JPH0411293A - Reducing device for interior car noise - Google Patents

Abstract

PURPOSE:To suppress residual noises into an optimum state by varying the latest adaptive filter coefficient sequence by a controller corresponding to a gear position and controlling a speaker so that the input of a microphone becomes minimum. CONSTITUTION:A means 9 which detects the gear position is provided and the gear position is detected and reported to the controller 5 which identifies the reverse transfer function of the transmission function G of the vibration system of a vehicle body excited by the vibration of an engine, so that the controller 5 selects the latest filter coefficient sequence H corresponding to the gear position. Thus, the filter coefficient sequence H which is converged on a last position is selected to perform adaptive sound elimination control, so residual noises up to the convergence of the selected filter coefficient sequence H are reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vehicle interior noise reduction device, and particularly to a device for actively reducing low-frequency noise in a closed space of a vehicle such as an automobile that has a periodic sound source. It is related to the device.

[Conventional technology]

Noise inside a vehicle such as a car is caused by the resonance phenomenon that occurs in the cabin, which forms a closed space, under certain conditions.
The vibrational force that is the cause of this is thought to be due to the rotational vibration component of the engine.

The measures initially taken to reduce such noise were passive, such as improving the coupling rigidity of the engine system, which is the source of vibration, and improving the coupling rigidity of the transmission system. We also tuned each mount and increased the rigidity of the panel for the sounding element inside the vehicle.
Furthermore, as a countermeasure against resonance, mass dampers, dynamic dampers, etc. were applied to the resonant parts.

Such passive means increase cost and weight, and are insufficiently effective.

On the other hand, in the case of a four-cylinder engine, the main cause of such cabin noise is thought to be the engine rotation order component, which is the two isothermal components of one rotation of the crankshaft, and is called the so-called engine rotation two-cycle component. , Japanese Patent Laid-Open No. 59-9699 and Utility Model Laid-Open No. 62-1270 are known as conventional techniques that attempt to actively reduce muffled sounds caused by such factors.
Publication No. 51 and the like have already been proposed.

In these conventional technologies, the ignition pulse is detected as a secondary component of engine rotation, and this pulse signal is processed in various ways to detect the opposite phase of each frequency component (rotational order component) of the noise observed at the driver's listening point in the vehicle interior. By separately adding sound from the speaker that has the same magnitude as the noise component, the noise level at the listening point is canceled out and reduced by the interference effect.

[Problem that the invention sought to solve]

However, the above-mentioned conventional example is a device for reducing only the muffled noise caused by the engine rotation secondary component of the noise inside the vehicle, and the rotation 2 due to engine explosion (rotation).
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 will not be optimal.

In addition, it is constantly affected by changes over time in the vehicle's engine system, mounting system, electrical system, etc., changes in the temperature characteristics of the electrical signal system, changes in the number of occupants, changes in the cabin temperature, etc., and the intrusion of some external disturbance. There was a problem that it was impossible to deal with the problem or the immediate response of the control could not be obtained.

Therefore, it is an object of the present invention to 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 that can quickly respond to various changes in vehicle conditions. purpose.

[Means to solve the problem] Above! In order to solve problem J, the vehicle interior noise reduction device according to the present invention identifies the engine vibration detection means and the inverse transfer function of the transfer function from the detection signal of the detection means to the ear of the vibration system of the vehicle body. an adaptive filter type controller;
The controller includes a speaker for outputting the output signal of the controller into the vehicle interior, a microphone for detecting all the noise in the vehicle interior, and a means for detecting the gear position, and the controller generates the latest adaptive filter coefficient sequence in response to the gear position. The speaker is controlled so that the input to the microphone is minimized.

Further, the present invention includes an engine rotation speed detection means, an adaptive filter type controller that identifies an inverse transfer function of a transfer function from a detection signal of the detection means to the ear of the vibration system of the vehicle body, and an output signal of the controller. The controller is equipped with a speaker that outputs to the interior of the vehicle, and a microphone that detects all the noise inside the vehicle, and the controller changes the latest adaptive filter coefficient series in accordance with the range of the engine rotation speed so that the input to the microphone is minimized. The above al1 problem can also be solved by controlling the speaker.

In this case, the engine rotation speed may be calculated using engine vibration detection means instead of the engine rotation speed detection means.

