JPH0532707U - Active Kyansel Muffler - Google Patents

Abstract

(57) [Abstract] [Purpose] In an active cancellation muffler, the effect of standing waves in the exhaust pipe on the pressure sensor is suppressed, and the exhaust noise of the internal combustion engine is reliably silenced. [Structure] A pressure wave output device 5 for outputting a compressional pressure wave is provided in an exhaust pipe 3, and drive control of this device is performed at least in accordance with a pressure detected by a pressure sensor 6 to silence an exhaust sound. Since the pressure sensor 6 is arranged so that the pressure receiving portion is located in the vicinity of the node of the standing wave formed in the exhaust pipe 3a, the influence of the standing wave is minimized and the pressure sensor 6 A signal corresponding to only the pressure of the combined wave of the pressure wave and the output pressure wave from the pressure wave output device 5 is output.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to an active cancellation muffler mounted on an internal combustion engine, and particularly to a pressure wave output device that outputs a compressional pressure wave in the exhaust pipe, and a pressure that detects the pressure of the combined wave of this output pressure wave and the pressure wave from the exhaust pipe. It concerns an active cancellation muffler equipped with a sensor.

[0002]

[Prior Art]

 As an active cancellation muffler, for example, as described in Japanese Utility Model Publication No. 63-190512, a speaker tube is provided at the outlet of an exhaust pipe, which is a noise outflow pipe, with respect to an internal combustion engine of a noise source. A cancel speaker is connected, and in response to a predetermined control signal from the control means, noise from the internal combustion engine, that is, a compression / dense pressure wave having a phase opposite to the pressure wave of the exhaust sound is output from the cancel speaker to cancel both pressure waves. It is known that the sound is muted by. In this active cancellation muffler, an error detection microphone is used as a device that detects the pressure wave (exhaust sound) from the exhaust pipe and the combined wave of the pressure wave from the speaker, and the forced cooling hand connected to the exhaust pipe is used. It is mounted on a terraced diffuser.

[0003]

[Problems to be solved by the device]

 Like the error detection microphone described in the above publication, the pressure sensor in the active cancellation muffler is generally arranged at the rear of the exhaust pipe. In the above publication, the error detection microphone is arranged behind the confluence of the cancel speaker output into the exhaust pipe, but the mounting position of the error detection microphone is not specified and it can be mounted at any position. Normally, a standing wave exists in the exhaust pipe, and depending on the mounting position, this standing wave may be superimposed on the pressure wave to be detected as noise, and the standing wave is present in the rotation signal of the internal combustion engine. Since they are not synchronized, the muffling effect of the cancel speaker is reduced.

Therefore, an object of the present invention is to provide an active cancellation muffler that suppresses the influence of a standing wave in the exhaust pipe on the pressure sensor and reliably muffles the exhaust sound of the internal combustion engine.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a pressure wave output device for outputting a compressional pressure wave in an exhaust pipe of an internal combustion engine, and a combination of the output pressure wave of the pressure wave output device and the pressure wave from the exhaust pipe. In the active canceller muffler, which is equipped with a pressure sensor for detecting the wave pressure at the pressure receiving part, and drives and controls the pressure wave output device in accordance with the pressure detected by the pressure sensor, the pressure sensor is formed in the exhaust pipe. The pressure receiving portion is arranged near the node of the standing wave.

[0006]

[Action]

 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 to form exhaust sound. On the other hand, the pressure wave output device outputs a coarse and dense pressure wave into the exhaust pipe. The pressure sensor detects the pressure wave from the pressure wave output device and the exhaust sound, that is, the pressure of the combined wave of the pressure waves in the exhaust pipe, and the pressure wave output device is drive-controlled at least according to the detected pressure. Thus, the pressure wave of the exhaust sound is canceled by the dense and dense pressure wave, and the exhaust sound disappears. In this case, since the pressure sensor is arranged so that the pressure receiving part is located near the node of the standing wave formed in the exhaust pipe, the influence of the standing wave is minimized. Outputs a signal substantially corresponding to the pressure of the composite wave.

