WO2016071961A1

WO2016071961A1 - Spherical ultrasonic wave transducer and underwater measurement device

Info

Publication number: WO2016071961A1
Application number: PCT/JP2014/079248
Authority: WO
Inventors: 敦浩林; 晴久広瀬; 舞田　雄一; 佐藤　桂一
Original assignee: 本多電子株式会社
Priority date: 2014-11-04
Filing date: 2014-11-04
Publication date: 2016-05-12
Also published as: JP5802886B1; JPWO2016071961A1

Abstract

The purpose of the present invention is to provide a spherical ultrasonic wave transducer that can be formed at low cost and with ease. An energy converting part 10 of a spherical ultrasonic wave transducer 6 includes a plurality of piezoelectric elements 14 and a spherical base 15. Each piezoelectric element 14 is mainly composed of a piezoelectric ceramic element piece 16 that has a tapered end portion 18 the width of which becomes smaller toward at least one side in the longitudinal direction, that has a convexly curved outer surface 21 and a concavely curved inner surface 22, and that is arc-shaped on the whole when seen from the side; and electrodes 26 and 27 are respectively provided on the outer surface 21 and the inner surface 22. The spherical base 15 is arranged such that the tapered end portions 18 of the piezoelectric elements 14 face one location on the spherical base 15 and support each piezoelectric element 14 from the inner surface 22 side thereof so as to form a spherical shell shape on the whole. Each piezoelectric element 14 vibrates in a vibration mode of a length direction natural frequency which corresponds to the length of the piezoelectric element, so as to expand and contract in the length direction.

Description

Spherical ultrasonic transducer, underwater measuring device

The present invention relates to a spherical ultrasonic transducer having an energy conversion unit that converts energy between acoustic energy and electric energy, and an underwater measuring device including the spherical ultrasonic transducer.

As a specific example of the spherical ultrasonic transducer, a non-directional ultrasonic sensor that transmits and receives ultrasonic waves using a respiratory vibration mode (radial vibration mode) of a sphere has been proposed (for example, see Patent Document 1). . In Patent Document 1, a hollow ultrasonic sensor having a spherical shape is configured by connecting two hemispherical piezoelectric vibrators (piezoelectric elements) having electrodes formed on the inner surface and the outer surface. Further, as shown in FIG. 16, an ultrasonic sensor 60 in which one piezoelectric element 61 is formed in a spherical shell shape having a surface area of hemisphere or more has been proposed. 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. Thus, the ultrasonic sensor 60 having no directivity can be obtained by making the piezoelectric element 61 for transmitting and receiving ultrasonic waves into a spherical shell shape. Furthermore, by increasing the size (diameter) of the piezoelectric element 61, the frequency of the ultrasonic wave (resonance frequency of respiratory vibration) is lowered, and the ultrasonic wave can be propagated further.

In Patent Document 2, an omnidirectional transducer is configured by attaching a plurality of piezoelectric ceramics (piezoelectric elements) to a polyhedron (for example, 12-sided polyhedron) housing.

JP 2001-8292 A JP 2010-212868 A

However, when producing a spherical ultrasonic transducer, a dedicated die is required to form the piezoelectric element 61 into a spherical shell. Further, in the spherical ultrasonic transducer, when the size of the sphere is increased in order to reduce the resonance frequency of the respiratory vibration, it is difficult to manufacture the piezoelectric element 61. More specifically, a large facility is required to produce the spherical shell-shaped piezoelectric element 61. In addition to this, since the element size is increased, it is easily deformed during firing, and the product yield is deteriorated. Therefore, there is a problem that the manufacturing cost of the spherical ultrasonic transducer increases.

Incidentally, since the transducer of Patent Document 2 is a polyhedron and is not a perfect sphere, it is necessary to sufficiently ensure the dimensional accuracy and assembly of each element in order to eliminate acoustic directivity. Cost becomes high.

The present invention has been made in view of the above problems, and an object thereof is to provide a spherical ultrasonic transducer that can be easily formed at low cost. Another object is to provide an underwater measurement apparatus that can reliably perform measurement in water with non-directionality using the spherical ultrasonic transducer.

