Heat exchanger for a snowmobile engine air intake

A snowmobile has a frame including a tunnel, at least one ski, an engine having an engine air inlet and a drive track operatively connected thereto and disposed at least partly below the tunnel around a rear suspension. A heat exchanger connected to the tunnel has a heat exchanger air inlet and a heat exchanger air outlet fluidly communicating with the heat exchanger air inlet and the engine air inlet. A snowmobile has a frame including an inverted U-shaped tunnel having top, left and right portions at least partly enclosing a space. A drive track, operatively connected to an engine, is disposed around a rear suspension and at least partly in the space. An air intake system has a heat exchanger surface disposed in or adjacent to the space. Air flowing through the intake system contacts the heat exchanger surface to be cooled thereby before entering the engine.

FIELD OF THE TECHNOLOGY

The present technology relates to heat exchangers for cooling air intake of snowmobile engines.

BACKGROUND

The efficiency of the combustion process in an internal combustion engine can be increased by decreasing the temperature of the air entering the engine for combustion. A decrease in air intake temperature provides a denser intake charge to the engine and allows more air and fuel to be combusted per engine cycle, increasing the output power of the engine. There is thus a need for a convenient and effective cooling system for removing heat from the air before its entry into the engine for the combustion process.

SUMMARY

According to one aspect of the present technology, there is provided a snowmobile includes a frame including a tunnel, at least one ski connected to the frame, an engine supported by the frame and having an engine air inlet, a rear suspension assembly connected to the tunnel, and a drive track disposed around the rear suspension assembly and at least in part below the tunnel. The drive track is operatively connected to the engine. A heat exchanger connected to the tunnel includes a heat exchanger air inlet and a heat exchanger air outlet. The heat exchanger air outlet is fluidly communicating with the heat exchanger air inlet and with the engine air inlet.

According to some implementations, the heat exchanger is connected to a forward portion of the tunnel.

According to some implementations, the heat exchanger includes a heat exchanger surface which contacts snow projected by the drive track while the snowmobile is being propelled along snow-covered ground.

According to n some implementations, the tunnel includes a left side portion and a right side portion, the heat exchanger air inlet and the heat exchanger air outlet being disposed laterally between the left and right side portions.

According to some implementations, the tunnel also includes a top portion connected to the left and right portions, the heat exchanger air inlet and the heat exchanger air outlet being disposed vertically higher than the top portion.

According to some implementations, the snowmobile further includes an air compressor fluidly communicating with the heat exchanger air inlet to deliver compressed air to the engine via the heat exchanger.

According to some implementations, the air compressor is a turbocharger. The engine has an engine exhaust outlet fluidly communicating with the turbocharger for operating the turbocharger. Exhaust gas flows out of the engine through the engine exhaust outlet and then to the atmosphere via the turbocharger.

According to some implementations, the tunnel includes a left side portion and a right side portion separated by a gap, at least a portion of the heat exchanger being aligned laterally with the gap.

According to some implementations, a drive sprocket is operatively connecting the engine to the drive track. At least a portion of the heat exchanger is disposed above a horizontal plane containing an axis of rotation of the drive sprocket.

According to some implementations, a portion of the drive track is disposed vertically lower than the heat exchanger such that a vertical plane containing an axis of rotation of a front drive sprocket intersects the heat exchanger.

According to some implementations, the heat exchanger air outlet includes a plurality of heat exchanger air outlets. The engine air inlet includes the plurality of engine air inlets. Each heat exchanger air outlet of the plurality of heat exchanger air outlets is in fluid communication with a corresponding one of the plurality of engine air inlets.

According to some implementations, an airbox is fluidly communicating with the engine. Air passes through the airbox before entering the engine.

According to some implementations, the heat exchanger includes a forward portion and a rearward portion. The tunnel includes a top portion and a front portion extending downwardly and forwardly from the top portion. The rearward portion of the heat exchanger is at least partially connected to the top portion of the tunnel, and the forward portion of the heat exchanger is at least partially connected to the front portion of the tunnel.

According to some implementations, a portion of the rearward portion is disposed higher than the forward portion.

According to some implementations, a drive sprocket operatively connects to the engine to the drive track and defines a sprocket axis. The heat exchanger has a heat exchanger air inlet and a heat exchanger air outlet. At least a portion of the heat exchanger air inlet and at least a portion of the heat exchanger air outlet are disposed on opposite sides of a vertical plane containing the sprocket axis.

According to some implementations, a drive sprocket operatively connects the engine to the drive track and defines a sprocket axis. The heat exchanger has a heat exchanger air inlet and a heat exchanger air outlet. At least a portion of the heat exchanger air inlet and at least a portion of the heat exchanger air outlet are disposed above a horizontal plane containing the sprocket axis.

According to some implementations, a throttle body has a throttle valve. The throttle valve is rotatable about a throttle valve rotation axis. The forward portion of the heat exchanger extends longitudinally forward of the throttle valve axis.

According to some implementations, the heat exchanger forms at least a portion of the forward portion of the tunnel.

