JP2009033382

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DESCRIPTION JP2009033382
An object of the present invention is to provide a speaker and a speaker device capable of driving
with a large amplitude while appropriately adjusting a spring characteristic relating to driving of
a voice coil. A magnetic gap is formed between an outer yoke (11) and an inner yoke, and a
constant DC current is constantly supplied to a position control coil (24) wound around a bobbin
(21). . In the reference position, the predetermined lengths at both ends of the position control
coil 24 cross the magnetic gap, and the Lorentz forces generated at each end are
counterbalanced. When the voice coil moves in the left or right direction, the length of the
position control coil 24 crossing the magnetic gap differs at the left end and the right end, and as
a result, the vector sum of Lorentz forces acting on the position control coil 24 is the movement
of the voice coil. And the opposite direction. As a result of the above, the voice coil is stabilized at
the reference position. [Selected figure] Figure 3
Speaker and speaker device
[0001]
The present invention relates to a speaker and a speaker device.
[0002]
Conventionally, as a speaker, an electrodynamic type, an electrostatic type, a piezoelectric type,
an electromagnetic type, and the like are known.
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Among them, electrodynamic speakers (dynamic speakers) are classified into moving coil type,
ribbon type, brat Hara type, and hiil type according to the structure of the diaphragm and its
vibration source, etc. The basics are electromagnetic force Thus, the diaphragm is driven, and the
high conversion efficiency can be obtained with a relatively simple structure, which is the
mainstream of the speaker. Above all, the moving coil type accounts for the majority of the
electrodynamic speaker, including a cone speaker and a dome speaker.
[0003]
As shown in FIG. 16, a cone-shaped speaker uses a conical diaphragm (cone diaphragm C), and a
voice coil Vc generating an electromagnetic force for driving the cone diaphragm C and a
magnetic circuit Mc. A damper D for keeping the voice coil Vc in a fixed position with respect to
the gap Gp of the magnetic circuit Mc, an edge E supporting the periphery of the cone diaphragm
C connected to the tip of the voice coil Vc, and these parts It comprises a frame F to be linked.
Then, by flowing a current based on the voice waveform in the voice coil Vc in the gap of the
magnetic circuit Mc, the voice coil Vc reciprocates in the direction perpendicular to the lines of
magnetic force to drive the directly connected cone diaphragm C.
[0004]
Now, in the above-mentioned cone type speaker, the damper D and the edge E are provided as a
structure for holding the vibration center of the voice coil Vc. However, when trying to hold the
voice coil at the vibration center position with such a mechanical spring structure, the vibration
of the diaphragm C strongly depends on their mechanical characteristics, so that problems occur
such as uneven sounding at every frequency. was there. In addition, there is also a problem that
even if the amplitude of the diaphragm C is increased, a limit occurs.
[0005]
In order to solve the problems caused by the mechanical support structure described above,
techniques as described below have been proposed. Non-Patent Document 1 shows a method for
solving the above-mentioned problems by using an air damper instead of the above-described
mechanical support structure. Patent Document 1 discloses a technique of controlling a reference
position of vibration by superimposing a bias current on a drive current of an audio signal in
each coil in a double voice structure. Patent Document 2 discloses a technique in which a third
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coil is provided at a position out of the magnetic field when the voice coil is at a stationary
position, and the third coil performs plaking at the time of operation. In this technique, the
reference vibration position is controlled by a mechanical structure as usual. Guy Lemarquand
"New structure of loudspeaker", Audio Engineering Society Convention Paper 6846 Presented at
the 120th Convention, May 2006. JP-A-2001-186589 JP-A-H11-164394
[0006]
In the technique of Non-Patent Document 1, the mechanical characteristics corresponding to the
spring constant are determined by the structure of the air damper, so there is a problem that the
degree of freedom in design is limited. In addition, an air chamber having a large volume relative
to the caliber is required.
