Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1996-01-18
1998-09-08
Dougherty, Thomas M.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310328, 310331, 310337, 310348, H04R 1700, H01L 4108
Patent
active
058049061
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a sound generating device.
BACKGROUND ART
As piezoelectric vibration plates, there are known unimorphs comprised of a disk-shaped thin metal plate with a piezoelectric ceramic layer formed on just one side and bimorphs comprised of a disk-shaped thin metal plate with piezoelectric ceramic layers formed on both sides. These unimorph and bimorph type piezoelectric vibration plates perform flexing oscillation wherein the centers of the piezoelectric vibration plates alternately flex in opposite directions when the voltage applied to the piezoelectric ceramic layers is changed. Known in the art is a speaker which uses such a flexing oscillation of a piezoelectric vibration plate to generate sound. In such a conventional speaker, the peripheral portion of the piezoelectric vibration plate was usually supported by the frame of the speaker, the center of the piezoelectric vibration plate was connected to an acoustic vibration plate, and the acoustic vibration plate was made to oscillate by the piezoelectric vibration plate so as to produce sound from the acoustic vibration plate (for example, see Japanese Unexamined Patent Publication (Kokai) No. 60-182300).
This piezoelectric vibration plate, however, has a high natural frequency and a high Q value at the resonance point and has the property of a reduction in the sound pressure level along with a fall in the frequency. Accordingly, there is the problem that when, like in the past, the oscillation of the piezoelectric vibration plate is merely directly transmitted to the acoustic vibration plate as it is, the sound becomes distorted and the bass sound pressure level is insufficient at the resonance point.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a sound generating device which is able to give a sufficiently high sound pressure level even in the bass region.
According to the present invention, there is provided a sound generating device provided with a driving device having a plurality of piezoelectric vibration plates which are arranged spaced from each other in an axial direction, wherein either of the peripheral portions or centers of adjacent piezoelectric vibration plates are connected to each other and adjacent piezoelectric vibration plates are made to flex in opposite directions from each other, the piezoelectric vibration plate positioned at one end of said plurality of piezoelectric vibration plates being connected to an acoustic vibration plate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional side view of a type I module,
FIG. 2 is a front view of the module shown in FIG. 1,
FIGS. 3(A), 3(B) are views for explaining the operation of the module shown in FIG. 1,
FIG. 4 is a cross-sectional side view of a type II module,
FIG. 5 is perspective view of the module shown in FIG. 4,
FIGS. 6(A), 6(B) are views for explaining the operation of the module shown in FIG. 4,
FIG. 7 is view showing various driving devices,
FIG. 8 is a cross-sectional side view of a speaker using the type I module shown in FIG. 1,
FIG. 9 is a partially enlarged cross-sectional side view of FIG. 8,
FIG. 10 is a cross-sectional side view of part of a speaker showing another embodiment,
FIG. 11 is a cross-sectional side view of part of a speaker showing still another embodiment,
FIG. 12 is a cross-sectional side view of a speaker using the type II speaker shown in FIG. 4,
FIG. 13 is a partially enlarged cross-sectional side view of FIG. 12,
FIG. 14 is a perspective view of the type II module,
FIG. 15 is a cross-sectional side view of part of a speaker showing another embodiment,
FIG. 16 is a cross-sectional side view of part of a speaker showing still another embodiment,
FIG. 17 is a cross-sectional side view of part of a speaker showing still another embodiment,
FIG. 18 is a cross-sectional side view of part of a speaker showing still another embodiment,
FIG. 19 is a cross-sectional side view of part of a speaker showing a modification of FIG. 18,
FIG. 20 is a cross-sectional side
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Dougherty Thomas M.
Shinsei Corporation
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