According to some implementations, the heat exchanger includes a top part and a bottom part. At least one of the top and bottom parts define a recess. The top and bottom parts define therebetween a passage formed in part by the recess. The heat exchanger air inlet fluidly communicates with the heat exchanger air outlet via the passage.

According to some implementations, the heat exchanger air inlet is disposed forwardly of the heat exchanger air outlet.

According to some implementations, an airbox fluidly communicates the heat exchanger with the engine. The airbox includes an airbox inlet fluidly communicating with the heat exchanger air outlet and an airbox outlet fluidly communicating with the engine air inlet.

According to some implementations, the airbox is disposed over a portion of the heat exchanger, the portion of the heat exchanger including the heat exchanger air outlet.

According to some implementations, the airbox outlet is defined in a front portion of the airbox.

According to some implementations, the heat exchanger is a first heat exchanger. A second heat exchanger is connected to the tunnel at least in part rearwardly of the first heat exchanger. The first and second heat exchangers are fluidly separate.

According to some implementations, a third heat exchanger is connected to the tunnel forwardly of the second heat exchanger. The third heat exchanger is at least one of: disposed forwardly and disposed downwardly of the first heat exchanger, the first and third heat exchangers being fluidly separate.

According to another aspect of the present technology, there is provided a snowmobile having a frame including a tunnel. The tunnel has an inverted U-shape and includes a top portion, a left side portion and a right side portion. The top, left side and right side portions at least partly enclose a space. At least one ski is connected to the frame. An engine is supported by the frame. A rear suspension assembly is connected to the tunnel. A drive track is disposed around the rear suspension assembly and at least in part disposed in the space enclosed by the tunnel. The drive track is operatively connected to the engine. An air intake system supplies air from the atmosphere to the engine air inlet. The air intake system has a heat exchanger surface being at least one of disposed in the space and disposed adjacent to the space. Air flowing through the intake system to the engine contacts the heat exchanger surface to be cooled thereby before entering the engine.

According to some implementations, the heat exchanger surface forms a part of the top portion of the tunnel.

According to some implementations, the heat exchanger surface is disposed in a gap defined in the top portion of the tunnel.

For purposes of this application, terms related to spatial orientation such as forwardly, rearward, upwardly, downwardly, left, and right, are as they would normally be understood by a driver of the vehicle sitting thereon in a normal riding position. Terms related to spatial orientation when describing or referring to components or sub-assemblies of the vehicle, separately from the vehicle, such as a heat exchanger assembly for example, should be understood as they would be understood when these components or sub-assemblies are mounted to the vehicle, unless specified otherwise in this application.

DETAILED DESCRIPTION

With reference toFIG. 1, a snowmobile10includes a forward end12and a rearward end14. The snowmobile10includes a vehicle body in the form of a frame or chassis16which, as can be seen inFIGS. 2A and 3, includes a tunnel18, an engine cradle portion20, a front suspension module22and an upper structure24.

An internal combustion engine26(schematically illustrated inFIG. 1) is carried in an engine compartment defined in part by the engine cradle portion20of the frame16. A fuel tank28, supported above the tunnel18, supplies fuel to the engine26for its operation. The engine26receives air from an air intake system100(FIG. 2) including an intake heat exchanger130(FIG. 2A). Air flowing into the engine26is first cooled by circulating through the intake heat exchanger130as will be described in greater detail below.

An endless drive track30is positioned at the rear end14of the snowmobile10. The drive track30is disposed generally under the tunnel18, and is operatively connected to the engine26through a belt transmission system (not shown) and a reduction drive (not shown). The endless drive track30is driven to run about a rear suspension assembly32connected to the frame16for propulsion of the snowmobile10. The endless drive track30has a plurality of lugs31extending from an outer surface thereof to provide traction to the track30.

The rear suspension assembly32includes drive sprockets34, idler wheels36and a pair of slide rails38in sliding contact with the endless drive track30. The drive sprockets34are mounted on a drive axle35and define a sprocket axis34a. The slide rails38are attached to the tunnel18by front and rear suspension arms40and shock absorbers42. It is contemplated that the snowmobile10could be provided with a different implementation of a rear suspension assembly32than the one shown herein.

A straddle-type seat60is positioned atop the fuel tank28. A fuel tank filler opening covered by a cap92is disposed on the upper surface of the fuel tank28in front of the seat60. It is contemplated that the fuel tank filler opening could be disposed elsewhere on the fuel tank28. The seat60is adapted to accommodate a driver of the snowmobile10. The seat60could also be configured to accommodate a passenger. A footrest64is positioned on each side of the snowmobile10below the seat60to accommodate the driver's feet.

At the front end12of the snowmobile10, fairings66enclose the engine26and the belt transmission system, thereby providing an external shell that not only protects the engine26and the transmission system, but can also make the snowmobile10more aesthetically pleasing. The fairings66include a hood68and one or more side panels which can be opened to allow access to the engine26and the belt transmission system when this is required, for example, for inspection or maintenance of the engine26and/or the transmission system. A windshield69connected to the fairings66acts as a wind screen to lessen the force of the air on the rider while the snowmobile10is moving.

