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DESCRIPTION JP2013162236

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DESCRIPTION JP2013162236
Abstract: An ultrasonic wave with sufficient sound pressure is output from a piezoelectric
electroacoustic transducer. A method of manufacturing a piezoelectric electroacoustic transducer
includes the steps of producing a plurality of ultrasonic transducers. The method of
manufacturing a piezoelectric electroacoustic transducer further comprises adding a weight of a
weight suitable for each of the plurality of ultrasonic transducers to each of the plurality of
ultrasonic transducers. Adjusting the fundamental resonant frequencies to the same frequency as
one another. [Selected figure] Figure 1
Method of manufacturing piezoelectric electroacoustic transducer, piezoelectric electroacoustic
transducer, and electronic device
[0001]
The present invention relates to a method of manufacturing a piezoelectric electroacoustic
transducer, a piezoelectric electroacoustic transducer, and an electronic device.
[0002]
The parametric speaker is configured to include a plurality (for example, several to several tens)
of ultrasonic transducers.
The parametric speaker uses, for example, an ultrasonic wave having a frequency of 20 kHz or
more as a carrier wave, and emits a modulated wave (such as an AM modulated wave or an FM
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modulated wave) modulated by an audio signal into air. Then, non-linearity occurs in the
amplitude of the sound wave in the air, and as a result, the voice signal is demodulated.
[0003]
In Patent Document 1, in order to shorten the vibration damping time of the conical resonator of
the ultrasonic ceramic microphone, the entire conical resonator is coated with an adhesive thinly,
or the inside of the conical resonator is It describes about the technique which provides an
adhesive agent in 1/3 or more of height.
[0004]
Japanese Utility Model Publication No. 58-030385
[0005]
In the parametric speaker, it is said that the sound pressure level is largely (about 40 dB)
attenuated when the carrier wave is demodulated to an audible sound.
Therefore, in order to reproduce an audible sound with sufficient sound pressure, it is necessary
to output ultrasonic waves with a sufficiently large sound pressure.
[0006]
The ultrasonic wave output from the parametric speaker is an ultrasonic wave synthesized from
ultrasonic waves output from a plurality of ultrasonic transducers.
Therefore, when the frequency of the ultrasonic waves output from the individual ultrasonic
transducers varies, cancellation of the ultrasonic waves output from the individual ultrasonic
transducers occurs, so that the ultrasonic waves output from the parametric speaker Total sound
pressure decreases.
[0007]
An object of the present invention is to provide a method of manufacturing a piezoelectric
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electroacoustic transducer capable of outputting an ultrasonic wave with sufficient sound
pressure from the piezoelectric electroacoustic transducer, the piezoelectric electroacoustic
transducer, and an electronic device. It is to provide.
[0008]
The present invention includes the steps of: producing a plurality of ultrasonic transducers; and
adding a weight of a weight suitable for each of the plurality of ultrasonic transducers to each of
the plurality of ultrasonic transducers. And adjusting the fundamental resonance frequencies of
the ultrasonic transducers to the same frequency as each other. The method for manufacturing a
piezoelectric electroacoustic transducer is provided.
[0009]
Further, the present invention has a plurality of ultrasonic transducers, and the plurality of
ultrasonic transducers are adjusted to the same fundamental resonance frequency by adding
weights of weights suitable for each of the plurality of ultrasonic transducers. The present
invention provides a piezoelectric electroacoustic transducer characterized by
[0010]
The present invention also includes a piezoelectric electroacoustic transducer, wherein the
piezoelectric electroacoustic transducer includes a plurality of ultrasonic transducers, and the
plurality of ultrasonic transducers have a weight suitable for each. Provided is a weight, and the
electronic device is characterized in that they are adjusted to the same fundamental resonance
frequency.
[0011]
According to the present invention, it is possible to output an ultrasonic wave with sufficient
sound pressure from the piezoelectric electroacoustic transducer.
