JPH094432A - Active noise control system for automobile - Google Patents

Abstract

(57) [Abstract] [Purpose] To suppress the progress of deterioration of the durability of the speaker by suppressing the operating rate of the speaker for generating sound waves that interfere with intake noise. [Structure] An intake noise is detected by a microphone, and a sound wave for canceling the intake noise is generated from a speaker provided in an air cleaner portion based on a detection signal of the microphone. Here, when the throttle valve opening TVO (S41) exceeds the reference opening (S42) (S42), it is estimated that the sound pressure of the intake noise also exceeds the predetermined value, and the driving of the speaker is executed ( S43), when the throttle valve opening TVO is equal to or smaller than the reference opening, it is determined that the sound pressure of the intake noise is sufficiently low and the need for silencing is low, and the driving of the speaker is stopped (S44).

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 quietness of an automobile. The active noise control means that a noise (primary sound) in an automobile is converted into another sound wave (secondary sound) having the same amplitude and opposite phase to the noise (primary sound) 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. Sound) to cancel the primary sound.

In order to reduce the intake system noise generated by the intake pulsation of the engine by the active noise control, a speaker is installed in the intake system which is the noise source and the intake system noise (pulsation is Noise) is detected by a microphone or the like, and a sound wave that cancels the detected noise is generated from the speaker, whereby intake noise can be positively reduced.

[0004]

By the way, in order to effectively cancel the intake noise, it is necessary to accurately generate a sound wave interfering with the intake noise from the speaker. If the characteristics of the sound wave actually generated change, the sufficient silencing effect cannot be obtained, and in some cases, the sound level generated by the speaker may worsen the noise level.

Degradation of the speaker occurs due to demagnetization due to heat generation during driving, strength change due to fatigue, and the like. In order to avoid the occurrence of deterioration of the durability of the speaker as described above, it is necessary to use an expensive speaker having excellent durability, which increases the cost of the system. On the other hand, when the grade of the speaker is lowered to suppress the cost increase, there is a problem that it is difficult to stably obtain a sufficient silencing effect for a long period of time.

The present invention has been made in view of the above problems, and it is possible to suppress the progress of deterioration of a speaker and to obtain a sufficient silencing effect for a long time by a relatively inexpensive speaker. To aim.

[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 corresponding to the intake sound. The sound wave generating means generates a sound wave in the intake system of the engine, and the intake noise canceling means generates the sound wave for canceling the intake sound based on the detection signal from the intake sound detecting means. The drive signal is output to.

Here, the noise canceling stopping means controls the drive control of the sound wave generating means by the intake noise canceling means.
The operation is selectively stopped based on at least one of the detection signal from the intake sound detecting means and the engine operating condition. In the vehicle active noise control device according to the invention of claim 2, the noise canceling stop means sets the sound pressure of the intake sound to a predetermined value or less based on at least one of the detection signal from the intake sound detecting means and the engine operating condition. When it is determined that, the drive control of the sound wave generating means by the intake noise canceling means is stopped.

In the vehicle active noise control system according to the invention of claim 3, the sound pressure of the intake sound is based on at least one of the throttle valve opening of the engine, the rotational speed, and the amplitude of the intake air amount. It is configured to determine. In the vehicle active noise control device according to the invention of claim 4, the noise canceling stop means causes the frequency of the intake sound to fall outside a predetermined range based on at least one of a detection signal from the intake sound detecting means and an engine operating condition. When it is determined that, the drive control of the sound wave generating means by the intake noise canceling means is stopped.

In the automobile active noise control system according to the invention of claim 5, the frequency of the intake noise is determined on the basis of the rotational speed of the engine.

[0011]

According to the active noise control system for an automobile according to the invention of claim 1, based on the detection result of the intake noise,
A sound wave for canceling the intake noise is separately generated in the intake system to cancel the intake noise. Here, instead of always canceling the intake noise due to the generation of the secondary sound, by selectively stopping based on at least one of the detection result of the intake sound and the operating condition of the engine,
The time (operating rate) for driving the sound wave generating means is reduced as much as possible, thereby suppressing the progress of deterioration of durability of the sound wave generating means.

According to the active noise control system for an automobile of the second aspect of the present invention, when the sound pressure of the intake sound is below a predetermined level, the secondary sound generation is stopped, and the sound pressure of the intake noise is high. , The secondary sound is generated only when it needs to be attenuated. According to the active noise control system for an automobile of the third aspect of the present invention, the sound pressure of intake noise is generally expected to increase when the engine is under high load and high rotation. The sound pressure level is determined based on at least one of the amplitudes of the intake air amounts.

