Abstract:
A continuously variable transmission assembly includes a driving pulley rotatable about a driving pulley axis and a driven pulley rotatable about a driven pulley axis. An endless belt operatively connecting the pulleys defines a belt reference plane, the driving and driven pulley axes passing therethrough. A housing encloses a space, the driving pulley, the driven pulley, and the belt being disposed at least in part therein. A driven pulley inlet and outlet defined in the housing are disposed closer to the driven pulley than the driving pulley. The driven pulley inlet, disposed on a first side of the belt reference plane, is configured to direct air from outside the housing into the space toward the driven pulley. The driven pulley outlet is disposed on a second side of the belt reference plane. Air flows from the space to the outside of the housing via the driven pulley outlet.

Description:
FIELD OF TECHNOLOGY 
     The present technology relates generally to continuously variable transmissions, and more specifically to continuously variable transmission assemblies. 
     BACKGROUND 
     Continuously variable transmissions (CVTs) are used in many kinds of wheeled and tracked vehicles to transfer power from the engine to the wheels or tracks of the vehicle. A CVT has a driving pulley and a driven pulley connected by an endless belt. Each pulley has a pair of opposing sheaves, at least one of which is axially moveable, holding the belt between them. The opposing pulley sheaves exert a clamping force on the belt to keep the belt engaged so that the rotational motion of the driving pulley can be transmitted to the driven pulley. The diameters of the driving pulley and the driven pulley are in inverse relationship due to the relatively fixed length of the belt spanning the two pulleys. The belt moves up and down the opposing pulley sheaves as the diameter of the pulley changes. This clamping force exerted on the belt by the opposing pulley sheaves and the motion of the belt against the surface of the sheaves generates a significant amount of heat. The amount of heat generated can be a problem in vehicles used on rugged terrains or those carrying large amounts of load, such as all-terrain vehicles and the like, which encounter frequent changes of speed and/or output torque required to negotiate the rough terrain. 
     There is thus a need for a CVT assembly which provides adequate cooling to prevent wear and damage, especially to the belt, due to excessive heat. 
     SUMMARY 
     It is an object of the present technology to ameliorate at least some of the inconveniences present in the prior art. 
     In one aspect, a continuously variable transmission (CVT) assembly includes a driving pulley rotatable about a driving pulley axis and a driven pulley rotatable about a driven pulley axis disposed parallel to the driving pulley axis. An endless belt operatively connects the driving pulley with the driven pulley. The belt defines a belt reference plane. The driving pulley axis and the driven pulley axis pass through the belt reference plane. A housing encloses a space. The driving pulley, the driven pulley, and the belt are disposed at least in part in the space. A driven pulley inlet defined in the housing and disposed on a first side of the belt reference is disposed closer to the driven pulley than to the driving pulley. The driven pulley inlet is configured to direct air from outside the housing into the space toward the driven pulley. A driven pulley outlet defined in the housing and disposed on a second side of the belt reference plane is disposed closer to the driven pulley than the driving pulley. Air flows from the space to the outside of the housing via the driven pulley outlet. 
     In another aspect, the driven pulley axis passes through the driven pulley inlet. 
     In another aspect, the driven pulley inlet is configured to direct air into the space in an axial direction with respect to the driven pulley. 
     In yet another aspect, the driven pulley outlet is disposed radially outwardly of the driven pulley axis. 
     In a further aspect, at least a portion of the driven pulley outlet is disposed radially outwardly of the driven pulley. 
     In another aspect, the driven pulley outlet is configured to direct air flowing therethrough in a direction generally perpendicular to the driven pulley. 
     In an additional aspect, the driven pulley includes an outer surface disposed on the first side of the belt reference plane and facing away from the belt, the outer surface of the driven pulley comprising fins, rotation of the driven pulley causing air from outside the space to be drawn into the space via the driven pulley inlet. 
     In an additional aspect, a driving pulley inlet is defined in the housing and disposed closer to the driving pulley than the driven pulley. The driving pulley inlet is configured to direct air from outside the housing into the space and toward the driving pulley. 
     In another aspect, the driving pulley inlet is disposed at least is part on the second side of the belt reference plane. 
     In an additional aspect, the driving pulley includes an outer surface disposed on the second side of the belt reference plane and facing away from the belt. The outer surface of the driving pulley has fins. Rotation of the driving pulley causes air from outside the space to be drawn into the space via the driving pulley inlet. 
