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JP2008092042

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DESCRIPTION JP2008092042
The present invention relates to a thin-type electrodynamic electroacoustic transducer, and it is
an object of the present invention to flatten frequency characteristics. In order to achieve this
object, according to the present invention, a magnetic gap is provided between a first magnet 1
and an outer position obliquely above the first magnet 1 and the first magnet 1. A second magnet
3 to be formed, a space in the upper surface direction of the first magnet 1 and a space in the
lower surface direction of the second magnet 3 are supported, and a diaphragm 7 capable of
oscillating in the vertical direction And a planar voice coil 9 supported by the diaphragm 7 so as
to be in parallel with the magnetic flux perpendicular to the vibration direction of the diaphragm
7. It is [Selected figure] Figure 1
Electrokinetic electroacoustic transducer
[0001]
The present invention relates to an electrodynamic electroacoustic transducer, and more
specifically, to an electronic apparatus such as a mobile phone, PDA (Personal digital assistants),
a television, a personal computer, a car navigation, a portable player, etc. The present invention
relates to an electrodynamic electroacoustic transducer that reproduces
[0002]
Conventionally, in electronic devices such as mobile phones and PDAs, thinning and reduction in
power consumption have progressed.
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1
Along with that, in the electro-acoustic transducers mounted on these, further miniaturization
and more efficiency are desired. The most common approach to increasing efficiency in
electroacoustic transducers is to increase the volume of the magnet. However, as the volume of
the magnet increases, the volume of the electroacoustic transducer itself increases. Then, in order
to realize miniaturization and high efficiency, an electrodynamic electroacoustic transducer 200
as shown in FIG. 5 has been proposed (see, for example, Patent Document 1). FIG. 5 is a crosssectional view of a conventional electrodynamic electroacoustic transducer 200.
[0003]
In FIG. 5, the electrodynamic electroacoustic transducer 200 includes a first magnet 211, a first
yoke 212, a second magnet 213, a second yoke 214, a diaphragm 215, a voice coil 216, and a
housing 217. Equipped with
[0004]
The first magnet 211 and the second magnet 213 are disposed facing each other on both sides of
the diaphragm 215 so as to sandwich the diaphragm 215.
A magnetic gap is formed between the opposing first magnet 211 and second magnet 213. The
surfaces of the first magnet 211 and the second magnet 213 opposite to the surface facing the
diaphragm 215 are respectively fixed to the first yoke 212 and the second yoke 214. In addition,
the first magnet 211 and the second magnet 213 are magnetized such that the polarities become
opposite in the vibration direction of the diaphragm 215.
[0005]
The first yoke 212 is shaped so as to surround a surface of the first magnet 211 excluding the
surface facing the diaphragm 215. Similarly, the second yoke 214 is shaped so as to surround
the surface of the second magnet 213 excluding the surface facing the diaphragm 215. In
addition, the first yoke 212 and the second yoke 214 are each fixed inside the housing 217.
[0006]
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The vibrating plate 215 is fixed inside the housing 217 having a sound hole, and is configured to
be positioned in a gap formed between the first magnet 211, the second magnet 213, and the
housing 217. The voice coil 216 is fixed to the diaphragm 215 and held in the magnetic gap.
Hereinafter, the operation of the electrodynamic electroacoustic transducer 200 will be
described.
[0007]
The first magnet 211 and the second magnet 213 are magnetized in opposite directions to be
opposite to each other. Therefore, the magnetic flux emitted from each magnet to the diaphragm
repels. Thereby, the magnetic flux vector bends substantially perpendicularly between the
magnetic gaps and draws a curve directed to the yoke to which each magnet is fixed. For this
reason, at the position of the voice coil 216 (hereinafter referred to as the voice coil position), a
magnetic field formed of magnetic flux perpendicular to the vibration direction of the diaphragm
215 is formed. When a current signal is supplied to the voice coil 216 disposed on such a
magnetic flux, a driving force proportional to the product of the magnitude of the current and the
magnetic flux density at the voice coil position is generated. Then, the diaphragm 215 is vibrated
by the driving force, and a sound is emitted.
