JPS5913500A - Transmitter/receiver of ultrasonic wave - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic wave transmitter/receiver having flat frequency characteristics in a wide frequency range and non-directivity by forming a piezo-electric element like a hemisphere and preventing the generation of a resonance point at the specific frequency. CONSTITUTION:A hemispherical piezo-electric element 11 consists of piezoelectric crystal such as zircon, lead titanate PZT, lithium niobate and rock crystal. An AC signal is applied to the 1st and 2nd electrodes 12, 13 to project ultrasonic waves to the sperical surface side through lead wires 14, 15 or ultrasonic waves are received, converted into an electric signals and outputted from the lead wires 14, 15. Being formed like a hemisphere, the piezo-electric element 11 has no resonance point at the specific frequency and flat frequency characteristics can be obtained in a wide frequency range. Even if the diameter of the piezo-electric element 11 is larger than the wave length of the used ultrasonic waves, the ultrasonic waves can be transmitted/received at about the same sensitivity in the whole directions of the spherical surface and almost non-directivity can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic transducer, and particularly to improvements in frequency characteristics and directivity characteristics.

For example, ultrasonic sound field measurements, 4-wah measurements, etc. are performed using the ultrasonic transducer 1. This is done using a so-called hydrophone. Generally, it is desirable for this type of transducer to have flat frequency characteristics over a wide frequency range of 1 MHz to 15 MHz and to be omnidirectional.

Figure 1 (1) (b) is a side view and a plan view showing an example of a conventional ultrasonic transducer. In the figure, 1 is made of zircon, lead titanate (PZT), lithium niobate ( It is a piezoelectric material such as LiNb0.) or crystal. Then, electrodes 2 and 3 are provided on the front and back surfaces of the piezoelectric body 10, respectively.
An alternating current signal of a certain frequency is applied to the electrodes 2 and 3 via lead wires 4.5 to excite them, so as to obtain ultrasonic waves.

By the way, in this type of ultrasonic transducer, for example, I M
It is desirable that the frequency characteristics be flat in a wide frequency range such as Hz to 15 MHz and non-directional in this range. However, with a disc-shaped ultrasonic transducer as shown in Figure 1, it is difficult to obtain flat frequency characteristics over a wide frequency range, although it may exhibit flat frequency characteristics in a limited frequency range. It is. Regarding directivity,
To make it omnidirectional, for example, the frequency is 10 MHz.
Since the wavelength in water is approximately 0.15 rran, the diameter of the piezoelectric body must be 0.15 m+++ or less. However, such dimensions are not possible in terms of vibrator manufacturing technology, and there is still a problem that a large number of radial vibration modes will occur if the diameter-to-thickness ratio of the piezoelectric body 1 is less than 5.

The present invention has been made in view of the above circumstances, and by preventing resonance points from occurring at specific frequencies, it is possible to obtain flat frequency characteristics over a wide frequency range, and also to obtain omnidirectionality. The purpose is to provide wave equipment.

An embodiment of the present invention will be described in detail below with reference to side sectional views and bottom views shown in FIGS. 2(a) and 2(b).

In the figure, 11 is Norcon, lead titanate (P) formed into a hemispherical shape.
ZT), = lithium oxide (1, lNb0.)
It is a piezoelectric body made of piezoelectric crystal such as l-quartz. A first electrode 12 is provided on the spherical surface of the piezoelectric body 11, and a second electrode 13 is provided on the bottom surface of the piezoelectric body 11.
2 and 13 are electrically insulated from each other and led out to the outside via lead wires 14 and 15, respectively, to constitute a transducer.

Note that the diameter of the bottom surface of the piezoelectric body 11 may be approximately 1 cm when used at a maximum frequency of approximately 15 MHz, for example.

Note that a portion of the first and second electrodes 12 and 13 may extend to the bottom surface or the spherical surface as long as they are insulated from each other.

With such a configuration, an alternating current signal is given to the first and second electrodes 12.13 through the lead wires 14.15 to emit ultrasonic waves to the spherical surface side, or to receive the ultrasonic waves and generate electricity. It can be converted into a signal and output from the lead wires 14 and 15. Since the piezoelectric body 11 has a hemispherical shape, it can be prevented from having a resonance point at a specific frequency, and flat frequency characteristics can be obtained over a wide frequency range. Even if the diameter of the piezoelectric body 11 is larger than the wavelength of the ultrasonic waves used, it is possible to transmit and receive ultrasonic waves with approximately the same sensitivity in all directions of the spherical surface, and it is possible to obtain approximately omnidirectionality. can.

FIGS. 3 and 4 are diagrams showing frequency characteristics and directivity characteristics, and the transducer of the above embodiment is indicated by curve A1, and the conventional transducer as shown in FIG. 1 is indicated by the number of curves B. As is clear from this figure, the frequency characteristics of the transducer of the above embodiment are approximately flat in the crowded range, and omnidirectionality can be obtained.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and, for example, piezoelectrics that are approximated to a spherical surface by a polygon consisting of a large number of planes as shown in the side sectional view and bottom view shown in FIGS. The body 11 may also be used. In this way, the spherical surface of the piezoelectric body 11 can be easily processed. Further, as shown in the side cross-sectional view and side view shown in FIG. You can also derive it via .15.

In this way, substantially uniform sensitivity can be obtained in any direction around the entire circumference of the transducer, and good directivity can be obtained.

As described in detail above, the present invention provides electrodes on the spherical surface and the bottom surface of a hemispherical piezoelectric material to transmit and receive ultrasonic waves, so that it is possible to obtain flat frequency characteristics over a wide frequency range, and also to have non-directional properties. Ultrasonic transducer can be provided.

[Brief explanation of the drawing]

FIG. 1 (IL) (b) is a side view and a plan view showing an example of a conventional ultrasonic transducer, and FIG. 2 (IL) (b) is a side sectional view and bottom view showing an example of the present invention. Figure, Figure 3,
Fig. 4 is a diagram comparing the frequency characteristics and directivity of the above embodiment and the conventional ultrasonic transducer, and Fig. 5 (,)
6(b) and FIG. 6(b) are views showing other embodiments of the present invention. 11... Piezoelectric body, 12.13... Electrode, 14.15
···Lead. Applicant's representative Patent attorney Takehiko Suzue Figure 1 (b) Figure 3 Figure 5 <8) (b) ＼ Figure 6 (a) (b)

Claims (1)

[Claims] 1) A superstructure comprising a piezoelectric body formed into a hemispherical shape, a first electrode formed on the spherical surface of the piezoelectric body, and a second electrode formed on the bottom surface of the piezoelectric body. Sound wave transducer. 2) The ultrasonic transducer according to claim 1, characterized in that the spherical portion of the piezoelectric body has a polygonal shape consisting of many planes. 3) The ultrasonic transducer according to claim 1, characterized in that the piezoelectric body is formed into a spherical shape and the surface thereof is divided into two to provide mutually insulated first and second electrodes.