JPH0719156B2 - Vehicle interior noise reduction device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle interior noise reduction device, and particularly to actively reduce low frequency noise in a vehicle interior closed space of a vehicle or the like having a periodic sound source. It relates to the device.

[Conventional technology]

The noise in the interior of a vehicle such as an automobile is caused by the resonance phenomenon of the interior of the closed space under certain conditions.
It is considered that the exciting force is due to the rotational order component due to the explosion of the engine.

The means originally adopted as a measure for reducing such noise is passive (passive). For example, the coupling rigidity is improved with respect to the engine system, which is a vibration source, and the transmission system is improved. Tuned each mount to increase the rigidity of the panel for the sounding body in the passenger compartment, and as a measure against resonance, mass dampers and dynamic dampers were applied to the resonance part.

Such a passive means causes an increase in cost and an increase in weight, and its effect is insufficient.

On the other hand, in the case of a four-cylinder engine, such a vehicle interior noise is a twice explosive component of one revolution of the crankshaft, and it is considered that the engine rotational order component, which is a so-called engine rotational secondary component, is the main factor. Japanese Patent Application Laid-Open No. 59-9699 and Japanese Utility Model Laid-Open No. 62-127051 have already been proposed as conventional techniques for actively reducing the muffled sound caused by such factors.

In these conventional techniques, an ignition pulse is detected as a secondary engine rotation component, the pulse signal is variously processed, and each frequency component (rotational order component) of the noise observed at the receiving point of the driver in the vehicle interior has a reverse phase. In addition, the noise level at the receiving point is offset and reduced by the interference effect by additionally adding the sound whose magnitude is the same as the noise component from the speaker.

[Problems to be Solved by the Invention]

However, the above-mentioned conventional example is a device for reducing only the muffled noise caused by the engine rotation secondary component in the vehicle interior noise.
Next, even if there is a noise component due to the rotation order component (explosion order component) other than the components, it cannot be removed, and the noise reduction is not optimal.

In addition, the engine system, the mount system, the electric system, etc. of the vehicle change over time, the temperature characteristics of the electric signal system, the occupants, the temperature in the passenger compartment, etc. There was a problem that it could not be dealt with or the responsiveness of control could not be obtained.

Therefore, the present invention can also realize a simple device that can remove not only the muffled noise caused by the secondary engine rotation component in the vehicle interior but also the other noise components and can immediately respond to various changes in vehicle conditions. To aim.

[Means for Solving the Problems]

In order to solve the above problems, in a vehicle interior noise reduction device according to the present invention, an engine vibration detection means and an inverse transfer function of a transfer function from a detection signal of the detection means to an ear of a vibration system of a vehicle body are identified. An adaptive controller, a speaker that outputs an output signal of the controller into the vehicle compartment, a microphone that detects noise in the entire vehicle compartment, and a unit that detects a change in the vehicle compartment state. The speaker is controlled so as to be minimized, and the adaptive step size is set to zero for a certain period of time or the output of the speaker is set to zero for a certain period of time when the state of the vehicle compartment changes.

[Action]

In the vehicle interior noise reduction device according to the present invention, as shown in the equivalent block diagram of FIG. 1, G is a total transfer function of the vehicle interior vibration system excited by engine vibration,
Based on the vibration of the engine, it consists of the transfer function by the engine mount (MTG), the transfer function by the torque rod, the transfer function by the cab mount, etc. This transfer function G causes the engine vibration to reach the ear by the vehicle interior space transfer path. It is observed in the form converted into vehicle interior noise Y (n).

In this case, the engine vibration itself is due to the secondary component of the engine rotation, but the vehicle interior noise Y observed at the ears is
(N) includes components other than the engine rotation secondary component due to the transfer function G.

This transfer function G is an unknown value, and the controller 5 identifies the inverse transfer function G ⁻¹ of this transfer function. The controller 5 detects the engine vibration signal X (n) detected by the engine vibration detection means and the microphone. Output signal e (n) is always input, and the speaker coefficient y (n) is generated by adaptively controlling the filter coefficient sequence H by the well-known LMS (Least Mean Square) method or the like based on these signals. Then, the vehicle interior noise Y (n) is canceled.

In this way, the elimination sound is generated by calculating until the vibration of the engine becomes a sound, but when the state of the vehicle interior changes and the transfer function of the vehicle interior changes, the muffling effect due to speaker output decreases. Or, in some cases, the control does not converge and diverges and the erased sound becomes noise.

Therefore, in the present invention, the means 8 for detecting the state change in the vehicle interior is provided, and when the state change in the vehicle interior is detected by this means, the adaptive step size μ of the controller 5 is set to zero for a certain period of time and the coefficient sequence is set. Do not update H, reduce engine noise by open control,
It is possible to accelerate the silencing effect of the system in a state where the coefficient sequence H is less disturbed when the state inside the vehicle is restored.

Further, in the present invention, when the state of the vehicle interior changes,
By prohibiting the output sound from the speaker, at least the noise inside the vehicle is prevented from becoming worse.

In this way, when the state of the vehicle interior changes and the transfer function G thereof changes, stopping the speaker output or stopping the update of the adaptive step size will cause the residual noise in the vehicle interior to disappear. It is possible to prevent it from becoming large and the adaptive control system from going mad, and to speed up the convergence speed in the subsequent normal control.

〔Example〕

FIG. 2 shows an embodiment of the vehicle interior noise reduction device according to the present invention, in which 1 is a vehicle interior, 2 is an engine of the automobile 1, and 3 is an engine vibration of the engine 2 is directly detected. An engine vibration sensor (which may be a knock sensor), 4 is a microphone for detecting the noise level in the vehicle compartment, and 5 is an inverse transfer function of the transfer function of the vibration system of the vehicle body excited by the vibration of the engine by the outputs of the sensors 3 and 4. A controller for identification, 6 is a speaker that produces a noise that reduces noise, 7 is an amplifier that amplifies a signal from the controller 5 to drive the speaker 6, and 8 is an opening and closing of a vehicle door (not shown) It is a door switch.

