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JPH10322786

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPH10322786
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker device used to convert an electrical signal to sound.
[0002]
2. Description of the Related Art A conventional inductive electromagnetic speaker device
comprises a vibration system for generating sound and a magnetic circuit for driving the
vibration system.
[0003]
The vibration system includes a diaphragm having a through hole at a central portion, a domeshaped cap provided on the diaphragm so as to close the through hole, and a cylindrical shape
having one end portion in the through hole of the diaphragm. And a flexible edge supporting the
diaphragm, and a damper having flexibility and vibration absorption.
[0004]
The magnetic circuit comprises a voice coil for vibrating the vibration system, a yoke for forming
a closed magnetic path, a magnet for applying a magnetic flux to the yoke, a top plate provided
adjacent to the magnet to form a magnetic gap, and a voice. And a drive coil for driving the coil.
[0005]
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The voice coil is formed of a metal foil such as aluminum and is provided on the outer periphery
of the bobbin of the vibration system.
The voice coil is connected at both ends and electrically shorted.
Then, the voice coil is disposed in the magnetic gap.
[0006]
The yoke is formed of a magnetic material in a disk shape, and a cylindrical center pole is
provided in a protruding manner at a central portion.
The center pole is inserted into the inner periphery of the bobbin of the vibration system.
[0007]
The magnet is formed in an annular shape having a central hole, and a center pole is inserted
through the central hole and provided on the yoke.
[0008]
The top plate is formed in an annular shape having a central hole by a magnetic material, and a
center pole is inserted through the central hole and provided on the magnet.
The top plate has a magnetic gap formed between the inner periphery and the outer periphery of
the center pole.
[0009]
The driving coil is formed in an annular shape by winding a coil wire made of copper, aluminum
or the like, and is provided by being wound around the outer periphery of the tip of the center
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pole.
[0010]
In the speaker apparatus described above, when current is supplied to the drive coil which is the
primary coil, the voice coil which is the secondary coil vibrates according to the law of Fleming
left hand, and the vibration is accompanied by the vibration of the voice coil. The board vibrates
to generate sound.
[0011]
The electromagnetic induction part of the magnetic circuit mentioned above is demonstrated
with reference to FIG. 10 shown by an equivalent circuit.
In this electromagnetic induction unit, as shown in FIG. 10, the direct current resistance of the
drive coil which is the primary coil is R1, the inductance of the drive coil is L1, the direct current
resistance of the voice coil which is the secondary coil is R2, and the voice coil Assuming that the
inductance of the magnetic circuit is L2, the input impedance Zin of this magnetic circuit is
calculated by Zin = (R1 + A2R2) + j.omega. (L1-A2L2) (Equation 1).
[0012]
However, it is assumed that A2 = ω2M2 / (ω2L22 + R22), M2 = k2L1L2, and the angular
frequency is ω.
[0013]
When the frequency is high, A2 = M2 / L22 = k2L1 / L2.
Therefore, the input impedance Zin is Zin = (R1 + k2R2L1 / L2) + jωL1 (1-k2) (Equation 2)
Further, in the case of the drive coil alone, Zin = R1 + jωL1 (Equation 3)
[0014]
By the way, as apparent from the comparison of Equations 2 and 3 described above, in the high
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frequency band, when a voice coil is attached, there is a disadvantage that the inductance is
reduced by the coupling coefficient k. is there.
[0015]
Therefore, in the high frequency band, the coupling coefficient k is calculated by measuring the
input impedance of the electromagnetic induction type speaker device, calculating the inductance
from the measured value, and comparing with the inductance of the drive coil.
[0016]
When the coupling coefficient k of the drive coil and the magnet is calculated using the abovedescribed calculation method, it is about 0.4, which has a problem in that the conversion
efficiency of the electromagnetic induction type speaker device is adversely affected.
The specific resistance value of the magnet used to measure this input impedance is 144 × 10
−8 Ωm.
[0017]
The above-described speaker device will be described with reference to FIG. 11 as to the
frequency characteristic of the input impedance as viewed from the side of the drive coil which is
the primary coil.
