JPS62470B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroacoustic transducer for passive sonar, and more particularly to an electroacoustic transducer for passive sonar used in shallow depths and wide ocean areas such as straits and continental shelves.

Conventionally, this type of electroacoustic transducer is used in the low frequency range, so it is difficult to sharpen the directivity, and especially when detecting a target sounding body at a distance, a sounding body other than the target directly above may interfere. It became.

Recently, an electroacoustic transducer has been proposed that uses a pressure gradient transducer that outputs an electrical signal based on the sound pressure difference between two points arranged horizontally to remove interfering sound waves directly above. The signal for comparing the phases necessary to determine the sound receiving direction of the transducer is obtained from a so-called pressure type transducer that outputs an electrical signal depending on the sound pressure at the sound receiving point, so pressure type conversion is possible. There were drawbacks such as the inability of the device to filter out interfering sound waves directly above it.

In the present invention, the reference signal necessary for determining the sound receiving direction of the pressure gradient transducer is outputted from a second-order pressure gradient transducer, that is, the difference between the individual signals of two pressure gradient transducers. The object of the present invention is to provide an electroacoustic transducer for azimuth measurement that eliminates the above-mentioned drawbacks and is not affected by interfering sound waves directly above the transducer.

According to the present invention, "a plurality of vibrators each having two electrodes provided on both sides of a polymeric piezoelectric material whose both sides are supported by fixing members and a diaphragm provided on at least one of the two electrodes are provided. The two vibrators are arranged as a pair in parallel and facing each other.
The electroacoustic transducer for measuring direction is characterized in that the direction of the target is measured from the sum and difference of the signals from the two vibrators.

Further, by arranging a plurality of sets of the above-mentioned vibrators orthogonally, it is possible to obtain an electroacoustic transducer for measuring direction, which measures a direction on a plane or a three-dimensional direction.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a vibrator subassembly used in a first embodiment of the present invention, in which a shows a perspective view and b shows a horizontal sectional view. In the first embodiment, a polymeric piezoelectric material 1 is wound onto a cylinder, and arc-shaped diaphragms 4a to 4d are attached to the cylinder in four directions at right angles, and the center of the polymeric piezoelectric material between the diaphragms is fixed. Member 6a
6d and 7 are also fixed together, and two sets of two opposing vibrators are orthogonally crossed. Electrodes 2a to 2d and 3a to 3d are provided on both sides of the polymer piezoelectric material.
is provided, and is divided at the position of the fixed member in order to separate the electrical signal output due to the vibration of each vibrator.

When sound waves arrive at the transducer according to the first embodiment from the outside, a sound pressure difference occurs between both surfaces of the diaphragm through which sound waves are difficult to pass, and the vibrator vibrates due to this sound pressure difference. This sound pressure difference is maximum in the direction where the normal direction of the vibrator and the direction of incidence of the sound wave are parallel, and is minimum in the direction where they are perpendicular to each other.

The vibration of the vibrator can easily obtain a large displacement, is transmitted to a polymeric piezoelectric material with high conversion efficiency, and is converted into an electrical signal.
It is output to a to 9d.

FIG. 2 shows a vibrator subassembly used in the second embodiment, in which a is a perspective view and b is a horizontal sectional view. In the second embodiment, the diaphragms 4'a to 4'd are flat plates, and the resonance frequency of the mechanical vibration resonance system in which the diaphragm is the mass and the polymeric piezoelectric material is elastic is the same as that of the first embodiment. It is lower than the example. The operation of each part in the second embodiment is the same as the operation of each part in the first embodiment.

In the first and second embodiments, the diaphragm is attached to both the front and back surfaces of the polymeric piezoelectric material, but it may also be attached to only one side. Further, although the polymer piezoelectric material is made of a single layer, it may be made of a double layer or more as long as the electrode is divided at the position of the fixing member.

FIG. 3 is a circuit diagram of the portion for obtaining azimuth information from the vibrator output in the first and second embodiments. The output signals are added by adders 14 and 16 to obtain pressure gradient transducer signals E〓x(θ,) and E〓y(θ,) in the x and y directions, respectively. Also, the output signal of the same vibrator is subtracted by subtracters 15 and 17, and x and y are
Obtain the signals E′x(θ,) and E′y(θ,) of the quadratic pressure gradient transducer in the respective directions of , and further convert these signals E′x(θ,) and E′y( θ,)
are added by an adder 18 to obtain a signal E'xy (θ,) of the quadratic pressure gradient type transducer in the xy plane.

