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Description 1, title of the invention
Ultrasonic transducer
3. Detailed Description of the Invention The present invention relates to a high pressure resistant
ultrasonic transducer. FIG. 1 shows an example of a conventional thickness vibration type
ultrasonic transducer, wherein 1 is an ultrasonic transducer, 2 is a Kirk rubber, 3 is a cable, and
4 is a waterproof molding material. The Kirk rubber 2 is provided on the rear surface of the
ultrasonic transducer 1, so that when the ultrasonic wave is incident from the front of the
transducer as shown by the arrow A, the ultrasonic transducer 1 vibrates accordingly The voltage
output is generated between the lines of the cable 3. However, as shown by the arrow B, when
the ultrasonic wave is incident from the back of the transducer, the sound insulation by the kilk
rubber 2 causes the sound wave to be an ultrasonic transducer It is hard to be transmitted to 1
and therefore the vibration is also small I and -1, so the voltage output is also small. As described
above, it is the kirkgo that the receiving sensitivity is high for the incident sound from the front
(hereinafter referred to as the front incident sound) and low for the incident sound from the rear
(hereinafter referred to as the rear incident sound). This is realized because the 42 specific
acoustic impedances are sufficiently low with respect to the acoustic medium such as water. The
ratio of the reception sensitivity to the front incident sound and the reception sensitivity to the
rear incident sound is referred to as an anteroposterior ratio, but in the transceiving EndPage: 1
unit according to the configuration of FIG. 1, an anteroposterior ratio of 20 dB or more can be
easily realized. . As described above, the Kirk rubber 2 has a low specific acoustic impedance,
which is the same as a small Young's modulus (bulk modulus), which is proportional to the
square root of the Young's modulus. Accordingly, in the conventional transducer using the Kirk
rubber 2 which is a material having a small Young's modulus b, the Kilk rubber 2 is compressed
by hydrostatic pressure, and the sound insulation of the Kilk rubber 2 is lost in the ocean with a
degree of joist. When Tsurushi and Kirk rubber 2 are compressed, the back sensitivity is high
even if the rear incident sound 1 is received, so that the front / back ratio deteriorates and
becomes less than O dB, and the reception sensitivity to rear incident sound becomes higher
Things are often too. In addition, the Kirk rubber 2 is compressed and deformed to cause other
components to undergo large cracks, which may result in cracks in the waterproof molding
material and loss of waterproofness, as shown in FIG. The water pressure resistance of the
conventional transducer was about 100 to 200 m in water depth. Although the above-mentioned
explanation F3A describes the operation as a wave receiver and its defects, a similar defect is
established at the time of operation as a wave transmitter from the principle of the reversibility
of the wave transmitter and receiver. That is the heat. The object of the present invention is to
solve these drawbacks by using a backing layer of a structure in which a metal plate is provided
on the back surface of an ultrasonic transducer by interposing a 1'11 interlayer material made of
a rubber material. Alternatively, it is characterized in that a plurality of layers are provided, and
the rubber material and gold (4 temporary wavelength V9 to 1446 of the wavelength of the
internal sound of thickness 'f't' r'Z are limited.
An embodiment of the present invention will be described with reference to FIGS. 2, 3 and 4. FIG.
In FIG. 2, 1 is an ultrasonic transducer, 3 is a cable, 4 is a waterproof molding material, 5 is a
rubber material, 6 is a metal plate, and the metal plate 6 is an ultrasonic transducer with the
rubber material 5 interposed. The rubber material 5 and the metal plate 6 which are provided on
the rear face of 1 and whose thickness is limited to 1/9 to 14 // 36 of the wavelength of each
internal sound wave-ultrasonic wave configured in this way A qualitative description of the
operation of the transducer is as shown in FIG. FIG. 3 is an operation explanatory diagram, as
indicated by arrow A (when the sound wave is incident from the front of the 3-transceiver, the
ultrasonic transducer 1 vibrates and the receiving voltage output is between the lines of the cable
3 Occurs on This is the same function as the conventional example shown in FIG. However, when
the sound wave is incident from the rear as shown by arrow B, the sound wave B1 reflected at
the boundary C between the jX waterproof molding 4 and the metal plate 6 and the boundary C
are transmitted to the metal plate 6 and the rubber 5 When the metal plate 6 has a thickness of
A wavelength, it is in phase with the wave sound B2 and is synthesized as a strong reflected
wave. On the other hand, when the rubber material 5 has a thickness of 14 wavelengths, it
transmits through the boundary C1b and is reflected by the boundary a between the rubber
material 5 and the ultrasonic transducer 1 to reciprocate, and the acoustic wave B5 reflected and
transmitted through the boundaries c and b. Then, the sound wave BIl that has reached the
boundary a is included in the boundary a and is in reverse phase, and mutually cancel each other.
Therefore, the vibration of the ultrasonic transducer 1 due to the backward incident sound is
small and the vibration is small b, so that the receiving sensitivity is low. The above explanation
is qualitative, and in fact, since it is 4- even though transmission 9 reflection is performed at
boundaries a, b and c in a multiple manner, the phenomenon is somewhat more complicated.
According to the present inventor's analysis on the transmission line model, the longitudinal ratio
FBR is equal to the open transmission coefficient due to the back incident sound. However, it is
necessary. Where zo: specific acoustic impedance of the ultrasonic transducer 1, Rw: specific
acoustic impedance of the sound field medium, zB: specific acoustic impedance when looking
backward from the boundary a, ko: wave number of the ultrasonic transducer 1, to : Thickness of
ultrasonic transducer 1. The aforementioned conditions are satisfied at most frequencies in the
embodiments of the present invention. In the embodiment shown in FIG. 2, a two-layered backing
composed of a rubber material 5 having 14 wavelengths at the reference frequency and a metal
plate 6 having 14 wavelengths is performed. When stainless steel is used as the metal plate 6,
the open EndPage: 2 is obtained. Here, Ω = ta ′ ′ (2 fq), f: frequency. The front-rear ratio FBR
can be expressed as a function of frequency as shown in FIG.
In FIG. 4, the FBR of 20 dB or more is in the range of 414 fQ 99, which corresponds to the 14/36
wavelength from the wedge wavelength. As described above, in the present embodiment, a metal
plate is provided on the rear surface of the ultrasonic transducer with an intermediate medium
made of a rubber material interposed, and the thickness of each of the rubber material and the
metal plate is By setting the wavelength V9 to 14/16 of the internal sound wave, it is possible to
set the front-to-back ratio of the receiving sensitivity to 20 dB or more, which can realize the
same performance as the front-to-back ratio at the shallow depth of the conventional ultrasonic
transmitter / receiver It is. In addition, it is not backed by a material with a small Young's
modulus, which is one of the same as a conventional ultrasonic transducer, and a rubber material
having a Young's modulus substantially the same as water, which is a sound field medium, and
an extremely Young's modulus. Because the backing is a two-layer structure with a large gold PA
rice, it can not lose noise due to reverse compression due to hydrostatic pressure, and the
secondary waterproof mo / li will be cracked and waterproof. There is no such thing as losing
money. In this embodiment, it is confirmed that there is no abnormality at a depth of 1500 m.
Although the above-described embodiment has described the case of using an 11-circle vibrator
that vibrates in thickness as a vibrator, it may be a vibrator that vibrates longitudinally, and as
shown in FIG. In the case of arrayed ultrasonic transducer arrays, the same effect can be
obtained, and further, a structure in which grooves are inserted halfway from the acoustic
emission surface of the 11 or more 11 d transducers, that is, a dicing type transducer is used The
same effect is produced also in the case of Further, in each of the above-described embodiments,
the case where one backing layer composed of a rubber material and a metal plate is provided is
described, but if a plurality of backing layers are provided, the front-rear ratio is even larger. The
coming is great. Although the operation and effects as a receiver have been described here, from
the principle of reciprocity of a transmitter-receiver, the same effects as described above are
produced even when operating as a transmitter. is there. As described above, according to the
present invention, since the rubber material and the metal plate each having 1/9 to 4/36
wavelength are used as the backing layer of the vibrator, the front / back ratio of the sensitivity
is 20 dB or more In addition, since the longitudinal ratio does not deteriorate even at a water
depth of 1500 m and cracks do not occur in the waterproof molding material, it is highly reliable
as an ultrasonic transducer for use in depth. In addition, in the case of high frequency ultrasonic
waves such as the MHz band, since the transducer becomes thin or reinforced by the backing
layer when using the present invention, there is an advantage that it becomes extremely strong 1
l-1 '.
2 is a cross-sectional view showing the structure of one embodiment of the present invention,
FIG. 3 is an operation explanatory diagram of FIG. 2, FIG. 4 is a diagram showing front / rear
ratio FBR as a function of frequency, and FIG. It is sectional drawing which shows a structure.
DESCRIPTION OF SYMBOLS 1 ··· Ultrasonic transducer 2 ··· Kirk rubber 3 · · · Cable 4 · · ·
Waterproof molding material 5 · · · Rubber material 6 · · · Gold 8-pressure plate 7 · · · ultrasonic
transducer patent applicant Oki Electric Industry Co., Ltd. Attorney Attorneys Kinji Kinkura
EndPage: 3 Procedure Amendment (Spontaneous) May 1951 Patent Office Secretary Nori
Kawahara No. 1, Display of the Case Patent No. 123122 Patent No. 123122 2, Title of the
Invention Ultrasonic Transducer 2, Title of the Invention Ultrasonic Transducer 3, Person with
Correction Case Patent Applicant Address Minato-ku, Tokyo Toranomon 1-chome 7- 12 Name
(029) OKI Industrial Co., Ltd. Representative Masao Miyake 4, agent
Ultrasonic transducer
5. Date of correction instruction date Spontaneous 6. Number of inventions to be increased by
correction 7 Target of correction "Description column of the invention". 8. Correction content ■,
page 10, line 10, "Is it thinner?" And correct it as "but thinner". = 2-EndPage: 5 Warning: Page