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JP2009260623

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DESCRIPTION JP2009260623
The present invention provides an electroacoustic transducer which can suppress the occurrence
of peaks and dips and can be miniaturized. A diaphragm (2) having a coil (3) formed on its
surface, and a magnet (7) arranged to face the diaphragm (2) so that magnetic lines of force
enter and exit in a direction perpendicular to the surface of the diaphragm (2). In the electroacoustic transducer, the thickness of the peripheral portion E of the diaphragm 2 is thinner than
the thickness of the central portion C of the diaphragm 2, and the coil 3 has the center of the
diaphragm 2 by a serpentine structure. The magnet 7 is formed in the portion C, and the magnet
7 is disposed in the gap portion 6 of the coil portion having the serpentine structure in a plan
view of the diaphragm 2, and the adjacent magnets 7 have different polarities. [Selected figure]
Figure 6
Electro-acoustic transducer
[0001]
The present invention relates to an electroacoustic transducer that converts an electrical signal
into voice, and more particularly to an electroacoustic transducer that suppresses the occurrence
of peaks and dips in frequency characteristics.
[0002]
2. Description of the Related Art In recent years, with the miniaturization of devices such as
mobile phones, the demand for downsizing and thinning of speakers and headphones used for
such devices has increased, and at the same time improvement in sound reproducibility has been
desired.
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[0003]
For example, in the conventional speaker, Lorentz force is applied to the current flowing through
the voice coil by the cylindrical voice coil attached to the diaphragm and the magnet disposed at
a position corresponding to the inside of the voice coil. , Vibrate the voice coil and the
diaphragm.
However, such a speaker is difficult to be thinned because the voice coil is cylindrical, and
vibration of the diaphragm is generated only in the vicinity of the location where the voice coil is
disposed. There was a problem that dips were likely to occur.
[0004]
In order to solve such problems, for example, a plurality of magnets are arranged in parallel in
parallel so that their magnetic poles are alternately reversed in polarity, and such two yokes have
the same polarity. There is a speaker in which a magnetic circuit is configured by arranging the
magnetic poles to face each other, and a diaphragm provided with a braking means is disposed
between the yokes (see Patent Document 1).
In such a speaker, since the entire surface of the diaphragm vibrates, it is possible to suppress
the occurrence of peaks and dips.
[0005]
Japanese Patent Application Laid-Open No. 52-89911
[0006]
However, the technique of Patent Document 1 has a problem that the voice coil pattern is
complicated and not suitable for miniaturization.
In addition, since the edge portion of the diaphragm having a uniform thickness is fixed to the
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frame, the amplitude can not be increased, and there is a problem in sound reproducibility.
[0007]
An object of the present invention is to provide an electroacoustic transducer which can suppress
the occurrence of peaks and dips and can be miniaturized in view of the above-mentioned actual
situation.
[0008]
In order to solve the above problems, in the electro-acoustic transducer according to the present
invention, a diaphragm having a coil formed on a surface, and the diaphragm face the magnetic
plate, and magnetic lines of force enter and exit in a direction perpendicular to the surface of the
diaphragm. An electro-acoustic transducer including a magnet arranged as described above,
wherein the thickness of the peripheral portion of the diaphragm is thinner than the thickness of
the central portion of the diaphragm, and the coil has the serpentine structure so as to make the
diaphragm The magnet is disposed in the gap between the coil portions forming the meandering
structure in a plan view of the diaphragm, and the polarities of the adjacent magnets are made
different.
[0009]
In this configuration, the electroacoustic transducer is configured by the diaphragm having the
coil formed on the surface, and the magnet disposed to face the diaphragm and allow magnetic
lines of force to enter and exit in the direction orthogonal to the surface of the diaphragm. It has
the following features.
First, the diaphragm is different in thickness between the peripheral portion where the
corrugation is formed and the central portion inside the corrugation.
