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DESCRIPTION JP2010130307

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DESCRIPTION JP2010130307
An object of the present invention is to reduce the weight of an operating side that vibrates
according to an audio signal. Prevent lead resonance. An electrode for taking out a detection
signal of capacitance is separated from the voice coil. A speaker is provided with electrodes
provided on a voice coil bobbin 4 and a center pole 5, and detects a capacitance formed between
them to output as an electric signal, and the electrode 16 on the voice coil bobbin 4 side is
grounded. The detection signal is taken out from the electrode 17 on the center pole 5 side.
[Selected figure] Figure 2
スピーカー
[0001]
The present invention relates to a speaker, and more specifically, detects a capacitance formed
between a voice coil bobbin and a center pole, detects the position of the voice coil bobbin based
on the detection result, and detects the capacitance of the diaphragm. The present invention
relates to a speaker for feedback control of operation.
[0002]
As a speaker which detects the electrostatic capacitance between a voice coil bobbin and a center
pole, and outputs it as an electric signal, there exist some which were disclosed by UnexaminedJapanese-Patent No. 2007-96652, for example.
12-04-2019
1
In this speaker, the first and second electrodes 103 and 104 are provided on the voice coil
bobbin 102 that vibrates together with the diaphragm 101, and a change in capacitance between
the center pole 105 and the stepped portion 105a is detected. ing. Leads 106 and 107 are
connected to the electrodes 103 and 104, and detection signals are output to the control circuit
through the leads 106 and 107. Each of the electrodes 103 and 104 is composed of two layers of
conductor films 103a and 103b, 104a and 104b.
[0003]
When the diaphragm 101 and the voice coil bobbin 102 are not in operation, the area of the first
electrode 103 facing the step portion 105a is equal to the area of the second electrode 104
facing the step portion 105a. The electrostatic capacitance between the first electrode 103 and
the step portion 105a (hereinafter referred to as the first electrode 103 side electrostatic
capacitance) and the electrostatic capacitance between the second electrode 104 and the step
portion 105a (hereinafter referred to as It is equal to the second electrode 104 side electrostatic
capacitance). Then, when the diaphragm 101 and the voice coil bobbin 102 operate, the first
electrode 103 side electrostatic capacitance and the second electrode 104 side electrostatic
capacitance have a relationship in which the other decreases by an amount corresponding to an
increase in one. The positions of the diaphragm 101 and the voice coil bobbin 102 are detected
based on the change in the capacitance, and feedback control is performed.
[0004]
The voice coil 108 is provided on the bobbin 109 of the voice coil bobbin 102, and when an
audio signal is input to the voice coil 108, the voice coil bobbin 102 and the diaphragm are
excited by the exciting action of the voice coil bobbin 102, the center pole 105 and the magnet 6.
101 vibrates (operates) in the front-rear direction (the direction of arrow A in FIG. 7), and a
sound corresponding to the audio signal is emitted. The bobbin 109 is provided with a
conductive film 110 that prevents noise from entering the electrodes 103 and 104 from the
voice coil 108.
[0005]
JP 2007-96652 A
[0006]
12-04-2019
2
However, in the above-described speaker, since the first and second electrodes 103 and 104 in
which the lead wires 106 and 107 are connected to the voice coil bobbin 102 are provided, the
side vibrating according to the audio signal (hereinafter referred to as the operation side) ), The
current required for operation becomes large and the efficiency becomes worse, and the
response of operation becomes worse.
Further, since the lead wires 106 and 107 extend from the operation side, the lead wires 106
and 107 also vibrate together, and the lead wires 106 and 107 resonate to deteriorate the
response of the operation of the diaphragm 101. There is a risk of Furthermore, since the voice
coil bobbin 102 is provided with the first and second electrodes 103 and 104 and the voice coil
108, noise from the voice coil 108 easily intrudes into the electrodes 103 and 104, and the heat
of the voice coil 108 is generated. Susceptible to
[0007]
An object of the present invention is to provide a speaker capable of reducing the weight on the
operation side and preventing resonance of the lead wire and separating an electrode for
extracting a detection signal of capacitance from the voice coil. .