     In another aspect, the driving pulley inlet is configured to direct air into the space in a direction generally perpendicular to the driving pulley axis. 
     In a further aspect, a driving pulley outlet defined in the housing and disposed closer to the driving pulley than the driven pulley is configured to direct air from the space to outside the housing. 
     In another aspect, the driving pulley outlet is configured to direct air flowing therethrough in a direction generally perpendicular to the driving pulley axis. 
     In an additional aspect, the driving pulley inlet is disposed at least in part on one of the first side and the second side of the belt reference plane. The driving pulley outlet is disposed at least in part on an other of the first side and the second side of the belt reference plane. 
     In another aspect, the driving pulley inlet is configured to direct air into the space and toward the driving pulley in a radial direction with respect to the driving pulley, and the driving pulley outlet is configured to direct air out of the space in the radial direction with respect to the driving pulley. 
     In another aspect, the housing includes a first cover extending at least in part on the first side of the belt reference plane, the driving pulley and the driven pulley. A second cover extends at least in part on the second side of the belt reference plane, the driving pulley and the driven pulley. The second cover is connected to the first cover to define the space therebetween. One of the driving pulley inlet and the driving pulley outlet is defined in the first cover. An other of the driving pulley inlet and the driving pulley outlet is defined in the second cover. 
     In a further aspect, one of the driven pulley inlet and the driven pulley outlet is defined in the first cover, and an other of the driven pulley inlet and the driven pulley outlet is defined in the second cover. 
     In another aspect, the driven pulley inlet and the driving pulley outlet are both defined in one of the first cover and the second cover, and the driven pulley outlet and the driving pulley inlet are both defined in an other of the first cover and the second cover. 
     In an additional aspect, a first cover extends on the first side of the belt reference plane, the driving pulley and the driven pulley. The driven pulley inlet is defined in the first cover. A second cover extends on the second side of the belt reference plane, the driving pulley and the driven pulley. The second cover is connected to the first cover to define the space therebetween. 
     In another aspect, the driven pulley outlet is defined in the second cover. 
     In a further aspect, the driving pulley is mounted on a driving shaft to rotate therewith about the driving pulley axis. The driving shaft extends through an opening in the housing, the opening being disposed on the second side of the belt reference plane. 
     In yet another aspect, a wall is disposed in the space and connected to the housing. The wall is disposed between driving pulley and the driven pulley and thereby defines a driving pulley space and a driven pulley space. The driving pulley is disposed in the driving pulley space, and the driven pulley is disposed in the driven pulley space. 
     In a further aspect, a driven pulley inlet duct is connected to the driven pulley inlet, and a driven pulley outlet duct is connected to the driven pulley outlet. 
     In an additional aspect, a vehicle includes a frame, at least one ground engaging member, which is one of: a ski, a track and a wheel, a motor connected to the at least one ground engaging member. A CVT assembly having at least one of the above aspects operatively connects the motor to the at least one ground engaging member. 
     For purposes of the present application, terms related to spatial orientation when referring to a vehicle and components in relation to the vehicle, such as “forwardly”, “rearwardly”, “left”, “right”, “above” and “below”, are as they would be understood by a driver of the vehicle, with the vehicle in a straight ahead orientation (i.e. not steered left or right), and in an upright position (i.e. not tilted). 
     Implementations of the present technology each have at least one of the above-mentioned object and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein. 
     Additional and/or alternative features, aspects, and advantages of implementations of the present technology will become apparent from the following description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present technology, 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: 
         FIG. 1A  is a left side elevation view of a multi-passenger recreational utility vehicle; 
         FIG. 1B  is a top plan view of the vehicle of  FIG. 1A ; 
         FIG. 2A  is a left side elevation view of the vehicle (shown in dotted lines) of  FIG. 1A  with a continuously variable transmission (CVT) assembly; 
         FIG. 2B  is a top plan view of the CVT assembly, the powerpack, the drivetrain, the wheels and the seats of the vehicle of  FIG. 1A ; 
         FIG. 3A  is a perspective view, taken from a front, left side of a portion of the powerpack of the vehicle, with air ducts of the CVT assembly removed for clarity; 
         FIG. 3B  is a top plan view of the portion of the powerpack portion of  FIG. 3A ; 
         FIG. 3C  is a left side elevation view of a portion of the powerpack with a left side cover of the CVT assembly removed to show the CVT of the CVT assembly; 
         FIG. 4  is a partially exploded perspective view, taken from a front, left side, of the CVT assembly of  FIG. 3A  with the air ducts removed for clarity; 
         FIG. 5A  is a perspective view, taken from a bottom, rear and left side, of the left cover of the CVT assembly of  FIG. 4 ; 
         FIG. 5B  is a perspective view, taken from a top, rear and right side, of the left cover of  FIG. 5A ; 
         FIG. 5C  is a left side elevation view of a right cover of the CVT assembly of  FIG. 4 ; 
         FIG. 6  is a cross-sectional view, taken along the line  6 - 6  of  FIG. 3C , of the CVT assembly of  FIG. 4 ; 
         FIG. 7A  is a perspective view, taken from a bottom, rear and left side, of another implementation of a left cover of the CVT assembly of  FIG. 4 ; and 
         FIG. 7B  is a perspective view, taken from a top, rear and right side, of the left cover of  FIG. 7A . 