In FIG. 11, the vertical axis indicates the input impedance, and the horizontal axis indicates the
frequency.
[0018]
Further, a line D connecting points □ shown in FIG. 11 indicates an input impedance in the case
of only the driving coil, and a line E connecting points 示 す shown in FIG. 11 is an input in the
magnetic circuit of the speaker device described above. The impedance is shown when the voice
coil is removed.
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A line F connecting points x shown in FIG. 11 indicates the input impedance in the abovedescribed magnetic circuit, which is a case where a voice coil is attached.
[0019]
As shown in FIG. 11, a drop in inductance occurs in the input impedance. That is, this magnetic
circuit has a problem that an unnecessary induced current which does not contribute to the
driving force flows in the circumferential direction of the yoke, the magnet and the top plate.
[0020]
Therefore, it is an object of the present invention to provide a speaker device capable of
improving the conversion efficiency by reliably preventing an induced current from flowing in
the circumferential direction of the magnet, the top plate, and the yoke.
[0021]
SUMMARY OF THE INVENTION In order to achieve the above object, the speaker apparatus
according to the present invention comprises a yoke, a magnet and a top plate, in the radial
direction, slits for current interruption for interrupting the current flowing in the circumferential
direction. Each is provided.
[0022]
According to the speaker device configured as described above, the conversion efficiency can be
improved by removing unnecessary induced currents that do not contribute to the driving force
of the vibration system, which flow in the radial direction of the yoke, the top plate and the
magnet, respectively. .
[0023]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A specific embodiment of the
present invention will be described below with reference to the accompanying drawings.
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As shown in FIG. 1, the speaker device 1 includes a vibration system 4 that generates sound and
a magnetic circuit 5 that drives the vibration system 4.
[0024]
As shown in FIG. 1, the vibration system 4 has a substantially conical diaphragm 11 having a
through hole at the center, and a dome-shaped cap 12 provided on the diaphragm 11 so as to
close the through hole. A cylindrical bobbin 13 having one end provided in a through hole of the
diaphragm 11, a voice coil 14 for vibrating the bobbin, and a flexible edge 15 connected to an
outer peripheral portion of the diaphragm 11; And a damper 16 for supporting the bobbin 13
and having flexibility and vibration absorption.
[0025]
As shown in FIG. 1, the voice coil 16 is formed of, for example, a metal foil such as aluminum,
and is wound around the outer periphery of the bobbin 13.
The voice coil 16 is connected at both ends and electrically shorted.
[0026]
The edge 15 and the damper 16 are displaceable in the front-rear direction which is the axial
direction of the center pole 20 of the magnetic circuit 5 described later.
The damper 16 has an elastic displacement portion in which a corrugated crease is formed and
supports the bobbin 13 movably.
[0027]
The magnetic circuit 5, which is an essential part of the present invention, comprises a yoke 17
forming a closed magnetic circuit, a magnet 18 for applying a magnetic flux to the yoke 17, and
a magnetic gap as shown in FIGS. A top plate 19 which forms a coil 22 and a drive coil 21 which
drives the voice coil 16 of the vibration system 4 are provided.
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[0028]
As shown in FIGS. 3 and 4, the yoke 17 is formed of a magnetic material in a disk shape, and a
cylindrical center pole 20 is provided in a protruding manner at a central portion.
And in this yoke 17, the slit 31 for electricity supply interruption | blocking which interrupts |
blocks the induced current which flows in the circumferential direction is provided in the radial
direction ranging over the outer peripheral part from the center of a center pole.
The center pole 20 is inserted into the inner peripheral portion of the bobbin 13 of the vibration
system 4.
[0029]
Further, although not shown, the yoke 17 is provided with a drawing hole for drawing out both
ends of the driving coil 21 to the outside of the magnetic circuit 5. Further, although not shown,
at the rear end of the yoke 17, there is provided a connecting part to which the both ends of the
driving coil 21 are connected, and a power supply source is connected to this connecting part.
