JPH0596899U - Noise control device - Google Patents

Abstract

(57) [Abstract] [Objective] The present invention reduces the signal processing time for noise elimination, improves the accuracy of the entire control system, and simplifies the configuration of signal processing in order to eliminate noise using a speaker. The purpose is to plan. A noise control device for observing noise from a noise source and forming a characteristic opposite to that of the noise at the spatial position in order to eliminate noise propagated from the noise source to a certain spatial position, The sine wave signal of the electromotive force of the alternator 1 provided in 100 is used to form a delay signal from the engine 100 to the spatial position.
Eliminate the noise caused by 0.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a noise control device for canceling noise by using a speaker, and particularly to shorten the signal processing time for canceling noise of an automobile or the like, improve the accuracy of the entire control system, and simplify the configuration of signal processing. To aim.

[0002]

[Prior Art]

 Conventionally, a passive muffling device such as a muffler has been used to reduce the noise generated from an internal combustion engine, etc., but improvements have been desired in terms of size, muffling characteristics, and the like. On the other hand, conventionally, an active noise control device has been proposed which cancels noise by outputting from a speaker a compensating sound of opposite phase and equal sound pressure to noise generated from a sound source. However, the frequency characteristics and stability of the active noise control device itself were not sufficient, and its practical application was delayed. As a result of the recent development of signal processing technology using digital circuits and expansion of the frequency range that can be handled, many practical noise control devices have been proposed (for example, JP-A-63-311396). This is a feedforward in which noise is detected by a noise source supplement microphone installed in the upper stream of the duct, and a signal processing circuit outputs a signal of opposite phase and equal sound pressure to the speaker installed downstream of the duct. This is a so-called 2-microphone / 1-speaker type active noise control system that combines a system and a feedback system that minimizes the muffling result by detecting the muffling result with a microphone for the muffling point. In this apparatus, an adaptive filter for forming a compensating sound of antiphase / isotone pressure is composed of a DSP (Digital Signal Processor), and is composed of a FIR (Finite Impulse Response) filter.

When the noise control device is installed in an automobile and used, an input signal of the adaptive filter in the feedforward system is a sine wave based on the frequency information of the engine rotation signal as a pulse. Was generated and input to the adaptive filter.

[0004]

[Problems to be solved by the device]

 However, in the conventional signal input method to the adaptive filter, the pulse signal of the engine rotation must be once converted into a sine wave, which causes a delay, which causes a time delay between the pulse signal and the signal from the feedback system. There is a problem that a shift occurs, the convergence time of the adaptive filter becomes long, and the control accuracy deteriorates. Moreover, 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 also increases.

Therefore, in view of the above problems, it is an object of the present invention to provide a noise control device capable of extracting an optimum signal from an automobile, shortening the convergence time of an adaptive filter, and reducing the hardware scale. To do.

[0006]

[Means for Solving the Problems]

 SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention observes noise from a noise source in order to eliminate noise propagating from the noise source to a certain spatial position, and reverses the characteristics of the noise at the spatial position. In a noise control device that forms characteristics, a sine wave signal of an electromotive force of an alternator, which is provided in an engine mounted on an automobile or the like and supplies electric power to an electronic device, is taken out by a transformer or the like and is used for example from a muffler from the engine. A delayed signal up to the spatial position such as the tail pipe of the above is formed, and the noise caused by the engine is canceled by the speaker. To form the delayed signal, it comprises either an analog delay device or a digital delay device for delaying the sine wave signal of the alternator. 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 a plurality of digital delay units are used to form the delay signal. It has a switch to be adjusted and a switch control section to control the operation of the switch based on a signal from a microphone showing a silencing 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 the signal from the microphone exhibiting the silencing effect at the spatial position. The diameter of the alternator pulley that receives the rotational driving force from the engine is changed to adjust the noise cycle of the engine to be eliminated. The number of poles of the alternator is made variable, and the number of poles is changed according to the rotation speed of the engine.

