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Electronic buzzer of a portable device (1) A part of a case made of a plastic member A diaphragm
part which is relatively thin and is formed in a non-circular shape than another part is provided,
and a piezoelectric part is provided on the diaphragm part The elements are fixed, a plurality of
resonance points are generated, and the plurality of resonance frequencies are set to a relatively
simple integer ratio, and the piezoelectric signal is a rectangular wave whose fundamental
frequency is the greatest common divisor of the plurality of resonance frequencies. Electronic
buzzer of portable equipment applied to the device. (2) The electronic buzzer according to the
first aspect of the present invention, wherein the diaphragm portion is formed in a rectangular
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic
buzzer of a portable device, and more particularly to a means for achieving high quality with an
easy structure of attaching a piezoelectric element to a plastic case. Heretofore, it has been
known that a piezoelectric element is attached to a metal plate or the like to form a sound
generation diaphragm, and a method of driving at a mechanical frequency close to the
mechanical resonance frequency and an efficient frequency has been adopted. However, since
the number of main resonance points is one, and the resonance frequency and the driving
frequency fluctuate due to manufacturing, or fluctuate due to the environment, it was difficult to
make the both coincide with each other. In the case of a diaphragm using a metal plate, one of
the disadvantages is that the Q value is relatively high, and the frequency characteristic of the
sound pressure is sharp near the resonance point. However, in order to make an efficient, high
quality buzzer, it is necessary to adjust the resonance frequency etc. Making the ci water
structure is a very difficult problem because the diaphragm needs to communicate with the open
air. The present invention has been proposed in view of the foregoing points, and it is an object
of the present invention to provide a high-quality buzzer with an easy structure in which a
piezoelectric element is directly attached to a plastic case. The drawings illustrate an embodiment
of the present invention and FIG. 1 is a cross-sectional view of a portable device. End page 1 is a
back case molded by plastic material, and is provided with a diaphragm portion 7 relatively
thinner than other portions. The #i piezoelectric element 2 is adhered to the inner surface of the
vibrating plate portion 63, which is a shell case 63 also made of a plastic material, and is a
module portion that operates the original functions of the 5Fi glass and 6Fi device. 4a and 4b are
patzkins for keeping waterproof. FIG. 2 is a plan view of the back case 1 in FIG. 1, in which a
diaphragm portion formed into a rectangular shape, 1 is a circular piezoelectric element. With
this configuration, when an electrical signal is applied to the piezoelectric element 2, the
diaphragm 7fA of the back case 1 vibrates mainly from k and emits a sound, but in FIG. Indicated.
That is, regardless of k which is one vibrating portion, by making the structure of the vibrating
plate portion complicated, it is possible to have a plurality of resonance phenomena. The
resonance generated in the vicinity of 2 x Hz in the figure is mainly due to the vibration of the
fundamental mode of the vibration unit 70, and the 4 H 'generated by 6 HHzk is generated by
the vibration of the higher mode. Although these resonance points depend on the thickness and
shape of the diaphragm portion 7 and the shape of the entire back case 1 as well, the frequency
characteristics shown in FIG. 3 can be obtained by appropriately selecting these. It is obtained.
The electronic buzzer having such characteristics has various advantages. That is, when a
rectangular wave signal having a fundamental frequency of 21 CHi which is the greatest
common divisor of 2 and 4 in the characteristic of FIG. 3 is applied to the piezoelectric element 1,
higher order signals such as rectangular wave signals # 12 KHz, 4 KHg, dKHg, etc. Since many
frequency components are also included, these resonance points can be used effectively after all.
Thus, although the desired sound pressure level can be obtained by overlapping of a plurality of
frequencies, as described above, severe management of the resonance frequency is not easy.
However, it is extremely unlikely that all resonance points fluctuate at the same time, and sound
pressure above a certain level can always be guaranteed. In this structure, the diaphragm unit 7
is exposed and it is easy to receive shadows due to the portable condition and the use condition.
For example, the vibration of the fundamental mode of the diaphragm unit is weak to the
external force in the thickness direction Tend to be vulnerable to external forces. But it is the
species that these occur at the same time. Also, since the back case 1 is made of a plastic material
and has a complicated shape, the Q value at the resonance point is low and relatively smooth
resonance characteristics are exhibited. The sound pressure at each resonance point as described
above In addition to the low specific gravity, it is advantageous against manufacturing variations
and fluctuations. Furthermore, plastic cases are generally injection molded and complex shapes
have the advantage of being easy to manufacture. As described above, according to the present
invention, the electronic buzzer can be formed as an electronic buzzer having a simple structure,
less variation, and good environmental characteristics, and no waterproof structure can be
produced by the electronic buzzer. As an electronic buzzer of a portable device using a low cost
case, the effect is sufficiently exhibited.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 5 is a cross-sectional view of a portable device
provided with an electronic buzzer according to the present invention, and FIG. 2 is a plan view
of the back case 1 in FIG. FIG. 3 is a diagram showing the characteristics of the electronic buzzer.
1 и и и и Back case 2 и и и и Piezoelectric element 3 и и и и и и Torso case 4a, 4b и и и и и и и и и и и и и и и и и и и и и
glass 6 и и и ... Module 7 иииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии ?
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