JPS62224199A - Piezoelectric element for sound wave transmission and reception - Google Patents

Abstract

PURPOSE:To realize mass production of a piezoelectric element provided with an electrode shape of short shading whose side lobe is suppressed, by forming at least one electrode of a piezoelectric plate to a specific shape. CONSTITUTION:A piezoelectric rubber plate 1 is formed to a waveform being symmetrical in the upper and lower directions, which has a prescribed length size (a) on an X axis, and a width size (b) on a Y axis, being shorter than the size (a), has the maximum width size b-1 in the center part of the length, and also, in which the width size decreases gradually toward both ends in the length direction and both end parts become the minimum width size b-2. The shape of the piezoelectric rubber plate 1 is shaped to the same shape as a window shape which is derived by a Kayser's window function shown in the expression, electrode layers 2, 3 of the same shape as a plane shape of the piezoelectric rubber plate 1 are formed on both its faces, and a polarized area 4 of the electrode layers 2, 3 is made to conform with the plane of the piezoelectric rubber plate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a piezoelectric element for transmitting and receiving waves, and its field of application is the transmission and reception of sound waves such as hydrophones and ultrasonic flaw detectors.

(Prior Art) In the design of a hydrohorn, in addition to the beam, side lobes are also important parameters to consider.

As shown in Figure 5.6, the sound wave characteristics of 2a and 21" h cedar boards whose sides are flat with the X glaze and the Y axis, respectively, are proportional to the number of eyebrow waves, area, and velocity, and are on the X axis. The directivity index is inversely proportional to the distance in the radial/j direction, and decreases as the angle θ increases, then increases again and reaches a maximum.

This is called a side lobe and reaches 20% or more in the case of a square plate, which is undesirable in the case of a hydrohorn etc. as it causes false detection. As this sidelobe suppression means, there are a method of changing the transfer response (amplitude shading) and a method of changing the transfer area (shape shading).

The latter shape shading is a parameter related to sidelobe suppression of the hydrohorn, and is also a window function. Many such window functions w(×〉) have been reported so far, but Kaeser's is the following (where g〉0).

This window function is said to be the optimal window because the beam width at the main pole is less widened.

(Problems to be Solved by the Present Invention) The present invention reflects the prior art regarding the electrode shape of a piezoelectric plate whose one surface is used as a sound wave transmitting/receiving surface, as described in the previous section, and enables mass production, which is essential for practical use. This is an issue that needs to be resolved.

(Means for Solving the Problems) The present invention aims to solve the problems described in the previous section, and it is possible to solve the problems described in the previous section by defining a predetermined length dimension (a) on the X-axis, and a predetermined length dimension (a) on the ) has a shorter medium dimension (1)) on the Y-axis, and consists of a piezoelectric plate, one of which is used as a sound wave transmission and reception surface, and excitation electrodes formed on both sides of the piezoelectric plate,
The shape of at least one 74-pole of the piezoelectric plate is a vertically symmetrical waveform having a maximum medium dimension at the center of the length of the piezoelectric plate and gradually decreasing the r width dimension toward both ends of the piezoelectric plate. An example of its implementation is that the waveform shape of the electrode in 11q is made the same as the window shape determined by the Kaeser window function.

Examples of the present invention will now be described.

(Example) As shown in Fig. 1.2, the present invention involves shaping a piezoelectric rubber plate or other piezoelectric plate that is easy to shape by cutting to match the shape of an electrode, and shaping piezoelectric plates on both sides of the plate. In the first embodiment, electrode layers of the same shape are formed in a planar shape, and one or both of the piezoelectric plates have a shape unrelated to the electrode shape, such as a rectangular shape, as shown in Figure tjS3.4. This device has a second embodiment in which an electrode layer is formed in a vertically symmetrical waveform.

In the first embodiment, the piezoelectric rubber plate 1 is
The piezoelectric rubber plate 1 has a predetermined length dimension (a) on the axis and a medium dimension (b) on the Y axis that is shorter than the specified length dimension (,), and the piezoelectric rubber plate 1 has the maximum medium dimension (,) at the center of the length. b-, ), and the shape of the piezoelectric rubber/ill is a vertically symmetrical waveform in which the medium dimension gradually decreases toward both ends in the length direction and the minimum medium dimension (b-z) is at both ends, and the shape of the piezoelectric rubber/ill is It is shaped into the same shape as the window shape determined by the above-mentioned Kaeser window function, and electrodes M2.3 having the same planar shape as the piezoelectric rubber plate 1 are formed on both sides of the window shape, and the polarization region 4 of the electrode layer 2.3 is piezoelectrically formed. This is made to match the plane of the rubber plate 1.

