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JP2000152378

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2000152378
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
flat acoustic transducer, and more particularly to a flat acoustic transducer such as a flat speaker,
a flat microphone, and a flat speaker which can be used as a microphone.
[0002]
2. Description of the Related Art FIG. 1 shows the basic configuration of a conventional flat
loudspeaker. The flat loudspeaker comprises a plurality of rod-like magnets 1 arranged in
parallel on the yoke 4, a vibrating membrane 2 provided close to and in parallel to the pole faces
of the rod-like magnets 1, and the rod-like magnet 1. A plurality of coils 3 are respectively
formed at positions facing the pole faces of the bar-like magnets on the vibrating membrane face
so that current can flow in the direction orthogonal to the generated magnetic field. Each coil 3 is
disposed at a position where most of the inner circumferential side of the coil faces the pole face
of the rod-like magnet, and the remaining part is disposed outside the position corresponding to
the outer edge of the rod-like magnet. Then, by passing an alternating current through each of
the coils 3, the current flowing through each of the coils 3 receives force from the magnetic field
of the bar-shaped magnet according to Fleming's left-hand rule, so that the vibrating film 2 is
perpendicular to the surface of the vibrating film. To convert the electrical signal into an acoustic
signal.
[0003]
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It is also possible to use the microphone as a microphone by vibrating the diaphragm 2 in a
direction perpendicular to the surface of the diaphragm and converting an acoustic signal into an
electrical signal according to Fleming's right-hand rule.
[0004]
However, in the above-described conventional flat type speaker, most of the coil is disposed at a
position facing the pole face of the rod-like magnet, and therefore, at the position facing the pole
face of the rod-like magnet A magnetic field in a direction perpendicular to the surface of the
vibrating film acts on the arranged coil portion.
Therefore, the force received from the magnetic field by the current flowing through the coil
portion is in the direction along the surface of the diaphragm. The force in the direction along the
vibrating membrane surface causes the vibrating membrane surface to be distorted, and a noise
component to the acoustic signal is generated, so that the sound quality is degraded.
[0005]
In addition, since a plurality of rod-shaped magnets are disposed so that the longitudinal
direction is parallel, the length of the portion interlinked with the magnetic field of each coil is
about twice the product of the long side of the rod-shaped magnet and the number of turns of
the coil Therefore, the ratio of the occupied area to the area of the vibrating film in the portion
linked to the magnetic field of the coil is low, and therefore the efficiency of the acoustic
conversion is deteriorated and sufficient sound volume can not be obtained, but sufficient sound
quality can be obtained. There was a problem of not being.
[0006]
The present invention has been made to solve the above-mentioned conventional problems, and
it is an object of the present invention to provide a flat acoustic transducer which reduces
distortion of a vibrating film to reduce noise components and improve sound quality. I assume.
[0007]
In order to achieve the above object, according to a first aspect of the present invention, the first
magnetic pole surface is substantially parallel to a first predetermined surface. A second magnet
surface arranged such that a first magnet disposed in the first magnetic pole surface and a
second magnetic pole surface having a polarity different from the polarity of the first magnetic
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pole surface face the first predetermined surface A second magnet disposed at a predetermined
distance from a portion facing the first magnetic pole surface on a second predetermined surface
so as to be substantially parallel to the second predetermined surface; A vibrating membrane
disposed between the first predetermined surface and the second predetermined surface so that
the other magnetic surface faces the second magnetic pole surface, and And the inner periphery
of the spiral is positioned in a region near the portion including the portion corresponding to the
outer edge of the first pole face of the vibrating membrane. As described above, in a region near
the portion including the portion corresponding to the outer edge of the first coil disposed on the
vibrating film and formed in a spiral shape and corresponding to the outer edge of the second
magnetic pole surface of the vibrating film. And a second coil disposed on the vibrating
membrane so as to locate the inner periphery of the spiral.
[0008]
The first magnet of the first invention has a first magnetic pole surface of one polarity (for
example, N pole) on a first predetermined surface such that the first magnetic pole surface is
substantially parallel to the first predetermined surface. It is arranged.
