Patent Publication Number: US-2023160442-A1

Title: Reduced shifting inertia continuously variable transmission clutch

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to provisional application 63/282,541 filed on Nov. 23, 2022. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     Not Applicable 
     REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON COMPACT DISC AND AN INCORPORATION-BY-REFERENCE OF THE MATERIAL ON THE COMPACT DISC 
     Not Applicable 
     STATEMENT REGARDING PRIOR DISCLOSURES BY AN INVENTOR OR JOINT INVENTOR 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     Continuously variable transmissions (CVT) are commonly used in light-weight vehicles such as all-terrain vehicles and snow mobiles. Clutches for CVTs operate by having a stationary sheave and a movable sheave. When the clutch is not spinning, the sheaves are at their maximum distance apart and the belt is at its point nearest the hub of the clutch. As the clutch spins faster, momentum acts on weights in the clutch causing them to spin out. As the weights spin out, they exert force on the back of the movable sheave forcing the movable sheave toward the stationary sheave. As the movable sheave moves toward the stationary sheave, the clutch belt is forced up the face of the sheaves into a “higher” gear to a point where the sheave faces are a minimal distance apart. As the speed of the clutch decreases, springs in the clutch push the movable sheave away from the stationary sheave. As the movable sheave moves away from the stationary sheave, the clutch belt moves toward the hub of the clutch placing the transmission in a “lower” gear. 
     The performance characteristics of a CVT may be adjusted by changing the spring weight on the movable sheave. A heavier spring will require a higher RPM for the transmission to shift to a higher gear. Conversely, a lower spring will permit the transmission to shift to a higher gear at a lower speed. Heavier weights will shift the transmission to a higher gear at a lower RPM. Conversely, lighter weights will require a higher RPM to shift the shift the transmission to a given gear. Different weight shapes, and distributing portions the weight differently along the length of the weight, can also alter the performance characteristics of a CVT. 
     CVT clutches are mechanically quite simple, but many CVT clutches require maintenance at relatively short intervals (often in under 500 miles). If a CVT clutch has not been shifting smoothly, the sheaves may become grooved which can exponentially increase performance degradation of the CVT clutch. Weights are installed on pins to permit them to rotate out and in due to momentum. The pins are geometrically positioned as chords about the rotating shaft. Friction between the on the weights and the pins can cause the weights to not move as easily as would be desirable resulting “sticky” shifting. Bushings are often installed between the weight and the pin on which the weight is installed. Bushings may also installed between the weight and the arms of the “spider.” These bushings decrease wear of the weight on the arms and pin. 
     DESCRIPTION OF RELATED ART INCLUDING INFORMATION DISCLOSED UNDER 37 CFR 1.97 AND 37 CFR 1.98 
     Not Applicable 
     BRIEF SUMMARY OF THE INVENTION 
     A clutch for a continuously variable transmission which reduces friction between moving parts by adding bearings at points of contact between the movable sheave and weights and between rollers and the spider. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG.  1    shows a clutch spider of the present invention. 
         FIG.  2    shows a roller bearing. 
         FIG.  3    shows a thrust needle bearing. 
         FIG.  4    shows clutch weights. 
         FIG.  5    shows a clutch weight pin. 
         FIG.  6    shows a movable sheave. 
         FIG.  7    shows a spacer of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The applicant&#39;s invention is a reduced friction primary clutch for a continuously variable transmission. Friction is reduced, and wear resistance is increased, by installing bearings at key locations. The applicant&#39;s improvement includes installing as many as 21 bearings in a primary clutch in various combinations of locations. Clutches are assembled symmetrically since they spin at high speed and balance is critical. Generally, primary clutches have 3 sets of features, though other sets of features are within the scope of the applicant&#39;s inventions. 
     In prior art clutches, roller bushing pins are installed in spider arms. In prior art clutches, a spacer  700  is installed on both sides of a bushing in the arm opening between the roller bushing and the sides of the opening on the roller pin. In a preferred embodiment of the applicant&#39;s invention, a sealed roller bearing  200  is used in place of the roller bushing on the roller bushing pin  500 . In a preferred embodiment of the applicant&#39;s invention, spacers  700  are installed between each side of the sealed roller bearing  200  and the insides of the opening of the arm. In a preferred embodiment, spacers  700  comprised of a low-friction polymer are used. In an alternative embodiment of the applicant&#39;s invention, thrust need bearings are used in place of spacers  700 . In certain embodiments of the applicant&#39;s invention, the arms of the spider  100  are modified  102  to accommodate the installation of bearings. In a preferred embodiment, a roller bearing  200  is installed in the spider arm on both sides of the opening such that the roller pin  500  may rotate within the spider arm supported by the bearings. 
