CA2057592C - Air cleaner/noise silencer assembly - Google Patents

Abstract

A combination air cleaner/noise silencer consisting of a two piece housing having a series of converging-diverging venturi. A conically-shaped cone directs the flow of air axially along and between a generally cylindrically shaped pleated paper type filter element. Optionally, a perforated member positioned downstream of the filter element reflects induction noise back to the engine source and aligns the air stream into a nearly uniform and parallel flow so as to be accurately measured by a mass air flow sensor. Both the perforated member and cone act to reflect engine generated induction noise back toward the engine.

Description

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AIR ~T.~.ANF.R/NOISE SILENCER ASSEMBLY

This invention relates in general to a combination engine air filter and noise silencer to provide both a source of clean air to an engine and to reduce induction noise generated by an engine. More particularly, the invention relates to a conical-like cone attached to a rustoconical-like air filter and a perforated conical-like member positioned down stream of the filter.

Combination air filters and noise silencers are known. One example of such a combination is shown and described in ~.S. Patent No. 4,713,097, issued to Grawi et al. December 15, 1987. Grawi et al. shows a combination air filter/noise silencer having upper and lower portions. The lower portion contains an air inlet and an air filter element from which clean air is supplied to the upper portion and to a chamber leading to the inlet of a venturi that extends at right angles to the chamber. Concentric with the venturi is a dead air space type resonating chamber having an inlet concentric with the outlet of the diffuser of the venturi. This results in engine noise feedback either being dissipated in the resonating chamber or captured in the diffuser portion of the venturi to be deflected by the tapering walls back to the engine.

2C5~592 A similar engine air filter/noise silencer is shown and described in U.S. Patent No. 4,790,864, issued to Kostun, December 13, 1988. Kostun features an air cleaner/noise silencer that includes a compact elongated housing having an air inlet at one end and a flat upright filter at the opposite end to which the air inlet is connected through the housing by an elongated sound attenuating first venturi.

Both the Grawi et al. and Kostun require the unfiltered air to abruptly change directions before passing through a flat filtering element. This change of direction creates a disturbance of the air flow through the filter and the outlet of the air cleaner.
Conically and frustoconically shaped air filters are known. One example is shown in U.S. Patent No.
4,065,276 issued to Nakaya et al., December 27, 1977.
Nakaya et al. also relates to an air cleaner~noise silencer. An air cleaner housing provides a chamber on the air intake side of the air cleaner. A
frustoconically shaped air cleaner element is positioned within a vibration-isolating cover. Air passes through ventilating windows and around a dish-shaped support plate. Air enters the filter at an angle approximately perpendicular to the filter. A perforated conical support member supports the interior of the filter.
Nakaya et al. does not contain noise silencing features to prevent the passage of induction noise through the air cleaner because it was intended to silence vibration induced resonance of the air cleaner assembly.

U.S. Patent No. 4,211,543, issued to Tokar et al., July 8, 1980 discloses a conical like air cleaner having a perforated conical support member. As was the _ 3 _ '2~
case in Nakaya et al., air is directed at an angle approximately perpendicular to the filter element causing turbulence in the air filter. Tokar et al. uses a perforated conical insert to support a reusable liner.

U.S. Patent No. 4,782,912 issued to Wandless, November 8, 1988, teaches an air cleaner/noise silencer using a conical-like insert in a snorkle-like air inlet.
The insert directs air to gradually tapering walls and provides good air pressure recovery. The interior of cone also acts to reflect engine induction noise back toward the source. But Wandless teaches the use of a flat filter element perpendicular to the air flow.
U.S. Patent 3,196,977 issued to Sanders, July 27, 1965, teaches the use of a series of nested perforated cones as a means of attenuating sound in a supersonic air stream. This invention primarily relates to noise created by the movement of air in a confined space. The perforated cones act as diffusers to attenuate both low frequency and high frequency components and to effect a substantial velocity reduction of the air stream. The diffusers do not provide a nearly uniform air stream nor do they reflect noise from a source down steam of the diffusers.

