Actively controlled induction noise using a quadrapole inlet

Abstract: An active noise attenuation assembly for an air induction system of an internal combustion engine is located in an air inlet duct leading to the engine. A fairing body is concentrically mounted within the duct and defines an annular space with the duct through which air travels. A loud speaker is mounted on the fairing body facing outwardly from the duct. A controller generates an electrical signal amplified and phase shifted from a noise field emanating from the engine. The signal is applied to the loudspeaker for broadcasting a sound field phase shifted from the noise field for attenuating the noise field. A transition housing having an outlet opening and an inlet opening forms a first pair of opposing channels and a second pair of opposing channels. The housing mates to the open end of the inlet duct. The first pair of opposing channels communicates with the speaker and the second pair of opposing channels communicates with the annular space.

Description: The subject invention relates to an improvement in noise reduction capabilities of an air induction system for an internal combustion engine. Active noise attenuation has been used to reduce engine noise emitted through air induction systems from the combustion chambers of internal combustion engines. One such example is pending United States Patent Application Number 08/872,506 "Active Noise Attenuation." Noise attenuation assemblies of this type are affixed inside an air inlet duct leading to the engine combustion chambers. The inlet duct includes an open end into which air is drawn for feeding the combustion chambers. The assembly includes a loud speaker mounted upon an internal housing. The internal housing forms an annular space with the inlet duct through which air travels. A controller generates an electrical signal from input from a primary microphone measuring a noise field emanating from the engine, and from an error microphone measuring un-attenuated noise. The electrical signal is amplified and phase shifted from the noise field and the signal is applied to the loudspeaker for broadcasting a sound field phase shifted from the noise field. Preferably, the phase shift is 180°. To generate a sound field strong enough to attenuate the noise field from the engine, the speaker needed is large relative to the amount of space available inside the assembly. Further, it is desirable to reduce vehicle mass and thus reduce the mass of components such as the speaker be reduced to amounts a low as is practicable to perform the requisite functions is a desirable goal. Therefore, it would be. desirable to provide apparatus that can reduce the strength of the noise field, and enable the use of smaller, lighter, and less powerful speaker. In WO 97/20307 there is described a system and method for reducing noise from an internal combustion engine using a duct housing receiving induction air flow to the engine. A space is defined within the duct housing surrounding a speaker enclosure associated with a speaker facing an open space upstream of the annular space. A sound transducer at the axial location where the annular space opens into the open space generates electrical signals corresponding to engine noise propagating through the air induction ducting. The signals are amplified and phase shifted driving the speaker to output canceling noises or sounds so as to at least reduce engine noise from the annular space. The speak enclosure length is set to enhance speaker performance in selected frequency bands of engine noise. Summary of the invention and advantages According to the invention there is provided an active noise attenuation assembly for an air induction system of an internal combustion engine, said assembly comprising: an air inlet duct leading to the engine having an open end into which air is drawn; a fairing body mounted within said air inlet duct defining an annular space with said inlet duct through which air travels; a loud speaker mounted on said fairing body facing outwardly from said air inlet duct; a controller for generating an electrical signal amplified and phase shifted from a noise field emanating from the engine and applying the signal to said loudspeaker for broadcasting a sound field phase shifted from the noise field thereby attenuating the noise field and characterised by; a transition housing affixed to said open end of said inlet duct which forms a first pair of opposing channels communicating with said speaker and a second pair of opposing channels communicating with said annular space. Preferably, the first and the second pair of channels terminate in an arrangement having each of the first channels positioned adjacent to at least one of the second channels. The arrangement of the channels at the inlet end of the housing facilitates the transfer of particulate matter between the first and second pairs of channels. Because the sound fields are out of phase, particulate matter is pushed and pulled between the first and second pairs of channels at the inlet end of the housing. The transfer of the particulate matter between the channels dampens the noise field reducing the output requirements of the loudspeaker for attenuating the noise field. Reduced output requirements allows for the reduction in the size and power of the loudspeaker resolving the problems associated with the prior art. According to the invention there is also provided a method of attenuating noise emanating from an internal combustion engine and travelling through a fresh air inlet opening of an air induction assembly comprises the steps of: providing a loudspeaker concentrically mounted within said assembly facing outwardly of said assembly; detecting the noise field emanating from the engine for determining the phase of the noise wave; broadcasting a sound field from said speaker out of phase of the noise field for attenuating the noise field, characterised by; separating the noise field emanating from the engine into a first pair of opposing channels and separating the sound field broadcast from the loudspeaker into a second pair of opposing channels, wherein said first and said second pair of channels terminate in an arrangement having each of said first channels positioned adjacent each of said second channels. Brief description of the drawings Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: Figure 1 is a partial sectional view of an embodiment of the invention showing the adjacent opposing channels; Figure 2 is an end view of the frame shown in Figure 1; and Figure 3 is a partial sectional view of an embodiment of the invention showing the filter cell attached; Figure 4 is a view in direction of section 4-4 in Figure 1 showing the