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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a conventional
piezoelectric speaker unit, and FIG. 2 is a cross-sectional view of a piezoelectric speaker unit
according to the present invention. 4.14 · · · · · · Piezoelectric elements, 3, 13 · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ......
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the construction
of a piezoelectric speaker unit. Heretofore, the structure of the sounding body using the
piezoelectric element has fixed the vibration node of the circular diaphragm or fixed the outer
periphery of the circular diaphragm in the thickness direction. For example, as shown in FIG. 1
which is a cross-sectional view of the main part of the prior art when incorporated in a
wristwatch, the piezoelectric element Between the metal back cover 1 with the sound release
hole 2 and the middle frame 7 supported by the case case 5 while keeping the waterproof
performance with the waterproof backing 6. Was. Therefore, the sound pressure is high only in
the vicinity of the resonance point, and in order to set the resonance point in the vicinity of
2000) Iz where human beings are most likely to take it, the diameter of the sounding body
becomes large and the arm? ″ン・、lj、1. In the case of a watch, it is necessary to provide
a sound-producing body on the back of the watch: 9 '· · 弄, and a waterproof sound-emitting hole
is provided on the back cover. It is often blocked and thick as a whole watch case (there were
many defects as a product. The present invention aims at reducing these drawbacks (Aims to be a
half, a speaker unit pressed inward with a conductive rubber pad at the periphery of the
diaphragm and held, and a conductive rubber pad serving as both a support and at least an
electrical connection. Do. Hereinafter, an embodiment of the present invention will be described
in detail with reference to FIG. 2 which is a sectional view thereof. The piezoelectric element 14
(2) 343 was attached to the lower surface of the titanium disk-shaped diaphragm 16 with a
conductive adhesive, and the metal coil spring 10 as a conductive elastic material was
conductively connected to the lower surface electrode of the piezoelectric element 14. The ring-
shaped conductive rubber packing 16 provided with a projection 16 a for connection with a
drive circuit (not shown) has an inner diameter slightly smaller than the outer diameter of the
diaphragm 16 and is constant when ringed on the diaphragm 16. The force is used to tighten and
connect the periphery of the vibration plate 16. A combination of the diaphragm 16 and the
packing 16 is press-fitted and fixed to a thin-walled metal plate 0-ended cylinder 0-cell 11 having
a sound emission hole 12 at the bottom thereof. An electric signal from a drive circuit (not
shown) is supplied to the lower surface electrode of the piezoelectric element through the
diaphragm 16 and the coil spring 10 through the pad 16 through the projection 16a, and the
piezoelectric element 14 is driven. Vibrates. The piezoelectric sounding body unit of the present
invention has a wide sound range (and it has been confirmed in experiments that it is not
necessary to increase the diameter of the sounding body, and the diaphragm is held by the case
of a bottomed cylinder. The connection of (3) 344 Nokin and the spring is enough.
Therefore, according to the present invention, the piezoelectric sounding body unit can be
miniaturized, and the influence on the whole watch can be reduced with respect to the thickness,
so that the location can be selected other than the back cover side, Similarly, while ensuring
waterproofness, the improvement of the sound emission efficiency, the improvement of the
degree of freedom of the design arrangement, the thinning of the wristwatch, and the like in
practice -3, '° 1' 1 trrl.