Patent ID: 12251655

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.

Referring toFIGS.1-2, an engine shown as an internal combustion engine100is illustrated according to an exemplary embodiment. The internal combustion engine100includes an engine block101having one or more cylinders, cylinder heads, pistons, and a crankshaft110. Each piston reciprocates in a cylinder along a cylinder axis to drive the crankshaft110. The crankshaft110rotates about a crankshaft axis112. The crankshaft110is positioned in part within a crankcase114. In an exemplary embodiment, the crankshaft110may be oriented horizontally (i.e., a horizontal engine) with the engine100in its normal operating position. In other embodiments, the crankshaft110is vertically oriented (i.e., a vertical engine) with the engine100in its normal operating position. The engine may include one cylinder or two or more cylinders. The engine100also includes an air-fuel mixing device128for supplying an air-fuel mixture to the cylinder (e.g., a carburetor, an electronic fuel injection system, a fuel direct injection system, etc.), an air filter assembly102, and a muffler120.

The engine100can be used on a variety of end products, including outdoor power equipment, portable jobsite equipment, and standby or portable generators. Outdoor power equipment includes lawn mowers, riding tractors, snow throwers, pressure washers, tillers, log splitters, zero-turn radius mowers, walk-behind mowers, riding mowers, stand-on mowers, pavement surface preparation devices, industrial vehicles such as forklifts, utility vehicles, commercial turf equipment such as blowers, vacuums, debris loaders, overseeders, power rakes, aerators, sod cutters, brush mowers, etc. Outdoor power equipment may, for example, use the engine100to drive an implement, such as a rotary blade of a lawn mower, a pump of a pressure washer, an auger of a snow thrower, and/or a drivetrain of the outdoor power equipment. Portable jobsite equipment includes portable light towers, mobile industrial heaters, and portable light stands.

Referring toFIGS.1-14, the engine100includes an air filter assembly102according to an exemplary embodiment. The air filter assembly102includes a filter element160positioned within a housing132formed by a cover134and a base136. In an exemplary embodiment, the air filter assembly102is horizontally oriented such that the filter element160is horizontally positioned within the housing132with the engine100in its normal operating position. In some embodiments, the crankshaft110of the engine100is vertically oriented and the air filter assembly102is horizontally oriented. The air filter assembly102is configured to provide two stages of filtering of incoming air prior to supplying the filtered air to the engine100for combustion processes. The first filtering stage includes cyclonic filtering of incoming air through the air filter assembly102. The cyclonic filtering is configured to remove large particles of debris prior to secondary filtering of the air. The second filtering stage includes filtering of the partially filtered air through the filter element160to remove smaller particles of debris from the incoming air. The filtered air is then sent to the air-fuel mixing device128of the engine100to be mixed with fuel prior to combustion in the cylinder of the engine100. The air filter assembly102is positioned directly above the air-fuel mixing device128of the engine100.

As shown inFIGS.9-10, the interior surface180of the cover134and the interior surface182of the base136combine to form an interior volume155(shown inFIG.6) of the air filter assembly102, with the interior surface180of the cover134at least partially forming the interior volume155and the interior surface182of the base136also at least partially forming the interior volume155. As shown inFIGS.13-14, the filter element160divides the interior volume155into a non-filtered volume149and a filtered volume159. The non-filtered volume149includes the space outside the filter element160and within the interior volume155, and the filtered volume159includes the space inside the filter element160. The cover134is designed to fasten and unfasten to the base136via aligned holes170(shown inFIGS.9-10) formed in both the base136and cover134. As shown inFIG.12, the cover134includes fasteners133extending therethrough and configured to fit within the holes170to fasten the cover134to the base136. The fasteners133are configured to rotate to lock and unlock the fastener133in and out of engagement with the holes170in the base136. In other embodiments, other types of fasteners may be used (e.g., hinges, snaps, screws, etc.). Opening the cover134allows for insertion, removal, and checking of the status of the filter element160(shown inFIGS.6-7) positioned within the interior volume155of the housing132. In some embodiments, the cover134and base136are molded from a plastic material. In other embodiments, at least one of the cover134and base136is stamped or assembled from aluminum, another material, or is formed from a combination of materials and manufacturing processes.

