JPS60102577A - Ultrasonic transmitter receiver - Google Patents

Abstract

PURPOSE:To attain to enhance the accuracy in distance measurement and ultrasonic image pick-up by eliminating air fluctuation caused by high speed scanning of ultrasonic beam, by providing an acoustic matching body. CONSTITUTION:The ultrasonic signal 4 emitted from a piezoelectric vibrator 1 is effectively passed through an ultrasonic wave propagating medium 6 such as water or an inert fluorine contained liquid such as silicone oil by the first acoustic matching body 5 provided to the front surface of the vibrator 1 and subsequently passed through the acoustic window 8 provided to the front surface of an ultrasonic cell 7 and efficiently emitted into air by the second acoustic matching body 9 provided to the front surface of the window to be converted to an ultrasonic signal 11. This signal 11 is reflected from an object 12 and received by the vibrator 1 through the same propagating route. Because the vibrator 1 is blocked from air 10 at this time, no air fluctuation is generated even if high speed scanning is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrasonic transducer used in an ultrasonic distance measuring device or the like.

Configuration of conventional examples and their problems The frequencies used in conventional aerial ultrasonic distance measuring devices are approximately 20 kHz to 1 kHz, which means that the ultrasonic wavelength is relatively long and the noise level is high. Highly accurate distance measurement of 1 or 10 cm
It was difficult to perform the following short-distance measurements.

For this reason, attempts have been made to use an ultrasonic transducer that can transmit and receive an ultra-high frequency of approximately 1 halo from several six songs. When this one-stone ultrasonic transducer is used in a distance measuring device or the like, fluctuations in the air due to wind, temperature changes, etc. cause large fluctuations in the ultrasonic wave transmission and reception signals, resulting in a deterioration in measurement accuracy. Particularly when performing fan-shaped scanning with an ultrasonic transducer to measure a wide range, air fluctuations caused by rotation of the ultrasonic transducer become a problem.

Furthermore, in the conventional ultrasonic transducer, as shown in FIG. It has become. As is well known, the characteristics of the material used for the acoustic matching body 2 are preferably close to the square of the product of the acoustic impedances of the pressure 14i vibrator 1 and the air, and therefore the piezoelectric vibration When a general piezoelectric ceramic material is used as the element 1, the acoustic impedance suitable for the acoustic matching body 2 corresponds to two layers m'·S of 0.1 to I.times.106. However, even if these ranges are used, the difference in acoustic impedance between the piezoelectric vibrator 1 and the air is extremely large, approximately 105:1, so the frequency band characteristics of the ultrasonic transducer are narrow and the response characteristics are poor. .

On the other hand, in a medical ultrasonic transducer, a method is well known in which a piezoelectric vibrator that transmits and receives several ultrasonic waves is mechanically scanned in a fan shape at high speed within an ultrasonic cell to obtain five ultrasonic tomograms. However, in this case, the object to which the ultrasonic waves propagate is the human body, and if VC ultrasonic waves are emitted in the air, the sensitivity will be extremely low and it will be difficult to use.

Purpose of the Invention The present invention has been made to solve the conventional problems as described above. The present invention provides an efficient ultrasonic transducer that can operate satisfactorily in the ultrasonic mantissa band and can be used in ultrasonic distance measuring devices, ultrasonic imaging devices, and the like.

Structure of the Invention In order to achieve this object, the present invention includes a piezoelectric vibrator, I
] E-electrical vibration excitation vibrator The first element provided in the 1iJ curve of the piezoelectric vibrator controls the acoustic matching with the liquid which is the sound wave propagation medium.
an ultrasonic cell with a built-in acoustic matching body; an acoustic window provided in front of the ultrasonic cell; a second acoustic matching body for efficiently transmitting and receiving ultrasonic waves into the air; Equipped with ultrasonic transmission and reception? +M (j:' 4iE is provided. With this configuration, even if the ultrasonic beam is scanned at high speed, there will be no air fluctuations and the loss of ultrasonic waves will be extremely small, and even in the high frequency range. It is possible to measure distances sufficiently.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view showing an ultrasonic transducer according to an embodiment of the present invention. In the figure, an ultrasonic signal 4 of several 6kll+ emitted from a piezoelectric vibrator 1 made of piezoelectric ceramic or the like is transmitted to a first acoustic matching body 5 (for example, a first acoustic matching body 5 made of tungsten epoxy A layered structure (or a two-layered structure consisting of Bacara and epoxy) efficiently absorbs water, oils such as silicone oil, or liquids such as fluorinated inert liquids such as Dyfloil and Fluorinert (trade name). super)−
The entire one-wave propagation medium 6 passes through the ultrasonic self-acoustic window 8 made of polyethylene or dimethylpentene, and the second acoustic matching body 91tl provided in front of the acoustic window 8 is made of silicone rubber membrane or plastic hollow. The ultrasonic signal 11 efficiently radiated into the air 10 by a single-layer tiled structure made of a silicone rubber membrane filled with spheres, or a two-layered structure made of two layers of silicone rubber or epoxy resin filled with hollow spheres with different acoustic impedances is the target. It is reflected by the object 12, passes through the same propagation path again, is received by the piezoelectric vibrator 1, and is determined by a signal processing system (not shown) at a distance = t nt
TL and ultrasound +@ are provided at home. 1, piezoelectric vibrator 1
When performing fan-shaped scanning, it is attached to the tip of a rotating system or reciprocating vibration system, making high-speed scanning possible. When scanning the rotation system here, the motor 14 provided in the scanner (71713) rotates the pulley 16 provided on the piezoelectric vibrator 1 side via the belt 16, and the piezoelectric vibrator 1 is rotated. Rotate.Here, 3 is the back load, 17 is the rotation center, and 18 is a sound absorber that absorbs unnecessary ultrasonic signals in the ultrasonic self, and is provided in the part other than the acoustic window 8. .

