JP2543093Y2 - Noise control device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise control apparatus for canceling noise using a speaker, and more particularly, to shortening a signal processing time for canceling noise of an automobile or the like, improving the accuracy of the entire control system, and configuring the signal processing. The purpose is to simplify the process.

[0002]

2. Description of the Related Art Conventionally, a passive silencer such as a muffler has been used to reduce noise generated from an internal combustion engine or the like. However, improvement has been desired from the viewpoints of size, silencing characteristics, and the like. On the other hand, conventionally, an active noise control device has been proposed in which a compensating sound having the opposite phase and the same sound pressure as the noise generated from the sound field is output from a speaker to cancel the noise. However, the frequency characteristics or stability of the active noise control device itself were not sufficient, and its practical use was delayed. In recent years, as a result of the development of signal processing technology using digital circuits and the expansion of the frequency range that can be handled, a number of practical noise control devices have been proposed (for example, Japanese Patent Laid-Open No. 63-3 / 1988).
No. 11396). This is a feedforward system that detects noise with a microphone for capturing the noise source installed upstream of the duct and outputs a signal of opposite phase and equal sound pressure from the speaker installed downstream of the duct by a signal processing circuit, and a silencer This is a so-called 2-microphone / 1-speaker type active noise control device that combines a feedback system that detects the obtained result with a microphone for a silencing point and minimizes the silencing result. In this apparatus, an adaptive filter for forming a compensation sound of opposite phase and equal sound pressure is provided by a DSP (Digit).
al SignalProcessor) and FI
R (Finite Impulse Responses)
e) It is composed of a filter.

When the noise control device is mounted on an automobile and used, an input signal of the adaptive filter in the feedforward system generates a sine wave based on frequency information of a pulse of an engine rotation signal. It was input to the adaptive filter.

[0004]

However, in the signal input method to the conventional adaptive filter, the pulse signal of the engine rotation has to be once converted into a sine wave, so that a delay is generated, and the delay is caused by the feedback system. , The convergence time of the adaptive filter becomes longer and the control accuracy deteriorates. In addition, since the pulse signal of the engine rotation is converted into a sine wave, the amount of signal processing increases and the scale of hardware increases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a noise control device which extracts an optimal signal from an automobile in consideration of the above-mentioned problems, shortens the convergence time of an adaptive filter, and reduces the scale of hardware. .

[0006]

According to the present invention, in order to solve the above-mentioned problems, in order to eliminate noise transmitted from a noise source to a predetermined spatial position, the noise from the noise source is observed and the spatial position is measured. A noise control device that produces characteristics that are the reverse of the noise characteristics of a vehicle
Power of the alternator that supplies power to the electronic equipment
For example, muffler te
Forming a delay signal up to the spatial position such as a rule pipe
And the number of poles of the alternator is made variable by the engine.
Eliminate noise. Either an analog delay or a digital delay for delaying the sine wave signal of the alternator to form the delay signal is provided. A plurality of analog delay units or a plurality of digital delay units for delaying the sine wave signal of the alternator to form the delay signal, and a switch for adjusting a delay time of the plurality of analog delay units or the plurality of digital delay units And a switch control unit that controls the operation of the switch based on a signal from a microphone that indicates a muffling effect at the spatial position. An adaptive filter is provided which receives the sine wave signal of the alternator and forms a cancellation signal so as to minimize the level of a signal from a microphone which exhibits a noise reduction effect at the spatial position.

[0007]

