Patent Publication Number: US-2022213958-A1

Title: Continuously variable transmission engine braking system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority to U.S. Provisional Application Ser. No. 63/133,498, same title herewith, filed on Jan. 4, 2021, and to U.S. Provisional Application Ser. No. 63/225,688, same title herewith, filed on Jul. 26, 2021, which both are incorporated in their entirety herein by reference. 
    
    
     BACKGROUND 
     Continuously variable transmissions (CVTs) provide a transmission system that automatically adjusts its gearing as needed. A typical CVT includes a drive sheave assembly and a driven sheave assembly. The drive sheave assembly is in operational communication with an engine and the driven sheave assembly is in operation a communication with a drivetrain of a vehicle. A belt provides operational communication between the drive sheave assembly and the driven sheave assembly. Each sheave assembly typically includes a fixed sheave and a movable sheave that are mounted on a post. A movable sheave activation assembly moves the movable sheave in relation to the fixed sheave to adjust a location of the belt in relation to a central axis of the sheave assembly to change the gearing by selectively causing the belt to ride up and down on engagement surfaces of the fixed and moveable sheaves. 
     Engine braking is a desired feature to help slow down a vehicle in certain situations. For example, if a vehicle is traveling down a steep hill, traditional braking systems to slow the vehicle may not be adequate. Engine braking is expressly desired in vehicles that are subject to extreme terrain such as, but not limited to, all-terrain vehicles (ATVs) and utility terrain vehicles (UTVs). Providing an engine braking system that includes a CVT can be a challenge since, during a typical engine braking situation, the fixed sheave and the moveable sheave of the drive sheave assembly are spaced away from each other with only an inner surface of the belt engaging a sleeve that is free to rotate on the post (to achieve an idle condition). A reliable efficient engine braking system for a CVT is desired. Further, it may be desired to have an engine braking system in a CVT that disengages when a certain threshold is reached to protect vehicle components. 
     SUMMARY OF INVENTION 
     The following summary is made by way of example and not by way of limitation. It is merely provided to aid the reader in understanding some of the aspects of the subject matter described. Embodiments provide a drive sheave assembly with an engine braking feature that includes a one-way engagement collar that is selectively received within a central recess of a fixed sheave. 
     In one embodiment, a drive sheave assembly of a continuously variable transmission is provided. The drive sheave assembly includes a post, a fixed sheave, a movable sheave, a sleeve, a one-way engagement collar and ramp members. The fixed sheave is statically mounted on the fixed post and includes a central recess. The fixed sheave further includes a plurality of sheave ramps within the central recess. The movable sheave is slidably mounted on the fixed post. The sleeve is rotatably mounted on the post. A mid-portion of the sleeve is positioned between the fixed sheave and the movable sheave and has an outer surface configured to engage an inner surface of a belt. A one-way engagement collar is mounted over an end portion of the sleeve. The one-way engagement collar is configured to rotate freely on the end portion of the sleeve when the sleeve rotates in a first direction and lock onto rotation of the sleeve when the sleeve rotates in a second direction. The one-way engagement collar further has a plurality of ramp pockets that extend axially in from an end surface of the one-way engagement collar. A ramp member is received within each ramp pocket of the plurality of ramp pockets in the one-way engagement collar. Each ramp member is configured to engage an associated sheave ramp of the plurality of sheave ramps in the central recess of the fixed sheave and move the one-way engagement collar axially to engage a side of the belt when the sleeve rotates in the second direction. 
     In another embodiment, a drive sheave assembly of a continuously variable transmission is provided. The drive sheave assembly includes a post, a fixed sheave, a movable sheave, a sleeve, a one-way engagement collar, a plurality of pairs of locking rollers and roller biasing members, and ramp members. The fixed sheave is statically mounted on the fixed post. The fixed sheave includes a central recess. The fixed sheave further includes a plurality of sheave ramps within the central recess. The movable sheave is slidably mounted on the fixed post. The sleeve is rotatably mounted on the post. A mid-portion of the sleeve is positioned between the fixed sheave and the movable sheave. The mid-portion of the sleeve includes an outer surface configured engage an inner surface of a belt. The one-way engagement collar mounted over an end portion of the sleeve. The one-way engagement collar has a plurality of locking pockets extending axially in from a side edge of the one-way engagement collar. The one-way engagement collar including a plurality of roller windows. Each roller window extending radially from an inside surface of the one-way engagement collar into an associated locking pocket. The one-way engagement collar further having a plurality of ramp pockets that extend axially in from an end surface of the one-way engagement collar. Each pair of locking roller and roller biasing member of the plurality of the locking rollers and roller biasing members received in an associated locking pocket of the one-way engagement collar. A portion of each locking roller extends through an associated roller window of the one-way engagement collar to engage the portion of the sleeve. Each locking pocket and associated pair of locking roller and roller biasing member being configured to allow rotation of the one-way engagement collar on the end portion of the sleeve when the sleeve rotates in a first direction and lock rotation of the one-way engagement collar onto the rotation of the sleeve when the sleeve rotates in a second direction. The ramp member is received within each ramp pocket of the plurality of ramp pockets in the one-way engagement collar. Each ramp member is configured to engage an associated sheave ramp of the plurality of sheave ramps in the central recess of the fixed sheave and move the one-way engagement collar axially to engage a side of the belt when the sleeve rotates in the second direction. 
