JPS6350885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic delay line in which one piezoelectric transducer having both input and output functions is attached to a delay medium such as glass. The present invention provides an ultrasonic delay line that improves conversion efficiency by correcting deviations in propagation paths caused by the directivity of the transmitted sound waves.

Waves emitted from a single source propagate with a certain spread from the source, so the strength varies depending on the direction of the source, and this phenomenon of waves is generally called directional. Directivity varies depending on the wave frequency, and waves with lower frequencies tend to propagate further away from the main axis of the emission source. Ultrasonic delay lines that utilize sound waves propagating in a delay medium have the disadvantage that the sound waves deviate from a predetermined propagation path due to the above-mentioned directivity, resulting in a reduction in mechanical-electrical conversion efficiency in the piezoelectric transducer element.

This drawback will be specifically explained with reference to FIG. 1, which shows a conventional delay line. In the figure, 1 is a glass plate serving as a delay medium, and an electrode 2 is formed on one side of this glass plate 1. 3 is a piezoelectric ceramic plate having both input and output functions, and this piezoelectric ceramic plate 3 is attached to the electrode 2 by soldering or the like. 4 is an electrode attached to the piezoelectric ceramic plate 3, and this electrode 4 and the electrode 2
Lead wires 5a and 5b are connected to these, respectively.

In FIG. 1, when a signal voltage is applied between lead wires 5a and 5b, the signal voltage is converted into a sound wave that vibrates mechanically by the piezoelectric ceramic plate 3, and the glass plate 1
The light propagates toward the reflection plane 1a of . At this time, since the sound waves have directivity, a sound wave component 6a propagates in the direction of the main axis, a sound wave component 6b that deviates from the direction of the main axis,
6c etc. occur. The sound wave component 6a propagating in the principal axis direction is incident on the reflection plane 1a of the glass plate 1 at an angle of 90°, returns to the piezoelectric ceramic plate 3 through the same reflection path as the incident path, and undergoes mechanical-electrical conversion. A signal voltage delayed by 2l/V (l is the illustrated length of the glass plate 1, V is the speed of the sound wave) from between the lead wires 5b and 5b is obtained. On the other hand, since the sound wave components 6b, 6c, etc. shifted from the principal axis direction are incident on the reflection plane 1a of the glass plate 1 at an angle other than 90°, the reflected waves 6'b, 6'c follow a reflection path different from the incident path. However, it does not return to the piezoelectric ceramic plate 3.

As explained above, in conventional ultrasonic delay lines, due to the directivity of the sound waves, sound wave components that do not reach the piezoelectric transducer are generated, and especially when the delay medium is long or the frequency of the sound waves is low, the sound wave components are The deviation from the main axis was large, resulting in a decrease in conversion efficiency.

In order to compensate for the above drawbacks, attempts have been made to increase the signal frequency and increase the dimensions of the piezoelectric transducer, but the signal frequency and piezoelectric transducer are not suitable for the ultrasonic delay line. The above method was not appropriate because of the

The present invention eliminates the above-mentioned conventional drawbacks, and provides an ultrasonic delay line equipped with a delay medium formed with a reflection curved surface that corrects deviation from the propagation path due to the directivity of the sound wave emitted from a piezoelectric transducer. It is something to do.

Embodiments of the present invention will be described below based on the drawings. FIG. 2 is a front view of an ultrasonic delay line in one embodiment of the present invention, and the same parts as in FIG. 1 showing the conventional example are given the same numbers. A feature of the present invention is that the sound wave reflecting surface 7a of the glass plate 7, which is a delay medium, is a part of a spherical surface with a radius R centered on the midpoint 0 of the sound wave emission surface of the piezoelectric ceramic plate 3. .

When the sound wave reflecting surface 7a of the glass plate 7 is formed in such a shape, the sound wave component 8a propagating in the main axis direction and the sound wave components 8b and 8c propagating in a direction shifted from the main axis are both reflected by the reflection surface 7a,
It passes through the same reflection path as the incident path and reaches the center of the reflection surface 7a. Since the piezoelectric ceramic plate 3 returns to the midpoint 0, no loss of sound waves occurs, and the conversion efficiency is improved compared to the conventional case.

FIG. 3 shows yet another embodiment of the ultrasonic delay line of the present invention. In this embodiment, the glass plate 9, which is a delay medium, has four flat surfaces 9a to 9d and one curved surface 9e, and the flat surface 9a has electrodes 2, 4, A piezoelectric ceramic plate 3, which is a piezoelectric transducer, and lead wires 5a and 5b are attached. The feature of this embodiment is that the number of reflective surfaces is large, and the shape of the curved surface 9e is processed into a curved surface such that the incident path of the sound wave and the reflection path are the same. That is, the sound wave components 10a, 10b, 10c radiated from the piezoelectric ceramic plate 3 are each on the plane 9.
d, 9c, and 9b are incident and reflected at different angles and incident on the curved surface 9e, but on the curved surface 9e, the incident path and the reflection path are the same, and the sound wave components 10a to 10b are incident on the curved surface 9e.
10c returns to the piezoelectric ceramic plate 3 along the same route. Such a curved surface 9e can be easily defined experimentally.

When the glass plate 9 is formed in this manner, the path of the sound wave becomes longer, so a longer delay time can be obtained, and the conversion efficiency can be significantly increased compared to the conventional method.

As explained above, the ultrasonic delay line of the present invention has the effect of increasing the conversion efficiency even more than conventional ones by processing the reflection surface of the delay medium into a predetermined curved surface, and has extremely high practical value. It is something.

[Brief explanation of the drawing]

Fig. 1 is a front view of a conventional ultrasonic delay line, Fig. 2 is a front view of an ultrasonic delay line in an embodiment of the present invention, and Fig. 3 is a front view of an ultrasonic delay line in another embodiment of the present invention. It is a diagram. 3...Piezoelectric conversion element (piezoelectric ceramic plate), 7, 9...
...Delay medium (glass plate), 7a, 9e...curved surface (reflecting surface).

Claims (1)

[Claims] 1 A piezoelectric transducer for both input and output is attached to one side of a delay medium such as a glass plate, and the sound wave reflecting surface of the delay medium is processed into a curved surface so that the sound wave's incident path and reflection path are the same. Ultrasonic delay line.