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JPH0651789

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DESCRIPTION JPH0651789
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
device for reducing interior noise, and more particularly to a device for reducing interior noise
used in a device for actively reducing low frequency noise in a closed space such as a car. .
[0002]
2. Description of the Related Art Noise in the interior of a vehicle such as a car is due to the fact
that the cabin forming the closed space causes a resonance phenomenon under certain
conditions, and the excitation force resulting therefrom is the rotational vibration of the engine. It
is considered to be due to the ingredients.
[0003]
An attempt to adaptively reduce such vehicle interior noise has recently been made, an example
of which is shown in FIG.
[0004]
In the figure, 1 is a vehicle such as a car, 10 is a compartment in the vehicle 1, 11 is an engine,
12 is an engine vibration sensor (may be a knock sensor) as means for detecting a reference
signal synchronized with the rotation of the engine 11. An engine speed sensor 13, a microphone
13 for detecting a noise level in the passenger compartment 10, a speaker 14 for generating a
noise reducing noise, and a seat 15 in the passenger compartment 10.
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[0005]
Further, 2 is a controller for identifying the reverse transfer characteristic of the transfer
characteristic of the vibration system of the vehicle body 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; an adaptive filter 22 for inputting a digital
output of the A / D converter 21; a D / A converter 23 for converting a digital output of the
adaptive filter 22 into an analog signal; A power amplifier 24 for supplying to the speaker 14
and an A / D converter 25 for converting an analog output of the microphone 13 into a digital
signal and supplying it to the adaptive filter 22 are constituted.
Reference numeral 26 denotes a filter for providing a space transfer characteristic between the
speaker and the microphone which is measured in advance using white noise or the like before
the vehicle travels.
[0006]
FIG. 6 shows a well-known example of the adaptive filter 22 shown in FIG. 5. As the adaptive
algorithm in this case, there are a well-known steepest descent method, a learning identification
method, an LMS method, etc. Use the method.
[0007]
In the figure, Z-1 represents a delay element for delaying the engine vibration X (n) for each
sample, and h (0) to h (n-1) represent the output signals of the respective delay elements Z-1.
The filter (tap) coefficients for multiplication are each, and each filter coefficient is updated for
each sample according to the LMS algorithm: h (n + 1) = h (n) +2 μe (n) X (n).
However, i = 0 ... n, μ is the step size described above, and the convolution step of multiplying
the filter coefficient by the engine vibration X (n) of each sample and adding is performed while
selecting the step size μ in this case Thus, an output signal y (n) to the speaker 14 is obtained.
[0008]
Then, by transmitting the speaker output y (n) to the microphone 13 via the vehicle
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compartment 10, an error component e (n) is reduced from the microphone 13 by a component
Y (n) attenuated by the vehicle compartment 10. = Y (n)-y (n) is generated, and the filter
coefficient is updated for each sample so that the microphone output e (n) converges to the
minimum value by the LMS algorithm described above. It is possible to identify the inverse
transfer characteristic of the space transfer system characteristics up to the interior of the
vehicle, and minimize the microphone output e (n), that is, the driver's ear noise.
[0009]
In the vehicle interior noise reduction apparatus as described above, basically, the object is to
reduce the noise generated in the in-line four-cylinder engine vehicle.
That is, vertical and rotational vibrations are generated at a frequency twice the engine speed
(second-order engine rotation) due to inertia force and inertia torque by the piston reciprocating
mass of the engine and combustion torque due to combustion in the cylinder. However, when
this noise propagates into the passenger compartment and becomes noise, and this noise
matches the resonance frequency of the passenger compartment, the sound pressure level
becomes extremely unpleasant noise.
[0010]
However, measures against such booming noise only reduce the specific harmonic component,
and improve the sound quality of the noise by increasing or decreasing the amplitude of any
harmonic component depending on the preference of the occupant existing in the vehicle
compartment It has the disadvantage of not being able to
[0011]
Therefore, in JP-A-3-203491, the sound pressure of the predetermined harmonic component is
arbitrarily changed at the observation point of the residual noise, thereby forming a sound
quality space according to the listener's preference and thus more comfortable. I try to get an
acoustic space.
