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JPWO2016071961

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DESCRIPTION JPWO2016071961
Abstract: To provide a spherical ultrasonic transducer that can be formed at low cost and easily.
The energy conversion unit 10 of the spherical ultrasonic transducer 6 has a plurality of
piezoelectric elements 14 and a spherical base 15. Each piezoelectric element 14 has a tapered
end 18 whose width decreases toward at least one side in the length direction, and has a
convexly curved outer surface 21 and a concavely curved inner surface 22 and is entirely
Electrodes 26 and 27 are respectively provided on the outer surface 21 and the inner surface 22
mainly with an element piece 16 made of piezoelectric ceramic that has an arc shape in a side
view. The spherical base 15 is disposed such that the tapered end 18 of each piezoelectric
element 14 faces one place, and supports each piezoelectric element 14 from the inner surface
22 side so as to be spherical as a whole. Each piezoelectric element 14 vibrates in the vibration
mode of the natural frequency in the length direction according to the length so as to expand and
contract in the length direction. [Selected figure] Figure 2
Spherical ultrasonic transducer, underwater measuring device
[0001]
The present invention relates to a spherical ultrasonic transducer having an energy conversion
unit that converts energy between acoustic energy and electrical energy, and an underwater
measurement device including the spherical ultrasonic transducer.
[0002]
As a specific example of a spherical ultrasonic transducer, an omnidirectional ultrasonic sensor
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1
that transmits and receives ultrasonic waves using a respiratory vibration mode (a vibration
mode in a radial direction) of a sphere has been proposed (see, for example, Patent Document 1).
.
In Patent Document 1, a spherical hollow ultrasonic sensor is configured by connecting two
hemispherical piezoelectric vibrators (piezoelectric elements) having electrodes formed on the
inner surface and the outer surface. Also, as shown in FIG. 16, an ultrasonic sensor 60 is also
proposed in which one piezoelectric element 61 is formed in the shape of a spherical shell having
a surface area equal to or greater than a hemisphere. The piezoelectric element 61 of the
ultrasonic sensor 60 is a hollow element having a cavity inside, and a pair of electrodes 62 a and
62 b are formed on the outer surface and the inner surface of the piezoelectric element 61. As
described above, by forming the piezoelectric element 61 for transmitting and receiving the
ultrasonic waves into a spherical shape, the ultrasonic sensor 60 without directivity can be
obtained. Furthermore, by increasing the size (diameter) of the piezoelectric element 61, the
frequency of the ultrasonic wave (the resonance frequency of the respiratory vibration) is
lowered, and it becomes possible to propagate the ultrasonic wave further.
[0003]
Further, in Patent Document 2, a transducer of omnidirectionality (nondirectionality) is
configured by attaching a plurality of piezoelectric ceramics (piezoelectric elements) to a housing
of a polyhedron (for example, a 12-sided polyhedron).
[0004]
JP 2001-8292 JP JP 2010-212868 JP
[0005]
However, when producing a spherical ultrasonic transducer, a dedicated mold is required to form
the piezoelectric element 61 into a spherical shape.
In the case of a spherical ultrasonic transducer, when the size of the sphere is increased to lower
the resonance frequency of respiratory vibration, it is difficult to manufacture the piezoelectric
element 61.
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More specifically, large-sized equipment is required to produce the spherical shell-like
piezoelectric element 61. In addition to this, when the element size becomes large, it becomes
easy to be deformed at the time of firing, and the product yield is deteriorated. Therefore, there is
a problem that the manufacturing cost of the spherical ultrasonic transducer is increased.
[0006]
Incidentally, since the transducer of Patent Document 2 is a polyhedron and not a perfect sphere,
it is necessary to sufficiently secure the dimensional accuracy and the assemblability of each
element in order to eliminate the acoustic directivity. The cost will be high.
[0007]
The present invention has been made in view of the above-mentioned problems, and an object
thereof is to provide a spherical ultrasonic transducer which can be formed at low cost and
easily.
Another object of the present invention is to provide an underwater measuring device which can
reliably perform measurement in water with no directivity using the above-mentioned spherical
ultrasonic transducer.
[0008]
In order to solve the above problems, the invention according to claim 1 is a spherical ultrasonic
transducer having an energy conversion unit for converting energy between acoustic energy and
electrical energy, wherein the energy conversion unit is The ratio of the length to the major part
is at least 2 times, and it has a tapered end that narrows toward at least one side in the length
direction, and has a convexly curved outer surface and a concavely curved inner surface And a
plurality of piezoelectric elements mainly composed of piezoelectric ceramic element pieces
having an arc shape in a side view as a whole and the electrodes provided on the outer surface
and the inner surface, and the tapered shape of the plurality of piezoelectric elements And a
support member for supporting the plurality of piezoelectric elements from the inner surface
side so as to form a hemispherical shell shape or a spherical shell shape as a whole. A plurality of
piezoelectric elements, so as to stretch the lengthwise, as its gist the spherical ultrasonic
transducer, characterized in that the oscillatable at the natural frequency vibration modes of a
length direction corresponding to the length.
