JP3005611B1 - Underwater ultrasonic transducer - Google Patents

Abstract

The present invention provides a small and light underwater ultrasonic transducer that has a wideband and high-efficiency acoustic radiation characteristics, can transmit high power, and is small and light. SOLUTION: A bolt 14 for applying a compressive stress to a piezoelectric ceramic laminate 11 is provided with a front mass 13 and a rear mass 12.
In the underwater ultrasonic transducer having the bolted Langevin vibrator engaged with the front mass 13, a concave portion is provided on the front surface of the front mass 13, and the bending diaphragm 1 is provided on the front surface of the front mass 13.
3 is fixed with a strong adhesive and a bolt 16 or by electron beam welding. The flexural vibration plate 15 has a rigid translational displacement due to expansion and contraction of the piezoelectric ceramic laminate 11 and a flexural displacement of the flexural vibration plate 15 supporting itself. The dimensions of the concave portion are optimally designed so that these two vibration modes are superimposed to achieve a wider band. The connection between the mechanical parts is made firmly by bolts and the like, so that a small and lightweight transducer which has high mechanical strength and can sufficiently withstand high-power transmission can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide-band piezoelectric transducer which is small and light in water and capable of transmitting high power.

[0002]

2. Description of the Related Art As a high-efficiency ultrasonic transducer capable of transmitting high power in a conventional frequency band underwater, a bolted Langevin type transducer (also known as Tonpills transducer (To)) as shown in FIG.
npilz Transducer)) (IEEE T
transaction on Sonics and U
ltrasonics, p. 220, Oct.
1986) has become widespread. FIG. 9 shows a front view and a sectional view of a conventional bolt-fastened Langevin type transducer. In FIG. 9, 11 is a piezoelectric ceramic laminate, 12 is a rear metal mass, 13 is a front metal mass,
14 is a bolt and 17 is a nut.

To increase the bandwidth of an underwater ultrasonic transducer, as shown in FIG. 10, an acoustic matching layer having a quarter wavelength with respect to the resonance frequency of the piezoelectric ceramic vibrator 81 is provided on the acoustic radiation side of the piezoelectric ceramic vibrator 81. Transducers provided with an E. 82 are known (IEEE Processedin).
gs, Vol. 131, Part F, No.
3, pp. 285-297, June 198
4).

Further, as a technique for broadening the bandwidth of a bolted Langevin type transducer, as shown in FIG. 11, a bolted Langevin vibrator and a cylindrical resonator 95 are used.
(JP-A-63-18800)
As shown in FIG. 12, a combination of a bolted Langevin resonator and a half-wavelength resonator 105 (Japanese Patent Laid-Open No. 62-258598), or a Langevin resonator 1110 as shown in FIG. Front Mass 115
A single or multiple acoustic matching layer (made of plastic) 116 having a quarter wavelength and a block 117 made of a material having an extremely low acoustic impedance as compared with water are disposed at the rear of the rear mass 115b in front of (a). JP-A-5-183
996 gazette).

In FIG. 11, reference numeral 96 denotes a vertical connector,
Reference numeral 98 denotes an acoustic radiation surface, and in FIG.
Is a longitudinal connector, and 108 is an acoustic radiation surface.
, 111a and 111b are piezoelectric vibrators, 115
a and 115b are a metal front mass and a metal rear mass, 118 is a hot-side electrode, 119a and 119b are ground-side electrodes, 1111a and 1111b.
Is an acoustic emission surface.

[0006]

In the conventional broadband technology using the acoustic matching layer, the bonding between the acoustic matching plate and the ceramic vibrator or the Langevin vibrator must rely solely on an epoxy-based adhesive. There is a possibility that the acoustic matching layer may be separated from the vibrator. Further, the material of the acoustic matching layer itself easily reaches a nonlinear region related to stress-strain at the time of high-power transmission, which causes a problem of distortion of a transmission waveform and deterioration of linearity of acoustic radiation power with respect to input power. Was. In a conventional transducer with an acoustic matching layer, the number of acoustic matching layers has been increased in order to further increase the bandwidth. In this case, however, the number of bonded portions increases, reliability becomes poor, and multiple However, it is not suitable for reducing the size and weight because of the matching layer.