[0007]

【Example】

 Hereinafter, preferred embodiments of an active cancellation muffler according to the present invention will be described with reference to the drawings. First, referring to FIG. 3 showing the overall configuration of an embodiment of the present invention, an exhaust pipe 3 is connected to an exhaust manifold 2 of an internal combustion engine 1. In the vicinity of the outlet of the exhaust pipe 3, a cylindrical expansion pipe 4 is mounted coaxially with the exhaust pipe 3 so as to surround the outlet thereof. A pressure wave output device 5 that outputs a compressional pressure wave is attached to the expansion pipe 4, and an exhaust pipe 3a coaxial with the exhaust pipe 3 is joined thereto. Therefore, the expansion pipe 4 is provided between the exhaust pipe 3 and the exhaust pipe 3a. The exhaust pipe 3a may be formed integrally with the expansion pipe 4.

The pressure wave output device 5 converts an electric signal into mechanical vibration, and is configured in the same manner as, for example, an electrodynamic type or electromagnetic type speaker. The pressure wave output device 5 may be one or plural, and is not limited to an electrodynamic type, an electromagnetic type speaker or the like, and the vibrating plate may be hydraulically driven to secure a high output.

Then, the pressure of the combined wave of the pressure wave from the exhaust pipe 3 and the output pressure wave of the pressure wave output device 5 is converted to an electric signal and output to a predetermined position of the exhaust pipe 3 a joined to the expansion pipe 4. The pressure sensor 6 is provided. That is, as shown by the broken line in FIG. 1, a standing wave is formed in the exhaust pipe 3a, and the pressure sensor 6 is arranged so that the pressure receiving portion is located near the node.

As shown in FIG. 2, for example, the structure of the pressure sensor 6 of the present embodiment has a bottomed cylindrical case 61, and a diaphragm 62, which is a pressure receiving portion, is arranged at an opening end 61a of the case, and has an annular shape. It is fixed by a retainer 67. The diaphragm 62 is arranged so as to be exposed near the node of the standing wave formed in the exhaust pipe 3a. That is, a flange 61b is formed on the outer periphery of the case 61, and the flange 61b abuts around a mounting hole formed in the exhaust pipe 3a and is joined to the exhaust pipe 3a by a bolt or the like.

The diaphragm 62 of this embodiment is a circular metal diaphragm, and an annular corrugated portion 62a is formed on the peripheral edge thereof as is apparent from FIG. The diaphragm 62 may be a non-metal diaphragm or may be a diaphragm. A small diameter communication hole 62b is formed in the center of the diaphragm 62. That is, the closed space is defined by the diaphragm 62 and the case 61, and the closed space can be communicated with the inside of the exhaust pipe 3a through only the communication hole 62b.

A strain gauge 63 as a strain detecting element is attached to the case 62 side of the corrugated portion 62 a of the diaphragm 62. The strain gauge 63 is an element that utilizes the piezoresistive effect and converts the strain generated in the waveform portion 62a into an electric quantity, and is attached along the curved surface of the waveform portion 62a. Then, it is connected to the pair of terminals 65 via the pair of leads 64. The terminal 65 is planted in a connector 66 and is supported by the case 61 via the connector 66. Then, the strain generated in the corrugated portion 62 a according to the pressure applied to the diaphragm 62 is converted into an electric quantity by the strain gauge 63 and detected through the lead 64 and the terminal 65.

Further, as shown in FIG. 3, a rotation signal detector 9 that outputs a rotation signal synchronized with the rotation of the internal combustion engine 1 is provided. The rotation signal detector 9 detects the rotation of the internal combustion engine 1, such as an ignition signal of the internal combustion engine 1, an output signal of a crank angle sensor (not shown) provided on the crankshaft, and a signal according to the pressure fluctuation in the cylinder. It detects the synchronized rotation signal. As a concrete example, a strain gauge (not shown) is attached to a bolt (not shown) that fastens the cylinder block, and the strain gauge detects the strain of the bolt due to the pressure fluctuation in the cylinder. It can be configured to output a signal according to the internal pressure fluctuation.

The output signal of the rotation signal detector 9 is supplied to the adaptive digital filter 10. This adaptive digital filter 10 is called an adaptive digital filter (ADF), detects information that affects the control system, automatically changes its own control characteristics in response to the change, and is concerned with load changes. Instead, it realizes adaptive control in which the optimum state is achieved.

Further, the output signal of the pressure sensor 6 is amplified through the input amplifier 11, the aliasing noise is blocked by the anti-aliasing filter 12, and then converted into a digital signal by the A / D converter 13. It is configured to be input to the adaptive digital filter 10. Then, 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, and then amplified by the power amplifier 16 to be output to the pressure wave output device 5. It is configured to be supplied as a drive signal.

