JPH02301399

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DESCRIPTION JPH02301399
[0001]
FIELD OF THE INVENTION The present invention relates to an ultrasonic ceramic microphone for
transmitting and receiving ultrasonic waves. 2. Related Art Conventionally, this type of ultrasonic
ceramic microphone has a configuration as shown in FIG. In FIG. 3, a piezoelectric vibrator 1 is
bonded to a metal diaphragm 2 to form a bimorph vibrator. The coupling shaft 3 is fixed to a
through hole provided in the central portion of the bimorph oscillator, and the conical resonator
4 is fixed to the root of the coupling shaft 3 to constitute a composite resonator. This composite
resonator is bonded and fixed to a convex portion 6N provided at the central portion of the
terminal plate 6 via an elastic adhesive 6, and the composite resonator and the terminal plate 5
are housed in a cylindrical case 77. The Problems to be Solved by the Invention In such a
conventional configuration, there is a problem that the shape of the terminal plate is complicated
and the fixing operation of the composite resonator is difficult to be stable, and the acoustic
conversion efficiency is significantly reduced with miniaturization. There was a problem.
SUMMARY OF THE INVENTION The present invention is to solve such problems, and it is an
object of the present invention to provide a small-sized and highly sensitive ultrasonic ceramic
microphone and to have a simplified configuration. Means for Solving the Problems In order to
solve the problems, the present invention is to form a bimorph vibrator by bonding a
piezoelectric vibrator to the bottom of a cylindrical vibrator having an opening at one end, and
the above bimorph vibrator The conical resonator is fixed to the central portion of the cylindrical
vibrator, the open end of the cylindrical vibrator is disposed on a support made of an elastic
member, and the support is fixed on a terminal plate, and the bimorph oscillator, the support The
terminal plate is housed in a cylindrical case. Operation With this configuration, the side
vibration interference of the bimorph vibrator using the cylindrical vibrator acts on the bimorph
as a vibration amplification function, so that high sensitivity can be achieved, and the open end of
the cylindrical vibrator With a predetermined side height, air resonance can be added to the
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vibration amplification action. Embodiment 1 FIG. 1 is a cross-sectional view of an ultrasonic
ceramic microphone according to an embodiment of the present invention, and FIG. 2 is an
exploded perspective view thereof. In FIGS. 1 and 2, a piezoelectric vibrator 8 is bonded to the
bottom of a cylindrical vibrating body 9 having an opening at one end to form a bimorph
vibrator. The material thickness and the bottom outer diameter of the cylindrical vibrator 9 at the
portion where the mechanical conversion is performed. The side height can set the natural
resonance frequency. In one embodiment of the present invention, the piezoelectric vibrator 8
has a thickness of 0.2 tx t and a diameter of 7. x. oHφ, thickness of cylindrical vibrator 9 0.36ff t,
outer diameter 9.
Qjffφ, height 5 M was set, and performance of 40 KHz frequency and sensitivity -42 dB / V / Pa
was obtained. In order to facilitate drawing of the lead wire 1 o from the bonding surface
electrode of the piezoelectric vibrator 8, a notch 9 a is provided in a part of the cylindrical
vibrating body 9. A conical resonator 11 is fixed to the central portion of the bimorph oscillator
via an adhesive 12. Reference numeral 13 denotes a support made of an elastic member, and the
support 13 is provided with an annular recess 13a, and the cylindrical vibrating member 9 is
disposed on the support 13 by fitting the open end thereof into the recess 13a. The support 13 is
fixed on the terminal plate 14. Here, it is also possible to provide a buckwheat portion at the
opening end of the cylindrical vibrating body 9 in order to give elasticity and firmly fix the
coupling between the support 13 and the cylindrical vibrating body 9. The effect of the present
invention can be obtained even if the adhesive is reinforced via an adhesive. A cylindrical case 16
has an emission port for emitting ultrasonic waves at one end, and a net 16 having a plurality of
holes is mounted at one end to protect the inside. The bimorph vibrator and the terminal plate
14 are housed. 17 is a lead wire, and 18 and 19 are terminals. Effects of the Invention As
described above, according to the present invention, by using a cylindrical vibrator for the
configuration of the bimorph vibrator, the side portion of the cylindrical vibrator is extended as
the vibration outer diameter with a small outer diameter. By using it, the vibration area can be
broadened, the vibration efficiency can be improved, and high sensitivity can be achieved. In
addition, since the cylindrical vibrator portion of the bimorph vibrator is fixed, an effect is
obtained that is easy to assemble and that the low frequency problem, which is a problem in
miniaturization design, is solved.
[0002]
Brief description of the drawings
[0003]
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FIG. 1 is a sectional view showing an ultrasonic ceramic microphone according to an embodiment
of the present invention, FIG. 2 is an exploded perspective view thereof, and FIG. 3 is a sectional
view showing a conventional ultrasonic ceramic microphone.
8 · · · Piezoelectric vibrators · · · · · · · · · · · · · · · · cylindrical vibration body, 10 · · · · · · · · · lead wire,
11 · · · · · · · · conical resonator, 12 · · · · · · · · · · · · · · · · · · 13 · · · Support body 14 · · · · · · · · · · · · · · · · ·
· cylindrical case, 16 · · · · net, 18. 19. · · ..... terminals. Name of Agent Attorney Attorney Shigefumi
Other 1 person Fig. 1 Fig. 2 ()
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