According to the active noise control device for an automobile of the fourth aspect of the invention, the intake noise is canceled by the generation of the secondary sound when the intake sound is in a frequency range that is offensive to the ears, and in other cases, the secondary noise is suppressed. The generation is stopped to suppress the operating rate of the sound wave generating means. According to the vehicle active noise control device of the fifth aspect of the present invention, since the frequency of the intake sound generally corresponds to the engine rotation speed, the frequency of the intake sound is determined based on the engine rotation speed. , Generates secondary sound only in a specific frequency range.

[0014]

Embodiments of the present invention will be described below. FIG.
1 illustrates a system configuration of 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 which works in conjunction 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, for example, a change in the resistance value of the heat-sensitive resistance arranged in the intake duct.

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 is performed based on a detection signal output from the crank angle sensor 11 at every predetermined crank angle. Speed Ne
Can be calculated. Further, a throttle sensor 12 for detecting the opening TVO of the throttle valve 7, a water temperature sensor 13 for detecting the engine cooling water temperature Tw, etc. are provided.

The control unit 9 calculates the basic injection pulse width Tp based on the intake air amount Qa detected by the air flow meter 10 and the engine speed Ne calculated based on the detection signal from the crank angle sensor 11. At the same time, the basic injection pulse width Tp is set to the cooling water temperature Tw.
The final injection pulse width T is corrected according to operating conditions such as
i is set, and an injection pulse signal having the injection pulse width Ti is output to the fuel injection valve 8 at every predetermined injection timing.

Here, the control unit 9 is
The air cleaner 2 functions also as a control unit of the active noise control device for a vehicle according to the present invention, and serves as a constituent element of the active noise control device 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 the sound in the intake system (intake system noise) is electrically supplied to the intake duct 3 between the throttle chamber 4 and the air flow meter 10. Microphone to convert to signal
22 (intake sound detection means) is provided. Further, on the upstream side of the air cleaner 2, there is provided a microphone 23 for detecting noise (residual residual sound) emitted as a result of noise cancellation by the speaker 21.

In order to reduce the intake system noise of the engine as automobile noise, the intake system noise (mainly intake pulsation noise) is detected based on the detection signal from the microphone 22, and the intake system noise (primary sound) is detected. ) And a sound wave (secondary sound) that cancels out the noise is provided in the intake system.
A drive signal is output to the speaker 21 so that the speaker 21 can generate it separately.

The flow chart of FIG. 3 shows a state of the noise reduction control. However, the drive control of the speaker 21 is not limited to the control shown in the flowchart of FIG. In this embodiment, the function as the intake noise canceling means is provided by the control unit 9 as software, as shown in the flow chart of FIG.

Step 21 (indicated as S21 in the figure).
In the following), it is determined whether or not it is within a predetermined sampling window for sampling the electric signal from the microphone 22, and if it is within the sampling window,
Proceed to step 22 and, as shown in FIG.
A value obtained by A / D converting the electric signal from 22 MRn (n = 1,
2, 3, ...) are sequentially stored. On the other hand, if it is not within the sampling window, that is, if it exceeds the sampling window, the routine proceeds to step 28, where all the values MRn read in the previous sampling window are cleared and new data is stored in the next sampling window. To do so.

When the electric signal from the microphone 22 is sequentially A / D converted and stored in the sampling window, in step 23, a predetermined value is obtained by Fourier transform or the like using the n data collected in the sampling window. A frequency component (for example, 80 to 150 Hz) is extracted (power spectrum PS1). In the next step 24, phase control for giving phase rotation of a predetermined angle θ1 for canceling the intake sound is performed on the extracted frequency component.

In step 25, a frequency component (for example, 150 to 300 Hz) in a frequency range different from the frequency component analyzed in step 23 is extracted (power spectrum PS
2) In the next step 26, a phase rotation of a predetermined angle θ2 is applied to the frequency component extracted in step 25. Then, in step 27, the frequency components subjected to the phase control are combined and then D / A-converted to produce the speaker 21.
Drive.

Here, in the case where the microphone 23 for detecting the cancellation residual sound is provided as in the present embodiment, the speaker 21 is provided so as to obtain the best muffling effect based on the detection result of the microphone 23. The output drive signal may be corrected. For example, if the phase of the sound wave generated from the speaker 21 and the phase of the actual intake noise are not exactly opposite in phase, the muffling effect will decrease, so the microphone 23
If the phase of the drive signal output to the speaker 21 is corrected so that the cancellation residual sound detected in step 1 is minimized, the influence of temporal changes and variations can be eliminated, and intake noise can be effectively reduced.

In the present embodiment, as described above, the speaker 21 is driven to reduce intake noise, but if the speaker 21 is deteriorated in durability, the silencing effect can be stably obtained for a long period of time. I can not do it. Therefore, in this embodiment, in order to prevent the deterioration of the durability of the speaker 21, the noise reduction control by driving the speaker 21 is limitedly executed to suppress the operation rate of the speaker 21 (noise cancellation). Stop means).