[For production]

In the vehicle interior noise reduction device according to the present invention, as shown in the equivalent block diagram of FIG. 1, G is the overall transfer function of the vehicle interior vibration system excited by engine vibration,
Based on engine vibration, it is composed of a transfer function (MTG) by the engine mount, a transfer function by torque rond, a transfer function by the cab mount, etc. This transfer function G allows engine vibration to be transferred to the inside of the vehicle through a transmission path to the ear. It is observed in the form converted into vehicle interior noise Y (n).

In this case, the engine vibration itself is due to the two components of engine rotation, but the cabin noise Y (
n) includes components other than the second order component of engine rotation 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. X (
n) and the output signal e(n) from the microphone, and based on these signals, the well-known L M
The speaker output y is adaptively controlled by the filter coefficient sequence H using the S (Least Mean 5quare) method etc.
(n) to offset the above-mentioned vehicle interior noise Y (n).

Here, the update amount of the filter coefficient sequence H is the step size μ
The tracking speed of the system changes depending on this step size μ.

Fill, IH' However, if control is performed using a common filter coefficient sequence for all gear positions, the time required for each gear change until the filter coefficient sequence converges to the value appropriate for that gear position is , the residual noise will increase.

Therefore, in the present invention, means 9 for detecting the gear position is provided, and by detecting the gear position and notifying the controller 5, the controller 5 selects the latest filter coefficient sequence corresponding to the gear position.

Furthermore, since the vibration mode differs depending on the range of the engine speed of the vehicle, if there is only one type of filter coefficient sequence, the residual noise will increase each time the engine speed changes until it converges to the optimum value.

Therefore, in the present invention, the controller 5 selects the latest filter coefficient sequence for each region of the engine speed detected by the means for detecting the engine speed.

In this case, the engine rotation speed can also be determined using engine vibrations from a means for detecting engine vibrations.

As shown in step 2, adaptive noise reduction control is performed by selecting the latest filter coefficient sequence that converged in the previous gear position or engine speed range, reducing residual noise until the selected filter coefficient sequence converges. can be done.

〔Example〕

FIG. 2 shows an embodiment of the vehicle interior noise reduction device according to the present invention, where ■ is the interior of the vehicle, 2 is the engine of the automobile 1, and 3 is a sensor for detecting engine vibration of the engine 2 ( (Can also be a non-stop sensor) or engine speed sensor,
4 is a microphone that detects the noise level inside the vehicle; 5 is a controller that uses the outputs of sensors 3 and 4 to identify the inverse transfer function of the transfer function of the vibration system of the vehicle body excited by engine vibration; and 6 is a controller that reduces noise. A speaker 7 that generates sound amplifies the signal from the controller 5 and sends it to the speaker 6
8 is a shift lever, and 9 is a gear position (gear position) sensor as means for detecting the gear position when the shift lever 8 is operated. In addition, as this gear position detecting means, a means for detecting the gear position in use may be provided in the gear box, control linkage, etc. Furthermore, in the case of an electronically controlled transmission, the current position is detected by the control unit. Alternatively, a signal indicating the gear position may be read.

FIG. 3 shows an embodiment of the controller shown in FIG. 2. In this embodiment, the controller is composed of an adaptive digital filter.
Examples include the descent method, learning identification method, and LMS method.
Here, the LMS method is used.

In addition, n Z-1 designates delay elements for delaying engine vibration X (n) for each sample, and n h(
0) to h (n-1) is an adaptive filter (tap) coefficient sequence H for multiplying each delay element z-', and each filter coefficient is determined by the LMS algorithm, that is, h (i+1
)=h(i)+2 p e(n) updated sample by sample according to X(ni). However, i=0...n-1
, μ is the step size mentioned above, and the second right-hand side of the above equation
2μe (n) in the term is calculated by the LMS unit 5o, and the filter coefficient sequence H is calculated for each gear position (or each gear position group) for the 1st gear as h(0) + ~ h (n-
1) +, 2nd gear is h (0) t~h (n-1)
t, 3rd gear is h (0) 3~h (n-1) 2
．． 4th gear is h(0)4~h(n-IL, 5th gear is h
(0)s to h (n-1)s are stored in the memory 51 in advance. However, once these filter coefficient sequences are initialized, they do not remain constant after that, but are rewritten and stored each time they are updated as shown in the above equation. Note that as the initial value, an optimal value obtained through experiments or the like is selected, but as the adaptive control progresses, it will be rewritten, so a particularly precise value is not required as the initial value.

