JPH0658129A - Active silencer - Google Patents

Abstract

PURPOSE:To stabilize a sound transfer characteristic between an acoustic wave output device and residual noise detector so as to ensure silencing performance in favorable conditions, in an active silencer. CONSTITUTION:An active silencer is provided in such constitution that an acoustic wave output device 5 and a residual noise detector 6 are provided in a housing 40 arranged in the vicinity of the outlet of the exhaust pipe 3 of an internal combustion engine 1, acoustic wave of antiphase outputted from the acoustic wave output device 5 is made to interfere with exhaust noise from the exhaust pipe 3, and the acoustic wave output device 5 is driven according to a signal detected by the residual noise detector 6 so as to carry out silencing. The acoustic wave output device 5 is enclosed, and also opening part is formed apart for a specified distance from the acoustic wave output device 5 in acoustic wave output direction. The residual noise detector 6 is arranged in the vicinity of the opening port part of the housing 40, and the exhaust pipe 3 is curve- firmed so that the outlet end part of the exhaust pipe 3 is positioned in an axial line connecting the opening port part and the wave output device 5 to each other, and the exhaust pipe 3 is installed in the housing 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active silencer mounted on an internal combustion engine, and in particular, it is provided with a sound wave output device for outputting a sound wave having a phase opposite to the exhaust sound from an exhaust pipe, and the sound deadening is performed by the interference effect of the sound waves. The present invention relates to an active silencer for performing.

[0002]

2. Description of the Related Art Recently, attention has been paid to an active silencer that actively silences sound by interfering sound waves with the exhaust sound of an internal combustion engine. For example, as described in Japanese Utility Model Application Laid-Open No. 63-118321, a speaker is provided in an exhaust pipe which is a noise outflow pipe for an internal combustion engine which is a noise source, and noise from the internal combustion engine is generated according to a predetermined control signal from the control means. That is, it is known that a compression pressure wave having a phase opposite to that of the exhaust sound, that is, a sound wave is output from a speaker, and the sound is canceled by the canceling action of both sound waves. Also,
Japanese Patent Publication No. 2-503219 discloses a structure of an exhaust muffler device in an active sound reduction system. That is, the speaker is provided symmetrically with respect to the axis of the exhaust pipe, and the annular chamber surrounding the exhaust pipe is formed as an anti-noise chamber.

[0003]

In any of the devices described in the above publications, the output sound wave of the speaker is reflected by the wall surface of the bent tube or the wall surface of the anti-noise chamber, and becomes a reflected sound of various characteristics and exhausted. It will be transmitted to the microphone near the exit of the tube.

4 and 5 show general arrangement examples of the speaker SP with respect to the exhaust pipe EX similarly to the devices described in the above publications. In these arrangement examples, sound waves output from the speaker SP are shown. Only part of the direct microphone MC
Is configured to be able to enter. In FIG.
A housing H1 is provided so as to surround the outlet of the exhaust pipe EX, and a speaker SP is arranged so as to output a sound wave in a direction orthogonal to the axis of the exhaust pipe EX. In the housing H1, an enclosure E1 is formed behind the speaker SP, and a mixer M1 including the front of the speaker SP and the outlet of the exhaust pipe EX is formed.
Further, in FIG. 5, a speaker SP is arranged so as to output a sound wave in a direction parallel to the axis of the exhaust pipe EX. In the housing H2 provided in the exhaust pipe EX, an enclosure E2 is formed behind the speaker SP, and a mixer M2 including the front of the speaker SP and the outlet of the exhaust pipe EX is formed. The opening of the mixer M2 is an exhaust pipe E
Although it has a diameter slightly larger than X, it has a diameter smaller than the main body of the housing H2 and has a diaphragm shape from the main body to the opening, and a wall surface is erected in front of the speaker SP.

In general, the characteristics of a speaker have a small output variation over a wide frequency band in the directional direction, that is, the sound wave output direction, but the output characteristics increase as the frequency increases in the direction perpendicular or oblique to the directional direction. Is reduced.
Therefore, as shown in FIG. 4, when the microphone MC is arranged perpendicularly or obliquely to the directivity direction of the speaker SP, the sound wave directly transmitted to the microphone MC is biased to a low frequency and a wide frequency. Not applicable to obi.