In order to solve the above problems, the invention described in claim 1 is a spherical ultrasonic transducer having an energy conversion unit that converts energy between acoustic energy and electric energy, wherein the energy conversion unit The ratio of length to large is more than twice, 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 as viewed from the side, each having an electrode on each of 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.

According to the first aspect of the present invention, in the energy conversion section, the element pieces of the plurality of piezoelectric elements have a ratio of the length to the maximum width of twice or more, and the width increases toward at least one side in the length direction. It has a tapered end portion that becomes narrower, has an outer surface curved in a convex shape and an inner surface curved in a concave shape, and has an arc shape as a whole in a side view. Further, by aligning the directions of the piezoelectric elements so that the tapered end portions of the plurality of piezoelectric elements are directed to one place, the 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 electric energy by virtue of the vibration of the piezoelectric element in the vibration mode in the length direction corresponding to the length, not the breathing vibration mode as in the prior art. As a result, it is possible to transmit and receive ultrasonic waves in the energy conversion unit. As described above, in the spherical ultrasonic transducer of the present invention, the spherical energy conversion unit is configured by using a plurality of piezoelectric elements warped in an arc shape instead of using the spherical piezoelectric elements as in the prior art. . Each piezoelectric element is formed such that 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 piezoelectric element becomes small, it is possible to form the piezoelectric element with accurate dimensions while suppressing deformation during firing. Furthermore, since the enlargement of the manufacturing equipment can be avoided, the spherical ultrasonic transducer can be manufactured easily and at low cost. The ratio of the length of the piezoelectric element to the maximum width of the element piece is 2 times or more, preferably 3 times or more, and more preferably 5 times or more. Moreover, 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.

The gist of a second aspect of the present invention is that, in the first aspect, the plurality of piezoelectric elements are arranged via gaps and are acoustically divided.

According to the second aspect of the present invention, since the plurality of piezoelectric elements are acoustically separated through the gaps in the spherical energy conversion section, each piezoelectric element is reliably vibrated in the longitudinal vibration mode. Can be made.

According to a third aspect of the present invention, in the second aspect, the gap is a linear gap having a width equal to or less than the maximum width, and is formed along a length direction of the piezoelectric element. The gist.

According to the third aspect of the present invention, since the linear gap is formed between the piezoelectric elements along the length direction, the piezoelectric element vibrates in the length direction and reliably performs energy conversion. be able to. The gap between each piezoelectric element is set to be equal to or smaller than the maximum width of the element piece, but is preferably equal to or smaller than ½ of the maximum width. The gap between the piezoelectric elements is more preferably 1/5 or less of the maximum width. Further, when the size of the element piece is increased, the gap between the piezoelectric elements is 1/10 or less of the maximum width. It is preferable that

According to a fourth aspect of the present invention, in any one of the first to third aspects, the piezoelectric element has a length corresponding to an arc having a central angle exceeding 90 ° by one element piece made of piezoelectric ceramics. The gist is that it is formed as described above.

According to the invention described in claim 4, it is possible to configure a spherical energy conversion unit having a surface area greater than a hemisphere by using a plurality of piezoelectric elements having a length corresponding to an arc whose central angle exceeds 90 °. it can. Further, since the piezoelectric element is formed by one element piece, there is no element piece joint as in the case where the piezoelectric element is formed by two or more element pieces. For this reason, it is possible to easily form the piezoelectric element, and it is possible to avoid a decrease in energy conversion efficiency at the joint portion of the element piece.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the plurality of piezoelectric elements have the tapered end portion arranged toward the top of the energy conversion portion. The gist is that a gap is formed in the top of the head.

According to the fifth aspect of the present invention, it is possible to reliably vibrate a plurality of piezoelectric elements at the top of the energy conversion unit.

The invention according to claim 6 is the spherical base having the element installation portion in which the outer surface is formed in a spherical shape in any one of the first to fifth aspects, and the energy conversion portion is The gist is that the plurality of piezoelectric elements are attached to the outer surface of the element installation portion.

According to the invention described in claim 6, in the spherical base, the plurality of piezoelectric elements are adhered to the outer surface of the element installation portion, thereby reliably supporting the plurality of piezoelectric elements so as to have a hemispherical shape or a spherical shell shape as a whole. can do.

