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[Detailed description of the invention] Piezoelectric acoustic transducer used in this invention for
alarm buzzers such as fire alarm, anti-separator, gas detector, intercom or uThMFi atmosphere;
Open to As shown in FIG. 1, a conventional piezoelectric acoustic transducer, for example, the
device of JP-B-44-16268, is a composite by bonding a diaphragm 8 and a piezoelectric element 4
provided with silver electrodes 4a on the front and back. The body 5 is formed, and this
composite 5 is provided with projections 8 facing the opening 1 and provided on the inner
surface on the side of the opening 1 in the case 2 'having the opening 1-1 smaller than the
diaphragm 3 in the-plane. While being supported, the oscillator circuit 71 is accommodated on
the back surface of the composite 5 in the case 21, and the lead plate 9 connects the diaphragm
3 and one silver electrode 4 a of the piezoelectric element 4 to the oscillator circuit 71. Then, in
the opening 1 of the case 2 '(the front surface of the case II' is joined to the case 2 'so that the
resonance cylinder 6 projecting forwardly communicates with the opening 1). 10 is a power
supply of the oscillation circuit 71. When the oscillation circuit 71 is energized from a power
supply #lO of the oscillation circuit 1 and the vibration element is added to the piezoelectric
element 4 through the oscillation circuit 7 ', the composite 5 is bent and oscillated, Sound waves
are generated from the opening 1 of the case 2 r and resonated by the resonance cylinder 6 to
increase the generated volume. The length a of the resonance cylinder 6 is usually 15 m.
Therefore, in this apparatus, the complex 5 and the oscillation circuit 7 'are housed in the case
21, so the case 2! In addition, only the portion of the resonance cylinder 6 protrudes forward of
the case 2 ', and as a whole, it becomes a cylinder having a convex cross section, which causes a
large size problem. The object of the present invention is to provide a piezoelectric acoustic
transducer having a structure which is easy to assemble in addition to the above-described
disadvantages and is compact and compact. In order to achieve this object, the present invention
resides in the construction of a piezoelectric acoustic transducer as described in the Tessen
model registration request. FIG. 2 shows an embodiment of the present invention, and the case is
composed of a case 11 which covers the opening l, a case 12 which pages the resonance
cylindrical portion 6, and a back lid 2. In this case, a disk-shaped composite body 5 in which a
diaphragm 8 'and a piezoelectric element 4 having silver electrodes 4 on the front and back sides
are accommodated, the driving IJ circuit 7 is provided around the resonance cylinder 6 , And
separated from the complex 5 by the partition wall 61. It is supported by the partition 6 'through
the support 8 at the node of the composite 517i vibration. It is preferable that the support 8 be a
foam, a rubber, an elastic contact, an agent or the like that does not suppress vibration as much
as possible. Also, although the support position has conventionally been the inner end face of the
resonance cylinder, the volume of the circuit portion 7 is larger if the partition 6 'is used rather
than the inner end face within the range where the resonance effect is not destroyed at i degree
as in the present invention. In addition to being able to take out, it is possible to make the overall
size smaller and more effective.
As shown in FIG. 2, the assembling method is also very much an hour wheel if it is separated
from the front lid 11 'and the back lid 2'. Sound waves are transmitted to the outside through
Table 11 and the space with a depth of d works as a resonance box, but on the contrary, it is
emitted by providing an opening in the lid 2 and it is possible to close the opening of the front
lid. It has the same effect. However, the volume is slightly lower. In addition, the front lid and the
back lid are both open and external reflection is effective. Although the composite 5 # 'i is usually
supported by the partition wall 6', it is also possible to support it from the front lid 11 and hold it
in a sand-in shape, in order to make it resistant to external vibration and impact. In the
piezoelectric acoustic transducer of the invention of Inno's invention, the composite body 5 is
bent and vibrated to generate a sound wave, and resonated in the resonance cylinder 6 to
increase the generated volume, as in the conventional device. According to the piezoelectric
acoustic transducer of the present invention, only the composite body 5 is housed in the case 2,
so the thickness of the case 2 can be thin, and the space portion of the outer periphery of the
resonance cylinder 6 of the oscillator circuit 7 can be obtained. Because of the consideration, the
overall size and size of the device has been reduced. =めることかできる。 That is, although the
diameter of the case 2I of the conventional device shown in FIG. 1 is 60- and the total thickness
of the case 2 'and the resonance cylinder 6 is 45 m, the device of this invention shown in FIG. In
the apparatus, the diameter of the case 2 is 60 mm, which is the same as in the prior art, or the
total thickness of the case 2 and the resonance cylinder 6 is 25%, and the device is compact or
small. The thickness of the resonance cylinder 6 is about 15 Mm, the inner diameter of the
resonance cylinder 6 is preferably about 28 fi, and the generated volume can be obtained as in
the prior art. The effect of the present invention is not lost even if the shape other than the
resonance cylinder 11 cylinder is changed, such as a square shape, and it is not continuous with
the opening 1, and even if a slight slit or hole is provided 4 I can not do it. Further, the
integration of the piezoelectric element 4 and the pregnancy moving plate 3 is also effective by
methods other than bonding.