JPS6248910A - Exhaust noise reduction equipment of engine - Google Patents

Abstract

PURPOSE:To keep exhaust noise constantly lower regardless of operating condition by disposing two pulse detectors and a pulse generator and controlling them by use of an adaptive control means. CONSTITUTION:The first pulse detector 2 is disposed in an exhaust passage 1 and a pulse generator 6 is disposed downstream with respect to said detector 2. The second pulse detector 4 is disposed at the crossing point of the pulse generated from the pulse generator 6 with exhaust pulse or at a lower course adjacent to said point. A signal from the first detector 2 is input into an adder 14 via both a variable band pass filter 10 and an A/D converter 18. A signal from the second detector 4 is input into a sequential-type establishing control system 8 via both a variable band pass filter 16 and an A/D converter 18. A howling preventive sequential-type establishing control system 20 optimizes howling so that it may be minimum and drives the pulse generator 6.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an engine exhaust noise reduction device, and more specifically, the present invention relates to an engine exhaust noise reduction device, and more specifically, it superimposes a pulsation whose phase is reversed on the exhaust pulsation propagating in the exhaust passage. The present invention relates to an exhaust noise reduction device that muffles exhaust noise.

(Prior art) Conventionally, mufflers with a multi-chamber structure that utilize resonance, diffusion, etc. are often used as devices to reduce engine exhaust noise. There is a problem with this.

As one method to solve this problem,
As seen in Japanese Patent No. 73517, a pulsation detector is provided in an exhaust passage of an engine to detect pressure fluctuations due to exhaust pulsation in the exhaust passage, and a branch pipe joins the exhaust passage downstream of the pulsation detector. and a pulsation generator provided at an upstream end of the branch pipe, and a pulsation whose phase is reversed with respect to the exhaust pulsation detected by the pulsation detector is output from the pulsation generator into the branch pipe. j control means, and by setting the pipe length of the branch pipe equal to the distance between the confluence with the branch pipe and the pulsation detector, the exhaust pulsation propagating in the exhaust passage of the engine can be controlled. An exhaust noise reduction device has been proposed that muffles exhaust noise by superimposing output pulsations of opposite phase.

(Problems to be Solved by the Invention) However, the propagation state of exhaust pulsation within the exhaust passage is not constant. That is, since the exhaust gas temperature or flow velocity changes depending on the operating state of the engine, the propagation state of exhaust pulsation is constantly changing.

Therefore, if the pulsation generator simply outputs a pulsation whose phase is reversed in response to the exhaust pulsation detected by the pulsation detector as in the conventional device, the position of the exhaust pulsation and the output pulsation at the superimposition point will be different. The phase difference is not always π/2 rad, and the absolute values of the pressures are not always equal.

For this reason, the conventional method of exhaust noise reduction can only be achieved under limited operating conditions.

In addition, in conventional devices, a separate branch pipe must be provided in the exhaust passage, and the length of the branch pipe must be equal to the distance between the confluence of the branch pipes and the pulsation detector. This is accompanied by structural restrictions, and as a result, there is a problem in that the device becomes larger.

The present invention has been made in consideration of the above-mentioned problems, and its technical problem is to reduce exhaust noise under any operating condition and to overcome structural constraints. An object of the present invention is to provide a device for reducing exhaust noise.

(Means and effects for solving the problem) The present invention adapts to changes in the propagation state of the exhaust pulsation propagating in the exhaust passage, and suppresses the exhaust pulsation in a phase opposite to the exhaust pulsation and in absolute pressure. In order to superimpose pulsations of equal value, the control system's transfer function is changed to follow changes in the transfer function in the exhaust passage due to changes in engine operating conditions, that is, changes in exhaust gas temperature and flow velocity in the exhaust passage. This is what I did.

