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FIELD OF THE INVENTION The present invention relates to the improvement of an ultrasonic
transducer, and relates to a bolt-clamped Langevin transducer which is most widely used among
ultrasonic transducers using a piezoelectric ceramic, which resonates at a desired frequency. It is
an object of the present invention to provide an ultrasonic transducer of a new mechanism which
has been miniaturized further than conventional ones on the premise of the above-described
structure. [Background Art] Conventional ultrasonic transducers include a piezoelectric type and
a magnetostrictive type, both of which are often used. From the efficiency point of view, the
piezoelectric type is superior, and the structure is simple, so it is used in a large proportion. As
far as piezoelectric ultrasonic transducers are said to be exclusively bolt-clamped Langevin types,
there are no products commercialized in other shops. By the way, in this Langevin-type vibrator,
two or an even number of piezoelectric ceramic disks polarized in the thickness direction are
stacked in opposite directions of polarization, and this is a cylindrical vibrator such as aluminum
or stainless steel. And these are strongly tightened with a bolt. A high frequency sinusoidal
voltage is applied to the piezoelectric ceramic to excite it in a thick vibration, and the vibration is
resonated by this vibration to amplify the amplitude, so the resonance frequency is determined
according to the length of the vibrator, and the low frequency root The disadvantage was that it
was not possible to make small, small-sized, low-frequency transducers at low frequencies. As
shown in FIG. 1, the conventional Langevin type vibrator sandwiches the terminal plate 6 with
the positive polarity side electrodes of the donut shaped piezoelectric vibrators 11 and 12 with a
thickness of 5 u, a diameter of 351 m and an inner diameter of 15 μm. The cylindrical vibrators
3 and 4 made of aluminum or iron and having a diameter of 35 inches are overlapped on the
outer side and clamped with a cap bolt 5 of a diameter Low. The terminal plate 7 is interposed
between the piezoelectric vibrator 12 and the cylindrical vibrator 3, and the cap bolt 5 is
dropped to a thickness of the bottom 7 m of the cylindrical vibrator 3. It has a structure in which
a torque wrench is tightened in the tag hole. Here, the cylindrical vibrator 3.4 is the shortest to
be adjusted to the half-wave resonant mode, and its length no is given by l = C / 4 f (1). C in the
formula is the velocity of sound of longitudinal waves, and in the case of aluminum, iron, steel,
etc., it shows a value in the range of 5.0 × 10 5 to 5.2 × 10 ′ w / S regardless of the material.
Therefore, when the ultrasonic transducer for 20 K 111i is made of aluminum, the length is 2!
The Lange-Pan ultrasonic transducer used near 20 to 20 KH 7i is approximately equal to
approximately 130 fi, and has a long length.
Since it is usual to take out the output from one end face, if you want to shorten the length of the
vibrator even if the characteristics are sacrificed to some extent, only one cylindrical vibrator 3
should be used and the other cylindrical shape The vibrator 4 may be shortened using a cylinder
of about 20 關 thickness made of stainless steel, but it would still not be possible to make it
shorter than 90 m. [Summary of the Invention] The present invention overcomes the drawbacks
of the above-described technology, and utilizes the fact that the resonance frequency in an
imaging actuator of the same dimension is significantly lower in bending mode than in the
vertical mode An object is achieved by an ultrasonic piezoelectric vibrator characterized in that a
beam-like bending resonator composed of a plurality of bending vibration plates is excited by a
piezoelectric vibrator to generate vertical vibration. Embodiments of the present invention will
now be described with reference to the drawings. Embodiment 1 An embodiment of an ultrasonic
piezoelectric transducer according to the present invention is shown in FIGS. 2 and 3. FIG.
Terminal plate 14.15 is stacked on a donut shaped piezoelectric vibrator 111 112 with an outer
diameter of 30 mm, an inner diameter of 14 m, and a thickness of 2 mm. The ultrasonic
piezoelectric vibrator was configured by tightening with a bolt 16 having a diameter of 20 °. 20
KH, through lead 17.18 connected to terminal plate 14.15! When a sine wave voltage of i + and
10 volts was applied, longitudinal vibration occurred. This transducer has a total length of 25 m
and can be significantly shortened as compared with 130 m of the conventional Langevin
transducer for 2 Q KHJ shown in FIG. The reason for this is that the beam resonator 12 is used,
and its structure is as shown in FIG. 3, in which radial teeth 121 are attached to a donut disk
having an outer diameter of 30 m and an inner diameter of 15 mm and a thickness of 3111. In
this example, a beam-shaped resonator having a thickness of 1 inch and a length of 6.3 teeth 121
is eight is illustrated. The length of the resonator in question here is determined by the length of
the cantilevered teeth. The relationship between the length l of the cantilever, the thickness H
and the resonance frequency, and fr is expressed by 5 × 10 ′ ′ + m in C, H = 1 ws, and fr2 2
× 10 ′, and l = 6.27 m. Since the resonance length of the cantilever is short as described above,
the total length of the ultrasonic piezoelectric transducer is extremely short, and can be reduced
to 25 in 20 KHg. Embodiment 2 The ultrasonic piezoelectric vibrator of Embodiment 1 is indeed
short, but since the beam resonator also has a function of a torsional connector, torsional
vibration is also parasitic. This torsional vibration is considerably suppressed by the bolt 16, but
energy loss occurs and the efficiency is reduced accordingly. Therefore, the ultrasonic
piezoelectric vibrator of this embodiment shown in FIG. 4 is improved to allow free vibration
without suppressing the free end of the cantilever, and the total length is 38 m for 20 KHg. .
