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JPS5654198

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DESCRIPTION JPS5654198
Page 1 Specification of the Invention The ultrasonic vibrator 1, the first resonator having a
plurality of resonant projections, and the second resonator having both end faces substantially
planar are opposed to each other with the piezoelectric element interposed therebetween. Let
these first one. A female screw is provided on one side of the second resonator, and a male screw
is provided on the other, and the male screw and the female screw are screwed through the
through holes provided in the piezoelectric element. An ultrasonic wave actuator characterized in
that an adhesive is interposed between and fixed to a second resonator and a piezoelectric
element.
Claims
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to ultrasonic
transducers used in underwater acoustic transducers and the like. 2 '@@ Conventionally, a
vibrator using a piezoelectric element has been used for relatively low frequency as a Langepa
buster. Conventionally, this is because the adhesive between the piezoelectric element and the
metal resonator had a large loss at high frequencies, and it was possible to use only one
piezoelectric element having a shape and a size matching the high frequency. Therefore,
conventionally, in the case where only the piezoelectric element is used, the piezoelectric element
is made smaller than the wavelength to a size that is considered to make piston movement, and a
plurality of such elements are used by being arrayed. 0 FIG. 1 Kn, a conventional vibrator used
for relatively high frequency is shown, and electrodes 2.3 are respectively provided on both end
faces of a plurality of piezoelectric elements 1 of equal length. The electrode 2 is provided and
embedded in a holding member 4 in a predetermined arrangement, leaving the vicinity of one
end of the crucible, and the holding member 4 is accommodated in the frame 5. FIG. 2 shows a
conventional vibrator having a low Qm, that is, a wide band frequency characteristic. In this case,
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a plurality of piezoelectric elements 6.7.8t-0 having different lengths are used, and the holding
member 4 is used. The sequence support EndPage: 13G) in the frame 5. However, in such a
conventional vibrator, the size of the piezoelectric element 1, 6 ° 67.8 generally has a
wavelength because it is necessary to cause the sound emission surface of the piezoelectric
element 1.6.7.8 to move in a piston. However, in order to make the directivity characteristic
sharper, it is necessary to use a large number of arrays, and the operation of arranging in the
holding material 4 is difficult. Further, since the piezoelectric element 1.6.7.8 has many required
performance items and is small even if it is expensive 1 ', there is a desire to reduce the number
of piezoelectric elements used in terms of cost reduction. An object of the present invention is to
provide an ultrasonic transducer capable of simplifying the arrangement operation and reducing
the number of expensive piezoelectric elements. The present invention is made by focusing
attention on the next point and the like by improving the adhesive and bonding technology, and a
first resonator having a plurality of resonant projections forming an acoustic radiation surface on
one end face of the piezoelectric element. The second resonator with its both end faces
substantially planarized at the other end face is l! r · contact, these first one. One female screw
rod is provided on one side of the second resonator, and an external thread is provided on the
other, and the external thread and the internal thread are screwed through the through holes
provided in the piezoelectric element, and the adhesive It is intended to achieve the purpose by
interposing and fixing.
Hereinafter, embodiments of the present invention will be described based on the drawings.
Here, the same or corresponding components in the respective embodiments use the same
reference numerals, and the description of the overlapping components is simplified or omitted.
3 to 6 show a first embodiment of the present invention. In FIG. 3, through holes are formed in
the central portion Kr1 of the disk-like piezoelectric element 11, electrodes 13 and 14 are
formed on the left and right end faces of the piezoelectric element 11 in FIG. -), (+) Is applied to
the electrode 14. The two piezoelectric elements 11 are disposed such that the electrodes 14 of
the same polarity face each other with one adhesive 15 as shown in FIG. 4, and one outer end
face of the two piezoelectric elements 11 is disposed The first resonator 16 is disposed with the
electrode 13 and the adhesive 15 interposed therebetween, and on the other outer end face, the
second resonator 17 on the side of the fifth page is made substantially planar on both lake
surfaces. It is disposed via the electrode 13 and the adhesive 15. The first of these. The area of
the end face of the second resonators 16 and 17 on the side of the piezoelectric element 11 is
substantially equal to the area of the end face of the piezoelectric element 11. On the surface of
the first resonator 16 on the side not in contact with the piezoelectric element 11, a plurality of
resonance projections 18 constituting an acoustic radiation surface are formed at the same
height. The height of the resonant projection 18 of the first resonator 16 is such that the total
length of the vibrator is half-wave resonant. In this case, the vibration amplitude is small in the
vicinity of the piezoelectric element 11. The vibration amplitude is maximized at the tip end face
of the resonance projection 18 so that sound waves can be emitted into a medium such as water.
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In addition, the thickness of these resonant projections 18 is made sufficiently thin as compared
with the wavelength, and the piston movement is performed at the end face 1. An externally
threaded portion 19 is integrally formed at the axial center of the first resonator 16 through the
through hole 12 of the piezoelectric element 11 and having one end projected on the opposite
side. Axial center of the second resonator 17? -It is screwed in the internal thread part 20 formed
in l. According to the sixth page, both the piezoelectric element 11 and the surface of the
piezoelectric element 11 and the first one. The air gap between the adhesive 15 and the second
resonators 16 and 17 is eliminated, and the thickness of the layer of the adhesive 15 is kept as
thin as possible to prevent the piezoelectric element 11 and the first . The second resonators 16
and 17 are fixed. Under the present circumstances, since the cross-sectional area of the
piezoelectric element 11 is large enough, fastening by external thread part 19 and internal
thread application of both valve pendulums 16 and 17 is carried out with a bolt like bolted
Langevin vibrator conventionally made. It is not necessary to tighten so as to apply a bias
compressive stress, but it is sufficient to fasten the layer of the adhesive 14 as thin as possible
and as uniformly as possible as a whole before the adhesive 14 is cured.