The air filter assembly102includes an air intake138, a debris outlet142, and a filter outlet168formed in the base136of the air filter assembly102. In other embodiments, the air intake138, debris outlet142, and filter outlet168can be formed elsewhere in the housing132(e.g., cover134). As shown inFIGS.8-9, the air intake138and debris outlet142are positioned on opposite sides and in opposite corners of the base136. This relative positioning facilitates the cyclonic air filtering processes described herein. Additionally, as shown inFIGS.8-9, the air intake138is positioned on the same side of the air filter assembly102as the filter outlet168. This relative positioning helps to position the air filter assembly102closely to the other components of the engine100, including the air-fuel mixing device128. The air intake138is positioned near the exterior of the engine100to draw in relatively cool and clean air. If the air intake were positioned closer to the interior of the engine, the likelihood of drawing in relatively warm and/or dirty air would increase. The positioning of components (e.g., fuel tank116, muffler120) due to the horizontally oriented crankshaft110of the engine100is beneficial in combination with the horizontally oriented air filter assembly102(along with the relative placement of the air intake138and filter outlet168) to keep the overall volume occupied by the engine100relatively compact. In other embodiments, the engine100may be vertically-shafted, while the air filter assembly102is horizontally oriented. As shown inFIG.2, the air filter assembly102extends outward from the fuel tank116to a distance similar to the muffler120. As shown inFIGS.1-2, the combination of the air filter assembly102and the muffler120has an overall width similar to the width of the fuel tank116. Positioning the filter outlet168on the same side of the air filter assembly102as the air intake138allows the air filter assembly102to fit within the overall footprint shared with the fuel tank116and the muffler120and be positioned directly above the air-fuel mixing device128. This helps to keep the overall volume occupied by the engine100relatively compact. If the filter outlet was positioned at the end of the air filter assembly opposite the air intake, the resulting air filter assembly would likely extend outside of the footprint defined the fuel tank and the muffler and increase the overall volume occupied by the engine.

As shown inFIG.11, the air intake138is formed within the base136of the housing132and is configured to direct air into the unfiltered volume149at an angle substantially tangential to a curved outer surface163of the filter element160to facilitate cyclonic filtering. In an exemplary embodiment, the air intake138extends from an outer surface of the base136to the interior surface182of the base136in a linear fashion such that the incoming air is not redirected upon entering the base136. The air intake138has an L-shaped cross-section. The air intake138includes a first portion135and a second portion139. The first portion135is larger in cross-sectional area than the second portion139. Air flowing through the first portion135may complete substantially one cyclonic pass around the filter160before joining with the air flowing through the second portion139, thereby entraining at least some of the air in the second portion139and facilitating the air flow through the second portion139. Beneficially, this may increase the air flow velocity through the air intake138. In some embodiments, the air intake138has a rectangular shaped cross-section. In some embodiments, the air intake138has a circular, oblong, square, or otherwise shaped cross-section. In an exemplary embodiment, the air intake138has a relatively small cross-sectional area so that a high incoming air flow velocity is maintained, while still allowing enough air to the engine100for combustion processes.

The debris outlet142includes a valve143(e.g., duckbill valve) that allows debris removed from the cyclonic air flow to exit the air filter assembly102and additionally prevents backflow of the air and debris into the air filter assembly102. The valve143opens and closes with changes in the pressure of the interior volume155. During periods of relatively low differential pressure (e.g., the difference in pressure between the interior volume155and the outside pressure) when a vacuum may exist within the interior volume155, the valve143closes and during periods of relatively high internal differential pressure, the valve143opens. As such, changes in the internal pressure during operation of the engine100(e.g., due to intake pressure pulses at the air intake conduit126caused by reciprocation of the piston) opens and closes the valve143. Additionally, due to the pressure differences, incoming air is drawn into the air filter assembly102at a relatively high velocity and is directed toward the debris outlet142, where it slows due to a relatively open space184(e.g., and lower pressure) around the debris outlet142. Larger debris is directed into or near the debris outlet142due to the decreased velocity of the air at the debris outlet142. A trough186(e.g., depressed pocket) is formed near the debris outlet142in the interior surface182of the base136. The trough186facilitates funneling or channeling debris toward the debris outlet142. Additionally, as described below, a last rib172is positioned next to the trough186and the debris outlet142to prevent debris blowback from the trough186. For example, debris may accumulate in the trough186when the engine100is stopped and air stops flowing through the air filter assembly102. When the engine100is restarted, air begins to flow through the air filter assembly102again and may disturb and re-entrain debris collected in the trough186. The placement of the last rib172next to the trough186helps to prevent re-entrainment of collected debris so that the collected debris instead exits the air filter assembly102through the debris outlet142. The trough186is discussed further below with reference toFIG.20.