According to a seventh aspect of the present invention, there is provided a spherical ultrasonic transducer according to any one of the first to sixth aspects of the present invention, and at least one of ultrasonic transmission and reception that is electrically connected to the spherical ultrasonic transducer. An underwater measuring device including a processing circuit for performing processing and provided in water is a gist thereof.

According to the seventh aspect of the invention, by using the spherical ultrasonic transducer, it is possible to reliably perform measurement in water at a relatively low cost. In addition, since the spherical ultrasonic transducer has omnidirectional directivity (omnidirectionality), it can detect a wide range and shorten the detection time.

As described in detail above, according to the first to sixth aspects of the invention, the spherical ultrasonic transducer can be easily formed at low cost. Moreover, according to the invention of Claim 7, measurement in water can be reliably performed with non-directionality.

The schematic block diagram which shows the seafloor crustal movement observation system of one Embodiment. Sectional drawing which shows the spherical ultrasonic transducer of one Embodiment. The perspective view which shows the energy conversion part of one Embodiment. The perspective view which shows the piezoelectric element seen from the outer surface side. The perspective view which shows the piezoelectric element seen from the inner surface side. The side view which shows 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 relationship between a frequency 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.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a seafloor crustal deformation observation system 1 that observes crustal deformation of the seabed.

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 portion of the observation ship 3. Although not shown, a plurality of the first underwater measurement devices 2 are provided at predetermined intervals in a predetermined area where crustal deformation needs to be observed. The depth of the seabed where the first underwater measuring device 2 is installed may be 1000 m or more, and the first underwater measuring device 2 has a structure capable of withstanding the water pressure.

The first underwater measurement device 2 includes an omnidirectional spherical ultrasonic transducer 6 capable of transmitting and receiving ultrasonic waves, and a transmission / reception circuit 7 electrically connected to the transducer 6. Similarly, the second underwater measuring device 4 includes a spherical ultrasonic transducer 6 capable of transmitting and receiving ultrasonic waves, and a transmission / reception circuit 7 electrically connected to the transducer 6. In this Embodiment, the spherical ultrasonic transducer 6 with which each underwater measuring device 2 and 4 is provided is an ultrasonic transducer which has the same structure. Note that in one of the first underwater measuring device 2 and the second underwater measuring device 4 (specifically, for example, the receiving-side underwater measuring device 4 provided at the bottom of the ship), the ultrasonic transducer 6 is used. Alternatively, underwater measurement may be performed using a microphone.

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 energy conversion unit 10 together with 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 transmission / reception wave surface for transmitting and receiving ultrasonic waves. In the first underwater measuring device 2 in the present embodiment, for example, the spherical ultrasonic transducer 6 is installed on the seabed with the spherical energy conversion unit 10 facing upward. On the other hand, in the second underwater measurement device 4, for example, the spherical ultrasonic transducer 6 is installed on the ship bottom with the spherical energy conversion unit 10 facing downward. In addition, the installation position (sea bottom, ship bottom) of each underwater measuring device 2 and 4 and the direction (vertical direction) of the spherical ultrasonic transducer 6 are not indispensable structures, and underwater measurement is performed by appropriately changing the installation position and orientation. May be.

As shown in FIG. 3, the energy conversion unit 10 includes a plurality (27 in this embodiment) of piezoelectric elements 14 and a spherical base 15 (support member) that supports the plurality of piezoelectric elements 14. ing. The plurality of piezoelectric elements 14 have a shape in which a spherical shell is divided into a plurality along the meridian direction.

More specifically, the piezoelectric element 14 of the present embodiment is mainly formed 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 portion 18 whose width becomes narrower 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 has an arc shape as a whole in a side view. . Further, the end 19 of the element piece 16 opposite to the tapered end 18 (the lower side in FIG. 3) is formed in a flat shape having a predetermined width. That is, the piezoelectric element 14 has a ship shape (skin shape) in which the spherical shell is divided into a plurality of parts around the central axis and one end portion 19 (lower end portion in FIG. 3) is cut off. And the some piezoelectric element 14 is arrange | positioned so that the taper-shaped edge part 18 sharpened at the acute angle may face one place (this embodiment top part 25 of the energy conversion part 10). In the piezoelectric element 14, a pair of

electrodes

26 and 27 made of silver are provided on the outer surface 21 and the inner surface 22 of the element piece 16.

