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DESCRIPTION JPS56102198

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DESCRIPTION JPS56102198
Description 1, title of the invention
Ultrasound transducer
3. Detailed Description of the Invention In the present invention, in an ultrasonic transducer
having an electro-acoustic transducer including a polymeric piezoelectric film, maximum power
can be supplied between the power source and the ultrasonic transducer, The present invention
relates to an ultrasonic transducer capable of distortion-free transmission of a reflected signal
that is converted into an electrical signal by the ultrasonic transducer. An ultrasonic transducer
for driving an ultrasonic transducer having a polymer piezoelectric film to emit ultrasonic waves
and receiving reflection of ultrasonic waves from an object and converting it into an electric
signal. In order for distortion-free transmission of the reflected signal that is supplied with
maximum power between the data and converted into an electrical signal by the ultrasonic
transducer, the impedance between the power supply and the ultrasonic transducer is The
characteristics must match. Furthermore, it is necessary to match this match as wide as possible
in order to operate at wide band frequencies or to have short pulse response characteristics. FIG.
1 shows the impedance characteristics with respect to the frequency of an ultrasonic transducer
using PZT (zircon-lead titanate ceramic), and FIG. 2 shows its matching circuit. As can be seen
from Fig. 1 EndPage: 1, the impedance characteristics of the ultrasonic transducer used for the
conventional PZT 'with respect to frequency have a large fluctuation with respect to the
frequency, and even if an impedance matching circuit using all passive elements is added. It can
be seen that the frequency band that can be regarded as uniform is narrow. For this reason, in
the conventional ultrasonic transducer using PZT ', improvement of the conversion efficiency and
transmission of a waveform without distortion are difficult to learn. Figure 2 shows the
impedance matching circuit in a conventional ultrasonic transducer using P'ZT gold, where 1 is a
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power source, 2 is a PZT electro-acoustic transducer, 3 I g coil, and 4 is a resistance. It shows. As
shown in FIG. 2, in the conventional ultrasonic transducer using PZT-, the coil 3 and the resistor
4 are all parallel to the electro-acoustic transducer 2, and the impedance is controlled in a
controlled manner. In contrast to the prior art, it has the disadvantage that power is consumed by
the resistor R and the loss is large. FIG. 3 shows the impedance characteristics with respect to the
frequency of the ultrasonic transducer of the piezoelectric polymer. As can be seen from FIG. 3,
in this type of ultrasonic transducer, the capacitive reactance X decreases gradually with respect
to the resistance Rld frequency, and the capacitive reactance X is almost as good as possible even
if it is attributed to the constant capacitance. It can be seen that it can be approximated.
In addition, this ultrasonic transducer has a unique operating center frequency determined by
the configuration of the electro-acoustic transducer including the polymer piezoelectric film. FIG.
3 is an example of an impedance characteristic in an underwater drive of an approximately 1⁄4
wavelength polyvinylidene fluoride piezoelectric film transducer having an operation center
frequency of the example i ′ ′ l of 6 MH 2. The resistance R and the resistance actance X as a
function of frequency (slow change in 7 'is that the' 1 mechanical coupling constant is small, the
resistance and capacitance are mainly due to the dielectric constant and dielectric loss of the
polymer piezoelectric film This is due to the fact that it is fixed and that the acoustic impedance
can be well matched. The present invention provides an ultrasonic transducer using an electroacoustic transducer having such impedance characteristics, in which the maximum power can be
supplied between the power source and the ultrasonic transducer, and at the same time the
electrical signal of the transducer is used. The purpose is to make it possible to transmit a
reflected signal that is converted into a signal with no distortion. Therefore, in the ultrasonic
transducer having the electro-acoustic transducer including the polymer piezoelectric film, the
ultrasonic transducer according to the present invention is characterized in that the electricity at
the operation center frequency determined by the configuration of the electro-acoustic
transducer is -When the resistance kR of the acoustic conversion element and the capacitive
reactance 2x are used, the inductive reactance equivalent to the capacitance actance X is
connected in all series, the cable characteristic impedance and the resistance R (!: '(R match For
the purpose of adding a transformer. Hereinafter, the present invention will be described with
reference to the entire drawings. FIG. 4 shows an embodiment of the impedance matching circuit
used in the present invention, wherein 11 is a connector, 12 is a transformer, 13 is a coil, and 14
is an electro-acoustic transducer including a polymer piezoelectric film. Respectively.
