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JP2007020154

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DESCRIPTION JP2007020154
PROBLEM TO BE SOLVED: To provide a speaker capable of accurately detecting the capacitance
formed between a center pole and a voice coil bobbin without being affected by disturbance
noise. SOLUTION: An electrostatic capacitance formed between a voice coil bobbin 4 configured
based on a non-metallic cylinder 21 and a center pole 5 is detected and output as an electric
signal. The outer surface is formed by forming the nonmagnetic inner copper foil 22 and the
inner copper plating 23 on the inner circumferential surface 21a and covering the inner copper
foil 22 and the inner copper plating 23 on the outer circumferential surface 21b of the
cylindrical body 21 via the cylindrical body 21. A copper foil 25 and an outer copper plating 26
are formed. Preferably, the inner resist 24 is formed on the inner copper plating 23 and the
outer resist 27 is formed on the outer copper plating 26. Further, it is preferable to ground the
outer copper plating 26. [Selected figure] Figure 3
スピーカー
[0001]
The present invention relates to a speaker, and more particularly to a speaker for detecting an
operating state of a diaphragm.
[0002]
A speaker equipped with an MFB (Motional Feed Back) circuit is known as a technology for
improving the sound quality of the speaker.
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1
The MFB circuit detects the operating state of the vibrating diaphragm based on an electrical
signal (hereinafter referred to as "audio signal") indicating audio information input to the
speaker, and feeds back the diaphragm based on the detection result. It is controlled, and this
makes it possible to eliminate the distortion of the sound that is likely to occur particularly in the
low tone range. Therefore, it is generally considered that the MFB circuit is effectively employed
in a small speaker which is considered to be difficult to reproduce in the low frequency range.
[0003]
For example, Patent Documents 1 to 5 are disclosed as the technology related to the MFB circuit.
In each of Patent Documents 1 to 5, the operation state of the diaphragm is detected by detecting
a change in capacitance formed between the electrodes. Specifically, an electrode (hereinafter
referred to as a "movable electrode") is fixed to a diaphragm or an electromagnetic coil called a
voice coil bobbin for vibrating the diaphragm, and the electrode is opposed to the movable
electrode. (Hereinafter, it is described as a "fixed electrode"), detects the electrostatic capacitance
changed by moving the movable electrode relative to the fixed electrode, and outputs it as a
detection signal. Then, the detection signal corresponding to the capacitance and the audio signal
are compared by the comparison device (for example, CPU), and the comparison result, that is,
the vibration based on the difference between the output level of the detection signal and the
output level of the audio signal Control the operation of the board as appropriate. JP-A-5279,644 JP-A-53-12319, JP-A-53-12320, JP-A-53-12,221, JP-A-57-96589
[0004]
However, since the electrostatic capacitance formed between the electrodes is very small, such as
several pF to several hundreds pF, it fluctuates under the influence of a slight amount of
electromagnetic waves, static electricity, and the like. For example, the diaphragm is generally
configured to vibrate by an excitation action by a voice coil bobbin, an iron core called a center
pole fitted to the voice coil bobbin, and a magnet generating a magnetic flux penetrating the
voice coil bobbin and the center pole. However, the capacitance between the electrodes
fluctuates under the influence of the excitation current flowing through the voice coil bobbin. In
addition, some electronic components incorporated in a speaker may emit electromagnetic waves
although they are weak, and the electromagnetic waves may propagate to the electrodes, which
may cause fluctuations in capacitance. In addition, the capacitance between the electrodes is set
by friction caused by mechanical phenomena such as vibration of parts incorporated in the
speaker, static electricity caused by various electromagnetic phenomena inside and outside the
13-05-2019
2
speaker, and around the speaker It is also conceivable that there is an influence of
electromagnetic waves output from certain electronic devices. As described above, in the
techniques of Patent Documents 1 to 5, there is a problem that the capacitance fluctuates and it
becomes impossible to detect the correct capacitance formed between the electrodes.
[0005]
In addition, although the movable electrodes used in Patent Documents 1 to 5 are made of metal
foil, when the metal foil reciprocates in a constant magnetic field, an eddy current is generated in
the metal foil, and thereby the correct static There was a problem that the capacity could not be
obtained. Due to the problems as described above, according to the prior art, the operation state
of the diaphragm can not be detected correctly, and the distortion of the sound in the low
frequency range can not be sufficiently eliminated.
