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A book a 1, the title of the invention
Multi-structured polymer piezoelectric film transducers
3. Detailed Description of the Invention The present invention relates to a high sensitivity
transducer for electroacoustic conversion, in which a plurality of polymeric piezoelectric films
are multiplexed. As shown in FIG. 1, a metal electrode 2.2 'is attached to the front and back of a
polymer piezoelectric film 1 such as polyvinylidene fluoride which has been subjected to
stretching and polarization processing, and an AC voltage e is applied between the eight back
electrodes. In the pressure dL film 1, stretching vibration 3.3 'parallel to the film surface is
generated. By bending the piezoelectric film 1 as shown in FIG. 2 and fixing its both ends 4.4 ', it
is possible to convert the stretching vibration of the film into a piston movement 5 perpendicular
to the film surface, and hence the film surface The sound wave can be emitted as an acoustic
emission surface. It is a curved type converter that utilizes this, and can be applied to a high
sound speaker, a headphone, and the like. On the other hand, this curved transducer is also
applied to a microphone. By the way, since this curved converter generally has low sensitivity, it
is not necessary to use the input terminal as EndPage: 1 if it is used as a high-tone speaker in
combination with other types of bass and mid-tone speakers. Need to be high, usually a boost
transducer is used. In addition to complicating the configuration of the components, the use of
this boost transducer not only makes the component impedance smaller in proportion to the
square of the boost ratio, it is inconvenient to match with the power supply. is there.
Furthermore, even if the input voltage is increased, it must be suppressed within the dielectric
breakdown limit of the piezoelectric film, and as a result, the maximum acoustic output of one
piezoelectric film has a limit. On the other hand, in the case of a conventional headphone
consisting of a curved transducer, if it is inserted into a jack for another type of headphone with
11 efficiency, the sound output will drop significantly as it is, so it is necessary to turn the knob
to increase the output direct pressure. There was a climb. The present invention has been made
to eliminate these drawbacks, and has a structure in which a large number of j-fold transducers
are superimposed. This will be explained by one aspect below. FIG. 3 shows a specific example of
the present invention, wherein a plurality of curved transducers 1a, 1b, 1c,..., In shown in FIG. 2
are arranged while being alternately inverted in orientation polarization. It is done. Here, the
valley-curved transducer is configured to be excited in an independent vibration mode. Moreover,
the electrodes on the front and back of each piezoelectric film are electrically connected in
parallel so as to be excited acoustically in the same phase, and are used as input / output
electrical terminals 6.6 '. The spacings 7a, 7b, 7c,-, 7n-1 of the respective curved transducers are
configured to be sufficiently short in comparison to the wavelength, so that the sound waves
independently radiated from the respective curved transducers are It is superimposed at the
sound receiving point sufficiently far from the transducer.
Therefore, an increase in output sound pressure proportional to the number of curved
transducers is obtained for the same input terminal. In order to obtain a sufficient superposing
effect, it is desirable that the total thickness 8 of the curved transducers be reduced to 1/10 or
less of the wavelength of the target sound wave. Next, a transducer made of a polyvinylidene
fluoride piezoelectric film will be described in detail based on FIG. 4 as another specific example.
FIG. 4 is a cross-sectional explanatory view in the case where five sheets of polyvinylidene
fluoride pressure '* 1 fU1a to 1e are stacked. In this specific example, the polarization directions
of the respective piezoelectric films are alternately reversed as indicated by the arrows, so to
excite the respective piezoelectric films in the same phase, the connection between the electrodes
is performed as illustrated. It is good. That is, thin waveguide plates 9a to 9f are inserted from
both sides, and both ends of the piezoelectric film are crimped from both the upper and lower
sides, lead wires are respectively connected, and one input terminal 6 and 4 'of the transducer is
plate 9b, 9dt 9'. And the other input terminal 6 'and the conductive plates 9a, 9c, 9e. Here, it is
preferable to interpose braided objects 10a to 10d between the respective 1: E electric films so
that the piezoelectric films do not come in direct contact with each other. Examples of such
reticulated objects include synthetic fibers such as nylon and vinylidene chloride resin, natural
fibers, glass fibers, metal fibers, etc. Small objects, preferably point contact objects, and soft
objects are used. In the absence of such a netlike object, vibrations of the piezoelectric films may
be coupled to each other. Preferably, the space between the vibrating membrane and the
vibrating membrane is not sealed so that each vibrating membrane can vibrate independently.
