JPH062398U - Active muffler muffler - Google Patents

Abstract

(57) [Abstract] [Purpose] As a speaker that is inexpensive, small, and lightweight, it is possible to improve the speaker mountability and also improve the heat resistance and stain resistance of the speaker / microphone. An active muffler muffler having muffling performance is provided. [Structure] First, an adaptive filter 13 synthesizes a primary source PSE having a high correlation with exhaust noise of the engine 1 as a cancellation signal, and a canceling sound is generated from a speaker 9 arranged through a sound absorbing material 10b in a resonance chamber 7b of a muffler body 5a. Will occur. Then, the noise reduction state is detected as an error signal by the error microphone 11 embedded in the sound absorbing material 10b, and the LM
The S arithmetic circuit 14 updates the filter coefficient of the adaptive filter 13 based on the primary source PSE and the error signal.
Further, since the noise is also reduced by the sound absorbing material 10b, the large speaker 9 is not required. Further, the sound absorbing material 10b prevents heat transfer to the speaker 9 and the error microphone 11 and also prevents adhesion of pollutants in the exhaust gas.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an active muffler that reduces engine exhaust noise by interfering with canceling noise.

[0002]

[Prior art]

 As is well known, among the various noises generated by a car, particularly in the case of engine exhaust noise, the power of the sound source is large and the exhaust muffler has significantly reduced noise, but It occupies a large part of the weight.

For such engine exhaust noise, for example, as shown in Japanese Utility Model Laid-Open No. 63-190513, an enclosure box is provided in the middle of an exhaust pipe connected to the engine, and an enclosure box is provided in the enclosure box. There is known a technology in which a speaker is provided in the vehicle, and the speaker produces a canceling noise against exhaust noise to more effectively reduce the noise.

In recent years, the LMS (Least Mean Square) algorithm (in order to simplify the calculation formula for obtaining the optimum filter coefficient, the fact that the correction formula of the filter is recursive is used, the mean square error is instantaneously calculated. The theory of approximation by square error), or a vehicle interior muffler noise reduction device using the MEFX (Multiple Error Filtered X) algorithm, which is an expansion of this LMS algorithm into multiple channels, has begun to be put into practical use. If a muffler can be applied to realize an active noise reduction muffler that reduces the exhaust noise by generating a canceling noise against the exhaust noise from the speaker installed in the exhaust pipe path, it will be more effective and stable for fine exhaust noise. It is possible to reduce it.

[0005]

[Problems to be solved by the device]

 However, in order to reduce the exhaust noise by canceling the noise, a speaker and a microphone with sufficient heat resistance are required because the speaker and the microphone are arranged in the exhaust pipe path. There are problems such as being contaminated. Furthermore, when trying to cancel out exhaust noise reaching 120 dB, the speaker inevitably becomes large in size and heavy in weight, which makes it difficult to mount the speaker and causes a problem that the speaker becomes expensive.

The present invention has been made in view of the above circumstances, and solves the problem of heat resistance of the speaker and the microphone and the problem of contamination of the speaker and the microphone due to exhaust gas, and also increases the size of the speaker and the accompanying speaker. It is an object of the present invention to provide an active muffler that can effectively and stably reduce exhaust noise by solving the problems of installation and cost increase.

[0007]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the active muffler muffler according to the present invention is filled in the resonance chamber of the muffler body with a cancellation signal synthesizing means for synthesizing a noise source signal having a high correlation with engine exhaust noise as a cancellation signal by an adaptive filter. The noise reduction state is provided as an error signal by arranging it through a sound absorbing material and embedding it in the sound absorbing material filled in the resonance chamber and a canceling sound generating means for generating the cancel signal as a canceling sound against noise. An error signal detecting means for detecting and a filter coefficient updating means for updating the filter coefficient of the adaptive filter based on the noise source signal and the error signal are provided.