[0007]
Further, in the technique of Patent Document 1, since the coil for holding the vibration center
position and the coil for inputting the audio signal are both used, the coil is at a position other
than the vibration center position to realize the operation. In this case, the coil is out of the area
of the magnetic gap, and problems occur when the utilization efficiency of the magnetic field is
lowered. In addition, it is necessary to apply a reverse bias to two voice coils, which causes a
problem when the drive circuit becomes complicated, and realizes a plurality of coils other than
the proposed purpose (for example, to realize MFB (motion feedback) Problems such as the
difficulty of using for
[0008]
Further, in the technique of Patent Document 2, when the voice coil is at the vibration center
position, the third coil needs to be at a position deviated from the magnetic field, and in that
state, Lorentz force for realizing damperless is There was a problem that I could not get it.
[0009]
The present invention has been made in view of the above-described problems, and an object
thereof is to provide a speaker and a speaker device capable of driving with a large amplitude
while the spring characteristic related to driving of a voice coil is appropriately adjusted. .
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[0010]
A speaker according to the present invention includes a cylindrical bobbin, a support mechanism
slidably supporting the bobbin in the axial direction thereof, a magnet and a magnetic path
forming member, and a magnetic gap which is a cylindrical gap by both of them. A magnetic path
forming frame in which a magnetic field is formed in the magnetic gap, the magnetic path
forming frame penetrating the inside and the outside of the bobbin in the magnetic gap, and
control to be wound around the bobbin A coil and first and second coils wound around one end
and the other end of the bobbin with the control coil interposed therebetween, wherein the
magnetic field is reverse in one end and the other end of the control coil When a constant
current is supplied to the control coil, when the bobbin slides from a predetermined position, the
control coil is pressed against the control coil in a direction to push it back. Characterized in that
it is configured such that a force is exerted.
[0011]
In the above configuration, the control coil may be provided between magnetic gaps formed such
that the magnetic field is in the opposite direction, or may be provided so that both ends overlap
the magnetic gaps.
[0012]
A speaker device according to the present invention is characterized by including the speaker
according to any one of the above and a circuit for supplying a constant current to the control
coil.
In the above configuration, output means may be provided which amplifies the input current and
supplies the amplified input current to the first and second coils in opposite directions.
[0013]
According to the speaker and the speaker device according to the present invention, it is possible
to appropriately adjust the spring characteristic related to the driving of the voice coil and to
drive with a large amplitude.
[0014]
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The best mode for carrying out the present invention will be described below with reference to
the drawings.
(A; Configuration) (A-1: Overall Configuration) FIG. 1 is a view showing the overall configuration
of the speaker 1.
Note that FIG. 1 shows the case where the voice coil is at the stationary position (reference
position).
The speaker 1 is roughly classified into a yoke which is a housing and a voice coil which slides in
contact with the yoke.
[0015]
(A-2; Configuration of Yoke) First, the configuration of the yoke will be described with reference
to FIG.
The yoke comprises an outer yoke 11 and an inner yoke. The outer yoke 11 is made of a
magnetic material such as iron and has a cylindrical shape whose rear (left side in the drawing) is
a bottom. The inner yoke has a substantially cylindrical structure, and a holding portion 12 fixed
to the bottom surface of the outer yoke 11, a rear plate 13 adjacent to the holding portion 12,
and a magnet 14 adjacent to the rear plate 13 , And a front plate 15 adjacent to the magnet 14.
[0016]
The magnet 14 is a permanent magnet that spontaneously has magnetism even without an
external magnetic field, and has a north pole on the front side (right side in the figure) and a
south pole on the rear side (left side in the figure). The front plate 15 and the rear plate 13 are
made of paramagnetic material which is magnetized in the direction when a magnetic field is
applied, and is magnetized by the magnet 14. A substantially cylindrical air gap is formed
between the outer yoke 11 and the front plate 15, and between the outer yoke 11 and the rear
plate 13, and a magnetic field in which the magnetic flux of the magnet 14 is concentrated is
formed in the air gap. Hereinafter, the air gap is referred to as a magnetic gap.
