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JPS5784382

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DESCRIPTION JPS5784382
Description 1, title of the invention
Piezoelectric, electronic clock with buzzer
3. Detailed Description of the Invention The present invention relates to a piezoelectric buzzer Fc
for a watch having a piezoelectric element attached to an outer case, in particular, a backing, the
main object of which is a buzzer sound when the watch is carried and not carried The pressure
difference is small (it is known that S1 and piezoelectric buzzers have a structure in which a
diaphragm such as a metal plate and a piezoelectric element are bonded by an adhesive etc. as is
well known. I have a back cover inside. All of them are simple in structure and can make a loud
noise with relatively little current consumption, and in recent years many products adopting
these alarm structures are marketed in the market. However, there are various problems in
practical use. This will be explained using some examples. FIG. 1 shows a piezoelectric buzzer
having a structure in which the piezoelectric element 2 is attached to the outer periphery of the
lt glass 1. In the case of this structure, since the windshield 1 which is a diaphragm is always
exposed to the surface, there is no sound pressure as long as the windshield is not touched when
carrying. Since the panel 3 is a large piece (the external case 4 is desired to have a small watch
with a large display area, the area where the piezoelectric element 2 can be attached is usually
very small. As a result, the sound pressure, the size of the piece, and the outer edge of the
windshield do not move in the vicinity of the center of the photographing movement, resulting in
a complicated vibration mode and a poor tone. A piezoelectric element having a structure in
which the lid 5VcIE electric element 2 is pasted to a thin plate, as shown in FIG. The sound
pressure is better than that of the single pregnancy mode which gives the lowest natural
frequency because the vibration is also driven near the center of the sound emission board.
However, the piezoelectric buzzer of FIG. 2 having such an advantage also has the back cover
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coming into contact with the arm (skin) when the watch is carried since the diaphragm is the
back cover, and the arm covers the vibrating portion. As a result, the sound pressure is reduced,
and the practical use of the present invention can be reduced by the sound pressure reduction as
much as possible, with the piezoelectric element directly attached to the back cover as shown in
FIG. It is an object of the present invention to provide a piezoelectric buzzer which is practical
and has a simple structure to be attached. In the following, according to the present invention,
the drive circuit of the piezoelectric buzzer sequentially connects the piezoelectric element 2 and
the booster coil 62 in parallel as shown in FIG. 3, adds the pulse wave 7 to this, and generates the
booster coil at the moment the pulse wave breaks. There are many systems in which a selfinduced voltage of 6 is applied to a piezoelectric element to generate a sound. The frequency
characteristic in the case of this driving method is as shown by the solid line in FIG. 4 when
measured without putting the back cover on the arm. The horizontal axis is frequency, and the
vertical axis is sound pressure.
When the period of application of the self-induction voltage of the booster coil to the
piezoelectric element is an integral fraction of the natural frequency fO of the piezoelectric
buzzer, the polarity of the voltage generated by the vibration of the piezoelectric element 2
matches the polarity of the applied voltage. Vibration is excited. As a result, as indicated by the
solid line in FIG. 4, the sound pressure increases at the position of the natural frequency fO and a
frequency that is an integral fraction of fo. Such a frequency characteristic is remarkable in the
case of snap type or iI--Keiji type in which the metal of the back cover and the case are directly
engaged with each other, with little vibration leakage from the back cover support. If the
engagement is loose, this is not the case with a structure in which seri or an elastic material is
interposed. Next, I check the time of carrying with the watch on my arm. The table looks like a
very natural portable condition, and the back cover is almost entirely sunk in the skin of the arm,
and the frequency characteristic at this time is as shown by the broken line in FIG. Even if the
watch is intentionally pressed strongly against the arm, this characteristic hardly changes, and it
is safe to think that the broken line in FIG. 4 is almost the frequency characteristic at the time of
carrying. The following results can be understood from the measurement results in Fig. 4 (1)
Vibration of the back cover is suppressed by the arm and the sound pressure is attenuated to the
