JPH0651789A - Reducing device for in-cabin noise - Google Patents

Abstract

PURPOSE:To obtain the reducing device for the in-cabin noise which can generate all higher harmonic components by generating higher harmonic signals of engine rotation half order. CONSTITUTION:The reference signal from a means 12 which detects the reference signal synchronized with the vibration of an engine 11 is not inputted directly to a controller 2, but inputted to a higher harmonic generating device 3 temporarily, which generates various higher harmonic signals of half cycles of the engine rotating speed, i.e., (0.5)th order. Further, the higher harmonic generating device 3 selects and adds desired higher harmonic signals among the higher harmonic signal of (0.5)th order of the engine rotation and supplies the result to the controller 2. In this case, noise reduction for the tone quality in various cabins 10 can be performed by previously finding desired higher harmonic signals by measurements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle interior noise reduction device, and more particularly to a vehicle interior noise reduction device used in a device for actively reducing low frequency noise in a vehicle interior closed space. .

[0002]

2. Description of the Related Art Noise in the interior of a vehicle, such as an automobile, is caused by the resonance phenomenon of a vehicle interior forming a closed space under certain conditions. It is believed that this is due to the ingredients and so on.

Attempts have been made recently to adaptively reduce such vehicle interior noise, one example of which is shown in FIG.

In the figure, 1 is a vehicle such as an automobile, 10 is a passenger compartment in the vehicle 1, 11 is an engine, and 12 is an engine 11.
Engine vibration sensor (which may be a knock sensor) or engine speed sensor as means for detecting a reference signal synchronized with the rotation of the vehicle, 13 is a microphone for detecting the noise level in the vehicle interior 10, and 14 is a sound for reducing noise. The generated speaker, and 15 are seats in the passenger compartment 10.

Reference numeral 2 is a controller for identifying the reverse transfer characteristic of the transfer characteristic of the vibration system of the vehicle body which is excited by the vibration of the engine by the outputs of the sensor 12 and the microphone 13, and converts the analog output of the sensor 12 into a digital output. A /
D converter 21, adaptive filter 22 that inputs the digital output of A / D converter 21, and D / A converter 23 that converts the digital output of adaptive filter 22 into an analog signal
A power amplifier 24 that amplifies this analog signal and supplies it to the speaker 14, and an A / D converter 25 that converts the analog output of the microphone 13 into a digital signal and supplies it to the adaptive filter 22. Reference numeral 26 is a filter that gives a spatial transfer characteristic between the speaker and the microphone, which is measured in advance by using white noise before traveling of the vehicle.

FIG. 6 shows a well-known example of the adaptive filter 22 shown in FIG. 5. As the adaptive algorithm in this case, the well-known steepest descent method, learning identification method, LMS method and the like can be mentioned. Here, the LMS method is used.

In the figure, Z ^-1 indicates a delay element for delaying the engine vibration X (n) for each sample, and h (0) to h (0) to h
(n-1) is a filter (tap) coefficient for multiplying the output signal of each delay element Z ^-1 and each filter coefficient is an LMS algorithm, that is, h (n + 1) = h (n) +2 μe (n) X (n) is updated for each sample. However, i = 0 ... n,
μ is the step size described above, and the output signal to the speaker 14 is obtained by performing the convolution operation of selecting the step size μ in this case and multiplying and adding the filter coefficient to the engine vibration X (n) of each sample. y
(n) is required.

By transmitting the speaker output y (n) to the microphone 13 via the vehicle interior 10, the error component e reduced from the microphone 13 by the component Y (n) attenuated by the vehicle interior 10. (n) = Y (n) -y (n) is generated and the filter coefficient is updated for each sample so that the microphone output e (n) is converged to the minimum value by the above LMS algorithm. It is possible to identify the reverse transfer characteristic of the vehicle interior space transfer system from the microphone to the microphone 13, and it is possible to minimize the microphone output e (n), that is, the noise around the driver's ears.

In the above vehicle interior noise reduction device,
Basically, the object is to reduce the muffled noise that is noticeably generated in an in-line 4-cylinder engine vehicle. That is, due to the inertial force and the inertial torque due to the piston reciprocating mass of the engine, and the combustion torque due to the combustion in the cylinder, vibrations in the vertical and rotational directions occur at a frequency twice the engine speed (secondary engine rotation). However, when this noise propagates into the vehicle interior and becomes noise, and this noise coincides with the resonance frequency of the vehicle interior, the sound pressure level becomes extremely unpleasant noise.

However, such countermeasures for muffled sound only reduce specific harmonic components, and increase or decrease the amplitude of arbitrary harmonic components depending on the taste of an occupant present in the vehicle cabin to improve the sound quality of noise. The disadvantage is that no improvements can be made.

In view of this, in Japanese Patent Laid-Open No. 3-203491, a sound quality space according to the taste of the listener is formed by arbitrarily changing the sound pressure of a predetermined harmonic component at the residual noise observation point. I try to get a more comfortable acoustic space.

