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JPH10336776

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH10336776
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker device used to convert an electrical signal to sound.
[0002]
2. Description of the Related Art Conventionally, as a speaker device, one configured as shown in
FIG. 4 is used. The speaker device 51 shown in FIG. 4 includes a vibration system 70 that
generates sound, a magnetic circuit unit 60 that drives the vibration system 70, and a frame 52
that supports the vibration system 70. The speaker device 51 is a so-called magnetic shield type,
and includes a shield cover 53 that covers the magnetic circuit unit 60 and prevents the leakage
of the magnetic flux of the magnetic circuit unit 60.
[0003]
The magnetic circuit unit 60 is disposed on the yoke 61 having the center pole 64, the drive
magnet 62 for applying a magnetic flux to the yoke 61, and the drive magnet 62, and the space
between the yoke 61 and the center pole 64. And a top plate 63 that constitutes the magnetic
gap G.
[0004]
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The yoke 61 is formed of a magnetic material in a disk shape, and a cylindrical center pole 64 is
provided in a protruding manner at a central portion.
The center pole 64 is inserted into an inner peripheral portion of a voice coil bobbin 65 of a
vibration system 60 described later. A driving magnet 62 is provided on the yoke 61.
[0005]
The driving magnet 62 is formed in an annular shape having a center hole 62 a, and the center
pole 64 is inserted into the center hole 62 a and provided on the yoke 61. For example, the yoke
61 side of the drive magnet 62 is magnetized in the S pole, and the top plate 63 side is
magnetized in the N pole. Then, in the yoke 61, the S pole side of the drive magnet 62 is
magnetized to the S pole.
[0006]
The top plate 63 is formed in an annular shape having a central hole 63 a of magnetic material,
and the center pole 64 is inserted into the central hole 63 a and provided on the drive magnet
62. The top plate 63 is magnetized such that the N pole side of the drive magnet 62 is an N pole.
[0007]
Further, by inserting the center pole 64 into the center hole 63 a of the top plate 63, a magnetic
gap G is formed between the center pole 64 and the outer peripheral portion of the center pole
64. Then, the base end side of the voice coil bobbin 75 of the voice coil bobbin 75 of the
vibration system 70 described later is inserted into the magnetic gap G.
[0008]
A cancel magnet 65 is provided on the back side of the yoke 61 to prevent the magnetic flux of
the drive magnet 62 from leaking to the outside of the magnetic circuit unit 60. The cancel
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magnet 65 is formed in an annular shape having a central hole 65 a and is provided on the back
side of the yoke 61. In the cancel magnet 65, the yoke 61 side is magnetized to the S pole, and
the back side is magnetized to the N pole.
[0009]
Further, in the speaker device 51, a shield cover 53 is provided so as to cover the magnetic
circuit unit 60 in order to further prevent the magnetic flux from leaking from the magnetic
circuit unit 60 to the outside. The shield cover 53 is formed of a magnetic material in a
substantially bottomed cylindrical shape, is attached to the back side of the cancel magnet 65,
and is magnetized to an N pole.
[0010]
Therefore, in the speaker device 51, the leakage flux leaking to the outside is reduced, and the
leakage flux leaking to the outside of the speaker box is reduced even when mounted in a small
speaker box not shown.
[0011]
Further, in the speaker device 51, the shield cover 53 and the top plate 63 are magnetized in the
same polarity, so that a short circuit of the magnetic flux from the top plate 63 to the shield
cover 53 is avoided. Leakage flux can be reduced without reducing strength.
[0012]
The vibration system 70 includes a substantially conical diaphragm 71 having a through hole 71
a at the center, a dome-shaped cap 72 provided on the diaphragm 71 so as to close the through
hole 71 a, and a diaphragm 71. A voice coil bobbin 75 having a cylindrical shape in which a tip
end side is connected to the through hole 71a of the diaphragm 71 and a voice coil 74 is
disposed on the base end side, a voice coil bobbin 75 And a damper 76 disposed between the
frames 52.
[0013]
The frame 52 is formed of a metal material in a substantially cylindrical shape whose diameter
increases from the rear end side toward the front end side.
