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DESCRIPTION JPS61133883

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DESCRIPTION JPS61133883
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
low frequency, high power underwater ultrasonic wave transmitter used for long distance sonar,
marine resource exploration, etc. (Prior Art) Since low frequency ultrasonic waves in water have
less propagation loss in comparison with that of high frequency waves and can reach further
distances, low frequency ultrasonic waves in fields such as sonar, marine resource exploration,
ocean current survey etc. The use of ultrasound has a number of advantages. Conventionally,
electrodynamic transducers and piezoelectric transducers are known as transmitters that emit
high intensity ultrasonic waves in water. Although an electrodynamic transducer can take a large
displacement, it is an inner cone to obtain a small-sized transducer at low frequency due to the
small generation force. On the other hand, in piezoelectric transducers, porcelain is used as the
electromechanical conversion material, and lead zirconate titanate based pressure is used, and
piezoelectric ceramics have an acoustic impedance that is about 20 times greater than that of
water. However, although the generated power is extremely large, there is a disadvantage that
the acoustic radiation can not take the displacement necessary for medium exclusion. Low
frequency-In consideration of the fact that the acoustic radiation impedance per unit radiation
area is extremely low, in order to achieve good acoustic radiation at low frequencies, the
displacement of the piezoelectric ceramic is further expanded to make the acoustic It is necessary
to do radiation. Hereinafter, a conventional piezoelectric transducer will be described. It is well
known that a bolt-clamped Langevin transducer is actively used in a frequency band of 3 kHz to
several tens of kHz as a transducer for transmitting strong ultrasonic waves in water. However,
when this transducer is to be operated at a low frequency band of 3 kHz or less, there is a
disadvantage that the weight and size become too large for practical use because it does not have
a displacement enlarging mechanism. . Therefore, as transducers whose miniaturization can be
achieved in the low frequency band, for example, I.I.Trans. On ultrasonics engineering (IB'BE
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Trans, on Ultrasonics Engineering), pp. 116-124 (19f 53. 11). As shown in Fig. 5, a flexing
transducer using the flexing vibration of the disc as shown in Fig. 5, or Journal on Acoustic
Society on America (J, Acoust, 8oc, Am,). Tol, 68, 44. pp. 1046-1052 (1980 ° 10). A bending
and elongation transducer using an oval shell as shown in FIG. 2 as described above is known.
(Problems of the Prior Art) FIG. 5-The bending transducer using a circular flat plate shown in the
figure uses a circular bimorph moving member as a wave transmitter as is well known. In FIG. 5,
10 is a lead zirconate titanate-based piezoelectric ceramic plate, 11 is a metal plate of nickel,
stainless steel or the like, and 10.11 constitutes a bimorph 4 rotor, and the bimorph moving
motor itself is an acoustic radiator And また12はキャビティ、13はハウジングケースである
。 However, since a large-area piezoelectric ceramic plate can not be obtained as the 10
piezoelectric ceramic plates, a bimorph oscillator is obtained by bonding a large number of
segment ceramic plates to the metal plate 11 in a mosaic manner. Is the current situation. That is,
since the large-area porcelain plate can not be used, the medium exclusion capability as a
transmitter is not sufficient and it is not suitable for high power transmission. In addition, even if
a large-area piezoelectric ceramic plate is obtained, the bimorph imaging actuator having a large
deflection compliance is considerably large, and it is not desirable to have a large medium
removing capability. When the piezoelectric ceramic columnar body 20 is stretched and
displaced in the long axis direction, the bending and elongation transducer shown in FIG. 6 is
displaced several times as large as the columnar body 20 as the shell 21 is shown by double
arrows in the figure. Is a transducer having a kind of displacement magnification mechanism that
contracts. (The displacement is indicated by an arrow by a quarter of the elliptical shell.) Because
this transducer uses an acoustic shell, it has a structurally greater rigidity than the bimorph disc.