The spherical base 15 includes an element installation portion 31 having an outer surface 30 formed into a spherical shape, and a disk-shaped base portion 32 provided below the element installation portion 31. And the spherical energy conversion part 10 is formed by affixing the some piezoelectric element 14 on the outer surface 30 of the element installation part 31 in the spherical base 15 via an adhesive agent. In the present embodiment, the outer surface 30 of the element installation 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 formed on the outer surface of the element installation portion 31 via an adhesive. 30 is adhered and fixed. In the present embodiment, a relatively soft adhesive is used to facilitate the vibration of the piezoelectric element 14.

The resin cover 12 is made of a material having an acoustic impedance close to the acoustic impedance value of seawater, specifically, urethane rubber. The resin cover 12 includes a cylindrical portion 35 and a hemispherical portion 36 that is integrally formed with the cylindrical portion 35 and is provided so as to close one end of the cylindrical portion 35, and an open end 37 on the other end side of the cylindrical portion 35. Is fixed in a state of being closed 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 portion 10.

In this Embodiment, the some piezoelectric element 14 which comprises the energy conversion part 10 is arrange | positioned through the

clearance gaps

41 and 42, and is divided acoustically. Specifically, in the energy conversion unit 10, a linear gap 41 along the meridian direction (the length direction of the element) is formed between two adjacent piezoelectric elements 14, and each piezoelectric element A gap 42 is formed in the top 25 where the 14 tapered ends 18 face each other.

As shown in FIG. 6, the concavely curved inner surface 22 (the inner surface of the energy conversion unit 10) of each piezoelectric element 14 has a spherical shape with a radius R 1 of 80 mm. Further, the convexly curved outer surface 21 (the outer surface of the energy conversion unit 10) of each piezoelectric element 14 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 center 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 latitude direction has a width L3 corresponding to an arc having a central angle of 1.33 °. That is, the gap 41 between the piezoelectric elements 14 has 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 the largest at the central portion 45 in the meridian direction in 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.

In the energy conversion unit 10, the plurality of piezoelectric elements 14 are arranged with a gap by a length L5 corresponding to a 1.5 ° arc with respect to the central axis Z 1 penetrating the crown 25. Accordingly, a gap 42 having a length (= 2 × L5) corresponding to an arc having a central angle of 3 ° is formed between the end portions 18 of the respective piezoelectric elements 14 facing each other at the top 25 of the energy conversion unit 10. Is formed.

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 electrode 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 meridian direction where the element width is widened in each piezoelectric element 14 using solder or the like. The second wiring 52 is connected to the negative electrode 27 exposed at the side surface portion of the piezoelectric element 14 through the gap 41 between the piezoelectric elements 14.

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 including an amplification circuit, an A / D conversion circuit, and the like, and performs processing for transmission and reception of ultrasonic waves. Each of the underwater measuring devices 2 and 4 includes, for example, an oscillator (not shown) that generates a 10 kHz drive signal and a control device (not shown) that comprehensively controls ultrasonic transmission / reception processing. The control device includes a known CPU (central processing unit), a memory, and the like.

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 using GPS. The seafloor crustal deformation observation system 1 uses the first underwater measurement device 2 and the second underwater measurement device 4 to measure the distance between the observation ship 3 and the seabed by transmitting and receiving 10 kHz ultrasonic waves. Then, based on the distance and the current position of the observation ship 3 acquired by GPS, the seabed position where the first underwater measuring device 2 is installed is observed. By observing the seafloor position regularly or by observing the seafloor position after an earthquake, the crustal deformation of the seabed is measured. In the seafloor crustal deformation observation system 1, the measurement accuracy of the seafloor position is increased by performing distance measurement a plurality of times while the observation ship 3 is moving.

