JPS62271600A - Piezoelectric type directional sound wave generating device - Google Patents

Abstract

PURPOSE:To expand a range where directivity can be controlled by coaxially arranging plural piezoelectric elements and exciting said elements by electrical signals with time delays. CONSTITUTION:Output signals from a signal source 25 are impressed on the piezoelectric elements 11-14 through delay elements with delay times tau1-tau4, and sequentially excited. Radial sounds from the piezoelectric elements 11-14 are strengthened with each other by canceling the time difference between signals at a distance (x) on a central axis and a space path difference to be concentrated on the place. Namely, by adjusting the time delay of the electric signal, the sound waves can be concentrated on any place in the space. As a result the titled device can be widely used for a sound emitting body in a hindrance detector, a distance meter and ultrasonic measuring instruments for hight of built-up snow, etc.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] This invention relates to a sound wave generator whose directivity can be electronically controlled.

[Conventional technology]

Sound wave generators include speakers, magnetostrictive sounding bodies, piezoelectric sounding bodies, etc. Among these, piezoelectric sounding bodies are small, lightweight, robust, inexpensive, and have relatively high conversion efficiency, so they are mainly used for simple applications. Its use is rapidly expanding.

[Problems that the invention attempts to solve]

Piezoelectric sounding bodies are expected to be applied to the field of measurement using ultrasonic waves, but the range of applications is limited because it is difficult to control the directivity of the emitted sound waves.

In the past, there have been examples in which piezoelectric elements are arranged in a straight line to control directivity, but the problem with method B is that the range in which directivity can be controlled is limited to a specific plane in space.

The present invention was made to solve the above problems, and an object of the present invention is to provide a piezoelectric directional sound wave generator whose directivity can be controlled over a wider range.

[Means for solving problems]

A piezoelectric directional sound wave generator according to the present invention includes piezoelectric elements arranged in a concentric ring shape and an exciter that excites these piezoelectric elements with electric signals having a time delay with respect to each other. .

[Effect]

In the invention of B, a plurality of piezoelectric elements arranged in a concentric ring shape are sequentially excited by No. 48 with a time delay from the exciter, and the sound waves radiated from the piezoelectric elements are
1 combined [obtain the directivity of 1 target.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1(a) and 1(b) show an embodiment of the present invention. FIG. 1(a) shows a front view of a piezoelectric element and a connection circuit of its exciter, and FIG. 1(b) shows an embodiment of the present invention. shows a side view of the piezoelectric element.

In this figure, piezoelectric elements 11, 12, 13, and 14 are arranged concentrically and are formed on the substrate 10. 21,2
In 2.23, the delay time is τl.

τ2. τ3. The delay element τ4 and 25 are signal sources, and these constitute the exciter 20.

Next, the operation will be explained.

The delay times r1 to τ4 of the delay elements 21 to 24 are respectively r, = (a-1-2b)''/2xS r2=4b(a+b)/2xS rs= b (2a+3 b)/2 x Sτ4=
0 However, S: Sound speed a: Distance b between piezoelectric elements 11 and 12 = Distance between piezoelectric elements 12 and 13 and 13 and 14 X: Distance from center axis −V.

In the above, when the output signal from the signal source 25 is applied to each of the piezoelectric elements 11 to 14 via each of the delay elements 21 to 24 and sequentially excited, the radiated sound waves from each of the piezoelectric elements 11 to 14 are as shown in FIG. As shown in b), the time difference and the spatial path difference of the signals cancel each other out at a distance of one distance 11tx from the central axis, and the sound waves strengthen each other and are concentrated here.

FIG. 2 shows a front view of a piezoelectric element and a connection circuit of its exciter, showing another embodiment of the present invention. Figure 1 (a) in Figure B
, (b) indicate the same parts.

Delay elements 25 to 30 have delay times of τ5 to τ10. In the embodiment B, each concentric piezoelectric element other than the center portion is divided into three equal parts 12a.

12b, 12c, 13a, 13b, 13c, 14a.

14b and 14e, and piezoelectric elements 12m and 13a.

(A7 14a is applied with the outputs of delay elements 22-24, piezoelectric elements 12b, 13b, 14b are applied with the outputs of delay elements 25-27, and piezoelectric elements 12c, 13c.

The outputs of the delay elements 28 to 3o are applied to 14C.

Therefore, as in the case of Fig. 1, the delay time of each delay element is y, = (a + 2b)''/2xS τ 2-, and 5 = 7. = 4 b (a - 1 - b)
/ 2 xsτ3=τ6−τe=b (2a +3
b)/2 x Sr1-r7-τ1゜=0 However, S: Speed of sound a = distance between piezoelectric elements 11 and 12a, 12 b, and 12c b: piezoelectric elements 12a and 13a, 13a and 14a, 12b and 13b, When the distances are 13b and 14b, 12c and 13c, and 13c and 14c, the radiated sound waves are concentrated at one distance gIx from the central axis.

By the way, in the embodiment B, each of the concentric piezoelectric elements other than the central part is divided into three parts, so by controlling the delay time of each delay element 21 to 30, the central axis It is possible to concentrate the radiated sound waves not only upward but also diagonally.

In the above embodiment, the piezoelectric elements are arranged concentrically, but the piezoelectric elements are not necessarily arranged concentrically, but may be arranged concentrically. , 1: It is also possible to sweep the emitted sound wave beam by electronically controlling each of the delay elements 21 to 30 using a CCD or the like. If a CCD is used as the delay element, the delay time can be changed proportionally by increasing or decreasing the clock frequency. When this method is applied to the embodiment of FIG. 1, the focus of the emitted sound waves can be changed by changing the clock frequency of the COD.

〔Effect of the invention〕

As explained above, in the present invention, a plurality of piezoelectric elements are arranged in a concentric ring shape, and each of these piezoelectric elements is excited with an electric signal having a time delay from each other, so that the time delay of the electric signal can be adjusted. This allows you to concentrate sound waves anywhere in space.

Therefore, the present invention is expected to be widely used as a sounding body for ultrasonic measurement, such as obstacle detectors, distance meters, and snow height measurement using ultrasonic waves.

[Brief explanation of the drawing]

Figures 1(a) and 1(b) show an embodiment of the invention. Figure 1(a) is a front view of a piezoelectric element and its exciter connection circuit, and Figure 1(b) is a piezoelectric element. Side view of the element, second
The figures are a front view of a piezoelectric element and a connection circuit diagram of its exciter, showing another embodiment of the invention. In the figure, 10 is a substrate, 11, 12, 13, 14 are piezoelectric elements, 20 is an exciter, 21, 22, 23, 24 is a delay element,
15 is a signal source.

Claims (1)

[Claims] A piezoelectric directional sound wave generator comprising a plurality of piezoelectric elements arranged in a concentric ring shape and an exciter that excites each piezoelectric element with an electric signal having a time delay with respect to each other.