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Oct. 4 i- □ 3rd Umezu 3rd, patent applicant Tokyo part for district Kitashin 6-chome 7th 35th
(218) N · knee Co., Ltd. representative Akio Morita [phase] Japan Patent Office published patent
bulletin ■ Japanese Patent Application Laid-Open No. 52446270, published in Japan. (1977) 4
° 7 Internal Code No. 644555, Specification 1, Title of Invention
Internal magnetic speaker
3. Detailed Description of the Invention The present invention relates to the improvement of the
magnetic circuit of P'3 magnet type Dinonxby force using an alnico magnet. Fig. 1 shows the rain
structure of the magnetic circuit of a known internal magnet type speaker, (υ is alnico magnet,
(2) is pole piece, (3) is plate, (4) is yoke, and (5) is I need it with a voice coil. In general, the
magnetization state of the magnetic material is represented by the strength H of the externally
applied magnetic field and the magnetic flux density B generated in the magnetic material by the
horizontal axis and the vertical axis, respectively. Is represented by As shown in FIG. 2, when the
intensity H of the external magnetic field is increased as shown in FIG. 2, the magnetic flux
density B increases in the direction of the arrow, and B is a predetermined size. When the
external magnetic field is turned to O at the point Bs, B decreases along the demagnetization
curve due to the hysteresis characteristic to become the residual magnetic flux density Br. In this
state, since the magnet (1) is magnetized, the magnetic flux density layer is further reduced than
Br due to the magnetic field produced by the magnet (1) and the resistance of the magnetic
circuit surrounding the stone (1). This point is the operating point P of the loudspeaker. When an
external magnetic field is applied in the opposite direction from this operating point P, B = O is
obtained, and the strength of the demagnetizing field at this time is referred to as the coercive
force 5. This Hc serves as a measure of the resistance to maintain the magnetic flux density B
against the demagnetizing field in the direction of reduction of the magnetic flux density Bit of
the magnet (1). FIG. 3 is an isometric circuit of the magnetic circuit of FIG. In FIGS. 3 and 41, the
flow of magnetic flux by h'Hdi stone (1) {circle over (1)} magnetomotive force 1 of magnet (1) (g:
gap magnetoresistance EndPage: 1 几 r nib V-) (3) Equivalent reluctance part generated at the
junction surface of yoke (4), pole piece and magnet (1), magnet (1) and yoke (4), etc .; equivalent
reluctance L + w of magnetic path through which magnetic flux leaking out of gap passes: The
length Lg of the magnet (1): gap length formula% formula% Next, the operating point P1, that is,
the Hd% Bd is determined by the following formula. Output:-= x Hr · Lr 殉 Lg □ ■ Bd-S −-Bt-8 L
B Bg-Sg □ ■ where Hr: strength of magnetic field of seven Hg: strength of magnetic field of gap
Bt of leakage circuit Magnetic flux density Bg: magnetic flux density of gap 5 L = 1 equilateral
cross section Sg of circuit; cross section 8 G of gap: cross section of ff 1 stone (1) from equation)
Hd + LIs-1 + Hr-Lr :, Tosulto 10 − 4 − τ where r is a coefficient of resistance of 0, where σ is a
relative permeability of the leak holding gap μ, −1 is 0, therefore, the equation of 5, 5 is a pi, □
1 m The operating point Fe of the perm magnet (1) can be obtained from the above {circle
around (1)} and equation (0).
Bd-ku vc, the magnet (1) 's given by n' (-meance p is determined, 8-yamaki-L □ n p: ': i4d8 + a ·
Lg-r, and the magnet (1) In the sense of use, an operating point p is defined at the point of BX) l
(Z) maximum product (second quadrant) in FIG. Here, when comparing the ceramic magnet
represented by Ba-Fe magnet and the cast magnet substituted for the alnico magnet as magnets
used for the speaker, as shown in FIG. Depending on the ceramic magnet, as shown by the
demagnetization mark, p! Since {circle around (v)} and {overscore (d)} 0) are large, the island has
a large-known shape of L 菖. As shown by the demagnetizing and bending woman in the case of a
几 cast magnet, p + z, Q and fi B d are large and I (d is small, and S 瓢 is a small pebble (L s has a
large 1 i shape). With such a shape of the circle)-Mosquitoes used on ceramic magnets for
mosquitoes have a magnetic circuit with an external magnet structure, and a speaker with cast
magnet for V '% as shown in Figure 1. It becomes a circle magnetic pole structure. In the 10,000
magnetic circuit, the magnetic flux generated by the first layer flowing through the voice coil (5)
flows out of the magnetic flux from the above magnet (this flux causes a demagnetizing field to
reduce the magnetic flux density Bd of the magnet (1) Become. When the dynamic magnetic field
strength -gII (dt is determined by the voice coil (5) applied to the magnet (1), the following
equation corresponding to the equation (1) holds. Hdx−Lxm = Hrt · Lr × Hg · Lg □ where Hg1:
magnetic field of the magnetic field of the gap due to the magnetomotive force of the voice coil
(5) magnetic name of the magnetic field corresponding to the Hr by “g” ) 1g 5 · LgEndPage: 2
Also Hgl-Lg = N · V just where N: Number of turns of voice coil (5) ■: Beik i straight of 4 flows so
■ Formula 5 is the alnico of Fig. 4 When the dynamic magnetic field ΔHd1 is applied at the
operating point P, the magnetic flux density of the magnet (1) decreases from Bd along the
demagnetization curve a in the direction of the arrow. It is magnetized. Next, when ΔHdr is
reduced, the magnetic flux density does not return on the original demagnetization curve fib, but
it returns along the minor hysteresis curve-、, the magnet (1) is pII sister, but ΔHdxftQ It does
not return to the operating point P, but returns to 21 points. As a result, the magnetic flux V of
magnet (1)! The i degree decreases from Bd to Bdx. Next, when the magnetic field ΔHd1 is
applied, the operating point starts from P1 and the operating point is P in the same manner as
described above. Back to (7), the magnetic flux density decreases from Bdt to Bdz.
