Abstract:
A vehicle with a continuously variable transmission (continuously variable transmission) includes a torque responsive clutch having a cam and at least one coupling. The cam has a plurality of projecting surfaces, and a plurality of slots being defined between the projecting surfaces. The slots of the cam are used to direct cam followers that move across the slot surfaces as the vehicle is driven forward or in reverse. As the vehicle adjusts from forward to reverse or vice versa, the cam followers may jump from one side of the slot to the other.

Description:
RELATED APPLICATIONS 
   The present application is related to a U.S. patent application Ser. No. 10/329,047 entitled “Continuously Variable Transmission with Two Piece Cam” by the same inventor and filed on an even date herewith. The entire disclosure of the above mentioned patent application is hereby incorporated by reference. 
   TECHNICAL FIELD 
   The present invention relates generally to recreational vehicles. More particularly, the present invention relates to drive systems for use with recreational vehicles. 
   BACKGROUND OF THE INVENTION 
   In recent years, recreational vehicles (e.g., snowmobiles) have gained widespread popularity. Snowmobiles are commonly used in hunting, trail riding and utility applications such as the wide variety of maintenance activities which take place on a farm. Perhaps the most common snowmobile application is trail riding. Trail riding on a snowmobile allows a snowmobile enthusiast to travel through areas that are not accessible by ordinary automobiles particularly during the winter months. Modern snowmobiles, can cover ground very rapidly and can cover great distances. Frequently, snowmobile enthusiasts ride their snowmobile for many hours straight and cover many miles. If the rider is subjected to excessive jarring while traveling over rough terrain, operator fatigue may result particularly during a long ride. During such long rides, a snowmobile may be used to carry a rider through a wide variety of terrain. 
   SUMMARY OF THE INVENTION 
   The present invention relates generally to recreational vehicles. More particularly, the present invention relates to drive systems for use with recreational vehicles. A vehicle in accordance with an exemplary embodiment of the present invention comprises an engine capable of rotating a crankshaft in a first direction and a second direction. A crankshaft of the engine is coupled to a drive shaft of the vehicle by a drive train. In one aspect of the present invention, the drivetrain includes a coupling linking a first rotating component of the drivetrain to a second rotating component of the drivetrain. The coupling may be advantageously adapted to absorb shock when the rotation of the crankshaft is changed from the first direction to the second direction or from the second direction to the first direction. In some exemplary implementations of the present invention, the first rotating component comprises a cam and the second rotating component comprises a cam mount. 
   In some exemplary implementations of the present invention, the coupling comprises at least one fastener for attaching the cam to the cam mount and an elastically deformable intermediate member. The elastically deformable intermediate member may advantageously comprise a sleeve having a bore dimensioned to receive the connecting fastener, and an outer surface dimensioned to engage the coupling portion of the cam. In some advantageous implementations, a body of the deformable intermediate member comprises polyurethane. Also in some advantageous implementations, the coupling portion of the cam comprises a slot. In some cases, the cam mount may comprise a plate that is fixed to a shaft. 
   A drive in accordance with an additional exemplary embodiment of the present invention comprises a cam having at least one coupling portion and at least one cam follower coupled to a sheave. The at least one cam follower preferably engages a camming surface of the cam. In some advantageous implementations, the drive further includes a coupling extending between the at least one coupling portion of the cam and a cam mount. In one aspect of the present invention, the coupling absorbs shock when a rotational direction of the sheave is changed from a first direction to a second direction or from the second direction to the first direction. 
   Various methods in accordance with the present invention may be used to create a vehicle providing an enhanced riding experience. One exemplary method in accordance with the present invention includes the steps of providing a new cam having a base and an elastically deformable intermediate member disposed within at least one coupling portion of the new cam. The elastically deformable intermediate member may comprise a sleeve having a bore extending there-through to receive a connecting fastener. The method further includes the steps of removing an old cam from a continuously variable transmission, installing the new cam onto the continuously variable transmission, and securing the new cam with the connecting fastener. 
   Various methods in accordance with the present invention may also be used to dampen a continuously variable transmission having a cam fixed to a base by a connecting fastener. One exemplary method in accordance with the present invention comprises the steps of removing the cam from the continuously variable transmission by loosening a fastener and removing material from the cam to create a coupling portion of the cam that is dimensioned to receive an elastically deformable intermediate member. An elastically deformable intermediate member may be inserted into the coupling portion of the cam. A connecting fastener may be inserted through a bore of the elastically deformable coupling. The cam may be secured to the base with the connecting fastener. In some implementations of the present invention, the coupling portion comprises a slot defined by the base. Also in some implementations of the present invention, the elastically deformable intermediate member comprises polyurethane. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a snowmobile including a drive system in accordance with an exemplary embodiment of the present invention. 
       FIG. 2  is a perspective view of a drive system in accordance with an exemplary embodiment of the present invention. 
       FIG. 3  is a plan view of a continuously variable transmission in accordance with an exemplary embodiment of the present invention. 
       FIG. 4  is a perspective view of a drive system in accordance with an additional exemplary embodiment of the present invention. 