As shown inFIGS.9and15, the debris outlet142is positioned in the base136in an opposite corner from the air intake138. Air moving from the air intake138is cyclonically filtered around the filter element160and is directed toward the space184located near the end162of the filter element160where the air flow slows, allowing the debris to exit the air flow and be drawn downward by gravity toward the debris outlet142. As such, debris in the incoming air is directed toward the debris outlet142instead of accumulating elsewhere within the base136. Without the debris outlet142positioned near the space184near the end162of the filter element160, debris may remain suspended in the air flow. An opening125(FIGS.8-9) in the ribs152in the base136allows any debris that may remain within the base136to move through the housing132toward the debris outlet142. Further, the debris outlet142is angled away (e.g., at approximately a 45 degree interior angle from a vertical plane that includes the longitudinal axis145of the filter element160when installed in the base136) from the housing132. The debris outlet142is positioned to direct debris exiting the air filter assembly102away from a spark plug of the engine100such that debris does not accumulate on the spark plug.

The filter outlet168is formed within the base136of the housing132and is configured to direct filtered air into an intake conduit126of the engine100. The filter outlet168is positioned within and in fluid communication with the filtered volume159of the filter element160. The filter outlet168is circular in cross-section. In other embodiments, the filter outlet168can be oblong, square, rectangular, or otherwise shaped in cross-section. As shown inFIGS.7and13, an outlet conduit156(e.g., passage) includes a first passage153that is formed in the base136of the housing and a second passage147formed in a neck or elbow158that includes the mounting flange177for securing the housing132to the air-fuel mixing device128of the engine100(e.g., via bolts or other fasteners inserted through the bolt holes154of the mounting flange177). The first passage153of the outlet conduit156is located below the interior volume155. This arrangement helps to provide a relatively compact air filter assembly102that can provide both a cyclonic filtering stage and a filter media filtering stage and route the air filtered by both filtering stages to the air-fuel mixing device128by allowing the air filter stages and the routing of the filter air in the first passage to occur within the same overall footprint but at different elevations within the air filter assembly102.

In some embodiments, the base136and the elbow158are formed as separate components and fastened together (e.g., by ultrasonic welding). In other embodiments, the base136and the elbow158are integrally formed as a single piece (e.g., a single plastic molded part). The outlet conduit156extends between the filter outlet168and a final outlet171formed on the mounting flange177of the elbow158. The final outlet171is formed within the mounting flange177of the elbow158and is in fluid communication with the outlet conduit156and the intake conduit126of the engine100. The final outlet171is circular in cross-section. In other embodiments, the final outlet171can be oblong, square, rectangular, or otherwise shaped in cross-section. The outlet conduit156is fluidly coupled by way of the intake conduit126to the air-fuel mixing device128. The intake conduit126is directly coupled to the air-fuel mixing device128. The intake conduit126may be separate or may be at least partially integrated with the engine block or cylinder head, and may be formed from metal, plastic, or other materials. The air filter assembly102is positioned directly above the air-fuel mixing device128of the engine100to allow the intake conduit126to be directly coupled to the air-fuel mixing device128and to eliminate any need for an intermediate conduit or hose connecting the air filter assembly102to the air-fuel mixing device128.

A gap157is formed between the interior surfaces180,182of the cover134and base136, respectively, and the curved outer surface163of the filter element160. As shown by airflow path192inFIG.13, the gap157is configured to facilitate cyclonic filtering by directing the incoming air flow around the filter element160within the interior volume155of the housing132. The gap157includes a gap distance187between the interior surfaces180,182and the curved outer surface163of the filter element. The gap distance187is sized such that an incoming air flow velocity is maintained, without impeding air flow due to the proximity of the filter element160relative to the interior surfaces180,182of the cover134and base136.

