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JP2009055602

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DESCRIPTION JP2009055602
The present invention provides an electroacoustic transducer that realizes better super high
frequency reproduction. An electro-acoustic transducer according to the present invention
includes a diaphragm having an elongated shape, an edge for vibratably supporting the
diaphragm, and one major surface of the diaphragm with its longitudinal direction parallel to the
longitudinal direction of the diaphragm. A rectangular parallelepiped shaped first magnet
provided on the side and magnetized in the short direction of the diaphragm to form a magnetic
gap on the side facing the one main surface of the diaphragm, and the longitudinal direction as
the longitudinal direction of the diaphragm Parallel to the first magnet and a gap, it is adjacent in
the width direction of the diaphragm, is magnetized in the direction opposite to the first magnet,
and forms a magnetic gap on the side opposite to one major surface of the diaphragm The
second magnet of rectangular parallelepiped shape is wound to form an elongated ring shape,
the longitudinal direction being parallel to the longitudinal direction of the diaphragm, and the
diaphragm being disposed such that each longitudinal portion is in each magnetic gap And a first
coil provided thereon. [Selected figure] Figure 8
Electro-acoustic transducer
[0001]
The present invention relates to an electroacoustic transducer, and more particularly to an
electroacoustic transducer that realizes ultra high frequency reproduction.
[0002]
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In recent years, media such as DVD and DVD-AUDIO have become widespread, and an electroacoustic transducer with a high reproduction band is desired in order to reproduce ultra-highrange sound included in these contents.
In order to realize such ultrahigh frequency range reproduction, electroacoustic transducers as
shown in FIGS. 22A to 22B and FIGS. 23A to 23C have been proposed (for example, Patent
Document 1 etc.). 22A and 22B are diagrams showing an example of the structure of a
conventional electroacoustic transducer, FIG. 22A is a front view, and FIG. 22B is a case where
the electroacoustic transducer is cut along the center line AA in the lateral direction of FIG. FIG.
23A to 23C show other examples of the structure of the conventional electroacoustic transducer,
FIG. 23A is a front view, and FIG. 23B is a case where the electroacoustic transducer is cut along
the center line AA in the longitudinal direction of FIG. FIG. 23C is a cross-sectional view of the
electro-acoustic transducer cut along the center line BB in the lateral direction of FIG. 23A.
[0003]
In FIGS. 22A-B, the electro-acoustic transducer comprises a yoke 901, a magnet 902, a
diaphragm 903, a spacer 904, and a coil 905. The yoke 901 has a concave shape and is made of
iron or the like which is a ferromagnetic material. The magnet 902 is formed of a flat neodymium
magnet magnetized in the thickness direction. The magnet 902 is fixed to the bottom of the
recess of the yoke 901 and forms magnetic gaps G 1 and G 2 with the yoke 901. The upper
surface of the magnet 902 and the upper surface of the yoke 901 are located on the same plane,
and a film-like diaphragm 903 is fixed to the upper surface via a spacer 904. The coil 905 is
patterned so as to be disposed on the diaphragm 903 and in the magnetic gaps G1 and G2. The
magnetic flux radiated from the magnet 902 is radiated substantially perpendicular to the upper
surface in the central portion of the magnet 902, emitted obliquely to the upper surface in the
peripheral portion, and penetrates the coil 905. When current flows through the coil 905 in such
a static magnetic field, a driving force is generated in a direction (vertical direction in FIG. 22B)
perpendicular to the diaphragm 903 and the diaphragm 903 vibrates in the vertical direction by
the generated driving force. Sound is generated. The driving force is proportional to the magnetic
flux in the direction perpendicular to the vibration direction of the diaphragm 903 among the
magnetic fluxes passing through the coil 905.
[0004]
In the electro-acoustic transducer shown in FIGS. 22A-B, as shown in FIG. 22A, the shape of the
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vibrating portion in which the coil 905 is patterned becomes an elongated shape. For this reason,
the resonant frequency of the resonant mode generated in the short direction of the vibrating
portion becomes high, and the peak dip due to the resonant mode is less likely to occur in the
very high frequency range. As described above, in the electroacoustic transducers shown in FIGS.
22A to 22B, by making the shape of the vibrating portion elongated, the disturbance of the
sound pressure frequency characteristic of the ultrahigh range due to the resonance mode is
improved.
[0005]
In FIGS. 23A-C, the electro-acoustic transducer comprises a frame 906, a yoke 907, a magnet
908, a diaphragm 909, a coil 910, and an edge 911. The frame 906 has a concave shape. The
yoke 907 has a concave shape and is made of iron or the like which is a ferromagnetic material.
The yoke 907 is fixed to the bottom of the recess of the frame 906. A rectangular parallelepiped
magnet 908 is fixed to the bottom of the recess of the yoke 907. The magnet 908 is, for example,
a neodymium magnet with an energy product of 44 MGOe, and is magnetized in the vibration
direction of the diaphragm 909 (vertical direction in FIG. 23C). As shown in FIG. 23C, the yokes
907 and the magnets 908 form magnetic gaps G1 and G2 by the magnetic flux φ on the
vibrating plate 909 side. The thick arrows in FIG. 23C indicate the magnetic flux φ. The
diaphragm 909 has a shape like an elongated land track (hereinafter referred to as an elongated
track shape), and is disposed above the magnet 908. The coil 910 is formed into an elongated
ring shape by winding a copper or aluminum wire a plurality of times, and is adhered to the
upper surface of the diaphragm 909 with an adhesive Ad. Each longitudinal portion of coil 910 is
disposed in magnetic gaps G1 and G2. Specifically, each longitudinal portion of the coil 910 is
disposed such that the center of its winding width is located immediately above the ends T1 and
T2 in the short direction of the magnet 908. The longitudinal direction of the magnet 908 and
the coil 910 is parallel to the longitudinal direction of the diaphragm 909. The edge 911 has a
semicircular cross-sectional shape, the inner peripheral end is fixed to the outer peripheral end
of the diaphragm 909, and the outer peripheral part is fixed to the upper surface of the frame
906. Thereby, the diaphragm 909 is supported by the edge 911 so as to be able to vibrate in the
vertical direction. When current flows through the coil 910 in the static magnetic field as shown
in FIG. 23C, driving force is generated in a direction perpendicular to the diaphragm 909
(vertical direction in FIG. 23C), and the generated driving force causes the diaphragm 909 to
move vertically. Vibration occurs and sounds are generated. The driving force is proportional to
the magnetic flux in the direction perpendicular to the vibration direction of the diaphragm 909
among the magnetic flux φ passing through the coil 910.
[0006]
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In the electroacoustic transducer shown in FIGS. 23A to 23C, as shown in FIG. 23A, the shape of
the diaphragm 909 is an elongated shape. For this reason, as in the electroacoustic transducers
shown in FIGS. 22A to 22B, the resonance frequency of the resonance mode generated in the
short direction of the diaphragm 909 becomes high, and it becomes difficult to cause peak dip
due to resonance in the ultra high frequency range. As described above, in the electroacoustic
transducers shown in FIGS. 23A to 23C, by making the shape of the diaphragm 909 into an
elongated shape, the disturbance of the sound pressure frequency characteristic of the ultrahigh
range due to the resonance is improved. JP 2001-211497 A
[0007]
Here, in order to realize better super high frequency reproduction, it is necessary to improve not
only the disturbance of the sound pressure frequency characteristic due to resonance but also
the reproduction sound pressure itself. In order to improve the reproduction sound pressure, it is
necessary to increase the driving force generated in the coil. Specifically, it is necessary to
increase the magnetic flux in the direction perpendicular to the vibration direction of the
diaphragm. In order to increase the magnetic flux in the direction perpendicular to the vibration
direction of the diaphragm, it is necessary to increase the width in the short direction of the
magnet 902 in the electroacoustic transducer shown in FIGS. In the case of FIG. 22B, it is
necessary to increase the width in the left-right direction of the magnet 902. In the
electroacoustic transducer shown in FIGS. 23A to 23C, the width in the short direction of the
magnet 908 needs to be increased. In the case of FIG. 23C, it is necessary to increase the width of
the magnet 908 in the left-right direction.
[0008]
However, in the conventional electroacoustic transducers shown in FIGS. 22A-B and 23A-C, the
magnetic flux in the direction perpendicular to the vibration direction of the diaphragm is
efficiently increased even if the width of the magnet 902 or the magnet 908 is increased. I could
not Hereinafter, the conventional electroacoustic transducer shown to FIG. 23A-C is mentioned as
an example, and the reason which can not increase magnetic flux efficiently is demonstrated in
detail.
[0009]
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In the electroacoustic transducer shown in FIGS. 23A to 23C, when the width in the short
direction of the magnet 908 is increased, the result is as shown in FIG. FIG. 24 is a cross-sectional
view of the electroacoustic transducer shown in FIGS. 23A to 23C in which the width in the short
direction of the magnet 908 is increased. In FIG. 24, the magnet 908 shown in FIG. 23C is
replaced with a magnet 908a having a larger width than the magnet 908 without changing the
width in the short side of the diaphragm 909, and the end in the short direction of the magnet
908a is T3 and It is assumed that it is T4. The reason why the width in the short direction of the
diaphragm 909 is not changed is to prevent the sound pressure frequency characteristic from
being disturbed in the very high frequency range. Also, in order to use the magnet 908a, the
frame 906 shown in FIG. 23C is replaced with the frame 906a, and the yoke 907 shown in FIG.