[0008]
In order to achieve the above object, the invention according to claim 1 is a speaker provided
with electrodes on a voice coil bobbin and a center pole, detecting a capacitance formed between
them, and outputting as an electric signal. The electrode on the side is grounded, and the
detection signal is taken out from the electrode on the center pole side.
Therefore, the lead wire is connected to the center pole electrode on the fixed side, and it is not
necessary to connect the lead wire to the voice coil bobbin electrode on the operation side. Also,
the electrode on the detection side is provided on the center pole, and the number of electrodes
provided on the voice coil bobbin is reduced accordingly. Furthermore, the electrode on the
detection side is provided at a position away from the voice coil of the voice coil bobbin.
[0009]
In the speaker according to claim 2, two center pole electrodes are arranged along the axial
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3
direction of the center pole at regular intervals, and when the voice coil bobbin operates, one of
the center pole electrodes is When the facing area of the voice coil bobbin side electrode
increases, the facing area of the other center pole side electrode and the voice coil bobbin side
electrode decreases by the amount of increase, and the one center pole side electrode and the
voice coil bobbin side electrode face When the area decreases, the voice coil bobbin side
electrode is arranged such that the opposing area between the other center pole side electrode
and the voice coil bobbin side electrode increases by the reduction amount, and the first obtained
by the one center pole side electrode The second electrical signal obtained by the other center
pole electrode is subtracted from the electrical signal. And it has a subtractor for outputting a
third electrical signal corresponding to the result of the subtraction.
[0010]
Therefore, when the voice coil bobbin operates, the facing area between one center pole side
electrode and the voice coil bobbin side electrode increases, and the facing area between the
other center pole side electrode and the voice coil bobbin side electrode When it decreases, the
capacitance formed between one center pole side electrode and the voice coil bobbin side
electrode increases, and by the amount of the increase, the capacitance is formed between the
other center pole side electrode and the voice coil bobbin side electrode Capacitance is reduced.
These capacitances are detected as first and second electrical signals by the center pole
electrodes together with disturbance noise. That is, in the first electric signal obtained from one
of the center pole electrodes, an electric signal indicating the true capacitance formed between
the one center pole electrode and the voice coil bobbin electrode and one of the center electric
signals The second electric signal obtained from the other center pole side electrode includes the
electric signal indicating the disturbance noise that has entered the pole side electrode, and the
second electric signal obtained from the other center pole side electrode is between the other
center pole side electrode and the voice coil bobbin side electrode An electric signal indicating a
true capacitance to be formed and an electric signal indicating a disturbance noise that has
entered the other center pole electrode are included. The phase of the electrical signal indicating
the true capacitance obtained by one of the center pole electrodes and the phase of the electrical
signal indicating the true capacitance obtained by the other center pole electrode are shifted by
π, Since the phase of the electrical signal indicating the disturbance noise obtained by one of the
center pole electrodes is the same as the phase of the electrical signal indicating the disturbance
noise obtained by the other center pole electrode, the first electricity is determined by the
subtractor. When the second electric signal is subtracted from the signal, the electric signal
indicating the disturbance noise obtained at each center pole electrode is canceled, and the
electric signal indicating the true capacitance obtained at each center pole electrode has the
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4
same phase. It is detected in the state of being added by.
[0011]
In the speaker according to claim 1, since the electrodes for detecting the capacitance are
separately disposed on the center pole side and the voice coil bobbin side, the number of
electrodes provided on the voice coil bobbin can be reduced, and the voice coil bobbin on the
operation side The weight of the can be reduced. Further, since the lead wire for taking out the
signal is connected to the center pole side electrode which is the fixed side, it is not necessary to
connect to the operation side, and the weight on the operation side can be reduced. For these
reasons, the diaphragm can be efficiently vibrated (high efficiency) with less electricity, and the
response of operation can be improved. Further, since the lead wire does not vibrate together
with the voice coil bobbin, resonance of the lead wire can be prevented. Furthermore, since the
number of electrodes provided on the voice coil bobbin can be reduced, the thickness of the
entire voice coil bobbin can be reduced.