[0012]

However, in Japanese Patent Laid-Open No. 3-203491, the reference signal generated by the reference signal generator which receives the output signal of the crank angle sensor as the noise generation state detecting means is the engine. Rotation 1
Harmonic order signals (1, 2,
3, ...) and does not include harmonic components of the 0.5th (half-order) engine rotation, it is possible to generate all of the 0.5-4th harmonic components of the engine rotation, which is highly comfortable for passengers. However, there is a problem in that it is not possible to appropriately reduce, for example, the noise caused by acceleration (engine rotation 0.5 to 1.5th harmonic component).

Therefore, it is an object of the present invention to realize a vehicle interior noise reducing apparatus capable of generating all desired harmonic components including an engine rotation 0.5th order component.

[0014]

In order to solve the above problems, the vehicle interior noise reducing apparatus according to the present invention, as shown in FIG. 1, is a means 12 for detecting a reference signal synchronized with the vibration of the engine 11. And a speaker 14 provided in the passenger compartment 10,
A microphone 13 for detecting vehicle interior noise, and the speaker 14 so as to minimize the input of the microphone by identifying the reverse transfer characteristic of the transfer characteristic up to the ear of the vibration system of the vehicle body 1 by the reference signal.
In the vehicle interior noise reduction device including an adaptive controller 2 for controlling a signal to the engine, the reference signal is input in front of the controller 2 to generate a harmonic order signal of engine revolution 0.5. In addition, a harmonic generator 3 for selecting a desired higher harmonic order signal from these signals, adding the selected higher harmonic order signal to the controller, and adding it to the controller is provided.

Further, in the present invention, the harmonic generator 3 may give amplitude control to the desired harmonic order signal in accordance with the engine frequency.

[0016]

In the present invention shown in FIG. 1, the engine 1 is used in the conventional vehicle interior noise reduction device.
Instead of directly inputting the reference signal from the means 12 for detecting the reference signal synchronized with the vibration of 1 into the controller 2,
The reference signal is once input to the harmonic generating device 3, and various harmonic order signals of 1/2 of the engine speed, that is, 0.5 engine speed are generated in the harmonic generating device 3.

At the same time, the harmonic generator 3 selects a desired harmonic order signal from the various harmonic order signals of the 0.5th order of engine rotation, adds them, and supplies them to the controller 2.

In this case, if the desired harmonic order signal is obtained in advance by measurement, it is possible to reduce noise for various sound qualities in the passenger compartment 10.

[0019]

FIG. 2 is a diagram showing an embodiment of a harmonic generator 3 in the vehicle interior noise reduction apparatus according to the present invention shown in FIG. 1. In this embodiment, the harmonic generator 3 is: Reference signal (engine pulse) synchronized with the vibration of the engine 11
A basic clock generation circuit 31 which receives an engine pulse from a sensor 12 as a means for detecting the frequency of the engine to generate a signal having a clock frequency of 2048 times in one revolution of the engine, and each harmonic number of an integer multiple of the engine revolution of 0.5. N sine wave generation modules 32-1 to 32-n (hereinafter sometimes collectively referred to as reference numeral “32”) that generate signals, and a control circuit 33 that gives a control signal to each of these modules 32. And a selection / addition circuit 34 that selects and adds from each output signal of the module 32 in accordance with a selection signal from the control circuit 33.

Each of the sine wave generating modules 32-1 to 32-n shown in FIG. 2 has a ROM 32a which stores sine wave data of the same amplitude which is different for every 0.5th order of engine rotation.
A counter 3 for generating an address signal to the ROM 32a by the clock from the basic clock generating circuit 31.
2b, a D / A converter 32c for converting the sine wave data read from the ROM 32a into an analog sine wave signal,
A low-pass filter (LPF) 32d for removing noise from the output signal of the D / A converter 32c, and a variable attenuator 32 for variably attenuating the output signal level of the filter 32d.
e and a variable attenuator 32e corresponding to the engine speed indicated by the clock from the basic clock generation circuit 31.
And an amplitude control section 32f for adjusting the output signal level of each sine wave generation module 32 by controlling the.

Next, the operation of the harmonic generator 3 will be described. First, the ROM 32 in the sine wave generating module 32.
As shown in the waterfall diagram of FIG. 3, the sound pressure (amplitude) level of a sine wave that is equal to the engine speed is stored in a for each engine speed 0.5 order component. It should be noted that, although FIG. 3 shows only the engine revolutions of the 2nd to 6th orders as an example, it is desirable to store as many integral multiples of the 0.5th order as possible.

Then, the basic clock generating circuit 31 synchronizes the output signal of the sensor 12 with the engine rotation 2048.
When the double clock signal is generated, it is counted by the counter 32b.
Is counted and the address of the ROM 32a is generated. In this case, carryover of the counter 32b is set so that an address of one cycle is generated in 4096 clocks.

