close

Вход

Забыли?

вход по аккаунту

?

JPH06311577

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH06311577
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
low frequency band high power underwater wave transmitter used for long distance sonar,
marine resource exploration and the like.
[0002]
2. Description of the Related Art Low-frequency sound waves in water have less propagation loss
compared to high-frequency sound waves and can reach farther distances, so they are low in
areas such as sonars, marine resource exploration, and ocean current surveys. The use of high
frequency sound waves has many advantages. For long distance propagation, it is also effective
to arrange the sound source at a large depth (about 1000 m).
[0003]
Conventionally, as such a low frequency wave transmitter, a piezoelectric type wave transmitter
using a lead zirconate titanate piezoelectric ceramic is used. The piezoelectric ceramic has an
advantage that the generated power is extremely large because the acoustic impedance is about
20 times or more as large as that of water. However, on the other hand, there is also a
disadvantage that the acoustic radiation can not take the displacement necessary for medium
exclusion. Therefore, in order to perform efficient acoustic radiation at low frequency, a device
04-05-2019
1
has been conventionally applied to further increase the displacement of the piezoelectric ceramic.
As a high power transmitter in a low frequency band (3 kHz or less), for example, Journal of
Acoustical Society of America (J. Acoust. Soc. Am. , Vo 1.68, no. As described in U.S. Pat. No.
4, pp. 1044-1052 (19800. 10), a bending and elongation transmitter using an elliptical shell
shown in FIG. 6 is known.
[0004]
SUMMARY OF THE INVENTION In the bending and elongation transmitter shown in FIG. 6, when
the active columnar body 20 made of piezoelectric ceramic is extended and displaced in the long
axis direction, the elliptical shell 21 is shown by the arrow in the figure. As shown, it is a
transmitter having a kind of displacement magnifying mechanism that contracts at a
displacement several times that of the columnar body 20 (only a quarter of the elliptical shell is
shown by an arrow).
[0005]
The resonance frequency of such a bending and elongation transmitter has a value twice or more
the resonance frequency of the elliptic shell 21 itself because the stiffness of the active columnar
body 20 is considerably larger than that of the shell.
That is, the low-frequency miniaturization of the bending and stretching transmitter can not be
achieved without considerably reducing the resonance frequency related to the bending and
stretching mode of the elliptical shell 21 itself having a certain dimension, and the shell in the
bending and stretching transmitter is A further reduction of its resonant frequency is desired.
However, for reasons to be described below, it is extremely difficult to miniaturize the elliptical
shell itself.
[0006]
In order to explain the operation of this elliptic shell, the major axis of the elliptic shell is made to
correspond to the x-axis, the minor axis to the y-axis, and the depth direction to the z-axis. . The
point at which the center of the thickness of the elliptical shell 21 intersects the x axis is (a, 0),
and the point at which the center of the elliptical shell 21 intersects the Y axis is (0, b). That is,
the major axis of the elliptical shell 21 is a, and the minor axis is b. Now, when the active
columnar body 20 is extended and the point P is displaced by + x in the + x direction, a
04-05-2019
2
displacement magnification mechanism of the elliptical shell itself causes a displacement several
times as large as -y in the -y direction at the point Q. It will pull in the medium as a whole shell.
On the other hand, when the active column shrinks, the shell as a whole acts in the direction of
removing the medium. In this case, the rotational displacement of the z-axis is zero at a
translational displacement as parallel to the x-axis of the elliptical shell taken along the x-axis and
as if the roller were nipped. Therefore, the restriction on the movement of the shell is increased
by the amount that rotation about the z axis is not permitted, and the resonance frequency of the
shell is increased. In the bending and elongation transmitter, the low frequency miniaturization is
extremely difficult because the resonance frequency of the elliptical shell itself is difficult to
lower for the reasons as described above.
[0007]
On the other hand, when the shape of the elliptical shell is changed, the shell resonance
frequency certainly lowers as b / a is increased and the circle is approached. However, in this
case, as the b / a is increased, the displacement magnification rate is significantly reduced
compared to the frequency decrease, and there is no merit of changing the shape to achieve
miniaturization. Also, it is recognized that the resonance frequency is lowered when the thickness
of the shell is reduced. However, in this case, not only the medium removing ability of the shell is
reduced, but also the water pressure resistance is significantly deteriorated.