[0006]
The present invention has been made to solve the above-described problems, and is a speaker
that can accurately detect the capacitance formed between electrodes without being affected by
disturbance noise such as electromagnetic waves and static electricity. Intended to be provided.
[0007]
In order to achieve such an object, the speaker according to the present invention detects a
capacitance formed between a voice coil bobbin formed based on a nonmetal cylinder and a
center pole and outputs it as an electric signal. And forming a non-magnetic first conductor film
on the inner peripheral surface of the cylinder, and covering the first conductor film on the outer
peripheral surface of the cylinder via the cylinder. It is characterized in that a conductor film is
formed.
[0008]
Therefore, according to this speaker, since the second conductive film blocks electromagnetic
waves from the outside, the capacitance formed between the first conductive film and the center
pole is maintained, and the voice coil bobbin and the center pole Changes in the capacitance
formed between
[0009]
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3
In the speaker of the present invention, the insulator film may be formed on the first and second
conductor films, and the insulator film may be formed on the first conductor film. And the
dielectric constant can be increased.
That is, the capacitance formed between the first conductor film and the center pole is increased,
and the influence of disturbance noise can be reduced.
In addition, the increase of the electrostatic capacitance can make it difficult to receive the
influence even if a weak electromagnetic wave from the outside penetrates, whereby a stable
detection result can be obtained.
Also, when the insulator film is formed on the second conductor film, the disturbance noise and
the second conductor film can be electrically insulated. Specifically, an inner insulator film is
formed on the inner peripheral surface of the first conductor film to detect the capacitance
formed between the first conductor film and the center pole. At the same time, an outer insulator
film is formed on the outer peripheral surface of the second conductor film, and a coil is wound
around the outer peripheral surface of the insulator film to constitute the voice coil bobbin.
[0010]
Further, in the above speaker of the present invention, if the second conductive film is grounded,
for example, the influence of alternating current flowing in the voice coil constituting the voice
coil bobbin or electromagnetic waves from the outside can be generated. It can be eliminated by
body membranes.
[0011]
In the above-described speaker of the present invention, when at least one of the first and second
conductor films is laminated, an eddy current which should be originally formed of the conductor
film of each layer flows. Eddy currents can be minimized because the circuit is broken and the
current is effectively confined in the individual layers.
For example, it is preferable that the first conductive film be composed of a plurality of stacked
conductive films.
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[0012]
In the speaker of the present invention, at least one of the plurality of slits and the plurality of
holes can be formed in at least one of the first and second conductor films. In this way, the eddy
current can be minimized because the eddy current loop that would otherwise be formed in the
conductor film is cut by the slits or holes. Specifically, one film of the conductor film consisting of
a plurality of laminated conductor films is made of a foil member, and in this foil member, a
plurality of slits and a plurality of holes for eddy current suppression are provided. It is
preferable to form at least one of them substantially equally.
[0013]
As described above, according to the speaker of the present invention, the nonmagnetic first
conductive film is formed on the inner peripheral surface of the cylindrical body, and the outer
peripheral surface of the cylindrical body is covered with the first conductive film via the
cylindrical body. Since the second conductor film is formed, electromagnetic waves from the
outside can be blocked by the second conductor film, and the capacitance formed between the
first conductor film and the center pole is very small. Even that can be detected correctly.
Therefore, since the reliability of the detection result is increased, for example, the detection
result can be effectively used for the MFB circuit, and the distortion of the sound emitted from
the speaker, which is a conventional problem, can be eliminated. This makes it possible to realize
a bass range comparable to a large speaker even with a small speaker.
[0014]
Further, in the above invention, when the insulator film is formed on the first and second
conductor films, the capacitance formed between the first conductor film and the center pole by
the first conductor film can be obtained. The capacitance can be increased to facilitate detection
of capacitance. In addition, the increase in the capacitance can make it less likely to be affected
by a weak electromagnetic wave from the outside. In addition, the insulator film on the second
conductor film can electrically insulate the second conductor film from the lead wire wound
around the voice coil bobbin, for example. Conduction to the first and second conductor films is
eliminated. Thereby, stable detection results can be obtained. For example, since the detection
result can be effectively used for the MFB circuit, distortion of the sound emitted from the
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speaker, which has been a problem in the prior art, can be eliminated more reliably. Therefore,
even if it is a small speaker, it is possible to realize a bass range comparable to a large speaker.