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[0009]
According to the invention of claim 1, in the energy conversion unit, the ratio of the length to the
maximum width is twice or more in the element pieces of the plurality of piezoelectric elements,
and the width increases toward at least one side in the length direction. It has a narrowing
tapered end, a convexly curved outer surface and a concavely curved inner surface, and is
generally arc-shaped in side view.
Further, by aligning the directions of the respective piezoelectric elements so that the tapered
end portions of the plurality of piezoelectric elements face one place, the respective piezoelectric
elements are arranged so as to have a hemispherical shell shape or a spherical shell shape as a
whole. Then, energy conversion is performed between acoustic energy and electrical energy by
vibrating the piezoelectric element not in the respiratory vibration mode as in the prior art but in
the vibration mode in the length direction according to the length. As a result, the energy
conversion unit can transmit and receive ultrasonic waves. As described above, in the spherical
ultrasonic transducer according to the present invention, the spherical energy conversion unit is
configured using a plurality of piezoelectric elements warped in an arc shape, instead of using
the spherical piezoelectric elements as in the prior art. . In each piezoelectric element, the ratio of
the length to the maximum width is twice or more, and the element width is relatively narrow. In
this case, since the size of each of the piezoelectric elements is reduced, it is possible to form the
piezoelectric elements with accurate dimensions by suppressing deformation at the time of firing.
Furthermore, since the upsizing of manufacturing facilities can be avoided, spherical ultrasonic
transducers can be manufactured easily and at low cost. The ratio of the length to the maximum
width of the element element of the piezoelectric element is twice or more, but is preferably
three times or more, and more preferably five times or more. Further, it is particularly preferable
to form the piezoelectric element so that the ratio of the length to the maximum width of the
element piece is 10 times or more and 20 times or less.
[0010]
According to a second aspect of the present invention, in the first aspect, the plurality of
piezoelectric elements are disposed through gaps and separated acoustically.
[0011]
According to the second aspect of the present invention, in the spherical energy conversion unit,
the plurality of piezoelectric elements are acoustically separated through the gaps, so that each
piezoelectric element can be reliably vibrated in the vibration mode in the longitudinal direction.
It can be done.
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[0012]
The invention according to claim 3 is that in claim 2, the gap is a linear gap having a width equal
to or less than the maximum width, and the gap is formed along the longitudinal direction of the
piezoelectric element. It is a summary.
[0013]
According to the third aspect of the invention, since linear gaps are formed along the length
direction between the piezoelectric elements, the piezoelectric elements vibrate in the length
direction to ensure energy conversion. be able to.
The gap between the piezoelectric elements is equal to or less than the maximum width of the
element piece, but is preferably equal to or less than 1⁄2 of the maximum width.
The gap between the piezoelectric elements is more preferably 1⁄5 or less of the maximum width,
and when the size of the element piece is larger, the gap between the piezoelectric elements is
1/10 or less of the maximum width It is preferable to
[0014]
In the invention according to a fourth aspect, in any one of the first to third aspects, the
piezoelectric element has a length corresponding to an arc whose central angle exceeds 90 ° by
one element piece made of piezoelectric ceramic. Its gist is that it is formed.
[0015]
According to the fourth aspect of the present invention, a spherical energy conversion portion
having a surface area of a hemisphere or more can be configured by using a plurality of
piezoelectric elements having a length corresponding to a circular arc whose central angle
exceeds 90 °. it can.
In addition, since the piezoelectric element is formed by one element piece, there is no joint of
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the element pieces as in the case of forming the piezoelectric element by two or more element
pieces.
For this reason, while being able to form a piezoelectric element easily, the fall of the energy
conversion efficiency in the junction part of an element piece can be avoided.
[0016]
In the invention according to a fifth aspect, in any one of the first to fourth aspects, the plurality
of piezoelectric elements have the tapered end portion disposed toward the top of the head in the
energy conversion unit. The gist is that a gap is formed at the top of the head.
[0017]
According to the fifth aspect of the present invention, the plurality of piezoelectric elements can
be reliably vibrated at the top of the energy conversion unit.
[0018]
In the invention according to claim 6, in any one of claims 1 to 5, the support member is a
spherical base having an element installation part whose outer surface is formed in a spherical
shape, and the energy conversion part is The gist of the present invention is that the plurality of
piezoelectric elements are attached to the outer surface of the element mounting portion.
[0019]
According to the invention as set forth in claim 6, in the spherical base, by adhering the plurality
of piezoelectric elements to the outer surface of the element mounting portion, the plurality of
piezoelectric elements are supported securely to have a hemispherical shell shape or spherical
shell shape as a whole. can do.
[0020]
The invention according to claim 7 is a spherical ultrasonic transducer according to any one of
claims 1 to 6, and at least one of ultrasonic wave transmission and reception electrically
connected to the spherical ultrasonic transducer. The gist of the present invention is an
underwater measuring device comprising a processing circuit for performing processing and
being provided in water.
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[0021]
According to the seventh aspect of the present invention, by using the spherical ultrasonic
transducer, measurement in water can be reliably performed at a relatively low cost.
In addition, since the spherical ultrasonic transducer has omnidirectionality (non-directionality),
it can detect a wide range, and can shorten the detection time.
[0022]
As described in detail above, according to the inventions of claims 1 to 6, the spherical ultrasonic
transducer can be formed easily at low cost.