Referring now toFIGS.12-14, the cover134and base136each include ribs150,152(e.g., angled protrusions) extending axially inward from the interior surfaces180,182of the cover134and base136, respectively. The ribs150,152are configured to facilitate a cyclonic filtering effect within the housing132of the air filter assembly102. As such, the ribs150,152direct incoming air to follow the contour of the gap157between the curved outer surface163of the filter element160and the interior surfaces180,182of the cover134and base136, respectively. In an exemplary embodiment, a last rib172is positioned near the trough186and the debris outlet142to prevent debris blowback from the trough186and the debris outlet142. The ribs150,152extend in toward a longitudinal center axis195of the air filter assembly102by a distance189. The longitudinal center axis195is located in the center of the interior volume155. In some embodiments, the longitudinal center axis195is included in a horizontal plane that defines a parting line between the cover134and the base136(e.g., the interface between the mounting flanges225and230of the base136and the cover134). The distance189is more than half of the gap distance187between the interior surfaces180,182and the outermost surface163of the filter media161. The filter media161may be pleated paper such that the outermost surface163is formed by a series of pleats or folds. The outermost surface163of the pleated paper filter media161defines a generally circular cross-sectional shape. The ribs150,152are of the same height around the circumference of the interior surfaces180,182of the housing132. In an exemplary embodiment, the ribs150in the cover134align with the ribs152in the base136to form one or more angled air channels151within the housing132. The alignment of the ribs150,152aids in directing the air flow to create the cyclonic filtering effect (e.g., helical flow) within the housing132. In some embodiments, the ribs150,152are helical (i.e., helical ribs) to help induce the cyclonic filtering effect. The dimensions of the ribs150,152are formed so as to facilitate desired air flow through the angled air channels151for the filtering process. The rib height (e.g., distance189) being greater than half of the gap distance187helps to maintain relatively high air flow velocity throughout the cyclonic filtering stage. Maintaining the relatively high air flow velocity aids in discharging debris near the debris outlet142. In some embodiments, the ribs150,152extend to a rib height (distance189) that brings the ribs150,152into contact with the outermost surface163of the filter media161, thereby forming closed channels in which the cyclonic air flow travels until the final channel which deposits debris toward the trough186. Applicant believes that relatively short rib heights (e.g., 25% or less of the gap distance187) allows too much of the air flow to short circuit across the cyclonic channels formed by the ribs150,152and reduces the efficiency on the cyclonic filtering operation. As shown inFIG.13, a first air channel174is narrower in width than the other air channels151. The narrow width of the first air channel174restricts the air flow through the first air channel174and increases the air flow velocity of the air flowing in from the air inlet138. Ensuring a relatively high air flow velocity at the start of the cyclonic filtering process near the end164of the air filter element160helps to maintain a relatively high air flow velocity throughout the cyclonic filtering process.

As shown inFIGS.8-10, the ribs150,152are axially arranged such that the desired air flow exit velocity is maintained (e.g., 30 feet per second debris outlet target velocity). Referring toFIG.8, the ribs150,152are arranged at an angle181relative to the interior surfaces180,182of the cover134and base136, respectively, and at an angle183relative to horizontal plane173. As shown inFIG.10, the ribs150,152are further arranged at an angle185relative to vertical plane175. The arrangement of the ribs150,152at angles181,183,185allow for a target air flow exit velocity to be maintained, with minimal drag on the incoming air. In some arrangements, the placement, angle, and dimensions of the ribs150,152are configured using a screw-pitch type measurement, such as designating a set number of ribs over a length of the air filter assembly102.

Referring toFIGS.5-7, the filter element160is positioned within the interior volume155(e.g., coupled to the base136). The filter element160includes an open or unsealed end or end portion164(FIG.5B) and a closed or sealed end or end portion162(FIG.5) with filter media161extending between the ends162,164. According to an exemplary embodiment, the filter media161and ends162,164combine to define a filtered volume, with the filter media161defining at least a portion of the filtered volume and the ends162,164defining at least a portion of the filtered volume. In some such embodiments, the filter media161is structured such that the filter media161has a closed-loop, such as the periphery of a circle, ellipse, rectangle, or other closed-loop shape.

Referring toFIGS.5-5B, the filter media161may be formed from different materials suitable for filtering debris from the intake air provided for combustion by the engine100by being permeable to air but largely preventing the ingress of dust and other contaminants from the unfiltered side to the filtered side. In some embodiments, the filter media161is pleated filter paper. In some embodiments, the filter media161is a cellulose filter media. In other embodiments, and as described further herein, the filter media161includes a debris-shedding filter material. In some embodiments, such debris-shedding media is a nanomedia and includes multiple layers of cellulose media. In an exemplary embodiment, the filter element160is substantially cylindrical in shape so as to facilitate the cyclonic filtering of incoming air prior to filtering by the filter media161by providing a curved outer surface163for the air to flow around during cyclonic filtering (i.e., the filter element160is symmetrical about a longitudinal center axis145). In embodiments including a pleated filter media161, the outermost surface163of the pleated filter media161defines a generally circular cross-sectional shape and is considered to create a cylinder shaped filter element160.

