JPH0916181A - Active silencer - Google Patents

Abstract

PURPOSE: To largely attenuate exhaust noise caused by a exhaust pipe of an internal-combustion engine. CONSTITUTION: A loudspeaker sound issuing body 3 and a resonance sound issuing body 4 are provided at both sides of exhaust downstream side end part of an exhaust pipe 2, each opening of the loudspeaker sound issuing body 3 and the resonance sound issuing body 4 are provided in parallel approaching to an opening of the exhaust pipe 2. A first loudspeaker 5 accommodated in the loudspeaker sound issuing body 3 and a second loudspeaker 6 accommodated in the resonance sound issuing body 4 are connected to a control device 10 through a signal line 9. A resonance frequency of a resonance box 21 provided at the resonance sound issuing body 4 is made 0.5-0.8 times as much as a low sound reproduction limit frequency of the first loudspeaker 5 in a condition in which it is accommodated in the loudspeaker sound issuing body 3, a pressure wave having an opposite phase to a pressure wave of an exhaust noise of an internal-combustion engine is issued from the loudspeaker sound issuing body 3 and the resonance sound issuing body 4 based on a command of the control device 10, and exhaust noise is silenced by superimposing both pressure waves and a pressure wave of exhaust noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active silencer for silencing noise by using a speaker.
The present invention relates to an active silencer that silences exhaust noise of an internal combustion engine.

[0002]

2. Description of the Related Art As an active silencer for silencing using a speaker, for example, an active silencer disclosed in Japanese Patent Laid-Open No. 5-39712 and FIG. 11 in Japanese Patent Laid-Open No. 2-310099 are disclosed. There is an active silencer. The active silencer disclosed in Japanese Patent Laid-Open No. 5-39712 uses an electric signal / sound wave converter to have a phase opposite to the noise from the noise source.
In an active silencer that eliminates the noise by outputting sound waves of equal sound pressure, the electric signal / sound wave converter has a resonance box that matches the resonance frequency of the noise emitted from the noise outlet. Is provided, and the sound waves of opposite phase and equal sound pressure amplified in the resonance box are superimposed on the noise to muffle the noise. The active silencer shown in FIG. 11 of JP-A-2-130099 has two upper and lower speakers arranged at the outlet of the duct, and the noise wave in the air discharged from the duct is It emits a sound wave of opposite phase and attenuates the noise by the canceling action of the noise wave and the sound wave.

[0003]

However, when both of the above active silencers are applied to silence exhaust noise of an internal combustion engine,
In the active silencer disclosed in Japanese Patent Laid-Open No. 5-39712, exhaust noise having the same frequency as the resonance frequency is silenced, but exhaust noise having a frequency different from the resonance frequency is not silenced, and the frequency range of the exhaust noise is However, there is a problem in that the silenced area is narrow. In the active silencer shown in FIG. 11, when speakers are mounted on both sides of the exhaust pipe, only a small speaker can be used because the speaker mounting space is small. However, when the speaker is made smaller, the sound pressure of low frequency sound becomes smaller, and there is a problem that the effect of silencing the low frequency sound of exhaust noise cannot be sufficiently exerted. Therefore,
The present invention has been made to solve the above problems, and an object of the present invention is to provide an active silencer capable of significantly reducing exhaust noise emitted from an exhaust port of an exhaust pipe.

[0004]

In order to solve the above-mentioned problems, the invention according to claim 1 outputs the pressure wave of the first speaker sound radiated from the accommodated first speaker to the outside as the first pressure wave. A speaker sound outflow body and a resonance box for resonating the second speaker sound pressure wave emitted from the housed second speaker, and the second pressure amplified by the second speaker sound pressure wave resonating in the resonance box. A resonance sound outflow body for outflowing waves to the outside, and the resonance frequency of the resonance box is 0.5 to 0.8 times the bass reproduction limit frequency of the first speaker in the state accommodated in the speaker sound outflow body. The first and second pressure waves having the opposite phase to the pressure wave of the exhaust noise of the internal combustion engine flow out to the outside from the speaker sound outflow body and the resonance sound outflow body. Characterized by superimposing a pressure wave to muffle the exhaust noise According to a second aspect of the present invention, in the active silencer according to the first aspect, the openings of the speaker sound outflow body and the resonance sound outflow body are arranged in parallel near an opening of an exhaust pipe of the internal combustion engine. Is characterized by.

The resonance frequency of the resonance box is set to 0.5 to 0.8 times the bass reproduction limit frequency of the first speaker in the state where the resonance frequency is accommodated in the speaker sound outflow body. When it is smaller than 0.5 times, the first and second pressure waves flow out from the resonance sound outflow body and the speaker sound outflow body, and when the first and second pressure waves and the pressure wave of exhaust noise are superposed, In the synthesized pressure wave in which the first pressure wave and the second pressure wave are superposed and synthesized, the sound pressure in the frequency range between the bass reproduction limit frequency and the resonance frequency becomes small, and the bass reproduction limit frequency This is because exhaust noise is not sufficiently silenced in a frequency range between the resonance frequency and the resonance frequency, and when the resonance frequency is set to be larger than 0.8 times the bass reproduction limit frequency,
This is because muffling of exhaust noise is not performed well in the low frequency range.