R receiving the address from the counter 32b
The OM 32a stores sine wave data having 4096 addresses and n cycles. Therefore, half of the engine speed, that is, the harmonic component data up to n times that of the 0.5th order sound is used as a reference. Will be stored.

Therefore, for example, the sine wave generating module 32
In the case of -1, n = 1 and 0.5-order component sine wave data is stored, and in the case of the sine wave generation module 32-2, n = 2 and sine wave data of the same frequency as the engine speed is stored. In the case of the sine wave generation module 32-3, n = 3 and 1.5 times the engine speed, that is, sine wave data of the 1.5th engine speed is stored. In the case of, n = 4 and the engine speed is 2
Five times, that is, the sine wave data of the above-described muffled sound is output.

In this way, the sine wave data read from each sine wave generation module 32 by the address from the counter 32b is converted into an analog signal by the D / A converter 32c, and noise is removed by the filter 32d. , Variable attenuator 32e.

The variable attenuator 32e is an amplitude control section 32f.
It is configured to be variably attenuated by a control signal from the amplitude control unit, which is a matrix of the output level of the sine wave with respect to the engine speed previously specified by the user (this can also be set from the control circuit 33). 32f
The variable attenuator 32 is controlled in accordance with the engine speed indicated by the clock from the basic clock generating circuit 31 by storing it in the.

The variable attenuator 32e and the amplitude control section 3
2f is not essential to the present invention, and the object of the present invention can be achieved by each harmonic order component of the same level stored in the ROM 32a, but by using the variable attenuator 32e and the amplitude controller 32f, Good control can be performed.

In this way, each sine wave generating module 3
Each of the harmonic order components is output from the variable attenuator 32e of 2-1 to 32-n to the selection / addition circuit 34. The selection / addition circuit 34 receives the desired harmonic order component by the selection signal from the control circuit 33. Is selected, added and output, and sent to the controller 2.

[0029] The selection signal from the control circuit 33 is determined by previously measuring whether the desired noise reducing effect by selecting the advance which 0.5 order component obtained. For example, in the case of a gurgling sound at the time of acceleration, the 0.5th to 1.5th order components are dominant, so these components may be selected and added. Actually, the noise spectrum (each frequency) in the passenger compartment is up to about 500 Hz, so that it is possible to sufficiently control up to 500 Hz by considering the fourth-order component.

Then, in this way, the harmonic generator 3
The controller 2, which has received various harmonic order components output from, can use the reference signal to which each engine rotation 0.5-order component is added for adaptive control.
As shown in Fig. 6 (b), the improved secondary and 2.5
It is possible to suppress the noise of the secondary and tertiary components.

[0031]

As described above, in the vehicle interior noise reducing apparatus according to the present invention, the reference signal synchronized with the vibration of the engine is input before the controller, and the harmonic order signal of the 0.5th engine rotation is input. A harmonic generator for generating a desired harmonic order signal from these signals and adding the selected harmonic order signal to the controller is provided. It is possible to generate the speaker sound of the component, and it is possible to appropriately reduce the sound quality with a desired sound quality for the occupant.

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing the structure of a vehicle interior noise reduction device according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a harmonic generation device used in the vehicle interior noise reduction device according to the present invention.

FIG. 3 is a waterfall diagram showing each harmonic order component stored in the ROM of the sine wave generation module used in the vehicle interior noise reduction device according to the present invention.

FIG. 4 is a waterfall diagram comparing the case where the engine rotation 0.5-order component is not included in the control and the case where it is included in the vehicle interior noise reduction device according to the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional vehicle interior noise reduction device.

FIG. 6 is a block diagram showing a general configuration of an adaptive filter.

[Explanation of symbols]

 1 Vehicle 2 Controller 3 Harmonic Generation Device 31 Basic Clock Generation Circuit 32 (32-1 to 32-n) Sine Wave Generation Module 33 Control Circuit 34 Selection / Addition Circuit 11 Engine 12 Engine Vibration Sensor (Engine Speed Sensor) 13 Microphone 14 Speaker 22 Adaptive filter In the figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A means for detecting a reference signal in synchronization with engine vibration, a speaker provided in a vehicle compartment, a microphone for detecting noise in the vehicle compartment, and a transfer characteristic of the reference signal to an ear of a vibration system of a vehicle body. In the vehicle interior noise reduction device including an adaptive controller that identifies the reverse transfer characteristic of the microphone and controls the signal to the speaker so that the input of the microphone is minimized, the reference signal is set in front of the controller. A harmonic generator for inputting to generate a harmonic order signal of 0.5th engine rotation, and for selecting and adding a desired harmonic order signal among these signals to give to the controller is provided. Vehicle interior noise reduction device. 2. The vehicle interior noise reduction device according to claim 1, wherein the harmonic generation device receives amplitude control of the desired harmonic order signal corresponding to the frequency of the engine. .