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[0017]
Since the N pole and the S pole of the magnet 14 are arranged as described above, the direction
of the magnetic field formed in the magnetic gap is the same as that of the front plate 15 in the
magnetic gap formed by the front plate 15. In the direction of the outer yoke 11 and in the
magnetic gap formed by the rear plate 13, from the outer yoke 11 to the rear plate 13.
[0018]
A sliding portion 16 is provided on the inner side surface of the outer yoke 11.
The sliding portion 16 is provided so as to protrude from the inner side surface of the outer yoke
11 to the inner yoke side, and is provided at a predetermined distance along the circumferential
direction of the inner side surface of the outer yoke 11. That is, the sliding portions 16 are
arranged radially as viewed from the axial center of the outer yoke 11. The bobbin 21 is formed
in a cylindrical shape, and is disposed so as to share an axial center with the above-described
cylindrical gap. In this manner, the bobbins 21 fitted in the gaps between the outer yoke 11 and
the inner yoke are supported movably in the axial direction by the aforementioned sliding
portion 16 so that their axial centers coincide with each other. There is. Since the outer yoke 11
and the bobbin 21 are in contact with each other at the tip of the projection structure, the
contact resistance generated when the bobbin 21 slides in contact with the outer yoke 11 is
extremely small, and the movement resistance can be ignored. . In this embodiment, in the outer
peripheral surface of the bobbin 21, the area in contact with the projection structure of the
sliding portion 16 is subjected to a smoothing process (for example, plating or the like) for
reducing friction.
[0019]
(A-3; Configuration of Voice Coil) Next, the configuration of the voice coil will be described. The
voice coil has a bobbin 21, a diaphragm 22, a rear coil 23, a position control coil 24 and a front
coil 25. The diaphragm 22 is a cone-shaped diaphragm, and is fixed to the outer periphery of the
front end of the bobbin 21. The diaphragm 22 is made of, for example, a paper obtained by
blending various fibers such as carbon fiber mainly made of wood pulp, a metal such as
aluminum or a ceramic, or a plastic such as polypropylene.
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[0020]
In addition, a coil is wound around the bobbin 21 and integrated. Here, a mode of winding the
coil around the bobbin 21 will be described. In the present embodiment, three coils are wound.
The front coil 25 is packed and wound at a position offset by a predetermined length from the
front end and the rear end of the front plate 15, with the voice coil in the reference position
shown in FIG. Similarly, the rear coil 23 is packed and wound at a position offset from the front
end and the rear end of the rear plate 13 by a predetermined length. The position control coil 24
is packed and wound so as to overlap the entire area of the magnet 14 and to overlap the front
plate 15 and the rear plate 13 by the same length.
[0021]
Here, a circuit for supplying current to the rear coil 23, the position control coil 24, and the front
coil 25 will be described with reference to FIG. Audio signals are supplied to the front coil 25 and
the rear coil 23 from the output end of the amplifier 30. In this case, as illustrated, the front coil
25 and the rear coil 23 are supplied with a common current. Further, to the position control coil
24, a direct current DC (Direct Current) of a fixed magnitude is supplied from the DC power
supply 31. As the DC power supply 31, a current supply means such as a DC constant current
circuit (switching regulator or the like) for converting a commercial power supply into a DC, or a
battery is used.
[0022]
FIG. 3 is an enlarged view of a region (around the magnetic gap) indicated by a broken line
shown in FIG. In FIG. 3, the cross sections of the rear coil 23, the position control coil 24, and the
front coil 25 are shown in two different display methods. The display method of the cross section
of the rear coil 23 (black circle in the circle) indicates that the current is supplied to the coil by
the amplifier 30 so that the direction from the back to the front of the paper is positive. The
display method of the cross section (cross in a circle) indicates that the current is supplied to the
coil so that the direction from the front side to the back side of the paper surface is a positive
direction. That is, currents of the same waveform are supplied to the rear coil 23 and the front
coil 25 in opposite directions. A direct current DC is supplied to the position control coil 24 by
the direct current power supply 31 in the direction from the back side of the drawing to the front
side. Note that the figure is for schematically representing the polarity of the current supplied to
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the rear coil 23, the position control coil 24, and the front coil 25, and accurately shows the
number of turns of the coil and the density of winding. is not. Also, the arrows written in the
magnetic gaps indicate the direction of the magnetic field formed in each magnetic gap.