whole, (2) Sound emission of the back cover is released into the atmosphere (air) As it changes
from sound to sound emission to the skin of the arm, an equivalent mass resulting from the
radiation impedance of the sound is added to the impression system of the back cover, and the
natural frequency of the back cover decreases. When the back cover is divided into a diaphragm,
the back cover mass is M, and the spring constant of the back cover is K)-, it is expressed by a
natural frequency fo (i) equation as well known in root dynamics. Assuming that the additional
mass resulting from the radiation impedance into the aforementioned skin rumor is m, it can be
expressed by the natural frequency fa equation of the back cover at the time of carrying. From
equation (3) and equation (2), the relationship of equation H will be derived from equation (3),
the reduction rate of the natural frequency of the back cover is determined by the ratio of quality
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1i of the back cover 5-M, 1-added mass m . This ratio is determined by the area and thickness of
the back cover, but as seen in the cloth market, a gentleman of the outer diameter with a
diameter of 15 on the diameter 15 side of Yuma In the case of using a back cover used for the
size of a product and directly attaching a piezoelectric element to this to make a piezoelectric
buzzer, a large change in size (1) Natural frequency f a, natural frequency f of the back cover
when not carrying. 60 to 70 people will be. As shown in FIG. 4, it is in the position of 60 to 70%
of fa and fo. By the way, it is the frequency characteristic at the time of non-carry shown by the
solid line. The frequency between 2 and 3 is a frequency at which the vibration of the
piezoelectric element does not coincide with the period of voltage application from the booster
coil.
とf。 The frequency interval of 2 is the high sound pressure frequency interval (for example f)
due to the excitation. Distance between b) and b) -12 wider. Therefore, the sound pressure
decreases as shown in the figure. Focusing on the frequency in the vicinity of this and fa, it can
be seen that there is a part where the sound pressure at the time of carrying becomes a part
where the sound pressure at the time of the emergency is higher or almost the same. Therefore,
the 6-EndPage of this fa is such that the piezoelectric buzzer sound pressure at the time of noncarrying becomes nearly the same as the sound pressure at the time of carrying around 2
frequencies, and the driving frequency of the piezoelectric buzzer is fa or less. It is possible to
obtain a piezoelectric buzzer that does not cause a difference in sound pressure between the 1
'clock and 1' clock when it is set to 7. However, in order to put this to practical use, it is
necessary to define the natural frequency of the back cover ° C 1 ° in the same way as in FIG.
4 when carrying on the case of changing the natural frequency of the back cover Investigate
frequency characteristics when not carrying. Fig. 5 shows the case where the natural frequency
of the back cover is as low as 5 KH2, Fig. 6 shows the case where the natural frequency of the
back cover is as high as 8 KH2, the solid line shows the frequency characteristics when the watch
is not carried and the broken line shows the frequency characteristic when carried As in FIG. 4,
the horizontal axis is the drive frequency of the buzzer and the vertical axis is the sound
pressure. In either case, no overlapping of the sound pressure is seen in the vicinity of the
natural frequency fa of the back cover at the time of carrying, as shown in FIG. Therefore, as
shown in Fig. 4, a piezoelectric showing a frequency characteristic, a piezoelectric buzzer that
can not feel the sound pressure difference between portable and non-portable can be realized by
realizing a buzzer, according to the present invention the natural frequency fo of the back cover
It is realized by specifying. The standard in defining fo is, needless to say, to reduce the sound
pressure difference at the buzzer drive frequency. As mentioned above, if the buzzer drive
frequency is switched from fo to fa according to the mobile status of the watch, high sound
pressure can always be obtained, but it is difficult to detect the status and it is turned off
automatically! 7 It is sad to feed. The drive frequency is therefore fixed. In the present invention,
as an example, 4096 H 2 easily obtained from the divider circuit is selected as the driving
frequency with an electronic watch having a 32768 H 2 quartz oscillator mounted on it. Since
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this frequency is also sensitive to human hearing, it is overlooked as the driving frequency of the
buzzer. FIG. 7 shows the sound pressure of the watch at the time of carrying the watch at 4096H
2 and at the time of not carrying it in the same manner as in FIG. 4, FIG. 5 and FIG. The
horizontal axis is the non-portable natural frequency (KH2) of the back cover, and the vertical
axis is the sound pressure.