[0012]
It is a flowchart of the manufacturing method of the piezoelectric type electroacoustic transducer
which concerns on 1st Embodiment.
It is a schematic plan view of a piezoelectric type electroacoustic transducer concerning a 1st
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embodiment.
It is a schematic cross section which shows the ultrasonic transducer | vibrator which the
piezoelectric type electroacoustic transducer which concerns on 1st Embodiment has.
It is a flowchart which shows a more specific example of the manufacturing method of the
piezoelectric-type electroacoustic transducer concerning 1st Embodiment.
It is a schematic diagram of the electronic device which concerns on 1st Embodiment.
It is a schematic cross section which shows the ultrasonic transducer | vibrator which the
piezoelectric type electroacoustic transducer which concerns on 3rd Embodiment has. It is a
schematic cross section which shows the ultrasonic transducer | vibrator which the piezoelectric
type electroacoustic transducer which concerns on a comparative example has.
[0013]
Hereinafter, embodiments of the present invention will be described using the drawings. In all
the drawings, the same components are denoted by the same reference numerals, and the
description thereof will be omitted as appropriate.
[0014]
First Embodiment FIG. 1 is a flowchart of a method of manufacturing a piezoelectric
electroacoustic transducer according to a first embodiment.
[0015]
The method of manufacturing the piezoelectric electroacoustic transducer according to the
present embodiment has the following steps.
(1) Step of Forming Multiple Ultrasonic Transducers (Step S1 in FIG. 1) (2) Adding a Weight of
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Weight Appropriate for Each of Multiple Ultrasonic Transducers to Each of Multiple Ultrasonic
Transducers Thereby adjusting the fundamental resonance frequencies of the plurality of
ultrasonic transducers to the same frequency as each other (step S2 in FIG. 2)
[0016]
FIG. 2 is a schematic plan view of the piezoelectric electroacoustic transducer 100 according to
the first embodiment.
[0017]
The piezoelectric electroacoustic transducer 100 according to the present embodiment has a
plurality of ultrasonic transducers 10.
The plurality of ultrasonic transducers 10 are adjusted to the same fundamental resonance
frequency by adding weights 17 having a weight suitable for each of them.
[0018]
In FIG. 2, in order to make it easy to understand the formation range of the weight 17, the
formation range of the weight 17 is hatched.
[0019]
FIG. 2 shows an example in which the plurality of ultrasonic transducers 10 are arranged in a
matrix in plan view.
However, the arrangement of the plurality of ultrasonic transducers 10 is not limited to this
example. For example, it is also possible to arrange a plurality of ultrasonic transducers 10 in a
row.
[0020]
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The plurality of ultrasonic transducers 10 are supported by, for example, a common support
portion 101. However, the ultrasonic transducer 10 may be supported by an individual support
(not shown).
[0021]
FIG. 3 is a schematic front cross-sectional view of the ultrasonic transducer 10 included in the
piezoelectric electroacoustic transducer 100 according to the first embodiment.
[0022]
The ultrasonic transducer 10 has, for example, a piezoelectric element 13 and a metal plate 14
joined to one surface of the piezoelectric element 13.
The piezoelectric element 13 is also referred to as a piezoelectric vibrator. The piezoelectric
element 13 is formed in a plate shape. The piezoelectric element 13 and the metal plate 14
constitute a diaphragm.
[0023]
The ultrasonic transducer 10 further includes a vibrating member 15 made of metal fixed to the
metal plate 14. A necessary amount of weights 17 is attached (added) to the vibrating member
15. That is, the weight 17 is added to the vibrating member 15 in the process of step S2 of FIG.
Thereby, the weight of the vibrating member 15 including the weight 17 is appropriately
adjusted. As a result, the fundamental resonance frequency of the ultrasonic transducer 10 is
adjusted to a desired frequency. The vibration of the fundamental resonance of the ultrasonic
transducer 10 can be approximated by a spring-mass model.
