JP2001355427A - Active muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the muffling effect by arranging plural speakers in an active muffler. SOLUTION: In this active muffler having a first noise detecting means, a means mounted at a downstream side of a duct and outputting a muffling signal, an operating means calculating a muffling signal of a phase opposite to that of a noise signal detected by the first noise detecting means, and a second noise detecting means mounted at a downstream side with respect to the output means on the duct mounted at a noise side, a muffling signal output means is mounted on a branch pipe branched from the duct, and plural muffling signal outputting means are arranged in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for enhancing a noise reduction effect by arranging a plurality of noise reduction signal output means in an active noise reduction device.

[0002]

2. Description of the Related Art Conventionally, a speaker for outputting a muffling signal is provided in a duct such as an engine exhaust gas pipe, an air supply duct, and a ventilation duct, and a signal having a phase opposite to that of noise in the duct is output from the speaker. Active silencers for silencing are known. In order to output the muffling signal, a branch pipe is branched from the duct and provided, and a speaker is disposed at an end of the branch pipe.

[0003]

However, if the sound pressure of the noise is high, the output of one speaker is insufficient, and the sound is insufficiently silenced. Further, if the speaker output is increased to sufficiently mute the sound, a problem occurs in durability. In view of the above, the present invention is intended to eliminate insufficient sound silencing by arranging a plurality of speakers in parallel.

[0004]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. That is, in the first aspect, the first noise detection means in the duct arranged on the noise side, the means for outputting a muffling signal arranged downstream of the duct, and the first noise detection means In an active noise reduction device having a calculation means for calculating a noise reduction signal having an opposite phase to the detected noise signal, and a second noise detection means disposed downstream of the output means, The muffled signal output means was arranged on the branch pipe arranged in the above manner, and a plurality of the muffled signal output means were arranged.

That is, in claim 2, the plurality of muffling signal output means are arranged in parallel.

That is, in claim 3, the plurality of muffling signal output means are attached at an angle of 45 degrees or less with respect to the axis of the branch pipe.

That is, in claim 4, the means for outputting the plurality of muffling signals are arranged at a position at the same distance from the axis on a plane perpendicular to the axis of the branch pipe.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration and control of an active silencer of the present invention, FIG. 2 is a plan sectional view showing an arrangement configuration of a speaker of the present invention, FIG. FIG.

First, an outline of an active noise reduction device will be described with reference to an example of an active noise reduction device 10 configured to mute exhaust noise of an engine generator. FIG. 1 shows a schematic configuration of the active silencer. A sound source passage duct 1 is connected to an exhaust pipe of an engine 2a of an engine generator 2 serving as a noise source (primary sound source) to form a one-dimensional sound field so that noise flows from left to right in FIG. On the noise source side of the sound source passage duct 1, that is, on the engine side (left side in FIG. 1), a first sound wave sensor 4 composed of a microphone is provided as first noise detection means. On the downstream side of the sensor 4 (on the right side in FIG. 1), a second sound sensor 6 composed of a microphone is provided as second noise detecting means.

The first sound wave sensor 4 of the sound source passage duct 1
A branch pipe 1a is arranged between the second sound wave sensor 6 and
A branch port 1b is opened in the branch pipe 1a, and a branch pipe 9 is communicated with an end of the branch port 1b. A speaker 3 as a sound output means and a cooling as a cooling means are connected to the end of the branch pipe 9. A fan 7 is arranged, a temperature sensor 13 is arranged near the speaker 3, and the temperature of the speaker 3 is detected. The speaker 3 is cooled by the cooling fan 7 so that the speaker 3 is not damaged by the heat transmitted from the sound source passage duct 1 via the branch pipe 9. A shielding plate 25 is disposed between the branch port 1b and the branch pipe 9, and when the cooling fan 7 or the generator 2b or the like fails, the shielding plate 25 is rotated to close the branch port 1b and branch pipe 9 Heat can be prevented from entering the side.

The first sound wave sensor 4, the second sound wave sensor 6, the cooling fan 7, the temperature sensor 13, the inverter 15, the engine 2 and the like are connected to the controller 5, and the speaker 3 is connected to the controller 5 via the amplifier 12. It is connected. Also, the emergency power supply 14 is an inverter 15,
The cooling fan 7 and the controller 5 are connected in parallel with the output of the generator 2a via the switching
And so on.

The first sound sensor 4 detects an exhaust sound which is noise, the speaker 3 outputs a sound wave having a phase opposite to the exhaust sound to mute the sound, and the second sound sensor 6 operates to mute the sound. Is monitored and fed back to the controller 5. The controller 5 is the first sound wave sensor 4
Calculates the noise canceling signal of the opposite phase to the noise signal detected by the above, controls the active noise canceling device 10 to calculate and output a signal for more efficiently canceling the noise from the feedback signal, and further controls the engine generator 2. And the alarm device 16 are controlled.

