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DESCRIPTION JPH09289699

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DESCRIPTION JPH09289699
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the
technical field of a speaker device for converting an electrical signal into sound.
[0002]
2. Description of the Related Art Conventionally, as shown in FIG. 9, a voice coil 107 mounted on
a movably supported diaphragm 105 provided with a magnetic circuit is positioned in a magnetic
gap portion 114 of the magnetic circuit. Speaker devices have been proposed. In this speaker
device, the electric signal supplied to the voice coil 107 is converted into the sound generated by
the vibration of the diaphragm 105.
[0003]
In such a speaker device, the voice coil 107 moves in the magnetic flux in the magnetic gap
portion 114 with the diaphragm 105 by supplying an electric signal, and the diaphragm 105 is
vibrated. Let The driving force for vibrating the diaphragm 105 is F, the magnetic flux density in
the magnetic gap 114 is B, the current flowing through the voice coil 107 is I, and the length of
the wire of the voice coil 107 is L. Then, is established.
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[0004]
The magnetic circuit of the speaker device has a yoke 102 which is substantially disk-shaped of
magnetic material and to which an annular drive magnet 103 is attached on the front surface. At
a central portion of the front surface of the yoke 102, a cylindrical center pole portion 101 is
provided so as to be coaxial with the drive magnet 103. On the front surface of the drive magnet
103, a disk-shaped plate 104 having a through hole at the center is attached. The through hole of
the plate 104 and the tip end side portion of the center pole portion 101 face each other to form
the magnetic gap portion 114.
[0005]
Then, a frame 108 supporting the diaphragm 105 is attached to the front surface of the plate
104, whereby a speaker device is configured. The voice coil 107 is attached to the rear surface of
the diaphragm 105 via a cylindrical bobbin 106. The voice coil 107 is located in the magnetic
gap portion 114.
[0006]
In the diaphragm 105, a through hole at a central portion to which the bobbin 106 is attached is
closed by a cap portion 112. Further, the diaphragm 105 is attached to the front end portion of
the frame 108 by a gasket 115 via the edge member 113 on the periphery side. The bobbin 106
is supported by the frame 108 via a damper 109.
[0007]
The lead wire 110 from the voice coil 107 is connected to the terminal portion 111 provided on
the frame 108.
[0008]
By the way, in the speaker apparatus as described above, particularly when the apparatus is
configured as a small-sized full-band speaker, the voice coil 107 is effective because the aperture
of the voice coil 107 is small. The length can not be increased, and the resonance sharpness Q0
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at the lowest resonance frequency can not be reduced.
If the resonance sharpness Q0 can not be reduced, sound reproduction in the low frequency
band can not be performed well.
[0009]
In addition, it is known that it is desirable that a speaker apparatus to be attached to a so-called
bass reflex type speaker box has a resonance sharpness Q0 of 0.58 when the speaker box is
sealed.
[0010]
In order to reduce the resonance sharpness Q0 in a small speaker device, it is necessary to
increase the effective length of the voice coil 107 or to increase the magnetic flux density in the
magnetic gap portion 114.
[0011]
When the effective length of the voice coil 107 is increased, the weight of the voice coil 107 is
increased, so that the reproduction characteristic of the high frequency band is deteriorated, and
the sound pressure level of the reproduction sound is lowered.
[0012]
In addition, if it is intended to improve the magnetic flux density in the magnetic gap portion
114, the weight of the magnet 103 is increased, which leads to an increase in size and weight of
the entire speaker device.
[0013]
Conventionally, as shown in FIG. 10, in order to improve the sound reproduction characteristics
in the low frequency band without lengthening the effective length of the voice coil 107 and
without enlarging the magnet 103. A speaker apparatus of the MFB (motional feedback) system
has been proposed.
[0014]
This MFB type speaker device has a portion configured in the same manner as the abovedescribed speaker device, and the coil bobbin is extended forward, and a drive coil 107a
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corresponding to the voice coil 107 on the rear end side of the coil bobbin. And the MFB
detection coil 107b is provided on the front end side of the coil bobbin.
[0015]
That is, as shown in FIG. 11, this coil bobbin has the front end portion of the rear end side bobbin
106a on which the drive coil 107a is attached to the rear end side outer peripheral portion and
the outer periphery of the MFB detection coil 107b on the front end side. The rear end portion of
the front end side bobbin 106b attached to the surface is butt-coupled to each other.