[0024]
The vibrating member 15 is fixed to the surface of the metal plate 14 opposite to the
piezoelectric element 13 side. The vibrating member 15 is fixed to the metal plate 14 by, for
example, an adhesive 16.
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[0025]
The piezoelectric element 13 is provided on the bottom plate 11 via a low elasticity column 12.
The diaphragm composed of the piezoelectric element 13 and the metal plate 14 is supported by,
for example, a plurality of columns 12. The support 12 is made of, for example, a low elastic
resin material.
[0026]
The bottom plate 11 is fixed on, for example, the support portion 101 (FIG. 2). The bottom plate
11 may be configured by a part of the support portion 101.
[0027]
The vibrating member 15 is formed, for example, in a hollow conical shape (inverted conical
shape). The shape of the outer peripheral surface of the vibrating member 15 and the shape of
the inner peripheral surface of the vibrating member 15 are each conical (inverted conical). That
is, in the case of the present embodiment, the vibrating member 15 is, for example, a metal cone.
The weight 17 is filled in the inner surface portion of the vibrating member 15. That is, in the
process of step S2 of FIG. 1, the weight 17 is filled in the inner surface portion of the vibrating
member 15.
[0028]
In the case of the present embodiment, the weight 17 is, for example, a filler containing a resin or
the like as a main component. The resin may be rubber. The filler is preferably an adhesive. By
applying the required amount of weight 17 to the inner surface of the vibrating member 15, the
inner surface can be filled with the weight 17.
[0029]
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The metal plate 14 is made of, for example, a metal such as phosphor bronze or 42 alloy. The
piezoelectric element 13 includes, for example, a piezoelectric ceramic (not shown) and an
electrode film (not shown) formed on one surface (the lower surface in FIG. 3) of the piezoelectric
ceramic. The metal plate 14 also functions as an electrode on the other surface (upper surface in
FIG. 3) of the piezoelectric element 13.
[0030]
In addition, as shown in FIG. 2, the planar shape of the metal plate 14 can be made into
polygonal shape (for example, octagon etc.), for example. However, the planar shape of the metal
plate 14 may be another shape (for example, a circle or the like). The planar shape of the
piezoelectric element 13 (FIG. 3) can be the same as that of the metal plate 14.
[0031]
Here, the piezoelectric-type electroacoustic transducer 100 inputs the modulation signal for the
parametric speaker to the plurality of ultrasonic transducers 10 to cause the ultrasonic
transducers 10 to oscillate ultrasonic waves. Further).
[0032]
The transport wave of the modulation signal is, for example, an ultrasonic wave having a
frequency of 20 kHz or more, and specifically, for example, an ultrasonic wave of 100 kHz.
The input unit 20 controls the ultrasonic transducer 10 so as to obtain a predetermined
oscillation output.
[0033]
The input unit 20 vibrates the piezoelectric element 13 by inputting a modulation signal to the
piezoelectric element 13.
[0034]
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The metal plate 14 and the vibrating member 15 vibrate by the vibration generated from the
piezoelectric element 13.
Due to this vibration, the vibrating member 15 oscillates a sound wave having a frequency of, for
example, 20 kHz or more. The vibrating member 15 is fixed to a central portion where the
displacement of the diaphragm made of the metal plate 14 and the piezoelectric element 13 is
maximum.
[0035]
The parametric speaker emits ultrasonic waves (transport waves) with AM modulation, DSB
modulation, SSB modulation, and FM modulation from the multiple oscillation sources into the
air, and the nonlinear characteristics when the ultrasonic waves propagate in the air , Make an
audible sound appear. Here, non-linear means transition from laminar flow to turbulent flow as
the Reynolds number indicated by the ratio of flow inertia action to viscosity action increases.
The sound waves are non-linear and propagate because the sound waves are finely disturbed in
the fluid. In the ultrasonic frequency band, in particular, the nonlinearity of the sound wave can
be easily observed. When ultrasonic waves are radiated into the air, harmonics associated with
the non-linearity of the sound waves are generated notably. In addition, sound waves are in a
dense / dense state in which concentration of molecular density occurs in the air. And, if time is
taken for air molecules to recover more than compression, air that can not be recovered after
compression collides with continuously propagating air molecules and a shock wave is
generated. This shock wave generates an audible sound.
