JPH05219588A - Low-frequency submarine ultrasonic transmitter - Google Patents

Abstract

PURPOSE:To obtain the compact and light low-frequency submarine ultrasonic transmitter. CONSTITUTION:An active disk body 30 generates diameter extending oscillation by impressed voltages or currents and with the displacement, a system integrating the active disk body 30 and metallic disks 31 generates bending oscillation. A ring 32 inserted to the part of joining the two metallic disks 31 plays the role of supporting the pseudo pin terminal of the bending oscillation for decreasing the frequency and increasing the volume velocity. Further, the active disk body 30 is arranged on the upside of the metallic disk 31 so as not to load pulling stress to the active disk body 30 under hydrostatic pressure, and the dimension is also designed so as to insert the active disk to the inside rather than a transforming point where compressing stress is changed into pulling stress. Thus, the transmitter can easily be made thin and lightweight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-frequency high-power underwater ultrasonic wave transmitter used for long-distance sonar and ocean resource exploration.

[0002]

2. Description of the Related Art Ultrasonic waves of low frequency in water have less propagation loss than those of high frequency waves and can reach farther, so that low frequency ultrasonic waves are used in fields such as sonar, ocean resource exploration, and ocean current research. The use of ultrasound has a number of advantages. BACKGROUND ART Conventionally, an electrodynamic wave transmitter and a piezoelectric wave transmitter are known as wave transmitters that emit intense ultrasonic waves in water. Although an electrodynamic wave transmitter can take a large displacement,
It is extremely difficult to obtain a small-sized transducer at a low frequency because the generated force is small. Further, the piezoelectric wave transmitter uses a lead zircon titanate-based piezoelectric ceramic as an electromechanical energy conversion material. The piezoelectric ceramic itself has an advantage that the generated force is extremely large because the acoustic impedance is about 20 times or more larger than that of water, but there is a drawback that the displacement necessary for removing the medium cannot be taken in acoustic radiation. Considering that the acoustic radiation impedance per unit radiation area becomes extremely small as the frequency becomes low, in order to perform efficient acoustic radiation at low frequencies, the displacement of the piezoelectric ceramic is further expanded to perform acoustic radiation. There is a need.

Conventionally, as a high power transmitter in a low frequency band (3 kHz or less), for example, a journal of
Acoustic Society of America (J.Acoust.Soc.Am., Vol.68,
No. 4, pp1046-1052 (1980.1
As described in (0)), a bending-extension transmitter using an elliptical shell shown in FIG. 4 is known.

[0004]

In the bending-extension transmitter shown in FIG. 4, the elliptical shell 21 is indicated by an arrow in the figure when the active columnar body 20 made of a piezoelectric ceramic is extended and displaced in the long axis direction. Thus, it is a wave transmitter having a kind of displacement magnifying mechanism that contracts with a multiple displacement of the columnar body 20. (Only a quarter portion of the elliptical shell is indicated by an arrow.) The resonance frequency of such a bending and extending transmitter has a stiffness of the active columnar body 20 that is considerably larger than that of the shell. The value is twice the resonance frequency or more. That is, the low frequency miniaturization of the flexural extension transmitter cannot be achieved without considerably reducing the resonance frequency of the elliptical shell 21 itself having a constant dimension with respect to the flexural extension mode. It is desired to further reduce the resonance frequency of itself. However, it is extremely difficult to miniaturize the low frequency of the elliptical shell itself for the reasons described below.

In order to explain the operation of this elliptical shell,
The major axis of the elliptical shell is the x-axis, the minor axis is the y-axis, and the depth direction is z.
Corresponding to the axis, a quarter of the elliptical shell is shown in FIG. The point at which the center of the thickness of the elliptical shell intersects the x axis is (a, 0), and the point at which it intersects the y axis is (0, b).
That is, the major axis of the elliptical shell is a and the minor axis is b. Now, when the active columnar body 20 extends and displaces the point P by ξ in the + x direction, the displacement magnifying mechanism of the elliptical shell itself causes a displacement of several times ξ in the −y direction at the point Q. The medium as a whole will draw in the medium. On the other hand, when the active columnar body contracts, the shell as a whole works in the direction of eliminating the medium. In this case, the cross section of the elliptical shell cut along the x-axis is parallel to the x-axis,
The translational displacement is zero, and the rotational displacement about the z-axis is zero, as if the roller were worn. Therefore, since the rotation around the z axis is not allowed, the constraint on the movement of the shell is increased and the resonance frequency of the shell is increased. In the flexural extension wave transmitter, the resonance frequency of the elliptical shell itself is not easily lowered for the above reasons, and it is extremely difficult to downsize the low frequency wave.

