JPS58124396A - Ultrasonic wave transceiver - Google Patents

Abstract

PURPOSE:To attain sharp directivity, excellent transmission and reception sensitivity and excellent pulse performance, by placing a thin plate having a plurality of open holes near the front of output side of an electroacoustic converter. CONSTITUTION:A coupling shaft 12 is arranged at the center of a sticked type piezoelectric element 11 and a diaphragm 13 is fitted to the shaft 12. The piezoelectric element 11 is fixed by bonding the node of the oscillation with an adhesives 15 having the elasticity to the tip of a support stand 14. In front of the diaphragm 13, the thin plate 23 having a circular open hole 22 and other open hole 22' provided on the concentric circle taking a straight line through the opening 22 and the coupling shaft 12 as a center. Thus, the ultrasonic wave transceiver having the sharp directivity, excellent transmission/reception characteristics and excellent pulse characteristics is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic transducer, which has sharp directivity characteristics, good pulse characteristics, and a main lobe to zydrobe ratio of 20 dB or more. Therefore, it is an object of the present invention to provide an ultrasonic transducer having extremely excellent performance with virtually no directionality.

Conventionally, so-called capacitive transducers, which emit ultrasonic waves by stretching and contracting plastic films with a thickness of about 100 pm using high voltage, and piezoelectric ceramic transducers have been used as devices for transmitting and receiving ultrasonic waves in the air. A typical example is an ultrasonic transducer that uses the vicinity of the resonance point or anti-resonance point of the flexural vibration state, which is excited by bonding , ri, etc., and the two types mentioned above have been mainly used. The former is generally used in a variety of ways because its characteristics change significantly due to changes in environmental conditions and it is expensive to change.

On the other hand, the latter has been widely used because it has significantly higher reliability and is less expensive than the former.

FIG. 1 shows a typical external structure of the piezoelectric type ultrasonic transducer that has been conventionally used. 1. A coupling shaft 2 is fixed through the center of the bonded piezoelectric element 1.
A diaphragm 3 is attached to the coupling shaft 2, and the vibration node of the bonded piezoelectric element 1 is fixed to the tip of a support base 4 with an elastic adhesive 6. In the figure, 6 and 6' are terminals, 7 is a housing that covers the bonded piezoelectric element, etc., and 8 is a protective mesh formed in a part of the -1 part of the flute body 7 and attached to a through hole. ,9,9
' is a lead wire electrically connecting the bonded piezoelectric element 1 and the ends A 6, 6'. FIG. 2 shows the pulse characteristics of the ultrasonic transducer having this structure. Here, the transmitted waveform when driven with a plurality of pulses or more is shown as a representative. FIG. 3 shows its directional characteristics, and it can be seen that the half-reduction angle of sound pressure is 37 degrees.

As is clear from Fig. 2, due to the high mechanical Q value of the piezoelectric ceramics and boxes that make up the bonded piezoelectric element, the rising and falling times are slow, and the time it takes to cool down is long. It lasted for more than 2 milliseconds. If the rise and fall of ultrasonic transmission and reception waves are slow as in 50-, for example, when measuring the distance of a moving object, it is necessary to obtain measurement information at short time intervals. In this case, it takes a long time for the received signal to reach its peak value, or when the reception signal goes down, the next signal will receive interference and accurate measurement information will not be obtained. The result was that they were unable to do so.

-Also, when transmitting and receiving waves using the same element,
It takes a considerable amount of time to immediately become ready for reception after transmitting waves2, and during that time, it has been impossible to obtain measurement information.

Furthermore, the smaller the object to be measured, the higher the resolution of the ultrasonic transducer must be, and increasing the resolution requires sharp directivity characteristics. In order to sharpen the directivity characteristics, it is necessary to make the sound source thicker and use a higher frequency, as is well known. However, increasing the frequency used has the disadvantage that sound attenuation increases significantly, so there is a limit to increasing the frequency used, and therefore the sound source must be made larger.

However, if an ultrasonic transducer using piezoelectric ceramics is required to have sharp directivity characteristics, the diaphragm, the bonded piezoelectric element, the support base that supports the piezoelectric element, etc. will be significantly affected. It has the disadvantage of becoming. Even if a large diaphragm is used, it is extremely difficult to make the piston vibrate uniformly. The current situation is that the directional characteristics are less sharp and sharp compared to that of the ``Hosoujin''.