[0036]
FIG. 4 is a flowchart showing a more specific example of the method of manufacturing the
piezoelectric electroacoustic transducer according to the first embodiment.
[0037]
First, a plurality of ultrasonic transducers 10 are created (step S11 in FIG. 4).
This process is the same as step S1 of FIG.
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[0038]
Next, correspondence relationship information indicating the correspondence relationship
between the additional weight of the weight 17 to the ultrasonic transducer 10 and the decrease
amount of the fundamental resonance frequency of the ultrasonic transducer 10 is prepared
(step S12 in FIG. 4). That is, if the weight 17 of weight is added to the ultrasonic transducer 10,
the basic resonance frequency can be reduced in advance, and it is checked in advance to create
information indicating the correspondence.
[0039]
If mass production of a large number of piezoelectric electroacoustic transducers 100 is
premised, if correspondence information is prepared at the initial stage of production, then
piezoelectric electroacoustics using that correspondence information. Transducer 100 can be
manufactured. Therefore, the order of steps S11 and S12 may be reversed.
[0040]
Next, a process (adjustment process) corresponding to step S2 of FIG. 1 is performed.
[0041]
First, the fundamental resonant frequency of each of the plurality of ultrasonic transducers 10 is
measured (step S13 in FIG. 4).
[0042]
Next, on the basis of the measurement result in step S13 and the correspondence information,
the individual ultrasonic vibrations required to adjust the fundamental resonance frequencies of
the plurality of ultrasonic transducers 10 to a predetermined target frequency The additional
weight of the weight 17 for each child 10 is determined (step S14 in FIG. 4).
For example, first, the difference between the measurement result of the fundamental resonance
frequency of a certain ultrasonic transducer 10 and the target frequency is calculated.
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Next, the additional weight corresponding to the difference is obtained by referring to the
correspondence information. This allows the required additional weight to be determined.
[0043]
Next, the weights 17 of the additional weight determined in step S14 are added to the plurality of
ultrasonic transducers 10 (step S15 in FIG. 4). As a result, the fundamental resonance frequency
of each of the plurality of ultrasonic transducers 10 can be finely adjusted and adjusted to a
target frequency within an appropriate frequency range. For example, it is preferable to finely
adjust the fundamental resonance frequency of each of the plurality of ultrasonic transducers 10
so that the variation in the fundamental resonance frequency of the plurality of ultrasound
transducers 10 falls within a frequency range of about ± 500 Hz.
[0044]
Here, in consideration of the ease of manufacture of the piezoelectric electroacoustic transducer
100, it is preferable that the weight 17 be, for example, filled in the bottom of the inner surface
of the vibrating member 15. However, the weight 17 may be added to other parts of the
vibrating member 15.
[0045]
The weight of the weight 17 of the ultrasonic transducer 10 of the piezoelectric-type
electroacoustic transducer 100 obtained by the above-described process is different for each
individual ultrasonic transducer 10 (except in the case of accidental coincidence).
[0046]
FIG. 7 is a schematic cross-sectional view showing an ultrasonic transducer 1000 included in a
piezoelectric electroacoustic transducer according to a comparative example.
The weight 17 is not added to the ultrasonic transducer 1000. For this reason, the weight of the
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plurality of ultrasonic transducers 1000 of the piezoelectric electroacoustic transducer according
to the comparative example is the weight on which the manufacturing variation is reflected as it
is. Therefore, in the case of the piezoelectric type electroacoustic transducer according to the
comparative example, the individual fundamental resonance frequencies of the plurality of
ultrasonic transducers 1000 largely disperse, and as a result, the total sound of ultrasonic waves
output from the piezoelectric type electroacoustic transducer The pressure may decrease.