23C is replaced with the yoke 907a.
[0010]
The difference in magnetic flux density at the coil position was compared between the case
where the magnet 908 in FIG. 23C was used and the case where the magnet 908a in FIG. 24 was
used. The comparison result is shown in FIG. In FIG. 25, the vertical axis is the magnetic flux
density. The magnetic flux density indicates the density of magnetic flux in the direction
perpendicular to the vibration direction of the diaphragm 909, and if the magnetic flux density is
high, it means that the magnetic flux in the direction perpendicular to the vibration direction of
the diaphragm 909 is large. The horizontal axis indicates the distance from the central axis O in
the lateral direction of the diaphragm 909, and the right direction in FIGS. 23C and 24 is a
positive direction. Further, in FIG. 25, the graph (a) shows the magnetic flux density distribution
when the magnet 908 of FIG. 23C is used, and the graph (b) shows the magnetic flux density
distribution when the magnet 908 a of FIG. ing.
[0011]
In the graph (a), the magnetic flux density is maximum at the positions of the end T1 and the end
T2. Then, as shown in FIG. 23C, the centers of the winding widths of the respective longitudinal
portions of the coil 910 are located immediately above the end portions T1 and T2. On the other
hand, in the graph (b), the magnetic flux density is maximum at the positions of the end portions
T3 and T4. Here, in FIG. 24, the width in the short direction of the diaphragm 909 is not changed
in order to prevent the sound pressure frequency characteristic from being disturbed in the ultra
high frequency range. That is, each longitudinal portion of the coil 910 in FIG. 24 is disposed at
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the same position as FIG. 23C, and is located at the ends T1 and T2. Therefore, it can be seen
from the graph (b) that the magnetic flux density at the position where the coil 910 is present in
FIG.
[0012]
Thus, in the conventional electroacoustic transducers shown in FIGS. 22A-B and 23A-C, the
magnetic flux in the direction perpendicular to the vibration direction of the diaphragm is
efficiently increased even if the width of the magnets 902 and 907 is increased. I could not
Therefore, with the conventional electroacoustic transducers shown in FIGS. 22A-B and 23A-C, it
has been difficult to realize better superhigh-frequency reproduction.
[0013]
Therefore, it is an object of the present invention to provide an electroacoustic transducer that
achieves better super high frequency reproduction by efficiently improving the reproduction
sound pressure in the ultra high frequency range.
[0014]
The electro-acoustic transducer according to the present invention solves the above-mentioned
problems, and the electro-acoustic transducer according to the present invention comprises a
diaphragm having an elongated shape, an edge for vibratably supporting the diaphragm, and a
longitudinal direction. A rectangular parallelepiped provided parallel to the longitudinal direction
of the diaphragm and provided on one main surface side of the diaphragm and magnetized in the
short direction of the diaphragm to form a magnetic gap on the side facing the one main surface
of the diaphragm The first magnet and the longitudinal direction are parallel to the longitudinal
direction of the diaphragm, and the first magnet and the transverse direction of the diaphragm
are adjacent to each other with an air gap therebetween, and magnetized in the opposite
direction to the first magnet A rectangular second magnet, which forms a magnetic gap on the
side facing the one main surface of the diaphragm, is wound to form an elongated ring shape,
and the longitudinal direction is parallel to the longitudinal direction of the diaphragm. Vibration
so that the longitudinal part is placed in each magnetic gap And a first coil provided above.
[0015]
According to the electro-acoustic transducer according to the present invention, in order to
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increase the magnetic flux in the direction perpendicular to the vibration direction of the
diaphragm to improve the reproduction sound pressure, the width in the vibration direction of
the diaphragm in the first and second magnets Should be increased.
Furthermore, even if the width in the vibration direction of the diaphragm in the first and second
magnets is increased, the position at which the magnetic flux density reaches the maximum value
does not change unlike the conventional case.
As a result, in the electroacoustic transducer according to the present invention, the magnetic
flux in the direction perpendicular to the vibration direction of the diaphragm can be efficiently
increased while preventing the sound pressure frequency characteristic from being disturbed in
the very high frequency range. Can be improved. As a result, it is possible to realize better super
high frequency reproduction.
[0016]
Preferably, it further comprises a first plate of ferromagnetic material provided to fill the air gap.
Further, the surfaces on the diaphragm side of the first and second magnets and the first plate
may be located on the same plane. In addition, a second plate provided on a pole surface
opposite to a pole surface in contact with the first plate in the first magnet, and a pole surface
opposite to a pole surface in contact with the first plate in the second magnet And a third plate
provided on In addition, if each surface on the diaphragm side in the second and third plates is
positioned on a plane closer to the diaphragm than each surface on the diaphragm side in the
first and second magnets and the first plate Good. Further, the cross section of the edge has a
shape that is convex on the other main surface side of the diaphragm, and the second and third
plates are arranged such that the respective surfaces on the diaphragm side face the edge. It is
good. In addition, each longitudinal portion of the first coil is disposed to face one or more of the
surfaces on the diaphragm side of the first and second magnets and the first to third plates. It is
good.
[0017]
Preferably, it is provided on the other main surface side of the diaphragm with the longitudinal
direction parallel to the longitudinal direction of the diaphragm, and disposed so as to be located
between the first and second magnets with respect to the position of the diaphragm in the short
direction. The third magnet further includes a third magnet having a rectangular parallelepiped
shape, and the third magnet has the same polarity as the polarity of each pole surface of the first
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and second magnets in contact with the air gap. It is preferable to be magnetized in the vibration
direction of the diaphragm so as to
[0018]
Preferably, in the diaphragm, the length in the short direction is equal to or less than half the
length in the longitudinal direction.
[0019]
Preferably, in the first coil, the length in the longitudinal direction is 60% or more of the length in
the longitudinal direction of the diaphragm.
[0020]
Preferably, the diaphragm and the first coil may be integrally formed.
[0021]
Preferably, each longitudinal portion of the first coil is such that the center position of the
winding width of each longitudinal portion coincides with the central position of the widths of
the first and second magnets with respect to the position in the width direction of the diaphragm.
It should be placed in
[0022]
Preferably, each longitudinal portion of the first coil is provided at a node position of the first
resonance mode in the lateral direction of the diaphragm.
[0023]
Preferably, the vibration on the inner circumferential side of the first coil is wound to form an
elongated ring shape, the longitudinal direction being parallel to the longitudinal direction of the
diaphragm and each longitudinal portion being disposed in the magnetic gap The device further
includes a second coil provided on the plate, and each longitudinal portion of the first and second
coils is positioned to suppress the first resonance mode and the second resonance mode in the
short direction of the diaphragm. It should be placed.
[0024]
Further, an electroacoustic transducer according to the present invention includes: a diaphragm
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having an elongated shape; a coil provided on one main surface side of the diaphragm; and a
magnet provided on the other main surface side of the diaphragm; Is located on the one main
surface between the end points of the diaphragm in the lateral direction of the magnet, and the
magnet is magnetized in the lateral direction of the diaphragm.
[0025]
The present invention is also directed to a portable terminal device, and the portable terminal
device according to the present invention includes the above-described electroacoustic
transducer and an apparatus housing in which the above-mentioned electroacoustic transducer is
disposed.
[0026]
The present invention is also directed to a vehicle, and the vehicle according to the present
invention includes the electro-acoustic transducer and a vehicle body in which the electroacoustic transducer is disposed.
[0027]
The present invention is also directed to a video device, and the video device according to the
present invention includes the electro-acoustic transducer and a device housing in which the
electro-acoustic transducer is disposed.
[0028]
According to the present invention, it is possible to provide an electroacoustic transducer that
realizes better super high frequency reproduction.
[0029]
First Embodiment The structure of an electroacoustic transducer according to a first embodiment
of the present invention will be described below with reference to FIGS. 1A to 1C.
1A to 1C are diagrams showing an example of the electroacoustic transducer according to the
first embodiment, and FIG. 1A is a front view, and FIG. 1B is a diagram of the electroacoustic
transducer cut along the center line AA in the longitudinal direction of FIG. FIG. 1C is a crosssectional view of the electro-acoustic transducer cut along the center line BB in the lateral
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direction of FIG. 1A.
[0030]
1A to 1C, the electroacoustic transducer according to the first embodiment includes a frame 101,
magnets 102 and 103, plates 104 to 106, a diaphragm 107, a coil 108, and an edge 109.
The frame 101 is made of nonmagnetic material and has a concave shape.
The diaphragm 107 has an elongated track shape and is disposed above the magnets 102 and
103 with an air gap.
The central axis O in FIG. 1C is the central axis in the lateral direction of the diaphragm 107.
[0031]
The magnets 102 and 103 have a rectangular parallelepiped shape, and are formed of, for
example, a neodymium magnet having an energy product of 44 MGOe.