Transformer 12 (having a primary winding, a secondary winding rL 2, and matching the
characteristic impedance of the power supply including the cable connecting the connector 11
and the power supply with the impedance between the electro-acoustic transducer 14 It is The
coil 13 has an inductance that makes series resonance at the operation center frequency with the
capacitance C of the electro-acoustic transducer 14. The electro-acoustic transducer 14 can be
configured, for example, as shown in FIG. 5 (i). In FIG. 5, 15 is a polymer piezoelectric film, 16
and 17 are additional layers, 8 is an electrode, and 19 is a copper plate. The electro-acoustic
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transducer shown in FIG. 5 (i) is the electro-acoustic transducer of the invention of Japanese
Patent Application No. 54-28850.
As the polymer piezoelectric film 15, for example, piezoelectricity is imparted by poling, and a
polymer film having piezoelectricity in the compression direction of the pancreas is used, and
such a polymer material for forming the whole polymer piezoelectric film is used. Polyvinylidene
fluoride or a copolymer thereof, polyvinyl chloride, polyacrylonitrile polymer, or a ferroelectric
material, for example, a polymer material mixed with a powder of lead zirconate titanate is used.
The EndPage: 2 additional layer 16 is added to the surface on the acoustic operation side of the
polymer piezoelectric film. The acoustically operating side of the polymer piezoelectric film
means that of the two film surfaces of the polymer piezoelectric film, transmission of sound
waves to a desired sound field propagation medium using the thickness imaging mode of the
polymer piezoelectric film, Alternatively, it refers to the facing towards the sound propagation
medium upon receipt of the sound waves from the desired sound propagation medium. The
additional layer 16i'X is made of a material whose acoustic impedance Z has a value close to or
equal to the impedance matching circuit of the polymer piezoelectric film 15. Z and Z above. It is
preferable that the relationship of 0.2 <Z / Z and <2 is satisfied, and 0.3 (Z / Z, (0.5 <Z / Z for 2
艷). It is more preferable that the relationship <2 is satisfied. On the other hand, when the
acoustic propagation medium is water, it is preferable that the relationship of Z / Zf ≧ 0.5 is
satisfied in relation to the acoustic impedance Zf of the water, and further, zf <Z / z. It is more
preferable that the relationship of Examples of the substance forming such an additional layer 16
include, for example, a polymer material, and examples of the polymer material include
polyethylene terephthalate, polycarbonate, PMMA, polystyrene, ABS, polyethylene, vinyl chloride,
polyimide, aromatic polyamide, Polyvinylidene fluoride or a mixture of these polymer materials
with an inorganic powder can be mentioned as a suitable example. In addition, in the case where
the shape-retaining property is entirely expected in the additional layer 16, a film molded by
interposing carbon fibers in these polymer materials can be used. Furthermore, it is also possible
to use a film in which a thin gold bottle (eg, stainless steel fiber) having a sufficiently small
diameter compared to the wavelength of the sound wave is mixed in the polymer material.
Furthermore, when it is desired to emphasize flexibility in a form in which the polymeric
piezoelectric film 15 and the additional layer 16 are integrated, for example, when it is desired to
move the transducer having a variable curvature in a desired direction, nylon may be used as the
additional layer 16, for example. , Polyurethane, silicone rubber seater can be used.