[0012]
Also, as in the speaker shown in FIG. 7, it is not necessary to provide a stepped portion in the
center pole, so it becomes possible to use existing parts as the center pole or its manufacturing
cost is reduced when manufacturing the center pole, The production cost of the speaker can be
reduced. Further, since it is not necessary to provide the step portion in the center pole, it is
possible to prevent the magnetic flux leakage from the side surface of the step portion, and the
magnetic flux for driving the diaphragm and the voice coil bobbin can be effectively used.
[0013]
Further, since an electrode (hereinafter referred to as a detection side electrode) for extracting a
detection signal of capacitance is provided on the center pole side, the detection side electrode
can be separated from the voice coil provided on the voice coil bobbin and An air layer can be
provided between them, and the effect of heat generation of the voice coil (for example, when the
center pole electrode has a stacked structure of a plurality of conductive layers, the insulation
resistance of the insulating layer between the conductive layers is reduced by heat) Can be
reduced. In addition, since the center pole electrode and the insulating layer are not easily
affected by the heat generation of the voice coil, the conductive layer and the insulating layer can
12-04-2019
5
be formed of an inexpensive material having a certain degree of heat resistance, and the cost is
high. The cost of manufacturing the speaker can be reduced because it is not necessary to
Furthermore, since the center pole electrode, which is the detection electrode, is not easily
affected by the heat generation of the voice coil, it can be easily deployed to a speaker used in an
environment where there is a possibility of temperature increase in an automobile or the like.
Further, since the center pole side electrode which is the detection side electrode is provided on
the center pole, the heat of the center pole side electrode and the insulating layer can be
dissipated to the center pole side electrode to cool them.
[0014]
Furthermore, since the center pole side electrode which is the detection side electrode can be
separated from the voice coil, noise caused by the voice coil is less likely to intrude into the
center pole side electrode, so-called crosstalk is prevented, The detection accuracy can be
improved, and the manufacturing cost can be reduced because it is not necessary to separately
provide a shield layer.
[0015]
Also, since the bobbin side electrode grounded is provided on the voice coil bobbin side, and this
is disposed between the voice coil and the center pole side electrode, the influence of noise
generated from the voice coil can be applied to the ground. Therefore, noise can be prevented
from entering the center pole electrode from the voice coil.
[0016]
Further, in the speaker according to claim 2, among the electric signals obtained by the two
center pole electrodes, a component indicating disturbance noise is canceled out, and it is formed
between the center pole electrode and the voice coil bobbin electrode. Only components that
show a true capacitance.
Thereby, for example, the third electric signal indicating the true capacitance formed between the
center pole side electrode and the voice coil bobbin side electrode can be effectively used for the
MFB (Mortional Feed Back) circuit, Distortion of the sound emitted from the speaker can be
eliminated.
[0017]
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6
Hereinafter, the configuration of the present invention will be described in detail based on the
best mode shown in the drawings.
[0018]
1 to 4 show an embodiment of a speaker according to the present invention.
The speaker 1 according to the present invention is provided with the electrodes 16 and 17 on
the voice coil bobbin 4 and the center pole 5, and detects the capacitance formed between them
to output as an electric signal. The electrode 16 is grounded and the detection signal is taken out
from the electrode 17 on the center pole 5 side.
That is, the capacitance type sensor is constituted by the electrode 16 on the voice coil bobbin 4
side and the electrode 17 on the center pole 5 side, and the displacement of the voice coil bobbin
4 is detected by this capacitance type sensor.
