Abstract:
A snowmobile is disclosed having a frame. A tunnel is formed in a rearward portion of the frame. An engine disposed on the frame. A drive track is disposed at least in part in the tunnel and is operatively connected to the engine for propulsion of the snowmobile. At least one ski is operatively connected to the frame at least in part forwardly of the drive track. A straddle seat is disposed on the frame at least in part above the drive track. A steering device is operatively connected to the at least one ski for steering the snowmobile. A radiator is disposed between the tunnel and the track. The radiator has a first side facing the track and a second side facing the tunnel. The second side is generally opposite the first side. At least a portion of the second side is spaced apart from the tunnel.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a snowmobile cooling system. 
       BACKGROUND OF THE INVENTION 
       [0002]    Most snowmobiles have a frame made of bent sheet metal and metal tubing. A forward portion of the frame forms an engine cradle for supporting an internal combustion engine. A rearward portion of the frame forms a tunnel generally having an inverted U-shape. A drive track is disposed at least in part in the tunnel and is driven by the engine to propel the snowmobile. The combustion of fuel in the engine produces a significant amount of heat, and some of this heat is absorbed from the engine by a coolant, such as a mixture of water and ethylene glycol, to maintain the engine at a suitable temperature. The hot coolant is then pumped to a radiator, where the heat is dissipated to the atmosphere. 
         [0003]    Referring to  FIG. 1 , during operation of a snowmobile, the rotation of the track  10  inside the tunnel  14  causes cold air and snow to circulate in the tunnel  14 . It is common to mount one or more radiators  16 ,  20 ,  24  at one or more positions on the inside of the tunnel  14 , facing the track  10 , so that the circulation of cold air and snow can be used to dissipate heat from the coolant flowing through the radiators  16 ,  20 ,  24  to cool the engine. The number of radiators and their size and positions within the tunnel  14  are dictated by the cooling requirements of the engine. The radiator  16  is positioned on the front wall  18  of the tunnel  14 , the radiator  20  is positioned on the top surface  22  of the tunnel  14 , and the radiator  24  is positioned on the inside of a rear portion  26  of the tunnel  14  in combination with a snow flap  28  to increase the quantity of snow that comes into contact with the radiator  24 . 
         [0004]    Referring to  FIG. 2 , in an alternative embodiment the radiator  30  may be constructed as part of the top surface  32  of the tunnel  34 , resulting in a reduced-weight snowmobile. 
         [0005]    Although these arrangements provide adequate cooling for the engine of the snowmobile, they have a number of disadvantages. 
         [0006]    When the radiator is positioned on the front wall of the tunnel, the metal frame conducts heat from the radiator to the engine compartment situated forwardly of the tunnel. As a result, the temperature of the engine compartment is increased, thereby reducing the effectiveness of the radiator to cool the engine. 
         [0007]    Regardless of where the radiator is positioned on the tunnel, heat from the radiator is transferred to the tunnel. Snow coming into contact with the warm tunnel melts and later re-freezes, resulting in ice build-up on one or more of the tunnel, the track and the rear suspension assembly. The ice build-up increases the weight of the snowmobile. In addition, water that re-freezes on the track and rear suspension assembly when the snowmobile is not in use can in some cases result in the suspension or the track becoming jammed, making the snowmobile difficult to move. 
         [0008]    In some snowmobiles, as described above, it is necessary to provide multiple radiators, to provide adequate cooling for the engine, resulting in increased weight of the snowmobile and increased cost of manufacture. 
         [0009]    Therefore, there is a need for a snowmobile having a radiator arrangement that provides efficient cooling of the engine of the snowmobile. 
         [0010]    There is also a need for a snowmobile having a radiator arrangement resulting in a lightweight cooling system. 
         [0011]    There is also a need for a snowmobile having a radiator arrangement that reduces or eliminates the likelihood of ice build-up on the components of the snowmobile. 
       SUMMARY OF THE INVENTION 
       [0012]    It is an object of the present invention to ameliorate at least some of the inconveniences present in the prior art. 
         [0013]    It is also an object of the present invention to provide a radiator spaced apart from the frame of the snowmobile. 
