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DESCRIPTION JPH0883081

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DESCRIPTION JPH0883081
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
active silencer in which exhaust noise is actively silenced by a secondary sound source.
[0002]
2. Description of the Related Art Conventionally, as an active type silencer in which exhaust noise
is actively silenced by a secondary sound source, for example, Japanese Patent Laid-Open No. 4350314, Japanese Utility Model Application Laid-Open No. 4-129817. The disclosures of JP-A-4119318, JP-A-4-91213, JP-A-4-14715, JP-A-4-8713 and the like are known.
[0003]
FIGS. 5 and 6 show an active silencer of this type, in which reference numeral 11 denotes a
silencer body having a rectangular cross-sectional shape.
The silencer main body 11 is divided into three by a partition wall 13 disposed at a
predetermined interval, a silencer chamber 15 is formed at the center, and speaker chambers 17
are formed on both sides of the silencer chamber 15.
[0004]
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An exhaust pipe 19 for passing exhaust gas G is inserted into the muffling chamber 15. A large
number of small holes are formed throughout the exhaust pipe 19 in a portion located in the
muffling chamber 15. 21 is formed.
[0005]
Openings 23 are formed in the pair of partition walls 13 at positions facing each other with the
exhaust pipe 19 at a center, and a speaker 25 as a secondary sound source is disposed in the
openings 23.
A protective plate 27 for protecting the speaker 25 is disposed in the opening 23 of the partition
13, and a large number of small holes 29 are formed in the protective plate 27.
[0006]
A sound absorbing material 31 made of glass wool, for example, is accommodated in the muffling
room 15 and the speaker room 17. Further, in the muffling chamber 15, a microphone 33 is
disposed, and the microphone 33 and the speaker 25 are connected via an inverting circuit 37
and a power amplifier 39.
[0007]
In such an active silencer, the noise of the exhaust gas G is detected by the microphone 33, and a
so-called active muffling is achieved by emitting an erasing sound of the opposite phase to the
detected noise from the speaker 25. To be done.
[0008]
However, in such a conventional active silencer, the sound emitted from the speaker 25 is
detected again by the microphone 33, so the sound emitted from the speaker 25 is the same.
There is a problem that a closed circuit is formed and howling tends to occur, and therefore a
sufficient silencing effect can not be obtained.
[0009]
The present invention has been made to solve such conventional problems, and it is an object of
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the present invention to provide an active silencer that can reliably prevent the occurrence of
howling.
[0010]
SUMMARY OF THE INVENTION In the active silencer of the present invention, a noise medium
passage for circulating a noise medium is formed in a silencer chamber formed in the silencer
body, and a noise medium passage is formed in the silencer chamber. An active silencer formed
by arranging a secondary sound source for emitting a sound wave toward the muffling chamber
in a secondary sound source chamber formed adjacent to each other via a partition wall, the
noise medium passage in the secondary sound source chamber And a downstream
communication hole formed at a position in front of the secondary sound source of the partition
to connect the muffling chamber and the secondary sound source chamber, and the partition
Between the downstream communication hole and the upstream communication hole in the
silencer chamber, and an upstream communication hole formed at a position behind the
secondary sound source and communicating the muffling chamber with the secondary sound
source chamber And the radiation sound of the secondary sound source from the downstream
communication hole A microphone disposed at a position where the emission sound of the
secondary sound source from the upstream communication hole has substantially the same
magnitude; and an inverting means for inverting an electric signal from the microphone and
outputting the electric signal to the secondary sound source It is possessed.
[0011]
According to a second aspect of the present invention, in the active type silencer, a noise medium
passage for circulating a noise medium is formed in a silencer chamber formed in the silencer
main body, and is formed adjacent to the silencer chamber via a partition wall. An active silencer
in which a secondary sound source for emitting a sound wave toward the muffling chamber is
disposed in the secondary sound source chamber, the downstream side and the upstream side of
the noise medium passage in the secondary sound source chamber; First and second secondary
sound sources to be disposed, and a downstream communication hole formed at a position of the
partition wall in front of the first secondary sound source and communicating the muffling
chamber and the secondary sound source chamber; An upstream communication hole formed at
a position in front of the second secondary sound source of the partition and communicating the
muffling chamber and the secondary sound source chamber, and the downstream
communication hole and the upstream communication hole in the muffling chamber And the first
secondary sound source from the downstream communication hole. A microphone disposed at a
position at which a shot sound and a radiation sound of the second secondary sound source from
the upstream communication hole have substantially the same magnitude; and an electric signal
from the microphone is inverted to generate the first two Inverting means for outputting to the
next sound source, and output means for outputting to the second secondary sound source
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without inverting the electric signal from the microphone.
