JP2671855B2 - Underwater acoustic transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater acoustic transmitter used for marine development research and the like, and more particularly to an underwater acoustic transmitter having a wide band characteristic.

[0002]

2. Description of the Related Art Heretofore, underwater acoustic transmitters, such as Langevin type, cylindrical type, and flextensional type, all use a natural vibration (resonance) frequency of the transmitter to radiate sound waves. Has been taken. These transmitters are mainly used for long-distance sonar, and how small and lightweight they are while reducing the frequency to improve the detection distance.
It was devised to be able to efficiently radiate powerful ultrasonic waves.

An example of such a conventional transmitter is an eye triple e-transaction on sonics and ultra sonics (IEEE Trasactio).
nSonics and Ultrasoics, p220- (1986.10)) and bolted Langevin type transducers, and Eye Triple E Transaction on Ultrasonics Engineering (IEEE Trasaction on Ul
There is a bending and extension transmitter using an elliptical shell described in trasoics Engineering, p116-124 (1963.11)).

[0004]

Underwater acoustic transmitters for marine development research are required to have wide band characteristics for the purpose of collecting and transmitting a large amount of information data. However, in the transmitter using the natural vibration (resonance vibration) frequency like the above-mentioned conventional underwater acoustic transmitter, if the band characteristic is wide band, It is necessary to increase the area of the sound wave emitting surface, and as a result, the size of the transmitter is increased. Further, in the conventional underwater acoustic wave transmitter, there is a limit to widening the frequency band because the downsizing of the wave transmitter is given priority.

[0005]

It is an object of the present invention to improve the disadvantages of the conventional example, and to obtain an acoustic radiation capability and a wide band characteristic close to spherical respiration with respect to the surroundings without increasing the size of the transmitter. It is an object of the present invention to provide an underwater acoustic transmitter capable of

[0006]

According to a first aspect of the present invention, a cubic support core made of a rigid material and six ends of the support core are attached at one end sides thereof, respectively.
The other end includes a piezoelectric actuator that is driven in a direction perpendicular to each surface of the support core. Then, a vibration plate is provided on the other end side of each piezoelectric actuator in parallel with each surface of the support core described above.

According to the second aspect of the present invention, each of the piezoelectric actuators described above is configured to drive the six diaphragms constituting the acoustic radiation surface in the same phase.

According to a third aspect of the present invention, each of the above-mentioned piezoelectric actuators is composed of an even number of stacked piezoelectric ceramic elements, and the polarization directions of the adjacent piezoelectric ceramic elements are arranged alternately in the stacking direction. It takes the structure.

According to a fourth aspect of the invention, each of the piezoelectric actuators described above has a structure in which the outside is molded with resin. This aims to achieve the above-mentioned object.

[0010]

When a drive voltage is applied to each of the piezoelectric actuators, each of which has one end side attached to each surface of the support core formed in a cubic shape, the other end side of each piezoelectric actuator is applied to each surface of the support core. On the other hand, they are driven in the respective vertical directions. As a result, the substantially square diaphragm connected to the other end of each piezoelectric actuator vibrates. Since each of the diaphragms forms six faces of a cube serving as an acoustic radiation surface, sound waves are radiated in all directions from the cubic acoustic radiation surface to surrounding water.

Then, at this time, each piezoelectric actuator performs non-resonant driving to vibrate each diaphragm at a frequency lower than the resonance frequency. As a result, each diaphragm vibrates corresponding to the drive voltage applied to each actuator and outputs a predetermined ultrasonic wave.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, the underwater acoustic transmitter 1 is
A support core 2 formed in a cubic shape by a highly rigid material is arranged in the center. One end side of the piezoelectric actuator 3 is attached to each surface of the support core 2. Then, the piezoelectric actuator 3
A substantially square diaphragm 4 is attached to the other end side of the.

As shown in FIG. 2, the piezoelectric actuator 3 is laminated in a direction perpendicular to the surface of the support core 2 and is formed in a hollow cylindrical shape by a piezoelectric ceramic element 6 formed in an annular shape. There is. On the upper and lower surfaces of each piezoelectric ceramic element 6, ring-shaped electrodes 7 and 8 connected to lead wires 9 and 10, respectively, are provided.