Further, in both FIG. 4 and FIG. 5, the main component of the sound wave in the direction of the speaker SP is the housing H.
It is input to the microphone MC after being reflected by the wall surfaces of 1, H2,
This reflected sound has a time delay and a phase shift from the direct sound,
Moreover, these values are not constant. Furthermore, the speaker S
Since the transmission path from P to the microphone MC is long, the acoustic transmission characteristics easily change due to temperature changes in the housings H1 and H2. From this, it is extremely difficult to control the muffling at the position of the microphone MC, and the desired muffling performance cannot be obtained.

Therefore, the present invention is an active silencer that includes a sound wave output device and a residual sound detector, and cancels sound by interfering sound waves of an opposite phase with the exhaust sound from the exhaust pipe. The purpose is to stabilize the acoustic transfer characteristics between the sound detector and the sound detector, and to secure good silencing performance.

[0008]

In order to achieve the above object, the present invention provides a sound wave output device and a residual sound detector in a housing arranged in the vicinity of an outlet of an exhaust pipe of an internal combustion engine. With respect to the exhaust sound of, in the active silencer for silencing by interfering the sound wave of the opposite phase output from the sound wave output device, by driving the sound wave output device according to the detection signal of the residual sound detector, The housing surrounds the sound wave output device, and an opening is formed at a predetermined distance from the sound wave output device in the sound wave output direction, and the residual sound detector is disposed in the vicinity of the opening, The exhaust pipe is bent and attached to the housing so that the outlet end of the exhaust pipe is located on the axis connecting the opening of the housing and the sound wave output device and opens toward the opening of the housing. In which it was kick it.

[0009]

In the active silencer having the above structure, when the internal combustion engine is started and rotated, the explosion sound generated in response to the explosion in each cylinder is transmitted through the exhaust sound path including the exhaust pipe and exhaust sound. And is discharged from the exhaust pipe. On the other hand, the sound wave output device operates in response to the detection signal of the residual sound detector, and a sound wave having an opposite phase is output in the housing, and the exhaust sound is canceled. In this case, the output sound wave of the sound wave output device is substantially directly transmitted to the residual sound detector arranged in the housing opening in the output direction, and the exhaust sound emitted from the outlet end of the exhaust pipe is Since they interfere on the same axis, the output sound waves having a small output fluctuation and a uniform phase over a wide frequency band reliably interfere with the exhaust sound.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of an active silencer according to the present invention will be described below with reference to the drawings. 1 and 2 relate to an embodiment of the present invention. First, referring to FIG. 1 showing the overall configuration, an exhaust pipe 3 is connected to an exhaust manifold 2 of an internal combustion engine 1, and a catalytic converter 9 is connected to the exhaust pipe 3. It is equipped. Therefore, the exhaust manifold 2, the catalytic converter 9, and the exhaust pipe 3 constitute an exhaust sound path for the internal combustion engine 1 which is an exhaust sound source. And the outlet end 3 of the exhaust pipe 3
An active silencer 4 is mounted near a. The active silencer 4 is provided with a sound wave output device 5 that outputs a sound wave, and a residual sound detector 6 that detects a residual sound in the vicinity of the outlet end 3 a of the exhaust pipe 3. Further, a rotation signal detector 7 that outputs a signal synchronized with the rotation of the internal combustion engine 1 is provided, and is connected to the adaptive controller 10 together with the residual sound detector 6. This adaptive controller 10 has an adaptive digital filter,
Based on the output signal of the rotation signal detector 7, the coefficient of the transfer function of the adaptive digital filter is updated by an adaptive algorithm corresponding to the output signal of the residual sound detector 6 so that the output signal of the residual sound detector 6 becomes minimum. The sound wave output device 5 is driven and controlled.

The active silencer 4 has a sound wave output device 5 housed in a housing 40 as shown in an enlarged view in FIG. 2, and an enclosure 40a is formed on the drive device 50 side of the sound wave output device 5. At the same time, the mixer 40b (mixing portion) is formed in the directional direction of the diaphragm 51 (indicated by a dashed arrow). The mixer 40b is provided with an opening 40c which is formed by a diaphragm and is separated from the sound wave output device 5 by a predetermined distance in the pointing direction.
Communicates with the atmosphere through. The enclosure 40a portion and the mixer 40b portion may be formed of different materials and the two portions may be joined together.

The sound wave output device 5 of this embodiment is a cone speaker type, and comprises a diaphragm 51 and a driving device 50 for driving the diaphragm 51. The driving device 50 is supported by the housing 40, and the diaphragm 51 is in the axial direction. It is arranged so as to vibrate and output a sound wave in the mixer 40b. The driving device 50 is an electrodynamic device that converts an electric signal into mechanical vibration of the diaphragm 51. When the driving signal of the AC voltage is supplied to the movable coil (not shown), the diaphragm 51 vibrates and the coarse and fine components are generated. A pressure wave or sound wave is output. The drive device 50 is not limited to the above, but a coil is wound around a core connected to a permanent magnet, and a drive signal is supplied to this coil to generate a vibration plate 51.
It is also possible to configure an electromagnetic type device that vibrates. Besides this, electrostatic type used in the field of speakers,
Various configurations such as electrostrictive type and magnetostrictive type can be adopted,
Further, the diaphragm 51 may be hydraulically driven to ensure high output.

The exhaust pipe 3 is attached from the front of the housing 40 (on the side of the internal combustion engine 1) so as to penetrate through the front wall 40d of the housing 40, and the outlet end 3a is in the mixer 40b in the direction of the opening 40c. It is open to. At this time, the exhaust pipe 3 is bent and formed in a substantially crank shape as shown in FIG. 2 so that the outlet end 3a is located on the axis connecting the opening 40c of the housing 40 and the sound wave output device 5.

Further, in the vicinity of the opening 40c of the housing 40, a residual sound detector 6 is provided substantially in the directional direction of the diaphragm 51, and the residual sound detector 6 causes the sound wave output device 5 to operate.
The residual sound due to the interference effect on the exhaust sound due to the output sound wave is detected, and a signal corresponding to this is output. Note that the residual sound detector 6 may take any form, such as a microphone and a pressure sensor, as long as it is a means for converting a pressure signal into an electric signal.

Next, the operation of the active silencer of this embodiment will be described. When the internal combustion engine 1 is started and rotated, the explosion sound generated in response to the explosion in each cylinder is transmitted through the exhaust sound path of the exhaust manifold 2, the catalytic converter 9 and the exhaust pipe 3 to form exhaust sound. Then, a rotation signal synchronized with the rotation of the internal combustion engine 1 is output to the adaptive controller 10. The residual sound in the vicinity of the opening 40c is detected by the residual sound detector 6 and output to the adaptive controller 10.

In the adaptive controller 10, the transfer function of the adaptive digital filter is identified as the transfer function of the exhaust sound path by an adaptive algorithm corresponding to the output signal of the residual sound detector 6 based on the output signal of the rotation signal detector 7. That is, the coefficient is updated so that the output signal of the residual sound detector 6 is minimized, and the drive signal is output to the sound wave output device 5 accordingly. When a drive signal is input to the drive device 50 of the sound wave output device 5, the diaphragm 51 is driven accordingly and vibrates at a predetermined frequency.
A sound wave having a phase opposite to that of the exhaust sound is output in b and interferes with the exhaust sound emitted from the outlet end 3a of the exhaust pipe 3. That is, the opening 40 of the housing 4 including the residual sound detector 6 is caused by the interference action of the sound wave of the opposite phase to the exhaust sound.
The exhaust noise is canceled in the opening cross section near c. Therefore, an appropriate sound deadening region is formed in the opening cross section near the opening 40c including the residual sound detector 6.

As described above, the adaptive controller 10 inputs the output signal of the rotation signal detector 7 and the detection signal of the residual sound detector 6, that is, the error signal, and cancels the output sound wave and the exhaust sound (residual area). The sound wave of the opposite phase is output from the sound wave output device 5 so that the residual sound at the installation position of the sound detector 6) is minimized. At that time, the signal output from the adaptive controller 10 is actually the sound dead region. The signal representing the output sound wave reaching the
From the sound transmission to the sound deadening area. Therefore, the adaptive controller 10 needs to correct the acoustic transfer characteristics from the sound wave output device 5 to the sound deadening region.

There are two methods for this correction. One is a method using a constant value as a correction value on the assumption that the transfer characteristic from the sound wave output device 5 to the residual sound detector 6 is constant. The other one is a method in which the correction value itself is sequentially identified and updated while performing active cancellation. The latter correction method requires a system for measuring the transfer characteristics from the sound wave output device 5 to the residual sound detector 6, and also increases the amount of calculation, which causes a change in a wide frequency band such as vehicle exhaust noise. If the target is a loud sound,
High-speed calculation is required for the noise reduction, and the cost becomes very expensive. Therefore, it is realistic to use the former correction method.