Further, according to the seventh aspect of the present invention, measurement in water can be
reliably performed with no directivity.
[0023]
BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram which shows the seafloor
crustal movement observation system of one Embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows the spherical ultrasonic
transducer of one Embodiment.
The perspective view which shows the energy conversion part of one embodiment.
FIG. 2 is a perspective view showing a piezoelectric element viewed from the outer surface side.
FIG. 2 is a perspective view showing a piezoelectric element viewed from the inner side. FIG. 2 is
a side view showing a piezoelectric element. The top view which shows a piezoelectric element.
The front view which shows a piezoelectric element. Explanatory drawing which shows the
measuring method of sound pressure. The graph which shows the relation between frequency
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and sound pressure. The graph which shows the directivity of a spherical ultrasonic transducer.
The perspective view which shows the energy conversion part of another embodiment. The
perspective view which shows the energy conversion part of another embodiment. The
perspective view which shows the energy conversion part of another embodiment. Sectional
drawing which shows the spherical ultrasonic transducer of another embodiment. The front view
which shows the conventional ultrasonic sensor which consists of a spherical-shell-shaped
piezoelectric element.
[0024]
An embodiment of the present invention will now be described in detail with reference to the
drawings.
[0025]
FIG. 1 shows a schematic configuration of a seafloor crustal movement observation system 1 for
observing the seafloor crustal movement.
[0026]
As shown in FIG. 1, the seafloor crustal movement observation system 1 includes a first
underwater measurement device 2 installed on the seabed and a second underwater
measurement device 4 provided on the bottom of the observation ship 3.
Although not shown, a plurality of first underwater measuring devices 2 are provided at
predetermined intervals in a predetermined area where observation of crustal deformation is
required.
In addition, the water depth of the seabed in which the 1st underwater measuring apparatus 2 is
installed may be 1000 m or more, and the 1st underwater measuring apparatus 2 has a structure
which can endure the water pressure.
[0027]
The first underwater measurement device 2 includes an omnidirectional spherical ultrasonic
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transducer 6 capable of transmitting and receiving ultrasonic waves, and a transmitting and
receiving circuit 7 electrically connected to the transducer 6. Similarly, the second underwater
measurement device 4 also includes a spherical ultrasonic transducer 6 capable of transmitting
and receiving ultrasonic waves, and a transmitting and receiving circuit 7 electrically connected
to the transducer 6. In the present embodiment, the spherical ultrasonic transducers 6 provided
in the underwater measurement devices 2 and 4 are ultrasonic transducers having the same
configuration. Note that, in one of the first underwater measuring device 2 and the second
underwater measuring device 4 (specifically, for example, the underwater measuring device 4 on
the receiving side provided on the bottom of the ship), the ultrasonic transducer 6 Instead of
using a microphone, underwater measurement may be performed.
[0028]
As shown in FIG. 2, the spherical ultrasonic transducer 6 includes a spherical energy conversion
unit 10 that converts energy between acoustic energy and electric energy, and an oil conversion
unit 10 together with an oil 11 that is an ultrasonic transmission medium. And a resin cover 12
to be accommodated. The surface of the energy conversion unit 10 in the spherical ultrasonic
transducer 6 functions as a transmitting and receiving wave surface for transmitting and
receiving ultrasonic waves. In the first underwater measurement device 2 in the present
embodiment, for example, the spherical ultrasonic transducer 6 is installed on the seabed with
the energy conversion unit 10 having a spherical shape facing upward. On the other hand, in the
second underwater measurement device 4, for example, the spherical ultrasonic transducer 6 is
installed on the bottom of the ship with the energy conversion unit 10 having a spherical shape
directed downward. Note that the installation positions (bottom and bottom of the ship) of the
underwater measurement devices 2 and 4 and the orientation (vertical direction) of the spherical
ultrasonic transducer 6 are not essential components, and the installation position and
orientation are appropriately changed to perform underwater measurement. May be
[0029]
As shown in FIG. 3, the energy conversion unit 10 includes a plurality of (27 in this embodiment)
piezoelectric elements 14 and a spherical base 15 (supporting member) for supporting the
plurality of piezoelectric elements 14. ing. The plurality of piezoelectric elements 14 have a
shape obtained by dividing the spherical shell into a plurality of parts along the longitudinal
direction.
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[0030]
More specifically, the piezoelectric element 14 of the present embodiment is formed mainly of
one element piece 16 made of piezoelectric ceramic made of, for example, PZT. The element
piece 16 of the piezoelectric element 14 has a tapered end 18 whose width decreases toward one
side in the length direction (upper side in FIG. 3). As shown in FIGS. 2 to 5, the element piece 16
of the piezoelectric element 14 has a convexly curved outer surface 21 and a concavely curved
inner surface 22 and is generally in an arc shape in a side view. . The end 19 of the element piece
16 on the opposite side (the lower side in FIG. 3) of the tapered end 18 is formed in a flat shape
having a predetermined width. That is, the piezoelectric element 14 has a ship-like shape (skinlike shape) obtained by dividing the spherical shell into a plurality of parts along the central axis
and cutting one end 19 (the lower end in FIG. 3). The plurality of piezoelectric elements 14 are
arranged such that the acute end of the tapered end 18 faces one point (in the present
embodiment, the top 25 of the energy conversion unit 10). In the piezoelectric element 14, a pair
of electrodes 26 and 27 made of silver is provided on the outer surface 21 and the inner surface
22 of the element piece 16.