The magnets 102 and 103 have the longitudinal direction parallel to the longitudinal direction of
the diaphragm 107 and are fixed to the bottom of the recess of the frame 101.
S1 in FIG. 1C indicates the central axis of the width of the magnet 102 in the lateral direction
(hereinafter referred to as the width central axis S1), S2 indicates the central axis of the width in
the lateral direction of the magnet 103 (hereinafter referred to as the width central axis S2 Is
shown.
The magnet 102 is magnetized in the lateral direction of the diaphragm 107 (left and right
direction in FIG. 1C).
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In FIG. 1C, the magnet 102 is magnetized in the right direction, the polarity of the left pole
surface is S pole, and the polarity of the right pole surface is N pole.
On the other hand, the magnet 103 is magnetized in the opposite direction to the magnet 102.
In FIG. 1C, the magnet 103 is magnetized in the left direction, the polarity of the magnetic pole
surface on the left is N, and the polarity of the magnetic pole surface on the right is S.
In FIG. 1C, the magnet 102 may be magnetized in the left direction, and the magnet 103 may be
magnetized in the right direction.
[0032]
The plates 104 to 106 have a plate shape and are made of a ferromagnetic material such as iron.
Plate 104 is disposed between magnets 102 and 103. The center of the width of the plate 104 in
the lateral direction of the diaphragm 107 is on the central axis O. The plate 105 is disposed on
the pole face opposite to the pole face in contact with the plate 104 in the magnet 102. The plate
106 is disposed on the pole face opposite to the pole face in contact with the plate 104 in the
magnet 103. The upper surfaces of the plates 104 to 106 and the upper surfaces of the magnets
102 and 103 are at the same height and located on the same plane.
[0033]
As shown in FIG. 1C, the magnetic gaps G1 and G2 of the magnetic flux φ are formed on the
vibrating plate 107 side of the magnets 102 and 103 by the magnets 102 and 103 and the
plates 104 to 106. The magnets 102 and 103 and the plates 104 to 106 constitute a magnetic
circuit for forming the magnetic gaps G1 and G2. The thick arrow in FIG. 1C indicates the
magnetic flux φ. Details of the magnetic flux φ will be described later.
[0034]
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The coil 108 is formed into an elongated ring shape by winding a copper or aluminum wire a
plurality of times, and the adhesive 108 adheres to the upper surface of the diaphragm 107 with
the longitudinal direction parallel to the longitudinal direction of the diaphragm 107. Here, the
coil 108 is formed in an elongated track shape that has a similar shape to the diaphragm 107.
Each longitudinal portion of coil 108 is disposed within magnetic gaps G1 and G2. In FIG. 1C,
each longitudinal portion of the coil 108 is arranged to be located near the width center axes S1
and S2. The respective longitudinal portions of the coil 108 may be disposed at least in the
magnetic gaps G1 and G2. Therefore, each longitudinal portion of coil 108 is disposed at a
position facing the inner surface of plates 105 and 106, that is, the upper surfaces of magnets
102 and 103, and the upper surfaces of plates 104 to 106. Good. More desirably, as will be
described later, each longitudinal portion of the coil 108 may be disposed such that the center of
its winding width is located on the width center axes S1 and S2.
[0035]
In addition, each longitudinal portion of the coil 108 is disposed in the vicinity of the position of
the node of the first resonance mode in the lateral direction of the diaphragm 107. Here, in FIG.
1C, the length in the short direction of the diaphragm 107 is 1, the left end of the diaphragm
107 is 0, and the right end is 1. At this time, one longitudinal portion of the coil 108 is disposed
at the 0.224 position, and the other longitudinal portion is disposed at the 0.776 position. More
desirably, the center of the winding width of each longitudinal portion of the coil 108 may be
disposed at the position of the node of the first resonance mode in the lateral direction of the
diaphragm 107. Further, the length in the longitudinal direction of the coil 108 is at least 60% or
more of the length in the longitudinal direction of the diaphragm 107.
[0036]
The edge 109 has a semicircular shape in which the cross-sectional shape is convex upward, the
inner peripheral end is fixed to the outer peripheral end of the diaphragm 107, and the outer
peripheral part is fixed to the upper surface of the frame 101. Thereby, the diaphragm 107 is
supported by the edge 109 so as to be able to vibrate in the vertical direction.
[0037]
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Next, the operation of the electroacoustic transducer according to the first embodiment will be
described. When an alternating current electrical signal is not input to the coil 108, a magnetic
flux φ as shown in FIG. 2 is generated by the magnets 102 and 103 and the plates 104 to 106.
FIG. 2 is a diagram showing the detailed flow of the magnetic flux φ. The magnets 102 and 103
are magnetized in the opposite direction. For this reason, the magnetic flux φ generated by the
magnet 102 enters the plate 104 from the pole face which is the N pole, and is radiated from the
upper surface of the plate 104 to the air gap above. The magnetic flux 磁 束 emitted from the
upper surface of the plate 104 passes through the upper side of the magnet 102 and enters the
plate 105. As a result, a magnetic field composed of magnetic flux perpendicular to the vibration
direction (vertical direction in FIG. 2) is formed above the magnet 102, and a magnetic gap G1 is
formed above the magnet 102. On the other hand, the magnetic flux φ generated by the magnet
103 enters the plate 104 from the pole face which is the N pole, and is radiated from the upper
surface of the plate 104 to the air gap above. The magnetic flux 放射 emitted from the upper
surface of the plate 104 passes above the magnet 103 and enters the plate 106. As a result, a
magnetic field composed of magnetic flux perpendicular to the vibration direction is formed
above the magnet 103, and a magnetic gap G2 is formed above the magnet 103.
[0038]
The magnetic flux density distribution in such a static magnetic field is shown in FIG. FIG. 3 is a
view showing a magnetic flux density distribution in FIG. 1C. The magnetic flux density
distribution here indicates the relationship between the distance from the central axis O in the
lateral direction of the diaphragm 107 and the magnetic flux density. In FIG. 3, the vertical axis is
the magnetic flux density. The magnetic flux density indicates the density of magnetic flux in the
direction perpendicular to the vibration direction of the diaphragm 107, and if the magnetic flux
density is high, it means that the magnetic flux in the direction perpendicular to the vibration
direction of the diaphragm 107 is large. The horizontal axis indicates the distance from the
central axis O in the lateral direction of the diaphragm 107, and the right direction in FIG. 1C is a
positive direction. Further, in FIG. 3, the width of the plate 104 in the lateral direction is 1 mm,
the width of the magnets 102 and 103 in the lateral direction is 2 mm, and the width of the
plates 105 and 106 in the lateral direction is 1 mm. The width of the magnets 102 and 103 and
the plates 104 to 106 in the direction is 8 mm.
[0039]
As can be seen from FIG. 3, the maximum value of the magnetic flux density was 0.6 [T], and the
position where the magnetic flux density became the maximum was 1.5 mm from the central axis
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O. This is the center of the width in the short direction of the magnets 102 and 103, and
coincides with the width center axes S1 and S2. For this reason, when the respective longitudinal
portions of the coil 108 are disposed near the width center axes S1 and S2, the driving force can
be efficiently generated in the coil 108. Furthermore, when the center of the winding width of
each longitudinal portion of the coil 108 is positioned immediately above the width central axes
S1 and S2, the driving force can be generated most efficiently in the coil 108.
[0040]
When an alternating current electrical signal is input to the coil 108, a driving force is generated
to be proportional to the magnetic flux direction perpendicular to the current direction flowing
through the coil 108 and the vibration direction of the diaphragm 107. By this driving force, the
diaphragm 107 bonded to the coil 108 vibrates, and the vibration is emitted as a sound.
[0041]
Next, features and effects of the electroacoustic transducer according to the present embodiment
described above will be described.
[0042]
First, the shape of the diaphragm 107 is elongated.
For this reason, it becomes difficult to produce the peak dip by resonance in a superhigh region,
and the disorder of the sound pressure frequency characteristic of the ultrahigh region by
resonance is improved. As for the aspect ratio of the diaphragm 107, when the length in the
longitudinal direction (longitudinal direction) is 1, it is desirable to set the length in the lateral
direction (short side direction) to 0.5 or less, that is, half or less. . The resonance frequency (first
resonance frequency) of the first resonance mode in the lateral direction is inversely proportional
to the square of the resonance frequency (first resonance frequency) of the first resonance mode
in the longitudinal direction. Therefore, assuming that the primary resonance frequency in the
longitudinal direction is fL1 [Hz] when the aspect ratio of the diaphragm 107 is 1: 0.5, the
primary resonance frequency fS1 in the lateral direction is 4 * fL1. Become. In addition, since the
resonance frequency (second resonance frequency) of the second resonance mode is 5.4 times
the first resonance frequency, the second resonance frequency fS2 in the short direction is 5.4 *
fS1 = It will be 5.4 * 4 * fL1 = 21.6 * fL1 [Hz]. From the above, when the aspect ratio of the
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diaphragm 107 is 1: 0.5, the disturbance of the sound pressure frequency characteristic can be
improved in the band up to the frequency 21.6 times the primary resonance frequency in the
longitudinal direction. it can. Furthermore, when the aspect ratio of the diaphragm 107 is 1: 0.3,
the first resonance frequency fS1 in the lateral direction is 11.1 * fL1 [Hz], so the second
resonance in the lateral direction is generated. The frequency fS2 is 60 * fL1. Therefore, in this
case, the disturbance of the sound pressure frequency characteristic can be improved in the band
up to a frequency 60 times the primary resonance frequency in the longitudinal direction. As
described above, the resonance suppression effect according to the present embodiment
becomes larger as the aspect ratio of the diaphragm 107 becomes larger, that is, as the
diaphragm 107 becomes thinner.