[0012]
According to a third aspect of the present invention, in the first or second aspect, the noise
medium passage is an exhaust pipe of a car.
[0013]
In the active silencer according to the first aspect of the present invention, in the microphone, the
emission sound of the front side of the secondary sound source from the downstream
communication hole and the rear side of the secondary sound source from the upstream
communication hole The radiated sound reaches and is detected, but the radiated sound on the
front side of the secondary sound source and the radiated sound on the rear side have opposite
phases because they are radiated from the same diaphragm.
[0014]
The microphones are disposed at positions where the sound emitted from the secondary sound
source from the downstream communication hole and the sound emitted from the secondary
sound source from the upstream communication hole have substantially the same magnitude. As
the electric signal of the above, the radiation sound on the front side of the secondary sound
source and the radiation sound on the rear side cancel each other.
[0015]
Therefore, the electric signal output from the microphone becomes an exhaust noise only signal,
and only this electric signal is inverted by the inverting means and output to the secondary
sound source, and the secondary sound source It is almost impossible for the emitted noise to
form a closed circuit.
[0016]
In the active silencer according to the second aspect of the present invention, in the microphone,
the radiation sound from the front side of the first secondary sound source from the downstream
communication hole and the second secondary sound source from the upstream communication
hole The radiation sound on the front side reaches and is detected, but the radiation sound on
the front side of the first secondary sound source and the radiation sound on the front side of the
second secondary sound source are only for the first secondary sound source Since the electric
signal from the inverted microphone is output, it is in the opposite phase.
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[0017]
Then, the microphone is positioned so that the sound emitted from the first secondary sound
source from the downstream communication hole and the sound emitted from the second
secondary sound source from the upstream communication hole have substantially the same
magnitude. As the electric signal of the microphone is disposed, the emission sound of the first
secondary sound source and the emission sound of the second secondary sound source cancel
each other.
[0018]
Therefore, the electrical signal output from the microphone is abbreviated to the signal of
exhaust noise only.
In the active silencer according to claim 3, exhaust noise from the engine in the exhaust gas of
the automobile is silenced.
[0019]
Embodiments of the present invention will be described below with reference to the drawings.
1 and 2 show a first embodiment of the active silencer according to claim 1, in which reference
numeral 41 denotes a silencer body having an elliptical cross-sectional shape.
[0020]
The silencer main body 41 is divided into three by a pair of partition walls 43 arranged at a
predetermined interval, a silencer chamber 45 is formed at the center, and speaker chambers 47
are formed on both sides of the silencer chamber 45. There is.
[0021]
An exhaust pipe 49 for circulating the exhaust gas G, which is a noise medium passage, is
inserted into the muffling chamber 45, and a large number of small holes are formed in a portion
of the exhaust pipe 49 located in the muffling chamber 45. 51 is formed.
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[0022]
A sound absorbing material 53 made of glass wool, for example, is accommodated in the muffling
chamber 45.
Thus, in this embodiment, a pair of speakers 55, which are secondary sound sources, are
disposed in the speaker room 47 toward the downstream side of the exhaust pipe 49.
[0023]
The pair of speakers 55 is disposed at a predetermined angle θ with respect to the exhaust pipe
49.
A downstream communication hole 57 communicating the muffling chamber 45 and the speaker
chamber 47 is formed at a position in front of the speaker 55 of the partition wall 43.
[0024]
Further, an upstream communication hole 59 for communicating the muffling chamber 45 and
the speaker chamber 47 is formed at a position behind the speaker 55 of the partition wall 43.
The microphone 61 is disposed between the downstream communication hole 57 and the
upstream communication hole 59 in the muffling chamber 45.
[0025]
The microphone 61 is disposed outside the exhaust pipe 49 in the muffling chamber 45, as
shown in FIG.
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Further, the microphone 61 is disposed at a position where the sound emitted from the speaker
55 from the downstream communication hole 57 and the sound emitted from the speaker 55
from the upstream communication hole 59 have substantially the same magnitude.
[0026]
The microphone 61 is connected to the filter 63.