Two skis70positioned at the forward end12of the snowmobile10are attached to the front suspension module22of the frame16through a front suspension assembly72. The front suspension module22is connected to the front end of the engine cradle portion20. The front suspension assembly72includes ski legs74, supporting arms76and ball joints (not shown) for operatively connecting to the respective ski leg74, supporting arms76and a steering column82.

A steering assembly80, including the steering column82and a handlebar84, is provided generally forward of the seat60. The steering column82is rotatably connected to the frame16. The lower end of the steering column82is connected to the ski legs74via steering rods (not shown). The handlebar84is attached to the upper end of the steering column82. The handlebar84is positioned in front of the seat60. The handlebar84is used to rotate the steering column82, and thereby the skis70, in order to steer the snowmobile10. A throttle operator (not shown) in the form of a thumb-actuated throttle lever is mounted to the right side of the handlebar84. Other types of throttle operators, such as a finger-actuated throttle lever and a twist grip, are also contemplated. A brake actuator (not indicated), in the form of a hand brake lever, is provided on the left side of the handlebar84for braking the snowmobile10in a known manner. It is contemplated that the windshield69could be connected directly to the handlebar84.

At the rear end of the snowmobile10, a snow flap94extends downward from the rear end of the tunnel18. The snow flap94protects against dirt and snow that can be projected upward from the drive track30when the snowmobile10is being driven. It is contemplated that the snow flap94could be omitted.

The snowmobile10includes other components such as a display cluster, and the like. As it is believed that these components would be readily recognized by one of ordinary skill in the art, further explanation and description of these components will not be provided herein.

With reference toFIG. 12, the tunnel18will now be described in more detail. The inverted U-shaped tunnel18is formed by a left side portion18aand a right side portion18a. Each side portion18ais made from a bent piece of sheet metal. Each side portion18ahas a horizontally extending top portion18b. The top portions18bof the left and right sides define a longitudinally extending gap18ctherebetween. Each side portion18ais bent laterally outwardly at its bottom edge to form a part of the corresponding footrest64. Each side portion18ahas an upper front edge18dthat extends downwards and forwards from the front end of the top portion18b, and a lower front edge18ethat extends downwards and forwards from the upper front edge18dto the front end of the bottom edge. The upper and lower front edges18d,18eof the left and right side portions18aform the front of the tunnel18.

A space19is defined by the left and right side portions18a, and the left and right top portions18b. The upper portion of the drive track30is disposed at least partly in the space19as can be seen clearly inFIG. 7. The drive sprockets34and the drive axle35are disposed in a forward portion of the space19enclosed by the forward portion of the tunnel18.

With reference toFIGS. 2A to 3, the engine26is an inline, two-cylinder, four-stroke, internal combustion engine. The two cylinders of the engine26are oriented with their cylindrical axes disposed vertically. It is contemplated that the engine26could be configured differently. For example, the engine26could have more or less than two cylinders, and the cylinders could be arranged in a V-configuration instead of in-line. It is contemplated that the engine26could be a two-stroke internal combustion engine, a carbureted engine, or any other suitable engine capable of propelling the snowmobile10.

The engine26receives air from the air intake system100via an engine air inlet102defined in the rear portion of each cylinder of the engine26. Each air inlet102is connected to a throttle body128of the air intake system100. The throttle body128comprises a throttle valve136(FIG. 2B) which rotates about a rotation axis136ato regulates the amount of air flowing through the throttle body128into the corresponding cylinder of the engine26. A throttle valve actuator134, is operatively connected to the throttle valve136to change the position of the throttle valve136and thereby adjust the opening of the throttle valve136with operation of the throttle lever on the handlebar84. It is also contemplated that the throttle valve actuator134could be in the form of an electric motor. The electric motor could change the position of the throttle valve136based on input signals received from an electronic control module (not shown) which in turn receives inputs signals from a position sensor associated with the throttle lever on the handlebars84. Further details regarding such drive-by wire throttle systems can be found in International Patent Application No. PCT/US2013/048803 filed on Jun. 29, 2013, the entirety of which is incorporated herein by reference. The intake system100includes a heat exchanger130for cooling intake as will be described in greater detail below.

The engine26is fluidly connected to the fuel tank28via a left fuel injector104connected to the top of the left cylinder and a right fuel injector104connected to the top of the right cylinder.

The fuel-air mixture in each of the left and right cylinders of the engine26is ignited by an ignition system (not shown). Engine output power, torque and engine speed are determined in part by the ignition timing, and also by various characteristics of the fuel-air mixture such as its composition, temperature, pressure and the like.

Exhaust gases resulting from the combustion process are expelled from the engine26via an exhaust system110. An exhaust outlet112is defined in the front portion of each cylinder of the engine26. The exhaust system110includes an exhaust conduit114which is connected to the exhaust outlets112of both cylinders and extends forwardly therefrom to direct exhaust gases out of the engine26.

Liquid coolant is also circulated through the engine26in order to cool the engine26. The coolant, which gets heated by absorbing heat from the engine26, is cooled by circulating through a coolant heat exchanger arrangement that includes a front heat exchanger assembly1000and a heat exchanger assembly1002(FIGS. 4 and 11) connected to the tunnel18.