Specifically, the peripheral portion is thinner than the thickness of the central portion. By
configuring in this manner, the amplitude of the diaphragm can be increased, peaks and dips can
be reduced, and sound reproducibility can be enhanced.
[0010]
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In addition, since the coil is formed by the meandering structure, the current flowing in the
adjacent part is in the reverse direction. Furthermore, the magnets are disposed in the gap
between the coil portions having a serpentine structure in a plan view of the diaphragm, and the
polarities of the adjacent magnets are made different. For this reason, when the direction of the
magnetic force of the magnet intersects the coil substantially at right angles, and current flows
through the coil, it is possible to effectively generate the Lorentz force. The Lorentz force is
transmitted from the coil to the diaphragm, and the diaphragm is efficiently vibrated, so that the
acoustic conversion efficiency can be enhanced. In particular, when the voice coil is formed on
substantially the entire surface of the central portion of the diaphragm, the entire diaphragm can
be vibrated in the same direction at the same time, thereby reducing peaks and dips.
[0011]
In one of the preferred embodiments of the electroacoustic transducer according to the present
invention, the coil has a meandering structure from one radial direction of the diaphragm to the
other radial direction, and adjacent to each other along the one radial direction. The parts are
aligned substantially parallel, and the magnet is a rod-like magnet.
[0012]
In this configuration, a coil can be formed on substantially the entire surface of the central
portion of the diaphragm with a simple wiring pattern, and the magnetic force of the bar-like
magnet acts on the coil. At the same time, it is possible to vibrate in the same direction, reducing
peaks and dips.
[0013]
Furthermore, in one of the preferred embodiments of the electroacoustic transducer according to
the present invention, the coil has a plurality of arc-shaped portions with different radii, and ends
of the plurality of arc-shaped portions are connected to each other It is formed as a single coil
connecting one point around the diaphragm to the center, and the magnet is a toroidal multipolar
magnetized magnet.
[0014]
In this configuration, the coil has a plurality of arc-shaped portions with different radii, and the
ends of the plurality of arc-shaped portions are connected to each other.
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Therefore, the coil can be formed on substantially the entire central portion of the diaphragm
with a simple wiring pattern.
Further, the magnetic force of the doughnut-shaped multipolar magnetized magnet acts on the
coil, and the generated Lorentz force vibrates the whole diaphragm simultaneously in the same
direction.
This can reduce peaks and dips. In addition, by using a multipolar magnetized magnet for the
magnet, the number of parts is reduced, so that the speaker can be further miniaturized.
[0015]
First Embodiment Hereinafter, a first embodiment of the electro-acoustic transducer of the
present invention will be described using the drawings. FIG. 1 is a perspective view of the electroacoustic transducer in this embodiment, FIG. 2 is a top view, FIG. 3 is a cross-sectional view, and
FIG. 4 is a bottom view. The electroacoustic transducer of this embodiment has a diaphragm 2
inside the frame 1, and a voice coil 3 is formed on the surface of the diaphragm 2 by metal foil.
In addition, a corrugation 4 is formed at the peripheral portion E of the diaphragm 2 to reinforce
the diaphragm 2 to provide flexibility and to suppress peaks and dips in frequency
characteristics.
[0016]
The rod-like magnet 7 is supported by the yoke 8, and the yoke 8 is supported by the frame 1. In
addition, on the bottom surface, a vent hole 9 is provided, and an acoustic resistance cloth 10 is
stretched. The acoustic resistance is intended to be flattened by the acoustic resistance cloth 10.
[0017]
The diaphragm 2 is formed of polyethylene terephthalate (PET) resin or the like. The central
portion C other than the peripheral portion E where the corrugation 4 is formed is laminated
with a polyimide resin such as polyetherimide (PEI) having high heat resistance and high rigidity.
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With such a configuration, the thickness of the peripheral part E of the diaphragm 2 becomes
thinner than that of the central part C, and the whole of the diaphragm 2 becomes easy to
vibrate, the amplitude becomes large, and the reproducibility of the sound It contributes to the
improvement.
