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DESCRIPTION JP2012134590

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DESCRIPTION JP2012134590
An oscillation device capable of narrowing down directivity of a sound wave with high efficiency
is provided. An elongated elastic member (120) having a pair of piezoelectric elements (110)
individually mounted at both ends is supported by a plurality of support members at the center.
As described above, since the cantilever support structure is used, the sound wave radiation
portion is limited to both ends of the piezoelectric vibrator including the elastic member 120 and
the piezoelectric element 110. For this reason, for example, when arranging a plurality of
piezoelectric vibrators, the sound emission positions of the adjacent piezoelectric vibrators can
be made close to each other. That is, by controlling the distance in the minor axis direction
between the piezoelectric vibrators, it is possible to suppress phase canceling of the sound waves
oscillated from the adjacent piezoelectric vibrators, and to narrow down the directivity of the
sound waves with high efficiency. it can. [Selected figure] Figure 1
Oscillator and electronic device
[0001]
The present invention relates to an oscillation device using a piezoelectric vibrator, and an
electronic device using the oscillation device.
[0002]
In mobile phones, we are working on the development of thin and stylish mobile phones that
have the commercial value of sound functions such as videophone and video playback and
hands-free phone functions, and there is a growing demand for the development of small-sized,
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1
high-volume electroacoustic transducers. There is.
In addition, from the viewpoint of privacy protection, there is a demand for development of a
superdirective speaker capable of forming a sound field only at a specific position. As
superdirective speakers, parametric speakers have been developed that use ultrasonic waves for
carrier waves such as voice to demodulate in a non-linear state in air.
[0003]
At present, there are various proposals as the above-described electroacoustic transducer (Patent
Document 1).
[0004]
JP 2000-134697 A
[0005]
However, in order to narrow down the directivity of the ultrasonic waves, as in the phased array
method, from the array probe in which a large number of small ultrasonic transducers are
arranged, a main beam is generated by synthesizing the ultrasonic waves oscillated with different
timings. The way it was done was taken.
In this case, since it is necessary to arrange a large number of piezoelectric transducers in an
array, there is a problem that the size of the ultrasonic device increases.
[0006]
The present invention has been made in view of the problems as described above, and provides a
small-sized oscillator having high directivity and an electronic device using such an oscillator.
[0007]
The oscillation device according to the present invention includes a pair of piezoelectric elements
that are expanded and contracted by application of an electric field, an elongated elastic member
having the pair of piezoelectric elements individually mounted at both ends, and a support that
supports the elastic member at the center. And a member.
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[0008]
A first electronic device of the present invention includes the oscillation device of the present
invention, and an oscillation drive unit that causes the oscillation device to output an ultrasonic
wave that is demodulated to a sound wave in the audible range.
[0009]
A second electronic device according to the present invention includes an oscillation device
according to the present invention, an oscillation drive unit that causes the oscillation device to
output an ultrasonic wave, and an ultrasonic wave detection that detects an ultrasonic wave
oscillated from the oscillation device and reflected by the object to be measured. And a distance
measuring unit for calculating the distance from the detected ultrasonic wave to the object to be
measured.
[0010]
Note that the various components of the present invention do not necessarily have to be
independent entities individually, but a plurality of components are formed as one member, and
one component is formed of a plurality of members. That one component is a part of another
component, that a part of one component overlaps with a part of another component, and so on.
[0011]
Furthermore, although the present invention defines the front, rear, left, right, upper, and lower
directions, this is defined for the sake of convenience in order to briefly explain the relative
relationship of the components of the present invention. It does not limit the direction of
manufacture or use.
Moreover, it is not necessary that the front, rear, left, right, upper and lower directions in the
present invention be completely geometrically orthogonal to each other, as long as the directions
are relatively in the front, rear, left, right, upper, lower or lower. It may be inclined in the
direction of
[0012]
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In the oscillation device of the present invention, an elongated elastic member having a plurality
of piezoelectric elements individually mounted at each end is supported by a support member at
the center.
Therefore, since the cantilever support structure is used, the radiation part of the sound wave is
limited to the end of the piezoelectric vibrator composed of the elastic member and the
piezoelectric element.
For this reason, for example, when a plurality of piezoelectric vibrators are arrayed and formed,
the sound emission positions of the adjacent piezoelectric vibrators can be made close to each
other.
That is, by controlling the distance in the minor axis direction between the transducers, it is
possible to suppress phase canceling of the sound waves oscillated from the adjacent
transducers, and it is possible to narrow down the directivity of the sound waves with high
efficiency.
[0013]
It is a schematic plan view which shows the structure of the electroacoustic transducer which is
an oscillation apparatus of embodiment of this invention.
It is a typical longitudinal front view which shows the structure of the principal part of an
electroacoustic transducer.
[0014]
An electroacoustic transducer 100 which is an oscillation device of the present embodiment will
be described below with reference to the drawings.
In the present embodiment, the directions of front, rear, left, right, upper and lower are defined
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and described. However, this is conveniently defined to simply explain the relative relationship of
components. Accordingly, there is no limitation on the direction of manufacture or use of a
product embodying the present invention.
[0015]
As shown in FIGS. 1 and 2, in the electro-acoustic transducer 100 according to the present
embodiment, a pair of piezoelectric elements 110 that stretch and move by application of an
electric field, and a pair of piezoelectric elements 110 are individually mounted at both ends. It
has an elongated elastic member 120 and a support member 130 which supports the elastic
member 120 at its center.
[0016]
More specifically, a plurality of piezoelectric elements 110 that expand and contract by the
application of an electric field, a plurality of elongated elastic members 120 on which the
plurality of piezoelectric elements 110 are individually mounted at each end, and a plurality of
elastic members 120 A plurality of support members 130 individually supporting each in the
center, and a main body frame 140 supporting the support members 130 such that the plurality
of elastic members 120 are arranged in a plan shape in the front, rear, left, and right .
[0017]
The aspect ratio of the elastic member 120 is, for example, 5 to 20 on one side.
Further, the elastic member 120 is made of, for example, phosphor bronze, nickel iron alloy,
stainless steel or the like having a total length of 20 to 100 mm, a total width of 3 to 10 mm, and
a thickness of 0.01 to 0.5 mm. , Plate thickness of 1 to 3 mm stainless steel.
The main body frame 140 has a planar shape and is formed in a rectangular shape in which four
sides are located in the front and rear, right and left, and a plurality of elastic members 120 are
long and thin in the front and rear direction.
[0018]
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In the electro-acoustic transducer 100 of the present embodiment, a rectangular piezoelectric
element 110 having an elongated shape in the left-right direction is formed on the entire upper
surface of each end of the rectangular elastic member 120. Further, a driver circuit 150 which is
an oscillation drive unit is connected to each of the plurality of piezoelectric elements 110.
[0019]
The mechanism of sound wave generation utilizes the stretching movement generated by the
application of an electric field to the piezoelectric element 110. Also, the frequency of ultrasonic
waves is limited to 20 kHz or more. Since the piezoelectric element 110 has a high mechanical
quality factor Q, energy is concentrated in the vicinity of the fundamental resonance frequency,
so high sound pressure levels can be obtained at the fundamental resonance frequency, but
sound pressure is attenuated in other frequency bands. It will
[0020]
In this configuration, since the ultrasonic wave limited to the specific frequency is oscillated, it is
rather advantageous that the mechanical quality factor Q of the piezoelectric element 110 is
high. In addition, since the fundamental resonance frequency of the piezoelectric vibrator is
affected by the shape of the piezoelectric element 110, the case where the resonance frequency
is adjusted to a high frequency band, for example, an ultrasonic wave band is advantageous in
downsizing.
[0021]
In this configuration, an ultrasonic wave modulated by FM (Frequency Modulation) or AM
(Amplitude Modulation) is oscillated, and the modulated wave is demodulated to reproduce an
audible sound by using a non-linear state (density state) of air. Sound is reproduced based on the
principle of so-called parametric speakers. In the electroacoustic transducer 100 according to the
present embodiment, the piezoelectric element 110 is configured to be limited to the oscillation
of the high frequency band, so that miniaturization can be achieved.
[0022]
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In the configuration as described above, in the electro-acoustic transducer 100 of the present
configuration, sound reproduction is performed using the principle of a parametric speaker that
uses an ultrasonic wave as a carrier wave of sound. By utilizing this principle of parametric
speaker, it is possible to form a superdirective sound field. In order to control the directivity of
sound waves, it is preferable to emit sound waves from a plurality of arrayed piezoelectric
vibrators as in the phased array method, and even in the electro-acoustic transducer 100 of this
configuration, it is arranged in an array By using a plurality of piezoelectric vibrators, it is
possible to form a superdirective sound field.
[0023]
In the electro-acoustic transducer 100 according to the present embodiment, each of a plurality
of elongated elastic members 120 having a plurality of piezoelectric elements 110 individually
mounted at each end individually with a plurality of support members 130 at the center. It is
supported and arranged in the front and rear, right and left on the main body frame 140. As
described above, since the cantilever support structure is used, the sound wave radiation portion
is limited to both ends of the piezoelectric vibrator including the elastic member 120 and the
piezoelectric element 110.
[0024]
Therefore, the sound emission positions of the adjacent piezoelectric vibrators can be made close
to each other. That is, by controlling the distance in the minor axis direction between the
piezoelectric vibrators, it is possible to suppress phase canceling of the sound waves oscillated
from the adjacent piezoelectric vibrators, and to narrow down the directivity of the sound waves
with high efficiency. it can.
[0025]
When driving the plurality of piezoelectric elements 110 by the driver circuit 150, the same
driving signal may be input to all to generate sound waves of high directivity with high efficiency,
and driving to be input to the plurality of piezoelectric elements 110 The signals may be
individually controlled to control the output direction of highly efficient and highly directional
sound waves.
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[0026]
The present invention is not limited to the present embodiment, and various modifications are
allowed without departing from the scope of the present invention.
For example, in the above-described embodiment, the electro-acoustic transducer 100 having a
unimorph structure in which only the upper surface of the elastic member 120 is restrained by
the piezoelectric element 110 is illustrated. However, an oscillating device having a bimorph
structure in which the upper surface and the lower surface of the elastic member 120 are
constrained by the two piezoelectric elements 110 can also be implemented. In this case, highvolume output can be performed more efficiently without increasing the size of the entire
apparatus.
[0027]
Moreover, in the said form, it assumed that the piezoelectric element 110 consists of one
piezoelectric layer. However, the piezoelectric element may have a laminated structure in which
piezoelectric layers and electrode layers are alternately laminated (not shown).
[0028]
Furthermore, in the above-described embodiment, it is exemplified that the rectangular
piezoelectric element 110 is formed in the entire area of the upper surfaces of both ends of the
rectangular elastic member 120. However, a small piezoelectric element (not shown) may be
formed on part of the upper surface of one end of the rectangular elastic member 120.
[0029]
Furthermore, in the above-described embodiment, it is assumed that the electronic apparatus has
the electro-acoustic transducer 100 connected to the driver circuit 150 which is an oscillation
drive unit. However, such an electro-acoustic transducer 100, an oscillation drive unit for causing
the electro-acoustic transducer 100 to output an ultrasonic wave, and an ultrasonic wave for
detecting an ultrasonic wave oscillated from the electro-acoustic transducer 100 and reflected by
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an object to be measured It is also possible to implement an electronic device (not shown) such
as a sonar having a detection unit and a distance measurement unit that calculates the distance
from the detected ultrasonic wave to the measurement object.
[0030]
As a matter of course, the embodiment and the plurality of modifications described above can be
combined as long as the contents do not conflict with each other. Further, in the embodiment and
the modification described above, the structure and the like of each part are specifically
described, but the structure and the like can be variously changed as long as the present
invention is satisfied.
[0031]
DESCRIPTION OF SYMBOLS 100 Electroacoustic transducer 110 Piezoelectric element 120
Elastic member 130 Support member 140 Body frame 150 Driver circuit
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