JPS6238100

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DESCRIPTION JPS6238100
[0001]
INDUSTRIAL FIELD OF THE INVENTION The present invention relates to a television receiver
having a cathode ray tube display, a measuring device, a magnetic recording device represented
by a floppy disk drive or a video tape recorder and the like, and a device in which the magnetism
generated by the speaker affects the performance of the device. It relates to the loudspeakers
used. Conventionally, a low leakage magnetic flux speaker of this type has a structure as shown
in FIG. 8 as shown in, for example, Japanese Utility Model Laid-Open Publication No. 56-128795.
That is, the bottom plate 2 provided with the center ball 1. Ring-shaped magnet3. The same ringshaped upper plate4. A low leakage magnetic flux magnetic circuit 7 is constituted by a magnetic
demagnetizing magnet 6 magnetized in the opposite direction to the magnet 3 and a shield cover
6 made of a ferromagnetic material such as iron directly bonded thereto with an adhesive. . As
shown in FIG. 7, the frame 8 is connected to the low leakage magnetic flux magnetic circuit 7
configured in this way, and the peripheral portion of the diaphragm 10 together with the gasket
9 is fixed to the peripheral portion of the frame 8 A voice coil 13 whose middle portion is
supported by a damper 12 is coupled to a central portion of 1 o so that the magnetic gap 11 of
the low leakage magnetic flux magnetic circuit 7 is correctly inserted. 14 was pasted and
constituted. Problems to be Solved by the Invention In recent years, a color television receiver
having a space-saving type design has become mainstream, and a television receiver having a
structure in which a speaker is attached to the side of the television body has increased. . Along
with this, it has become necessary to reduce the magnetic flux on the back of the speaker and on
the back of the magnetic circuit in order to approach the back of the speaker or the CRT. Next,
the problems of the conventional example will be described with reference to FIG. In FIG. 9, 16,
16 ° 17.18 is a representative of the magnetic path through which the magnetic flux generated
by the magnetic shielding magnet 6 passes. In the conventional low leakage magnetic flux
magnetic circuit configuration, the line of magnetic force does not pass through the cross section
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of the shield cover 6 as in 17.18 because the magnetic shielding magnet 5 and the shield cover 6
are directly surface-contact bonded with an adhesive. There are many things that take the
magnetic path that jumped out to the back. When the television cathode ray tube is positioned on
the back of the low leakage flux magnetic circuit 7, the magnetic lines of force jumping out to the
back of the low leakage flux magnetic circuit 7 change the traveling direction of electrons inside
the cathode ray tube, causing color shift or distortion in the cathode ray tube display image. Etc.
image degradation occurs. Conventionally, the material thickness of the shield cover 6 has been
increased as a method of reducing the magnetic flux emerging from the back of the magnetic
circuit, but with this method, the material cost of the shield cover 6 is high and the shield cover is
not expensive. There is a problem that it is difficult to increase the thickness of the shield cover
6, for example, a large press is required to form 6.
Therefore, the present invention provides a speaker capable of reducing the leakage flux on the
back of the magnetic circuit without increasing the thickness of the shield cover. Means for
Solving the Problem In order to solve this problem, the present invention relates to a material
other than iron, nickel and cobalt, that is, a magnetoresistive material made of a material other
than a ferromagnetic material, between the magnet for shielding and the shield cover. By
interposing, the magnetic shielding magnet and the shield cover are separated by 0.3 mm or
more. Air may be used as the magnetoresistive material referred to here, and a resin or
nonmagnetic material may be used. The use of a diamagnetic material such as FeO, Coo, MnO or
NiFe as the magnetoresistive material makes it easy to guess that a more effective effect will
appear. By this configuration, it is possible to form a magnetic resistance between the magnet for
shielding and the shield cover, and to reduce the leakage flux to the rear surface. EXAMPLES
Hereinafter, one example of the present invention will be described. FIG. 1 shows a crosssectional structure of a loudspeaker according to an embodiment of the present invention. In FIG.
1, bottom play with center ball 24) 25. ! J tang magnet 26. Low-leakage flux magnetic circuit
with a ring-shaped upper plate 27 and a nonmagnetic material 3o having a thickness of 0.3+ m
or more interposed between the magnetic shield 28 and the shield cover 29 magnetized in the
direction opposite to the magnet 26 Configure 31 The frame 32 is connected to the low leakage
magnetic flux magnetic circuit 31 configured as described above, and the peripheral portion of
the diaphragm 34 is fixed to the peripheral portion of the frame 32 together with the gasket 33.
A voice coil 37 whose middle part is supported by a damper 36 is coupled so that the magnetic
gap 35 of the magnetic flux magnetic circuit 31 is correctly inserted, and a dust gap 38 is
attached to the upper surface of the central part of the diaphragm 34 . The back side leakage flux
of the speaker configured as described above will be described with reference to FIG. FIG. 2
shows the magnetic flux of the low leakage magnetic flux magnetic circuit of the speaker in one
embodiment of the present invention. In this figure, a nonmagnetic material 30 having a
thickness of 0.3 mm or more is interposed between the magnetic shielding magnet 28 and the
shield cover 29. The nonmagnetic material 30 acts as a magnetic resistance. The magnetic flux
generated from the magnetic shield magnet 28 takes the magnetic paths 20, 21, 22 and 23.
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However, since the magnetic paths 22 and 23 have the nonmagnetic material 3o having a
thickness of 0.3 throat or more, the nonmagnetic As compared with the case where the body 30
is not provided, the magnetic flux generated by the magnetic shield magnet 28 is more
concentrated in the magnetic paths 20 and 21.