According to the present invention, an engine mounted on an automobile or the like is provided.
Alternator installed in the power supply to supply power to electronic equipment
From the engine using a sinusoidal signal of the electromotive force
Delay to the spatial position such as the tail pipe of the muffler
A delay signal is formed and the number of poles of the alternator is made variable.
By changing the number of poles according to the engine speed,
The noise frequency that changes with the engine speed
it can. By eliminating the noise from the engine by the speaker, a sine wave signal having substantially the same waveform shape as the noise signal is delayed, so that the time required for waveform shaping is not required, and the signal processing time can be reduced. In order to form the delay signal, by providing either an analog delay unit or a digital delay unit for delaying the sine wave signal of the alternator, signal processing is possible, so that the configuration is simplified. Further, in order to form the delay signal, a plurality of analog delay units or a plurality of digital delay units for delaying the sine wave signal of the alternator and a delay time of the plurality of analog delay units or the plurality of digital delay units are adjusted. The delay can be easily adjusted by including the switch and the switch control unit that controls the operation of the switch based on a signal from the microphone that indicates the sound deadening effect at the spatial position. Further, the control of the delay is improved by providing an adaptive filter which receives the sine wave signal of the alternator and forms a cancellation signal so as to minimize the level of the signal from the microphone which exhibits the noise reduction effect at the spatial position.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a noise control device according to a first embodiment of the present invention. Throughout the drawings, similar components are denoted by similar symbols or reference numerals. As shown in the figure, the noise control device is mounted on an automobile or the like and has a space P
The rotation driving force of the engine 100 is received by a pulley, which will be described later, via a belt 101 for transmitting the rotation driving force from the crankshaft of the engine 100, which gives noise with the transmission characteristic Hx to the engine 100. Generate electricity,
An alternator 1 having a first object of supplying power to various mounted electronic devices by a battery 103 connected to a rectified constant voltage 102 for rectifying the AC electromotive force and adjusting the rectified constant voltage to a constant voltage; A transformer 2 connected in parallel to 102 and connected to its primary coil to reduce the AC voltage of the alternator 1; a capacitor 3 connected to the secondary coil of the transformer 2 for removing a DC component; A resistor 4 for adjusting the input impedance of the subsequent stage, and an amplifier 5 for inputting an AC signal of the alternator 1 via the resistor 4
A low-pass filter 6 for removing high-frequency components contained in an output signal of the amplifier 5, an analog delay device 7 connected to an output side of the low-pass filter 6 for delaying a signal, The power amplifier 8 includes a power amplifier 8 for power-amplifying the delay signal from the analog delay unit 7 and a speaker 9 for canceling noise with a sound wave inverted by a driving current from the power amplifier 8.

FIG. 2 is a diagram showing a pulley portion of the alternator of FIG. The driving force from the engine 100 is supplied to the pulley 1-1 of the alternator 1 shown in FIG. By the way, the noise generated by the engine 100 includes the fundamental frequency of the explosion sound and its harmonics, but the frequencies that cause discomfort to humans are not equal, and it is found that the specific ones have a large influence. ing. Therefore, by adjusting the diameter D of the pulley 1-1, the frequency of the signal input to the noise control device is formed, so that a specific unpleasant noise is muted.

In the analog delay unit 7 shown in FIG.
The delay of the signal from the alternator 1 is adjusted in consideration of the transfer characteristic Hx in order to form the noise from the speaker 9 inverted at the P position in the space with respect to the noise from 00. Although the noise from the engine 100 includes various frequencies as described above, since the noise is generated by the rotation of the engine 100, the signal waveform usually has a sine wave. Since one sine wave waveform of the alternator 1 is specified and processed as it is, the processing time can be significantly reduced. In the related art, when a pulse signal representing the number of revolutions of the engine 100 is directly input to an adaptive filter, a convergence time is long because a sine wave is formed so as to minimize the feedback signal. In order to avoid this, a sine wave generator may be provided in the preceding stage in advance, but time is required for signal formation, which results in a signal with a round-trip delay, which limits the control accuracy of feedback control. Was. According to the present embodiment, the process for forming these sine waves can be omitted. Instead, the circuit is composed of the transformer 2, the capacitor 3, and the resistor 4, so that the circuit configuration can be simplified. This embodiment shows the basic idea of the present invention, and the control of the delay unit 7 will be described below.

FIG. 3 is a diagram showing a noise control device according to a second embodiment of the present invention. In the second embodiment of this figure, the components different from the first embodiment are a plurality of analog delay units 10-1, 10-2,.
, 10-n, and one of the analog delay units 10-1, 10-2,..., 10-n.
, 11-n, the other of which is connected to the output of the power amplifier 8 and the microphone 12 which is installed at the position P in the space and supplements the sound-absorbing sound. And the microphone 12
A low-pass filter 13 for removing high-frequency components of a signal from the A / D converter, and an A / D converter 14 (Analog t) for converting an analog signal of the low-pass filter 13 into a digital signal.
o Digital Converter) and the switches 11-1 and 11-2 so that the signal from the A / D converter 14 is minimized.
.., 11-n.

According to this embodiment, the noise can be controlled by easily adjusting the delay of the sine wave generated in the alternator 1.
FIG. 4 is a diagram showing a noise control device according to a third embodiment of the present invention. The third embodiment of this figure is intended to make the analog delay unit 7 of the first embodiment a digital one.
Therefore, the A / D converter 16 connected to the low-pass filter 6, the digital delay unit 17 connected to the A / D converter 16, and the power amplifier 8 connected to the digital delay unit 17 A different component comprising a D / A converter 18 for outputting is provided.

FIG. 5 is a diagram showing a noise control device according to a fourth embodiment of the present invention. In the fourth embodiment, the analog delay unit 10 of the second embodiment is designed to be a digital one. For this reason, an A / D converter 16 connected to the low-pass filter 6 and , A digital delay unit 17 connected to the A / D converter 16, and a plurality of digital delay units 19-1, 19-2,.
19-n, and one of the digital delay units 19-1, 19-2,.
9-n are connected to the power amplifiers 8 respectively.
, 11-n,..., 11-n
, A microphone 12 installed at the P position in the space to capture the sound-absorbing sound, a low-pass filter 13 for removing high-frequency components of a signal from the microphone 12, and a low-pass filter 13 A / D converter 14 (An
a to digital converter) and the switches 11-1 and 11-1 so that the signal from the A / D converter 14 is minimized.
,..., 11-n.

