JPS5888999A - Ultrasonic wave transmitter and receiver - Google Patents

Abstract

PURPOSE:To obtain a sharp directivity and an excellent pulse characteristics, by providing a diaphragm at the center of a sticked type piezoelectric element, elastically fixing the surrounding of a diaphragm to a case with a buffer member and providing a thin plate having an opening in the front and a horn. CONSTITUTION:A diaphragm 13 is fitted to a coupling shaft 12 arranged at the center of a sticked type piezoelectric element 11. The surrounding of the diaphragm 13 is elastically fixed to the inside of a cylindrical case 17 via a buffer member 20 such as an elastic rubber formed in a circular ring. A sound absorbing member 21 is sticked at the bottom of the case 17. A circular opening 22 taking a straight line through the shaft 12 as a center, and a thin plate 23 having another opening 22' provided concentrically with the opening 22 are provided in front of the diaphragm 13, and the case 17 and the thin plate 23 are inserted to the bottle neck of a parabolic horn 24. Leads 19, 19' electrically connect the element 11 and terminals 16, 16'. Through the constitution of an ultrasonic wave transmitter/receiver like this, a sharp directivity and an excellent pulse characteristic can be obtained and accurate measuring information can be obtained in a short time interval.

Description

[Detailed description of the invention] The present invention has sharp directional characteristics, and has pulse characteristics on page 3. This invention relates to an ultrasonic transducer that has been improved.

A bonded piezoelectric element made of piezoelectric ceramics is often used as a transducer for ultrasonic waves in the air. ing. Furthermore, since the mechanical impedance of air as a medium is significantly smaller than that of piezoelectric ceramics, the bonded piezoelectric element is coupled to the diaphragm to reduce the mechanical impedance.

The structure of a conventional ultrasonic transducer is shown in FIG.

This involves penetrating and fixing a coupling shaft 2 to the center of the bonded piezoelectric element 1, attaching a diaphragm 3 to the coupling shaft 2, and directing the vibration nodes of the bonded piezoelectric element 1 to the tip of the support base 4. It was fixed with an elastic adhesive 5. 6,6
' is a terminal, 7 is a case that covers the bonded piezoelectric element, etc., 8
9 and 9' are lead wires electrically connecting the bonded piezoelectric element 1 and the terminals 6 and 6'.

Figure 2 shows the pulse characteristics of the ultrasonic transducer with the above structure, and shows the transmitted waveform when driven by multiple . The rise and fall times were slow, reaching more than 2 milliseconds.

For example, when measuring the distance of a moving object, when using such a conventional ultrasonic transducer, it is necessary to obtain measurement information at short time intervals, and the rise and fall times are extremely long, so the received signal is It takes time to reach the peak value. Alternatively, the next signal was received before the received signal fell, causing interference and making it impossible to obtain accurate measurement information.

Furthermore, when transmitting and receiving waves using a single element, it takes a considerable amount of time to transmit waves and become ready for reception immediately, and during that time, measurement information cannot be obtained.

Furthermore, in order to increase the resolution of the object to be measured, sharp directional characteristics are required.

As is well known, sharp directional characteristics can be achieved by increasing the size of the sound source and increasing the frequency used.
As the frequency used increases, the attenuation of the sound increases by a significant amount, so there is a limit to how high the frequency can be raised, and it is necessary to make the sound source larger.

When ultrasonic transducers using piezoelectric ceramics are required to have sharp directivity characteristics, there is a drawback that the diaphragm, the bonded piezoelectric element, and the support base that supports the bonded piezoelectric element become significantly large. Even if a large diaphragm is used,
It was extremely difficult to achieve uniform piston vibration, and although the sound source was made larger, the directional characteristics were generally not sharp.

On the other hand, when trying to sharpen the directional characteristics by using a horn, a horn is added to a conventional ultrasonic transceiver and the mechanical Q
It has not been easy to improve the pulse characteristics by reducing the

Therefore, the present invention provides a diaphragm at the center of a bonded piezoelectric element, and elastically fixes the periphery of the diaphragm to a case with an elastic material such as elastic rubber so as to suppress mechanical vibration. By adding a thin plate with an opening in the front and a horn, an ultrasonic transducer with sharp directional characteristics and good pulse characteristics is provided.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 3 is a sectional view of this embodiment.

A diaphragm 13 made of metal or resin is attached to a coupling shaft 12 arranged at the center of the bonded piezoelectric element 11. The peripheral portion of the diaphragm 13 is elastically fixed to the inner surface of the cylindrical case 17 via a cushioning material 2o such as elastic rubber formed in an annular shape so as to suppress mechanical vibrations. . A sound absorbing material 21 is attached to the bottom of the case 17.

A thin plate 23 is installed in front of the diaphragm 13, and has a circular opening 22 centered on a straight line passing through the coupling shaft 12, and another opening 22' provided on a circumference concentric with the opening 22. ,
The case 17 and the thin plate 23 are fitted into the throat of the parabolic horn 24. 19.19' is the bonded piezoelectric element 11 and terminal 1
This is a lead wire that electrically connects 6.16'.

The openings 22 and 22' of the thin plate 23 are determined by the size of the bonded piezoelectric element 11, the size of the diaphragm 13, and the cushioning material 2o.
Although the shape changes depending on the inner diameter of the tube, typical shapes are shown in FIGS. 4 to 16.