With reference toFIGS. 11A to 11D, the front heat exchanger1000has a body1004defining an internal volume, an outlet pipe1006and an inlet pipe1008. The pipes1006,1008are welded to the body1004. Fins1010are formed on the back of the body1004. The front heat exchanger1000extends from the left side lower front edge18dto the right side front edge18dof the tunnel18, thus defining in part the front of the tunnel18.

The heat exchanger1002is disposed on the top portions18aover the gap18cof the tunnel18. The heat exchanger assembly1002thus defines partly a top of the tunnel18. The heat exchanger1002has a body1012, an inlet pipe1014, an outlet pipe1016, and a connector1018. Fins1020are formed on the bottom of the body1012. The body1012is formed by being extruded. The extrusion process forms two passages1022,1024. A connector1018, also formed by extrusion, is connected to the back of the two passages1022,1024to fluidly connect the two together thereby forming a single passage. The passages1022,1024are capped at their front end. The inlet pipe1014is welded at a front of the passage1022and the outlet pipe1016is welded at a front of the passage1024.

A pipe1014aconnects the inlet pipe1014of the heat exchanger assembly1002to the engine26to receive hot coolant from the engine26. Another pipe1016aconnects the outlet pipe1016of the heat exchange assembly1002to the inlet pipe1008of the heat exchanger assembly1000to allow coolant to flow from the heat exchanger assembly1002to the heat exchanger assembly1000. Another pipe (not shown) connects the outlet pipe1006of the heat exchanger assembly1000to the engine to return cooled coolant to the engine.

During operation of the snowmobile10, coolant flows from the engine26to the heat exchanger1002. In the heat exchanger1002, coolant first flows through the passage1022, then through the connector1018, and then through the passage1024. From the passage1024the coolant flows to the heat exchanger1000. From the heat exchanger1000, the coolant is returned to the engine26.

The coolant in the heat exchangers1000,1002is cooled by a combination of air flowing along the surfaces of the heat exchanger assemblies1000,1002and snow being projected on the surfaces of the heat exchanger assemblies1000,1002by the drive track of the snowmobile.

The air intake system100will now be described in more detail with reference toFIGS. 2A to 3. The air intake system100includes a secondary airbox122, an air compressor124, and an intake heat exchanger130, in addition to the left and right throttle bodies128mentioned above.

Ambient air enters the secondary airbox122, and then flows through the secondary airbox122into the air compressor124which compresses the air. Compressed air from the air compressor124is then directed through the heat exchanger130into the left and right throttle bodies128. From the left throttle body128, the air enters the left cylinder of the engine26via the left engine air inlet102. From the right throttle body128, the air enters the right cylinder of the engine26via the right engine air inlet102.

The secondary airbox122is disposed above the front suspension module and extends rearwards above the engine26. Air enters the secondary airbox122through an inlet123in the front portion of the snowmobile10. An outlet125is defined in the middle portion on the right side of the secondary airbox122. A conduit142connects the outlet125to the air compressor124disposed on the right side of the engine26. It is contemplated that the secondary airbox122could be omitted and that ambient air could directly enter into the turbocharger inlet140without going through the secondary airbox122.

In the illustrated implementation, the air compressor124is in the form of a turbocharger. The turbocharger124includes a compressor turbine (not shown) and an exhaust turbine (not shown). Air flowing past the rotating compressor turbine is compressed thereby. The rotation of the compressor turbine is powered by the exhaust turbine, which is in turn rotated by exhaust gases expelled from the engine26and being directed to flow over the blades of the exhaust turbine.

The turbocharger124includes an ambient air inlet140connected to the secondary airbox122via the air conduit142. The turbocharger124includes a compressed air outlet144connected to a conduit146. The conduit146fluidly connects the turbocharger124with the heat exchanger130. The conduit146extends upwards from the turbocharger124into the secondary airbox122, then rearwards through the secondary airbox122, and then downwards into the heat exchanger130. The secondary airbox122surrounds a portion of the conduit146but the portion of the conduit146is sealed from the secondary airbox122. It is contemplated that the conduit146could not pass through the interior of the secondary airbox122.

The turbocharger124is connected to the exhaust system110for powering the exhaust turbine for compressing air. The turbocharger124includes an exhaust gas inlet148connected to the exhaust conduit114for receiving exhaust gases from the exhaust system110. The turbocharger124includes an exhaust gas outlet149connected to a muffler150for expelling exhaust gases as can be seen inFIG. 4. Exhaust gases expelled from the engine26flows through the exhaust conduit114and via the exhaust inlet148into the exhaust turbine side of the turbocharger124. After flowing over the exhaust turbine, the exhaust gases flow out via the exhaust gas outlet149into the muffler140, and then through the muffler150into the atmosphere via an outlet152of the muffler150.

It is contemplated that the air compressor124could be a supercharger, in which the compressor turbine is directly powered by the engine26. The supercharger would have an ambient air inlet140and a compressed air outlet142but would not be connected to the exhaust system110of the engine26. It is also contemplated that the air compressor124could be omitted, and the heat exchanger130could receive air directly from the secondary airbox122or from the atmosphere when the secondary airbox122is also omitted.