In some embodiments, the ends162,164are formed from a rigid material, such as plastic, cardboard, composite, aluminum, or other materials. In some embodiments, the end162is formed from a harder material than the end164(i.e., the end162has a greater durometer than the end164). For example, the end162may be formed from a hard urethane foam having a relatively high durometer (e.g., a Type 3 urethane foam) and the end164may be formed from a soft urethane foam have a relatively low durometer (e.g., a Type 2 urethane foam). The end162formed from the harder material includes a standoff, projection, or boss121that extends outward from a main portion or body122of the end162(i.e., away from the filter media161). The boss121is centrally located on the body122(i.e., the outer diameter123of the boss121and the outer diameter124of the body122are both centered at the longitudinal center axis145of the filter element160). The outer diameter123of the boss121is less than the outer diameter124of the body122. The end164formed from the softer material includes an opening197formed through the body198of the end164that allows filtered air from within the filter media161to exit the filter element160. The softer material helps to form a seal between the end164and the conduit or duct (e.g., filtered air passageway) to which the filter element160is attached.

In some embodiments, the filter media161is made from a debris-shedding media. In such a case, the filter media161is configured to shed debris due to vibration. The debris-shedding media is constructed so that vibrations within a particular or predetermined frequency range cause debris to fall off of the filter material. In some embodiments, during warm-up of an engine from a stopped condition to idle speeds of the engine100(e.g., 3600 revolutions per minute (RPM)), the engine100vibrates in the frequency range of 10 Hz to 30 Hz. This vibration of the engine causes debris to fall off of the filter media161. The debris shed from the filter media161can be carried by the cyclonic air flow through the housing132and directed out of the valve143of the debris outlet142.

As shown inFIG.5A, in some embodiments, the filter element160includes a guard or shield148that protects the filter media161from impacts. As shown inFIG.5A, the guard148is an expanded metal cage that surrounds the filter media161. When the filter element160becomes clogged with debris, a user may remove the filter element160and shake it to remove the accumulated debris. In certain instances, the user may strike a solid object with the filter element160to help knock the accumulated debris off of the filter media161. The guard148protects the filter media161from damage that could otherwise be caused by such an impact.

As shown inFIGS.13-14, the opening197has the same size and shape as a protrusion or boss169of an air filter conduit or duct156that surrounds the filter outlet168. The opening197receives the boss169surrounding the filter outlet168to support the filter element160on the boss169and create a seal178between the end164and the boss169to prevent filtered air from reentering the interior volume155from within the filter element160. As shown inFIG.13, the seal178extends longitudinally for a distance of contact between the end164of the filter element160and the boss169and, as shown inFIG.11, circumferentially around the area of contact between the end164of the filter element160and the boss169. The filter element160may additionally be supported within the base136by a protrusion137. The protrusion137may support the weight of the filter element160at an outer surface163of the end162. The protrusion137may be an annular ring shape so as to be of a similar shape as the outer surface163of the filter element160. In some embodiments, as shown inFIGS.20-21, the protrusion137is an air foil shape so as to both support the filter element160and direct the cyclonic air flow toward the space184and debris outlet142. In other embodiments, the filter element160is only supported by the engagement between the end164and the boss169surrounding the filter outlet168. In an exemplary embodiment, the end162is positioned proximate the debris outlet142and the end164is positioned proximate the air inlet138. As shown inFIGS.13-14, the filter element160is horizontally positioned within the housing132to align the longitudinal center axis145of the filter element160with the longitudinal center axis195of the base136of the air filter assembly102. The boss169surrounding the filter outlet168is similarly horizontally oriented with boss169extending horizontally outward from the surface166along the center axis195. When the filter element160is removed from the housing132, the boss169shields the filter outlet168from a direct path for any debris falling off of the filter element160. In some embodiments, the boss169has a length of 0.5 inches or more. The horizontal arrangement of the filter element160and the boss169means debris from the filter element160is less likely to fall off and enter the filter outlet168as compared to a vertically positioned filter and boss, in which any debris falling off of the filter element would have a clear path to the outlet.