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A holding portion 52a for holding the vibration system 70 is formed on the front end side of the
frame 52, and an outer peripheral portion of an edge 73 of the vibration system 70 is fixed to the
holding portion 52a via an annular gasket 54. ing.
Further, the frame 52 is provided with a connecting portion 56 electrically connected to the
voice coil 74 via the tinsel wire 55 at the outer peripheral portion.
[0014]
In the speaker device 51 configured as described above, when a current is supplied to the voice
coil 74 inserted into the magnetic gap G, an electromagnetic force acts on the voice coil 74, and
the voice coil bobbin 75 is in the magnetic gap G. Move up and down.
Then, with the movement of the voice coil bobbin 75, the diaphragm 71 vibrates.
[0015]
By the way, the speaker device 51 of the magnetic shield type as described above includes a
cancel magnet 65 which is magnetized in the opposite direction to the drive magnet 62, and a
shield cover 53 which covers the magnetic circuit portion 60. Leakage of the magnetic flux to the
outside of the speaker device 51 is sufficiently prevented.
[0016]
However, this speaker device 51 is provided with the cancel magnet 65 on the back side of the
yoke 61 as a means for preventing the leakage of the magnetic flux of the magnetic circuit unit
60 and the shield cover 53 so as to cover the magnetic circuit unit 60. As a result, the structure
becomes complicated and the assembly operation becomes complicated.
[0017]
Therefore, a speaker device has been proposed in which the shield cover 53 is directly attached
to the back side of the yoke 61 without providing the cancel magnet 65, and magnetic shielding
is performed only by the shield cover 53.
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[0018]
In this speaker device, since the shield cover 53 is directly attached to the back side of the yoke
61, it is magnetized in the same polarity as the yoke 61. Therefore, the shield cover 53 has a
polarity opposite to that of the top plate 63. It is magnetized.
As a result, the magnetic flux flowing from the top plate 63 is short-circuited to the shield cover
53, resulting in a problem that the magnetic strength is reduced.
[0019]
Therefore, it is an object of the present invention to propose a speaker device that has a simple
configuration and is easy to assemble, and that does not reduce the magnetic strength.
[0020]
In order to achieve the above-mentioned object, the speaker device according to the present
invention has the inner peripheral surface of the substantially bottomed cylindrical shield cover
attached to the bottom surface of the yoke and the outer periphery of the driving magnet. The
minimum separation distance from the surface is made larger than the thickness of the drive
magnet, and means is provided between the yoke and the shield cover to make the both fit
relative to each other.
[0021]
In this speaker device, since the minimum separation distance between the inner surface of the
peripheral wall of the shield cover and the outer peripheral surface of the drive magnet is larger
than the thickness of the drive magnet, the magnetic flux from the top plate may be shorted to
the shield cover. It is prevented.
[0022]
Further, since the speaker device is provided with means for relatively fitting the yoke and the
shield cover between the yoke and the shield cover, positioning of the shield cover with respect
to the yoke is facilitated.
[0023]
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Further, in the speaker device according to the present invention, in order to achieve the abovedescribed object, a first magnet having magnetic force opposite to each other and the inner
surface of a peripheral wall of a substantially bottomed cylindrical shield cover attached to the
bottom of the yoke. Between the yoke and the shield cover, such that the minimum separation
distance between the second magnet and the outer peripheral surface of the support member to
which the base end side is attached is larger than the thickness of the first magnet; A means is
provided to make the two fit relative to each other.
[0024]
In this speaker device, since the minimum separation distance between the inner surface of the
peripheral wall of the shield cover and the outer peripheral surface of the support member is
larger than the thickness of the first magnet, the magnetic flux from the top plate may be shorted
to the shield cover It is prevented.
[0025]
Further, since the speaker device is provided with means for relatively fitting the yoke and the
shield cover between the yoke and the shield cover, positioning of the shield cover with respect
to the yoke is facilitated.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings.
[0027]
First Embodiment As shown in FIGS. 1 and 2, the speaker device 1 according to the present
invention includes a vibration system 20 generating sound, a magnetic circuit unit 10 driving the
vibration system 20, and vibration. A frame 2 for supporting the system 20 and a shield cover 3
for preventing the leakage of magnetic flux from the magnetic circuit unit 10 are provided.