[0031]
The spherical base 15 has an element mounting portion 31 in which the outer surface 30 is
formed in a spherical shape, and a disk-shaped base portion 32 provided below the element
mounting portion 31. Then, the plurality of piezoelectric elements 14 are attached to the outer
surface 30 of the element mounting portion 31 in the spherical base 15 via an adhesive, whereby
the spherical energy conversion portion 10 is formed. In the present embodiment, the outer
surface 30 of the element mounting portion 31 is formed with the same curvature as the inner
surface 22 of the piezoelectric element 14, and the entire inner surface 22 of the plurality of
piezoelectric elements 14 is the outer surface of the element mounting portion 31 via an
adhesive. Adhesively fixed to 30. In the present embodiment, a relatively soft adhesive is used to
make the piezoelectric element 14 easily vibrate.
[0032]
The resin cover 12 is made of a material whose acoustic impedance is close to the value of the
acoustic impedance of seawater, specifically, urethane rubber. The resin cover 12 has a
cylindrical portion 35 and a hemispherical portion 36 integrally formed with the cylindrical
portion 35 and provided to close one end of the cylindrical portion 35, and the open end 37 at
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the other end side of the cylindrical portion 35. Are fixed in a closed state by the base portion 32
of the spherical base 15. In this state, the hemispherical portion 36 of the resin cover 12 is
disposed so as to cover the energy conversion unit 10.
[0033]
In the present embodiment, the plurality of piezoelectric elements 14 constituting the energy
conversion unit 10 are disposed through the gaps 41 and 42 and are acoustically separated.
Specifically, in the energy conversion unit 10, a linear gap 41 along the meridian direction (the
longitudinal direction of the element) is formed between two adjacent piezoelectric elements 14
and each piezoelectric element is formed. A gap 42 is formed in the top 25 of the fourteen
tapered ends 18 facing each other.
[0034]
As shown in FIG. 6, the concavely curved inner surface 22 (the inner surface of the energy
conversion portion 10) of each piezoelectric element 14 has a spherical shape with a radius R1
of 80 mm. The convexly curved outer surface 21 of the piezoelectric elements 14 (the outer
surface of the energy conversion unit 10) has a spherical shape with a radius R2 of 85 mm. That
is, the thickness T1 of the piezoelectric element 14 is 5 mm. As shown in FIGS. 6 to 8, the length
L1 in the radial direction of the piezoelectric element 14 has a length corresponding to an arc
having a central angle of 132.9 °, and the length L2 in the latitude direction (element Width)
has a length corresponding to an arc having a central angle of 12.0 °. Further, the gap 41
between the piezoelectric elements 14 adjacent in the direction of the weft line has a width L3
corresponding to a circular arc having a central angle of 1.33 °. That is, the gaps 41 between
the piezoelectric elements 14 have a width L3 of about 1/9 of the element width L2. The width L
2 of the piezoelectric element 14 and the width L 3 of the gap 41 are largest at the central
portion 45 in the longitudinal direction of the energy conversion unit 10. In the present
embodiment, each piezoelectric element 14 has a ratio of the length L1 to the maximum width
L4 of about 11 times, and has a relatively elongated element shape.
[0035]
In the energy conversion unit 10, the plurality of piezoelectric elements 14 are arranged with a
gap of a length L5 corresponding to an arc of 1.5 ° with respect to the central axis Z1
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penetrating the crown 25. Therefore, in the top 25 of the energy conversion unit 10, a gap 42
having a length (= 2 × L5) corresponding to a circular arc having a central angle of 3 ° is
provided between the end portions 18 of the respective piezoelectric elements 14 facing each
other. It is formed.
[0036]
As shown in FIG. 2, in the plurality of piezoelectric elements 14, one electrode 26 (plus electrode)
provided on the outer surface 21 is all connected to the same first wiring 51, and the other is
provided on the inner surface 22. The electrodes 27 (minus electrodes) are all connected to the
same second wiring 52. The first wiring 51 is joined to the central portion 45 in the longitudinal
direction in which the element width of each piezoelectric element 14 is increased using solder
or the like. In addition, the second wiring 52 is connected to the negative electrode 27 exposed
to the side surface portion of the piezoelectric element 14 via the gap 41 between the
piezoelectric elements 14.
[0037]
As shown in FIG. 1, the wiring 50 (first wiring 51 and second wiring 52) extending from the
ultrasonic transducer 6 is connected to the transmission / reception circuit 7. The transmission /
reception circuit 7 is a processing circuit provided with an amplification circuit, an A / D
conversion circuit, etc., and performs processing for transmission and reception of ultrasonic
waves. In addition, each of the underwater measurement devices 2 and 4 includes an oscillator
(not shown) that generates a drive signal of, for example, 10 kHz, and a control device (not
shown) that collectively controls ultrasonic wave transmission and reception processing. The
control device is configured to include a known CPU (central processing unit), a memory, and the
like.