     
    
    
     DETAILED DESCRIPTION 
     Implementations of the present technology will be described with respect to a multi-passenger recreational utility vehicle. However, it is contemplated that aspects of the implementations of the present technology could also be used on other wheeled or tracked vehicles having continuously variable transmissions (CVTs), such as snowmobiles, motorcycles, all-terrain vehicles, and the like. 
       FIGS. 1A and 1B  illustrate a vehicle  10  having a front end  2 , a rear end  4 , a left side  7  and a right side  9 , consistently defined with the forward travel direction. The vehicle  10  includes a frame  12  to which all other parts of the vehicle  10  are connected, directly or indirectly. 
     The vehicle  10  includes a pair of front wheels  14 A and a pair of rear wheels  14 B. Each of the wheels  14 A,  14 B has a tire  15 . Each front wheel  14 A is suspended from the front portion  12 A of the frame  12  via a front suspension  13 A. Each rear wheel  14 B is suspended from the rear portion  12 B of the frame  12  via a rear suspension  13 B. It is also contemplated that the vehicle  10  could have six or more wheels. 
     The vehicle  10  has an open-air cockpit area  20  disposed generally in the middle portion of the vehicle  10 . The cockpit area  20  includes four seats: a front left seat  17 A, a front right seat  19 A, a rear left seat  17 B and a rear right seat  19 B to accommodate a driver and three passengers (collectively referred to herein as riders). The front seats  17 A,  19 A are laterally spaced apart from each another. The rear seats  17 B  19 B are laterally spaced apart from each other and are longitudinally spaced apart from the front seats  17 A,  19 A. Each of the seats  17 A,  19 A,  17 B,  19 B is a bucket seat. It is contemplated that the vehicle  10  could have only a front left seat  17 A and a front right seat  19 A. It is also contemplated that a pair of laterally spaced seats,  17 A and  19 A,  17 B and  19 B, could be replaced by a bench seat. 
     The cockpit area  20  has openings  24  on the left and right sides  7 ,  9  of the vehicle  10  through which the riders can enter and exit the vehicle  10 . A lateral cover (not shown) or a door (not shown) could be selectively disposed across each opening  24 . The lateral covers would be disposed across the openings  24  when the riders are riding the vehicle  10  and could be opened by the driver and/or passenger when they desire to enter or exit the cockpit area  20 . 
     The cockpit area  20  has a floor  21 , and a front wall  23  disposed forward of a steering wheel  28 . A dashboard, having a display cluster mounted thereto, is attached to the upper portion of the front wall  23 . The display cluster includes a number of screens and dials for the operation of the vehicle, such as a speedometer, odometer, engine speed indicator, fuel gauge, an engine temperature gauge, and the like. 
     A roll cage  30  is connected to the frame  12  and is disposed above the cockpit area  20 . The roll cage  30  is an arrangement of metal tubes, and is connected to the frame  12  in front of the cockpit area  20  and rearward of the cockpit area  20 . 
     A steering assembly  26 , including the steering wheel  28 , is disposed in front of the driver seat, which in this implementation, is the front left seat  17 A. The seats  17 B,  19 A,  19 B are passenger seats. The steering assembly  26  is operatively connected to the two front wheels  14 A to permit steering of the vehicle  10 . The left side  7  is the driver side, the right side  9  is the passenger side and. It is contemplated that the steering wheel  26  could be disposed in front of the right seat  19 A, wherein the right side  9  would be the driver side, the left side  7  would be the passenger side, and the seats  17 A,  17 B,  19 B would be passenger seats. Steering devices other than a steering wheel are also contemplated, such as a steering handle, for example. 