[0028]
The magnetic circuit unit 10 is disposed on the back side of the speaker device 1 and includes a
yoke 11 formed of a magnetic material.
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The yoke 11 has a cylindrical center pole 13 protruding from a central portion of a flat plate
portion 12 formed in a disk shape.
[0029]
A driving magnet 14 is disposed on the flat plate portion 12 of the yoke 11.
The driving magnet 14 is formed in an annular shape having a central hole 14a, and the center
pole 13 of the yoke 11 is inserted into the central hole 14a.
A step 12a is annularly formed at the center of the flat plate 12 of the yoke 11 so as to surround
the outer periphery on the base end side of the center pole 13. The step 12a is a center of the
drive magnet 14. The drive magnet 14 is positioned by fitting the hole 14a.
[0030]
A top plate 15 which constitutes a magnetic gap G between the drive magnet 14 and the center
pole 13 of the yoke 11 is disposed on the drive magnet 14.
The top plate 15 is formed in an annular shape having a central hole 15a of a magnetic material,
and the center pole 13 of the yoke 11 is inserted into the central hole 15a, whereby a magnetic
gap G is formed between the center plate 13 and the center pole. Configured.
[0031]
Here, for example, the magnet 14 is magnetized such that the yoke 11 side is S pole and the top
plate 15 side is N pole.
The yoke 11 is magnetized to the S pole, and the top plate 15 is magnetized to the N pole.
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[0032]
A shield cover 3 is attached to the bottom of the flat plate portion 12 of the yoke 11 to prevent
the magnetic flux from leaking from the magnetic circuit unit 10 to the outside.
The shield cover 3 is formed of a magnetic material in a cylindrical shape with a bottom, the
bottom portion is attached to the bottom surface of the flat plate portion 12 of the yoke 11, and
the peripheral wall is disposed to cover the outer peripheral side of the magnetic circuit portion
10. .
The shield cover 3 is magnetized with the same magnetic pole as the yoke 11, that is, the
magnetic pole opposite to the top plate 15.
[0033]
In the speaker device 1, the shield cover 3 covers the magnetic circuit unit 10 as described
above, so that the magnetic flux of the magnetic circuit unit 10 is prevented from leaking to the
outside.
[0034]
By the way, in the speaker device 1, since the shield cover 3 is magnetized in the magnetic pole
opposite to the top plate 15, the minimum separation distance w1 between the inner surface of
the peripheral wall of the shield cover 3 and the outer peripheral surface of the drive magnet 14
is for driving If the thickness is smaller than the thickness t 1 of the magnet 14, the magnetic
flux directed from the top plate 15 to the flat plate portion 12 of the yoke 11 disposed across the
drive magnet 14 is closer to the shield cover 3 than the flat portion 12 of the yoke 11. It will
short circuit.
Therefore, in the speaker device 1, when the shield cover 3 is attached to the bottom surface of
the flat plate portion 12 of the yoke 11, the minimum separation distance w1 between the inner
surface of the peripheral wall of the shield cover 3 and the outer peripheral surface of the drive
magnet 14 is driven. The inner diameter of the shield cover 3 is set to be larger than the
thickness t1 of the magnet.
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The speaker device 1 is positioned such that the central portion of the bottom of the shield cover
3 coincides with the central portion of the flat plate portion 12 of the yoke 11.
[0035]
Thus, the speaker device 1 sets the minimum separation distance w1 between the inner surface
of the peripheral wall of the shield cover 3 and the outer peripheral surface of the drive magnet
14 to be larger than the thickness t1 of the drive magnet 14 to make the magnetic circuit unit 10
It is suppressed that the magnetic flux of the magnetic flux is short-circuited to the shield cover
3, and the reduction of the magnetic flux density of the magnetic circuit unit 10 is prevented.
[0036]
Further, the speaker device 1 is provided with a stepped portion 3a which forms a step in the
direction of separating from the drive magnet 14 on the outer peripheral portion of the bottom
of the shield cover 3, and the outer peripheral portion of the bottom of the shield cover 3 It is
desirable to separate from
[0037]
Thus, the speaker device 1 can further prevent the short circuit of the magnetic flux of the
magnetic circuit unit 10 by separating the outer peripheral portion of the bottom of the shield
cover 3 from the driving magnet 14.
