JPH0411536A - Car interior noise reducing device - Google Patents

Abstract

PURPOSE:To permit the disposal of various changes of the vehicle conditions by controlling a speaker so that the input of a microphone becomes min. by allowing a controller to vary the step size in proportion to the gear ratio. CONSTITUTION:When a vehicle in traveling is at a gear position having a high gear ratio, the driving torque is large, and the engine revolution sensitivity reacts to the accelerator operation, and in order to properly eliminate the noise due to the reacted engine revolution, the step size mu is increased, and the following performance in the control is improved. When the low gear ratio is used, the reaction of the engine revolution becomes nonsensitive for the accelerator operation, and the step size mu is reduced, and the residual noise is reduced. Accordingly, the output signal y(n) supplied to a speaker 6 through an amplifier 7 is obtained by carrying out the convolution calculation in which the engine vibration X(n) of each sample is multiplied by the filter coefficient. The output e(n) of a microphone 4 is generated by subtracting the speaker output y(n) from the sound pressure Y(n) which is actually measured at the ear of a driver.

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. has tuned each mount, and increased the rigidity of the panel for the sounding body inside the vehicle.
Furthermore, as a countermeasure against resonance, mass dampers, Guinamisoku 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 a two-time explosion component per crankshaft rotation, and is called the so-called engine rotation second order component. Conventional techniques for actively reducing the muffled sound caused by such factors include Japanese Patent Application Laid-Open No. 599699 and Japanese Utility Model Application No. 62-12705.
Publication No. 1 etc. 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 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 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 for Solving the Problems] In order to solve the above problems, the vehicle interior noise reduction device according to the present invention includes an engine vibration detection means and a detection signal from the detection means to the ear of the vibration system of the vehicle body. an adaptive controller for identifying an inverse transfer function of a transfer function of the controller; a speaker for outputting an output signal of the controller into a vehicle interior; a microphone for detecting total vehicle interior noise; and means for detecting a gear ratio. controls the speaker so that the input to the microphone is minimized by changing the adaptive step size in proportion to the gear ratio.

[Function] In the vehicle interior noise reduction device according to the present invention, as shown in the equivalent Bronk diagram of FIG. 1, G is the overall transfer function of the vehicle interior vibration system excited by engine vibration, and
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 second-order engine rotation component, 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-' of this transfer function. The well-known LMS (Least Mean 5
The speaker output y (n) is generated by adaptively controlling the filter coefficient sequence H using the square method or the like to cancel the above-mentioned vehicle interior noise Y (n).

Here, the update amount of the filter coefficient sequence H is determined by the step size μ, and the larger the step size μ, the larger the update amount each time, and the faster the convergence of the adaptive operation. Since the amount updated each time increases, the optimum value may be exceeded, resulting in increased residual noise.

On the other hand, when the step size μ is small, it gradually approaches the optimum value, so it is easy to settle down to the optimum value and the residual noise is reduced, but the amount of update at one time is also small, so it takes time for convergence.

In this way, the following speed of the system changes depending on the step size μ, but when the vehicle is currently running in gear, the driving torque is is large, and the engine rotation is sensitively reflected in the accelerator operation, that is, the opening and closing of the throttle (or fuel injection pump). Therefore, if the step size μ is determined by prioritizing the followability of a system with such a high gear ratio. , 5th gear, etc., the step size μ is too large, resulting in a large residual error.

On the other hand, if the step size μ is set small in accordance with a low gear ratio, followability at a high gear ratio will deteriorate.

Therefore, in the present invention, a means 9 for detecting a gear ratio is provided, and by detecting the gear ratio and notifying the controller 5, the controller 5 adjusts the step size μ in proportion to the gear ratio, as shown in FIG. control greatly.

Therefore, if an adaptive controller in which the step size changes in accordance with the gear ratio as in the present invention is used, the system will be able to follow the system at high gear ratios (low gear positions) where the engine speed responds sensitively to accelerator operation. On the other hand, at low gear ratios (high gear positions) such as 5th gear, the response of engine rotation to accelerator operation is slow, so reducing the step size μ can reduce residual noise. can.

〔Example〕

FIG. 3 shows an embodiment of the vehicle interior noise reduction device according to the present invention, in which 1 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 ( 4 is a microphone that detects the noise level in the vehicle interior; 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; 6 7 is an amplifier that amplifies the signal from the controller 5 and drives the speaker 6, 8 is a shift lever 1, and 9 is a gear ratio detection means when the shift lever 8 is operated. This is a gear position (gear stage) sensor. In addition, as this gear ratio detection means, a means for detecting the gear position in use may be provided in the gearbox, control linkage, etc. Furthermore, in the case of an electronically controlled transmission, the control unit detects the current position. A signal indicating the gear position may also be read.

FIG. 4 shows an embodiment of the controller shown in FIG. 3. In this embodiment, it is composed of an adaptive digital filter, and adaptive algorithms include the well-known steepest descent method, learning identification method, etc. Examples include the LMS method, and the LMS method is used here.

In addition, n Z-Is represent delay elements for delaying engine vibration X (rl) for each sample, and n h
(0) to h (n-1) are filter (tap) coefficients 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 and μ are the step sizes described above.

In this case, the step size μ is normally as shown in FIG.
It becomes smaller as μ, → μ2 → μ, →〃, →μ, →, and becomes proportional to the gear ratio.

In other words, when a running vehicle is in a high gear ratio, the driving torque is large and the engine rotation responds sensitively to accelerator operation. The step size μ may be increased to improve control followability. When a low gear ratio is used, the response of engine rotation to accelerator operation becomes slow, so by reducing the step size μ, residual noise can be reduced.

By selecting the step size μ as above,
An output signal y (n) to be output to the speaker 6 via the amplifier 7 is obtained by performing a convolution operation in which the engine vibration X (n) of each sample is multiplied by the filter coefficient and added.

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 (nl = Y (n
) -y (nl 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 function 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. I can do it.

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

〔Effect of the invention〕

As described above, the vehicle interior noise reduction device according to the present invention uses an adaptive controller that changes the adaptive step size in proportion to the gear ratio being used to suppress the vehicle interior vibration system up to the ears due to engine vibration. The inverse transfer function of the transfer function is identified by the engine vibration signal and the microphone output, and the speaker cancels out the cabin noise caused by the engine vibration. All of the components can be canceled out, and residual noise can be optimally suppressed at any gear position compared to the case where the step size is fixed.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing the principle of the vehicle interior noise reduction device according to the present invention. FIG. 2 is a diagram showing changing the step size according to the present invention. FIG. 3 is a schematic configuration diagram showing an embodiment of the vehicle interior noise reduction device according to the present invention, and FIG. 4 is a diagram showing an embodiment of the controller used in the present invention. , 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 (1)

[Claims] An engine vibration detection means, an adaptive controller that identifies an inverse transfer function of a transfer function from the detection signal of the detection means to the ear of the vibration system of the vehicle body, and a speaker that outputs an output signal of the controller into the vehicle interior; Equipped with a microphone that detects all vehicle interior noise and a means for detecting gear ratio,
A vehicle interior noise reduction device characterized in that the controller changes an adaptive step size in proportion to the gear ratio to control the speaker so that input to the microphone is minimized.