     In yet another embodiment, a vehicle that includes a drivetrain, an engine, and a continuously variable transmission is provided. The continuously variable transmission is in operational communication between the drivetrain and the engine to couple torque between the engine and the drivetrain. The continuously variable transmission includes at least one sheave assembly. The at least one sheave assembly further includes a post a fixed sheave, a movable sheave, a sleeve, a one-way engagement collar, and ramp members. The fixed sheave is statically mounted on the fixed post. The fixed sheave includes a central recess. A plurality of sheave ramps are located within the central recess. The movable sheave is slidably mounted on the fixed post. The sleeve is rotatably mounted on the post. A mid-portion of the sleeve is positioned between the fixed sheave and the movable sheave. The mid-portion of the sleeve has an outer surface that is configured to engage an inner surface of a belt. The one-way engagement collar is mounted over an end portion of the sleeve. The one-way engagement collar is configured to rotate freely on the end portion of the sleeve when the sleeve rotates in a first direction and lock onto rotation of the sleeve when the sleeve rotates in a second direction. The one-way engagement collar further has a plurality of ramp pockets that extend axially in from an end surface of the one-way engagement collar. The ramp member is received within each ramp pocket of the plurality of ramp pockets in the one-way engagement collar. Each ramp member is configured to engage an associated sheave ramp of the plurality of sheave ramps in the central recess of the fixed sheave and move the one-way engagement collar axially to engage a side of the belt when the sleeve rotates in the second direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments can be more easily understood and further advantages and uses thereof will be more readily apparent, when considered in view of the detailed description and the following figures in which: 
         FIG. 1A  is a side view of a drive sheave assembly of a CVT with an engine braking system in an inactivated configuration according to one exemplary embodiment; 
         FIG. 1B  is a side view of the drive sheave of a CVT of  FIG. 1A  with the engine braking system in an activated configuration according to one exemplary embodiment; 
         FIG. 2  is an unassembled view of the drive sheave assembly of  FIG. 1A ; 
         FIG. 3  is an end perspective view of a one-way engagement collar according to one exemplary embodiment; 
         FIG. 4  is a side perspective view of a fixed sheave and the one-way engagement collar according to one exemplary embodiment; 
         FIG. 5  is an end perspective view of a sleeve according to one exemplary embodiment; 
         FIG. 6A  is a cross-sectional side view of the drive sheave assembly of  FIG. 1A  with the engine braking system in the inactivated configuration; 
         FIG. 6B  is a close-up partial cross-sectional side view of the drive sheave assembly of  FIG. 6A  illustrating the engine braking system in the inactivated configuration; 
         FIG. 7A  is a cross-sectional side view of the drive sheave assembly of  FIG. 1B  with the engine braking system in the activated configuration; 
         FIG. 7B  is a close-up partial cross-sectional side view of the drive sheave assembly of  FIG. 7A  illustrating the engine braking system in the activated configuration; 
         FIG. 8  is a block diagram of vehicle that includes the drive sheave assembly of  FIG. 1A  according to one exemplary embodiment; 
         FIG. 9  is an unassembled side view of an engine braking system according to another exemplary embodiment; and 
         FIG. 10  is an end view of the one-way engagement collar mounted on the sleeve in the engine braking system of  FIG. 9 . 
     
    
    
     In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the subject matter described. Reference characters denote like elements throughout Figures and text. 
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the claims and equivalents thereof. 
     Embodiments provide a CVT with an engine braking system (EBS) (CVT EBS) that implements a one-way engagement collar to selectively engage a portion of a belt during an engine braking situation to clamp down on the belt with an associated sheave assembly. Some embodiments are further configured to disengage the engine braking feature when a threshold is reached to protect vehicle components. 
