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JPH04128500

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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 JPH04128500
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic transducer used in a fish finder or the like and used underwater, and more particularly
to an improvement of the transducer structure.
[0002]
2. Description of the Related Art Conventionally, ultrasonic transducers have been used in fish
finders and the like. A fish finder is a device that transmits ultrasonic waves in water and receives
a reflected wave from a reflector such as a fish school to know the size, distance, etc. of the fish
school. Therefore, in a fish finder or the like, a device for transmitting and receiving ultrasonic
waves, that is, an ultrasonic transducer is essential.
[0003]
An ultrasonic transducer is usually constructed using an ultrasonic transducer formed of a
piezoelectric material. FIG. 3 shows the configuration of an ultrasonic transducer according to a
conventional example, and the ultrasonic transducer shown in this figure is an ultrasonic
transducer 10 formed of a piezoelectric ceramic material such as PZT. Is equipped.
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[0004]
Electrodes 12 and 14 of silver or the like are coated on the surface of the ultrasonic transducer
10. Signal cables 16 and 18 are connected to the electrodes 12 and 14 by soldering or the like,
respectively. The vibrator 10 is polarized by applying a voltage in a predetermined direction
between the electrodes 12 and 14, and is placed inside the metal case 20. A sound insulating
material 22 is filled in the metal case 20. The sound insulation material 22 is a material such as
cork, polyurethane resin, etc., and has a function of enhancing the radiation efficiency of the
ultrasonic transducer 10. The ultrasonic transducer 10 is sealed with, for example, a urethane
resin together with the sound insulation member 22. The layer 24 of urethane resin functions as
a so-called matching layer. Here, the matching layer means the acoustic impedance of the
ultrasonic transducer 10 (35 × 10 6 kg / m 2 s when formed from PZT) and the acoustic
impedance of seawater 1.5 × 10 6 kg / m 2 s. It is a layer that secures the target consistency by
the so-called λ / 4 matching technology.
[0005]
Therefore, when it is intended to transmit water into a conventional ultrasonic transducer having
such a configuration, a voltage is supplied between the signal cables 16 and 18 and ultrasonic
vibration is generated by this voltage. The child 10 is excited. Then, the ultrasonic transducer 10
transmits ultrasonic waves in the upper direction of the figure, and the ultrasonic waves are
reflected by a reflector such as a fish school in water. The reflected wave is again received by the
ultrasonic transducer 10 through the matching layer 24, and the signal cables 16 and 18 output
signals relating to reception. If the signal relating to transmission is, for example, a pulse signal,
the time difference between the transmission time and the arrival time of the pulse relating to the
reception can be used to know the distance to the fish school. You can know the scale of
[0006]
As described above, conventionally, it has been possible to construct a fish finder or the like
using an ultrasonic transducer.
[0007]
In the case of applying an ultrasonic transducer to a device such as a fish finder, it is necessary to
increase the transmission power and increase the reception sensitivity in order to look as far as
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possible.
However, in order to increase the transmission power, it is necessary to increase the shape of the
ultrasonic transducer, which results in the problem of an increase in the size of the apparatus.
Further, in order to improve the receiving sensitivity, it is preferable to use an ultrasonic
transducer formed of a piezoelectric material having a hole, which has been previously proposed
by the applicant of the present application (Japanese Patent Laid-Open No. 1-172281). This
material has a large g constant representing the amount of charge generated per 1 N of applied
force, and therefore has high reception sensitivity as compared with a vibrator formed of a
material having no holes. On the other hand, the mechanical strength is weak due to the presence
of the holes, and when a large amount of transmission power is injected, mechanical destruction
or the like occurs, so that the transmission power can not be increased.
[0008]
The present invention has been made to solve these problems, and it is an object of the present
invention to provide an ultrasonic transducer capable of increasing the transmission power and
improving the receiving sensitivity. To aim.
[0009]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is
directed to an ultrasonic transducer for transmitting waves which is formed of a piezoelectric
material and transmits ultrasonic waves by application of a voltage. In order to receive ultrasonic
waves related to the reflection from the reflector via the transmitting ultrasonic transducer, the
transmitting ultrasonic transducer is on the opposite side of the transmitting direction of the
ultrasonic waves. And a receiving ultrasonic transducer having a smaller radiation surface than
the transmitting ultrasonic transducer.