In such a configuration, when a desired voltage is applied to the electrodes 13 and 14, electricity
and vibration are converted by the piezoelectric element 11, and this vibration is converted to
the first one. It is transmitted to the second resonator 16 ° 17. At this time, since the second
resonator 17a which is the back side diaphragm and the outer end face thereof are planar, the
piston movement is not performed, but the radiation end face of the resonator 16 on the acoustic
radiation side is a resonant collisional surface. Since the section 18 is made sufficiently narrow as
compared with the wave EndPage: 27 page 1 length, a piston movement is performed, and a
sound wave is emitted into a medium such as water. According to this embodiment, since the
expensive piezoelectric elements 11 are reduced and the acoustic radiation surface is configured
using the inexpensive first resonators 16 ', it can be provided at a very low cost as a whole. The
respective resonant projections 18 can be sufficiently deflected as compared with the
wavelength, so that the vibration of the end face can be effectively piston-operated with the
respective resonant projections 18 in the same phase. Furthermore, the first one. Since the
second co-1 '' pendulum 16, 17 is joined by the fastening of the external thread 19 and the
internal thread 20, the thickness of each layer of adhesive 15 can be made extremely thin and
low loss, and 1st. Positioning of the second resonators 16 and 17 is facilitated, which has a great
effect on the assembling operation, and is also inexpensive. 7 and 8 show a second embodiment
of the present invention, in which the heights of the resonance projections in the first
embodiment are made different. That is, in the present embodiment, the male screw portion 19 is
opposed to the both end surfaces of the piezoelectric element 110 via the electrodes 13 and 14
and the adhesive 15, and is fastened through the through hole 12 of the piezoelectric element
169 = 1. And the female screw portion 20 attached first. Among the second resonators 16 and
17, a plurality of, e.g., a plum-shaped, five resonance projections disposed integrally with the first
resonator 16 are one of the left ends in FIG. The three resonance projections 22 in the central
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vertical direction in FIG. 7 are at the middle height, and the one resonance projection 23 at the
right end in FIG. 7 is the lowest. There is. These resonant projections 21, 22 and 23 are designed
to resonate at a half wavelength at each height, and viewed from the end face of the vibrator,
they are arranged as if having a staggered complex resonance, and each of the resonant
projections 21 to 21 The vibration amplitude is maximized at its end face, and the sound wave is
emitted into the medium. In such a configuration, when a predetermined voltage is applied to the
electrode 13.degree. 14 of the piezoelectric element 11, the characteristics shown in FIG. 9 are
exhibited.
That is, in FIG. 9, when the frequency is taken along the horizontal axis and the sound pressure is
taken along the vertical axis, a characteristic P having a peak of sound pressure centered at a
relatively low frequency f1 due to the highest resonance projection 21. Is obtained, and a
characteristic Q with a peak of sound pressure centered on the intermediate frequency f2 is
obtained by the resonance projection 22 at the middle 9 pages 1 height, and is relatively high by
the lowest resonance projection n. A characteristic R with a peak of sound pressure centered on
the frequency f is obtained, and the frequency f, f2. It can be seen that f, there is a small
mountain, and a complex composite characteristic T is obtained, and an extremely broad band
(low Qrn) electroacoustic transducer can be realized. According to the present embodiment as
described above, the same effect as that of the first embodiment can be obtained, and there is
also an effect that a low Qm, a wide band, and a vibrator can be obtained. In addition, it can
change suitably according to necessity to the number of resonance protrusions, height, etc. in
implementation, and a male screw part and a female screw part are 1st 1. An external thread or
an internal thread may be provided in any of the second resonators, as long as they can be
screwed to each other. As described above, according to the present invention, it is possible to
provide an inexpensive ultrasonic transducer that can reduce the number of expensive
piezoelectric elements and can be applied to relatively high frequency regions.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 10 is a cross-sectional view showing another
example of a conventional ultrasonic transducer, and FIG. 3 is used in a first embodiment of an
ultrasonic transducer according to the present invention. A side view of the piezoelectric element,
FIG. 4 is a left side view of the first embodiment of the present invention, FIG. 5 is a half sectional
front view of FIG. 4, FIG. 6 is a right side view of FIG. The figure is a left side view of the second
embodiment of the present invention, FIG. 8 is a front elevational view of a half section of FIG. 7,
and FIG. 9 is a diagram showing sound pressure-frequency characteristics of the second
embodiment. 11: Piezoelectric element, 12: through hole, 13, 14: electrode, 15 ′ ′: adhesive,
16: first resonator, 17: second resonator, 18 , 21, 22, 23 · · · Resonant protrusion, 19 · · Male
thread, male and female threads. Agent patent attorney Masamoto Akimoto EndPage: 3 Figure 1
Figure 2 Figure 3 Figure 4 Figure 5 Figure 7 Figure 2 Figure 9 · 131 EndPage: 4
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