That is, as shown in the flow chart of FIG. 5, first, various parameters for determining whether or not the conditions for performing the noise reduction control are read (step 31), and then the read parameters are set. Based on the result, it is determined whether or not the condition for performing the noise reduction control is satisfied (step 32). Then, when the condition for performing the noise reduction control is satisfied, the drive signal is output to the speaker 21 as shown in the flowchart of FIG. 3 (step 33), but the condition for the noise reduction control is satisfied. If not, the drive signal output to the speaker 21 is stopped (step 34).

In this way, by limiting the output of the drive signal to the speaker 21 and lowering the operating rate of the speaker 21, it is possible to suppress the progress of deterioration of the durability of the speaker 21, and thus the speaker 21 Noise reduction control using can be effectively performed for a long period of time. Therefore, even if the speaker 21 which does not have high durability and is relatively inexpensive is used, it is possible to obtain a good silencing effect for a long period of time.

Here, it is preferable that the condition for performing the noise reduction control is that the sound pressure of the intake sound exceeds a predetermined value. When the sound pressure of the intake sound is sufficiently low, the request for noise reduction is low, and the effect of the cancellation due to the generation of the secondary sound is small, so that the harmful effect of stopping the driving of the speaker 21 is small. Therefore, if the drive of the speaker 21 is stopped and the unnecessary drive is avoided when the sound pressure of the intake air is below a predetermined level, the speaker 21 can be secured while ensuring the necessary effect of reducing the intake noise.
It is possible to reduce the operating rate of.

The sound pressure of the intake sound can be directly detected based on the detection signal of the microphone 22 and can be estimated from the operating condition of the engine. The sound pressure of the intake sound is
Since it is predicted that the engine load will increase substantially corresponding to the increase in the engine load, as shown in the flowchart of FIG. 6, based on the throttle valve opening TVO representing the engine load,
It may be configured to selectively determine whether or not to drive the speaker 21.

In the flowchart of FIG. 6, first,
The throttle valve opening TVO is read (step 41), and then it is determined whether or not this throttle valve opening TVO is less than or equal to a reference opening corresponding to a predetermined sound pressure (step 42).
If the throttle valve opening TVO exceeds the reference opening,
Since the sound pressure of the intake sound is estimated to exceed a predetermined value,
The intake sound is canceled by the drive control of the speaker 21 based on the detection result of the microphone 22 (step 4
3).

On the other hand, when the throttle valve opening TVO is less than the predetermined opening, the sound pressure of the intake sound is also estimated to be less than the predetermined opening. Therefore, the drive control of the speaker 21 based on the detection result of the microphone 22 is performed. To stop the speaker 21
Is unnecessary driven (step 44). In addition, the main intake noise is generated with the intake pulsation,
It is estimated that the larger the intake pulsation width is, the louder the intake sound is. Therefore, as shown in the flow chart of FIG. 7, the speaker 21 is based on the amplitude (pulsation width) of the intake air amount Qa detected by the air flow meter 10. It may be configured to selectively determine whether or not to drive.

In the flowchart of FIG. 7, first,
The intake air amount Qa is read (step 51), and then the amplitude ΔQa of the intake air amount Qa is calculated (step 52).
Then, it is determined whether or not the amplitude ΔQa is less than or equal to a reference value corresponding to a predetermined sound pressure (step 53). When the amplitude ΔQa exceeds the reference value, it is estimated that the sound pressure of the intake sound also exceeds the predetermined value. Therefore, the intake sound is canceled by the drive control of the speaker 21 based on the detection result of the microphone 22 ( Step 54).

On the other hand, when the amplitude ΔQa is less than the predetermined value, it is estimated that the sound pressure of the intake sound is also less than the predetermined value, so the drive control of the speaker 21 based on the detection result of the microphone 22 is stopped. Thus, the speaker 21 is prevented from being driven unnecessarily (step 55). Here, the condition for performing the noise reduction control may be that the frequency of the intake sound is within a predetermined range. That is, when the intake sound in the frequency range to be reduced is generated, the speaker
21 is driven to generate a secondary sound to cancel the intake sound. However, when the intake sound of a frequency with a relatively low need for reduction is generated, the speaker 21 is stopped and the speaker 21 is stopped. To reduce the utilization rate of.

The frequency of the intake sound may be directly detected from the detection signal of the microphone 22, but the frequency of the intake pulsation, which is the main factor of the intake sound, is determined by the engine speed Ne.
Therefore, the frequency of the intake sound can be estimated from the engine rotation speed Ne and the driving of the speaker 21 can be selectively stopped. The flowchart of FIG. 8 shows an embodiment in which the frequency determination of the intake sound based on the engine rotation speed Ne and the sound pressure determination of the intake sound based on the throttle valve opening TVO are combined.

