JPH0960515A - Exhaust tone quality improving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a feeling of running by improving a tone quality, by silencing or making a sound relating to an exhaust sound of an engine. SOLUTION: A signal frequency information arithmetic part 21 calculates from an engine speed signal frequency information correlated to this engine speed, and a silencing reference signal generating part 22 generates a silencing reference signal based on this signal frequency information. A microphone 17 detects an engine exhaust sound as a signal, and a silence control part 24, receiving this silencing reference signal and a control point signal, generate a silencing signal by using an applicable filter so as to minimize this control point signal. A sound making signal generating part 23 generates a sound making signal based on the signal frequency information, an exhaust sound control part 26 generates an exhaust sound control signal by adding a sound making signal to this silencing signal, and a sonic signal is output toward a muffler 16 of an engine from a speaker 18, so as to improve an exhaust sound to a desired tone quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust sound quality improving device for improving the sound quality by muffling or making sound of exhaust sound generated from an exhaust system of a vehicle.

[0002]

2. Description of the Related Art A vehicle engine generally obtains an output by igniting a mixture of gasoline and air and repeating combustion and expansion. At this time, exhaust gas is discharged from the engine, but since this exhaust gas causes a large amount of noise, it passes through a silencer (muffler) before being released into the atmosphere, and acoustic energy is consumed with a resistance as low as possible. However, this muffler loses its power while reflecting the sound waves that have entered the inside of the expansion chamber from wall to wall, and if the internal structure is complicated, the muffling effect While increasing, it becomes exhaust resistance and engine output decreases.

Therefore, for example, an active cancellation muffler which outputs a sound signal of a predetermined frequency in response to the exhaust sound of the engine to suppress the exhaust sound is disclosed in, for example, Japanese Patent Laid-Open No. 4-5.
It is proposed in Japanese Patent No. 6642 or Japanese Patent Laid-Open No. 4-203406.

The one disclosed in Japanese Patent Application Laid-Open No. 4-56642 discloses a frequency component of a specific order determined by the number of revolutions of the engine among the noise signals from the first microphone that collects the exhaust sound immediately after it is emitted from the engine. The first rotation synchronization filter that blocks the passage of noise signals other than the above and decomposes the noise signal for each order component, and converts the sound pressure level of the noise signal from this filter to a constant level for each frequency by the constant sound pressure device. After that, a sound signal is output from a speaker through an amplifier, and a noise signal from a second microphone that collects a combined sound obtained by combining the sound from the speaker and the exhaust sound is decomposed into order components by the second rotation synchronization filter. Then
The control device compares the sound pressure level at the order peak of the noise signal from this filter with the target exhaust discharge sound pressure level at the order peak, and controls the gain of the amplifier to obtain the order peak of the noise signal from the microphone. The gain of the amplifiers before and after the speaker is controlled so that the sound pressure level at the target sound pressure level approaches the target exhaust discharge sound pressure level, and an optimum exhaust sound color can be generated with good responsiveness.

Further, in the one disclosed in Japanese Patent Laid-Open No. 4-203406, the adaptive digital filter responds to the output impulse of the edge detecting means, and based on the output signal of the pressure wave detecting means, the transfer function thereof is set to the exhaust sound path. Is set to be equal to the transfer function of the pressure wave output means, and in response to this, a drive signal is output to the pressure wave output means. The pressure wave of the exhaust sound that is output and output from the exhaust sound path is canceled, and the exhaust sound disappears.In this case, the number of taps of the adaptive digital filter is set according to the rotation of the internal combustion engine, which reduces the tap noise. It is possible to muffle the sound in an optimum state in all operating conditions of the internal combustion engine from the time of rotation to the high speed, and the adaptive response is adjusted by the impulse response synchronized with the rotation of the internal combustion engine. By controlling so identified the transfer function of the barrel filter the transfer function of the exhaust sound path can mute under optimum conditions until high rotation from at low rotation of the internal combustion engine.

[0006]

However, each of the devices disclosed in the above publications has a problem that the exhaust sound quality of the engine cannot be sufficiently improved.
That is, in the one disclosed in Japanese Patent Application Laid-Open No. 4-56642, since the rotary synchronous filter that decomposes the noise signal for each order component is a fixed type, the noise signal of the exhaust sound to be output after the initial setting is If it changes, it cannot respond to this. The muffler of a vehicle has a muffler that changes its muffling effect due to changes in temperature and aging of the built-in muffling material, which changes the exhaust noise after passing through the muffler. In the technology disclosed in the above publication,
It is not possible to cope with this change in exhaust noise, and it is not possible to sufficiently exert the silencing effect.

