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TECHNICAL FIELD The present invention relates to a speaker using a pressure of a unimorph,
bimorph or the like by using an air acoustic transducer. Conventionally, in a loudspeaker of this
type, as shown in M1 (a), a unimorph piezoelectric transducer 1 in which a piezoelectric element
plate 1a and a metal plate 1b are bonded together or two as shown in FIG. 1 (b) Using a bimorph
piezoelectric transducer 1 in which the piezoelectric element plates 1 asa 'are bonded together,
and supporting both ends of the piezoelectric transducer 1 with a fixing jig 2.2 as shown in FIG.
The attachment is fixed to 3 and the converter 1 itself acts as a diaphragm, or as shown in FIG. 3,
a diaphragm 4 is further attached separately from the converter 1 or the like. By the way,
although typical piezoelectric elements generally used as a piezoelectric transducer are lead
titanate and lead zirconate titanate, these elements have elastic coefficients of about 7, 5 to 8 x
10 "d) 'ne / In the case of a cd, and because the internal loss is very small, if it is vibrated, sharp
resonance occurs at a specific frequency, which is not preferable for a speaker aiming at uniform
reproduction. As a means for suppressing this, as shown in FIG. 4, one in which a damping
material 5 such as rubber is added to the back surface of the converter 1 has been
conventionally proposed, but this is not sufficient to suppress the resonance of the piezoelectric
element. The The present invention has been made in view of such a point, and is to provide a
piezoelectric speaker having excellent vibration absorption characteristics and stable
characteristics with few peaks and valleys on frequency characteristics. The invention will now
be described according to the examples shown in the drawings. In the embodiment shown in
FIGS. 5 and 6, in the conventional similar loudspeakers shown in FIGS. 2 and 3, in particular, a
lead-based metallic damping material 6 is provided between the piezoelectric transducer 1 and
the frame 3. It arranges and supports the center of the piezoelectric transducer 1. The material of
the damping material 6 is preferably a lead metal having a large specific gravity and a large
internal loss, and in order to control the elastic coefficient, an alloy with tin, nickel, etc. and a
composite material are easy to process and economical. It is effective at the point. As for the
shape and mounting method of the braking material 6, not only fixing in the vicinity of the center
of the converter 1 but also fixing a part of the braking material 6 at an arbitrary point and fixing
its peripheral portion to the frame 3 The negative effect of the additional mass of the damping
material 6 is alleviated and the effectiveness of the damping material 6 is doubled by 0. The
damping material 6 is fixed at one point or two points as in the embodiment shown in FIGS.
However, multiple points may be fixed, and the selection may be freely changed according to the
size of the converter 1 and the required bandwidth of the speaker. Further, in the embodiment
shown in FIG. 7, the radiation area of the converter 1 is fixed so that the metal damping material
6 is fixed at multiple points between the converter 1 and the frame 3 and impedance matching
with air is made on the front surface of the converter 1. An acoustic case 8 having an opening 7
smaller than the opening 7 is covered.
The frequency characteristics of the piezoelectric speaker according to the present invention
configured as described above are as shown by broken lines 1 and 2 in FIG. 8 (however, the
broken lines in FIG. 8 are FIG. 5 and the dashed lines are FIG. 7). (Corresponding to the
embodiment shown in FIG. 8), the sharp resonance which is clearly noticeable when compared
with the characteristics of the conventional loudspeaker shown in FIG. 8 (indicated by the solid
line in FIG. 8) (corresponding to the prior art of FIG. It exhibits uniform flat characteristics. As
described above, according to the piezoelectric speaker of the present invention, a speaker
having stable characteristics can be obtained only by arranging the lead-based metal damping
material between the piezoelectric transducer and the frame and fixing the both members.
Brief description of the drawings
1 (a) and 1 (b) both show the structure of a unimorph and bimorph used in a furnace
piezoelectric speaker, and FIGS. 2 to 4 show the structure of a conventional piezoelectric speaker,
and FIG. 7 to FIG. 7 are structural diagrams of the embodiment of the present invention, and FIG.
8 is a frequency characteristic diagram comparing the speaker of the present invention and the
conventional speaker.
1 · · · Piezoelectric transducer, 3 · · · · · · · · · · · · · · · · · · · · · · · · · metal damping material, 8 · · · · · · · ·
sound case agent patent attorney Fuhiko Ai
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description, jps5822000
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