That is, in the embodiment shown in the flowchart of FIG. 8, the region where the intake sound in the frequency range to be reduced in advance exceeds a predetermined sound pressure is set as the intake sound canceling region by the drive of the speaker 21, and the engine rotation speed is set. Ne and throttle valve opening TVO are specified as parameters. Then, the actual throttle valve opening TV detected by each sensor
O and engine speed Ne are read (step 6
1) Then, it is determined whether or not the current operating condition corresponds to the cancellation region (step 62).

Here, if the current operating condition falls within the cancellation region, the speaker 21 is driven to cancel the intake noise (step 63), but if it does not fall within the cancellation region, the speaker is canceled. 21 drive is stopped to reduce the operation rate of the speaker 21 (step 64).
The progress of deterioration of durability of the speaker 21 is suppressed. In this embodiment, the microphone 22 is used as the intake sound detecting means, but since the intake air pulsation, which is the main cause of the intake system noise, is detected by the air flow meter 10, the intake sound detecting means is used. It may be configured to be used as.

[0038]

As described above, according to the active noise control system for an automobile of the invention of claim 1, the intake noise is not always canceled by the generation of the secondary sound, but the detection result of the intake noise is obtained. And by selectively stopping it based on at least one of the operating conditions of the engine, the time (operating rate) for driving the sound wave generating means is reduced as much as possible,
Thus, there is an effect that the progress of deterioration of durability of the sound wave generating means can be suppressed.

According to the active noise control system for an automobile of the second aspect, the sound pressure of the intake noise is high, and the secondary sound is generated only when it is necessary to attenuate it, and the sound wave generating means is generated. There is an effect that the operating rate of can be reduced. According to the vehicle active noise control device of the third aspect, the sound pressure level is indirectly determined based on at least one of the throttle valve opening of the engine, the rotation speed, and the amplitude of the intake air amount. There is an effect that can be.

According to the active noise control system for an automobile of the fourth aspect of the present invention, the secondary sound can be selectively generated only in the frequency range where silencing is required.
There is an effect that the operating rate of the sound wave generating means can be reduced. According to the vehicle active noise control system of the fifth aspect of the present invention, the frequency of the intake sound is indirectly determined based on the engine speed, and the secondary sound is limited only in the frequency range where the noise reduction is required. Can be generated, and thus, the operation rate of the sound wave generating means can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic configuration of an active noise control system for a vehicle according to the present invention.

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

FIG. 3 is a flowchart showing active noise control according to the embodiment.

FIG. 4 is a diagram showing how sampling of microphone output is performed in the embodiment.

FIG. 5 is a flowchart showing a basic configuration of speaker selective drive control in the embodiment.

FIG. 6 is a flowchart showing an example of selective drive control of a speaker based on a throttle valve opening.

FIG. 7 is a flowchart showing an example of selective drive control of the speaker based on the amplitude of the intake air amount.

FIG. 8 is a flowchart showing an example of selective drive control of a speaker based on a throttle valve opening and an engine rotation speed.

[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 12 Throttle Sensor 21 Speaker 22, 23 Microphone

Claims (5)

[Claims] 1. An intake sound detecting means which is interposed in an intake system of an engine and outputs a detection signal corresponding to intake sound; a sound wave generating means which generates a sound wave in the intake system of the engine; and the intake sound detecting means. The intake noise canceling means for driving the sound wave generating means to generate a sound wave for canceling the intake sound based on the detection signal from the intake noise canceling means, and the drive control of the sound wave generating means by the intake noise canceling means are controlled by the intake sound detecting means. An active noise control device for an automobile, comprising: a noise canceling stop means for selectively stopping the stop signal based on at least one of the detection signal of the engine and the engine operating condition. 2. The noise canceling stop means, when it is determined that the sound pressure of the intake sound is below a predetermined level based on at least one of a detection signal from the intake sound detecting means and an engine operating condition, The active noise control system for an automobile according to claim 1, wherein the drive control of the sound wave generating means by the intake noise canceling means is stopped. 3. The sound pressure of the intake sound is determined based on at least one of the throttle valve opening of the engine, the rotation speed, and the amplitude of the intake air amount.
An active noise control device for a vehicle as described above. 4. The noise canceling stop means, when it is determined that the frequency of the intake sound is out of a predetermined range based on at least one of a detection signal from the intake sound detecting means and an engine operating condition, The active noise control system for an automobile according to claim 1, wherein the drive control of the sound wave generating means by the intake noise canceling means is stopped. 5. The active noise control system for a vehicle according to claim 4, wherein the frequency of the intake noise is determined based on the engine speed.