JPH0719155B2 - 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 an inverse phase of each frequency component (rotational order component) of noise observed at a listening point of a driver in a vehicle compartment is detected. In addition, the noise level at the listening point is offset / reduced by the interference effect by additionally adding a 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.
Even if there is a noise component due to a rotation order component (explosion order component) other than the next component, 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 realize a simple device that can remove not only the muffled noise caused by the secondary component of engine rotation in the vehicle interior but also 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 vehicle body vibrations from the road surface, and the controller inputs the microphone. The speaker is controlled so as to be minimized, and when the vehicle body vibration exceeds a threshold value, the output to the speaker is stopped for a certain period of time.

Further, in the present invention, the engine speed detecting means, an adaptive controller for identifying the inverse transfer function of the transfer function from the detection signal of the detecting means to the ear of the vibration system of the vehicle body, and the output signal of the controller is the vehicle output signal. A speaker that outputs indoors,
A microphone for detecting noise in the entire cabin and a means for detecting vehicle body vibration from the road surface are provided, and the controller controls the speaker so that the input of the microphone is minimized, and when the vehicle body vibration exceeds a threshold value. The above problem can also be solved by setting the adaptive step size to zero for a certain period of time.

[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. This 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 based on these signals, the filter coefficient sequence H is adaptively controlled by the well-known LMS (Least Mean Square) method or the like to generate the speaker output y (n). Then, the vehicle interior noise Y (n) is canceled.

In this way, an erasing sound is generated by calculating the vibration of the engine until it becomes a sound.However, the vibration of the engine itself as well as the vibration from the road surface to the vehicle body can be mixed into the engine vibration detection means. The vibration of a route different from that described above is added, and the sound and noise output from the speaker are out of phase with each other, so that not only the noise cannot be silenced, but also the in-phase component is added, which may worsen the noise.

When the noise deteriorates, the indoor noise including the noise caused by the vibration from the road surface is used as an input for updating the adaptive coefficient sequence of the controller, so that the coefficient sequence is disturbed and the noise from the engine cannot be erased.

Therefore, in the present invention, the vehicle body vibration from the road surface is separately measured.
When the detected vehicle vibration is large enough to exceed the threshold value, the output noise from the speaker is prohibited for a certain period of time to prevent the deterioration of vehicle interior noise.

Further, the engine vibration X (n) shown in FIG. 1 detects the engine speed instead of the means for detecting the engine vibration itself, and identifies the inverse transfer function of the transfer function up to the ear of the vibration system of the vehicle body. It is possible to eliminate the indoor noise (however, the response is slightly inferior to the case of directly detecting the engine vibration), but in this case, only the microphone picks up the vehicle vibration from the road surface as sound. Since it is not mixed in the engine speed detecting means, μ = 0 is set even when the vibration from the road surface is large so that the adaptive controller does not update the step size μ with the microphone error signal including the noise from the road surface. It is enough to do it.

Therefore, when the vehicle body vibration from the road surface is larger than the threshold value as in the present invention, the speaker output is stopped or the update of the adaptive step size is stopped depending on whether the engine vibration is directly detected or indirectly detected. , It is possible to prevent the residual noise in the passenger compartment from becoming large due to vibration noise from other than the assumed route, and to prevent the adaptive control system from going mad, and to accelerate the convergence speed in the subsequent normal control. Become.

〔Example〕

FIG. 2 shows an embodiment of a vehicle interior noise reduction device according to the present invention. 1 is a vehicle interior, 2 is an engine of an automobile 1, 3 is an engine for directly detecting engine vibration of an engine 2. A vibration sensor (or a knock sensor) or an engine speed sensor that detects the engine speed from the engine speed, 4 is a microphone that detects the noise level in the passenger compartment, and 5 is the vibration of the engine due to the outputs of sensors 3 and 4. A controller for identifying the inverse transfer function of the transfer function of the vibration system of the vehicle body excited by the above, 6 is a speaker for producing a sound that reduces noise, 7 is an amplifier for amplifying the signal from the controller 5 and driving the speaker 6, 8 is a wheel (tire),
Reference numeral 9 denotes a suspension such as a coil spring and a leaf spring for the wheel 8, and 10 a vibration sensor for detecting a vehicle body vibration with respect to a road surface above the suspension 9.

