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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a conventional
small piezoelectric buzzer, FIG. 2 is a longitudinal sectional view of the small piezoelectric buzzer
of the present invention, and FIG. 3 is a pressure and caulking pressure in one embodiment of the
present invention. FIG. 4 is a chart showing the relationship between variations in resonant
frequency, and FIG. 4 is a chart showing the relationship between variations in caulking pressure
and resonant frequency in a buzzer of a conventional structure. In the figure, 1... Vibrator 2. Part,
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end part.
DETAILED DESCRIPTION OF THE INVENTION This invention relates to a small piezoelectric
buzzer used in calculators and watches. 10 In recent years, the demand for calculators has
increased, and as clocks are made into ICs, there is an increasing demand for replacing sound
producing bodies such as speakers and electromagnetic buzzers with piezoelectric buzzers which
consume less power. This type of piezoelectric buzzer is required to be smaller than the
conventional one, unlike the conventional one. For example, a watch buzzer is usually less than
15 al in diameter and requires stability of the acoustic output. In the conventional piezoelectric
buzzer, as shown in FIG. 1, the vibrator (1) in which the vibrating plate (2) and the piezoelectric
element (3) are bonded to each other as T <T, is used. (Page 1) λ2. Put the circumference of the
vibrator (1) on the step (5) and cover the back of the shilling (8) and fold the case end (7). Hold
the back cover (8). However, since the piezoelectric buzzer of this structure uses the resonance
phenomenon of the vibrator, if the vibrator becomes smaller, the influence of the peripheral five
fixed parts appears significantly, and the acoustic output largely changes due to some fluctuation
of the fixed condition. Therefore, conventionally, this kind of small piezoelectric buzzer has been
extremely difficult to place. It was found that when the cause of the variation in resonance
frequency was varied by jO, the bending displacement of the transducer peripheral portion was
changed due to a slight change in the pressing surface of the pressing portion around the
vibrator. This invention proposes a small-sized piezoelectric buzzer with little variation in
resonant frequency by attaching the vibrator peripheral portion to a metal case 15 with an
elastic body interposed, based on the above findings. That is, as shown in FIG. 2, in this invention,
the vibrator (1) formed by bonding the diaphragm (2) and the piezoelectric element (3) is housed
in a metal case (4), and the peripheral portion of the vibrator is In the case. (Page 2) An elastic
body (6) consisting of a step (5) K contact, and an O-ring made of neoprene 1 rubber, for
example, is applied to one side, and the case end (7) is bent inward to The vibrator peripheral
portion is pressed and fixed via 6) to form a small piezoelectric buzzer. Although the drawing
shows the case where the O-ring is used as an elastic body 5, the elastic body is not limited to
this, and one having a shape that swallows the peripheral portion of the vibrator or one that
partially abuts Various things can be used. Next, an embodiment of the invention will be
described. r。 Piezoelectric element made of zircon and lead titanate with a thickness of 8 and a
thickness of 0.15 fl is bonded with an epoxy resin to a diaphragm consisting of a phosphor
bronze disk with 13 diameter and 04 thickness 51 + 11 and a vibration frequency of 4 kgz I
made a child.
This is housed in an aluminum case -1 ° of diameter 14 鱈 and thickness 2.8 fl shown in FIG. 2,
a neoprene rubber O-ring is applied to the periphery of the vibrator and the case end is inward. It
was bent and stuck firmly. In addition, various caulking pressures at the time of pressing and
fixing were changed to test for variations in resonance frequency. その。 The results are shown
in FIG. Also, for comparison, rounding, the conventional structure shown in FIG. 1 with the same
dimensions as in the above embodiment (but with case dimensions of 14 m in outer diameter and
55 fl thickness) and various caulking pressures of the back cover. The variation K of the resonant
frequency was tested. The results are shown in FIG. 4. As a result, the conventional piezoelectric
buzzer has a large variation in resonance frequency even if the caulking pressure can be made
constant, but the practice of this invention caulked with an elastic body interposed. In the case,
even if the caulking pressure is changed, it can be seen that the variation of the resonance
frequency is within ± 0.2 kuz or so, and 10 practical problems do not occur. Next, using the
buzzer of the present invention made by caulking pressure 1 plum and the conventional buzzer,
the acoustic output at the on-axis IQcm was measured and compared by pulse voltage driving of
voltage 10 v 1 repetition 4 kaz. 15 It is required that the variation of the sound pressure on the
actual river is 2 dB or less as a standard deviation, but according to this device, the effect of
characteristic improvement is remarkable from the test result of Table 1, and the buzzer which
can be practically used sufficiently It is understood that it can be obtained. η (Page 4) Table 1
Test results □ As described above, this invention is to obtain a piezoelectric buzzer with little
fluctuation of resonance frequency by pressing and fixing piezoelectric electrons into a metal
case via an elastic body. And the thickness of the buzzer is reduced to half that of the
conventional one, and the piezoelectric element is exposed to the outside, which makes the
electrical connection easier and so on. Is demonstrated.