[0047]
On the other hand, in the case of the piezoelectric-type electroacoustic transducer 100 according
to the present embodiment, as described above, the weight 17 of the weight suitable for each of
the plurality of ultrasonic transducers 10 is the same as that of the plurality of ultrasonic
transducers 10. It is attached to each. Thus, the fundamental resonance frequencies of the
plurality of ultrasonic transducers 10 are adjusted to the same frequency. For this reason, it is
possible to suppress the cancellation of the ultrasonic waves output from each of the plurality of
ultrasonic transducers 10. Accordingly, the total sound pressure of the ultrasonic waves output
from the piezoelectric electroacoustic transducer 100 can be made as large as expected.
[0048]
FIG. 5 is a schematic view of a portable terminal device 150 as an example of the electronic
device according to the first embodiment.
[0049]
As shown in FIG. 5, the portable terminal device 150 has a housing 151 and a piezoelectric
electroacoustic transducer 100 provided in the housing 151.
The configuration of the piezoelectric electroacoustic transducer 100 is as described above.
[0050]
The housing 151 is formed with a sound emission hole (not shown) for emitting a sound wave
output from the piezoelectric electroacoustic transducer 100. The support portion 101 is fixed
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to, for example, a circuit board (not shown) or the housing 151 of the mobile terminal device
150.
[0051]
The mobile terminal device 150 is, for example, a mobile phone, a PDA (Personal Digital
Assistant), a small game device, a laptop personal computer, or the like.
[0052]
According to the first embodiment as described above, the following effects can be obtained.
[0053]
The method of manufacturing a piezoelectric electroacoustic transducer according to the present
embodiment includes the step of forming a plurality of ultrasonic transducers 10.
The manufacturing method further includes adding a weight 17 having a weight suitable for each
of the plurality of ultrasonic transducers 10 to each of the plurality of ultrasonic transducers 10
so that fundamental resonance frequencies of the plurality of ultrasonic transducers 10 are
obtained. Are adjusted to the same frequency as each other.
Therefore, the cancellation of the ultrasonic waves output from each of the plurality of ultrasonic
transducers 10 can be suppressed. Therefore, the total sound pressure of the ultrasonic waves
output from the piezoelectric electroacoustic transducer 100 can be made as a sufficient
magnitude as expected.
[0054]
More specifically, for example, the ultrasonic transducer 10 has a piezoelectric element 13, a
metal plate 14 joined to the piezoelectric element 13, and a vibrating member 15 made of metal
fixed to the metal plate 14. ing. In this case, the adjusting step (step S2 in FIG. 1) can be
performed by adding the weight 17 to the vibrating member 15.
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[0055]
More specifically, for example, the vibrating member 15 is formed in a hollow conical shape. In
this case, the adjusting step (step S2 in FIG. 1) can be performed by filling the weight 17 in the
inner surface portion of the vibrating member 15.
[0056]
The method of manufacturing a piezoelectric-type electroacoustic transducer according to the
present embodiment shows, for example, the correspondence between the added weight of the
weight 17 to the ultrasonic transducer 10 and the decrease amount of the fundamental resonant
frequency of the ultrasonic transducer 10 The method further includes the step of preparing the
correspondence information. Then, in the adjusting step (step S2 in FIG. 1), the following steps
are performed. A step of measuring the fundamental resonance frequency of each of the plurality
of ultrasonic transducers 10 Based on the measurement result in the step of measuring and the
correspondence information, the fundamental resonance frequency of the plurality of ultrasonic
transducers 10 is specified. A process of determining the additional weight of the weight 17 for
each ultrasonic transducer 10 necessary for adjusting to the target frequency The weights 17 of
the additional weight determined in the above-described determining process are added to the
plurality of ultrasonic transducers 10 In this case, since the additional weight can be determined
using the correspondence information, adjustment of the fundamental resonance frequency can
be easily and efficiently performed.
[0057]
Further, since the weight 17 is made of, for example, a resin, the weight of the weight 17 can be
easily finely adjusted.