The intake heat exchanger130of the implementations illustrated inFIGS. 2A to 13also provides a voluminous chamber for equalizing air pressure of the airflow entering the engine26. The heat exchanger130is therefore also a primary airbox for the snowmobile10. The heat exchanger130is thus a combined heat exchanger and airbox for entering the engine26. It is however contemplated that a primary airbox could be formed separately from the heat exchanger130.

The intake heat exchanger130will now be described in detail with reference toFIGS. 2A to 13.

The heat exchanger130includes a body162having a forward portion164and a rearward portion166. With reference toFIG. 2A, the rearward portion166is at least partially rearward of the throttle bodies128. The forward portion164extends below and at least partially forward of the throttle bodies128and their common throttle valve axis136a. A vertical plane136bcontaining the axis136aintersects the heat exchanger130. The rearward portion166of the body162forms the airbox.

The heat exchanger130is disposed forward of the coolant heat exchanger1002and fastened to the tunnel18. The rearward portion166is supported by the left side top18band disposed partly over the left portion of the gap18c. The forward portion164extends forward from the rearward portion166to the front of the tunnel18formed by the upper front edges18dthat extends at a downward and forward angle from the top18b. It is contemplated that the forward portion could extend further downward than as shown in the figures to the lower front portion formed by the edges18e. It is contemplated that the heat exchanger130could be fastened to the right side portion18b, or to both top portions18b. It is contemplated that the heat exchanger130could be disposed on the right side of the gap18c, or over the middle of the gap18cwhile being supported by one or both of the top portions18b. It is also contemplated that the heat exchanger130could extend along the entire width of the gap18cfrom the left side portion18ato the right side portion18a.

With reference toFIGS. 9 and 10, the rearward portion166has a front wall166a, a rear wall166b, left and right side walls166c, a top wall166dand a bottom wall166e. The left and right side walls166care disposed vertically and parallel to each other in the lower portion. An upper portion of the left wall166cis angled inwards towards the right side wall166c. An upper portion of the right side wall166cis angled towards the left side wall166c. The front surface166ais angled forwardly and upwardly from the tunnel18. The top wall166dis perpendicular to the front wall166a. The rear wall166bis parallel to the front wall166ain the middle portion. An upper portion of the rear wall166bis angled rearwardly and downwardly from the top wall166d. A lower portion of the rear wall is disposed vertically.

The height of the rearward portion166between the top166dand bottom walls166eis larger than its lateral width between the left and right side walls166c, and its longitudinal depth between the front and rear walls166a,166b. The lateral width of the rearward portion166is greater than the longitudinal depth of the rearward portion166. It is contemplated that the lateral width could be smaller than, or equal to, the longitudinal depth. The walls166a,166b,166c,166d,166eof the rearward portion166define a voluminous interior chamber for expansion of air flowing therein.

An inlet conduit170extends partly above the top wall166dof the rearward portion166. The conduit146is clamped around the portion of the inlet conduit170disposed above the top wall166d. The inlet conduit170extends through an aperture170aformed in the top wall166dand through the interior volume enclosed by the rearward portion166into the forward portion164.

Two laterally spaced outlets172are defined in the front wall166aof the rearward portion166above the forward portion164. Each outlet172is surrounded by a tubular projection projecting forwardly from the front wall166a. The left outlet172is connected to the left cylinder of the engine26via the left throttle body128and the left air inlet102. The right outlet172is connected to the right cylinder of the engine26via the right throttle body128and the right air inlet102. The inlet conduit170is disposed laterally between the two outlets172.

With reference toFIG. 7, the inlet aperture170ais disposed longitudinally rearward of a vertical plane34ccontaining the sprocket axis34a. The vertical plane34apasses through the tubular projection surrounding the outlet172. The inlet170and a portion of the outlet172are therefore disposed on opposite sides of the vertical plane34c. The inlet170and the outlets172are both disposed vertically above a horizontal plane344containing the sprocket axis34a.

The forward portion164of the heat exchanger130includes a top wall164d, a bottom wall164e, a front wall164a, and left and right side walls164c. The bottom wall164eextends forwardly and downwardly from the bottom wall166eof the rearward portion166. The top wall164dextends from the front wall166aof the rearward portion166to the front wall164aof the forward portion164.

The forward portion164encloses an interior volume that is smaller than the interior volume enclosed by the rearward portion166. The height of the forward portion164between the top wall164dand the bottom wall164eis smaller than that of the rearward portion166. The lateral spacing between the left and right side walls164cof the forward portion164decreases towards the front wall164aof the forward portion164. The height of the forward portion164is smaller than the lateral spacing between the left and right side walls164c. The constricted spacing between the top and bottom walls164d,164eof the forward portion164ensures that a majority of the air flowing within the interior volume defined by the forward portion164comes in contact with the bottom wall164eto be cooled thereby.

