JPH1124672A - Muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a muffler for propagating a silencing sound wave into a sound absorbing duct through a resonance duct in which a sound wave generator can be protected from water drops within the resonance duct while dispensing with a draining hole and its performance can be held over a long period. SOLUTION: A speaker 4 as a sound wave generator is provided in a position higher than a sound absorbing duct 1 so as to propagate a silencing sound wave from it into the sound absorbing duct 1 through a resonance duct 3. Water drops generated by cooling a high-temperature exhaust gas carried into the resonance duct 3 and condensing the contained moisture are guided into the lower sound absorbing duct 1 along the inner wall of the resonance duct 3, and evaporated there. Since no water drop is collected in the resonance duct 3, a draining hole is dispensed with. The speaker 4 can be effectively protected from the water drops, and its durability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a muffler using active noise control (ANC) technology.

[0002]

2. Description of the Related Art FIG. 4 shows a silencer (Japanese Patent Application No. 9-50867) proposed earlier by the present applicant. this is,
This is to prevent the noise of the engine 2 as a noise source near one open end 1a of the sound absorbing duct 1 from being propagated outward from the other open end 1b. Hereinafter, the details will be described.

A noise detector 7 is mounted on the lower wall of the sound absorbing duct 1 near the opening end 1a, and its output (noise detection signal) x is supplied to a sound deadening signal generator 9 shown in detail in FIG. Is done. A silencing deviation detector 6 is attached to the lower wall near the other open end 1b, and its output (silencing deviation detection signal) e is supplied to the silencing signal generator 9. The muffling signal y formed by the muffling signal generator 9 is supplied to the speaker 4 as a sound wave generator, from which muffling sound waves having the same magnitude as the noise and having the opposite phase are emitted. The speaker 4 is provided inside a speaker box 5 provided at the lower end of the resonance duct 3, and its vibrating cone can freely vibrate.

Referring to FIG. 3, an output x of noise detector 7 is supplied to an adaptive filter (hereinafter abbreviated as ADF) 18 and a delay filter 17 via an amplifier 15 and an A / D converter 16. . In addition, the silencing deviation detector 6
Is supplied to a coefficient calculator 19 via an amplifier 22 and an A / D converter 23. The ADF 18 has N taps, the coefficients of which are updated by the output of the coefficient calculator 19. The delay filter 17 has an acoustic transfer characteristic corresponding to a path from the speaker 4 to the muffling deviation detector 6. That is, the coefficient of the delay filter 17 is determined in consideration of the time delay, and is measured or identified in advance. Further, the coefficient calculator 19 is an adaptive algorithm for sequentially calculating the optimum coefficient to be given to the ADF 18. The muffling signal generator 9 has a configuration using the above-described well-known ANC control technology.

The speaker box 5 has a pair of ring-shaped dust seals 13a, 13b on its upper end flange 5a.
And the resonance duct 3 with the speaker mounting ring 12 interposed.
Although not shown, it is fixed to a flange portion 3a formed at a lower end portion by, for example, a bolt. A drain hole 11 is formed near the flange portion 3a of the resonance duct, and a drain pipe 10 is fitted into the drain hole 11.

As described above, in this conventional example, the resonance duct 3
Is mounted so that its axis or center line Y-Y extends downward with respect to the axis or center line XX of the sound-absorbing duct 1. 4 is prevented from being deteriorated or damaged. Further, the exhaust gas is cooled inside the resonance duct 3, and water contained in the exhaust gas condenses to become water droplets and tends to accumulate at the lower end portion of the resonance duct 3 (indicated by reference numeral W in FIG. 5). The speaker 4 is protected from water droplets by discharging the water to the outside through the drain pipe 10.

[0007]

However, the water droplet W
Contains solids such as rust and carbon powder, which may clog the drain hole 11 and make drainage impossible. Further, since the corrosive components such as acid and alkali are contained in the exhaust gas of the engine, the adhesion of the corrosive water droplets not only deteriorates and damages the speaker 4 but also causes the inside of the resonance duct 3 to be damaged. There is also a problem that rust is generated on the wall surface. Further, there is a problem that sound-absorbing sound waves leak to the outside from the drain holes.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of the above problem.
An object of the present invention is to provide a muffler capable of effectively protecting a speaker from water droplets in a resonance duct and maintaining the performance of the speaker for a long time.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to provide a noise detector for detecting noise of a noise source (corresponding to, for example, the reference numeral 7 in the embodiment, the same applies hereinafter), and a muffling deviation for detecting a muffling deviation. A detector (6) and the noise detector (7)
(X) and the output (e) of the silencing deviation detector (6), and receives a sound wave having the same magnitude and opposite phase as the noise through the resonance duct (3) in the sound absorbing duct (1). And a muffling signal generator (9) for forming a muffling signal (y) to be generated from the sound wave generator (4) toward the sound absorber (4). ), The sound wave generator (4)
The sound absorbing device according to claim 1, wherein said sound absorbing sound is transmitted through said resonance duct (3) into said sound absorbing duct (1).