[0058]
In addition, the piezoelectric-type electroacoustic transducer 100 according to the present
embodiment has a plurality of ultrasonic transducers 10, and a plurality of ultrasonic transducers
10 are added with weights 17 having a weight suitable for each. Are adjusted to the same
fundamental resonance frequency.
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Therefore, the cancellation of the ultrasonic waves output from each of the plurality of ultrasonic
transducers 10 can be suppressed. Therefore, the total sound pressure of the ultrasonic waves
output from the piezoelectric electroacoustic transducer 100 can be made as a sufficient
magnitude as expected.
[0059]
Second Embodiment In the above-described first embodiment, an example in which the weight
17 has resin, rubber, or the like as a main component has been described. On the other hand, in
the second embodiment, a weight is formed using solder. That is, in the case of the present
embodiment, the weight is a solder. The other configuration is the same as the piezoelectric
electroacoustic transducer 100 according to the first embodiment described above in the
piezoelectric electroacoustic transducer according to the second embodiment.
[0060]
The electronic device according to the second embodiment is different from the piezoelectric
electroacoustic transducer 100 according to the first embodiment only in that it has a
piezoelectric electroacoustic transducer according to the second embodiment. This is different
from the electronic device according to the first embodiment (for example, the mobile terminal
device 150 (see FIG. 5)). In the other points, the electronic device according to the second
embodiment is configured in the same manner as the electronic device according to the first
embodiment.
[0061]
Also in the second embodiment, the same effect as in the first embodiment can be obtained.
[0062]
Third Embodiment FIG. 6 is a schematic front cross-sectional view showing an ultrasonic
transducer 10 provided in a piezoelectric electroacoustic transducer according to a third
embodiment.
[0063]
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In the first embodiment described above, an example in which the weight 17 is mainly made of
resin, rubber or the like has been described.
On the other hand, in the third embodiment, the weight 17 is formed using a metal (a metal other
than solder).
That is, in the case of the present embodiment, the weight 17 is a metal other than solder.
[0064]
The weight 17 can be adjusted by adjusting the area and thickness of the metal other than the
solder added to the inner surface of the vibrating member 15. The addition of the metal to the
inner surface portion of the vibrating member 15 can be performed, for example, by cutting out
a previously formed metal film to a necessary size (that is, a necessary weight) and attaching it to
the inner surface portion of the vibrating member 15. If necessary, weight control by thickness is
also possible by laminating and attaching the metal film to a plurality of layers. The metal may be
added to the inner surface of the vibrating member 15 by vapor deposition of metal.
[0065]
The other configuration is the same as the piezoelectric electroacoustic transducer 100
according to the first embodiment described above in the piezoelectric electroacoustic transducer
according to the third embodiment.
[0066]
The electronic device according to the third embodiment only has the piezoelectric
electroacoustic transducer according to the third embodiment in place of the piezoelectric
electroacoustic transducer 100 according to the first embodiment. This is different from the
electronic device according to the first embodiment (for example, the mobile terminal device 150
(see FIG. 5)).
In the other points, the electronic device according to the third embodiment is configured in the
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same manner as the electronic device according to the first embodiment.
[0067]
Also in the third embodiment, the same effect as in the first embodiment can be obtained.
[0068]
Although the above-mentioned each embodiment explained the example whose oscillating
member 15 is a conical metal cone, the shape of oscillating member 15 is not restricted to this
example.
For example, the vibrating member 15 may have a flat plate portion and a shaft portion
depending from the center of the flat plate portion, and the shaft portion may be fixed to the
metal plate 14.
[0069]
DESCRIPTION OF SYMBOLS 10 ultrasonic transducer 11 bottom plate 12 post 13 piezoelectric
element 14 metal plate 15 vibrating member 16 adhesive 17 weight 20 input part 100
piezoelectric type electroacoustic transducer 101 support part 150 portable terminal device 151
case 1000 piezoelectric type electroacoustic transducer
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