     Referring to  FIGS. 1A and 1B  side views of a drive sheave assembly  100  of a CVT EBS of an example embodiment is illustrated. The drive sheave assembly  100  is part of a CVT such as CVT  304  discussed below. The drive sheave assembly  100  (or drive clutch assembly) includes a fixed sheave  102  and a movable sheave  104 . The movable sheave  104  is configured to move axially in relation to the fixed sheave  102  under control of a movable sheave activation assembly  140 . In one embodiment, the axial location of the movable sheave  104  on a post of the drive sheave assembly  100  is based off centrifugal forces the drive sheave assembly is experiencing due to rotation of the drive sheave assembly  100 . The drive sheave assembly  100  includes a one-way engagement collar  120  which is in a retracted configuration in  FIG. 1A .  FIG. 1B  illustrates the one-way engagement collar  120  in a belt engaging configuration which would occur during an engine braking situation. 
     An unassembled view of the drive sheave assembly  100  is illustrated in  FIG. 2 . As illustrated, the drive sheave assembly  100  includes the fixed (or stationary) sheave  102  that is statically mounted on a post  110 . The drive sheave assembly  100  further includes seals  112  and  128 , thrust washers  126  and  130 , bias members  132  and  136 , spring cup  134  and nut  141 . Further illustrated are ramp members  114 , bullets  116  (caps) and bias members  118  that work with the one-way engagement collar  120  to selectively activate (move axially) the one-way engagement collar  120  to engage a belt  200  (shown in  FIG. 7A ) of the CVT. The movable sheave activation assembly  140  includes a main bias member  136 . 
       FIG. 3  illustrates a closeup side perspective view of the one-way engagement collar  120 , ramp members  114 , bullets  116  and bullet bias members  118  (springs). Each ramp member  114  includes a ramped surface  114   a  which extends between a first end  114   b  to a ramp stop portion  114   d  at a second end  114   c.  The one-way engagement collar  120  is generally ring shaped with a central opening having a first end surface  120   a  and second end surface  120   b  (best illustrated in  FIG. 2 ). The one-way engagement collar  120  includes spaced ramp pockets  121  that extend into the first end surface  120   a  of the one-way engagement collar  120 . Each ramp member  114  is received with an associated end ramp pocket  121  such that the ramp surface  114   a  of each ramp  114  is facing outward from the one-way engagement collar  120 . 
     The one-way engagement collar  120  further includes a plurality of bullet pockets  123  that radially extend into the one-way engagement collar  120  from an interior surface  120 c of the one-way engagement collar  120 . Each bullet  116  and bullet bias member  118  is received within an associated bullet pocket  123  in the one-way engagement collar  120 . The one-way engagement collar  120  may further include a plurality of spaced voids  125 , which in one example, is used to reduce the overall weight of the one-way engagement collar  120 . 
       FIG. 4  illustrates that the fixed sheave  102  includes a central recess  103  in this example embodiment. Within the central recess  103  is located sheave ramps  105 . Each sheave ramp  105  is positioned to engage a ramped surface  114   a  of an associated ramp member  114 . The sheave ramp/ramp member arrangement is configured to selectively move the one-way engagement collar  120  axially as discussed below in detail.  FIG. 4  also illustrates a bullet  116  received within an associated bullet pocket  123  in the one-way engagement collar  120 . 
     Referring to  FIG. 5 , a close-up side view of the sleeve  106  and how the bullets  116  interact with the sleeve is illustrated. The sleeve  106  in one embodiment is an idler bearing that includes bearings  107  that are position partially within an inner surface  106   b  of the sleeve  106  to engage the post  110 . A mid-portion  106   e  of the sleeve  106  includes an outer surface  106   a  that engages an inner surface of belt of the CVT (shown in  FIG. 6A ). An end portion  106   c  of the sleeve  106  includes a sleeve ramp portion  109  in this example. A ridge portion  111  separates the end portion  106   c  from the mid-portion  106   e.  As illustrated in  FIG. 6A  the mid-portion is positioned between the fixed sheave  102  and the movable sheave  104 . 
     The sleeve ramp portion  109  includes a plurality of sleeve ramps  109   a,  Each of the radially positioned sleeve ramp  109   a  terminates with a sleeve ramp stop  109   c  which starts the next sleeve ramp  109   a,  As illustrated, the bullets  116 , biased by the associated bullet bias members  118  that are received within bullet bores  115  of the bullets  116 , ride along the ramps  109   a  of the sleeve ramp portion  109 . When the sleeve  106  rotates in a first direction, the bullets  116  simply ride over the ramps  109   a  with the bullet bias members  118  forcing the bullets  116  to engage the surfaces of ramps  109   a  even as they pass over the sleeve ramp stops  109   c  (i.e., they snap over the sleeve ramp stops  109   c  when the sleeve rotates in the first direction). When the sleeve  106  rotates in the other direction (second direction), such as when a drivetrain is overrunning the rotation provided by the engine, the bullets  116  engaging the sleeve ramp stops  109   c  lock rotation of the one-way engagement collar  120  (which houses the bullets  116 ) with rotation of the sleeve  106 . 
