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JP2004297318

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DESCRIPTION JP2004297318
An electro-acoustic electro-acoustic transducer which prevents excessive deformation of a
diaphragm due to wind pressure even when the diaphragm is formed of a thin film. In the
electrodynamic electroacoustic transducer 10 in which the film thickness of the diaphragm 12 is
set to a value of 15 μm or less, a diaphragm stopper 30 is provided as a deformation preventing
structure on the upper surface of the central portion of the yoke 26. Then, when the diaphragm
12 is deformed by a predetermined amount or more beyond the maximum amplitude at the time
of ringing, the diaphragm 12 is made to abut on the inner peripheral side portion 12A positioned
on the inner peripheral side of the voice coil 16. When the foldable portable communication
device on which the electroacoustic transducer 10 is mounted is folded, wind pressure acts on
the diaphragm 12 through the sound release hole 20 a formed in the cover 20, but the
diaphragm stopper 30 Prevents the diaphragm 12 from being deformed excessively. [Selected
figure] Figure 1
Electro-acoustic transducer
TECHNICAL FIELD [0001] The present invention relates to a so-called electrodynamic
electroacoustic transducer. In general, an electrodynamic electroacoustic transducer comprises a
diaphragm, a voice coil having a front end fixed to the diaphragm, and a cylindrical magnetic gap
for accommodating the rear end of the voice coil. And a magnetic circuit unit formed. At that
time, as described in, for example, Patent Document 1, in many electroacoustic transducers, a
cover is provided to cover the diaphragm from the front side in order to protect the diaphragm. A
sound emission hole is formed in the cover for radiating the sound from the diaphragm forward.
[Patent Document 1] Japanese Patent Application Laid-Open No. 11-146487 SUMMARY OF THE
INVENTION In recent years, the size of the liquid crystal screen has been increased in portable
communication devices such as portable telephones. It has been demanded that the electro-
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acoustic transducer to be mounted be miniaturized. However, when the electroacoustic
transducer is miniaturized, its lowest resonance frequency rises, and it becomes impossible to
obtain the desired frequency characteristics. On the other hand, if the thickness of the diaphragm
is reduced and set to a value of 15 μm or less, it is possible to effectively suppress the increase
in the lowest resonance frequency. However, when the diaphragm is formed of a thin film as
described above, the following problems occur. That is, in a foldable portable communication
device, when it is folded, a large wind pressure acts on the diaphragm through the sound output
hole of the cover of the electroacoustic transducer, but at this time the diaphragm is a thin film If
configured, there is a problem that the diaphragm is excessively deformed by the wind pressure.
And, if the diaphragm is deformed in this way, there is a problem that the acoustic characteristics
set at the time of manufacture may be disturbed. The present invention has been made in view of
such circumstances, and in the electrodynamic electroacoustic transducer, even when the
diaphragm is formed of a thin film, the diaphragm is excessively deformed by wind pressure. It is
an object of the present invention to provide an electro-acoustic transducer which can prevent in
advance. SUMMARY OF THE INVENTION The present invention achieves the above object by
providing a predetermined deformation preventing structure.
That is, in the electro-acoustic transducer according to the present invention, a diaphragm, a
voice coil whose front end is fixed to the diaphragm, and a magnetic magnetic tube in which a
cylindrical magnetic gap for accommodating the rear end of the voice coil is formed. A circuit
unit and a cover provided so as to cover the diaphragm from the front side and having a sound
emission hole formed for radiating the sound from the diaphragm forward, the film thickness of
the diaphragm In the electro-acoustic transducer in which the value is set to a value of 15 .mu.m
or less, the diaphragm is excessively deformed by the wind pressure acting on the diaphragm
through the sound release hole in at least one of the diaphragm, the magnetic circuit unit and the
cover. It is characterized in that a deformation preventing structure is provided to prevent the
problem. The sound output hole may be single or plural. The deformation preventing
structure is not particularly limited in its specific configuration, as long as the diaphragm can
be prevented from being excessively deformed by the wind pressure acting on the diaphragm
through the sound output hole of the cover. It is not limited. The term excessively deform
means to deform so large that it can not immediately return to the original diaphragm shape
beyond the maximum amplitude at the time of ringing. As shown in the above configuration, the
electro-acoustic transducer according to the present invention comprises a diaphragm, a voice
coil having a front end fixed to the diaphragm, and a rear end of the voice coil. A magnetic circuit
unit in which a cylindrical magnetic gap to be accommodated is formed, and a cover provided so
as to cover the diaphragm from the front side and having a sound emission hole for radiating
sound from the diaphragm forward The film thickness of the diaphragm is set to a value of 15
μm or less, but at least one of the diaphragm, the magnetic circuit unit and the cover is affected
by wind pressure acting on the diaphragm through the sound release hole. Since the deformation
preventing structure is provided to prevent excessive deformation, the following effects can be
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obtained. That is, in a foldable portable communication device equipped with the electro-acoustic
transducer according to the present invention, when it is folded after use, the electro-acoustic
transducer has a large diaphragm through the sound output hole. Although wind pressure acts,
since the electro-acoustic transducer is provided with a deformation preventing structure, this
wind pressure can prevent the diaphragm from being excessively deformed.