[0043]
Second, each longitudinal portion of the coil 108 is disposed in the vicinity of the position of the
node of the first resonance mode in the lateral direction of the diaphragm 107. Therefore, it is
possible to suppress the first resonance mode in the lateral direction of the diaphragm 107, and
the disturbance of the sound pressure frequency characteristic in the ultrahigh range is further
improved. Furthermore, the length in the longitudinal direction of the coil 108 is at least 60% or
more of the length in the longitudinal direction of the diaphragm 107. For this reason, the
longitudinal direction of the diaphragm 107 is driven on the entire surface, so that the resonance
mode in the longitudinal direction of the diaphragm 107 can be suppressed, and the disturbance
of the sound pressure frequency characteristic in the ultrahigh range is further improved. Thus,
each longitudinal portion of the coil 108 is disposed in the vicinity of the position of the node of
the first resonance mode in the lateral direction of the diaphragm 107, or the longitudinal length
of the coil 108 corresponds to the longitudinal direction of the diaphragm 107. By extending the
reproduction band with no disturbance in the sound pressure frequency characteristics to a
higher frequency than the case where only the shape of the diaphragm 107 is elongated by
making the length at least 60% or more. Can.
[0044]
Third, each longitudinal portion of the coil 108 is arranged to be located on or near the width
center axes S1 and S2. For this reason, the driving force can be generated efficiently in the coil
108. As a result, the reproduction sound pressure can be improved.
[0045]
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15
Fourth, the magnets 102 and 103 are magnetized in the lateral direction of the diaphragm 107.
Here, in the conventional electroacoustic transducer shown in FIGS. 23A to C, in order to increase
the magnetic flux in the direction perpendicular to the vibration direction of the diaphragm to
improve the reproduction sound pressure, as shown in FIG. It was necessary to increase the
width in the short direction. However, since the width in the short direction of the diaphragm
909 can not be changed, the magnetic flux in the direction perpendicular to the vibration
direction of the diaphragm can not be efficiently increased. On the other hand, the
electroacoustic transducer according to the present embodiment has a structure provided with
the magnets 102 and 103 magnetized in the lateral direction of the diaphragm 107. Therefore, in
the electro-acoustic transducer according to the present embodiment, in order to increase the
magnetic flux in the direction perpendicular to the vibration direction of the diaphragm to
improve the reproduction sound pressure, the vibration direction of the diaphragm 107 in the
magnets 102 and 103 (FIG. 1C) It is sufficient to increase the width of the vertical direction of
Furthermore, even if the width in the vibration direction of the diaphragm 107 in the magnets
102 and 103 is increased, the position at which the magnetic flux density reaches the maximum
value does not change unlike the conventional case. As a result, in the electro-acoustic transducer
according to the present embodiment, it is possible to efficiently increase the magnetic flux in the
direction perpendicular to the vibration direction of the diaphragm while preventing the sound
pressure frequency characteristic from being disturbed in the very high frequency range. As a
result, it is possible to realize better super high frequency reproduction. In the electro-acoustic
transducer according to the present embodiment, the expanding direction of the magnet is
different by 90 degrees from the conventional one. For this reason, the electroacoustic
transducer which concerns on this embodiment is suitable for the diaphragm of elongate shape.
[0046]
Hereinafter, the fourth content will be verified with reference to FIGS. 4 and 5. FIG. 4 is a
perspective view of a magnetic circuit (magnets 102 and 103 and plates 104 to 106)
constituting the electro-acoustic transducer shown in FIG. 1C as viewed obliquely. In FIG. 4, the
lateral direction of the magnets 102 and 103 is taken as the X axis, the longitudinal direction as
the Y axis, and the vibration direction of the diaphragm 107 as the Z axis. FIG. 5 is a diagram
showing the relationship between the change in the width of the vibration direction of the
diaphragm 107 in the magnets 102 and 103 and the change in the magnetic flux density
distribution.
[0047]
11-05-2019
16
In FIG. 4, in order to increase the magnetic flux density, the magnets 102 and 103 may be
extended not in the X axis direction but in the Z axis direction. That is, in the process of
increasing the magnetic flux density, it is not necessary to increase the width of the magnets 102
and 103 in the X-axis direction. Here, with H being the width of the magnets 102 and 103 in the
Z-axis direction, how the magnetic flux density changes when H is changed will be described with
reference to FIG. In FIG. 5, the graph (a) shows the same magnetic flux density distribution as
that shown in FIG. 3, that is, when H = 8 mm. The graph (b) shows the magnetic flux density
distribution when H = 13 mm. The maximum value of the magnetic flux density is 0.6 [T] in the
graph (a), and the maximum value of the magnetic flux density is 0.85 [T] in the graph (b).
Moreover, in the graphs (a) and (b), the position at which the magnetic flux density is maximum
is 1.5 mm in both cases. From these, when H is increased, the position at which the magnetic flux
density becomes maximum changes by 1.5 mm even though the maximum value of the magnetic
flux density is increased from 0.6 [T] to 0.85 [T]. I understand that I did not. As described above,
in the present embodiment, the magnetic flux density can be increased without changing the
arrangement position of each longitudinal portion of the coil 108.
[0048]
Fifth, the upper surface of the plate 104 and the upper surfaces of the magnets 102 and 103 are
at the same height and located on the same plane. The effects of this configuration will be
described with reference to FIGS. 6 and 7. FIG. 6 is a structural cross-sectional view of an
electroacoustic transducer for illustrating the relationship between the position of the upper
surface of the plates 104 to 106 and the magnetic flux density distribution. FIG. 7 is a diagram
showing the relationship between the position of the upper surface of the plates 104 to 106 and
the magnetic flux density distribution.
[0049]
In FIG. 6, the electroacoustic transducer includes a frame 101a, magnets 102a and 103a, plates
104a to 106a, a diaphragm 107a, a coil 108a, and an edge 109a. The structure of the
electroacoustic transducer shown in FIG. 6 differs from the structure shown in FIG. 1C in that the
height of the upper surface of the plate 104a is higher than the upper surfaces of the magnets
102a and 103a. The other structure is basically the same as the structure shown in FIG. 1C, so
the description will be omitted.
11-05-2019
17
[0050]
The upper surface of the plate 104a is positioned higher than the upper surfaces of the magnets
102a and 103a by δH. That is, the plate 104a is structured such that it is protruded by δH
from the upper surfaces of the magnets 102a and 103a. In this structure, the magnetic flux 放射
radiated from the plate 104a is radiated not only from the upper surface of the plate 104a but
also from the side surface of the protruding part. Among these, the magnetic flux 放射 radiated
from the side enters the plates 105a and 106a without penetrating the coil 108a. Here, since the
magnetic flux べ き to be radiated from the plate 104a is constant, the magnetic flux 貫通
passing through the coil 108a is decreased by an amount that the magnetic flux 放射 radiated
from the side surface of the protruding part does not penetrate the coil 108a. I will.
[0051]
In FIG. 7, the vertical axis represents the magnetic flux density, and the horizontal axis represents
the distance from the central axis O in the lateral direction of the diaphragm 107a, and the right
direction in FIG. 6 is the positive direction. In FIG. 7, the width of the plate 104a in the short side
direction is 1 mm, the width of the magnets 102a and 103a in the short side direction is 2 mm,
and the width of the plates 105a and 106a in the short side direction is 1 mm. The width of the
magnets 102a and 103a and the plates 105a and 106a in the direction is 8 mm. Graph (a) of FIG.
7 shows the magnetic flux density distribution when the top surface of the plate 104a is at the
same height as the top surfaces of the magnets 102a and 103a (when δH is 0). Graph (b) of FIG.
7 shows the magnetic flux density distribution when the upper surface of the plate 104a is 0.5
mm higher than the upper surfaces of the magnets 102a and 103a (when δH is 0.5). It can be
seen from FIG. 7 that graph (b) has a lower magnetic flux density than graph (a). Thus, higher
magnetic flux density can be obtained by positioning the upper surface of the plate 104 and the
upper surfaces of the magnets 102 and 103 on the same plane.
[0052]
As described above, according to the electro-acoustic transducer according to the present
embodiment, it is possible to efficiently improve the reproduction sound pressure in the very
high frequency range, and it is possible to realize better super high frequency range
reproduction.
[0053]
11-05-2019
18
In the present embodiment, the plates 104 to 106 are used, but they may be omitted as shown in
FIG.