       FIG. 6A  illustrates a cross-sectional side view of the drive sheave assembly  100 . As illustrated, the movable sheave activation assembly  140  in this embodiment includes the main bias member  136 , which in this embodiment is a compression spring, and a plurality of fly weights  142  and associated stationary members  144 . The main bias member  136 , positioned between the spring cup  134  and a portion of the movable sheave activation assembly  140 , exerts a force on the movable sheave  104  away from the fixed sheave  102 . This condition may occur at vehicle idle where the sleeve  106  rotates freely on the post  110  in the first direction of the drive sheave assembly  100  and no torque if transferred to the belt  200 . As the rotational speed of the drive sheave assembly increases, such as when a vehicle throttle is increases, the fly weights  142  engaging the stationary members  144  counter the main bias member force causing the movable sheave  104  towards the fixed sheave  102 . This action results in the belt  200  being clamped between the fixed and movable sheaves  102  and  104  therein coupling torque between the sheaves  102  and  104  and the belt  200 . As the speed of the drive sheave assembly increases and decreases, the belt moves up and down engagement surfaces the fixed and movable sheaves  102  and  104  therein changing gearing by changing the distance of the belt  200  from a central axis of the drive sheave assembly  100 . Further, as the rotational speed of the drive sheave assembly  100  decreases the bias force from the main bias member  136  overcomes the force of the flyweight/stationary member  144  arrangement and the belt rides back down towards the sleeve  106 . 
       FIG. 6A  illustrates the drive sheave assembly  100  in an operating configuration where engine braking is not needed. This operating configuration may occur when a vehicle is idling while on relatively even terrain. In this configuration, belt  200  has an inner surface that rides on the outer surface  106   a  of the sleeve  106 . Only a portion of the belt  200  is illustrated in  FIG. 6A . Since the sleeve  106  is free to rotate in a first direction in relation to the post  110 , no torque from the drive sheave assembly  100  is coupled to the belt  200  in this idle configuration. 
       FIG. 6B  illustrates a close-up illustration of the engine braking assembly in the idle operation configuration. As illustrated, the one-way engagement collar  120  is received within the central recess  103  (or cavity) of the fixed sheave  102  with the second end  120   b  (or engaging end surface  120   b ) of the one-way engagement collar  120  being flush with a conical faced engaging surface  102   a  of the fixed sheave  102 . Since the sleeve  106  is rotating in the first direction in this idle configuration, the bullets  116  are sliding over the sleeve ramps  109   a  of the sleeve ramp portion of the sleeve  106  allow rotation between the one-way engagement collar  120  and the sleeve  106 . 
     Also illustrated in  FIG. 6B  is the position of seal  112  in a groove in a surface of the central recess  103  of the fixed sheave  102 . In one example embodiment, the seal  112  is an O-ring seal. Further in an embodiment, the seal is a quad ring seal. Also illustrated is the position of seal  128  in an inside groove in the inner surface of the one-way engagement collar  120 . In one embodiment the seal is a Teflon™ PTFE seal with or without an O-ring energizer. The seals  112  and  128  are positioned to prevent debris, such as belt debris, from getting to the ramped features (bullet/sleeve ramp and ramp member/sheave ramp features). Also illustrated in  FIG. 6B  is the positioning of bias member  132  (engine braking bias member) between the thrust washer  130  and another side of the spring cup  134 . Bias member  132  in this embodiment is a compression wave spring  132 . The function of bias member  132  is to exert a force on the sleeve/one-way engagement collar assembly to retain the one-way engagement collar  120  within the central recess  103  of the fixed sheave  102  when an engine braking condition is not present. 
       FIG. 7A  illustrates a side view of the drive sheave assembly  100  in an engine braking configuration. In this configuration, the one-way engagement collar  120  moves out from the central recess  103  of the fixed sheave  102  to engage a side portion of the belt  200 . This action causes the drive sheave assembly  100  (the one-way engagement collar  120  and the movable sheave  104 ) to clamp down on the belt  200  therein coupling torque between a drivetrain of a vehicle and the engine to allow engine braking to occur.  FIG. 7B  illustrates a close-up view of the engine braking assembly during the engine braking condition. 