Next, the leakage flux measurement results of the present invention will be described. FIG. 3 is a
schematic view of a speaker showing the measurement position of the leakage flux. In FIG. 3, the
leakage flux was measured by moving the measurement point in the direction of the arrow 40
outward from the center of the speaker at a position 20 throats away from the bottom of the low
leakage magnetic flux magnetic circuit 39 on the back side. The specific structural dimensions of
the low-leakage flux magnetic circuit of the measurement speaker are, in FIG. Inner diameter
φ22 酊, height 8rra Magnet for demagnetization is outer diameter φ35 mm, inner diameter
φ1am + n, height 5 fields, shield cover thickness 0.6 throat, nonmagnetic material 3o with
aluminum thickness 0.8 shell Used ones. FIG. 4 is a graph showing the movement distance on the
horizontal axis and the magnetic flux density on the vertical axis as a result of measuring the
leakage flux of the speaker. In this figure, the solid line 41 represents the leakage flux in the
embodiment of the present invention, and the broken line 42 represents the leakage flux of the
conventional speaker. The conventional speaker referred to here has no nonmagnetic material
between the magnetic shielding magnet and the shield cover, and directly connects the magnetic
shielding magnet and the shield cover with an adhesive. As described above, according to the
present embodiment, by interposing the nonmagnetic material 3 ° between the magnetic
shielding magnet 28 and the shield cover 29, it is possible to reduce the leakage flux on the rear
side of the speaker. Next, another embodiment of the present invention will be described with
reference to the drawings. FIG. 5 shows a low leakage flux magnetic circuit structure of a speaker
according to another embodiment of the present invention. Bottom plate 44 with center ball 43
in FIG. Ring shaped magne) 45. 47. A magnet for demagnetization magnetized in the opposite
direction to the ring-shaped upper plate 46 ° magnet 46 serving as a master. The shield cover
48 constitutes a low leakage magnetic flux magnetic circuit, and a plurality of dowels 49 are
mounted on the lower surface of the magnetic shield magnet 47, and the shield magnet 48 and
shield cover 48 are formed by the dowels 49 of the magnetic shield magnet 47. Joined at
multiple points. The dowels 49 of the magnetic shield magnet 49 are formed by the mold shape
at the time of sintering press during the manufacturing process of the magnet, and in this
example, they are dowels with a height of 0.5 throat. Usually, the magnet used is one obtained by
polishing this dowel, but in this example, only one side was polished and the other side was used
without polishing. Next, the leakage flux on the back side of the speaker configured as described
above will be described. FIG. 6 shows the magnetic flux of this low leakage magnetic flux
magnetic circuit.
In FIG. 6, the bonding area of the dowel 49 and the shield cover 48 is much smaller than the
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bonding area of the magnetic shielding magnet and the shield cover without the dowel. For this
reason, magnetic resistance can be substantially generated between the magnetic shielding
magnet 47 and the shield cover 48. In this case, air is the magnetoresistive material. The
magnetic flux generated by the magnetic shielding magnet 47 takes the magnetic paths
57.degree. 5B, 59. 60, but since the magnetic paths 59.degree. 60 have the dowels 49, the
magnetic resistance of air enters. As compared with the case where the magnetic shielding
magnet and the shield cover are directly joined without the dowel 49, the magnetic flux
generated by the magnetic shielding magnet is more concentrated by the magnetic path 57.58.
Next, the leakage flux measurement result of the speaker configured in this way is 1 when
indicated by the one-dot chain line in FIG. As described above, according to the present invention,
the leakage magnetic flux on the rear side of the speaker can be reduced by utilizing air as the
magnetoresistive material by utilizing the dowels 49 of the magnetic shield magnet 47. Effect of
the Invention As described above, according to the present invention, by interposing a
magnetoresistive material of 0.3 mm or more between the magnetic shielding magnet and the
shield cover, it is possible to reduce the leakage flux on the rear side of the speaker, and its
practical effect There is a big one.
[0002]
Brief description of the drawings
[0003]
1 is a cross-sectional view of a speaker according to an embodiment of the present invention, FIG.
2 is a cross-sectional view showing the flow of magnetic flux of the low leakage magnetic flux
magnetic circuit, and FIG. 3 is an explanatory view showing measurement of leakage flux of the
speaker. Fig. 4 is a leakage flux characteristic diagram of the back of the speaker, Fig. 6 is a
sectional view of a low leakage magnetic flux magnetic circuit of the speaker according to
another embodiment of the present invention, and Fig. 6 is a flow of magnetic flux of the low
leakage magnetic flux circuit. 7 is a cross-sectional view of the conventional speaker, FIG. 8 is a
cross-sectional view of the low leakage magnetic flux magnetic circuit of the same speaker, and
FIG. 9 is a cross sectional view showing the flow of magnetic flux of the low leakage magnetic
flux magnetic circuit. It is.
24 ..... center ball, 25 ...... bottom freight, 26 ...... magnet, 27 ...... upper Great, 28 ...... magnetically
shielded magnet, 29
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· · · · · · · · · · · · · · · · · · · · · · non-magnetic material, 31 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
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· · · · · · · · · Diaphragm · · · · · · · · · · · · · · magnetic gap, 36 · · · bottom plate, 45 · · · · · · · · · · · · · · · · · · · ·
························································································
· · · · · · · · · · · · · · · · · · · · · · ·. ... Magnet for demagnetization, 48 ... Shield cover, 49 ... Dowel. Name of
Agent Attorney Nakao Toshio and 1 other person Fig. 3 Yu 4 Figure 重力 'Gravity IJE iit! (Mm)
Fig. 5 Fig. 8 Fig. 9
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