FIG. 8 is a structural cross-sectional view of the electro-acoustic transducer according to the first
embodiment in which the plates 104 to 106 are omitted. Even in the structure shown in FIG. 8, in
order to increase the magnetic flux in the direction perpendicular to the vibration direction of the
diaphragm to improve the reproduction sound pressure, the vibration direction of the diaphragm
107 in the magnets 102 and 103 (vertical direction in FIG. The width of) should be increased.
Also, even if the width in the vibration direction of the diaphragm 107 in the magnets 102 and
103 is increased, the position at which the magnetic flux density reaches the maximum value
does not change unlike the conventional case. Therefore, even with the structure shown in FIG. 8,
it is possible to realize better super high frequency reproduction than in the prior art. Further, if
only the magnets 102 and 103 magnetized in the short direction of the diaphragm 107 are
provided, it is possible to realize better super high frequency reproduction than before.
Therefore, as shown in FIGS. 9 and 10, only one of the plate 104 and the plates 105 and 106
may be omitted. FIG. 9 is a structural cross-sectional view of the electro-acoustic transducer
according to the first embodiment in which the plates 105 and 106 are omitted. FIG. 10 is a
structural cross-sectional view in the short direction of the electroacoustic transducer according
to the first embodiment in which the plate 104 is omitted.
[0054]
In the present embodiment, the magnets 102 and 103 are formed of neodymium magnets, but
the present invention is not limited to this. The magnets 102 and 103 may be made of ferrite,
samarium cobalt or the like according to the target sound pressure, the shape of the magnet, or
the like. Further, in the present embodiment, the magnets 102 and 103 have a rectangular
parallelepiped shape, but may have another shape such as an elliptic cylindrical shape.
[0055]
In the present embodiment, although the cross-sectional shape of the edge 109 is semicircular, it
is not limited to this. The cross-sectional shape of the edge 109 may be determined to satisfy the
minimum resonance frequency and the maximum amplitude, and may be, for example, a wave
shape, an elliptical shape, or the like.
11-05-2019
19
[0056]
In the present embodiment, the coil 108 is adhered to the upper surface of the diaphragm 107
with the adhesive Ad, but the coil 108 and the diaphragm 107 may be integrally formed.
[0057]
In the present embodiment, the electro-acoustic transducer includes the magnets 102 and 103,
but one of the magnets may be omitted.
For example, in FIG. 1C, when the magnet 102 is omitted, the width in the short direction of the
magnet 103 is set to be equal to or larger than the distance between the width center axes S1
and S2. In addition, the coil 108 is divided into two at the central axis O, and current in the same
direction is supplied to each of the divided longitudinal parts. As a result, due to the magnetic
gap G2 formed above the magnet 103, driving forces in the same direction are generated in each
of the longitudinal portions of the divided coils. As described above, when one of the magnets
102 and 103 is omitted, an inexpensive magnetic circuit can be realized by the amount of
omission of the magnet.
[0058]
Second Embodiment The structure of an electroacoustic transducer according to a second
embodiment of the present invention will be described below with reference to FIGS. 11A to 11C.
11A to 11C are diagrams showing an example of the electroacoustic transducer according to the
second embodiment, and FIG. 11A is a front view, and FIG. 11B is a diagram of the
electroacoustic transducer cut along the center line AA in the longitudinal direction of FIG. FIG.
11C is a cross-sectional view of the electro-acoustic transducer cut along the center line BB in the
short direction of FIG. 11A.
[0059]
11A-C, the electro-acoustic transducer according to the second embodiment comprises a frame
101, magnets 102 and 103, plates 104-106, a diaphragm 107, coils 108 and 208, and an edge
11-05-2019
20
109. The electro-acoustic transducer which concerns on this embodiment is further equipped
with the coil 208 with respect to the electro-acoustic transducer which concerns on 1st
Embodiment, and the arrangement position of the coil 108 differs. The other configuration is
given the same reference numeral as that of the first embodiment, and the detailed description is
omitted. Hereinafter, differences will be mainly described.
[0060]
The coil 208 is formed into an elongated ring shape by winding a copper or aluminum wire a
plurality of times. Here, the coil 208 is formed in an elongated track shape that has a similar
shape to the diaphragm 107 and the coil 108. The coil 208 is bonded to the upper surface of the
diaphragm 107 on the inner peripheral side of the coil 108 with an adhesive Ad with the
longitudinal direction parallel to the longitudinal direction of the diaphragm 107. Each
longitudinal portion of coil 208 is disposed within magnetic gaps G1 and G2. The longitudinal
length of the coil 208 is shorter than that of the coil 108 but is at least 60% or more of the
longitudinal length of the diaphragm 107.
[0061]
The arrangement positions of the coils 108 and 208 will be described in detail below. Each
longitudinal portion of coils 108 and 208 is disposed at a position that can suppress both the
first and second resonant modes in the width direction of diaphragm 107. Here, in FIG. 11C, the
length in the short direction of the diaphragm 107 is 1, the left end of the diaphragm 107 is 0,
and the right end is 1. At this time, the respective longitudinal portions of the coil 108 are
disposed at the positions of 0.1130 and 0.8770, and the respective longitudinal portions of the
coil 208 are disposed at the positions of 0.37775 and 0.62225. If arranged at this position, the
first and second resonance modes can be suppressed.
[0062]
Further, the longitudinal portions of the coils 108 and 208 are arranged such that the distances
from the reference central axes S1 and S2 of the magnets 102 and 103 are equal. In FIG. 11C,
the distance from the width center axis S1 to the left longitudinal portion of the coil 108 and the
distance from the width center axis S1 to the left longitudinal portion of the coil 208 are the
same. Similarly, the distance from the width center axis S2 to the right side longitudinal portion
11-05-2019
21
of the coil 108 and the distance from the width center axis S2 to the right side longitudinal
portion of the coil 208 are the same. Here, as understood from FIG. 3 described above, the
magnetic flux density is maximum at the width center axes S1 and S2. In the magnetic flux
density distribution in the region where the distance is 0 or more, the left and right sides of the
width center axis S2 are symmetrical with respect to the width center axis S2. Similarly, in the
magnetic flux density distribution in the region where the distance is smaller than 0, the left side
and the right side of the width central axis S1 are symmetrical with respect to the width central
axis S1. Therefore, if the longitudinal portions of coils 108 and 208 are arranged as shown in
FIG. 11C, the magnetic flux densities obtained in the longitudinal portions of coils 108 and 208
will be approximately equal. This provides the most balanced driving force. In order to arrange
the longitudinal portions of the coils 108 and 208 as shown in FIG. 11C, for example, the width
in the short direction of the magnets 102 and 103 may be appropriately adjusted.
[0063]
Next, the operation of the electroacoustic transducer according to the second embodiment will be
described. When an alternating current electrical signal is not input to the coils 108 and 208, the
magnets 102 and 103 and the plates 104 to 106 generate a magnetic flux φ as shown in FIG.
11C. The magnets 102 and 103 are magnetized in the opposite direction. For this reason, the
magnetic flux φ generated by the magnet 102 enters the plate 104 from the pole face which is
the N pole, and is radiated from the upper surface of the plate 104 to the air gap above. The
magnetic flux 磁 束 emitted from the upper surface of the plate 104 passes through the upper
side of the magnet 102 and enters the plate 105. As a result, a magnetic field composed of
magnetic flux perpendicular to the vibration direction (vertical direction in FIG. 11C) is formed
above the magnet 102, and a magnetic gap G1 is formed above the magnet 102. On the other
hand, the magnetic flux φ generated by the magnet 103 enters the plate 104 from the pole face
which is the N pole, and is radiated from the upper surface of the plate 104 to the air gap above.
The magnetic flux 放射 emitted from the upper surface of the plate 104 passes above the magnet
103 and enters the plate 106. As a result, a magnetic field composed of magnetic flux
perpendicular to the vibration direction is formed above the magnet 103, and a magnetic gap G2
is formed above the magnet 103. In such a static magnetic field, as shown in FIG. 3, the magnetic
flux density is maximum at the width center axes S1 and S2. Therefore, the magnetic flux density
obtained in each longitudinal portion of the coils 108 and 208 becomes substantially equal, and
the most balanced driving force is obtained.
[0064]
11-05-2019
22
When an alternating current electrical signal is input to coils 108 and 208, a driving force is
generated so as to be proportional to a magnetic flux direction perpendicular to the current
direction flowing through coils 108 and 208 and the vibration direction of diaphragm 107. The
driving force vibrates the diaphragm 107 bonded to the coils 108 and 208, and the vibration is
emitted as a sound.
