Abstract:
This disclosure generally includes description of a clutch for a continuous variable transmission (CVT), more particularly to the drive clutch of a CVT for immovably coupling a spider portion to a CVT shaft during reverse rotation or acceleration or deceleration of the CVT shaft.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This non-provisional application claims priority from U.S. provisional application Ser. No. 61/577,185 filed Dec. 19, 2011. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates generally to a clutch for a continuous variable transmission (CVT) more particularly to the drive clutch of a CVT, and specifically to a system for not allowing the spider of a CVT to unthread in a primary drive CVT. 
         [0003]    Split sheave, belt-driven, continuously variable transmissions (CVT&#39;s) are used in a variety of recreational type off-road vehicles such as snowmobiles, golf carts, all-terrain vehicles (ATV&#39;s), as well as automobiles, and motorcycles, and the like. CVT&#39;s, as their name implies, do not require shifting through a series of forward gears, but rather provide a continuously variable ratio that automatically adjusts as the vehicle speeds up or slows down, thus providing relatively easy operation for the rider. 
         [0004]    A typical CVT transmission is made up of a split sheave primary drive clutch connected to the output of the vehicle engine (often the crankshaft) and split sheave secondary driven clutch connected (often through additional drive train linkages) to the vehicle axle. An endless, flexible, generally V-shaped drive belt is disposed about the clutches. Each of the clutches has a pair of complementary sheaves, one of the sheaves being movable with respect to the other. The effective gear ratio of the transmission is determined by the positions of the movable sheaves in each of the clutches. The primary drive clutch has its sheaves normally biased apart (e.g., by a coil spring), so that when the engine is at idle speeds, the drive belt does not effectively engage the sheaves, thereby conveying essentially no driving force to the secondary driven clutch. The secondary driven clutch has its sheaves normally biased together (e.g., by a compression spring, as described below, so that when the engine is at idle speeds the drive belt rides near the outer perimeter of the driven clutch sheaves. 
         [0005]    The spacing of the sheaves in the primary drive clutch usually may be controlled by centrifugal flyweights. Centrifugal flyweights are typically connected to the clutch shaft so that they rotate centrifugally along with the engine shaft speed. As the engine shaft rotates faster (in response to increased engine speed) the flyweights also rotate faster and pivot further outwardly, urging the movable sheave more toward the stationary sheave. The more outwardly the flyweights pivot, the more the moveable sheave is moved toward the stationary sheave. This pinches the drive belt, causing the belt to begin rotating with the drive clutch, the belt in turn causing the driven clutch to begin to rotate. Further movement of the drive clutch&#39;s movable sheave toward the stationary sheave forces the belt to climb outwardly on the drive clutch sheaves, increasing the effective diameter of the drive belt path around the drive clutch. Thus, the spacing of the sheaves in the drive clutch changes based on engine speed. The drive clutch therefore can be said to be speed sensitive. 
         [0006]    As the sheaves of the drive clutch pinch the drive belt and force the belt to climb outwardly on the drive clutch sheaves, the belt (being effectively unstretchable) is pulled inwardly between the sheaves of the driven clutch, decreasing the effective diameter of the drive belt path around the driven clutch. This movement of the belt outwardly and inwardly on the drive and driven clutches, respectively, smoothly changes the effective gear ratio of the transmission in variable increments. 
         [0007]    Split-sheave, belt driven CVTs are typically mechanical devices, that is, the mechanical parameters are established when the CVT is assembled. Once the CVT drive is assembled, the gear ratio depends on these set mechanical parameters as well as clutch spacing and belt length/width. For example, the gear ratio depends on the distance between the drive clutch sheaves. The distance between the drive clutch sheaves is determined by the amount of force produced by the flyweights against the movable sheave. As the flyweights are eventually connected to the engine shaft through the clutch shaft, the amount of the flyweight force depends on the speed of rotation of the engine shaft. 
         [0008]    For some vehicles to be moved in reverse, the drive shaft of the motor must rotate in the opposite direction as when the vehicle is moving forward. This may cause problems with portions of the CVT. 
         [0009]    Also when travelling forward, engines and drivetrains may accelerate in either forward or reverse direction, therefore CVTs and CVT clutches and clutch shafts may accelerate in either direction. This may cause a spider portion of the clutch to tend to decouple from the clutch shaft. 