[0038]
Furthermore, the seafloor crustal movement observation system 1 according to the present
embodiment includes a position information acquisition device (not shown) that determines the
current position of the ship by GPS. The seafloor crustal movement observation system 1
measures the distance between the observation ship 3 and the sea bottom by transmitting and
receiving 10 kHz ultrasonic waves using the first underwater measurement device 2 and the
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second underwater measurement device 4. And based on the distance and the present position of
the observation ship 3 acquired by GPS, the seabed position where the 1st underwater measuring
device 2 is installed is observed. The crustal deformation of the seabed is to be measured by
regularly observing the seabed position or observing the seabed position after an earthquake or
the like. Further, in the seafloor crustal movement observation system 1, the measurement
accuracy of the seabed position is enhanced by performing the distance measurement a plurality
of times while the observation ship 3 is moving.
[0039]
Evaluation of the spherical ultrasonic transducer 6 configured as described above was
performed. Here, as shown in FIG. 9, in water, the spherical ultrasonic transducer 6 is installed so
that the energy conversion unit 10 faces upward, and the microphone 55 is disposed above the
transducer 6 at a distance of 1 m. Do. Then, a voltage Vpp having a potential difference of 200 V
is applied to each of the electrodes 26 and 27 of each piezoelectric element 14 of the energy
conversion unit 10 at a frequency of 10 kHz for 3 cycles, and the sound pressure (dB) observed
using the microphone 55 The relationship between the frequency and the frequency (kHz) was
measured. The results are shown in FIG. Furthermore, Table 1 shows the sound pressure at 10
kHz (dB), the maximum sound pressure (dB), the frequency (kHz) at the maximum sound
pressure, and the bandwidth (kHz at -6 dB) obtained as the measurement results. ) Is shown.
Further, as a comparative example, the relationship between the sound pressure and the
frequency was also measured in a conventional product (overseas product), and the results are
shown in FIG. 10 and Table 1. The conventional product is a transducer which is not spherical
but polyhedral, and has a structure in which a regular polygonal piezoelectric element is attached
to each surface.
[0040]
As shown in FIG. 10 and Table 1, the spherical ultrasonic transducer 6 (example) of the present
embodiment has a sound pressure at 10 kHz and a maximum sound pressure higher than that of
the conventional product, and the frequency dependence of the sound pressure is It was almost
equal to the conventional product.
[0041]
Also, the impedance of the ultrasonic transducer 6 at 5 kHz to 15 kHz was measured.
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As a result, the mechanical quality factor Qm in the ultrasonic transducer 6 of the present
embodiment is lower than that of the conventional product, and the frequency dependency is
less. Furthermore, it was confirmed that the impedance of the ultrasonic transducer 6 is lower
than that of the conventional product, and the response in the reception waveform (not shown)
of the microphone 55 is better than that of the conventional product.
[0042]
Further, the directivity of the spherical ultrasonic transducer 6 was measured. The measurement
results are shown in FIG. Here, while keeping the distance D1 between the spherical ultrasonic
transducer 6 and the microphone 55 at 1 m, the measurement position of the microphone 55 is
moved along the circumferential direction. Specifically, position P0 in the horizontal direction
(horizontal position on the right in FIG. 9) is set as the reference position (position at an angle of
0 °), and position P0 → position P45 (position at an angle of 45 °) → position P90 (angle) The
microphone 55 is moved along the circumferential direction in the following order: position 90
° → position P135 (angle 135 °) → position P180 (angle 180 °), and the sound pressure at
each position P0 to P180 Was measured. The measurement frequency is 10 kHz. Moreover, it
measured similarly about the directivity of the conventional product as a comparative example,
and the measurement result is shown in FIG.
[0043]
As shown in FIG. 11, when the spherical ultrasonic transducer 6 of the present embodiment is
used, the directivity is lower than that of the conventional product, and the measurement sound
pressure is larger than that of the conventional product. Specifically, in the case of the
conventional product, a sound pressure of 181 dB to 186 dB was measured at each measurement
position of P0 to P180, and particularly the sound pressure at position P90 was small. On the
other hand, in the spherical ultrasonic transducer 6 of the present embodiment, the sound
pressure of 184 dB to 186 dB is measured at each measurement position of P0 to P180, and the
sound pressure difference at each measurement position is 2 dB. The sound pressure difference
was less than 5 dB. In the spherical ultrasonic transducer 6, the sound pressure at the position
P90 is 186 dB, which is about 5 dB larger than that of the conventional product.
[0044]
As described above, it was confirmed that by using the spherical ultrasonic transducer 6
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according to the present embodiment, it is possible to configure the omnidirectional underwater
measurement devices 2 and 3 with good transmission and reception sensitivity.
[0045]
Therefore, according to the present embodiment, the following effects can be obtained.
[0046]
(1) In the spherical ultrasonic transducer 6 of the present embodiment, in the energy conversion
unit 10, the directions of the piezoelectric elements 14 are aligned so that the tapered end
portions 18 of the plurality of piezoelectric elements 14 face one place. Each piezoelectric
element 14 can be arranged to have a spherical shape as a whole.
Then, energy conversion is performed between acoustic energy and electrical energy by vibrating
the piezoelectric element 14 not in the respiration vibration mode as in the prior art but in the
vibration mode in the length direction according to the length.