The spherical ultrasonic transducer 6 configured as described above was evaluated. Here, as shown in FIG. 9, the spherical ultrasonic transducer 6 is installed in the water so that the energy conversion unit 10 faces upward, and the microphone 55 is arranged at a distance of 1 m above the transducer 6. To do. Then, a voltage Vpp having a potential difference of 200 V is applied to each

electrode

26 and 27 of each piezoelectric element 14 of the energy conversion unit 10 at a frequency of 10 kHz for 3 cycles, and a sound pressure (dB) observed using the microphone 55. And the frequency (kHz) were measured. The result is shown in FIG. Further, Table 1 shows the sound pressure (dB) at 10 kHz, the maximum sound pressure (dB), the frequency at the maximum sound pressure (kHz), and the bandwidth of the maximum sound pressure −6 dB (kHz) obtained as a result of the measurement. ). As a comparative example, the relationship between sound pressure and frequency was also measured for a conventional product (overseas product), and the results are shown in FIG. The conventional product is a transducer having a structure in which a regular polygonal piezoelectric element is attached to each surface, not a spherical shape but a polyhedral shape.

As shown in FIG. 10 and Table 1, the spherical ultrasonic transducer 6 of this embodiment (example) has higher sound pressure at 10 kHz and maximum sound pressure than the conventional product, and the frequency dependence of sound pressure is It was almost equal to the conventional product.

Further, the impedance of the ultrasonic transducer 6 at 5 kHz to 15 kHz was measured. 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 reduced. Furthermore, it was confirmed that the impedance of the ultrasonic transducer 6 was lower than that of the conventional product, and the response in the received waveform (not shown) of the microphone 55 was better than that of the conventional product.

Further, the directivity of the spherical ultrasonic transducer 6 was measured. The measurement results are shown in FIG. Here, the measurement position of the microphone 55 is moved along the circumferential direction while keeping the distance D1 between the spherical ultrasonic transducer 6 and the microphone 55 at 1 m. Specifically, the position P0 in the horizontal direction (the horizontal position on the right side in FIG. 9) is set as a reference position (position where the angle is 0 °), and position P0 → position P45 (position where the angle is 45 °) → position P90 (angle) Is moved along the circumferential direction in the order of position P135 (position where the angle is 135 degrees) → position P180 (position where the angle is 180 degrees), and the sound pressure at each position P0 to P180. Was measured. The measurement frequency is 10 kHz. Further, the directivity of a conventional product as a comparative example was measured in the same manner, and the measurement result is shown in FIG.

As shown in FIG. 11, when the spherical ultrasonic transducer 6 of the present embodiment is used, the directivity is less than that of the conventional product, and the measured sound pressure is larger than that of the conventional product. Specifically, in the case of the conventional product, the sound pressure of 181 dB to 186 dB was measured at each of the measurement positions P0 to P180, and the sound pressure at the position P90 was particularly 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 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.

Thus, it was confirmed that by using the spherical ultrasonic transducer 6 of the present embodiment, it is possible to configure the omnidirectional underwater measuring devices 2 and 3 with good transmission and reception sensitivity.

Therefore, according to the present embodiment, the following effects can be obtained.

(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. The piezoelectric elements 14 can be arranged so as to have a spherical shell shape as a whole. And energy conversion is performed between acoustic energy and electric energy by the piezoelectric element 14 vibrating in the vibration mode in the length direction corresponding to the length, not the breathing vibration mode as in the prior art. As a result, the energy conversion unit 10 can transmit and receive ultrasonic waves. As described above, the spherical ultrasonic transducer 6 of the present embodiment does not use the spherical shell-shaped piezoelectric element 61 (see FIG. 16) as in the prior art, but a plurality of piezoelectric elements 14 (in a circular arc shape) ( A spherical energy conversion unit 10 is configured using FIG. 3 to FIG. The plurality of piezoelectric elements 14 constituting the spherical energy conversion unit 10 are all the same shape. Specifically, each piezoelectric element 14 is formed so that 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 piezoelectric element 14 is reduced, the piezoelectric element 14 can be formed with an accurate dimension while suppressing deformation during firing. Furthermore, since it is possible to avoid an increase in the size of the manufacturing equipment, the spherical ultrasonic transducer 6 can be manufactured easily and at low cost.

(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 arranged via the gaps 41 and are acoustically divided. Therefore, each piezoelectric element 14 can be reliably vibrated in the vibration mode in the length direction. The gap 41 is a linear gap having a width L3 that is about 1/9 of the maximum width L4. In this case, since the gap 41 between the piezoelectric elements 14 becomes small, energy conversion can be reliably performed over the entire circumference of the energy conversion unit 10.

(3) In the spherical ultrasonic transducer 6 of the present embodiment, the piezoelectric element 14 is formed to have a length L1 corresponding to an arc having a central angle exceeding 90 °, and thus has a surface area equal to or greater than a hemisphere. The spherical energy conversion unit 10 can be easily configured. Further, since the piezoelectric element 14 is formed by one element piece 16 made of piezoelectric ceramic, there is no element piece joint as in the case where the piezoelectric element is formed 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.

(4) In the spherical ultrasonic transducer 6 of the present embodiment, the plurality of piezoelectric elements 14 are provided with a tapered end 18 toward the top 25 of the energy conversion unit 10, and A gap 42 is formed. If it does in this way, in the top part 25 of energy conversion part 10, a plurality of piezoelectric elements 14 can be vibrated reliably, and energy conversion efficiency can be raised.

(5) In the seafloor crustal deformation observation system 1 according to the present embodiment, in the first underwater measurement device 2 and the second underwater measurement device 4, the spherical ultrasonic waves are arranged so that the top portions 25 of the energy conversion unit 10 face each other. A transducer 6 is arranged. That is, in the first underwater measurement 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 measurement device provided on the bottom of the ship. 4, the spherical ultrasonic transducer 6 is provided so that the top 25 of the energy conversion unit 10 faces downward. If it does in this way, transmission / reception of the ultrasonic wave between each ultrasonic transducer 6 can be performed reliably, and distance measurement can be performed correctly.

(6) In the seafloor crustal deformation observation system 1 of the present embodiment, the first underwater measurement device 2 may be installed on the seabed having a water 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 the crustal movement of the seabed can be observed reliably.

In addition, you may change embodiment of this invention as follows.

In the ultrasonic transducer 6 of the above embodiment, each piezoelectric element 14 constituting the energy conversion unit 10 has a length L1 corresponding to an arc having a center angle of 132.9 ° and a center angle of 12 °. Although it has the width L2 corresponding to the arc, the length L1 and the width L2 may be appropriately changed as long as they are formed in an elongated arc shape. However, when configuring 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 an arc whose central angle exceeds 90 °. Further, in order to sufficiently secure the surface area of the energy conversion unit 10, it is preferable to form each piezoelectric element 14 so as to have a length L1 corresponding to an arc having a central angle of 100 ° or more. Furthermore, considering the installation on the spherical base 15, it is preferable that the plurality of piezoelectric elements 14 have a length L1 corresponding to an arc having a central angle of 170 ° or less.

In the ultrasonic transducer 6 of the above embodiment, each piezoelectric element 14 constituting the energy converting unit 10 is formed by one element piece 16 made of piezoelectric ceramics, but is not limited thereto. 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 ceramics in the length direction. . 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, and 16e made of piezoelectric ceramics in the length direction. But you can. 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 using an adhesive without a gap. The cured product of the adhesive that joins the element pieces 16 a to 16 e is harder than the cured product of the adhesive that fixes the

piezoelectric elements

14 a and 14 b to the spherical base 15. 12 has a length L1 corresponding to an arc having a central angle of 90 °, and the piezoelectric element 14b of 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 acoustic energy and electrical energy. Energy conversion can be performed. In this case, the individual element pieces 16a to 16e are small in size, but the element pieces 16a to 16e are joined to form the

piezoelectric elements

14a and 14b, thereby forming relatively large spherical

energy conversion units

10A and 10B. be able to. For this reason, the enlargement of a manufacturing facility can be avoided and the manufacturing cost of a spherical ultrasonic transducer can be reduced.

