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DESCRIPTION JPH04156200

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DESCRIPTION JPH04156200
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
magnetic circuit for driving a speaker, and more particularly to a speaker magnetic circuit which
is lightweight and has a high gap magnetic flux density. (Prior Art) A speaker incorporated in an
audio system or the like converts an electrical signal from an amplifier into an acoustic signal
and outputs the acoustic to the outside. Currently, dynamic speakers that convert electrical
signals into acoustic signals by the action of magnetic flux and electromagnetic force have
become the mainstay. As such a dynamic speaker. There are cone type speakers, dome type
speakers, horn type speakers, flat type speakers and the like. FIG. 15 shows a cone type speaker
as an example of the dynamic type speaker. As shown in the figure, a cylindrical pole portion 2
and a yoke base 3 are provided in a yoke 1 of a cone type speaker. A ring-shaped plate 4 is
disposed on the yoke base 3, and a magnet 5 is held between the plate 4 and the yoke base 3. In
the magnetic gap G formed by the gap between the plate 4 and the ball portion 2, a cylindrical
voice coil 6 is disposed movably in the arrow a-b direction. A frame 7 is attached to the plate 4. A
diaphragm 9 is disposed between the edge 8 of the frame 7 and the voice coil 6. The voice coil 6
is held at a fixed position in the magnetic gap by the damper 1o. In the figure, reference numeral
11 denotes a terminal, and reference numeral 12 denotes a lead. Then, when the voice coil 6
moves in the direction of the arrow a or b by the action of the magnetic flux from the magnet 5
and the electromagnetic force from the voice coil 6, the diaphragm 9 vibrates, whereby the
sound is radiated to the outside. By the way, in the magnetic circuit in the above-mentioned
conventional cone-shaped speaker, for example, as shown in FIG. 16, the sectional shapes of the
yoke 1, the magnet 5 and the plate 4 are respectively rectangular. It is assumed. For this reason,
the efficiency of the magnetic flux φD to the magnetic gap G, which should be originally
required, is reduced by the generation of the leakage fluxes φA, φB and φC. Further, although
the outer peripheral portion of the magnet 5 acts as a magnetic guard for the va leakage fluxes
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φA and φB, the contribution of the upper and lower corner portions is small. That is, the lines of
magnetic force from the magnet 5 pass through the inside of the yoke 1, the plate 4 and the
magnet 5. At this time, the leakage fluxes .phi.A, .phi.B and .phi.C spreading to the outer
periphery of the yoke 1, the plate 4 and the magnet 5 are considered to be large in magnetic flux
density.
For this reason, the efficiency of the magnetic flux φD to the magnetic gap, which should be
originally required, is lowered by the generation of the leakage fluxes φA, φB and φC, resulting
in a reduction of the conversion efficiency. In order to prevent such a reduction in conversion
efficiency, for example, as shown in FIG. 17, a magnetic circuit in which a yoke base 3 is provided
with a teno (13) is disclosed in Japanese Utility Model Application Publication 46-8272.
However, in such a magnetic circuit, although the leakage magnetic fluxes φA and φB are
reduced by providing the yoke base 3 with the taper 13, the conversion efficiency of the
magnetic flux φD to the magnetic gap which should be originally required is enhanced. There is
a limit to Furthermore, since the shape is simply provided with the taper 13, there is a limit to
the weight reduction and cost reduction of the magnetic circuit. That is, in spite of the provision
of the taper 13 in the yoke base 3, the leakage magnetic flux φB is still generated from the outer
peripheral edge portions of the yoke base 3 and the plate 4. Although it is possible to achieve
some weight reduction and cost reduction by adjusting the taper angle of the taper 13,
considering the distribution state of the magnetic flux density inside the iron material, the
magnetic flux density is still small. This is also because a portion, that is, a useless portion
remains, and it is not possible to obtain an optimum shape in light of weight reduction and cost
reduction. Incidentally, regardless of the magnetic circuit shown in FIGS. 16 and 17, in the other
magnetic circuits, there is also a magnetic circuit in which a hollow portion is provided along the
axial direction of the ball portion 2. This hollow portion is, for example, in the case of a coaxial
type composite speaker, a bolt 6 for coaxially attaching another speaker. In addition, in the case
of a large diameter speaker, it is a vent for improving the movement of the diaphragm. As
described above, in the case where the hollow portion is provided along the axial direction of the
ball portion 2, the weight is reduced by the hollow portion. However, the contribution of weight
reduction due to the hollow portion is insufficient in practice. Therefore, due to such limitations,
particularly in the case of a small-sized car-mounted speaker, the improvement of the sound
quality, the reduction in weight and the reduction in cost will be hindered. The present invention
has been made in view of such circumstances, and it is an object of the present invention to
provide a speaker magnetic circuit which can improve sound quality, reduce weight and reduce
cost. (Means for Solving the Problems) In order to achieve the above object, according to the
present invention, there is provided a speaker magnetic circuit in which a magnet is sandwiched
between a yoke base and a plate. The apparatus is characterized in that a taper having an
inwardly curved shape is provided such that the thickness of
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(Operation) In the speaker magnetic circuit of the present invention, the outer periphery of the
yoke base is provided with a tapered shape which is curved inward so that the thickness of the
outer periphery is reduced at least at the yoke base. Since it is possible to prevent the leakage
flux generated from the part as much as possible, the magnetic flux density of the gap can be
increased. Further, at least the thickness of the yoke base which contributes to weight reduction
of the magnetic circuit, for example, to the yoke base of the conventional magnetic circuit shown
in FIG. It becomes thinner than it. As a result, weight reduction of the magnetic circuit can be
achieved, and cost reduction can be achieved simultaneously. (Embodiment) The details of an
embodiment of the present invention will be described below with reference to the drawings. FIG.