[0012]
However, in Japanese Patent Laid-Open No. 3-203491, a reference signal generated by a
reference signal generator receiving an output signal of a crank angle sensor as noise generation
state detecting means is an engine. Comfort is good for the passenger because it is a harmonic
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order signal (1, 2, 3,...) Of integral multiples with the first order rotation as a radix and does not
include the 0.5 order (half order) harmonics of the engine rotation. It is not possible to generate
all of the high engine rotation 0.5 to 4 harmonic components, and for example, to preferably
reduce the goro noise at the time of acceleration (engine rotation 0.5 to 1.5 harmonic
components) There was a problem that it was impossible.
[0013]
Therefore, an object of the present invention is to realize a vehicle interior noise reduction device
capable of generating all desired harmonic components including the engine rotation 0.5 order
component.
[0014]
[Means for Solving the Problems] In order to solve the above-mentioned problems, a device for
reducing noise in a vehicle cabin according to the present invention comprises means 12 for
detecting a reference signal synchronized with the vibration of the engine 11, as shown in FIG.
The speaker 14 provided in the vehicle compartment 10, the microphone 13 for detecting
vehicle interior noise, and the reverse transfer characteristic of the transfer characteristic to the
ear of the vibration system of the vehicle body 1 are identified by the reference signal. In the
vehicle interior noise reduction device provided with an adaptive controller 2 for controlling the
signal to the speaker 14 to be minimized, the reference signal is input before the controller 2 and
the engine rotation 0.5 order And a harmonic generator 3 for selecting and adding a desired
harmonic order signal among them and providing the same to the controller.
[0015]
Further, in the present invention, the harmonics generator 3 may provide amplitude control to
the desired harmonic order signal in accordance with the engine frequency.
[0016]
In the present invention shown in FIG. 1, the reference signal from the means 12 for detecting
the reference signal synchronized with the vibration of the engine 11 is directly sent to the
controller 2 in the vehicle interior noise reduction device conventionally used. Rather than input,
the reference signal is once input to the harmonic generation device 3, and in this harmonic
generation device 3, various harmonic order signals having half the engine speed, that is, the
engine rotation 0.5 order Generate.
[0017]
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At the same time, the harmonics generator 3 selects and further adds desired harmonic order
signals in the various 0.5th order engine rotation signals to the controller 2.
[0018]
In this case, if the desired harmonic order signal is obtained in advance by measurement, noise
reduction can be performed on the sound quality in various passenger compartments 10.
[0019]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 2 is a view showing an
embodiment of the harmonics generator 3 in the vehicle interior noise reduction apparatus
according to the present invention shown in FIG. 1. In this embodiment, the harmonics generator
3 is: A basic clock generation circuit 31 which receives an engine pulse from a sensor 12 as a
means for detecting a reference signal (engine pulse) synchronized with the vibration of the
engine 11 and generates a signal of a clock frequency of 2048 times per engine rotation; N sine
wave generating modules 32-1 to 32-n (hereinafter, sometimes collectively referred to as "32")
which generate harmonic order signals of integer multiples of rotation 0.5 order, and these
modules 32. A control circuit 33 for supplying a control signal to each of 32. A selection /
addition circuit 34 for selecting and adding according to a selection signal from control circuit
33 among output signals of module 32. It is configured.
[0020]
Further, each sine wave generation module 32-1 to 32-n shown in FIG. 2 has ROM 32a storing
sine wave data of the same amplitude different every engine rotation 0.5 order, and a basic clock
generation circuit for this ROM 32a. Noise from the output signal of the D / A converter 32c, a
counter 32b that generates an address signal by the clock from 31; a D / A converter 32c that
converts sine wave data read from the ROM 32a into an analog sine wave signal; A low pass filter
(LPF) 32d for removing the signal, a variable attenuator 32e for variably attenuating the output
signal level of the filter 32d, and a variable attenuation corresponding to the engine speed
indicated by the clock from the basic clock generation circuit 31 For controlling the output signal
level of each sine wave generation module 32 by controlling It is composed of a width control
section 32f.