Further, although the one disclosed in Japanese Patent Laid-Open No. 4-203406 uses an adaptive digital filter, it can cope with a change in exhaust noise, but
It is insufficient in terms of improving exhaust noise. That is,
The driver reduces exhaust noise to seek quietness in the passenger compartment, while listening to the exhaust noise to understand the driving condition of the engine.
In addition, they are satisfied with the feeling of the engine sound that suits the running performance. Therefore, as in the technique disclosed in the above-mentioned publication, if the exhaust noise is simply turned off, the driver feels uncomfortable and cannot obtain sufficient traveling comfort.

The present invention solves such a problem, and provides an exhaust sound quality improving apparatus for improving the running feeling by improving the sound quality by muffling or making noise to the exhaust sound of the engine. The purpose is to provide.

[0009]

The exhaust sound quality improving apparatus of the present invention for achieving the above object is a signal frequency information calculation for calculating signal frequency information from a signal correlated with the rotation speed of an engine mounted on a vehicle. Means, and a muffling reference having a plurality of frequencies including a frequency that is a non-integer multiple of the frequency having a signal having a high correlation with the engine speed based on the signal frequency information calculated by the signal frequency information calculating means. A muffling reference signal generating means for generating a signal, and an integral multiple frequency with respect to a frequency having a signal highly correlated with the engine speed based on the signal frequency information calculated by the signal frequency information calculating means. A sound production signal generation means for producing a sound production signal having a plurality of frequencies, and a control point signal detection for detecting the exhaust sound of the engine as a signal at a control point. Means, a secondary sound source for outputting a sound wave signal toward the exhaust sound generating portion of the engine, a silencing reference signal from the silencing reference signal generating means, and a control point signal from the control point signal detecting means. And a silencing control means for generating a silencing signal for controlling the secondary sound source by using an adaptive filter so that the control point signal is minimized, and the silencing signal generation for the silencing signal from the silencing controller. Exhaust sound control means for adding the sound producing signals from the means to generate an exhaust sound control signal for controlling to a desired exhaust sound and outputting it to the secondary sound source.

Therefore, the signal frequency information calculating means calculates signal frequency information correlated with the engine speed from the engine speed,
The muffling reference signal generating means generates a muffling reference signal based on this signal frequency information, and the control point signal detecting means detects engine exhaust sound as a signal, and the muffling control means uses the muffling reference signal and the control point. In response to the signal, a noise reduction signal is generated using an adaptive filter so that the control point signal is minimized, while the sound production signal generation means generates a sound production signal based on the signal frequency information, and exhaust sound control is performed. The means adds the sound production signal to the muffling signal to generate an exhaust sound control signal and outputs the exhaust sound control signal to the secondary sound source, and the secondary sound source directs to the exhaust sound generating portion of the engine based on the exhaust sound control signal. The exhaust sound is improved to a desired sound quality by outputting the sound wave signal.

Further, the exhaust sound quality improving apparatus of the present invention is characterized in that it is provided with a sound deadening / sound changeover means for outputting the sound deadening signal or only the sound deadening signal to the exhaust sound control means in response to a driver's operation. To do.

Therefore, when the driver operates the noise reduction / sound production switching means, the exhaust noise is silenced or produced to improve the sound quality.

Further, in the exhaust sound quality improving apparatus of the present invention, the muffling reference signal generating means includes a steady state signal generating section for generating a muffling reference signal in a steady driving state of the engine, and an unsteady state of the engine. A non-steady-state signal generation unit that generates a silencing reference signal in, and a signal switching unit that selectively outputs the silencing steady-state reference signal and the silencing non-steady-state reference signal according to the driving state of the engine. It is characterized by having.

Therefore, the signal switching unit outputs a muffling steady-state reference signal during steady driving of the engine such as constant speed operation of the vehicle, and outputs a muffling unsteady reference signal during unsteady driving of the vehicle such as accelerated driving. Therefore, the engine exhaust sound is surely reduced by the silencing reference signal according to the sound quality.

Further, in the exhaust sound quality improving apparatus of the present invention, the sound producing signal producing means is capable of producing plural kinds of sound producing signals, and a desired sound producing signal is selectively produced according to the operation of the driver. It is characterized by being able to output.