1 shows one embodiment of the speaker magnetic circuit of the present invention. As shown in
the figure, the yoke 15 of the magnetic circuit is provided with a cylindrical ball portion 16 and a
yoke base 17. A ring-shaped plate 18 is disposed on the yoke base 17, and a magnet 19 is held
between the plate 18 and the yoke base 17. Here, on the yoke base 17 and the plate 18, tapers
17a and l8a are respectively formed so that the thickness of the outer peripheral edge portions
thereof becomes thin. Each of the tapers 17 a and 18 a is curved inward of the yoke base 17. In
the magnetic gap formed by the gap between the plate 18 and the ball portion 16, a cylindrical
voice coil (not shown) is disposed movably in the vertical direction. In the magnetic circuit of
such a configuration, the taper 17a. The thickness of the outer peripheral edge portion of each of
the yoke base 17 and the plate 18 is reduced by 18 a, so that the occurrence of the leakage flux
φB in the conventional magnetic circuit can be prevented. However, since the thickness of the
outer peripheral edge of each yoke base 17 and plate 18 is limited by the processing accuracy or
the like, some leakage flux φB is generated. ここで、l! An ideal shape of the magnetic circuit
of FIG. 1 is, for example, as shown in FIG. That is, the thickness of the outer peripheral edge of
each yoke base 17 and plate 18 is reduced to such an extent that the tip has an acute angle.
Here, the action of each of the tapers 17a and 18a will be described with reference to FIG. First,
as shown in the figure, the outer diameter of the magnet 19 is XI, the inner diameter is I2, and
the diameter of the ball portion 16 is I3.
When the magnetic flux density inside the magnet 19 is Bm, the flange thickness t of the yoke
base 17 at which the internal magnetic flux density Bi of the yoke 15 is constant is determined.
Here, the leakages φA and φB at the outer peripheral portion of the magnet 19 do not exist, and
all the magnetic flux inside thereof flows into the yoke 15. (2) In the case of x2 ≦ X ≦ X +, the
magnetic flux existing between X − X + is φm (X) Near C (XI2-X ′ ′) Bm. On the other hand,
the magnetic flux inside the flange of the yoke 15 is φ1 (x) = 2π · Xt-Bi, and from φm = φi, x
(I12−I2) Bm = 2πΦXt−B1- °, t (x) = (X + 2 I 2) B m / (2 x-Bi) x 3 X X X X 2, the magnetic flux
existing between x-x 1 is m m (x) = π (XI "-X 22) B m. On the other hand, the magnetic flux
inside the flange of the yoke 15 is φm (x) = 2π x t-Bi t (x) = (x + 2 X 22) B m / (2 x-Bi) Then, the
inclination at X "X t If it finds | requires, the conditions called dt (x) / dx = Bm / (2Bi) * (-X12 /
x2-1) dt (x) / dt (x = X +) =-Bm / Bi will be obtained. Considering this condition, t (x) = (cl / x)-c2 x
(cl) when x2 X X 1 x1. c2 is a constant), and the outer shape of the yoke base 17 is indented
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inward. In the case of X3 ≦ X ≦ x2, t (x) = c 3 / x (c 3 is a constant), and again, the shape of the
lower color of the yoke base 17 is curved inward. Note that this value is obtained as that without
the leakage flux φA. Therefore, in an actual heavy air circuit, part of the magnetic flux does not
pass through the ball portion 16 where the leakage magnetic flux φA exists. For this reason,
although the rate of increase of the brim thickness is smaller than this expression, the condition
that the shape of the lower surface of the yoke base 17 is inscribed is not changed. This can be
confirmed by numerical calculation such as finite element method. Note that the above
considerations also apply to the shape of the plate 18, and the taper 18a is curved inward. FIG. 4
is a magnetic field line distribution diagram obtained by simulating magnetic field lines
generated in the magnetic circuit of the ideal shape in FIG. 1 As can be understood from this
distribution map, magnetic lines of force g1 emitted from the N pole of the magnet 19 are
concentrated at the outer peripheral edge of the plate 18 and are guided to the magnetic gap G
as a magnetic flux g2 passing through the inside of the plate 18.
