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JPS57178294

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complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPS57178294
Description of Invention
Small electromagnetic buzzer
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compact
electromagnetic buzzer used for an alarm device of a watch or the like. A conventional small
electromagnetic buzzer includes a case (horn) constituting a resonance box, an annular endPage:
1 permanent magnet fixed to the bottom, a drive coil disposed in the hollow hole of the
permanent magnet, and a drive coil It requires a very large number of parts, such as an iron core
arranged in a hollow hole and a diaphragm fixed to the upper end surface of the permanent
magnet and opposed to the iron core, and the assembly thereof is troublesome. There is a
disadvantage that the gap adjustment with the above-mentioned diaphragm is necessary. The
present invention removes the disadvantages of the above prior art, and an embodiment thereof
will be described below. In the first embodiment shown in the first example, the case constituting
the resonance filter comprises an upper case 1 and an upper case 2 in this embodiment, both of
which are made of ordinary nonmagnetic plastic. A sound emission hole 5 is opened at the center
of the bottom plate (top plate) of the upper case 1. The vibration @ 4 provided on the bottom
plate portion of the lower case 2 is formed integrally with the lower case 2 by a two-color
molding method using a magnetic plastic mixed with magnetic powder. The diaphragm 4 is
magnetized in the thickness direction as shown in FIG. 2 using a barium ferrite or samarium
cobalt based ferromagnetic material. The diaphragm 4 is formed thin at its periphery 'and thick
at its central portion, and its inside is flat. Inside the case, a drive coil 6 held by a holder 5 is
disposed. As shown in FIG. 3, the holder 5 has its mounting piece 7 fixed by the positioning
projection 8 of the bottom plate portion of the case 2 and the drive coil 6 closely opposes the
diaphragm 4 via the required air gap. . Although an iron core 9 for concentrating magnetic flux is
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inserted and fixed in the central hole of the drive coil 6, the iron core 9 is not always necessary.
There is a gap between the holder 5 and the bottom plate portion of the case 2, When a drive
signal is supplied to the drive coil 6, the magnetic flux and the diaphragm 4 magnetically interact
with each other to vibrate, and this vibration causes the air in the case 1.2 to resonate to
generate sound. Can. Next, the second embodiment will be described with reference to FIG. 4. In
this embodiment, both the upper nurse 101 and the lower case 102 constituting the case are
formed of nonmagnetic plastic, as in the first embodiment. However, the diaphragms 104g and
1044 similar to the above embodiment are integrally provided in each of the cases 101 and 102,
respectively.
The shape of each diaphragm 104g, 104 & is determined so as to have a resonant frequency as a
member, and one of the diaphragms 104g, 104 & is such that the high-pitched part and the other
part share the low-pitched part. A pair of drive coils 106. 106 are disposed in the cases 101 and
102 in pairs with the respective diaphragms 104 a and ?104. The supporting structure of the
drive coil 106 is the same as that of the first embodiment, and the same reference numerals as in
the first embodiment are given. Further, in this embodiment, the sound output hole 105 is
opened in the side wall of the case. The small electromagnetic buzzer of the present invention
configured as described above can be configured with a very small number of parts, its assembly
is simple, and gap adjustment and the like are unnecessary. Furthermore, in the case provided
with a pair of diaphragms, high-power sound can be generated, and if the resonance frequencies
of the diaphragms are made different at that time, wide frequency response characteristics can
be obtained, and an alarm clock Best for generating melody alarm sound in etc. In each of the
above-described embodiments, it is also possible to use a soft magnetic material such as iron
instead of the magnetic powder.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 relate to a first embodiment, and FIG. 1 is a
sectional view of FIG. 2 is an enlarged cross-sectional view of the main part of the diaphragm,
FIG. 3 is a cross-sectional view of FIG. 1 and FIG. 1-soda line, and FIG. 4 is a cross-sectional view
of FIG. 1.2, 101. 102 иииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии Dia. EndPage or more: ?
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