JPS53143625

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DESCRIPTION JPS53143625
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a conventional
microphone element, FIG. 2 is a perspective view of a conventional piezoelectric microphone with
the same microphone element, and FIGS. 3A and 3B are respectively the same The wave form
diagram of the input sound wave of a piezoelectric microphone and an output wave. Fig. 4 is a
view showing the basic configuration of another conventional piezoelectric microphone, Fig. 5 is
a perspective view of the same piezoelectric microphone, Fig. 6 and Fig. 7 are operation
explanatory diagrams of the same piezoelectric microphone, and Fig. 8 Figures A and B are
waveform diagrams of the input sound wave and the output wave of the same piezoelectric
microphone. FIG. 9 is a perspective view of a piezoelectric microphone according to an
embodiment of the present invention, FIG. 10 is a basic configuration diagram of the same
piezoelectric microphone, and FIGS. 11 and 12 are each an explanation of the operation of the
same piezoelectric microphone. Figure 13A. FIG. 14B is a waveform diagram of human-powered
acoustic waves and medium-force waves of the same piezoelectric type microphone, and FIG.
14A to FIG. 14B are schematic views of other embodiments Ω of the present invention. 8.8 ′
········· Frame, 9, 9 ′ ······ High molecular piezoelectric film, 10 ········ Case, Ml 2 M 2 ······ Microphone
element. 88 '\ M,' I, M21 '713 / 2-8θ' 1 λ
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric
microphone using a polymeric piezoelectric film, which improves sound pressure sensitivity and
reduces distortion. And vibration noise is intended to be removed. First, a conventional
piezoelectric microphone of this type will be described with reference to FIGS. 1 to 3. FIG. 1
shows a microphone element, and 1) is a polymer piezoelectric film 2.1 mm such as a
polyfluorinated vinylitin film, and a stain electrode is formed on both sides by vapor deposition,
etc. / C'G-- (2). A curved conductive frame 2 is adhered to one surface of the frame 20 along the
curvature of the polymeric piezoelectric film 1 or the frame 20. When the polymeric piezoelectric
film 1 is bonded to the frame 2, the electrode on one surface of the polymeric piezoelectric film 1
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and the conductive frame 2 are in a conducting state. 3, 31 are lead wires connected to the other
electrode of the polymeric piezoelectric film 1 and the frame 2, respectively. The microphone
element is attached to the opening surface of the case 4 as shown in FIG. 2 to become a
piezoelectric microphone. As shown in FIG. 2, when a high voltage P is applied to the polymeric
piezoelectric film 1, a signal is obtained between the lead wires 3 and 31. 3A shows the
waveform of the input sound wave applied to the polymer piezoelectric film 1, and FIG. 3B shows
the output waveform of the piezoelectric microphone. The polymer piezoelectric film 1 is curved,
The magnitude of the output voltage 3 is somewhat different between the extension direction
and the contraction direction of the polymer piezoelectric film 1, so that the output voltage is
distorted as shown in FIG. 3B. In addition, when the above-described conventional piezoelectric
microphone is used as a built-in microphone of a tape recorder, for example, there is a drawback
that vibration of a motor or the like is transmitted to generate vibration noise. Therefore, the
present inventors have already proposed a piezoelectric microphone shown in FIGS. 4 and 5 for
the purpose of improving sensitivity and preventing vibration noise. In FIGS. 4 and 5, M and M2
are microphone elements formed by bonding the polymer piezoelectric film 1 and 11 on one side
of the curved frame 2 and 2 °, respectively. Are fixed to the both open ends of the square
cylindrical case 6 respectively. 6 ° 6 'is a lead connected to one electrode of the polymeric
piezoelectric film 1, 11 respectively. Next, the operation of the piezoelectric microphone shown
in FIGS. 4 and 5 will be described with reference to FIGS. 6 and 7. FIG. 6.) As shown in FIG. 6,
when the sound pressure P is applied, a signal is generated in both microphone elements M1 and
M2, and an added output is generated between 46.6 'on the lead wire.
Thus, according to the piezoelectric microphone shown in FIGS. 4 and 5, the sensitivity is
improved as compared with the piezoelectric microphone shown in FIGS. Further, according to
the piezoelectric microphone shown in FIGS. 4 and 6, vibration noise is not generated. That is, as
shown in FIG. 7, when vibration of F is applied to the piezoelectric microphone, each of the
polymeric piezoelectric films 1, 1 ′ ′ of each of the microphone elements M, M is in the
original position according to the law of inertia. Since one polymer piezoelectric film 1 is
stretched and the other polymer piezoelectric film 11 is compressed in order to solve the
problem, an opposite output is generated, and an output is not generated between the read wires
6 and 6 '. Noise due to vibration does not occur. As described above, according to the
piezoelectric microphone shown in FIGS. 4 and 5, the sensitivity is improved, and the generation
of vibration noise can be prevented. However, this piezoelectric microphone can not eliminate
the occurrence of distortion −). 8A shows the waveform of the input sound wave applied to the
piezoelectric microphone, and FIG. 58B shows the output waveform generated between the lead
wires 6, 6 '. As apparent from FIG. 8B, in the piezoelectric microphones shown in FIGS. 4 and 5,
there is a difference in the magnitude of the output voltage between the extension direction and
the contraction direction of the polymer piezoelectric film 1, 1 ′ ′. Because of this, distortion
occurs. The present invention eliminates the above-mentioned conventional drawbacks, and one
embodiment of the present invention will be described below with reference to FIGS. 9 and 10. In
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FIGS. 9 and 10, 8.8 'is a curved frame, respectively, and polymeric piezoelectric films 9, 9' are
adhered to one side of this frame 8, 81 to form a microphone element M 5 M 2 There is. The
polarization direction of each of the polymeric piezoelectric films 9, 9 'is as shown in FIG. This
microphone element Ml1M. Are respectively attached to both openings of the square cylindrical
case 1o. The microphone elements M and M2 are disposed such that the curved surfaces of both
the microphone elements M and M2 are parallel to each other. 11 is connected to a frame 8 or a
lead wire, 12 is connected to one electrode of the polymer piezoelectric fiber 6 frame 9 'or a lead
wire, 13 is one of a frame 8' and a polymer piezoelectric film 9. It is a lead connected to the
electrode. Next, the operation of this embodiment will be described with reference to FIG. 11 and
FIG. As shown in FIG. 11, when a sound pressure P is applied, one polymer piezoelectric film 9
"stretches" and the other polymer piezoelectric film 9 '"shrinks", and both microphone elements
M, M2 Voltage is generated between the lead wires 11.12 by adding both chamber pressures.
For this reason, the sensitivity is improved as compared with the conventional example using one
microphone element. Further, according to the present embodiment, since one polymer
piezoelectric film "stretches" and the other polymer piezoelectric film "shrinks" when a sound
pressure is applied, no distortion occurs. FIG. 13A shows the waveform of the input sound wave
applied to the piezoelectric microphone shown in FIG. 9 and FIG. 10, and FIG. 13B shows the
output waveform generated between the lead wires 11.12. 12) shows the operation when
vibration of F-- 'is added to the piezoelectric microphone of this embodiment, both 7 polymer
piezoelectric films 9, 91 are in the original position (dotted line) according to the law of inertia.
In order to try to stay in, both output voltages are canceled. As described above, according to this
embodiment, noise due to vibration does not occur. FIGS. 14A-0 respectively show other
embodiments of the present invention, and the operation of each of these embodiments is
completely the same as that of the previous embodiment. The present invention has a
configuration like that of the present invention. According to the present invention, the
sensitivity is improved, distortion is not generated, and vibration noise can be removed.
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