FIG. 6 is a diagram showing a noise control apparatus according to a fifth embodiment of the present invention. The components different from the fourth embodiment of FIG. 5 are an adaptive filter 20 composed of an FIR filter for inputting a signal from the low-pass filter 6 and outputting the signal to the D / A converter 18; The adaptive filter 20 is controlled so that the signal level from the A / D converter 14 is minimized.
A coefficient adjusting unit 21 for adjusting the filter coefficient of the D / A
A low-pass filter 22 for removing high-frequency components from the converter 18. Further, the alternator 1 is an alternator having a variable number of poles, and detects the number of revolutions based on a signal from the low-pass filter 6, thereby switching the number of poles to the noise control device. The section 23 may be provided. Here, if the number of poles of the alternator 1 is p, the number of rotations of the rotor is n, and the frequency of the electromotive force generated in the stator is f, then f = p × n holds. The adaptive filter 20 adjusts the signal from the alternator 1 so that the signal from the microphone 12 is minimized.

FIG. 7 is a diagram for explaining the frequency of noise controlled by the pole number control in FIG. As shown in FIG. 10A, the primary level is higher than the secondary level at the frequency of the noise when the engine 100 rotates at a low speed, but as shown in FIG. As the number increases, the level of the secondary noise may be higher than the primary level. Therefore, when the rotational speed is low, the pole number p
Is set low, and the number of poles of the alternator 1 is switched by the pole number switching unit 23 to further increase the noise effect in order to change the setting so that the number of poles p increases when the rotation speed increases.

[0016]

According to the present invention, as described above, according to the present invention, a delay signal from the engine to the spatial position is formed using a sine wave signal of an electromotive force of an alternator provided in the engine. By eliminating noise from the engine, a sine wave signal having substantially the same waveform shape as that of the noise signal is delayed, so that the time required for waveform shaping is not required, and the signal processing time can be reduced and signal processing can be performed. Is simplified.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a noise control device according to a first embodiment of the present invention.

FIG. 2 is a view showing a pulley portion of the alternator of FIG. 1;

FIG. 3 is a diagram illustrating a noise control device according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a noise control device according to a third embodiment of the present invention.

FIG. 5 is a diagram illustrating a noise control device according to a fourth embodiment of the present invention.

FIG. 6 is a diagram illustrating a noise control device according to a fifth embodiment of the present invention.

FIG. 7 is a diagram illustrating the frequency of noise controlled by the pole number control in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Alternator 1 ... 1 Pulley 2 ... Transformer 5 ... Amplifier 6 ... Low-pass filter 7 ... Analog delay unit 9 ... Speaker 12 ... Microphone 10 ... Analog delay unit 11 ... Switch 15 ... Switch control unit 17 ... Digital delay unit 19 ... Digital delay unit 20 ... Adaptive filter 23 ... Pole number switching unit 100 ... Engine 101 ... Belt

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-178846 (JP, A) JP-A-3-204354 (JP, A) JP-A-2-41955 (JP, A) 1647 (JP, U) Actually open 63-1252 (JP, U)

Claims (4)

(57) [Scope of request for utility model registration] 1. A noise control device for observing noise from a noise source and forming a characteristic opposite to the characteristic of the noise at the spatial position in order to eliminate noise transmitted from the noise source to a certain spatial position. , Alternator provided in engine (100)
Using the sine wave signal of the electromotive force of (1), the engine (10
0) to the spatial position.
The number of poles of the tunator (1) is made variable and the engine (10
A noise control device characterized by eliminating the noise according to 0) . 2. The noise according to claim 1, further comprising an analog delay (7) or a digital delay (17) for delaying the sine wave signal of the alternator (1) to form the delay signal. Control device. 3. A plurality of analog delays (10) or a plurality of digital delays (19) for delaying the sine wave signal of the alternator (1) to form the delay signal.
And a switch (11) for adjusting the delay time of the plurality of analog delay units (10) or the plurality of digital delay units (19).
And a microphone (1) showing a sound deadening effect at the spatial position.
The noise control device according to claim 1, further comprising a switch control unit (15) that controls the operation of the switch (11) based on the signal from (2). 4. An adaptive filter (20) which receives a sine wave signal of said alternator (1) and forms an erasure signal so as to minimize the level of a signal from a microphone (12) exhibiting a muffling effect at said spatial position. The noise control device according to claim 1, comprising: (21).