JPH04181900A - Slip vibration type transducer - Google Patents

Abstract

PURPOSE:To attain a broad band at high frequencies and high sensitivity by fixing electrode faces of same polarity of a couple of piezoelectric vibrators to both sides of a T-shaped leg of a sound receiving plate so that the lengthwise direction of the T-shaped leg and the polarization direction of the piezoelectric vibrator are matched with each other and fixing each of the other electrode faces of a couple of the piezoelectric vibrators to a housing and a side wall of a slot respectively. CONSTITUTION:A positive electrode face of piezoelectric vibrators 1a, 1b is fixed to a leg of a sound receiving plate 2a having a T--shaped cross section and the leg is inserted to a slot of a housing 5 and the side wall of the slot and a negative electrode face of each piezoelectric vibrator are fixed. Electrodes 12a, 12b are provided to both end faces of the piezoelectric ceramic 11 of a rectangular parallelepiped shape of the piezoelectric vibrator in the broadwise direction (t) and polarization (P) is applied in the lengthwise (l) direction orthogonal to the broadwise direction. When an electric field is applied between the electrodes 12a, 12b, a strain (xsi1, xsi2) is caused to both the faces of the electrodes 12a, 12b in opposite directions along the polarization direction and when a stress (T1, T2) is applied in opposite directions between the faces of the both electrodes 12a, 12b along the polarization direction, an electric signal is generated between both electrodes 12a, 12b, as the so--called slip vibration mode.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic device used underwater, which is an acoustic device that can obtain high sensitivity especially for transmitting waves at high frequencies and receiving waves over a wide band. Regarding transducers.

[Prior Art] Conventionally, this type of transducer has a structure in which piezoelectric vibrators 21a to 21i are sandwiched between sound receiving plates 22a to 22i and a casing 25, and fixed with adhesive, as shown in FIG. have.

FIG. 5(a) is a diagram showing a piezoelectric vibrator of a conventional transducer, and FIG. 5(b) shows the sensitivity characteristics of FIG. 5(a).

As shown in FIG. 5(a), the piezoelectric vibrator is provided with electrodes 32a to 32C' on the end faces in the longitudinal direction (g') of rectangular parallelepiped piezoelectric ceramics 31a and 31b.

The configuration was such that polarization (P) and stress signals (T) were applied in the same direction. A so-called longitudinal effect piezoelectric conversion mode is used.

[Problems to be Solved by the Invention] However, such a piezoelectric vibrator has problems as shown in FIG. 5(b).
As shown in , it combines stress signals in the width direction (W') and thickness direction (t'), and also has a so-called transverse effect piezoelectric conversion mode, so it can be used as a transducer for broadband wave reception. To use the resonant frequency fr (N') derived in the direction (β'), use the resonant frequency fr (w') in the other direction.
, fr (t') must be lower than 1. Therefore, the width (W') must be shorter than the length (β'), and the piezoelectric vibrator must be made shorter than the length (β') to satisfy the required acoustic radiation surface length. The disadvantage was that it had to be divided.

Furthermore, the piezoelectric strain constant (d) (amount of strain per unit electric field), which is a parameter of transmitting sensitivity, the voltage output constant (g) (electric field strength per unit stress), which is a parameter of receiving sensitivity, or the longitudinal effect. value d. and gss, which are lower than the piezoelectric constants dl and g+ in the case of sliding vibration, resulting in a drawback of low sensitivity.

Therefore, two technical problems of the present invention are to eliminate these drawbacks by using the sliding vibration of the piezoelectric vibrator and converting it into longitudinal vibration of the sound receiving plate. The present invention provides a transducer with a simple structure, and a wide vibrator that takes advantage of the property that resonance is not converted into piezoelectricity.

[Means for Solving the Problem] According to the present invention, electrodes are provided on both end faces in the thickness direction of a rectangular parallelepiped piezoelectric ceramic, a pair of piezoelectric vibrators polarized in the length direction perpendicular to the thickness direction, and a T-shaped piezoelectric vibrator. In the transducer, the transducer includes a sound receiving plate made of a columnar elastic body having a cross section, and a housing provided with a groove portion for accommodating the pair of piezoelectric vibrators and the sound receiving plate, wherein both sides of the T-shaped leg of the sound receiving plate Then, the electrode surfaces of the pair of piezoelectric vibrators having the same polarity are fixed so that the longitudinal direction of the T-shaped legs and the polarization direction of the piezoelectric vibrators coincide.

A shear vibration type transducer is obtained, characterized in that the other electrode surfaces of the pair of piezoelectric vibrators are fixed to the housing and the side wall of the groove.

[Example code] Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a partially sectional perspective view of an embodiment according to the invention.

As shown in Figure 1, the sound receiving plate has a T-shaped cross section.

The ten electrode surfaces of the piezoelectric vibrators 1a and lb are fixed to the legs of the piezoelectric vibrators 2a, and these are further inserted into the grooves of the housing 5, and the side walls of the two grooves and the electrode surfaces of each piezoelectric vibrator are fixed.