Therefore, a specific sound producing signal is output from the sound producing signal generating means in response to the driver's operation.
The driver can change the exhaust sound to a desired sound quality.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings and examples.

FIG. 1 is a block diagram showing the overall structure of an exhaust sound quality improving apparatus according to an embodiment of the present invention, FIG. 2 is a control block in the exhaust sound quality improving apparatus of this embodiment, and FIG. 3 is a control block of a system control unit. FIG. 4 is a block for explaining the control algorithm in the system control unit, FIGS. 5 and 6 are flowcharts showing the control of the exhaust sound quality improving apparatus of this embodiment, and FIG. 7 is a flowchart for explaining the method of calculating the reference frequency and the initial angular velocity. A time chart, FIG. 8 is a graph showing the noise level reducing effect of the exhaust sound quality improving apparatus of this embodiment, and FIGS. 9 and 10 show the noise level reducing effect of each order component by the exhaust sound quality improving apparatus of this embodiment. A graph is shown.

In the exhaust sound quality improving apparatus of this embodiment, as shown in FIG. 1, an engine 12 is mounted on the front of a vehicle 11, and a silencer (silencer) 13 and a resonator ( An exhaust pipe 15 having a resonator 14 interposed therein is extended rearward, and a muffler (silencer) 16 is attached to an end portion. In the vicinity of the muffler 16, a microphone 17 as a control point signal detecting means for detecting exhaust noise at a control point is attached. A speaker 18 as a secondary sound source that outputs a sound wave signal is attached near the muffler 16.

Further, the exhaust sound quality improving apparatus of the present embodiment has a signal frequency information calculation unit 21 for calculating signal frequency information from a signal correlated with the number of revolutions of the engine 12, and an engine 12 based on this signal frequency information. A signal having a high correlation with the rotation speed, for example, a muffling reference signal generation unit 22 that generates a muffling reference signal having a plurality of frequencies including a frequency that is a non-integer multiple of the frequency of the engine pulse, and the signal frequency information. Based on the sound producing signal generator 23 for producing a sound producing signal having a plurality of frequencies including an integral multiple of the engine pulse frequency, the muffling reference signal and the microphone 17 control the exhaust sound at the control point. Mute control unit 2 which receives the control point signal detected as the signal of 1 and generates a mute signal for controlling the speaker 18 so that this control point signal becomes minimum (preferably 0). And a sound increase signal and a control point signal in which the microphone 17 detects the exhaust sound as a signal at the control point to generate a sound increase signal for controlling the speaker 18 so as to obtain an optimum exhaust sound. 25, and an exhaust sound control section 26 including an adder for controlling the speaker 18 by generating an exhaust sound control signal for improving the exhaust sound quality by adding a sound production signal to the mute signal.

The engine pulse of the engine 12 is input from the engine control unit (ECU) 27 to the signal frequency information calculation section 21. The detection signal of the microphone 17 is controlled by the microphone amplifier 19, and the speaker 18 is controlled by the control signal from the speaker amplifier 20.

Now, the components of the exhaust sound quality improving apparatus of the above-described embodiment will be described in detail.

As shown in FIG. 2, the signal frequency information calculator 21 calculates the signal frequency information from the engine pulse (ignition pulse) as a signal correlated with the engine speed from the ECU 27, and is not shown. The signal frequency information calculation unit 21 has the functions of a counter that counts the number of engine pulses and a frequency calculator that calculates the engine pulse frequency from the number of engine pulses counted by the counter.

The ECU 27 receives detection signals from the engine speed sensor, the engine load sensor, etc., and outputs a signal for controlling the ignition timing of the engine 12 and a signal for controlling the fuel supply (air-fuel ratio control). It is a well-known thing that consists of a microprocessor, memory, etc.
An engine pulse (ignition pulse) can be easily taken out from the ECU 27.

The counter and the frequency calculator are realized by software in order to maintain the causal relationship between the input engine pulse and the detection signal of the microphone. That is, if the above means is realized by hardware instead of software, the causal relationship between the input engine pulse and the microphone signal disappears due to the non-linearization of the timing difference and the time delay.

Next, the calculation method by the signal frequency information calculation unit 21 will be described. First, from the cycle of the engine ignition pulse (engine pulse), the initial angular velocity ω and the reference frequency F can be expressed as sin θ = sin (W · T _SAMPLE ) = sin (2πF _SIGNAL · T _SAMPLE ) ... (1) it can.

