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JP2003259478

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2003259478
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic apparatus in which a microphone and a speaker are integrated, and more particularly to
an acoustic apparatus capable of preventing the occurrence of howling and improving the
sensitivity of the microphone.
[0002]
2. Description of the Related Art When a microphone and a speaker are stored in a state in which
they are brought close to each other in a single housing, the sound (vibration) emitted from the
speaker is picked up by the microphone and converted into an electrical signal to be emitted by
the speaker. Also, the phenomenon that the microphone picks up may be repeated to cause socalled howling (oscillation state).
[0003]
For this reason, in a conventional communication device such as a mobile phone, the method of
separating the microphone and the speaker as far as possible and avoiding the howling by
preventing the microphone from picking up the sound emitted from the speaker is taken. ing.
[0004]
Alternatively, measures have been taken to provide a dedicated electronic circuit or software
inside a speech apparatus such as in a mobile phone to prevent the howling.
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[0005]
However, there is a problem that it is difficult to miniaturize a communication device such as a
portable telephone if the above-mentioned means for increasing the distance between the
microphone and the speaker is used.
[0006]
In particular, if the microphone and the speaker can be integrated without causing howling, the
size of the communication device can be dramatically reduced.
[0007]
Further, in the means using a dedicated electronic circuit, there is a problem that it is difficult to
achieve cost reduction because the circuit configuration becomes complicated.
[0008]
Furthermore, in the means using software, it is necessary to secure a dedicated memory, which
causes a problem that the amount of memory that can be used by the user is reduced.
[0009]
SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned
conventional problems, and it is an object of the present invention to prevent occurrence of
howling with a simple structure in an audio apparatus provided with a microphone and a
speaker.
[0010]
According to the present invention, there is provided an acoustic apparatus, wherein a support
comprises a sound producing unit for generating a sound and a sound collecting unit operated by
sound pressure generated externally. Are provided with a first diaphragm for sound generation, a
drive coil for vibrating the first diaphragm, and a magnetic circuit for generating a magnetic field
linking the drive coil, and the sound collection unit A second diaphragm for sound, a detection
coil operating together with the second diaphragm, and a magnetic circuit for generating a
magnetic field linking the detection coil are provided, and the first diaphragm vibrates. An
auxiliary coil to be vibrated together with the first diaphragm during a sounding operation, and a
current circuit including the detection coil and the auxiliary coil are provided, and the second
vibration is generated by the sounding operation of the first diaphragm. The diaphragm of was
vibrated To come, the induced current generated in the auxiliary coil, so as to cancel the induced
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current generated in the detection coil, is characterized in that the current circuit is formed.
[0011]
In this acoustic device, when the first diaphragm is driven to perform a sounding operation, an
induced current is generated in the auxiliary coil that vibrates together with the first diaphragm.
When the first diaphragm is driven, the second diaphragm of the sound collecting unit vibrates,
and at this time, the induced current generated in the detection coil is canceled by the current
generated in the auxiliary coil in the current circuit. .
Therefore, the occurrence of howling can be suppressed.
[0012]
Preferably, the drive coil and the auxiliary coil are attached to the same side of the first
diaphragm.
[0013]
According to this structure, when the second diaphragm is vibrated by the external sound, the
first diaphragm is also vibrated in the same direction.
At this time, since the current induced in the auxiliary coil is superimposed on the current
induced in the detection coil, the sensitivity as a microphone in the sound collecting unit
becomes high.
[0014]
Further, when the drive coil and the auxiliary coil are located in a common magnetic circuit, the
magnetic circuit can be easily configured.
[0015]
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Furthermore, it is preferable that the drive coil, the detection coil, and the auxiliary coil have the
same winding direction, and the direction of the magnetic field linking the drive coil, the
detection coil, and the auxiliary coil be the same.
[0016]
Also, for example, in the current circuit, the drive coil and the auxiliary coil are connected in
series or in parallel.
[0017]
However, in the current circuit, in addition to the drive coil and the auxiliary coil, a transistor, a
resistor and other electronic elements are combined so that the induced current of the drive coil
and the auxiliary coil is canceled during the sound generation operation. May be
[0018]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a cross-sectional view of
an acoustic device showing an embodiment of the present invention, and FIGS. 2 and 3 show an
example of a current circuit including a detection coil and an auxiliary coil. B functions as a
microphone.
[0019]
The acoustic device 1 shown in FIG. 1 has a frame 2.
The frame 2 is formed by injection molding using a synthetic resin material, die-cast molding
using an aluminum alloy, a zinc alloy, or the like.