Among the present invention is directed towards a noise attenuating air cleaner which produces a minimal air flow constriction and linearly directs the flow of air through a mass air flow sensor. The invention also provides engine induction noise attenuation through the use of noise reflection surfaces and a resonating chamber. The symmetrical nature of the construction of the air filter/noise silencer assembly provides a space efficient compact design.

': ~' , The invention provides, in one aspect thereto, an air cleaner assembly comprising a housing having first and second air passages. The first passage contains an ambient air inlet extending through the housing for the flow of air into and through the first passage in one direction and a second passage containing an air outlet extending through the housing. A cone is positioned coaxially in the inlet. The cone has an apex portion situated upstream in the inlet and a base portion situated downstream in the inlet. A frustoconical filter is positioned coaxial with and adjacent to the base portion of the cone and extends through the first passage. The filter is shaped to have an apex portion situated upstream in the inlet and a base portion situated downstream in the inlet. The filter separates the first and second passage. The filter optionally contains a perforated member positioned downstream of the filter, the member being shaped to have an apex portion and a base portion, the apex of which points in the direction of the cone. The member is mounted in a position to be impacted by air passing through the filter.
The cone directs the flow of incoming air axially along and between the filter pleats. The perforated member aligns the air stream into a nearly uniform flow so as to be accurately measured by a mass air flow sensor. Both the perforated member and cone act to reflect engine generated induction noise back toward the engine.

The filter element apex has pleats extending radially beyond the base portion of the cone. The cone - 5 ~

acts to direct the flow of air axially along and between the pleats of the filtering element. The invention positions the air filtering element within a diffusing chamber to minimize the total space required by the air cleaner/noise silencer assembly.

These as well as other features and advantages of the invention will become more apparent to one of ordinary skill in the art upon reference to the following detailed description and drawings in which:

Figure l is an exploded perspective view of the air cleaner/noise silencer assembly of the invention.

Figure 2 is a longitudinal cross-sectional view of the air cleaner/noise silencer assembly shown in Figure l without the interior perforated cone.
Figure 3 is a cross-sectional view of the air cleaner/noise silencer assembly shown in Figure 2 taken along the line III-III.

Figure 4 is a cross-sectional view of the air cleaner/noise silencer assembly shown in Figure 2 taken along the line IV-IV.

Figure 5 is a longitudinal cross-sectional view of the air cleaner/noise silencer assembly shown in Figure l with the interior perforated cone.

Figure 6 is a longitudinal cross-sectional view of an alternative embodiment of the air cleaner/noise silencer assembly.

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An exploded view of the air cleaner/noise silencer assembly 10 is shown in Figure 1. Air cleaner/noise silencer assembly 10 comprises an air cleaner housing 12 and a resonator housing 14. Housings 12 and 14 are generally cylindrical and attached to one another by means of one or more closure clamps 15. Internal of air cleaner/noise silencer assembly 10 are air cleaner 20 and mass air flow sensor 40. Optionally, air cleaner/noise silencer assembly 10 includes a perforated cone 30 positioned down stream of air cleaner 20.

Air cleaner housing 12 is designed to be easily IS disengageable from resonator housing 14 to permit the replacement of air cleaner 20. Air dleaner housing 12 comprises a snorkle-shaped air inlet 16 for receiving unfiltered air. Resonator housing 14 includes an air outlet (not shown) to supply filtered air to an engine (not shown).

Referring to Figures 2 through 5, air inlet 16 comprises a steeply convergent venturi 60 for receiving unfiltered air. The air flow then passes through a 2s slightly divergent venturi 62 of approximately 3.50 until it reaches the main body of air cleaner housing 12. The main body of air cleaner housing 12 comprises a widely diverging venturi passage 64 which leads into and forms the exterior walls of expansion chamber 68. Within expansion chamber 68 is air cleaner 20.

