JP2010263362

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DESCRIPTION JP2010263362
[PROBLEMS] To reduce the restriction on the reciprocating motion of a vibration system to
prevent the deterioration of sound quality. SOLUTION: A speaker 1 forms a magnetic circuit by
fixing magnets 12 and 14 to a case 2, and a voice coil bobbin 31 provided with a voice coil 33 is
inserted so as to cover the magnets 12 and 14. There is. A pair of vibration control members 34
and 35 is disposed on the outer periphery of the voice coil bobbin 31 on the back side so as to
sandwich the voice coil 33. The voice coil 33 is inserted into the magnetic flux concentration
section 18, and the magnetic fluid 20A is injected therein. The outer periphery of the diaphragm
32 fixed to the voice coil bobbin 31 is movably supported by the case 2 via the magnetic fluid
20B. [Selected figure] Figure 1
スピーカー
[0001]
The present invention relates to a speaker for sound reproduction. More particularly, the present
invention relates to a dynamic type speaker having an edgeless damperless structure using
magnetic fluid.
[0002]
As a speaker for sound reproduction, there is known a dynamic type speaker which reproduces
sound by supplying current to a voice coil disposed in a magnetic flux concentration portion and
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vibrating a diaphragm. This type of dynamic speaker has a structure in which the diaphragm and
the voice coil bobbin are supported by the edge and the damper.
[0003]
Here, the damper has a role of supporting the oscillating system including the diaphragm and the
voice coil and the voice coil bobbin so as to accurately reciprocate without contacting the
magnetic circuit wall. Furthermore, the damper has the role of suppressing (braking and
dumping) the inertia of the vibration system by aligning the center of vibration of the voice coil
and the center of the magnetic flux concentration portion. In addition, the edge has a role similar
to that of the damper, and also has a role of blocking sound waves so that sound waves of
opposite phase radiated to the front and back sides of the diaphragm do not interfere with each
other.
[0004]
The edge and the damper are at different positions on the axis in the direction of vibration.
Therefore, the vibration system is supported at two points, and its movement is surely controlled.
As a result, the voice coil can reciprocate without contacting the magnetic circuit wall in the
narrow magnetic flux concentration section.
[0005]
In order to play such a role, it is desirable that the damper and the edge have a stronger control
force. On the other hand, in the speaker's original purpose of faithfully converting an electric
signal into a sound wave, its control power is a drag and leads to distortion of reproduced sound.
Furthermore, since the edge and the damper themselves have natural vibrations, the vibration of
the edge and the damper may cause unnecessary sound waves, that is, distortion, and may make
the reproduced sound muddy. Therefore, in the conventional speaker, the magnetic fluid is
injected into the magnetic flux concentration portion at the arrangement position of the voice
coil, and the vibration system is supported via the magnetic fluid to suppress distortion of the
reproduced sound.
[0006]
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JP, 2006-5852, A
[0007]
However, in the conventional speaker, since the edge has a configuration mechanically connected
to the frame, it is not possible to sufficiently reduce the restriction on the reciprocation of the
vibration system.
Therefore, it has been desired to develop a speaker capable of reproducing higher quality sound
by removing distortion of reproduced sound. The present invention has been made in view of
such circumstances, and its main object is to reduce the restriction on the reciprocation of the
vibration system to prevent the deterioration of the sound quality.
[0008]
According to one aspect of the present invention, a magnetic circuit including a case made of a
magnetic material and a magnet, a diaphragm inserted reciprocally movably in the opening on
the front side of the case, and the diaphragm fixed And a voice coil bobbin on which a voice coil
to which an electric signal is input and which is inserted and which is input, is wound around the
voice coil in a moving direction of the diaphragm and is made of a nonmagnetic material. A first
magnetic fluid injected into a first magnetic flux concentration portion formed between a pair of
vibration control members, the magnet and the case, and in which the voice coil and part of the
vibration control members are immersed And a second magnetic fluid disposed in a second
magnetic flux concentration portion formed between the diaphragm and the case.