[0008]
That is, in the case of a bending and elongation transmitter as shown in FIG. 6, it is difficult to
realize a transmitter having high power characteristics at a large depth use and being compact.
[0009]
Therefore, it is easy to think of a structure as shown in FIG. 8 as a compact transmitter that
overcomes the disadvantages of such conventional transducers.
In the wave transmitter shown in FIG. 8, two disc-shaped vibrators in which the active disc body
40 made of piezoelectric ceramic is inserted into the metal disc 41 having the main surface
recessed are prepared, and these are prepared as the active disc body 40. Are bonded together
with bolts 42 so that they are on the outer surface side. As a driving principle of this transmitter,
a disk-like vibration consisting of an active disk 40 and a metal disk 41 in which the active disk
04-05-2019
3
40 is fitted using a radial expansion vibration in which the active disk 40 is displaced in the
radial direction. The system is designed to expand the displacement by converting it into bending
vibration of the body. This transmitter structure has the advantage that it can be easily made
thinner and lighter without deteriorating the water pressure resistance characteristics. However,
there is a limit to the water pressure resistance, and since the periphery of the metal disk is fixed,
there is also a limit to high power. Therefore, improvements are required for deep use and high
power.
[0010]
An object of the present invention is to provide a low-frequency transmitter which is compact
and lightweight, and is excellent in high power characteristics at a large depth use.
[0011]
SUMMARY OF THE INVENTION In order to achieve the above object, a low frequency
underwater wave transmitter according to the present invention combines a Helmholtz resonator
and a bending disk resonator to make the resonance frequencies coincide with each other. A low
frequency underwater wave transmitter for outputting a large amplitude sound wave, wherein
the Helmholtz resonator has a cylindrical cavity and a slit formed on the side of the cylindrical
cavity, the slit serving as a mass And a resonator that resonates with the cylindrical cavity as a
compliance, the bending disk type resonator has a disk and an active disk, and vibrates in
bending, and the disk is a cylinder of the Helmholtz type resonator. The active disk is made of a
circular piezoelectric ceramic and is fitted and mounted on the disk.
[0012]
Further, the cylindrical cavity of the Helmholtz resonator is filled with oil and subjected to
pressure compensation with respect to the external pressure.
[0013]
The active disk is formed by combining a plurality of piezoelectric ceramic segments, and the
plurality of piezoelectric ceramic segments are combined in a polygonal shape.
[0014]
Further, the piezoelectric ceramic segments combined in the polygon are provided at a portion
excluding the center of the disk, which is optimized to maximize mechanical output energy.
04-05-2019
4
[0015]
The transmitter according to the present invention improves the problems of the prior art by
adopting the above structure.
FIG. 1 shows an example of the transmitter of the present invention.
In FIG. 1, reference numeral 30 denotes an active disk using a circular piezoelectric ceramic.
The active disk body 30 is polarized in the thickness direction, and by inputting the piezoelectric
in the polarization direction, the radial vibration is excited.
Furthermore, the active disc 30 is bonded by means of a strong adhesive to the inside of the
recess of the metal disc 31 made of a material of high mechanical strength such as high tensile
steel.
The configuration of the active disk body 30 and the metal disk 31 forms a bending disk type
resonator. This bending disk type resonator causes bending vibration as shown in FIG. 2 when a
voltage is applied to the active disk body 30 by fixing its outer peripheral portion and making the
middle portion free. It is. In FIG. 2, the solid line indicates the vibration mode at the time of
bending, and the broken line indicates the shape at the time of steady state.
[0016]
In the wave transmitter of the present invention, two bent disk resonators composed of metal
disks into which such an active disk body is inserted are prepared, and these are used at both
ends of the cylindrical Helmholtz resonator 33. It is constituted by joining with a bolt 32 and a
strong adhesive. As shown in FIG. 3, the Helmholtz resonator is a resonator in which the slits 34
formed on the side surfaces resonate with the mass and the cavity inside the cylinder becomes
compliance.