An internal wall176separates the interior of the forward portion164into a left chamber180and a right chamber180. The internal wall176is disposed forward of the inlet conduit170. The internal wall176extends longitudinally from the front of the inlet conduit170towards the front wall164aof the forward portion164. A left branch of the internal wall176branches off towards left side wall164cof the forward portion164. A right branch of the internal wall176branches off towards right side wall164cof the forward portion164.

A number of longitudinally extending fins174are project upwards from the inner surface of the bottom wall164e. The fins174enhance cooling of the air flowing through the interior volume of the forward portion164. In each chamber180, some of the longitudinal fins174are in front of the inlet conduit170, while the remaining fins174are disposed laterally outwardly of the inlet conduit170.

Compressed air from the turbocharger124flows through the inlet conduit170into the interior volume of the forward portion164. A portion of the airflow flows forward from the inlet conduit176into the right chamber180flowing past the fins174. The right branch of the internal wall176then directs this airflow rightward and then rearward past the fins174and the front wall166aof the rearward portion166into the interior volume enclosed thereby. Similarly, a portion of the airflow flows forward from the inlet conduit176into the left chamber180flowing past the fins174. The left branch of the internal wall176then directs this airflow leftward and then rearward past the laterally outward fins174and the front wall166aof the rearward portion166into the interior volume enclosed thereby. The left and right airflows partially mix while flowing upwards in the interior volume of the rearward portion166before flowing out through either the left or the right heat exchanger outlet172. The voluminous chamber defined by the rearward portion166enables equalization of pressure and temperature of air flowing therethrough to the outlet172.

As can be seen best inFIGS. 7 and 8, the left drive sprocket34and the left side of the drive axle35are disposed under the heat exchanger130. The drive axle35is longitudinally aligned with the heat exchanger130. The forward portion164of the heat exchanger130extends longitudinally forward of the left drive sprocket34while a rear edge of the rearward portion166is longitudinally aligned with the rear edge of the left drive sprocket34as seen from the dashed lines34bshown inFIG. 7. Thus, a projection of the heat exchanger130onto a horizontal plane intersects with the left drive sprocket34and a portion of the drive axle35. The motion of the drive track30around the drive sprockets34inside the space19projects snow, ice and water onto the bottom wall of the heat exchanger130. This snow/ice/water being projected onto the bottom surface of the heat exchanger130helps to cool the air flowing inside the heat exchanger130. A number of fins could be provided on the bottom166e,164eof the heat exchanger130to increase the surface area receiving the snow/ice/water and to thereby enhance cooling efficiency of the heat exchanger130.

It is contemplated that the forward portion164and the rearward portion166could be formed separately as a heat exchanger and airbox respectively. The separately formed heat exchanger164and airbox166could also be disposed separately from one another while being fluidly connected.

With reference toFIGS. 13 to 17, another implementation of an air intake system100′ will now be described. The air intake system100′ is similar to the air intake system100described above and will only be discussed below in detail with regard to the differences. Features of the air intake system100′ that are similar to the corresponding features of the air intake system100have been labeled with the same reference numbers.

The air intake system100′ includes an air compressor124, and an intake heat exchanger240(FIG. 17), a primary airbox266, and a throttle body268. The intake heat exchanger240is formed as part of a heat exchanger assembly200.

The secondary airbox122included in the previous implementation has been omitted. Also, in contrast to the air intake system100, the air intake system100′ includes a primary airbox266that is separate from the intake heat exchanger240, and a single throttle body268instead of the left and right throttle bodies128of the previous implementation. Ambient air enters the air compressor124which compresses the air. Compressed air from the air compressor124flows into the intake heat exchanger240. From the intake heat exchanger240, air flows through the throttle body268into the primary airbox266and finally into the engine26via the left and right engine air inlets102.

The air compressor124is an exhaust gas driven turbocharger as in the previous implementation. It is however contemplated that the air compressor124could be a supercharger. It is also contemplated that the air compressor124could be omitted. The turbocharger124includes an ambient air inlet140which directly receives ambient air. The turbocharger124includes a compressed air outlet144connected to a conduit146which extends rearwards from the turbocharger124into the intake heat exchanger240.

As can be seen inFIG. 17, the intake heat exchanger240has an inlet256connected to an inlet pipe260, and an outlet258connected to an outlet pipe262. The conduit146connects to the inlet pipe260. The throttle body268is connected to the outlet pipe262.

The tubular throttle body268extends vertically upwards from the intake heat exchanger240to an airbox inlet270of the airbox266. A throttle valve actuator274is connected to the throttle valve (not shown) in the throttle body268.

With reference toFIG. 15, the airbox266has an L-shaped body with a vertically extending forward portion and a horizontally extending rearward portion. The forward portion rests on the curved portion of the heat exchanger assembly200and extends upwards therefrom. The rearward portion extends rearward from the upper portion of the forward portion. The rearward part is disposed spaced from the heat exchanger assembly200. The rearward portion is disposed above the outlet258of the intake heat exchanger240.

The airbox inlet270is defined in the bottom wall of the rearward portion. Two laterally spaced airbox outlets272are defined in the front wall of the airbox266. The left airbox outlet272is connected to the left cylinder via a left intake conduit280. The right airbox outlet272is connected to the right cylinder via a right intake conduit280. Each intake conduit280has a cylindrical flute portion282(FIG. 17) which is disposed inside the airbox266and aids in noise suppression. The portion of each intake conduit280disposed between the airbox266and the engine26increases in diameter from the airbox266towards the engine26.

