling. On the other
hand, when the thickness exceeds 1 mm, the electric field strength of the piezoelectric body 70 is
reduced. This leads to a decrease in energy conversion efficiency.
[0019]
The upper electrode 72 and the lower electrode 74 are made of a material having electrical
conductivity, such as silver or silver / palladium alloy. Silver is a general purpose material with
low resistance, and is advantageous in terms of manufacturing cost and manufacturing process.
In addition, a silver / palladium alloy is a low resistance material excellent in oxidation resistance
and excellent in reliability. The thickness of the upper electrode 72 and the lower electrode 74 is
preferably 1 to 50 μm. If the thickness is less than 1 μm, uniform molding becomes difficult.
On the other hand, if it exceeds 50 μm, the upper electrode 72 or the lower electrode 74
becomes a constraining surface with respect to the piezoelectric body 70, resulting in a decrease
in energy conversion efficiency.
[0020]
The oscillation device 100 includes a control unit 90 and a signal generation unit 92. The signal
generation unit 92 is connected to the piezoelectric vibrator 10 and generates an electric signal
to be input to the piezoelectric vibrator 10. The control unit 90 is connected to the signal
generation unit 92, and controls the generation of the signal by the signal generation unit 92.
The control unit 90 controls the generation of the signal of the signal generation unit 92 based
on the information input from the outside, whereby the output of the oscillation device 100 can
be controlled.
[0021]
When using the oscillation device 100 as a parametric speaker, the control unit 90 inputs a
modulation signal as a parametric speaker via the signal generation unit 92. In this case, the
piezoelectric vibrator 10 uses a sound wave of 20 kHz or more, for example, 100 kHz as the
transport wave of the signal. When the oscillation device 100 is used as a normal speaker, the
control unit 90 may directly input an audio signal to the piezoelectric vibrator 10 via the signal
generation unit 92. Moreover, when using the oscillation apparatus 100 as a sound wave sensor,
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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 92 causes the piezoelectric vibrator 10 to generate a sound wave of the
resonance frequency of the piezoelectric vibrator 10.
[0022]
The principle of operation of the parametric speaker is as follows. The principle of 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 nonlinear 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 nonlinearly 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. The parametric speaker can form a sound field only around the user and is
excellent in terms of privacy protection.
[0023]
Next, in the present embodiment, the principle of suppressing the growth of the crack generated
in the piezoelectric vibrator 10 will be described. FIG. 3 is a cross-sectional view for explaining
the effect of the oscillator 100 shown in FIG. As shown in FIG. 3A, the piezoelectric vibrator 10
made of ceramic which is a brittle material has cracks 14 as shown in FIG. It may occur. The
crack 14 generated in the piezoelectric vibrator 10 grows when the oscillation device 100 is
driven, and causes an electrical connection failure, attenuation of piezoelectric characteristics,
and the like.
[0024]
In the present embodiment, the vibrating member 20 restrains the piezoelectric vibrator 10 via
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the gel material 12. Therefore, as shown in FIG. 3 (b), the gel material 12 intrudes into the crack
14 and fills the inside of the crack 14. The gel material 12 is solidified by the heat generated in
the piezoelectric vibrator 10 when the oscillation device 100 is driven. The crack 14 generated in
the piezoelectric vibrator 10 is reinforced by solidification of the gel material 12 filling the inside
of the crack 14. Thereby, the growth of the crack generated in the piezoelectric vibrator is
suppressed. The gel material 12 may be heated and solidified before the oscillation device 100 is
driven. Also in this case, the gel material 12 filling the inside of the crack 14 is solidified, and the
crack 14 generated in the piezoelectric vibrator 10 can be reinforced.
[0025]
FIG. 4 is a cross-sectional view showing an oscillation device 104 according to a comparative
example, and corresponds to FIG. 1 in the present embodiment. The oscillation device 104
according to the comparative example has the same configuration as the oscillation device 100
according to the present embodiment except that the gel material 12 is not provided. FIG. 5 is a
graph showing the relationship between drive voltage and vibration displacement in the
oscillators according to the present embodiment and the comparative example. FIG. 5 shows
changes in vibration displacement when the drive voltage is increased.
[0026]
As shown in FIG. 5, in the oscillation device 104 according to the comparative example, as the
drive voltage is increased, the vibration displacement is greatly reduced at a certain point
(breaking point indicated by a circle in FIG. 5). It is considered that this is because the crack 14
generated in the piezoelectric vibrator 10 has grown as the oscillation device 104 is driven. On
the other hand, in the oscillation device 100 according to the present embodiment, when the
drive voltage is increased, the decrease in vibration displacement does not occur at the breaking
point in FIG. As described above, according to the oscillation device according to the present
embodiment, it is understood that the growth of the crack accompanying the driving of the
oscillation device can be suppressed, and the reliability of the oscillation device can be improved.
[0027]
Next, the effects of the present embodiment will be described. According to the present
embodiment, the piezoelectric vibrator 10 is restrained by the vibrating member 20 via the gel
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material 12. For this reason, it is possible to suppress the growth of cracks accompanying driving
of the oscillation device. Therefore, the reliability of the oscillator can be improved.
[0028]
FIG. 6 is a cross-sectional view showing the oscillation device 102 according to the second
embodiment, and corresponds to FIG. 1 in 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 piezoelectric vibrator 10 is provided on one surface of the
vibrating member 20 and the other surface opposite to the one surface. The structure of
[0029]
As shown in FIG. 6, the oscillation device 102 has a bimorph structure in which the piezoelectric
vibrator 10 is provided on both the one surface and the other surface of the vibrating member
20. The piezoelectric vibrator 10 provided on one surface of the vibrating member 20 and the
piezoelectric vibrator 10 provided on the other surface of the vibrating member 20 have
polarization directions opposite to each other. The piezoelectric vibrator 10 provided on one
surface of the vibrating member 20 and the piezoelectric vibrator 10 provided on the other
surface of the vibrating member 20 are both restrained by the vibrating member 20 via the gel
material 12.
[0030]
Also in this embodiment, the same effect as that of the first embodiment can be obtained. The
polarization directions of the piezoelectric vibrator 10 provided on one surface of the vibrating
member 20 and the piezoelectric vibrator 10 provided on the other surface of the vibrating
member 20 are opposite to each other. Therefore, when one is contracted, the other is expanded.
Therefore, it is possible to increase the vibration amplitude.
[0031]
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.
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[0032]
DESCRIPTION OF REFERENCE NUMERALS 10 piezoelectric vibrator 12 gel material 14 crack 20
vibrating member 22 elastic member 30 supporting member 70 piezoelectric member 72 upper
electrode 74 lower electrode 90 control unit 92 signal generating unit 100 oscillating device 102
oscillating device 104 oscillating device
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