     As discussed above, engine braking occurs when a vehicle&#39;s drivetrain causes the belt  200  to overrun the sleeve (move the sleeve in an opposite or second direction). This can occur, for example, when the vehicle is at idle while going down a steep hill. In this situation, the belt  200 , which rides on the sleeve during idle, rotates the sleeve  106  in an opposite direction (second rotational direction) from its normal direction (first rotational direction) provided by a rotational output of the engine. Rotation of sleeve  106  in the second direction causes the bullets  116  in the one-way engagement collar  120  to engage the sleeve ramp stops  109   c  on the sleeve ramp portion  109  of the sleeve  106  therein locking rotation of the one-way engagement collar  120  with rotation of the sleeve  106 . This causes each ramp member  114  housed within the ramp pockets  121  of the one-way engagement collar to move in relation to the ramp members associated sheave ramp  105  in the central recess  103  of the fixed sheave  102  therein moving the one-way engagement collar out of the central recess  103  to engage the belt  200 . This clamps the belt  200  between an engagement surface of the one-way engagement collar  120  and an engagement surface of the moveable sheave  104  therein coupling torque between the drive sheave assembly  100  and the belt  200 . 
     One feature of the engine braking assembly is that the function of the engine braking can be disconnected under certain conditions even when the drivetrain is overrunning the sleeve  106 . This may be desired to protect the vehicle components during extreme conditions. This feature is accomplished with the configuration of the one-way feature in the one-way engagement collar  120 . The bullet bias members  118  within the cavity of the bullets  116  may be selected to exert a select mount of bias force to engage the sleeve ramps  109   a  and sleeve ramp stops  109   c  of the sleeve ramp portion  109  of the sleeve  106 . The bias force may be selected so that a predetermined amount of centrifugal force caused by rotation of one-way engagement collar  120  counters the bias force provided by the bullet bias members  118 . This causes the bullets  116  to move back into their associated bullet pockets  123  in the one-way engagement collar  120 . When this happens, the bullets  116  no longer engage the sleeve ramp stops  109   c  of the sleeve ramps  109   a  of the sleeve  106 . The one-way engagement collar  120  is then again free to rotate in relation to the sleeve  106 . This allows each ramp member  114  housed within the ramp pockets  121  of the one-way engagement collar  120  to move in relation to the ramp members associated sheave ramp  105  in the central recess  103  of the fixed sheave  102  aided by bias member  132  (which may be a wave spring) therein moving the one-way engagement collar into the central recess  103  away from the belt  200 . Once the centrifugal force lessens, the bias force from the bullet bias members  118  overcomes the centrifugal force and the bullets  116  once again extend out from there associated bullet pockets  123  to engage the sleeve ramp stops  109   c  to enact the engine braking by axially moving the one-way engagement collar  120  to engage a portion of the belt  200 . 
     Referring to block diagram of  FIG. 8 , an example vehicle  300  implementing a drive sheave assembly  100  is illustrated. The drive sheave assembly  100  is part of a CVT  304  that further includes the belt  200  (or endless looped member) and a driven sheave assembly  306 . The drive sheave assembly  100  is in operational communication with an engine  302 . The driven sheave assembly  306  is in operational communication with the drive sheave assembly  100  via the belt  200  to selectively communicate torque between the drive sheave assembly  100  and the driven sheave assembly  306 . 
     The driven sheave assembly  306  is in communication with the drivetrain that, in this example, includes a gear box  308 , a front and rear drive shaft  310  and  312  (or prop shafts), front and rear differentials  314  and  316 , front half shafts  318 a and  318 b, rear half shafts  322   a  and  322   b,  front wheels  320   a  and  320   b  and rear wheels  324   a  and  324   b.    
     As discussed above, an engine braking system that includes the one-way engagement collar  120  is activated when torque from the drivetrain communicated through the driven sheave assembly  306  and belt  200  to the drive sheave assembly  100  tries to overrun the sleeve  106  (move the sleeve in the second direction). This may occur when the engine  302  is at idle while the vehicle  300  is traveling down a hill. This overrunning of the sleeve  106  causes the bullets  116 , within the bullet pockets  123  of the one-way engaging collar  120 , to engage the sleeve ramp stops  109   c  of the sleeve  106  therein locking rotation of the one-way engagement collar  120  with the sleeve  106 . As the one-way engagement collar  120  is overrunning (rotating with the sleeve  106 ), the ramp members  114  in the ramp pockets  121  slide on the sheave ramps  105  which axially moves the one-way engagement collar  120  to engage a side portion of the belt  200 . This causes the drive sheave assembly  100  to clamp down on the belt  200  coupling torque between the belt and the engine  302  to the enable engine braking. When the belt  200  is no longer overrunning the sleeve  106  (rotating in the second direction), which will occur when the engine revolutions increase or when the terrain pitch the vehicle is encountering has been reduced, the engine braking system is disengaged. Further, as discussed above, the engine braking system may be designed to disengage when an overrunning torque reaches a predefined threshold to protect components of the vehicle  300 . Although,  FIG. 8  illustrates a continuously variable transmission engine braking system being used in a vehicle with wheels, other types of vehicles using a CVT such as, but not limited, vehicles that use one or more tracks may implement the continuously variable transmission engine braking system. 