The solid line is the sound pressure when not carrying, and the broken line is the sound pressure
when carrying. Black circles and white circles are measured points. From FIG. 7, if the natural
frequency of the back cover, that is, the piezoelectric and buzzer is defined between 5.5 KHz and
7 KHz, the sound pressure difference when carrying 2 and not carrying is extremely small. The
present invention sets a natural frequency of the piezoelectric buzzer between 5.5 KH2 and 7
KHz in a piezoelectric buzzer which uses as a sound emitting plate a back lid to which a
piezoelectric element is directly attached for the above reasons. As shown in FIG. 7, the same
applies to the buzzer drive frequency near 4 KHz. By the way, the shape is determined from the
relationship between the back cover of a watch on the market, snatching, design or total
thickness, etc., and in the case of a thin back cover in general, the present invention is not
completely considered. It is easy to adjust the natural frequency rise by increasing the thickness,
but if the pressure resistance of @ is required, the back cover is very near, and the natural
frequency is also + OK Hz; l! j! In order to practice the invention reached at f4, the natural
frequency must be lowered. Therefore, an example of the concrete measures will be described
below. FIG. 8 is an example of chopping the natural frequency of the back cover, in which a part
of the thickness 9- of the back cover 12 is thin (excluding the sticking part of the piezoelectric
element 11) so as to surround the piezoelectric element The groove is formed in a circular shape.
This groove portion is used by the present applicant for positioning at the time of pasting the
piezoelectric element. However, proper selection of the groove width and depth has the effect of
lowering the natural frequency of the back cover. FIG. 9 shows the relationship between groove
depth and sound pressure. The horizontal axis is the depth of the groove divided by the thickness
of the back cover, and the vertical axis is the natural frequency of the back cover. Since the figure
shows a book using a back cover with a thickness of 08 mm, in the case of a groove width above
1 mm and 11 mm, the tendency does not change as shown in FIG. From this figure, it is possible
to significantly reduce the natural frequency of the back cover by providing the groove depth of
y 4 or more of the back cover member for a groove width of 1 mm or more. FIG. 10 shows
another example, in the case where a circular piezoelectric element 16 is attached to a square
back cover 15, flat-neck shaped force is provided at four corners of the back cover; Also in this
case, the groove depth is 74 or more on the back cover plate. As described below, by setting the
natural frequency of the back cover to 55 to 7 KHz, it is a simple structure that uses the back
cover of the watch row case for 10-EndPage: 3 sound emission board, when carrying and not
carrying The significance of the present invention is great, since it is possible to provide a
piezoelectric buzzer that breaks the common sense that does not cause a difference in sound
pressure.
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4. Brief description of the drawings Fig. 1 A cross-sectional view of a piezoelectric buzzer having
a structure in which a piezoelectric element is attached to a windshield. FIG. 2 is a clock sectional
view having a piezoelectric buzzer of a structure in which a piezoelectric element is attached to a
back cover. Fig. 3 is a drive circuit diagram of the sweat city buzzer. 4, 5 and 6 are frequency
characteristic diagrams for explaining the present invention. FIG. 7 is a view for explaining the
buzzer sound pressure when the watch is carried and not carried. FIG. 8 is a cross-sectional
perspective view explaining an example of the back cover which implemented this invention. FIG.
9 is an explanatory drawing for explaining and clarifying the effect of FIG. FIG. 10 is a
perspective view of another embodiment of the back cover according to the present invention. 1 ·
· · · 2 windshield · · · piezoelectric element · · · · · · · · · 4 · · exterior case · · · back cover 6 · · Boost
coil 7 · · pulse wave 11 · · I + piezoelectric element 12 · · back cover 15 · · · Back cover 16 · · ·
Piezoelectric element or more Applicant Suwa Seiko Co., Ltd. Sabisu Hashiri top attorney 7S 5 \ \
5 Figure 2 Figure 37-Single Prison needle EndPage: 417 Figure EndPage: 5
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