As described above, according to the present invention, in the electrodynamic electroacoustic
transducer, even when the diaphragm is formed of a thin film, excessive deformation of the
diaphragm due to wind pressure is prevented in advance. Can. And thereby, it is possible to
eliminate the possibility that the acoustic characteristics set at the time of manufacture may be
disturbed. By the way, most of the electro-acoustic transducers mounted on the portable
communication device have an inner peripheral side portion located on the inner peripheral side
of the voice coil in the diaphragm formed in a substantially convex spherical shape. The inner
circumferential portion is easily deformed into a substantially concave spherical shape by wind
pressure. Therefore, in the above configuration, when the diaphragm is deformed by a
predetermined amount or more beyond the maximum amplitude at the time of ringing, the
above-described deformation preventing structure is configured by the diaphragm stopper
provided so as to abut on the inner peripheral side portion. If so, deformation of the diaphragm
can be prevented by a simple configuration. Alternatively, in the above configuration, the
deformation preventing structure can be configured by setting the cross-sectional shape in the
radial direction of the inner peripheral side portion of the diaphragm to be uneven. In this
deformation preventing structure, the rigidity of the inner peripheral side portion of the
diaphragm can be enhanced, so that excessive deformation of the inner peripheral side portion
can be prevented. Even when such a deformation preventing structure is employed, deformation
of the diaphragm can be prevented by a simple configuration. Although it is the inner peripheral
side that is particularly easily deformed in the diaphragm, if the radial cross-sectional shape of
the outer peripheral side located on the outer peripheral side of the voice coil is set to be uneven,
deformation of the diaphragm is prevented Can be achieved more reliably. Instead of this, it is
possible to configure the above-mentioned deformation preventing structure by forming the
inner peripheral side portion of the diaphragm in a substantially concave spherical shape. In this
deformation preventing structure, by forming the inner peripheral side portion of the diaphragm
in a substantially concave spherical shape from the beginning, it is possible to prevent the inner
peripheral side portion from being deformed excessively. Even when such a deformation
preventing structure is employed, deformation of the diaphragm can be prevented by a simple
configuration. Further, in the above configuration, the above-mentioned deformation preventing
structure is configured by forming a sound emission hole for radiating the sound from the
diaphragm forward in an annular portion located in front of the voice coil in the cover. It is also
possible.
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In this deformation preventing structure, it is possible to prevent excessive deformation of the
inner peripheral side portion and the outer peripheral side portion by applying a wind pressure
to a relatively high rigidity portion of the diaphragm. When such a deformation preventing
structure is adopted, the deformation of the diaphragm can be prevented by a simple
configuration only by devising the formation position of the sound output hole. Alternatively, in
the above configuration, the deformation preventing structure can be configured by forming the
sound output hole in the peripheral wall portion of the cover. In this deformation preventing
structure, it is possible to prevent excessive deformation of the inner peripheral side portion and
the outer peripheral side portion by preventing a large wind pressure from acting directly on the
diaphragm in the direction perpendicular to the surface. . Even when such a deformation
preventing structure is adopted, the deformation of the diaphragm can be prevented by a simple
configuration in which only the formation position of the sound output hole is devised. Further,
in the above configuration, when the diaphragm is deformed by a predetermined amount or
more beyond the maximum amplitude at the time of ringing, the deformation is prevented by the
voice coil stopper provided so as to abut the rear end of the voice coil from the rear side. By
configuring the structure or a part of the structure, it is possible to prevent in advance the
excessive deformation of the entire diaphragm and the application of an excessive force on the
diaphragm. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the
present invention will be described with reference to the drawings. FIG. 1 is a side sectional view
showing an electroacoustic transducer 10 according to an embodiment of the present invention
in a state of being disposed upward, and FIG. 2 is a plan view thereof. As shown in these figures,
the electro-acoustic transducer 10 according to this embodiment is an electrodynamic electroacoustic transducer having an outer diameter of about 5 to 20 mm, and is a foldable type. It is
used as a receiver or a speaker in a state mounted on a portable communication device such as a
portable telephone. The electro-acoustic transducer 10 includes a diaphragm 12, a frame 14
supporting an outer peripheral edge 12 a of the diaphragm 12, a voice coil 16 whose front end is
fixed to an annular flat portion 12 b of the diaphragm 12, and A magnetic circuit unit 18 in
which a cylindrical magnetic gap for accommodating the rear end portion of the voice coil 16 is
formed, and a cover 20 which covers the diaphragm 12 from the front side. The thickness of the
diaphragm 12 is set to a value of 15 μm or less (for example, about 10 μm).