[0019]
As shown in FIG. 1, the speaker 1 includes, for example, a damper 2, a diaphragm 3, a voice coil
bobbin 4, a center pole 5, magnets 6 and 7, a yoke 8, a case 9, a frame 10, a connecting member
11, a center cap 12, and It has a box-like speaker box (not shown) that functions as a housing. A
center pole 5, magnets 6, 7 and a yoke 8 are housed in a case 9 formed in a cylindrical shape
with a bottom, and they are fixed to the inner wall surface of the case 9 with an adhesive, a screw
or the like. The center pole 5 is made of, for example, iron, and is provided at a substantially
cylindrical center pole main body 5a, a substantially disk shaped flange 5b formed at the base
end of the center pole main body 5a, and a tip of the center pole main body 5a. It comprises a
nonmagnetic plate 5e. The plate 5 e is for preventing the leakage of the magnetic flux from the
tip of the center pole body 5 a, and is provided to project beyond the yoke 8. Therefore, a
magnetic flux for operating the voice coil bobbin 4 and the diaphragm 3 is formed through the
magnet 6, the yoke 8, the center pole body 5a, the flange 5b, and the magnet 6. The center pole
5 is disposed in the case 9 such that the axis 5 d of the center pole body 5 a coincides with the
center of the bottom surface 9 b of the case 9. The center pole 5 and the case 9 are connected to
a speaker box (not shown) and grounded.
12-04-2019
7
[0020]
The magnet 7 is formed in a substantially annular shape. The magnet 7 is disposed so that the
center thereof is located at the center of the bottom 9 b of the case 9, and is fixed to the bottom
9 b with an adhesive. The bottom surface of the flange 5 b is fixed to the surface on the opening
9 a side of the magnet 7 with an adhesive. The magnet 6 is formed in a substantially annular
shape. The magnet 6 is disposed so that the center thereof is located at the center of the bottom
9 b of the case 9, and is fixed to the surface of the flange 5 b opposite to the opening 9 a with an
adhesive. The yoke 8 is made of iron and is disposed so that the center thereof coincides with the
axis 5d of the center pole body 5a, and is fixed to the surface of the magnet 6 facing the opening
9a with an adhesive.
[0021]
An electrode on the center pole 5 side (hereinafter referred to as a center pole electrode) 17
detects an electrostatic capacitance formed between itself and the bobbin side electrode 16 and
is provided on the side circumferential surface 5 c of the center pole 5. ing. In the present
embodiment, two center pole electrodes 17 are arranged at regular intervals along the axis 5 d of
the center pole 5. Further, in the present embodiment, the center pole electrode 17 is configured
by laminating two conductive layers 40 and 41 between the three insulating layers 18. However,
the present invention is not necessarily limited to these configurations. When the two center pole
electrodes 17 are distinguished from each other, the one on the plate 5e side is called a center
pole electrode 17A, and the one on the flange 5b side is called a center pole electrode 17B.
Similarly, when the conductive layers 40 and 41 of the center pole electrode 17A and the
conductive layers 40 and 41 of the center pole electrode 17B are distinguished, they are referred
to as conductive layers 40A and 41A and conductive layers 40B and 41B, respectively.
[0022]
The voice coil bobbin 4 is composed of a substantially cylindrical bobbin 13 whose front end and
rear end are open, and a voice coil 14. The bobbin 13 is formed by rounding a flexible printed
circuit (FPC) into a cylindrical shape. The bobbin 13 has a diameter slightly larger than the outer
diameter of the center pole body 5 a, and the voice coil 14 is wound around the outer peripheral
surface of the bobbin 13. The voice coil 14 is disposed to cross a magnetic path formed between
the yoke 8 and the center pole body 5a. Further, an electrode (hereinafter referred to as a bobbin
side electrode) 16 on the voice coil bobbin 4 side is attached to the inner peripheral surface of
12-04-2019
8
the bobbin 13. The bobbin side electrode 16 is formed over the entire circumference of the
bobbin 13 and is grounded. A wire for grounding the bobbin electrode 16 and a wire connected
to the voice coil 14 are printed on a flexible wiring board as the bobbin 13. The voice coil bobbin
4 configured in this manner is inserted into the gap between the inner peripheral surface 8a of
the yoke 8 and the side peripheral surface 5c of the center pole body 5a. That is, in the voice coil
bobbin 4, an air gap is formed between the inner peripheral surface 8a of the yoke 8 and the
voice coil 14, and an air gap is formed between the inner peripheral surface 5c of the center pole
body 5a. The center pole 5a is covered from the opening on the rear end side. Each terminal
provided on the flexible wiring board as the bobbin 13 is connected to a predetermined circuit by
a light conductor such as a gold thread, for example.