Further, in a transducer in which a bolted Langevin vibrator and a cylindrical resonator or a half-wavelength resonator, which are cited as examples of the prior art, are combined with each other, the phases of the vibrator and the resonator are opposite to each other. The resonance frequency of the mode is used to increase the bandwidth, and the mechanical strength is increased by joining each part with bolts and nuts. However, these transducers are structurally large. That was an inevitable problem.

An object of the present invention is to realize a small and light underwater ultrasonic transducer which has a wide band, high efficiency acoustic radiation characteristics, can transmit high power, and is small.

[0009]

According to the present invention, a piezoelectric ceramic laminate having a through hole therein is disposed between a front mass and a rear mass, and the piezoelectric ceramic laminate is passed through the through hole of the piezoelectric ceramic laminate. An underwater ultrasonic transducer having a bolted Langevin vibrator engaged with a mass and the rear mass and provided with a bolt for applying a compressive stress to the piezoelectric ceramic laminate, wherein a recess is provided on a front surface of the front mass, An underwater ultrasonic transducer is obtained, wherein a bending diaphragm is fixed to the front surface of the mass.

Further, according to the present invention, there is provided an underwater ultrasonic transducer, wherein the diameter of the concave portion on the front surface of the front mass is set to 60% to 90% of the total diameter of the front surface of the front mass. can get.

According to the present invention, the flexural diaphragm is selected from the group consisting of an Al alloy, a Ti alloy, a fiber reinforced plastic such as carbon fiber, and a fiber reinforced metal based on Al or Mg. An underwater ultrasonic transducer characterized by using one material that is lightweight and has high strength characteristics is obtained.

Further, according to the present invention, the longitudinal vibration fundamental resonance mode of the bolted Langevin vibrator and the bending vibration mode of the bending vibration plate fixed to the front surface of the front mass are in opposite phases. Underwater ultrasonic transducer is obtained.

According to the present invention, the bending vibration resonance frequency of the bending vibration plate fixed to the front surface of the front mass is set to be higher than the longitudinal vibration basic resonance frequency of the bolted Langevin vibrator. Thus, an underwater ultrasonic transducer is obtained.

According to the present invention, furthermore, a slit is formed in the front mass near the joint between the front mass and the piezoelectric ceramic laminate one round toward the front surface of the front mass. An ultrasonic transducer is obtained.

Further, according to the present invention, the bending vibration plate is fixed to the front mass by attaching the bending vibration plate to the front surface of the front mass with an adhesive and further fixing with a bolt. Underwater ultrasonic transducer is obtained.

Further, according to the present invention, the underwater ultrasonic wave is characterized in that the bending vibration plate is fitted into the recess of the front mass, and the bending vibration plate is welded to the front mass by electron beam welding. A transducer is obtained.

According to the present invention, there is provided an underwater ultrasonic transducer, wherein a soft material is inserted into a gap between the concave portion of the front mass and the bending vibration plate.

Further, according to the present invention, there is provided an underwater ultrasonic transducer, wherein a plurality of convex portions are provided on the bottom surface of the concave portion of the front mass.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front view and a sectional view of an underwater ultrasonic transducer according to a first embodiment of the present invention.

Referring to FIG. 1, this underwater ultrasonic transducer includes a front metal mass 13 and a rear metal mass 12.
And a hollow piezoelectric ceramic laminate 11 having a through hole therein, and a bolt 14 engaged with the front metal mass 13 and the rear metal mass 12 through the through hole of the piezoelectric ceramic laminate 11. It has a bolted Langevin vibrator. The bolt 14 cooperates with a nut 17 engaged with the bolt 14 to apply a compressive stress to the piezoelectric ceramic laminate 11.