Since F _SIGNAL = 1 / T _SIGNAL , assuming that the number of pulses counted in T _SIGNAL is n, sin θ = sin (2π · (T _SAMPLE / n / F _CLOCK )) ) = Sin (2π · (T _SAMPLE · F _CLOCK / n)) = sin (2π · (F _CLOCK / F _SAMPLE · n)) (2)

Thus, if the number of pulses n (n is a natural number) counted during T _SIGNAL is measured, the known information F
_The frequency information sin θ can be obtained from _CLOCK and F _SAMPLE , and this calculation is performed by the signal frequency information calculation means 21.

The pulse counter clock F
_CLOCK (cycle T _CLOCK ), A / D sampling clock F _SAMPLE (cycle T _SAMPLE ), engine ignition pulse F
_SIGNAL (cycle T _{SI GNAL} ), timing generator timing, and digital signal processor (DSP) timing are shown in FIG.

Based on the signal frequency information calculated by the signal frequency information calculation unit 21, the muffling reference signal generation unit 22 is a non-integer multiple of the frequency of the engine pulse (a signal correlated with the engine speed). Generating a reference signal having a plurality of frequencies including the frequency of
In the present embodiment, the muffling reference signal generator 22 has a mode 0 map 22a and a mode 1 map 22b.

The mode 0 map 22a is for generating a reference signal at the time of engine steady operation such as constant speed running of the vehicle, and includes a reference signal (ΣX _i sin
θ _i ) is output. On the other hand, mode 1 map 22
Reference character b is used to generate a reference signal during engine unsteady operation such as acceleration / deceleration running of the vehicle, and a proximity order component (for example, a crank rotation 0.5-order frequency component or a crank rotation 0.25).
A reference signal (ΣY _i sin θ _i ) including a non-integer multiple frequency component of the fundamental frequency component such as the next frequency component is output. Each of the maps 22a and 22b is equivalently composed of a plurality of oscillators and an adder for adding the outputs of the respective oscillators.

The muffling reference signal generator 22 also has a function of a changeover switch 22c for selecting the output of the mode 0 map 22a or the output of the mode 1 map 22b. The changeover switch 22c receives the changeover control signal,
The output of the mode 0 map 22a is selected as a reference signal during steady operation, and the mode 1 map 22b is selected during unsteady operation.
The output of is selected as a reference signal.

Based on the signal frequency information calculated by the signal frequency information calculation unit 21, the sound generation signal generation unit 23 has a plurality of frequencies including a frequency that is an integral multiple of the frequency of the engine pulse. Signal (ΣZ _i sin θ _i )
Is generated and output.

An angle change gradient D (Δsin θ) per unit time obtained from the signal frequency information calculated by the signal frequency information calculation unit 21 is input to the sound production control unit 25. In the sound production control unit 25, the gain G is obtained according to the angle change gradient D, and the attenuator (AT
This gain G is multiplied at T). At this time, the gain G
The threshold values a, b, and c of the angle change gradient D for obtaining the value are preset. Then, this angle change gradient D = Δsin θ can be obtained from the following equation. Note that θ
_OLD is the signal frequency information obtained one time ago. Δsin θ = sin (θ _OLD + (2π ・ (F _CLOCK / F _SAMPLE・ n))) ・ ・ (3)

Further, the sound production control section 25 receives the control point signal (error signal) from the microphone 17 and sets the output level of the sound production signal. Using a smoothing circuit, the pseudo average power P of the error signal is calculated by the following equation. At this time, E is the absolute value of the error signal, and a is a coefficient of 0.999. P _n = aP _n-1 + (1-a) E (4)

The set level Y of the average power P thus obtained is obtained from the functional expression Y = aP + b, and Y is multiplied by the level adjusting unit (LVL). In setting the sound production exhaust level, two types of mode levels are set in this embodiment. This mode level is the mode switch 3
1 is used by the driver to make a selection. For example, a mode level 1 is capable of generating a sound-producing signal that makes the driver feel light, and a mode level 2 is a structure that makes the driver feel powerful. A sound signal can be generated, and parameters of such mode levels 1 and 2 are stored in advance.