         [0014]    In one aspect, the invention provides a snowmobile comprising a frame. A tunnel is formed in a rearward portion of the frame. An engine is disposed on the frame. A drive track is disposed at least in part in the tunnel. The drive track is operatively connected to the engine for propulsion of the snowmobile. At least one ski is operatively connected to the frame at least in part forwardly of the drive track. A straddle seat is disposed on the frame at least in part above the drive track. A steering device is operatively connected to the at least one ski for steering the snowmobile. A radiator is disposed between the tunnel and the track. The radiator has a first side facing the track and a second side facing the tunnel. The second side is generally opposite the first side. At least a portion of the second side is spaced apart from the tunnel. 
         [0015]    In a further aspect, at least 25% of the second side is spaced apart from the tunnel. 
         [0016]    In a further aspect, at least 50% of the second side is spaced apart from the tunnel. 
         [0017]    In a further aspect, at least 75% of the second side is spaced apart from the tunnel. 
         [0018]    In a further aspect, the entire second side is spaced apart from the tunnel. 
         [0019]    In a further aspect, an air passage is between the second side of the radiator and the tunnel. 
         [0020]    In a further aspect, when the snowmobile is being operated in the forward direction, the direction of air flow along the first side is opposite the direction of air flow along the second side. 
         [0021]    In a further aspect, the radiator is disposed at least in part forwardly of the track. 
         [0022]    In a further aspect, the tunnel has a front wall. The second side of the radiator faces the front wall of the tunnel. 
         [0023]    In a further aspect, the second side of the radiator generally follows a contour of the front wall of the tunnel. 
         [0024]    In a further aspect, the top wall of the tunnel has a downwardly-extending projection disposed generally rearwardly of the air passage. 
         [0025]    In a further aspect, when the snowmobile is being operated in a forward direction, an area of reduced air pressure is created at a rearward opening of the air passage. 
         [0026]    In a further aspect, when the snowmobile is being operated in the forward direction, the direction of air flow along the first side is opposite the direction of air flow along the second side. 
         [0027]    In a further aspect, the first side of the radiator is generally arcuate. 
         [0028]    In a further aspect, the track is supported by a plurality of axles. One of the plurality of axles is a forwardmost axle. The first side of the radiator forms a generally circular arc having a center of curvature approximately at an axis of rotation of the forwardmost axle. 
         [0029]    In a further aspect, the radiator has an inlet and an outlet. The inlet and the outlet communicate with an interior of the radiator via the second side. The inlet and the outlet pass through the front wall of the tunnel. 
         [0030]    In a further aspect, the first side of the radiator has a plurality of fins projecting outwardly therefrom in the direction of the track. The second side of the radiator has generally flat sections. 
         [0031]    In a further aspect, the first side of the radiator has a first plurality of fins projecting outwardly therefrom in the direction of the track. The second side of the radiator has a second plurality of fins projecting outwardly therefrom. 
         [0032]    In a further aspect, the second plurality of fins contact the tunnel. 
         [0033]    For purposes of this application, terms relating to spatial orientation, such as “forwardly”, “rearwardly” and “transversely” are defined consistently with a forward travel direction of the snowmobile. 
         [0034]    Embodiments of the present invention each have at least one of the above-mentioned objects and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present invention that have resulted from attempting to attain the above-mentioned objects may not satisfy these objects and/or may satisfy other objects not specifically recited herein. 
