JP2939667B2 - Active cancel muffler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active cancel muffler mounted on an internal combustion engine, and more particularly to an active cancel muffler provided with an adaptive digital filter.

[0002]

2. Description of the Related Art As an active cancel muffler,
For example, as described in Japanese Utility Model Laid-Open Publication No. 63-118321, a speaker tube is provided at an outlet of an exhaust pipe as a noise discharge pipe for an internal combustion engine as a noise source, and a cancel speaker is connected to the speaker pipe. In response to the predetermined control signal from, the noise from the internal combustion engine, that is, the pressure wave of the opposite phase to the pressure wave of the exhaust sound is output from the cancellation speaker,
There is known a type in which noise is canceled by a canceling action of both pressure waves. The invention described in this publication focuses on the directional characteristics of the pressure wave from the cancellation speaker.
It simply describes that the arithmetic processing is performed in accordance with the processing conditions predetermined by the PU.

In recent years, an input analog signal is converted into a digital value, processed appropriately by a digital signal processing circuit, converted into an analog signal again, and output. Attention has been paid to a digital filter having a predetermined characteristic.

With this digital filter, information affecting the control system is detected, and its control characteristics are automatically changed in accordance with the change, thereby realizing adaptive control for achieving an optimum state regardless of a change in load. This can be done with adaptive digital filters (adaptive digital filters,
ADF) is being studied for use in various controls. In particular, in the acoustic field, in order to cancel an echo generated through an acoustic path between a speaker and a microphone, use of the acoustic echo canceller to generate and identify a pseudo echo signal substantially equal to the echo has attracted attention. I have. still,
Adjusting the former transfer function so that the transfer function of the adaptive digital filter becomes equal to the transfer function of the unknown system and the prediction error becomes zero is called "identifying the unknown system".

[0005]

In the aforementioned active cancel muffler, the internal combustion engine is a source of exhaust noise, and the exhaust sound path of the exhaust manifold and the exhaust pipe can be called an acoustic path. May be applicable, but there are many problems in consistency with the problems specific to the internal combustion engine, and it is not immediately applicable.

For example, Japanese Utility Model Application Laid-Open No. 63-118321, cited above.
In the system described in Japanese Patent Application Laid-Open Publication No. H10-209, since the exhaust sound is output in synchronization with the rotation of the internal combustion engine, the frequency of the noise pressure wave (exhaust sound) is detected by the crank angle sensor. Since it takes several milliseconds for the signal to be transmitted through the exhaust sound path and output from the outlet of the exhaust pipe, a delay occurs in the input / output signal to the control unit. Therefore, even if a control unit equipped with an adaptive digital filter is used, for example, when the internal combustion engine rotates at a high speed, such as during acceleration / deceleration, and the change in exhaust sound is fast, that is, the fluctuation period of the exhaust sound is short. In such a case, the noise reduction effect is significantly reduced. Moreover,
The delay time in the above-mentioned exhaust sound path is not constant, but constantly fluctuates according to changes in exhaust temperature, exhaust flow speed, exhaust density, and the like.

Accordingly, the present invention provides an active cancel muffler that utilizes an adaptive digital filter and can muffle sound without being affected by the delay of the exhaust sound in the exhaust sound path and the fluctuation of the delay time. The purpose is to do.

[0008]

In order to achieve the above object, an active cancel muffler according to the present invention comprises: an expansion pipe arranged to surround an output port of an exhaust sound path including an exhaust pipe of an internal combustion engine; A pressure wave output unit for outputting a compression / dense pressure wave in the expansion pipe, a pressure detection unit disposed near an output port of the exhaust sound path to output a signal corresponding to the output pressure wave, and synchronized with rotation of the internal combustion engine. Rotation detection means for outputting a signal, delay correction means for detecting a delay time of the exhaust sound transmitted through the exhaust sound path, and correcting the output signal of the rotation detection means to be delayed by the delay time; An output signal of the pressure detection means and an output signal of the rotation detection means corrected through the delay correction means; and a transfer function of the adaptive digital filter is The pressure wave output means so as to identify the transfer function of the path is obtained and a filter means for controlling the drive.

The active cancel muffler delay correction means corrects the output signal of the rotation detection means so as to be delayed by a predetermined delay time, and sets the delay time corresponding to the operating state of the internal combustion engine in advance. The delay time stored in the storage means is selected according to the operating state of the internal combustion engine, and the delay time of the delay means is updated and set.

[0010]

In the above active cancel muffler, when the internal combustion engine is started and rotated, an explosion sound generated in response to an explosion in each cylinder is transmitted through an exhaust sound path including an exhaust pipe to form an exhaust sound. Then, a signal synchronized with the rotation of the internal combustion engine is output from the rotation detecting means. The output signal of the rotation detecting means is corrected by the delay correcting means so as to be delayed by the delay time of the exhaust sound, and is supplied to the filter means. On the other hand, a signal corresponding to the output pressure wave output from the exhaust sound path is detected by the pressure detection means and output to the filter means.

The filter means responds to the output signal of the rotation detecting means corrected through the delay correcting means, and based on the output signal of the pressure detecting means, changes the transfer function of the adaptive digital filter to the transfer function of the exhaust sound path. The drive signals are set to be equal to each other, and a drive signal is output to the pressure wave output means accordingly. The compression wave is output from the pressure wave output means to the output port of the exhaust sound path in response to the drive signal, and the pressure wave of the exhaust sound output from the exhaust sound path is canceled, so that the exhaust sound is reduced.

In the delay correction means having the delay means and the storage means, a delay time corresponding to the operation state of the internal combustion engine is stored in the storage means in advance, and the delay time is stored in the storage means in accordance with the operation state of the internal combustion engine. The stored delay time is selected,
The delay time of the delay means is updated and set. Then, the output signal of the rotation detecting means is delayed by a predetermined delay time by the delay means and supplied to the filter means.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the active cancel muffler according to the present invention will be described below 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 1. Therefore, an exhaust sound path is constituted by the exhaust manifold 2 and the exhaust pipe 3 for the internal combustion engine 1 which is an exhaust sound source. An expansion pipe 4 is mounted near the outlet of the exhaust pipe 3 so as to be coaxial with the exhaust pipe 3 and surrounds the outlet, and an actuator 5 is accommodated in the expansion pipe 4. The actuator 5 constitutes the pressure wave output means according to the present invention, and is composed of an electrodynamic or electromagnetic speaker, and outputs a compression / decompression pressure wave. The number of the actuators 5 may be one or more.
Further, the diaphragm is not limited to the electrodynamic type speaker, and may be configured to hydraulically drive the diaphragm in order to secure high output.

In the vicinity of the outlet of the exhaust pipe 3, a pressure sensor 6 for outputting a signal corresponding to the output pressure wave of the exhaust pipe 3 and the expansion pipe 4 is provided. The pressure sensor 6 constitutes a pressure detecting means according to the present invention, and may be in any form as long as it is means for converting a pressure signal into an electric signal such as a microphone.

The internal combustion engine 1 is provided with a control device 9 for controlling its operation, and various data indicating the intake air amount, the fuel injection amount, the engine speed, the exhaust temperature and the like of the internal combustion engine 1 are inputted. The fuel injection amount and the like are set in accordance with the calculation result calculated based on these, and the internal combustion engine 1 is operated in a desired state. Since this is well known, detailed description is omitted.

A rotation signal detector 7 for outputting a rotation signal synchronized with the rotation of the internal combustion engine 1 constitutes a rotation detecting means according to the present invention. For example, an ignition signal of the internal combustion engine 1 and a crank angle provided on a crankshaft are provided. An output signal of a sensor (not shown),
It detects a rotation signal synchronized with the rotation of the internal combustion engine 1, such as a signal corresponding to a fluctuation in cylinder pressure. As a specific example, a strain gauge (not shown) is attached to a bolt (not shown) for fastening the cylinder block, and the strain gauge detects the distortion of the bolt caused by the fluctuation in the pressure in the cylinder. It can be configured to output a signal corresponding to the internal pressure fluctuation.

The output signal of the rotation signal detector 7 is configured to be input to an adaptive digital filter 10 via a delay correction device 8. As shown in FIG. 2, the delay correction device 8 has a central processing unit (hereinafter, referred to as a CPU) 8a constituting a storage means and a digital delay 8b serving as a delay means, and according to a delay time set by the CPU 8a, The signal supplied from the rotation signal detector 7 to the adaptive digital filter 10 is delayed by the digital delay 8b.

The digital delay 8b reads out the data at intervals of a predetermined time, sequentially stores the data, and when outputting data exceeding the allowable storage amount, delays the data by the time of the product of the interval time and the number of stored data. The description is omitted because the configuration is well known. Thus, the delay time can be set to a desired value by appropriately changing the number of data stored at this time.

In the CPU 8a, the delay time of the exhaust sound corresponding to various operating states of the internal combustion engine 1 is stored in advance as so-called map data M. In addition, the data A of the intake air amount, the data F of the fuel injection amount, the data R of the engine speed, the data T of the exhaust gas temperature and the like are inputted to the CPU 8a via the control device 9, and these data are inputted. , The map data M is referred to, and a delay time according to the operating state of the internal combustion engine 1 at that time is set.

The output signal of the pressure sensor 6 is supplied to an input amplifier 11
, And after aliasing noise is prevented by the anti-aliasing filter 12, the signal is converted into a digital signal by the A / D converter 13 and input to the adaptive digital filter 10. . The output digital signal of the adaptive digital filter 10 is converted into an analog signal by the D / A converter 14, smoothed by the smoothing filter 15, amplified through the power amplifier 16, and supplied to the actuator 5 as a drive signal. It is configured to:

The adaptive digital filter 10 has a digital filter 10f, and an adaptive algorithm 10a for sequentially controlling coefficients of a multiplier constituting the digital filter 10f. The transfer function of the digital filter 10f is changed to the exhaust manifold 2 and the exhaust filter. Each coefficient is set via the adaptive algorithm 10a so as to identify the transfer function of the exhaust sound path of the pipe 3.

The above-mentioned adaptive digital filter 10 can be realized by forming an integrated circuit using a multiplier, an adder, etc. In this embodiment, as shown in FIG. 3, a digital signal processor (DSP) 10p, a memory 10m,
The filter function is realized by the / D converter 13 and the D / A converter 14, and the filter function can be easily changed by changing the program. The memory 10m may be built in the digital signal processor 10p.

Next, the operation of the active cancel muffler of this embodiment will be described. When the internal combustion engine 1 starts and rotates, an explosion sound generated in response to an explosion in each cylinder is transmitted through an exhaust sound path of the exhaust manifold 2 and the exhaust pipe 3 to form an exhaust sound. Therefore, the exhaust sound is mainly constituted by the sound of the exponent order component. Further, a rotation signal synchronized with the rotation of the internal combustion engine 1 is output from the rotation signal detector 7. This rotation signal is corrected via the delay correction device 8 and input to the digital signal processor 10p shown in FIG.

In the CPU 8a of the delay correction device 8,
A predetermined delay time is selected based on map data M stored in advance according to the current operating state of the internal combustion engine 1,
The delay time of the digital delay 8b is updated and set.
The output rotation signal of the rotation signal detector 7 is delayed by the delay time set in this way, and the digital signal processor 10p performs processing as described later according to the delayed rotation signal, and outputs a digital signal. This output digital signal is converted to an analog signal via a D / A converter 14, smoothed by a smoothing filter 15, amplified by a power amplifier 16, and
Is driven.

The expansion tube 4 is moved by the actuator 5.
A pressure wave is formed in the inside and is output so as to surround the pressure wave of the exhaust sound. That is, both pressure waves are combined and output so as to cancel each other. This output pressure wave is detected by the pressure sensor 6 and amplified via the input amplifier 11, and is output as an error signal to the anti-aliasing filter 1.
After that, the signal is input to the A / D converter 13.

In the adaptive digital filter 10, the adaptive algorithm 10 is used in accordance with the rotation signal corrected by the delay correction device 8 and the output signal of the pressure sensor 6.
The coefficient of the transfer function of the digital filter 10f is updated by a, and the transfer function is controlled so as to be identified as the transfer function of the exhaust sound path of the exhaust manifold 2 and the exhaust pipe 3. That is, control is performed so that the output of the pressure sensor 6 is minimized.

The operation of the delay correction device 8 during this time will be described in detail with reference to FIG. First, in step 101, the control device 9 determines whether or not data such as the data A of the intake air amount can be transmitted to the CPU 8a. That is, in steps 102 to 105, data A of the intake air amount to the internal combustion engine 1, data F of the fuel injection amount to the internal combustion engine 1, data T indicating the temperature of the exhaust gas from the exhaust pipe 3, and The data R of the number of revolutions is
8a. Subsequently, in step 106, the map data M is referred to based on these input data, and a delay time according to the driving state at that time is set.
Then, in step 107, the delay time is output to the digital delay 8b, and the output signal of the rotation signal detector 7 is delayed according to the delay time.

As described above, in the present embodiment, between the rotation signal detector 7 and the adaptive digital filter 10,
Since the delay correction device 8 is interposed, the exhaust pipe 3 is also protected against exhaust noise when the internal combustion engine 1 rotates at a high speed such as during acceleration / deceleration.
A good silencing effect can be obtained without being affected by the delay within and the delay time.

In the above embodiment, the delay correction means according to the present invention has a delay means and a storage means, and the delay time of the exhaust sound can be detected indirectly. The delay correction device 8 may be configured to directly detect the delay time of the exhaust sound and correct the rotation signal.

[0030]

Since the present invention is configured as described above, the following effects can be obtained. That is, according to the active cancel muffler of the present invention, the rotation signal synchronized with the rotation of the internal combustion engine is corrected by the delay correction means so as to be delayed by a predetermined delay time, for example, according to the operating state of the internal combustion engine. The control by the adaptive digital filter is performed using a transfer function set in accordance with the output signal of the internal combustion engine and the output signal of the pressure detection means. Irrespective of the delay and the fluctuation of the delay time.

[Brief description of the drawings]

FIG. 1 is a block diagram of an active cancel muffler according to one embodiment of the present invention.

FIG. 2 is a block diagram of a delay correction device according to one embodiment of the present invention.

FIG. 3 is a block diagram of a configuration for realizing an adaptive digital filter according to an embodiment of the present invention.

FIG. 4 is a flowchart illustrating a control operation of the delay correction device according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust manifold (exhaust sound path) 3 Exhaust pipe (exhaust sound path) 4 Expansion pipe 5 Actuator (pressure wave output means) 6 Pressure sensor (pressure detecting means) 7 Rotation signal detector (rotation detecting means) 8 Delay Correction device (delay correction means) 10 Adaptive digital filter (filter means) 10p Digital signal processor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-168913 (JP, A) JP-A-3-31039 (JP, A) JP-A-3-50998 (JP, A) JP-A-4- 358712 (JP, A) JP-A 63-118321 (JP, U) JP-A 2-86297 (JP, U) JP-T 2-503219 (JP, A) (58) Fields surveyed (Int. Cl. ⁶ , DB name) F01N 1/00 G10K 11/16

Claims (2)

(57) [Claims] 1. An expansion pipe arranged to surround an output port of an exhaust sound path including an exhaust pipe of an internal combustion engine, pressure wave output means for outputting a compression / dense pressure wave in the expansion pipe, and the exhaust sound path. Pressure detection means arranged near the output port of the engine for outputting a signal corresponding to the output pressure wave, rotation detection means for outputting a signal synchronized with the rotation of the internal combustion engine, and exhaust gas transmitted through the exhaust sound path A delay correcting means for detecting a sound delay time and correcting the output signal of the rotation detecting means so as to be delayed by the delay time; and an adaptive digital filter, wherein the output signal of the pressure detecting means and the delay correcting means are Filter means for driving and controlling the pressure wave output means so as to input the output signal of the rotation detection means corrected through the filter and to identify the transfer function of the adaptive digital filter as the transfer function of the exhaust sound path. An active cancel muffler characterized by comprising: 2. The delay correcting means corrects the output signal of the rotation detecting means so as to be delayed by a predetermined delay time, and sets and stores in advance the delay time corresponding to the operating state of the internal combustion engine. 2. A delay unit according to claim 1, further comprising a storage unit configured to select a delay time stored in the storage unit and update and set the delay time of the delay unit according to an operation state of the internal combustion engine. Active cancel muffler.