As described above, the angle change gradient D per unit time calculated from the signal frequency information is output to the sound production control section 25. This angle change gradient D is switched by the muffling reference signal generation section 22. It is output to the switch 22c and used as a threshold value for detecting the operating state of the engine 12. That is, when the angle change gradient (Δsin θ) exceeds the desired threshold value TH1, it is determined that the acceleration / deceleration operation is being performed, the mode 1 map selection signal is output, and the angle change gradient (Δsin θ) is determined as desired. Threshold value TH2 (TH2 <TH
1) When it becomes the following or less, it is judged that it is a steady operation and mode 0
It is designed to output a map selection signal.

By the way, the system control unit 41 of the noise reduction control section 24 and the exhaust noise control section 26 is arranged in the trunk room. The system control unit 41 has a muffling control switch 32. As shown in FIG. 3, the reference signal from the muffling reference signal generating unit 22 and the detection signal from the microphone 17 are input, and the system control unit 41 is fed to the speaker 18. A control signal is output.

This system control unit 41
Is a digital signal processor (hereinafter referred to as DSP) 42, RAM 43, 44, 45, EP-ROM 4
6, status control register (hereinafter referred to as SCR) 47, clock generator 48, serial port 4
9, a low pass filter 50, 51, 52, A / D converters 53, 54, a D / A converter 55, a timing generator 56, a DSP 42, a RAM 43,
44, 45, EP-ROM 46, SCR 47, A / D converters 53, 54 and D / A converter 55 are photoelectric converters (O).
/ E) and optical fiber with electro-optical converter (E / O) 5
7 are connected.

Then, these DSP 42, RAM 4
The muffler control section 24 is composed of 3, 44, 45, EP-ROM 46, SCR 47, and clock generator 48. Here, the DSP 42 is used for calculation for silencing control (active noise cancellation).
RAM43,44,45, EP-ROM4 on the bus of 2
6, SCR47 is arranged.

The RAMs 43, 44 and 45 store control programs, and the SCR 47 controls address allocation with the DSP 42. EP-ROM
Reference numeral 46 is characteristic information of the muffler transmission system [the transmission system from the speaker 18 to the exhaust sound control point, the microphone 17, the speaker 18,
Including the frequency characteristics (time delay) of each amplifier 19, 20]
Etc. are stored.

The clock generator 48 generates an operation clock for the DSP 42. The low-pass filters 50, 51, 52, the A / D converters 53, 54, and the D / A converter 55 include a microphone 17, a speaker 18, and a muffling control unit 2.
The analog signal detected by the microphone 17 at the interface with the digital filter 4 is filtered by the low-pass filter 51 and then converted into a digital signal by the A / D converter 54.
While being input to the muffling control unit 24, the secondary source signal from the muffling control unit 24 is converted to an analog signal by the D / A converter 55, filtered by the low-pass filter 52, and output to the speaker 18. It has become so.

The low-pass filters 50, 51, 52
In order to prevent aliasing from the speaker 18, the one that cuts the band output above the maximum control frequency is used. The timing generator 56 generates a timing pulse that determines the input / output timing of the A / D converters 53, 54 and the D / A converter 55. The DSP 42 starts / stops by writing a command in the control register. Has become. The serial port 49 is an external terminal for connection with an external computer. In addition, this system is an onboard RO when the power is turned on.
The control program is booted by M to operate as a stand-alone device.

By the way, in the present embodiment, the mute control section 24 of the system control unit 41 controls the engine pulse signal from the ECU 27 (a reference signal is generated based on this engine pulse signal) and the control detected by the microphone 17. In response to the point signal, the control point signal is configured as a control means using an adaptive filter so as to control the sound wave signal output from the speaker 18 so that the control point signal becomes minimum (preferably 0). Furthermore, in the present embodiment, the muffling control unit 24 is adapted to perform muffling control using an adaptive filter that uses an algorithm based on the least square error estimation method (LMS method).

In this embodiment, the exhaust sound control point (microphone 17) is output from the speaker 18 in advance before the muffling control is performed.
The characteristic (transfer function) C of the muffling transfer system including the transfer system up to the installation position) is measured. This measurement is performed as follows. That is, the characteristic C of the sound deadening transmission system is measured by outputting the M-sequence random sound (white noise) from the speaker 18 and detecting it by the microphone 17.

After that, the muffling control section 24 performs muffling control using the measured characteristic information of the muffling transmission system as correction information of the reference signal. That is, the reference signal is filtered by the filter having the characteristic information C ′ of the measured sound transmission system, and the filter coefficient is updated from this and the control point signal detected by the microphone 17 by using the algorithm by the LMS method. I will do it.