         [0035]    Additional and/or alternative features, aspects, and advantages of embodiments of the present invention will become apparent from the following description, the accompanying drawings, and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]    For a better understanding of the present invention, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where: 
           [0037]      FIG. 1  is a schematic cross-sectional view of a prior art snowmobile tunnel, taken along the longitudinal centerline of the tunnel; 
           [0038]      FIG. 2  is a perspective view, taken from a rear, left side, of a prior art frame assembly for a snowmobile; 
           [0039]      FIG. 3  is a perspective view, taken from a front, right side, of a snowmobile in accordance with aspects of the present invention; 
           [0040]      FIG. 4  is a cross-sectional view of a front portion of the tunnel and radiator of the snowmobile of  FIG. 3 , taken along the longitudinal centerline of the snowmobile of  FIG. 3 ; 
           [0041]      FIG. 5  is a partial cut-away perspective view of the tunnel and radiator of  FIG. 4 ; 
           [0042]      FIG. 6  is a cross-sectional view of a front portion of the tunnel and radiator of a snowmobile according to an alternative embodiment; and 
           [0043]      FIGS. 7A-7C  are schematic cross-sectional views of snowmobile tunnels, taken along the longitudinal centerline of the tunnel, showing various embodiments of radiator arrangements. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]    Referring to  FIG. 3 , a snowmobile  100  will be described. The snowmobile  100  has a forward end  102  and a rearward end  104  which are defined consistently with a travel direction of the vehicle. The snowmobile  100  has a frame  105  including a tunnel  106  and an engine cradle  108 . The tunnel  106  generally consists of one or more pieces of sheet metal bent to form an inverted U-shape. The tunnel  106  extends rearwardly along the longitudinal centerline of the snowmobile  100  and is connected at the front to the engine cradle  108 . An engine  110  (schematically illustrated) is supported by the engine cradle  108 . A number of fairings  112  are supported on the frame  105  to provide aesthetic appeal and to shield some components of the snowmobile  100  from the elements. A straddle seat  114  is provided above the tunnel  106  for accommodating a rider and, optionally, one or more passengers. Footrests  115  extend outwardly from the tunnel  106  to support the feet of the rider and passengers. 
         [0045]    A pair of skis  116  at the front end  102  of the snowmobile  100  are connected to the frame via a suspension system  118 . A steering assembly  120  is provided generally forwardly of the seat  114 , and is connected to the skis  116  in a known manner such that turning the steering assembly  120  turns the skis  116  to steer the snowmobile  100 . It should be understood that the snowmobile  100  may alternatively have only a single ski  116 . 
         [0046]    At the rear end  104  of the snowmobile  100 , an endless track  122  is supported by a rear suspension system  124 . The rear suspension system  124  includes a pair of slide rails  126  in sliding contact with the track  122 . The upper portion of the track  122  is disposed in the tunnel  106 . The track  122  is driven by the engine  110  via a transmission (not shown) to propel the snowmobile  100 . 
         [0047]    A cooling system circulates a liquid coolant through the engine  110  to absorb some of the heat generated by the combustion of fuel in the engine  110  and maintains the engine  110  at a suitable operating temperature. The coolant is then circulated to a radiator  128  ( FIG. 4 ) that will be described below in further detail, to dissipate the heat to the atmosphere. 
         [0048]    Referring now to  FIGS. 4 and 5 , the radiator  128  will be described. 
         [0049]    The radiator  128  is mounted inside the tunnel  106 , between the front wall  130  of the tunnel  106  and the track  122 . The radiator  128  is held in position by fasteners  129  such as bolts inserted through the front wall  130  of the tunnel  106  and received in the recesses  131  of the radiator. Each fastener  129  is held in position by a corresponding nut  141 . A spacer  143  disposed on the fastener  129  maintains the second side  134  of the radiator  128  in a position spaced apart from the front wall  130 . A portion of the radiator  128  is disposed forwardly of the track  122 . It is contemplated that the entire radiator  128  may be disposed forwardly of the track  122 . A first side  132  of the radiator  128  faces a forward portion of the track  122 . The first side  132  is generally arcuate and forms a generally circular arc with its center of curvature approximately at the axis of rotation  133  of the forwardmost axle  135  supporting the track  122 , such that the first side  132  and the track  122  form an air passage  137  of approximately uniform width therebetween. A plurality of fins  139  extend outwardly from the first side  132 , generally in the direction of the track  122 , to provide increased thermal contact between the radiator  128  and the air passage  137 . 