[0038]
Further, in the speaker device 1, means for relative fitting between the shield cover 3 and the
yoke 11 is provided in order to accurately position the shield cover 3 with respect to the yoke
11.
For example, as shown in FIGS. 1 and 2, a recess 16 is formed in the center of the bottom of the
flat plate portion 12 of the yoke 11, and a protrusion 4 is formed in the center of the bottom of
the shield cover 3.
Then, by fitting the projection 4 formed on the shield cover 3 into the recess 16 formed on the
yoke 11, the central portion of the bottom of the shield cover 3 coincides with the central portion
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of the flat portion 12 of the yoke 11. It is positioned at
[0039]
In the speaker device 1, an engagement hole 17 for positioning is provided in the center of the
recess 16 formed in the flat plate portion 12 of the yoke 11, and the through hole 5 is formed in
the center of the protrusion 4 formed in the shield cover 3. The shield cover 3 may be positioned
relative to the yoke 11 by engaging a positioning pin (not shown) with the engagement hole 17
through the through hole 5.
In this case, the through hole 5 provided in the shield cover 3 also functions as a hole for
removing air when the shield cover 3 is attached to the yoke 11.
[0040]
Thus, by providing means for causing the both to be fitted relative to each other between the
shield cover 3 and the yoke 11, accurate positioning of the shield cover 3 with respect to the
yoke 11 can be easily performed. The minimum separation distance w1 between the inner
surface and the outer peripheral surface of the drive magnet 14 can be easily set.
Further, since the speaker device 1 can accurately position the shield cover 3 with respect to the
yoke 11, a short circuit of the magnetic flux from the top plate 15 to the shield cover 3 is avoided
without increasing the outer diameter of the shield cover 3 more than necessary. And can be
made smaller.
[0041]
In the speaker device 1 according to the present invention, as shown in FIG. 2, the demagnetizing
magnet 6 made of a rubber magnet or the like may be disposed on the inner surface of the
peripheral wall of the shield cover 3.
The side facing the top plate 15 is magnetized in the same magnetic pole as the top plate 15, and
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the side facing the yoke 11 is magnetized in the same magnetic pole as the yoke 11.
[0042]
As described above, the speaker device 1 is magnetically shielded in the side facing the top plate
15 on the inner peripheral wall of the shield cover 3 in the same magnetic pole as the top plate
15 and on the side facing the yoke 11 in the same magnetic pole as the yoke 11 By arranging the
magnet 6, short circuit of the magnetic flux from the top plate 15 toward the yoke 11 to the
shield cover 3 is further suppressed, and a reduction in the magnetic flux density of the magnetic
circuit portion 10 is prevented.
[0043]
A frame 2 supporting the vibration system 20 is attached on the top plate 15 by screwing or the
like.
The frame 2 is formed of a metal material in a substantially cylindrical shape whose diameter is
increased from the base end side toward the front end side.
[0044]
The vibration system 20 supported by the frame 2 is provided with a substantially conical
diaphragm 21.
The diaphragm 21 is disposed on the front side of the speaker device 1, and a through hole 21a
is formed in the center. The front side opening of the through hole 21a is closed by a domeshaped cap 22 so that dust and the like from the front side of the diaphragm 21 are prevented
from entering. Further, the diaphragm 21 is configured such that deformation in the radial
direction is prevented by closing the through hole 21 a with the cap 22.
[0045]
A flexible annular edge 25 is attached to the front outer periphery of the diaphragm 21. The
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11
edge 25 is fixed at its outer peripheral end to the holding portion 2 a formed on the front outer
periphery of the frame 2 through the annular gasket 7, and connects the diaphragm 21 to the
frame 2, The diaphragm 21 is vibratably supported.
[0046]
A voice coil bobbin 24 on which a voice coil 23 is wound around an outer peripheral surface is
attached to the back side of the diaphragm 21. The voice coil bobbin 24 is formed in a cylindrical
shape whose inner diameter is slightly larger than the outer diameter of the center pole 13 of the
yoke 11, and the base end portion projects from the diaphragm 21 toward the back side of the
speaker device 1. Thus, the tip end side is connected to the through hole 21 a of the diaphragm
21. The voice coil 23 is wound around the outer peripheral surface of the voice coil bobbin 24 on
the base end side. Both ends of the voice coil 23 are soldered and electrically connected to
connection portions 9 to which external signals provided on the outer peripheral portion of the
frame 2 are input via the tinsel wires 8.