Next, the basic algorithm of this system will be described in detail. First, the mute control (active noise control) of this system is Filtered-X LMS.
An adaptive FIR filter using an algorithm is used.
As shown in FIG. 4, T is the characteristic of the vehicle body transmission system [including the acoustic transmission characteristic from the noise source to the control point (the installation position of the microphone 17)], W is the adaptive FIR filter, and C is the characteristic of the sound deadening transmission system [ Control point from speaker 17 (installation position of microphone 17)
Including the acoustic transfer characteristics up to], C'is a model of C, LM
S is the LMS algorithm.

This system uses the reference signal X from the noise source.
(T) (this reference signal is different during steady operation and during acceleration / deceleration) is input and convolved by FIR to obtain the output Y (t). Y (t) = ΣW (i) X (t−i) (5) In addition, with respect to the equation (5), the sum is obtained for i = 0 to N−1.

When the present system outputs -Y (t), the error signal E at the control point is obtained due to the transfer characteristic of the sound field. E (t) = T (z) X (z) -C (z) Y (z) (6) Further, in order to maintain the causal relationship between the reference signal X (t) and the error signal E (t). Filter X (t) to d
Find (t). d (t) = ΣC ′ (i) X (t−i) (7) It should be noted that the equation (7) is also adapted to take the total sum for i = 0 to N−1.

Then, the error signals E (t) and d
From (t), using the LMS algorithm, the filter coefficient W
Update (i). That is, Wn (i) = Wo (i) + kE (t) d (t−i) (i = 0 to N−1) (8) where Wn (i) is the updated filter coefficient, Wo
(I) is a filter coefficient before updating, and k is an updating coefficient.

As a result, the filter converges on the optimum filter which minimizes the error signal. Further, the error E is determined by the reference signal X, the filter coefficient W, and the sound deadening transmission system characteristic C. That is, it is necessary to consider C above in the preceding stage of the LMS algorithm used to maintain the causal relationship between the input data and the error. Therefore, in this system, the adaptive algorithm is the Filtered-X-LMS algorithm, and this C is identified before the start of adaptive control.

In this way, W will converge on the Wiener filter if a sufficient time elapses after the start of control, and if it is ideal, then W =-(T / C). That is,
W will perform forward modeling of T and inverse modeling of C at the same time. At this time, when the input noise signal is X, the output of T is TX, the output of W is represented by (-TX / C), and the output of C is (-TX /
C) .C = -TX.

That is, the error signal E becomes 0 at the addition point (see P) which is the evaluation point (control point). Here, when T and C are expressed in polar coordinates, they are expressed by W = (T / C) exp [-j (θt−θd)] (9). Considering the actual machine model, the engine intake sound measured in the vehicle compartment is caused by the engine rotation (vibration), and therefore is always larger than the delay of T (θt−θd).
Indicates a positive value. In other words, W is considered to be controllable because it becomes a delay element.

Here, the control flow of the exhaust sound quality improving apparatus of this embodiment will be described. First, as shown in FIG.
In the C identification procedure performed before the start of adaptive control, in step A1, A / D, D / A conversion, control registers, counters, etc. are initialized, and A / D conversion is started, and in step A2. , M-sequence signals are generated. After that, in step A3, adaptive filter calculation is performed, D / A conversion is further started, and in step A4, the operation of updating the adaptive filter coefficient is repeated to identify the characteristics of the muffling transmission system. is there.

After that, as shown in FIG. 6, first, in step B1, A / D, D / A conversion, control registers, counters, etc. are initialized, and further, the silence transmission measured in advance. The reference signal is generated after reading the characteristic information (initial impulse response) of the system. That is, in step B2, engine pulses are counted, in step B3, the reference frequency (F) is calculated, in step B4, the initial angular velocity ω is calculated, and in step B5, the change gradient D (Δsin θ) is calculated. do. And step B
In 6 to B12, processing for generating a silence signal is performed. That is, in step B6, the gain mode is selected, and if it is during steady operation, the mode 0 map is selected and a reference signal corresponding thereto is generated (steps B7 and B9), while during acceleration / deceleration operation, In step B6, a mode 1 map is selected and a reference signal corresponding to it is generated (step B
8, B9). After that, A / D and D / A conversion is started, adaptive filter calculation is performed, and adaptive filter coefficients are updated (steps B10 to B12).

