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JP2001128285

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DESCRIPTION JP2001128285
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
low leakage flux speaker.
[0002]
2. Description of the Related Art In a magnetic circuit of a speaker, it is ideal that the magnetic
flux generated from the magnet is all collected in the magnetic gap where the voice coil is
originally installed. However, in a normal magnetic circuit, a leakage flux is generated. I will.
Therefore, when the speaker is used in proximity to a video apparatus such as a television
receiver, the magnetic flux leaked from the speaker may cause disturbance of the image.
Therefore, a speaker with low leakage flux is required for a speaker used in proximity to a
television receiver. Conventionally, as low-leakage flux speakers, in addition to the main magnet,
a cancel magnet is installed, and the magnetic circuit and cancel magnet are surrounded by a
shield cover, so that low-leakage flux speakers that reduce leakage flux are particularly close to
visual equipment. Used as a speaker to install.
[0003]
SUMMARY OF THE INVENTION In the conventional low-leakage flux type speaker, the reduction
of the leakage flux to the outside of the speaker is insufficient. In particular, the reduction of the
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leakage flux from the frame end and the leakage flux in the side direction of the speaker is
insufficient. In addition, if the magnetic flux of the main magnet is reduced in order to reduce the
leakage flux, there is a problem that the performance of the speaker is degraded.
[0004]
The present invention has been made to solve the above-described conventional problems, and
an object of the present invention is to provide a low leakage flux type speaker that reduces the
leakage flux to the outside of the speaker without degrading the performance of the speaker. It is
to do.
[0005]
A speaker according to the present invention comprises a magnetic circuit having a center pole, a
front plate, a back plate, and a main magnet disposed between the front plate and the back plate.
The first cancel magnet, which is magnetized in reverse polarity to the main magnet and installed
on the back side of the back plate, and a shield cover installed so as to surround the magnetic
circuit and the first cancel magnet. A second cancel magnet, which is magnetized in the reverse
polarity to the main magnet, is provided on the back side of the shield cover.
[0006]
In a preferred embodiment, the magnetic flux density of the second cancel magnet is smaller
than the magnetic flux density of the main magnet and the magnetic flux density of the first
cancel magnet.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present
invention will be specifically described below, but the present invention is not limited to these
embodiments.
[0008]
FIG. 1 is a cross-sectional view of a low leakage flux speaker according to a preferred
embodiment of the present invention.
The speaker 16 includes a diaphragm 1, a dust cap 2, a voice coil 3, a damper 4, a frame 5, an
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edge 6, and a magnetic circuit 7.
The magnetic circuit 7 has a center pole 8, a front plate 9, a back plate 10, and a ring-shaped
main magnet 11 disposed between the front plate 9 and the back plate 10.
A gap formed between the center pole 8 and the front plate 9 defines a magnetic gap 12.
One end of the voice coil 3 is disposed in the magnetic gap 12.
[0009]
A ring-shaped first cancel magnet 13 is installed on the back plate 10 on the opposite side to the
surface on which the main magnet 11 is installed. The first cancel magnet 13 is magnetized in
the opposite polarity to the main magnet 11. That is, the main magnet 11 and the first cancel
magnet 13 are disposed such that the same magnetic poles face each other via the back plate 10.
By installing the first cancel magnet 13, the leakage flux generated from the main magnet 11 is
canceled by the magnetic flux generated from the first cancel magnet 13. Therefore, the leakage
flux will be reduced.
[0010]
The magnetic circuit 7 and the first cancel magnet 13 are surrounded by a shield cover 14
formed of a magnetic material. By installing the shield cover 14, leakage of the leakage flux to
the outside of the speaker 16 can be reduced.
[0011]
The second cancel magnet 15 is disposed on the opposite side of the surface of the shield cover
14 to which the first cancel magnet 13 is in proximity. The second cancel magnet 15 is
magnetized in reverse polarity to the main magnet 11. That is, the second cancel magnet 15 is
magnetized to the same polarity as the first cancel magnet 13. Therefore, the first cancel magnet
13 and the second cancel magnet 15 are installed such that the different magnetic poles face
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each other via the shield cover 14. The shape of the second cancel magnet 15 may be any
suitable shape, but typically it is ring-shaped or cylindrical. The second cancel magnet 15 is
disposed coaxially with the main magnet 11 and the first cancel magnet 13. Preferably, the
magnetic flux density of the second cancel magnet 15 is smaller than the magnetic flux density
of the main magnet 11 and the magnetic flux density of the first cancel magnet 13. If the
magnetic flux density of the second cancel magnet 15 is larger than the magnetic flux density of
the main magnet 11 and the first cancel magnet 13, the magnetic flux from the second cancel
magnet 15 increases the leakage flux. Preferably, the magnetic flux density of the first cancel
magnet 13 is 60 to 80 gauss, and the magnetic flux density of the second cancel magnet 15 is 10
to 30 gauss, with respect to the magnetic flux density of 100 gauss of the main magnet 11. By
installing the second cancel magnet 15 on the rear surface of the shield cover 14, it is possible to
guide the leakage flux in the side direction of the speaker in the front-rear direction of the
speaker. Therefore, the leakage flux in the lateral direction of the speaker can be extremely
reduced.