The piezoelectric ceramic elements 6 adjacent to each other are laminated such that the polarization directions thereof are alternately arranged with respect to the lamination direction,
The number of laminated layers is set to an arbitrary even layer (six layers in the embodiment shown in FIG. 2). By arranging the piezoelectric ceramic elements 6 as shown in FIG. 2, the ring-shaped electrodes 7 sandwiched between the adjacent piezoelectric ceramic elements 6,
8 can also be used as the electrodes of both piezoelectric ceramic elements 6 adjacent to each other. Further, each electrode 21 is connected to the lead wires 9 and 10 of the same polarity every other in the stacking direction of the piezoelectric ceramic element 6.

Each of the above-mentioned diaphragms 4 is made of a highly rigid and lightweight material, and is provided in parallel with each surface of the support core 2. Six vibrating plates 4 are provided corresponding to the six surfaces of the support core 2, and constitute a cubic acoustic radiation surface that surrounds the cubic support core 2 in a similar shape as a whole. Further, diagonal chamfered portions 5 are formed on the four sides of each diaphragm 4 on the side facing the support core 2, and are arranged in a cube shape.
The gap between the diaphragms 4 is reduced.

As a concrete example, the piezoelectric actuator 3 has an outer diameter of 30 mm, an inner diameter of 15 mm and a thickness of 7 mm.
The piezoelectric ceramic element 6 made of lead zirconate titanate-based material of [mm] was laminated in six layers (total height 42 [mm]) so that the polarization directions were alternately opposite polarities.
With respect to each piezoelectric ceramic element 6, the electrodes 7 and 8 and the lead wires 9 and 10 were connected so that the polarities of the applied voltages would alternate.

Six piezoelectric actuators 3 having the above-described structure are prepared, and as shown in FIG.
The underwater acoustic wave transmitter 1 was assembled by joining the underwater acoustic wave transmitter 1 and the vibration plate 4, respectively. Each piezoelectric actuator 3 and support core 2 are
Screw holes were formed in each of the six surfaces of the support core 2, and bolts were passed through the piezoelectric actuator 3 in the stacking direction. As the support core 2, a block of stainless material processed into a cubic shape having a side of 60 [mm] was used. Further, as the diaphragm 4, a square plate made of carbon fiber resin (C-FRP) having a side length of 140 mm and a thickness of 15 mm was used. Further, since the piezoelectric actuator 3 portion maintains watertightness,
The urethane resin 11 having a thickness of 3 [mm] was molded on the outside and sealed.

The underwater acoustic wave transmitter 1 constructed as described above includes the piezoelectric ceramic elements 6 of the piezoelectric actuator 3.
Between the electrodes 7 and 8 provided on the
When a voltage is applied from the outside through 0 and 0, the piezoelectric ceramic element 6 expands and contracts in the stacking direction according to the voltage. By this expansion and contraction, the vibration plate 4 attached to the other end side of the piezoelectric actuator 3 vibrates, and this vibration is transmitted to water, which is a transmission medium of sound waves around the transmitter, and is radiated as sound waves. .

The expansion and contraction of the piezoelectric actuator 3 is performed not at its natural vibration (resonance) frequency fr but at a frequency considerably lower than fr, that is, a non-resonant frequency. On the vibration plate 4 attached to the other end of each piezoelectric actuator 3, a displacement having a magnitude corresponding to the drive voltage applied to the piezoelectric actuator 3 through the lead wires 9 and 10 can be obtained. Therefore, it is possible to obtain a large displacement by increasing the drive voltage.

Vibration at a non-resonant frequency is inferior in energy efficiency as compared with the case where the diaphragm 4 is driven in resonance, but instead, it is possible to widen the band characteristic of the sound wave radiated to the surroundings. it can.

The diaphragm 4 of the underwater acoustic transmitter 1 is
Since they are combined in a cubic shape, all the six sides of the cube formed by the diaphragm 4 are acoustic emission surfaces. Therefore, in the underwater acoustic wave transmitter 1, a large sound wave radiation area can be obtained even though the overall size is small.

Further, the voltages synchronized with the piezoelectric ceramic elements 6 of the six piezoelectric actuators 3 are supplied to the lead wires 9 and 1.
0, and thereby vibrating the six diaphragms 4 constituting the cubic acoustic radiation surface in phase,
The acoustic impedance per unit radiation area can be made large like a respiratory sphere. That is, the non-resonant underwater acoustic wave transmitter of the present embodiment has a structure in which the acoustic load is sufficiently applied despite its small size.

Therefore, the band characteristic of the transmitter according to the present embodiment has a very flat wide band characteristic exceeding 100%, and the transmission level obtained with respect to the amplitude of the acoustic radiation surface. Is much larger than a single-sided emission transmitter or a double-sided emission transmitter such as a flextensional type transmitter.

The natural vibration (resonance) frequency of the wave transmitter of the above-mentioned embodiment is about 15 [KHz]. This wave transmitter was placed in a water tank, each diaphragm 4 constituting the acoustic radiation surface was driven in phase, and the sound pressure at a point 1 [m] away from the acoustic radiation surface was measured. As shown, 10
At 0 [Hz], a sound pressure of 181 [dBrel μPa] was obtained, and a wide band characteristic of about 200 [%] or more could be obtained.

Further, the frequency of the sound radiated around the transmitter depends on the characteristics of the piezoelectric actuator 3,
It is in the range of several tens [Hz] to several hundreds [Hz].

[0026]

As described above, according to the present invention,
Due to the action of the cubic acoustic radiation surface composed of six almost square diaphragms, it is possible to make the acoustic radiation area close to spherical respiration without increasing the size of the transmitter. Since the piezoelectric actuator is used to drive the diaphragm, sound waves are radiated by non-resonant vibration, so that a very flat broadband characteristic can be obtained.

Further, when the six vibrating plates constituting the acoustic radiation surface are constituted so that the respective piezoelectric actuators are driven in the same phase, a predetermined ultrasonic wave is generated in the same environment as the breathing ball. It can be transmitted and output at the same time.

Further, when each piezoelectric actuator is composed of an even number of laminated piezoelectric ceramic elements and the polarization directions of adjacent piezoelectric ceramic elements are alternately arranged in the lamination direction, the driving efficiency of the piezoelectric actuator is increased. The number of electrodes for applying a driving voltage to each piezoelectric ceramic element can be reduced, and the structure can be simplified.

Furthermore, when the outside of the piezoelectric actuator is made of a resin such as urethane to have a watertight structure, it is possible to reliably prevent water from entering the electrode portion of the piezoelectric actuator. It is possible to provide an unprecedented excellent underwater acoustic transmitter capable of increasing the durability of the.

[Brief description of the drawings]

FIG. 1 is a partially omitted perspective view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing the configuration of the piezoelectric actuator disclosed in FIG.

FIG. 3 is a diagram showing a transmission characteristic of the embodiment of FIG.

[Explanation of symbols]

 1 Underwater Acoustic Wave Transmitter 2 Support Core 3 Piezoelectric Actuator 4 Vibration Plate 5 Chamfer 6 Piezoelectric Ceramic Element 7,8 Electrode 9,10 Lead Wire 11 Urethane Resin

Claims (4)

(57) [Claims] 1. A cubic support core made of a rigid material, and one end side attached to each of six faces of the support core, the other end side being driven in a direction perpendicular to each face of the support core. And a piezoelectric actuator, and a vibration plate is provided on the other end side of each of the piezoelectric actuators in parallel with each surface of the support core. 2. The underwater acoustic wave transmitter according to claim 1, wherein each of the piezoelectric actuators is configured to drive six diaphragms constituting an acoustic radiation surface in the same phase. 3. The piezoelectric actuator comprises an even number of stacked piezoelectric ceramic elements, and the polarization directions of adjacent piezoelectric ceramic elements are arranged alternately in the stacking direction. The underwater acoustic wave transmitter according to item 1 or 2. 4. The underwater acoustic transmitter according to claim 1, wherein the piezoelectric actuator has a structure in which the outside is molded with resin.