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JPS5572394

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DESCRIPTION JPS5572394
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a conventional
speaker magnetic circuit, FIG. 2 is an equivalent circuit diagram of heat conduction of the
speaker, and FIG. 3 is a speaker magnetic circuit in an embodiment of the present invention. 4 is
a cross-sectional view taken along the line AA 'of FIG. 3. FIG. 5 is an equivalent circuit diagram of
heat conduction of the speaker. 7 ... Yoke, 8 ... Center pole, 9 ... Through hole, 10 ... Mcnet, 11 ...
Yoke, 12 ... Slit, 13 ... Heat dissipation plate, 14 ... Slit, 15: heat sink, 16: coil bobbin, 17: voice
coil, 18: magnetic fluid.
DETAILED DESCRIPTION OF THE INVENTION The present invention is excellent in the heat
radiation effect of the magnetic circuit, and is resistant to input, '' "" "'-"' rflncf; Ex% covhb. ・ No!
In general, in the speaker, the input resistance is determined by the heat generation of the voice
coil with respect to the input. If the thermal conductivity of the magnetic circuit is increased, the
input resistance of the speaker is improved. FIG. 1 shows a conventional speaker magnetic
circuit. In FIG. 1, 1 is a yoke having a center pole 2 integrally formed at the center of the upper
surface, 3 is an annular magnet defined on the upper surface of the yoke 1, 4 is an annular yoke
fixed on the upper surface of the magnet 3. An annular magnetic gap is formed between the
inner peripheral surface of the yoke 4 and the outer peripheral surface of the center ball 2. A coil
bobbin 5 has a voice coil 6 wound around the coil bobbin 6. The voice coil 6 is arranged in the
magnetic gearing. The coil bobbin 5 is supported by a damper (not shown), and a diaphragm (not
shown) is fixed to the upper part. In FIG. 1, when an electric signal is applied to the voice coil 6,
the voice coil 6 and the coil bobbin 5 move up and down to the body of the negative coil 3. By
applying the electric signal to the nice 3-coil 6 Joule heat is generated in the voice fill 6 and the
temperature of the voice coil 6 rises. The temperature of the voice coil 6 rises to 100 to 150 °
C. when a large input is applied, and eventually the voice coil 6 is broken. FIG. 2 shows an
equivalent circuit of heat conduction of the magnetic circuit in the prior art. In FIG. 2, Tm is a
voice coil serving as a heat source, and this heat source Tm generates heat Q6. RYA is the heat
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transfer resistance of air between the voice coil 6 and the yoke 4 + RPA is the heat transfer
resistance of air between the voice coil 6 and the center ball 2-RY, h "rp is the heat transfer
resistance of the yoke 4-center ball 2, respectively In RY, IRPA 'is the heat transfer resistance
between the respective yoke 4 and the center ball 2 and the outside air. As described above, the
heat generated by the voice coil 6 is roughly divided and dissipated to the outside air through the
two heat conduction circuits. However, in the above conventional example, the heat conduction
circuit has a large heat conduction resistance RYAl of the air layer between the voice coil 6 and
the yoke 4 and the air coil between the voice coil 6 and the cell 4 and the knee 4; The thermal
conductivity of the magnetic circuit is poor and the temperature of the voice coil rises due to the
presence of the large heat conduction resistance RPA.
The present invention eliminates the above-mentioned conventional drawbacks, and an
embodiment of the present invention will be described below with reference to FIGS. 3 and 4. In
FIGS. 3 and 4, 7 is a yoke integrally formed with the center ball 8, 9 is a through hole formed in
the center ball 8, 1o is an annular magnet fixed to the upper surface of the yoke 7, 11 Is an
annular yoke fixed to the upper surface of the magnesia 10, and an annular magnetic gap is
formed between the inner peripheral surface of the yoke 11 and the outer peripheral surface of
the center ball 8. A plurality of slits 12 are radially formed on the upper surface of the yoke 11,
and a metal heat sink 13 having a good thermal conductivity such as copper or aluminum is
fitted to the slits 12. Reference numeral 14 denotes a plurality of slits formed radially on the
upper surface of the center ball 8, and the slits 14 are made of metal, such as copper, ani-11, or
aluminum, having a good thermal conductivity. And-are fitted. One end of the heat dissipation
plate 15 protrudes into the through hole 9 of the center ball 8, 16 is a coil bobbin, 17 is a voice
coil wound around the coil bobbin 16, and the voice coil 17 is the above. It is arranged in the
magnetic gap. 18 is a magnetic fluid filled in the magnetic gap. The magnetic fluid 1B is obtained
by dispersing a ferrite powder such as ferrite in a solvent such as an ester, and the heat
conductivity is good. FIG. 5 shows an equivalent circuit of heat conduction of the magnetic circuit
of the above embodiment. In FIG. 5, FLYG is the heat transfer resistance of the magnetic fluid 18
filled between the voice coil 17 and the yoke 11, and RPQ is the same as that of the magnetic
fluid 18 filled between the voice coil 17 and the center ball 8. Heat transfer resistance-Ryys RPP
is heat transfer resistance of yoke 11 and center ball 8 respectively. "YYA, RPPA is heat transfer
resistance with outside air of each yoke 11 and center ball 8. RYCIRPC is heat release. The heat
transfer resistance RYCAlhPcA of the temperature 13 ° 16 is a heat transfer resistance to the
heat radiation fi 136− ·· −16 with the outside air. As described above, in the present invention,
since the magnetic gap is filled with the magnetic fluid whose heat conduction resistance is about
A compared to air, the heat conduction from the voice coil 17 to the yoke 11 and the center ball
B is improved. Since the heat dissipation 11ii 13115 is attached to the yoke 11 and the center
ball 8, the thermal conductivity is significantly improved. The yoke 11 and the center ball 8 are
generally made of iron, but the heat conduction resistance of the heat sink 13.16 made of steel
or aluminum is about 2 of iron.
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Further, in the present invention, the heat dissipating plate 13.16 is made to project above the
yoke 11 and the center ball 8 and is made to project into the through hole 9 circle of the center
ball 8, so that the heat dissipating effect is enhanced. Further, in the present invention, the yoke
11 and the center ball 8 are radially formed with a slippin 12.14, and the heat dissipation plate
13.15 is fitted to the slit 12.14. The heat dissipation effect 7 can be improved without disturbing
the flow of one bundle because the flux in the direction 8 passes through in the direction in
which the magnetic flux passes (r is formed ","). The present invention is as described above, and
has the advantage that the heat radiation effect can be enhanced without disturbing the magnetic
flux of the magnetic circuit, and the input resistance of the speaker can be improved.
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