As can be seen fromFIGS. 21 to 23, the intake heat exchanger240is disposed above the drive axle35, and is longitudinally aligned with the sprockets34. In this position, the bottom part209of the intake heat exchanger240can be cooled by snow projected by the drive track30during operation of the snowmobile10. The intake heat exchanger inlet256is disposed longitudinally forward of the sprocket axis34aand is longitudinally aligned with a portion of the sprocket34. The intake heat exchanger outlet258is disposed longitudinally rearward of the rotation axis34aand is longitudinally aligned with a portion of the sprocket34. The drive axle axis34ais disposed longitudinally between the intake heat exchanger inlet256and the intake heat exchanger outlet258such that inlet256is on an opposite side of a vertical plane containing the axis34athan outlet258. It is contemplated that the inlet256and outlet258positions could be reversed.

Turning now toFIGS. 18 to 23, the heat exchanger assembly200will be described in more detail. The heat exchanger assembly200includes a coolant liquid heat exchanger242in addition to the intake heat exchanger240.

In the implementation of the tunnel18illustrated inFIGS. 13 to 23, the upper front edge18dconnecting the top18bto the lower front edge18eis curved. The upper front edge18dcurves continuously in a downward and a forward direction from the top18ainstead of being angled downwards and forwards therefrom as in the tunnel18illustrated inFIGS. 2 to 12.

The heat exchanger assembly200extends from the left side portion18ato the right side portion18aacross the gap18c. The heat exchanger assembly200extends from the left side top18bto the right side top18bthereby forming a majority of the top of the tunnel18. The heat exchanger assembly200also extends from the left side front edges18d,18eto the right side front edges18d,18e, thereby forming a majority of the front of the tunnel18. The heat exchanger assembly200is fastened, welded or otherwise connected to the side portions18a. Trims98are disposed near the top of each side portion18ato hide the connection between the heat exchanger assembly200and the side portions18aof the tunnel18.

The heat exchanger assembly200has a front portion202, a rear portion204and a middle portion206between the front and rear portions202,204. As can be seen, the front portion202is curved down from the middle portion206such that the front portion202extends below the middle portion206. The front portion202also extends below the sprocket axis34a. The front portion202extends over the entire front of the tunnel18.

As best seen inFIGS. 20 and 21, the heat exchanger assembly200is made of three main parts: a top part208, a bottom part209and another bottom part210. The bottom part209is joined to the top part208to form the intake heat exchanger240. The bottom part210is joined to a top part208to form the engine coolant heat exchanger242.

The top part208is made of a piece of sheet metal that is curved. The top part208is flat in the front portion202, and then curves rearwards toward the middle portion206. The top part208is flat in the middle and rear portions206,204. The top portion208also has four apertures214,216,256and258, each of which serves as an inlet or outlet to one of the heat exchangers240,242as will be described below.

The bottom part209is curved when viewed from a lateral side and has a recess252with a border254around it. The border254is used to weld or otherwise join the bottom part209to the bottom of the top part208such that the recess252forms a passage with the top part208. The bottom part209is joined to the top part208in part along the front portion202and in part along the middle portion206. As a result, the recess252is also curved to follow the curvature of the top part208. As can be seen, the recess252is generally L-shaped. Since the recess252and the top part208define the shape of the passage, the passage formed by the recess252is generally L-shaped. As seen from a lateral side of the heat exchanger assembly200, the passage is curved. It is contemplated that the recess252could have other shapes.

The bottom part209is made of a piece of sheet metal that is curved to match the curvature of the top part208. Once curved, the bottom part209is stamped to form the recess252. The piece of sheet metal from which the bottom part209is made is initially shaped such that only a border254is left around the recess252. Alternatively, it is contemplated that the sheet metal could be cut after the recess252has been formed so as to only leave the border254around the recess252.

The aperture256of the top part208forms an inlet for the passage formed by the recess252of the bottom part209. The aperture256connects to an end of the laterally extending arm of the L-shaped passage. The inlet256is thus disposed on the front end of the right side of the top of the tunnel18. The aperture258of the top part208forms an outlet of the passage formed by the recess252of the bottom part209. The aperture258connects to the end of the longitudinally extending arm of the L-shaped passage. The outlet258is thus disposed longitudinally rearward of the inlet256and laterally centered on the top of the tunnel18.

An inlet pipe260is welded or otherwise joined to the top part208around the inlet256. The inlet pipe260is disposed angled forwardly and upwardly from the top part210. An outlet pipe262is welded or otherwise joined to the top part208around the outlet258. The outlet pipe is disposed extending vertically upwards from the top part210. It is contemplated that the orientation of the pipes260,262could be different than as shown herein.

