JPH02111198A - Ultrasonic transducer - Google Patents

Abstract

PURPOSE:To reduce a side lobe near a main lobe by splitting an electrode formed to one face of a piezoelectric substance into plural electrodes concentrically and decreasing the degree of polarization of the piezoelectric substance beneath the split electrodes stepwise toward the outside. CONSTITUTION:An electrode 14 having a diameter slightly smaller than a diameter of a piezoelectric ceramic vibrator 12 is formed to nearly the entire left side face and three split electrodes 16, 18 and 20 are formed to the right side face of the piezoelectric ceramic vibrator 12 concentrically. The degree of polarization beneath the split electrodes 16-20 of the piezoelectric ceramic vibrator 12 is decreased stepwise toward the outside (peripheral part) from the center for each of the split electrodes 16, 18 and 20. Thus, the side lobe at 10 deg. and 350 deg. giving a large effect on the resolution is reduced to nearly a half as nearly 14dB.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to ultrasonic transducers, and more particularly to ultrasonic transducers that can be used in underwater communication equipment, such as underwater sonar.

(Prior Art) In this type of ultrasonic transducer, the piezoelectric ceramic vibrator 1 is uniformly polarized as indicated by the arrow -C in FIG. Further, on the main surface of the disc-shaped piezoelectric ceramic vibrator 1, full-surface electrodes 2 and 3 are formed facing each other.

When an alternating current voltage of a predetermined frequency is applied between the entire surface electrodes 2 and 3, the piezoelectric ceramic vibrator 1 vibrates and emits ultrasonic waves.

The directional characteristics of the ultrasonic waves emitted in this way are shown in FIG. The directivity characteristic shown by the main lobe shown in FIG. 5 is sharp and is generally inversely proportional to D/λ, where D is the diameter of the piezoelectric ceramic vibrator 1 and λ is the wavelength of the ultrasonic wave.

[Problem to be solved by the invention]

However, in such an ultrasonic transducer, the directional characteristics generally have relatively large side lobes, as shown in FIG. For example, the main lobe (0°
) in the vicinity of ±10° (100 and 350'),
The side lobe was as high as 25 dB, and the difference from the main lobe was small, so the angular resolution was not very good.

Therefore, a primary object of the present invention is to provide an ultrasonic transducer with good angular resolution.

[Means to solve the problem]

In an ultrasonic transducer in which electrodes are formed on each of two opposing surfaces of a piezoelectric material, the electrode formed on one surface of the piezoelectric material is concentrically divided into a plurality of parts, and the piezoelectric material directly below the divided electrodes is This ultrasonic transducer is characterized in that the degree of polarization of the ultrasonic transducer is gradually decreased toward the outside.

[Effect]

The electrode formed on one surface of the piezoelectric material is concentrically divided into a plurality of parts, but during the zero polarization process in which a full-surface electrode is formed on the other surface, an external electrode is formed between the divided electrode and the full-surface electrode. A DC voltage is applied that gradually decreases toward the opposite direction. Therefore, the degree of polarization of the piezoelectric material directly under each divided electrode is
It gradually becomes smaller as it goes outward.

With this structure, on the radiation surface of the piezoelectric vibrator,
In the past, the piston moved uniformly over the entire surface, but the piston moves with an amplitude distribution that is maximum at the center and gradually decreases toward the periphery. Therefore, the side lobes, especially the side lobes near the main lobe, become small.

〔Effect of the invention〕

According to this invention, the side lobes near the main lobe are reduced, so the angular resolution of the main lobe is improved.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

〔Example〕

FIG. 1 is an illustrative cross-sectional view showing one embodiment of the present invention.
FIG. 2A is a right side view, and FIG. 2B is a left side view. The ultrasonic transducer 10 includes a piezoelectric ceramic vibrator 12,
For example, the piezoelectric ceramic vibrator I2 has a diameter of 50φ and a thickness of 12.
It is composed of 5111111 ceramic firing units. And on the left side (other side), there is a
Electrode 1 with a diameter slightly smaller than the diameter of piezoelectric ceramic vibrator 12
4 is formed. On the right side (one side) of the piezoelectric ceramic vibrator 12, three divided electrodes 16, 18 and 2 are arranged concentrically.
0 is formed.

The polarization treatment for imparting piezoelectricity to the piezoelectric ceramic vibrator 12 is performed on each of the electrodes 16 to 20 and the electrode.

This is done by applying a DC voltage between the In this embodiment, for example, if a PV voltage is applied between the divided electrode 16 and the entire surface electrode 14, the divided electrode 18
The voltage applied between the entire surface electrode 14 is 0.7 PV, and the voltage applied between the divided electrode 20 and the entire surface electrode 14 is 0.
It is set to 2PV. When a polarization voltage is applied at such a ratio, the degree of polarization directly below each of the divided electrodes 16 to 20 of the piezoelectric ceramic vibrator 12 increases from the center toward the outside (periphery), as shown by the arrows in FIG. Each segmented electrode 16, 18 and 20 becomes progressively smaller.

In such an ultrasonic transducer 10, for example, 200 kHz is applied between the entire surface electrode I4 and the electrodes 16 to 20.
When an alternating current voltage of z is applied, ultrasonic waves are emitted, and their directional characteristics are shown in FIG.

At this time, since the degree of polarization of the piezoelectric ceramic vibrator 12 is not uniform, a movement occurs in which the amplitude decreases from the center toward the periphery. Therefore, the main lobe (0
”) is slightly smaller than the conventional one shown in Figure 5, but the 10° and 3° angles have a large effect on resolution.
The side lobe at 50°, which used to be nearly 24 dB, has been halved to about 14 dB. Therefore, the difference between the main lobe and the side lobe becomes large as a result, and the resolution is significantly improved.

In the above embodiment, three divided electrodes 16, 18 and 20 were formed on one surface of the piezoelectric ceramic vibrator 12, but the number of divided electrodes may be any number greater than or equal to two.

[Brief explanation of the drawing]

FIG. 1 is an illustrative cross-sectional view showing one embodiment of the present invention. 2A and 2B are a right side view and a left side view, respectively, of the FIG. 1 embodiment. FIG. 3 is a graph showing the directional characteristics of the embodiment shown in FIG. FIG. 4 is an illustrative cross-sectional view showing an example of a conventional ultrasonic transducer. FIG. 5 is a graph showing the directivity characteristics of a conventional ultrasonic transducer. In the figure, 10 is an ultrasonic transducer, 12 is a piezoelectric ceramic vibrator, 14 is a full surface electrode, and 16 to 20 are electrodes. Figure 2B Patent Applicant Murata Manufacturing Co., Ltd. Representative Patent Attorney Yama 1) Yoshihito 4 Figure 2A

Claims (1)

[Scope of Claims] In an ultrasonic transducer in which electrodes are formed on each of two opposing surfaces of a piezoelectric body, the electrode formed on one surface of the piezoelectric body is concentrically divided into a plurality of parts, and a portion directly below the divided electrodes is provided. An ultrasonic transducer characterized in that the degree of polarization of the piezoelectric body is gradually decreased toward the outside.