[0009]
Further, according to another aspect of the present invention, in the speaker according to claim
1, the pair of vibration control members is a first vibration control member disposed on the back
side of the voice coil, and the voice coil. A second vibration control member disposed on the front
surface side of the first vibration control member, and a portion of the front surface side of the
first vibration control member is inserted into the first magnetic fluid, and the back surface side
of the second vibration control member A speaker is provided, characterized in that a portion of
the second magnetic fluid is inserted into the first magnetic fluid.
[0010]
Further, according to another aspect of the present invention, in the speaker according to claim 1
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or 2, the magnet includes a first magnet fixed to the case, and a magnetic material to the first
magnet. And a second magnet attached to the first magnet and the second magnet, and the first
magnet and the second magnet are disposed such that the opposing surfaces of the first magnet
and the second magnet have the same magnetic pole, and The first magnetic flux concentration
portion may be formed therebetween.
[0011]
Further, according to another aspect of the present invention, in the speaker according to the
third aspect, the second magnet is disposed on the front side closer to the diaphragm than the
first magnet. A third magnetic fluid is filled in the gap between the front end of the magnet and
the inner peripheral surface of the voice coil bobbin.
[0012]
According to the present invention, since the vibration system is supported by the magnetic fluid
on each of the front side and the back side of the speaker, the restriction on the movement of the
vibration system is reduced, and distortion of reproduced sound is suppressed.
[0013]
FIG. 1 is a cross-sectional view showing a configuration of a speaker according to an embodiment
of the present invention.
FIG. 2 is a cross-sectional view taken along the line I-I of FIG.
FIG. 3 is an enlarged view of a part of FIG. 1 and shows a configuration around the first magnetic
flux concentration portion.
FIG. 4 is a cross-sectional view showing a modification of the speaker.
[0014]
The best mode for carrying out the invention will be described in detail with reference to the
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drawings.
In the following description, the side on which high-temperature sound is output is referred to as
the front, and the other side is referred to as the back.
FIG. 1 shows a cross-sectional view of the speaker according to the present embodiment. The
speaker 1 has a case 2 in which a vibration system 3 is vibratably supported. Case 2 is
manufactured from a magnetic material such as iron and functions as a yoke. A substantially
circular opening 4 is formed in the front surface 2A of the case 2, and the inner peripheral
surface of the opening 4 has a convex and a curved surface 4A inward in a sectional view. As
shown in FIGS. 1 and 2, a recess 2 </ b> B is formed in the center of the case 2. Furthermore, a
plurality of holes 5 and 6 are formed around the recess 2B. These holes 5 and 6 are arranged at
predetermined intervals, for example, at equal intervals on the circumference of a fixed distance
from the axis m1 coinciding with the center of the recess 2B, and communicate the inside of the
case 2 with the back surface 2C of the case 2 ing. These holes 5 and 6 are used to vent air and
pass cables.
[0015]
In the case 2, a magnet unit 11 is accommodated. The magnet unit 11 has a first magnet 12
inserted into the recess 2 B and a second magnet 14 connected to the front surface of the first
magnet 12 via the insertion plate 13. The first magnet 12 is fixed to the case 2 using a hole 15
formed at the center of the recess 2B, and the outer diameter thereof is smaller than the inner
diameter of the recess 2B. Furthermore, the length of the first magnet 12 along the axis m1 is
shorter than the length of the recess 2B along the axis m1. In this embodiment, the first magnet
12 is fixed to the case 2 such that the N pole is disposed on the back side and the S pole is
disposed on the front side. The second magnet 14 has an outer diameter substantially the same
as that of the first magnet 12 and is disposed such that the back side has the same polarity as the
front side of the first magnet 12. That is, in this embodiment, the back surface of the second
magnet 14 is an S pole, and the front surface is an N pole.
[0016]
As the first and second magnets 12 and 14, permanent magnets, for example, magnets using
neodymium having a high magnetic flux density and a very strong magnetic force are used. The
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insertion plate 13 in close contact with the first and second magnets 12 and 14 is made of, for
example, a magnetic material such as iron. Since the two magnets 12 and 14 are arranged such
that the same poles face each other, the insertion plate 13 is strongly excited to the same one
kind of magnetic pole as the magnetic poles of the two magnets 12 and 14 arranged close to
each other. Ru. For example, when the first and second magnets 12 and 14 have their S poles
facing each other, the insertion plate 13 is also excited to the S pole. Then, between the insertion
plate 13 thus excited and the case 2 closely attached to the first magnet 12 on the back side,
more specifically, the outer peripheral surface of the insertion plate 13 and the recess 2 B of the
case 2 A first magnetic flux concentration portion 18 is formed between the inner
circumferential surface and the inner circumferential surface.
[0017]
The vibration system 3 includes a voice coil bobbin 31 removably inserted into the case 2, and a
diaphragm 32 attached to a front end of the voice coil bobbin 31. The voice coil bobbin 31 has a
cylindrical shape, and the outer diameter thereof is smaller than the inner diameter of the recess
2 B of the case 2. Furthermore, the inner diameter is larger than the outer diameter of the
magnet unit 11. A voice coil 33 is wound around the outer periphery of the rear end of the voice
coil bobbin 31. The voice coil 33 is formed by winding a conducting wire around the outer
periphery of the voice coil bobbin 31 without a gap. The conducting wire of the voice coil 33 is
electrically connected to an amplifier (not shown). Furthermore, a pair of vibration control
members 34 and 35 are attached to the outer periphery of the voice coil bobbin 31 so as to
sandwich the voice coil 33. The vibration control members 34 and 35 are made of nonmagnetic
material, and are in close contact with each other so that no gap is formed between the vibration
control members 34 and 35 in the axial direction. The outer diameters of the pair of vibration
control members 34 and 35 are larger than the outer diameter of the voice coil 33 and smaller
than the inner diameter of the recess 2 B of the case 2. Therefore, as shown in FIG. 3, a step is
generated at the boundary between each of the vibration control members 34 and 35 and the
voice coil 33. In addition, in FIG. 3, although the voice coil 33 is the structure which wound the
conducting wire in 1 layer, you may wind a conducting wire in double or more.
[0018]
Here, a magnetic fluid 20A (first magnetic fluid) is injected and held in the first magnetic flux
concentration portion 18 formed between the case 2 and the insertion plate 13. The magnetic
fluid 20A is injected in an amount capable of immersing the whole of the voice coil 33 and part
of the pair of vibration control members 34, 35. Specifically, the first vibration control member
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34 is disposed on the back side of the voice coil 33, and a portion of the front side is directed in
the second direction d2, that is, from the back 2C side of the case 2 to the front 2A side. Is
inserted into the magnetic fluid 20A. The second vibration control member 35 is disposed on the
front side of the voice coil 33, and a part of the back side thereof is directed to the magnetic fluid
20A from the first direction d1, that is, from the front 2A side to the back 2C side of the case 2. It
is inserted. Thus, the first magnetic circuit of the speaker 1 returns from the N pole of the first
magnet 11 through the case 2 to the magnetic fluid 20A, the insertion plate 14 and the S pole of
the first magnet 11. It is formed.
[0019]
Furthermore, the diaphragm 3 is fixed to one end on the front side of the voice coil bobbin 31. At
the end on the front side, at least one hole 36 is formed on the rear side of the attachment
position of the diaphragm 3. This hole 36 is used as an air vent when reciprocating the vibration
system 3.