On the other hand, when the shape of the elliptical shell is changed, b
The shell resonance frequency surely decreases as / a is increased and approaches a circle. However, in this case, as b / a is increased, the displacement enlargement ratio is greatly reduced as compared with the frequency reduction, and therefore there is no merit of changing the shape and reducing the size. It is also recognized that the resonance frequency is lowered when the thickness of the shell is reduced. However, in this case, there is a drawback that not only the capacity of the shell for removing the medium is lowered but also the water pressure resistance characteristic is significantly deteriorated.

An object of the present invention is to provide a non-directional transmitter which is small in a low frequency band and has excellent high power characteristics by eliminating the above drawbacks of the conventional transducer.

[0008]

A wave transmitter according to the present invention comprises two plate-like vibrating bodies each having an active body using a piezoelectric ceramic and a disc having the active body fitted therein, and having a Young's modulus higher than that of the disc material. A low-frequency underwater ultrasonic wave transmitter, characterized in that active bodies are bonded to each other via a low material ring so that they are on the outer surface side.

[0009]

The wave transmitter according to the present invention has the above-mentioned structure to solve the problems of the prior art. The following is a description with reference to the drawings.

FIG. 1 shows an example of the transmitter of the present invention. The operating principle of the transmitter of FIG. 1 will be described in detail. In FIG. 1, reference numeral 30 denotes an active disk body using a piezoelectric ceramic, which is adapted to excite the radial expansion vibration by inputting voltage or current. The active disk body is bonded to the inside of the recess of the metal disk 31 made of a material having high mechanical strength such as high-strength steel by a strong adhesive. In FIG. 1, two metal disks in which such an active disc body is fitted are prepared, and a ring 3 made of a material having a lower Young's modulus and a higher strength than metal is used.
They are joined via an adhesive and a bolt tightening 35. Further, the outer periphery thereof is molded with urethane resin 34 or the like via a protective plate 33.

When the active disc body is displaced by ξ ₁ ,
The joint part of the two metal disks serves as a support end, and the system of the active disk body and the metal disk is displaced by ξ ₂ . At this time, ξ ₂ is larger than ξ ₁ and ξ ₂ >
ξ ₁ . This is repeated, and the system in which the active disk body and the metal disk are integrated vibrates flexibly.

In the wave transmitter of the present invention, since the active disk body and the metal disk vibrate integrally, it is possible to easily reduce the thickness and weight. Further, in order to lower the frequency, a feature is that a ring 32 made of a material having a Young's modulus lower than that of metal and having high strength is sandwiched between two metal disks. 3A and 3B show vibration modes with and without the ring 32 (solid line) and without (dotted line). By inserting the ring 32, the bending vibration of the system in which the active disk body and the metal disk are integrated is performed in a state in which the supporting portion is close to the pin end support, and the frequency can be lowered. Furthermore, as shown in FIG. 3, the amplitude of the vibration mode is large, that is, the volume velocity is large, and a large sound pressure can be produced.

Although the active disc body used in the wave transmitter of the present invention tends to be slightly fragile in tensile stress, the wave disc drive of the present invention has two active disc members as shown in FIG. By fitting it to the outer surface of the metal disk and then determining the diameter of the active disk to be 60 to 75% of the diameter of the entire transmitter by stress analysis using the finite element method, It is possible to apply only compressive stress. Therefore, the low-frequency underwater ultrasonic wave transmitter according to the present invention is excellent in water pressure resistance and has a deep depth (water depth of 500 m).
It is possible to use the In the present invention, the outer shape of the active body is preferably a circle or a rectangle, but is not limited to this. The material of the disc is not necessarily limited to metal.