[0006]

The first pressure wave having the opposite phase to the pressure wave of the exhaust noise flows out from the speaker sound outflow body, and has the opposite phase to the pressure wave of the exhaust noise from the resonance sound outflow body and is accommodated in the speaker sound outflow body. When the second pressure wave having a resonance frequency of 0.5 to 0.8 times the bass reproduction limit frequency of the first speaker in the open state flows out, the first pressure wave and the second pressure wave cause exhaust noise. The exhaust noise is silenced by being superimposed on the pressure wave. On this occasion,
When the openings of the speaker sound outflow body and the resonance sound outflow body are brought close to the opening of the exhaust pipe of the internal combustion engine, the first pressure wave and the second pressure wave are generated.
The pressure wave and the pressure wave of the exhaust noise are superposed well.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1, an exhaust pipe 2 is connected to an engine 1, and a speaker sound outflow body 3 and a resonance sound outflow body 4 are arranged on both sides of an exhaust downstream side end portion of the exhaust pipe 2, The openings of the sound outflow body 3 and the resonance sound outflow body 4 are juxtaposed in parallel with the openings of the exhaust pipe 2. A first speaker 5 housed in the speaker sound outflow body 3, a second speaker 6 housed in the resonance sound outflow body 4, and a microphone 7 provided behind the exhaust pipe 2 (right side in the figure). A tachometer 8 provided in the engine 1 is connected to the control device 10 via a signal line 9.

The exhaust pipe 2 is composed of an exhaust upstream front pipe portion 11 connected to the engine 1 and an exhaust downstream tail pipe portion 12, and the front pipe portion 11 and the tail pipe portion 12 form a sub muffler 13. Connected through. The sub-muffler 13 includes a perforated pipe 13a having a plurality of holes and a casing 13b surrounding the perforated pipe 13a, and has a function of attenuating high-frequency exhaust sound. Further, as the sub-muffler 13, a sound absorbing material such as glass wool wound around the perforated pipe 13a may be used, and the exhaust resistance hardly rises as compared with the case where only the exhaust pipe 2 is used. An exhaust noise outlet 14 for discharging exhaust noise is formed at an end portion on the exhaust downstream side of the tail pipe portion 12, exhaust noise generated in the engine 1 passes through the front pipe portion 11, and high frequency exhaust noise is attenuated by the sub muffler 13. The exhaust noise of other frequencies flows out from the exhaust noise outlet 14 through the tail pipe portion 12.

The speaker sound outflow body 3 comprises a speaker housing 15 for housing the first speaker 5 and a speaker tube 16 provided on the front surface of the first speaker 5. In the speaker housing 15, the diaphragm 17 is disposed on the speaker tube 16 side, and the first speaker 5 is housed so that the drive unit 18 is stored inside the speaker housing 15. The speaker tube 16 is provided with a speaker sound outlet 19 in front of the first speaker 5 in the same direction as the exhaust noise outlet 14, and has the same frequency and the same phase as the speaker sound pressure wave radiated from the first speaker 5. Pressure wave (hereinafter referred to as the first speaker sound pressure wave) can flow out from the speaker sound outlet 19 as the first pressure wave to the outside.

The resonance sound outflow body 4 comprises a speaker housing 20 for accommodating the second speaker 6 and a Helmholtz type resonance box 21 provided on the front surface of the second speaker 6.
The speaker housing 20 includes a diaphragm 22 and a resonance box 21.
The second speaker 6 is housed so that the drive unit 23 is housed inside the speaker housing 20.
1, a resonance sound outlet 24 is provided in front of the second speaker 6 in the same direction as the exhaust noise outlet 14, and a speaker sound pressure wave radiated from the second speaker 6 (hereinafter referred to as second speaker sound pressure). A pressure wave obtained by causing the resonance box 21 to resonate in the resonance box 21 and amplified can flow out from the resonance sound outlet 24 as a second pressure wave to the outside. Note that, as shown in FIG. 2, the resonance frequency of the resonance box 21 is set to 0.6 times the bass reproduction limit frequency (see FIG. 2) of the first speaker 5 accommodated in the speaker housing 15. .

