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JPS54118086

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DESCRIPTION JPS54118086
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a conventional
piezoelectric buzzer sounding body, FIG. 2 is a view showing an example of an oscillation circuit,
and FIG. 3 is a drawing of a sounding body portion of the piezoelectric buzzer of the present
invention. Explanatory drawing of an Example, FIG. 4 is a figure which shows an example of an
oscillation circuit, FIG. 5, FIG. 6, FIG. 6, FIG. 7 and FIG. Fig. 9 is an explanatory view of a sounding
body used for an experiment as a comparative example, Fig. 10, and Fig. 11 are results of a
comparative experiment, and Fig. 10 is a frequency-output voltage characteristic curve diagram.
FIG. 11 is an oscillation waveform diagram. 11: elastic thin plate, 12: piezoelectric ceramic plate,
13: pickup electrode, 14: excitation electrode.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric
buzzer of the type provided with two types of electrodes, one of which detects the alternating
pressure signal detected on one side by feedback, and supplies it to the other to make it oscillate.
The present invention relates to a piezoelectric buzzer in which the return characteristic is
improved by changing the electrode pattern of. In general, a piezoelectric buzzer bonds and
integrates a piezoelectric plate to an elastic thin plate made of metal or plastic, bakes an
electrode on the exposed surface of the piezoelectric plate, applies a high frequency voltage to
the piezoelectric plate, and elastically expands and shakes it. The deformation bimorph type
structure using one piezoelectric plate polarized in the thickness direction as the piezoelectric
plate and the two piezoelectric plates are polarized in the opposite direction as the piezoelectric
plate is made to generate sound by bending movement of the thin plate There is a laminated
bimorph type structure, and there are various structures such as a small size and a cone-shaped
elastic thin plate. By the way, in order to cause such a piezoelectric buzzer to sound (2), as
described above, if the high frequency room pressure is marked on the piezoelectric plate to
drive it, it is not good. For this reason, a self-oscillation circuit is connected. However, to simplify
the circuit configuration, the exposed surface of the piezoelectric plate 2 bonded and integrated
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to the elastic thin plate 1 as shown in FIGS. 1A and 1B. The pickup electrode 3 is provided on a
small part of the outer peripheral edge of the light emitting diode 4. A part of the pickup
electrode 3 is provided separately from the pickup electrode 3 and the excitation electrode 4 is
provided over almost the entire remaining surface. There is a system in which an oscillation
circuit including R2 and R3 and one transistor Q1 is formed, and a signal from the pickup
electrode 3 is fed back to the base for amplification to drive the excitation electrode 4. However,
such conventional royal frost bussers may become unstable in oscillation due to mechanical and
acoustical load fluctuations and fluctuations in ambient temperature, and oscillations may be
stopped in severe cases. There was a big problem left. The object of the present invention is to
provide a human piezoelectric buzzer which overcomes the drawbacks of the prior art as
described above and provides a stable oscillation with a good feedback characteristic. (3) That is,
the present invention is made by finding that the cause of the excavation instability of the
conventional specific gravity buzzer is due to the inappropriate shape of the pickup box rod.
Since the conventional pick amplifier electrode (dimensions, only part of the outer edge of the
piezoelectric plate is formed as a lip, it can only partially detect the phase of the vibration period
of the piezoelectric plate, hence the specific circuit constant) Since oscillation occurred only
within a narrow range, the oscillation becomes unstable when there is a change in characteristics
such as the piezoelectric constant due to a change in temperature.
The present invention: In order to solve such a disadvantage, the mold bar shape is devised, and
the excitation electrode and the pickup electrode are respectively provided on the exposed
surface of the pressure fI 'plate fixed to the elastic thin plate, The 'Yamakawa signal detected by
the pick-up electrode is feedback amplified and applied to the excitation electrode 1 to form an
oscillation circuit 1 so as to make it ring 1 It is a piezoelectric bushing that includes an outer
peripheral edge or a shape that simultaneously includes a part of the outer edge and the center
of the piezoelectric plate. (4) The present invention will be described in detail with reference to
the drawings. A. 3 FIGS. A and B show an embodiment of a propellent body portion of a positive
voltage buzzer according to the present invention, wherein a circular piezoelectric magnetic plate
12 is similarly formed of a circular elastic thin plate 11 made of stainless steel, brass or the like.
And the annular pickup electrode 13 is formed so as to include all the outer peripheral edge
portions of the piezoelectric ceramic plate 12, and the circular excitation electrode 14 is formed
in the central portion at a small distance from it. It is. The piezoelectric ceramic plate 12 is
polarized in the thickness direction. Such a sounding body can be driven by a very simple circuit
as shown in FIG. That is, a current limiting resistor Ra and an NPN transistor Q2 are connected in
series between the collector supply DC voltage Vc and the ground, the collector is connected to
the excitation electrode 14, the pickup electrode 13 to the base, and the elastic thin plate 11 to
the ground. A base current control resistor Rh is connected between the base and the collector.