Further, the second magnet is arranged such that a second magnetic pole surface of a polarity
(for example, S pole) different from the polarity of the first magnetic pole surface faces the first
predetermined surface. It is disposed at a position separated by a predetermined distance from a
portion facing the first magnetic pole surface on the second predetermined surface so as to be
substantially parallel to the predetermined surface.
[0009]
In addition, a vibrating film is disposed between the first predetermined surface and the second
predetermined surface such that one surface faces the first magnetic pole surface and the other
surface faces the second magnetic pole surface. It is done.
[0010]
Thereby, the magnetic field generated from each magnet is directed from the first pole face to
the second pole face or from the second pole face to the first pole face, and the first pole face and
the second pole face The magnetic field in the area between the two magnets, and thus the
magnetic field in the area between the first magnet and the second magnet, is directed
substantially parallel to the vibrating membrane surface.
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[0011]
A first coil and a second coil formed in a spiral shape are disposed on the vibrating membrane.
The first coil includes a portion corresponding to the outer edge of the first pole face of the
vibrating membrane, and the inner periphery of the spiral, and hence the inner periphery of the
coil, is located in a region near the portion corresponding to the outer edge. It is arranged
corresponding to the 1 magnet.
In addition, the second coil also includes the portion corresponding to the outer edge of the
second magnetic pole surface of the vibrating membrane and the inner periphery of the spiral in
the region near the portion corresponding to the outer edge, similarly to the first coil. It is
arranged corresponding to the second magnet so that the inner circumference is located.
[0012]
In this manner, each of the first coil and the second coil is arranged such that the inner periphery
of the coil is located in a region near the portion corresponding to the outer edge including the
portion corresponding to the outer edge of the corresponding pole face. Also, as described above,
the magnetic field in the region between the first magnet and the second magnet points in a
direction substantially parallel to the vibrating membrane surface, and thus the second coil of the
first coil A magnetic field directed in a direction substantially parallel to the vibrating membrane
surface acts on a portion from the inner periphery to the outer periphery adjacent to the coil and
a portion from the inner periphery to the outer periphery adjacent to the first coil of the second
coil.
[0013]
For this reason, when power is supplied to the first coil and the second coil, the direction in
which the current is received from the magnetic field is substantially orthogonal to the vibrating
membrane surface, and the force in the direction along the vibrating membrane surface
decreases. Sound quality can be improved by reducing noise components.
[0014]
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The first coil and the second coil may be arranged such that the inner circumference of the coil is
located in the region inside the pole face of the portion corresponding to the outer edge of the
pole face, but the inner circumference of the coil is the pole face It is effective to arrange so as to
be located in a region corresponding to the outer edge of the magnetic pole surface, preferably in
a region outside the pole surface from the portion corresponding to the outer edge of the pole
surface.
If arranged in this manner, the component of the magnetic field linked to the coil increases in the
direction parallel to the vibrating film surface, so the vibration component in the direction along
the vibrating film surface, that is, the noise component is extremely reduced. Can be improved.
[0015]
Note that, by arranging the vibrating film close to and facing the first magnetic pole surface and
the second magnetic pole surface, the vibrating film surface acting on mutually adjacent parts of
the first coil and the second coil. And the component of the magnetic field directed in a direction
substantially parallel to
[0016]
The first coil is adjacent to the second coil by passing a current in the same direction to the part
where the first coil is adjacent to the second coil and the part where the second coil is adjacent to
the first coil. A large acoustic signal is generated because the current flowing from each of the
portions from the inner circumference to the outer circumference and the second coil from the
inner circumference to the outer circumference adjacent to the first coil receives the same
direction of force from the magnetic field. be able to.
[0017]
In order to apply current in the same direction to each coil, current may be applied
independently to each coil, but as described below, the coils may be connected by connecting the
first coil and the second coil, etc. The current may be conducted in the same direction through
the portion adjacent to the second coil of the first coil and the portion adjacent to the first coil of
the second coil.
That is, when the winding direction of the first coil and the second coil is the same, as shown in
FIGS. 2A and 2B, the inner circumferential side of the first coil L1 and the second coil L2 The
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outer circumferences of the first coil L1 and the second coil L2 are continuous.
[0018]
When the winding directions of the first and second coils are different from each other, one of
the first coil L1 and the second coil L2 is wound as shown in FIGS. 3 (A) and 3 (B). The inner
circumference side and the other outer circumference side are made continuous, or as shown in
FIG. 3C, the inner circumference sides and the outer circumference sides of the first coil L1 and
the second coil L2 are made continuous.
In addition, in FIG.2 and FIG.3, the arrow shows the electricity supply direction.
[0019]
According to a second invention, a first magnet disposed on the first predetermined surface such
that the first magnetic pole surface is substantially parallel to the first predetermined surface,
and the first magnetic pole surface A second pole surface of a polarity different from the polarity
is substantially parallel to a second predetermined surface disposed to face the first
predetermined surface. A second magnet disposed at a position separated by a predetermined
distance from the portion facing the first magnetic pole surface, and one surface facing the first
magnetic pole surface and the other surface being the second magnetic pole surface And a
vibrating film disposed between the first predetermined surface and the second predetermined
surface, and formed in a spiral shape, and an outer edge of the first magnetic pole surface of the
vibrating film. A first coil disposed on the vibrating membrane such that the inner periphery of
the spiral is positioned in a region near the portion including the portion corresponding to The
spiral is formed in a spiral shape in a direction opposite to that of the coil, and the inner
periphery of the spiral is positioned in a region near the portion including the portion
corresponding to the outer edge of the first pole face of the vibrating membrane. A second coil
disposed at a position overlapping the first coil of the diaphragm and having an inner peripheral
end continuous with an inner peripheral end of the first coil, and a spiral shape in the same
direction as the second coil The diaphragm is disposed on the diaphragm so that the inner
periphery of the spiral is located in a region near the portion including the portion corresponding
to the outer edge of the second magnetic pole surface of the diaphragm, as well as being formed.
A third coil whose end is continuous with the outer peripheral end of the second coil, and a spiral
shape in the same direction as the first coil, and corresponds to the outer edge of the second
magnetic pole surface of the vibrating membrane So that the inner circumference of the spiral is
located in the area near the site including the The disposed position overlapping the third coil of
the vibrating membrane, and in which the inner peripheral edge configured to include a fourth
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coil continuous to the inner peripheral end of said third coil.
[0020]
In the second invention, the inner peripheral end of the first coil and the inner peripheral end of
the second coil are made continuous, and the inner peripheral end of the third coil and the inner
end of the fourth coil are made continuous. Therefore, each continuous portion is located at a site
that is not easily affected by the magnetic field in the direction along the surface of the vibrating
membrane.
As a result, the current flowing through each continuous portion is unlikely to receive the force
in the direction along the surface of the vibrating film, so the influence of noise and the like can
be minimized.
[0021]
Further, the second coil and the third coil are continuous at the outer peripheral end of the coil,
and a magnetic field in the direction along the surface of the diaphragm acts on the outer
peripheral portion of the coil.
Therefore, the current flowing through the continuous portion in the outer peripheral portion of
the coil receives a force in the direction orthogonal to the surface of the vibrating membrane, so
that the influence of noise and the like can be minimized as described above.
[0022]
In the second invention, the first coil is disposed on one side of the vibrating membrane, the
second coil is disposed on the other side of the vibrating membrane, and the inner peripheral end
penetrates the vibrating membrane. And the third coil is disposed on the other surface of the
vibrating membrane, and the fourth coil is disposed on the one surface of the vibrating
membrane. The inner peripheral end can penetrate the vibrating membrane and be continuous
with the inner peripheral end of the third coil.
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As described above, by arranging the coils on both sides of the diaphragm, the diaphragm can be
efficiently used.
[0023]
In the second invention, the first coil, the second coil, the third coil, and the fourth coil constitute
one set of coil groups, and the outer peripheral end of the first coil and the fourth coil of the
adjacent coil group A plurality of coil groups can be arranged so as to be continuous with the
outer peripheral end of the coil.
Also in this case, since the coils of the adjacent coil groups arranged on the same surface are
continuous at the outer peripheral end of each coil, the influence of noise and the like can be
minimized as described above. .