During operation, ambient air enters via the inlet140into the turbocharger124where the air is compressed. Compressed air flows out of the turbocharger124via the outlet144and the conduit146. The air then flows through the inlet pipe260via the inlet256into the passage formed by the bottom portion209. Air flows along the laterally extending arm of the L-shaped passage from the right side of the tunnel18to the left side thereof, and then into the longitudinally extending arm of the L-shaped passage. The air then flows rearward in the longitudinally extending L-shaped arm along the top of the tunnel18to the outlet258. From the outlet258, air flows upward into the throttle body268via the outlet pipe262. The throttle valve actuator274regulates the air flowing upwards through the throttle body168into the airbox266. From the airbox266, some of the air flows out via the left conduit280inserted through the left outlet272into the left cylinder of the engine26. The remaining air flows out through the right conduit280inserted through the right outlet272into the right cylinder of the engine26.

The bottom part210is curved and disposed surrounding the bottom part209. The bottom part210has a recess222with a border224around it. The border224is used to weld or otherwise join the bottom part210to the bottom of the top part208such that the recess222forms a passage with the top part208. The passage formed by the bottom part210is fluidly separate from the passage formed by the bottom part209.

The shape of the passage is defined by the shape of the recess222. A passage portion228is disposed in the forward portion202. Passage portions230,234are disposed in the middle and rear portion206,204. A passage portion232is disposed in the rear portion204. The passage portion228extends laterally in the forward portion and below the bottom part209. The passage portion228is connected to the passage portion230extending longitudinally along a left side of the bottom part209. The passage portion234extends longitudinally along a right side of the passage formed by the bottom part209. The laterally extending passage portion232connects the left passage230with the right passage234rearward of the bottom part209.

The bottom part210is made of a piece of sheet metal that is curved down at its front such that its curvature matches the curvature of the top part208. Once curved, the bottom part210is stamped to form a recess222. The piece of sheet metal from which the bottom part210is made is initially shaped such that only a border224is left around the recess222, thereby reducing the weight of the bottom part110. Alternatively, it is contemplated that the sheet metal could be cut after the recess222has been formed so as to only leave the border224around the recess222. It is also contemplated that the sheet metal could not be cut.

The aperture216of the top part208forms an inlet, and the aperture214forms an outlet of the passage formed by the recess222of the bottom part210. The inlet216and outlet214connect to opposite ends of the passage formed by the bottom part210. The inlet216is connected to the front end of the right passage portion234. The inlet214is connected to the right end of the front passage portion228. The outlet214is thus disposed longitudinally forward of and vertically lower than the inlet216. The inlet216and the outlet214are positioned on opposite sides of a vertical plane34ccontaining the axis34a. The inlet216and the outlet214are also positioned on opposite sides of a horizontal plane34dcontaining axis the34a. The inlet216is disposed longitudinally rearward of the inlet256of the passage formed by the bottom portion209. The outlet214is disposed longitudinally forward of and vertically lower than the inlet256of the passage formed by the bottom portion209. It is contemplated that the positions of the inlet216and outlet214could be interchanged.

As can be seen inFIGS. 18 and 19, an inlet pipe220is welded or otherwise joined to the top part208around the inlet216and an outlet pipe218is welded or otherwise joined to the top part208around the outlet214. The inlet pipe220is disposed angled forwardly and upwardly from the middle portion206of the top part210. The outlet pipe218is disposed horizontally and extending forwards from the front portion of the top part210. It is contemplated that the orientation of the pipes260,262could be different than as shown herein.

As can be seen inFIGS. 21 and 23, the passage portion228is located forwardly of the sprocket axis34a. As the track30passes around the sprockets35, it projects snow onto the portion of the bottom part210defining the passage portion228. Making the passage portion228wide and long increases the amount of cooling obtained from this projected snow since a large surface is exposed to the projected snow. The passage portions230,232,234are cooled by snow projected onto the bottom part210by the drive track30as well as cool ambient air flowing over the top part208.

During operation of the engine26, the hot engine coolant flows from the engine26through a pipe (not shown) connected to the inlet pipe220, then through the inlet pipe220and the inlet216into the passage formed between the top and bottom parts208,210. From the inlet216, the engine coolant flows through the passage portions234,232,230, and228. From the portion228of the passage, the coolant flows out of the passage via the outlet214, through the outlet pipe218and finally through a pipe (not shown) connected between the outlet pipe218and the engine26to return the now cooled coolant to the engine26.

Although in the present implementation, passage formed by the bottom part210is used to circulate and thereby cool the engine coolant, it is contemplated that it could be used to cool other motor fluids such as, for example, oil used to lubricate the engine26.

It is contemplated that the passage portion228could be fluidly separate from the passage portions230,232,234to form a third heat exchanger that is separate from the intake heat exchanger240and the coolant heat exchanger242. It is contemplated that the passage portion228could be omitted from the bottom part210and be included instead in bottom part209so as to be a part of the intake heat exchanger240instead of the coolant heat exchanger242.

It is contemplated that the apertures214,216,256,258could be anywhere on the top part208as long as the geometry of the passage discussed above is modified accordingly.

Other implementations of the heat exchanger assembly200are contemplated and described in further detail in Unites States Provisional Patent Application No. 61/872,204 filed on Aug. 30, 2013, the entirety of which is included herein by reference.