[0030]
As shown in FIGS. 3 and 4, the magnet 18 is formed in an annular shape having a center hole 18
a, and the center pole 20 is inserted into the center hole 18 a and provided on the yoke 17. The
magnet 18 is provided with a slit 32 for current interruption in the radial direction for
interrupting the induced current flowing in the circumferential direction. Further, for example,
the yoke 18 side of the magnet 18 is magnetized in the N pole, and the driving coil 21 side is
magnetized in the S pole.
[0031]
The top plate 19 is formed in an annular shape having a central hole 19a of magnetic material as
shown in FIGS. 3 and 4, and the center pole 20 is inserted through the central hole 19a and
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provided on the magnet 18. . The top plate 19 is provided with a slit 33 for current interruption,
which cuts off the induced current flowing in the circumferential direction, in the radial direction.
[0032]
The top plate 19 forms a magnetic gap 22 between the inner peripheral portion of the central
hole 19 a and the outer peripheral portion of the center pole 20, and the voice coil 16 is
disposed in the magnetic gap 22.
[0033]
As shown in FIG. 1, the drive coil 21 is provided on an outer peripheral portion of a tip end
portion of the center pole 20 by winding a coil wire made of, for example, copper, aluminum or
the like.
Therefore, as shown in FIG. 1, the drive coil 21 is provided at a position facing the inner
peripheral portion of the voice coil 16.
[0034]
Further, as shown in FIG. 1, the speaker device 1 is provided with a substantially bottomed
cylindrical cover member 34 for protecting the diaphragm 11 at the outer peripheral portion of
the diaphragm 11.
[0035]
Then, in the magnetic circuit 5, the yoke 17, the magnet 18 and the top plate 19 align the
respective slits 31, 32, 33 for current interruption in order to prevent the induced current
flowing in the circumferential direction of the magnetic circuit 5. Are arranged and assembled to
match each other.
[0036]
In the speaker device 1 configured as described above, when current is supplied to the drive coil
21 that is the primary coil, the voice coil 16 that is the secondary coil vibrates according to the
law of Fleming's left hand. As the voice coil 16 vibrates, the diaphragm 11 vibrates to generate
sound.
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[0037]
The above-described speaker device 1 will be described with reference to FIG. 5 as to the
frequency characteristic of the input impedance as viewed from the side of the drive coil 21
which is the primary coil.
In FIG. 5, the vertical axis indicates the input impedance, and the horizontal axis indicates the
frequency.
[0038]
Further, a line A connecting points □ shown in FIG. 5 indicates the input impedance in the case
of only the driving coil 21 and a line B connecting points 示 す shown in FIG. 5 indicates the
magnetic circuit of the speaker device 1 described above. The input impedance at 5 is shown
when the voice coil 16 is removed.
Further, a line C connecting points x shown in FIG. 5 indicates the input impedance in the
magnetic circuit 5 described above, and is a case where the voice coil 16 is attached.
[0039]
As shown in FIG. 5, the decrease in inductance of the input impedance hardly occurs.
That is, the unnecessary induction current which does not contribute to the driving force does
not flow in the magnetic circuit 5.
[0040]
As described above, in the speaker device 1, the yoke 17, the magnet 18, and the top plate 19 in
which the slits 31, 32, 33 for current interruption are provided make the slits 31, 32, 33 for
current interruption coincide with one another on a straight line. Since the unnecessary induction
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current does not flow in the circumferential direction of the magnetic circuit 5 by being disposed,
the conversion efficiency can be improved.
[0041]
In addition, although the yoke 17, the magnet 18, and the top plate 19 which form the magnetic
circuit 5 of the speaker apparatus 1 mentioned above made the slits 31, 32 and 33 for electricity
supply interruption mutually correspond, they are provided for each electricity supply
interruption. Another magnetic circuit 35 disposed without making the slits 31, 32, 33 coincide
with each other will be described with reference to FIG. 6 and FIG.