       FIGS. 9 and 10  illustrates yet another example embodiment of an engine braking system  400  that would be included in a drive sheave assembly  100  of a CVT  304  as discussed above. This example embodiment includes a sleeve  406 . The sleeve includes an outer surface  406   a  that is designed to engage in inner surface of a belt, such as belt  200  discussed above and an inner surface  406   b.  A ridge portion  406 d extends from the outer surface  406   a  of the sleeve  406  that separates the outer surface  406   a  designed to engage the belt  200  and an end portion  406   c  of the sleeve  406  designed to engage an inner surface of a one-way engagement collar  412 . In this embodiment, the end portion  406   c  does not include ramps. The outer surface of the end portion  406   c  is a smooth surface with a consistent diameter. 
     The one-way engagement collar  412  in this example, includes a plurality of locking pockets  411  extending axially in an end surface  412   a  of the one-way engagement collar  412 . Each locking pocket  411  is configured to receive a locking roller  416  and associated compression spring  418  (roller biasing member  418 ). Each locking pocket  411  includes a roller window  411 a that allows a portion of an associated locking roller  416  to engage the end outer surface  406   c  of the sleeve  406 . The configuration of each locking pocket  411  with its associated locking roller  416  and compression spring  418  allows the one-way engagement collar  412  to rotate freely in relation to the sleeve  406  in a first direction while locking rotation of the one-way engagement collar  412  with the sleeve  406  in a second direction (which would occur in during an engine braking situation). In particular, a cam profile in each locking pocket  411  prevents the locking roller  416  from rotating as it is wedged between the cam profile in its associated locking pocket  411  and the end outer surface  406   c  of the sleeve  406  during an engine braking situation. Retainer plates  422  and fasteners  424  are used in this example to retain the locking rollers  416  and compression springs  418  within their associated locking pockets  411  in the one-way engagement collar  412 . 
     The one-way engagement collar  412  in this example also includes ramp pockets  413  that are configured to receive ramp members  420 . Like ramp members  114  discussed above. The ramp members  420  are configured to engage sheave ramps  105  located within a central recess  103  of a fixed sheave  102 . When the one-way engagement collar  412  locks rotation with the sleeve  406  in an engage braking situation, the ramp members  420 /engage sheave ramps  105  move the one-way engagement collar  412  to engage a side of the belt to enhance engine braking. 
     The engine braking system  400  further includes a lip seal  407  to keep grease retained inside a bearing of the sleeve  406  as wells as seals  408  and  414  and thrust washer  410 . Seal  414  is positioned between an outer surface of the one-way engagement collar  412  and an interior surface of the central recess of the fixed sleeve in an example embodiment. 
     EXAMPLE EMBODIMENTS 
     Example 1 includes a drive sheave assembly of a continuously variable transmission, the drive sheave assembly includes a post, a fixed sheave, a movable sheave, a sleeve, a one-way engagement collar and ramp members. The fixed sheave is statically mounted on the fixed post and includes a central recess. The fixed sheave further includes a plurality of sheave ramps within the central recess. The movable sheave is slidably mounted on the fixed post. The sleeve is rotatably mounted on the post. A mid-portion of the sleeve is positioned between the fixed sheave and the movable sheave and has an outer surface configured to engage an inner surface of a belt. A one-way engagement collar is mounted over an end portion of the sleeve. The one-way engagement collar is configured to rotate freely on the end portion of the sleeve when the sleeve rotates in a first direction and lock onto rotation of the sleeve when the sleeve rotates in a second direction. The one-way engagement collar further has a plurality of ramp pockets that extend axially in from an end surface of the one-way engagement collar. A ramp member is received within each ramp pocket of the plurality of ramp pockets in the one-way engagement collar. Each ramp member is configured to engage an associated sheave ramp of the plurality of sheave ramps in the central recess of the fixed sheave and move the one-way engagement collar axially to engage a side of the belt when the sleeve rotates in the second direction. 