[0008]

[Work]

 In the above-described configuration, first, the cancel signal synthesizing means synthesizes the noise source signal having a high correlation with the engine exhaust noise as the cancel signal by the adaptive filter. Next, the cancel signal is generated as a canceling sound for the noise by the canceling sound generating means arranged via the sound absorbing material filled in the resonance chamber of the muffler body. Then, the noise reduction state is detected as an error signal by the error signal detection means embedded in the sound absorbing material filled in the resonance chamber, and the noise source signal and the error signal are detected by the filter coefficient updating means. Based on this, the filter coefficient of the adaptive filter is updated. Further, the exhaust noise of the engine is also reduced by the sound absorbing material filled in the resonance chamber of the muffler main body, so that the particularly large canceling sound generating means is not required. Further, the sound absorbing material in the resonance chamber prevents heat transfer to the canceling sound generating means and the error signal detecting means, and also prevents adhesion of pollutants contained in the exhaust gas of the engine.

[0009]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. 1 to 5 show an embodiment of the present invention, FIG. 1 is a schematic diagram of a system of an active muffler muffler, FIG. 2 is an explanatory diagram of the structure of an active muffler muffler, and FIG. 3 is an effect confirmation test of the active muffler muffler. Fig. 4 is a schematic diagram of the equipment, Fig. 4 is an explanatory diagram of the results of the effect confirmation test of the active muffler muffler without cancellation noise, and Fig. 5 is an explanatory diagram of the results of the effect confirmation test of the active muffler muffler with the cancellation noise. is there.

In FIG. 1, reference numeral 1 denotes an engine, an exhaust pipe 3 is communicated with the engine 1 through an exhaust manifold 2, and a catalytic converter 4 is provided at an inlet of the exhaust pipe 3 for active muffling. It is connected to the muffler 5.

As shown in FIG. 2, the muffler main body 5a of the active muffler muffler 5 is divided into a speaker chamber 7a on the exhaust pipe inlet side and a resonance chamber 7b on the exhaust pipe outlet side by a partition plate 6. The exhaust pipe 3 inserted into the speaker chamber 7a penetrates the partition plate 6 and is inserted into the resonance chamber 7b, and is bent so as to secure a predetermined length in the resonance chamber 7b. And communicates with a tail pipe 8 provided outside the resonance chamber 7b. The exhaust pipe 3 in the resonance chamber 7b has a plurality of holes 3a.

Further, in the speaker chamber 7a, a speaker 9 as a canceling sound generating means for generating a canceling sound toward the resonance chamber 7b is arranged, and is filled with a sound absorbing material 10a such as glass wool. There is. In the resonance chamber 7b, an error microphone 11 as an error signal detecting means for detecting a reduced state of exhaust noise as an error signal is arranged and filled with a sound absorbing material 10b such as glass wool.

Further, in FIG. 1, reference numeral 12 indicates a canceling sound generating device, and an adaptive filter 13 as a canceling signal synthesizing means of the canceling sound generating device 12 and an LMS (Least Mean Square) arithmetic circuit as a filter coefficient updating means. A noise source signal (primary source) PSE having a high correlation with the exhaust noise is input to the control unit 14.

The primary source PSE is, for example, a signal obtained by shaping and processing a signal from an ignition pulse, a fuel injection pulse, a crank angle sensor (not shown), or the like in a predetermined manner, or the load information of the engine based on these signals. Is a signal that reflects the above or a signal that directly detects the exhaust noise, and has a high correlation with the exhaust noise.

Further, the adaptive filter 13 is a FIR (Finite Impulse Response) filter having a predetermined number of taps and capable of updating the filter coefficient. The adaptive filter 13 convolution-adds the primer resource PSE with the filter coefficient to produce a cancel signal, and outputs D The signal is output to the A / A converter 15 and can be generated as a canceling sound from the speaker 9 via the amplifier 16.

Further, the LMS operation circuit 14 receives the error signal from the error microphone 11 and the primary source PSE, calculates a filter correction amount based on these signals, and outputs the error from the error microphone 11. This circuit updates the filter coefficient of the adaptive filter 13 so that the signal becomes minimum.