[0008]
In a general electrodynamic electroacoustic transducer, the thickness of the voice coil is made
thicker in the vibration direction of the diaphragm, whereas in the conventional example, the
thickness of the voice coil 216 is thinner in the surface direction of the diaphragm 215
Configure. Therefore, it was possible to make the thickness of the electrodynamic electroacoustic
transducer 200 thinner than that of the conventional electroacoustic transducer. UnexaminedJapanese-Patent No. 2004-32659
[0009]
Incidentally, as described above, a planar coil is used as the voice coil disposed on the magnetic
flux perpendicular to the vibration direction of the diaphragm.
[0010]
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Loudspeakers like leaf tweeters with diaphragms to which planar coils are fixed generally use a
structure that utilizes the magnetic flux that leaks to the top of the magnetic gap of the magnetic
circuit, so a structure that efficiently extracts the magnetic flux applied to the voice coil It is
difficult to take.
Therefore, in order to increase the magnetic flux density applied to the voice coil, the magnetic
circuit is also enlarged.
[0011]
On the other hand, in the case of the sound slim having a repulsive magnetic field as shown in
FIG. 5, although the magnetic flux density can be made smaller and smaller than the magnetic
circuit such as leaf tweeter, the magnetic circuit is disposed on the center front of the diaphragm
Be done. Therefore, there is a problem that the sound emitted from the diaphragm interferes with
the magnetic circuit at the front position, and it becomes difficult to realize the flatness of the
frequency characteristic particularly in the high frequency band.
[0012]
An object of the present invention is to realize flatness of frequency characteristics in a high
frequency band without interference in a magnetic circuit.
[0013]
In order to achieve this object, the present invention is directed to a first magnet and a second
magnet disposed at an outer position obliquely above the first magnet to form a magnetic gap
between the first magnet and the first magnet. A diaphragm supported so as to pass through a
space in the upper surface direction of the first magnet and a space in the lower surface direction
of the second magnet, and capable of vibrating in the vertical direction, the first magnet, and the
second And a flat voice coil supported by the diaphragm so as to be disposed between the
magnet and the magnetic flux in a parallel relationship with the magnetic flux perpendicular to
the vibration direction of the diaphragm.
[0014]
As described above, in the electrodynamic electroacoustic transducer according to the present
invention, a magnetic gap is formed between the first magnet and an outer position obliquely
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above the first magnet and the first magnet. , A diaphragm supported so as to pass vertically
through the space in the upper surface direction of the first magnet and the space in the lower
surface direction of the second magnet, and the first magnet And a flat voice coil supported by
the diaphragm so as to be in parallel with the magnetic flux perpendicular to the vibration
direction of the diaphragm. Therefore, the magnetic circuit is not arranged in front of the
diaphragm, and the sound emitted from the diaphragm is not interfered with the magnetic
circuit, thereby achieving the flatness of the frequency characteristic in the high region. To do
That.
[0015]
An embodiment of the electrodynamic electroacoustic transducer of the present invention will be
described below with reference to the drawings.
[0016]
FIG. 1 is a structural cross-sectional view of the electrodynamic electroacoustic transducer
according to the first embodiment of the present invention, showing only one side cross section
from the center.
[0017]
In FIG. 1, the lower plate 2 is fixed to the upper surface of the first magnet 1, and the second
magnet 3 is disposed at an outer position above the first magnet 1.
An upper plate 4 is fixed to the lower surface of the second magnet 3.
The first and second magnets are magnetized in the same direction in the central axis direction.
A yoke 5 is fixed to the lower surface of the first magnet 1, and the yoke 5 is extended to the
upper surface position of the second magnet 3 and is attached to the yoke 6 fixed to the upper
surface of the second magnet 3. It is joined.