     The front and rear wheels  14 A,  14 B are connected to a motor  50  ( FIG. 3A ) via a powertrain  52 . In the illustrated implementation, the motor  50  is an internal combustion engine, but it is contemplated that the motor  50  could be other than an internal combustion engine, for example, and electric motor or a hybrid. The engine  50  is mounted to the frame  12  and has a portion disposed between the right seats  19 A,  19 B and the left seats  17 A,  17 B. A console  18  positioned between the right seats  19 A,  19 B and the left seats  17 A,  17 B covers the engine  50 . The console defines in part a central cooling tunnel allowing air to flow from the front end of the vehicle  10  to the rear end of the vehicle  10  to cool the engine  50  and other components of the vehicle  10 . 
     The engine  50  is a four-stroke V-twin engine. Accordingly, the engine  50  has two cylinders  50 A,  50 B extending at an angle from each other. It is contemplated that other types of engines could be used. For example, the engine  50  could be a two-stroke engine with in-line cylinders. It is also contemplated that the engine  50  could have more than two cylinders  50 A,  50 B, or only one cylinder. Each cylinder  50 A,  50 B has an intake port (not shown) connected to an air induction system  54 . A fuel injector (not shown) injects fuel into the engine  50  and a spark plug (not shown) ignites the fuel-air mixture to initiate the combustion cycle. Each cylinder  50 A,  50 B has an exhaust port (not shown) connected to an exhaust manifold (not shown) to remove exhaust gases resulting from the combustion process from the engine  50 . Exhaust gases flow out of the exhaust manifold and outside the vehicle  10  via an exhaust system including a muffler  58 . 
     The air induction system  54  includes an intake manifold  64 , a plenum chamber  66  connected upstream of the intake manifold  64  and a throttle body  68  connected upstream of the plenum chamber  66 . When the engine  50  is operating, air flows sequentially through the throttle body  68 , the plenum chamber  66 , the intake manifold  64  and then through the intake ports into the cylinders  50 A,  50 B of the engine  50 . The intake manifold  64  separates the flow of air from the plenum chamber  66  into two branches, each of the branches being connected to an air intake port of a corresponding cylinder  50 A,  50 B of the engine  50 . The plenum chamber  66  equalizes the pressure of air entering the cylinders and also acts as an acoustic silencer to dampen the noise generated by the engine  50 . The throttle body  68  regulates the flow of air to the engine  50  by adjusting the position of a throttle plate (not shown) disposed inside the throttle body  68 . An electric motor  70  mounted to a right side of the throttle body  68  controls the throttle plate inside the throttle body  68  for regulating airflow therethrough into the engine  50 . 
     The engine  50  has a crankshaft (not shown) extending horizontally and laterally. The crankshaft is operatively connected, via the powertrain  52 , to the two front wheels  14 A as well as the two rear wheels  14 B to propel the vehicle  10 . It is contemplated that the engine  50  could be operatively connected only to the front wheels  14 A or only to the rear wheels  14 B. 
     With reference to  FIG. 2B , the powertrain  52  includes a continuously variably transmission (CVT)  102  and a transmission  120 . 
     The CVT  102  is disposed on a left side of the engine  50 . With reference to  FIG. 3C , the CVT  102  includes a driving pulley  110  mounted on a driving pulley shaft  116  connected to the crankshaft for rotation therewith, a driven pulley  112  disposed on a driven pulley shaft  118  for rotation therewith, and a CVT belt  114  disposed around both pulleys  110 ,  112  to transmit torque from the driving pulley  110  to the driven pulley  112 . In the illustrated implementation, the driving pulley shaft  116  is coaxial with and connected to the engine crankshaft, but it is contemplated that the driving pulley shaft  116  could be the engine crankshaft. It is also contemplated that the driving pulley shaft  116  could not be coaxial with the engine crankshaft. The driving pulley  110 , the driving pulley shaft  116 , and the engine crankshaft rotate about a driving pulley axis  111 . The driven pulley  112  and the driven pulley shaft  118  rotate about a driven pulley axis  113  that is parallel to the driving pulley axis  111 . A belt reference plane  115  (best seen in  FIG. 6 ) is defined by the center of the belt  114 . The belt reference plane  115  is equidistant from the left and right edges of the belt  114 . Each of the pulleys  110 ,  112  includes a movable sheave that can move axially relative to a fixed sheave to modify an effective diameter of the corresponding pulley  110 ,  112 . The moveable sheaves move in response to changes in engine speed and torque requirement of the wheels  14 A,  14 B. The effective diameters of the pulleys  110 ,  112  are in inverse relationship. The effective diameter of the driving pulley  110  generally increases with its rotation speed (rotations per minute, or RPM). In the illustrated implementation, the moveable sheave of the driving pulley  110  is disposed on the left side of the belt  114  while the moveable sheave of the driven pulley  112  is disposed on the right side of the belt  114 . A centrifugal clutch system  117  is disposed on the left side of the driving pulley  110  and is connected to its moveable sheave for changing the diameter of the driving pulley  110  in response to the rotational speed of the driving pulley shaft  116 . In the illustrated implementation, the CVT  102  is a purely mechanical CVT  102 , in which the diameter of the driving pulley  110  generally increases with increasing rotational speed of the driving pulley  110  (i.e. with increasing engine speed). It is also contemplated that the CVT  102  could be an assisted CVT having a hydraulic, pneumatic, or other system to control the effective diameter of the pulleys  110  or  112 . 