The magnetic line of force g3 representing the magnetic gap G is introduced into the yoke 15
from the end face of the yoke 15 on the magnetic gear tube G side, and is led to the 'S pole side
of the magnet 19 as a magnetic line g4. At this time, the magnetic lines of force g1 in the magnet
19 have substantially the same directivity as shown by the arrows. Further, the level of the
magnetic flux density is also very high distribution in the magnetic gap G, as shown by equal
magnetic flux density lines L1 to L3 □. On the other hand, the leakage fluxes φ1 and φ2
spreading to the outside of the magnet 19, the plate 18 and the yoke 15 have a very low
magnetic flux density. As a result, the magnetic flux φ passing through the magnetic gap G
becomes large, and magnetic lines of force act efficiently on the voice coil and the like. On the
other hand, in the conventional magnetic circuit, as shown, for example, in FIG. 5 and FIG. 6, the
degree of concentration of magnetic lines of force at magnetic gap G due to equal magnetic flux
density lines L1 to L3 is small. Further, the leakage magnetic fields φ1 and φ2 are larger than
those of the present embodiment. That is, for example, in the magnetic circuit consisting of yoke
1, plate 4 and magnet 5 etc. having a rectangular cross section shown in FIG. 16, leakage flux
.phi.A flowing from plate 4 to yoke base 3 bypassing magnet 5 and magnetic gap This is because
the leakage flux φB flowing from the plate 4 to the ball portion 2 does not pass through G and
thus increases. Further, FIG. 7 shows the performance and weight of the magnetic circuit in this
embodiment in comparison with the conventional magnetic circuit. In the figure, Bg indicates the
magnetic flux density of the gap, φg indicates the magnetic flux in the gap, and φm indicates
the total magnetic flux in the magnet. As can be understood from the figure, in the case of Bg (T),
the difference between o and tessler is superior to that of the conventional example {circle
around (6)} which has the best characteristics. In addition, the weight and total weight of each
portion show extremely low values as compared with the conventional examples 1 and 2. FIG. 8
shows another embodiment in which the cross-sectional shape of the magnetic circuit of FIG. 1 is
changed. In the drawings described below, the same parts as those in FIG. 1 are given the same
reference numerals, and duplicate explanations are omitted. That is, in the magnetic circuit
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shown in the figure, the recess 16 a is formed on the lower side of the cylindrical ball portion 16
of the yoke 15. Such a recess 16a is relatively easy to obtain even by forging, and it is possible to
reduce the weight of the magnetic circuit although it is slight. FIG. 9 shows still another
embodiment in the case where the cross-sectional shape of the magnetic circuit of FIG. 8 is
changed, and a concave portion 16b is also formed on the upper side of the cylindrical ball
portion 16 of the yoke 15. There is.
Thus, by providing the recess 16b on the upper side in addition to the recess 16a provided on
the lower side of the ball portion 16, it becomes possible to bring about more II quantification as
compared with the magnetic circuit of FIG. FIG. 10 shows another embodiment in the case where
the cross-sectional shape of the magnetic circuit of FIG. 9 is changed. In the cylindrical pole
portion 16 of the yoke 15, a through hole 16c is formed along the axial direction. It is provided.