[0015]
Further, in the above invention, if the second conductive film is grounded, for example, the
influence of the alternating current flowing in the voice coil bobbin constituting the voice coil
bobbin or the electromagnetic wave from the outside can be treated as the second conductor. It
can be eliminated by the membrane. Thereby, the capacitance formed between the first
conductor film and the center pole can be detected more accurately. For example, since the
detection result can be effectively used for the MFB circuit, distortion of the sound emitted from
the speaker, which has been a problem in the prior art, can be eliminated more reliably.
Therefore, even if it is a small speaker, it is possible to realize a bass range comparable to a large
speaker.
[0016]
Further, in the above-mentioned present invention, when at least one of the first and second
conductor films is laminated, the conductor film of each layer cuts off a circuit in which an eddy
current originally flows and the current is It can be effectively confined in the individual layers
and eddy currents can be minimized. Thereby, the capacitance formed between the first
conductor film and the center pole can be detected more accurately without being affected by the
eddy current. For example, since the detection result can be effectively used for the MFB circuit,
distortion of the sound emitted from the speaker, which has been a problem in the prior art, can
be eliminated more reliably. Therefore, even if it is a small speaker, it is possible to realize a bass
range comparable to a large speaker.
[0017]
In the above invention, when at least one of the plurality of slits and the plurality of holes is
formed in at least one of the first and second conductor films, the conductor film is normally It is
possible to cut the loop of the eddy current that should be formed in the plurality of slits or
holes, and to minimize the eddy current. Thereby, the capacitance formed between the first
conductor film and the center pole can be detected more accurately without being affected by the
eddy current. For example, since the detection result can be effectively used for the MFB circuit,
13-05-2019
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distortion of the sound emitted from the speaker, which has been a problem in the prior art, can
be eliminated more reliably. Therefore, even if it is a small speaker, it is possible to realize a bass
range comparable to a large speaker.
[0018]
Hereinafter, the configuration of the present invention will be described in detail based on the
best mode shown in the drawings.
[0019]
One Embodiment of the speaker of this invention is shown in FIGS. 1-3.
The speaker 1 according to the present invention detects the capacitance formed between the
voice coil bobbin 4 configured based on the non-metal cylinder 21 and the center pole 5 and
outputs it as an electric signal. A nonmagnetic inner copper foil (first conductive film) 22 and an
inner copper plating (first conductive film) 23 are formed on the inner peripheral surface 21 a of
the cylindrical body 21, and a cylindrical body is formed on the outer peripheral surface 21 b of
the cylindrical body 21. An outer copper foil (second conductive film) 25 and an outer copper
plating (second conductive film) 26 for covering the inner copper foil 22 and the inner copper
plating 23 are formed through 21.
[0020]
As shown in FIG. 1, the speaker 1 includes diaphragms 2 and 3, a voice coil bobbin 4, a center
pole 5, magnets 6 and 7, and a yoke 8. Case 9 is formed in a bowl shape. The case pole 9, the
magnets 6 and 7, and the yoke 8 are housed in the case 9, and they are fixed to the inner wall
surface of the case 9 with an adhesive or a screw. The center pole 5 is made of iron, and includes
a cylindrical center pole body 5a and a disk-like flange 5b formed at the base end of the center
pole body 5a. The center pole 5 is disposed in the case 9 such that the tip end portion of the
center pole body 5 a protrudes from the approximate center of the opening 9 a of the case 9 to
the outside of the case 9.
[0021]
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7
The center pole 5 and the case 9 are connected to a housing (not shown) called an enclosure and
grounded. A ring-shaped magnet 6 centered on the center pole body 5a is magnetically attracted
to the surface of the flange 5b facing the opening 9a. A substantially disc-like yoke 8 is
magnetically attracted to the surface of the magnet 6 facing the opening 9a, and the magnet 6 is
sandwiched between the yoke 8 and the flange 5b. A ring-shaped magnet 7 having the same
shape as the magnet 6 is disposed between the surface of the flange 5b facing the bottom 9b of
the case 9 and the bottom 9b. The magnet 7 is disposed at the bottom 9 b such that the pole on
the side contacting the flange 5 b has the same polarity as the pole on the side contacting the
flange 5 b of the magnet 6. As a result, a stable magnetic flux loop (described later) is formed
between the magnet 6, the yoke 8 and the center pole 5.