As a result, the energy conversion unit 10 can transmit and receive ultrasonic waves. As
described above, in the spherical ultrasonic transducer 6 according to the present embodiment, a
plurality of piezoelectric elements 14 (see FIG. 16) that are curved in a circular arc are used
instead of the spherical shell piezoelectric element 61 (see FIG. 16) as in the prior art. The
spherical energy conversion unit 10 is configured using FIGS. 3 to 5). Further, the plurality of
piezoelectric elements 14 constituting the spherical energy conversion unit 10 all have the same
shape. Specifically, in each piezoelectric element 14, the ratio of the length L1 to the maximum
width L4 is about 11 times, and the element width is relatively narrow. In this case, since the size
of each of the piezoelectric elements 14 is reduced, the deformation at the time of firing can be
suppressed low, and the piezoelectric elements 14 can be formed with accurate dimensions.
Further, since the enlargement of the manufacturing equipment can be avoided, the spherical
ultrasonic transducer 6 can be manufactured easily and at low cost.
[0047]
(2) In the spherical ultrasonic transducer 6 of the present embodiment, the plurality of
piezoelectric elements 14 in the spherical energy conversion unit 10 are disposed through the
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gaps 41 and are acoustically separated. Therefore, each piezoelectric element 14 can be reliably
vibrated in the vibration mode in the longitudinal direction. Further, the gap 41 is a linear gap
having a width L3 of about 1/9 of the maximum width L4. In this case, since the gaps 41
between the piezoelectric elements 14 are reduced, energy conversion can be reliably performed
over the entire circumference of the energy conversion unit 10.
[0048]
(3) In the spherical ultrasonic transducer 6 of the present embodiment, the piezoelectric element
14 is formed to have a length L1 corresponding to a circular arc whose central angle exceeds 90
°, and therefore has a surface area larger than a hemisphere. The spherical energy conversion
unit 10 can be easily configured. Further, since the piezoelectric element 14 is formed of one
element piece 16 made of piezoelectric ceramic, there is no bonding portion of the element
pieces as in the case of forming the piezoelectric element by two or more element pieces. For this
reason, while being able to form the piezoelectric element 14 easily, the fall of the energy
conversion efficiency in the junction part of the element piece 16 can be avoided.
[0049]
(4) In the spherical ultrasonic transducer 6 of the present embodiment, the plurality of
piezoelectric elements 14 have the end 18 tapered toward the top 25 of the energy conversion
unit 10, and the top 25 has a tapered end 18. A gap 42 is formed. In this way, the plurality of
piezoelectric elements 14 can be reliably vibrated at the top 25 of the energy conversion unit 10,
and the energy conversion efficiency can be enhanced.
[0050]
(5) In the seafloor crustal movement observation system 1 of the present embodiment, in the first
underwater measuring device 2 and the second underwater measuring device 4, each spherical
ultrasonic wave is made so that the tops 25 of the energy conversion unit 10 face each other. A
transducer 6 is arranged. That is, in the first underwater measuring device 2 installed on the
seabed, the spherical ultrasonic transducer 6 is provided so that the top 25 of the energy
conversion unit 10 faces upward, and the second underwater measuring device provided on the
bottom of the ship In 4, the spherical ultrasonic transducer 6 is provided such that the top 25 of
the energy conversion unit 10 is directed downward. In this way, transmission and reception of
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ultrasonic waves between the ultrasonic transducers 6 can be performed reliably, and distance
measurement can be performed accurately.
[0051]
(6) In the seafloor crustal movement observation system 1 according to the present embodiment,
the first underwater measurement device 2 may be installed on the sea floor at a depth of 1000
m or more. Even in this case, since the energy conversion unit 10 of the ultrasonic transducer 6
is spherical, it can sufficiently withstand the water pressure, and crustal deformation of the
seabed can be reliably observed.
[0052]
The embodiment of the present invention may be modified as follows.
[0053]
In the ultrasonic transducer 6 according to the above-described embodiment, each piezoelectric
element 14 constituting the energy conversion unit 10 has a length L1 corresponding to a
circular arc having a central angle of 132.9 ° and a central angle of 12 °. Although the width
L2 corresponding to the arc is provided, the length L1 and the width L2 may be appropriately
changed as long as they are formed in an elongated arc shape.
However, in the case of forming the energy conversion unit 10 having a hemispherical surface or
more, it is preferable to form each piezoelectric element 14 so as to have a length L1
corresponding to a circular arc whose central angle exceeds 90 °. Further, in order to ensure a
sufficient surface area of the energy conversion unit 10, it is preferable to form each
piezoelectric element 14 so that the central angle has a length L1 corresponding to an arc of 100
° or more. Furthermore, in consideration of installation on the spherical base 15, the plurality of
piezoelectric elements 14 preferably have a length L1 corresponding to an arc having a central
angle of 170 ° or less.
[0054]
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-In the ultrasonic transducer 6 of the said embodiment, although each piezoelectric element 14
which comprises the energy conversion part 10 was formed by one element piece 16 made from
piezoelectric ceramics, it is not limited to this. For example, as shown in FIG. 12, the plurality of
piezoelectric elements 14a constituting the energy conversion unit 10A may be formed by
joining two element pieces 16a and 16b made of piezoelectric ceramic in the length direction. .
