JPS6123913Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the structure of a piezoelectric vibrator.

As piezoelectric vibrators for high-frequency ultrasound, longitudinal vibrating vibrators are often used, which have a large electromechanical coupling coefficient and a simple vibration configuration. Conventionally, when arranging longitudinal oscillators to have a wide sound wave radiation surface for the purpose of sharp directivity synthesis, a large number of single longitudinal oscillator oscillators were arranged in a direction parallel or perpendicular to the sound wave radiation surface. ing. Furthermore, as shown in Figs. 1 and 2, a plurality of longitudinal oscillators having the same resonant frequency are connected at the nodes of vibration displacement, on the sound wave emission surface side, or on the opposite side thereof. Composite longitudinal vibration type vibrators are also widely used.

However, these conventional longitudinal vibration type vibrators,
The mechanical resonance characteristics are sharp and the mechanical Q is large, so the transmitting/receiving frequency band cannot be widened, and the waveform of the pulse-modulated carrier wave has a slow rise due to a transient phenomenon. For this reason, if a wide sound wave radiation surface with a small mechanical Q is required, use a Languevin type vibrator or a combination of two or more types of single longitudinal vibrator type vibrators with close resonance frequencies. In order to reduce the mechanical Q as
A large number of vibrators were arranged. As an improved version of this, as shown in Figs. 3 and 4, thin grooves are formed in the piezoelectric material in a direction perpendicular to the sound wave radiation surface, and each part separated by the thin grooves is used as a node of longitudinal vibration. Alternatively, they may be joined at the sound wave emitting surface or the opposite surface, and each section separated by a thin groove may have dimensional steps so that it has two or more types of close resonance frequencies, and the entire transducer can be used as a single transducer to generate longitudinal vibrations. A composite longitudinal vibration type vibrator has been proposed.

However, even with such an improved structure, a vibrator requires a step of forming grooves in the vibrator, which is a major obstacle to mass production at low cost. Second, since each vibrator is considered an independent vibrator, the process of pulling out lead terminals for inputting and outputting electrical signals from each vibrator becomes complicated, and at the same time, the lead wires are protected against external shocks and vibrations. There is also a high risk of disconnection. Thirdly, the vibrator having such a structure has a drawback of low mechanical strength and low manufacturing yield.

It is an object of the present invention to eliminate the above-mentioned drawbacks and provide a highly reliable broadband vibrator in large quantities and at low cost.

The vibrator of the present invention is characterized by using thickness longitudinal vibration instead of conventional longitudinal vibration. For example, if we use a piezoelectric material that can strongly excite only the thickness longitudinal vibration, such as the Pb _1-x Sr _x Ti _1-y (Mn1/3Sb2/3) _y O _3- based material that the author has already proposed, This is a thickness longitudinal oscillator which is convenient and characterized in that its thickness is non-uniform.

The present invention will be described below by way of examples with reference to the drawings.

Figures 5a, b, c, d, e, and f show an example of the structure of a thickness vibrator according to the present invention. For example, in a longitudinal vibrator with a substantially plate shape such as a substantially circular plate or a substantially rectangular plate made of sintered Pb _1-x Sr _x Ti _1-y (Mn1/3Sb2/3) _y O ₃ material, It is characterized by continuous or stepwise change, and the upper and lower surfaces of the vibrator are entirely coated with metal electrode films and are polarized in the thickness direction.

The structure shown in FIG. 5a has a two-step difference, and by forming a vibrator having two dimensional steps in this way, it can be used at three adjacent resonant frequencies. Although the figure shows a case where there are three types of resonance frequencies, the resonance frequencies may change continuously as shown in figure b.

Further, as shown in FIG. 3C, the frequency at the center may be lower than that at the periphery. Alternatively, a rectangular vibrator may be used as shown in figures e and f.

FIG. 6 is a sensitivity resonance frequency characteristic diagram when the thickness longitudinal vibrator having the structure of FIG. 5a having three types of closely resonant frequencies according to the present invention is driven individually. The mechanical Q of a thickness longitudinal vibrator is determined by the material of the vibrator, but generally the mechanical Q is quite large. However, the sensitivity frequency characteristic of the embodiment of the present invention, which combines thickness longitudinal vibrators having three types of closely resonant frequencies, is as shown by the curve in FIG. 7, and has a very wide band. Therefore, according to the present invention, it is possible to select a wide range of transmission and reception frequencies, and it is possible to improve the rise of the transmission and reception waveforms due to transient phenomena during transmission and reception.

As described above, the thickness longitudinal vibrator according to the present invention allows broadband transducers to be provided in large quantities and at low cost with good yield.

Note that if the present invention is implemented using an ordinary zircon-lead titanate-based piezoelectric material, it is not effective because a large number of transverse effect vibrations are excited in the frequency range below the thickness vibration. Therefore, the structure of the present invention is limited to materials whose electromechanical coupling coefficient for thickness vibration is sufficiently larger than the electromechanical coupling coefficient for transverse effect vibration.

[Brief explanation of the drawing]

FIGS. 1 and 2 are perspective views of a vibrator using conventional compound longitudinal vibration having a single resonant frequency. FIGS. 3 and 4 are perspective views of a conventional composite vibrator using longitudinal vibration having three different types of resonance frequencies. Figures 5a, b, c, d, e, and f are piezoelectric thickness longitudinal vibrators with non-uniform thickness according to the present invention. Figure 6 shows the fifth
FIG. 7 is a diagram showing individual frequency sensitivity characteristics of the three types of vibrators in the embodiment of the present invention shown in FIG. 7; FIG. be.

Claims (1)

[Scope of utility model registration request] A piezoelectric thickness longitudinal vibrator constructed using a piezoelectric material in which the electromechanical coupling coefficient of thickness longitudinal vibration is sufficiently larger than the electromechanical coupling coefficient of longitudinal vibration transverse effect, characterized in that the thickness is configured to be non-uniform. Piezoelectric vibrator.