JPS62231591A - Piezoelectric wave transmitter-receiver - Google Patents

Abstract

PURPOSE: To improve a directional characteristic in a wave transmitter and to improve an S/N in a wave receiver by forming a common electrode covering almost the entire surface on one side, a main electrode in the center on the other side and an auxiliary electrode on the periphery and impressing a voltage so that it can be high in the center and decrease gradually in the peripheral direction. CONSTITUTION:The common electrode 2 to cover the entire surface is formed on one surface of a disk-like piezoelectric rubber sheet 1. On the other surface the circular main electrode 3 is formed in the center, and the auxiliary electrodes 4 and 5 sequentially surrounding the electrode 3 not so as to touch the electrode 3 are formed. Conductive rubber or the like are used for the electrodes 2-5. A DC voltage is impressed on the piezoelectric rubber sheet 1 between the common electrode 2 and the main electrodes 3-5 so that the voltage can be maximum in the main electrode 3 and gradually decrease in the auxiliary electrodes 4 and 5 in that order. Thus the impressed voltage of the main electrode 3 becomes maximum, and each resistance 11 gradually reduces the voltage impressed on the auxiliary electrodes 4 and 5.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is used for underwater transmitters, underwater microphones, etc., which are equipped with a piezoelectric plate such as a flexible sheet or a piezoelectric ceramic plate. Regarding piezoelectric transducers.

<Prior art> Piezoelectric organic materials such as polyvinylidene fluoride, polyvinyl fluoride, polyvinylidene chloride, polyvinyl chloride, and nylon, or strong organic materials such as lead zirconate titanate and lead titanate in the organic materials of synthetic rubber and synthetic resin. A piezoelectric flexible sheet such as a piezoelectric organic ceramic composite made of a mixture of dielectric ceramic particles has an acoustic impedance close to that of water. Therefore, the piezoelectric flexible sheet is used to transmit and receive acoustic waves propagating in water.

Furthermore, some piezoelectric ceramic plates are used as underwater piezoelectric transducers.

In addition, a piezoelectric transducer using this type of piezoelectric plate can also be applied to transmit and receive sound waves in the air.

This type of piezoelectric transducer is used as a wave transmitter by applying an alternating voltage between the upper and lower electrodes of a piezoelectric plate, and the piezoelectric plate receives sound waves and generates a signal voltage from between the 'FL' poles. used as a receiver.

<Problems to be Solved by the Invention> By the way, the piezoelectric plate applied to the piezoelectric transducer having a known configuration has a uniform thickness in the plane direction, and the maximum vibration 11 is located in the center. In addition to the main pole that produces , a plurality of sub-poles (side lobes) occur in the peripheral direction.

Therefore, when a piezoelectric plate is used as a wave transmitter, when an alternating voltage is applied to the upper and lower electrodes, the maximum amplitude occurs around the main pole, and secondary vibrations around multiple secondary poles simultaneously occur. This occurs frequently, and as shown in FIG. 5, the wave transmission direction is diffused, causing the problem that the wave is transmitted in an unnecessary direction, the phase of the sound is disturbed, and the directivity is deteriorated. In addition, when a piezoelectric plate is used as a wave receiver, the sub-pole picks up waves from various directions other than the sound waves to be detected, generating noise and causing S
/N ratio will be lowered.

An object of the present invention is to provide a piezoelectric transducer equipped with a piezoelectric plate that can reduce transmission and reception of waves at the sub-pole as much as possible.

Means for Solving Problems> The present invention forms a common electrode covering almost the entire surface on the negative side, and a main electrode in the center of the other side, and a common electrode in the peripheral direction of the negative side. ~ A piezoelectric plate that is polarized in the thickness direction by forming multiple sub-electrodes, applying a maximum voltage to the main electrode, and applying a voltage that gradually decreases toward the periphery of each sub-electrode. It is characterized by having the following.

Effect> Since the voltage applied to the piezoelectric plate was high at the center and gradually lowered toward the periphery, the center was highly polarized compared to the periphery. Therefore, the piezoelectric effect and electrostrictive effect are enhanced in the central portion.

Therefore, when used as a wave transmitter, the sub-vibration at the sub-pole is relatively reduced compared to the main vibration at the main pole.

Furthermore, when used as a wave receiver, the central part has higher sensitivity than the surrounding area, and the signal voltage generated from the main pole becomes larger. Therefore, the threshold value of the signal voltage in the control circuit can be increased, and the signal picked up by the sub-pole is canceled.