[0023]
(B: Operation) Next, the operation of the speaker 1 having the above configuration will be
described.
[0024]
(B-1: When Audio Signal is not Supplyed) An operation when an audio signal is not supplied to
the speaker 1 will be described.
As described above, the direct current DC is constantly supplied to the position control coil 24
even when the audio signal is not supplied. Since the position control coil 24 is wound so that the
predetermined length at both ends crosses the magnetic gap when the voice coil is at the
reference position shown in FIG. Lorentz force constantly works from the magnetic field formed
in the gap. The characteristics of the Lorentz force will be described below.
[0025]
The direction of the Lorentz force is derived from Fleming's left-hand rule from the direction of
the magnetic field in the magnetic gap and the direction of the current crossing the magnetic
field. At the front end of the position control coil 24, a Lorentz force acting backward (left
direction in the drawing) acts on the position control coil 24, while at the rear end of the position
control coil 24, a forward Lorentz force on the position control coil 24 work. At this time, since
the lengths of the position control coils 24 crossing the respective magnetic gaps are equal at the
front end and the rear end of the position control coil 24, the Lorentz forces are equal in size and
equal in opposite directions.
[0026]
Next, consider the above Lorentz force when the voice coil moves slightly forward or backward.
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FIG. 4 is a diagram showing a case where the voice coil has moved slightly by a small amount in
the forward direction. 5 is an enlarged view of a region (around the magnetic gap) indicated by a
broken line in FIG.
[0027]
At this time, the length of the front end of the position control coil 24 crossing the magnetic gap
is longer than the rear end of the position control coil 24. The Lorentz force acting on the coil is
proportional to the length of the coil across the magnetic gap, so the force acting on the front
end of the position control coil 24 (leftward in the figure) is greater than the force acting on the
rear end (rightward in the figure). Therefore, the vector sum of Lorentz forces is leftward and in
the opposite direction to the movement of the voice coil. On the other hand, when the voice coil
is moved backward, the sum of the Lorentz forces generated is in the opposite direction (forward
direction) to the movement of the voice coil by the same mechanism as described above.
[0028]
To summarize the above, when the voice coil moves in any direction back and forth from the
reference position, the Lorentz force acting on the entire position control coil 24 is in the
direction opposite to the direction of the movement. Therefore, the voice coil is stabilized at the
position of the reference. The Lorentz force to the current flowing through the position control
coil 24, which acts in the direction opposite to the movement of the voice coil, is hereinafter
referred to as "electrical spring force". Further, the position of the reference at which the voice
coil is stabilized by the electric spring force is hereinafter referred to as a "reference position".
[0029]
(B-2: When Audio Signal is Supplyed) An operation when an audio signal is supplied to the
speaker 1 will be described. The front coil 25 and the rear coil 23 are supplied with a current of
a waveform based on the audio signal. For example, an audio signal representing a sound with a
frequency of 800 Hz (pure tone) is input as an alternating current of a 800 Hz sine wave. Since
the front coil 25 and the rear coil 23 are wound around the bobbin 21 so as to vertically cross
the magnetic field formed in the magnetic gap, when current is supplied to the front coil 25 and
the rear coil 23, Lorentz force is generated from the magnetic field formed in the magnetic gap.
Hereinafter, driving of the voice coil by the Lorentz force will be described.
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[0030]
Here, for example, the case where the current of the waveform shown in FIG. 6 is supplied to the
front coil 25 and the rear coil 23 will be described. For example, in section A, current flows in the
front coil 25 from the front to the back of the drawing, and in the rear coil 23 from the back of
the drawing to the front. In this case, although the currents flowing through the front coil 25 and
the rear coil 23 are in opposite directions, the magnetic fields formed in the magnetic gaps
traversed by the respective coils are also in the opposite directions. Are the same forward
direction (right direction in the figure)). As a result, the voice coil is driven forward by the
Lorentz force.