As described above, this underwater ultrasonic transducer has a hole formed at the center of the rear metal mass 12 and the front metal mass 13, and is formed by the rear metal mass 12, the front metal mass 13, the bolt 14, and the nut 17. A static stress bias can be applied to the portion of the piezoelectric ceramic laminate 11. Since the strength of piezoelectric ceramics against tension is only a fraction of the strength against pressure, the bolted Langevin vibrator having such a means for applying a static compressive stress is particularly excellent when forcibly excited with high power. It can be said that it is.

In this underwater ultrasonic transducer, a concave portion is further provided in the center of the front surface of the front metal mass 13, and a bending diaphragm 15 is fixed to the periphery of the front surface of the front metal mass 13.

The bending vibration plate 15 is a vibration plate that generates bending vibration, and is made of a metal such as an Al alloy or a Ti alloy, a fiber reinforced plastic such as carbon fiber, and a fiber reinforced metal whose base material is Al or Mg. Selected from a group,
It is preferable to be composed of one material that is lightweight and has high strength characteristics.

The bending vibration plate 15 is provided with a strong adhesive and bolts 16 on the peripheral portion of the front surface of the front metal mass 13.
The vibration mode fixed to the periphery is excited at the time of bending vibration. Instead, the front metal mass 1
It is more effective to completely integrate the joining of the bending vibration plate 15 to the peripheral portion on the front surface of the substrate 3 by an electron beam welding method or the like.

As shown in FIG. 2, a bending vibration plate 15 is fitted into the inner peripheral wall of the concave portion of the front metal mass 13, and the bending vibration plate 15 is welded and joined to the front metal mass 13 by electron beam welding. It is more effective to completely integrate the front metal mass 15 and the front metal mass 13.

As apparent from FIGS. 1 and 2, in these transducers, the connection between the mechanical parts is made firmly by bolts or the like, and the mechanical strength is much higher than that of the conventional transducer with a matching layer. , Which can withstand high power transmission.

The transducer according to the present invention shown in FIGS. 1 and 2 has two resonances as a natural resonance frequency: a frequency fl of a longitudinal vibration mode in which the entire transducer undergoes a translational displacement, and a frequency f2 of a fixed bending mode around the bending diaphragm 15. Mode exists.

FIG. 3 shows a vibration mode diagram of a result of the finite element method analysis for the translational displacement longitudinal vibration mode of the transducer of FIGS. 1 and 2, and FIG. 4 shows a peripheral fixed bending vibration mode of the transducer of FIGS. 1 and 2. And a vibration mode diagram of a finite element method analysis result. 3 and 4
Here, a half-section model that is axisymmetric with respect to the transducer of the present invention is drawn, and the broken line shows the configuration of the original steady state, and the solid line shows several times the actual displacement. FIG. 4 is a displacement mode diagram enlarged in FIG.

With respect to these two resonance modes, the diameter of the concave portion (depression) on the front surface of the front metal mass 13 is set to 6 times the total diameter of the front surface of the front metal mass 13 by finite element analysis.
By designing so as to be 0% to 90%, the resonance frequency f2 of the bending vibration mode is higher than the resonance frequency fl of the longitudinal vibration mode, and a wider band is achieved by superimposing the two modes. This is a characteristic of the transducer of the present invention.

The two vibration modes have phases opposite to each other. That is, in the longitudinal vibration mode of the translational displacement, when the bolted Langevin vibrator extends, it vibrates so as to extend in the direction of excluding the medium also on the acoustic radiation surface as shown in FIG.
In the bending mode of the bending vibration plate, when the bolted Langevin vibrator contracts as shown in FIG. 4, the bending vibration vibrates in the direction of removing the medium. By driving the phases opposite to each other,
Each mode is superimposed, and the band is widened.

FIG. 5 shows the frequency characteristics of the transmission level of the transducers of FIGS. Although there are two peak points of the sound wave level, they are superimposed to have a broadband characteristic.