[0020]
In the embodiment shown in the drawings, the frame 2 is formed in a dish shape of a synthetic
resin material, and an opening 2A having a large internal diameter is formed at the central
portion.
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A concave lower yoke 3 made of a magnetic material is fitted in the opening 2A.
In this embodiment, a support is formed by the frame 2 and the lower yoke 3.
And, a sound producing unit A and a sound collecting unit (microphone) B are provided on the
support.
[0021]
A small diameter opening 3A is formed at the center of the lower yoke 3, and a microphone case
(center pole) 4 is attached to the opening 3A.
The microphone case 4 is formed in a tubular shape of a synthetic resin material or a
nonmagnetic metal material.
[0022]
In the sound generation unit, the first diaphragm 11 is provided on the support.
The diaphragm 11 is formed of a paper material, a laminate material of a paper material and a
resin film, or a paper material impregnated with a resin.
The edge 11 a on the outer peripheral side of the diaphragm 11 is fixed to the upper surface of
the stepped portion 2 B formed on the outer peripheral portion of the frame 2.
Further, a hole is opened at the central portion of the diaphragm 11, and an edge 11b on the
inner peripheral side around the hole is fixed to the outer peripheral surface on the front side of
the microphone case 4, and the diaphragm 11 are vibratably supported.
[0023]
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A cylindrical bobbin 13 extending in the Z2 direction is fixed to the lower surface of the
diaphragm 11, and a drive coil C1 is wound around the outer peripheral surface thereof.
Further, a cylindrical bobbin 12 concentric with the bobbin 13 is fixed to the inner peripheral
side of the bobbin 13, and an auxiliary coil C0 is wound around the bobbin 12.
[0024]
A ring-shaped permanent magnet 5 and an upper yoke 6 formed of a magnetic material are fitted
on the outer periphery of the microphone case 4 in a superimposed state.
The permanent magnet 5 is magnetized such that the upper surface side and the lower surface
side are reversed magnetic poles. For example, the Z1 side is magnetized to the N pole and the
Z2 side is magnetized to the S pole.
A driving gap G1 is formed between the outer peripheral surface of the upper yoke 6 and the
inner surface of the outer peripheral portion of the lower yoke 3, and the bobbin 13 and the
driving coil C1, and the bobbin 12 and the auxiliary coil C0. Is located.
[0025]
The magnetic field generated by the permanent magnet 5 constitutes a magnetic circuit from the
upper yoke 6 to the inner surface of the outer peripheral portion of the lower yoke 3 in the gap
G1. In the magnetic circuit, the drive coil C1 and the auxiliary coil A magnetic field in the same
direction is linked to C0.
Further, the winding directions of the drive coil C1 and the auxiliary coil C0 are the same.
[0026]
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In this embodiment, the permanent magnet 5, the upper yoke 6, the gap G1, the drive coil C1 and
the lower yoke 3 constitute a magnetic drive unit serving as a vibration generating unit. A sound
generator A is composed of the magnetic drive unit and the diaphragm 11. The permanent
magnet 5, the upper yoke 6, the gap G 1, the auxiliary coil C 0 and the lower yoke 3 constitute an
auxiliary magnetic drive unit for howling prevention.
[0027]
A sound collection unit B functioning as a microphone is provided in the microphone case 4. In
the sound collecting portion B, a cup-shaped internal yoke 7 is fixed, and the lower surface of a
cylindrical permanent magnet 8 is closely fixed to the center of the bottom surface. Further, on
the upper surface of the permanent magnet 8, a disk-shaped opposing yoke 9 is fixed. The inner
yoke 7 and the opposing yoke 9 are both formed of a magnetic material. On the inner peripheral
surface of the upper end of the inner yoke 7, a protruding portion 7a protruding in the center
direction approaching the opposing yoke 9 is formed, and between the protruding portion 7a
and the side surface of the opposing yoke 9 for detection Gap G2 is formed. A magnetic circuit
for detection is formed by the inner yoke 7, the permanent magnet 8 and the opposing yoke 9.
[0028]
Further, a second diaphragm 21 formed in a substantially W-shaped cross section is provided in
the inside of the microphone case 4, and the outer edge portion of the second diaphragm 21 is
circumferentially fixed to the inner wall of the microphone case 4. ing. A cylindrical bobbin 22 is
fixed to the center of the second diaphragm 21 and a detection coil C2 is wound around the
outer peripheral surface of the bobbin 22. The second bobbin 22 having the detection coil C2 is
accommodated in the gap G2.