The directivity of the signal E〓x(θ,) of the pressure gradient transducer in any direction (θ,) is as shown in Figure 4 at low frequencies with wavelengths longer than the dimensions of the diaphragm, and the direction of reception from the +x direction is as follows. There is a phase difference of 180 degrees between the sound signal and the signal received from the -x direction. Similarly, for the signal E〓y(θ,), +
There is a phase difference of 180 degrees between the signal received from the y direction and the signal received from the -y direction.

Signal E〓′x(θ,
) in any direction (θ, ) is as shown in FIG. 5, and the signal received from the +x direction and the signal received from the −x direction are in phase.

By comparing the phase of this signal E 〓' You can identify where you have arrived based on the direction.

Signal E〓′y(θ,
) also has similar properties regarding the y-direction and is used to identify the y-direction.

Among the above four types of signals, when the signals E〓′x(θ,) and E〓′y(θ,) from the second-order pressure gradient converter are added by the adder 18, the result shown in FIG. 6 is obtained. The directional signal E〓′xy(θ,) becomes the output signal E〓′xy(θ,), and this output signal E〓′xy(θ,) becomes the signal E〓x of the pressure gradient type transducer.
(θ,) and E〓y(θ,) can be both direction identification signals.

The upper limit frequency of the signals of the pressure gradient transducer and the secondary pressure gradient transducer according to the first and second embodiments is limited by the size of the diaphragm with respect to the wavelength, and the lower limit frequency is limited by the diaphragm and the polymer piezoelectric material. However, since the elasticity of the polymer piezoelectric material is lower than that of other piezoelectric materials, the resonant frequency of the mechanical vibration resonance system is low, making it a broadband electroacoustic transducer for azimuth measurement.

Note that the resonance frequency of the mechanical vibration resonance system can be adjusted by the dimensions of the polymeric piezoelectric material, the curvature of bending, and the mass of the diaphragm.

As explained above, the present invention is arranged facing each other,
A set of two diaphragms that receive sound waves on each side,
It consists of a polymeric piezoelectric material that converts the vibrations of the diaphragm into electrical signals, and a fixing member that fixes the vibration nodes of the polymeric piezoelectric material. By configuring so as to obtain the sound receiving direction, it is possible to efficiently select the sound receiving direction over a wide band.

[Brief explanation of the drawing]

FIG. 1 is a perspective view a and a horizontal sectional view b of a first embodiment of the present invention, and FIG. 2 is a diagram showing a second embodiment of the present invention.
Fig. 3 is a circuit diagram showing an embodiment of the present invention in a block diagram, and Fig. 4 shows the directivity according to the output signal of the pressure gradient transducer. Figure 5 is a diagram showing the directivity due to the output signal of the secondary pressure gradient type transducer, Figure 6 is a diagram showing the directivity due to the output signal of the secondary pressure gradient type converter
The figure shows the directivity of a signal obtained by adding the output signal of a secondary pressure gradient transducer in the x direction and the output signal of a secondary pressure gradient transducer in the y direction. 1... Polymer piezoelectric material, 2, 2a to 2d,
2', 2'a to 2'd...outer surface electrodes, 3a to 3d,
3'a to 3'd...Inner surface electrode, 4, 4a to 4d,
4', 4'a to 4'd... diaphragm, 6, 6a to 6
d, 6', 6'a to 6'd, 7, 7'...fixing member,
8a-8d, 8'a-8'd, 9a-9d, 9'a
~9'd... Lead wire, 10-13... Vibrator partial assembly, 14, 16, 18... Adder, 15, 1
7...Subtractor.

Claims (1)

[Scope of Claims] 1. A plurality of vibrators each having a diaphragm provided on at least one of two electrodes provided on both sides of a polymeric piezoelectric material whose both sides are supported by fixing members, An electroacoustic transducer for measuring direction, characterized in that a set of transducers are arranged facing each other in parallel, and the direction of a target is measured from the sum and difference of signals from the two transducers. 2. The electroacoustic transducer for azimuth measurement according to claim 1, characterized in that a plurality of sets of the two vibrators arranged opposite to each other are arranged orthogonally.