In operation, outside air flows into the air intake138of the air filter assembly102. The air intake138is positioned such that incoming air enters the housing132tangentially to the filter element160and naturally flows into the cyclonic airflow path192established within the gap157. The incoming air is not redirected during passage through the air intake138. In an exemplary embodiment, the incoming air is not forced into the housing132using a fan, and instead air is drawn into the housing132using pressure pulses created from the reciprocation of the piston during operation of the engine100. Outside air moves past the air intake138and whatever air enters the air intake138naturally flows from the air intake138into the unfiltered volume149of the housing132and toward the debris outlet142.

Once inside the housing132, the incoming air is cyclonically filtered prior to being filtered by the filter element160. The air flows around the filter element160in the gap157formed between the outer surface163of the filter element160and the interior surfaces180,182of the cover134and base136. During cyclonic filtration, large particles are filtered from the incoming air and directed toward the debris outlet142. The incoming air completes at least two turns or cyclonic passes around the filter element160within the gap157prior to being filtered by the filter element160. Partially filtered air then flows through the filter media161of the filter element160where smaller particles of debris are filtered out of the air. The filtered air flows into the filter outlet168, through outlet conduit156, through the final outlet171and into the intake conduit126of the engine100. As shown inFIGS.13-14, the filter outlet168is in fluid communication with the filtered volume159and is sealed against the end164of the filter element160such that only filtered air is directed to the engine100.

Referring toFIG.13, the air filter assembly102includes a first end portion165and a second end portion167. End164of the filter element160is positioned proximate the first end portion165and end162of the filter element160is positioned proximate the second end167such that the filter element160is horizontally oriented about center axis195. As noted above, the air intake138is positioned on the same side (e.g., first end165) of the air filter assembly102as the filter outlet168. The positioning of the air intake138relative to the filter outlet168results in three passes of the air flow within the air filter assembly102prior to entering the air-fuel mixing device128.

The incoming air flows into the air intake138positioned on the first end165and into the cyclonic airflow path192established within the gap157toward the second end167as designated by first airflow pass105. Accordingly, when completing the first airflow pass105(e.g., completing at least one cyclonic air flow turn or pass around the filter element160), the incoming air moves from the air intake138toward the debris outlet142positioned proximate the second end portion167. The overall flow of air in the first airflow pass105is in a first direction from the first165toward the second end167. The flow of air in the first airflow pass105moves cyclonically around the filter element160but in a horizontal overall direction generally from end165toward end167Next, the air flows through the filter media161of the filter element160and toward the filter outlet168positioned proximate the first end165as designated by second airflow pass107. As such, the second airflow pass107is substantially parallel but opposite in direction to the first airflow pass105. The flow of air in the second airflow pass107moves in a horizontal overall direction generally from end167toward end165, which is opposite in direction to the first air flow pass105. Finally, the air flows into the filter outlet168and turns back toward the second end167as designated by third airflow pass109prior to entering elbow158that connects to the air-fuel mixing device128. The outlet conduit156is configured to direct air in the third airflow pass109toward the final outlet171in a substantially parallel direction to the first airflow pass105and second airflow pass107. Additionally, the third airflow pass109is in substantially the same direction as the first airflow pass105, but opposite in direction as the second airflow pass107. The flow of air in the third air flow pass109moves in a horizontal overall direction generally from end165toward end167, which is the same direction as the first air flow pass105and opposite the second air flow pass107. The three air flow passes105,107, and109are arranged in counter flow arrangements to the adjacent air flow pass or passes so that the air moving through the three air flow passes travels in a first direction in the first air flow pass105, is redirected in a second opposite direction in the second air flow pass107, and returns to the first direction in the third air flow pass109. Arranging the three air flow passes105,107, and109helps to provide a relatively compact air filter assembly102that can provide both a cyclonic filtering stage and a filter media filtering stage and route the air filtered by both filtering stages to the air-fuel mixing device128. Air flow passes are considered to be substantially the same direction when one air flow pass falls within plus or minus 25 degrees of the bearing of the referenced air flow pass in the same direction of travel. Air flow passes are considered to be substantially the opposite direction when one air flow pass falls within plus or minus 25 degrees of the bearing of the referenced air flow pass in the opposite direction of travel.

The ribs150,152create a cyclonic filtering effect within the housing132of the air filter assembly102. As mentioned above, the position, dimension, and angle of the ribs150,152are configured to maintain a target exit velocity (e.g., 30 ft/s) at the debris outlet142. Additionally, the position, dimension, and angle of the ribs150,152may be selected such that incoming air completes at least two cyclonic passes in the gap157prior to entering the filter element160. The combination of the target exit velocity and at least two cyclonic filtering passes increases the amount of debris removed from the air during the cyclonic filtering stage.