[0065]
Here, each longitudinal portion of coils 108 and 208 is disposed at a position where both of the
primary resonance mode and the secondary resonance mode in the lateral direction of
diaphragm 107 can be suppressed. Therefore, it is possible to suppress the primary resonance
mode and the secondary resonance mode in the lateral direction of the diaphragm 107, and to
flatten the sound pressure frequency characteristics up to the frequency at which the third
resonance mode occurs. . The diaphragm 107 has an elongated shape, and the lateral direction of
the diaphragm 107 is shorter than the longitudinal direction. Therefore, the respective resonance
frequencies of the first resonance mode and the second resonance mode in the width direction of
the diaphragm 107 become very high frequencies. For example, when a polyimide material
having a thickness of 50 μ, a length in the longitudinal direction of 55 mm, and a length in the
lateral direction of 5 mm is used as the diaphragm 107, the first to third in the lateral direction
of the diaphragm 107 are used. Resonant frequencies of the next resonant mode are
approximately 4 kHz, 22 kHz, and 55 kHz, respectively. Therefore, when the first resonance
mode and the second resonance mode are suppressed, the sound pressure frequency
characteristic can be made flat to 55 kHz.
[0066]
The length in the longitudinal direction of the coils 108 and 208 is at least 60% or more of the
length in the longitudinal direction of the diaphragm 107. For this reason, the entire surface is
driven in the longitudinal direction of the diaphragm 107, so that the resonance mode in the
longitudinal direction of the diaphragm 107 can be suppressed, and the disturbance of the sound
pressure frequency characteristic in the ultrahigh range is further improved.
[0067]
As described above, according to the electro-acoustic transducer according to the present
11-05-2019
23
embodiment, the respective longitudinal portions of the coils 108 and 208 have the primary
resonance mode and the secondary resonance mode in the lateral direction of the diaphragm
107. It is placed at a position where both can be suppressed. Therefore, it is possible to suppress
the primary resonance mode and the secondary resonance mode in the lateral direction of the
diaphragm 107, and to flatten the sound pressure frequency characteristics up to the frequency
at which the third resonance mode occurs. .
[0068]
Further, according to the electro-acoustic transducer according to the present embodiment, the
longitudinal portions of the coils 108 and 208 have the same distance from the reference with
respect to the width center axes S1 and S2 of the magnets 102 and 103. It is arranged to
become. Thereby, the most balanced driving force can be obtained.
[0069]
Third Embodiment The structure of an electroacoustic transducer according to a third
embodiment of the present invention will be described below with reference to FIGS. 12A to 12C.
12A to 12C are diagrams showing an example of the electroacoustic transducer according to the
third embodiment, and FIG. 12A is a front view, and FIG. 12B is a diagram showing the
electroacoustic transducer cut along the center line AA in the longitudinal direction of FIG. FIG.
12C is a cross-sectional view of the case where the electroacoustic transducer is cut along the
center line BB in the lateral direction of FIG. 12A.
[0070]
12A to C, the electroacoustic transducer according to the third embodiment includes a frame
101, magnets 102 and 103, plates 104, plates 305 and 306, a diaphragm 107, a coil 108, and
an edge 109. The electroacoustic transducer according to the present embodiment differs from
the electroacoustic transducer according to the first embodiment only in that the plates 105 and
106 are replaced with the plates 305 and 306. The other configuration is given the same
reference numeral as that of the first embodiment, and the detailed description is omitted.
Hereinafter, differences will be mainly described.
11-05-2019
24
[0071]
Plates 305 and 306 are plate shaped in shape and are made of a ferromagnetic material such as
iron. The plate 305 is disposed on the pole face opposite to the pole face in contact with the plate
104 in the magnet 102. The plate 306 is disposed on the pole face of the magnet 103 opposite
to the pole face in contact with the plate 104. The upper surface of the plate 104 and the upper
surfaces of the magnets 102 and 103 are at the same height and located on the same plane. On
the other hand, the upper surfaces of the plates 305 and 306 are higher than the upper surfaces
of the magnets 102 and 103 and located on a plane close to the diaphragm 107. This can be
understood from the perspective view shown in FIG. FIG. 13 is a perspective view of a magnetic
circuit (magnets 102 and 103, plates 104, plates 305 and 306) constituting the electroacoustic
transducer shown in FIG. 12C as viewed from an oblique direction. Further, the plates 305 and
306 are disposed below the edge 109 having a cross-sectional shape which is convex upward,
and at a position facing the edge 109. Also, the width of the plates 305 and 306 in the lateral
direction of the diaphragm 107 is smaller than the width of the edge 109. With this
configuration, the amplitude of the diaphragm 107 can prevent the edge 109 from contacting
the plates 305 and 306.
[0072]
Next, the operation of the electroacoustic transducer according to the third embodiment will be
described. When an alternating current electrical signal is not input to the coil 108, the magnets
102 and 103, the plate 104, and the plates 305 and 306 generate a magnetic flux φ as shown in
FIG. 12C. The magnetic flux φ is shown only on one side in FIG. 12C, but is generated on both
sides of the plate 104. The magnets 102 and 103 are magnetized in the opposite direction. For
this reason, the magnetic flux φ generated by the magnet 102 enters the plate 104 from the
pole face which is the N pole, and is radiated from the upper surface of the plate 104 to the air
gap above. The magnetic flux 放射 radiated from the upper surface of the plate 104 passes
through the upper side of the magnet 102 and enters the plate 305. As a result, a magnetic field
composed of magnetic flux perpendicular to the vibration direction (vertical direction in FIG.
12C) is formed above the magnet 102, and a magnetic gap G1 is formed above the magnet 102.
On the other hand, the magnetic flux φ generated by the magnet 103 enters the plate 104 from
the pole face which is the N pole, and is radiated from the upper surface of the plate 104 to the
air gap above. The magnetic flux 放射 emitted from the upper surface of the plate 104 passes
through the top of the magnet 103 and enters the plate 306. As a result, a magnetic field
composed of magnetic flux perpendicular to the vibration direction is formed above the magnet
103, and a magnetic gap G2 is formed above the magnet 103.
11-05-2019
25
[0073]
Here, the upper surfaces of the plates 305 and 306 are higher than the upper surfaces of the
magnets 102 and 103 and located on a plane close to the diaphragm 107. For this reason, the
magnetic flux φ is guided to the upper surfaces of the raised plates 305 and 306, respectively,
and the magnetic flux φ passing through the coil 108 is increased. In the structure shown in FIG.
12C, the coil 108 is fixed to the upper surface of the diaphragm 107. Therefore, when the upper
surfaces of the plates 305 and 306 are higher than the diaphragm 107, the magnetic flux
penetrating the coil 108 is most likely to be the largest. FIG. 14 shows a change in magnetic flux
density distribution when the upper surfaces of the plates 305 and 306 are raised by 1.0 mm
higher than the upper surfaces of the magnets 102 and 103.
[0074]
In FIG. 14, the vertical axis represents the magnetic flux density, and the horizontal axis
represents the distance from the central axis O in the lateral direction of the diaphragm 107, and
the right direction in FIG. 12C is the positive direction. Further, in FIG. 14, the width of the plate
104 in the lateral direction is 1 mm, the width of the magnets 102 and 103 in the lateral
direction is 2 mm, and the width of the plates 305 and 306 in the lateral direction is 1 mm. The
width of the magnets 102 and 103 in the direction is 8 mm. Graph (a) of FIG. 14 shows the
magnetic flux density distribution when the top surfaces of the plates 305 and 306 are at the
same height as the top surfaces of the magnets 102 and 103. The graph (b) of FIG. 14 shows the
magnetic flux density distribution when the upper surfaces of the plates 305 and 306 are higher
by 1.0 mm than the upper surfaces of the magnets 102 and 103.
[0075]
In the graph (a), as in the first embodiment, the positions at which the magnetic flux density
reaches the maximum value coincide with the width center axes S1 and S2. On the other hand, in
the graph (b), the magnetic flux density is generally higher than the graph (a). This is because the
magnetic flux φ is guided to the upper surfaces of the raised plates 305 and 306, respectively.
The magnetic flux density can be increased by making the upper surfaces of the plates 305 and
306 higher than the upper surfaces of the magnets 102 and 103 in this manner. In the graph (b),
the magnetic flux density increases in the direction from the position of the width center axes S1
and S2 to the plates 305 and 306 as compared with the graph (a). Therefore, in order to obtain
11-05-2019
26
the driving force most efficiently, each longitudinal portion of the coil 108 may be disposed at a
position shifted from the position of the central axes S1 and S2 toward the plates 305 and 306.
[0076]
When an alternating current electrical signal is input to the coil 108, a driving force is generated
to be proportional to the magnetic flux direction perpendicular to the current direction flowing
through the coil 108 and the vibration direction of the diaphragm 107. By this driving force, the
diaphragm 107 bonded to the coil 108 vibrates, and the vibration is emitted as a sound.
[0077]
As described above, according to the electroacoustic transducer according to the present
embodiment, the upper surfaces of the plates 305 and 306 are higher than the upper surfaces of
the magnets 102 and 103, and are located on a plane close to the diaphragm 107 side. As a
result, compared to the first embodiment, the driving force obtained by the coil 108 can be
increased, and the reproduction sound pressure in the ultrahigh range can be further increased.
[0078]
Fourth Embodiment The structure of an electroacoustic transducer according to a fourth
embodiment of the present invention will be described below with reference to FIGS. 15A to 15C.
FIGS. 15A to 15C are diagrams showing an example of the electroacoustic transducer according
to the fourth embodiment, FIG. 15A is a front view, and FIG. 15B is a cutting of the
electroacoustic transducer at a longitudinal center line AA of FIG. FIG. 15C is a cross-sectional
view in the case where the electroacoustic transducer is cut along the center line BB in the lateral
direction of FIG. 15A.