It is considered to be a better transducer for high power transmission than the transducer using
the bimorph disc of FIG. However, there is a strong shape dependence of the elliptical shell in the
performance of the flexion-elongation transducer shown in FIG. In comparison with the major
axis diameter, the minor axis a is smaller, that is, a flat elliptical shell with a large eccentricity,
but theoretically the displacement magnification rate increases and the acoustic radiation
efficiency also improves. Unfortunately, however, this elliptical shell can not have any shape for
the reasons given below. First and foremost, the shape is flatter and more and more stress is
concentrated near where the shell's curvature is large. The second reason is that the storage
space for the piezoelectric ceramic and the electronic device must be taken. From these facts, it is
practically impossible to tweak the ratio a / b of the minor axis to the major axis by 0.3 or less.
Therefore, although the portion of the elliptical shell that is displaced at the maximum] with
respect to the displacement of the piezoelectric ceramic columnar body 20 is the portion of the
short axis, the a / b must be 0.3 or more. Only 5 to 7 times displacement occurs at most.
In addition, since the direction of displacement of the short-axis portion and the long-sleeve
portion is completely opposite, this transducer has a large useless movement with respect to the
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medium exclusion. That is, the displacement of the short axis portion has a disadvantage that the
medium displacement is small, and the average displacement effective for acoustic radiation is
considerably smaller than the maximum displacement when averaged over the surface area of
the elliptical shell. SUMMARY OF THE INVENTION It is an object of the present invention to
eliminate such drawbacks of the conventional transducers and to provide a transmitter which is
compact and excellent in high power characteristics in a low frequency band. The present
invention relates to an active column using a piezoelectric ceramic, an inactive column disposed
along the active column, and a hinge and a lever connected to both ends of the two columns. A
low frequency underwater ultrasonic wave transmitter characterized in that it comprises: a
displacement magnifying mechanism comprising: and an acoustic radiator connected to the
displacement magnifying mechanism via a connecting rod. (Detailed Description of
Configuration) The transmitter according to the present invention improves the problems of the
prior art by using a displacement expanding mechanism and an acoustic radiator. Hereinafter, it
demonstrates according to drawing. FIG. 1 shows one structural example of the transmitter of the
present invention, and the operation principle of the transmitter of FIG. 1 will be described in
detail. In the figure, reference numeral 31 denotes an active columnar body using a piezoelectric
ceramic, which can excite longitudinal vibration by applying a voltage. Two inactive columns 32
are arranged along the active column. A hinge 33 is attached to both ends of the two types of
columns, and a lever 34 is connected to the hinge 33. In order to perform the rigid body rotation
of the lever 34, the non-active columnar body 32 is designed to have a longitudinal displacement
[1 i in 1 month; Hinge 33 is designed to be relatively rigid against longitudinal displacement, and
to be flexible against bending displacement (although when the lever 34 is rotated, the hinge 33
will perform bending displacement) Be done. It is needless to say that the lever 34 is better as it
is completely rigid even with respect to bending displacement as well as U <position. That is, the
hinges 33 and the levers 34 serve to expand the vertical displacement of the base body and the
active columnar body to a large one by lever principle. The displacement magnification ratio is
the ratio of the distance between the hinge coming out of the active column 31 and the hinge
coming out of the non-active column, and the distance between the hinge coming out of the nonactive column and the output point of the lever. Is determined by Therefore, the displacement
magnification can be set arbitrarily in design by changing the geometrical shape.