Thus, by providing the through holes 16c in the pole portion 16 along the axial direction, it is
possible to further reduce the weight as compared with the magnetic circuit of FIG. As described
above, in each of the embodiments described above, the yoke base and the plate are provided
with a tapered shape that is curved inward so that the thickness of the outer peripheral edge
portion is reduced. For this reason, it is possible to prevent, in particular, the leakage flux
generated from the outer peripheral edge of the yoke base as much as possible, it is possible to
increase the magnetic flux density of the gap. Further, at least the thickness of the yoke base
which contributes to weight reduction of the magnetic circuit, for example, to the yoke base of
the conventional magnetic circuit shown in FIG. It becomes thinner than it. As a result, weight
reduction of the magnetic circuit can be achieved, and cost reduction can be achieved
simultaneously. In each of the above-described embodiments, the case has been described in
which the yoke base and the plate each have a tapered shape curved inward, but the present
invention is not limited to this example and the taper may be provided only in the yoke base. . In
this case, it is possible to prevent, as much as possible, the leakage flux generated from at least
the outer peripheral edge of the yoke base. In each of the above-described embodiments,
although the case where the cross section of the magnet is rectangular has been described, the
present invention is not limited to this example. For example, as shown in FIG. For example, as
shown in FIG. 12, the corner may be cut. As described above, by setting the cross-sectional shape
of the magnet to a curved shape or a cut shape, weight reduction of the magnetic circuit can be
further promoted. In addition, since the cost of the expensive magnetic material can be reduced,
cost reduction of the magnetic circuit can be promoted at the same time. Furthermore, since the
magnetic flux density inside the magnet is made more uniform, it is possible to suppress the local
occurrence of low temperature demagnetization, so the magnetic flux density of the gap can be
further increased. Incidentally, the cross section of the ideal magnetic circuit in FIGS. 11 and 12
has, for example, the shape shown in FIGS. 13 and 14.
In the magnetic circuits shown in FIGS. 11 and 12, only the case where the cross-sectional shape
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of the magnet is changed has been described, but not limited to this example, the cross-sectional
shapes of the pole portions are shown in FIGS. As shown, a recess or a through hole may be
provided together. In this case, weight reduction and cost reduction of the magnetic circuit can
be achieved simultaneously. In addition, only the yoke base may be provided with the taper, and
in this case, it is possible to prevent, as much as possible, the leakage magnetic flux generated
from at least the outer peripheral edge of the yoke base as described above. (Effects of the
Invention) As described above, according to the magnetic circuit of the present invention, at least
the yoke base is provided with a tapered shape which is curved inward so that the thickness of
the outer portion a becomes thin. Possible to prevent the leakage flux generated from the outer
peripheral edge of the yoke base as much as possible. Because of this, the magnetic flux density
of the gap can be increased. Further, at least the thickness of the yoke base which contributes to
weight reduction of the magnetic circuit, for example, to the yoke base of the conventional
magnetic circuit shown in FIG. It becomes thinner than it. As a result, weight reduction of the
magnetic circuit can be achieved, and cost reduction can be achieved simultaneously.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view showing one embodiment of the speaker magnetic circuit of the
present invention, FIG. 2 is a cross-sectional view showing its ideal shape, and FIG. 3 is a result of
each taper in the ideal cross-sectional shape of FIG. 4 is a cross-sectional view for explaining the
action, FIG. 4 shows a distribution of magnetic lines of force simulating magnetic lines of force
generated in the magnetic circuit of the ideal shape in FIG. 2, FIG. 5 and FIG. FIG. 7 is a diagram
showing distribution of magnetic field lines in which the generated magnetic field lines are
simulated, FIG. 7 is a view comparing performance and weight in the magnetic circuit of FIG. 1
with a conventional magnetic circuit, and FIG. 10 is a sectional view showing another
embodiment in the case of changing the sectional shape of the pole portion, FIG. 9 is a sectional
view showing still another embodiment in the case of changing the sectional shape of the pole
portion of the magnetic circuit, FIG. Other than the case of changing the cross-sectional shape of
the pole part of the magnetic circuit FIG. 11 is a cross-sectional view showing another
embodiment in the case of changing the cross-sectional shape of the magnet of FIG. 1, and FIG.
12 is still another embodiment in the case of changing the cross-sectional shape of the magnet.
13 and 14 are sectional views showing the ideal shape of the magnetic circuit of FIGS. 11 and 12,
and FIG. 15 is a cone type speaker as an example of a conventional dynamic type speaker. Cross
sections shown in FIGS. 16 and 17 are cross sections showing the main parts.
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DESCRIPTION OF SYMBOLS 15 ... Yoke 16, 16 ... pole part, 16a, 16b ... recessed part, 16c ...
penetration hole, 17a, 18a ... taper, 17 ... yoke base, 18 ... plate , 9 ... magnet. Patent Assignee
Pioneer Co., Ltd. Agent Patent Attorney 心 淳 淳 弁 弁 倉 倉 11 11 11 11 11 11 11 14 図 14
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