By repeating the above operation, the magnetic flux density of the permanent magnet (1)
decreases in both directions, and as a result, the magnetic flux density Bg of the gap decreases
and the output is attenuated. In the case of the ceramic magnet, the ratio of the magnetic
permeability to the dynamic magnetic field and the reversible magnetic permeability due to
minor hysteresis time is about 1.2, and the dynamic magnetic field is applied to the two in a
substantially equal manner. Although the first operating point can be maintained, in the case of
the Alnico magnet, the above-mentioned demagnetizing action becomes large tr because the ratio
is as large as about 3.5. In order to reduce the amount of demagnetization due to this
demagnetization, the number of turns N of the voice coil (5) is reduced according to {circle over
(1)} based on the above equation (0). (3) Limit the voice coil input (increase resistance) Increase
00% L + a. ■ Make r smaller. Although it is conceivable that these borons are set by themselves
(8) to obtain the required sensitivity of the speaker, their variable range is extremely narrow. The
present invention has been developed in view of the above-mentioned problems in an internal
magnetic disk loudspeaker and is intended to limit the magnetic flux due to a dynamic magnetic
field flowing through the magnet by covering the magnetic phase with a highly conductive
substance. I'm sorry. FIG. 6 shows the first embodiment of the present invention, in which a short
ring (6) made of a highly conductive substance is provided by adhesion or the like on the aspect
of the alnico magnet (1). Copper, Al, silver or the like can be used as the short ring (6). FIG. 7
shows a second embodiment, in which the short ring (6) is provided on the road half of the
circumferential surface of the magnet (1). Is Figure 8 the third implementation? The U is shown,
and the short ring (6) is apt to be placed in the lower half of the phase of the magnet (1).
According to the configuration of FIGS. 6 to 8 described above, the magnetic flux of the dynamic
magnetic field by the voice coil (5) is consumed as the vortex 't * ii by the 4' high short ring (6), I
ask you to prevent demagnetization of the magnet (1). It is possible to make the amount of
demagnetization small without changing the design elements of items (1) to (9) described above.
(9J Next, experimental results of the present invention will be described. Test speaker 25 釧
aperture cone speaker N: 140, Lg: 1.211% Sg: 35rnxxπx5mm 8 * XLm: Xx X 30 mm Alnico
magnet (p-26) 0 Shito ring for Ii (6) t-Do not set threat. After 1 degree magnet M magnetic field
(10% 000 gauss), under normal test @ load and 5 W load, no loss of electric resistance of 4.7-was
observed immediately after T magnet. 2. Immediately after the magnetization of the magnet
(10,000 gauss), when the load was 0 W in the trough of the dog, next, demagnetization of 6.8
pruning was observed after N magnetic susceptibility.
0 Shiotoring (6) t-If provided t 3 @ 3, immediately after magnet magnetization (10,000 Gax),
when maximum load of valley entry cuff 0 W is loaded and 9 o'clock, demagnetization of 5.8-is
recognized from N magnetic direct provisional And next. As described above, the
demagnetization from immediately after the layer magnetization to the stable state of the magnet
(deduction from Br to the operating point P in FIG. 2) is referred to as “1. In the case of "+
101EndPage: 34.7 There is a second. And when the short ring (6) is not provided, "2. "There is
16.8-4.7-12.1% demagnetization like" ", but when the short ring (6) is provided, it is 5.8-4.7 -1, 1
Large one! One stone is practically negligible. Further, the effect can be further enhanced by
setting the cross-section at-large of the short ring (6). The present invention is particularly
effective when used for a bass speaker with a large amplitude of voice coil current. The present
invention is an alnico magnet for use in a vhft, internal magnet type speaker, in which at least a
part of the circumferential surface of the alnico magnet is covered with a ring-shaped conductive
material, a dynamic magnet from a voice coil It is possible to prevent the demagnetization of the
alnico magnet due to the rise without changing the initial design contents.
4. Brief description of the drawings. FIG. 1 is a diagram showing four components of a magnetic
circuit in a conventional internal magnetic speaker, FIG. 2 is a magnetization threatening diagram
of a magnetic material, and FIG. 4 is an alnico magnet and Ba- 6 to 8 are structural views of a
magnetic circuit showing the first to third embodiments of the present invention, respectively. In
the reference numerals used in the drawings, (]) is an alnico magnet, (2) is a pole piece, (3) is a
plate, (4) is a yoke, (5) is a voice coil, and (6) is a short ring. is there. Agent Masaru Tsuchiya 1
[Oh Hanashi l Tsuita Hiroshi I Matsuda Osamu EndPage: 4 notes 6. Inventors, patent applicants
and agents other than the previous period Fig. 7 Fig. 8 (2) Patent applicants (3) Agent 〒 160
Patent Office Secretary Katayama Stone Number 1, display of case Patent application No.
120141 1, the title of the invention, the name of the invention within the name of the invention,
the relationship between the person making the correction, the patent applicant 4, the agent 6,
the number 7 of the invention to be increased by the correction, the target of the correction
"EndPage: 5 (11, specification ii !: ll.11 ll. 19", "Fig. 3, Fig. 3 is an equivalent circuit diagram of
Fig. 1," and correct it. (2), page 20, line 20 "Curve diagram," corrects one complete curve
diagram, and Fig. 5 enlarges the demagnetization curve in Fig. 4 and corrects it to a nine
demagnetization curve diagram. One or more--'; lQn-EndPage: 6
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