According to the present invention, the sound wave generator (4) is provided above the sound absorbing duct (1), and the resonance duct (3) is extended upward from the sound absorbing duct (1). The water droplets adhering to the inner wall of (1) are guided to the lower sound absorbing duct (1), and are removed by evaporating again. Therefore, a drain hole is unnecessary, and since water droplets are less likely to adhere to the front surface of the sound wave generator (4), the durability of the sound wave generator (4) can be improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show the present embodiment, and the same reference numerals are given to portions corresponding to FIG.
The detailed description is omitted. That is, in the present embodiment, the speaker 4 is connected to the sound absorbing duct 1 as illustrated.
The sound absorbing noise is propagated through the resonance duct 3 into the sound absorbing duct 1 from above. The resonance duct 3 is disposed such that its axis YY is inclined upward by θ = 45 ° with respect to the axis XX of the sound absorbing duct 1, and the lower end of the resonance duct 3 is arranged as shown in FIG. It is attached to the side wall surface of the sound absorbing duct 1.

In this embodiment, a film 25 is provided so as to cover the front surface of the speaker 4. The film 25 is provided close to the speaker 4 and is made of, for example, PTFE (polytetrafluoroethylene) having heat resistance, acid resistance, and alkali resistance, which is known by the trade name of Teflon.

The muffling signal generator 9 forms a muffling signal y based on the output x of the noise detector 7 and the output e of the muffling deviation detector 6 and supplies it to the speaker 4. Thereby, the speaker 4
Generates a sound-absorbing sound wave having the same magnitude as the noise and having the opposite phase. At this time, the muffling signal generator 9 sequentially adjusts the muffling signal y supplied to the speaker 4 so that the sound pressure level of the noise becomes zero at the position of the muffling deviation detector 6.
On the other hand, since the sound-absorbing sound wave is propagated through the resonance duct 3 into the sound-absorbing duct 1, the sound pressure level thereof is sufficiently high, so that the noise can be efficiently eliminated.
Therefore, the noise level exhausted from the opening end 1b is sufficiently attenuated or set to zero.

When the high-temperature exhaust gas flowing in the sound absorbing duct 1 reaches the inside of the resonance duct 3, the heat is radiated by the heat transferred to the resonance duct 3 and is cooled. Then, moisture contained in the exhaust gas is condensed to form water droplets. These water droplets flow downward along the inner wall of the resonance duct 3 and evaporate again due to the high temperature inside the sound absorbing duct 1.

Therefore, according to the present embodiment, since no water drops accumulate inside the resonance duct 3, a drain hole as in the prior art is not required, and thus sound leakage from the hole can be eliminated. Also, a film 25 is provided on the front of the speaker 4.
Is provided, the speaker 4 is not directly exposed to the exhaust gas, so that the adhesion of moisture in the exhaust gas is surely prevented, and the heat of the exhaust gas and corrosive gas such as acid and alkali are removed. The speaker 4 can be reliably protected,
Its performance can be maintained for a long time.

Although the embodiment of the present invention has been described above, the present invention is, of course, not limited to this, and various modifications can be made based on the technical concept of the present invention.

For example, in the above embodiment, the resonance duct 3 is arranged with its axis YY inclined at 45 ° with respect to the axis XX of the sound absorbing duct 1. The present invention is not limited to this, and is applicable to the angle range of 0 ° <θ <180 °. That is, any angle may be used as long as the speaker 4 is positioned above the sound absorbing duct 1.

In the above embodiment, the resonance duct 3 is attached only to the left wall of the sound absorbing duct 1 in FIG. 2. However, the resonance duct is also attached to the right wall, and the resonance duct 3 is similarly attached to this end. A speaker 4 may be provided. in this case,
The level of the sound-absorbing sound wave to the sound-absorbing duct 1 can be doubled.

In the above embodiment, the noise source is described as an engine. However, the present invention can be applied to other general noise sources. Further, the film 25 provided on the front surface of the speaker 4 may be omitted depending on the temperature and components of the exhaust gas or depending on the length of the resonance duct 3.

Further, although the muffling signal generator 9 is constituted by the ANC circuit shown in FIG. 3, it is not limited to this and may be constituted by various known ANC circuits.

[0022]

As described above, according to the sound deadening device of the present invention, since water droplets do not accumulate inside the resonance duct, the water droplets are prevented from adhering to the front surface of the sound wave generator, and the sound wave is generated. The durability of the vessel can be improved and its performance can be maintained for a long time. Also, the inner wall of the resonance duct does not rust. Further, since the drain hole can be made unnecessary, the sound-absorbing sound wave does not leak to the outside, so that the sound-absorbing effect can be enhanced.

[Brief description of the drawings]

FIG. 1 is a partially cutaway view of a noise reduction device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line [2]-[2] in FIG.

FIG. 3 is a block diagram illustrating an example of a muffling signal generation device.

FIG. 4 is a partially cutaway view of a conventional silencer.

FIG. 5 is an enlarged view of the main part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sound absorption duct 2 Engine 3 Resonance duct 4 Speaker 6 Noise reduction deviation detector 7 Noise detector 9 Noise reduction signal generator

Claims (3)

[Claims] A noise detector for detecting noise of a noise source;
A silencing deviation detector that detects a silencing deviation, receives an output of the noise detector and an output of the silencing deviation detector, and transmits sound waves having the same magnitude and opposite phase as the noise through the resonance duct in the sound absorbing duct. And a muffling signal generator for forming a muffling signal for generating a muffling signal from the sound wave generator, wherein the sound wave generator is provided at a position above the sound absorbing duct, and muffling from the sound wave generator is provided. A sound deadening device, wherein a sound wave for use is propagated into the sound absorbing duct through the resonance duct. 2. The muffler according to claim 1, wherein a heat-resistant, acid-resistant and alkali-resistant film is provided close to the sound generator so as to cover a front surface of the sound generator. . 3. The muffler according to claim 1, wherein the noise source is an engine and generates high-temperature exhaust gas.