On the other hand, there is a method to make the directional characteristics sharper by using a horn etc. in front of the vibrating part, but since the mechanical Q value of the horn is good, the pulse characteristics are extremely poor. Adding +1 to 7 to make the pointing ('!-) sharper, and also lowering its mechanical 01 characteristic, improving the pulse characteristics was not only difficult to achieve, but also improving the transmitting and receiving sensitivity. 9-1 The present invention solves the above-mentioned problems of ultrasonic transducers with horns by improving the output characteristics of electroacoustic transducers. We have realized an ultrasonic transducer that has a number of features such as good transmitting/receiving sensitivity characteristics, extremely good pulse characteristics, a main lobe to zydlobe ratio of 120 dB or less, and virtually no directivity [7] It is something.

Hereinafter, one embodiment of the present invention will be described in detail using the drawings.

FIG. 4 is a sectional view showing the structure of this embodiment.

A coupling shaft 12 is disposed at the center of the bonded piezoelectric element 11, and a diaphragm 13 made of metal or resin is attached to the coupling shaft 12. The bonded piezoelectric element 11 is fixed by bonding its vibration nodes to the tip of the support base 14 with an elastic adhesive 15. In front of the diaphragm 13, there is a circular opening 22 and an opening 22.
A thin plate 23 having one layer of apertures 22' provided on a concentric circumference centered on a straight line passing through the coupling axis 12 is installed.

For example, in this case, the apertures 22.22 are located on the diaphragm 13.
It is located in front of the abdomen of the odd-order vibrations from the center of the oscillation, but it may also be constructed by combining odd-number and even-order vibrations. The casing 17 and the thin plate 23 that cover the laminated piezoelectric element 11 and the like are inserted into the throat of the parabolic horn 24. The lead wires 19 and 19' are used to electrically connect the bonded piezoelectric element 11 and the terminals 16 and 16'. Although not shown here, this basic configuration is, for example, a capacitive ultrasonic transducer or an ultrasonic transducer made of PVDF, etc.
It was experimentally confirmed that similar effects can be obtained if the device excites higher-order vibrations.

The shape of the openings 22, 22' of the thin plate 23 changes depending on the size and thickness of the bonded piezoelectric element 11, the size and thickness of the diaphragm 13, the opening angle of the center, etc. Representative ones are selected and shown in Figs. 5 to 18. Fig. 6 (A) is a 11/- side view, and Fig. (B) is a sectional view. Note that the bonded piezoelectric element 11 has a diameter of 9.1 mm, a thickness of 0.6 mm, and a diameter of 1 mm for the diaphragm 13.
7ml 1l! FIG. 19 shows an example of the position of the vibration node on the diaphragm 13 when the thickness is 0.1 depth, determined from Chladny's sand diagram.

The thin plate shown in FIGS. 5 to 7 and located near the output side of the electroacoustic transducer has a diameter of 3.0 mm located on the center axis of the hatched area (A) shown in FIG. Vibration node 83 forming a ring around the hole in the shaft, 10.0m
Each has an aperture on its vibrating abdomen that spans 1~
I'm here. Here, it was confirmed that an effect similar to that of Habo can be obtained if the above-mentioned 8.3 trrm is within the range of 7 to 83 pus squared in terms of product. Furthermore, it was confirmed that the same effect can be obtained if the area of the opening in the center is within the range of approximately 0.5 to 28 square meters. As mentioned above, the opening portion is
Habo electroacoustic transducer odd or even orders (not shown)
It is located on the front of the abdomen where it vibrates.

V-', 7-- 'j Fig. 8''... and the thin plate shown in Fig. 9, the diameter (minimum side) of the opening provided in the center is 3.3 axillary; The diameter of the hole is 0.8M, and the diameter of the hole is 13.5m in the latter part.
The width of the opening above 16.3rBm is 0.2-0.8m
It is m. A slope of 5 to 20 degrees is provided around each of the central openings. This slope has a very large effect on reducing side ropes.

The thin plate shown in Fig. 10, like the thin plates shown in Figs. 8 and 9, has an increased number of openings in order to reduce the side ropes, and at the same time has a center hole ( A semicircular hole with an opening area of 7 to 83 mm square (corresponding to an opening area of 0.5 to 28 mm square), with a diameter of 21 or 3 times or larger, respectively. have.