[0018]
The wiring pattern of the voice coil 3 in this embodiment has a meandering structure from one
radial direction of the diaphragm 2 to the other as shown in FIG. The parts to be arranged are
aligned so as to be substantially parallel. The voice coil 3 is directly formed by metal paste
printing (screen printing, offset printing, inkjet printing, etc.) technology represented by silver.
However, the metal used is not limited to silver, and other metals may be used.
[0019]
The action portion 5 in the present invention is a portion of the voice coil 3 that is largely
affected by the Lorentz force, and in the case of the wiring pattern of FIG. 2, the linear portion of
the voice coil 3 aligned substantially parallel is the action portion It will be 5. A voice coil 3
(dotted line portion in FIG. 2) having the same shape is also formed on the back surface of the
diaphragm, and is connected to the surface through the through hole 11. In the present
embodiment, the voice coil 3 is formed on both sides of the diaphragm 2. However, the voice coil
3 may be formed on only one side.
[0020]
Here, referring to FIG. 3, as is apparent from the drawing, the bar-like magnet 7 is disposed at a
position corresponding to the gap 6 of the wiring pattern of the voice coil 3 of the present
embodiment. As shown in FIG. 5, the rod-like magnet 7 has magnetic poles in the vertical
direction with respect to the surface to be disposed. Therefore, the current direction of the action
unit 5 and the magnetic force direction from the magnet 7 are orthogonal to each other, and
Lorentz force acts on the charge flowing through the action unit 5. In the present embodiment,
although the rod-like magnet 7 shown in FIG. 5 is used, it is also possible to use a multipolar
magnet on a plane magnetized in stripes. In this case, it is more advantageous to use a rod-like
magnet because the magnetic force is weakened by the cancellation of the magnetic force.
Moreover, the number of linear parts of the voice coil 3 functioning as the action part 5 can be
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changed as appropriate, and accordingly, the number of rod-like magnets 7 can also be changed.
[0021]
Next, the operation principle of the electroacoustic transducer of the present embodiment will be
described using FIGS. 6 and 7. Hereinafter, in the figure, the symbol x indicates the action part 5
in which current flows from the front to the back with respect to the paper, and the mark ●
indicates the action part 5 in which current flows from the back to the paper with respect to the
paper. I assume. It can be seen from FIG. 6 that the current directions flowing in the adjacent
action parts 5 are different from each other. When current flows in the direction of (a) in FIG. 2,
current flows from the front to the back with respect to the action parts 5a, 5c and 5e, and in the
action parts 5b, 5d and 5f, from the back to the front A current will flow. At this time, a
downward Lorentz force (arrow in FIG. 6) acts on each action portion 5, and accordingly, the
diaphragm 2 is also subjected to a force in the same direction.
[0022]
On the other hand, FIG. 7 is a figure at the time of supplying an electric current to (b) direction of
FIG. In this case, current flows from the back to the front direction in the action parts 5a, 5c, 5e,
and current flows from the front to the back direction in the action parts 5b, 5d, 5f. However,
since the direction of the magnetic force is the same as that in FIG. 6, the Lorentz force that acts
is the upward direction opposite to that in FIG. 6 (arrow in FIG. 7). Accordingly, along with that,
the diaphragm 2 also receives an upward force.
[0023]
Second Embodiment Next, a second embodiment of the electro-acoustic transducer of the present
invention will be described. FIG. 8 is a top view of the electro-acoustic transducer in the second
embodiment, FIG. 9 is a cross-sectional view, and FIG. 10 is a bottom view. The present
embodiment differs from the first embodiment in the wiring pattern of the voice coil 3 and the
magnet 7.
