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JP2008035260

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DESCRIPTION JP2008035260
[PROBLEMS] To prevent an abnormal sound generated by contact between a voice coil and a
center pole in a speaker. SOLUTION: In a speaker 1 for detecting a capacitance formed between a
voice coil 4 and a center pole 5 and outputting it as an electric signal, a portion of the center pole
5 which can be in contact with the voice coil 4 is It was made to coat with non-electroconductive
material 6. [Selected figure] Figure 1
スピーカー
[0001]
The present invention relates to a speaker. More specifically, the present invention relates to a
speaker that detects a capacitance formed between a voice coil and a center pole and outputs it
as an electrical signal.
[0002]
A speaker equipped with an MFB (Mortional Feed Back) circuit is known as a technology for
improving the sound quality of the speaker. The MFB circuit detects an operating state of a
vibrating plate based on an electrical signal (also referred to as a voice signal) indicating audio
information input to a speaker, and performs feedback control of the diaphragm based on the
detection result. This makes it possible to eliminate the distortion of sound that is particularly
likely to occur in the low tone range. Therefore, it is generally considered that the MFB circuit is
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1
effectively employed in a small speaker which is considered to be difficult to reproduce in the
low frequency range.
[0003]
The MFB circuit detects the operating state of the diaphragm 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 for
vibrating the diaphragm, and the electrode (hereinafter referred to as the electrode) is opposed
to the movable electrode. The fixed electrode is fixed, and the electrostatic capacitance detected
by the movable electrode moving relative to the fixed electrode is detected by the detector, and
this is converted by the conversion circuit into an electrical signal (also called a detection signal).
Convert to) and output. Then, the detection signal and the audio signal are compared by a
comparison device (for example, CPU), and the operation of the diaphragm is appropriately made
based on the comparison result, that is, the difference between the output level of the detection
signal and the output level of the audio signal. Control.
[0004]
As a conventional speaker which detects the change of the electrostatic capacitance formed
between the voice coil which is an electrode and a center pole as mentioned above, converts it
into an electric signal, and outputs it, for example, as shown in FIG. A cylindrical voice coil 101 in
which a magnetic circuit is formed by a magnet 105 and a yoke 104 having a cylindrical center
pole 103, and a coil 102 is wound in an annular gap 107 between the center pole 103 and the
yoke 104. The voice coil 101 and the diaphragm 106 are connected to each other and supported
by a frame (not shown) to vibrate the diaphragm 106 to generate sound (Japanese Patent
Application Laid-Open No. 2003-101118).
[0005]
JP-A-53-12320
[0006]
However, in the speaker of Patent Document 1, there is a problem that when the voice coil 101
as the electrode and the center pole 103 come in contact with each other, an abnormal signal is
generated to generate an abnormal sound.
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2
For this reason, it is difficult to say that a good sound generation state is secured even when, for
example, the speaker itself vibrates or an abnormal input occurs.
[0007]
Then, an object of this invention is to provide the speaker which can prevent the abnormal sound
which generate | occur | produces when a voice coil and a center pole contact.
[0008]
In order to achieve such an object, a speaker according to the present invention is a speaker that
detects a capacitance formed between a voice coil and a center pole and outputs it as an electric
signal, at least one of the voice coil and the center pole. And at least a portion where the voice
coil and the center pole can be in contact with each other is coated with a non-conductive
material.
[0009]
Therefore, according to this speaker, the voice coil and the center pole are in contact with each
other since the portion where at least one of the voice coil and the center pole can come in
contact with the center pole is coated with the nonconductive material. However, both are not
electrically connected and short circuit is prevented.
[0010]
According to the speaker of the present invention, even when the voice coil and the center pole
are in contact with each other, the two are not electrically connected and short circuiting is
prevented, and even when both are in contact, no abnormal signal is generated. Since no
abnormal sound is emitted, a good sound generation state can be ensured even if, for example,
the speaker itself vibrates or an abnormal input occurs.
[0011]
Hereinafter, the configuration of the present invention will be described in detail based on the
best mode shown in the drawings.
[0012]
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An example of embodiment of the speaker of this invention is shown in FIG.1 and FIG.2.
The speaker 1 detects a capacitance formed between the voice coil 4 and the center pole 5 and
outputs it as an electric signal, and a portion which can be in contact with the voice coil 4 of the
center pole 5 Is coated with the non-conductive material 6.