[0047]
Further, the voice coil bobbin 24 is disposed on the outer peripheral side of the center pole 13 of
the yoke 11 so that the voice coil 23 is positioned in the magnetic gap G. The voice coil bobbin
24 is supported movably from the front side to the back side of the speaker device 1 by a
damper 26 disposed between the voice coil bobbin 24 and the frame 2.
[0048]
The damper 26 is a so-called corrugation damper, and a large number of annular uneven
portions are concentrically formed from the central hole to the outer peripheral portion. Then,
the damper 26 supports the voice coil bobbin 24 by inserting the voice coil bobbin 24 into the
center hole.
[0049]
The damper 26 allows a large displacement easily by forming an annular uneven portion
concentrically, and when the voice coil bobbin 24 is driven, the voice coil bobbin 24 is viewed
from the front side of the speaker device 1 from the back side. Support for linear vibration over
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the side.
[0050]
The assembly method of the speaker apparatus 1 comprised as mentioned above is demonstrated
below.
First, an adhesive is applied onto the flat plate portion 12 of the yoke 11, and the drive magnet
14 is fixed and attached via the adhesive. The driving magnet 14 is provided in alignment with
the central axis of the center pole 13 by inserting and positioning the stepped portion 12a
formed in the flat plate portion 12 of the yoke 11 in the central hole 14a. Then, the center pole
13 of the yoke 11 is inserted into the center hole 14 a of the drive magnet 14, and the drive
magnet 14 is disposed on the outer peripheral side of the center pole 13. The drive magnet 14 is
magnetized in a desired magnetic pole direction after the adhesive is dried and solidified.
[0051]
An adhesive is applied onto the drive magnet 14 and the top plate 15 is fixed and attached via
the adhesive. The center plate 13 of the yoke 11 is inserted into the center hole 15 a of the top
plate 15, and the top plate 15 is disposed on the outer peripheral side of the center pole 13.
Under the present circumstances, in order to make magnetic gap G formed between top plate 15
and center pole 13 of yoke 11 into a predetermined interval, the state where the gap guide jig
which is not illustrated is provided in the perimeter of center pole 13 The top plate 15 is
attached to the drive magnet 14.
[0052]
The frame 2 is mounted on the top plate 15. The frame 2 may be attached on the top plate 15 in
advance by a method such as caulking before the top plate 15 is attached to the drive magnet 14,
or the top plate 15 may be attached to the drive magnet 14. After being attached, it may be
attached on the top plate 15 by screwing or the like.
[0053]
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13
Next, the outer peripheral portion of the damper 26 is fixed to the frame 2 via an adhesive. Then,
the voice coil 23 is positioned in the magnetic gap G of the magnetic circuit unit 10 at the outer
periphery of the center pole 13 and the inner periphery of the voice coil bobbin 24 and the outer
periphery of the center pole 13 are concentrically not shown. A voice coil spacer is provided. The
voice coil 23 is attached to the outer peripheral surface on the base end side of the voice coil
bobbin 24 with the voice coil spacer provided.
[0054]
The voice coil bobbin 24 is attached to the frame 2 via the damper 26 by attaching the inner
peripheral portion of the damper 26 to the voice coil bobbin 24 via an adhesive.
[0055]
Then, after the adhesive is dried and solidified, the tinsel wire 8 connected to the voice coil 23 of
the voice coil bobbin 24 is soldered to the connection portion 9 provided on the frame 2.
[0056]
The back side inner peripheral portion of the diaphragm 21 is attached to the outer peripheral
portion on the tip end side of the voice coil bobbin 24 through an adhesive.
Further, after the voice coil spacer is removed, the cap 22 is attached to the inner peripheral
portion or the tip end portion of the voice coil bobbin 24 via an adhesive so as to close the
through hole 21a.
Then, the edge 25 is attached to the front outer periphery of the diaphragm 21. The edge 25 is
attached to the holding portion 6 formed on the front side of the frame 2 via the gasket 5.