Air cleaner 20 comprises a generally conically shaped air directing hollow cone 22 centered in the Z~7S9Z

throat area of passage 64. Attached to the base of cone 22 is a filter element 24. Filter element 24 can be generally cylindrically shaped but is more preferably generally frustoconically shaped as shown in Figure 2.
The frustoconical shape provides better pressure recovery. Filter element 24 comprises a pleated paper type filtering material about a generally frustoconically shaped wire screen 25 which supports the filter element.
Other suitable materials may be used for filter element 24 such as expanded foam, as well as natural and synthetic fabric pleated material such nylon, polyester and cotton.

Filter element 24 has an area of smallest cross section referred to as an apex portion which is adjacent and attached to the base portion of cone 22. A urethane ring 26 radially spaces filter element 24 and supports air cleaner 20 within passage 64. The largest cross section of filter 24, referred to as a base portion, is embedded within ring 26. Ring 26 is formed about the base portion of filter element 24 and wire screen 25.

Individual pleats 27 are radially spaced about the air cleaner/noise silencer as shown in Figure 3.-Finger like projections 23 are also evenly spacedradially about cone 22. Fingers 23 can be used to maintain an open space between pleats 27 so that the flow of air is directed by cone 22 a distance axially along and between pleats 27 before passing through filter element 24 as shown in Figure 2.

Air cleaner 20 is designed to be easily replaceable. Cone 22 can be either removably or permanently attached to the apex portion of filtering element 24. The preferred embodiment of cone 22 is a 2~57592 light weight plastic cone which is permanently affixed to the apex portion of filtering element 24. Cone 22 can have radially spaced projections 23 to evenly space pleats 27 about cone 22 and maintain a space for air to flow between the pleats.

Pleats 27 extend radially a distance beyond the base portion of cone 22. Pleat ends 28 are sealed to the flow of air by heat bonding as shown in Figure 4 and are intended to be directly impacted by the incoming flow of unfiltered air. The flow of unfiltered air passes about the exterior surface of filter element 24 and discrete contaminant particles are filtered from the flow of air as shown in Figure 2. The flow of filtered air passes through air cleaner 20 and is directed to mass air flow sensor 40.

Mass air flow sensor 40 comprises a converging venturi 34 receiving the flow of air from air cleaner 20. Venturi 34 is not required for the invention but permits the use of a mass air flow sensor of smaller diameter than the base of filter element 24. The flow of air is directed parallel to assembly center line A. The air flow passes through diverging venturi passage 36 and exits the air cleaner through outlet 18.

Resonating chamber 42 comprises the space between resonator housing 14 and the exterior surface of mass air flow sensor 40. Resonator chamber 42 contains a resonator inlet 44 concentric about the outlet of diverging venturi 36 spaces radially and axially therefrom. Outlet 18 is spaced axially and radially down stream of venturi 36 to permit a 3.5~ expansion of the airflow. This expansion acts as a pressure recovery for air entering the engine. Resonating chamber 42 receives induction noise from the engine through air outlet 18 and resonator inlet 44.

The axial spacing between outlet 18 and venturi 36, the internal diameter of mass air flow sensor 40 as well as the dimensions of chamber 42 can be appropriately sized to cancel a specific engine induction noise frequency or a broad range of frequencies. A method for sizing an expansion chamber such as resonator 42 is taught in Eriksson, L. J., Thawani, P. T., and Hoops, R.
H., "Acoustical Design and Evaluation of Silencers", Sound and Vibration, July 1983, pp 20-27; "Noise and Vibration Control", chapter 3.2.1, Leo Beranek, McGraw-Hill Book Company, 1971; and "Noise Control for Internal Combustions Engines", chapter 12.2, Donald E. Baxa, Wyley-Interscience, 1981.

Optionally located concentrically within filter 20 is a generally conically shaped perforated member 30 as shown in Figure 5. A seating ring 32 extends radially from the base of perforated member 30 and retains perforated member 30 coaxial within air cleaner 20.
Perforated member 30 is positioned down stream of ait cleaner 20 and receives a flow of filtered air. The flow of filtered air passes through the perforations of perforated member 30 and through mass air flow sensor 40 in a uniform and parallel path. The perforations tend to straighten the flow of air as it passes through perforated member 30. This straightening aligns the air flow in a nearly parallel path to assembly center line A.
This uniform and parallel air flow path increases the efficiency of the air cleaner as well as the accuracy of mass air flow sensor 40. As will be described in more detail, perforated member 30 also acts . ~
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2~7592 to reflect induction noise back to the engine and reduce the amount of noise which passes through the air cleaner/noise silencer assembly lO.

