JPH04203408A - Active cancel muffler - Google Patents

Abstract

PURPOSE:To eliminate certainly noise in every cylinder by selecting transfer function data corresponding to each cylinder in order in every cylinder of an internal combustion engine according to the output rotational signal of a rotation detecting means, and setting transfer function of an adaptive digital filter. CONSTITUTION:Transfer function responding to output impulse of an edge detecting means 8 by an adaptive digital filter 10 is set on the basis of the output signal of a pressure wave detecting means 6 so as to equalize the transfer function with transfer function of exhaust noise passages 2, 3, and driving signal is outputted to a pressure wave outputting means 5 according thereto. Compression wave is outputted from the pressure wave outputting means 5 to outlets of the exhaust noise passages 2, 3 according to the driving signal so as to break away pressure wave of exhaust noise outputted from the exhaust noise passages 2, 3. In this case, transfer function of the adaptive digital filter 10 is set in every cylinder in which exhaust noise is generated out of respective cylinders in an internal combustion engine 1, according to the output rotational signal of a rotation detecting means 7. It is thus possible to eliminate noise pertinently in every cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active cancellation muffler installed in an internal combustion engine, and more particularly to an active cancellation muffler equipped with an adaptive digital filter.

[Prior art] As an active cancellation muffler, for example, the
As described in Japanese Patent No. 3-118321, a speaker pipe is provided at the exit of an exhaust pipe serving as a noise outflow pipe for an internal combustion engine that is a noise source, a canceling speaker is connected to this speaker pipe, and a predetermined signal from a control means is provided. It is known that, in response to a control signal, a canceling speaker outputs a compression wave having a phase opposite to the pressure wave of the noise from the internal combustion engine, that is, the exhaust sound, and the sound is muffled by the canceling action of both pressure waves. The idea described in the publication focuses on the directional characteristics of pressure waves from a canceling speaker, and the active cancellation control means performs arithmetic processing on various input information by a CPU according to predetermined processing conditions. It is only briefly explained.

By the way, recently, an input analog signal is converted into a digital quantity, processed appropriately in a digital signal processing circuit, and then converted back into an analog signal and output, and a predetermined characteristic is established between the input analog signal and the output analog signal. Digital filters that provide

This digital filter detects information that affects the side system and automatically changes its own control characteristics in response to changes in the information, realizing adaptive control that maintains the optimal state regardless of changes in load. This is called an adaptive digital filter (ADF), and its use for various controls is being studied. In particular, in the field of acoustics, in order to eliminate echoes generated through the acoustic path between a speaker and a microphone, attention has been paid to their use in acoustic echo cancellers that generate and identify pseudo-echo signals that are approximately equal to the echoes. There is. Note that adjusting the transfer function of the adaptive digital filter so that it is equal to the transfer function of the unknown system and the prediction error becomes zero is called "J to identify the unknown system."

[Problems to be Solved by the Invention] In the above-described active canceling muffler, the internal combustion engine is the source of exhaust noise, and the exhaust sound path of the exhaust manifold and exhaust pipe can be called an acoustic path. However, there are many problems in compatibility with the problems specific to internal combustion engines, and it is not immediately applicable. For example, if a noise detector is mounted near the exhaust manifold outlet of an internal combustion engine in accordance with the general arrangement to detect pressure waves from the noise source, it is necessary to detect not only temperature changes in the external environment but also high-temperature exhaust gas. Durability is an issue as it will be exposed. The above-mentioned Japanese Utility Model Application Publication No. 63-118321 focuses on the fact that the frequency of the pressure wave of exhaust noise increases in proportion to the rotation speed of the internal combustion engine, and indirectly detects the angular velocity of the crankshaft using a crank angle sensor. The purpose is to detect the frequency of noise pressure waves. However, this cannot be directly applied to an adaptive digital filter.

Furthermore, the exhaust noise of the internal combustion engine has a correlation for each cylinder as shown in FIG. 6 (in FIG. 6, #1 to #4 indicate cylinder numbers). For this reason, when an adaptive digital filter is used in an active cancellation muffler, it is difficult to muffle the noise by only ill m corresponding to the rotation of the internal combustion engine.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an active canceling muffler that uses an adaptive digital filter and can reliably muffle exhaust noise of an internal combustion engine without being affected by differences between cylinders.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a pressure wave output means that opens at an output port of an exhaust sound path including an exhaust pipe of an internal combustion engine and outputs a compression wave. a pressure wave detection means disposed near the output port of the sound path and outputting a signal corresponding to the output pressure wave; a rotation detection means outputting a rotation signal corresponding to the rotation of the internal combustion engine; and an output rotation of the rotation detection means. It has edge detection means that outputs an impulse synchronized with the rotation of the internal combustion engine based on the signal, and an adaptive digital filter, and the output rotation signal of the rotation detection means is determined from transfer function data of the same number as the number of cylinders of the internal combustion engine. Accordingly, the transfer function data corresponding to each cylinder of the internal combustion engine is selected sequentially to set the transfer function of the adaptive digital filter, and the output signal of the pressure wave detection means is inputted to the edge detection means. The filter means drives and controls the pressure wave output means so that the transfer function of the adaptive digital filter is identified with the transfer function of the exhaust sound path according to an output impulse.