channels at the outlet end of the transition housing of an embodiment of the invention; and Figure 5 is a view in direction of section 5-5 in Figure 1 showing the channels at the inlet end of the transition housing of an embodiment of the invention. Detailed description of the preferred embodiment Referring to the Figure 1, an active noise attenuation assembly is generally shown at 10. The assembly 10 includes an air inlet duct 12, which leads to an internal combustion engine 14. Air is channeled through the duct 12 into internal combustion chambers (not shown) within the engine 14 as is known in the art of internal combustion engines. The duct 12 includes an open end 16 into which air is drawn. The duct 12 is widest at the open end 16 and narrows as it approaches the engine 14. A fairing body 18 is concentrically mounted within the air inlet duct 12 and defines an annular space 20 with the inlet duct 12 through which the air travels. The fairing body 18 is hollow and generally contoured to the shape of the duct 12. A loudspeaker 26 is mounted on the fairing body 18 facing outwardly from the air inlet duct 12. As best shown in Figure 2, the duct 12 includes a frame 22 for affixing the fairing body 18 to the duct 12. The frame 22 includes equally spaced radial bars 24 so as to allow maximum air flow through the annular space 20. The frame 22 includes spaced apertures 28 for receiving fasteners (not shown) to mount the loudspeaker 26 to the fairing body 18. The fairing body 18 is affixed to an inner ring 30 of the frame 22 by a series of tabs 32. The loudspeaker 26 is arranged to broadcast in an opposite direction of the air flow. The loudspeaker 26 forms a closed-chamber 34 with the fairing body 18. A controller 36 is secured inside the chamber 34 to the fairing body 18. The controller 36 generates an electrical signal amplified and phase shifted (preferably by, 180°, but other shifts come within the scope of this invention) from a noise field emanating from the engine 14. The noise field travels from the combustion chambers of the engine through the duct 12 in the opposite direction of the air flow. The controller 36 drives the loudspeaker 26 by applying the signal to the loudspeaker 26. Therefore, the loudspeaker 26 broadcasts a sound field that is phase shifted from the noise field. Phase shifting the sound field from the noise field attenuates the noise field generated by the engine 14 as is known in the art of active noise control. Again a 180° shift is most preferred, but shifts approximately equal to 180°, but shifts approximately equal to 180° are also capable of performing a good deal of benefits of this invention. The noise field is detected by a primary microphone 38. The primary microphone 38 signals the controller 36 with the measured noise field from which the controller 36 determines the phase of the noise field. The primary microphone 38 is affixed to the duct 12 in a location determined to measure the noise field prior to being attenuated by the loudspeaker 26. Thus, the optimum location is between the fairing body 18 and the engine 14. A transition housing 40 is mated to the duct 12. The transition housing 40 includes an outlet end 42 and an inlet end 44. The outlet end 42 is mated to the open end 16 of the inlet duct 12. The housing forms a first pair of opposing channels 46 and a second pair of opposing channels 48. The channels 46, 48 terminate at the inlet end44 in an arrangement positioning each of the first channels 46 adjacent each of the second channels 48 (Figure 1). The structure of the channels 46, 48 is shown schematically in Figure 1. The first pair of opposing channels 46 communicates with the loudspeaker 26. The second pair of opposing channels 48 communicates with the annular space 20. The noise field emanates through the annular space 20 into the second pair of opposing channels 48 against the flow of air. The loudspeaker 26 broadcasts the sound field through the first pair of opposing channels 46 phase shifted from the noise field emanating from the engine 14 through the second pair of opposing channels 48. The sound field emanating from the loudspeaker 26 through the first pair of opposing channels 46 attenuates the sound field emanating from the engine 14 through the second pair of opposing channels 48 at the inlet end 44. Locally attenuating the noise field in this manner prevents the noise field from traveling far away from the source. The adjacent arrangement of the channels 46, 48 at the inlet end 44 facilitates the transfer of particulate matter between the first and second channels 46, 48 due to the proximity of each of the first channels 46 to the second channels 48. Additionally, the 180° phase shift between the noise field and the sound field increases the amount of particulate matter transferred between the channels 46, 48 by pushing and pulling the particulate matter between the channels 46, 48. The strength of the noise field is significantly dampened by the transfer of particulate matter. Thus, the size and power requirements of the loudspeaker 26 that is necessary to attenuate the noise field is significantly reduced. An error microphone 49 is positioned adjacent the outlet end 42 for detecting un-attenuated noise. The error microphone 49 senses both the noise field and the sound field and signals the controller 36 to adjust the phase of the sound field to improve the attenuating properties of the sound field. As shown in Figure 3, a filter cell 50 is affixed at the inlet end 44 of the transition housing 40 for filtering air entering the inlet end 44. The filter cell 50 includes filter media 52 through which the air is drawn into a central cavity 54. The error microphone 49 is located in or near the cavity 54. The noise field is attenuated in the cavity 54 before it can leave the filter cell 50 through the media 52. As best shown in Figures 4 and 5, the first channels 46 form a twisting path from the inlet end 44 of the housing 40 to the speaker 26. The second channels 48 form a twisting path from the inlet end 44 of the housing 40 to the annular space 20. As seen in Figure 4, the first channels 46 combine to form a circular space to mate with the speaker 26, while the second channels 48 combine to form a concentric ring around the first channels 46 to mate with the annular space 20. As seen in Figure 5, the first channels 46 are positioned in an opposing relationship being separated by the second channels 48 at the inlet end 44 of the housing 40. When oriented in this manner, each of the first channels 46 is adjacent at least one of the second channels 48 to facilitate the transfer of particulate matter between the first and second channels 46, 48. The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.