[0021]
Next, the operation of the harmonic wave generator 3 will be described. First, in the ROM 32a in
the sine wave generation module 32, as shown in the waterfall diagram of FIG. The level is stored
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for each engine speed 0.5 order component.
Although only engine rotations 2 to 6 are shown in FIG. 3 as an example, it is desirable to store
as many 0.5 order integer multiple components as possible.
[0022]
When the basic clock generation circuit 31 generates a clock signal of 2048 times synchronized
with the engine rotation from the output signal of the sensor 12, this is counted by the counter
32b to generate an address of the ROM 32a.
In this case, the carry over of the counter 32b is set so that an address of one cycle is generated
at 4096 clocks.
[0023]
The ROM 32a that receives the address from the counter 32b stores sine wave data that has n
cycles of 4096 addresses, so that it is half the engine speed, that is, based on the 0.5th
component sound The harmonic component data up to n times is stored.
[0024]
Therefore, for example, in the case of the sine wave generation module 32-1, the sine wave data
of the 0.5 order component is stored at n = 1, and in the case of the sine wave generation module
32-2, n = 2 and the engine rotational speed. The sine wave data of the same frequency is stored,
and in the case of the sine wave generation module 32-3, 1.5 times the engine rotational speed at
n = 3, that is, the 1.5th-order sine wave data of the engine rotation is stored. In the case of the
sine wave module 32-4, n = 4 and 25 times the engine speed, that is, the sine wave data of the
mumble sound described above is output.
[0025]
Thus, the sine wave data read from each sine wave generation module 32 by the address from
the counter 32b is converted to an analog signal by the D / A converter 32c, and after the noise
is removed by the filter 32d, variable attenuation Is provided to the vessel 32e.
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[0026]
The variable attenuator 32e is configured to perform variable attenuation according to the
control signal from the amplitude control unit 32f, and this is a matrix of sine wave output levels
with respect to the engine rotation speed designated in advance by the user (this is The variable
attenuator 32 is controlled in accordance with the engine rotational speed indicated by the clock
from the basic clock generation circuit 31 by storing (can be set) in the amplitude control unit
32f.
[0027]
The variable attenuator 32e and the amplitude control unit 32f are not essential to the present
invention, and the objects of the present invention can be achieved by the harmonic order
components of the same level stored in the ROM 32a, but the variable attenuator 32e By using
and the amplitude control unit 32f, better control can be performed.
[0028]
In this manner, each harmonic order component is output from the variable attenuators 32e of
the sine wave generation modules 32-1 to 32-n to the selection and addition circuit 34. The
desired harmonic order components are selected, added and output by the selection signal 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 can be obtained by selecting the previously which 0.5-order
component.
For example, in the case of rattling during acceleration, the 0.5th to 1.5th order components are
dominant, and these components may be selected and added.
In fact, since the noise spectrum (each frequency) in the passenger compartment is up to about
500 Hz, up to 500 Hz can be sufficiently controlled in consideration of the fourth order
component.
[0030]
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And the controller 2 which received the various harmonic order components outputted from the
harmonic wave generator 3 in this way can use the reference signal to which each engine
rotation 0.5 order component is added for adaptive control. Therefore, as shown in FIG. 4 (a), the
improved second, 2.5, and 3 as shown in FIG. The noise of the next component can be
suppressed.
[0031]
As described above, in the vehicle interior noise reduction apparatus according to the present
invention, the reference signal synchronized with the engine vibration is input before the
controller, and the 0.5th harmonic order signal of the engine rotation is input. And a harmonic
generator for selecting and adding a desired harmonic order signal among them and giving it to
the controller, so that various engine rotations 0.5 orders underlying vehicle interior noise are
generated. The component speaker sound can be generated, and it is possible to appropriately
reduce the sound quality desired by the occupant.
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