The alarm device 16 includes a lamp 17 and a buzzer 19.
The cooling fan 7 is constantly driven while the engine generator 2 is operating, and when the engine generator 2 is stopped, it is determined that the detection value of the temperature sensor 13 is equal to or higher than the first set temperature. Then, the driving of the cooling fan 7 is continued by the power from the emergency power supply 14, and when the temperature becomes equal to or lower than the second set temperature, the cooling fan 7 is stopped. In addition, after the engine generator 2 is stopped by connecting the timer 18 to the controller 5, the cooling fan 7 is driven for a set time to prevent the speaker 3 from being damaged by the residual heat. Alternatively, the cooling fan 7 is stopped when the time reaches earlier. Further, when the temperature of the temperature sensor 13 becomes equal to or higher than the third set temperature, the temperature is abnormally increased. In this case, the alarm device 16 is operated to make the operator recognize and stop the engine generator 2.

A passive silencer 11 composed of a sound-tuning tube is disposed between the branch tube 1a and the first sound wave sensor 4. In this embodiment, a primary sound-tuning tube 11a and a secondary sound-tuning tube 11b are provided.
Are arranged in series to form a passive silencer 11. The passive silencer 11 silences and reduces high frequency noise. However, in the present embodiment, the passive silencer 11 is arranged upstream of the sound source passage duct 1, but may be arranged in the middle or downstream of the sound source passage duct 1. The passive silencer 11 is, for example, formed in a substantially cylindrical shape, and has a sound absorbing member provided on an inner peripheral portion thereof, and is configured to muffle noise passing through the passive silencer by the sound absorbing member. . The internal volume of the passive silencer 11 provided with a sound absorbing member therein is set such that the effect of silencing high frequency noise is enhanced.

A branch pipe 9 is connected to the branch port 1b. The branch pipe 9 is formed of a pipe. In this embodiment, a T-shaped branch pipe 1a is used to facilitate assembly. Connected. Further, the branch pipe 9 is bent in an L-shape in order to reduce the mounting space for the branch pipe 9, and in order to facilitate manufacture, in this embodiment, as shown in FIG.
It is configured to be bent 90 degrees by cutting at 5 degrees and joining one by rotating 180 degrees.

A speaker box 30 is disposed at an end of the branch pipe 9 opposite to the branch port 1b, and a plurality of speakers 3, 3,... And the cooling fan 7 are housed therein, and the other end of the speaker box 30 is connected to the introduction pipe 2 through the valve 26.
7 are communicated to allow the outside air to be introduced to cool the speakers 3, and so on.
The valve 26 is closed to prevent high heat from reaching the control room or the like via the introduction pipe 27.

Next, the arrangement of the speaker 3 serving as the muffling signal output means of the present invention will be described. In the speaker box 30, a plurality of speakers 3, 3... Are arranged in parallel, and a cooling fan 7 for cooling is arranged on the back surface thereof. As shown in FIG.
Are arranged so that the distance from the branch opening 1b is equal, and the center line O1 in the output direction of the speaker 3 has an angle θ with respect to the center line (axial center) O2 of the branch pipe 9 of 45 degrees or less (θ ≦
45). For example, as shown in FIG. 2, when two speakers 3 are arranged, they are arranged symmetrically with respect to the center line O2 of the branch pipe 9. In addition,
If the angle θ is larger than 45 degrees, the reflection of the sound wave in the branch pipe 9 increases, and the propagation loss increases. In this way, the sound pressure of the silencing signal output from the two speakers 3 is increased, so that loud noises can also be silenced.

When three or more loudspeakers 3 are provided in order to further enhance the silencing effect, the center line O2
, The center line O2 coincides with the center of the regular polygon, and the speaker 3 is arranged at the position of the vertex when the regular polygon is formed. In other words, the speakers 3, 3,... Are arranged on a plane perpendicular to the center line O2 at equal intervals on a circumference having the same distance from the center line O2.
However, each speaker 3 is arranged at an angle equal to or smaller than the angle θ as described above. For example, when four speakers 3 are arranged, the speakers 3, 3,... Are arranged at the vertices of a square centered on the center line O2, as shown in FIG. However, if the plane is perpendicular to the center line O2 of the branch pipe 9, the intervals between the speakers may not be equal.

When a plurality of speakers 3 are arranged, the speakers 3 which can output sounds having different sound qualities and heights can be combined and arranged. For example, if many low-pitched noises are included, increase the number of woofers.If many high-pitched noises are included, place many tweeters, and efficiently match the noise quality and pitch. It silences.

