JPS5370224

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DESCRIPTION JPS5370224
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are explanatory views of a
conventional example, FIG. 3 to FIG. 6 are explanatory views of a method of manufacturing a
microphone of this invention, and FIG. It is sectional drawing of an Example. 4 · · · oval metal
frame, 5 · · · piezoelectric film, 9 · · · · metal case.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microphone
which uses a film of a piezoelectric polymer material as a vibrating film. In the conventional
microphone of this type, as shown in FIG. 1, a rectangular frame 2k obtained by bending the
piezoelectric film 1 is attached along its curvature, and this is attached to the case 3 as shown in
FIG. It is. Metal electrodes are vapor-deposited on both sides of the piezoelectric film 1, and a
voltage generated by application of sound pressure is generated between the electrodes. The
rectangular frame 2 is usually made of metal, and at the same time as adhesion, it is electrically
conducted to the single-sided electrode of the piezoelectric film 1 (1) N7 'or 2-degree). The other
electrode of the piezoelectric film 1 is connected to the case 3, and the voltage generated by the
piezoelectric film 1 K is taken out to the outside by the case 3 and the rectangular frame 2. A
conventional microphone using such a rectangular frame 2 has a drawback that it is not suitable
for mass production because it is not easy to assemble. That is, in order to maintain the air
tightness of the microphone, a method of pressing the rectangular frame 2 against the case 3 is
generally used, and this is usually performed by this process bending, but in the case of the
rectangular frame 2, an equal force is obtained. In addition to this, it causes air leakage and
causes variations in the characteristics. For this reason, the assembly of this food microphone has
become a mass-productive thing K which used the adhesive and the caulking together.
Furthermore, in the conventional microphone in which the piezoelectric film 1 is rectangular, the
piezoelectric film 10 divided vibration occurs, and there is also an intermittence b in which peaks
and troughs of the characteristic tend to appear in the high region of the sensitivity frequency
characteristic. Therefore, an object of the present invention is to provide a microphone (2)
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rophone which can be mass-produced and can prevent split vibration of a piezoelectric film. One
embodiment of this invention is manufactured as follows. That is, as shown in FIG. 3, after the
piezoelectric film 5 is attached to the elliptical flat metal frame 4, it is bent in the major axis
direction so that the outline of the plan view becomes circular, as shown in FIG. Let's do it. Front
views and side views of this state are shown in FIGS. 5 and 6, respectively. When the metal frame
4 and the piezoelectric film 5 are attached, both are pressure-bonded in order to electrically
conduct the deposited metal electrode of the piezoelectric film 5 and the metal frame 4 on the
bonding surface. At this time, a conductive adhesive may be used. In addition, since tension in the
major axis direction of the elliptical flat metal frame 4 is increased by bending, when the
piezoelectric film 5 is attached in a state where tension is uniformly applied, the central portion
of the piezoelectric film 5 Then, it becomes a structure so that it may become depressed from the
curvature surface of the metal frame 4.
In order to prevent this, it is preferable that the tension in the major axis direction is previously
made weak to the piezoelectric film 5 without sticking to wrinkles at the time of pasting, and that
a large tension is applied in the minor axis direction. (3) FIG. 7 shows a cross-sectional view of
one embodiment of the microphone of the present invention. The piezoelectric film 5 is attached
to the metal frame 4 in a tensioned state, and the vapor deposition metal electrode on one side of
the piezoelectric film 50 is electrically connected to the metal frame 4. The metal frame 4 is
connected to the center pin 8 by a ring 6 and a lead 7. The other vapor deposition metal
electrode of the piezoelectric film 5 is connected to a metal case 9 such as aluminum by contact.
The insulator 10 constitutes a back cavity and at the same time, when the circumference of the
case opposite to the piezoelectric film 5 of the case 9 is crimped, the elastic film presses the
vibrating film 7 to keep the airtightness. Still, the upper surface of the case 9 functions as a waist
for the piezoelectric film 5, and several holes are opened. The sound absorbing material 11
packed in the insulator 10 of the back cavity is for preventing the generation of standing waves.
In this microphone, the output of both surfaces of the piezoelectric film 5 is directly taken out
from the case 9 and the center pin 8, but in the insulator 10 of the back cavity, preamp insertion
for impedance conversion, (4) low impedance output It is possible to take out from the center bin
8. As described above, 1) The microphone according to the present invention has a circular outer
shape of the frame, so that in the caulking type an equal force is applied to the frame and there is
no variation in characteristics due to air leakage, so that it can be assembled without using an
adhesive. , Improve the nobleness. In addition, since the circumferential length of the curvature
of the piezoelectric film is continuously changed, it is possible to prevent divided vibration.
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