[0010]
The second aspect of the present invention is characterized in that the transmitting ultrasonic
transducer is formed of a non-perforated material and the receiving ultrasonic transducer is
formed of a perforated material.
[0011]
According to claim 3 of the present invention, the transmitting ultrasonic transducer is made of a
piezoelectric ceramic material, and the receiving ultrasonic transducer is made of an organic
piezoelectric material or a composite piezoelectric material in which a piezoelectric ceramic
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powder is mixed with rubber. It is characterized in that it is formed.
[0012]
In the present invention, transmission and reception are performed by different ultrasonic
transducers.
That is, the transmission is performed by the transmission ultrasonic transducer having a
relatively large shape, and the reception is provided on the back surface of the transmission
ultrasonic transducer and has a smaller radiation surface. It is done by a sonic transducer.
If the force applied to the ultrasonic transducer for transmission is F1, the sound pressure is P1,
the force applied to the ultrasonic transducer for reception is F2, and the sound pressure is P2,
then As a result of the ultrasonic transducer receiving ultrasonic waves through the transmitting
ultrasonic transducer, F1 = F2, so the sound pressure P = (S1 / S2) P1 applied to the receiving
ultrasonic transducer Become.
Here, S1 is the transmission area of the transmission ultrasonic transducer, and S2 is the
reception area of the reception ultrasonic transducer.
Here, since S1> S2, the sound pressure P2 is larger than P1. Therefore, an ultrasonic transducer
having a high sound pressure as compared to the case where transmission and reception are
performed using a single transducer, and thus improved reception sensitivity, can be obtained.
Furthermore, in claim 2, a non-perforated material capable of taking relatively large injection
power is used as a material for forming a transmitting ultrasonic transducer, and as a material
for forming a receiving ultrasonic transducer. A perforated material with relatively good
reception sensitivity is used. Therefore, in addition to the effect obtained in claim 1, an effect of
improving the transmission power and improving the receiving sensitivity can be obtained.
[0013]
The third aspect of the present invention has the same effect as the second aspect of the present
invention. That is, in the third aspect, an organic piezoelectric material or a composite
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piezoelectric material is used as a material for forming the receiving ultrasonic transducer.
Similar to the above-described perforated material, these have the effect of enhancing the wave
receiving sensitivity.
[0014]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the
present invention will be described below based on the drawings. The same components as those
in the conventional example shown in FIG.
[0015]
FIG. 1 shows a transducer structure of an ultrasonic transducer according to an embodiment of
the present invention, and FIG. 2 shows its assembly state. As shown in FIG. 1, in the present
embodiment, in addition to the ultrasonic transducer 10 formed of a PZT material not containing
pores, an ultrasonic transducer 26 formed of a PZT material containing pores is used. It is done.
The vibrator 10 which does not include the holes is formed, for example, of 50 mφ, and the
vibrator 26 which includes the holes is, for example, a 5 to 10 mφ vibrator. Electrodes 28 and
30 made of silver or the like are formed on the upper and lower surfaces of the vibrator 26,
respectively. The electrode 28 is bonded to the electrode 14 of the vibrator 10 by an epoxy resin
32 having conductivity. The ultrasonic transducer 26 is a vibration produced by, for example,
mixing 10% to 40% (volume ratio) of methacrylic resin with PZT powder and performing steps
such as pressure molding, firing, formation of the electrodes 28 and 30 with silver, etc. It is a
child. In this vibrator, the methacrylic resin is burnt out during firing, and pores are formed in
the portion where the methacrylic resin was present. As a result, a vibrator having a larger g
constant can be obtained as compared with the vibrator 10 in which the material containing no
void is formed.
[0016]
Thus, the vibrator structure composed of the two vibrators 10 and 16 is enclosed in the metal
case 20 in the same manner as the conventional example shown in FIG. In this case, since the
electrodes 14 and 28 are electrically connected by the epoxy resin 32, the signal cable 18
functions as a cable for both electrodes 14 and 18. Moreover, in this embodiment, a signal cable
34 related to the electrode 30 is provided.