         [0010]    Representative of the prior art is U.S. Pat. No. 5,562,555 which discloses a variable speed belt drive having adjustable mass and moment of inertia camweights for use primarily in conjunction with snowmobile, golf cart, all terrain vehicle and small automobile engines. In one version, the camweight includes a series of perforations or score lines surrounding a cross section of the camweight arm. The perforations define a volume that may be snapped or cut off of the arm with a suitable tool. Also, a series of bores are formed through the arm. In order to increase the mass of the arm, a molten metal or similar flowable material may be poured into one or more of the bores and allowed to cure. In another version of the invention, a reduced cross section arm serves as a base onto which shims are added or reoriented in order to achieve the desired mass and moment of inertia characteristics. 
         [0011]    What is needed is a secure locking method and system for locking the spider to the clutch shaft. With a need, also, for simplicity and serviceability. 
       SUMMARY 
       [0012]    The present disclosure is directed to systems and methods which provide generally secure attachment of a spider to the clutch shaft where the clutch shaft is driven or accelerated and/or decelerated bidirectionally. The systems and methods disclosed herein may inhibit the spider from uncoupling from the shaft. 
         [0013]    The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying drawings, which are incorporated in and form part of the specification in which like numerals designate like parts, illustrate embodiments of the present disclosure and together with the description, serve to explain the principles of the disclosure. In the drawings: 
           [0015]      FIG. 1  is a plan view of a CVT system according to an embodiment of the disclosure. 
           [0016]      FIG. 2  is a plan view of a CVT drive clutch system according to an embodiment. 
           [0017]      FIG. 3  is a plan view a spider portion coupled to a shaft according to an embodiment. 
           [0018]      FIG. 4  is a plan view of a spider and locking device generally coupled to a shaft and to each other according to an embodiment. 
           [0019]      FIG. 5  is a plan view of a shaft according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  shows a plan view of a CVT system  100 . System  100  may include a primary drive pulley  110 , a secondary driven pulley  120 , and a belt  130 . Each of primary drive pulley  110  and secondary driven pulley  120  may include a fixed or stationary sheave (not shown) and a moveable sheave (not shown). The moveable sheave may be moved with respect to the stationary sheave to allow belt  130  to move within the pulleys  110 ,  120 . This may change the distance of belt  130  with respect to the drive  112  and driven shafts  122 , thereby changing an effective gear ratio, which in turn changes the speed of driven shaft. Typically drive shaft  112  is coupled to the shaft of a motor, and runs at a generally constant speed, once the motor ramps up to speed. 
         [0021]    Primary drive pulley  110  may be mounted and/or generally coupled to drive shaft  112 . Similarly, a secondary driven pulley  120  may be coupled to a driven shaft  122 . This may be accomplished via many known methods and systems. Any method or system of coupling capable of being used for this purpose may be used. This disclosure is not limited by the method or system of coupling of the pulleys to the respective shafts. 
         [0022]    As shown, if the moveable sheave of the primary drive pulley  110  is moved away from the stationary sheave, belt  130 A would ride further down in primary drive pulley  110 . This would cause the speed of driven shaft  122  to generally decrease. If the moveable sheave of secondary driven pulley  122  is moved away from the stationary sheave, this would cause the belt  130 A to ride lower in the driven pulley  120 , which would cause the rotational speed of driven shaft  122  to generally increase (if the primary drive shaft  112  speed was held constant). In this manner, the ratio of speed of the relatively constant rotational speed of the drive shaft  112  and the driven shaft  122  can be constantly varied and controlled. 
         [0023]      FIG. 2  shows a primary drive clutch system  200  according to an embodiment. System  200  may include a stationary sheave  220 , a moveable sheave  230 , a shaft  210 , a spider portion  240 , and a housing  250 . Moveable sheave  230  may be moved with respect to stationary sheave  220 , which causes belt (not shown) to move toward and away from shaft  210 . This would cause the ratio of rotational speed of the shaft  210  to driven shaft (not shown) to change, and thereby change the speed of the vehicle this system  200  is a part of. 
         [0024]    System  200  may include shaft  210 . In an embodiment, shaft  210  may be coupled to the drive shaft of a vehicle or the shaft of the drive motor of the vehicle. Housing  250  may rotate directly or indirectly with shaft  210 . 
         [0025]    As explained above, moveable sheave  230  may be biased away from stationary sheave  220 , and as shaft rotates, the configuration of weights (not shown) and housing  250  may cause moveable sheave  230  to move closer to stationary sheave  220 . This may change the diameter at which a belt will ride between the sheaves, which will change the characteristics of the clutch system  200 . 
         [0026]      FIG. 3  shows an embodiment of a portion of system  200 , which may include a spider portion  240 . Spider portion  240  may be coupled to housing  250  and considered a separate portion of the system. Spider portion  240  may be coupled to shaft  210  and to housing  250 . This configuration would facilitate spider portion  240  and housing  250  generally rotating with shaft  210 . Furthermore, spider portion may slide up and down the housing towers, because the housing may be part of, or coupled to, moveable sheave  220 . 
