JPS60173997A - Supersonic wave transducer assembly - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic transducer assembly incorporating a piezoelectric ultrasonic transducer, and particularly to an ultrasonic transducer assembly incorporating a piezoelectric ultrasonic transducer with a relatively high Q chain and a relatively narrow resonant frequency bandwidth. This invention relates to an assembly incorporating a sonic transducer.

Transducers made from refractory piezoelectric materials, such as lithium niobate, can operate at temperatures above 600° C. and thus can be used in fast reactor cores.

However, the strength of the ultrasound signal conventionally derived from lithium niobate transducers has not been considered adequate for such applications. Lithium niobate transducers typically have very narrow frequency resonances, and may have a Q factor of 5000, for example.

The Q factor is the ratio of the resonant frequency to the difference between the frequencies on both sides of the resonant frequency, when the ultrasound signal at the frequencies on both sides is 3 dB smaller than the ultrasound signal at the resonant frequency. Defined as a ratio.

The transducer assembly of the present invention is an R
Tuning with an inductor in parallel with the transducer as described by , D., Legge greatly improves the strength of the ultrasound signal over that which can be achieved. that the transducer is tuned with an inductor in series such that the maximum impedance of the circuit occurs at the frequency of the maximum impedance of the transducer itself;
For example, ``Piezo electric ceramic 2.x (r'1ezo-e
Electric Ceramics)”, Mull
J. van Randcraa in ard 1974
It was suggested by t and R8 mouth, 5etter inton d. However, this requires very precise tuning to achieve satisfactory signal strength.

Ultrasonic transducer assemblies provided in accordance with the present invention include a piezoelectric transducer, a cable, and an inductor electrically connected to each other in series, such that the inductance of the inductor and the length of the cable minimize the impedance of the transducer assembly. has a value such that the frequency is substantially the same as the natural resonant frequency of the piezoelectric transducer, ie the frequency at which the impedance of the piezoelectric transducer is at a minimum.

Preferably, the piezoelectric transducer is a stium niobate transducer.

The invention will be further explained with reference to the accompanying drawings, by way of example only.

In FIG. 1, transducer assembly 10 includes:
It includes a stium niobate Z-plate transducer 12 with a nominal resonant frequency of 4 MIIz enclosed within a steel shell 14 having a base 16. One side of the transducer 12 is glued to a base 16 that acts as a half-wave diaphragm, and an electrode 18 is attached to the transducer 1.
It is provided on the other side of 2. Electrical connection to both sides of transducer 12 is made via a coaxial cable 20 having an outer conductor 22 connected to housing 14 and a core 24 connected to electrode 18. At a distance "p" along the cable 20, the core 24 has an inductance "L".
The outer conductor 22 is connected to one terminal of the inductor 26 at +f f
It's on sale.

A second coaxial cable 3 with an outer conductor 32 and a core 34
0 connects the transducer 10 to the signal generator 36, the outer conductor 32 is connected to the casing 28, and the core 3
4 is connected to the other terminal of the inductor 26.

During operation of the transuser assembly 10, when the transuser 12 is excited by the signal generator 3G, an ultrasonic wave h'i is emitted, and the amplitude of this ultrasonic wave is determined by the excitation frequency, the distance pulse l'', and the inductance L. ” depends on.

FIG. 2 shows a graph when the frequency of the signal generator 36 is varied for an arbitrary value of the distance "p" and the inductance "L", and the frequency of the signal generator 36 is changed.
The admittance of has a maximum value at the frequency P[5'', i.e. the impedance has a minimum value), and a minimum value at the frequency ``f,'', where the frequency ``fS'' and ゛go,''' are the distances ``A'' and the inductance ``L''. At a frequency of ``5'', the current and voltage are in phase.

Without the inductor 26, the atomicotance of the transuser 12 alone exhibits a similar variation with frequency, with an admittance maximum at the natural resonant frequency of the transuser 12 and an admittance minimum at a slightly different frequency. However, the frequencies at which these maximum and minimum values occur are much lower than “f,” and “f,”.
The difference between the maximum and minimum admittance values is much smaller than the difference in admittance between "'f," and "r,".

When the inductor 26 is present, the overall response is an admittance minimum Δ' at frequency ``f,'' and a generally smaller admittance maximum B
and the minimum admittance value B' corresponding to only the transuser 12.

However, since FIG. 2 shows the case where the frequency "R5" is adjusted to match the natural resonant frequency of the transducer 12, the maximum admittance A is equal to the natural resonant frequency of the transducer 12. Match. Therefore, maximum values A and B match.

FIG. 3 shows the experimentally determined maximum signal strength of the ultrasonic signal emitted by the transducer 12 for various values of length 'β'' and inductance 'L'' without inductor 26. 1. For any combination of length '1' and inductance 'L', the signal generator 36 (see FIG. 1) Frequency “f5”
Maximum signal strength is achieved when exciting transducer 12 (see FIG. 2). When adjusting the length p'' and the inductance ``Lp'' so that the frequency ``fS'' matches the natural resonant frequency of only the transducer 12,
An optimal signal strength (in this case +28 dB) is achieved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a transducer assembly. FIG. 2 is a graph showing the admittance variation of the assembly of FIG. 1 versus frequency. FIG. 3 is a graph of the variation in signal strength emitted from the assembly of FIG. 1 versus inductance and cable length. 12. Piezo electric transformer user 20...cable, 26...inductor # $'f
e'+m f I! (''60,313 Showa Year Month Day 1, Incident Indication 1982 Patent Application No. 225653 2
, Title of the invention Ultrasonic transducer assembly 3,
Relationship with the case of the person making the amendment Applicant 4 agent

Claims (1)

[Claims] In an ultrasonic transducer assembly including a piezoelectric transducer, a cable, and an inductor electrically connected to each other in series, the inductance L of the inductor 26 and the length of the cable 20! is the frequency f at which the impedance of the transducer assembly is at its minimum value
5 has a value such that the natural resonant frequency of the piezoelectric transducer 12 is substantially the same as the natural resonant frequency of the piezoelectric transducer 12.