[0020]
The diaphragm 32 has a cone shape whose diameter increases toward the front surface about
the axis m1, and is closed by a dome-shaped center cap 32A whose central opening protrudes
toward the front surface. Furthermore, the outer periphery of the diaphragm 32 is folded back
parallel to the axis and toward the back. The folded back end 32B is disposed so as to at least
partially overlap the curved surface 4A of the case 2 in the axial direction. In this embodiment,
the diaphragm 32 is made of a nonmagnetic material such as aluminum or magnesium. A second
magnetic flux concentration portion 21 is formed on the curved surface portion 4A of the front
surface 2A of the case 2 by the magnet unit 11. The second magnetic flux concentration portion
21 is formed at a position where the curved surface portion 4A and the end 32B of the vibrating
body 32 face each other.
[0021]
Here, the second magnetic flux concentration portion 21 between the diaphragm 32 and the case
2 holds the magnetic fluid 20 B (second magnetic fluid). Furthermore, since the second magnet
14 is slightly smaller than the inner diameter of the voice coil bobbin 31, the magnetic fluid 20C
(also in the gap between the inside of the voice coil bobbin 31 and the end of the front side of the
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second magnet 14) The third magnetic fluid is held. The voice coil bobbin 31 is also supported
by the second magnet 14 by the magnetic fluid 20C. Note that the support of the voice coil
bobbin 31 by the magnetic fluid 20C is not an essential element in the present embodiment.
[0022]
It is desirable that the voice coil bobbin 31 and the vibration control members 34, 35 be made of
a material that is inert, insoluble, non-swelling, and non-permeable to the magnetic fluids 20A,
20B. That is, metals including alloys such as aluminum, magnesium and titanium, resins such as
polypropylene, polyethylene, PET, polyimide and fluorine resin, paper, non-woven fabric, glass
fiber, carbon fiber, aramid fiber and the like Etc. are used.
[0023]
Next, the operation of this embodiment will be described. When the speaker 1 is connected to an
amplifier (not shown) to generate sound such as sound or voice, an electric signal from the
amplifier is input to the voice coil 33. When an electrical signal flows through the voice coil 31
disposed in the magnetic circuit, a force is generated by electromagnetic induction. Since the first
and second magnets 12 and 14 are fixed to the case 2, the vibration system 3 including the voice
coil bobbin 31 and the diaphragm 32 fixed to the same is arranged along the axis m1 in the first
direction d1 or Move in the second direction d2. Then, the movement amount and the movement
direction of the vibration system 3 change with the change of the electric signal, whereby the
vibration occurs, and as a result, the sound is output from the diaphragm 32.
[0024]
At this time, since the end portion of the tip end side of the diaphragm 32 is supported by the
case 2 via the magnetic fluids 20A to 20C, the vibration system 3 can move back and forth
smoothly. Furthermore, on the tip end side of the voice coil bobbin 31, the voice coil bobbin 31 is
supported by the second magnet 14 via the magnetic fluids 20A to 20C. That is, the vibration
system 3 is supported at three places, the outer periphery of the diaphragm 32 and the inside of
the front side of the voice coil bobbin 31 and the outside of the back side of the voice coil bobbin
31, and does not contact the magnetic circuit wall. Correct reciprocation, thereby suppressing
distortion of the reproduced sound. Although the tip end side of the voice coil bobbin 31 is
closed by the magnetic fluid 20C, since the hole 36 is provided on the tip end side of the staying
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position of the magnetic fluid 20C, when vibrating the vibration system 3, the voice coil bobbin
31 The air inside the front of the is discharged to the outside. For this reason, the presence of the
magnetic fluid 20C is not the resistance of the drive of the vibration system 3.
[0025]
Here, in the speaker 1, vibration control members 34 and 35 are provided so as to sandwich
both ends of the voice coil 33 in the advancing and retracting direction of the vibration system 3.
A part of each of the vibration control members 34, 35, specifically, a part of the front side of the
first vibration control member 34 is immersed in the magnetic fluid 20A as shown in FIG. A part
of the back side of the member 35 is immersed in the magnetic fluid 20A. As described above,
since the outer diameter of the vibration control members 34 and 35 is larger than the outer
diameter of the voice coil 33, the area crossing the magnetic flux in the first magnetic flux
concentration portion 18 is larger than that of the voice coil 33. Is larger. For this reason, the
displacement force generated by the vibration control members 34 and 35 crossing the magnetic
flux becomes larger than the displacement force generated by the voice coil 33.