     In the illustrated implementation of the CVT  102 , when the driving pulley diameter increases, its moveable (left) sheave moves rightwardly towards the fixed (right) sheave, resulting in the moveable (right) sheave of the driven pulley  112  moving rightwardly away from its fixed (left) sheave to decrease the diameter of the driven pulley  112 . The belt  114  and the belt reference plane  115  thus move rightwardly when the driving pulley diameter increases, for example, in response to an increase in torque required at the driven shaft  118 . The reverse happens when the diameter of the driving pulley  110  decreases. It is contemplated that the position of the fixed and moveable sheaves could be other than that shown herein. It is also contemplated that both sheaves of the driving pulley  110 , and/or the driven pulley could be moveable. 
     In the illustrated implementation of the CVT  102 , when viewed from a left side, as in  FIG. 3C , the driving pulley  110  and the driven pulley  112  rotate in a counterclockwise direction. It is however contemplated that the rotation of the pulley  110 ,  112  could be in the opposite direction. 
     The CVT  102  is enclosed in a CVT housing  200  which will be described below in further detail. The CVT  102  and the CVT housing  200  are part of a CVT assembly  100 . 
     The transmission  120  is disposed rearwardly of the engine  50 . The transmission  120  transfers torque from the transversely extending driven pulley shaft  118  to a longitudinally extending front driveshaft  121  and a longitudinally extending rear driveshaft (not shown). The transmission  120  includes different gear sets, the combination of the gear sets being selected based on the position of a gear selector  40  provided near the steering wheel  28 . 
     The front driveshaft  121  passes through the engine  50  and connects to a secondary front driveshaft  122  via a universal joint  124 . From the universal joint  124 , the secondary front driveshaft  122  extends forwardly and toward the right of the vehicle  10  to another universal joint  126 . The universal joint  126  connects the secondary front driveshaft  122  to a differential  128 . The differential  128  connects, via universal joints  130 , to left and right drive axles  132 . Each drive axle  132  is connected to a corresponding one of the front wheels  14 A via a universal joint (not shown). 
     The rear driveshaft connects via a universal joint  140  to a differential  142 . The differential  142  connects, via universal joints  144 , to left and right drive axles  146 . Each drive axle  146  is connected to a corresponding one of the rear wheel  14 B via universal joint  148 . 
     The vehicle  10  has other features and components such as headlights and handles. As it is believed that these features and 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. 
     The CVT assembly  100  will now be described in detail with reference to  FIGS. 2A to 7B . The CVT assembly  100  includes a CVT housing  200  defining a space  201  and the CVT  102  disposed in the space  201 . The driving pulley  110  is disposed in the front portion of the space  201 , and the driven pulley  112  is disposed in the rear portion thereof. The CVT assembly  100  also includes air ducts  202 ,  204 ,  206 ,  208  connected to the housing  200 . 
     The CVT housing  200  includes a left cover  220  disposed to the left of the CVT  102 , and a right cover  230  disposed to the right of the CVT  102 . The left and right covers  220 ,  230  are connected together to define the space  201  therebetween. The right cover  230  is disposed on a left side of the engine  50  and the transmission  120 , and connected thereto. Openings  240 ,  250 ,  260  and  270  are defined in the CVT housing  200 . 