As is apparent from the above description, in the transducer of the present invention, a quarter of the front of the front mass is provided.
A wavelength matching layer or the like is not required, and a bending vibration plate having a thickness enough to excite bending vibration may be added. The thickness of this diaphragm is also optimally designed by finite element analysis.
Therefore, it can be said that the transducer of the present invention has a small size and a lightweight shape as well as a wide band.

The shape of the front metal mass 13 is shown in FIG.
Although FIG. 2 shows a circular shape, the same effect can be obtained with a rectangular shape.

As a method of driving the transducer of the present invention at a lower frequency, as shown in FIG. 6, the front metal mass 13 near the junction between the front metal mass 13 and the piezoelectric ceramic laminate 11 is added to the front metal mass 13.
It is also effective to insert the slit 66 one round toward the front surface. By providing the slit 66, it is possible to reduce the compliance of the front metal mass 13 and reduce the frequency. Regarding the depth of the slit 66,
By the numerical analysis of the finite element method, it is possible to appropriately design and realize driving at a desired frequency.

For the purpose of improving the working depth of the transducer of the present invention, as shown in FIG. 7, for example, onion skin paper (lamination) is provided on the air gap layer between the concave portion of the front metal mass 13 and the bending diaphragm 15. Another feature of the present invention is to dispose a soft material 127 as described above to fill the air gap layer and enhance the water pressure resistance against external water pressure. In FIG. 7, the joining between the bending vibration plate 15 and the front metal mass 13 is a welding joint, but the present invention is similarly applied to a joint structure using a bolt and a strong adhesive as shown in FIG. 1. Function. Similar effects can be obtained regardless of whether the radiation surface is a disk or a rectangle.

Further, since the underwater ultrasonic transducer is used in water, it must be molded with a resin or the like. During the molding process, a load of about several t is applied to the transducer. In order to prevent the bending vibration plate from plastically deforming under the load, FIG.
As shown in (1), a feature of the present invention is that a plurality of convex portions are provided as plastic deformation stoppers 137 on the bottom surface of the concave portion of the front metal mass 13. Even if a load as large as several t is applied to the bending vibration plate 15 during the molding process, the bending vibration plate 15 is bent during the application of the load and comes into contact with the plastic deformation stopper 137. Thus, there is an effect that the bending diaphragm 15 can return to the original model after the molding process without plastic deformation.

Although FIG. 8 shows the welding of the bending diaphragm 15 and the front metal mass 13 by welding, the present invention can also be applied to a structure of a bolt and a strong adhesive as shown in FIG. Works similarly. Similar effects can be obtained regardless of whether the radiation surface is a disk or a rectangle.

Hereinafter, FIGS. 1, 2, 6, 7, and 8 will be described.
The embodiment shown in (1) will be described in detail.

(Embodiment 1) In the transducer according to the first embodiment of the present invention shown in FIG. 1, the piezoelectric ceramic laminate 11 is composed of a large number of lead zirconate titanate-based piezoelectric ceramics polarized in the thickness direction. The adjacent rings are arranged so that the polarization directions are opposite to each other, and the rings are electrically connected and driven in parallel. Reference numerals 12 and 13 denote metal masses, which form a rear mass and a front mass, respectively. Bolt 14 is Cr-M
It is made of o-steel and applies a static compression bias to the piezoelectric ceramic ring together with the nut 17. Reference numeral 15 denotes a flexural vibration plate made of an Al alloy. The flexural vibration plate 15 is firmly fixed to the front metal mass 13 in the vicinity of the circumference by a strong epoxy adhesive and bolts 16.

The size of the recess of the front metal mass 13 is such that the bandwidth can be widened by simulating the transmission sensitivity characteristics using the finite element method. The diameter of the recess (depression) is about 75% of the diameter of the radiation surface. By the same simulation, the thickness of the bending vibration plate 15 was determined such that the resonance frequency of the bending vibration mode of the bending vibration plate 15 was higher than the resonance frequency of the longitudinal vibration fundamental resonance mode of the Langevin vibrator. In this case, in the transmission voltage sensitivity characteristic, the specific bandwidth can be obtained twice or more as compared with the case where the bending diaphragm is not provided.