         [0050]    A second side  134  of the radiator  128 , generally opposite the first side  132 , faces the front wall  130  of the tunnel  106  and is spaced apart therefrom. The second side  134  generally follows the contour of the front wall  130 . An air passage  138  is formed in the space between the radiator  128  and the front wall  130  of the tunnel  106 . The air passage  138  reduces heat transfer from the radiator  128  to the tunnel  106  and thus reduces or eliminates the likelihood of ice build-up on the frame  105 . In addition, the flow of air  154  through the passage  138  contributes to cooling the second side  134  of the radiator  128  as will be discussed below in further detail. Other positions are contemplated for the radiator  128 , as will be described in further detail below. It is further contemplated that a thermally insulating material may be provided between the radiator  128  and the tunnel  106  instead of, or in addition to, the air passage  138  to reduce heat transfer to the tunnel  106 . The second side  134  is made of generally flat sections. It is contemplated that the second side  134  has fins  145  projecting outwardly therefrom The fins  145  are oriented generally parallel to the flow of air  154  along the second side  134 , so as not to interfere with the flow of air  154 . It is contemplated that the fins  145  may alternatively have a different orientation, for example the fins  145  may be oriented transversely. It is further contemplated that the fins  145  may extend far enough away from the second side  134  that they contact the front wall  130 , in which case the spacers  143  may be omitted. It is further contemplated that the second side  134  may alternatively be formed of flat sections only, without the fins  145 . 
         [0051]    A downwardly-extending projection is formed in the top wall  136  of the tunnel  106 , generally rearwardly of both the radiator  128  and the air passage  138 . The projection  140  prevents snow or other debris from being thrown by the track  122  into the air passage  138  and obstructing the air flow therethrough. The projection  140  additionally creates an upward flow of air  154  ( FIG. 4 ) through the air passage  138 , as will be described below in further detail. 
         [0052]    An inlet  142  and an outlet  144  of the radiator  128  pass through apertures in the front wall  130  of the tunnel  106  and allow the cooling system of the engine  110  to communicate with the interior  146  of the radiator  128  via the second side  134  of the radiator  128 . Hot coolant from the engine  110  enters the interior  146  of the radiator  128  via the inlet  142  and returns to the engine  110  via the outlet  144  after it has been at least partially cooled by the radiator  128 . 
         [0053]    Referring to  FIG. 4 , the operation of the radiator  128  will be described. When the snowmobile  100  is being operated in the forward direction (indicated by the arrow), the engine  110  drives the track  122  to rotate in the direction  146 . The rotation of the track  122  causes the circulation  148  of cold air and snow within the tunnel  106 , which in turn induces the circulation  149  of cold air along the first side  132  of the radiator  128 , in the direction of rotation  146  of the track  122 . The cold air and snow contact the first side  132  of the radiator  128 , in particular the fins  139 , and absorb heat from the radiator  128 , thereby cooling the coolant circulating therein. The projection  140  induces a turbulent air flow  150  in the area of the rearward opening  152  of the air passage  138 . The air flow  150  creates an area of reduced pressure at the opening  152 . The reduced pressure causes cold air  154  to be drawn through the air passage  138 , along the second side  134  of the radiator  128  in the direction shown. The cold air  154  contacts the second side  134  of the radiator  128 , and absorbs heat from the radiator  128 , further cooling the coolant circulating therein. As can be seen, the circulation of cold air  154  is in the direction opposite that of the circulation  149 . 
         [0054]    Both the first side  132  and the second side  134  of the radiator  128  are used for dissipating the heat from the engine  110  to the atmosphere. As a result of the increased surface area of the radiator  128  that is used to dissipate heat to the atmosphere, the radiator  128  can provide adequate cooling for the engine  110 , in some cases without the need for a second radiator, resulting in a lightweight vehicle with a compact cooling system. The absence of a second radiator along the top wall  136  of the tunnel  106  additionally reduces the likelihood of ice build-up on components disposed beneath the rear portion of the tunnel  106 , such as the track  122  and the rear suspension system  124 . 
