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Internal combustion engine with secondary air pump for catalystRelated Patent Categories: Power Plants, Internal Combustion Engine With Treatment Or Handling Of Exhaust Gas, By Means Producing A Chemical Reaction Of A Component Of The Exhaust Gas, Condition Responsive Control Of Reactor Feed, Pressure, Or By-pass, Air Feed To Reactor Modulated Or Diverted By ControlInternal combustion engine with secondary air pump for catalyst description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060156711, Internal combustion engine with secondary air pump for catalyst. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to small internal combustion engines of the type used with lawnmowers, lawn and garden tractors, other utility implements, or with sport vehicles, for example. In particular, the present invention relates to an air pump for supplying secondary air to an exhaust system of the engine upstream of a catalyst element to facilitate operation of the catalyst element. [0003] 2. Description of the Related Art [0004] The exhaust systems of small internal combustion engines include mufflers for reducing the noise of the exhaust output from the combustion chamber(s) of the engines. The exhaust systems include an exhaust passage connecting the combustion chamber to the muffler, wherein the muffler is either mounted directly to the engine, or is located remote from the engine and is connected to the engine by an exhaust pipe. Within the muffler, the pressure waves associated with the exhaust gases are dampened before the exhaust gases are vented to the atmosphere in order to reduce noise. [0005] Additionally, some exhaust systems of small internal combustion engines also include a catalyst element for oxidizing components of the exhaust gas, such as unburnt hydrocarbons. The catalyst element requires a supply of atmospheric air including oxygen, referred to as "secondary air", in order to carry out the oxidation reaction. The secondary air is typically supplied to the catalyst element via a venturi-type device associated with either the exhaust passage or muffler, wherein secondary air is drawn into the stream of exhaust gas from the atmosphere. Alternatively, an air pump driven from the engine supplies a stream of secondary air from the atmosphere to the exhaust passage or muffler upstream of the catalyst. [0006] A problem with the foregoing methods of supplying secondary air to the catalyst is that venturi-type devices associated with the exhaust passage or muffler may not be effective for drawing a sufficient quantity of secondary air into the exhaust gas stream. Further, many air pumps which are typically used to supply secondary air to the catalyst element, such as diaphragm-type pumps, often are not powerful enough to supply a robust stream of secondary air to the exhaust gas stream and additionally, tend to take up additional space around the engine. Finally, other types of air pumps may reduce the overall power output of the engine. [0007] What is needed is a secondary air pump for the exhaust system of an engine which is an improvement over the foregoing. SUMMARY OF THE INVENTION [0008] The present invention provides a secondary air pump for a small internal combustion engine for supplying secondary air to the exhaust system of the engine upstream of a catalyst element. The air pump includes a thinly-profiled pump housing attached to the crankcase of the engine, an inlet in fluid communication with the atmosphere, and an outlet in fluid communication with the exhaust system of the engine upstream of the catalyst element. First and second impellers within the pump housing and are driven by the crankshaft and camshaft of the engine, respectively, and cooperate with one another and with the pump housing to define a plurality of moving working spaces which convey air from the inlet to the outlet during running of the engine. [0009] In one embodiment, the first impeller is driven by the crankshaft and includes a pair of lobes, and a second impeller is driven from the camshaft and includes four lobes. The lobes of the first and second impellers do not directly engage the pump housing or one another, but rather are disposed in close cooperation with the pump housing and with one another to define a plurality of moving working spaces within the pump housing. Therefore, operation of the air pump does not create friction between the moving parts of the air pump which could otherwise reduce the power output of the engine. [0010] Additionally, in one embodiment, the air pump includes a housing body and a cover, the housing body attached to the crankcase of the engine via a plurality of fasteners, and the cover attached to the housing body via a plurality of fasteners to enclose the air pump. The housing body and cover each have a thin profile, allowing the air pump to be positioned with the a space between the crankcase and a flywheel which is mounted to an end of the crankshaft extending externally of the crankcase. Ends of the crankshaft and camshaft which extend externally of the crankcase project directly into the air pump housing, and the first and second lobes are drivingly connected to the foregoing shafts. In this manner, the air pump has a compact construction which does not increase the overall size or profile of the engine. [0011] In one form thereof, the present invention provides an internal combustion engine, including an engine housing; first and second shafts rotatably supported by the engine housing; and an air pump, including a pump housing; an inlet in fluid communication with the atmosphere; an outlet in fluid communication with an exhaust system of the engine; first and second impellers disposed within the pump housing and driven respectively by the first and second shafts, the impellers cooperating with one another and with the pump housing to define a plurality of moving working spaces which convey air from the inlet to the outlet upon rotation of the first and second impellers. [0012] In another form thereof, the present invention provides an internal combustion engine, including an engine housing; a crankshaft rotatably supported by the engine housing; an additional shaft driven from the crankshaft and rotatably supported by the engine housing; an exhaust system including an exhaust passage and a catalyst element; and an air pump, including a pump housing including an inlet in fluid communication with the atmosphere and an outlet in fluid communication with the exhaust passage at a location upstream of the catalyst element; and first and second impellers disposed within the pump housing and driven respectively by the crankshaft and the additional shaft, the impellers each including a plurality of lobes in meshing cooperation with one another to define moving working spaces which convey air from the inlet to the outlet upon rotation of the first and second impellers. [0013] In a further form thereof, the present invention provides an internal combustion engine, including an engine housing; first and second shafts rotatably supported by the engine housing; and an air pump, including a pump housing; an inlet in fluid communication with the atmosphere; an outlet in fluid communication with an exhaust system of the engine; and means within the pump housing for conveying air from the inlet to the outlet upon rotation of the first and second shafts. BRIEF DESCRIPTION OF THE DRAWINGS [0014] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: [0015] FIG. 1 is a perspective view of portions of an internal combustion engine including a secondary air pump in accordance with the present invention; [0016] FIG. 2 is a perspective view of the engine portions of FIG. 1, showing components of the secondary air pump in exploded view, viewed from above; [0017] FIG. 3 is a perspective view of the engine portions of FIG. 1, showing components of the secondary air pump in exploded view, viewed from below; [0018] FIG. 4 is a top view of the impellers of the air pump shown in an arbitrary position within a pump cycle thereof; [0019] FIG. 5 is a continuation of FIG. 4, showing the impellers in an advanced position from that of FIG. 4; [0020] FIG. 6 is a continuation of FIG. 5, showing the impellers in an advanced position from that of FIG. 5; [0021] FIG. 7 is a continuation of FIG. 6, showing the impellers in an advanced position from that of FIG. 6; Continue reading about Internal combustion engine with secondary air pump for catalyst... Full patent description for Internal combustion engine with secondary air pump for catalyst Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Internal combustion engine with secondary air pump for catalyst patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Internal combustion engine with secondary air pump for catalyst or other areas of interest. ### Previous Patent Application: Hybrid vehicle and method for operating a hybrid vehicle Next Patent Application: Exhaust gas treatment system Industry Class: Power plants ### FreshPatents.com Support Thank you for viewing the Internal combustion engine with secondary air pump for catalyst patent info. 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