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[0017]
When ultrasonic waves are to be transmitted into water using the ultrasonic transducer
according to this embodiment, a predetermined voltage is applied between the signal cables 16
and 18 from the transmitter. This voltage, that is, the transmission signal, is converted into
ultrasonic waves in the vibrator 10 and is transmitted into water through the matching layer 24
formed of urethane resin. In this case, since non-perforated (ie, dense) PZT is used as a material
for forming the vibrator 10, relatively large transmission power can be maintained.
[0018]
Further, when the ultrasonic wave transmitted in this manner is reflected by the fish school etc.
and received, the ultrasonic wave related to the reception is received by the vibrator 26 through
the matching layer 24 and the vibrator 10. Be done. Since the vibrator 26 is formed of a material
having holes, the reception sensitivity is high, and since the electrode area is smaller than that of
the vibrator 10, reception is performed with sound pressure enhanced according to the area
ratio. . Therefore, the voltage appearing between the signal cables 18 and 34 is higher than that
in the case where the wave is received only by the vibrator 10. That is, the sensitive voltage is
high, and a good reception operation is realized.
[0019]
Furthermore, in this embodiment, since all the transmission operations are performed in the
vibrator 10, mechanical distortions associated with the injection of the transmission power occur
only in the vibrator 10. Therefore, the breakage of the vibrator 10 or 26 due to the mechanical
strain hardly occurs.
[0020]
As described above, according to this embodiment, it is possible to increase the transmission
power without causing mechanical damage and to improve the sensitivity for reception.
[0021]
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In the above description, PZT is assumed as a material for forming the vibrators 10 and 26, but it
may be another type of piezoelectric ceramic material.
That is, in addition to Pb (Zr, Ti) O3: lead zirconate titanate (PZT), BaTiO3: barium titanate,
PbTiO3: lead titanate may be used. Furthermore, the means for forming the pores may be other
than the mixture of PMMA.
[0022]
Further, the vibrator 26 may be formed of other than the piezoelectric ceramic having the holes.
For example, the sensitivity improvement due to the area ratio can be realized even when formed
from non-voided Pb (Zr, Ti) O3, BaTiO3 or Pb (Zr, Ti) O3. Alternatively, an organic piezoelectric
material or a composite piezoelectric material may be used, and in this case, the sensitivity
improvement due to the material is also realized. As the organic piezoelectric material, for
example, PVDF: polyvinylidene fluoride, PVDF copolymer, P (VDF / TrFE): copolymer of
vinylidene fluoride and ethylene trifluoride, P (VDCN / VAc): vinylidene cyanide Examples of
composite piezoelectric materials include NBR: copolymer of butadiene and acrylonitrile, SBR:
radical copolymer of butadiene and styrene or urethane rubber mixed with piezoelectric ceramic
powder. You can mention the materials you
[0023]
As described above, according to the present invention, the transmission ultrasonic transducer
using a relatively large area and the ultrasonic transducer for receiving a relatively small area are
used to transmit Since the wave is received by the wave receiving ultrasonic transducer via the
ultrasonic transducer, the transmission power can be increased to improve the wave receiving
sensitivity.
[0024]
According to the second aspect of the present invention, since the transmitting ultrasonic
transducer is formed from the non-perforated material and the receiving ultrasonic transducer is
formed from the perforated material, the receiving sensitivity can be increased. It is possible to
enhance.
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[0025]
According to the third aspect, the same effect as that of the second aspect can be obtained, and in
addition, the processing at the time of manufacturing the ultrasonic transducer for wave
reception can be simplified.
[0026]
Brief description of the drawings
[0027]
1 is a side view showing a transducer structure in an ultrasonic transducer according to an
embodiment of the present invention.
[0028]
2 is a cross-sectional view showing the assembled state of this embodiment.
[0029]
3 is a cross-sectional view showing the configuration of an ultrasonic transducer according to a
conventional example.
[0030]
Explanation of sign
[0031]
10, 26 vibrator 12, 14, 28, 30 electrodes
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