[0024]
A plurality of the above-mentioned coil groups can be stacked and arranged in the thickness
direction of the coil.
[0025]
In the first and second inventions, a pair of magnets consisting of a first magnet and a second
magnet, a first coil provided corresponding to each of the first magnet and the second magnet,
and A pair of coils consisting of a second coil (in the second invention, the first coil to the fourth
coil), and a corresponding vibrating portion between the first magnet and the second magnet on
the vibrating surface is 1 Since it becomes a unit and this vibration part is realized as an
independent vibration surface, one unit of each can be realized as an independent speaker.
[0026]
By arranging the plurality of first magnets and the plurality of second magnets, a large number
of magnets can be arranged as compared with the case where rod-shaped magnets are arranged
in parallel, and the number of coils is also the same as the number of magnets. Since the number
or multiples thereof are arranged, the sum of lengths of portions interlinked with the magnetic
field of the coil is lengthened to increase the ratio of the area occupied by the coil on the
vibrating membrane surface to improve the acoustic conversion efficiency. Also, the sound
quality can be improved.
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[0027]
By arranging the first magnet on the first predetermined surface and arranging the second
magnet on the second predetermined surface, the first predetermined surface side of the first
magnet and the second magnet can be obtained. Since no magnetic path is formed on the second
predetermined surface side of the magnetic head, the material forming the first predetermined
surface and the second predetermined surface may be any material such as metal, wood, plastic,
etc. other than the magnetic substance. it can.
[0028]
In the present invention, the vibrating membrane vibrates due to the force received from the
magnetic field by the current flowing through the coil, but if the portion where the same coil
group of the vibrating membrane is arranged does not vibrate integrally, a large acoustic output
can not be obtained or sound is generated. Distorted or noisy.
Therefore, it is necessary to increase the hardness of the vibrating film in the arrangement
portion where the coil is arranged.
On the other hand, the entire vibrating membrane must be able to vibrate freely in the direction
orthogonal to the surface of the vibrating membrane, so the hardness of the portion other than
the portion where the coil of the vibrating membrane is disposed is lowered to make the coil of
the vibrating membrane It is necessary for the arrangement portion to be easily displaced in the
direction orthogonal to the surface of the vibrating membrane.
Therefore, in the first and second inventions, it is preferable to make the hardness of the
arrangement portion where the first coil and the second coil of the vibrating film are arranged
higher than the hardness of the portion other than the arrangement portion.
As a result, the hardness of the portion supporting the vibrating membrane around the
arrangement portion is reduced, and therefore the vibrating membrane can be vibrated
efficiently.
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[0029]
The configuration of the vibrating membrane with high hardness of the coil placement portion
can be obtained by applying a coating to the coil placement portion of the vibrating membrane
so that the hardness of the vibrating membrane around the coil placement portion is higher than
that of the vibrating membrane. The vibrating membrane on which the coil is disposed is
attached to the other vibrating membrane material having a hardness lower than that of the
vibrating membrane while being disposed on the coil disposition portion, and the hardness of the
coil disposition portion is greater than the hardness of the portion around the coil disposition
portion It can also be obtained by raising it.
[0030]
In the first invention and the second invention, the first magnetic pole surface is substantially
parallel to the first predetermined surface, and the first magnetic pole surface faces the same
side as the first magnetic pole surface of the first magnet. And a third magnet disposed on a first
predetermined surface so as to be adjacent to the magnet at a predetermined distance, and the
first magnetic pole surface is substantially parallel to the second predetermined surface and of
the second magnet At least one of the fourth magnets disposed on the second predetermined
surface may be further disposed adjacent to the second magnet at a predetermined distance so as
to face the same side as the second magnetic pole surface.