[0057]
Finally, an adhesive is applied to the bottom surface of the flat plate portion 12 of the yoke 11,
and the shield cover 3 is attached to the bottom surface side of the flat plate portion 12 of the
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yoke. At this time, the shield cover 3 is attached to the bottom surface side of the flat plate
portion 12 of the yoke so that the projection 4 provided on the shield cover 3 is relatively fitted
in the recess 16 provided in the flat plate portion 12 of the yoke 11 Thus, the shield cover 3 can
be positioned relative to the yoke 11.
[0058]
In the speaker device 1 assembled as described above, when the drive current corresponding to
the acoustic signal is supplied to the voice coil 23, the diaphragm 21 is vibrated by the action of
the drive current and the magnetic field of the magnetic circuit unit 10. Sound reproduction is
performed.
[0059]
In the speaker device 1, the shield cover 3 directly attached to the yoke 11 covers the magnetic
circuit unit 10, so that the magnetic flux of the magnetic circuit unit 10 is prevented from leaking
to the outside. You can get
[0060]
Further, in the speaker device 1, the minimum separation distance w 1 between the inner surface
of the peripheral wall of the shield cover 3 and the outer peripheral surface of the drive magnet
14 is larger than the thickness t 1 of the drive magnet 14. It is suppressed that a magnetic flux
short-circuits to shield cover 3, and a fall of magnetic flux density of a magnetic field of magnetic
circuit part 10 is prevented.
[0061]
Furthermore, the speaker device 1 is provided with means for relatively fitting the both between
the shield cover 3 and the yoke 11 so that accurate positioning of the shield cover 3 with respect
to the yoke 11 can be easily performed. The minimum separation distance w1 between the inner
surface of the peripheral wall and the outer peripheral surface of the drive magnet 14 can be
easily set.
And since this speaker apparatus 1 can perform accurate positioning with respect to the yoke 11
of the shield cover 3, the outer diameter of the shield cover 3 can be made into the minimum
required size, and it can respond also to size reduction.
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[0062]
Second Embodiment As shown in FIG. 3, the speaker device 31 has a vibration system 20 for
generating sound, a magnetic circuit unit 40 for driving the vibration system 20, and a frame for
supporting the vibration system 20. 32 and a shield cover 33 for preventing leakage of magnetic
flux from the magnetic circuit unit 40.
[0063]
And this speaker apparatus 31 has the 1st and 2nd magnets 44 and 45 by which the magnetic
circuit part 40 was magnetized by the mutually opposite magnetic pole, and these 1st and 2nd
magnets 44 and 45 are both It is characterized in that it functions as a drive magnet and one
functions as a cancel magnet that cancels the other leakage flux.
The speaker system 31 has the same configuration as that of the first embodiment in regard to
the vibration system 20, and therefore, the vibration system 20 will be described in detail using
the same reference numerals as in the first embodiment. Omit.
[0064]
The magnetic circuit unit 40 is provided on the back side of the speaker device 31 and includes a
yoke 41 formed of a magnetic material to form a closed magnetic path.
The yoke 41 has a cylindrical center pole 43 protruding from a central portion of a flat plate
portion 42 formed in a disk shape.
[0065]
The first magnet 44 is disposed on the flat plate portion 42 of the yoke 41.
The first magnet 44 is formed in an annular shape having a central hole 44a, and the center pole
43 of the yoke 41 is inserted into the central hole 44a. Further, at the central portion of the flat
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plate portion 42 of the yoke 41, there is formed a step portion 42a which forms a step in an
annular manner so as to surround the outer periphery on the base end side of the center pole 43.
The first magnet 44 is positioned by fitting the center hole 44 a of the magnet 44.
[0066]
A first plate 46 is disposed on the first magnet 44 to form a first magnetic gap G1 with the center
pole 43 of the yoke 41. The first plate 46 is formed in an annular shape having a central hole 46
a of a magnetic material, and the center pole 43 of the yoke 41 is inserted into the central hole
46 a to form a first plate 46 between the first plate 46 and the center pole 43. Of the magnetic
gap G1. The voice coil 23 of the vibration system 20 is disposed in the first magnetic gap G1.