The filter 63 suppresses frequency components other than the exhaust noise in the electric
signal from the microphone 61.
[0027]
The filter 63 is connected to the inverting circuit 67 via the power amplifier 65.
The power amplifier 65 amplifies the electrical signal from the filter 63.
The inverting circuit 67 inverts the electric signal from the power amplifier 65 and outputs the
inverted signal to the speaker 55.
[0028]
In the above-mentioned active silencer, the microphone 61 has the radiation sound from the
front side of the speaker 55 from the downstream communication hole 57 and the radiation
sound from the rear side of the speaker 55 from the upstream communication hole 59. Although
it arrives and is detected, the radiation sound on the front side of the speaker 55 and the
radiation sound on the rear side are in opposite phase because they are radiated from the same
diaphragm.
[0029]
Since the microphone 61 is disposed at a position where the sound emitted from the speaker 55
from the downstream communication hole 57 and the sound emitted from the speaker 55 from
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the upstream communication hole 59 have substantially the same magnitude, As the electric
signal of the microphone 61, the radiation sound on the front side of the speaker 55 and the
radiation sound on the rear side cancel each other.
[0030]
Therefore, the electric signal output from the microphone 61 becomes an exhaust noise only
signal, and only this electric signal is inverted by the inverting circuit 67 and output to the
speaker 55. It is almost impossible for the emitted noise to form a closed circuit.
[0031]
In the above-mentioned active silencer, the sound emitted from the speaker 55 from the
upstream communication hole 59 mainly flows up the exhaust pipe 49 toward the upstream side,
and downstream from the downstream communication hole 57. Exhaust noise is mainly silenced
by the radiation emitted towards the side.
[0032]
In the above-described active type silencer, the microphone 61 has substantially the same
magnitude as the radiated sound of the speaker 55 from the downstream communication hole 57
and the radiated sound of the speaker 55 from the upstream communication hole 59. As the
electric signal of the microphone 61 is such that the radiation sound on the front side of the
speaker 55 and the radiation sound on the rear side cancel each other, the electric signal output
from the microphone 61 is only exhaust noise. Therefore, only this electric signal is inverted by
the inverting circuit 67 and output to the speaker 55, so that the radiation sound from the
speaker 55 substantially does not form a closed circuit, and generation of howling occurs. It can
be reliably prevented.
[0033]
Further, in the above-described embodiment, the microphone 61 is disposed outside the exhaust
pipe 49 in the muffling chamber 45 and the microphone 61 is separated from the exhaust gas.
Therefore, the imbalance of the transfer function due to the Doppler effect of sound is effective.
Can be prevented.
[0034]
Further, in the above-mentioned active silencer, it is not necessary to provide the speaker
chamber 47 with a function as a resonance chamber, so by using the speaker chamber 47 as an
extension chamber, the active silencer can be made compact. can do.
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[0035]
Further, in the above-described active silencer, the static pressure balance between the front and
rear of the diaphragm of the speaker 55 can be sufficiently secured by the downstream
communication hole 57 and the upstream communication hole 59. It can be placed at any
position of the pipeline system.
[0036]
Furthermore, since the traveling directions of the noise to be silenced and the erasure noise
substantially coincide with each other, phase matching can be performed up to a high frequency,
and the silencing frequency can be improved to the high frequency side.
FIG. 3 shows another embodiment of the active silencer according to the first aspect of the
present invention. In this embodiment, the speaker chamber 47 is formed only on one side of the
muffling chamber 45, and the speaker 55 is formed in the speaker chamber 47. Is
accommodated parallel to the exhaust pipe 49.
[0037]
Also in the active silencer of this embodiment, substantially the same effect as that of the first
embodiment can be obtained.
FIG. 4 shows an embodiment of the active silencer according to the second aspect of the present
invention. In this embodiment, in the speaker chamber 47, first and second downstream and
upstream sides of the exhaust pipe 49 are provided. Speakers 55, 69 are disposed.
[0038]
Therefore, the back surface of the first speaker 55 and the second speaker 69 are opposite to
each other.
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At a position in front of the first speaker 55 of the partition wall 43, a downstream
communication hole 57 communicating the muffling chamber 45 and the speaker chamber 47 is
formed.
[0039]
Further, an upstream communication hole 59 communicating the muffling chamber 45 and the
speaker chamber 47 is formed at a position in front of the second speaker 55 of the partition
wall 43.