The back additional layer 17 can also be made of the same material as the additional layer 16. In
the electro-acoustic transducer of FIG. 5 (i) or (ii), it has frequency-impedance characteristics as
shown in FIG. 3 and the additional layer 16 does not exist and @ 5 (g) What is shown also has a
frequency-impedance characteristic as shown in FIG. The method of determining the inductance
L of the coil 13 is as follows. The specific operating center frequency f of the electro-acoustic
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transducer 14 and the chapter C of the electro-acoustic transducer 14 are determined from the
configuration of the electro-sound 1 transducer 14 -If the inductance L of the coil 13 connected
in series to the acoustic conversion element 14 is a value determined, the electro-acoustic
conversion element 14 and the coil 13 resonate for 1w at the operation center frequency, and
the reactance becomes zero. As a representative value of the resistance Rk at the time of series
resonance, the characteristic impedance of the power supply / R = ("/ rL2 n 2) is arranged as
shown in FIG. Then, the connector 11, the transformer 12, the coil 13, and the electro-acoustic
transducer 14 are housed in one holder. FIG. 6 shows an example of the frequency-impedance
characteristic of the ultrasonic transducer of the present invention to which an impedance
matching circuit is added. As can be seen from this figure, at the operating center frequency (6
MHz), the reactance component is zero, and the impedance of the ultrasonic transducer as seen
from the missing part of the transformer 12 is a pure resistance of about 50 ohms. FIG. 7 is a
cross-sectional view of one embodiment of the ultrasonic transducer according to the present
invention, wherein 11α is a cable connector, 11b is a main connector, 20 is a plastic cover, 21 is
a shielding metal Reference numeral 22 denotes a support metal plate, 23 denotes water, 24
denotes an ultrasonic wave, 25 denotes an object, and 26 denotes a cable. Reference numeral
12.13 and 14 indicate transformers and coil electro-acoustic transducers as in FIG. 4, and the
EndPage of the 41st slot: 3 connector 11 is the cable connector portion 11α. And the main body
side connector portion 11 / l. The substrate on which the transformer 12 and the coil 13 are all
mounted is attached to the supporting metal plate 22, and the supporting metal plate 22 is
integrated with the main body side connector portion 11h. When assembling an ultrasonic
transducer, the inside of the plastic cover 20 (with shield rough metal;-tube 21? Next, the main
body side connector portion 11h, the transformer 12, the coil 13 and the like are inserted, and
finally the electro-acoustic transducer 14 is screwed.
In the example of FIG. 6, water 23 is used as an acoustic propagation medium for one history,
and the ultrasonic waves 24 emitted from the harmful air-sound 4 conversion element 14
propagate in the water 23. The ultrasonic waves 24 reflected by the object 25 are received by
the electro-acoustic transducer 14 and converted into electric signals. The reflected signal
converted into the electrical signal is propagated to a predetermined device through the cables
26. As apparent from the above description, according to the present invention, it is possible to
supply maximum power between the source and the ultrasonic transducer and to be electrically
converted by the ultrasonic transducer. It becomes possible to transmit by reflected signal-+ =
distortion.
4. Brief description of the drawings Fig. 1 shows the impedance characteristics of a PZT-based
ultrasonic transducer with frequency, and Fig. 2 shows the impedance matching circuit in a
conventional PZTk-based ultrasonic transducer. Fig. 3 is a diagram showing the impedance
characteristics of the piezoelectric polymer ultrasonic transducer with respect to frequency, Fig.
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3 is a block diagram of one embodiment of the impedance matching circuit used in the present
invention, and Fig. 5 is FIG. 6 shows an example of the electro-acoustic transducer used in the
present invention, FIG. 6 shows the frequency-impedance characteristic of the acoustic
transducer of the present invention to which the impedance matching circuit is added, and FIG.
FIG. 1 is a cross-sectional view of one embodiment of an ultrasonic transducer of the invention.
11: connector, 12: transformer, 13: coil, 14: electro-acoustic transducer including polymeric
piezoelectric film, 15: polymeric piezoelectric film, 16 and 17: Additional layer, 18: electrode, 19:
copper plate, 20: plastic cut <-121: shield metal tube, 22: support metal plate, 23: water, 24 ...
ultrasonic waves, 25 ... objects, 26 ... cables. Patent Applicant Higashi Shiseido Patent Attorneys
Attorneys Attorneys Kyoya Four Sections Figure 2 End Page: 4 Figure 3 (a) (a) () \) (=) (b) (b) (to)
Figure 7 EndPage: 5
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