The control unit 10 is arranged near the exhaust noise outlet 14 to detect residual noise, a tachometer 8 attached to the engine 1 to detect the rotational speed of the engine 1, The first housed in the speaker sound outflow body 3
It is connected to the speaker 5 and the second speaker 6 housed in the resonance sound outflow body 4, generates a speaker drive signal based on the information acquired by the microphone 7 and the tachometer 8, and outputs the speaker drive signal to the first speaker drive signal. 1 speaker 5 and 2nd speaker 6
Output to

Next, the operation of this embodiment will be described.
The control device 10 generates a speaker control signal based on the information on the residual noise detected by the microphone 7 and the information on the rotational speed of the engine 1 detected by the tachometer 8, and outputs the speaker control signal from the control device 10. First speaker 5 and second
Output to the speaker 6. A first speaker sound pressure wave is radiated from the first speaker 5 in response to the speaker control signal input to the first speaker 5, and the first speaker sound pressure wave flows out from the speaker sound outlet 19 as a first pressure wave. To do. Further, in response to the speaker control signal input to the second speaker 6, a second speaker sound pressure wave is radiated from the second speaker 6, and the second speaker sound pressure wave resonates in the resonance box 21 and is amplified. The generated pressure wave flows out from the resonance sound outlet 24 as a second pressure wave. The first and second pressure waves have the opposite phase to the pressure wave of the exhaust noise, the first pressure wave flows out from the speaker sound outlet 19, and the second pressure wave is the resonance sound outlet 24. When flowing out of the exhaust noise, the first and second pressure waves are superimposed on the pressure wave of the exhaust noise flowing out of the exhaust noise outlet 14. Moreover, when the speaker sound outlet 19 and the resonance sound outlet 24 are placed close to the exhaust noise outlet 14, the first pressure wave, the second pressure wave, and the pressure wave of the exhaust noise are superposed well.

In FIG. 2, the relationship between the sound pressure level and frequency of the first pressure wave flowing out from the speaker sound outlet 19 is represented by a.
The relationship between the sound pressure level and the frequency of the second pressure wave flowing out from the resonance sound outlet 24, which is resonated and amplified in the resonance box 21, is shown in b, and the first pressure wave and the second pressure wave are shown. The relationship between the sound pressure level and the frequency of the combined pressure wave in which the first and second pressure waves are combined is shown in c. Further, in FIG. 3, the relationship between the sound pressure level of the combined pressure wave and the frequency is shown in c, and the relationship between the sound pressure level of the exhaust noise flowing out from the exhaust noise outlet 14 and the frequency is shown in d.

As can be seen from FIG. 3, the relationship c between the sound pressure level and frequency of the combined pressure wave having a phase opposite to that of the pressure wave of exhaust noise is d.
Similar to Therefore, the first pressure wave flowing out from the speaker sound outlet 19 and the second pressure wave flowing out from the resonance sound outlet 24.
When the pressure wave and the pressure wave of the exhaust noise flowing out from the exhaust noise outlet 14 are superposed, they have an opposite phase to the pressure wave of the exhaust noise and are similar to the frequency-sound pressure level relationship of the exhaust noise. The combined pressure wave having the frequency-sound pressure level relationship described above is superimposed on the pressure wave of the exhaust noise, and the exhaust noise is effectively silenced.

[0015]

According to the present invention, exhaust noise of an internal combustion engine can be reliably and efficiently silenced, and the respective openings of the speaker sound outflow body and the resonance sound outflow body are arranged close to the opening of the exhaust pipe of the internal combustion engine. When installed, the superposition of pressure waves flowing out from each opening is good, and exhaust noise can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an active silencer that is an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a sound pressure level and a frequency of a pressure wave flowing out from the speaker sound outflow body and the resonance sound outflow body of the above-described embodiment.

FIG. 3 is a diagram showing the relationship between the sound pressure level and frequency of the combined pressure wave shown in FIG. 2 and the relationship between the sound pressure level and frequency of the pressure wave of exhaust noise.

[Explanation of symbols]

 3 Speaker sound outflow body 4 Resonance sound outflow body 5 1st speaker 6 2nd speaker 21 Resonance box

Claims (2)

[Claims] 1. The first radiated from the housed first speaker
A speaker sound outflow body that flows out to the outside by using the speaker sound pressure wave as the first pressure wave, and a resonance box that resonates the second speaker sound pressure wave radiated from the housed second speaker. A resonance sound outflow body that outflows the second pressure wave amplified by resonating in the resonance box to the outside, and the first speaker in a state where the resonance frequency of the resonance box is accommodated in the speaker sound outflow body. Bass reproduction limit frequency of 0.5
.About.0.8 times, and the first and second pressure waves having the opposite phase to the pressure wave of the exhaust noise of the internal combustion engine flow out from the speaker sound outflow body and the resonance sound outflow body to the outside. And the pressure wave of the exhaust noise are superimposed to muffle the exhaust noise. 2. The active silencer according to claim 1, wherein the openings of the speaker sound outflow body and the resonance sound outflow body are juxtaposed near an opening of an exhaust pipe of the internal combustion engine. Active silencer.