         [0055]    Referring now to  FIG. 6 , the operation of an alternative embodiment of a radiator  228  will be described according to a second embodiment. Where the embodiment of  FIG. 6  has features similar to those shown in  FIG. 4 , they have been given similar reference numbers differing only in the first digit. Some features common to both embodiments are not indicated in  FIG. 6  and will not be described again in detail. When the snowmobile  100  is being operated in the forward direction (indicated by the arrow), the track  222  is driven by the engine  110  to rotate in the direction  246 . The rotation of the track  222  causes the circulation of cold air  248  and snow within the tunnel  206 , which induces a circulation  249  of cold air and snow along the first side  232  of the radiator  228 , in the direction of rotation  246  of the track  222 . The cold air and snow contact the first side  232  of the radiator  228 , in particular the fins  239 , and absorb heat from the radiator  228 , thereby cooling the coolant circulating therein. The top wall  236  of the tunnel  206  does not have a feature corresponding to the projection  140  of the embodiment of  FIG. 4 . A portion  250  of the cold air  248  is directed toward the opening  252  and drives cold air  254  through the air passage  238 , along the second side  234  of the radiator  228 . The cold air  254  contacts the second side  234  of the radiator  228 , and absorbs heat from the radiator  228 , further cooling the coolant circulating therein. As can be seen, the circulation of cold air  254  is in the same direction as that of the cold air  248 . 
         [0056]    Referring now to  FIGS. 7A-7C , a number of possible positions are contemplated for the radiator  128 . Referring to  FIG. 7A , the radiator  128 A is installed in the position shown in  FIG. 4 , at a forward portion of the tunnel  106 , generally forwardly of the track  122 . The radiator  128 A is spaced apart from the front wall  130 , and an air passage  138 A is formed therebetween. Referring to  FIG. 7B , the radiator  128 B is installed along the top wall  136  of the tunnel  106 , generally above the track  122 . The radiator  128 B is spaced apart from the top wall  136 , and an air passage  138 B is formed therebetween. Referring to  FIG. 7C , the radiator  128 C is installed at a rearward portion of the tunnel  106 , generally rearwardly of the track  122 . The radiator  128 C is spaced apart from the top wall  136  and the rear wall  156  of the tunnel  106 , and an air passage  138 C is formed therebetween. A snow flap  158  may be provided rearwardly of the track  122  to increase the circulation of cold air and snow in the vicinity of the radiator  128 C. 
         [0057]    Referring now to  FIGS. 8A-8D , a number of alternative shapes are contemplated for the second side  134  of the radiator  128 . 
         [0058]    Referring to  FIG. 8A , a lower portion  135 A of the second side  134 A of the radiator  128 A is in contact with the front wall  130  and an upper portion  136 A of the second side  134 A is spaced apart from the front wall  130 . It is contemplated that the lower portion  135 A may comprise 25%, 50% or 75% of the area of the second side  134 A, with the upper portion  136 A comprising the remainder. It should be understood that the transfer of heat to the tunnel  106  will be reduced to a greater extent if the area of the upper portion  136 A is larger relative to the area of the lower portion  135 A. 
         [0059]    Referring to  FIG. 8B , the second side  134 B of the radiator  128 B is spaced apart from the front wall  130 . The fins  145 B extend outwardly from the second side  134 B and contact the front wall  130 . The fins  145 B are oriented transversely. In this embodiment, the fins  145 B act as spacers between the second side  134 B and the front wall  130 , and a separate spacer  143  is not needed. 
         [0060]    Referring to  FIGS. 8C and 8D , the second side  134 C of the radiator  128 C has two lateral portions. One lateral portion  135 C is in contact with the front wall  130  and the other lateral portion  136 C is spaced apart from the front wall  130 . It is contemplated that the second side  134 C may have more than two lateral portions, for example left and right lateral portions  135 C in contact with the front wall  130  and a central lateral portion  136 C spaced apart from the front wall  130 . It is contemplated that the lateral portion  135 C may comprise 25%, 50% or 75% of the area of the second side  134 C, with the lateral portion  136 C comprising the remainder. It should be understood that the transfer of heat to the tunnel  106  will be reduced to a greater extent if the area of the upper portion  136 C is larger relative to the area of the lower portion  135 C. 
         [0061]    Modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present invention is therefore intended to be limited solely by the scope of the appended claims.