[0007]

[Action]

 According to the present invention, a sine wave signal of an electromotive force of an alternator, which is provided in an engine mounted on an automobile or the like and supplies electric power to an electronic device, is taken out by a transformer or the like and is used from the engine, for example, a tail pipe of a muffler. By forming a delay signal up to the above spatial position and canceling noise from the engine with the speaker, a sine wave signal having substantially the same waveform shape as the noise signal is subjected to delay processing. The time for signal processing is no longer required, and the signal processing time can be shortened. In order to form the delay signal, by providing either an analog delay device or a digital delay device that delays the sine wave signal of the alternator, signal processing can be performed, 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 a plurality of digital delay units are set. The delay can be adjusted easily by having the switch to be adjusted and the switch control unit to control the operation of the switch based on the signal from the microphone showing the sound deadening effect at the spatial position. Further, the delay control is improved by providing an adaptive filter which inputs the sine wave signal of the alternator and forms a cancellation signal so as to minimize the level of the signal from the microphone exhibiting the silencing effect at the spatial position. .. Furthermore, by changing the diameter of the pulley of the alternator that receives the rotational driving force from the engine to adjust the noise cycle to be canceled by the engine, an integral multiple harmonic of the fundamental frequency generated by the engine is generated. Removal can be done arbitrarily. By varying the number of poles of the alternator and changing the number of poles in accordance with the engine speed, it is possible to eliminate the noise frequency that changes with the engine speed.

[0008]

【Example】

 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. Note that, throughout the drawings, the same components are denoted by the same symbols or reference numerals. As shown in the figure, the noise control device is provided with a belt 10 for transmitting a rotational driving force from a crankshaft of an engine 100, which is mounted on an automobile or the like and gives noise to a position P having a space with a transmission characteristic Hx. A rotary driving force of the engine 100 is received by a pulley to be described later via 1 to generate an AC electromotive force corresponding to the rotational speed of the engine 100, and the AC electromotive force is rectified to be adjusted to a constant voltage. An alternator 1 whose first purpose is to supply electric power to various on-board electronic devices by a battery 103, and a primary coil for reducing the AC voltage of the alternator 1 connected in parallel to the rectified constant voltage 102. A transformer 2 connected to the transformer 2, a capacitor 3 connected to the secondary coil of the transformer 2 for removing a direct current component, and a resistor 4 for adjusting the input impedance of the latter stage, An amplifier 5 for inputting the AC signal of the alternator 1 via a resistor 4, a low pass filter 6 for removing high frequency components contained in the output signal of the amplifier 5, and a low pass filter 6 for the low pass filter 6. An analog delay unit 7 connected to the output side for delaying a signal, a power amplifier 8 for power-amplifying the delay signal from the analog delay unit 7, and an inversion erased by a drive current from the power amplifier 8. And a speaker 9 for canceling noise with a sound wave.

FIG. 2 is a diagram showing a pulley portion of the alternator of FIG. As described above, the driving force from the engine 100 is supplied to the pulley 1-1 of the alternator 1 shown in this figure. By the way, the noise generated by the engine 100 includes the fundamental frequency of its explosion sound and its harmonics, but the frequencies that cause discomfort to humans are not equal to each other, and specific ones have a great influence. I know it. Therefore, the diameter D of the pulley 1-1 is adjusted to form the frequency of the signal input to the noise control device so that a particular unpleasant noise is silenced.

In the analog delay device 7 of FIG. 1, the alternator 1 is considered in consideration of the transfer characteristic Hx in order to form the muffling from the speaker 9 which is inverted at the P position in space with respect to the noise from the engine 100. The delay of the signal from is adjusted. Although the noise from the engine 100 includes various frequencies as described above, the signal waveform is usually a sine wave because it is generated by the rotation of the engine 100. Since one sine wave of the alternator 1 is specified and processed as it is, the processing time can be remarkably shortened. Conventionally, when a pulse signal representing the number of revolutions of the engine 100 is directly input to the adaptive filter, the feedback signal is minimized to form a sine wave, so that the convergence time is long. In addition, in order to avoid this, a sine wave generator was sometimes installed in the previous stage in advance, but it took time for signal formation, and it became a signal with a lap delay, which limits the control accuracy of feedback control. Was occurring. According to the present embodiment, the process for forming these sine waves can be omitted, and instead of this, the transformer 2, the capacitor 3 and the resistor 4 are used, so that the circuit configuration can be simplified. Become. This embodiment shows the basic idea of the present invention, and the control of the delay device 7 will be described below.

FIG. 3 is a diagram showing a noise control device according to a second embodiment of the present invention. The second embodiment of the present drawing is different from the first embodiment in that it has an analog delay unit 10 composed of a plurality of analog delay units 10-1, 10-2, ... , One of which is connected to the output of each of the analog delay units 10-1, 10-2, ..., 10-n and the other of which is input to the power amplifier 8 by switches 11-1, 11-2 ,. A switch 11 formed of −n, a microphone 12 installed at a P position in the space to supplement a sound wave, a low pass filter 13 for removing a high frequency component of a signal from the microphone 12, and a low pass filter. A / D converter 14 (Analog to Digital Converter) for converting the analog signal of the pass filter 13 into a digital signal, and the switches 11-1 and 1 so that the signal from the A / D converter 14 is minimized. A switch controller 15 for switching between 1-2, ..., 11-n.

According to the present embodiment, noise can be controlled by easily adjusting the delay of the sine wave generated by 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 the present invention is intended to make the analog delay device 7 of the first embodiment a digital one, and therefore, an A / D converter 16 connected to the low-pass filter 6 and It has different components including a digital delay unit 17 connected to the A / D converter 16 and a D / A converter 18 connected to the digital delay unit 17 and outputting to the power amplifier 8.

FIG. 5 is a diagram showing a noise control device according to a fourth embodiment of the present invention. The fourth embodiment of the present invention is intended to make the analog delay device 10 of the second embodiment a digital one, and therefore, the A / D converter 16 connected to the low-pass filter 6 is used. , A digital delay unit 17 connected to the A / D converter 16, and a digital delay unit consisting of a plurality of digital delay units 19-1, 19-2, ... 19 and one of them is connected to the output of each of the digital delay devices 19-1, 19-2, ..., 19-n, and the other is connected to the power amplifier 8 by switches 11-1, 11-2 ,. ..., a switch 11 composed of 11-n, a microphone 12 installed at a P position in the space to supplement a sound wave, and a low-pass filter 13 for removing a high frequency component of a signal from the microphone 12. The low-pass filter A / D converter 14 (Analog to Digital Converter) for converting the analog signal of the converter 13 into a digital signal, and the switches 11-1, 11-to minimize the signal from the A / D converter 14. , ..., 11-n are provided, and different components including a switch control unit 15 are provided.

FIG. 6 is a diagram showing a noise control device according to a fifth embodiment of the present invention. A component different from that of the fourth embodiment of FIG. 5 is an adaptive filter 20 configured by an FIR filter for inputting a signal from the low pass filter 6 and outputting it to the D / A converter 18, A coefficient adjusting unit 21 that adjusts the filter coefficient of the adaptive filter 20 so that the signal level from the A / D converter 14 is minimized, and a high frequency component from the D / A converter 18 is removed. The low-pass filter 22. Further, the alternator 1 is an alternating current generator having a variable number of poles, and the number of rotations is detected by the signal from the low-pass filter 6 to switch the number of poles to the noise control device. The part 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 to minimize the signal from the microphone 12.

FIG. 7 is a diagram for explaining the frequency of noise controlled by the pole number control in FIG. As shown in this figure (a), although the primary level is higher than the secondary level at the noise frequency when the engine 100 rotational speed is low, as shown in this figure (b) As the number increases, the secondary noise level may be higher than the primary level. Therefore, in order to change the setting so that the number of poles p is set low when the number of revolutions is low and the number of poles p is increased when the number of revolutions increases, the number of poles of the alternator 1 is changed by the number of poles switching unit 23. Can be switched to further secure the noise effect.

[0016]

[Effect of the device]

 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 by using a sine wave signal of an electromotive force of an alternator provided in the engine to generate a noise caused by the engine. By eliminating the sine wave signal, the sine wave signal that has almost the same waveform as the noise signal is delayed, so the time required for waveform shaping is not required, and the signal processing time can be shortened and signal processing can be performed, which simplifies the configuration. Turn into.

[Brief description of drawings]

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

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

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

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

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

FIG. 6 is a diagram showing 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.

[Explanation of symbols]

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

Claims (6)

[Scope of utility model registration request] 1. A noise control device for observing noise from a noise source and forming a characteristic opposite to that of the noise at the spatial position in order to eliminate noise propagated from the noise source to a certain spatial position. , The sine wave signal of the electromotive force of the alternator (1) provided in the engine (100) is used.
A noise control device, wherein a delay signal from 0) to the spatial position is formed to eliminate noise caused by the engine (100). 2. Noise according to claim 1, comprising either an analog delay (7) or a digital delay (17) for delaying the sinusoidal signal of the alternator (1) to form the delayed 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 delayed 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 that exhibits a muffling effect at the spatial position).
The noise control device according to claim 1, further comprising a switch control section (15) for controlling the operation of the switch (11) based on a signal from the (2). 4. An adaptive filter (20) for inputting the sine wave signal of the alternator (1) and forming a cancellation signal so as to minimize the level of the signal from the microphone (12) exhibiting a silencing effect at the spatial position. , 21). 5. The noise cycle to be eliminated of the engine (100) is adjusted by changing the diameter of the pulley (1-1) of the alternator (1) which receives the rotational driving force from the engine (100). 1. The noise control device according to 1. 6. The noise control device according to claim 1, wherein the number of poles of the alternator (1) is made variable, and the number of poles is changed according to the rotation speed of the engine 100.