The rear end side bobbin 106a is configured in the same manner as the coil bobbin 106 of the
above-described speaker device.
And the said cap part 112 is not provided in the front side of this coil bobbin.
[0016]
The MFB speaker device has an MFB magnetic circuit portion in which the MFB detection coil
107 b is positioned in the magnetic gap portion 121.
The MFB magnetic circuit unit includes a sub-frame 117 attached to the front end of the frame
108, a sub yoke 118 attached to the rear surface of the central portion of the sub frame 117, and
an MFB attached to the rear surface of the sub yoke 118 Magnet 116 and an annular sub plate
120 attached to the rear surface of the MFB magnet 116.
A cylindrical center pole portion 119 protrudes rearward at a central portion of the rear surface
portion of the sub yoke 118, and enters a through hole in the central portion of the sub plate
120.
The inner peripheral surface of the through hole of the sub plate 120 and the outer peripheral
surface of the rear end side of the center pole 119 of the sub yoke 118 face each other to form a
magnetic gap 121.
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[0017]
That is, the MFB magnetic circuit unit has substantially the same configuration as the magnetic
circuit of the above-mentioned speaker device, and is arranged to face the magnetic circuit.
[0018]
In this MFB type speaker device, when the coil bobbin is driven with the diaphragm 105 by
supplying a drive current to the drive coil 107a, the MFB detection coil 107b is the MFB
magnetic circuit. It is moved within the magnetic gap part 121 of the part.
Then, in the MFB detection coil 107b, the moving speed of the MFB detection coil 107b, the
effective length of the MFB detection coil 107b, and the magnetic flux density in the magnetic
gap portion 121 of the MFB magnetic circuit unit are proportional. An electromotive voltage of a
different voltage is generated as a detection voltage.
[0019]
In the MFB speaker device, the resonance sharpness Q0 at the lowest resonance frequency can
be reduced by appropriately amplifying the current corresponding to the detection voltage and
feeding it back to the drive coil 107b.
[0020]
However, in such a speaker apparatus of the MFB system, although it is not necessary to increase
the size of the drive coil 107a and the magnetic circuit in which the drive coil 107a is located in
the magnetic gap portion 114, the MFB magnetic circuit Since it is necessary to provide a circuit
part and the above-mentioned MFB detection coil 107b, the system configuration of the entire
speaker apparatus is increased in size and complexity.
[0021]
Therefore, the present invention is proposed in view of the above-mentioned situation, and the
deterioration of the reproduction characteristic of the high frequency band and the deterioration
of the reproduction characteristic of the high frequency band are brought about without causing
the enlargement of the device configuration, complication and weight increase. To solve the
problem of providing a speaker device in which the resonance sharpness at the lowest resonance
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frequency is reduced and the sound reproduction in the low frequency band is favorably
performed without causing the reduction of the sound pressure level of the reproduced sound. It
is
[0022]
[Means for Solving the Problems] In order to solve the above-mentioned problems, in the speaker
device according to the present invention, a magnetic circuit having a magnetic gap portion, a
driving coil and an MFB detecting coil are attached to each other in a mutually overlapping
manner. A coil bobbin supported so as to be movable in a state where a driving coil and an MFB
detecting coil are positioned in the magnetic gap portion, and a diaphragm supported by the coil
bobbin.
[0023]
Further, according to the present invention, in the above speaker device, the drive coil is
mounted on the outer peripheral surface of the coil bobbin, and the MFB detection coil is
mounted on the outer peripheral surface of the drive coil. It is assumed to be superimposed on
the
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings.
[0025]
The speaker device according to the present invention, as shown in FIG. 1, is configured to have a
magnetic circuit and a frame 8 supported on the magnetic circuit.
[0026]
The magnetic circuit has a disk-shaped yoke 2 made of a magnetic material, and an annular
magnet 3 fixed to the front surface of the yoke 2.
The magnet 3 is magnetized so as to generate a magnetic flux in the thickness direction, that is,
so that the front surface portion and the rear surface portion become magnetic poles.
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At the center of the front surface of the yoke 2, a cylindrical center pole portion 1 is integrally
protruded.
The magnet 3 is coaxial with the center pole portion 1.