[0023]
When the voice coil bobbin 4 operates, when the facing area of one of the center pole side
electrode 17 and the bobbin side electrode 16 increases, the bobbin side electrode 16 increases
the other center pole side electrode 17 and the bobbin side by the amount of increase. When the
facing area with the electrode 16 decreases and the facing area with one of the center pole
electrode 17 and the bobbin electrode 16 decreases, the other center pole electrode 17 and the
bobbin electrode 16 face with each other by an amount corresponding to the decrease. It is
arranged to increase the area. That is, in the cross section shown in FIG. 2, when the voice coil
bobbin 4 is not in operation, the middle position between the center pole electrodes 17A and
17B faces the center in the width direction of the bobbin electrode 16 and the center pole
electrode The outer ends 17 c and 17 d of 17 A and 17 B are disposed so as to project beyond
both ends 16 a and 16 b of the bobbin side electrode 16.
[0024]
In the present embodiment, lead wires 42, 43, 44, and 45 are connected to the two conductive
layers 40A, 41A, 40B, and 41B of the center pole electrodes 17A and 17B, and connected to a
bootstrap circuit (not shown). The impedance of the conductive layers 41A and 41B on the fifth
side is raised to function as a so-called bootstrap electrode. By doing this, the conductive layers
40A and 40B and the bobbin side electrode 16 can constitute a capacitor that is not easily
affected by disturbance noise. Then, an electric signal (first electric signal or second electric
signal) indicating the capacitance of the capacitor configured as described above is input to the
subtractor 31. In addition, as a bootstrap circuit, use of the well-known circuit currently disclosed
by Unexamined-Japanese-Patent No. 2007-20153 is possible, for example.
12-04-2019
9
[0025]
A frame 10 is fixed to the surface on the opening 9 a side of the yoke 8 with an adhesive. The
other end of the frame 10 is fixed to the edge of an opening (not shown) formed in the front
plate of the speaker box with an adhesive or a screw. The inner peripheral surface of the damper
2 is fixed to the outer peripheral surface of the bobbin 13 with an adhesive, and the outer
peripheral surface of the damper 2 is fixed to the inner peripheral surface of the frame 10 with
an adhesive. Thus, the voice coil bobbin 4 is held by the damper 2 between the inner peripheral
surface of the yoke 8 and the side peripheral surface 5c of the center pole body 5a. The
diaphragm 3 functions as so-called cone paper, and the inner peripheral portion thereof is fixed
to the outer peripheral surface of the bobbin 13 with an adhesive, and the outer peripheral
portion is connected to the frame 10 via the connecting member 11. . The center cap 12 includes
a dome-shaped main body and a ridge formed along the outer peripheral edge of the main body,
and the ridge is fixed to the diaphragm 3 with an adhesive. Thus, the opening 13 a on the tip end
side of the bobbin 13 is covered by the center cap 12.
[0026]
As shown in FIG. 3, the speaker 1 is provided with a comparator 29, a power amplifier 30, a
subtractor 31, and a feedback circuit 32. An electrical signal (hereinafter referred to as "audio
signal") indicating audio information input to the input terminal 33 is input to the power
amplifier 30 via the comparator 29 formed of an integrated circuit. The voice signal amplified by
the power amplifier 30 is input to the voice coil bobbin 4. When an audio signal flows through
the voice coil 14 of the voice coil bobbin 4, the voice coil bobbin 4 vibrates in the front-rear
direction (the direction of arrow A shown in FIG. 1) by the excitation action. Along with this, the
diaphragm 3 also vibrates and a sound is emitted from the speaker 1.
