GB2105609A - Supplemental air filter for internal combustion engines - Google Patents

Abstract

A supplemental air filter (20) for an internal combustion engine comprises a porous foam filter element (42) positioned across an air inlet opening (26) to an air filter housing (24) for the engine. The supplemental filter (20) is used in conjunction with a conventional air filter element (37) in the housing, is substantially self cleaning by virtue of engine vibration and provides improved filtering of air along with enhanced distribution of intake air around and a greatly extended life of the conventional filter element. Filter element 42 is located in a wire cage which is shown hooked over the housing side wall but could be removably or permanently secured by other means. <IMAGE>

Description

SPECIFICATION Supplemental air filter for internal combustion engines The present invention relates to air filters for internal combustion engines.

Conventional automobile internal combustion engines include some means for filtering dirt and dust from intake air to the engine. Usually the filter comprises an air filter housing mounted on top of a carburettor or an air inlet to the engine in the case of fuel-injected engines, which housing has an opening in communication with the carburettor throat or air inlet. The housing may be of any particular configuration suitable to engine design requirements and an appropriately shaped filter element is in the housing around the opening to the carburettor. An air intake opening is formed through the housing, whereby atmospheric air passes through the opening to the interior of the housing and is drawn through the filter element for cleaning prior to induction into the engine.

Although conventional filter elements function well when new, the performance of the element rapidly decreases with use, particularly when the vehicle is operated in a dusty environment. The element then presents an increased resistance to a flow of air therethrough, resulting in enrichment of the air-fuel mixture to the engine, increases in pollutants and decreases in engine performance.

An object of the present invention is to provide a substantially self-cleaning supplemental air filter for internal combustion engines, which in combination with a conventional air filter increases the filtration of air inducted by the engine.

In accordance with the present invention there is provided, the combination of a supplemental air filter and an air filter assembly for an internal combustion engine, the air filter assembly including a housing having an air inlet opening thereto and an air outlet opening therefrom and a filter element in said housing separating said inlet and outlet openings, and said supplemental air filter comprising filter means mounted on said housing in communication with and across said air inlet opening, such that air flows through said filter means and is filtered prior to flowing through said filter element to said air outlet opening, wherein said housing has a base wall and a side wall and a cover which rests on and seals with an upper end of said side wall, said inlet opening is formed through said side wall and said outlet opening is formed through said base wall, and said filter means is mounted on said side wall to interior of said housing over and completely across said inlet opening and between said inlet opening and said filter element.

The invention is further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a conventional air filter housing for an automobile internal combustion engine, showing a supplemental air filter, structured in accordance with the invention, within the housing; Fig. 2 is a perspective view of the supplemental air filter, and Fig. 3 is a cross sectional elevation view taken substantially along the lines 3-3 of Fig. 1.

Referring to Fig. 1, a supplemental air filter 20 mounts on a rim 22 of an internal combustion engine air cleaner housing 24 to extend over and across an air inlet opening 26 in communication with a snorkel or inlet pipe 28 of the housing. As is conventional, the housing has an opening 30 therethrough, such as for example, in a lower base wall 32, whereby in a carburetted engine, the housing mounts on top of a carburettor 34 with the opening in communication with the air inlet to the carburettor. The carburettor, in turn, mounts on an engine intake manifold 36, thereby to supply an air-fuel mixture to the engine. It is to be understood, of course, that while a carburetted engine has been illustrated, for fuel-injection engines the housing opening 30 would communicate with the otherwise provided air inlet to the engine.

In a preferred use of the supplemental air filter, a conventional air filter element 37 is disposed within the filter housing 24. For the annular housing shown, the filter element is annular and positioned to rest on the base 32 about the opening 30 and within a space defined by a housing side wall 38. A cover 39 for the housing rests on the upper rim 22 of the side wall 38 and is detachably connected by means of a wing nut fastened to a threaded post 40 extending upwardly from the throat of the carburettor and through an opening in the cover. With the cover in place, the bottom surface of the filter element 37 seals with the housing base wall 32 and a top surface seals with a lower surface of the cover, such that the filter element 37 completely surrounds and encloses the opening 30, whereby atmospheric air inducted by the engine first passes through the filter element.

Referring also to Figs. 2 and 3, the supplemental air filter 20 comprises a porous foam filter element 42 encased or sandwiched within a reinforcing mesh screen 44. The foam element is of sufficient height and width to extend across the entire periphery of the opening 26 in the side wall 38 and may be of any suitable thickness. The foam element may advantageous!y be low density, flame retardant or polyurethane foam, and the wire mesh screen a galavnized wire screen. The screen is formed at its upper end into a hook 46, whereby the hook may be placed over the rim 22 of the housing to support the supplemental air filter on and in the housing and over the opening 26.Although the hook extends over the rim of the housing, it does not interefere with the normal seai formed between the housing and cover, and only normal tightening of the wing nut is required to form a seal between the cover and housing. When installed, the cover clamps the supplemental air filter in position in the housing and over the opening 26, so that all of the air flowing through the opening passes through the supplemental filter prior to entering the interior of the air cleaner housing and flowing through the conventional filter element.