In the spherical ultrasonic transducer 6 of the above embodiment, the plurality of

piezoelectric elements

14, 14 a, 14 b have a tapered upper end 18 disposed toward the top 25 of the

energy conversion unit

10, 10 A, 10 B. Although arranged 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 a spherical energy conversion unit is configured by the plurality of piezoelectric elements. Specifically, for example, as illustrated in FIG. 14, the energy conversion unit 10 C may be configured by arranging a plurality of piezoelectric elements 14 c in a direction different from the meridian direction. In the energy conversion unit 10 C of FIG. 14, the tapered end portions 18 a of the piezoelectric elements 14 c are arranged so as to face the side portions 57 instead of the top portion 25. In FIG. 14, only one end portion 18a of the piezoelectric element 14c is shown, but the other end portion 18a not shown is also tapered at an acute angle. That is, each piezoelectric element 14c has a tapered shape in which both end portions 18a are sharpened at an acute angle, and each end portion 18a has a spherical shape so as to face one place (a side portion 57 disposed opposite to the energy conversion portion 10C). It is arranged in the element installation part 31 of the base 15. As a result, each piezoelectric element 14 c is supported so as to have a hemispherical shell shape on the outer surface 30 of the element installation portion 31.

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 12 A has a cylindrical portion 38 and a spherical portion 39 formed integrally with the cylindrical portion 38. In the resin cover 12A, the length of the cylindrical portion 38 in the axial direction (vertical direction in FIG. 15) is shorter than the length of the cylindrical portion 35 (see FIG. 2) in the resin cover 12 of the above-described embodiment. Is smaller than the diameter of the cylindrical portion 35. In the resin cover 12A, the spherical portion 39 is provided at a position facing the energy conversion portion 10 and has an area larger than a hemisphere. 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 size. In contrast, in the resin cover 12 A 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 A, the cylindrical portion 38 has a shape constricted 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) is above and below the energy conversion unit 10. It becomes uniform. In this case, the ultrasonic transmission / reception sensitivity in the spherical ultrasonic transducer 6A can be increased.

In the above embodiment, in the spherical base 15 having the element installation part 31 having the outer surface 30 formed into a spherical shape, the energy conversion unit 10 is bonded to the outer surface 30 of the element installation part 31 by attaching the plurality of piezoelectric elements 14. Although formed, a support member other than the spherical base 15 may be used. Specifically, the supporting member may be any member that 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 unit 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 a quarter wavelength in the length direction of the piezoelectric element 14. If it does in this way, the piezoelectric element 14 can be vibrated reliably in the state which fixed the piezoelectric element 14 to the fixing | fixed part of the supporting member.

In the above embodiment, the spherical ultrasonic transducer 6 functions as an ultrasonic transmitter / receiver capable of transmitting / receiving ultrasonic waves. It may function as a receiver dedicated to receiving sound waves. Specifically, for example, when the spherical ultrasonic transducer 6 provided in the first underwater measuring device 2 is made to function as a transmitter dedicated to transmitting ultrasonic waves, the second underwater measuring device 4 on the receiving side is spherical. A distance may be measured by providing a microphone instead of the ultrasonic transducer 6.

In the above embodiment, the submarine crustal deformation observation system 1 including the pair of underwater measurement devices 2 and 4 is embodied, but is not limited thereto. For example, the observation system may be configured to provide one underwater measuring device 4 on the bottom of the ship and detect the presence or absence of obstacles existing in the water, the distance of the obstacles, 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 obstacles in the water are received by the piezoelectric elements 14 of the ultrasonic transducer 6. A control device (not shown) determines the presence or absence of an obstacle present in the water based on the received signal. Further, the control device detects the distance of the obstacle based on the propagation time of the ultrasonic wave. Furthermore, you may comprise the underwater measuring device 4 so that the direction where an obstruction exists can be specified. Specifically, in the underwater measurement device 4, a dedicated receiving circuit is provided for each piezoelectric element 14 of the ultrasonic transducer 6 or for each of a plurality of adjacent piezoelectric elements 14. Further, the piezoelectric elements 14 are 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 each piezoelectric element 14 of the ultrasonic transducer 6. In this way, the spherical ultrasonic transducer 6 is configured as a directivity ultrasonic transducer, and the direction in which the obstacle exists is based on the magnitude of the ultrasonic reception signal detected by each reception circuit. Can be specified.

Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiments described above are listed below.