       FIG. 5  is a diagrammatic view of a drive system in accordance with an additional exemplary embodiment of the present invention. 
       FIG. 6  is a perspective view of a cam assembly in accordance with an additional exemplary embodiment of the present invention. 
       FIG. 7  is a perspective view of an intermediate member in accordance with an exemplary embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following detailed description should be read with reference to the drawings, in which like elements in different drawings are numbered identically. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. Accordingly, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. 
     FIG. 1  is a perspective view of a snowmobile  150  including a drive system  152  in accordance with an exemplary embodiment of the present invention. Snowmobile  150  has a chassis  154  defining a tunnel  156 . In the embodiment of  FIG. 1 , a drive track  158  can be seen extending from tunnel  156 . In the embodiment of  FIG. 1 , drive track  158  comprises an endless loop that is supported by a rear suspension  160 . In a preferred embodiment, drive track  158  is operatively connected to an engine by a drivetrain so that drive track  158  may be used to propel snowmobile  150 . In some embodiments of the present invention drive track  158  may be used to propel snowmobile  150  in both a forward direction and a reverse direction. In  FIG. 1 , it may also be appreciated that snowmobile  150  includes a plurality of skis  162 . Although a snowmobile is illustrated in  FIG. 1 , it is the be appreciated that a drive system in accordance with the present invention may be used in conjunction with various types of vehicles. Examples of such vehicles include ATVs, golf carts and the like. 
     FIG. 2  is a perspective view of a drive system  152  in accordance with an exemplary embodiment of the present invention. Drive system  152  of  FIG. 2  may be used, for example, to propel a snowmobile such as the one illustrated in the previous figure. Drive system  152  includes a drive track  158  that is illustrated using phantom lines in  FIG. 2 . Drive track  158  may be driven by two drive sprockets  164  that are fixed to a drive shaft  166 . Drive shaft  166  is preferably adapted to be used to urge motion of drive track  158 , such that drive shaft  166  and drive track  158  propel a vehicle. 
   Drive system  152  of  FIG. 2  also includes a jack shaft  168 . In the embodiment of  FIG. 2 , jack shaft  168  and drive shaft  166  are connected to one another by a speed reduction mechanism  170 . In a preferred embodiment, speed reduction mechanism  170  is configured to provide a desired reduction in rotational velocity. Speed reduction mechanism  170  may comprise various elements without deviating from the spirit and scope of the present invention. Examples of elements which may be suitable in some applications include gears, sprockets, belts and chains. 
   A cam mount  172  is fixed to jack shaft  168  in the embodiment of  FIG. 2 . A cam  174  is coupled to cam mount  172 . Cam  174  interfaces with a driven clutch  176 . Driven clutch  176  is connected to a drive clutch  178  by a drive belt  190 . In the embodiment of  FIG. 2 , drive clutch  178  is fixed to a crankshaft  180  of an engine  182 . In a preferred embodiment, engine  182  is capable of rotating crankshaft  180  in both a first rotational direction  184  and a second rotational direction  186 . 
   With reference to  FIG. 2 , it may be appreciated that rotation of crankshaft  180  is transferred via a drivetrain  188  to drive shaft  166  so as to cause rotation of drive shaft  166 . In the embodiment of  FIG. 2 , drivetrain  188  comprises drive clutch  178 , drive belt  190 , driven clutch  176 , jack shaft  168 , and speed reduction mechanism  170 . Drive shaft  166  causes movement of drive track  158  such that drive track  158  propels a vehicle. When crankshaft  180  is rotated in a first rotational direction  184  the vehicle is propelled in a forward direction  192 . When crankshaft  180  is rotated in a second rotational direction  186 , vehicle is propelled in a reverse direction  194 . 
     FIG. 3  is a plan view of a continuously variable transmission  296  in accordance with an exemplary embodiment of the present invention. Continuously variable transmission  296  includes a drive clutch  278 , a driven clutch  276 , and an endless drive belt  290  disposed about the drive clutch  278  and driven clutch  276 . Driven clutch  276  includes a pair of opposed sheaves which together define a generally V-shaped “pulley” within which drive belt  290  rides. One of the sheaves is axially movable (i.e., movable in the direction parallel to the axis of driven clutch  276 ), and the other sheave is axially stationary. 
   Continuously variable transmission  296  includes a cam  274  that is preferably adapted to urge the sheaves of driven clutch  276  toward one another. In the embodiment of  FIG. 3 , cam  274  is coupled to a cam mount  272 . Also in the embodiment of  FIG. 3 , cam mount  272  is fixed to a drive shaft  266 . The drive clutch  278  is similarly configured from a pair of opposed sheaves, one being axially movable and the other being axially stationary. As shown in  FIG. 3 , cam  274  includes a first cam surface  202  which contacts a cam follower  206  when cam  274  is turning in a first direction. Also as shown in  FIG. 3 , cam  274  includes a second cam surface  204  which contacts a cam follower  206  when cam  274  is turning in a second direction. 