     In one embodiment of the applicant&#39;s invention, a bearing (clutch weight pin bearing)  200  is installed in the pin hole of each clutch weight  402 . The clutch weight  402  is then installed in a movable sheave  600 . In a preferred embodiment, the clutch weight pin bearing  200  is a sealed roller bearing. 
     A conventional movable sheave is configured with two holes, adjacent each weight, to accommodate a bolt or pin, onto which a clutch weight  402  is installed. In one embodiment of the applicant&#39;s invention, bearings  200  are installed in these holes  602  in the movable sheave  600 . In certain embodiments, the movable sheave is further configured with holes whereby the bearings in the movable sheave may be lubricated. 
     In one embodiment of the applicant&#39;s invention, these spacers  700  are replaced with thrust needle bearings  300 . Certain clutch weights  402  are wider adjacent the pin hole  406  than where they contact the movable sheave  404 . The width of the clutch weight  410  may also be reduced  414 , at least adjacent the pin hole, if necessary to account for any increased thickness of the needle thrust bearings  300  compared to the width of the spacer(s)  700  while leaving the portion  412  which contacts the movable sheave unaltered. In certain prior art clutches spacers are not installed between the weight  402  and the movable sheave  600 . In these configurations, the width of the clutch weight  410  may also be reduced (at least adjacent the pin hole)  414  to accommodate the width of the thrust roller bearings  300 . In a preferred embodiment, needle thrust bearings  300  are installed on. 
     A movable sheave  600  is configured with two holes  602 , adjacent an opening  604 . A clutch weight  402  is installed in the opening. The clutch weight  402  is held in place by a bolt or pin  606  passing through the holes  602  and through a pin hole in the clutch weight. In the case of a bolt  606 , a nut  608  is preferably installed on the bolt  606 . In a conventional movable sheave  600 , spacers  700  may be installed on either side of the clutch weight  402  between the clutch weight and the sides of the opening  604  in the movable sheave  600 . In one embodiment of the applicant&#39;s invention, the spacers  700  on either side of the clutch weight  402  are replaced by thrust needle bearings  300 . In a preferred embodiment, the holes  602  adjacent the opening  604  are configured to accommodate roller bearings  200 . In a preferred embodiment, the width of the clutch weight  410  is reduced adjacent the pin hole  414  in the clutch weight. The width of the clutch weight contacting the spider  412  is preferably unchanged. In an alternative embodiment of the applicant&#39;s invention, a roller bearing is installed in the clutch weight pin hole between the clutch weight and the bolt or pin on which the clutch weight is installed. In certain embodiments, the movable sheave  600  is configured with a plurality of orifices through which lubricant may be passed to lubricate roller bearings installed in the movable sheave  600 . 
     In certain embodiments, bearings are installed in the spider to reduce friction between the weights and the spider. In a conventional spider, a bushing is installed in the weight opening of the spider on a pin or bolt each arm of the spider. A bushing is used to reduce friction between the weight and the spider and because the weight contacts the spider at slightly different points as the clutch RPM changes. Because the bushing must rotate on the pin, a significant gap generally exists between the bushing and pin. In a preferred embodiment of the applicant&#39;s invention, an inner bearing  200  is installed in the spider arm replacing a bushing of a conventional clutch. Replacing the bushing with a bearing in the present invention allows the bearing to be installed with little gap (even a force fit between the pin and inner bearing in certain embodiments) between the pin and bearing. The reduced gap results in decreased pin wear because the bearing will remain more coaxial with the pin than with a conventional configuration using a bushing. In an alternative embodiment, more than on bearing  200  is installed on the pin between the ridges of the spider arm. Using multiple bearings can decrease over-all weight, thereby reducing inertial momentum, and reduce surface contact area between the weights and the spider. 
     In certain embodiments, outer bearings  200  are installed in the arms  201  of the spider. In this embodiment, the outer bearings are installed between the pin and ridge of the spider which holds the pin supporting either the bushing of a conventional clutch spider or the pin supporting the bearing of the present improved clutch spider. In various combinations the outer bearings may be used, the inner bearing may be used, or all may be used together within the scope of the present invention. 
     For purposes of this disclosure, including claims, plurality means one or more unless otherwise explicitly indicated.