With such a circuit configuration, since the oscillation circuit can be formed of only one
transistor and two resistors, it is extremely advantageous from the viewpoint of (5) reduction in
the number of parts and reduction in the number of assembling steps. The voltage detected by
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the pickup electrode 13 and fed back to the base of the transistor Q2 is in reverse phase to the
voltage applied to the excitation electrode 14, so self-oscillation occurs, and the polarized
piezoelectric ceramic plate 12 spreads and vibrates. Since the elastic thin plate 11 is attached,
the elastic thin plate +1 is bent and vibrated to generate sound. Since vibration is transmitted
from the central portion in the radial direction from the central portion of the piezoelectric
ceramic plate 12, all frequencies of the imaging motion that propagate when the pickup
electrode 13 is provided on all the outer peripheral edges as shown in FIG. Since the component
can be detected and the vibration in the vicinity of the resonance frequency of the sounding body
with the best air acoustic efficiency can be always captured, the feedback characteristic becomes
good and the oscillation can be stably performed. The letters A and B in FIG. 6 and in FIG. 1 and
FIG. 1 are other embodiments of the sound producing portion of the piezoelectric buzzer
according to the present invention.
FIG. 5 shows a rectangular piezoelectric ceramic plate 12, which is attached to the center of a
circular elastic thin plate 11, and all the outer peripheral edges on the dew surface (6) of the
piezoelectric S rever 12 are detected. The pickup electrode 13 is formed in a frame shape so as to
include a portion, and the rectangular excitation electrode 14 is formed in the central portion. In
FIG. 6, the shape of the piezoelectric ceramic plate 12 is a quarter disk, which is attached to the
center of the elastic thin plate 11, and the pickup electrode 13 and the excitation electrode 14
also have shapes corresponding thereto. In Fig. 1-7, the circular piezoelectric ceramic plate 12 is
used, and the electrode pattern is changed. In any case, in each of the following embodiments,
the pickup electrode 13 is orange so as to include all the outer peripheral edge portions of the
piezoelectric plate, and the same function and effect as those of the above-described 1 and 3 can
be exhibited. In this case, since the piezoelectric ceramic plate 12 is in the wide-angle shooting
mode, many phase components are detected by the pickup electrode provided on the outer
peripheral portion, and only the reverse phase component of them is fed back to the base of the
transistor. Oscillations can be obtained. V8 Figs. A and B are other embodiments, in which a
region including the central portion of the circular piezoelectric ceramic plate 12 and a part of
the outer edge portion at the same time is the pickup electrode 13 The excitation electrode 14 is
shaped to the remaining area at an interval of 7). Also in this case, the feedback characteristic is
good because many phase components can be sensed as described above. Next, comparative
experiments conducted to prove the effectiveness of the present invention will be described. The
electrode shape used in the experiment is the one shown in the present invention, as shown in
FIG. 3 and FIG. At intervals, the rest of the piezoelectric ceramic plate 22 is the one on which the
exciter clamp 24 is formed. Of course, also in this case, the piezoelectric ceramic plate 22 is
attached to the elastic thin plate 21 at the same time. It is an ilo diagram showing frequency
characteristics of an output voltage with a constant input terminal for such three types of
electrode-shaped sounding bodies. ???? fbl and (c) respectively correspond to the cases of o,
3 and 8 and 1 and 9 respectively. As apparent from Fig. 10, fal, (bl sample is higher than the
output voltage, tel sample: the output voltage obtained from the pick-up pole is lower, and the
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harmonic output and the fundamental output The pressure ratio is about the same. ????
Fang 11 figures, 3 ?, 18 figures 1. . FIG. 4 shows an oscillation waveform when the collectorcoupled base feedback oscillation circuit (see FIG. 4) of the transistor is configured for the
sounding body of FIG. 4 and FIG. 9, respectively.
???? fbl, ((cl corresponds to the sounding body in +3 in FIG. 8 and in FIG. 9 in 9). As is clear
from the oscillation waveform of fang 11, fa) and ibl show stable oscillation waveforms, but (in
the case of cl, feedback of frequency components other than the fundamental wave or many
phase components including antiphase etc. Because of oscillation due to noise, it appears as noise
near the ground level (GND). Therefore, as shown in FIG. 9, when the pick-up electrode is
provided at a part of the outer edge of the piezoelectric ceramic plate, the output signal detected
from the pick-up electrode is a. As shown in FIG. 11 (C: иии, the noise in the vicinity of the ground
level becomes large and the oscillation becomes unstable, as the signal / 'Wte sound ratio
decreases. Therefore, the number of excavated frequencies (9) changes discontinuously due to
mechanical and acoustical load fluctuation, fluctuation of co-imaging frequency (fundamental
wave) due to temperature change, and so on. On the contrary, the product of the present
invention does not cause such a disadvantage. In the present invention, as described in detail in
the description, the pickup electrode is shaped so as to include all the outer edges of the
piezoelectric ceramic plate or to simultaneously include a central portion and a part of the outer
edges. Since all phase components are detected and feedback amplified, the resonance frequency
inherent to the piezoelectric buzzer sounding body is always captured and oscillates stably, so
variations in the material and shape of the sounding body and changes in the ambient
temperature Regardless of the reason, it can operate efficiently and can have excellent practical
effects such as lack of excavating failure and oscillation stoppage etc.
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