FIG. 3 shows an embodiment of the controller shown in FIG. 2, which is composed of an adaptive digital filter, and is known as an adaptive algorithm, such as the steepest descent method, the learning identification method, or the like. , LMS method, etc., 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.

In this case, by selecting the step size μ, the convolution operation of multiplying and adding the engine vibration X (n) of each sample by the filter coefficient is performed to output the output signal y (n to the speaker 6 via the amplifier 7. ) 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 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, when the engine vibration sensor 3 is used as means for detecting engine vibration in the embodiment of FIG. 2, when the vehicle gets over a seam or a step position on the road surface, the vibration sensor
Although the output of 10 is a large value, when the vibration output is a large value that exceeds the threshold value, the output sound from the speaker 6 and the vehicle interior noise are out of phase with each other as described above, and the sound cannot be silenced or the same phase. Since the components may be added to deteriorate the noise, the LMS unit 50 controls the output control unit 51 so as not to generate the speaker output y (n) when the vehicle body vibration> the threshold value.

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 can also be achieved.

On the other hand, when the engine speed sensor 3 is used instead of the engine vibration sensor in the embodiment of FIG. 2, the engine speed is converted into the engine frequency to perform the above-mentioned control. Since there is no direct means for detecting the amplitude of engine vibration, this amplitude is estimated by the input of the microphone 4 to perform control (thus, the control itself has a convergence speed faster than that when an engine vibration sensor is used). Will be slow).

Therefore, the vehicle body vibration from the road surface does not enter the sensor 3, but the vibration sound due to the vehicle body vibration is still input to the microphone 4, and the error signal becomes the microphone output e (n) due to this, and the filter ( Tap) Coefficient sequence h (0)
Since ~ h (n-1) is disturbed and the control does not converge, the step size μ is set to 0 and open control without feedback is performed in order to prohibit the update of the coefficient sequence.

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).

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.

〔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, the vehicle body vibration from the road surface becomes a threshold value. When it exceeds the limit, the speaker output for silence is stopped for a certain period of time, so when the vibration input from the road surface is large and the vibration detection means attached to the engine cannot accurately measure the vibration caused by the engine, When the sound cannot be silenced because the phase and sound pressure are deviated, it is possible to prevent the speaker output sound from being stopped and at least to increase the noise.

Further, when the adaptive controller controls the speaker using the engine speed detecting means so as to minimize the input of the microphone, when the vibration of the vehicle body from the road surface exceeds the threshold value, the adaptive step size is set to zero for a certain period of time. Since it is configured so that the effect is reduced while there is vibration noise from the road surface, the engine noise is eliminated by the open control to reduce the disturbance of the adaptive control coefficient sequence when returning to the normal step size control. Therefore, the subsequent restoration of the muffling effect becomes faster.

[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 or engine speed sensor, 4 is a microphone, 5 is a controller, 6 is a speaker, and 10 is a vibration sensor. 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 cabin, and a means for detecting vehicle body vibration from the road surface are provided, and the controller controls the speaker so that the input of the microphone is minimized and the vehicle body vibration is reduced. A vehicle interior noise reduction device characterized by stopping output to the speaker for a certain period of time when a threshold value is exceeded. 2. An engine speed detecting means, an adaptive controller for identifying an inverse transfer function of a transfer function from a detection signal of the detecting means to the ears of a vibration system of a vehicle body, and an output signal of the controller for a vehicle interior. A speaker for outputting noise to the entire vehicle interior, and means for detecting vehicle body vibration from the road surface, and the controller controls the speaker so that the input of the microphone is minimized and the vehicle body vibration is detected. A vehicle interior noise reduction device characterized in that the adaptive step size is set to zero for a certain period of time when exceeds a threshold value.