JPH1136843A - Silencer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a silencer capable of preventing generation of abnormal noise and preventing loss of sound generation efficiency for silencing while protecting a sound generator from heat and corrosive gas. To provide. SOLUTION: A speaker 4 which is a sound wave generator is connected to a resonance tube 2.
6 and is made of a heat-resistant material in order from the sound-absorbing duct 31 to a position serving as a node of the sound-absorbing sound wave S that resonates and vibrates inside the resonance pipe 26 through the sound-absorbing duct 31.
A shielding film 60 and a second shielding film 61 made of a material having water resistance, acid resistance and alkali resistance are provided. Thus, while protecting the speaker 4 from heat and corrosive gas, it is possible to vibrate the shielding films 60 and 61 faithfully with the temporal variation of the sound wave S and not to impair the generation efficiency of the sound wave S.

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 Active noise control (A)
As is well-known, a noise reduction device using the NC) technology introduces a noise reduction sound wave having the same magnitude and the opposite phase as the noise into the internal space of the sound absorption duct through which the noise propagates, and causes interference with the noise sound wave. Thus, a silencing effect is obtained. The sound-absorbing sound waves are emitted from a sound wave generator, and some of them are configured so that the front surface faces the inside of the sound-absorbing duct, and others are attached to the sound-absorbing duct via a resonance tube. In the latter case, in particular, there is an advantage that the sound wave for silencing can be efficiently generated by a predetermined resonance vibration inside the resonance tube.

In the case where the ANC silencer is applied to a noise source (for example, an automobile engine) that emits a high-temperature exhaust gas containing a corrosive gas such as an acid or an alkali, separately from the noise, the above-described conventional configuration has a problem. However, the sound wave generator has been damaged or broken down due to the adhesion of heat, corrosive gas or moisture, and had a problem in its durability. To solve this,
For example, as shown in FIG. 5, in a configuration in which a speaker 4 as a sound wave generator is attached to a sound absorbing duct 1 via a resonance tube 6, heat, water, acid, and alkali are present near the opening end of the resonance tube 6. There is a technique of providing a resistant shielding film 7 to partition between the speaker 4 and the internal space of the sound absorbing duct 1. The shielding film also has flexibility and sound permeability, and allows sound waves S (indicated by dashed lines in the figure) emitted from the speaker 4 to penetrate into the sound absorbing duct, thereby performing the original noise reduction effect on the noise P. The speaker 4 is protected from heat and exhaust gas.

[0004]

However, there is a problem that the sound wave generation efficiency of the speaker 4 is impaired depending on the position where the shielding film 7 is provided. That is, since the sound wave S oscillates at a predetermined resonance frequency inside the resonance tube 6, if the shielding film 7 is located at the antinode of the sound wave S as shown in FIG. Shielding film 7
In addition to generating flapping noise, the characteristics of the sound-absorbing sound wave S may be disturbed, and the desired sound-absorbing effect may be impaired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and it is an object of the present invention to prevent the generation of abnormal noise and protect the sound generation means from heat and corrosive gas so as not to impair the efficiency of generating sound for noise reduction. An object of the present invention is to provide a muffler capable of performing the above.

[0006]

An object of the present invention is to provide a noise detector (2) for detecting noise from a noise source (e.g., corresponding to a reference symbol P in a first embodiment described later; the same applies hereinafter). And a noise reduction deviation detector (3) for detecting a noise reduction deviation level; an output (x) of the noise detector (2) and an output (e) of the noise reduction deviation detector (3); Forming a sound deadening signal (y) for generating a sound wave (S) having the same magnitude and opposite phase from the sound wave generator (4) into the sound absorbing duct (31) via the resonance tube (25). And a sound deadening signal generator (5) that generates a node of the sound wave (S) vibrating at a predetermined resonance frequency inside the resonance pipe (25). ) And the interior space of the sound absorbing duct (31), heat resistance Acid resistance, shielding film having at least one resistance of the alkali resistance and water resistance (4
According to a fifth aspect of the present invention, there is provided a silencer including:

[0007] The above-mentioned problem is caused by the noise of the noise source (for example, the reference symbol P in the second and third embodiments described later).
Is equivalent to The same applies hereinafter. ) Noise detector (2)
And a silencing deviation detector for detecting a silencing deviation level (3)
And the output (x) of the noise detector (2) and the output (e) of the silencing deviation detector (3), the sound wave (S) having the same magnitude as the noise (P) and having the opposite phase. The resonance tube (2
And a silencing signal generator (5) for generating a silencing signal (y) for generation from the sound wave generator (4) into the sound absorbing duct (31) via the sound generator (6, 27). A first shield having heat resistance at a position on the sound absorbing duct (31) side among a plurality of positions serving as nodes of the sound waves (S) vibrating at a second or higher resonance frequency inside the resonance tube (26). A film (60) is provided, and a second shielding film (61) having at least one of water resistance, acid resistance and alkali resistance is provided at a position on the side of the sound wave generator (4). To solve the problem.