[0031]
Now, also in the section A, the position control coil 24 is supplied with the direct current DC. By
the direct current DC, Lorentz force (electric spring force) according to the amount of movement
acts in the direction (backward) opposite to the movement of the voice coil. The force acting on
the entire moved voice coil is the sum of the driving force based on the audio signal and the
electric spring force. Then, the voice coil moves to a position where the electric spring force and
the driving force are balanced. Therefore, in section A, the voice coil moves to a position ahead of
the reference position.
[0032]
On the other hand, when the current flows in the negative direction as in section B in FIG. 6, the
direction of the Lorentz force acting on the front coil 25 and the rear coil 23 is both backward
(backward in FIG. Direction). And with the movement of the voice coil, an electric spring force in
the opposite direction (forward) of movement is generated. As a result, the voice coil moves to a
position behind the reference position.
[0033]
Since the current supplied to the front coil 25 and the rear coil 23 is based on the audio
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waveform, the current value is oscillating. Therefore, the operations as described in the sections
A and B are alternately repeated, and the voice coil moves (oscillates) back and forth in
accordance with the audio signal waveform. When the voice coil vibrates, the diaphragm 22 also
vibrates in conjunction with the voice coil, and sound is generated based on the waveform of the
audio signal.
[0034]
(C: Summary) As described above, the voice coil is stabilized to the reference position by the
electric spring force acting on the position control coil 24 when the audio signal is not supplied.
Then, when an audio signal is supplied, it vibrates corresponding to the waveform of the audio
signal by the driving force based on the audio signal and the electric spring force by the position
control coil 24.
[0035]
In the past, mechanical support members such as edges and spiders have been used to support
the voice coil and to determine the vibration reference position. Therefore, depending on the
material and shape of the support member, the vibration of the voice coil is limited, and an
undesirable force is applied to the voice coil. However, the technology according to the present
invention can be used to support the vibration reference position without providing the support
members, and at the time of sound generation, the voice coil can be vibrated centering on the
reference position to solve the above problems. be able to.
[0036]
(D; Modifications) Although the embodiments of the present invention have been described
above, the present invention can be implemented in various aspects as follows. Note that various
embodiments described below can be implemented in combination as appropriate.
[0037]
(1) In the said embodiment, an example of the structure which concerns on an electrical spring
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force was shown. However, the aspect of the electric spring force may be controlled by
controlling the winding method of the position control coil 24, the current value of the direct
current DC, and the magnetic field formed in the magnetic gap as follows. The density at which
the position control coil 24 is wound around the bobbin 21 may be as follows. (A) The density at
which the position control coil 24 is wound around the bobbin 21 may be uniformly increased, in
which case the electric spring force corresponding to the movement is increased. Conversely,
when the density is lowered, the electric spring force is reduced. (B) The density at which the
position control coil 24 is wound around the bobbin 21 may be locally increased, in which case
the electric spring force is variously controlled according to the movement of the voice coil. For
example, if the position control coil 24 is wound with a high density near the center of the
winding width and a low density at both ends, a large electric spring makes it difficult for the
voice coil to move as the movement of the voice coil increases. Power works. Further, the value
of the direct current supplied to the position control coil 24 may be set as follows. (C) When the
direct current value supplied to the position control coil 24 is set high, the electric spring force
becomes large. On the contrary, when it is set small, the electric spring force becomes small. (D)
The direct current value supplied to the position control coil 24 may be set to different values
depending on the type of music and the type of acoustic space. By doing so, it is possible to emit
a sound of acoustic characteristics suitable for the situation. For example, a variable output DC
power supply 32 as shown in FIG. 7 may be provided, and the output value may be selected by
the switches SW1 to SWn. Further, as shown in FIG. 8, a function of outputting a control signal
instructing the output value of the DC power supply 32 to the amplifier 30 is added, and the DC
power supply 32 changes the output value according to the supplied control signal. Just do it. In
this case, the amplifier 30 may be provided with a selection switch, and the contents of the
control signal may be changed according to the state of the switch, or the result from analysis of
the audio signal or an audio device (external device) supplying the audio signal. The amplifier 30
is provided with a function of automatically identifying the type of music (by performing
processing such as processing of specifying a genre by detecting a sound range or detecting a
beat) and a type of sound space by a signal in the amplifier 30, The control signal may be output
according to the type of acoustic space. (E) The strength of the magnetic field formed in the
magnetic gap may be changed by replacing the magnet 14 or changing the interval of the
magnetic gap.