That is, in order to automatically adapt to changes in the transfer function in the exhaust passage, an adaptive control system is used based on the principle of an FIR filter. a first pulsation detector for detecting exhaust pulsation in the exhaust gas, and a first pulsation detector provided downstream from the first pulsation detector;
A pulsation generator that outputs pulsations toward the inside of the exhaust passage, and a pulsation generator that is provided at a point where the output pulsation from the pulsation generator and the exhaust pulsation that propagates inside the exhaust passage, or near the downstream side thereof, a second pulsation detector that detects pulsation in the passageway; and a second pulsation detector that receives signals from the first pulsation detector and the second pulsation detector and outputs an adaptively optimized signal to the pulsation generator. The configuration includes adaptive control means that performs the following steps.

With this configuration, no matter the operating condition, it can respond to the state of exhaust pulsation propagating in the exhaust passage, and adaptively optimize output pulsation to reduce exhaust pulsation and output pulsation. This means that the pulsation at the superimposed point is always minimized.

(Example) An example of the embodiment will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an exhaust passage that discharges exhaust gas from the engine into the atmosphere, and in the middle of the exhaust passage 1 there is a first pulsation detection device that detects the exhaust pulsation propagating inside the exhaust passage 1 as sound. A first microphone 2 as a detector and a second microphone 4 as a second pulsation detector are provided. It is assumed that the microphone 1 is located downstream of the microphone 2 of the microphone 1.

In addition, a speaker 6 as a pulsation generator is installed in the exhaust passage 1.
is arranged near the second microphone 4 facing into the exhaust passage 1, and the positional relationship of the second microphone 4 is such that the exhaust sound propagating inside the exhaust passage 1 and the sound output from the speaker 6 are separated. It is said to be located at the superimposition point with, or near the downstream side of.

The output sound output from the speaker 6 into the exhaust passage 1 is based on the output signal Y from the sequential establishment control system 8. The exhaust sound signal and the detected exhaust sound signal from the second motor and f4 can be input.

Between the sequential establishment control system 8 and the first microphone 2, a first
From the microphone 2 side of
A synchronized A/D converter 12 and a force multiplier 14 are provided, and the υp% and sound detected by the first microphone 2 are used as a digitized main input signal X for sequential establishment control. It is input to system 8.

Moreover, between the sequential type establishment control system 8 and the second microphone 4,
From the second microphone 4 side, the variable band filter 16, A/
A D converter 18 is provided, and the exhaust sound detected by the second microphone 4 is input to the sequential establishment control system 81 using the digitized reference human power ε and I7.

The output signal y from the sequential type establishment control system 8 is input to the sequential type establishment control system 20 for howling prevention, which is provided in parallel with the sequential type establishment control system 8. On the other hand, human power is applied to the speaker 6 through the D/A converter 22 and the amplifier 24.

1-The sequential type establishment control system 20 for housing prevention IF includes:
In addition, the confidence from the ship allocation calculator 14 is input 7), and the output signal from the housing prevention sequential establishment control system 20 is E.
It is input to the assigner 14.

Next, the sequential establishment control system 8 will be explained with reference to FIGS. 2 and 3.

In order to simplify the explanation, FIG. In the figure, the dashed line indicates sound, and the solid line indicates signal transmission by the upper air system. In addition, the third closed line is a flowchart of calculations in the sequential establishment control system 8.

First, the main objective of the present invention is to change the acoustic transfer function H in the exhaust passage 1 due to changes in the operating conditions (changes in the exhaust gas temperature IW and flow velocity) due to changes in the operating conditions of the engine (iC1). It is only necessary to temporarily change the transfer function G so that the exhaust pulsation transmission sound A and the output sound B from the speaker 6 are always superimposed in opposite phases and with equal absolute values.

Therefore, in order to cope with changes in the acoustic transfer function H in the exhaust passage 1, it was decided to use an adaptive control system based on the known principle of an FIR filter.

That is, the calculation formula in the sequential establishment control system 8 is based on the following formula.

The value of the main input from the first microphone 2 at the discretization time tk is xk (Fig. 3, step 3), and the value of the main input from the second microphone 4 is
The value of the reference input from εk (Fig. 3, Step 6),
If the value of the output to the speaker 6 is yk, then the output yk of the control system 20 is obtained as follows (Figure 53, step 4).

As understood from the above equation (1), it is necessary to adjust N parameters ωki in order to optimally control the output yk. This parameter ωki is adjusted according to the following formula. Note that μ in the following formula is a constant.