Air flow is assisted by streamlining all portions of the air cleaner/noise silencer lO which directly contact the air stream. Inlet 16 is provided with a relatively narrow opening owing to the effective pressure recovery of venturi 62 and passage 64. The angle of venturi 62 was selected to slow the air flow and aid in pressure recovery. Passage 64 surrounding chamber 68 is also diverging, but not to as large a degree as the throat area of passage 64 or venturi 62 because part of the air flow is being progressively removed through the filter element.

While not wishing to be bound by the following theories, it is believed that sound attenuation for air cleaner/noise silencer assembly lO occurs through the individual and cooperative noise silencing features described above. Resonating chamber 42 partially cancels induction noise entering the air cleaner/noise silencer.
The series of converging/diverging venturi also assist in canceling induction noise that passes through air cleaner/noise silencer assembly lO by dissipating sound waves along the air passage walls. The converging/diverging venturi cause an area change in the air flow path which causes a change in the impedance of noise passing through the air cleaner/noise silencer 3~ assembly. The change in impedances reflects noise back to its source. Expansion chamber 68 contains cone 22 to limit high frequency noise propagation. Cone 22 causes a change in the cross sectional area of throat passage 62, thus creating an impedance change which reflect noise back toward the engine. Ring 26 and venturi 34 act as an 2~57592 acoustic contraction yielding the air cleaner/noise silencer assembly a multi-chamber device. This contraction is also a change in impedance. Mass air flow sensor 40 acts as an acoustic extension into resonator 42. The length and diameter of mass air flow sensor 42 together with the dimensions of resonator 42 cooperatively act to effectively attenuate noise.

The cylindrical shape of air cleaner/noise silencer assembly l0 limits the amount of shell noise that can be radiated by the housing to the passenger compartment. This differs from direct transmission loss through the structure, which is independent of the housing's rounded shape. Additionally, the designs shown in Figures l-S do not provide a linear sound path for the engine induction noise to travel nor a planar wall surface that reflects induction noise through air cleaner/noise silencer assembly l0.

Engine induction noise traveling through air cleaner/noise silencer l0 begins at outlet 18. Venturi 36 acts as the first means to reflect noise back to the engine. When air cleaner/noise silencer assembly l0 contains perforated member 30, induction noise is partially reflected from the interior of perforated member 30 back toward the engine. The angle and perforations of member 30 can be selected to reflect noise partially out of phase from the noise source. This out of phase reflection assists in the overall noise cancellation. If the air cleaner/noise silencer assembly lacks perforated member 30, noise is reflected by the interior surface of cone 22. Sound which passes through filter element 24 is again reflected back toward the engine by the walls of passage 64. Only a relatively 2C57~;92 small amount of noise escapes the air cleaner through air inlet 16.

The invention described provides a compact design for an air cleaner/noise silencer assembly.
Resonator chamber 42 can be efficiently housed concentrically about mass air flow sensor 40. Filter element 24 is located in the throat section of passage 64. The linear arrangement of air cleaner 20 and mass air flow sensor 40 provides a smooth and nearly parallel flow of air through the mass air flow sensor. This uniform and near parallel flow of air is useful for an accurate measurement of air volume by the mass air flow sensor.
The invention also provides an effective design for reducing the pressure drop of air passing through air cleaner/noise silencer assembly 10. Filter element 24 is centrally located in expansion chamber 68. As air passes through inlet 16, it encounters the widely diverging walls of venturi 24 which results in a large pressure drop in expansion chamber 68. The decreased pressure in expansion chamber 68 is believed to permit a greater volume of air to pass through filter element 24.
Expansion chamber 68 acts to increase the velocity of the air flow while simultaneously reducing the air pressure.
The increased velocity combined with reduced pressure enhances the overall volumetric efficiency of the air cleaner. Air flowing through expansion chamber 68 remains generally parallel with the walls of venturi passage 64. Air is directed axially by the walls of passage 64 along and through air cleaner 20 mounted within expansion chamber 68.

2C~759~

The flow of air around cone 22 and axially along and between pleats 27 is believed to minimize the disturbance in the air stream caused by air cleaner 20.
This axial flow of air minimizes air turbulence in the air cleaner and noise generated therefrom. Additionally, the decreased turbulence assists in the measuring capability of mass air flow sensor 40. The axial relationship between the flow path and filter element reduces the likelyness of large particulates puncturing the filter element. By evenly distributing the incoming air flow radially around the filter element, the total filtering element is used. Dust is loaded uniformly on the filter element. This increases the capacity of the air cleaner for a given area of filtering element. The air flow through filter element 24 remains smooth and uniform even when it is partially loaded with dust, thus increasing the accuracy of mass air flow sensor 40 under all normal driving conditions.

An alternative embodiment of the invention is shown in Figure 6. This alternative embodiment integrates the air directing cone, perforated member and air filter into one assembly to simplify construction.
Air cleaner 20' comprises a pleated filter element 24' supported by a conically shaped member 30'. An apex portion 22' of member 30' is not perforated and serves the same function as cone 22 in Figures 1-5. The perforated base portion 31 of member 30' permits the flow of air though air cleaner 20' while reflecting engine induction noise. Perforated base portion 31 supports filter element 24' w-ithout the need of a wire screen.
Perforations 33 are angled forward to better receive the flow of air passing through filter element 24'. Engine induction noise is reflected from the hollow interior of apex portion 22' back toward the engine.

2~7S92 From the foregoing description of the preferred embodiments, it is seen that the invention provides a two piece air cleaner/noise silencer assembly which combines a noise reducing series of converging-diverging venturi together with a resonator chamber and noise reflecting cone. The design provides for a smooth non-turbulent flow of air through the air cleaner and mass air flow sensor. Its linear compact configuration provides for a packaging advantage in locating the air cleaner/noise silencer assembly in a crowded engine compartment bay.

It is possible to modify the invention by using a series of perforated cones positioned either before or after the air cleaner to further reflect engine induction noise. Alternatively, the air cleaner/noise silencer assembly can be made without a perforated cone located downs-tream of the air cleaner assembly. This is useful to save cost and weight when maximum noise silencing is not a requirement.

While the invention has been shown and described in its preferred embodiments, it will be clear to those skilled in the arts to which it pertains that many changes and modifications may be made thereto without departing from the scope of the invention as set forth in the following claims.

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Claims (26)

1. An air cleaner assembly comprising:
a housing having first and second air passages, said first passage containing an ambient air inlet extending through said housing for the flow of air into and through said first passage in one direction, and said second passage containing an air outlet extending through said housing;
a cone coaxially positioned in said inlet, said cone having an apex portion situated upstream in said air inlet and a base portion situated downstream in said air inlet; and a frustoconical filter positioned coaxially with and adjacent to said base portion of said cone and axially extending through said first passage and ending at said second passage, said filter being shaped to have apex portion situated upstream in said air inlet and a base portion situated downstream in said air inlet, said filter separating said first passage from said second passage.

2. The air cleaner assembly of Claim 1 further comprising a noise reducing resonator cooperating with said air outlet to suppress noise.

3. The air cleaner assembly of Claim 2 wherein said resonator comprises a closed chamber having a resonator inlet concentric with said air outlet and axially spaced therefrom so as to allow sound waves to pass into said chamber and thereby dissipate.
:

4. The air cleaner assembly of Claim 3 wherein said housing further comprises said resonator, and said resonator is concentric about said second passage.

5. The air cleaner assembly of Claim 1 wherein said air inlet and said first passage comprise a first convergent-divergent noise attenuating venturi.