As exemplified above, the aspect of the electric spring force may be set as appropriate by the
user. As described above, by electrically setting the spring characteristics, it is possible to realize
an acoustic effect that is difficult to realize depending on the mechanical support member.
[0038]
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(2) In the above embodiment, the case where both ends of the position control coil 24 are wound
so as to cross the magnetic gap by the same predetermined length and stabilized at the reference
position has been described. However, the winding method of the position control coil 24 and the
supply mode of the direct current DC are not limited to the modes described in the above
embodiment, and stabilization to the reference position is possible even in the following manner.
Example 1 For example, as shown in FIG. 9, the winding width of the position control coil 24 may
be from the front end of the front plate 15 to the rear end of the rear plate 13 so as not to
overlap the magnetic gap. In that case, the position control coil 24 causes a current to flow from
the back side to the front side in the drawing in a region surrounded by a broken line in FIG.
When the voice coil is at the reference position, the Lorentz force does not work because the
position control coil 24 does not cross the magnetic gap, but when the voice coil moves, for
example, forward, the front end of the position control coil 24 crosses the magnetic gap
Therefore, Lorentz force acts on the portion of the position control coil 24 which has newly
crossed the magnetic gap, and the voice coil receives force in the direction (backward direction)
opposite to the moving direction. When the voice coil moves backward, it receives Lorentz force
forward. As described above, the voice coil is stabilized at the reference position, as in the above
embodiment.
[0039]
(Example 2) Also, as shown in FIG. 10, two position control coils 24 (hereinafter referred to as
24B and 24F when distinguishing the two) are provided, and the position control coil 24F is a
front plate The both ends of the magnetic gap formed by 15 may be shifted forward and wound,
and the position control coil 24B may be wound so as to shift both ends backward with respect
to the magnetic gap formed by the rear plate 13. In that case, the DC power supply 31 may
supply current to the position control coil 24 so that the DC current flows from the front to the
back of the drawing in the region A surrounded by the broken line in FIG.
[0040]
It is apparent that the vector sum of Lorentz forces acting on the position control coils 24B and
24F is 0 when the voice coil is at the reference position shown in FIG. The Lorentz force which
works when the voice coil moves forward will be described. FIG. 11 shows the positional
relationship between the position control coil 24 and the magnetic gap when the voice coil
shown in FIG. 10 moves forward. In the drawing, the front coil 25 and the rear coil 23 are not
shown. At this time, a Lorentz force is generated in the forward direction in the position control
coil 24F, and a backward Lorentz force is generated in the position control coil 24B. Since the
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position control coil 24B has a longer length across the magnetic gap than the position control
coil 24F, the Lorentz force on the position control coil 24B is larger than the Lorentz force on the
position control coil 24F. As a result, the vector sum of Lorentz forces generated in the position
control coil 24 is directed backward (leftward in the drawing) opposite to the movement of the
voice coil. Even when the voice coil moves backward, Lorentz force works in the opposite
direction (forward direction) to the movement, but the description is omitted here. Thus, the
voice coil is also stabilized at the reference position according to the above aspect.
[0041]
(Example 3) Also, as shown in FIG. 12, two position control coils 24 (referred to as 24b and 24f
in the case of distinguishing the two) are provided, and the position control coil 24f is formed by
the front plate 15 The position control coil 24b is wound from a position offset backward from
the front end of the magnetic gap by a predetermined length to a position offset backward from
the rear end of the magnetic gap, and is wound in a position opposite to the position control coil
24f. It is good. In that case, direct current DC is supplied to the position control coil 24 from the
back side to the front side in the area B surrounded by the broken line in FIG.
