JPH1122051A - Muffling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a muffling device which can enhance the durability of a sound wave generating means by protecting the sound wave generating means while eliminating the pressure difference between spaces at the front and rear of the sound wave generating means. SOLUTION: A communicating pipe 22 communicating a space 24 at the back of a speaker 4 with the inner space of a sound absorbing duct 1 is provided, and a shutter 23 capable of shutting the movement of fluid in the inner space of the sound absorbing duct 1 is provided downstream from the connection point J between the communicating pipe 22 and the sound absorbing duct 1. Thus, during muffling control, the pressure difference between the front and back of the diaphragm of the speaker 4 is eliminated, and when the device is stopped the shutter is closed to prevent outside air form entering the space 24 at the back of the speaker 4, thus enabling the driving part of the speaker 4 to be protected from moisture and bedewing.

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 Japanese Patent Laid-Open No.
No. 334172. The silencer according to this conventional example is shown in FIG. 5, in which a back space 9 of a speaker 4 that generates a sound-absorbing sound wave having the same magnitude as the noise P and an opposite phase toward the internal space of the sound absorbing duct 1 is sealed. The resonance tube 6 is defined by a casing (or enclosure) 5 and has a back space 9 communicating with the interior space of the sound absorbing duct 1.
Is formed. The resonance tube 6 is set to resonate at a main frequency of the noise P.

[0003] With the conventional silencer constructed as described above, the pressure in the sound absorbing duct 1 is introduced into the back space 9 of the speaker 4 through the resonance pipe 6, so that both the front and back sides of the speaker 4 can be used. Eliminate the pressure difference between the spaces,
The speaker 4 is accurately driven and mechanical fatigue of the speaker 4 is prevented. Further, the speaker 4 and the resonance tube 6 efficiently generate sound for noise reduction, and have sufficient sound power in a frequency region to be noise-reduced. I'm trying to get

[0004]

However, in the above-described conventional silencing device, when the device is stopped, outside air flows from the discharge end (right side in the drawing) of the sound absorbing duct 1 through the sound absorbing duct 1 to the speaker 4. In communication with the rear space 9 of the vehicle. At this time, an appropriate waterproof treatment such as a fluororesin coating is applied to the front surface of the speaker 4 so that the speaker 4 can be protected from the humidity of the outside air. Therefore, there is a problem that the speaker drive unit such as the voice coil and the magnetic circuit is damaged by dew condensation and moisture, and it is difficult to secure the durability of the speaker 4 for a long period of time. In particular, when applied to an engine generator system, usually 10
Although it is necessary to guarantee for a year, the durability cannot be ensured by the conventional configuration at all.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a sound muffler capable of protecting the sound wave generating means and improving its durability while eliminating a pressure difference between the front and rear spaces of the sound wave generating means. The task is to provide

[0006]

The above object is achieved by a noise detector (2) for detecting noise of a noise source (for example, corresponding to a reference symbol P in the embodiment, the same applies hereinafter), and a noise reduction deviation level. It receives the output of the noise elimination deviation detector (3) to be detected, the output (x) of the noise detector (2) and the output (e) of the noise elimination deviation detector (3), and is equal in magnitude to the noise (P). And sound waves having opposite phases are generated by sound wave generation means (4, 4a,
4b, 25) and a muffling signal generating device (7) for forming a muffling signal (y) for generation into the sound absorbing duct (1). 4b, 25), there is provided a communication pipe (22) for communicating the internal space of the closed casing (21) defining the back space (24) with the internal space of the sound absorbing duct (1), and the communication pipe (22). ) And a shutter (23) capable of prohibiting the movement of fluid in the internal space in the internal space of the sound absorbing duct (1) downstream of the connection point (J) between the sound absorbing duct (1). The noise reduction device is characterized in that:

According to the present invention, the communication pipe (22) connects the internal space of the closed casing (21) with the internal space of the sound-absorbing duct (1) to thereby produce sound wave generating means (4, 4a, 4).
4b, 25), the pressure difference between the front surface and the back surface is eliminated, and the inside of the sound absorbing duct (1) is located downstream of the connection point (J) between the communication pipe (22) and the sound absorbing duct (1). By providing a shutter (23) capable of prohibiting the movement of fluid in the space, the shutter (2) can be provided when the operation of the apparatus is stopped.
3) is closed to prevent outside air from reaching the back space (24) of the sound wave generating means (4, 4a, 4b, 25) via the communication pipe (22). Thereby, the back surface of the sound wave generating means (4, 4a, 4b, 25) can be reliably protected from the humidity of the outside air, etc.
4a, 4b, 25) can be improved in durability.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example in which a muffler according to each embodiment of the present invention is applied to an engine generator system will be described with reference to the drawings. In the drawings, the same reference numerals are given to portions corresponding to the conventional example, and detailed description thereof will be omitted.