Further, as shown in FIG. 13, the plurality of piezoelectric elements 14b constituting the energy
conversion unit 10B are formed by joining three element pieces 16c, 16d, 16e made of
piezoelectric ceramic in the length direction. May be. When the piezoelectric elements 14a and
14b as shown in FIGS. 12 and 13 are formed, the element pieces 16a to 16e are mechanically
joined with an adhesive without gaps. The cured product of the adhesive for bonding the element
pieces 16 a to 16 e is harder than the cured product of the adhesive for fixing the piezoelectric
elements 14 a and 14 b to the spherical base 15. Further, the piezoelectric element 14a in FIG.
12 has a length L1 corresponding to an arc having a central angle of 90 °, and the piezoelectric
element 14b in FIG. 13 has an arc having a central angle of 133 ° as in the above embodiment.
It has a corresponding length L1. Even if the energy conversion units 10A and 10B are
configured as shown in FIGS. 12 and 13, the piezoelectric elements 14a and 14b vibrate at a
frequency corresponding to the length in the meridian direction, and between the acoustic
energy and the electrical energy Energy conversion can be performed. In this case, although the
size of the individual element pieces 16a to 16e is small, the relatively large spherical energy
conversion parts 10A and 10B are formed by joining the element pieces 16a to 16e to form the
piezoelectric elements 14a and 14b. be able to. For this reason, the upsizing of the
manufacturing equipment can be avoided, and the manufacturing cost of the spherical ultrasonic
transducer can be reduced.
[0055]
In the spherical ultrasonic transducer 6 according to the above-described embodiment, the
plurality of piezoelectric elements 14, 14a, 14b have the upper end 18 tapered toward the top
25 of the energy conversion units 10, 10A, 10B. Although it was arrange | positioned along the
meridian direction, it is not limited to this. The arrangement of the plurality of piezoelectric
elements is not particularly limited as long as the spherical energy conversion unit is configured
by the plurality of piezoelectric elements. Specifically, for example, as shown in FIG. 14, the
energy conversion unit 10C may be configured by arranging a plurality of piezoelectric elements
14c in a direction different from the meridian direction. In the energy conversion unit 10C of FIG.
14, the tapered end 18a of each piezoelectric element 14c is arranged to be directed not to the
top 25 but to the side 57. Although only one end 18 a of the piezoelectric element 14 c is
illustrated in FIG. 14, the other end 18 a (not illustrated) is also tapered with an acute angle. That
is, each piezoelectric element 14c has a spherical shape so that both end portions 18a are
tapered with an acute angle and each end portion 18a faces one point (side portions 57 disposed
04-05-2019
18
opposite to each other in the energy conversion unit 10C) It is disposed in the element mounting
portion 31 of the base 15. As a result, the respective piezoelectric elements 14 c are supported
on the outer surface 30 of the element mounting portion 31 so as to have a hemispherical shell
shape.
[0056]
In the spherical ultrasonic transducer 6 of the above embodiment, the resin cover 12 has a shape
having the cylindrical portion 35 and the hemispherical portion 36. However, like the spherical
ultrasonic transducer 6A shown in FIG. The shape may be changed. The resin cover 12A has a
cylindrical portion 38 and a spherical portion 39 integrally formed with the cylindrical portion
38. In the resin cover 12A, the length in the axial direction (vertical direction in FIG. 15) of the
cylindrical portion 38 is shorter than the length of the cylindrical portion 35 (see FIG. 2) in the
resin cover 12 of the above embodiment. Is smaller than the diameter of the cylindrical portion
35. Further, in the resin cover 12A, the spherical portion 39 is provided at a position facing the
energy conversion unit 10, and has an area of a hemisphere or more. In the spherical ultrasonic
transducer 6 of the above embodiment, the outer diameter of the cylindrical portion 35 and the
outer diameter of the hemispherical portion 36 in the resin cover 12 are the same. On the other
hand, in the resin cover 12A shown in FIG. 15, the outer diameter of the cylindrical portion 38 is
smaller than the outer diameter of the spherical portion 39. That is, in the resin cover 12 </ b> A,
the cylindrical portion 38 has a shape that is narrowed with respect to the spherical portion 39.
Thus, when the spherical ultrasonic transducer 6A is configured using the resin cover 12A, the
distance between the outer surface of the energy conversion unit 10 and the inner surface of the
resin cover 12A (spherical portion 39) at the upper and lower portions of the energy conversion
unit 10 is Become uniform. In this case, the transmission / reception sensitivity of ultrasonic
waves in the spherical ultrasonic transducer 6A can be enhanced.
[0057]
In the above embodiment, in the spherical base 15 having the element installation portion 31 in
which the outer surface 30 is formed in a spherical shape, the energy conversion unit 10 is
formed by attaching the plurality of piezoelectric elements 14 to the outer surface 30 of the
element installation portion 31. Although formed, support members other than the spherical
base 15 may be used. Specifically, the support member may be any one as long as it supports the
plurality of piezoelectric elements 14 from the inner surface 22 side so as to have a
hemispherical shell shape or a spherical shell shape as a whole. For example, the energy
conversion unit 10 may be formed using a frame-shaped support member having a fixing portion
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that fixes a part of the inner surface 22 of each piezoelectric element 14. In this case, the fixing
portion is provided at a position corresponding to 1⁄4 wavelength in the longitudinal direction of
the piezoelectric element 14. With this configuration, the piezoelectric element 14 can be reliably
vibrated in a state in which the piezoelectric element 14 is fixed to the fixing portion of the
support member.