     The left cover has a front side portion  222  extending on a left side of the driving pulley  110 , and a rear side portion  224  extending rearwards from the front portion  222  on a left side of the driven pulley  112 . The left cover  220  has a rim portion  223  that extends rightwardly from the front and rear side portions  222 ,  224 . A front rim portion  223   a  extends generally vertically and is disposed longitudinally forward of the CVT  102 . A rear rim portion  223   b  extends generally vertically and is disposed longitudinally rearward of the CVT  102 . An upper rim portion  223   c  extends generally horizontally and is disposed vertically higher than the CVT  102 . A lower rim portion  223   d  extends generally horizontally and is disposed vertically lower than the CVT  102 . As can be seen in  FIG. 6 , the belt reference plane  115  passes through the left cover  220 , specifically the rim portion  223  of the left cover  220 . Through-holes  221  are defined at the edge of the rim portion  223  as can be seen in  FIGS. 5A to 5B  for connecting the left cover  220  to the right cover  230 . 
     Ribs  286  are formed on the inner surface (surface facing the CVT  102 ) of the left cover  220 . The ribs  286  are disposed between the driving pulley  110  and the driven pulley  112 . The ribs  286  provide structural reinforcement to the left cover  220  and also help to direct airflow within the space  201  as will be described below. 
     The opening  240  is defined in the rear portion  224  of the left cover  220 . The opening  240  is generally circular in shape and coaxial with the driven pulley axis as can be seen best in  FIG. 6 . The left sheave of the driven pulley  112 , which in the illustrated implementation is the fixed sheave of the driven pulley  112 , faces leftward towards the opening  240 . The left sheave has fins  280  formed on its outer surface, i.e. the surface facing away from the belt  114  towards the opening  240 . When the driven pulley  112  rotates, the rotating fins  280  act as a fan drawing air via the opening  240  into the space  201  enclosed by the housing  200 . The opening  240  is therefore referred to as the driven pulley inlet  240  hereinafter. In general, the amount of air drawn into the space  201  increases as the driven pulley  112  rotates faster. As the rotational speed (rpm) of the driven pulley  112  is generally proportional to the vehicle speed, the amount of air being drawn into the space  201  via the inlet  240  also increases with the vehicle speed. 
     In the implementation of  FIGS. 5A to 5B , an inlet pipe flange  242  is connected to the housing  200  around the inlet  240 . The inlet pipe flange  242  has a pipe portion  242   a  that defines an inlet passage  244  that fluidly connects to the inlet  240  and also provides a surface for attachment of the air duct  202 . In the illustrated implementation, the inlet passage  244  has a circular cross-section and has similar dimensions as the inlet  240 . The inlet passage  244  is disposed coaxially with the driven pulley axis  113 . The pipe portion  242   a  of the inlet pipe flange  242  is connected at one end to a flange portion  242   b  that extends outwardly away from the passage  244 . The flange portion  242   b  is connected to the left cover  220  by bolts  246  inserted through through-holes defined in the flange portion  242   b  and aligned with corresponding through-holes of the left cover  220 . In the implementation of  FIGS. 7A to 7B , the inlet pipe flange  242  is formed integrally with the left cover  220 . As the driven pulley  112  rotates about the driven pulley axis  113 , air from outside the housing  200  is drawn through the inlet passage  244  and the inlet  240  into the space  201 . The air flowing into the space  201  thus flows in an axial direction of the driven pulley  112  and toward the driven pulley  112  to cool the driven pulley  112  and the belt  114 . 
     The opening  270  is defined in the front rim portion  223   a . The opening  270  is disposed longitudinally forward of the driving pulley  110 , and thus closer to the driving pulley  110  than the driven pulley  112 . The opening  270  is generally elliptical in cross-section. The opening  270  is connected to a pipe  272  which is formed integrally with the left cover rim portion  223 . The pipe  272  defines a passage  274  fluidly communicating with the opening  270  and having a central axis  275 . The air duct  208  is connected to the pipe  262 . The passage  274  has a generally elliptical cross-section. The central axis  275  ( FIG. 5B ) of the passage  274  extends forwardly and rightwardly from the opening  270  as best seen in  FIG. 6 . As can be seen in  FIG. 6 , the belt reference plane  115  passes through the opening  270  and the passage  274 . The central axis  275  is disposed in a direction generally perpendicular to the driving pulley axis  111 . 