When using the above-mentioned ultrasonic transducer,
, the transducer 1 is scanned at high speed within the ultrasonic self which is cut off from the air 10, and the first and second sounds #a! The combinations 5 and 9 provide acoustic matching between the piezoelectric vibrator 1 and the liquid ultrasonic propagation medium 6, and between the ultrasonic propagation medium 6 and air 10, respectively.

As described above, according to this embodiment, the piezoelectric vibrator 1 is isolated from the air 10, so even if the piezoelectric vibrator 1 is mechanically fed by the scanning mechanism 13, no air fluctuation occurs. In other words, distance measurement can be performed relatively stably even when ultrasonic signals of several hundred yen or more are transmitted and received in the air.

By selecting paulownia wood for the ultrasonic propagation medium 6, the first and second acoustic matching bodies 5 and 9 can be constructed from an easily available matching layer (A material), improving sensitivity and frequency band characteristics. , it is possible to efficiently transmit and receive ultrasonic waves in the air.

Note that the shape of the piezoelectric vibrator 1 may be a concave vibrator or a flat & camera element with an acoustic lens attached thereto for focusing, as is generally well known. Further, the shape of the ultrasonic cell is not limited to a cylindrical shape either.

FIG. 3 is a sectional view showing another embodiment of the present invention. The ultra-blind transmitter/receiver has piezoelectric vibrating elements 19 and 5 which are arranged adjacent to each other and which are scanned electronically, and a first acoustic matching body 20 provided in front thereof in the same way as in the previous embodiment, and an ultrasonic wave Propagation medium 21
an acoustic window 23 provided on its ni1 surface, a second acoustic matching body 24 provided on its fjiJ 1fjl, and a surrounding sound absorbing body 25. Sound absorber 26 on the back
It consists of

In such an ultrasonic transducer, the piezoelectric vibrator group 19 is sequentially switched electronically for transmission and reception, so that distortion due to vibration and durability are reduced because it does not depend on mechanical constant strain.
ll restrictions etc. will be relaxed. Furthermore, piezoelectric vibrating element group 19
The ratio of the acoustic impedance between the and 'MA sound wave propagation medium 21 is approximately (10 to 30):1, and the first acoustic matching body 20
Broadband frequency characteristics can be obtained by Furthermore, the acoustic impedance ratio between the ultrasonic propagation medium 21, the acoustic window 23, and the air 27 in the second acoustic matching body 24 is as follows:
When all combinations such as water and soft polyethylene are combined, approximately 3X10
3:1, which is the ratio in the conventional structure (105:
Compared to 1), it is extremely small, it is easier to obtain acoustic matching, and it is possible to obtain broadband characteristics. This leads to an improvement in pulse responsiveness, making it possible to transmit and receive short ultrasonic pulse signals, and leading to improved accuracy in ultrasonic distance measurement.

More than the effects of the invention, the present invention includes a piezoelectric vibrator installed in an ultra-I wave cell filled with an ultrasonic propagation medium, a first acoustic matching body provided in front of the piezoelectric vibrator, Provides an ultra ff1Ji transducer characterized by comprising an acoustic window provided in a cell for advancing and retracting ultrasonic signals, and a second acoustic matching body provided on the outer surface of the acoustic window. Since the piezoelectric vibrator is isolated from the air, there is no air fluctuation even during high-speed mechanical scanning.
The advantage of γi is that it can efficiently radiate ultrasonic waves into the air using different types of acoustic matching bodies, which improves accuracy when used as a transducer for ultrasonic distance measurement or ultratotal wave imaging for one image. /I'.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional ultrasonic wave transducer for airborne use, Fig. 2 is a sectional view of an ultrasonic transducer for aerial use according to an embodiment of the present invention, and Fig. 3 is a sectional view of an ultrasonic wave transducer for use in the air according to an embodiment of the present invention. It is the same sectional view in an Example. 1... Piezoelectric vibrator, 5, 20... First acoustic matching body, 6, 21... Ultrasonic propagation medium, 7, 22
... Ultrasonic cell, 8 ... Acoustic window, 9,2
4...Second acoustic matching body, 13...Scanning mechanism, 14...Motor, 16...Belt,
19...Piezoelectric vibrating element group.

Claims (3)

[Claims] (1) a piezoelectric vibrator installed in an ultrasonic cell filled with an ultrasonic wave propagation medium; 5. a first acoustic matching body provided in front of the piezoelectric vibrator; 1. An ultrasonic transducer comprising: an acoustic window through which an ultrasonic signal passes; and a second acoustic matching body provided on an outer surface of the acoustic window. (2) The ultrasonic transducer according to claim 1, wherein the pressure 7L transducer is mechanically rotated or oscillated within the ultrasonic cell.・ (3) The piezoelectric vibrator is composed of a group of multiple piezoelectric vibrating elements,
2. The ultrasonic transducer according to claim 1, wherein said piezoelectric vibrating element group is electronically scanned.