[0058]
In the above embodiment, the spherical ultrasonic transducer 6 functions as an ultrasonic
transducer capable of transmitting and receiving ultrasonic waves. However, a transmitter
dedicated to transmission of ultrasonic waves, a supersonic wave transmitter, or the like may be
used. It may be made to function as a receiver dedicated to the reception of sound waves.
Specifically, for example, in the case where the spherical ultrasonic transducer 6 provided in the
first underwater measurement device 2 is made to function as a transmitter dedicated to the
transmission of ultrasonic waves, the spherical shape in the second underwater measurement
device 4 on the reception side A microphone may be provided instead of the ultrasonic
transducer 6 to perform distance measurement.
[0059]
-Although the said embodiment was embodied in the seafloor crustal movement observation
system 1 provided with a pair of underwater measurement apparatuses 2 and 4, it is not limited
to this. For example, one underwater measuring device 4 may be provided at the bottom of the
ship, and the observation system may be configured to detect the presence or absence of an
obstacle existing in the water, the distance of the obstacle, and the like using the underwater
measuring device 4. In this case, the piezoelectric elements 14 of the ultrasonic transducer 6 are
driven to transmit ultrasonic waves, and the ultrasonic waves reflected by the obstacle in the
water are received by the piezoelectric elements 14 of the ultrasonic transducer 6. The controller
(not shown) determines the presence or absence of an obstacle existing in the water based on the
received signal. The control device also detects the distance of the obstacle based on the
propagation time of the ultrasonic wave. Furthermore, the underwater measuring device 4 may
be configured to be able to specify the direction in which the obstacle exists. Specifically, in the
underwater measuring device 4, a dedicated receiving circuit is provided for each of the
piezoelectric elements 14 of the ultrasonic transducer 6 or for each of a plurality of adjacent
piezoelectric elements 14. Further, each piezoelectric element 14 is simultaneously driven by the
transmission circuit, and ultrasonic waves are transmitted from the ultrasonic transducer 6 in all
directions. Then, the ultrasonic waves reflected by the obstacle in the water are received by the
04-05-2019
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respective piezoelectric elements 14 of the ultrasonic transducer 6. In this way, the spherical
ultrasonic transducer 6 is configured as an ultrasonic transducer having directivity, and the
direction in which the obstacle is present based on the magnitude of the ultrasonic reception
signal detected by each reception circuit. Can be identified.
[0060]
Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the
embodiments described above will be listed below.
[0061]
(1) In any one of the first to sixth aspects, the plurality of piezoelectric elements in the energy
conversion unit has a shape obtained by dividing a spherical shell into a plurality of parts along
its meridian direction. Sound transducer.
[0062]
(2) The spherical ultrasonic transducer according to any one of claims 1 to 6, wherein the
piezoelectric element has a length corresponding to an arc of 100 ° or more and 170 ° or less.
[0063]
(3) The spherical ultrasonic transducer according to any one of claims 1 to 6, further comprising
a resin cover that accommodates the energy conversion unit together with the ultrasonic
transmission medium.
[0064]
(4) In any one of claims 1 to 3, the piezoelectric element is adapted to a circular arc having a
central angle exceeding 90 ° by joining two or more element pieces made of piezoelectric
ceramic in the longitudinal direction. A spherical ultrasonic transducer characterized by being
formed to have a desired length.
[0065]
(5) In the technical idea (4), the cured product of the adhesive for bonding two or more of the
element pieces in the piezoelectric element is harder than the cured product of the adhesive for
fixing the piezoelectric element to the support member A spherical ultrasonic transducer
characterized by
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[0066]
(5) The underwater measuring device according to claim 7, wherein a wire is connected to a
central portion in the length direction in which the width is maximum in each electrode of the
plurality of piezoelectric elements.
[0067]
(6) In claim 7, in the plurality of piezoelectric elements, one of the electrodes provided on the
outer surface is connected to the same first wiring, and the other electrode provided on the inner
surface is the same second wiring The underwater measuring device characterized by connecting
to.
[0068]
(7) The underwater measuring device according to claim 7, wherein the spherical ultrasonic
transducer is acoustically nondirectional.
[0069]
(8) The underwater measuring apparatus according to claim 7 is provided, and the spherical
ultrasonic transducer is installed on the seabed in a state where the energy conversion part
having a spherical shape is directed upward, and observation of crustal deformation of the
seabed is Seafloor crustal movement observation system characterized by
[0070]
2, 4 Underwater measuring device 6, 6A spherical ultrasonic transducer 7 transmitting /
receiving circuit 10 as a processing circuit 10A to 10C energy converting portion 14, 14a to 14c
piezoelectric element 15 spherical base 16 as a supporting member 16a to 16e: element pieces
18, 18a: tapered end portion 21: outer surface 22: inner surface 25: crown portion 26, 27:
electrode 30: outer surface 31: element setting portion 41, 42: gap
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