[0018]
Here, assuming that the first and second magnets 1 and 3 are magnetized as shown in FIG. 2, a
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flow of magnetic flux as indicated by arrows is generated to form a parallel magnetic field.
[0019]
The diaphragm 7 is disposed so as to pass through a space in the upper surface direction of the
magnet 1 and a space in the lower surface direction of the magnet 3, and a support portion on
the outer periphery thereof is supported by a support 8 fixed to the yoke 5. There is.
The diaphragm 7 can vibrate in the vertical direction.
[0020]
The second magnet 3 is provided outside the first magnet at a predetermined distance, and a flat
voice coil 9 is disposed in this space.
The voice coil 9 is supported by the diaphragm 7 in parallel relationship with the magnetic flux
perpendicular to the vibration direction of the diaphragm 7, and is disposed on the magnetic flux
constituting the parallel magnetic field.
[0021]
When a current signal is supplied to the voice coil 9 disposed on such a magnetic flux, a driving
force proportional to the product of the magnitude of the current and the magnetic flux density
at the voice coil position is generated.
Then, the diaphragm 7 is vibrated by the driving force and a sound is emitted.
[0022]
As shown in FIG. 2, the yoke 6 has a structure in which it protrudes inward from the inner
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diameter of the second magnet 3 in the portion where the second magnet 3 is fixed. That is, the
sound hole formed on the front side of the electrodynamic electroacoustic transducer becomes a
sound hole having a small inner diameter by the yoke 6. However, such a structure can be taken
when the thickness of the second magnet 3 is sufficiently large and the diaphragm 7 contacts the
second magnet 3 before the diaphragm 7 contacts the projecting portion of the yoke 6. It is.
[0023]
The flow of magnetic flux between the first magnet 1 and the second magnet 3 is a flow as
shown by the arrow in FIG. FIG. 2 is a diagram showing magnetic flux flow represented by
vectors by magnetic field analysis of an example of the magnetic circuit in the present
embodiment by the finite element method. Further, the magnetic flux density at the voice coil
position is as shown in FIG. FIG. 3 is a diagram showing the magnetic flux density at the voice
coil position by curves. That is, FIG. 3 is a diagram comparing the magnetic flux density at the
voice coil position when there is an extension of the yoke and when there is no extension of the
yoke.
[0024]
As shown in FIG. 3, the magnetic flux density at the voice coil position becomes larger when
there is an overhang, and a larger driving force can be obtained than when there is no overhang.
[0025]
A horn 10 is provided on the outer periphery of the front surface of the electrodynamic
electroacoustic transducer including the second magnet 3.
[0026]
In the present embodiment, the diaphragm 7 has a curved surface projecting forward in the
center, has a curved surface projecting backward on the outer periphery, and has a curved
surface projecting backward on the outer periphery, and voices between those curved surfaces
Although the one provided with a flat surface for supporting the coil 9 was used, the voice coil 9
may be supported using a film-like diaphragm 11 as shown in FIG. The support substrate 12
provided on the outer periphery may be fixed to the lower surface of the upper plate 4.
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Furthermore, an equalizer 13 may be disposed in front of the center of the diaphragm to realize
flatness of the frequency characteristic at a further higher frequency.
[0027]
As described above, according to the present invention, since the magnetic circuit that interferes
with the sound emitted from the diaphragm is not disposed in the center front of the diaphragm,
it is possible to realize the flattening of the frequency characteristic, and in particular It is useful
for realizing a thin and high-pitched speaker (tweeter).
[0028]
Cross-sectional view of an electrodynamic electro-acoustic transducer according to an
embodiment of the present invention. Enlarged cross-sectional view for explaining the operation
of the main part of the transducer. Magnetic characteristic view of the transducer. Cross section
of a conventional electrodynamic electroacoustic transducer
Explanation of sign
[0029]
1 first magnet 3 second magnet 7 diaphragm 9 voice coil
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