JPS61196697A - Low frequency underwater ultrasonic transmitter - Google Patents

Abstract

PURPOSE:To obtain a small-sized, light-weight transmitter of excellent acoustic radiation efficiency, by employing a non-active column material of both large rigidity and strength and forming a first step displacement enlargement mechanism by the small hinges and 2 1- stage displacement enlargement mechanism coming out from 2 pieces of small hinges and each non-active column material. CONSTITUTION:In order that a small hinge 23 makes the moment of rotation large given to a first step lever 23, the comparative rigidity is large against the vertical displacement, and is designed so that a lever 24 is easy to turn and displacement easy. Further, the displacement enlarged in an output point of a first step lever is transmitted to a long hinge 26, and with the long hinge 26' protruding from a pedestal 25 with this, a second stage control is turned. Hereupon, since the angle of rotation of a second step lever since the vertical displacement output from the first step lever 24 becomes a few times the vertical displacement output from an active column-shaped form 21, it becomes a few times the angle of rotation of the first step lever 24. The vertical displacement output from the second step cover drivers a piston acoustic radiation matter 29 with sharp increase.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a directional high-power transmitter used in a large array in a low frequency band for use in long-distance sonar, marine resource exploration, etc. It is something.

(Conventional technology and its problems) Low-frequency ultrasonic waves have less propagation loss underwater than high-frequency waves and can reach longer distances, so they are useful in fields such as sonar, ocean resource exploration, and ocean current research. There are a number of advantages to using low frequency ultrasound. Conventionally, electrodynamic transducers and piezoelectric transducers have been known as transmitters that emit powerful ultrasonic waves underwater. Although electrodynamic transducers can handle large displacements, they generate small forces, making it extremely difficult to obtain small transducers with low frequencies. In contrast, piezoelectric transducers use zirconium titanate-based piezoelectric ceramics as the electromechanical transducer material, and piezoelectric ceramics have an acoustic impedance that is approximately 20 orders or more higher than that of water, so the generated force is extremely large. Although this method has the advantage of having the following advantages, it has the disadvantage of not being able to take the necessary displacement to exclude the medium in sound radiation. Considering that the acoustic radiation impedance per unit radiation area becomes extremely small as the frequency decreases, in order to achieve efficient acoustic radiation at low frequencies, it is necessary to further expand the displacement of the piezoelectric ceramic to reduce sound bud radiation. There is a need to do. A conventional piezoelectric transformer will be described below.

The bolt-on Langevin transducer is a transducer that transmits powerful ultrasonic waves underwater at 3KHz.
It is well known that it is actively used in the frequency band of up to several tens of KHg. However, if this transducer is to be operated in a low frequency band of 3 KHz or less, it has the disadvantage that its weight and dimensions become too large to be of practical use because it does not have a displacement amplification mechanism.

Therefore, as a transducer that can be miniaturized in the low frequency band, for example, R, S, Woollett +"
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A bending type transducer that utilizes bending vibration of a disc as shown in FIG. 2 is known.

The bending transducer using a circular flat plate shown in FIG. 2 uses a circular bimorph vibrator as a transmitter, as is well known. In the figure, 10 is a zirconate lead titanate based piezoelectric ceramic plate, 11 is a metal plate such as nickel stainless steel, etc. 10.11 constitute a bimorph vibrator, and the bimorph vibrator itself serves as an acoustic radiator. Also, 12 is a cavity, 13 is a housing case,
When the transducer I of the deep-sea berth is activated, silicone oil is put into the cavity of the deep-sea berth to balance the internal and external pressures. 14 is a rubber diaphragm. However, since it is not possible to produce a piezoelectric ceramic plate with a large area as the piezoelectric ceramic plate 10, a bimorph resonator is obtained by bonding a large number of segmented ceramic plates to the metal plate 11 in a mosaic manner. This is the current situation. That is, since a piezoelectric ceramic plate with a large area cannot be used, the medium exclusion ability as a wave transmitter is insufficient, and it is not suitable for high power characteristics. Further, even if a piezoelectric ceramic plate with a large area can be obtained, bimorph resonators have a fairly large bending compliance due to their structure, so it is impossible to expect such a large medium expulsion ability.

(Objective of the Invention) The present invention eliminates the drawbacks of the conventional low frequency underwater ultrasonic transducer, and provides a small size and excellent high power characteristic in the low frequency band, and it is also possible to arrange a large number of transducers and use them as an array. The purpose of this invention is to provide a directional transmitter.

(Structure of the Invention) The transmitter of the present invention uses an active columnar body made of piezoelectric ceramic on a pedestal with high rigidity, and an inactive columnar body with high rigidity and strength placed between the active columnar body. , two short hinges coming out of the active column and two short hinges coming out of each inactive column.
The first stage levers form a first stage displacement magnification mechanism, and the long hinges that transmit the displacement output from each first stage lever, the long hinges protruding from the pedestal, and the second stage levers connected to these A low-frequency underwater ultrasonic wave having a second-stage displacement magnification mechanism and a mechanism for transmitting the expanded displacement output from the second-stage lever to the piston acoustic radiator through a connecting rod connected to the second-stage lever. It is a sound wave transmitter.

(Function) The transmitter of the present invention solves the problems of the prior art by having the above two-stage displacement amplifying mechanism and the piston acoustic radiator. The explanation will be given below according to the drawings.