A microphone 61 is disposed between the downstream communication hole 57 and the upstream
communication hole 59 in the muffling chamber 45.
[0040]
The microphone 61 is disposed at a position where the sound emitted from the first speaker 55
from the downstream communication hole 57 and the sound emitted from the second speaker
55 from the upstream communication hole 59 have substantially the same magnitude. It is done.
[0041]
The microphone 61 is connected to the filter 63.
The filter 63 suppresses frequency components other than the exhaust noise in the electric
signal from the microphone 61.
[0042]
The filter 63 is connected to the inverting circuit 67 via the power amplifier 65.
The power amplifier 65 amplifies the electrical signal from the filter 63.
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The inverting circuit 67 inverts the electric signal from the power amplifier 65 and outputs the
inverted signal to the first speaker 55.
[0043]
The output from the power amplifier 65 is directly input to the second speaker 69 via the output
terminal 71.
In the above-described active silencer, the microphone 61 receives the radiation sound from the
front side of the first speaker 55 from the downstream communication hole 57 and the radiation
from the front side of the second speaker 69 from the upstream communication hole 59.
Although the sound reaches and is detected, the radiation sound on the front side of the first
speaker 55 and the radiation sound on the front side of the second speaker 69 are detected from
the microphone 61 which is inverted only by the first speaker 55. Since electrical signals are
output, they are in opposite phase.
[0044]
The position where the sound emitted from the first speaker 55 from the downstream
communication hole 57 and the sound emitted from the second speaker 69 from the upstream
communication hole 59 have substantially the same magnitude. As an electric signal of the
microphone 61, the radiation sound of the first speaker 55 and the radiation sound of the second
speaker 69 cancel each other.
[0045]
Therefore, the electrical signal output from the microphone 61 is abbreviated to a signal of
exhaust noise only.
Also in the active silencer of this embodiment, substantially the same effect as that of the first
embodiment can be obtained.
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[0046]
In the embodiment described above, the active silencer of the present invention has been
described as applied to the silencing of exhaust noise of the exhaust pipe 49 of a car, but the
present invention is limited to such an embodiment. For example, the present invention can be
widely applied to noise reduction of a motor of a refrigerator or the like.
[0047]
As described above, in the active silencer according to claim 1, the microphone comprises the
radiation sound of the secondary sound source from the downstream communication hole and
the secondary sound source from the upstream communication hole. Since the radiated sound is
disposed at substantially the same magnitude, the radiated sound on the front side of the
secondary sound source and the radiated sound on the rear side cancel each other out as the
electric signal of the microphone, and are output from the microphone The electrical signal
becomes an exhaust noise only signal, and only this electrical signal is inverted by the inverting
means and output to the secondary sound source, and the sound emitted from the secondary
sound source forms a closed circuit. Can be substantially eliminated, and the occurrence of
howling can be reliably prevented.
[0048]
In the active silencer according to the second aspect of the present invention, in the microphone,
the radiation sound of the first secondary sound source from the downstream communication
hole and the radiation sound of the second secondary sound source from the upstream
communication hole are substantially the same. As the electric signal of the microphone is
arranged at the same size, the radiation sound of the first secondary sound source and the
radiation sound of the second secondary sound source cancel each other, and the electric signal
from the secondary sound source It is almost impossible for the radiated sound to form a closed
circuit, and the occurrence of howling can be reliably prevented.
[0049]
According to the third aspect of the present invention, there is an advantage that the exhaust
noise from the engine in the exhaust gas of the automobile can be effectively muffled.
[0050]
Brief description of the drawings
[0051]
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1 is a longitudinal sectional view showing a first embodiment of the active silencer of claim 1;
[0052]
2 is a cross-sectional view of FIG.
[0053]
3 is a cross-sectional view showing another embodiment of the active silencer of claim 1; FIG.
[0054]
4 is a cross-sectional view showing an embodiment of the active silencer of claim 2.
[0055]
5 is a cross-sectional view showing an example of a conventional active silencer.
[0056]
6 is a cross-sectional view of FIG.
[0057]
Explanation of sign
[0058]
41 silencer body 43 partition wall 45 silencer chamber 47 speaker chamber 49 exhaust pipe 55
speaker 57 downstream communication hole 59 upstream communication hole 61 microphone
67 reverse circuit 69 second speaker 71 output terminal
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