In the active cancel muffler, the filter means includes the same number of adaptive digital filters as the number of cylinders of the internal combustion engine, and the filter means sequentially detects each cylinder of the internal combustion engine in accordance with the output rotation signal of the rotation detection means. The pressure wave output means may be driven and controlled by selecting an adaptive digital filter corresponding to the pressure wave output means.

[Operation] When the internal combustion engine starts and rotates, the explosion sound generated in response to the explosion in each cylinder is transmitted through the exhaust sound path including the exhaust pipe, and an exhaust sound is formed. Further, a rotation signal corresponding to the rotation of the internal combustion engine is output from the rotation detection means to the edge detection means. The edge detection means converts the rotation signal into an impulse, and the impulse synchronized with the rotation of the internal combustion engine is output to the adaptive digital filter. On the other hand, a signal corresponding to the output pressure wave output from the exhaust sound path is detected by the pressure wave detection means and output to the adaptive digital filter.

In the adaptive digital filter, the transfer function is set to be equal to the transfer function of the exhaust sound path based on the output signal of the pressure wave detection means in response to the output impulse of the edge detection means, and the pressure wave output means is set to be equal to the transfer function of the exhaust sound path. A drive signal is output to.

In response to this drive signal, a compression wave is output from the pressure wave output means to the output port of the exhaust sound path, and the pressure wave of the exhaust sound output from the exhaust sound path is canceled out, causing the exhaust sound to disappear. In this case, transfer function data corresponding to each cylinder of the internal combustion engine is sequentially selected, or an adaptive digital filter corresponding to each cylinder is selected, and the transfer function of the adaptive digital filter is set. In other words, the transfer function of the adaptive digital filter is set for each cylinder of the internal combustion engine that generates the self-exhausted low noise according to the output rotation signal of the rotation detection means, so that an appropriate silencing effect can be applied to each cylinder. will be held.

[Embodiments] Hereinafter, preferred embodiments of the active cancellation muffler according to the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which an exhaust pipe 3 is connected to an exhaust manifold 2 of an internal combustion engine l. Therefore, for the internal combustion engine 1 which is the exhaust sound source, the exhaust manifold 2
The exhaust pipe 3 constitutes an exhaust sound path. Near the exit of the exhaust pipe 3, a speaker pipe 4 is installed coaxially with the exhaust pipe 3 and surrounding the exit, and an actuator 5, which is an electromagnetic or electrodynamic speaker and outputs a compression pressure wave, is installed as a speaker. It is housed within the tube 4. These actuator 5 and speaker tube 4 constitute pressure wave output means according to the present invention. The actuator 5 may be one or more, and is not limited to an electromagnetic speaker or the like, and may be configured to hydraulically drive the diaphragm using an electromagnetic valve to ensure high output.

Further, near the exit of the exhaust pipe 3, there is a pressure sensor 6 that outputs a signal corresponding to the output pressure waves of the exhaust pipe 3 and the speaker pipe 4.
Or is provided. This pressure sensor 6 constitutes the pressure wave detecting means according to the present invention, and may be of any type as long as it is a means for converting a pressure signal into an electrical signal, such as a microphone.

On the other hand, the internal combustion engine 1 is provided with a rotation signal detector 7 that outputs a pulse signal synchronized with the rotation of the engine. This rotation signal detector 7 constitutes the rotation detecting means according to the present invention, and is provided facing a rotary plate (not shown) that rotates in synchronization with the internal combustion engine 1, for example, and is arranged to face a rotary plate (not shown) that rotates in synchronization with the internal combustion engine 1. Although the sensor is a well-known detector such as an electromagnetic induction pickup that outputs an electric signal, an ignition signal from a well-known ignition signal generator (not shown) may be used as the rotation signal. An edge detector 8, which is edge detection means according to the present invention, is connected to the rotation signal detector 7, and an impulse synchronized with the rotation of the internal combustion engine l is output based on the rotation signal input thereto.

The output impulses of the edge detector 8 are arranged to be fed to an adaptive digital filter IO. Further, the output signal of the pressure sensor 6 is amplified via an input amplifier 11, converted to a digital signal by an A/D converter 12, and inputted to an adaptive digital filter 10. The output digital signal of the adaptive digital filter IO is converted into an analog signal by a D/A converter 13, amplified via a power amplifier 14, and supplied to the actuator 5 as a drive signal.

The adaptive digital filter IO is the digital filter 10
f, and sequentially controls the multiplier coefficients constituting the multiplier coefficient] Oa is configured, and the transfer function of the digital filter IOf is the transfer function of the exhaust sound path of the exhaust manifold 2 and the exhaust pipe 3. Each coefficient is set via an adaptive algorithm loa to identify the respective coefficients.

In this embodiment, the number of cylinders of the internal combustion engine l (for example, 4 cylinders)
The same number of transfer function data H1 to H4 are prepared, and - among them is appropriately selected as described later.

The above-mentioned adaptive digital filter IO can be realized by making it into an integrated circuit using multipliers, adders, etc., but in this embodiment, as shown in FIG.
The filter function can be easily changed by changing the program. oscillator 10s
is used for sampling, and the memory lOm may be built in the digital signal processor 10p. Note that since these are well known, their explanation will be omitted.

Furthermore, the digital signal processor IOp includes a cylinder counter IOc that is driven according to the output of the edge detector 8.
is connected, and the transfer function of the digital filter 10f is set according to the value of the cylinder counter IOc. Note that a counter program for the cylinder counter IOc may be provided in the program of the digital signal processor IOp.

Next, the operation of the active cancel muffler of this embodiment will be explained. When the internal combustion engine 1 starts and rotates, the explosion noise generated in response to the explosion in each cylinder is transmitted through the exhaust sound path of the exhaust manifold 2 and the exhaust pipe 3, forming an exhaust sound. Therefore, the exhaust sound is mainly composed of the harmonic components of the explosion. Further, a rotation signal corresponding to the rotation of the internal combustion engine is outputted from the rotation signal detector 7 to the edge detector 8. The edge detector 8 converts the rotation signal into an impulse, and the impulse synchronized with the rotation of the internal combustion engine 1 is input to the digital signal processor IOp. In response to this impulse, the digital signal processor lQp
The signal is processed in the manner described later and a digital signal is output. Then, the output digital signal is converted into an analog signal via the D/A converter 13, and then amplified by the power amplifier 14, and the actuator 5 is driven.

As a result, a compression wave is formed in the speaker tube 4, and is output so as to surround the pressure wave of the exhaust sound. That is, both pressure waves are combined and output so that they cancel each other out. This output pressure wave is detected by the pressure sensor 6, amplified via the input amplifier 11, converted into a digital signal by the A/D converter 12, and then inputted as an error signal to the digital signal processor 10p. Then, the adaptive algorithm 10a updates the coefficients so that the transfer function of the digital filter 10f is identified with the transfer function of the exhaust sound path of the exhaust manifold 2 and the exhaust pipe 3.

The operation of the digital signal processor lOp during this time will be explained with reference to FIG. First, step 10
At 0, the cylinder counter 10c is reset to 0 as an initial condition. Next, in step 101, it is determined whether or not it is the conversion timing according to the sampling signal of the oscillator 10s, and if it is the conversion timing, step 10
2, it is determined whether or not there is an input from the edge detector 8. When an edge is detected, that is, when there is an impulse input, the cylinder counter 10c is incremented by 1 in step 103. And step 1
At step 04, it is determined whether or not the value of the cylinder counter 10c is less than or equal to the number of cylinders of the internal combustion engine l. If it is determined that the value exceeds the number of cylinders, the value of the cylinder counter 10c is set to 1 at step 105, and step Proceed to step 106. Cylinder counter lOC
If the value is less than or equal to the number of cylinders of the internal combustion engine l, the process directly proceeds to step +06.

In step 106, transfer function data (for example, H) corresponding to the value (for example, 2) of the cylinder counter 10c is selected, and in step +07, 1 is input to the digital filter IOf.Meanwhile, in step 102, the output impulse is If it is determined that there is no
8, "0" is input to the digital filter 10f. Therefore, a transfer function is calculated according to the former "l" signal, and in step 109 the digital filter 10
A digital signal is output from f.

Note that this output digital signal is converted into an analog signal by the D/A converter 13, and the actuator 5 is driven by the output analog signal.

Further, in step 110, the output signal of the pressure sensor 6 is A/D converted and input as a digital signal to the digital filter 10f, and in step 111, the coefficients of the digital filter 10f are updated according to the adaptive algorithm 10a, and the transfer function is It is set to be equal to the transfer function of the sound path, and the process returns to step 101. In this way, the above steps are repeated so that the output of the pressure sensor 6 is minimized.

As mentioned above, the exhaust sound of the internal combustion engine 1 is mainly composed of the sound of the harmonic component of the explosion, so by inputting an impulse synchronized with the rotation of the internal combustion engine 1, the sound of the high harmonic component can be extracted. In addition, the order of the adaptive digital filter IO can be reduced and the structure can be simplified. Moreover, since the transfer function of the digital filter IOf set for each cylinder that generates the exhaust sound of the internal combustion engine l is controlled to be identified with the transfer function of the exhaust sound path, it will affect the difference in exhaust sound for each cylinder. The silencing effect can be performed in an optimal state without being affected.

FIG. 4 is a block diagram showing another embodiment of the present invention, in which, for example, four adaptive digital filters +01 to +104, the same number as the number of cylinders of a four-cylinder internal combustion engine l, are provided, and edge detectors 81 to 104 are provided, respectively. 84 is connected. Also, between the rotation signal detector 7 and the edge detectors 81 to 84, and between the input amplifier 11 and the adaptive digital filters 101 to 1
04, decoders 15 and 16 are respectively interposed. The rest of the configuration is the same as that of the embodiment shown in FIG. 1, so a description thereof will be omitted.

According to this embodiment, one of the edge detectors 81 to 84 is sequentially selected according to the output signal of the rotation signal detector 7, and one of the adaptive digital filters 101 to 104 is selected based on the output impulse. The actuator 5 is driven and controlled so that the transfer function of one of the adaptive digital filters is identified as the transfer function of the exhaust sound path. Regarding this embodiment, the operation when the internal combustion engine 1 has two cylinders is shown in the flowchart of FIG. In this figure, the same step numbers are given to the same processes as in the flowchart of FIG. 3. Here, the same process as step 103 is performed in step 112, and step 113 or step 1
14, "1" is input to the digital filter corresponding to the value of the cylinder counter 10c, or "0" is input to the digital filter corresponding to the value of the cylinder counter lOC.
is input.

[Effects of the Invention] Since the present invention is configured as described above, it produces the effects described below.

That is, according to the active cancellation muffler of the present invention,
Since the transfer function of the adaptive digital filter is controlled to be identified with the transfer function of the exhaust sound path using an impulse response synchronized with the rotation of the internal combustion engine, sound can be reliably silenced with a simple configuration.

Moreover, since the transfer function of the digital filter set for each cylinder that generates the exhaust sound of the internal combustion engine is controlled so as to be identified with the transfer function of the exhaust sound path, it is not affected by differences in exhaust sound for each cylinder. It is possible to ensure an optimal sound deadening effect without any noise.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an active cancellation muffler according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of an adaptive digital filter, and FIG. 3 is a flowchart showing the control operation of the digital signal processor. ,
FIG. 4 is a block diagram of an active cancellation muffler according to another embodiment of the present invention, FIG. 5 is a flowchart showing the control operation of the digital signal processor, and FIG. 6 is a characteristic diagram of exhaust sound of an internal combustion engine. . 1... Internal combustion engine. 2...Exhaust manifold (exhaust sound path). 3...Exhaust pipe (exhaust sound path). 4...Speaker tube (pressure wave output means). 5...actuator (pressure wave output means). 6...Pressure sensor (pressure wave detection means). 7... Rotation signal detector (rotation detection means). 8... Edge detector (edge detection means).

Claims (2)

[Claims] (1) A pressure wave output means that is opened at an output port of an exhaust sound path including an exhaust pipe of an internal combustion engine and outputs a compression wave; pressure wave detection means for outputting a pressure wave; rotation detection means for outputting a rotation signal corresponding to the rotation of the internal combustion engine; and edge detection for outputting an impulse synchronized with the rotation of the internal combustion engine based on the output rotation signal of the rotation detection means. and an adaptive digital filter, which sequentially generates a transfer function corresponding to each cylinder of the internal combustion engine according to the output rotation signal of the rotation detection means, from the same number of transfer function data as the number of cylinders of the internal combustion engine. Select data to set the transfer function of the adaptive digital filter, input the output signal of the pressure wave detection means, and set the transfer function of the adaptive digital filter in accordance with the output impulse of the edge detection means. filter means for driving and controlling the pressure wave output means so as to identify the transfer function of the active cancel muffler. (2) A pressure wave output means that is opened at an output port of an exhaust sound path including an exhaust pipe of an internal combustion engine and outputs a compression wave; pressure wave detection means for outputting a pressure wave; rotation detection means for outputting a rotation signal corresponding to the rotation of the internal combustion engine; and edge detection for outputting an impulse synchronized with the rotation of the internal combustion engine based on the output rotation signal of the rotation detection means. and a number of adaptive digital filters equal to the number of cylinders of the internal combustion engine, and selecting an adaptive digital filter corresponding to each cylinder of the internal combustion engine sequentially for each cylinder in accordance with an output rotation signal of the rotation detection means. Setting the transfer function of the adaptive digital filter, inputting the output signal of the pressure wave detection means, and identifying the transfer function of the adaptive digital filter as the transfer function of the exhaust sound path according to the output impulse of the edge detection means. an active canceling muffler comprising filter means for driving and controlling the pressure wave output means so that the pressure wave output means is driven and controlled.