In the diaphragm 12, the inner peripheral side portion 12A located on the inner peripheral side
of the annular flat portion 12b is formed in a convex spherical shape, and the outer peripheral
side portion 12B located on the outer peripheral side of the annular flat portion 12b is in the
radial direction The cross-sectional shape is set to a convex arc shape. The diaphragm 12
vibrates within the range of the maximum amplitude shown by a two-dot chain line in FIG. 1
when the electroacoustic transducer 10 rings. The frame 14 is formed in a ring shape, and an
annular flange portion 14 a is formed at the outer peripheral end thereof. A diaphragm support
portion 14b for supporting the diaphragm 12 is formed on the inner peripheral side of the
annular flange portion 14a in the frame 14. A plurality of diaphragm support portions 14b are
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provided on the inner peripheral side of the diaphragm support portion 14b in the
circumferential direction. The sound release hole 14c is formed. A pair of terminal plates 28 to
which the coil terminals of the voice coil 16 are conductively fixed is embedded and fixed to the
frame 14. The magnetic circuit unit 18 is made of a steel base 22 formed in a substantially tray
shape, a magnet 24 formed in a relatively thick disc shape, and a steel made in a relatively thin
disc shape. It comprises a yoke 26 and is fixed to the inner peripheral end of the frame 14 at the
outer peripheral part of the base 22. The cover 20 is a steel plate formed in a substantially
reverse tray shape and made of steel, and is fixed to the diaphragm support portion 14 b of the
frame 14 at the outer peripheral edge thereof. A circular sound emission hole 20a for radiating
the sound from the diaphragm 12 forward is formed in the center of the cover 20. In the present
embodiment, a diaphragm stopper 30 made of a synthetic resin and formed in a disc shape
having a small diameter is provided on the upper surface of the central portion of the yoke 26 in
the magnetic circuit unit 18. The diaphragm stopper 30 abuts against the inner peripheral side
portion 12A when the diaphragm 12 is deformed by a predetermined amount or more beyond
the maximum amplitude at the time of ringing, as a deformation preventing structure for
preventing the diaphragm 12 from being deformed excessively. It is supposed to work. In the
present embodiment, a synthetic resin voice coil stopper 32 formed in a ring shape is provided at
the lower end of the inner peripheral wall of the peripheral wall of the base 22 of the magnetic
circuit unit 18 as another deformation preventing structure. . The voice coil stopper 32 is in
contact with the rear end of the voice coil 16 from the rear side when the diaphragm 12 is
deformed by a predetermined amount or more beyond the maximum amplitude at the time of
ringing.
Next, the function and effect of the present embodiment will be described. Although the electroacoustic transducer 10 according to the present embodiment is mounted on a foldable portable
communication device as described above, it is used as a receiver or a speaker. When the
portable communication device is folded after use, a large wind pressure acts on the electroacoustic transducer 10 through the sound output hole 20 a of the cover 20 on the diaphragm 12.
At this time, since the diaphragm 12 is formed of a thin film, the convex spherical inner
peripheral portion 12A tends to be deformed into a concave spherical shape by wind pressure.