[0022]
The substantially disc-shaped yoke 8 is substantially orthogonal to the longitudinal axis of the
cylindrical center pole body 5a, and the magnet 6 is arranged such that the inner circumferential
surface thereof faces the outer circumferential surface 5d of the center pole body 5a. The air gap
is formed between the inner peripheral surface of the yoke 8 and the outer peripheral surface 5d
of the center pole body 5a. Further, in the case 9, the substantially disk-shaped yoke 8 is in close
proximity with the inner peripheral surface facing the center pole main body 5 a and the outer
peripheral surface facing the inner wall surface of the case 9. It is arranged as.
[0023]
The voice coil bobbin 4 is composed of a cylindrical bobbin 10 having an open front end and a
rear end, and a coil 11 wound around the outer periphery of the bobbin 10. As the coil 11, a
conductor such as an enameled wire or a copper wire may be used, and it may be determined
appropriately. Although not shown, the bobbin 10 is attached to the case 9 so as to be slidable in
the front-rear direction (the direction of the arrow A in the drawing), and can thereby vibrate in
the front-rear direction by an excitation operation described later. The inner diameter of the
bobbin 10 is slightly larger than the outer diameter of the center pole body 5a, and the bobbin
10 is placed on the center pole body 5a. That is, the coil 11 is opposed to the inner peripheral
surface of the yoke 8, and the bobbin 10 is covered on the center pole main body 5a so that the
outer peripheral surface 5c of the center pole main body 5a and the inner peripheral surface of
the bobbin 10 become substantially parallel. As a result, the inner peripheral surface of the yoke
8 comes close to the coil 11, and the inner peripheral surface of the bobbin 10 comes close to
the outer peripheral surface 5c of the center pole main body 5a. A constant flux loop is always
13-05-2019
8
formed in the direction of the arc arrow in the figure. The magnet 6 and the yoke 8 may be
installed at a place where a constant magnetic flux can be formed between the center pole 5, the
magnet 6 and the yoke 8, and the installation place may be appropriately determined. good.
[0024]
A frame 12 is bonded to the surface of the yoke 8 exposed to the outside of the case 9 with an
adhesive. In addition, the frame 12 is joined to the above-described housing (not shown) by a
screw or an adhesive and is grounded. The diaphragms 2 and 3 are attached to the bobbin 10.
The diaphragm 2 is a thin plate having a plurality of bent portions, and one end thereof is joined
to the outer peripheral surface of the bobbin 10 and the other end is bonded to the frame 12
with an adhesive. The diaphragm 3 functions as so-called cone paper, and one end thereof is
joined to the outer peripheral surface of the bobbin 10 and the other end is connected to the
frame 12 through the joint 13. The center cap 14 is made of aluminum or the like and includes a
dome-shaped main body and a ridge formed along the outer peripheral edge of the main body,
and the ridge is joined to the diaphragm 3 with an adhesive. ing. Thus, the opening 10 a of the
bobbin 10 is covered by the center cap 14.
[0025]
As shown in FIG. 2, an electrical signal (hereinafter referred to as "audio signal") indicating audio
information input to the input terminal 15 is input to the power amplifier 17 through the
comparator 16 consisting of a CPU (Central Processing Unit). Be done. The voice signal amplified
by the power amplifier 17 is input to the voice coil bobbin 4. That is, a current indicating a voice
signal flows through the coil 11 of the voice coil bobbin 4, and the voice coil bobbin 4 is moved
in the front-rear direction by the excitation action of this current and the magnetic flux formed
between the center pole 5, the magnet 6, and the yoke 8. It vibrates in the direction of arrow A
shown in FIG. Along with this, the diaphragms 2 and 3 also vibrate and sound is emitted from the
speaker 1.
[0026]
The speaker 1 is provided with a detector 18, a converter 19, and a feedback circuit 20. The
detector 18 is a so-called capacitor composed of the center pole 5 and the inner copper plating
23 (see FIG. 3) of the voice coil bobbin 4, and a capacitance is formed by this capacitor. The
13-05-2019
9
detector 18 inputs the capacitance formed by the center pole 5 and the inner copper plating 23
to the converter 19 as an electrical signal. The converter 19 amplifies the electrical signal input
from the detector 18 and inputs it as a detection signal to the comparator 16 via the feedback
circuit 20. The comparator 16 compares the audio signal input from the input terminal 15 with
the detection signal in response to the input detection signal. Then, the comparison result, that is,
the output level of the audio signal and the output level of the detection signal are compared, and
the difference is calculated. Next, the power amplifier 17 adjusts the output level of the audio
signal based on the calculation result and inputs it to the voice coil bobbin 4. Then, the voice coil
bobbin 4 vibrates based on the audio signal input from the power amplifier 17. Although not
shown, the converter 19 is composed of an inductance, an oscillation circuit, a detection circuit, a
low pass filter, and the like. The feedback circuit 20 is not particularly illustrated, but includes an
integration circuit, a buffer amplifier, an electronic volume, an addition circuit, and the like.