When the gear position of the currently running vehicle is, for example, 3rd gear, the output signal from the gear position sensor 9 causes the controller 5 to
is the filter coefficient sequence h(0)s to h(n-
Select IL and give it as an initial value as a coefficient for each filter tap.

Then, by giving a predetermined step size μ,
By performing a convolution operation in which the filter coefficient sequence h (0) i to h (n-1) z is multiplied and added to the engine vibration X (n) of each sample, an output signal is output to the speaker 6 via the amplifier 7. y(n) is found.

By subtracting this speaker output y (n) from the sound pressure Y (n) actually observed near the driver's ear, the output from the microphone 4 e (n) = Y (n
) −y (n) is generated, and based on this, LM
By updating the filter coefficients using the S algorithm, it is possible to gradually identify the inverse transfer coefficient G-1 of the transfer function G of the vibration system in the vehicle interior, and the microphone output e (n) can be converged to the minimum value. be able to.

It should be noted that the engine vibration signal It can be converged.

The value of the initial filter coefficient sequence h(OL~h(n-1)s) is updated as sampling progresses, and is rewritten and stored in the memory 51 each time sampling is performed.

Therefore, when changing from 3rd gear to 4th gear, the latest value immediately before the gear change is retained in the memory 51 as the optimum value for 3rd gear, and when the next time the gear is changed to 3rd gear, , this latest value is stored in memory 51
It will be read out more easily.

In the above embodiment, one of the plurality of filter coefficient sequences H is selected based on the output of the gear position sensor 9, but the engine rotation obtained from the engine vibration sensor or the engine rotation speed sensor 3 is The number may be divided into several regions and a plurality of filter coefficient sequences H may be stored in the memory 51 corresponding to each region.

In this case, the filter coefficient sequence H in the memory 51 is selected in accordance with the engine speed range, and after the same adaptive operation as described above is performed, it is stored again in the memory 51 as the latest value. . Note that various rotation speed ranges can be provided for this engine, but if it is too small, the residual noise will become large until the coefficient sequence converges, and if it is too large, the capacity of the memory 51 will become large and a high processing speed will be required. Therefore, it is desirable to take both of these into consideration when setting.

(Effects of the Invention) As described above, the vehicle interior noise reduction device according to the present invention uses an adaptive controller that selects an adaptive filter coefficient sequence in accordance with the gear position or engine speed range in use. The inverse transfer function of the transfer function of the cabin vibration system up to the ear due to engine vibration is identified from the engine vibration signal and the microphone output, and the speaker cancels out the cabin noise due to the engine vibration. It is possible to cancel out all rotational order components caused by engine explosion other than the radial component, and to optimally suppress residual noise in any gear position or engine speed range compared to the case where the filter coefficient sequence is fixed. I can do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the principle of a vehicle interior noise reduction device according to the present invention. FIG. 2 is a schematic configuration diagram showing an embodiment of the vehicle interior noise reduction device according to the present invention. FIG. 3 is a diagram showing an embodiment of the controller used in the present invention. In the figure, 1 is a vehicle interior, 2 is an engine, 3 is an engine vibration sensor, 4 is a microphone, 5 is a controller, 6 is a speaker, and 9 is a gear position sensor. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] (1) An engine vibration detection means, an adaptive filter type controller that identifies the inverse transfer function of the transfer function from the detection signal of the detection means to the ear of the vibration system of the vehicle body, and outputs the output signal of the controller into the passenger compartment. a speaker for detecting noise, a microphone for detecting all vehicle interior noise, and a means for detecting a gear position, and the controller selects the latest filter coefficient sequence corresponding to the gear position so that the input to the microphone is minimized. A vehicle interior noise reduction device characterized by controlling the speaker. (2) An engine rotation speed detection means, an adaptive filter type controller that identifies the inverse transfer function of the transfer function from the detection signal of the detection means to the ears of the vibration system of the vehicle body, and an output signal of the controller that is transmitted to the vehicle interior. The controller is equipped with a speaker that outputs an output, and a microphone that detects all vehicle interior noise, and the controller selects the latest filter coefficient sequence corresponding to the engine rotation speed region and operates the speaker so that the input to the microphone is minimized. A vehicle interior noise reduction device characterized by control. (3) The vehicle interior noise reduction device according to claim 2, wherein the engine rotation speed is calculated using engine vibration detection means instead of the engine rotation speed detection means.