FIG. 3 shows an embodiment of the controller shown in FIG. 2. This embodiment is composed of an adaptive digital filter, and is known as an adaptive algorithm such as a steepest descent method, a learning identification method, The LMS method and the like can be mentioned, but the LMS method is used here. Reference numeral 51 is an output control unit 51 for controlling the speaker output y (n) by the LMS unit 50.

Further, n number of Z ⁻¹ indicates a delay element for delaying the engine vibration X (n) for each sample, and n number of h (0)
~ H (n-1) is a filter (tap) coefficient for multiplying each delay element Z ^-1 and each filter coefficient is LMS
Updated sample by sample according to the algorithm: h (n + 1) = h (n) + 2μe (n) X (n). However, n = 0 ... i, μ
Is the step size described above.

By selecting the step size μ in this case, a convolution operation of multiplying and adding the engine vibration Y (n) of each sample by the filter coefficient is performed, and the output signal y (n ) Is required.

The speaker output y (n) is subtracted from the sound pressure Y (n) actually observed at the driver's ears, so that the output e (n) from the microphone 4 e (n) = Y (n) -y (n).
When the filter coefficient is updated again for each sample by the LMS algorithm, the inverse transfer function G ^-1 of the transfer function G of the space transfer system in the vehicle interior can be identified in real time, and the microphone output e (n) can be converged to the minimum value.

Now, in the embodiment of FIG. 2, when the driver opens the door during idling or when a passenger in the passenger seat gets in or out, the door switch 8 is turned on (or off) in response to this.

In such a case, the filter (tap) coefficient sequence h
Since (0) to h (n-1) are disturbed and the control does not go toward convergence, the update of the coefficient sequence is prohibited.
The step size μ is set to 0 and open control is performed without feedback.

In this case, as a method of returning the step size μ to the normal value, it is immediately returned from the time when the vehicle body vibration <threshold value (t4 in FIG. 4), or the time when the vehicle body vibration <threshold value (t4 in FIG. 4). ) To a normal value after a certain time, vehicle body vibration <threshold value (t4 in Fig. 4) μ
Is returned by a function of time (for example, a linear function of time).

When the door switch 8 operates as described above, the LMS unit 50 controls the output control unit 51 to output the speaker output y.
(N) may not be generated.

In this way, the engine noise will remain the same and at least not worsen.

In this case, as shown in FIG. 4, the period during which the speaker output is stopped starts from the zero cross point t2 next to the time t1 when the vehicle vibration> threshold value, and starts from the zero cross point t2 next to the vehicle vibration <threshold value t3. It is preferable that the output control unit 51 controls by the time when the cross point t4 is reached. This is to prevent the impact sound from being generated from the speaker 6 due to its input / output, but if it is set at least from the time point t1 for a certain period of time, it is possible to prevent the jitter when the vehicle body vibration frequently goes up and down the threshold value. The purpose of the period can also be achieved.

It should be noted that the engine vibration signal X (n) is not always a steady signal in which the average value or the root mean square value does not change with time, but if the appropriate sampling number and tap number are used, control can be performed even in a transient state. Can be converged.

In the above-mentioned embodiment, the effect is most effective when the speaker is installed at the door, but the effect can be obtained even in the normal vehicle interior position.

Further, although the door switch is used as a means for detecting the change in the vehicle interior state, it goes without saying that the change in the vehicle interior state can be similarly detected by using a window opening / closing sensor or the like.

〔The invention's effect〕

As described above, in the vehicle interior noise reduction device according to the present invention, when the adaptive controller controls the speaker so that the input of the microphone is minimized by using the engine vibration detection means, it is adapted when the state of the vehicle interior changes. Since the step size is configured to be zero for a certain period of time, the effect within that period is reduced, but the engine control noise sequence is eliminated by the open control so that the adaptive control coefficient sequence is returned when returning to the normal step size control. Is less disturbed, and therefore the muffling effect is restored more quickly thereafter.

Further, when the state of the vehicle interior changes, the output of the speaker may be set to zero instead of setting the adaptive step size to zero. In this case, it is necessary to stop the speaker output sound and at least prevent the noise from increasing. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing in principle a vehicle interior noise reduction device according to the present invention, and FIG. 2 is a schematic configuration diagram showing an embodiment of a vehicle interior noise reduction device according to the present invention. FIG. 3 is a diagram showing an embodiment of a controller used in the present invention, and FIG. 4 is a waveform diagram showing the control state of the output sound of the speaker according to the present invention. In the figure, 1 is a passenger compartment, 2 is an engine, 3 is an engine vibration sensor, 4 is a microphone, 5 is a controller, 6 is a speaker, and 8 is a door switch. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. An engine vibration detecting means, an adaptive controller for identifying an inverse transfer function of a transfer function from a detection signal of the engine detecting means to an ear of a vibration system of a vehicle body, and an output signal of the controller in a vehicle compartment. A speaker for outputting, a microphone for detecting noise in the entire vehicle interior, and a means for detecting a change in the vehicle interior state are provided, and the controller controls the speaker so that the input of the microphone is minimized and the state of the vehicle interior. A vehicle interior noise reduction device characterized by setting the adaptive step size to zero for a certain period of time when there is a change. 2. When the state of the passenger compartment changes, instead of setting the adaptive step size to zero, the output of the speaker is changed for a certain period of time.
The vehicle interior noise reduction device according to claim 1, wherein the device is set to zero.