[0027]
As shown in FIG. 3, the bobbin 10 has a cylindrical body 21, an inner copper foil (first conductive
film) 22, an inner copper plating (first conductive film) 23, an inner resist (inner insulator film)
24, and an outer A copper foil (second conductive film) 25, an outer copper plating (second
conductive film) 26, and an outer resist (outer insulating film) 27 are provided.
[0028]
The cylindrical body 21 is to be a base of the voice coil bobbin 4 and, as shown in FIG. 4, is
formed by forming a substantially rectangular sheet 28 made of polyimide into a cylindrical
shape.
The inner copper foil 22 corresponding to the size and shape of the sheet 28 is adhesive 29 (see
FIG. 3) on one side of the sheet 28, that is, the side corresponding to the inner peripheral surface
21a of the cylindrical body 21 (see FIG. 3). It is pasted by). A plurality of circular holes 22a are
formed in the inner copper foil 22 in a matrix at a constant pitch in the horizontal direction and
the vertical direction. In the inner copper foil 22, the holes 22a do not have to be arranged
regularly, but may be arranged irregularly. Further, as shown in FIGS. 5 to 7, a plurality of slits
22 b may be formed in the inner copper foil 22. In this case, the slits 22b may be arranged along
the longitudinal direction of the inner copper foil 22 as shown in FIG. Further, as shown in FIG. 6,
the slits 22b may be arranged to be inclined. Further, as shown in FIG. 7, the slits 22b may be
alternately arranged. The arrangement of the slits 22 b formed in the inner copper foil 22 can be
changed as appropriate.
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10
[0029]
As shown in FIG. 3, the inner copper plating 23 is applied to the inner copper foil 22 formed in
this manner. Thereby, a copper film layer composed of the inner copper foil 22 and the inner
copper plating 23 is formed. An inner resist 24 made of rubber is coated in a film form on the
inner copper plating 23. A terminal 31 is provided on the inner copper plating 23 formed on the
inner copper foil 22 via a lead wire 30 fixed by soldering, and the terminal 31 is connected to the
converter 19. As a result, an electrical signal indicating capacitance formed between the voice
coil bobbin 4 and the center pole body 5a, that is, between the inner copper plating 23 and the
outer peripheral surface 5c of the center pole body 5a is input to the converter 19. Ru.
[0030]
As shown in FIG. 8, on the other surface of the sheet 28, that is, the surface corresponding to the
outer peripheral surface 21 b (see FIG. 3) of the cylindrical body 21, substantially rectangular
outer copper foil corresponding to the inner copper foil 22. 25 are attached by an adhesive 32
(see FIG. 3). As shown in FIG. 3, an outer copper plating 26 is applied to the outer copper foil 25.
As a result, a copper film layer composed of the outer copper foil 25 and the outer copper plating
26 is formed on the outer peripheral surface 21 b of the cylindrical body 21. In addition, the
outer copper plating 26 is connected to the above-described housing (not shown) and grounded.
An outer resist 27 made of rubber is coated in a film form on the outer copper plating 26.
[0031]
The bobbin 10 sequentially laminates the inner copper foil 22, the inner copper plating 23, and
the inner resist 24 on one surface of the sheet 28, ie, the inner peripheral surface 21a of the
cylindrical body 21 as described above. After the outer copper foil 25, the outer copper plating
26, and the outer resist 27 are sequentially laminated on the other surface, ie, the outer
peripheral surface 21b of the cylindrical body 21, both ends of the sheet 28 in FIG. It is made by
laminating and forming in a cylindrical shape. Thus, when the bobbin 10 is formed, the outer
copper foil 25 and the outer copper plating 26 are formed so as to cover the inner copper foil 22
and the inner copper plating 23 on the outer peripheral surface 21 b of the cylindrical body 21
via the cylindrical body 21. It will be formed. Then, the voice coil bobbin 4 is formed by winding
the coil 11 around the outer peripheral surface of the bobbin 10, that is, the outer side resist 27.