[0013]
The speaker 1 includes a damper 2, a diaphragm 3, a voice coil 4, a center pole 5, a magnet 7, a
yoke plate 8, and a yoke case 9.
[0014]
The yoke case 9 is formed in a bowl shape having a circular cross section.
[0015]
The yoke plate 8 is formed in a disk shape having a through hole 8a at a central portion.
Further, the yoke plate 8 is formed to have a diameter at least larger than the diameter of the
opening of the yoke case 9.
The yoke plate 8 is fixed to the end face of the yoke case 9 on the opening side in a state where
the through hole 8 a is positioned substantially at the center of the opening of the yoke case 9.
[0016]
The magnet 7 is formed in a disk shape having a constant thickness.
Then, one surface of the disk-shaped magnet 7 and the inner bottom surface 9a of the yoke case
9 are bonded, and the magnet 7 is fixed to substantially the center of the inner bottom surface
9a.
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4
[0017]
The center pole 5 is made of iron and has a columnar center pole body 5a, a band-like protrusion
5b formed around the outer peripheral surface of the center pole body 5a in the middle of the
center pole body 5a, and a base of the center pole body 5a. It is comprised from the flange 5c
formed in the end.
The end face on the flange 5c side of the center pole 5 is bonded to the magnet 7 fixed to the
inner bottom surface 9a of the yoke case 9, and the axis of the columnar center pole body 5a is
substantially perpendicular to the inner bottom surface 9a. The center pole 5 is fixed in a state of
being positioned approximately at the center of the inner bottom surface 9a.
[0018]
The outer peripheral surface of the strip-like protrusion 5b of the center pole 5 is coated with a
non-conductive material 6, as shown in FIG.
The non-conductive material 6 may be any material that has insulating properties and can be
thinly coated. Specifically, for example, a fluorine resin is coated at a thickness on the order of
microns.
[0019]
When the end face of the center pole 5 on the side of the flange 5c on the base end side is
adhered to the magnet 7, the positions of the band-like protrusion 5b and the through hole 8a of
the yoke plate 8 substantially coincide with each other. The tip end portion 5a is formed and
disposed so as to protrude from the through hole 8a to the outside of the yoke case 9.
[0020]
The center pole 5 and the yoke case 9 are connected to a housing (not shown) called an
enclosure and grounded or grounded.
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5
[0021]
The voice coil 4 is composed of a cylindrical bobbin 4a whose both ends are open and a coil 4b
wound in a band around the outer periphery of the bobbin 4a.
[0022]
The inner diameter of the bobbin 4a is slightly larger than the outer diameter of the band-shaped
protrusion 5b of the center pole 5, that is, an air gap is formed between the inner peripheral
surface of the bobbin 4a and the outer peripheral surface of the band-shaped protrusion 5b of
the center pole 5. The inner diameter is adjusted and formed to be
Then, it is inserted into the inside of the yoke case 9 from the through hole 8a of the yoke plate
8, and covers at least the band-like protrusion 5b to cover the center pole main body 5a.
[0023]
The coil 4b is wound around the outer periphery of the bobbin 4a at a position facing the
through hole 8a of the yoke plate 8 in a state where the bobbin 4a is put on the center pole main
body 5a.
Specifically, for example, a conductor such as an enameled wire or a lead is used as the coil 4b.
[0024]
The through hole 8a of the yoke plate 8 is the air between the outer peripheral surface of the coil
4b wound around the outer periphery of the bobbin 4a and the inner peripheral surface of the
through hole 8a in a state where the bobbin 4a is covered with the center pole body 5a. The
diameter is adjusted to form a gap.
[0025]
The damper 2 and the diaphragm 3 are attached to the bobbin 4 a of the voice coil 4.
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The damper 2 is a circular thin plate having a plurality of bent portions and a hole for allowing
the bobbin 4a to penetrate in the center, and the edge of the hole in the center is bonded to the
outer peripheral surface of the bobbin 4a with an adhesive. Are adhesively bonded to the frame
12.
The diaphragm 3 functions as a so-called cone paper, and is formed in a mortar shape having a
hole at the bottom for allowing the bobbin 4a to pass through, and the edge of the hole at the
bottom is bonded to the outer peripheral surface of the bobbin 4a with an adhesive. The outer
peripheral edge is joined to the frame 12 through the joint 13.