On the other hand, corresponding to the process of generating the mute signal,
In steps B13 to B15, processing for generating a sound production signal is performed. That is, in step B13, a sound production signal is generated and A
Start the / D conversion, calculate the adaptive filter,
The sound production level is adjusted (steps B14 and B15).

Then, in step B16, an exhaust noise control signal is generated based on the muffling signal and the sound production signal thus output. That is, an exhaust sound control signal that produces a desired exhaust sound for the driver is generated by muting or making sound for each frequency component of the exhaust sound.

Explaining this concretely, the driver selects the exhaust sound quality according to his / her preference. That is, when the driver simply wants to muffle the exhaust sound, the muffler control switch 32 is turned on and the mode changeover switch 31 is turned off. Then, with respect to each frequency of the exhaust sound generated from the engine D, the inverse frequency signals are output from the speaker 18, so that the sound is silenced for each frequency. Also,
When the driver wants to make an exhaust sound with a light and powerful feeling, the mute control switch 32 is turned on and the mode switch 31 is set to the mode level 1 or the mode level 2. Then, with respect to each frequency of the exhaust sound generated from the engine 12, by outputting a frequency signal of a reciprocal number and a frequency signal of a positive number from the speaker 18, respectively, a certain frequency component is silenced and a certain frequency component is produced. , The desired exhaust sound quality is obtained.

Now, the sound deadening effect of the exhaust sound quality improving apparatus of the present embodiment will be described. As shown in FIG. 8, the noise level of the exhaust sound is divided into C3 order component, C6 order component, overall component and frequency, and 60 km /
Exhaust noise was measured at two vehicle speeds, h and 100 km / h. As can be seen from the graphs, the noise level is reliably reduced in all cases compared to the conventional case.

Further, FIG. 9 shows the muffling effect at the time of full-open constant speed running, and FIGS. 10 to 13 show the muffling effect at the time of full-open non-constant speed running. As can be seen from this graph, each order component It can be seen that the sound deadening effect is noticeable.

[0061]

As described above in detail with reference to the embodiments, according to the exhaust sound quality improving apparatus of the present invention, the signal frequency information calculating means calculates the signal frequency information correlated with the engine speed from the engine speed. The muffling reference signal generating means generates a muffling reference signal based on the signal frequency information, and the control point signal detecting means detects engine exhaust noise as a signal, and the muffling control means controls the muffling reference signal and the control signal. While receiving the point signal to generate a muffling signal using an adaptive filter so that this control point signal is minimized, the sound production signal generation means generates a sound production signal based on the signal frequency information,
The exhaust sound control means adds the sound production signal to this muffling signal to generate an exhaust sound control signal and outputs it to the secondary sound source. This secondary sound source is sent to the exhaust sound generating unit of the engine based on the exhaust sound control signal. Since the sound wave signal is output toward, the arbitrary order component synchronized with the signal that correlates with the engine speed can be input as a reference signal to the adaptive filter according to the engine operating state at any amplitude level. The exhaust sound can be reliably silenced in any frequency band, while the exhaust sound can be adjusted by synthesizing the sound production signal with the silencing signal. As a result, the exhaust sound quality is improved and the driving feeling is improved. The ring can be improved.

Further, according to the exhaust sound quality improving apparatus of the present invention, the sound deadening / noise switching means for outputting only the sound deadening signal or the sound deadening signal to the exhaust sound control means in accordance with the operation of the driver is provided. When the driver operates the sound making switching means, the exhaust sound is silenced, or the sound is made and sound quality is improved, so that the exhaust sound quality can be improved.

Further, according to the exhaust sound quality improving apparatus of the present invention, the muffling reference signal generating means and the steady state signal generating section for generating the muffling reference signal in the steady driving state of the engine and the unsteady state of the engine. Since it has a non-steady state signal generation unit that generates a muffling reference signal and a signal switching unit that selectively outputs from the muffling steady state reference signal and the muffling non-steady state reference signal according to the driving state of the engine, signal switching Depending on the sound quality, the part outputs a muffling steady-state reference signal during steady-state engine driving such as constant-speed driving of the vehicle, and outputs a muffling non-steady-state reference signal during unsteady driving such as vehicle acceleration. The exhaust noise can be surely reduced by the noise reduction reference signal.

Further, according to the exhaust sound quality improving apparatus of the present invention, the sound producing signal producing means can produce plural kinds of sound producing signals, and the desired sound producing signal can be selectively selected according to the operation of the driver. Since a specific sound production signal is output to the driver according to the operation, the driver can change the exhaust sound to a desired sound quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an exhaust sound quality improving apparatus according to an embodiment of the present invention.

FIG. 2 is a control block diagram in the exhaust sound quality improving apparatus of the embodiment.

FIG. 3 is a block diagram showing details of a system control unit.

FIG. 4 is a block diagram illustrating a control algorithm in the system control unit.

FIG. 5 is a flowchart illustrating a control method of this embodiment.

FIG. 6 is a flowchart illustrating a control method according to this embodiment.

FIG. 7 is a time chart for explaining a method of calculating a reference frequency and an initial angular velocity.

FIG. 8 is a graph showing the noise level reduction effect of the exhaust sound quality improvement device of the present embodiment.

FIG. 9 is a graph showing the noise level reduction effect for each order component during constant speed running by the exhaust sound quality improvement device of the present embodiment.

FIG. 10 is a graph showing the noise level reduction effect for each order component during non-constant speed running by the exhaust sound quality improvement device of the present embodiment.

FIG. 11 is a graph showing the noise level reduction effect for each order component during non-constant speed running by the exhaust sound quality improvement device of the present embodiment.

FIG. 12 is a graph showing the noise level reduction effect for each order component during non-constant speed running by the exhaust sound quality improvement device of the present embodiment.

FIG. 13 is a graph showing the noise level reduction effect for each order component during non-constant speed running by the exhaust sound quality improving apparatus of the present embodiment.

[Explanation of symbols]

 12 engine 15 exhaust pipe 16 muffler 17 microphone (control point signal detecting means) 18 speaker (secondary sound source) 21 signal frequency information calculation unit 22 muffling reference signal generating unit 23 sound making signal generating unit 24 muffling control unit 25 sound making Control unit 26 Exhaust noise control unit 27 Engine control unit (ECU) 31 Mode changeover switch 32 Silence control switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naohisa Koike 5-33-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation

Claims (4)

[Claims] 1. A signal frequency information calculating means for calculating signal frequency information from a signal correlated with the number of revolutions of an engine mounted on a vehicle, and the engine based on the signal frequency information calculated by the signal frequency information calculating means. And a muffling reference signal generating means for generating a muffling reference signal having a plurality of frequencies including a frequency that is a non-integer multiple of a frequency having a signal highly correlated with the number of revolutions, and is calculated by the signal frequency information calculating means. Sound producing signal producing means for producing a sound producing signal having a plurality of frequencies including an integral multiple of the frequency having a signal highly correlated with the engine speed based on the signal frequency information, and the engine. Control point signal detecting means for detecting the exhaust sound of the engine as a signal at the control point, and a secondary sound source for outputting a sound wave signal toward the exhaust sound generating section of the engine. And receiving the muffling reference signal from the muffling reference signal generating means and the control point signal from the control point signal detecting means, and using the adaptive filter to minimize the control point signal to the secondary sound source. A muffling control means for generating a muffling signal for controlling, and an exhaust noise control signal for controlling the muffler signal from the muffling control part to a desired exhaust noise by adding the muffler signal from the noise-making signal generating means. And an exhaust sound control means for generating and outputting the generated sound to the secondary sound source. 2. The exhaust sound quality improving apparatus according to claim 1, further comprising a sound deadening / sound changeover means for outputting only the sound deadening signal or the sound deadening signal to the exhaust sound control means according to a driver's operation. A characteristic exhaust sound quality improvement device. 3. The exhaust sound quality improvement apparatus according to claim 1, wherein the muffling reference signal generating means generates a muffling reference signal in a steady driving state of the engine, and a non-operation of the engine. A non-steady state signal generation unit that generates a silencing reference signal in a steady state, and a signal switching unit that selectively outputs the silencing steady reference signal and the silencing non-steady reference signal according to the driving state of the engine. An exhaust sound quality improvement device characterized by having. 4. The exhaust sound quality improving apparatus according to claim 1, wherein the sound producing signal producing means is capable of producing a plurality of types of sound producing signals, and selects a desired sound producing signal according to a driver's operation. The exhaust sound quality improvement device, which is characterized in that it can be output as desired.