Embodiment 2 A transducer according to a second embodiment of the present invention shown in FIG. 2 is the same as the transducer according to the first embodiment of the present invention shown in FIG. 1 except for the following points. .

That is, the bending diaphragm 15 made of an Al alloy
Is firmly connected to the front metal mass 13 by the electron beam welding method on the inner peripheral wall of the front concave portion as if it were an integrated structure.

The concave portion of the front metal mass 13 has a size that can achieve a wide band by simulating the transmission sensitivity characteristics using the finite element method. %, And the same simulation was performed to determine the thickness of the bending vibration plate 15 such that the resonance frequency of the bending vibration mode of the bending vibration plate 15 was higher than the resonance frequency of the longitudinal vibration fundamental resonance mode of the Langevin vibrator. In this case, in the transmission voltage sensitivity characteristic, the specific bandwidth can be obtained twice or more as compared with the case where the bending diaphragm is not provided.

Embodiment 3 The transducer according to the third embodiment of the present invention shown in FIG. 6 is the same as the transducer according to the second embodiment of the present invention shown in FIG. 2 except for the following points. .

That is, in order to reduce the frequency with a small size,
As shown in FIG.
One turn was inserted into the front metal mass 13 near the joint between the piezoelectric ceramic laminate 11 and the piezoelectric ceramic laminate 11.

In this case, the frequency can be reduced as compared with the transducer of the second embodiment.

Fourth Embodiment A transducer according to a fourth embodiment of the present invention shown in FIG. 7 is the same as the transducer according to the second embodiment of the present invention shown in FIG. 2 except for the following points. .

That is, the soft material 127 formed by laminating a plurality of onion skin papers is buried in the gap layer between the concave portion of the front metal mass 13 and the bending diaphragm 15.

Fifth Embodiment A transducer according to a fifth embodiment of the present invention shown in FIG. 8 is the same as the transducer according to the second embodiment of the present invention shown in FIG. 2 except for the following points. .

That is, a plastic deformation stopper 1 having two ring-shaped convex shapes on the bottom surface of the concave portion of the front metal mass 13.
37 were provided at substantially equal intervals. The diameter of the concave portion (depression) is set to about 75% of the diameter of the radiation surface, and the plastic deformation stopper 13 is formed.
The height of 7 was set to about 1/2 of the gap layer.

[0052]

As described above, according to the present invention,
A small and lightweight underwater ultrasonic transducer that can transmit high power and has high efficiency and wide bandwidth can be realized.

The present invention is applicable to fish school detection and the like.

[Brief description of the drawings]

FIG. 1 is a front view and a sectional view showing an underwater ultrasonic transducer according to a first embodiment of the present invention.

FIGS. 2A and 2B are a front view and a sectional view showing an underwater ultrasonic transducer according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a vibration mode at the time of resonance in a translational displacement longitudinal vibration mode of the underwater ultrasonic transducer of FIGS. 1 and 2;

4 is a diagram illustrating a vibration mode at the time of resonance in a bending vibration mode of a bending vibration plate of the underwater ultrasonic transducer of FIGS. 1 and 2. FIG.

5 is a diagram illustrating an example of a band characteristic of the underwater ultrasonic transducer of FIGS. 1 and 2. FIG.

FIG. 6 is a front view and a sectional view showing an underwater ultrasonic transducer according to a third embodiment of the present invention.

FIG. 7 is a front view and a sectional view showing an underwater ultrasonic transducer according to a fourth embodiment of the present invention.

FIG. 8 is a front view and a sectional view showing an underwater ultrasonic transducer according to a fifth embodiment of the present invention.

FIG. 9 is a front view and a sectional view showing a conventional bolted Langevin type transducer.

FIG. 10 is a diagram showing a conventional underwater ultrasonic transducer with a matching layer.