[0079]
15A to 15C, the electro-acoustic transducer according to the fourth embodiment includes a
frame 101, magnets 102 and 103, plates 104 to 106, a diaphragm 107, coils 108 and 208, an
edge 109, support members 401 and 402, And a magnet 403. The electroacoustic transducer
11-05-2019
27
which concerns on this embodiment differs only in the point further equipped with the
supporting members 401 and 402 and the magnet 403 with respect to the electroacoustic
transducer which concerns on 2nd Embodiment. The other configuration is given the same
reference numeral as that of the second embodiment, and the detailed description is omitted.
Hereinafter, differences will be mainly described.
[0080]
The magnet 403 has a rectangular parallelepiped shape, and is formed of, for example, a
neodymium magnet having an energy product of 44 MGOe. The magnet 403 is disposed above
the diaphragm 107 so that the center in the short direction of the diaphragm 107 coincides with
the central axis O. The magnet 403 is disposed with its longitudinal direction parallel to the
longitudinal direction of the diaphragm 107, and the longitudinal end portions are fixed to the
support members 401 and 402, respectively. The support members 401 and 402 are fixed to the
frame 101. The magnet 403 is magnetized in the vibration direction of the diaphragm 107
(vertical direction in FIG. 15C). The polarities of the magnetic pole surfaces facing the upper
surface of the diaphragm 107 of the magnet 403 are the same as the polarities of the respective
magnetic pole surfaces in contact with the plate 104 of the magnets 102 and 103. In the
example of FIG. 15C, the polarity of the magnetic pole surface facing the upper surface of the
diaphragm 107 of the magnet 403 is N, and the polarity of each magnetic pole surface
contacting the plate 104 of the magnets 102 and 103 is also N There is.
[0081]
Each longitudinal portion of coils 108 and 208 is disposed at a position that can suppress both
the first and second resonant modes in the width direction of diaphragm 107. Further, the
longitudinal portions of the coils 108 and 208 are arranged such that the distances from the
reference central axes S1 and S2 of the magnets 102 and 103 are equal.
[0082]
Next, the operation of the electroacoustic transducer according to the fourth embodiment will be
described. When an alternating current electrical signal is not input to the coils 108 and 208, a
magnetic flux φ as shown in FIG. 15C is generated by the magnets 102, 103, 403 and the plates
104 to 106. The magnets 102 and 103 are magnetized in the opposite direction. For this reason,
11-05-2019
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the magnetic flux φ generated by the magnet 102 enters the plate 104 from the pole face which
is the N pole, and is radiated from the upper surface of the plate 104 to the air gap above. Here,
the lower surface of the magnet 403 is an N pole. For this reason, the magnetic flux φ radiated
from the upper surface of the plate 104 is forced to change in the horizontal direction. Then, the
magnetic flux φ changed in the horizontal direction passes over the magnet 102 and enters the
plate 105. As a result, a magnetic field composed of magnetic fluxes perpendicular to the
vibration direction (vertical direction in FIG. 15C) more than in the second embodiment is formed
above the magnet 102, and the magnetic gap G1 is formed above the magnet 102. . On the other
hand, the magnetic flux φ generated by the magnet 103 enters the plate 104 from the pole face
which is the N pole, and is radiated from the upper surface of the plate 104 to the air gap above.
Here, the lower surface of the magnet 403 is an N pole. For this reason, the magnetic flux φ
radiated from the upper surface of the plate 104 is forced to change in the horizontal direction.
Then, the magnetic flux φ changed in the horizontal direction passes above the magnet 103 and
enters the plate 106. As a result, a magnetic field composed of magnetic flux perpendicular to the
vibration direction (vertical direction in FIG. 15C) more than the second embodiment is formed
above the magnet 103, and the magnetic gap G2 is formed above the magnet 103. . Thus, by
arranging the magnet 403, it is possible to further increase the magnetic flux perpendicular to
the vibration direction as compared to the second embodiment. FIG. 16 shows a change in
magnetic flux density distribution when the magnet 403 is disposed.
[0083]
In FIG. 16, the vertical axis represents the magnetic flux density, and the horizontal axis
represents the distance from the central axis O in the lateral direction of the diaphragm 107, and
the right direction in FIG. 15C is the positive direction. Further, in FIG. 16, the width of the plates
104 to 106 in the lateral direction is 1 mm, the width of the magnets 102 and 103 in the lateral
direction is 2 mm, and the width of the magnets 102 and 103 in the vibration direction of the
diaphragm 107 is 8 mm. There is. The graph (a) of FIG. 16 shows the magnetic flux density
distribution when the magnet 403 is not disposed. The graph (b) of FIG. 16 shows the magnetic
flux density distribution when the magnet 403 is disposed.
[0084]
In the graph (a), as in the first embodiment, the positions at which the magnetic flux density
reaches the maximum value coincide with the width center axes S1 and S2. On the other hand, in
the graph (b), the magnetic flux density is generally higher than the graph (a). This is because the
magnetic flux φ emitted from the upper surface of the plate 104 is forced to change in the
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horizontal direction by the magnet 403. Thus, the magnetic flux density can be increased by
arranging the magnet 403. In the graph (b), the magnetic flux density is larger as it is closer to
the central axis O.
[0085]
When an alternating current electrical signal is input to coils 108 and 208, a driving force is
generated so as to be proportional to a magnetic flux direction perpendicular to the current
direction flowing through coils 108 and 208 and the vibration direction of diaphragm 107. The
driving force vibrates the diaphragm 107 bonded to the coils 108 and 208, and the vibration is
emitted as a sound.
[0086]
Here, each longitudinal portion of coils 108 and 208 is disposed at a position where both of the
primary resonance mode and the secondary resonance mode in the lateral direction of
diaphragm 107 can be suppressed. Therefore, it is possible to suppress the primary resonance
mode and the secondary resonance mode in the lateral direction of the diaphragm 107, and to
flatten the sound pressure frequency characteristics up to the frequency at which the third
resonance mode occurs. .
[0087]
As described above, according to the electro-acoustic transducer of the present embodiment, the
magnet 403 is further provided to the second embodiment. As a result, the magnetic flux
perpendicular to the vibration direction can be further increased than in the second embodiment,
and the reproduction sound pressure in the ultrahigh range can be further increased.
[0088]
In the present embodiment, the plates 105 and 106 may be plates 305 and 306 as shown in FIG.
FIG. 17 is a structural cross-sectional view of an electroacoustic transducer when the plates 105
and 106 of FIG. 15C are the plates 305 and 306. Plates 305 and 306 are the same as shown in
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FIG. 12C, and the top surfaces of plates 305 and 306 are higher than the top surfaces of magnets
102 and 103 and lie on a plane close to diaphragm 107. Here, FIG. 18 shows a change in
magnetic flux density distribution when the upper surfaces of the plates 305 and 306 are made
1.0 mm higher than the upper surfaces of the magnets 102 and 103.
[0089]
In FIG. 18, the vertical axis represents the magnetic flux density, and the horizontal axis
represents the distance from the central axis O in the lateral direction of the diaphragm 107, and
the right direction in FIG. 17 is the positive direction. In FIG. 18, the width of the plate 104 in the
short side direction is 1 mm, the width of the magnets 102 and 103 in the short side direction is
2 mm, and the width of the plates 305 and 306 in the short side direction is 1 mm. The width of
the magnets 102 and 103 in the direction is 8 mm. The graph (a) of FIG. 18 is the same as the
graph (a) of FIG. Graph (b) of FIG. 18 shows the magnetic flux density distribution when the
upper surfaces of the plates 305 and 306 are higher by 1.0 mm than the upper surfaces of the
magnets 102 and 103.
[0090]
In the graph (a), as in the first embodiment, the positions at which the magnetic flux density
reaches the maximum value coincide with the width center axes S1 and S2. On the other hand, in
the graph (b), the magnetic flux density is generally higher than the graph (a). Specifically, in the
vicinity of the central axis O, the magnetic flux density is increased because the magnetic flux φ
emitted from the upper surface of the plate 104 is forced to change in the horizontal direction by
the magnet 403. On the other hand, in the vicinity of the plates 305 and 306, the magnetic flux
density is increased because the magnetic flux φ is led to the upper surfaces of the raised plates
305 and 306, respectively. By thus making the upper surfaces of the plates 305 and 306 higher
than the upper surfaces of the magnets 102 and 103, the magnetic flux density can be uniformly
increased regardless of the distance from the central axis O.
[0091]
In order to raise the operating point of the magnet 403, a yoke made of a ferromagnetic material
such as iron may be further provided on the top surface of the magnet 403. At this time, it is
desirable to make the width of the yoke equal to or smaller than the width of the magnet 403 in
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the short direction of the diaphragm 107 so as not to prevent the radiation of sound above the
diaphragm 107.