The difference from Example 1 is that two beam resonators 22.23 are used so as to form a
symmetrical figure, and in this case, the thickness of the teeth is 2 絽, the length is 8.9 m, and the
width is 7 Dew. The torsional vibration does not act on the bolt 27 since free vibration is
permitted at the contact surfaces of both teeth. Therefore, the spring washer 30 is inserted
between the end face plate 26 and the beam resonator 23 so that the amplitude of the
longitudinal vibration is not suppressed. Here, as the number of teeth increases, the strength of
longitudinal vibration increases, but the number of manufacturing steps also increases. On the
contrary, the strength of the longitudinal vibration does not have to be so large, but a vibrator
that is easy to make may be required. In the figure, 21.212 is a doughnut-shaped piezoelectric
vibrator 24.25 is a terminal plate, and 28.29 is a lead wire. Embodiment 3 An embodiment of an
ultrasonic piezoelectric transducer which is easy to manufacture will be described below. In the
resonator of the second embodiment shown in FIG. 4, two teeth of 8.9 dew are in contact with
each other, so the tooth length of this portion is 17.8 m. Assuming that the contact surfaces of
the teeth are welded, the teeth are no longer cantilevered beams but are fixed beams at both
ends, and the relationship between the beam length l, the thickness H and the resonance
frequency f is not the equation (2). Here, if H = 2 m, fr-20 x ay, C: 5 X 106 關 / S, then J = 22, 4
關. If a cylinder with a length of 28.4 酩, an outer diameter of 30 m, an inner diameter of 26 m,
one end is open and the other end has a thickness of 3 thick is equally divided into 16 parts
along the circumference and deleted every other It is possible to have 2 teeth of length 25.4 mtx
and a width of about 6 teeth with eight round bottoms. A hole of 15 顛 in diameter is drilled in
the round bottom of 3 關 in thickness. Next, tap a 8 mm disc with a diameter of 7 m and a
diameter of 30 m as shown in Fig. 6, and make a hill with a diameter of 15 battles around it, and
remove 4 u of the outside to make a thickness of 3 m The outer periphery of the disk 321 having
the hill-like projections 323 of the screw holes 324 is equally divided into 16 equal parts, and a
groove of 2 m in depth is cut every other one. The eight teeth 322 described above were fitted
into the grooves and welded to form a beam resonator 32. A donut-shaped piezoelectric vibrator
31 ° 312 and a terminal plate 33. 34 are overlapped on this resonator 32, and the end plate is
tightened with a bolt 35 having a diameter of 8 sm and a length of 34 to make an ultrasonic
piezoelectric vibrator. When a sine wave voltage of 20 x H 7 l, 10 volts was applied to the lead
wire 36. 37 soldered to the terminal plate 33. 34, longitudinal vibration was excited in the
ultrasonic piezoelectric vibrator and the end plate was violently vibrated. Since this vibration has
a form in which the circumferential part is a tooth and is diverted with respect to the bolted part
at the center of the end face plate, the central part of the end face plate has a small amplitude
and the outer peripheral part has a large amplitude.
What has been described above is an example of the ultrasonic piezoelectric vibrator of the
present invention, in which the total length of the vibrator is shortened by using a resonator
utilizing the resonance of the bending mode of the beam. Beam resonators also have cantilever
beams, fixed-end beams and other variations of these. In addition, since the beam illustrated the
cylindrical vibrator ¦ oscillator, although arrange ¦ positioned along radial arrangement ¦
positioning or circumference, not only this but it can not be overemphasized that it can arrange
along a side, when a vibrator is prismatic. [Advantage of the Invention] As described above, since
the beam resonator comprising a plurality of flexural diaphragms is excited by the piezoelectric
vibrator to generate warping, a conventional Langevin ultrasonic transducer is used. In
comparison, the overall length of the transducer can be significantly shortened, and the
ultrasonic device utilizing this can be miniaturized.
Brief description of the drawings
1 is a front view of a conventional Langevin-type vibrator, FIG. 2 is a front view of a Langevintype vibrator according to a first embodiment of the present invention, and FIG. 3 is a side view
of a resonator used for the vibrator. FIG. 4 is a front view of a Langevin-type vibrator according
to a second embodiment of the present invention, FIG. 5 is a front view of a Langevin-type
vibrator according to a third embodiment of the present invention, and FIG. It is a side view of
the resonator to be used.
11.21, 31 ······ Donut-shaped piezoelectric vibrator, ··· · · · · · · · · · · · · · · · · · · · · · · · · · · · donut-shaped
piezoelectric vibrator, 12 · · · · bending vibrator, 22 23.23 · · · · · · · · · · · · · · · beam-like resonator.
Figure 1 Figure 21 Figure 3 Figure 4 Figure 5 Figure 6
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