     Example 2 includes the drive sheave assembly of Example 1, further wherein the one-way engagement collar further has a plurality of locking pockets extending axially in from the end surface of the one-way engagement collar. The one-way engagement collar includes a plurality of roller windows. Each roller window extends radially from an inside surface of the one-way engagement collar into an associated locking pocket. A plurality of pairs of locking rollers and roller biasing members are received in an associated locking pocket of the one-way engagement collar. A portion of each locking roller extends through an associated roller window of the one-way engagement collar to engage the end portion of the sleeve. Each locking pocket and associated pair of locking roller and roller biasing member are configured to rotate freely on the end portion of the sleeve when the sleeve rotates in the first direction and lock onto rotation of the sleeve when the sleeve rotates in the second direction. 
     Example 3 includes the drive sheave assembly of Example 2, further including a plurality or retainer plates and fasteners. Each retaining plate and at least one associated fastener of the plurality or retainer plates and fasteners are configured to cover an associated locking pocket to retain an associated pair of locking roller and roller biasing member within the associated locking pocket. 
     Example 4 includes the drive sheave assembly of Example 1, further wherein the end portion of the sleeve includes a plurality of sleeve ramps. Each sleeve ramp terminates with a ramp sleeve stop. The one-way engagement collar has a plurality of bullet pockets that extend radially in from an interior surface of the one-way engagement collar. 
     Example 5 includes the drive sheave assembly of Example 4, further including a plurality of bullets. Each bullet includes a bore. Each bullet further configured to be received within an associated bullet pocket of the plurality of bullet pockets in the one-way engagement collar. A bullet bias member is received in each bore of each bullet to provide a bias force an associated bullet of the plurality of bullets to engage an associated sleeve ramp and ramp sleeve stop of the plurality of the sleeve ramps of the sleeve ramp portions of the sleeve. 
     Example 6 includes the drive sheave assembly of Example 5, wherein the bullet bias members are configured to provide a select amount of force that can be countered by a defined centrifugal force provided by a rotation rate of the one-way engagement collar. 
     Example 7 includes the drive sheave assembly of any of the Examples 1-6, further including at least one seal positioned between the sleeve and the one-way engagement collar. 
     Example 8 includes the drive sheave assembly of any of the Examples 1-7, further including at least one seal positioned between the fixed sheave and the one-way engagement collar. 
     Example 9 includes the drive sheave assembly of any of the Examples 1-8, further including an engine braking bias member configured to exert an axial force on the one-way engagement member into central recess of the fixed sheave. 
     Example 10 includes the drive sheave assembly of any of the Examples 1-9, further including an engine braking system that is configured to disengage the one-way engagement collar from the belt when a centrifugal force threshold is reached during an engine braking condition. 
     Example 11 includes the drive sheave assembly of any of the Examples 1-10, wherein the one-way engagement collar is configured to be received within the central recess of the fixed sheave during non-engine braking conditions and to extend at least partially out of the central recess to engage the side of the belt during an engine braking condition. 
     Example 12 includes a drive sheave assembly of a continuously variable transmission, the drive sheave assembly includes a post, a fixed sheave, a movable sheave, a sleeve, a one-way engagement collar, a plurality of pairs of locking rollers and roller biasing members, and ramp members. The fixed sheave is statically mounted on the fixed post. The fixed sheave includes a central recess. The fixed sheave further includes a plurality of sheave ramps within the central recess. The movable sheave is slidably mounted on the fixed post. The sleeve is rotatably mounted on the post. A mid-portion of the sleeve is positioned between the fixed sheave and the movable sheave. The mid-portion of the sleeve includes an outer surface configured engage an inner surface of a belt. The one-way engagement collar mounted over an end portion of the sleeve. The one-way engagement collar has a plurality of locking pockets extending axially in from a side edge of the one-way engagement collar. The one-way engagement collar including a plurality of roller windows. Each roller window extending radially from an inside surface of the one-way engagement collar into an associated locking pocket. The one-way engagement collar further having a plurality of ramp pockets that extend axially in from an end surface of the one-way engagement collar. Each pair of locking roller and roller biasing member of the plurality of the locking rollers and roller biasing members received in an associated locking pocket of the one-way engagement collar. A portion of each locking roller extends through an associated roller window of the one-way engagement collar to engage the portion of the sleeve. Each locking pocket and associated pair of locking roller and roller biasing member being configured to allow rotation of the one-way engagement collar on the end portion of the sleeve when the sleeve rotates in a first direction and lock rotation of the one-way engagement collar onto the rotation of the sleeve when the sleeve rotates in a second direction. The ramp member is received within each ramp pocket of the plurality of ramp pockets in the one-way engagement collar. Each ramp member is configured to engage an associated sheave ramp of the plurality of sheave ramps in the central recess of the fixed sheave and move the one-way engagement collar axially to engage a side of the belt when the sleeve rotates in the second direction. 
