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BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1a and 1b are side views showing the operation
of a piezoelectric ceramic, FIG. 2 is a perspective view of a piezoelectric ceramic direct emission
type speaker of this invention, and FIG. 3 is a sectional view of the same. 22 is a piezoelectric
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement
of a direct emission type speaker using piezoelectric ceramic. As is well known in the art,
piezoelectric on ceramic acts as a piezoelectric body by performing a polarization operation to
align the polarization of each domain by applying a DC voltage in the thickness direction of the
ceramic. Then, by applying an electric field in the thickness direction, the shape is changed to
perform electro-mechanical or: [e. In order to use such a piezoelectric ceramic as a diaphragm of
a speaker, as shown in FIG. ? Bimorph-type piezoelectric ceramic / plate in which two plates of
the piezoelectric ceramic element plate 1.1 are pasted with the same poles facing each other, or
the piezoelectric ceramic element plate 1 is attached to the metal plate 2 as shown in FIG. The
thing of the composition which wore is appropriate. This is because the piezoelectric ceramic
having such a configuration vibrates so that its central portion is curved by applying an AC signal
(audio signal) to both electrodes, and as a result, it emits an acoustic wave. Therefore, in the
following description, the piezoelectric ceramic refers to the two configurations. When adopting
such a piezoelectric ceramic for a direct radiation type speaker, the following drawbacks must be
solved. First of all, the piezoelectric ceramic has an extremely sharp Q at its resonance frequency,
so the reproduction bandwidth is extremely narrow, and it is used for a speaker that reproduces
a very limited frequency band like a tweeter-1 or spear eater. It is also difficult to do. This
invention supports the piezoelectric ceramic at at least two points, and the positions of the
supporting points are different in each of the three piezoelectric ceramics. The second 2- ° C.
penetration will be described in detail below. Tsukanaka No. 2-Hit to λ, 21 is a support, and the
support (the support 21 has at least two or more pieces per piezoelectric ceramic to support the
piezoelectric ceramic 22) The piezoelectric ceramic 22 is attached to the upper end surface of
the protrusion 21a with a rubber adhesive or the like. The bonding positions of the piezoelectric
ceramic 22 and the protrusion 21 a are different in each piezoelectric ceramic 22. For example,
in the figure, the first mold type ceramic (left side in the figure) is diagonally 02 points, the
second piezoelectric ceramic is 2 points on the vertical axis, and the third piezoelectric ceramic is
2 points on the left and right axis Are supported respectively. It is well known that the vibration
body changes the vibration collection depending on the position of its support.
Therefore, as in the present invention, each of the four piezoelectric ceramics has a different
resonance frequency by changing the supporting position of each one of the n electric ceramics.
In such a configuration, when an audio signal is manually applied to a lead wire connected to
each piezoelectric ceramic, each lower-type ceramic exhibits a vibration corresponding to the
audio signal, but as described above, the inter-resonance wave number of each piezoelectric
ceramic is different. Therefore, the respective resonance peaks are coupled in a static manner,
and the overall frequency characteristic is broadened. Furthermore, the frequency characteristics
increase the number of piezoelectric ceramic and change the support position variously so that
the resonance frequency is continuously generated, make the shape and size of the piezoelectric
ceramic different, and change the material of the piezoelectric ceramic, Furthermore, by using a
material having an appropriate internal loss for the projections 21 a of the support 21 or by
interposing an elastic material between the support 21 and the piezoelectric ceramic 22, the
frequency characteristic between resonance frequencies can be made more flat. It is possible. As
described above, the present invention supports a plurality of piezoelectric ceramics at two or
more points respectively, and by making the supporting positions of the respective piezoelectric
ceramics different, the resonance frequencies of the respective ones are made different, thus a
wide band It is suitable for high-quality sound speakers, and can be used to enhance playback.