[0092]
The electro-acoustic transducers according to the first to fourth embodiments described above
can also be mounted on video equipment such as personal computers and televisions. The
electro-acoustic transducers according to the first to fourth embodiments are disposed in an
apparatus housing provided in the video apparatus. Hereinafter, as a specific example, the case
where the electro-acoustic transducer according to the first embodiment is mounted on a flatscreen television as a video device will be described. FIG. 19 is a diagram showing a flat-screen
television.
[0093]
In FIG. 19, the flat-screen television 50 includes a display unit 51, an apparatus housing 52, and
an electro-acoustic transducer 53. The display unit 51 is configured by a plasma display panel or
a liquid crystal panel, and displays an image. An equipment housing 52 for mounting the
electroacoustic transducer 53 is disposed on both sides of the display unit 51. In the device
housing 52, a dustproof net having a sound hole is installed at a place where the electroacoustic
transducer 53 is mounted. Alternatively, a sound hole is formed in the device housing 52 itself.
The electro-acoustic transducer 53 has the same structure as that of the electro-acoustic
transducer according to the first embodiment, and is disposed such that the radiation surface of
the sound faces the viewer. Although the electro-acoustic transducer 53 is attached to the device
housing 52 in FIG. 19, it may be attached to the inside of a different device housing. For example,
it may be mounted on a substrate inside the flat screen television 50.
[0094]
Next, the operation of the flat-screen television 50 shown in FIG. 19 will be described. The radio
wave output from the base station is received by the antenna. The radio wave received by the
antenna is input to the flat-screen television 50, and is converted into a video signal and an audio
signal by an electric circuit (not shown) inside the flat-screen television 50. The video signal is
displayed on the display unit 51, and the audio signal is emitted as sound in the electroacoustic
transducer 53.
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[0095]
In the flat panel television 50, the width of the device housing 52 is made as thin as possible in
order to make the width of the display unit 51 as large as possible relative to the entire width,
that is, to achieve a large screen. Therefore, a narrow width (width in the short side direction) of
the electroacoustic transducer 53 mounted on the device housing 52 is also required. On the
other hand, in the electroacoustic transducer 53, the magnetic flux in the direction perpendicular
to the vibration direction of the diaphragm can be efficiently increased while narrowing the
lateral width of the electroacoustic transducer 53, and the reproduction sound pressure can be
improved. it can. As a result, better super-high frequency reproduction can be realized, and the
electro-acoustic transducer 53 is useful in video equipment such as the flat-screen television 50
which achieves a large screen.
[0096]
In addition, the electroacoustic transducers according to the above-described first to fourth
embodiments can also be mounted on portable terminal devices such as a mobile phone and a
PDA. The electro-acoustic transducer which concerns on the 1st-4th embodiment is arrange ¦
positioned inside the apparatus housing provided in the portable terminal device. Hereinafter, as
a specific example, a case where the electroacoustic transducer according to the first
embodiment is mounted on a mobile phone which is a mobile terminal device will be described.
FIG. 20 is a diagram showing a mobile phone.
[0097]
In FIG. 20, the mobile phone 60 includes an apparatus housing 61 and an electroacoustic
transducer 62. The electro-acoustic transducer 62 has the same structure as the electro-acoustic
transducer according to the first embodiment, and is disposed inside the device casing 61.
[0098]
Next, the operation of the mobile phone 60 shown in FIG. 20 will be briefly described. For
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example, when an incoming radio wave is received by an antenna (not shown) of the mobile
phone 60, an electric circuit (not shown) inside the mobile phone 60 generates an incoming
voice signal. The generated audio signal is emitted as sound in the electroacoustic transducer 62.
[0099]
In the mobile phone 60, thinning is achieved, and the thickness of the device housing 61 is
configured as thin as possible. Therefore, a narrow width (width in the short side direction) of the
electroacoustic transducer 62 mounted on the device housing 61 is also required. On the other
hand, in the electroacoustic transducer 62, the magnetic flux in the direction perpendicular to
the vibration direction of the diaphragm can be efficiently increased while narrowing the lateral
width of the electroacoustic transducer 62, and the reproduction sound pressure can be
improved. it can. As a result, better super-high frequency reproduction can be realized, and the
electro-acoustic transducer 62 is useful in a portable terminal device such as a portable
telephone 60 for achieving thinning.
[0100]
In addition, the electroacoustic transducers according to the above-described first to fourth
embodiments can be mounted on a vehicle such as an automobile as an on-vehicle
electroacoustic transducer. The electro-acoustic transducer which concerns on the 1st-4th
embodiment is arrange ¦ positioned inside the vehicle body. Hereinafter, the case where the
electroacoustic transducer which concerns on 1st Embodiment is mounted in the door of a motor
vehicle is demonstrated as a specific example. FIG. 21 is a view showing a door of a car.
[0101]
In FIG. 21, a door 70 of a car has a window portion 71, a door main body 72, a low frequency
electro-acoustic transducer 73, and a high frequency electro-acoustic transducer 74. The lowrange electro-acoustic transducer 73 is an electro-acoustic transducer mainly for emitting lowrange sound. The high-frequency electro-acoustic transducer 74 is an electro-acoustic transducer
that mainly emits high-frequency sound, and has the same structure as the electro-acoustic
transducer according to the first embodiment. The low-range electro-acoustic transducer 73 and
the high-range electro-acoustic transducer 74 are disposed inside the door body 72. In the high-
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range electro-acoustic transducer 74, the magnetic flux in the direction perpendicular to the
vibration direction of the diaphragm can be efficiently increased, and the reproduction sound
pressure can be improved. As a result, it is possible to provide an in-car listening environment
capable of better super high frequency reproduction.
[0102]
The electro-acoustic transducer according to the present invention can realize better super-high
frequency reproduction, and is applied to an audio set, an electronic device such as a television, a
personal computer, a mobile phone, a PDA, and the like.
[0103]
FIG. 1A is a front view of the electro-acoustic transducer according to the first embodiment. FIG.
1A is a cross-sectional view of the electro-acoustic transducer taken along the longitudinal center
line AA in FIG. 1A. FIG. 1C shows a detailed flow of magnetic flux φ in the case of cutting the
magnetic flux density distribution in FIG. 1C showing a detailed flow of magnetic flux φ a
perspective view magnet 102 when the magnetic circuit constituting the electroacoustic
transducer shown in FIG. And 103 show the relationship between the change in the width of the
vibration direction of the diaphragm 107 and the change in the magnetic flux density
distribution, and the relationship between the position of the upper surface of the plates 104 to
106 and the magnetic flux density distribution FIG. 6 is a cross-sectional view showing the
relationship between the position of the upper surface of the plate 104 to 106 and the magnetic
flux density distribution, and the cross-sectional view of the electroacoustic transducer according
to the first embodiment in which the plates 104 to 106 are omitted. Structural cross-sectional
view of the electro-acoustic transducer according to the first embodiment in which the gates 105
and 106 are omitted The cross-sectional structural cross-section of the electro-acoustic
transducer according to the first embodiment in which the plate 104 is omitted FIG. 11A is a
front view of the electro-acoustic transducer according to the second embodiment. FIG. 11A is a
cross-sectional view of the electro-acoustic transducer cut along the longitudinal center line AA
in FIG. 11A. FIG. 12A is a front view of the electro-acoustic transducer according to the third
embodiment, and FIG. 12A is a cross-sectional view of the electro-acoustic transducer taken
along the longitudinal center line AA of FIG. 12A. Sectional view when the electroacoustic
transducer is cut along the center line BB The perspective view of the magnetic circuit
constituting the electroacoustic transducer shown in FIG. Top surface The figure which shows the
change of the magnetic flux density distribution at the time of making it 1.0 mm higher than the
front view of the electroacoustic transducer concerning 4th Embodiment at the time of cutting an
electroacoustic transducer in center line AA of the longitudinal direction figure 15A. 15C shows
the change of the magnetic flux density distribution when the magnet 403 is arranged. The
plates 105 and 106 of FIG. Structural cross-sectional view of the electroacoustic transducer in
the case of 306 A view showing a change in magnetic flux density distribution when the upper
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surfaces of the plates 305 and 306 are made 1.0 mm higher than the upper surfaces of the
magnets 102 and 103 Figure showing a telephone Figure showing a car door Front view of a
conventional electro-acoustic transducer The electro-acoustic transducer is cut at the center line
AA in the short direction of the view 22A Sectional view Front view of the conventional
electroacoustic transducer Sectional view when the electroacoustic transducer is cut along the
longitudinal center line AA of FIG. 23A The electroacoustic transducer is cut along the lateral
center line BB of FIG. 23A FIG. 23A to FIG. 23C are sectional views when the width in the width
direction of the magnet 908 is increased in the electroacoustic transducers shown in FIGS.
Explanation of sign
[0104]
101, 101a Frames 102, 103, 102a, 103a, 403 Magnets 104 to 106, 104a to 106a, 305, 306
Plates 107 Vibrators 108, 208 Coils 109, 109a Edges 401, 402 Support members 50 Flat panel
television 51 Display 52, 61 device housing 53, 62 electroacoustic transducer 60 mobile phone
70 door 71 window 72 door main body 73 electroacoustic transducer for low frequency 74
electroacoustic transducer for high frequency
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