The damper 2 and the diaphragm 3 are formed of a flexible material, and the voice coil 4 is
supported so as to be capable of vibrating in the axial direction of the cylindrical bobbin 4a.
[0026]
The frame 12 is formed in a mortar shape having a hole for penetrating the bobbin 4a
substantially at the center of the bottom.
The bottom portion is bonded to the yoke plate 8 with an adhesive, and the outer peripheral edge
portion is bonded to a housing called the enclosure with a screw or an adhesive and grounded.
[0027]
An opening 4 c opposite to the yoke case 9 of the voice coil 4 is covered by a center cap 14. The
center cap 14 is made of aluminum or the like, and includes a dome-shaped main body portion
14 a and a collar portion 14 b formed along the outer peripheral edge of the main body portion
14 a. In the center cap 14, the flange portion 14 b is bonded to the diaphragm 3 with an
adhesive and fixed to the diaphragm 3.
[0028]
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According to the speaker 1 configured as described above, an audio signal is input to the voice
coil 4, that is, a current indicating the audio signal flows through the coil 4b of the voice coil 4,
and this current, the center pole 5, the magnet 7, and the current The voice coil 4 vibrates in the
axial direction of the cylindrical bobbin 4 a by the excitation action of the magnetic flux formed
between the yoke case 9 and the yoke plate 8. Along with this, the damper 2 and the diaphragm
3 vibrate and sound is emitted from the speaker 1.
[0029]
Then, according to the speaker 1 of the present invention, the outer peripheral surface of the
band-like protrusion 5b of the center pole 5 which may come in contact with the inner peripheral
surface of the bobbin 4a of the voice coil 4 is coated with the nonconductive material 6
Therefore, even if the voice coil 4 and the center pole 5 are in contact with each other, no
abnormal signal is generated due to the contact between the two, and therefore the generation of
an abnormal sound is prevented.
[0030]
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, in the present embodiment, the outer peripheral surface of the strip-like protrusion
5b, which is a portion facing the voice coil 4 of the center pole 5, is coated with the nonconductive material 6; The opposite portion to the center pole 5 may be coated with the
nonconductive material 6, or the opposite portion of both the center pole 5 and the voice coil 4
may be coated with the nonconductive material 6. Specifically, as shown in FIG. 3, a portion
facing the strip-like protrusion 5b, which is a portion which may come into contact with the striplike protrusion 5b of the center pole 5 on the inner circumferential surface of the bobbin 4a of
the voice coil 4. May be coated with the non-conductive material 6 in a strip shape. At this time,
since the voice coil 4 vibrates in the axial center direction of the cylindrical bobbin 4 a, the nonconductive material 6 is coated in a band in a range in which the maximum amplitude of the
vibration of the voice coil 4 is considered. Further, as shown in FIG. 4, a portion of the inner
peripheral surface of the bobbin 4 a of the voice coil 4 facing the strip shaped protrusion 5 b of
the center pole 5 is coated in a strip shape with the nonconductive material 6 and the voice of
the center pole 5 The outer peripheral surface of the strip-like protrusion 5 b, which is a portion
that can be opposed to and in contact with the coil 4, may be coated with the non-conductive
material 6.
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[0031]
Furthermore, the present invention is applicable to a speaker having any configuration as long as
it is a speaker that detects an electrostatic capacitance formed between a voice coil and a center
pole and outputs it as an electric signal. The configuration of the speaker of the invention is not
limited to the configuration of the speaker 1 of this embodiment.
[0032]
It is a longitudinal cross-sectional view which shows an example of embodiment of the speaker of
this invention.
It is an enlarged longitudinal cross-sectional view of the opposing part of the center pole and
voice coil of embodiment of FIG. 1, and the coating part by a nonelectroconductive material. It is
an enlarged longitudinal cross-sectional view of the opposing part of the center pole and voice
coil of other embodiment, and the coating part by a nonelectroconductive material. It is an
enlarged longitudinal cross-sectional view of the opposing part of the center pole and voice coil
of other embodiment, and the coating part by a nonelectroconductive material. It is a longitudinal
cross-sectional view which shows the conventional speaker.
Explanation of sign
[0033]
1 speaker 4 voice coil 5 center pole 6 non-conductive material
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