In both figures, a is a plan view and b is a sectional view.

Next, FIG. 17 shows the pulse characteristics of the ultrasonic transducer having the structure of the present invention. It is clear from this that the pulse rise and fall times are less than 0.3 milliseconds.

Figure No. 4 shows changes in the half-decrease angle of sound pressure, wave transmission sensitivity, and rise time when the inner diameter of the buffer material 2o is changed. As the inner diameter of the buffer material 2o decreases, the rise time decreases, but the sound pressure half-reduction angle increases slightly and the wave transmission sensitivity also decreases. If the inner diameter is further reduced, the side ropes will also increase (not shown). Therefore, it can be seen that the inner diameter of the cushioning material 20 has an optimum value once the sizes and thicknesses of the bonded piezoelectric element 11 and the diaphragm 13 are determined. The bonded piezoelectric element 11 has a diameter of 9.1 fins and a thickness of about 0.6111 mm, the diaphragm 13 has a conical shape with a bottom diameter of about 17 nm, and the horn 24 has a diameter of about 66 fins, and the thin plate 23 has a diameter of about 66 fins.
is an experimental value for the one shown in FIG.

In FIG. 19, the diameter of the bonded piezoelectric element 11 is approximately 9.1 mm.
When changing the thickness, the sound pressure half-reduction angle, transmission sensitivity,
Rise time and drive frequency (frequency with maximum sensitivity)
This shows the changes in each.

As the thickness of the bonded piezoelectric element 11 increases, the drive frequency increases and the half-reduction angle of sound pressure decreases, but the wave transmission sensitivity decreases and the rise time also increases.

As the diameter of the diaphragm 23 increases, the wave transmission sensitivity increases, but the rise time also increases, so the diameter may be determined depending on the application. When spatially uniform directivity (for example, vertically and horizontally) is required, the diaphragm 13 is of a conical shape,
A trumpet shape, a bowl shape, etc. are good.

FIG. 20+IL) shows the directivity characteristics of the electrical production according to the present invention when the thin plate 23 is installed in front of the diaphragm 13. In the figure (bl indicates the directional characteristics before installation).

It can be seen that according to the present invention, the side ropes are greatly reduced. Almost spatially uniform directional characteristics can now be obtained.

9B-7・In addition, by integrating the case 17 and the thin plate 23, it is not only possible to obtain even more spatially uniform directivity characteristics, but also the variation in characteristics is reduced, making assembly easier. Mass production is coming soon.

Furthermore, noise resistance was improved by making the integrally formed case 17 and thin plate 23 conductive and connecting them to ground.

As described above, according to the present invention, it has sharp directivity characteristics and good pulse characteristics, and it has become possible to obtain accurate measurement information at short time intervals. 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 of an embodiment of the ultrasonic transducer of the present invention;
FIGS. 4 to 16 show the structure of typical examples of the thin plate, and those (-) are front views, FIG. 17 is a cross-sectional view of the ultrasonic transducer of the present invention. FIG. 18 is a diagram showing an example of the 1° las characteristic, FIG. 18 is a diagram showing the relationship between the inner diameter of the buffer material of the ultrasonic transducer of the present invention, the half-decrease angle of sound pressure, the wave transmission sensitivity, and the rise time. Similarly, FIG. 20 is a diagram showing the relationship between the thickness of the bonded piezoelectric element, sound pressure half angle, wave transmission sensitivity, rise time, and drive frequency, and FIG. 20 is a diagram also showing the effect of the thin plate. 11...・Bonded piezoelectric element, 13...
・Diaphragm, 17... Case, 20...
Cushioning material, 21...Sound absorbing material, 22, 22'...
...Opening, 23...Thin plate, 24...
··Horn. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 13 Figure 14 Figure 15 Figure 17 - 1C vs. Figure 18 Figure 19 Figure 20

Claims (1)

[Claims] (1) A bonded piezoelectric element with a diaphragm provided in the center, a case enclosing the bonded piezoelectric element, and a periphery of the diaphragm and an inner surface of the case. a thin plate with an opening installed in front of the bonded piezoelectric element; and a horn for enclosing and fixing the case and the thin plate; An ultrasonic transducer characterized in that a diaphragm is elastically fixed to the case. (2) The ultrasonic transducer according to claim 1, wherein the bonded piezoelectric element is disk-shaped and has a conical diaphragm in the center thereof. (3) The ultrasonic transducer according to claim 1, characterized in that a sound absorbing material is attached inside the case. (4) The ultrasonic transducer 0 according to claim 1, wherein the thin plate has a plurality of openings. (5) The thin plate having an opening on a circumference concentric with the center is a disk. 3. The ultrasonic transducer according to claim 2, wherein the ultrasonic transducer has a shape. (6) The ultrasonic transducer according to claim 5, wherein the opening of the thin plate is sloped. (Katana) An ultrasonic transducer according to claim 5, characterized in that the thickness of the thin plate is different from the thickness of the center part and the peripheral part. The ultrasonic transducer according to item 1. (9) The ultrasonic transducer according to claim 1, wherein the thin plate and the case are made conductive and connected to earth. (1o) The ultrasonic transducer according to claim 1, characterized in that the thin plate, the case, and the horn are integrally formed.