6. The air cleaner assembly of Claim 1 wherein said second passage comprises a second converging venturi connected at one end to said filter and at the other end to a throat of minimum cross-sectional area, said throat being connected to à second diverging venturi of gradually increasing cross-sectional area connected to said air outlet.

7. The air cleaner assembly of Claim 6, wherein a mass air flow sensor is integrated as a part of said throat.

8. The air cleaner assembly of Claim 1 further comprising a perforated conical-like member positioned down stream of said filter, said member being shaped to have an apex portion and a base portion, the apex of which points in the direction of said cone, said member being mounted in a position to be impacted by air passing through said filter.

9. The air cleaner assembly of Claim 1 further comprising a wire screen positioned adjacent and down stream of said filter, said screen supporting said filter.

10. The air cleaner assembly of Claim 1 further comprising a perforated member conforming to and supporting said filter, said member position adjacent and downstream of said filter.

11. An air cleaner/noise silencer assembly for an internal combustion engine having an air induction system comprising:
a housing having internal walls, said walls defining first and second air passages and a resonator chamber, said resonator chamber being concentric about said second passage;
a snorkle-shaped air inlet extending through said housing for the flow of air into and through said first passage, said air inlet comprising a first convergent-divergent noise attenuating venturi;
a hollow cone spaced apart form said internal walls and coaxially positioned in said cone having an apex portion situated upstream in said air inlet and a base portion situated downstream in said air inlet, said cone reflecting induction system noise back toward said engine; and a frustoconical filter positioned coaxially with and adjacent said cone and axially extending through said first passage and ending at said second passage, said filter being shaped to have an apex portion situated upstream in said air inlet and a base portion situated downstream in said air inlet, said filter separating said first passage from said second passage.

12. The air cleaner/noise silencer assembly of Claim 11 further comprising a perforated conical-like member positioned down stream of said filter, said member being shaped to have an apex portion and a base portion, the apex of which points in the direction of said cone, said member being mounted in a position to be impacted by air passing through said filter.

13. The air cleaner/noise silencer assembly of Claim 12 wherein said perforated member conforms to and supports said filter.

14. The air cleaner/noise silencer of Claim 11 wherein said air inlet comprises a first convergent-divergent noise attenuating venturi.

15. The air clean/noise silencer assembly of Claim 11 wherein said second passage comprises a second converging venturi connected at one end to said filter and at the other end to a throat of minimum cross-sectional area, said throat being connected to a second diverging venturi of gradually increasing cross-sectional area connected to said air outlet, said second diverging venturi having tapering walls for deflecting noise back into said engine induction system.

16. The air cleaner/noise silencer assembly of Claim 11 wherein said resonator comprises a closed chamber having a resonator inlet thereto concentric with said air outlet and spaced radially and axially therefrom for the dissipation of sound waves therebetween into said chamber.

17. The air cleaner/noise silencer assembly of Claim 11 wherein said filter comprises a filtering element made of pleated paper.

18. The air cleaner/noise silencer assembly of Claim 11 and further comprising a wire screen positioned adjacent and down stream of said filter, said screen supporting said filter.

19. An air filter comprising:
a frustoconical-like filtering element made of pleated material, said element having an apex portion and a base portion, said apex pleats being sealed to the passage of air and directing air axially between said pleats a distance before passing through said element.

20. The air filter of Claim 19 wherein said filter comprises a series of radially spaced upstanding pleated segments.

21 The air filter of Claim 20 and further comprising a hollow conical-like cone, said cone being shaped to have an apex portion and a base portion, said cone base portion being coaxial with and attached to said filter apex portion.

22. The air filter of Claim 21 wherein said filter apex portion is larger in diameter than said cone base portion.

23. The air filter of Claim 22 wherein said filter comprises a filtering element made of pleated paper.

24. The air filter of Claim 23 wherein said cone directs the flow of air a distance axially along said element and between said pleats of paper.

25. The air filter of Claim 24 wherein said apex pleats are sealed by heat bonding.

26. The air filter of Claim 25 wherein said cone base portion further comprises a plurality of fingers projecting axially between said pleats of paper, said fingers radially spacing said apex pleats about said ring.