FIG. 1 shows a first embodiment of the present invention. The noise detector 2 and the silencing deviation detector 3 detect the noise P and the silencing deviation level, respectively, and supply their detection outputs x and e to the silencing signal generator 7. Hereinafter, FIG.
The details of the muffling signal generator 7 will be described with reference to FIG.

The output x of the noise detector 2 is supplied to the amplifier 11, A /
An adaptive filter (hereinafter abbreviated as ADF) 14 and a delay filter 13 via a D converter 12
Supplied to 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, considering the time delay, the delay filter 1
A coefficient of 3 is determined, which 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 an adaptive algorithm for sequentially calculating the optimum coefficient to be given to the ADF 14. 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 the muffling sound having the same magnitude as the noise P and having the opposite phase is generated in the sound absorbing duct 1. Generated towards. The muffling signal generator 7 has a configuration using the above-described well-known ANC control technology.

The pressure balance hole 10 formed in the sound absorbing duct 1 is connected to the other end of a communication pipe 22 having one end connected to the back space 24 of the speaker 4 which is a sound wave generating means defined by a closed casing 21. Thus, the back space 24 communicates with the internal space of the sound absorbing duct 1. Further, the sound absorbing duct 1 on the downstream side of the connection point J between the communication pipe 22 and the sound absorbing duct 1, that is, on the right side in the drawing.
Is provided with a shutter 23 capable of prohibiting movement of fluid (exhaust gas or air) in the internal space.

The present embodiment is configured as described above. Next, this operation will be described.

During operation of the generator, the shutter 23 is in an open state, and discharges noise P emitted from a noise source (engine) (not shown) toward the discharge end (right side in the figure) of the sound absorbing duct 1. The noise P is detected by the noise detector 2, and an output signal x thereof is supplied to a muffling signal generator 7. The muffling signal generating device 7 forms a muffling signal y for generating a muffling sound wave having the same magnitude and opposite phase as the noise P from the speaker 4 toward the internal space of the sound absorbing duct 1. The silencing deviation between the silencing sound wave emitted from the speaker 4 and the noise P is detected by the silencing deviation detector 3, and the output signal e thereof
Is supplied to the muffling signal generator 7. The coefficient calculator 15 receiving the signal e successively updates the coefficient value of the ADF 14 so that e → 0, and controls the driving of the speaker 4 so that the noise P becomes zero at the position of the silencing deviation detector 3 as a result. .

At this time, since the front surface of the speaker 4, that is, the internal space of the sound absorbing duct 1, and the rear surface of the speaker 4, that is, the rear space 24, can have the same pressure,
Can be driven without causing a pressure difference between the front surface and the rear surface.

When the operation of the generator is stopped, the shutter 23
Takes a closed state. Thus, movement of dust and air through the shutter 23 is prohibited. Therefore, it is possible to prevent outside air from reaching the discharge end of the sound absorbing duct 1 and the internal space thereof, and the space 24 behind the speaker 4 via the communication pipe 22, so that the voice coil and the magnetic circuit of the speaker 4 can be prevented. The drive unit can be reliably protected from moisture and dew, so that the durability of the speaker 4 can be further improved as compared with the related art.

FIG. 3 shows a second embodiment of the present invention. Parts corresponding to those in the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

The sound wave generating means in the present embodiment comprises a speaker 4 and a passive radiator 2 arranged in parallel with the speaker 4.
5 The passive radiator 25 is connected to the frame 3
1, diaphragm (cone) 32, suspensions 33, 34
The suspensions 33 and 34 and the weight 35 are set so that a resonance system is constituted by the rear space 24 vibrated by driving the speaker 4. The front surface of the diaphragm 32 is subjected to a waterproof treatment such as a fluororesin coating, similarly to the diaphragm 42 of the speaker 4.

That is, in the present embodiment, the sound wave generating means is provided with a resonance structure so as to efficiently generate loud sound for sound reduction. Further, the passive radiator generally corresponds to the resonance tube 6 in the conventional silencer described with reference to FIG. 5, but compared with the conventional phase inversion type structure, the resonance (resonance) of the resonance tube 6 itself is improved. And the equivalent mass of the vibration system of the passive radiator can be changed quite freely, so that there are advantages such as less dimensional restrictions compared to the resonance tube 6.