The center pole portion 1 is inserted into the central through hole of the magnet 3.
[0027]
Attached to the front surface of the magnet 3 is a top plate 4 which is formed of a magnetic
material and has a through hole at its central portion.
The tip end side portion of the center pole portion 1 is inserted into the through hole in the
central portion of the top plate 4.
[0028]
That is, when the top plate 4 is attached to the magnet 3, a gap guide is inserted between the
outer peripheral surface of the center pole portion 1 and the inner peripheral surface of the
through hole at the central portion of the top plate 4. The top plate 4 is adhered to the magnet 3
with the plate 4 positioned relative to the center pole 1.
Then, after the adhesive for bonding the top plate 4 to the magnet 3 is solidified, the top plate 4
is positioned with respect to the center pole portion 1 by removing the gap guide. It is fixed.
[0029]
The magnetic gap portion 14 is formed such that the inner circumferential surface portion of the
through hole at the central portion of the top plate 4 and the outer circumferential surface
portion of the middle portion of the center pole portion 1 face each other.
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[0030]
The frame 8 is made of a material having sufficient rigidity such as metal, and is formed in a
cylindrical shape whose front end side is expanded in a substantially conical shape, and its rear
end side portion is fixed to the front surface portion of the top plate 4 .
[0031]
A peripheral portion of the diaphragm 5 is attached to the holding portion on the front end side
of the frame 8 by a gasket 15 via an edge member 13.
The gasket 15 is formed by annularly winding a strip of paper coated with an adhesive.
[0032]
The edge member 13 is formed to have flexibility and is displaceable in the front-rear direction.
The edge member 13 is formed in an annular shape, and has a shape bulging in a cylindrical
surface shape with respect to the front side (the sound emitting direction).
The edge member 13 is formed of paper, cloth or rubber.
[0033]
The diaphragm 5 is formed in a substantially conical shape, and has a through hole at its central
portion.
The coil bobbin 6 is fitted and attached to the through hole in the central portion of the
diaphragm 5. The coil bobbin 6 is formed in a cylindrical shape, and supports the diaphragm 5 at
a front end side portion. The front end of the coil bobbin 6 is closed by a cap 12.
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[0034]
The coil bobbin 6 is desirably formed to be lightweight while having high rigidity. Therefore, it is
desirable that the coil bobbin 6 be formed by rounding a synthetic resin material such as paper
or cloth impregnated with epoxy resin, a glass-epoxy board (glass fiber material solidified with
epoxy resin), etc. into a cylindrical shape. Further, the coil bobbin 6 may be formed of a metal
plate, paper or the like.
[0035]
The drive coil 7b and the MFB (motional feedback) detection coil 7a are bonded to the outer
peripheral surface of the rear end side of the coil bobbin 6 as shown in FIGS.
[0036]
The drive coil 7b is wound and formed in a cylindrical shape, and has a lead wire.
These lead wires are soldered to the tinsel wire 10 and connected to the input terminal 11
attached to the frame 8 through the support member via the tinsel wire 10.
[0037]
The MFB detection coil 7a is wound and formed in a cylindrical shape, and is overlapped and
attached to the outer peripheral surface side of the drive coil 7b. The MFB detection coil 7a has a
lead wire. These lead wires are soldered to a tinsel wire different from the tinsel wire connected
to the drive coil 7b, and are connected to a detection voltage output terminal (not shown)
provided on the frame 8 through the tinsel wire. Ru. The MFB detection coil 7a may have a high
impedance, and in order to increase a detection voltage to be described later, the MFB detection
coil 7a is formed of a thin wire and has a large number of turns as compared with the drive coil
7b. .
[0038]
The reason why the MFB detection coil 7a is attached to the upper side of the drive coil 7b is that
attachment (winding) to the coil bobbin 6 is easy, and if the ease of attachment is not taken into
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consideration, the drive is performed. The coil 7b may be attached to the upper side of the MFB
detection coil 7a.
[0039]
The driving coil 7 b and the MFB detecting coil 7 a are located in the magnetic gap portion 14.
That is, each of the coils 7b, 7a is coaxial with the center pole portion 1, and is advanced between
the center pole portion 1 and the inner surface of the through hole in the central portion of the
top plate 4. There is.