According to the present invention, a shielding film (45, 60, 6) is provided at a position inside a resonance tube (25, 26, 27) which is a node of a sound-absorbing sound wave (S) vibrating at a predetermined resonance frequency.
By providing 1), the above problem is solved. In other words, the vibration velocity of the air is a minimum value (zero) at the position of the node of the sound wave, and the shielding film can be vibrated faithfully in accordance with the temporal change in the density of the sound wave.

[0009]

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

FIG. 1 shows a silencer according to a first embodiment of the present invention. The noise detector 2 includes a sound absorbing duct 31
Is supported by an elastic support member 36 made of rubber, for example, inside a casing 34 integrally attached via a gasket 33 to a connection portion 32 provided on the side wall of the casing. Heat resistance between the connection portion 32 and the gasket 33,
A coating 35 made of a material (for example, mica) having water resistance, acid resistance, and alkali resistance is provided. The connecting portion 32 and the gasket 33, and the gasket 33 and the casing 34 are connected by bolts (not shown).

The silencing deviation detector 3 also has a connection 5
2 is supported by an elastic support member 56 made of rubber, for example, inside a casing 54 integrally attached to the gasket 2 via a gasket 53, and a film having the same configuration as the film 35 is provided between the connection portion 35 and the gasket 53. 55 are provided.

[0012] A sound wave for noise reduction (a noise P) is formed based on the output x of the noise detector 2 and the output e of the noise reduction deviation detector 3.
A muffling signal y for generating a sound wave (S) having the same magnitude and opposite phase is supplied from the muffling signal generator 5 to the speaker 4 as a sound wave generator. FIG. 2 shows details of the muffling signal generator 5. The output x of the noise detector 2 is supplied to an adaptive filter (hereinafter abbreviated as ADF) 14 and a delay filter 13 via an amplifier 11 and an A / D converter 12. The ADF 14 has N taps, the coefficients of which are updated by the output of the coefficient calculator 15. The delay filter 13 has an acoustic transfer characteristic corresponding to a path from the speaker 4 to the muffling deviation detector 3. That is, the coefficient of the delay filter 13 is determined in consideration of the time delay, and is measured or identified in advance. The output e of the silencing deviation detector 3 is supplied to a coefficient calculator 15 via an amplifier 16 and an A / D converter 17. The coefficient calculator 15 is AD
This is an adaptive algorithm for sequentially calculating the optimum coefficient to be given to F14. The muffling signal y formed by the ADF 14
Is supplied to the speaker 4 via the D / A converter 18 and the amplifier 19, from which a sound-absorbing sound wave having the same magnitude as the noise P and having the opposite phase is generated into the sound absorbing duct 31. The muffling signal generator 7 is a known AN as described above.
The configuration uses the C control technology.

The speaker 4 includes a connecting portion 4 of the sound absorbing duct 31.
2, a resonance tube 25 composed of two members 25a and 25b
And a casing 44 integrally fixed via a mounting member 46 supporting the speaker 4.
Defines the back space. In addition, connection part 4
It is assumed that the resonance tube 2 and the resonance tube 25 and the resonance tube 25 and the casing 44 are connected by bolts, not shown.

The sound wave S for silencing emitted from the speaker 4
In FIG. 1, the length of the resonance tube 25 is set so as to vibrate at a secondary resonance frequency, for example, inside the resonance tube 25 as illustrated. In the present embodiment, the shielding film 45 that partitions the internal space of the sound absorbing duct 31 and the speaker 4 is provided at a position that serves as a node of the sound-absorbing sound wave. That is, the shielding film 45 is located at a position where the vibration speed of the air is low and the density of the sound wave S is large (the sound pressure level is high) inside the resonance tube 25.
Is provided, it is possible to vibrate the shielding film 45 faithfully with respect to the time variation of the sound wave S and to prevent unnecessary vibration (fluttering). In the present embodiment, the shielding film 45 is made of a material having all of heat resistance, acid resistance, alkali resistance and water resistance, for example, mica.

Therefore, according to the present embodiment, the speaker 4, the noise detector 2, and the silencing deviation detector 3 can be protected from the heat of the exhaust gas and the corrosive gas.
The flapping of the film 45 can be prevented, and generation of abnormal noise can be prevented. Accordingly, the sound-absorbing sound wave S can be efficiently transmitted to the internal space of the sound-absorbing duct 31 without impairing the sound-wave generation efficiency of the speaker 4, and thus the sound-muffling effect can be enhanced.

FIG. 3 shows a second embodiment of the present invention. In the figure, parts corresponding to those in the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Although not shown, the noise detector 2
In addition, it is assumed that the silencing deviation detector 3 is provided in the same manner as in the first embodiment.