[0017]
04-05-2019
5
The operating principle of the transmitter according to the present invention is to increase the
amplitude of the acoustic radiation surface, that is, expand the amount of medium exclusion, by
matching the resonance frequency of the Helmholtz resonator with the resonance frequency of
the bending disk resonator. , High power radiation is possible. The resonance frequency of the
Helmholtz resonator can be varied by adjusting the slit 34 formed on the side surface of the
cylinder to an appropriate size. Further, the inside of the cavity of the Helmholtz resonator is
filled with silicone oil 35 so as to be able to withstand a large depth of use to achieve pressure
balance. Generally, when oil is filled inside the transmitter and pressure compensation is
performed, the displacement of the acoustic radiation surface is considerably suppressed.
However, the transmitter according to the present invention is the bending vibration of the
bending disk resonator and the Helmholtz resonator. Since the synergetic effect of respiratory
vibration is used, it is characterized in that it is not subject to much oil displacement control. The
transmitter according to the present invention can operate at a water depth of 1000 m or more
by the pressure balance mechanism. Although not shown in FIG. 1, the outer periphery of the
wave transmitter according to the present invention is molded with a urethane resin in order to
maintain watertightness.
[0018]
The active disc used in the wave transmitter of the present invention tends to be somewhat
fragile in tensile stress, but in the present invention, the active disc 30 is fitted to the outer
surface of the metal disc 31 as shown in FIG. Further, by determining the diameter of the active
disk body 30 to about 60 to 75% of the diameter of the entire transmitter by stress analysis by
the finite element method, only compressive stress is applied to the active disk body 30 under
hydrostatic pressure. It can do so.
[0019]
Further, in the present invention, the outer shape of the active body is desirably a disk in terms
of excellent simplicity, but is not limited thereto.
For example, in order to actively use the longitudinal effect longitudinal vibration of the
piezoelectric ceramic, a plurality of piezoelectric ceramic segments 50, 50,... Are radially
arranged from the center of the metal disk 51 as shown in FIGS. The structure is also effective.
52はボルトである。 Although a plurality of piezoelectric ceramic segments 50, 50,... Are
arranged in a regular octagon in FIG. 4, the present invention is not limited to this and any array
04-05-2019
6
of regular polygons may be used.
[0020]
In the above structure, the piezoelectric ceramic segment 50 is not disposed at the center of the
metal disk 51. There are the following reasons for this. When the piezoelectric ceramic is filled to
the center, the width of the piezoelectric ceramic segment 50 near the center is small, so that the
compliance becomes very large. This affects the compliance of the entire piezoelectric ceramic
segment group, and raises the compliance as compared with the case where the piezoelectric
ceramic is not disposed at the center of the metal disk 51. If the compliance is high, the
mechanical output energy is low and the efficiency is poor. Therefore, the arrangement position
of the piezoelectric ceramic segment group is optimized to the position where the mechanical
output energy is maximized by numerical analysis. Specifically, it is as follows.
[0021]
The figure which extracted one block (fan-shaped piezoelectric ceramic segment group) of the
piezoelectric ceramic segment group in FIG. 5 (a) is shown. When this block is eight
(arrangement octagon), six piezoelectric ceramic segments in one block (n = 6), and one block
length Ln = 90 mm, L0 is a variable, and mechanical output energy Wm The calculation result of
the segment start position (L0) dependency is shown in FIG. 5 (b). The input electric field is
calculated as 300 V / mm. From this, it is known that high mechanical output energy can be
obtained by designing the start position of the piezoelectric ceramic segment to be 30 mm to 40
mm from the center of the transmitter, thereby being optimized.
[0022]
Embodiments of the present invention will be described with reference to the drawings.
[0023]
Example 1 In FIG. 1, the diameter of the active disk 30 is 104 mm, the thickness is 7 mm, the
diameter of the metal disk 31 is 160 mm, the thickness 14 mm, the thickness 7 mm, and the
outer diameter of the Helmholtz resonator 33 And the inner diameter of 13 mm and the height
of 140 mm.