In place of the piezoelectric rubber plate 1, it is also possible to use a piezo plate other than rubber, such as a piezoelectric ceramic or a 7-shell salt plate, shaped as shown in Figure #S1.

The second embodiment is a rectangular piezoelectric plate 1 such as a piezoelectric ceramic or a piezoelectric rubber plate.
An electrode 12.13 having the same shape as the electrode 2.3 shown in FIG. match.

However, in this embodiment, one electrode forming surface is used for sound wave emission and wave reception. For example, if the forming surface of electrode 12 is used, electrode 13 corresponds to the entire area of electrode 12. Even if the shape is rectangular, elliptical, etc., the polarization effect is uniform.

The formation of each electrode in the first embodiment and the second embodiment is made of silver! It is applied using conventionally known methods such as baking a film or gluing silver foil.

(For use) Chloroprene rubber and lead titanate in a volume ratio of 40:60.
Horizontal (a)
b) x thickness = 100 x 20 x 2 ++n.

Electrodes 12 with a thickness of 0.5+am made of a conductive rubber material containing silver powder are placed on the front and back surfaces of a piezoelectric rubber plate 11 formed into a rectangular size.
．． In the structure of the rectangular plate shown in Fig. 3.4, in which the electrode 12.13 is integrally adhered, the upper and lower sides of the electrode 12.13 are defined by the formula of the cape-window relationship: i=LOOmm, b=20+am,
The results of measuring the directivity characteristics of the piezoelectric element of the present invention, which was shaped into a vertically symmetrical waveform along the function curve determined under the condition of Da = 3π, are as follows! @ As shown in Figure 7, we confirmed that the side lobe was suppressed to -30 dB or less. This also proves the effectiveness of the present invention. Note that FIG. 8 shows the measurement results of the directional characteristics of a conventional rectangular plate (=100 ma+5b=20, α=0), in which many side lobes are observed.

(Effects) The wave transmitting and receiving piezoelectric element of the present invention has a predetermined length dimension (, ) on the Y-axis and a middle dimension (, ) on the Y-axis that is shorter than the length dimension (a).
b), which consists of a piezoelectric plate whose one side is used as a sound wave transmitting/receiving surface, and excitation electrodes formed on both sides of the piezoelectric plate, in which the shape of at least one electrode of the piezoelectric plate is The piezoelectric plate has a vertically symmetrical waveform having a maximum dimension at the center and a gradually decreasing middle dimension toward both ends of the piezoelectric plate, and the symmetrical waveform shape of at least one electrode is defined by the Kaeser window function. This is an embodiment in which the window shape is the same as that determined by the formula, and this configuration makes it possible to mass produce piezoelectric elements having an electrode shape with shape shading that suppresses side lobes.
(g) It produces an effect that can be applied to applications such as hydrophones and ffi sonic flaw detectors.

[Brief explanation of drawings]

1 to 4 show embodiments of the present invention, FIG. 1 is a partially cutaway plan view of the first embodiment, FIG. 2 is a side view taken along the line A-Ai in FIG. The example plan view, Figure 4 is Figure 3B-
B-line cut side view, PtIJ5 figure is a perspective view for illustration purposes only,
FIG. 6 is a side view of the same, FIG. 7 is a directional characteristic diagram of a piezoelectric element for wave transmission and reception according to the present invention, and FIG. 8 is a directional characteristic diagram of a conventional piezoelectric element for wave transmission and reception.

Claims (1)

[Claims] 1) A predetermined length dimension (a) on the X-axis and the length dimension (a
), the piezoelectric plate has a width dimension (b) on the Y axis that is shorter than A transmission/reception device characterized in that the shape of at least one electrode of the plate is a vertically symmetrical waveform having a maximum width at the center of the length of the piezoelectric plate and gradually decreasing the width toward both ends of the piezoelectric plate. Piezoelectric element for waves. 2) Claim 1, characterized in that the waveform shape of the electrode is the same as the window shape determined by the following Kaeser window function formula ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (where α>0) A piezoelectric element for transmitting and receiving waves as described in .