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A so-called double vibration structure in which the second buzzer is completely disposed on the
outer side of the first diaphragm to which the pressure buzzer of the electronic watch is attached
to the entire piezoelectric element through the air spring? 2. A piezoelectric buzzer device for an
electronic watch according to claim 1, wherein in the piezoelectric buzzer device, the resonance
frequency of the outer second diaphragm is set equal to or lower than the resonance frequency
of the first diaphragm.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the broadening of
the frequency characteristics of a compact piezoelectric buzzer for a heavy-duty watch,
particularly to the broadening in the low frequency range. Buzzers using piezoelectric elements
have been conventionally used in electronic watches, but they have a diaphragm diameter of 20
mm or more. It is desirable to minimize the size of the buzzer as much as possible in order to
properly arrange the buzzer on the watch and to make the watch thinner. On the one hand,
reducing the recoil vibration hypotheses all means that the resonant frequency of the diaphragm
increases. Conventionally, in the case of a piezoelectric buzzer having a diaphragm to which the
entire piezoelectric element has been attached, there has been a drawback that the reduction in
diameter is extremely difficult. The present invention, other than these drawbacks of the
piezoelectric buzzer, is to provide a buzzer which is in an appropriate area where the resonance
frequency r is likely to be emitted even if the diameter is reduced. FIG. 1 shows the basic strong
driver S1] driving circuit of a small-sized frost "fuser". 1 is a drive input signal, 2 is a piezoelectric
diaphragm, 3 is a coil for boosting. The driving voltage of the piezoelectric diaphragm 2 is
boosted as shown in FIG. 2 because it utilizes the induction voltage of the coil disposed in parallel
with the piezoelectric diaphragm. FIG. 3 shows an example of frequency analysis of generated
sound. In this case, the drive frequency in FIG. 1 is 2 KHz. In the frequency analysis of sound [the
harmonic component of 2 KHz or more appears more than the component of 2 KHz, (1) that the
resonance frequency of the piezoelectric diaphragm is 2 KHz or more (in this case, 8 to 1 kHz)
and (2) Driving Frost ░ Pressure Wave EndPage: 1 is originally inspired by the fact that it has
harmonic components as shown in FIG. This is a piezoelectric vibration! It appears whenever the
resonant frequency of the l? 1 plate is greater than the drive frequency and the drive voltage
waveform contains harmonics rather than pure sine waves. It is an elephant, and it appears well
in a small piezoelectric buzzer made small in vibration Pak Igk. After this, the sound of the small
piezoelectric buzzer was often offensive in that it contained many harmonic components. The
present invention is intended to eliminate these drawbacks and to facilitate the miniaturization of
the buzzer diameter while suppressing the generation of harmonic components. FIG. 4 shows a
piezoelectric buzzer according to the invention. The piezoelectric element plate 1 and the
diaphragm 2 are integrated to constitute a piezoelectric diaphragm 3, which is the conventional
one as shown in FIG. 1, FIG. 2 and FIG. The feature of the present invention is that the second
diaphragm 4 is disposed on the first diaphragm via an air spring, and the resonance frequency
thereof is set equal to or lower than that of the first diaphragm 3. is there.
The so-called speeding up and flying is performed via an air spring between the diaphragm and
the second diaphragm in FIG. 1, but the second diaphragm is also lower than the first diaphragm.
It can be viewed as a filter, which allows the similar frequency components of the vibration of the
first diaphragm to be prioritized and recovered. The states 9 and 10 shown in FIG. 5 show the
frequency characteristics of the second diaphragm and the first diaphragm, respectively. Is the
first diaphragm harmonic as already mentioned? Although many noises are generated and the
sound becomes unpleasant, the harmonics can be suppressed by arranging the second
diaphragm on top of it. In particular, if the resonance frequency f2 of the second diaphragm is
matched to the original drive frequency, the sound generated from the piezoelectric diaphragm
matches the original fundamental frequency regardless of including many harmonics. Can be
taken out preferentially. Thus, it is a first advantage of the present invention that the second
diaphragm has a function of a low pass filter for suppressing harmonic components. Further,
according to the second advantage of the present invention, since the inside of the buzzer is
protected from the external pressure by the second diaphragm, the piezoelectric element plate of
the internal pressure / electric diaphragm and the diaphragm can be thinned, and the
piezoelectric diaphragm itself The resonance frequency of 1 is to go down. When the
piezoelectric ceramic material is highly brittle and particularly thin, it is necessary to use external
force, or the second diaphragm plays this role. As described above, if the entire structure
according to the present invention is used, the generation of harmonics due to the
miniaturization of the compact piezoelectric buzzer can be avoided, and a comfortable sound can
be generated.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a drive circuit of a small pressure type buzzer,
FIG. 2 is a drive voltage applied to a piezoelectric element plate at the time of driving, FIG. 3 is an
example of frequency analysis of sound pressure waveform obtained from a piezoelectric
diaphragm, FIG. 4 is a cross-sectional view of a double-structured piezoelectric buzzer according
to the present invention, and FIG. 5 shows frequency characteristics of the second diaphragm
and the piezoelectric diaphragm. 1 и и и Drive input signal 2 и и и Piezoelectric diaphragm 5 и и и и
Boosting coil 4 и и и и и Piezoelectric element plate 5 и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
и и и и и on the frequency analysis example of the piezoelectric diaphragm 6-EndPage: ?
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jps5557176, description
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