Claims: An active noise attenuation assembly (10) for an air induction system of an internal combustion engine (14), said assembly comprising: an air inlet duct (12) leading to the engine (14) having an open end (16) into which air is drawn; a fairing body (18) mounted within said air inlet duct (12) defining an annular space (20) with said inlet duct (12) through which air travels; a loud speaker (26) mounted on said fairing body (18) facing outwardly from said air inlet duct (12); a controller (36) for generating an electrical signal amplified and phase shifted from a noise field emanating from the engine (14) and applying the signal to said loudspeaker (26) for broadcasting a sound field phase shifted from the noise field thereby attenuating the noise field and characterised by ; a transition housing (40) affixed to said open end (16) of said inlet duct (12) which forms a first pair of opposing channels (46) communicating with said speaker (26) and a second pair of opposing channels (48) communicating with said annular space (20). An assembly (10) as set forth in claim 1 wherein each of said first pair of channels (46) are positioned adjacent at least one of said second pair of channels (48) at an end opposite (44) said open end (16) of said inlet duct (12). An assembly (10) as set forth in claim 2 wherein said speaker (26) broadcasts said sound field through said first pair of opposing channels (46) phase shifted from the noise field emanating from the engine (14) through said second pair of opposing channels (48). An assembly (10) as set forth in claim 3 wherein said sound field emanating from said speaker (26) through said first pair of opposing channels (46) attenuates the noise field emanating from the engine (14) through said second pair of opposing channels (48). An assembly (10) as set forth in claim 4 wherein the strength of the noise field emanating from the engine (14) through said second pair of opposing channels (48) is dampened by transfer of particulate matter between said first (46) and said second (48) pairs of opposing channels. An assembly (10) as set forth in claim 4 wherein said air inlet duct (12) includes a primary microphone (38) for detecting the phase of the noise field emanating from the engine (14) and signaling said controller (36). An assembly (10) as set forth in claim 6 including an error microphone (49) for measuring both the noise field and the sound field and signaling said controller (36) to adjust the phase of the sound field to improve attenuation the noise field. An assembly (10) as set forth in claim 1 wherein said fairing body (18) forms a closed chamber with said speaker (26). An assembly (10) as set forth in claim 8 wherein said controller (36) is disposed within said chamber formed by said fairing body (18) and said speaker (26). A method of attenuating noise emanating from an internal combustion engine (14) and travelling through a fresh air inlet opening of an air induction assembly comprises the steps of: providing a loudspeaker (26) concentrically mounted within said assembly facing outwardly of said assembly; detecting the noise field emanating from the engine (14) for determining the phase of the noise wave; broadcasting a sound field from said speaker (26) out of phase of the noise field for attenuating the noise field, characterised by ; separating the noise field emanating from the engine (14) into a first pair of opposing channels (46) and separating the sound field broadcast from the loudspeaker into a second pair of opposing channels (48), wherein said first (46) and said second pair of channels (48) terminate in an arrangement having each of said first channels positioned adjacent each of said second channels. A method as set forth in claim 10 further including the step of dampening the noise field emanating from the engine (14) by passing particulate matter between said first pair (46) and said second (48) pair of opposing channels. A method as set forth in claim 11 further including the step of detecting both the noise field and the sound field and adjusting the phase of the sound field to improve attenuation the noise field.

Inventors: MCLEAN IAN R, MCLEAN, IAN R.
Applicants: SIEMENS VDO AUTOMOTIVE INC, SIEMENS VDO AUTOMOTIVE INC.
Application year: 2000
Main classification: F02M35
IPC codes: F02B27, F02M35