However, since the former correction method is premised on the condition that "the transfer characteristic from the sound wave output device 5 to the residual sound detector 6 is always constant", the frequency range is wide and the change is drastic, and the environment is also large. It is not easy to apply it to exhaust noise that has a sharp temperature change. According to the present embodiment, as described above, the output sound wave of the sound wave output device 5 is transmitted substantially directly to the residual sound detector 6 which is substantially in the same direction as the output direction, and the outlet end of the exhaust pipe 3 is also provided. Since the exhaust sound emitted from the portion 3a coaxially interferes, it is possible to stabilize the acoustic transfer characteristics from the sound wave output device 5 to the residual sound detector 6, and to obtain high characteristics with small output fluctuation in a wide frequency band. It is possible to maintain the characteristics and obtain the phase aligned characteristics. Therefore, the sound deadening performance is improved, and the desired sound deadening performance can be secured.

FIG. 3 shows another embodiment of the active silencer of the present invention. In the embodiment shown in FIG. 2, the exhaust pipe 3 is attached through the front wall 40d of the housing 40. In this embodiment, the side wall 41e is attached to the housing 41 which is a cylindrical body having a bottom and which is symmetrical in the axial direction.
An enclosure 41a is formed on the drive device 50 side of the sound wave output device 5, and a mixer 41b is formed in the directivity direction of the diaphragm 51. The opening 41c is the mixer 41b.
It is coaxial with but has a small diameter and forms a diaphragm aperture. The residual sound detector 6 is provided in the vicinity of the opening 41c, and therefore is located in the directivity direction of the diaphragm 51.
On the other hand, the exhaust pipe 3 is bent into a substantially crank shape, penetrates the side wall 41e obliquely with respect to the housing 41, and the outlet end 3a is positioned on the axis connecting the residual sound detector 6 and the opening 41c. Installed on.

Therefore, in this embodiment, the opening 41 is formed.
The arrangement relationship among the c, the exhaust pipe 3, the sound wave output device 5, and the residual sound detector 6 is the same as that of the embodiment of FIG.
Can be formed in a small size. Moreover, since the housing 41 is symmetrical in the axial direction, strength can be obtained and the sound wave output state can be uniform. The housing 41 can be formed in various shapes as long as the above-mentioned arrangement relationship is maintained. The exhaust pipe 3 is an enclosure 41a.
Since it can be installed apart from the sound wave output device 5, it is possible to prevent thermal influence of the exhaust pipe 3 on these.

[0022]

Since the present invention is configured as described above, it has the following effects. That is, in the active silencer of the present invention, the exhaust pipe is attached to the housing so that the outlet end of the exhaust pipe is located on the axis connecting the sound wave output device and the opening of the housing. Since the output sound wave of the opposite phase interferes with the exhaust sound, and the ratio of the output sound wave to be the reflected sound is low and the transmission path is short, the influence of the temperature becomes less likely. Thus, the acoustic transfer characteristics between the sound wave output device and the residual sound detector are stable, and good silencing performance can be secured.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of an embodiment of an active silencer of the present invention.

FIG. 2 is an enlarged sectional view of an active silencer according to an embodiment of the present invention.

FIG. 3 is a sectional view of another embodiment of the active silencer of the present invention.

FIG. 4 is a cross-sectional view showing an example of a general arrangement of speakers with respect to an exhaust pipe and an example of a housing shape.

FIG. 5 is a cross-sectional view showing another general arrangement example of the speakers with respect to the exhaust pipe and another housing shape example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust manifold 3 Exhaust pipe 4 Active silencer 5 Sound wave output device 6 Residual sound detector 7 Rotation signal detector 10 Adaptive controller 40 Housing 50 Drive device

Claims (1)

[Claims] 1. A sound wave output device and a residual sound detector are provided in a housing arranged in the vicinity of the outlet of an exhaust pipe of an internal combustion engine, and an anti-phase output of the sound wave output device from the exhaust wave from the exhaust pipe is provided. In an active silencer for interfering sound waves and driving the sound wave output device in response to a detection signal of the residual sound detector to muffle sound, the housing surrounds the sound wave output device and outputs the sound wave. An opening is formed at a predetermined distance from the device in the sound wave output direction, the residual sound detector is disposed in the vicinity of the opening, and the exhaust gas is provided on an axis connecting the opening of the housing and the sound wave output device. An active silencer characterized in that the exhaust pipe is bent and attached to the housing so that the outlet end of the pipe is located and opens toward the opening of the housing.