[0031]
Thereby, the magnetic field generated from the first predetermined surface side of the first
magnet and the third magnet is from the magnetic pole surface of the first magnet to the
magnetic pole surface of the third magnet or the magnetic pole surface of the third magnet The
magnetic field generated toward the pole face of the first magnet and from the second
predetermined face side of the second magnet and the fourth magnet is the pole face of the
fourth magnet from the pole face of the second magnet, or Since the magnetic pole surface of the
fourth magnet is directed to the magnetic pole surface of the second magnet, by forming the first
predetermined surface and the second predetermined surface on a plate-like member made of a
magnetic material, a plate member Acts as a magnetic path so that the magnetic flux can pass
only through the magnetic path and not leak to the outside, so that a stronger magnetic field can
be generated on the vibrating film side, thereby making a larger acoustic signal. Can occur.
[0032]
In the first and second inventions, at least one of a portion facing the second magnetic pole
surface on the first predetermined surface and a portion facing the first magnetic pole surface on
the second predetermined surface, By further arranging a magnet provided with a magnetic pole
surface having the same polarity as the opposing magnetic pole surface, a magnetic field
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component facing in a direction substantially parallel to the vibrating film surface in the region
between the first magnet and the second magnet is Since the amount of current can be increased
further, the direction of the force received by the magnetic field from the magnetic field in the
first coil and the second coil is substantially orthogonal to the vibrating membrane surface, and
the force along the vibrating membrane surface is Since the amount of noise is reduced, the noise
component can be further reduced to improve the sound quality and the sound pressure.
[0033]
When a plurality of first magnets and second magnets are arranged, the magnetic flux weakens
in the periphery of the arrangement portion of the first magnet and the second magnet, so that
the first magnet positioned in the periphery of the arrangement portions It is effective to dispose
the above-mentioned magnet (a magnet provided with a pole face having the same polarity as the
facing pole face) so as to face each of the second and third magnets.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment in which the
present invention is applied to a speaker will be described in detail with reference to the
drawings.
In the present embodiment, as shown in FIG. 4, the holding plate 20 is formed of a rectangular
plate-like member in which a large number (36 in the present embodiment) of holes 20A are
formed in a matrix.
In a portion surrounded by four adjacent holes 20A, each of a large number of permanent
magnets m formed flat in a row and in a column direction and having a square shape with the
same polarity (for example, N pole) The magnetic pole surface of) is fixedly arranged by bonding
or the like with the top facing upward.
Therefore, each of the permanent magnets m is disposed on the surface of the holding plate 20
so that the pole faces are substantially parallel to the surface of the holding plate 20.
[0035]
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A holding plate 30 having the same configuration as the holding plate 20 is disposed on the
upper surface side of the holding plate 20 so as to be parallel to the holding plate 20.
In the holding plate 30, a large number of holes 30A are formed in a matrix.
The drilling position of the hole 30A of the holding plate 30 is the same as the drilling position of
the hole 20A of the holding plate 20.
[0036]
Each of permanent magnets M is fixedly arranged at each of the portions surrounded by the four
adjacent holes 30A of the holding plate 30 and not opposed to the portions where the permanent
magnets of the holding plate 20 are fixed. . Each of the permanent magnets M is fixedly disposed
with a magnetic pole surface of a different polarity (for example, S pole) from the magnetic pole
of the magnetic pole surface of the permanent magnet m facing downward. Therefore, each of
the permanent magnets M is disposed at a position at a predetermined distance from the portion
facing the permanent magnet m on the surface of the holding plate 30 while the pole faces are
substantially parallel to the surface of the holding plate 30 .
[0037]
The holding plates 20 and 30 can be formed of plastic or wood, in addition to metals such as iron
and aluminum.
[0038]
Between the holding plate 20 and the holding plate 30, one side faces in close proximity to the
pole face of the permanent magnet m, and the other side approaches in proximity to the pole
face of the permanent magnet M, A vibrating membrane 26 is disposed.
[0039]
The vibrating film 26 is made of a polymer film such as polyimide or polyethylene terephthalate,
and is coated with a high-grade material to form a coil placement portion 26A having a high
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rectangular hardness in which a plurality of coils are disposed in the central portion. It is formed.
Therefore, the entire circumferential portion 26B of the coil placement portion 26A has a
hardness lower than that of the coil placement portion 26A.
