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JPS59193497

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DESCRIPTION JPS59193497
[0001]
The present invention relates to a piezoelectric buzzer, and more particularly, to an improvement
of a piezoelectric buzzer for generating an acoustic wave of a specific frequency by applying an
electric force to a sounding body having a piezoelectric element attached to an elastic thin plate
and bending the sounding body. . Heretofore, various so-called piezoelectric buzzers have been
provided which utilize the characteristic of vibrating at a specific frequency when an electric
force is applied to the piezoelectric element, and a typical example shown in FIG. 1 is generally
used. The However, such a conventional piezoelectric buzzer has a problem that it can not
sufficiently meet the recent demand for downsizing and thinning of electronic parts. That is, the
piezoelectric buzzer shown in the figure is roughly constituted by a flat cylindrical case 10, a
back lid 121, a sound emitting body 14 and a printed wiring board 18 on which electronic
components 16 such as resistors and transistors are mounted. 14 adheres a substantially discshaped piezoelectric element 2 o to the central portion of the substantially disc-shaped elastic
thin plate 22, and further holds the elastic thin plate 22 with an adhesive 24 such as silicone
rubber on the ceiling surface of the case 10. It was adhered to the provided protrusion 26. The
pudding 1 to wiring board 18 are engaged with the inner side surface of the case 10 below the
sound producing body 14, and the back cover 12 is fitted to the inner side surface of the case 1o
below this. The The piezoelectric buzzer having such a structure not only requires the printed
wiring board 18 but also electrically connects the electrode portion of the sounding body 14 and
the printed wiring board 18 with the lead 28 ( Since the case 10 is relatively narrow, this
connection operation is troublesome and has become a factor of cono 1 to up. Further, in order
to miniaturize and thin the piezoelectric buzzer with the above-mentioned structure, the
electronic component 16 mounted on the printed wiring board 18 may be removed in a laid
state, or the electronic component 16 may be used. It is conceivable to replace it with a chip part
or the like developed in recent years, but the effects of these components have not been able to
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sufficiently meet the demand for downsizing and thinning. The present invention has been made
under the background as described above, and its object is to provide a piezoelectric buzzer
capable of downsizing and thinning without increasing the production cost i ~. It is in. In order to
achieve this object, the present invention is a piezoelectric buzzer in which a piezoelectric
element is adhered to an elastic thin plate, and a conductive pattern portion having a
predetermined shape is formed in the vicinity of the edge on the upper surface side of the
piezoelectric element. The electronic component is fixed on the upper side to constitute an
oscillation circuit, and the fixed part of the electronic component is characterized as forming a
nodal point of the sound generator.
Hereinafter, preferred embodiments of the present invention will be described with reference to
the accompanying drawings. In the following description, the same reference numerals as in the
above-described conventional example denote the same or corresponding parts. 2 and 3 show an
embodiment of the piezoelectric buzzer according to the present invention. The piezoelectric
buzzer shown in the figure includes a case 10 made of a flat cylindrical synthetic resin or the like
with a lower opening, and a sound producing body 14 in which a disc-like piezoelectric element
20 is stuck on a disc-like elastic thin plate 22. It is roughly composed of A thin film conductive
member 30 is formed on the piezoelectric element 20 by evaporation or the like, and the
conductive portion '830 is divided to form a drive electrode 30a and a feedback electrode 30b,
and these electrodes are formed. 30a, 30b and the oscillation circuit are electrically connected to
vibrate the sounding body 14 at a specific natural vibration frequency, but the piezoelectric
buzzer shown in FIG. It has the features described below. That is, the feedback electrode 30b
made of the conductive member 30 is further divided in the vicinity of the upper surface side
edge 1 of the piezoelectric element 20 to form a pattern portion 30C having a predetermined
shape, and a transistor and a resistor are formed on the pattern portion 30C. , Etc., to constitute
an oscillation circuit, and the fixing portion of these electronic components 16 is a nodal point
(node of vibration) of the above-mentioned sounding body 14. In this case, the electronic
component 16 may be an electronic component 16 having a usual lead wire, but a chip
component and a melf component are more preferable because they can be made smaller and
thinner. Further, the connection point of the lead wire 32 for external connection is also a nodal
point of the sounding body 14 as in the fixing portion of the electronic component 16, and the
elastic thin plate 22 and the case 10 are fixed by the adhesive 24. It is desirable that the point be
a nodal point of the sound generator 14 in order to maintain the electrical characteristics of the
piezoelectric buzzer. Now, when the connection lead wire 32 of the piezoelectric buzzer
configured as described above is connected to a predetermined power supply, self-oscillation is
performed by the oscillation circuit composed of the electronic component 16 and the sounding
body 14, thereby generating piezoelectric Since the vibration of the element 20 is adhered on the
elastic thin plate 22, it becomes a bending vibration and generates a sound wave of a constant
natural vibration frequency determined by the thickness, diameter and the like of the sounding
body 14. The nodal point at which the frequency of the sound wave is constant means that the
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nodal point which becomes the vibration node is distributed concentrically because the elastic
thin plate 22 and the piezoelectric element 20 are circular. If the natural vibration frequency of is
set, it can be calculated relatively easily.
Therefore, it is relatively easy to set the connection point of the fixing portion of the electronic
component 16 and the lead wire 32 for external connection as the nodal point. In this case, it
should be noted that the fixed portions and the like of these electronic components 16 do not
affect the natural vibration frequency of the piezoelectric buzzer by positioning them at the nodal
point of the sound generator 14 at all. For this reason, the bending vibration of the sounding
body 14 is efficiently performed, and there is almost no loss of electric-sound conversion. And
the fact that the pudding 1 to wiring board 18 on which the conventional electronic component
16 is mounted becomes unnecessary can have a great effect on making the piezoelectric buzzer
smaller and thinner. As in the prior art, the troublesome connection work in the narrow space
between the pudding 1-wiring board 18 and the sounding body 14 becomes unnecessary, which
can greatly contribute to the improvement of the productivity and the cost reduction. As
described above, according to the piezoelectric buzzer of the present invention, an oscillation
made up of a sounding body formed by sticking a piezoelectric element to which an
electroconductive thin film electrode is fixed on an elastic thin plate and an electronic component
connected to the electrode In a piezoelectric buzzer comprising a circuit, a pattern portion having
a predetermined shape is formed in the vicinity of the upper surface side edge portion of the
piezoelectric element, the electronic component is fixed on the pattern portion to configure the
oscillation circuit, and the electronic component Is characterized in that it does not become the
nodal point of the sounding body, and it can be miniaturized and thinned without impairing the
electrical characteristics of the piezoelectric beech, and at the same time the productivity is
improved. Cost reduction is also possible.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view showing an example of a conventional piezoelectric buzzer.
FIGS. 2 and 3 show an embodiment of the piezoelectric buzzer according to the present
invention, FIG. 2 is a plan view showing the formation of the sounding body and the oscillation
circuit, and FIG. 3 is housed in the case It is a fragmentary sectional view of a state. 10 и и и Case
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12 и и и Back cover 14 и и и и и и и Sounding body 16 и и и и и electronic components 18 и и и и и и и printed
wiring board 20 и и и Piezoelectric element 22 иииии Elastic thin plate 24 ииииии Adhesive 26
ииииииииииииииииииииииииииииииии Lead wire 30a ииииииии Drive electrode 30b иии .... feedback electrode 30c и и и и и и
pattern portion 32 ......... external connecting lead wire applicant Fujidenkikagaku Ltd. allowance
actuary Attorney - IroKensuke 569
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