It has been found advantageous if the screen 44 is not too finely meshed, thereby to allow high frequency vibrations in the foam filter element 42.

This enables the foam to vibrate at various frequencies, one of which is derived from an air flow therethrough, whereby the tuning length of the inlet pipe 28 is not affected, and the others from engine and road induced vibrations and harmonics. Consequently, use of the supplemental air filter does not adversely affect the tuning length and design considerations built into the air filter housing by the manufacturer of the automobile but instead, as will be described, enhances the efficiency of the filter system and the performance, efficiency and emissions of the engine.

Experiments have shown that use of the supplemental air filter 20 results in an air-fuel mixture which is about 0.1 to 0.3 points leaner than would otherwise be the case without its use, that the device causes incoming air to be more uniformly diffused around the normal factoryprovided filter element, and that timed acceleration is better when the device is used than when it is not.

Obviously, obtaining a leaner air-fuel mixture and improved performance when the supplemental air filter is employed means that an increased volume of air is inducted by the engine.The incongruity of increasing the air flow when the deivce is used can be reconciled by considering the improved air distribution that occurs within the air cleaner housing. In the absence of the device, and despite any air dams in the housing opposite from the air inlet opening, incoming air strikes and forms a dirty spot on the air cleaner element opposite to the opening, and there is a poor and turbulent distribution of air to the remaining areas of the element, in consequence of which the element offers an increased resistance to a flow of air therethrough.

However, when the supplemental air filter is used, and as has been found by observing the distribution of tracer amounts of talcum powder introduced into the air cleaner housing inlet, a very uniform, tranquil and nonturbulent distribution of air occurs around the entirety of the periphery of the conventional filter element, so that the resistance then offered by the element to a flow of air therethrough decreases. In essence, the combined air flow resistance offered by the supplemental and conventional air filters is less than the resistance offered by the conventional air filter along in the absence of the supplemental filter.

The supplemental air filter is also substantially self-cleaning. It has been experimentally impregnated with copious amounts of dirt, dust and other debris by introducing the same into the housing inlet while an engine was running, and while the engine air-fuel ration, vacuum and pollution factors changed negatively, they never decreased to below what they were when the vehicle was operated unaer standard conditions and the device not employed. Then, as the car was driven the device restored itself by vibrating out of the foam element 42 and to the bottom of the device and the lower surface of the inlet pipe 28 large deposits of the dirt and debris previously impregnated therein, without allowing any of the debris to pass to the interior of the air cleaner housing.Engine performance therefore again improved, and if desired any residual debris in the device may readily be removed by washing it with water. Thus, the improved results obtained in use of the device are maintained substantially constant without degradation. At the same time, the entire filtering area of the conventional air filter element is uniformly used, and not primarily just the limited area thereof directly across from the housing opening, so that the conventional element is preserved to an extent that it may never need replacement or, if replacement is required, it would be at very extended intervals.

The supplemental air filter of the invention therefore allows the conventional factory filter to do what it was intended to do for a significantly longer period and with better results, and due to the self-cleaning nature of the device there is no noticeable change in vehicle economy or performance as mileage builds up, while in a vehicle not so equipped gradual clogging of the conventional air filter element causes a gradual diminution in the performance characteristics of the vehicle.

In addition, while the filter material 42 has been described as a porous polyurethane foam, other types of material having suitable properties could just as readily be used, for example wool, glass fibre, steel wool and certain types of porous plastics materials. In addition, instead of being attached to the rim of the air cleaner housing and over the housing opening 26 by means of the hooked portion 46, the device could just as readily be magnetically or adhesively held in place over the opening, or could be held by rivetting, spot welding or any other suitable affixing or mounting means.

Claims (5)

1. The combination of a supplemental air filter and an air filter assembly for an internal combustion engine, the filter assembly including a housing having an air inlet opening thereto and an air outlet opening therefrom and a filter element in said housing separating said inlet and outlet openings, and said supplemental air filter comprising filter means mounted on said housing in communication with said air inlet opening, such that air flows through said filter means and is filtered prior to flowing through said filter element to said air outlet opening, wherein said housing has a base wall and a side wall and a cover which rests on and seals with an upper end of said side wall, said inlet opening is formed through said side wall and said outlet opening is formed through said base wall, and said filter means is mounted on said side wall to interior of said housing over and completely across said inlet opening and between said inlet opening and said filter element.

2. The combination as claimed in claim 1, wherein said filter means is mounted on said upper end of said side wall above said inlet opening and extends towards, over and across said inlet opening.

3. The combination as claimed in claim 2, wherein said filter means comprises a porous filter material and a reinforcing screen mesh around said filter material extending beyond an upper end of said filter material and formed into a hook thereat, and wherein said hook extends over said upper end of said side wall above said inlet opening and is captured between said cover and said upper end to mount said filter means in said housing and over and across said inlet opening.

4. The combination as claimed in claim 1,2 or 3, wherein said filter means comprises a porous polyurethane foam material.

5. A combination of a supplemental filter and an air filter assembly constructured substantially as herein described with reference to and as illustrated in the accompanying drawings.