[0029]
The permanent magnet 8, the opposing yoke 9, the gap G2, the detection coil C2 and the inner
yoke 7 constitute a magnetic detection unit, and the magnetic detection unit and the second
diaphragm 21 constitute the sound collection unit B. ing. In this embodiment, the direction of the
magnetic field is the same in the drive gap G1 and the detection gap G2, and the winding
direction of the detection coil C2 is the same as the winding direction of the drive coil C1 and the
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auxiliary coil C0. It is in the direction.
[0030]
The detection coil C2 and the auxiliary coil C0 are located in the same current circuit. For
example, as shown in FIG. 2, the coils C2 and C0 are connected in series, or connected in parallel
as shown in FIG.
[0031]
Further, a resonance plate 31 covering the first diaphragm 11 and the second diaphragm 21 is
fixed to the stepped portion 2B of the frame 2. A plurality of holes are bored in the resonance
plate 31.
[0032]
The operation of the above-mentioned acoustic device will be described below. When an audio
signal is given to the drive coil C1 of the sound generation unit A, the first diaphragm 11 is
vibrationally driven in the Z direction as illustrated by the electromagnetic force generated by the
magnetic flux linking the drive coil C1 and the current flowing in the drive coil C1. A sound
corresponding to the audio signal is generated from the first diaphragm 11 forward (in the Z1
direction).
[0033]
At this time, the sound pressure emitted forward from the first diaphragm 11, that is, the
vibration due to air density in the space in the front is given to the second diaphragm 21, and the
second diaphragm 21 It is made to vibrate. Then, a current I1 is induced in the detection coil C2
that vibrates together with the second diaphragm 21. In FIG. 2A and FIG. 3A, the direction of the
current I1 at a certain point is indicated by an arrow.
[0034]
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However, when the first diaphragm 11 is vibrated, a current I0 flows through the auxiliary coil
C0 vibrating with it. The amplitude direction of the vibration of the first diaphragm 11 and the
amplitude direction of the vibration of the second diaphragm 21 are opposite to each other, and
the phases of the vibrations in both the diaphragms 11 and 21 differ by 180 degrees. Therefore,
as shown in FIG. 2A or 3A, the current I0 generated in the auxiliary coil C0 is in the direction to
cancel the current I1 induced in the detection coil C2. Therefore, even if the first diaphragm 11 is
driven to generate sound and the second diaphragm 21 is driven by the sound pressure, the
current does not substantially flow from the detection coil C2, and therefore howling can be
prevented.
[0035]
The number of turns of the detection coil C2 and the auxiliary coil C0 are determined according
to the difference in the magnetic field strength between the permanent magnet 5 and the
permanent magnet 8 and the difference in the gap distance between the driving gap G1 and the
detecting gap G2. By adjusting the ratio of the number of turns, it is possible to configure so as to
almost cancel the currents I0 and I1.
[0036]
Next, when a sound is generated in the space in front of the resonance plate 31 (Z1 side), the
sound wave is transmitted to the inside through the hole of the resonance plate 31 and the
second sound collecting unit B in the microphone case 4 is generated. The diaphragm 21 is
vibrated and operates as a microphone.
[0037]
At this time, the detection current I2 is induced in the detection coil C2 by the vibration of the
second diaphragm 21 of the sound collection unit B.
In FIGS. 2B and 3B, the direction of the current I2 at a certain point is indicated by an arrow.
When the second diaphragm 21 is vibrated by the sound pressure from the outside, the first
diaphragm 11 is also vibrated by the sound pressure. The phase of the vibration of the first
diaphragm 11 at this time and the phase of the vibration of the second diaphragm 21 are the
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same. Therefore, as shown in FIGS. 2B and 3B, the direction of the current I3 induced in the
auxiliary coil C0 is the same as the direction of the current I2 induced in the detection coil C2.
[0038]
Therefore, the detection sensitivity in the sound collection unit B when functioning as a
microphone is amplified, and detection with high sensitivity is possible.
[0039]
Although the drive coil C1 and the auxiliary coil C0 are wound around different bobbins 12 and
13 in the above embodiment, the present invention is not limited to this, and one bobbin may be
used. The drive coil C1 and the auxiliary coil C0 may be provided.
[0040]
As described above, in the present invention, when functioning as a speaker, the current
collected in the auxiliary coil of the sound generation unit cancels the current induced in the
detection coil of the sound collection unit, and the sound collection unit is thus realized. Since the
vibration of the diaphragm can be suppressed, it is possible to prevent the occurrence of howling.
[0041]
Also, when functioning as a microphone, the detection sensitivity of the entire acoustic device
can be amplified by the current induced in the auxiliary coil of the sound generation unit and the
current induced in the detection coil of the sound collection unit, and detection with high
sensitivity is achieved. It becomes possible.
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