The adaptive digital filter 10 has a digital filter 10f, and an adaptive algorithm 10a for sequentially controlling the multiplier coefficients constituting the digital filter 10f is configured. The transfer function of the digital filter 10f is the exhaust manifold 2 and the exhaust pipe. Each coefficient is set via the adaptive algorithm 10a so as to be identified with respect to the transfer function of the exhaust sound path of No. 3. Adjusting the former transfer function so that the transfer function of the digital filter becomes equal to the transfer function of the unknown system and the prediction error becomes zero is called “identifying the unknown system”.

The adaptive digital filter 10 can be realized by forming an integrated circuit using a multiplier, an adder, etc., but in the present embodiment, a digital signal processor (not shown), a memory (not shown), a rotation signal This 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. Since these are well known, their description is omitted.

Next, the operation of the active cancellation muffler of this embodiment will be described. When the internal combustion engine 1 starts and rotates, the explosion sound 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 to form exhaust sound. A rotation signal synchronized with the rotation of the internal combustion engine 1 is input from the rotation signal detector 9 to the adaptive digital filter 10. In accordance with this rotation signal, the adaptive digital filter 10 processes it as described later and outputs a digital signal. Then, the output digital signal is converted into an analog signal through the D / A converter 14, smoothed by the smoothing filter 15, amplified by the power amplifier 16, and the pressure wave output device 5 is driven.

Then, the pressure wave output device 5 outputs the coarse and dense pressure waves into the expansion pipe 4 so as to surround the pressure waves of the exhaust sound. That is, both pressure waves are combined so as to cancel each other out. The pressure of this composite wave is detected by the pressure sensor 6, supplied to the input amplifier 11, and amplified. After that, the signal is converted into a digital signal by the A / D converter 13 through the anti-aliasing filter 12, and then input to the adaptive digital filter 10 as an error signal. Then, the adaptive algorithm 10a updates the coefficient so that the transfer function of the digital filter 10f is identified as the transfer function of the exhaust sound path of the exhaust manifold 2 and the exhaust pipe 3.

With respect to the above operation, a standing wave shown by a broken line in FIG. 1 is formed in the exhaust pipe 3a, but the pressure sensor 6 is arranged so that the diaphragm 62 is exposed near the node. The effect of the standing wave is minimal, and it substantially responds only to the pressure of the composite wave synthesized in the expansion tube 4. Thus, in the pressure sensor 6, the diaphragm 62 vibrates according to the pressure of the synthetic wave, and the waveform portion 62a is distorted. This strain is converted into an electric quantity by the strain gauge 63 and supplied to the input amplifier 11 via the lead 64 and the terminal 65. At this time, the exhaust pressure from the exhaust pipe 3, that is, the back pressure is applied to the pressure sensor 6. However, since the change of the back pressure is relatively gentle at several hertz or less, the back pressure is the communication hole 62b. It is also transmitted to the other side of the diaphragm 62 via and is canceled.

[0021]

[Effect of the device]

 Since the present invention is configured as described above, it has the following effects. That is, according to the active cancellation muffler of the present invention, the pressure sensor is disposed so that the pressure receiving portion is located in the vicinity of the node of the standing wave formed in the exhaust pipe. A signal corresponding to only the pressure of the output wave of the device and the combined wave of the exhaust sound is output, so that the exhaust sound can be reliably silenced without being affected by the standing wave noise in the exhaust pipe.

[Brief description of drawings]

FIG. 1 is a sectional view of a pressure sensor mounting portion in an embodiment of an active cancellation muffler of the present invention.

FIG. 2 is a sectional view of a pressure sensor in one embodiment of the active cancellation muffler of the present invention.

FIG. 3 is a block diagram of an active cancellation muffler according to an embodiment of the present invention.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Exhaust Manifold 3, 3a Exhaust Pipe 4 Expansion Pipe 5 Pressure Wave Output Device 6 Pressure Sensor 9 Rotation Signal Detector 10 Adaptive Digital Filter

Claims (1)

[Scope of utility model registration request] 1. A pressure wave output device for outputting a compressional pressure wave into an exhaust pipe of an internal combustion engine, and a pressure of a combined wave of the output pressure wave of the pressure wave output device and the pressure wave from the exhaust pipe at a pressure receiving portion. In an active cancellation muffler that includes a pressure sensor for detecting, and drives and controls the pressure wave output device in accordance with at least the pressure detected by the pressure sensor, the pressure sensor is provided near a node of a standing wave formed in the exhaust pipe. An active canceling muffler, characterized in that the pressure receiving portion is disposed at the position.