[0024]
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In the wiring pattern of the voice coil 3 in the second embodiment, as shown in FIG. 8, the voice
coil 3 has a plurality of arc-shaped portions, and the end portions of the plurality of arc-shaped
portions are connected to each other. In such a wiring pattern, the plurality of arc-shaped
portions function as the acting portion 5. In the present embodiment, as in the first embodiment,
the voice coil 3 is formed at the central portion C of the diaphragm 2 by the metal paste printing
technique, and the voice of the surface of the diaphragm 2 is formed through the through holes
11. The coil 3 and the voice coil 3 on the back surface are connected.
[0025]
In the wiring pattern of the voice coil 3 of the present embodiment, as described above, the
action portion 5 is formed of five concentric circular arcs. Therefore, two doughnut-shaped
multipolar magnetized magnets 7a and 7b as shown in FIG. As shown in FIG. 11, each of the
multipolar magnetized magnets 7a and 7b has three magnetic poles in the radial direction, and
the magnetic poles are reversed to each other. In the present embodiment, two multipolar
magnetized magnets 7a and 7b are used, but the present invention is not limited to this. For
example, one multipolar magnetized magnet may be used, and it is also possible to use a toroidal
magnet having different magnetic poles in the vertical direction with respect to the surface to be
disposed. In the latter case, six donut shaped magnets 7 are required to correspond to the
pattern of the voice coil 3 of FIG. Here, the number of arcs of the voice coil 3 formed
concentrically can be changed as appropriate, and the magnetic pole characteristics and the like
of the magnet 7 used can be changed accordingly.
[0026]
12 and 13 are schematic views showing the operation principle of the electro-acoustic
transducer of the second embodiment. FIG. 12 shows the current direction, the magnetic force
direction, and the Lorentz force direction of each action portion 5 when a current is supplied in
the direction of (c) of FIG. In this case, a downward Lorentz force acts on each action portion 5.
On the other hand, FIG. 13 shows the directions of the current, the magnetic force and the
Lorentz force when the current in the direction of (d) of FIG. 8 flows, and the upward force acts
on each action portion 5 I understand.
[0027]
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As described above, according to the electro-acoustic transducer of the present invention, the
Lorentz force due to the magnetic force acts on the voice coil formed over substantially the entire
surface of the central portion of the diaphragm to vibrate the entire diaphragm. Can.
Furthermore, since the peripheral portion of the diaphragm is formed thinner than the central
portion, the diaphragm is easily vibrated, and the amplitude of the diaphragm can be increased.
As a result, the peaks and dips are reduced and the sound reproducibility is improved.
[0028]
In the above-described embodiment, the magnet is disposed on one side of the diaphragm, but in
actual use, the magnets are disposed on both sides of the diaphragm in order to enhance the
acoustic conversion efficiency.
[0029]
Perspective view of the first embodiment of the electroacoustic transducer according to the
invention Top view of the first embodiment of the electroacoustic transducer according to the
invention cross section of the first embodiment of the electroacoustic transducer according to the
invention electroacoustic according to the invention Bottom view of the first embodiment of the
transducer Figure showing the magnet used in the first embodiment of the electroacoustic
transducer according to the invention Schematic diagram representing the principle of operation
of the first embodiment of the electroacoustic transducer according to the invention Schematic
showing the operation principle of the first embodiment of the electroacoustic transducer Top
view of the second embodiment of the electroacoustic transducer according to the present
invention Cross section of the second embodiment of the electroacoustic transducer according to
the present invention Bottom view of the first embodiment of the acoustic transducer Diagram
showing the magnet used in the second embodiment of the electroacoustic transducer according
to the present invention Schematic diagram representing the operation principle of the second
embodiment of the electroacoustic transducer according to the present invention Electroacoustic
conversion Schematic diagram illustrating the operation principle of the second embodiment of
the
Explanation of sign
[0030]
1: Frame 2: Diaphragm 3: Voice coil 4: Corrugation 5: Active part 6: Gap part 7: Magnet 8: Yoke
9: Air vent 10: Cross for acoustic resistance 11: Through hole C: Central part E: Peripheral part
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