[0012]
FIG. 2 is a flux distribution diagram of a magnetic flux density of 2 gauss showing a leakage flux
from the low leakage flux type speaker in the present invention. FIG. 3 is a cross-sectional view of
the low leakage magnetic flux type speaker according to the present invention installed at the top
of the television receiver, showing the distribution of the leakage flux of 2 gauss magnetic flux
density from the speaker to the television receiver. . In FIG. 3, the magnetic flux indicated by a
solid line is the leakage flux from the low leakage magnetic flux speaker according to the present
invention. The leakage flux from the conventional low leakage flux speaker is shown by a broken
line for comparison. By installing the second cancel magnet 15 on the back of the shield cover 14
in combination with the first cancel magnet 13 and the shield cover 14, as shown in FIGS. It can
be seen that the distribution is extremely reduced. Further, the magnetic flux leaking from the
end of the frame 5 is extremely reduced. Therefore, when the speaker 16 according to the
present invention is used in proximity to a video apparatus such as a television receiver, the
leakage flux reaching the cathode ray tube of the television receiver can be reduced, and image
distortion can be extremely reduced. . Thus, the speaker of the present invention is suitably used
as a speaker used in proximity to various video devices.
[0013]
Hereinafter, the operation of the low leakage flux speaker according to the present invention will
be described. In the low leakage magnetic flux type speaker according to the present invention, a
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second cancel magnet 15 magnetized in a reverse polarity to the main magnet 11 is installed on
the back surface of the shield cover 14 surrounding the magnetic circuit 7 and the first cancel
magnet 13.
[0014]
By installing the second cancel magnet 15 on the back side of the shield cover 14 in combination
with the first cancel magnet 13 and the shield cover 14, not only the leakage flux from the
speaker 16 is reduced but also the side direction of the speaker 16 Leakage magnetic flux is
induced in the front-rear direction of the speaker 16. Therefore, when the speaker 16 is installed
close to the television receiver as shown in FIG. 3, the leakage flux in the side direction of the
speaker 16 affecting the television receiver is reduced. Although the leakage flux in the front-rear
direction of the speaker 16 is increased, it does not overlap the television receiver, so it does not
affect the television receiver. In the speaker 16 of the present invention, the second cancel
magnet 15 is installed on the back surface of the shield cover 14, but the magnetic flux from the
second cancel magnet 15 only changes the distribution of the leakage magnetic flux. Therefore,
the magnetic flux from the second cancel magnet 15 does not affect the television receiver.
[0015]
Further, by installing the second cancel magnet 15 on the back side of the shield cover 14, the
leakage flux leaking from the end of the frame 5 to the outside of the speaker 16 through the
shield cover 14 and the frame 5 which are magnetic bodies is extremely Reduced.
[0016]
As described above, the speaker 16 in the present invention can significantly reduce the leakage
flux in the side direction of the speaker and the leakage flux from the end of the frame 5.
Therefore, when the speaker 16 in the present invention is installed close to the television
receiver, the disturbance of the image of the television receiver can be extremely reduced.
[0017]
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Further, in the speaker of the present invention, in order to reduce the leakage flux, the second
cancel magnet is installed on the back surface of the shield cover instead of reducing the
magnetic flux density of the main magnet. That is, the speaker of the present invention can
reduce the leakage flux even when using the main magnet with a large magnetic flux density.
Therefore, the leakage flux can be reduced without degrading the performance of the speaker.
[0018]
EXAMPLES Examples of the present invention will be specifically described below, but the
present invention is not limited to these examples.
[0019]
(Example 1) Leakage flux was measured by the usual method for the low leakage flux speaker
according to the present invention.
FIG. 4 shows the position at which the leakage flux is measured in XY coordinates. The
longitudinal direction of the speaker (the vibration direction of the diaphragm) was set to the X
axis, and the side direction of the speaker (the direction perpendicular to the vibration direction
of the diaphragm) was set to the Y axis. The measurement results are shown in FIG. 5 and FIG.
FIG. 5 shows the position (i.e., Y coordinate position) of the speaker in the lateral direction of the
speaker (i.e., Y coordinate position) and the leakage flux in front of the speaker (i.e., X coordinate)
15 mm (indicated by?), 25 mm (indicated by?), 35 mm (indicated by .DELTA.) Is a graph showing
the relationship with 6 shows the speaker front position (ie, X) in the speaker side direction (ie, Y
coordinate) of 25 mm (indicated by x), 35 mm (indicated by Δ), 45 mm (indicated by ▪), 55 mm
(indicated by ♦). It is a graph which shows the relationship between coordinate position) and a
leakage magnetic flux.
[0020]
Comparative Example 1 Leakage flux was measured in the same manner as in Example 1 for a
low leakage flux type speaker conventionally used. The measurement results are shown in FIG. 7
and FIG. FIG. 7 shows the position (i.e., Y coordinate position) and the leakage flux in the side
direction of the speaker at 15 mm (i.e., X coordinate) 15 mm (indicated by?), 25 mm (indicated
by?), 35 mm (indicated by?). Is a graph showing the relationship with FIG. 8 shows the speaker
front position (i.e., X) in the speaker side direction (i.e., Y coordinate) 25 mm (indicated by x), 35
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mm (indicated by?), 45 mm (indicated by?), 55 mm (indicated by?). It is a graph which shows the
relationship between coordinate position) and a leakage magnetic flux.
[0021]
As apparent from FIGS. 5 and 7, in the front direction of the speaker of the present invention, the
leakage flux from the vicinity of 0, that is, the frame end is particularly reduced. Further, as
apparent from FIGS. 6 and 8, the leakage flux in the side direction of the speaker of the present
invention is extremely reduced.
[0022]
According to the present invention, by providing the second cancel magnet having a
predetermined magnetic flux density at a predetermined position, the magnetic flux in the
longitudinal direction of the speaker is increased and the magnetic flux in the side direction of
the speaker is reduced. Become. Therefore, the speaker in the present invention can prevent the
disturbance of the image of the television receiver even when used in proximity to the video
apparatus such as the television receiver. Further, the speaker of the present invention reduces
the leakage flux without reducing the magnetic flux density of the main magnet, and therefore
does not degrade the performance of the speaker.
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