[0042]
It is apparent that the vector sum of Lorentz forces acting on the position control coils 24b and
24f is 0 when the voice coil is at the reference position shown in FIG. The Lorentz force which
works when the voice coil moves forward will be described. FIG. 13 shows the positional
relationship between the position control coil 24 and the magnetic gap when the voice coil
shown in FIG. 12 moves forward. In the drawing, the front coil 25 and the rear coil 23 are not
shown. At this time, Lorentz force is generated backward in the position control coil 24f, and
forward Lorentz force is generated in the position control coil 24b. Since the position control coil
24f has a longer length across the magnetic gap than the position control coil 24b, the Lorentz
force on the position control coil 24f is larger than the Lorentz force on the position control coil
24b. As a result, the vector sum of Lorentz forces generated in the position control coil 24 is
directed backward (leftward in the drawing) opposite to the movement of the voice coil. Even
when the voice coil moves backward, Lorentz force works in the opposite direction (forward
direction) to the movement, but the description is omitted here. Thus, the voice coil is also
stabilized at the reference position according to the above aspect.
[0043]
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In any of the above Examples 1 to 3, when the voice coil is at the reference position, the Lorentz
force does not act on the energized position control coil 24, or even if it acts, the vector sum of
the Lorentz forces generated Is zero. Further, in any of the above winding methods, when the
voice coil is moved in the back or forth direction from the reference position by a small amount,
the magnetic gap formed by the position control coil 24 and the front plate 15 and the rear plate
13 The amount of coil crossing the point fluctuates, and the vector sum of Lorentz forces
generated in the entire position control coil 24 is in the opposite direction to the above
movement. In this way, the voice coil is stabilized at the reference position.
[0044]
As described above, various modes are possible for the winding method of the position control
coil 24 and the supply mode of the direct current DC, but the point is that the Lorentz force
acting on the position control coil 24 when the voice coil is at the reference position. The direct
current of the position control coil 24 is such that the vector sum of Lorentz forces acting on the
position control coil 24 when the vector sum is 0 and the voice coil moves in either direction
back and forth is opposite to the direction of the movement. It is sufficient if DC is supplied.
[0045]
(3) In the above-described embodiment, the case where the projection structure is provided as
the sliding portion 16 that supports the voice coil slidably inside the outer yoke 11 has been
described.
However, the support mechanism is not limited to the above embodiment. An example is given
below and demonstrated.
[0046]
(A) Mechanism by Magnetic Fluid FIG. 14 is a view showing a cross section of a speaker 1
employing a magnetic fluid supporting mechanism. The magnetic fluid is a liquid in which fine
magnetic particles, the surface of which is treated with a surfactant, are suspended in a medium.
On the inner side of the outer yoke 11, a recess structure 18 is provided, which consists of a
magnet. By flowing the magnetic fluid 19 into the recess structure 18, the magnetic fluid is
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fluidly held in the recess structure 18. The bobbin 21 is made of a nonmagnetic material having
a smooth surface and is inserted into the inner side surface of the outer yoke 11. At this time, the
outer peripheral surface of the bobbin 21 is held in the outer yoke 11 via the magnetic fluid 19.
That is, the voice coil is held floating in the magnetic fluid 19. And, even when the voice coil
vibrates as described in the above embodiment, the magnetic fluid 19 is held in the recess
structure 18 as it is because an attractive force is generated with the magnet constituting the
recess structure 18. . As described above, since the voice coil is held between the outer yoke 11
and the magnetic fluid 19 via the magnetic fluid 19, the contact resistance that occurs even when
the voice coil vibrates in the outer yoke 11 can be reduced. it can. In addition, since the outer
yoke 11 and the voice coil do not slide in direct contact with each other, there is no problem such
as wear of the contact point. The resistance generated between the voice coil and the outer yoke
11 may be controlled by changing the flow resistance of the magnetic fluid 19. In that case, the
characteristics of the magnetic fluid may be controlled by changing the chemical composition of
the surfactant or liquid medium used when producing the magnetic fluid 19.