In addition, a coil arrangement part is formed by forming a vibrating film with a film of constant
hardness with a polymer film such as polyimide or polyethylene terephthalate, and forming a
large number of holes around the coil arrangement part along the outer edge of the coil
arrangement part. The hardness of the entire circumferential portion of the coil may be lower
than the hardness of the coil placement portion.
[0040]
The vibrating membrane 26 is fixed to a frame (not shown) at a peripheral entire circumferential
portion 26B where the hardness of the vibrating membrane is low. The size of the opening of the
frame is such that all the permanent magnets fixed on the holding plate are included.
[0041]
The coil arrangement portion 26A of the vibrating membrane 26 is formed in a spiral shape
corresponding to each of the permanent magnets m and M, and a coil pair L11 consisting of a
pair of coils arranged on both the front and back sides of the coil arrangement portion 26A. A
coil group C configured by arranging a plurality (24 in this embodiment) of L 38 is arranged.
Further, as shown in FIG. 5, each coil pair L11 to L38 is formed so as to be wound in a spiral so
as to be substantially similar to the outer edge of the magnetic pole surface of the permanent
magnets m and M. The inner circumference Li of the coil L, which is the circumference, is located
in a region outside the pole face from the portion M 'corresponding to the outer edge of the pole
face, and as shown in FIG. ing.
[0042]
Such a coil can be configured by forming a copper thin film on the coil arrangement portion of
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the vibrating film 26 by a lamination or deposition method and etching the copper thin film so
that the planar shape becomes a spiral. And each coil is covered with an insulating material.
[0043]
Between the vibrating membrane 26 and the plurality of pole faces, it is made of a soft material
such as non-woven fabric, sponge, glass wool, or urethane foam to prevent the coil and the pole
face from coming in contact with each other by vibration of the vibrating membrane.
Alternatively, the damper may be held.
[0044]
As shown in FIG. 6, in the coil pairs L11 to L38, a plurality of (four in the present embodiment)
coil pairs are connected in series to form a plurality (six in the present embodiment) small coil
groups G1 to G6. Are configured.
The small coil groups G1 to G6 are connected in parallel.
[0045]
The winding direction and the connection state of the small coil groups G1 to G6 will be
described with reference to FIG. In addition, since the winding direction and the connection state
of each coil are the same, in the following, one coil pair connected in series adjacent in the long
side direction of the vibrating membrane will be described, and the winding direction of the other
coil pair The description of the connection state is omitted. Further, a coil (corresponding to a
first coil of the second invention) disposed on the surface of the coil placement portion of one
coil pair is referred to as LA1, and a coil disposed on the back surface of the coil placement
portion (second invention A coil (corresponding to the second coil) is LB1, a coil (corresponding
to the fourth coil of the second invention) disposed on the surface of the coil disposition portion
of the other coil pair is disposed on the back surface of the coil disposition portion The described
coil (corresponding to the third coil of the second invention) is described as LB2.
[0046]
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The coil LA1 is formed to wind clockwise from the outside to the inside, and the coil LB1 is
formed to wind clockwise from the inside to the outside, and the coil LB2 is wound from the
outside to the inside. The coil LA2 is formed to be wound in the clockwise direction, and the coil
LA2 is formed to be wound in the counterclockwise direction from the inside to the outside.
Therefore, the winding direction of the coil disposed on one side of the coil placement portion is
the same direction from the inside to the outside (or from the outside to the inside).
[0047]
The inner end of the coil LA1 is connected to the inner end of the coil LB1 vertically penetrating
the coil disposition portion of the vibrating membrane 26 from the front surface to the back
surface. The outer end of the coil LB1 extends along the back surface of the coil placement
portion and is connected to the outer end of the coil LB2. The inner end of the coil LB2 is
connected to the inner end of the coil LA2 vertically penetrating the coil disposition portion of
the vibrating membrane 26 from the back surface to the front surface. The outer end of the coil
LA2 extends along the surface of the coil placement portion and is connected to the outer end of
an adjacent coil (not shown).
[0048]
The coils of each small coil group are connected in series by repeating the winding direction and
the connection state described above.