In order to arrange a plurality of speakers 3,
As shown in FIG. 4, a large number of branch ports 1b of a branch pipe 1a 'are provided, and a speaker 3 is provided at each of the branch ports 1b.
And the branch pipes 9, 9... To which the cooling fan 7 is attached. When the plurality of speakers 3, 3... Are arranged, one speaker 3 mutes the sound when the size is small, and the number of speakers 3 according to the size when the size is small. 3 can be muted.

The operation of the active silencer constructed as described above will be described. That is, when the engine generator 2 is operated, when the engine is operated and the exhaust gas is exhausted from the sound source passage duct 1, the accompanying exhaust sound is detected by the first sound wave sensor 4, and the detection signal is transmitted to the controller 5. When the detection signal is input, the controller 5 generates a silence signal having the same amplitude and opposite phase. The silencing signal is output to the speakers 3, 3,... Via the amplifier 12, so that a silencing sound wave is output. Since the noise-reducing sound wave is made to have the same amplitude in the opposite phase to the exhaust sound emitted from the sound source passage duct 1, the exhaust sound is canceled by the noise-reducing sound wave, and the sound-muffling action is performed. .
.. Can be effectively silenced against loud noises by the silencing signals output from the plurality of speakers 3. The sound can be silenced by the appropriate number of speakers 3, so that energy can be saved and the sound can be silenced efficiently. Further, a synthetic sound wave of the exhaust sound and the sound wave for silencing is detected (monitored) by the second sound wave sensor 6, and the result of the silencing operation is fed back to the controller 5, and the silencing signal is corrected so that the silencing operation is performed more sufficiently. Because

[0022]

As described above, the present invention has the following advantages. That is, as in claim 1,
A first noise detection unit disposed on a duct disposed on the noise side, a unit disposed downstream of the duct and outputting a muffling signal, and a noise signal detected by the first noise detection unit, In an active silencer having a calculating means for calculating a muffling signal of a phase and a second noise detecting means arranged downstream of the output means, a muffling signal is supplied to a branch pipe branched from the duct and arranged. Since the output means is arranged and the plurality of muffling signal output means are arranged, muffling signals from the plurality of muffling signal output means are added, and the muffling effect can be enhanced with respect to loud noise passing through the duct. It is. Further, when the noise is low, one of them is selected to output the muffling signal, so that the sound can be efficiently muted as an output matching the magnitude of the noise.

According to a second aspect of the present invention, since the plurality of muffling signal output means are arranged in parallel, the muffling signals are simultaneously transmitted in the same phase as the sound waves, so that the sound pressure can be added and the noise with high sound pressure can be reduced. To enhance the noise reduction effect.

According to a third aspect of the present invention, the plurality of muffling signal output means are mounted at an angle of 45 degrees or less with respect to the axis of the branch pipe, so that reflection of the muffling signal is suppressed to suppress noise such as resonance and beat. The signal can be prevented from being disturbed, and the loss can be reduced.

According to a fourth aspect of the present invention, the means for outputting the plurality of muffling signals includes a plane perpendicular to an axis of the branch pipe.
Since the microphones are arranged at the same distance from the axis, the muffling signals can be added according to the number of speakers, so that the muffling can be efficiently performed and the arrangement space can be efficiently arranged.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration and control of an active silencer.

FIG. 2 is a plan sectional view showing an arrangement configuration of the speaker of the present invention.

FIG. 3 is a front view of the same.

FIG. 4 is a plan view showing another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sound source passage duct 1b Branch 3 Speaker 4 First sound wave sensor 5 Controller 6 Second sound wave sensor 7 Cooling fan 9 Branch pipe

Claims (4)

[Claims] 1. A first noise detecting means disposed on a duct disposed on a noise side, a means disposed on a downstream side of the duct for outputting a muffling signal, and a noise detected by the first noise detecting means. In an active silencer having a calculating means for calculating a muffling signal having an opposite phase to the signal, and a second noise detecting means arranged downstream from the output means,
An active silencer wherein a silencing signal output means is arranged in a branch pipe branched from the duct, and a plurality of the silencing signal output means are arranged. 2. The active silencer according to claim 1, wherein said plurality of silence signal output means are arranged in parallel. 3. The active noise reduction device according to claim 1, wherein said plurality of noise reduction signal output means are attached at an angle of 45 degrees or less with respect to the axis of said branch pipe. 4. The active device according to claim 1, wherein said plurality of noise canceling signal output means are arranged at a position at the same distance from the axis on a plane perpendicular to the axis of the branch pipe. Silencer.