     Example 13 includes the drive sheave assembly of Example 12, further including a plurality or retainer plates and fasteners. Each retaining plate and at least one associated fastener of the plurality or retainer plates and fasteners are configured to cover an associated locking pocket to retain an associated pair of locking roller and roller biasing member within the associated locking pocket. 
     Example 14 includes the drive sheave assembly of any of the Examples 12-13, wherein the one-way engagement collar is configured to be received within the central recess of the fixed sheave during non-engine braking conditions and to extend at least partially out of the central recess to engage the side of the belt during an engine braking condition. 
     Example 15 includes the drive sheave assembly of any of the Examples 12-14, wherein each ramp pocket of the plurality of the ramp pockets includes a cam profile that allows for the rotation of the one-way engagement collar on the end portion of the sleeve when the sleeve rotates in the first direction while locking rotation of the one-way engagement collar onto the rotation of the sleeve when the sleeve rotates in the second direction. 
     Example 16 includes a vehicle that includes a drivetrain, an engine, and a continuously variable transmission. The continuously variable transmission is in operational communication between the drivetrain and the engine to couple torque between the engine and the drivetrain. The continuously variable transmission includes at least one sheave assembly. The at least one sheave assembly further includes a post a fixed sheave, a movable sheave, a sleeve, a one-way engagement collar, and ramp members. The fixed sheave is statically mounted on the fixed post. The fixed sheave includes a central recess. A plurality of sheave ramps are located within the central recess. The movable sheave is slidably mounted on the fixed post. The sleeve is rotatably mounted on the post. A mid-portion of the sleeve is positioned between the fixed sheave and the movable sheave. The mid-portion of the sleeve has an outer surface that is configured to engage an inner surface of a belt. The one-way engagement collar is mounted over an end portion of the sleeve. The one-way engagement collar is configured to rotate freely on the end portion of the sleeve when the sleeve rotates in a first direction and lock onto rotation of the sleeve when the sleeve rotates in a second direction. The one-way engagement collar further has a plurality of ramp pockets that extend axially in from an end surface of the one-way engagement collar. The ramp member is received within each ramp pocket of the plurality of ramp pockets in the one-way engagement collar. Each ramp member is configured to engage an associated sheave ramp of the plurality of sheave ramps in the central recess of the fixed sheave and move the one-way engagement collar axially to engage a side of the belt when the sleeve rotates in the second direction. 
     Example 17 includes he vehicle of Example 16, wherein the at least one sheave assembly further wherein the one-way engagement collar further has a plurality of locking pockets extending axially in from the end surface of the one-way engagement collar. The one-way engagement collar includes a plurality of roller windows. Each roller window extends radially from an inside surface of the one-way engagement collar into an associated locking pocket. A plurality of pairs of locking rollers and roller biasing members are included. Each pair of locking roller and roller biasing member of the plurality of the locking rollers and roller biasing members are received in an associated locking pocket of the one-way engagement collar. A portion of each locking roller extends through an associated roller window of the one-way engagement collar to engage the end portion of the sleeve. Each locking pocket and associated pair of locking roller and roller biasing member are configured to rotate freely on the end portion of the sleeve when the sleeve rotates in a first direction and lock onto rotation of the sleeve when the sleeve rotates in a second direction. 
     Example 18 includes the vehicle of any of the Examples 16-17, further including a plurality or retainer plates and fasteners. Each retaining plate and at least one associated fastener of the plurality or retainer plates and fasteners configured to cover an associated locking pocket to retain an associated pair of locking roller and roller biasing member within the associated locking pocket. 
     Example 19 includes the vehicle of Examples 16 wherein the end portion of the sleeve of at least one sheave assembly further includes a plurality of sleeve ramps. Each sleeve ramp terminating with a ramp sleeve stop. The one-way engagement collar has a plurality of bullet pockets that extend radially in from an interior surface of the one-way engagement collar. 
     Example 20 includes the vehicle of Example 19, wherein the at least one sheave assembly further includes a plurality of bullets. Each bullet includes a bore. Each bullet is further configured to be received within an associated bullet pocket of the plurality of bullet pockets in the one-way engagement collar. A bullet bias member is received in each bore of each bullet to provide a bias force on an associated bullet of the plurality of bullets to engage an associated sleeve ramp and ramp sleeve stop of the plurality of the sleeve ramps of the sleeve ramp portions of the sleeve. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.