[0047]
(B) Bearing Support Mechanism FIG. 15 is a cross-sectional view of the speaker 1 adopting a
bearing support mechanism. A conventional ball bearing mechanism 17 is provided on the inner
side surface of the outer yoke 11. The outer peripheral surface of the bobbin 21 is processed to
be smooth by plating or the like, and is inserted into the inner side surface of the outer yoke 11
provided with the ball bearing mechanism 17. At this time, the bobbin 21 is held in the outer
yoke 11 via the ball bearing mechanism 17. When the voice coil vibrates as described in the
above embodiment, the voice coil slides smoothly. Further, since the outer yoke 11 and the voice
coil are in contact with each other through the ball bearing mechanism 17, there is no problem
that the contact portion is significantly abraded.
[0048]
(C) Support mechanism by damper The structure of the speaker shown in this modification is the
same as that of the conventional speaker except for one difference. The one point difference is
the mechanical property of the edge. In a conventional speaker, a material such as a fibrous
material or a urethane foam is generally used as a material forming the edge. When the voice coil
is held by such a support member, a support member with very low elasticity may be used. For
example, the thickness of the support member may be thinly processed, or a support member
made of a weak material may be used. By doing so, it is possible to suppress that the spring
characteristics of the support member have a large influence on the driving of the voice coil.
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[0049]
(4) In the above embodiment, the case where the amplifier 30 and the DC power supply 31 are
provided separately from the speaker 1 has been described. However, the speaker 1 and the DC
power supply 31 may be combined and housed in the same speaker enclosure or the like. Also,
the amplifier 30, the DC power supply 31, and the speaker 1 may be combined and housed in the
same speaker enclosure or the like. In this case, a DC power supply 31 may be provided in the
amplifier 30. That is, the DC constant current source may be incorporated in the circuit in the
amplifier 30.
[0050]
(5) In the above embodiment, the case where the sliding portion 16 is provided on the inner side
surface of the outer yoke 11 has been described. However, the sliding portion 16 may be
provided on the inner side surface of the bobbin 21.
[0051]
It is a sectional view of a speaker concerning the above-mentioned embodiment. It is a circuit
diagram which supplies an electric current to a speaker. It is an enlarged view of a magnetic gap.
It is sectional drawing of the speaker at the time of a voice coil moving. It is an enlarged view of a
magnetic gap when a voice coil moves. It is a figure showing the current supplied to the front coil
and the back coil. It is the figure which showed the supply aspect of direct current DC as
described in a modification (1). It is the figure which showed the supply aspect of direct current
DC as described in a modification (1). It is sectional drawing of the speaker which concerns on a
modification (1). It is sectional drawing of the speaker which concerns on a modification (2). It is
an enlarged view of the magnetic gap which concerns on a modification (2). It is sectional
drawing of the speaker which concerns on a modification (2). It is an enlarged view of the
magnetic gap which concerns on a modification (2). It is sectional drawing of the speaker
provided with the support mechanism by the magnetic fluid which concerns on a modification
(3). It is sectional drawing of the speaker provided with the bearing mechanism which concerns
on a modification (3). It is the figure which showed the structure of the conventional moving coil
type ¦ mold speaker.
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Explanation of sign
[0052]
DESCRIPTION OF SYMBOLS 1 ... Speaker, 11 ... External yoke, 12 ... Holding part, 13 ... Rear plate,
14 ... Magnet, 15 ... Front plate, 16 ... Sliding part, 17 ... Ball bearing mechanism, 18 ... Concave
structure, 19 ... Magnetic fluid , 21 ... bobbin, 22 ... diaphragm, 23 ... rear coil, 24 ... position
control coil, 25 ... front coil, 30 ... power supply, 31, 32 ... DC power supply
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