The thin plates shown in Figures 11 to 13 have a parabolic or conical cross section with a thin wall thickness at the center of the ultrasonic output [1" i side or 0 side and the inlet side, and are formed into a nozzle shape where only the center part of the straddle is thick. According to this, the side ropes were extremely shaped and exhibited minute sawtooth directivity characteristics.

In the thin plates shown in FIGS. 14 to 17, the thickness of the central part of the ultrasonic wave output side ζ is increased, and Q is the thickness of the center part of the ultrasonic input side.

Similar to the thin plates shown in Figures 11 to 13, Zydolov exhibits a very well-shaped, saw-like minute directional characteristic. just,
Regarding sensitivity, it was found that it was significantly lower than Part 1.

The thin plate of FIG. 18 has a plurality of openings near the output side of the electroacoustic transducer. These openings are made up of a collection of small round holes, each arranged on the circumference of at least two or three layers of holes. As a result, the side rope 71 is reduced and its tip shape is very rounded. Furthermore, it was confirmed that when the small round hole was shielded in the shape of a half-moon or a cross, not only the side rope was further reduced, but also the shape of the tip became rounder.

Next, the directivity characteristics of the ultrasonic transducer having the structure of the present invention described above, measured using the thin plate shown in FIG. 18, are shown in FIG. 2o, and the pulse characteristics are shown in FIG. 21. . Although the angle at which the side lobe occurs changes depending on the structure of the thin plate, other characteristics are very similar, so typical characteristics of each are shown. FIG. 20(A) shows the directional characteristics when the thin plate 23 is installed in front of the diaphragm 13, and FIG. 20(B) shows the directional characteristics before the thin plate 23 is installed. It was clearly seen that the half-reduction angle continued to become sharper and the sidelobes were significantly reduced. The transmission sensitivity is also 114d.
It increased by 120dB from B. By receiving only the same direction components, it is now possible to improve the difference in attenuation. From Figure 21, the rise of the pulse,
It can be seen that both fall characteristics are extremely good at 0.5 milliseconds. This dramatically improved the spatial quality that could not be achieved with conventional methods. It also became easier to assemble and mass produce. Moreover, since the configuration is extremely simple, it is possible to achieve a low price. Furthermore, by interposing the thin plate, the vibrating part is not directly exposed to the outside, and a high level of safety can be guaranteed, and this has many useful effects.

As mentioned above, the ultrasonic wave transmitting/receiving device according to the present invention has a plurality of openings near the output side of the electroacoustic transducer,
In addition, these are a collection of small holes, and the thin plates are arranged to form at least two or more circumferences, so they have sharp directivity characteristics and good wave transmitting and receiving sensitivity characteristics, making it possible to transmit sound waves. It is extremely useful for ultrasonic word measurement that requires sharp directional characteristics such as the distance used.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the structure of a conventional ultrasonic transducer, FIG. 2 is a view showing its pulse characteristics, and FIG. 3 is a view showing its directivity characteristics. Fig. 4 is a sectional view of an embodiment of an ultrasonic transducer according to the present invention. Diagram showing the nodes of the diaphragm, No. 20
The figure shows the effect of the thin plate on the directivity characteristics, and FIG. 21 shows the pulse characteristics. 11... Bonded piezoelectric element, 12...
...Coupling shaft, 13...Diaphragm, 14...
Holder, j 5------Adhesive, 16, 16'-
-----One terminal, 22゜22'...Opening part, 2
3... thin plate, 24... horn. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 5 (A) (F31 Figure 6 (A) (E') Figure 7 (A) (B) Figure 8 (A) (B) Figure 9 (AI (f3) Figure 10 Figure (A) (B. Figure 11 (A) (B) Figure 12 (A) 7B Figure 13 (A)
Total I〕n -; Deng y- Color also
(B) Figure 19 (B) Figure 21 11! (Prisen)

Claims (4)

[Claims] (1) The electroacoustic transducer has a plurality of apertures near the output side, the aperture is made up of a collection of small holes, and at least the small holes are arranged on a double or more circumference. 1. An ultrasonic transducer characterized by having a thin plate. (2) The ultrasonic transducer according to claim 1, wherein the aperture of the thin plate is located approximately in front of the abdomen of odd-order or even-order vibrations of the electroacoustic transducer. . (3) The opening of the thin plate is arranged in a ring shape over the center of the electroacoustic transducer and around the opening on the central axis. Ultrasonic transducer. (4) A part of the opening provided near the output side of the electroacoustic transducer is located substantially in front of the vibration node of the electroacoustic transducer. Ultrasonic transducer described.