(1) In any one of claims 1 to 6, the plurality of piezoelectric elements in the energy conversion unit have a shape obtained by dividing a spherical shell into a plurality along the meridian direction. Sonic transducer.

(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 ° to 170 °.

(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.

(4) The piezoelectric element according to any one of claims 1 to 3, wherein the piezoelectric element corresponds to an arc having a central angle exceeding 90 ° by joining two or more element pieces made of piezoelectric ceramics in a length direction. A spherical ultrasonic transducer characterized by being formed to have a length to be

(5) In the technical idea (4), the cured product of the adhesive that joins two or more of the element pieces in the piezoelectric element is harder than the cured product of the adhesive that fixes the piezoelectric element to the support member. A spherical ultrasonic transducer.

(5) The underwater measurement device according to claim 7, wherein, in each electrode of the plurality of piezoelectric elements, a wiring is connected to a central portion in the length direction where the width is maximum.

(6) In the seventh aspect, in the plurality of piezoelectric elements, one electrode provided on the outer surface is connected to the same first wiring, and the other electrode provided on the inner surface is connected to the same second wiring. An underwater measuring device connected to the underwater measuring device.

(7) The underwater measuring device according to claim 7, wherein the spherical ultrasonic transducer is acoustically omnidirectional.

(8) The apparatus includes the underwater measurement device according to claim 7, wherein the spherical ultrasonic transducer is installed on the seabed with the spherical energy conversion unit facing upward, and the crustal movement of the seabed is observed. A characteristic ocean bottom crustal deformation observation system.

2,4 ... Underwater measuring device

6,6A ... Spherical ultrasonic transducer

7: Transmission / reception circuit as a processing circuit

10, 10A-10C ... Energy conversion section

14, 14a-14c ... Piezoelectric element

15 ... Spherical base as support member

16, 16a to 16e ... element piece

18, 18a ... Tapered end

21 ... Outer surface

22 ... Inside

25 ... the top of the head

26, 27 ... Electrodes

30 ... Outer surface

31 ... Element installation part

41, 42 ... gap

Claims

A spherical ultrasonic transducer having an energy conversion unit that converts energy between acoustic energy and electrical energy,

The energy converter is

The ratio of the length to the maximum width is twice or more, and has a tapered end portion that becomes narrower toward at least one side in the length direction, and has a convexly curved outer surface and a concavely curved inner surface. A plurality of piezoelectric elements each having an electrode formed on each of the outer surface and the inner surface, the main component being an element piece made of piezoelectric ceramic that has an arc shape as a whole in a side view;

A support member configured to support the plurality of piezoelectric elements from the inner surface side so that the tapered end portions of the plurality of piezoelectric elements are directed to one place and have a hemispherical shell shape or a spherical shell shape as a whole;

The plurality of piezoelectric elements can vibrate in a vibration mode having a natural frequency in the length direction corresponding to the length so as to expand and contract in the length direction.

A spherical ultrasonic transducer.
The spherical ultrasonic transducer according to claim 1, wherein each of the plurality of piezoelectric elements is arranged via a gap and is acoustically divided.
The spherical ultrasonic transducer according to claim 2, wherein the gap is a linear gap having a width equal to or smaller than the maximum width, and is formed along a length direction of the piezoelectric element.
4. The piezoelectric element according to claim 1, wherein the piezoelectric element is formed by one element piece made of piezoelectric ceramic so as to have a length corresponding to an arc having a central angle exceeding 90 °. A spherical ultrasonic transducer according to 1.
2. The plurality of piezoelectric elements, wherein the tapered end portion is disposed toward the top of the energy conversion unit, and a gap is formed in the top. 5. The spherical ultrasonic transducer according to any one of 4 above.
The support member is a spherical base having an element installation portion whose outer surface is formed in a spherical shape, and the energy conversion unit is configured by attaching the plurality of piezoelectric elements to the outer surface of the element installation portion. The spherical ultrasonic transducer according to claim 1, wherein:
The spherical ultrasonic transducer according to any one of claims 1 to 6,

A processing circuit electrically connected to the spherical ultrasonic transducer and performing at least one of transmission and reception of ultrasonic waves;

And an underwater measuring device provided in the water.