The shape of each piezoelectric film used in the present invention is not limited to a curved type
as shown in FIG. 2 to FIG. 4, but a cylindrical shape or a cylindrical or spherical shape with a part
of the circumference chipped. It may be spherical, for example hemispherical, partially missing.
In this case, in order to maintain such a shape, it is preferable to use means such as lining an
elastic material such as foamed polyurethane. Although polyvinylidene fluoride has been
described in the above specific example, the polymer piezoelectric film used in the present
invention is not limited to vinylidene fluoride homopolymer, and a copolymer containing
vinylidene fluoride as a main component, or any of these as a main component (A vinylidene
fluoride tree such as a composition), a vinyl fluoride resin, and further, a composition in which a
piezoelectric substance is dispersed in a polymer of EndPage: 2 general. A laminate or the like
which makes any of these-one may be used.
Moreover, although the case where the polarization direction of the piezoelectric film was
alternately reversed was demonstrated in the specific example, Wang! The polarization directions
of the films may be aligned in the same direction. In either case, the electrode 2.2 'of the pressure
i film may be electrically connected in parallel with the input / output electrical terminal 6.6'. The
following method is extremely simple as a method of manufacturing a transducer in which the
polarization direction of the piezoelectric film is alternately reversed. Immediately after the
piezoelectric film 51 is bent as shown in FIG. 5 (a), a mesh-like object is inserted between the
piezoelectric films 51 (not shown) but bent, as shown in FIG. 5 (b). A metal frame 11 which
serves as an electrode lead wire and also serves as a frame for holding the pressure is inserted
and pressure-bonded and held from the vertical direction of the figure, as shown in FIG. 5 (C).
The transducer can be easily manufactured by placing it on the backing object 12 and holding it
in a curved shape. FIG. 6 shows the experimental results to clarify the effect of the present
invention, in which the sound pressure level is taken on the vertical axis, the number of
piezoelectric films is taken on the horizontal axis, and the experiment is conducted for a sound
wave having a frequency of 10,000 Hz. is there. In the case of the five-layer stack, an output
increase of 14 dB or more is obtained. Moreover, as is clear from FIG. 6, it is possible to increase
the sensitivity as the number of stacked piezoelectric films increases. Therefore, when used in
combination with a low-pitched or medium-sounding speaker, according to the present invention,
a sufficiently high sensitivity which is not necessary can be obtained according to the present
invention even when a conventional step-up transducer is required. As described above,
according to the present invention, each piezoelectric vibrating film can be excited in an
independent mode without coupling with each other, and it is possible to acoustically and wore
and to improve the sensitivity. Can provide a transducer having excellent characteristics in a
wide band.
4. Brief description of the drawings. FIG. 1 is an explanatory view showing the piezoelectric
action of the polymer piezoelectric film. FIG. 2 is an explanatory view of the electroacoustic
conversion and action of the curved transducer, and FIG. FIG. 4 is an explanatory view of an
example, FIG. 4 is a sectional explanatory view of another embodiment according to the present
invention, FIG. 5 is an explanatory view showing an example of a method of manufacturing a
transducer according to the present invention, and FIG. The vertical axis is the sound pressure
level (dB), and the vertical axis is the number of piezoelectric films. la, lb ... pressure + i, 1 m, 2.2
mm 74, person 3 '... stretching vibration direction, 4.4' ... T4 both ends of the rolling film, 5 ...
bending pressure Piston movement direction, 6, a /,, human output fusion tRri, 7a, 7b-и и и
Piezoelectric piezoelectric ? distance, + jl. 8 иии Total thickness of transducer, 9a, 9b и и и Sheet i,
10a, 10b и и и Reticulated body, 11 и и и Metal holding frame, Yoshio Kawaguchi + 1 mouth and fang
20EndPage: 3 fangs 3 Figure 4 Figure 5 End Page: ?
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description, jps55115799
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