The boss121of the filter element160has an outer diameter123that is small relative to the outer diameter124of the body122of the end162of the filter element160so that the boss121does not interfere with the cyclonic air flow near the end162of the filter element160. In one embodiment, the outer diameter123of the boss121is no larger than half the outer dimeter124of the body122to avoid interfering with the cyclonic air flow near the end162of the filter element160.

Using the dimensions of the air intake138, housing132, ribs150,152, gap157, and other components described herein, the velocity of the air flow within the housing132during cyclonic filtering is maintained at appropriate values so as to reduce any possible turbulent air flow and maintain laminar flow of the incoming air. Maintaining laminar flow within the housing132during cyclonic filtration is desirable for maximum possible cyclonic filtering. The target velocity of the air at the debris outlet142is approximately 30 feet per second (ft/s) to maintain laminar flow for desirable cyclonic filtering. In other arrangements, the target velocity of the air at the debris outlet142can be more or less than 30 ft/s.

Cyclonic filtering of intake air prior to filtering by a filter element as described above can facilitate longer engine runtime with a single filter. Because a large portion of debris is filtered prior to the air entering the filter, less debris is accumulated on the filter media. Thus, a filter assembly with cyclonic filtering will allow longer engine runtimes with a single filter. During filter testing conducted by Applicant, the air filter assembly102enabled the test engine to run longer (5 hours versus almost 2 hours) before being starved for air to the combustion process and collect less debris on the filter element (5 grams versus 2 grams), indicating improved cyclonic filtering, when compared to a conventional air filter assembly.

An alternative embodiment of the base136is illustrated inFIGS.16-21. As shown inFIGS.17-19, the air filter conduit156includes a crossbar200(bar, wall, projection) positioned in the filter outlet168. As illustrated the crossbar200is set back from the edge of the boss169of the air filter conduit156. In other embodiments, the crossbar200extends to the edge of the boss169. As illustrated, the crossbar200is positioned vertically within the filter outlet168and positioned in the center of the filter outlet168. In other embodiments, the crossbar200is positioned horizontally within the filter outlet168or at other angles within the filter outlet168. In some embodiments, the crossbar200is one of multiple crossbars arranged in a grid or mesh within the filter outlet168. As shown inFIG.19, the crossbar200functions to limit insertion of the boss121of the filter element160into the air filter conduit156. When the filter element160is properly installed in the interior volume155of the housing132, the end162of the filter element160including the boss121is positioned away from the air filter conduit156. The inclusion of the crossbar200within the air filter conduit156prevents improper installation of the filter element160with the end162positioned near the air filter conduit156by limiting insertion of the boss121into the air filter conduit156. As shown inFIG.19, when a user attempts to improperly install the filter element160in this manner, the boss121contacts the crossbar200and the opposite end164of the filter element160cannot be positioned within the interior volume155. This arrangement error proofs assembly of the filter element160into the housing132so that the filter element160can only be positioned within the interior volume155when oriented in a first orientation with the first end162of the filter element160positioned near a first housing end portion205with the boss121in contact with the first housing end portion205, and the second end164of the filter element160positioned near a second housing end portion210with the boss169or other portion of the air filter conduit156positioned within the opening197of the second end164. In a second orientation of the filter element160, the first end162of the filter element160is positioned near the second housing end portion210with the boss121in contact with the crossbar200of the filter outlet168, thereby preventing installation of the filter element160within the interior volume155, as shown inFIG.19.

As shown inFIG.20, the first housing end portion205includes a wall215that is in contact with the boss121when the filter element160is properly installed within the interior volume155. In some embodiments, a recess220(shown in broken lines) is formed in the wall215and at least a portion of the boss121is positioned within the recess220when the filter element160is properly installed in the interior volume155. As shown inFIG.13, when the filter element160is properly installed within the interior volume155with the boss121contacting the first housing end portion205, the first end162of the filter element160exerts a force on the air filter element160directed toward the second housing end portion210and the air filter conduit156to form the seal178between the second end164of the filter element160and the air filter conduit156. The relatively hard first end162of the filter element160does not compress or deflect when the boss121contacts the first housing end portion205and forces the relatively soft second end164of the filter element160onto the air filter conduit156. The relatively soft material of the second end164is chosen to help form an air tight seal178between the second end164and the air filter conduit156.