Therefore, according to the present embodiment, it is possible to efficiently generate a sound-absorbing sound wave while obtaining the same effects as those of the above-described first embodiment, thereby further improving the sound-absorbing effect. be able to.

FIG. 4 shows a third embodiment of the present invention. Parts corresponding to those in the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

In this embodiment, the sound wave generating means is constituted by two speakers 4a and 4b, and a changeover switch 27 as a changeover means for selecting any one of the two speakers 4a and 4b is provided. And the other speaker 4b is connected to the passive speaker in the above-described second embodiment.
The same operation as that of the radiator 25 is performed. That is, one of the speakers 4a is selected as the first sound source by the changeover switch 27, and the speaker 4a is driven by supplying a muffling signal to the speaker 4a. Are driven in resonance. At this time, the driving section of the speaker 4b is set in a non-short-circuit state so as not to hinder the vibration of the diaphragm 42.

When any abnormality occurs in the speaker 4a, for example, when the speaker 4a breaks down due to disconnection due to overcurrent of the voice coil or the like, the changeover switch 27 is switched to drive the other speaker 4b as the second sound source. At the same time, one speaker 4
a is made to act as a passive radiator.

Therefore, according to the present embodiment, when one speaker breaks down, the other speaker can be driven instead, while exhibiting the same effect as the second embodiment. As a result, the desired sound power can be maintained as a whole of the sound wave generating means, whereby the reliability of the device can be improved.

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 communication pipe 2
The shutter 23 is disposed in the internal space of the sound absorbing duct 1 between the connection point J between the sound absorbing duct 2 and the sound absorbing duct 1 and the sound wave generating means. Even if it is arranged near the discharge end of the duct 1, an effect equivalent to or greater than that of each of the above embodiments can be obtained. That is, it is possible to eliminate the necessity of strictly performing the waterproof treatment performed on the front surface of the sound wave generator.

In the second embodiment, one passive radiator 25 is provided in parallel with the speaker 4.
The number of the passive radiators may be two or more. Similarly, in the third embodiment, three or more speakers are arranged side by side, and when an abnormality is detected in one of the speakers,
By switching the changeover switch 27 as a changeover means, normal speakers may be sequentially selected and driven from among the remaining speakers. Thereby, the durability and reliability of the sound wave generating means can be further improved.

[0027]

As described above, according to the sound deadening device of the present invention, the communication pipe is provided for communicating the internal space of the closed casing and the internal space of the sound absorbing duct which defines the space behind the sound wave generating means. A shutter is provided in the internal space of the sound absorbing duct downstream of the connection point between the communication pipe and the sound absorbing duct, so that movement of fluid in the internal space can be prohibited. While eliminating the pressure difference between them, the sound wave generating means can be effectively protected, and the durability and reliability thereof can be further improved. In particular, it is effective for emergency power generators that are constantly stopped.

[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 cross-sectional view illustrating a main part of a muffler according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a main part of a muffler according to a third embodiment of the present invention.

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 sound absorbing duct 2 noise detector 3 noise reduction deviation detector 4 speaker 4 a speaker 4 b speaker 7 noise reduction signal generator 21 closed casing 22 communication pipe 23 shutter 24 back space 25 passive radiator 27 switch

Claims (4)

[Claims] A noise detector for detecting noise of a noise source;
A muffling deviation detector that detects a muffling deviation level, receives an output of the noise detector and an output of the muffling deviation detector, and outputs a sound wave having the same magnitude and opposite phase as the noise in the sound absorbing duct from the sound wave generator A sound deadening signal generating device for forming a sound deadening signal for generating the sound wave toward the sound absorbing device, wherein an internal space of a closed casing defining a back space of the sound wave generating means and an internal space of the sound absorbing duct are communicated. And a shutter capable of prohibiting movement of fluid in the internal space is provided in an internal space of the sound absorbing duct downstream of a connection point between the communication tube and the sound absorbing duct. Sound silencer. 2. A passive sound generator comprising: a sound wave generator driven by the muffling signal; and a resonance system juxtaposed with the sound wave generator and driven by the vibration of air inside the closed casing. The muffler according to claim 1, comprising a radiator. 3. The sound wave generator includes two or more sound wave generators, and any one of the sound wave generators is selected by a switching means and driven by the muffling signal. 2. The muffler according to claim 1, wherein resonance is caused by vibration of air inside the closed casing. 4. When an abnormality is detected in the sound wave generator driven by the muffling signal, the switching means is configured to supply the muffling signal to a normal sound wave generator among the remaining sound wave generators. 4. The muffler according to claim 3, wherein the sound wave generator in which the abnormality is detected is caused to resonate by vibration of air in the closed casing.