     Turning now to  FIGS. 4, 5C and 6 , the right cover  230  has a portion  232  extending vertically on a right side of the CVT  102 . A rim portion  234  of the right cover  230  extends laterally inwardly (leftwardly) from the edges of the portion  232  around the CVT  102 . A front rim portion  234   a  extends generally vertically and is disposed longitudinally forward of the driving pulley  110 . A rear rim portion  234   b  extends generally vertically and is disposed longitudinally rearward of the driven pulley  112 . An upper rim portion  234   c  disposed vertically higher than the CVT  102  extends generally horizontally and a lower rim portion  234   d  disposed vertically lower than the CVT  102  extends generally horizontally. In the illustrated implementation, the right cover  230  is entirely disposed on a right side of the belt reference plane  115 . It is however contemplated that the belt reference plane  115  could pass through the right cover rim portion  234  instead of the left cover rim portion  223 , or could pass through both. 
     Ribs  284  are formed on the inner surface (surface facing the CVT  102 ) of the right cover  230 . The ribs  284  are disposed between the driving pulley  110  and the driven pulley  112 . The ribs  284  provide structural reinforcement to the right cover  230  and also help to direct airflow within the space  201  as will be described below. 
     A driving shaft opening  236  extends through the vertical portion  232  of the right cover  230 . The driving pulley shaft  116  extends from the crankshaft of the engine  50  disposed on a right side of the right cover  230 , through the opening  236 , to connect to the driving pulley  110  disposed on the left side of the right cover  230 . The driving shaft opening  236  is surrounded by a boss. Through-holes  237  are defined through the boss. Bolts are inserted through the holes  237  into the casing of the engine  50  to connect the right cover  230  to the engine  50 . 
     Similarly, a driven shaft opening  238  extends through the vertical portion  232  of the right cover  230 . The driven shaft opening  238  is disposed longitudinally rearward of the driving shaft opening  236  and receives the driven pulley shaft  118  extending therethrough. A right end of the driven pulley shaft  118  is connected to the transmission  116  disposed on the right side of the right cover  230 , and the driven pulley  112  is mounted on the left end of the driven pulley shaft  118  disposed inside the space  201 . The driven shaft opening  238  is surrounded by a boss. Through-holes  239  are defined through the boss. Bolts are inserted through the holes  239  into the casing of the transmission  120  to connect the right cover  230  to the transmission. 
     Through-holes  231  are defined at the edge of the rim portion  234  as best seen in  FIG. 5C . The through-holes  231  are aligned with the through-holes  221  of the left cover rim portion  223 . Bolts are inserted through the aligned holes  221 ,  231  to connect the left cover  220  to the right cover  230 . 
     The opening  250  is defined in the rear rim portion  234   b  just below the upper rim portion  234   c . The opening  250  is thus closer to the driven pulley  112  than the driving pulley  110 . The opening  250  is disposed vertically higher than the driven shaft opening  238 . The opening  250  has an elliptical shape. A pipe  252  is connected to the opening  250  and defines a passage  254  having a central axis  255 . The air duct  204  is connected to the pipe  252 . In the illustrated implementation, the pipe  252  is formed integrally with the rim portion  234 , but it is contemplated that the pipe could be formed as a separate piece and attached to the rim portion  234 . As can be seen in  FIG. 5C , the central axis  255  of the passage  254  is disposed in a direction generally tangential to the driven pulley  112 . It is contemplated that the central axis  255  could be disposed in a direction generally perpendicular to the driven pulley axis  113  without being tangential to the driven pulley  112 . It is contemplated that the central axis  255  could be disposed in a direction other than perpendicular to the driven pulley axis  113 . 
     The opening  260  is defined in the front portion of the right cover front rim portion  234   a . The opening  260  is thus closer to the driving pulley  110  than the driven pulley  112 . The opening  260  is disposed longitudinally forward of the driving shaft opening  236 . A portion of the opening  260  extends vertically lower than the driving shaft opening  236 . The opening  260  has an elliptical shape. A pipe  262  is connected to the opening  260  and defines a passage  264  having a central axis  265 . In the illustrated implementation, the pipe  262  is formed integrally with the rim portion  234 , but it is contemplated that the pipe could be formed as a separate piece and attached to the rim portion  234 . The duct  206  is connected to the pipe  262 . As can be seen in  FIG. 5C , the central axis  265  of the passage  264  extends upwardly and forwardly away from the opening  260 . As can be seen from  FIG. 6 , the central axis  265  is disposed generally parallel to the belt reference plane  115  and perpendicular to the driving pulley axis  111  when viewed from the top. It is contemplated that the central axis  265  could be disposed tangentially with respect to the driving pulley  110 . The right (fixed) sheave of the driving pulley  110  has fins  282  ( FIG. 4 ) formed on its outer surface, i.e. the surface facing away from the belt  114 . When the driving pulley  110  rotates in a counter-clockwise direction (as viewed from a left side), the rotating fins  282  act as a fan drawing air via the opening  260  into the space  201  enclosed by the housing  200 . 