However, in the present embodiment, the diaphragm stopper 30 provided at the central portion
of the yoke 26 abuts on the central portion of the inner peripheral side portion 12A to be
deformed to prevent further deformation. Accordingly, it is possible to prevent the inner
peripheral side portion 12A from being deformed into a concave spherical shape in advance. As
described above, according to the present embodiment, since the diaphragm stopper 30 is
provided as a deformation preventing structure, although the diaphragm 12 is formed of a thin
film, the diaphragm 12 is excessively deformed by the wind pressure. Can be prevented in
advance. And thereby, it is possible to eliminate the possibility that the acoustic characteristics
set at the time of manufacture may be disturbed. Furthermore, in the present embodiment, the
voice coil stopper 32 provided at the lower end portion of the inner peripheral wall of the base
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22 abuts on the rear end portion of the voice coil 16 from the rear side, and the diaphragm 12 is
largely deformed rearward. As a result, it is possible to prevent in advance the diaphragm 12
from being deformed unexpectedly or the force exerted on the diaphragm 12 being exerted. In
the present embodiment, the diaphragm stopper 30 is formed in a disk shape and provided on
the upper surface of the central portion of the yoke 26. However, the diaphragm 12 has a
predetermined amplitude or more exceeding the maximum amplitude at the time of ringing. Of
course, any other shape or arrangement may be adopted as long as it is configured to be able to
contact the inner peripheral side portion 12A when deformed. Further, in the present
embodiment, the material of the diaphragm stopper 30 and the voice coil stopper 32 has been
described as a synthetic resin, but the specific material is not particularly limited. A soft resin
such as a thermoelastomer can be employed.
Alternatively, it is also possible to adopt a hard resin, and it is also possible to adopt a material
other than a synthetic resin such as, for example, rubber or metal. FIG. 3 is a view similar to FIG.
1 showing a first modification of the embodiment. As shown in this figure, in the present
modification, the diaphragm stopper 30 as in the above embodiment is not provided, and instead,
the radial cross-sectional shape of the inner peripheral portion 12A of the diaphragm 12 is
uneven It is set in a shape, and this constitutes a deformation preventing structure. Further, in
the present modification, the radial cross-sectional shape of the outer peripheral side portion 12B
of the diaphragm 12 is also set to be uneven. Also in this modification, the basic configuration of
the electroacoustic transducer 10 is the same as that of the above-described embodiment, and
the voice coil stopper 32 is also the same as that of the above-described embodiment. In the
deformation preventing structure of the present modification, by increasing the rigidity of the
inner peripheral side portion 12A of the diaphragm 12, it is possible to prevent the inner
peripheral side portion 12A from being deformed excessively. Even when such a deformation
preventing structure is adopted, the deformation of the diaphragm 12 can be prevented by a
simple configuration. Further, in the present modification, the rigidity of the outer peripheral side
portion 12B of the diaphragm 12 can be enhanced, so that deformation of the diaphragm 12 can
be prevented more reliably. FIG. 4 is a view similar to FIG. 1 showing a second modification of
the embodiment. As shown in this figure, in the present modification, the sound output hole 20a
is not formed at the central portion of the cover 20 as in the above embodiment, but is formed at
the annular portion of the cover 20 located in front of the voice coil 16. Thus, the deformation
preventing structure is configured. At this time, a plurality of sound release holes 20a are formed
at predetermined intervals in the circumferential direction. Also in this modification, the basic
configuration of the electroacoustic transducer 10 is the same as that of the above-described
embodiment, and the voice coil stopper 32 is also the same as that of the above-described
embodiment. In the deformation preventing structure of the present modification, the sound
output hole 20 a is formed in the annular portion of the cover 20 located in front of the voice
coil 16, so that the annular flat portion having a relatively high rigidity in the diaphragm 12.
Since wind pressure can be applied to 12b, excessive deformation of the inner peripheral side
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portion 12A and the outer peripheral side portion 12B can be prevented.