The configuration of the magnetic circuit 35 is the same as that of the magnetic circuit 5
described above, so the same members are denoted by the same reference numerals and the
description thereof will be omitted.
[0042]
In the magnetic circuit 35, as shown in FIGS. 6 and 7, an annular insulating sheet member 36
made of an insulating material is disposed between the yoke 17 and the magnet 18. Further, in
the magnetic circuit 35, an annular insulating sheet material 37 formed of an insulating material
is disposed between the magnet 18 and the top plate 19. That is, in the magnetic circuit 35, the
insulating sheets 36 and 37 reliably prevent the induced current from flowing in the
circumferential direction of the magnetic circuit 35.
[0043]
The yokes 17, the magnets 18 and the top plate 19 of the magnetic circuit 35 are assembled in
such a manner that the slits 31, 32, 33 are not matched with each other, as shown in FIGS. ing.
[0044]
According to this magnetic circuit 35, the insulating sheet members 36 and 37 are respectively
disposed between the yoke 17 and the magnet 18 and between the magnet 18 and the top plate
19, so that the slits 31 for current conduction are interrupted. There is no need to match 32, 33
and assemble.
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[0045]
Still another magnetic circuit 45 will be described with reference to FIG. 8 and FIG.
The configuration of the magnetic circuit 45 is the same as that of the above-described magnetic
circuits 5 and 35, so the same members are denoted by the same reference numerals and the
description thereof will be omitted.
[0046]
As shown in FIGS. 8 and 9, an insulating film 46 formed of an insulating material is formed on
the magnet 18 provided in the magnetic circuit 45, and the whole is covered with the insulating
film 46.
The magnetic circuit 45 is in an insulating state between the yoke 17 and the magnet 18 and
between the magnet 18 and the top plate 19 by the insulating film 46 formed on the magnet 18,
and thus the magnetic circuit 45 is formed. It is reliably prevented that the induced current flows
in the circumferential direction of
[0047]
The yoke 17, the magnet 18 and the top plate 19 of the magnetic circuit 45 are assembled in
such a manner that the slits 31, 32, 33 are not matched with each other, as shown in FIGS. There
is.
[0048]
According to the magnetic circuit 45, since the insulating film 46 is formed on the magnet 18, it
is not necessary to assemble the slits for current conduction 31, 32, and 33 in unison.
[0049]
In the speaker device 1 according to the present invention, only the yokes 31, the magnets 18,
and the top plate 19 are provided with the slits 31, 32 and 33 for current interruption, but a
plurality of slits for current interruption may be provided if necessary. May be further provided.
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[0050]
As described above, according to the speaker device of the present invention, the slits for current
interruption are respectively provided in the radial direction of the yoke, the top plate and the
magnet, so that they are unnecessary in the circumferential direction of the magnetic circuit.
Conversion current can be improved.
[0051]
Brief description of the drawings
[0052]
1 is a partial cross-sectional view showing a speaker device according to the present invention.
[0053]
2 is a plan view showing a magnetic circuit of the speaker device.
[0054]
3 is a side view showing the magnetic circuit.
[0055]
4 is an exploded perspective view showing the magnetic circuit.
[0056]
5 is a diagram showing the frequency characteristics of the input impedance in the speaker
device.
[0057]
6 is a plan view showing another example of the magnetic circuit.
[0058]
7 is a side view showing another example of the magnetic circuit.
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[0059]
FIG. 8 is a plan view showing still another example of the magnetic circuit.
[0060]
9 is a side view showing still another example of the magnetic circuit.
[0061]
10 is a diagram showing an equivalent circuit of the electromagnetic induction portion of the
conventional speaker device.
[0062]
FIG. 11 is a diagram showing frequency characteristics of input impedance in the conventional
speaker device.
[0063]
Explanation of sign
[0064]
DESCRIPTION OF SYMBOLS 1 Speaker apparatus, 5 magnetic circuit, 17 yoke, 18 magnet, 19 top
plate, 20 center pole, 22 magnetic gap, 31, 32, 33 Slit for electric current interruption
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