         [0027]    In an embodiment, spider portion  240  may be coupled to shaft via portion  214 . That is spider portion  240  and shaft  210  are threaded to couple to each other in a generally threadingly-type and/or turning type coupling. It will be appreciated that other coupling structures, methods, and/or substances may be used to couple spider  240  to shaft  210 . 
         [0028]    When shaft  210  rotates in a generally forward direction F, spider portion  240  may generally tend to tighten with respect to shaft  210 . When shaft  210  rotates in a generally reverse direction R, spider portion  240  may generally tend to loosen, and/or unthread with respect to shaft  210 . Furthermore, when shaft  210  accelerates or decelerates the mass and momentum of spider  240  and/or housing  250  may cause the spider  240  to generally uncouple from shaft  210 . This may be a problem when the shaft  210  must rotate bidirectionally for forward and reverse of the vehicle (not shown) or if the shaft accelerates in the reverse direction, or during acceleration or deceleration of shaft  210 . 
         [0029]      FIG. 4  illustrates a portion of a system, according to an embodiment. This Figure shows the addition of a securing member  400 . As described above, spider  240  may be coupled to shaft  210 . Securing member  400  may also be coupled to shaft  210 , and further coupled to the spider  240 . 
         [0030]    Shaft  210  may further include reverse threads  216  (compared to the spider threads), which may be configured to threadingly mate with threads of securing member  400 . With this configuration, when shaft rotates generally in the reverse direction R, securing member  400  may generally tend to tighten to the face of the spider  240 . Further, when shaft rotates in the reverse direction R, Spider  240  which would otherwise tend to loosen from the shaft will be prevented from loosening by the locking device which would tend to tighten. This configuration inhibits spider  240  and housing  250  from loosening or unthreading from shaft  210  when shaft  210  is rotating or accelerating in the reverse direction R. 
         [0031]    When shaft  210  rotates generally in the forward direction, as described above, spider may generally tighten with respect to shaft  210 . With this situation, securing member  400  may not be needed to inhibit the general unthreading of spider  240  with respect to shaft  210 . 
         [0032]    This configuration may enhance the coupling of spider  240  and system  200  to shaft  210  regardless of direction of rotation, while keeping the attachment location and other portions of the system easily adjustable, serviceable, and separable. 
         [0033]    In some embodiments, spiders may be generally locked in position with respect to shaft  210  in service, regardless of direction of rotation. In this embodiment, when the shaft rotates in the forward direction, the spider will tend to generally tighten with respect to the shaft. When the shaft rotates generally in the reverse direction, the spider may tend to unthread or loosen from the shaft towards the securing member. The securing member will tend to move toward the spider and inhibit the unthreading to the spider with respect to the shaft. 
         [0034]    In embodiments, spiders may need to have the location on the shaft to be moveable and fine-tuned. Once the spider is located, it may need to be locked in place. This configuration enhanced this fine tuning of the spider. 
         [0035]      FIG. 5  shows a plan view of a shaft  210 , according to an embodiment. Shaft  210  may include a corresponding locking structure  212 . Corresponding locking structure  212  may include spider locking portion  214  and securing portion locking portion  216 . 
         [0036]    The spider  240  bears upon a shoulder  217  on shaft  210  as it is secured to the shaft with securing member  400 . 
         [0037]    In an embodiment, spider locking portion  214  may be generally forward threads on shaft  210 . In this embodiment, spider  240  may have corresponding threads such that shaft  210  will generally threadingly couple to spider  240 . 
         [0038]    In an embodiment, securing portion locking portion  216  may be generally reverse threads on shaft  210 . In this embodiment, securing portion  400  may have corresponding threads such that shaft  210  will generally threadingly couple to securing portion  400 . 
         [0039]    It will be appreciated that any suitable securing and/or inhibiting system, method, configuration, and/or substance may be used for this purpose for any portion of the system, without straying from the teachings of this disclosure. 
         [0040]    Furthermore, this system and method of the securing member  400 , and corresponding securing and/or locking configuration may be used to secure stationary sheave  220  to shaft  210 , either in the primary drive CVT clutch or a secondary driven CVT clutch. This is not explicitly shown in the drawings, but one skilled in the art should know how to accomplish this. In some configurations, stationary sheave  220  may be overmolded or formed integrally with shaft  210 . This configuration may save money, complexity, and/or manufacturing time. 
         [0041]    Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods, and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. The disclosure disclosed herein may suitably be practiced in the absence of any element that is not specifically disclosed herein.