[0040]
That is, when the coil bobbin 6 to which the drive coil 7 b and the MFB detection coil 7 a are
attached is attached to the diaphragm 5, between the outer peripheral surface of the center pole
portion 1 and the inner peripheral surface of the coil bobbin 6 With the voice coil spacer
inserted, the coil bobbin 6 is adhered to the diaphragm 5 in a state where the coil bobbin 6 is
positioned with respect to the center pole portion 1. Then, after the adhesive for bonding the coil
bobbin 6 to the diaphragm 5 is solidified, the voice coil spacer is removed so that the coil bobbin
6 is positioned with respect to the center pole portion 1, It is fixed.
[0041]
The front end side portion of the coil bobbin 6 is suspended movably in the front-rear direction
by the rear end side portion of the frame 8 via a flexible and vibration absorbing damper 9.
[0042]
The damper 9 is formed of a cloth or a material such as paper in a substantially disc shape
having a plurality of concentric bending portions (corrugation portions) serving as displacement
portions, and has a circular through hole at the central portion. ing.
The outer peripheral surface portion of the coil bobbin 6 is joined to the inner peripheral edge
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portion of the through hole at the central portion, and the outer peripheral edge portion of the
damper 9 is attached to the frame 8 to suspend the coil bobbin 6.
[0043]
In the speaker device according to the present invention configured as described above, an
electric signal is supplied as a drive current to the drive coil 7 b through the input terminal 11,
whereby the coil bobbin 6 becomes the center pole portion 1. The diaphragm 5 is vibrated to
reproduce the sound.
[0044]
In this speaker device, when the coil bobbin 6 is driven, the MFB detection coil 7a is moved
within the magnetic gap portion 14. In this MFB detection coil 7a, the moving speed of the MFB
detection coil 7a An electromotive voltage of a voltage proportional to the effective length of the
MFB detection coil 7a and the magnetic flux density in the magnetic gap portion 14 is generated
as a detection voltage.
That is, the voltage ES of the electromotive force generated in the MFB detection coil 7a has the
magnetic flux density in the magnetic gap portion 14 as B, the effective length of the MFB
detection coil 7a as L, and the moving speed of the coil bobbin 6 And let v be. If the direct
current resistance of the MFB detection coil 7a is R, then the current I flowing through the MFB
detection coil 7a is: The current I is always reverse to the drive current flowing through the drive
coil 7b. Then, the current I is output as a detection output for MFB (motional feedback) via the
detection voltage output terminal.
[0045]
The detection output for MFB (detection voltage ES) is amplified by gain β by feedback circuit
16 as shown in FIG. 5, amplified by gain A by MFB amplifier 17, and transmitted to drive coil 7b.
Be fed back. In this speaker device, control of the resonance sharpness Q0 at the lowest
resonance frequency is possible by such amplification and feedback of the detection output for
MFB, and reproduction characteristics in the low frequency band can be controlled.
[0046]
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That is, let Q00 be the resonance sharpness at the lowest resonance frequency when the motion
of MFB (motional feedback) is not performed, and Q01 be the resonance sharpness at the lowest
resonance frequency when the motion of MFB (motional feedback) is performed. In the velocity
type MFB, Q01 = Q00 / (1 + Aβ (F2 / F1)). Here, A is the gain of the MFB amplifier 17, β is the
gain of the feedback circuit 16, and F 1 is the force coefficient of the drive coil 7 b (F 1 = B · L 1
(B is the magnetic gap portion 14 Magnetic flux density L1 is the effective length of the drive coil
7b), and F2 is the force coefficient of the MFB detection coil 7a (F2 = B · L2 (L2 is the effective
length of the MFB detection coil 7a) ).
[0047]
Here, when the feedback difference D at the lowest resonance frequency f0 is defined as D = (1 +
Aβ (F2 / F1)) / Q00, Q01 = Q00 / D. This is equivalent to D times the damping factor of the
amplifier. Incidentally, in this velocity type MFB, as shown in the following [Table 1], the sound
pressure and the lowest resonance frequency f0 are invariant to the state in which the MFB is not
performed. In this velocity type MFB, as shown in FIG. 6, the resonance sharpness Q0 changes at
the lowest resonance frequency f0.
