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Description 1, title of the invention
Piezoelectric type electroacoustic transducer
3. Detailed Description of the Invention The present invention relates to a piezoelectric type
electroacoustic transducer having wide band characteristics. Generally, as shown in FIG. 1, the
pressure-type electroacoustic transducer, for example, a piezoelectric speaker, is constructed by
attaching the cone 2 to the other end of the piezoelectric bimorph 1 fixed at one end. With such
a structure, a flat response portion is generated in the region below the resonance frequency fO
of the entire vibration system including the piezoelectric bimorph 1 and the cone 2 as shown in
FIG. A speaker is configured using this flat response portion. Therefore, such a speaker has a
disadvantage that the output of the frequency range to be used is lower than the output of the
resonance frequency fo and the egg weight is large, and the thickness of the entire shape is large
because the cone is provided. It also has the disadvantage of: The present invention is an
improvement on all the above-mentioned conventional drawbacks, and it is an efficient, thin and
simple-structured piezoelectric by making use of the maximum output sound at the resonance
frequency fO as it is to exhibit a wide band frequency characteristic. Type electro-acoustic
transducer. In the following, the drawings of the present invention are drawn? Detailed
description with reference) 0 EndPage: 1 In FIG. 2, 3 is a disk-like moving plate made of, for
example, a metal plate, and a plurality of vibrating bars 3-1. 3-2 ... by punching. -3-n is formed.
One end of the diaphragm peripheral side is integrally connected to the diaphragm 3 VC so that
each of the vibrating bars 3-1. 3-2... 3-n extends from the periphery of the diaphragm 3 toward
the center. Each other end is formed at a free end to act as a cantilever. In particular, in the state
where the free end is positioned near the center of the diaphragm 3, the lengths of the respective
vibrating bars 3-1. 3-2 are formed so as to ascend each other. It is done. 4-1.4-2... 4-n is a
piezoelectric element attached with an adhesive or the like on each vibrating reed, and the length
'2 of each piezoelectric element is proportional to the length of each vibrating reed It is set. A
composite of such a vibrating reed and a piezoelectric element is referred to as a piezoelectric
bimorph in this specification. The resonant frequency of the piezoelectric bimorph is defined as
follows, and piezoelectric bimorphs different in length Il'r have different resonant frequencies f1,
f2,. As described above, the diaphragm 3 provided with a plurality of piezoelectric bimorphs is
fixed to the ring-shaped frame 5 at the periphery thereof. The periphery is fixed to the frame 5
with a 6I1 ′ ′ diaphragm and the central part is supported at the free end of each piezoelectric
bimorph. Although not shown, each piezoelectric element [electrodes are provided on both
surfaces, electrodes on the upper side of the diaphragm 3 are connected to each other by the
metal diaphragm 3, and electrodes on the other side are connected to each other by lead wires or
the like .
Then, when a commercial signal is applied between the electrode on one side and the electrode
on the other side commonly connected, the corresponding piezoelectric bimorph vibrates
according to the frequency of the signal, and the diaphragm 6 is driven. Ru. As a result, the
diaphragm 6 can be driven at an efficiency substantially equal to the maximum output at each
resonance point over a wide frequency range including the resonance frequencies f1 to frL of the
piezoelectric bimorph. The frequency characteristic is as shown in FIG. 4 (bl. FIG. 3 shows
another embodiment, in which 7 is a rectangular metal diaphragm inclined on one side and
provided with a plurality of slits having different lengths from the inclined side. Striped strips 71.7-2... 7-n constitute swinging pieces having different lengths, and piezoelectric elements 8-1.82 on each vibrating piece ..... 8-n is attached. The diaphragm 7 is fixed to the frame 9 on the
opposite side of the inclined side. A diaphragm whose periphery is fixed to the frame 9 has its
central portion supported by each vibrating reed. The other configurations and operation modes
of the present embodiment are substantially the same as those of the 10th embodiment. The
description thereof is omitted. In each of the above embodiments, it is necessary to vibrate the
plurality of bimorphs independently of each other. Therefore, in order to avoid the mechanical
coupling of multiple bimorphs by the diaphragm 6.10 as much as possible, the diaphragm 6.10,
the plastic sheet etc. according to the rigidity of the bimorph, regardless of the conventional
paper cone, etc. It is preferable to use a thin sheet of a suitable tension. Each of the above
embodiments can be used as a scale generator if the resonance frequencies of a plurality of
piezoelectric bimorphs are made to correspond to sounds such as "do-"--° degrees, and thin
radios, microcomputer output devices, and voice synthesizers Etc. can also be used for special
speakers. Although each of the above embodiments illustrates a speaker, the present invention
can also be used as a pickup or a microphone. The plurality of piezoelectric bimorphs 1 l-1 r 畏 1
of the above embodiments. Although the resonance frequency is made different by changing, the
present invention may be made to make the resonance frequency be different by changing both
the thickness of the bimorph (the l-r length and the thickness). As described above, according to
the present invention, a plurality of piezoelectric bimorphs having resonance frequencies slightly
different from each other are provided on the same plane, and the free ends of these bimorphs
are supported by one diaphragm. Since the resonant characteristics of the above are combined
and used, it is possible to obtain an efficient thin-shaped and simple-structured piezoelectric
electroacoustic transducer.
4. Brief description of the drawings. FIG. 1 is a schematic view of a conventional piezoelectric
speaker, FIG. 2 is a full view of one embodiment of a piezoelectric transducer according to the
present invention, EndPage: 2 FIG. The figure (b) is a plurality of piezoelectric bimorphs? 3 is a
full view of another embodiment, and FIG. 3 (a) is a cross-sectional view, and FIG. The plan view
shown in FIGS. 4 (a) and 4) is the frequency characteristics of the prior art and the present
invention, respectively. 3.7 diaphragms 3-1,..., -3-7L, 7-1... 7-n are vibrating bars, 4-1. -1,... 8-n
are piezoelectric elements, 6.10. Patent applicant: Tadada Manufacturing Co., Ltd. (7) Fig. 11 ¥ 1
Fig. 2 (17) Fig. 3 (long) 0 (17) B-77-1 Fig. 4 (Il) (d) EndPage: 3
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