[0067]
The base end of the frame 32 is attached to the first plate 46 by screwing or the like. The frame
32 is formed of a metal material in a substantially cylindrical shape whose diameter is increased
from the base end side toward the front end side. The vibration system 20 is supported by the
frame 32.
[0068]
On the base end of the frame 32, a second magnet 45 is provided, which is magnetized to a
magnetic pole opposite to the first magnet 44. The second magnet 45 is formed in an annular
shape having a center hole 45a, and the center pole 43 of the yoke 41 is inserted into the center
hole 45a.
[0069]
A second plate 47, which forms a second magnetic gap G2 with the center pole 43 of the yoke
41, is disposed on the second magnet 45. The second plate 47 is formed in an annular shape
having a central hole 47a of a magnetic material, and the center pole 43 of the yoke 41 is
inserted into the central hole 47a. The magnetic gap G2 is formed. The voice coil 23 of the
vibration system 20 may be disposed not only in the first magnetic gap G1 but also in the second
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magnetic gap G2.
[0070]
For example, as shown in FIG. 3, the yoke 41 side of the first magnet 44 is magnetized in the N
pole, and the first plate 46 side is magnetized in the S pole, and the yoke 41 is associated with
this as the N pole. Is magnetized to the S pole, the first plate 46 side of the second magnet 45 is
magnetized to the S pole, and the second plate 47 side is magnetized to the N pole, and the
second plate 47 is accordingly magnetized to the N pole As a result, the magnetic circuit unit 40
is configured. At this time, the frame 32 having the base end attached to the first plate 46 is
magnetized in the same S pole as the first plate 46 and the second magnet 45.
[0071]
A shield cover 33 is attached to the bottom of the flat plate portion 42 of the yoke 41 to prevent
the magnetic flux from leaking from the magnetic circuit portion 40 to the outside. The shield
cover 33 is formed of a magnetic material in a cylindrical shape with a bottom, the bottom
surface is attached to the bottom surface of the flat plate portion 42 of the yoke 41, and the
peripheral wall is disposed to cover the outer peripheral side of the magnetic circuit portion 40 .
The shield cover 33 is magnetized to the same magnetic pole as the yoke 41, that is, the
magnetic pole opposite to the frame 32.
[0072]
In the speaker device 31, the shield cover 33 covers the magnetic circuit unit 40 as described
above, so that the magnetic flux of the magnetic circuit unit 40 is prevented from leaking to the
outside.
[0073]
By the way, in the speaker device 31, since the shield cover 33 is magnetized in the magnetic
pole opposite to the frame 32, the minimum separation distance w2 between the inner surface of
the peripheral wall of the shield cover 33 and the outer peripheral surface of the first magnet 44
is The magnetic flux directed from the first plate 46 to the flat plate portion 42 of the yoke 41
disposed across the first magnet 44 is closer than the flat plate portion 12 of the yoke 41 if the
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thickness t 1 of the magnet 44 is smaller than The shield cover 3 is shorted.
Therefore, in the speaker device 31, when the shield cover 33 is attached to the bottom surface
of the flat plate portion 42 of the yoke 41, the minimum separation distance w2 between the
inner surface of the peripheral wall of the shield cover 33 and the outer peripheral surface of the
frame 32 is first. The inner diameter of the shield cover 33 is set to be larger than the thickness t
2 of the magnet 44. The speaker device 31 is positioned so that the central portion of the bottom
surface of the shield cover 33 coincides with the central portion of the flat plate portion 42 of
the yoke 41.
[0074]
Thus, the speaker device 31 sets the minimum separation distance w2 between the inner surface
of the peripheral wall of the shield cover 33 and the outer peripheral surface of the frame 32 to
be larger than the thickness t2 of the first magnet 44. It is suppressed that a magnetic flux shortcircuits to shield cover 33, and a fall of magnetic flux density of magnetic circuit part 40 is
prevented.
[0075]
Further, in the speaker device 31, means for relative fitting between the shield cover 33 and the
yoke 41 is provided in order to accurately position the shield cover 33 with respect to the yoke
41.