[0048]
As described above, since the velocity type MFB can reduce the resonance sharpness Q0 at the
lowest resonance frequency, it is effective in a small-sized speaker device in which it is difficult to
reduce the resonance sharpness Q0. That is, with the speed type MFB, the resonance sharpness
Q0 may be set to 0.58 and attached to a bass reflex type speaker box, and the resonance
sharpness Q0 may be set to 1.0 for a closed type speaker. It may be attached to a box.
[0049]
Then, when a circuit (CR circuit) having differential characteristics is inserted in the feedback
circuit 16, a voltage obtained by differentiating the velocity, that is, a voltage proportional to the
acceleration is fed back, and an acceleration type MFB is performed. In this acceleration type
MFB, as shown in the above [Table 1], Q01 = Q00 · √Df01 = f0 / √DD = 1 + (AβF1F2 / MMRE)
= 1 + (A11f0 / Q0) = 1 + (Aβ (F2 / F1) / Q0). Here, f01 is the lowest resonance frequency when
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performing acceleration type MFB. This is equivalent to the mass of the speaker system being
multiplied by D. Incidentally, in this acceleration type MFB, the sound pressure decreases by 20
log D (dB) as compared with the state where MFB is not performed. In this acceleration type
MFB, as shown in FIG. 7, the lowest resonance frequency f0 and the resonance sharpness Q0
change.
[0050]
When a circuit (CR circuit) having integral characteristics is inserted in the feedback circuit 16, a
voltage obtained by integrating the speed, that is, a voltage proportional to the amplitude is fed
back, and the amplitude type MFB is performed. In this amplitude type MFB, as shown in the
above [Table 1], Q01 = Q00 · √Df01 = f0 · √D. Here, f01 is the lowest resonance frequency
when the amplitude type MFB is performed. This is equivalent to multiplying the stiffness of the
vibration system of the speaker device by D. Incidentally, in this amplitude type MFB, the sound
pressure is unchanged with respect to the state where the MFB is not performed. In this
amplitude type MFB, as shown in FIG. 8, the lowest resonance frequency f0 and the resonance
sharpness Q0 change.
[0051]
As described above, in the speaker device according to the present invention, the drive coil and
the MFB detection coil located in one magnetic gap portion are attached to the coil bobbin
attached to the diaphragm. .
[0052]
Therefore, in this speaker device, the resonance sharpness at the lowest resonance frequency can
be controlled and reduced by executing the MFB (motional feedback) operation based on the
electromotive force generated in the MFB detection coil.
And in this speaker apparatus, the enlargement of the magnetic circuit by providing the said coil
for MFB detection is suppressed.
[0053]
That is, the present invention does not cause an increase in the size of the device configuration, a
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complication, or an increase in weight, and does not cause a deterioration in reproduction
characteristics of the high frequency band or a reduction in sound pressure level of reproduction
sound. It is possible to provide a speaker device in which the resonance sharpness at the lowest
resonance frequency is reduced and the sound reproduction in the low frequency band can be
performed well.
[0054]
Brief description of the drawings
[0055]
1 is a longitudinal sectional view showing the configuration of the speaker device according to
the present invention.
[0056]
2 is a perspective view showing a configuration of a coil bobbin of the above speaker device.
[0057]
3 is a longitudinal sectional view showing the configuration of the voice coil bobbin.
[0058]
4 is an enlarged longitudinal sectional view of the main part showing the configuration of the
main part of the voice coil bobbin.
[0059]
5 is a circuit diagram showing the configuration of the MFB feedback circuit.
[0060]
6 is a graph showing the sound pressure characteristics of the velocity type MFB speaker device.
[0061]
7 is a graph showing the sound pressure characteristics of the additive MFB speaker device.
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[0062]
8 is a graph showing the sound pressure characteristics in the speaker device of the amplitude
type MFB method.
[0063]
9 is a longitudinal sectional view showing the configuration of a conventional speaker device.
[0064]
10 is a longitudinal sectional view showing another example of the configuration of the
conventional speaker apparatus.
[0065]
11 is an exploded perspective view showing the configuration of the coil bobbin of the
conventional speaker device.
[0066]
Explanation of sign
[0067]
1 center pole portion 2 yoke 3 magnet 4 top plate 5 diaphragm 6 coil bobbin 7a MFB detection
coil 7b drive coil 8 frame 14 magnetic gap portion
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