[0049]
When current I is applied from the outer end of coil LA1 of the small coil group connected in
series, current I flows in the direction indicated by the arrow in FIG. 7, so that coils LA1 and LA2
extend from the inner circumference to the outer circumference adjacent to each other. A current
flows in the same direction in the portion and the portions from the inner circumference to the
outer circumference adjacent to each other of the coils LB1 and LB2.
[0050]
Further, adjacent small coil groups, ie, small coil group G1 and small coil group G2, small coil
group G2 and small coil group G3, small coil group G4 and small coil group G5, small coil group
G5 and small coil group G6. The winding directions are formed to be opposite to each other.
[0051]
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The holding plates 20 and 30 to which the plurality of permanent magnets are fixed, the frame to
which the vibrating film 26 to which the coil group consisting of the plurality of coils is arranged
is fixed, and the damper The lower surface side of the support plate 20 and the upper surface
side of the holding plate 30 are covered with a cloth covering material, and a frame to which the
vibrating film 26 having the coil group is fixed is held between the holding plate 20 and the
holding plate 30 Thus, the peripheral edge is supported by a support member (not shown) and
assembled as a flat speaker.
[0052]
FIG. 8 is a cross-sectional view along the coil pair L18, L28, L38 in which the damper and the
covering material of the flat type speaker assembled as described above are omitted.
The magnetic pole surface of the permanent magnet m fixed to the lower holding plate 20
opposite to the holding plate 30 and the holding plate 20 of the permanent magnet M fixed to
the upper holding plate 30 are opposed Because each pole surface is close to and opposed to the
vibrating film 26 with a polarity different from that of the magnetic pole surface on the rotating
side, the magnetic flux generated from the permanent magnet is directed from the pole surface of
the N pole to the pole surface of the The magnetic field of the region between the permanent
magnets m and M which is closest to the surface is directed in a direction substantially parallel to
the vibrating film surface.
[0053]
Since coil pairs L18, L28 and L38 are disposed on the front and back surfaces of the vibrating
membrane, magnetic fields linked in a direction substantially parallel to the vibrating membrane
surface are linked to each coil.
When current I in the direction shown in FIG. 7 is supplied to the coils, as shown in FIG. 8,
currents in the same direction flow in the portions from adjacent inner circumferences to outer
circumferences of adjacent coils and all coils have the same direction. And, since the force F is
applied in the direction perpendicular to the film surface of the vibrating film, the vibrating film
is displaced in the direction perpendicular to the film surface.
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Therefore, by energizing the coil with an electric signal representing the sound to be generated,
the vibrating film vibrates in response to the electric signal, and an acoustic signal can be
generated.
In FIG. 7, H indicates the direction of the magnetic field.
[0054]
Furthermore, since a large number of holes are bored in the holding plate 20 and the magnetic
shield member 28, acoustic signals pass through the holes and the flat speaker is output from
both the front and back sides.
[0055]
Although the example in which the periphery of the vibrating film 26 is attached to the frame
has been described above, as shown in FIG. 9, the holding plate is formed of the housing 40 and
a cloth impregnated with urethane foam or synthetic resin, etc. The vibrating membrane 26 may
be held by storing the vibrating membrane 26 in the housing 40 in a state where the periphery
of the vibrating membrane 26 is held by the support 38.
[0056]
Since the configuration as shown in FIG. 9 is equivalent to connecting the holding plate to which
the permanent magnet m is fixed and the holding plate to which the permanent magnet M is
fixed, the housing 40 is made of a magnetic material. A magnetic flux flows from the N pole of
the magnet M through the housing 40 to the S pole of the permanent magnet m, and a magnetic
path is formed in the housing 40, so the magnetic flux on the vibrating film side can be
strengthened.
[0057]
Therefore, the magnetic flux can be strengthened by configuring the holding plate to which the
permanent magnet m is fixed by a yoke and the holding plate to which the permanent magnet M
is fixed by a yoke and connecting the yokes at least partially.
[0058]
In the first embodiment, since the permanent magnets fixed to one holding plate have the same
polarity of the pole faces facing in the same direction, the permanent magnets are compared with
the case where the pole faces are alternately reversed and disposed. The effect of simplifying the
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arrangement work of the is obtained.