As described above, in the present modification, the deformation of the diaphragm 12 can be
prevented by a simple configuration in which only the formation position of the sound output
hole 20a is devised. FIG. 5 is a view similar to FIG. 1 showing a third modification of the
embodiment. As shown in this figure, in the present modification, the sound output hole 20a is
formed not in the central portion of the cover 20 but in the peripheral wall portion, thereby
constituting a deformation preventing structure. At this time, a plurality of sound release holes
20a are formed at predetermined intervals in the circumferential direction. Also in this
modification, the basic configuration of the electroacoustic transducer 10 is the same as that of
the above-described embodiment, and the voice coil stopper 32 is also the same as that of the
above-described embodiment. In the deformation preventing structure of the present
modification, by forming the sound output hole 20 a in the peripheral wall portion of the cover
20, the direct wind direction does not act directly on the diaphragm 12. As a result, excessive
deformation of the inner circumferential portion 12A and the outer circumferential portion 12B
can be prevented. As described above, also in the present modification, it is possible to prevent
the deformation of the diaphragm 12 by a simple configuration in which only the formation
position of the sound output hole 20a is devised. FIG. 6 is a view similar to FIG. 1 showing a
fourth modification of the embodiment. As shown in this figure, in the present modification, the
inner peripheral side portion 12 A of the diaphragm 12 is formed in a concave spherical shape,
thereby constituting a deformation preventing structure. In the above embodiment, the magnetic
circuit unit 18 is configured as an internal magnet type unit in which the magnet 24 is disposed
on the inner peripheral side of the voice coil 16, but in the present modification, the voice coil 16
is The magnet 24 is arranged on the outer peripheral side of the unit as an external magnet type
unit. The configuration other than this is the same as that of the above embodiment, including
the point that the voice coil stopper 32 is provided. In the deformation preventing structure of
the present modification, since the inner peripheral side portion 12A of the diaphragm 12 is
initially formed in a concave spherical shape, a large wind pressure acts on the diaphragm 12
through the sound release hole 20a. Also, unlike the substantially convex spherical shape, since it
is difficult to physically deform further in the concave direction, it is possible to prevent the inner
peripheral side portion 12A from being deformed excessively. Even when such a deformation
preventing structure is adopted, the deformation of the diaphragm 12 can be prevented by a
simple configuration.
In this modification, since the magnetic circuit unit 18 is configured as an external magnet type
unit, even if the inner peripheral side portion 12 A of the diaphragm 12 is formed into a concave
spherical shape, the inner peripheral side at the time of ringing Interference of the portion 12A
with the magnetic circuit unit 18 can be easily avoided. Although the voice coil stopper 32 is
provided as another deformation preventing structure in addition to the respective deformation
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preventing structures in the above embodiment and each modification, the voice coil stopper is
described. Even in the configuration in which 32 is not provided, excessive deformation of the
inner peripheral side portion 12A which is particularly easily deformed in the diaphragm 12 can
be prevented in advance. Alternatively, in the above-described embodiment and each
modification, even when the voice coil stopper 32 is provided even in the configuration in which
the respective deformation preventing structures are not provided, the entire diaphragm 12 is
largely deformed and thus the voice coil stopper 32 is provided. Unreasonable force acting on
the diaphragm 12 can be prevented in advance. Further, the deformation preventing structures
of the above-described embodiment and the respective modified examples may be appropriately
combined and used. In this case, deformation of the diaphragm 12 can be prevented more
effectively. Furthermore, in the electro-acoustic transducer 10 according to the above-described
embodiment and each modification, the outer shape of the diaphragm 12 is described as being
circular, but, for example, the outer shape other than circular such as oval or square Also in the
electro-acoustic transducer provided with the diaphragm, it is possible to obtain the same
operation and effect as those described above by adopting the same configuration as that of the
above-described embodiment and the respective modifications. BRIEF DESCRIPTION OF THE
DRAWINGS FIG. 1 is a side cross-sectional view showing an electro-acoustic transducer according
to an embodiment of the present invention disposed upward, and FIG. 2 is a diagram showing the
electro-acoustic transducer disposed upward FIG. 3 is a plan view showing a first modification of
the embodiment, similar to FIG. 1, and FIG. 4 is a view similar to FIG. 1 showing a second
modification of the embodiment. A diagram similar to FIG. 1 showing a third modification of the
embodiment [FIG. 6] A diagram similar to FIG. 1 showing a fourth modification of the
embodiment [Description of the reference numerals] 10 electroacoustic transducer 12
diaphragm 12A Inner part 12B Outer part 12a Outer peripheral part 12b Annular flat part 14
Frame 14a Annular flange part 14b Diaphragm support part 14c Sound output hole 16 Voice coil
18 Magnetic circuit unit 20 Cover 20a Sound output hole 22 Base 24 magnet 26 yoke 28
terminal plate 30 diaphragm stopper 32 voice coil stopper
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