[0014]

[Embodiment 1] An embodiment of the present invention will be described with reference to FIG. In FIG. 1, the diameter of the active disc body 30 is set to 104
mmφ, thickness 7 mm, diameter of metal disk 31 is 160
mmφ, 14 mm thick, 7 thick
mm, the inner diameter of the insertion ring 32 is 150 mm, the outer diameter is 160
mm and a thickness of 2 mm. Therefore, the dimensions of the entire wave transmitter are 160 mmφ × 32 mm before the molding. Next, a lead zircon titanate-based piezoelectric ceramic for the active disk body 30, and stainless steel SUS for the metal disk 31.
304 and the insertion ring 32 have a fiber reinforced plastic (F
RP) was applied to make a prototype. The resonance frequency of the prototyped wave transmitter in air is 3544 Hz. About 19.5 times the displacement of the active disk body is obtained in the central part of the system where the active disk body and the metal disk are integrated.

Next, this wave transmitter was placed in a water tank and driven with high power, and the sound pressure at a point 1 m away from the acoustic radiation surface was measured. At 3000 Hz, the sound pressure was 203 dBre.
A sound pressure of 1 μmPa was obtained. The Q value in water was 3.4, which was a very low value. As for directivity, it was almost omnidirectional.

There is also a method of using an aluminum alloy instead of stainless steel as the metal disk. In this case, since the acoustic impedance of the aluminum alloy is lower than that of stainless steel, it is advantageous for matching with water, and it is clear that the Q value can be further reduced.

[0017]

Second Embodiment Next, an embodiment of the present invention will be described with reference to FIG. In FIG. 2, the disk type shown in FIG. 1 is changed to a rectangular type, and as the active body 40, a plurality of lead zircon titanate-based piezoelectric ceramics polarized in the width direction are arranged. At this time, the vibration mode of the active body becomes vertical effect vertical vibration with high conversion efficiency. In FIG. 2, the metal part is a rectangular metal shell 4
1, and stainless steel SUS304 is applied to this portion. FRP42 is applied to a material with a low Young's modulus inserted between two metal shells. In this case, FRP42
Is used as two plates.

In FIG. 2, the length of the active body 40 is 9
6 mm, width 85 mm, thickness 7 mm, metal shell 41 has a length of 96 mm, a width of 112 mm and a thickness of 14 m
m, the thin portion was 7 mm, and the length of each FRP 42 was 96 mm, the width was 14 mm, and the thickness was 2 mm. The resonance frequency of the prototyped transmitter in air is 3598.
It was Hz, and about 11.5 times the displacement of the active body was obtained in the central part of the system in which the active body and the metal shell were integrated.

Next, this wave transmitter was put in a water tank and driven with high power, and the sound pressure at a point 1 m away from the acoustic radiation surface was measured. As a result, 201 dBre at 3000 Hz.
A sound pressure of 1 μmPa was obtained. Q value in water is 4.5,
The directivity was almost omnidirectional.

[0020]

As described above, according to the present invention, it is possible to obtain an omnidirectional high power transmitter which is small in size and light in weight and has excellent acoustic radiation efficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing a structural example of a wave transmitter of the present invention.

FIG. 2 is a diagram showing another example of the wave transmitter of the present invention.

FIG. 3 is a diagram showing vibration modes of the wave transmitter of the present invention.

FIG. 4 is a diagram showing a conventional bending and stretching wave transmitter.

FIG. 5 is a diagram showing an elliptical shell used in a conventional bending and stretching wave transmitter.

[Explanation of symbols]

 20 Active Columnar Body 21 Elliptical Shell 30 Active Disc Body 31 Metal Disk 32 Material with Young's Modulus Lower than Metal Ring 33 Protective Plate 34 Urethane Resin 35 Bolt 40 Active Body 41 Metal Shell 42 FRP 43 Protective Plate 44 Urethane Resin 45 Bolt

Claims (4)

[Claims] 1. A plate-shaped vibrating body comprising an active body using a piezoelectric ceramic and a disc in which the active body is fitted, and two active bodies are formed on the outer surface side of each other through a material having a Young's modulus lower than that of the disc material. A low-frequency underwater ultrasonic wave transmitter characterized by being bonded so that 2. The low-frequency underwater ultrasonic transmitter according to claim 1, wherein the plate-shaped piezoelectric ceramic having a circular outer shape is an active plate. 3. The low-frequency underwater ultrasonic wave transmitter according to claim 1, wherein a plate-shaped piezoelectric ceramic having a rectangular outer shape is an active plate. 4. The low-frequency underwater ultrasonic wave transmitter according to claim 1, claim 2, or claim 3, wherein the diameter of the active body is 60 to 75% of the diameter of the whole wave transmitter. Characteristic low frequency underwater ultrasonic wave transmitter.