[0027]
In the feedback circuit 32, the comparator 29, and the power amplifier 30, the following
feedback control is performed based on the third electric signal input from the subtractor 31.
The subtractor 31 subtracts the second electric signal obtained by the other center pole
electrode 17 from the first electric signal obtained by the one center pole electrode 17, and a
third electric signal corresponding to the result of the subtraction. It outputs a signal. In this
embodiment, the second electric signal obtained by the center pole electrode 17B is subtracted
12-04-2019
10
from the first electric signal obtained by the center pole electrode 17A, and the third electric
signal corresponding to the subtraction result is fed back to the feedback circuit 32. Output to
The subtractor 31 includes, for example, a differential amplifier.
[0028]
The feedback circuit (MFB circuit) 32 performs predetermined signal processing on the third
electric signal input from the subtractor 31, and inputs a feedback signal corresponding to the
processing result to the comparator 29. The comparator 29 compares the feedback signal with a
predetermined reference value in response to the feedback signal input from the feedback circuit
32, calculates the difference therebetween, and corrects the audio signal based on the calculation
result. Correction signal is input to the power amplifier 30. The power amplifier 30 corrects the
output level of the audio signal based on the correction signal input from the comparator 29, and
inputs the corrected audio signal to the voice coil bobbin 4. The feedback circuit 32 is configured
of an integration circuit, a buffer amplifier, an electronic volume, an addition circuit (not shown),
and the like.
[0029]
When an audio signal is input to the voice coil 14 and the voice coil bobbin 4 vibrates based on
the audio signal, one of the two center pole electrodes 17A and 17B and the bobbin electrode 16
are vibrated with the vibration. The facing area increases, and the facing area of the other
electrode and the bobbin electrode 16 decreases by the amount of increase. That is, the
capacitance formed between one electrode and the bobbin electrode 16 increases, and the
capacitance formed between the other electrode and the bobbin electrode 16 decreases by the
amount of the increase. It will be. These electrostatic capacitances are detected by the electrodes
17A and 17B together with disturbance noise, and are input to the subtractor 31 as first and
second electrical signals.
[0030]
The first electric signal includes an electric signal indicating a true electrostatic capacitance
formed between the center pole side electrode 17A and the bobbin side electrode 16, and an
electric signal indicating a disturbance noise intruding into the center pole side electrode 17A.
And the second electrical signal includes an electrical signal indicating a true electrostatic
capacitance formed between the center pole electrode 17B and the bobbin electrode 16, and a
disturbance that has entered the center pole electrode 17B. And an electrical signal indicating
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11
noise.
[0031]
As described above, the capacitance formed between one electrode and the bobbin electrode 16
increases, and the capacitance formed between the other electrode and the bobbin electrode 16
increases by the amount of the increase. Since it decreases, as shown in FIG. 4, a voltage
waveform 34 of an electric signal showing a true capacitance formed between the center pole
side electrode 17A and the bobbin side electrode 16, and a center pole side electrode 17B The
voltage waveform 35 of the electric signal indicating the true capacitance formed between the
bobbin 16 and the electrode 16 is in reverse phase.
Further, since the disturbance noise is generated due to, for example, the current flowing through
the voice coil 14, as shown in FIG. 4, the voltage of the electric signal indicating the disturbance
noise which has entered the center pole electrode 17A. The waveform 36 is in phase with the
voltage waveform 37 of the electrical signal indicating the disturbance noise that has entered the
center pole electrode 17B.
[0032]
The subtractor 31 subtracts the second electrical signal from the first electrical signal in
response to the first and second electrical signals being input. Among the signal components of
the first and second electrical signals, the signal component indicating the true capacitance
formed between the center pole side electrode 17A and the bobbin side electrode 16 indicates
the center pole side electrode 17B and the bobbin side electrode 16 When the signal component
indicating the true capacitance formed between them is subtracted, these signal components are
in anti-phase relation, and as a result, as shown in the voltage waveform 38 of FIG. An electric
signal can be obtained by adding the same signal component to the signal component indicating
the true capacitance formed between the electrode 17A and the bobbin electrode 16. On the
other hand, among the signal components of the first and second electric signals, when the signal
component indicating the disturbance noise intruding into the center pole electrode 17B is
subtracted from the signal component indicating the disturbance noise intruding into the center
pole electrode 17A, Since the signal components are in phase, they cancel each other as shown
by the voltage waveform 39 in FIG. Then, the subtractor 31 adds the electrical signal
corresponding to the voltage waveform 38 and the electrical signal corresponding to the voltage
waveform 39 and outputs the result as a third electrical signal.
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12
[0033]
As described above, since the third electrical signal obtained by the subtractor 31 does not
include the signal component indicating the disturbance noise, accurate feedback control can be
performed.
[0034]
In the speaker 1 of the present invention, the electrodes 16 and 17 constituting a sensor for
detecting the capacitance between the center pole 5 and the voice coil bobbin 4 are separately
disposed on the center pole 5 side and the voice coil bobbin 4 side. Therefore, the number of
electrodes provided on the voice coil bobbin 4 on the operation side can be reduced, and the
weight of the voice coil bobbin 4 can be reduced.
Further, since the lead wires 42, 43, 44 and 45 for taking out signals are connected to the center
pole side electrode 17 which is the fixed side, it is not necessary to connect to the voice coil
bobbin 4 which is the operation side. Weight can be reduced. For these reasons, the diaphragm 3
can be efficiently vibrated (high efficiency) with less electricity, and the response of operation
can be improved. Further, since the lead wire does not vibrate together with the voice coil bobbin
4, resonance of the lead wire can be prevented. Furthermore, since the number of electrodes
provided on the voice coil bobbin 4 can be reduced, the thickness of the entire voice coil bobbin
4 can be reduced.
[0035]
Further, as in the speakers shown in FIGS. 7 and 8, it is not necessary to provide a step on the
center pole 5, so that existing parts can be used as the center pole 5 or when the center pole 5 is
manufactured The manufacturing cost can be reduced, and the manufacturing cost of the
speaker 1 can be reduced. Further, since it is not necessary to provide the step portion in the
center pole 5, it is possible to prevent the magnetic flux leakage from the side surface of the step
portion, and the magnetic flux for driving the diaphragm 3 and the voice coil bobbin 4 can be
used effectively.
[0036]
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13
Further, since an electrode (hereinafter referred to as a detection side electrode) for taking out a
detection signal of capacitance is provided on the center pole 5 side, the detection side electrode
can be separated from the voice coil 14 of the voice coil bobbin 4 and between them An air layer
can be provided on the surface of the voice coil 14 (for example, when the center pole electrode
17 has a laminated structure of a plurality of conductive layers 40 and 41, the insulation
resistance of the insulating layer 18 is Can be reduced. Further, since the center pole electrode
17 and the insulating layer 18 are not easily affected by the heat generation of the voice coil 14,
the conductive layers 40 and 41 and the insulating layer 18 can be formed of an inexpensive
material having a certain degree of heat resistance. Since it is not necessary to use expensive
materials having high heat resistance, the manufacturing cost of the speaker 1 can be reduced.
Furthermore, since the center pole electrode 17 which is the detection side electrode is not easily
affected by the heat generation of the voice coil 14, it is easy to deploy to a speaker used in an
environment where there is a possibility of temperature increase in cars and the like. Further,
since the center pole electrode 17 as the detection electrode is provided on the center pole 5, the
heat of the center pole electrode 17 and the insulating layer 18 can be dissipated to the center
pole electrode 17 to cool them. In particular, in the present embodiment, since the center pole 5
is made of iron, the center pole side electrode 17 and the insulating layer 18 can be cooled well.