For example, as shown in FIG. 3, a recess 48 is formed in the central portion of the bottom
surface of the flat plate portion 42 of the yoke 41, and a protrusion 34 is formed in the central
portion of the bottom surface of the shield cover 33. Then, by fitting the projection 34 formed on
the shield cover 33 into the recess 48 formed on the yoke 41, the central portion of the bottom
surface of the shield cover 33 matches the central portion of the flat portion 42 of the yoke 41. It
is positioned at
[0076]
In the speaker device 31, an engagement hole 49 for positioning is provided at the center of the
recess 48 formed in the flat plate portion 42 of the yoke 41, and the through hole 35 is formed
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at the center of the protrusion 34 formed in the shield cover 33. The shield cover 33 may be
positioned relative to the yoke 41 by engaging a positioning pin (not shown) with the
engagement hole 49 through the through hole 35. In this case, the through holes 35 provided in
the shield cover 33 also function as holes for performing air removal when the shield cover 33 is
attached to the yoke 41.
[0077]
Thus, by providing means for causing the both to be fitted relative to each other between the
shield cover 33 and the yoke 41, accurate positioning of the shield cover 33 with respect to the
yoke 41 can be easily performed. The minimum separation distance w2 between the inner
surface and the outer peripheral surface of the frame 32 can be easily set. Further, since the
speaker device 31 can accurately position the shield cover 33 with respect to the yoke 41, the
outer diameter of the shield cover 33 can be minimized and the size can be reduced.
[0078]
In the speaker device 31 configured as described above, when the drive current according to the
acoustic signal is supplied to the voice coil 23, the diaphragm 21 is vibrated by the action of the
drive current and the magnetic field of the magnetic circuit unit 40. , Sound reproduction is
performed.
[0079]
In the speaker device 31, the shield cover 33 directly attached to the yoke 41 covers the
magnetic circuit unit 40, so that the magnetic flux of the magnetic circuit unit 40 is prevented
from leaking to the outside. You can get
[0080]
Further, since the speaker device 31 has the minimum separation distance w2 between the inner
surface of the peripheral wall of the shield cover 33 and the outer peripheral surface of the
frame 32 larger than the thickness t of the first magnet 44, the magnetic flux of the magnetic
circuit portion 40 Is suppressed from being short-circuited to the shield cover 33, and a
reduction in the magnetic flux density of the magnetic circuit unit 40 is prevented.
[0081]
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Further, the speaker device 31 is provided with means for relatively fitting the both between the
shield cover 33 and the yoke 41 so that accurate positioning of the shield cover 33 with respect
to the yoke 41 can be easily performed. The minimum separation distance w2 between the inner
surface of the peripheral wall and the outer peripheral surface of the frame 32 can be easily set.
Further, since the speaker device 31 can accurately position the shield cover 33 with respect to
the yoke 41, the outer diameter of the shield cover 33 can be minimized and the size can be
reduced.
[0082]
According to the speaker device of the present invention, the shield cover directly attached to the
yoke prevents the leakage of the magnetic force of the magnetic circuit portion, so that the
structure is simplified and the assembly is simplified.
[0083]
Further, in this speaker device, the minimum separation distance between the inner surface of
the peripheral wall of the shield cover and the outer peripheral surface of the drive magnet or
the outer peripheral surface of the frame is greater than the thickness of the drive magnet. Can
be suppressed from shorting to the shield cover, and a decrease in the magnetic force of the
magnetic circuit portion can be prevented.
[0084]
Further, since the speaker device is provided with means for making the both fit relative to each
other between the yoke and the shield cover, positioning of the shield cover with respect to the
yoke becomes easy, and the inner peripheral wall of the shield cover and the outer peripheral
surface of the drive magnet And the minimum separation distance with can be set accurately.
[0085]
Brief description of the drawings
[0086]
1 is a longitudinal sectional view showing a speaker device according to the present invention.
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[0087]
2 is a longitudinal sectional view showing a speaker device according to the present invention.
[0088]
3 is a longitudinal sectional view showing another speaker device according to the present
invention.
[0089]
4 is a longitudinal sectional view showing a conventional speaker device.
[0090]
Explanation of sign
[0091]
Reference Signs List 1 speaker device, 2, 32 frame, 3, 33 shield cover, 10, 40 magnetic circuit
portion, 11, 41 yoke, 13, 43 center pole, 14 driving magnet, 44 first magnet, 45 second magnet
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