As shown in FIG. 2(a), the piezoelectric vibrator has electrodes 12a on both end faces in the thickness direction (1) of a rectangular parallelepiped piezoelectric ceramic 11.
12b is provided, and polarization (P) is added in the length (N) direction perpendicular to the thickness direction. When an electric field is applied between the electrodes 12a and 12b, the planes of the picture electrodes 12a and 12b generate distortions (ζ2, ζ2) in opposite directions along the polarization direction. When stress (T, , T2) is applied in opposite directions to each other, the picture electrodes 12a and 12b
An electrical signal is generated between them. It exhibits a so-called slip vibration mode.

By fixing the same polarity electrodes 12a and 12b of the piezoelectric vibrator to both sides of the leg of the sound receiving plate, and terminating the other electrode surfaces in a nearly rigid housing, as shown in FIG. 3(a), Sliding vibrations of the piezoelectric vibrators 1a and lb are converted into longitudinal vibrations of the sound receiving plate 2a. Incidentally, FIG. 3(b) shows a conventional vibration mode.

Therefore, in the case of this embodiment, since the piezoelectric vibrator operates in a sliding vibration mode, its resonance frequency is determined by the thickness of the piezoelectric vibrator (1
) and other dimensions.

The length g1 width W can be arbitrarily selected since they are not piezoelectrically converted as an inconvenient spurious resonance. In addition, the smaller the thickness t, the higher the resonant frequency, making it suitable for high-frequency transmitters.Furthermore, in the case of receiving waves, it is sensitive to hydrostatic pressure below the resonant frequency, so the receiving sensitivity shown in Figure 2 (b) It can be used as a wideband delivery transducer as shown by the curve Rv.

By the way, the piezoelectric constants d15 and g+s of the sliding vibration mode
are longitudinal vibration, piezoelectric constants of longitudinal effect d33 and g3301.5
The transducer of the present invention has a higher sensitivity than the conventional system because it has a value of ~2 times as much.

In the embodiment of the present invention, a piezoelectric vibrator is used.

Cushioning materials 3a~, 4a~ and air chambers 7a~ are provided to prevent unnecessary braking of 1b, sound receiving plate, and 2a.

In order to simplify the drawing, the isolation coating from water, which is an external medium, and the cable for leading out the lead are omitted, but the details are omitted because they do not relate to the basic requirements of the present invention.

In addition, steps are provided on the sound receiving plate, piezoelectric vibrator, and side wall of the groove of the housing for reinforcement and dimensioning.

This does not affect the basic operating principle of the present invention.1 Furthermore, it is possible to taper the thickness of the piezoelectric vibrator, the two legs of the sound receiving plate, etc., and thereby strengthen and increase the dimensions. shall be included within the scope.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an underwater ultrasound transducer which has the advantages of particularly high frequency, wide band, and high sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional perspective view of an embodiment of the present invention, and FIG.
) is an explanatory diagram of the structure of the piezoelectric vibrator used in the present invention, and Fig. 2 (
b) is the transmission (S~) and reception (R) according to the embodiment of the present invention.
Fig. 3 (a) and (b) are explanatory diagrams of vibration modes of the embodiment of the present invention and the conventional example, Fig. 4 is a partial cross-sectional perspective view of the conventional example, and Fig. 5 (a) is an explanatory diagram of the structure of a piezoelectric vibrator used in a conventional example, and FIG. 5(b) is a sensitivity characteristic diagram according to the conventional example. In the figure, 1a to 1f, 21a to 21i = piezoelectric vibrator, 2a to 2c, 22a to 22i - sound receiving plate, 3a
-3f, 23a -23f-Buffer material, 4a-4
f. 24a to 24g...Cushioning material, 5.25...Casing,
6a-6f, 26a to 26 f=-lead wire, 7a
~7c. 27a-27f-air chamber, 11.31a, 31b・
...Piezoelectric ceramic, 12a, 12b, 32a~B2 (
···electrode. Figure 3 (α) (fixed) Cb)

Claims (1)

[Claims] 1. electrodes are provided on both end faces in the thickness direction of a rectangular parallelepiped voltage ceramic, a pair of piezoelectric vibrators polarized in the length direction perpendicular to the thickness direction, and a sound receiving plate made of a columnar elastic body having a T-shaped cross section; In the transducer comprising the piezoelectric vibrator and a housing provided with a groove for housing the sound receiving plate, electrode surfaces of the pair of piezoelectric vibrators have the same polarity on both sides of the T-shaped leg of the sound receiving plate. are fixed so that the longitudinal direction of the T-shaped leg matches the polarization direction of the piezoelectric vibrator, and each of the other electrode surfaces of the pair of piezoelectric vibrators is fixed to the housing and the side wall of the groove. A sliding vibration type transducer characterized by: