JP2934794B2 - 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, when a noise detector is mounted near the exhaust manifold outlet of an internal combustion engine in accordance with a general arrangement to detect a pressure wave of a noise source, not only the temperature change of the external environment but also the high-temperature exhaust gas Since it is exposed, durability becomes a problem. 63-118 mentioned above
Japanese Patent No. 321,321 pays attention to the fact that the frequency of the pressure wave of the exhaust noise increases in proportion to the rotation speed of the internal combustion engine, and detects the angular velocity of the crankshaft with a crank angle sensor and indirectly detects the frequency of the noise pressure wave. You are going to.

However, this cannot be directly applied to an adaptive digital filter. In particular, a slight shift in the phase occurs for each rotation due to the fluctuation of the rotation speed of the internal combustion engine, so that it is difficult to mute the sound based on the detection output of the noise detector. SUMMARY OF THE INVENTION It is an object of the present invention to provide an active cancel muffler that can detect a signal accurately and can surely mute sound by control using an adaptive digital filter.

[0007]

In order to achieve the above object, an active cancel muffler according to the present invention has a pressure wave output opening at an output port of an exhaust sound path including an exhaust pipe of an internal combustion engine, and outputting a compression / dense pressure wave. Means, a pressure wave detecting means arranged near the output port of the exhaust sound path and outputting a signal corresponding to an output pressure wave, and an engine pressure detecting means outputting a signal corresponding to a cylinder pressure fluctuation of the internal combustion engine. An output signal of the pressure wave detecting means, and a transfer function of the adaptive digital filter is identified as a transfer function of the exhaust sound path according to an output signal of the engine pressure detecting means. Filter means for driving and controlling the pressure wave output means.

The active cancel muffler further includes an edge detecting means for outputting an impulse synchronized with a fluctuation in the cylinder pressure of the internal combustion engine based on an output signal of the engine pressure detecting means. It is preferable that the filter means drives and controls the pressure wave output means in accordance with the impulse.

[0009]

When the internal combustion engine starts and rotates, 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. Further, a signal corresponding to the pressure fluctuation generated in the cylinder of the internal combustion engine is output from the engine pressure detecting means. On the other hand, a signal corresponding to the output pressure wave output from the exhaust sound path is detected by the pressure wave detecting means and output to the adaptive digital filter.

In the adaptive digital filter, the transfer function is set so as to be equal to the transfer function of the exhaust sound path based on the output signal of the pressure wave detecting means in response to the output signal of the engine pressure detecting means. A drive signal is output to the wave output means. In response to this drive signal, the pressure wave output means outputs a compression pressure wave to the output port of the exhaust sound path, and the pressure wave of the exhaust sound output from the exhaust sound path is cancelled, so that the exhaust sound disappears.

Further, in the apparatus provided with the edge detecting means, the engine pressure signal is converted into an impulse by the edge detecting means, and an impulse synchronized with the rotation of the internal combustion engine is output to the adaptive digital filter. Then, 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 detecting means in response to the output impulse of the edge detecting means,
In response, a drive signal is output to the pressure wave output means.

[0012]

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. In the vicinity of the outlet of the exhaust pipe 3, a speaker pipe 4 is mounted coaxially with the exhaust pipe 3 so as to surround the outlet, and an actuator 5 composed of an electromagnetic or electrodynamic type speaker and outputting a coarse / dense pressure wave is provided. It is housed in a tube 4. The actuator 5 and the speaker tube 4 constitute a pressure wave output unit according to the present invention. The actuator 5
May be one or more, and the present invention is not limited to an electromagnetic speaker and the like, and the diaphragm may be hydraulically driven by an electromagnetic valve in order to secure high output.

In the vicinity of the outlet of the exhaust pipe 3, the exhaust pipe 3
And a pressure sensor 6 for outputting a signal corresponding to the output pressure wave of the speaker tube 4. The pressure sensor 6 constitutes a pressure wave detecting means according to the present invention. If the pressure sensor 6 is a means for converting a pressure signal into an electric signal, such as a microphone,
Any mode may be used.

On the other hand, the internal combustion engine 1 is provided with an engine pressure sensor 7 for outputting a signal corresponding to a variation in cylinder pressure.
In the engine pressure sensor 7, for example, a strain gauge (not shown) is attached to a bolt (not shown) for fastening a cylinder block of the internal combustion engine 1, and the strain gauge detects a distortion of the bolt caused by a fluctuation in cylinder pressure. It detects and outputs a signal corresponding to the in-cylinder pressure fluctuation. Alternatively, the pressure at the outlet of an exhaust valve (not shown) to the internal combustion engine 1 may be detected. In this case, a strain gauge is attached to the exhaust valve, or a tightening bolt (not shown) of the exhaust manifold 2 is used. It is advisable to attach a strain gauge to (). Thus, the engine pressure sensor 7 having these strain gauges constitutes an engine pressure detecting means according to the present invention. The engine pressure sensor 7 of the present embodiment is connected to an edge detector 8 as an edge detecting means according to the present invention, and outputs an impulse synchronized with the rotation of the internal combustion engine 1 based on a signal input thereto.

The output impulse of the edge detector 8 is supplied to an adaptive digital filter 10. Also, the output signal of the pressure sensor 6 is
1 through the anti-aliasing filter 12
After the aliasing noise, ie, aliasing noise, is suppressed, 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 a multiplier coefficient constituting the digital filter 10f. The transfer function of the digital filter 10f is changed to the exhaust manifold 2 and the exhaust pipe. Each coefficient is set via the adaptive algorithm 10a so as to identify the transfer function of the exhaust sound path of No. 3.

The adaptive digital filter 10 can be realized by being integrated into a circuit using a multiplier, an adder and the like. In this embodiment, as shown in FIG. 2, a digital signal processor (DSP) 10p, a memory 10m, an edge It is realized by the detector 9, the A / 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. Since these are well known, the description is omitted.

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 signal corresponding to the in-cylinder pressure fluctuation of the internal combustion engine 1 is output from the engine pressure sensor 7 to the edge detector 8. This output signal is converted into an impulse by the edge detector 8, and an impulse synchronized with the in-cylinder pressure fluctuation of the internal combustion engine 1 is input to the digital signal processor 10p. According to the impulse, the digital signal is processed in the digital signal processor 10p as described later and a digital signal is output. Then, the output digital signal is converted into an analog signal via a D / A converter 14, smoothed by a smoothing filter 15, amplified by a power amplifier 16, and the actuator 5 is driven.

As a result, a dense pressure wave is formed in the speaker tube 4 and is output so as to surround the exhaust sound pressure wave.
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, amplified through the input amplifier 11, passed through the anti-aliasing filter 12, converted into a digital signal by the A / D converter 13, and then sent to the digital signal processor 10p as an error signal. input. Then, the digital filter 10f is generated by the adaptive algorithm 10a.
The coefficient is updated so that the transfer function of the exhaust manifold 2 and the transfer function of the exhaust sound path of the exhaust pipe 3 are identified.

During this time, the digital signal processor 1
The operation at 0p will be described with reference to FIG. First, in step 101, the system is initialized and each coefficient is cleared. Next, at step 102, an in-cylinder pressure value X based on the output signal of the engine pressure sensor 7 is detected. Proceeding to step 103, the pressure value X is input to the digital filter 10f, and the output value Y is set. Then, in step 104, the output value Y is output to the D / A converter 14. The output value Y is converted into an analog signal by the D / A converter 14, and the actuator 5 is driven based on the output analog signal.

Further, in step 105, the output signal of the pressure sensor 6 is A / D converted and the digital filter 1
At 0f, the A / D conversion value E is read. Then, at step 106, the conversion value E is applied to the adaptive algorithm 10a, the coefficient of the digital filter 10f is updated accordingly, the transfer function is set to be equal to the transfer function of the exhaust sound path, and the process returns to step 102. Thus, the above steps are repeated so that the output of the pressure sensor 6 is minimized.

As described above, since the exhaust sound of the internal combustion engine 1 is mainly composed of the sound of the order component of the explosion,
By inputting an impulse synchronized with the in-cylinder pressure fluctuation of the internal combustion engine 1, sounds of higher order components can be silenced, and the order of the adaptive digital filter 10 is reduced and the structure is simplified. In particular, since it is possible to respond to the exhaust sound having large fluctuations without causing a phase shift, a good sound deadening effect can be obtained.

FIG. 4 shows another embodiment of the present invention.
The A / D converter 13 is used without providing the edge detector 9 as compared with the active cancel muffler of the above-described embodiment. As a result, the circuit configuration becomes as shown in FIG. 5, and the output signals of the engine pressure sensor 7 and the pressure sensor 6 are input in parallel to the multiplexer 17 via the input amplifiers 8, 11 and the anti-aliasing filters 18, 12, respectively. Are sequentially selected here and input to the A / D converter 13. As described above, according to the present embodiment, the digital signal processor 10P can be configured without the edge detector 9 that directly supplies a signal to the digital signal processor 10P, thereby facilitating the manufacture.

[0024]

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 transfer function of the adaptive digital filter is controlled so as to be identified as the transfer function of the exhaust sound path according to the in-cylinder pressure fluctuation of the internal combustion engine.
It is possible to surely mute the exhaust noise that fluctuates greatly.

[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 showing a configuration of an adaptive digital filter according to one embodiment of the present invention.

FIG. 3 is a flowchart illustrating a control operation of the digital signal processor according to one embodiment of the present invention.

FIG. 4 is a block diagram of an active cancel muffler according to another embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an adaptive digital filter according to another 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 Speaker tube (pressure wave output means) 5 Actuator (pressure wave output means) 6 Pressure sensor (pressure wave detection means) 7 Engine pressure sensor ( Engine pressure detecting means) 8 edge detector (edge detecting means) 10 adaptive digital filter (filter means) 10p digital signal processor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01N 1/00

Claims (2)

(57) [Claims] 1. A pressure wave output means which opens at an output port of an exhaust sound path including an exhaust pipe of an internal combustion engine and outputs a compression / dense pressure wave,
A pressure wave detecting means arranged near the output port of the exhaust sound path and outputting a signal corresponding to an output pressure wave; an engine pressure detecting means outputting a signal corresponding to a cylinder pressure fluctuation of the internal combustion engine; A filter for inputting an output signal of the pressure wave detecting means, and controlling the pressure wave so that a transfer function of the adaptive digital filter is identified as a transfer function of the exhaust sound path according to an output signal of the engine pressure detecting means. An active cancel muffler comprising: a filter means for driving and controlling an output means. 2. An edge detecting means for outputting an impulse synchronized with an in-cylinder pressure fluctuation of the internal combustion engine based on an output signal of the engine pressure detecting means, wherein the filter means responds to an output impulse of the edge detecting means. 2. The active cancel muffler according to claim 1, wherein said pressure wave output means is drive-controlled.