JPS5885698A - Ultrasonic transmitter and receiver - Google Patents

Abstract

PURPOSE:To make a directional pattern sharp, by providing a conical diaphragm having a larger bottom surface than a laminated surface, on the center part of a lamination type element, and adding a buffer material to the circumferential part, in an ultrasonic transmitter and receiver using the lamination type element. CONSTITUTION:On the center part of a lamination type element 1, a coupling shaft 2 which has been pierced and fixed is provided, and to this shaft 2, a conical diaphragm 3 having a bottom surface of a larger area than a laminated surface of the lamination type element 1 is fitted. Also, a buffer plate 10 is fitted to the circumferential part of the diaphragm 3 in order to suppress mechanical vibration. Subsequently, the node part of vibration of the lamination type element 1 is elastically fixed to the tip of a supporting base 4 with an elastic adhesive agent 5. As a diameter D of the diaphragm 3 becomes layer, an acoustic pressure half-value angle becomes small like a curve A, and a sharp directional pattern is shown.

Description

[Detailed Description of the Invention] The present invention provides a super-coupled transducer using a bonded piezoelectric element.
The present invention aims to provide an ultrasonic transducer with improved transmitting/receiving sensitivity characteristics and pulse characteristics (transient characteristics).

A piezoelectric ceramic bonded element is often used as a transducer for ultrasonic waves in the air, and is made to be used at the resonance point and anti-resonance point of the flexural vibration of the bonded element. Furthermore, since the mechanical impedance of air is significantly smaller than that of piezoelectric ceramics, the bonded element is combined with the diaphragm to reduce the mechanical impedance.

The structure and characteristics of a conventional ultrasonic transducer are shown in Figures 1 and 2.
Illustrated in the diagram. As shown in Figure 1, a bonding shaft 2 is provided in the center of the bonded piezoelectric element 1 and is fixed through the bonding shaft 2, and a diaphragm 3 is attached to the bonding shaft 2. The joints were fixed to the tip of the support base 4 with an elastic adhesive 6. 6 and 6' are terminals, 7 is a case that covers the laminated piezoelectric element 1, etc., 8 is a protective mesh attached to a through hole formed in the upper part of the case 7, and 9
, 9' are lead wires electrically connecting the terminals 6, 6' of the bonded piezoelectric element 1.

FIG. 2 shows the pulse characteristics of the ultrasonic transducer having the above structure. This shows the transmission waveform when the stacked piezoelectric element 1 was driven with a plurality of pulses, and the rise and fall times were slow, reaching more than 2 milliseconds.゛When it is necessary to obtain measurement information at short time intervals using such a conventional ultrasonic transducer, the signal received by the receiver has a long rise and fall time. The next signal was received before the signal fell, and accurate measurement information could not be obtained.

In addition, when transmitting and receiving waves using a single element, it takes a long time to transmit and immediately become ready for reception, and measurement information cannot be obtained during the time it takes to become ready for reception. I couldn't.

Furthermore, when ultrasonic transducers using piezoelectric ceramics were required to have sharp directivity characteristics, diaphragms, bonded piezoelectric elements, and bonded piezoelectric elements were supported. Also, depending on the size of the case, the position of the bonded piezoelectric element in the case, the position of the diaphragm, the bonding conditions between the diaphragm and the bonded piezoelectric element, and the bonded piezoelectric element and the support, the directional characteristics and sensitivity characteristics may vary significantly. It varied, had poor reproducibility, and was unsuitable for mass production.

Therefore, the present invention provides a conical diaphragm having a bottom surface larger than the bonding surface of the bonded piezoelectric element in the center of the bonded piezoelectric element, and a cushioning material such as elastic rubber on the periphery of the conical diaphragm. By adding this, we have realized an ultrasonic transducer that is small but exhibits sharp directivity characteristics, good transmitting and receiving sensitivity characteristics, and steep pulse characteristics.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a sectional view of this embodiment.

A coupling shaft 2 is provided through and fixed in the center of the bonded piezoelectric element 1, and a diaphragm 3 made of metal or resin is attached to the coupling shaft 2. The diaphragm 3 is a conical diaphragm having a bottom surface larger in area than the bonding surface of the bonded piezoelectric element 1.

6/5. −8+・Furthermore, a cushioning material 1o such as elastic rubber is attached to the periphery of the diaphragm 30 so as to suppress mechanical vibration. Then, the vibration nodes of the bonded piezoelectric element 1 are elastically fixed to the tip end of the support base 4 with an elastic adhesive 6. 6 and 6' are the elements;
7 is a case that covers the bonded piezoelectric element 1, etc.; 8 is a protective mesh attached to a through hole formed in the upper part of the case 7; 9°9' is the bonded piezoelectric element 1 and terminals 6, 6;
This is the lead wire that electrically connects .

FIG. 4 shows the pulse characteristics of the ultrasonic transducer having the above structure. As is clear from the figure, the rising and falling times of the pulse were less than 0.2 milliseconds.

6 and 6 show changes in directivity characteristics (sound pressure half-reduction angle and ratio of side rope to main rope) and wave transmission sensitivity when the diameter of the bottom surface of the diaphragm 3 is changed. . As is clear from A in FIG. 6, as the diameter of the diaphragm 3 increases, the half-reduction angle of the sound pressure decreases. Shows sharp directional characteristics. Diameter of bonded piezoelectric element 1 -196.

As shown in Figure B, the ratio of the side rope to the main lobe reaches its maximum value when the diameter D of the diaphragm 3 is 15 [+a], and decreases as D increases at 15 (mn). . As shown in FIG. 6, the transmitting sensitivity increases as D increases.

FIGS. 7 and 8 respectively show changes in the half-reduction angle of the sound pressure and the wave transmission sensitivity when the height t of the case 7 is changed. When the ratio of the height h to the diameter of the diaphragm 3 is %, the half-reduction angle of the sound pressure and the wave transmission sensitivity hardly change even if the height of the case 7 is changed in the range of 12 to 16 cm.

As described above, the present invention not only exhibits a smaller size and sharper directivity, better transmitting/receiving sensitivity characteristics, and steeper pulse characteristics than conventional ultrasonic receivers. , variations in properties due to manufacturing conditions have been significantly reduced, making mass production easier. Therefore, the ultrasonic transducer of the present invention is extremely useful for ultrasonic applied measurements that require sharp directional characteristics, such as distance meters using sound waves.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional ultrasonic transducer, and FIG. 2 is a diagram showing its pulse characteristics. FIG. 3 is a sectional view showing one embodiment of the ultrasonic transducer of the present invention, FIG. 4 is a diagram showing its pulse properties, and FIGS. diameter and directional characteristics,
Figures 1 and 8 are diagrams showing the relationship between the height of the case of this ultrasonic heat transmitter/receiver and the directivity characteristics and sensitivity characteristics, respectively. 1... ... Bonded piezoelectric element, 3 ... Vibration plate, 4 ... Support stand, 6 ... Elastic adhesive, 6, 6' ... Terminal , 7... Case, 10... Cushioning material. Name of agent Patent attorney Satoshi Nakao, Isamu and 1 other person 2m Figure 4 j (mm ω゛) 5 Figure. p, , j Kokan Station I) Diameter D (+nH) 6 Oka 1 Grip t's Naokai D[-1

Claims (4)

[Claims] (1) A laminated piezoelectric element having a diaphragm in the center is elastically fixed to a support base and housed in a case, and a cushioning material is provided around the diaphragm. Ultrasonic transducer. (2) The ultrasonic transducer according to claim 1, wherein the bonded piezoelectric element having a diaphragm in the center is disk-shaped. (3) The diaphragm has a conical shape, and the diameter of its bottom surface is 1 to 3 times the diameter of the laminated piezoelectric element. Ultrasonic transducer. (4) Ultrasonic wave transmission and reception according to claim 1, characterized in that the diaphragm has a conical shape, and the ratio of its height to the diameter of the bottom surface is 0.3 to 0.5. vessel.