<Example> An embodiment of the invention will now be described with reference to FIG. 1.2.

l is a disc-shaped piezoelectric rubber sheet, which is an example of a piezoelectric material, and is made of synthetic rubber with piezoelectric ceramic powder such as lead titanate, barium titanate, lead zirconate titanate, etc. dispersed therein; A common electrode 2 covering the entire surface is formed. Further, on the other surface, a circular main electrode 3 and sub-electrodes 4.5 sequentially surrounding the electrode 3 in a non-contact manner are formed at the center thereof. The electrodes 2 to 5 are made of conductive rubber or the like.

The stop layer comb sheet 1 includes a common electrode 2 and main electrodes 3 to 5.
In the meantime, a DC voltage is applied so that the main electrode 3 is at its maximum, and the auxiliary electrode 4 and the auxiliary electrode 5 become lower in this order.

As a result, a high voltage is applied to the piezoelectric rubber sheet 1 at its center, and the piezoelectric rubber sheet 1 is highly polarized, and the degree of polarization gradually decreases toward the periphery.

As a means for applying voltage to the electrodes 3-5, a common DC power source is used as shown in FIG. 3, and a circuit 10 is used which is connected in parallel to each electrode 3-5. In the circuit IO, one resistor 11 is connected to the sub-electrode 4, and two resistors 11 are connected to the sub-electrode 5. As a result, the voltage applied to the main electrode 3 becomes maximum, and each resistance resistor 11 causes the sub-electrode 4. The voltage applied to the sub-electrode 5 will gradually decrease.

When such a circuit 10 is used, it can also be applied to the case where the piezoelectric rubber sheet 1 is made to oscillate.

In this case, an alternating voltage is applied to the circuit 10. This applied voltage is also applied to the common electrode 2. The vibration is maximum between the main electrodes 3, and therefore the vibration at the main electrode is maximum. Also, when used as a receiver, one circuit 1o can be used as is, and the resistor 11 attenuates the signal from the sub-pole, so that the signal from the common electrode 2. A large signal voltage can be extracted from between the main electrodes 3.

Therefore, by using the configuration of the circuit 10, excellent wave transmission and reception can be achieved in addition to the effects of the present invention.

The means for applying voltage to the main electrode 3 to the sub-electrode 5 may be applied by different power sources, and various means may be provided.

Further, the piezoelectric rubber sheet 1 may have various shapes such as a rectangular shape.

When the directional characteristics of the piezoelectric rubber sheet 1 manufactured by this polarization were tested, the results were as shown in FIG. 4, and it was shown that the secondary vibrations were suppressed to less than -30 dB and were significantly reduced. In other words, it was confirmed that the directivity was improved.

<Effects of the Invention> As described above, the present invention is characterized in that the voltage applied to the piezoelectric plate provided to the piezoelectric transducer is high at the center and gradually lowered toward the periphery. The area is highly polarized compared to the surrounding area, and the piezoelectric effect and electrostrictive effect are high at the center, which serves as the main pole, and are relatively low at the periphery. Therefore, in the transmitter, the sub-vibration at the sub-pole is significantly reduced compared to the main vibration at the main pole, and the directivity characteristics are improved. In addition, in the receiving type, the signal voltage generated from the main pole is dramatically larger than that generated at the sub-pole.
A good signal corresponding to the sound wave to be detected can be obtained, and there are excellent effects such as an improvement in the S/N ratio.

[Brief explanation of drawings]

The accompanying drawings show an embodiment of the present invention, in which FIG. 1 is a longitudinal side view, FIG. 2 is a perspective view thereof, FIG. 3 is a longitudinal side view showing a polarizer, and FIG. 4 is a directional characteristic diagram of the present invention. FIG. 5 is a directional characteristic diagram of a conventional configuration. 1; Piezoelectric rubber sheet 2; Common electrode 3; Main electrode 4,
5; Sub-electrode 10; Circuit Figure 1

Claims (1)

[Claims] On one side, a common electrode is formed that covers almost the entire surface, and on the other side, a main electrode is formed in the center, and the main electrode is formed in the peripheral direction.
forming a plurality of sub-electrodes and applying a maximum voltage to the main electrode;
A piezoelectric transducer comprising a piezoelectric plate that is polarized in the thickness direction by applying a voltage to each sub-electrode so that it gradually decreases toward the periphery.