Figure 1 shows an example of the configuration of a transmitter according to the present invention.
The operating principle of the transmitter shown in the figure will be explained in detail. In the figure, 21 is an active columnar body made of piezoelectric ceramic.
By applying a voltage, longitudinal vibration can be excited. 22 is an inactive columnar body, 23 is a short hinge, and 24 is a first stage lever. In order to perform rigid body rotation of the lever 24 well, the inactive columnar body 22 and the pedestal 25 are designed to have high rigidity. . In addition, the short hinge 23 has relatively high rigidity against vertical displacement in order to increase the rotational moment given to the first stage lever 24, and is flexible against bending displacement so that the lever 24 can easily rotate. Designed to be. On the other hand, lever 2
Needless to say, 4 is superior as it is close to a complete hull. The short hinge 23 and lever 24 function to further increase the vertical displacement of the active columnar body based on the principle of leverage. Further, the enlarged displacement at the output point of the first stage lever is transmitted to the long hinge 26, which together with the long hinge 26' extending from the base 25 causes the second stage lever 27 to rotate. Here, the rotation angle of the second stage lever 27 is such that the vertical displacement output from the first stage lever 24 is several times the vertical displacement output from the active columnar body 21. It is clear that it will be several times as large. The vertical displacement output from the second stage lever is further expanded by this principle and transmitted to the connecting rod 28, just like the first stage displacement magnification mechanism, and when the piston acoustic radiator 29 is driven with a large amplitude, It is possible. In the second stage displacement amplifying mechanism composed of the first stage lever 27 and long hinges 26 and 26', the long hinge 26
．． It is convenient that the rigidity against vertical displacement of 26' is large in order to increase the force transmitted to the second stage lever 27, and in order not to hinder the rotation of the second stage lever, the long hinge 26. The smaller the rigidity against displacement, the better. Similarly, it is better for the connecting rod 28 to have a high rigidity against vertical displacement, and a low rigidity against bending displacement.

The transmitter of the present invention has the advantage that a small displacement of the active columnar body 21 is outputted as a large displacement at the acoustic radiation end face through a two-stage displacement amplification mechanism, and highly efficient acoustic radiation is possible. In addition to this, when the mass M of the piston acoustic radiator 29 is converted to the active columnar body side, the equivalent mass is the square of the displacement magnification rate of the actual mass M, so there is a significant low frequency. Miniaturization can be achieved.

Furthermore, the transmitter of the present invention has the advantage that the displacement magnification rate can be independently and arbitrarily set by the geometric position and shape of the lever and hinge, which is different from the conventional flat plate or This is something that was completely absent from the displacement amplification mechanism by the shell itself. The reason for this is that when increasing the equivalent mass of a transmitter using a flat plate or shell, the thickness of the flat plate or shell must be increased, but in this case the bending stiffness increases and the resonant frequency increases. This is because the result is as follows. Furthermore, when the plate thickness is made thinner, the resonant frequency decreases, but it becomes impossible to maintain the rigidity required for acoustic radiation.

In FIG. 1, reference numeral 30 indicates an O-ring, which is provided in order not to impede the piston movement of the piston youth radiator 29 and to obtain smooth contact with the cabinet 38. Further, in FIG. 1, the arrows indicate the displacements that occur in each part when the active columnar body is extended. In the transmitter of the present invention, when the transmitter is exposed to hydrostatic pressure, the active columnar body The structure is such that pressure is exerted on the The piezoelectric ceramics that make up the active columns are brittle against tension but extremely strong against pressure. This has the advantage that there is no problem at all even if the pressure between the inside and outside of the port 31 is not balanced.

(Example) An underwater ultrasonic wave transmitter shown in FIG. 1 will be described as an example of the present invention. The active columnar body 21 has an electromechanical coupling coefficient of 0.61 and a relative permittivity of ε crystal/ε.

, <:1 oso, a zirconate lead titanate based piezoelectric ceramic was used, and a high tensile strength steel was used for the portion connected to the short hinge 23. Similarly lever 24.27, hinge 23.2
6.26', high tensile steel was used for the connecting rod, stainless steel was used for the pedestal 25, and aluminum alloy was used for the piston acoustic radiator 30. In this example, the displacement magnification rate of the first stage displacement magnification mechanism is 3 times, and the displacement magnification rate of the second stage displacement magnification mechanism is 4 times. Therefore, the displacement magnification rate of the entire transmitter of this example is It is 12 times more. In addition, this transmitter has a resonant frequency of 1.5KHz and can withstand high power driving.
The maximum transmitter dimension for the wavelength of the resonant frequency is 0.0
It is 8. That is, when manufacturing a high power transmitter of, for example, 200 Hz using the transmitter according to the present invention, the maximum size is 60 crn, resulting in significant miniaturization.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to obtain a low-frequency high-power transmitter that is small and lightweight and has excellent acoustic radiation effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a conventional bending transducer. In the figure, 10 piezoelectric ceramic plates, 11 metal plates, 12 a cavity, 13 a housing case, 14 a diaphragm, 21 an active columnar body, 22 an inactive columnar body, 23 a short hinge, and 24 a first stage. Lever, 25 is pedestal, 26.26' is long hinge, 27 is second stage lever, 2
8 is a connecting rod, 29 is a piston acoustic radiator, 30 is an O-ring, 31 is a cabinet, )"r"4'6・
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Claims (1)

[Claims] An active columnar body made of piezoelectric ceramic installed on a pedestal, an inactive columnar body placed across the active columnar body, each of two short hinges protruding from the active columnar body, and each non-active columnar body placed on both sides of the active columnar body. two first-stage levers connected to the short hinges protruding from the active columnar body; two second-stage levers connected to each of the first-stage levers and the pedestal via long hinges; A low frequency underwater ultrasonic transmitter comprising a piston acoustic radiator connected to a two-stage lever via a connecting rod.