Next, the operation of the embodiment having the above configuration will be described. First, exhaust noise from the engine 1 is propagated together with the exhaust into the active muffler muffler 5 through the exhaust manifold 2, the catalytic converter 4, and the exhaust pipe 3. Further, the exhaust noise propagating in the active muffler muffler 5 reaches the resonance chamber 7b via the speaker chamber 7a along the exhaust pipe 3 arranged in the muffler main body 5a. Exhaust noise is ejected together with the exhaust from a plurality of holes 3a formed in the exhaust pipe 3 in the resonance chamber 7b, and is reflected and interfered with noise (especially, noise) while passing through the sound absorbing material 10b such as glass wool. , High frequency noise) is reduced. Since the pollutants contained in the exhaust are removed by the sound absorbing material 10b, they are provided toward the error microphone 11 and the resonance chamber 7b arranged in the common chamber 7b. It is possible to prevent contaminants from adhering to the speaker 9. Further, the sound absorbing material 10b acts as a heat insulating material, and heat is effectively prevented from being transferred to the error microphone 11 and the speaker 9.

On the other hand, signals from the engine 1, for example, ignition pulse, fuel injection pulse, crank angle sensor (not shown), etc., which are formed and processed in a predetermined manner, or these signals are transmitted to the engine. A signal having a high correlation with the exhaust noise, such as a signal reflecting the load information or a signal directly detecting the exhaust noise, is used as a noise source signal (primary source) PSE and the adaptive filter 13 of the canceling noise generator 12 and the LMS arithmetic circuit. 14 is input.

The primary source PSE input to the adaptive filter 13 is convolution product-added with the filter coefficient of the adaptive filter 13 and output as a cancellation signal to the D / A converter 15 and, via the amplifier 16, via the amplifier 16. It is generated as a canceling sound that cancels the exhaust noise from the speaker 9 provided in the speaker room 7a of the main body of the muffler 5a.

Therefore, in the resonance chamber 7b of the main body of the muffler 5a, the exhaust noise and the canceling noise interfere with each other to reduce the exhaust noise (particularly, the noise in the low frequency range), and at the same time, the resonance chamber 7b. The error microphone 11 provided therein detects the result of the interference between the exhaust noise and the canceling noise, and sends the result to the LMS arithmetic circuit 14 as an error signal.

Then, in the LMS arithmetic circuit 14, a filter correction amount is obtained from the error signal from the error microphone 11 and the primary source PSE, and the error signal from the error microphone 11 is minimized so that The LMS algorithm for updating the filter coefficient of the adaptive filter 13 is performed.

Next, in the resonance chamber 7b, the exhaust noise, which has been significantly reduced in noise, is exhausted to the outside of the vehicle through the tail pipe 8 together with the exhaust.

Next, referring to FIGS. 3 to 5, a speaker vibration test conducted to confirm the effect of this embodiment will be described. FIG. 3 shows an outline of the experimental apparatus. A vibration speaker 31 is arranged as a virtual noise source on the upstream side of the exhaust pipe 3 of the active noise muffler 5, and the noise generated by the vibration speaker 31 can be measured. A sound level meter (a) 36 is provided in the middle of the exhaust pipe 3. Further, the vibration speaker 31 is connected to the oscillator 33 via the amplifier (a) 32. Further, the speaker 9 of the active muffler muffler 5 is connected to a variable phase shifter (phase shifter) 35 via an amplifier (b) 34, and the phase shifter 35 is connected to the oscillator 33. Further, a noise meter (b) 37 is arranged at a portion 10 mm from the exit of the tail pipe 8 of the active noise muffler 5 so that noise at this portion can be detected. The noise meter (b) 37 is an FFT. It is connected to the analyzer 38.

With the experimental apparatus having the above-mentioned configuration, first, the noise reduction effect was measured in the state where the canceling sound was not generated from the speaker 9 of the active muffler muffler 5 (base state), and the results shown in FIG. 4 were obtained.