FIG. 11 is a diagram showing a conventional underwater ultrasonic transducer in which a bolted Langevin vibrator and a cylindrical resonator are combined.

FIG. 12 is a diagram showing a conventional underwater ultrasonic transducer in which a bolted Langevin vibrator and a half-wavelength resonator are combined.

FIG. 13 is a diagram showing an ultrasonic transducer in which a plurality of matching layers are added to a conventional Langevin transducer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Piezoelectric ceramic laminated body 12 Rear metal mass 13 Front metal mass 14 Bolt 15 Flexural vibration plate 16 Bolt 17 Nut 66 Slit 127 Soft material 137 Plastic deformation stopper

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kunichi Murakami 102-6-8-102 Namiki, Kanazawa-ku, Yokohama-shi, Kanagawa-ken (56) References JP-A-62-176396 (JP, A) JP-A-61-18299 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04R 1/44 330 G01S 7 / 52 H04R 17/10 330

Claims (10)

(57) [Claims] 1. A piezoelectric ceramic laminate having a through hole therein is disposed between a front mass and a rear mass, and the piezoelectric ceramic laminate is engaged with the front mass and the rear mass through the through hole of the piezoelectric ceramic laminate. In an underwater ultrasonic transducer having a bolted Langevin vibrator provided with a bolt for applying compressive stress to a piezoelectric ceramic laminate, a concave portion is provided on the front surface of the front mass, and a bending diaphragm is fixed to the front surface of the front mass. Underwater ultrasonic transducer characterized by the following. 2. The underwater ultrasonic transducer according to claim 1, wherein a diameter of the concave portion on the front surface of the front mass is 60% or less of a total diameter of the front surface of the front mass.
An underwater ultrasonic transducer characterized by being set to 90%. 3. The underwater ultrasonic transducer according to claim 1, wherein the bending vibration plate includes an Al alloy,
i alloy, fiber reinforced plastic such as carbon fiber, and A
An underwater ultrasonic transducer using one material having light weight and high strength characteristics selected from the group consisting of l or Mg-based fiber-reinforced metal. 4. The underwater ultrasonic transducer according to claim 1, wherein the longitudinal vibration fundamental resonance mode of the bolted Langevin vibrator and the bending diaphragm fixed to the front surface of the front mass. Wherein the bending vibration modes of the underwater ultrasonic transducer are opposite to each other. 5. The underwater ultrasonic transducer according to any one of claims 1, 2, 3 and 4, wherein the underwater ultrasonic transducer is fixed to the front surface of the front mass with respect to a fundamental longitudinal vibration frequency of the bolted Langevin vibrator. An underwater ultrasonic transducer, wherein the bending vibration resonance frequency of the bending vibration plate is set to be higher. 6. The underwater ultrasonic transducer according to claim 1, wherein the front mass is provided near the junction between the front mass and the piezoelectric ceramic laminate. An underwater ultrasonic transducer, wherein a slit is engraved around the front surface of the ultrasonic transducer. 7. The underwater ultrasonic transducer according to claim 1, wherein the bending diaphragm is attached to the front surface of the front mass with an adhesive, and furthermore, is bolted. An underwater ultrasonic transducer, wherein the bending diaphragm is fixed to the front mass by fixing. 8. The underwater ultrasonic transducer according to any one of claims 1, 2, 3, 4, 5, and 6, wherein the bending diaphragm is fitted inside the concave portion of the front mass, and is attached to the front mass. An underwater ultrasonic transducer, wherein the bending vibration plate is welded and joined by electron beam welding. 9. The underwater ultrasonic transducer according to claim 1, wherein the gap between the concave portion of the front mass and the bending diaphragm is soft. Underwater ultrasonic transducer characterized by inserting a material. 10. The underwater ultrasonic transducer according to claim 1, wherein a plurality of convex portions are provided on a bottom surface of the concave portion of the front mass. An underwater ultrasonic transducer, characterized in that: