JP2012134591

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DESCRIPTION JP2012134591
An oscillation device capable of narrowing down directivity of sound waves with high efficiency
is provided. Since an electroacoustic transducer (100) utilizes a cantilever support structure, a
radiating portion of a sound wave is limited to an end portion of a piezoelectric vibrator (110).
Therefore, the sound emission positions of the adjacent piezoelectric vibrators 110 can be made
close to each other. That is, by controlling the distance in the minor axis direction between the
piezoelectric vibrators 110, it is possible to suppress the phase canceling of the sound waves
oscillated from the adjacent piezoelectric vibrators 110, and narrow down the directivity of the
sound waves with high efficiency. be able to. [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, handsfree phone functions, etc. There is.
In addition, from the viewpoint of privacy protection, there is a demand for development of a
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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 transducers
(Patent Documents 1 and 2).
[0004]
Utility model registration No. 3068450 Japanese Patent Laid-Open No. 2000-13469
[0005]
However, in order to narrow down the directivity of the ultrasonic waves, as in the phased array
method, an array probe in which a large number of minute ultrasonic transducers are arrayed
generates a main beam synthesized with the ultrasonic waves transmitted at 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 comprises a plurality of piezoelectric
elements that move in an expanding and contracting manner by the application of an electric
field, a plurality of elongated elastic members having a plurality of piezoelectric elements
individually attached to one end, and the other ends of the plurality of elastic members. And a
frame-like support member for supporting.
[0008]
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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]
In the oscillation device of the present invention, a plurality of piezoelectric elements are
individually mounted on one end of a plurality of elongated elastic members whose other ends
are supported by a frame-shaped support member.
Since the cantilever support structure is used, the radiation part of the sound wave is limited to
the end of the vibrator composed of the elastic member and the piezoelectric element.
Therefore, the sound emission positions of the adjacent transducers can be made close to each
other.
That is, by controlling the distance between the transducers in the minor axis direction, 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.
[0011]
It is a schematic plan view which shows the structure of the electroacoustic transducer which is
an oscillation apparatus of embodiment of this invention.
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It is a schematic longitudinal front view which shows the structure of an electroacoustic
transducer.
It is a schematic plan view which shows the structure of the electroacoustic transducer of one
modification. It is a schematic plan view which shows the structure of the electroacoustic
transducer of another modification.
[0012]
The electroacoustic transducer 100 which is an oscillation apparatus of this Embodiment is
demonstrated below with reference to FIG. 1 and FIG. As shown in FIG. 1, the electro-acoustic
transducer 100 of the present embodiment has an elongated shape in which a plurality of
piezoelectric elements 111 that move in an elastic manner by application of an electric field and
a plurality of piezoelectric elements 111 are individually attached A plurality of elastic members
112 and a frame-like support member 120 supporting the other ends of the plurality of elastic
members 112 are included.
[0013]
In the electro-acoustic transducer 100 of the present embodiment, the support member 120 is
formed in a rectangular shape in a planar shape, and the elastic member 112 has the other end
supported by two opposing sides of the support member 120. More specifically, the support
member 120 is formed in a rectangular shape having a planar shape and having four sides on
the front, rear, left, and right, and a plurality of elastic members 112 are arrayed in an elongated
shape in the left to right direction. The aspect ratio of the elastic member 112 is, for example, 3
to 10.
[0014]
However, the elastic members 112 are arranged in two left and right rows, and the piezoelectric
element 111 is attached to the left end of the elastic member 112 on the right side, and the
piezoelectric element 111 is attached to the right end of the elastic member 112 on the left side.
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In the electro-acoustic transducer 100 of the present embodiment, the rectangular piezoelectric
element 111 is formed on the entire area of one end upper surface of the rectangular elastic
member 112.
[0015]
In the electro-acoustic transducer 100 of the present embodiment, a driver circuit 130, which is
an oscillation drive unit that causes an acoustic wave in an audible range to be output to the
piezoelectric vibrator 110 including the piezoelectric element 111 and the elastic member 112,
is connected.
[0016]
The mechanism of sound wave generation utilizes the stretching movement generated by the
application of an electric field to the piezoelectric element 111.
Also, the frequency of ultrasonic waves is limited to 20 kHz or more. Since the piezoelectric
element 111 has a high mechanical quality factor Q, energy is concentrated in the vicinity of the
fundamental resonance, so a high sound pressure level can be obtained at the fundamental
resonance frequency, but the sound pressure is attenuated in other frequency bands. .
[0017]
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 111 is
high. In addition, since the fundamental resonance frequency of the piezoelectric vibrator is
affected by the shape of the piezoelectric element 111, the case where the resonance frequency
is adjusted to a high frequency band, for example, an ultrasonic wave band is advantageous for
downsizing.
[0018]
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
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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 111 is configured to be limited to oscillation of a
high frequency band, so that miniaturization can be achieved.
[0019]
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 110 as in the phased array method, and the electro-acoustic transducer 100 of this
configuration is also arranged in an array shape. The super-directional sound field can be formed
by using the plurality of piezoelectric vibrators 110 arranged.
[0020]
In the electroacoustic transducer 100 according to the present embodiment, the plurality of
piezoelectric elements 111 are individually attached to one end of the plurality of elongated
elastic members 112 whose other ends are supported by the frame-shaped support member 120
as described above It is done.
[0021]
As described above, since the cantilever support structure is used, the sound wave radiation
portion is limited to the end portion of the piezoelectric vibrator 110 including the elastic
member 112 and the piezoelectric element 111.
Therefore, the sound emission positions of the adjacent piezoelectric vibrators 110 can be made
close to each other. That is, by controlling the distance in the minor axis direction between the
piezoelectric vibrators 110, it is possible to suppress the phase canceling of the sound waves
oscillated from the adjacent piezoelectric vibrators 110, and narrow down the directivity of the
sound waves with high efficiency. be able to.
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[0022]
When driving the plurality of piezoelectric elements 111 by the driver circuit 130, the same
driving signal may be input to all of them to generate sound waves of high directivity with high
efficiency, and driving to be input to the plurality of piezoelectric elements 111 The signals may
be individually controlled to control the output direction of highly efficient and highly directional
sound waves.
[0023]
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 112 is restrained by
the piezoelectric element 111 is illustrated. However, it is also possible to implement an
oscillating device having a bimorph structure in which the upper surface and the lower surface of
the elastic member 112 are constrained by the two piezoelectric elements 111. In this case, highvolume output can be performed more efficiently without increasing the size of the entire
apparatus.
[0024]
Further, in the above embodiment, the elastic members 112 are arranged in two left and right
rows, and the piezoelectric element 111 is attached to the left end of the elastic member 112 on
the right, and the piezoelectric element 111 is attached to the right end of the elastic member
112 on the left Illustrated that.
[0025]
However, as in the electroacoustic transducer 200 illustrated as an oscillation device in FIG. 3, a
plurality of elastic members 112 may be formed in a bowl shape in four directions from the four
sides of the rectangular support member 120.
Furthermore, as in the electroacoustic transducer 300 illustrated as an oscillation device in FIG.
4, the support member 310 may be formed in a circular shape, and the plurality of elastic
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members 112 may be formed in a radial manner.
[0026]
Moreover, in the said form, it assumed that the piezoelectric element 111 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).
[0027]
Furthermore, in the above-described embodiment, it is exemplified that the rectangular
piezoelectric element 111 is formed on the entire surface of the one end upper surface of the
rectangular elastic member 112. However, a small piezoelectric element (not shown) may be
formed on part of the upper surface of one end of the rectangular elastic member 112.
[0028]
Further, in the above embodiment, the elastic members 112 are arranged in two left and right
rows, and the piezoelectric element 111 is attached to the left end of the elastic member 112 on
the right, and the piezoelectric element 111 is attached to the right end of the elastic member
112 on the left Illustrated that. However, for example, a single row structure in which the elastic
member 112 is not formed on one of the left and right is also feasible.
[0029]
Furthermore, in the above embodiment, an electronic device in which the driver circuit 130,
which is an oscillation driver, is connected to the electroacoustic transducer 100 is assumed.
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
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.
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[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]
100 electro-acoustic transducer 110 piezoelectric vibrator 111 piezoelectric element 112 elastic
member 120 support member 130 driver circuit 200 electro-acoustic transducer 300 electroacoustic transducer 310 support member
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