     FIG. 4  is a perspective view of a drive system  352  in accordance with an additional exemplary embodiment of the present invention. Drive system  352  of  FIG. 4  includes an engine  382  and a drive clutch  378  that is fixed to a crankshaft of engine  382 . In a preferred embodiment, engine  382  is capable of rotating the crankshaft in both a first direction and a second direction that is different from the first direction. Various methods and apparatus may be used to rotate the crankshaft in a first direction and a second direction without deviating from the spirit and scope of the present invention. Examples of methods and apparatus that may be suitable in some applications can be found in U.S. Pat. Nos. 5,161,489; 5,782,210; 5,794,574; 5,964,191; 6,039,010; 6,044,807; 6,098,574; 6,234,119; and 6,237,546. The entire disclosure of each of these U.S. patents is herby incorporated by reference. 
   Drive clutch  378  is connected to a driven clutch  376  by a drive belt  390 . Driven clutch  376  is connected to a drive shaft  366  by a speed reduction mechanism  370 . In a preferred embodiment, speed reduction mechanism  370  is configured to provide a desired reduction in rotational velocity. Speed reduction mechanism  370  may comprise various elements without deviating from the spirit and scope of the present invention. Examples of elements which may be suitable in some applications include gears, sprockets, belts and chains. 
     FIG. 5  is a diagrammatic view of a drive system  452  in accordance with an additional exemplary embodiment of the present invention. Drive system  452  includes an engine  482 . In the exemplary embodiment of  FIG. 5 , engine  482  is capable of rotating a crankshaft  480  in a first direction and a second direction. Crankshaft  480  of engine  482  is connected to a drive shaft  466  via a drivetrain  488 . In the embodiment of  FIG. 5 , drivetrain  488  includes a drive clutch  478 , a driven clutch  476 , a cam  474 , and a cam follower  406 . 
   In the embodiment of  FIG. 5 , cam  474  is coupled to drive shaft  466  via a cam mount  472  and a coupling  424 . As shown in  FIG. 5 , cam  474  includes a first cam surface  402  which contacts a cam follower  406  when crankshaft  480  is turning in a first direction. Also as shown in  FIG. 5 , cam  474  includes a second cam surface  404  which contacts a cam follower  406  when crankshaft  480  is turning in a second direction. In some advantageous embodiments of the present invention, coupling  424  is capable of absorbing shock when the rotation of the crankshaft  480  is changed from the first direction to the second direction or from the second direction to the first direction. As shown in  FIG. 5 , coupling  424  extends between a coupling portion  426  of cam  474  and a fastener  422 . In the embodiment of  FIG. 5 , coupling  424  comprises a spring  428  and a damper  430 . 
     FIG. 6  is a perspective view of a cam assembly  532  in accordance with an additional exemplary embodiment of the present invention. Cam assembly  532  includes a cam  574  that is coupled to a cam mount  572  at a coupling  524 . In the embodiment of  FIG. 6 , coupling  524  comprises an intermediate member  520  which extends between a coupling portion  526  of cam  574  and a fastener  522 . In the embodiment of  FIG. 6 , coupling portion  526  of cam  574  includes a slot  534  which is dimensioned to receive intermediate member  520 . 
   In the embodiment of  FIG. 6 , cam  574  includes a first cam surface  502  which is preferably dimensioned to contact a cam follower when cam  574  is turning in a first direction. Also as shown in  FIG. 6 , cam  574  includes a second cam surface  504  which is preferably dimensioned to contact a cam follower when cam  574  is turning in a second direction. In some advantageous embodiments of the present invention, coupling  524  is capable of absorbing shock when the rotation of cam  574  is changed from the first direction to the second direction or from the second direction to the first direction. 
     FIG. 7  is a perspective view of intermediate member  720  in accordance with an exemplary embodiment of the present invention. With reference to  FIG. 7 , it may be appreciated that intermediate member  720  comprises a body  736  defining a bore  738 . Bore  738  is preferably dimensioned to receive a connecting fastener. In the embodiment of  FIG. 7 , bore  738  includes a counter bore  742  and a through hole  744 . In a preferred embodiment, an outer surface  740  of intermediate member  720  is dimensioned to engage a coupling portion of a cam. In the embodiment of  FIG. 7 , body  736  of intermediate member  720  has a generally arcuate shape. 
   In some useful embodiments of the present invention, body  736  of intermediate member  720  comprises a reversibly deformable material. For example, intermediate member  720  may comprise an elastomeric material. The term elastomeric generally refers to a rubberlike material (e.g., a material which can experience about a 7% deformation and return to the undeformed configuration). Examples of elastomeric materials include rubber (e.g., natural rubber, silicone rubber, nitrile rubber, polysulfide rubber, etc.), thermoplastic elastomer (TPE), butyl, polyurethane, and neoprene. 
   The complete disclosures of all patents, patent applications, and publications are hereby incorporated by reference as if individually incorporated. Having thus described the various exemplary embodiments of the present invention, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached. Thus, it is to be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the invention&#39;s scope which is, of course, defined in the language in which the appended claims are expressed.