[0059]
Next, a second embodiment of the present invention will be described.
As shown in FIG. 10B, in the yoke 32 according to the present embodiment, a plurality of yokes
32 are arranged adjacent to each other at a predetermined interval so that the polarities are
alternately inverted in the direction along one side of the yoke 32. A plurality of magnet rows
consisting of permanent magnets M are provided.
The plurality of permanent magnet arrays are spaced apart twice as far apart as the permanent
magnets M in the array, and the corresponding permanent magnets of the adjacent magnet
arrays have the same polarity.
[0060]
Further, in the yoke 22, a plurality of permanent magnets m are formed at the same interval as
the intervals of the permanent magnets M in a direction parallel to the magnet array of the yoke
32 at a position facing the middle portion of the magnet array of the yoke 32 Magnet array is
fixed.
The polarities of the permanent magnets m of this magnet array are arranged in the reverse
order of the magnet arrays provided in the yoke 32, and opposite to the polarity of the pole face
of the permanent magnet M closest to the permanent magnet m when assembled as a speaker. It
is arranged to be polar.
[0061]
The yoke 22 and the yoke 32 are formed by a rectangular plate-like member in which a large
number of holes are formed in a matrix, and each of the permanent magnets is disposed at a
portion surrounded by four adjacent holes. The same shape as the plate 20 and the holding plate
30 is the same as that of the holding plate 30 except that the material is a magnetic material.
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[0062]
When the diaphragm in which the coil pair described in the first embodiment is disposed is
disposed between the yoke 22 and the yoke 32 and assembled as a planar speaker, as shown in
FIG. 10A.
[0063]
The magnet M of the present embodiment is fixed to the yoke 32 which is a magnetic body.
Therefore, the magnetic flux from the N pole (surface on the side fixed to the yoke 32) of the
magnet M whose magnetic pole surface of the S pole is substantially parallel to the surface of the
yoke 32 forms the magnetic path in the yoke 32. The magnetic pole surface of the N pole passes
through the S pole (the surface fixed to the yoke 32) of the magnet M, which is substantially
parallel to the surface of the yoke 32.
Further, the magnetic flux from the N pole (surface on the side fixed to the yoke 22) of the
magnet m whose magnetic pole surface of the S pole is substantially parallel to the surface of the
yoke 22 forms a magnetic path in the yoke 22. The magnetic pole surface of the N pole passes
through to enter the S pole (the surface fixed to the yoke 22) of the magnet M substantially
parallel to the surface of the yoke 22.
Thereby, a magnetic flux with high density can be generated on the vibrating film side.
[0064]
In the second embodiment, since the magnetic path can be formed without connecting the facing
yokes, the manufacturing cost can be reduced.
[0065]
Further, between the magnets M and m, similarly to the magnetic flux illustrated in FIG. 8, it is
possible to generate a magnetic flux along the surface of the vibrating film, thereby reducing
noise components and improving sound quality. it can.
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[0066]
In the first and second embodiments, the magnetic pole surface of the magnets M and m is
described to face the holding plate or the yoke, but the holding plate or the portion of the yoke
facing the magnetic pole surface of the magnet M, Also, another permanent magnet having a pole
face of the same polarity as the facing pole face may be disposed on at least one of the portions
facing the pole face of the magnet m.
By arranging this other permanent magnet, it is possible to further increase the magnetic flux
density along the vibrating membrane.
[0067]
As described above, according to the present invention, the magnetic field in the region between
the first magnet and the second magnet is disposed so as to turn in a direction substantially
parallel to the vibrating film surface, and Since each of the first coil and the second coil includes
a portion corresponding to the outer edge of the corresponding pole face and is arranged such
that the inner periphery of the coil is located in the region near the portion corresponding to the
outer edge When a magnetic field directed in a direction substantially parallel to the film surface
becomes linked to the first coil and the second coil, and current flows through the first coil and
the second coil, the current received from the magnetic field The direction is substantially
orthogonal to the vibrating membrane surface, and the force in the direction along the vibrating
membrane surface is extremely small, so that the noise component can be reduced and the sound
quality can be improved. .
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