04-05-2019
7
The Helmholtz-type resonator 33 has four shaft-shaped protrusions that project in the inner
diameter direction of the Helmholtz-type resonator 33, and the slits 34 penetrate each of the
protrusions into the inside and outside of the Helmholtz-type resonator 4 The length of the slit
34 is adjusted so as to coincide with the resonance frequency of the bending disk type wave
transmitter. Therefore, the dimensions of the entire transmitter become 160 mmφ × 168 mmφ
at the stage before molding.
[0024]
Next, a lead zirconate titanate piezoelectric ceramic was used for the active disk 30, an aluminum
alloy A7065-T6 was used for the metal disk 31 and the Helmholtz resonator 33, and a trial was
conducted. Further, the inside of the cavity of the Helmholtz resonator 33 was filled with silicone
oil 35, and the whole transmitter was molded with a urethane resin in order to maintain
watertightness.
[0025]
The resonant frequency in air of the prototyped transmitter is 3435 Hz. Next, this transmitter
was placed in a water tank and driven with high power, and the sound pressure at a point 1 m
away from the acoustic radiation surface was measured, and a sound pressure of 203 dBrel μPa
was obtained at 2880 Hz. The Q value in water was also a fairly low value of 4.5. The directivity
was almost omnidirectional. In the water pressure resistance test also, it was confirmed that the
pressure resistance could be up to 500 atm.
[0026]
(Embodiment 2) Another embodiment of the present invention will be described with reference
to FIG. 1 and FIG. In FIG. 1, the bending disk type wave transmitter is replaced with one using
longitudinal effect longitudinal drive as shown in FIG. In FIG. 4, the diagonal length of the
piezoelectric ceramic segment 50 is 180 mmφ thickness 7 mm, the diameter of the metal disk
51 195 mmφ, the thickness 14 mm thick, 7 mm thin, the Helmholtz resonator 33 outer
diameter 195 mm φ, internal diameter The 15 mm height was designed to be 150 mm. Although
the outer shape of the piezoelectric ceramic segment 50 is configured as an octagon in FIG. 4, the
04-05-2019
8
outer shape is not necessarily limited to an octagon, and may be a regular polygon. The number
of slits 34 of the Helmholtz resonator 33 is four, and the length thereof is adjusted to match the
resonance frequency of the bending disk resonator. Therefore, the dimension of the entire
transmitter becomes 195 mmφ × 178 mmφ at the stage before molding.
[0027]
Next, a lead zirconate titanate-based piezoelectric ceramic was used for the piezoelectric segment
50, and an aluminum alloy A7065-T6 was used for the metal disk 51 and the Helmholtz
resonator 33. Further, the inside of the cavity of the Helmholtz resonator 33 was filled with
silicone oil 35, and the whole transmitter was molded with a urethane resin in order to maintain
watertightness.
[0028]
The resonant frequency in air of the prototyped transmitter is 2650 Hz. Next, this transmitter
was placed in a water tank and driven at high power, and the sound pressure at a point 1 m away
from the acoustic radiation surface was measured, and a sound pressure of 205 dBrel μPa was
obtained at 2040 Hz. The Q value in water was also 5.2. The directivity was non-directional, and
even in the pressure resistance test, it was confirmed that it could withstand up to 500
atmospheres.
[0029]
As described above, according to the present invention, it is possible to obtain a low frequency
wave transmitter capable of high power radiation by matching the resonance frequencies of a
bending disk resonator and a Helmholtz resonator. The pressure compensation is performed by
filling oil in the cylindrical cavity of the Helmholtz resonator, because the synergetic effect of the
bending vibration of the bending disk resonator and the respiratory vibration of the Helmholtz
resonator is used. Also, it is possible to perform high power radiation in large depth use without
being subjected to displacement control by oil. In addition, since the disk-like or polygonal shape
is used as the vibrating body, the outer dimensions of the transmitter can be reduced in size as
compared with the conventional case where an elliptical shell is used.
04-05-2019
9
Документ
Категория
Без категории
Просмотров
0
Размер файла
20 Кб
Теги
jph06311577
1/--страниц
Пожаловаться на содержимое документа