The parameter ω is sequentially updated according to the equation (2), and the 11'' force y obtained from the equation (1) is optimized (Fig. 283, step 7). That is, the output y is adjusted so that the reference human force ε from the second microphone 4 is minimized.
k will be controlled.

By the way, in this embodiment, since the exhaust pulsation in the exhaust passage l is detected as sound by the first microphone 2, a howling problem occurs in the output f from the speaker 6, and this causes the The exhaust sound detected by the first microphone 2 includes a howling component.

Therefore, after removing the howling component from the sound detected by the first microphone 2, it is necessary to input the sound to the sequential establishment control system 8 manually.

The sequential establishment control system 20 for howling prevention described in -1- is provided for this purpose, and the calculations in the sequential establishment control system 20 for howling prevention are similar to those of the sequential establishment control system 8. Similarly, calculations are performed using equations (1) and (2) above.

Here, in the howling prevention sequential establishment control system 20, the output signal y from the sequential establishment control system 8 is the above-mentioned main input value, and the output signal X from the adder 14 is the above-mentioned main input value. This becomes the reference input value.

Therefore, the output signal y' output from the howling prevention sequential establishment control system 20 to the adder 14 according to equations (1) and (2) above has a residual difference between the output signal y' and the actual howling component. Optimization is performed to minimize the howling component, and the adder 14 removes the howling component from the detected sound detected by the first microphone 2.

As a result, the optimized output sound is always outputted from the speaker 6 regardless of the operating condition while solving the above-mentioned howling problem, and an effective exhaust noise reduction effect can be obtained. . According to experiments, about 30dB
A reduction effect was obtained. In the embodiment, the initial values in the sequential establishment control system 8 and the howling prevention sequential establishment control system 20 are set based on the idle operating state.

This is intended to shorten the time required for optimization.

Moreover, since the above-mentioned bandpass filter 1O116 is a mutually interlocking variable filter, the A/D converter 12.
In addition to removing the aliasing effect during conversion to a digital signal by 18, the exhaust sound quality can be freely changed.

Therefore, according to this embodiment, the sequential establishment control system 8 allows the exhaust pipe to be reduced by the output sound output from the speaker 6, no matter what operating state the engine is in.

In addition, by the sequential establishment control system 20 for howling prevention,
It is possible to reduce exhaust noise while solving the problem of howling.

Furthermore, since the bandpass filter 16 is made variable, the quality of the exhaust sound can be changed freely, making it easy to obtain an audibly preferable exhaust sound.

As described above, the applied control means of the present invention may perform analog processing.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, exhaust noise is reduced by employing an adaptive control system, and therefore the exhaust pulsating body propagating in the exhaust passage is reduced. The output pulsation corresponding to the width condition can be superimposed on the exhaust pulsation, and it is possible to obtain the effect of reducing exhaust noise regardless of the operating condition, and there are fewer restrictions on the mechanical structure of the device. It can be a device.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram according to an embodiment of the present invention, FIG. 2 is a block diagram of an adaptive control system, and FIG. 3 is a flowchart showing an example of control according to the present invention. 1: Exhaust passage 2: First microphone (first pulsation detector) 4: Second microphone (second pulsation detector) 6: Speaker (pulsation generator) 8: Sequential establishment control system (adaptive Control means)gI Figure 3

Claims (1)

[Claims] (1) A first pulsation detector provided in an exhaust passage of the engine to detect exhaust pulsation in the exhaust passage; and a first pulsation detector provided downstream of the first pulsation detector to detect pulsation toward the inside of the exhaust passage. a pulsation generator that outputs pulsation, and a pulsation generator that is provided at a superimposition point of the output pulsation from the pulsation generator and the exhaust pulsation propagating in the exhaust passage, or near the downstream side thereof, and detects the pulsation in the exhaust passage. 2 pulsation detectors; and adaptive control means for receiving signals from the first pulsation detector and the second pulsation detector and outputting adaptively optimized signals to the pulsation generator. An engine exhaust noise reduction device characterized by: