JPH08254163A - Active noise control device for automobile - Google Patents

Abstract

PURPOSE: To prevent a situation that noise is inversely worsened through adaptive control by a method wherein when a sound wave by which intake noise is offset through processing of a detecting signal for intake noise is generated, adaptive control to regulate signal processing characteristics on a given operation condition is prohibited. CONSTITUTION: Air is sucked in an engine 1 from an air cleaner 2 through intake systems 3-6. Meanwhile, a control unit 9 controls a fuel injection valve 8 based on detecting signals from an airflow meter 10 and a crank angle sensor 11. In this case, a speaker 21 to generated a sound wave in an intake system is arranged in an air cleaner 2 part and a microphone 22 to convert a sound in the intake system into an electric signal is arranged in a spot situated upper stream of an air cleaner 2. A sound wave for offsetting intake pulsation noise is generated from a speaker 21. An offset remaining sound is detected by a microphone 22 and adaptive control to adjust the characteristics of signal processing to generate a noise signal for generating a sound wave. Further, when adaptive control is regulated on a given operation condition, an adaptive control is prohibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise control system for a vehicle, which actively reduces noise in a vehicle by interference of separately generated sound waves, and more particularly to a technique for reducing intake system noise of an engine.

[0002]

2. Description of the Related Art In recent years, a technique called active noise control has been proposed as a technique for ensuring the quietness of an automobile. In view of the fact that the sound is a kind of wave phenomenon in which a change in the density of air propagates in the air, the active noise control is similar to noise (primary sound) in a vehicle, and another sound wave (secondary sound) having the same amplitude but opposite phase (secondary sound). Sound) to cancel the primary sound.

[0003]

In the case of reducing the intake system noise (intake sound) generated by the intake pulsation of the engine by the active noise control, a speaker is provided in the intake system, which is a noise generation source. By installing, the intake noise can be efficiently reduced. Here, it is possible to deal with the error factors of the physical dimensions of the intake system, changes over time, changes in acoustic characteristics due to dirt and dust, and fluctuation factors such as characteristic variations and durability deterioration of speakers and microphones used for active noise control. For that purpose, it is desirable to apply so-called adaptive control for adjusting the characteristics of the secondary sound generated from the speaker to be optimum according to the fluctuation.

Specifically, for example, while a detection signal of an air flow meter that indicates an intake pulsation is digitally processed to generate a drive signal for a speaker, a cancellation residual due to generation of a sound wave from the speaker is left. A characteristic in the digital signal processing (for example, a coefficient of a FIR filter) so that sound is detected by a microphone and a control error detected by the microphone is minimized.
May be adjusted.

When model reference adaptive control is used as the adaptive control and the acoustic transfer characteristics in the intake system are identified and the filter characteristics are matched, the intake noise (intake pulsation noise) is the nth order of the engine speed. Since the limited acoustic energy distribution is mainly composed of components (for example, third- and sixth-order components in a 6-cylinder engine) (see FIG. 5), the frequency range in which the above identification can be performed is limited corresponding to the acoustic energy distribution. Occurs. For this reason, in the adaptive control, there are cases where the filter characteristics cannot be adapted, or the adaptive control is adjusted in the direction to worsen the noise.

The present invention has been made in view of the above problems, and in active noise control in which a sound wave is separately generated to cancel intake noise, adaptive control based on the detection result of the cancellation residual sound is appropriately performed. Therefore, it is intended to stably obtain the effect of canceling intake noise.

[0007]

Therefore, an active noise control system for an automobile according to the invention of claim 1 is constructed as shown in FIG. In FIG. 1, the intake sound detecting means is inserted in the intake system of the engine and outputs a detection signal correlated with the intake sound.

The signal processing means processes the detection signal from the intake sound detecting means to generate a drive signal for generating a sound wave that cancels the intake sound. Then, the sound wave generating means generates a sound wave based on the drive signal generated by the signal processing means. Here, the cancellation residual sound detecting means detects the cancellation residual sound by the sound wave generating means, and the adaptive control means, the signal processing characteristic in the signal processing means based on the cancellation residual sound detected by the cancellation residual sound detecting means. Adjust.

On the other hand, the adaptive control prohibiting means prohibits the adjustment of the signal processing characteristic by the adaptive controlling means in a predetermined engine operating state. In the vehicle active noise control device according to the invention of claim 2, the predetermined engine operating state in which the adjustment of the signal processing characteristic is prohibited by the adaptive control prohibiting means is determined based on the engine load and the engine rotation speed. And

In the vehicle active noise control system according to the invention of claim 3, the intake noise detecting means is an intake air amount detecting means for detecting the intake air amount of the engine. In the vehicle active noise control device according to the invention of claim 4, both the sound wave generating means and the cancellation residual sound detecting means are provided in the intake system of the engine.

In the vehicle active noise control system according to the present invention, the signal processing means includes a finite length impulse response circuit, and the adaptive control means comprises coefficient multiplication in the finite length impulse response circuit. The configuration is such that the phase is adjusted by changing the coefficient of the instrument. In the automobile active noise control system according to the invention of claim 6, the adaptive control means adjusts the signal processing characteristic so as to match the reference model of the acoustic transfer characteristic in the intake system.

[0012]

According to the active noise control device for an automobile of the present invention, by processing the detection signal of the intake noise, a drive signal for generating a sound wave for canceling the intake noise is generated, and the drive signal is generated. The sound wave is generated based on Further, by detecting the residual sound remaining as a result of the cancellation of the intake noise by the sound wave, the adaptive control for adjusting the signal processing characteristic is performed so that the generation control of the sound wave is optimally performed.

However, depending on the operating conditions of the engine, it may be impossible to adapt the characteristics of the signal processing or the noise may be adjusted in a direction that deteriorates the noise. The adaptive control for adjusting the processing characteristic is prohibited, and it is avoided that the applied control is adjusted in the direction of worsening the noise. According to the vehicle active noise control device of the invention of claim 2, the adaptive control is prohibited at a predetermined engine load and engine speed, so that the change in the frequency component of the intake noise and the sound pressure level of the noise. The condition that makes it impossible to adapt the signal processing characteristic is determined by the change of.

According to the active noise control system for an automobile of the third aspect, the main intake noise is
The intake pulsation noise is reduced by using the detected value of the intake air amount that changes due to the intake pulsation as a detection signal that correlates with the intake sound. Claim 4
According to the vehicle active noise control device of the invention of claim 1, the sound wave for canceling the intake system noise is generated in the intake system that is the noise generation source, and the canceling noise is detected in the intake system. The cancellation and the residual sound after cancellation can be detected without being greatly affected by the disturbance.

According to the active noise control system for an automobile of the fifth aspect, the finite impulse response circuit (F
In the configuration in which the intake sound detection signal is processed by the IS filter), the coefficient of the coefficient multiplier of the finite impulse response circuit is changed to change the phase characteristic of the sound wave separately generated with respect to the intake sound detection signal. According to the vehicle active noise control device of the sixth aspect, the model reference adaptive control is used, and the signal processing characteristics such as phase control are adjusted by referring to the model of the acoustic transfer characteristics in the intake system.

[0016]

Embodiments of the present invention will be described below. Figure 2
1 shows a system configuration of an engine mounted on an automobile in an embodiment, in which air is sucked into an engine 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, an intake collector 5, and an intake manifold 6.

The throttle chamber 4 is provided with a throttle valve 7 interlocking with an accelerator pedal (not shown) to adjust the intake air amount of the engine 1. An electromagnetic fuel injection valve 8 is provided for each cylinder in a branch portion of the intake manifold 6, and fuel injected from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator is injected into the intake manifold 6. Supply.

The fuel injection valve 8 is intermittently driven to open according to an injection pulse signal sent from a control unit 9 having a built-in microcomputer, and according to the pulse width of the injection pulse signal calculated by the control unit 9. The fuel injection amount is controlled. Intake duct 3 upstream of the throttle chamber 4
Is provided with an air flow meter 10 for detecting the intake air amount Qa of the engine 1. Here, the air flow meter 10 detects the intake air flow rate Qa of the engine as a mass flow rate based on a change in the resistance value of the heat-sensitive resistance disposed in the intake duct, for example, and the intake air amount in the present embodiment. It corresponds to the detection means.

In this embodiment, the detection signal of the air flow meter 10 is used as a signal correlating with the intake pulsation noise for the purpose of silencing the intake pulsation noise. Is also equivalent. Further, a crank angle sensor 11 for extracting a rotation signal of the engine 1 from a crank shaft or a cam shaft is provided, and the engine rotation speed Ne is determined based on a detection signal output from the crank angle sensor 11 at every predetermined crank angle. It can be calculated.

Further, the throttle sensor 12 for detecting the opening TVO of the throttle valve 7 and the engine cooling water temperature T
A water temperature sensor 13 for detecting w is provided. The control unit 9 calculates the basic injection pulse width Tp based on the engine speed Ne calculated based on the intake air amount Qa detected by the air flow meter 10 and the detection signal from the crank angle sensor 11, and The final injection pulse width Ti is set by correcting the basic injection pulse width Tp according to the operating conditions such as the cooling water temperature Tw, and the injection pulse signal of the injection pulse width Ti is supplied to the fuel injection valve 8 at a predetermined injection timing. Output every time.

Here, the control unit 9 is
The air cleaner 2 functions also as a control unit of the active noise control system for a vehicle according to the present invention, and serves as a constituent element of the active noise control system for a vehicle.
A speaker 21 (sound wave generating means) for generating a sound wave in the intake system is provided in the section, and a microphone 22 (cancellation residual sound detecting means) for converting the sound in the intake system into an electric signal is provided upstream of the air cleaner 2. There is.

In the present embodiment, in order to reduce the intake system noise of the engine as the vehicle noise, especially the noise generated due to the intake pulsation, the intake air amount detection signal Qa from the air flow meter 10 is used to reduce the noise. By generating a drive signal for generating a sound wave for canceling the intake pulsation noise and outputting the drive signal to the speaker 21, a sound wave for canceling the intake pulsation noise is generated. Further, the result of the cancellation (cancellation residual sound) is detected by the microphone 22, and so-called adaptive control is performed to adjust the characteristics in the signal processing for generating the drive signal from the intake air amount detection signal Qa. There is.

The contents of the active noise control performed in the control unit 9 will be described in detail with reference to the control block diagram of FIG. The functions of the control block diagram of FIG. 3 correspond to the signal processing means and the adaptive control means. A predetermined frequency component is extracted from the detection signal Qa from the air flow meter 10 by passing through the band pass filter A. In this embodiment, 1k
Fixing Hz to the maximum frequency, the width of the extracted frequency ω _L
Is set as a function of the engine rotation speed Ne.

The detection signal Qa passed through the bandpass filter A is subjected to frequency and amplitude detection (B),
Gain adjustment (C) is performed to match the amplitude of the intake pulsation noise that is actually generated. Then, the gain-adjusted detection signal Qa is output to an adaptive FIR filter (finite length impulse response circuit) D in which the coefficient of the coefficient multiplier is adjusted, and the FIR filter D delays the phase by a predetermined value Lω. After being processed, it is output to the speaker 21 as a drive signal. That is, the drive signal for the speaker 21 is generated by the frequency filter A, the gain adjustment C, and the phase control D of the detection signal Qa.

The predetermined value Lω is set to a value that is in antiphase with respect to the noise phase at the time when the intake pulsation noise reaches the speaker 21, so that the sound wave generated from the speaker 21 becomes the intake pulsation noise. Will interfere with and cancel the noise. On the other hand, whether or not the phase adjustment is optimally performed is determined based on the cancellation residual sound (error sound) detected by the microphone 22, and the coefficient multiplication in the FIR filter D is performed based on the determination result. Optimal control for adjusting the coefficient of the container is performed.

Specifically, the speaker 21 and the microphone
The acoustic transfer function model C ′ between the speaker 22 and the microphone 22 is set in advance so that the acoustic transfer function C between the actual speaker 21 and the microphone 22 matches the model.
The coefficient (phase operation amount) is adjusted using an LMS (least mean square) algorithm E. The acoustic transfer function model C ′ is defined by the distance between the speaker 21 and the microphone 22, the inner diameter, and the sound reflection.

By the way, when the acoustic transfer function is identified and the characteristics of the FIR filter (the coefficient of the coefficient multiplier) are matched as described above, the main component of the intake noise is the engine speed n.
Since it is the next component, and the acoustic energy distribution is limited as shown in FIG. 5, the frequency range in which the identification can be performed is limited, which makes it impossible to apply the FIR filter, and on the contrary, it causes noise. It may also be adjusted in a direction that worsens.

Therefore, as shown in the flow chart of FIG. 4, operating conditions for which it is not appropriate to perform adaptive control of the FIR filter in advance are based on the basic injection pulse width Tp representing the engine load and the engine rotation speed Ne. The basic injection pulse width Tp and engine rotation speed Ne at the present time are read in advance (S1), and it is determined whether or not this read data corresponds to a region characterized as an operating condition in which adaptive control should be prohibited. (S2) If the operating condition is such that the adaptive control should be prohibited, the adaptive control for identifying the acoustic transfer function (acoustic transfer characteristic) is prohibited (S3: adaptive control prohibiting means).

Therefore, under operating conditions where it is difficult to properly apply the FIR filter, it is possible to avoid worsening the noise by the adaptive control, and it is possible to achieve stable silencing under all operating conditions. In particular, by adopting a configuration in which the adaptive control is prohibited under the conditions of the engine load and the rotation speed, it is possible to optimally adapt the signal processing characteristics by changing the frequency component of intake noise and the sound pressure level of noise. It is possible to reliably determine the condition that disappears.

In the above embodiment, the adaptive control in the phase control is shown, but it is obvious that the same effect can be obtained even if the adaptive control in the gain or frequency adjustment is performed. Further, although the FIR filter is used in the present embodiment, it is not limited to such a configuration, and a configuration using, for example, wavelet transform may be used.

[0031]

As described above, according to the vehicle active noise control apparatus of the invention of claim 1, the adaptive control of the system for generating the sound wave for canceling the intake noise tends to worsen the noise. There is an effect that it can be avoided in advance, and intake noise can be canceled in a stable manner.

According to the active noise control device for an automobile of the second aspect of the invention, since the adaptive control is prohibited at a predetermined engine load and engine rotation speed, the change in the frequency component of the intake noise and the noise noise. There is an effect that it is possible to reliably determine the condition in which the signal processing characteristic cannot be adapted, by the change in the pressure level.

According to the vehicle active noise control system of the third aspect of the present invention, the intake system noise generated with the intake pulsation is detected based on the detected value of the intake air amount, and the intake pulsation noise can be reduced. There is an effect. According to the vehicle active noise control device of the fourth aspect, the sound wave for canceling the intake system noise is generated in the intake system, which is the noise generation source, and the canceling noise is detected in the intake system. There is an effect that the noise cancellation and the cancellation residual sound can be accurately detected without being significantly affected by the disturbance.

According to the vehicle active noise control system of the fifth aspect of the present invention, the finite impulse response circuit (F
By changing the coefficient of the IS filter), there is an effect that the phase of the sound wave to be generated can be appropriately controlled and the intake noise can be effectively canceled. According to the vehicle active noise control device of the sixth aspect of the invention, by adjusting the signal processing characteristics such as phase control with reference to the model of the acoustic transfer characteristics in the intake system, various fluctuation factors in the acoustic transfer characteristics can be obtained. Even if there is, there is an effect that the signal processing characteristics can be appropriately adjusted according to this.

[Brief description of drawings]

FIG. 1 is a basic configuration block diagram of an apparatus according to the invention of claim 1.

FIG. 2 is a diagram showing a system configuration in an embodiment.

FIG. 3 is a control block diagram showing active noise control in the embodiment.

FIG. 4 is a flowchart showing a process of prohibiting adaptive control in the embodiment.

FIG. 5 is a diagram showing a frequency characteristic of intake noise.

[Explanation of symbols]

 1 Engine 2 Air Cleaner 3 Intake Duct 4 Throttle Chamber 5 Intake Collector 6 Intake Manifold 7 Throttle Valve 9 Control Unit 10 Air Flow Meter 11 Crank Angle Sensor 21 Speaker 22 Microphone

Claims (6)

[Claims] 1. An intake sound detecting means which is interposed in an intake system of an engine and outputs a detection signal correlated with the intake sound, and a sound wave which processes the detection signal from the intake sound detecting means to cancel the intake sound. A signal processing means for generating a drive signal for generating a sound wave, a sound wave generating means for generating a sound wave based on the drive signal generated by the signal processing means, and a cancellation residual for detecting a cancellation residual sound by the sound wave generating means. Sound detection means, adaptive control means for adjusting signal processing characteristics in the signal processing means based on the cancellation residual sound detected by the cancellation residual sound detection means, and signal processing by the adaptive control means in a predetermined engine operating state An active noise control device for an automobile, comprising: adaptive control prohibiting means for prohibiting characteristic adjustment. 2. The vehicle according to claim 1, wherein a predetermined engine operating state in which adjustment of signal processing characteristics is prohibited by the adaptive control prohibiting means is determined based on an engine load and an engine rotation speed. Noise control device for automobiles. 3. The active noise control system for an automobile according to claim 1, wherein the intake noise detecting means is an intake air amount detecting means for detecting an intake air amount of the engine. 4. The active noise control system for an automobile according to claim 1, wherein both the sound wave generating means and the cancellation residual sound detecting means are provided in an intake system of the engine. 5. The signal processing means includes a finite length impulse response circuit, and the adaptive control means performs phase adjustment by changing a coefficient of a coefficient multiplier in the finite length impulse response circuit. Claim 1 characterized by the above-mentioned.
The active noise control device for a vehicle according to any one of items 1 to 4. 6. The adaptive control means according to claim 1, wherein the adaptive control means adjusts the signal processing characteristic so as to match the reference model of the acoustic transfer characteristic in the intake system. Active noise control system for automobiles.