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11
[0032]
As described above, according to the speaker 1 having the structure shown in FIGS. 1 to 5, when
an audio signal is input to the input terminal 15, the voice coil bobbin 4 vibrates based on the
audio signal, and this vibration causes vibration. Plates 2 and 3 vibrate. The vibration of these
diaphragms causes the speaker 1 to generate sound. The operating state of the diaphragms 2
and 3 at this time is recognized by detecting the capacitance formed between the voice coil
bobbin 4 and the center pole body 5a. That is, the facing area of the inner copper plating 23 of
the voice coil bobbin 4 and the outer peripheral surface 5c of the center pole body 5a changes,
and thereby, the capacitance formed between the outer copper plating 32 and the outer
peripheral surface 5c changes. . This change in capacitance corresponds to the displacement of
the diaphragms 2 and 3. Since the capacitance detected in this way is very small (about several
pF to several hundreds pF), in the case of a conventional speaker, it constitutes a magnetic field
or a speaker generated by the current flowing through the coil 11 There is a possibility that it
may change under the influence of disturbance noise such as electromagnetic waves output from
various electronic devices (not shown).
[0033]
However, in the speaker 1 of the present invention, since the outer copper foil 25 and the outer
copper plating 26 are formed on the outer peripheral surface 21 b of the cylindrical body 21,
these block the current flowing in the coil 11 and electromagnetic waves coming from outside. .
Further, since the outer resist 27 is formed between the outer copper plating 26 and the coil 11,
the outer copper plating 26 and the coil 11 can be electrically insulated by the outer resist 27.
This eliminates the possibility that the current flowing through the coil 11 is conducted to the
outer copper plating 26 and the outer copper foil 25. Further, since the outer copper plating 26
is grounded, the current flowing to the coil 11 and electromagnetic waves from the outside are
absorbed by the outer copper plating 26. Furthermore, since the inner resist 24 is interposed
between the outer copper plating 26 and the outer peripheral surface 5c of the center pole main
body 5a, the dielectric constant of the capacitor constituted by the outer copper plating 26 and
the center pole main body 5a is increased. That is, the capacitance can be increased. Therefore,
the true capacitance formed between the outer copper plating 26 and the outer peripheral
surface 5c of the center pole main body 5a is accurately determined without the influence of the
current flowing in the coil 11 or the electromagnetic wave entering from the outside. It can be
detected.
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[0034]
Generally, when a conductor is moved in a fixed magnetic field, an eddy current flows on the
surface of the conductor, but in the present invention, the inner copper foil 22 and the inner
copper on the inner circumferential surface 21 a of the cylindrical body 21 Since the plating 23
is formed and the copper film layer consisting of the outer copper foil 25 and the outer copper
plating 26 is formed on the outer peripheral surface 21b of the cylindrical body 21, the circuit in
which the eddy current flows is cut to effectively cut the current. It can be confined within the
membrane layer, which can suppress eddy currents. Furthermore, since the plurality of holes 22a
are formed substantially equally over the entire inside copper foil 22 which is a foil member, the
circuit of the eddy current can be cut by the holes 22a, thereby further suppressing the eddy
current. Can. Therefore, it is possible to more accurately detect the true capacitance formed
between the outer copper plating 26 and the outer peripheral surface 5c of the center pole body
5a without being affected by the eddy current.
[0035]
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. For example, as shown in FIG. 9, the inner copper foil 36
configured similarly to the above-described inner copper foil 22 is attached to the inner
circumferential surface 21a of the cylindrical body 21, and the inner resist 24 is attached
thereon. Then, the outer copper foil 37 configured in the same manner as the outer copper foil
25 described above is attached to the outer peripheral surface 21 b of the cylindrical body 21 so
as to cover the inner copper foil 36 via the cylindrical body 21. Paste 27 Further, in the same
manner as in the above embodiment, the outer copper foil 37 is grounded, and the terminal 31 is
connected to the inner copper foil 36 via the lead wire 30. With this configuration, the outer
copper foil 37 can block the penetration of the electromagnetic wave from the outside and the
conduction of the current flowing through the coil 11 as in the above embodiment.