As shown inFIGS.18-21, the base136includes a mounting flange225that is arranged to align with and contact a corresponding mounting flange230of the cover134(as shown inFIG.6) when the cover134is attached to the base136. The mounting flange225is arranged in a horizontal plane that includes the longitudinal center axis195of the housing132. The mounting flange225includes a recessed channel235that receives a gasket (not shown) to form a seal between the mounting flanges225and230of the base136and the cover134. The channel235is formed between an outer wall240and an inner wall245. Near the air intake138, the inner wall245stops and the channel235is open to the air intake138. One or more stakes or projections250are provided to help keep the gasket within the channel235near the air intake138. The stakes250extend above the channel235so that the gasket is positioned between the stakes250and the outer wall240. If the base136and the cover134are not properly sealed by the gasket, the lack of a seal may result in pressure loss in the interior volume155which could negatively impact the velocity of the cyclonic air flow. The gasket helps to prevent any moisture (e.g., rain) from entering the interior volume, which could negatively impact the function of the filter media161if the filter media161got wet.

As shown inFIGS.19-21-, the portion of the mounting flange225near the first housing end portion205includes a first fastener opening170A. In some embodiments, as illustrated, the first fastener opening170A includes a threaded insert252for coupling with a threaded fastener. A second fastener opening170B is formed in an elbow255or other structure of the air filter conduit156. In some embodiments, as illustrated, the second fastener opening170B includes a threaded insert254for coupling with a threaded fastener. The elbow255extends above the mounting flange225and provides the structure for forming a portion of the air filter conduit156. As shown inFIG.19, the entrance to the first fastener opening170A is spaced apart from the entrance to the second fastener opening170B by a distance260. In the normal operating position of the air filter assembly102, the entrance to the second fastener opening170B is located at a vertical elevation above the vertical elevation of the entrance to the first fastener opening170A. Using the structure of the elbow255as a location for the second fastener opening170B helps to reduce the material needed to form the base136by making dual use of the elbow255as both the structure of a portion of the air filter conduit156and the structure for receiving a fastener for attaching the cover134to the base136. This arrangement also helps to keep the housing132relatively compact by allowing the portion of the mounting flange225near the second housing end portion210to be narrower than the portion of the mounting flange225near the first housing end portion205by not having to accommodate the space and material needed for the second fastener opening170in the mounting flange225. As shown inFIG.13, with the cover134and the base136in in an attached configuration in which the base mounting flange225is aligned with and in contact with the cover mounting flange230, a third fastener opening170C in the cover134is aligned with the first fastener opening170A and a fourth fastener opening170D in the cover134is aligned with the second fastener opening170B. A first fastener133A is inserted into the third fastener opening170C and the first fastener opening170A and attached to the base136(e.g., threads of the fastener133A engage threads of the first fastener opening170A or the threaded insert252). A second fastener133B is inserted into the fourth fastener opening170D and the second fastener opening170B and attached to the base136(e.g., threads of the fastener133B engage threads of the second fastener opening170B or the threaded insert254).

FIGS.20-21also illustrate the trough186that leads to the debris outlet142. The trough186includes a relatively wide entrance262that narrows to a relatively narrower exit265. The relatively wide entrance262helps to gather debris and direct debris toward the exit265of the trough186. The trough186is also pitched or angled between the entrance262to the exit265to direct debris from the entrance262toward the exit265. This arrangement helps to funnel debris filtered from the air flow by the cyclonic filtering process from the entrance262toward the exit265.

An alternative embodiment of the cover134is illustrated inFIGS.23and24. The cover134includes a first housing end127and a second housing end129. The cover134includes two ribs141positioned at the first housing end127. The ribs141protrude from an interior wall193formed within the first housing end127. The first housing end127is configured to receive the boss121on the first end162of the filter element160. As shown inFIG.24, when assembled properly, the boss121of the filter element160fits between the ribs141and seals against wall193. The ribs141limit the lateral movement of the first end162about longitudinal axis195of the filter housing132. The ribs141are spaced apart from the boss121at a lateral distance131on each side of the boss121. In some embodiments, the lateral distance131is approximately 1.5 millimeters (mm). The ribs141project from the wall193on the first housing end127a projection distance191. In some embodiments, the projection distance191is approximately 2 mm.

The construction and arrangements of the air filter assembly, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.