As shown in the results of FIG. 4, the active noise muffler 5 according to the present embodiment has a large noise reduction effect even in the base state, and particularly shows a stable and high noise reduction effect from 600 Hz or higher.

Next, a canceling sound was generated from the speaker 9 of the active muffling muffler 5 to measure the noise reduction effect, and the results shown in FIG. 5 were obtained. Here, an experiment was performed by manually adjusting the level and phase of the canceling sound using the oscillator 33 and the phase shifter 35. That is, first, the oscillator 33 adjusts the frequency, the amp (a) 32 adjusts the noise level of the sound level meter (b) 37 to about 85 dB, and the level is measured by the FFT analyzer 38. . Next, the amplifier (b) 34 is turned on to adjust the level, and the phase shifter 35 adjusts the phase. Then, the adjustment of the amplifier (b) 34 and the phase shifter 35 is repeated, and the level is measured by the FFT analyzer 38.

As shown in FIG. 5, it was possible to confirm a stable noise reduction in the entire frequency range where the measurement was performed in the state where the canceling sound was present.

As described above, according to the present embodiment, the sound absorbing material reduces the particularly high frequency range of noise, and the canceling noise reduces the particularly low frequency range of noise. The silencing performance can be obtained.

Further, since not only the canceling sound but also the sound absorbing material is designed to reduce the noise, it is possible to reduce the output of the speaker generating the canceling sound, and to reduce the size and weight of the speaker. It is easy to secure the space to install the speaker and attach the speaker, and the speaker can be inexpensive.

Further, if the frequency of the canceling sound synthesized by the adaptive filter can be selectively set, it becomes possible to cancel only a specific frequency.

[0031]

[Effect of device]

 As described above, according to the present invention, the muffler body is provided with a sound absorbing material filled in the resonance chamber to generate a canceling sound for noise, and a sound absorbing material filled in the resonance chamber. By installing an error microphone that is embedded and detects the noise reduction state as an error signal, it is possible to obtain stable and comprehensive sound deadening performance by the canceling sound and the sound absorbing material. The speaker can be installed easily, and the sound absorbing material effectively prevents heat transfer to the speaker and the error microphone, and also effectively prevents the exhaust of the speaker and the error microphone from being contaminated. Can be prevented.

[Brief description of drawings]

FIG. 1 is a system schematic diagram of an active muffler muffler according to an embodiment of the present invention.

FIG. 2 is an explanatory view of the structure of an active muffler muffler according to an embodiment of the present invention.

FIG. 3 is a schematic view of the device for the effect confirmation test of the active muffler muffler according to the embodiment of the present invention.

FIG. 4 is an explanatory view of the result of the effect confirmation test of the active muffler muffler in the state in which there is no cancellation sound according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of the result of the effect confirmation test of the active muffler muffler in the state with the canceling sound according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 engine 3 exhaust pipe 5 active muffler muffler 5a muffler body 7a speaker room 7b resonance chamber 8 tail pipe 9 speaker (offset sound generating means) 10a sound absorbing material 10b sound absorbing material 11 error microphone (error signal detecting means) 12 offset sound generating apparatus 13 Adaptive filter (cancellation signal combining means) 14 LMS arithmetic circuit (filter coefficient updating means) PSE Primary source (noise source signal)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Keitaro Yokota 1-7-2 Nishishinjuku, Shinjuku-ku, Tokyo Inside Fuji Heavy Industries Ltd.

Claims (1)

[Scope of utility model registration request] 1. A cancel signal synthesizing means for synthesizing a noise source signal having a high correlation with exhaust noise of an engine as a cancel signal by an adaptive filter, and a sound absorbing material filled in a resonance chamber of a muffler main body for providing the canceling. A canceling sound generating means for generating a signal as a canceling sound for noise, an error signal detecting means for detecting a noise reduction state as an error signal by being embedded in the sound absorbing material filled in the resonance chamber, and the noise source signal. An active muffler muffler comprising: a filter coefficient updating means for updating the filter coefficient of the adaptive filter based on the error signal.