[0036]
Further, in the above embodiment, the inner copper foil 22 formed substantially uniformly over
the plurality of holes 22a is used substantially, but the present invention is not limited to this. A
plurality of holes 22a and a plurality of holes shown in FIGS. The slits 22b may be used in
combination with any of the patterns formed substantially uniformly throughout. Moreover, you
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13
may use combining the pattern of the slit 22b shown to each of FIGS. 5-7. In the above
embodiment, the holes 22a are formed in a circular shape, but the shape, size, number and the
like of the size, size, etc. of the copper foil are expected to be generated on the copper foil and on
the copper foil. It may be set appropriately according to various conditions such as the size of the
current, as long as it can cut the circuit of the eddy current formed on the copper foil. In addition,
the width, shape, arrangement, combination, number, etc. of the slits 22b shown in each of FIGS.
It may be set appropriately according to the size of the current, etc., as long as it can reliably cut
the circuit of the eddy current formed on the copper foil.
[0037]
In the above embodiment, the plurality of holes 22a are formed in the inner copper foil 22 which
is a foil member, but the present invention is not limited to this. A slit similar to the slit 22b of 7
may be formed. Thereby, the eddy current generated on the outer copper foil 25 can be
suppressed more reliably.
[0038]
In the above embodiment, a double copper film layer composed of the inner copper foil 22 and
the inner copper plating 23 is formed on the inner circumferential surface 21 a of the cylindrical
body 21, and the outer copper foil 25 and the outer copper are formed on the outer
circumferential surface 21 b of the cylindrical body 21. Although the double copper film layer
formed of the plating 26 is formed, the invention is not limited thereto, and a triple or quadruple
copper film layer may be formed, and the number of laminated layers can be appropriately
changed.
[0039]
In the above embodiment, the inner copper foil 22 is attached to the inner peripheral surface 21a
of the cylindrical body 21, the inner copper plating 23 is further coated thereon, and the outer
copper foil 25 is adhered to the outer peripheral surface 21b of the cylindrical body 21.
Furthermore, the outer copper plating 26 was applied thereon, and a copper film layer was
formed on each of the inner peripheral surface 21a and the outer peripheral surface 21b of the
cylindrical body 21, but copper is deposited to form the inner peripheral surface of the
cylindrical body 21. A copper film layer may be formed on each of the surface 21a and the outer
peripheral surface 21b.
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14
Thus, the method of forming a copper film layer can be changed suitably.
[0040]
In the above embodiment, the inner resist 24 is formed on the inner copper plating 23 and the
outer resist 27 is coated on the outer copper plating 26. However, the inner resist 24 and the
outer resist 27 formed in a thin film are inner copper plated 23 and An adhesive may be attached
to the outer copper plating 26. As described above, each resist may be formed in a film shape,
and the method of forming it may be changed as appropriate.
[0041]
In the above embodiment, the copper film layer is formed on the inner peripheral surface 21a
and the outer peripheral surface 21b of the cylindrical body 21. However, without limitation
thereto, for example, an aluminum layer made of aluminum or a conductive plastic layer is
formed The nonmagnetic conductive film may be appropriately formed on the inner peripheral
surface 21 a and the outer peripheral surface 21 b of the cylindrical body 21.
[0042]
In the above embodiment, the cylindrical body 21 is made of polyimide, but the material is not
limited to this, and it may be, for example, paper, and can be appropriately changed as long as it
is made of an insulator.
[0043]
It is sectional drawing which shows the structure of the speaker of this invention.
It is a functional block diagram which shows the electric constitution of a speaker.
It is a sectional view showing composition of a voice coil bobbin, a center pole, and a part of
yoke. It is a top view which shows the structure of inner side copper foil. It is a top view which
shows the structure of inner side copper foil. It is a top view which shows the structure of inner
side copper foil. It is a top view which shows the structure of inner side copper foil. It is a top
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view which shows the structure of outer side copper foil. It is another embodiment in the present
invention, and is a sectional view showing composition of a voice coil bobbin, a center pole, and a
part of yoke.
Explanation of sign
[0044]
REFERENCE SIGNS LIST 1 speaker 4 voice coil bobbin 5 center pole 5 a center pole main body
21 cylindrical body 21 a inner circumferential surface 21 b outer circumferential surface 22, 36
inner copper foil (first conductive film) 22 a hole 22 b slit 23 inner copper plating (first
conductive film) 24 inner resist (inner insulator film) 25, 37 outer copper foil (second conductor
film) 26 outer copper plating (second conductor film) 27 outer resist (outer insulator film)
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