     As mentioned above, the counter-clockwise rotation (when viewed from a left side of the CVT  102 ) of the driven pulley  112  draws air from outside the housing  200  into the space  201  toward the driven pulley  112 . As can be seen in  FIGS. 2A and 2B , the air duct  202  connected to the inlet pipe  242  extends leftward therefrom and then upward to draw air in from a left side  7  of the vehicle  10 . The opening of the air duct  202  is covered with a mesh and provided with a filter to prevent entry of large debris. 
     The counter-clockwise rotation of the driven pulley  112  also pushes air inside the space  201  out through the opening  250 . As such, the opening  250  is referred to hereinafter as the driven pulley outlet  250 , the pipe  252  is referred to hereinafter as the driven pulley outlet pipe  252 , the passage  254  is referred to hereinafter as the driven pulley outlet passage  254 , and the central axis  255  is referred to hereinafter as the driven pulley outlet axis  255 . As can be seen in  FIGS. 2A and 2B , the air duct  204  connected to the outlet pipe  252  extends upwardly therefrom, then rearwardly, and then rightwardly below the rear right seat  19 B to its outlet (not shown) which expels air to a right side  9  of the vehicle  10 . The opening of the air duct  204  is covered with a mesh to prevent entry of large debris. 
     The counter-clockwise rotation (when viewed from a left side of the CVT  102 ) of the driving pulley  110  tends to draw air from outside the housing  200  into the space  201  via the passage  264  and the opening  260 . As such, the opening  260  is referred to hereinafter as the driving pulley inlet  260 , the pipe  262  is referred to hereinafter as the driving pulley inlet pipe  262 , the passage  264  is referred to hereinafter as the driving pulley inlet passage  264 , and the central axis  265  is referred to hereinafter as the driving pulley inlet axis  265 . As can be seen in  FIGS. 2A and 2B , the air duct  206  connected to the inlet pipe  262  extends forwardly therefrom below the cockpit floor  21 , then upwardly in front of the front wall  23 , and finally leftwardly to draw air in from a left side  7  of the vehicle  10 . The opening of the air duct  206  is covered with a mesh and provided with a filter to prevent entry of large debris. 
     The counter-clockwise of the driving pulley  110  also pushes air inside the space  201  outside the housing  200  via the opening  270  and the passage  274 . As such, the opening  270  is referred to hereinafter as a driving pulley outlet  270 , the pipe  272  is referred to hereinafter as the driving pulley outlet pipe  262 , the passage  274  is referred to hereinafter as the driving pulley outlet passage  274 , and the central axis  175  is referred to hereinafter as the driving pulley outlet axis  275 . As can be seen in  FIGS. 2A and 2B , the air duct  208  connected to the outlet pipe  272  extends forwardly and upwardly therefrom, then rearwardly above the CVT housing  200 , then upwardly rightwardly below the rear right seat  19 B to its outlet (not shown) which expels air to a right side  9  of the vehicle  10 . The opening of the air duct  208  is covered with a mesh to prevent entry of large debris. 
     Thus, cool air flows into the space  201  via the inlets  240 ,  260 . After cooling the CVT  102 , including the pulleys  110 ,  112  and the belt  114 , heated air flows out of the space  201  via the outlets  250 ,  270 . Air flowing in through the driven pulley inlet  240  cools the driven pulley  112  and thereby the belt  114 . Air flowing in through the driving pulley inlet  260  cools the driving pulley  110  and thereby the belt  114 . 
     The ribs  284  formed on the inner surfaces of the right cover  230  help to direct part of the air flowing in through the driving pulley inlet  260  leftward towards the driving pulley  110  instead of flowing rearwardly and out via the driven pulley outlet  250 . Similarly the ribs  284  formed on the inner surface of the left cover  220 , help to prevent some of the air flowing in through the driven pulley inlet  240  from flowing out through the driving pulley outlet  270 . 
     In the illustrated implementation, the housing  200  is made of plastic, and formed by molding. It is however contemplated that the housing  200  could be formed of any suitable material and/or process. 
     Modifications and improvements to the above-described implementations of the present technology 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 technology is therefore intended to be limited solely by the scope of the appended claims.