In the present embodiment, inside the resonance tube 26 composed of the two members 26a and 26b, a node of the sound-absorbing sound wave S vibrating at the secondary resonance frequency is provided in the same manner as in the first embodiment. The first shielding film 60 and the second shielding film 61 are provided at the two positions, respectively. this house,
The first shielding film is made of a material having heat resistance, such as glass cloth, carbon cloth, silica cloth, or ceramic paper.
a and 26b. Also, the other second
The shielding film 61 is formed of a fluororesin having acid resistance, alkali resistance and water resistance, such as polytetrafluoroethylene (trade name: Teflon), and is disposed between the resonance tube 26 and the casing 44 via the dust seal 50. The speaker 4 is provided near the front surface. That is, in the present embodiment, the second shielding film 61 is provided at the position of the speaker 4 which serves as a node of the sound-absorbing sound wave S. Therefore, the area of the second shielding film 61 is made larger than the area of the first shielding film 60 so that the sound-absorbing sound waves emitted from the speaker 4 are efficiently propagated inside the resonance tube 26. The connections between the members are made by fastening bolts (not shown), as in the first embodiment.

Therefore, according to the present embodiment, the same effects as in the first embodiment can be obtained, and the front surface of the speaker 4 is covered with the second shielding film 61. The durability of the speaker 4 can be improved as compared with the configuration of the first embodiment in which the speaker 4 is directly exposed to the inside of the speaker 26.

FIG. 4 shows a third embodiment of the present invention. In the drawings, parts corresponding to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Also in this embodiment, it is assumed that a noise detector 2 and a silencing deviation detector 3 are provided, although not shown.

That is, in this embodiment, three members 2
The first shielding film 60 is placed at a position on the side of the sound absorbing duct 31 as shown in FIG. 3 among the nodes of the sound-absorbing sound wave S vibrating at the third resonance frequency inside the resonance tube 27 composed of 7a, 27b and 27c. The second shielding film 61 is provided at a position closer to the speaker 4 than that. Here, first,
The second shielding films 60 and 61 are respectively composed of two members 27a and 27b and 27b and 27c constituting the resonance tube 27.
Are secured by bolts (not shown), and are made of the same material as in the second embodiment. According to this embodiment, the same effects as those of the above embodiments can be obtained.

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

For example, in each of the above embodiments, the vibration mode of the sound-absorbing sound wave inside the resonance tube has been described as the secondary or tertiary resonance vibration. The invention is applicable. That is,
In accordance with the vibration mode of the sound-absorbing sound wave determined by the length of the resonance tube and the driving frequency of the speaker, a shielding film may be provided at a position serving as a node of the sound wave.

Similarly, in the above-described second and third embodiments, the first and second two shielding films 60 and 61 are provided. However, depending on the nature of the noise source or the exhaust gas discharged from the noise source. Thus, the physical properties (heat resistance, water resistance, chemical resistance, etc.) of the shielding film and the number of disposed shielding films can be appropriately changed and applied irrespective of the resonance mode.

[0024]

As described above, according to the sound deadening device of the present invention, the shielding film is arranged at a position which becomes a node of the sound deadening sound wave vibrating at a predetermined resonance frequency inside the resonance tube. As a result, the sound generator can be protected from heat and corrosive gas, while preventing abnormal noise,
It is possible to prevent the generation efficiency of the sound-absorbing sound wave from being impaired. Thereby, the silencing effect can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a silencer according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a muffling signal generation device.

FIG. 3 is a sectional view of a main part showing a silencer according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a main part showing a silencer according to a third embodiment of the present invention.

FIG. 5 is a sectional view of a main part showing a conventional silencer.

[Explanation of symbols]

 Reference Signs List 2 noise detector 3 noise reduction deviation detector 4 speaker 5 noise reduction signal generator 25 resonance tube 26 resonance tube 27 resonance tube 31 sound absorption duct 45 shielding film 60 first shielding film 61 second shielding film P noise S sound-absorbing sound wave

Claims (4)

[Claims] A noise detector for detecting noise of a noise source;
A muffling deviation detector for detecting a muffling deviation level, receiving an output of the noise detector and an output of the muffling deviation detector, and generating a sound wave having the same magnitude and opposite phase as the noise through a resonance tube. And a muffling signal generator for forming a muffling signal for generating the sound from the vessel toward the inside of the sound absorbing duct, the muffler being provided at a position serving as a node of the sound wave vibrating at a predetermined resonance frequency inside the resonance tube. A muffling device provided with a shielding film that separates the sound wave generator and the internal space of the sound absorbing duct and has at least one of heat resistance, acid resistance, alkali resistance and water resistance. 2. A noise detector for detecting noise of a noise source,
A muffling deviation detector for detecting a muffling deviation level, receiving an output of the noise detector and an output of the muffling deviation detector, and generating a sound wave having the same magnitude and opposite phase as the noise through a resonance tube. And a muffling signal generating device for forming a muffling signal for generating the muffled signal from the vessel into the sound absorbing duct. The muffler serves as a node of the sound wave vibrating at a second or higher resonance frequency inside the resonance tube. Among the plurality of positions, a first shielding film having heat resistance is provided at a position on the sound absorbing duct side, and has at least one of water resistance, acid resistance, and alkali resistance at the position on the sound wave generator side. A silencer comprising a second shielding film. 3. The muffler according to claim 2, wherein the second shielding film is disposed near a front surface of the sound wave generator. 4. The method according to claim 2, wherein the first shielding film is made of glass cloth, carbon cloth, silica cloth or ceramic paper, and the second shielding film is made of fluororesin. Silencer.