[0037]
Furthermore, since the center pole side electrode 17 which is the detection side electrode can be
separated from the voice coil 14, noise caused by the voice coil 14 hardly enters the center pole
side electrode 17 and so-called crosstalk is prevented to The detection accuracy of the
capacitance can be improved, and the conductor film 110 for preventing the noise intrusion
required for the speaker shown in FIGS. 7 and 8 can be dispensed with, and the manufacturing
cost can be reduced. .
[0038]
Further, since the bobbin side electrode 16 grounded is provided on the voice coil bobbin 4 side
and this is disposed between the voice coil 14 and the center pole side electrode 17, noise
generated from the voice coil 14 is generated. Can be dropped to the ground, and noise can be
prevented from entering the center pole electrode 17 from the voice coil 14.
[0039]
The above-described embodiment is an example of the preferred embodiment of the present
invention, but is not limited to this, and various modifications can be made without departing
from the scope of the present invention.
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14
[0040]
For example, in the above description, the bootstrap circuit is provided, and the conductive layer
41 of the center pole electrode 17 is made to function as a bootstrap electrode. However, the
present invention is not limited to this configuration. Only the conductive layers 40A and 40B
closer to the bobbin side electrode 16 may be used as the detection side electrodes, and the
conductive layers 41A and 41B farther from the bobbin side electrode 16 may be grounded.
In this case, in addition to the capacitor formed between the bobbin side electrode 16 and the
conductive layers 40A and 40B, a capacitor is also formed between the conductive layers 40A
and 40B and the conductive layers 41A and 41B. Thus, detection can be performed based on the
sum of the capacitances of two capacitors for each of the electrodes 17A and 17B.
That is, since the first and second electric signals that are detection signals of the center pole
electrodes 17A and 17B can be amplified and input to the subtractor 31, electrostatic
capacitance can be detected with high accuracy.
In addition, as a circuit which forms two capacitors, use of the well-known circuit currently
disclosed by Unexamined-Japanese-Patent No. 2007-20153 is possible, for example.
[0041]
Further, in the above description, the two electrodes 17A and 17B are provided as the center
pole electrode 17. However, the two electrodes 17A and 17B are not necessarily provided, and
may be one. In this case, for example, as shown in FIG. 6, the electrodes 16 and 17 are disposed
such that the center of the bobbin electrode 16 faces one end of the center pole electrode 17, or
the center of the center pole electrode 17 It is preferable that the electrodes 16 and 17 be
disposed so that each of the electrodes 16 and 17 faces one end of the bobbin side electrode 16,
and the position of the voice coil bobbin 4 be detected by the change in electrostatic capacitance
between both electrodes 16 and 17.
[0042]
12-04-2019
15
In the above description, the center pole electrode 17 is formed by laminating the two conductive
layers 40 and 41. However, the center pole electrode 17 is formed by laminating one or three or
more conductive layers. It may be configured.
[0043]
In the above description, the detection signal of the center pole electrode 17A is the first electric
signal, and the detection signal of the center pole electrode 17B is the second electric signal.
However, the present invention is not necessarily limited thereto. The detection signal of the
electrode 17B may be a first electric signal, and the detection signal of the center pole electrode
17A may be a second electric signal.
[0044]
It is sectional drawing which shows 1st Embodiment of the speaker of this invention.
It is sectional drawing which expands and shows the part shown by II circle of FIG.
It is a functional block diagram which shows the electric constitution of the speaker of FIG. It is a
figure which shows the voltage waveform of the signal component of the 1st-3rd electrical signal.
It is sectional drawing which shows 2nd Embodiment of the speaker of this invention, and
expands and shows the part corresponding to FIG. It is sectional drawing which shows 3rd
Embodiment of the speaker of this invention, and expands and shows the part corresponding to
FIG. It is sectional drawing of the conventional speaker. It is sectional drawing which expands
and shows the part corresponding to FIG. 2 of the speaker of FIG.
Explanation of sign
[0045]
1 speaker 4 voice coil bobbin 5 center pole 31 subtractor
12-04-2019
16
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