JPH02138889A - Transmitter-receiver of ultrasonic wave - Google Patents

Abstract

PURPOSE:To attenuate transmitted vibrations quickly and thereby to enable detection of an object located at a short distance by bonding and fixing a piezoelectric vibrator to a metal case with an ultrasonic wave absorber interposed therebetween. CONSTITUTION:An ultrasonic wave absorber 7 is provided inside a metal case 9, and a piezoelectric vibrator 1 transmitting and receiving an ultrasonic wave on the front side is provided on said ultrasonic wave absorber 7. Moreover, a piezoelectric vibrator 1 transmitting and receiving a 1/4 wave is provided in front of said vibrator, and an acoustic matching layer 6 of 1/4 is provided in front of the 1/4-wave vibrator. Furthermore, a screwing part 8 for fixing an ultrasonic wave transmitter-receiver to a fixing element is provided in the rear of the metal case 9. While the ultrasonic wave absorber 7 is filled up in the whole of the rear part of the metal case 9, the thickness of the screwing part 8 is made small and the ultrasonic wave absorber 7 is filled up also inside of the part 8, whereby the resonance of the entire metal case 9 is held down. Accordingly, the ringing of the ultrasonic wave transmitter-receiver can be shortened and the detection of an object at a short distance is enabled.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is based on emitting pulsed ultrasonic waves and measuring the time it takes for the ultrasonic waves to reflect from an object to be detected and return. , the distance to the object to be detected and the ultrasonic transducer used in the ultrasonic measuring device for non-contact detection of the right position.

Conventional technology In general, ultrasonic transducers that transmit and receive airborne ultrasonic waves are widely used to detect the position of products and detect the presence or absence of objects. Some devices using high frequencies of 100KH2 to several MHz have also appeared.

Two examples of such ultrasonic transducers are shown in FIGS. 3 and 4, respectively.

The ultrasonic transducer d in Fig. 3, the piezoelectric vibration A1 which performs spreading vibration, the resin case 72 which acts as a wavelength acoustic mariching layer and increases the efficiency of transmitting and receiving ultrasonic waves into the air. It has been established. .

On the other hand, FIG. 4 shows an ultrasonic transducer having a piezoelectric vibrator 1 that performs thickness longitudinal vibration. 111% wavelength acoustic matching layer 6 on the piezoelectric vibrator 1, and an ultrasonic absorption layer on the back side to lower the Q of the piezoelectric vibrator 1 (to reduce ringing and absorb ultrasonic waves to the back side) A body 7 is housed in a metal holder 9 and attached to the holder 3.

Problems to be Solved by the Invention However, in the case of a resin case type as shown in FIG. 3, when the piezoelectric vibrator 1 spreads and vibrates, the resin case 72 also resonates, and even after the ultrasonic wave is transmitted, the resin case 72 remains unchanged. The vibration continues for a long time, and this vibration is captured by the piezoelectric vibrator 1 as ringing.

As a result, when attempting to detect the position of an object using this ultrasonic transducer, ringing of the transmission signal that drives the ultrasonic transducer remains for a long time. Therefore, when an ultrasonic wave transmitted from a transducer hits an object to be detected, is reflected, returns to the transducer, and is received again, the received signal is hidden by this ringing, making position detection impossible.

In addition, although the type shown in FIG. 4 has been improved to reduce belling compared to the above-mentioned type, the effect is insufficient. In other words, since the piezoelectric vibrator 1 is fixed to the metal case 79 with the adhesive 10, when a transmission signal is input to the piezoelectric vibrator 1 from the lead wire 11.12VC, the vibration of the piezoelectric vibrator 1 is not sufficiently absorbed. The ringing of the transmitted wave remains for a long time when it is transmitted to the steel case 79.

Therefore, the present invention aims to provide an ultrasonic transducer capable of shortening transmission ringing and detecting an object at a close distance.

A means for solving the problems and a means of the present invention for solving the above-mentioned problems is to adhesively fix a piezoelectric vibrator to a metal case via an ultrasonic absorber.

In other words, with the above means, the vibrations generated from the piezoelectric vibrator are less likely to be transmitted to the metal case 7, and the transmitted vibrations can be quickly attenuated, so the ringing of the transmitted signal is reduced and this As a result, objects at close range can be detected.

Actual case Embodiments of the present invention will be described below with reference to the drawings.

6. FIGS. 1 and 2 are cross-sectional views of ultrasonic transducers showing embodiments of the present invention, respectively. In the embodiment shown in FIG. 1, an ultrasonic absorber 7 is provided in a metal turf 9, and a piezoelectric vibrator 1 that transmits and receives ultrasonic waves from the front side is placed on the ultrasonic absorber 7 via the ultrasonic absorber 7. A 'A-wave acoustic matching layer 6 is provided on the front surface thereof. The piezoelectric vibrator 1 has a metal case 79.
The acoustic matching layer 6 is also in a non-contact state with the metal case 79. The acoustic matching layer 6 is made of a material with low acoustic impedance, such as porous resin or silicone rubber, which has good compatibility with air, and is formed into one or two layers. The metal case 79 includes the ultrasonic absorber 7 and the piezoelectric vibrator 10
The first step is to minimize the area of nearby contact points.
As shown in the figure, a notch 13 may be provided in the inner wall surface, or as shown in FIG. 2, notches 13 and 14 may be provided at two locations. Signal cable 1 for inputting or outputting signals
1 is connected to the back electrode of the piezoelectric vibrator 1 , and the ground cable 12 is connected to the metal case 79 and the surface electrode of the piezoelectric vibrator 1 . By connecting the ground cable 6 and the base 12 in this manner, interference caused by external noise is prevented. A screw tightening portion 8 is provided at the rear of the metal case 79 for fixing the ultrasonic transducer to a fixed portion. Since the presence of such a screwed portion 8 is disadvantageous for shortening the ringing, in this embodiment, the entire rear part of the metal case 79 is filled with the ultrasonic absorber 7, and the thickness of the screwed portion 8 is The thickness was reduced, and the inside of this was also filled with the ultrasonic absorber 7. These make it possible to suppress the resonance of the entire metal turf 9 and shorten the ringing of the ultrasonic transducer.

Effects of the Invention As described above, according to the present invention, it is possible to shorten the ringing of transmission from an ultrasonic transducer, and it is possible to detect an object at a close distance.

[Brief explanation of the drawing]

FIGS. 1 and 2 are sectional views of an ultrasonic transducer according to an embodiment of the present invention, and FIGS. 3 and 4 are sectional views of a conventional ultrasonic transducer. γ \ 1...Piezoelectric vibrator, 6...Acoustic matching layer, 7...Ultrasonic absorber, 8...Screw tightening part, 9...・Metal case.

Claims (2)

[Claims] (1) Consists of a metal case, a piezoelectric vibrator that is housed in the metal case and transmits and receives ultrasonic waves from the front of the metal case, and an ultrasonic absorber that is adhesively fixed to the back of the piezoelectric vibrator. , an ultrasonic transducer in which the piezoelectric vibrator is fixed to a metal case via an ultrasonic absorber. (2) A screw tightening part for attaching the metal case is formed on the rear surface of the metal case, and this screw tightening part has a hollow part inside, and this hollow part is filled with an ultrasonic absorber. The ultrasonic transducer according to scope 1.