Furthermore, the enlarged displacement at the output point of the lever is transmitted to the
acoustic radiator 36 by the connecting rod 35 connected to the lever 34 to produce efficient
acoustic radiation. The transmitter according to the present invention has an advantage that the
small displacement of the active columnar body is outputted to the sound emitting end through
the displacement 犬 4 groove and a large displacement is outputted, and highly efficient acoustic
emission is possible. In addition to this, if the mass of the lever 34 and the sound of the i radiator
36 is multiplied by the pH of the active column 4, the like (: ffi 'tx-t approximately squared
magnification of displacement) As a result, even if the actual mass of 34.36 is small, the
equivalent mass can be increased, so that the frequency can be significantly reduced. Also, in the
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transmitter of the present invention, the mass of the lever 34 and the acoustic radiator 36 can be
arbitrarily set independently of the displacement magnification factor, and it is possible to use
conventional flat plates and shells. It does not exist in the displacement magnification
mechanism. This is because, in the case of using a flat plate or shell, when it comes to applying
equivalent mass, it is necessary to increase the plate thickness of the flat plate or shell, but in this
case rigidity increases and co-root frequency increases. It is because it brings about the result. On
the other hand, in the conventional transmitter, while the plate thickness has been reduced, the
number of resonance circles #: decreases, but there is a disadvantage that acoustic radiation (in
which necessary rigidity can not be maintained). Note that 37 in FIG. 1 indicates an O-1 ring,
which is provided timely to obtain a smooth contact with the cabinet 38 without interfering with
the piston movement of the piston radiator 36. Further, in FIG. 1, the connecting rod 35 projects
from the inside of the lever 34 and is connected to the acoustic radiator 34 via the non-active
column 32, the active column 31, and the lever 34. In this case, avoid the mechanical contact
between the connecting rod 35 and 32.3], 34 and avoid the position of 32. 31. 34 or the inactive
column 32 and lever lamix have a candle for tension. Although it is extremely strong against
pressure, in consideration of this, in FIG. 1, when the transmitter is exposed to hydrostatic
pressure, the structure is such that the active columnar packing pressure acts. That is, by
adopting such a structure, the transmitter shown in FIG. 1 can operate at a shallow depth l
without any pressure balance between the internal and external pressure of the cabinet 38. In
the above, the transmitter having the structure in which the connecting rod 35 is extended from
the inside of the lever 34 shown in FIG. 1 has been described, but the structure as shown in FIG.
A transmitter is of course also possible.
In this case, when the hydrostatic pressure acts on the acoustic radiator, the active column 314 is
in tension. However, in the case of operation at shallow depth, this problem can be solved by
incorporating a mechanism for applying pressure to the active columnar body in advance. When
operating at shallow depth, it is necessary to provide a pressure balance structure, but it is
needless to say that this is also necessary for the transmitter shown in FIG. On the other hand, a
transmitter having a configuration in which the active columnar members 31 and the acoustic
radiators 36 are disposed orthogonal to each other is also possible, which is shown in FIGS. 3 and
4. It goes without saying that the transmitter shown in FIG. 3 performs the same operation as the
transmitter shown in FIG. 1 and the transmitter shown in FIG. 41 performs the same operation as
the transmitter shown in FIG. Yes. Although the example described above is an example in which
the f-echo radiator is two examples, the present invention (this invention also includes a
configuration in which one acoustic radiator is provided and one or more displacement
amplification mechanism portions are formed at the end of the columnar body . Embodiment 1
An underwater ultrasonic wave transmitter shown in FIG. 1 will be described as one embodiment
q of the present invention. The electromechanical coupling coefficient 3 M is 0.61, the relative
permittivity ε1. / Ε. The active columnar body 31 is produced by alternately laminating 1080
zirconium lead titanate based piezoelectric ceramics and internal 'vt, q', and the hinge 32, lever
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34, connecting rod 35i is high tensile steel, acoustic radiator 36 Used aluminum alloy. The
acoustic radiator has a circular shape with a diameter of 50 CIrL, and the displacement
magnification ratio of this transmitter is about six times. The cabinet 38 is made of FRPg, and the
total weight of the transmitter is 43 Kf. Next, this transmitter was immersed 20 m below the
water surface, and the resonance frequency was measured to obtain 350 Hz. In addition, when
high power drive was performed and sound pressure was measured 1 m from the acoustic
radiation surface, sound pressure of 180 dB re 1 μPa or more could be easily obtained.
Incidentally, if it is attempted to realize a high power transmitter having a resonance frequency
of 3501 Tz using a conventional bolt-clamped Langevin oscillator, the mass is theoretically 500
K9 or more and can not be put to practical use. (Effects of the Invention) As described above,
according to the present invention, it is possible to obtain a low-frequency high-power
transmitter which is compact and lightweight and has excellent acoustic radiation efficiency.
[0002]
Brief description of the drawings
[0003]
Fig. 1, Fig. 2, Fig. 3, Fig. 4 show examples of the present invention, Fig. 5 shows a conventional
bending transducer, and Fig. 6 shows a conventional bending elongation transducer. Figure
showing a server.
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