[0026]
Therefore, when the vibration system 3 moves in the first direction d1 and the second vibration
control member 35 enters the inside of the magnetic fluid 20A by the same amount as the
movement amount of the vibration system 3 along with this movement, the displacement force
by that amount Becomes larger. The displacement force acts as a force to move the vibration
system 3 in the opposite direction to the first direction d1, that is, in the second direction d2.
This force increases as the volume of the second vibration control member 35 entering the
magnetic fluid 20A increases, so the larger the moving amount of the vibration system 3 in the
first direction d1, the more the original position of the vibration system 3 is. The power to return
to On the other hand, when the vibration system 3 moves in the second direction d2 and the first
vibration control member 34 enters the magnetic fluid 20A by the same amount as the
movement amount of the vibration system 3 along with this movement, the displacement force is
growing. The displacement force acts as a force to move the vibration system 3 in the opposite
direction to the second direction d2, that is, in the first direction d1. Similarly to the above, this
force increases as the volume of the first vibration control member 34 entering the magnetic
fluid 20A increases, so the larger the moving amount of the vibration system 3 in the second
direction d2, the vibration system The force to return 3 to the original position is increased.
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[0027]
As described above, since the vibration system 3 always receives the force on the opposite side of
the moving direction of the vibration system 3 from the magnetic circuit by the presence of the
pair of vibration control members 34 and 35, the vibration system 3 moves in one direction. It is
prevented from passing and stable reciprocation is possible. Further, since the voice coil 33 and
the pair of vibration control members 34 and 35 are disposed such that the balance point of the
exhaust force is at the initial position (prescribed position) of the vibration system, the amplitude
center of the voice coil 33 and the first And the center of the magnetic flux concentration portion
18 can be matched.
[0028]
As a result, as in the prior art, it is possible to reproduce sound without mechanically joining the
edge portion of the vibration system or providing a damper. In addition, since the first magnetic
flux concentration portion 18 is filled with the magnetic fluid 20A, the sound wave of the reverse
phase generated on the back side of the diaphragm 32 is blocked. Further, since the magnetic
flux is concentrated by the insertion plate 13, the first and second magnets 12 and 14 can be
miniaturized, and the speaker 1 can be manufactured inexpensively.
[0029]
Further, at the time of assembling this speaker 1, the lead wire of the voice coil 33 may be
connected, and the vibration system 3 may be inserted into the magnetic flux concentration
portions 18 and 21. A speaker can be easily manufactured in a short time without the need for
alignment and bonding required when mechanically joining conventional edges or providing a
damper, and jigs necessary for these operations. .
[0030]
As shown in FIG. 4, the third magnet 51 may be attached to the back surface 2 </ b> C of the
case 2. As the third magnet 51, a permanent magnet, for example, a magnet using neodymium
having a high magnetic flux density and a very strong magnetic force is used, and the same
magnetic poles as the first magnet 12 are disposed to face each other. Thereby, the magnetism
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passing through the case 2 is intensified. The yoke 52 attached to the back side of the third
magnet 51 is attached to prevent concentration of the magnetic flux on the back side of the third
magnet 51, but is not an essential component.
[0031]
Also, the speaker 1 may be mounted in a cabinet to constitute a speaker system.
[0032]
Reference Signs List 1 speaker 2 case 3 vibration system 4 opening 12 first magnet 13 insertion
plate (magnetic body) 14 second magnet 18 first magnetic flux concentration portion 20A
magnetic fluid (first magnetic fluid) 20B magnetic fluid (second) Magnetic fluid) 20C Magnetic
fluid (third magnetic fluid) 21 Second magnetic flux concentration part 31 Voice coil bobbin 32
Diaphragm 32B end part 33 Voice coil 34 First vibration control member 35 Second vibration
control member 36 Hole
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