Engine braking primary clutch for CVT systems

A continuously variable transmission (CVT) system including a primary clutch assembly with an engine braking assembly is provided. The primary clutch assembly includes first and second sheave assemblies, a cylindrical sleeve coupler and an engine braking assembly. The first sheave portion has a centrally extending post. The cylindrical sleeve coupler is rotationally mounted on a portion of the post. The sleeve coupler has an engaging surface that is configured to engage an inner face of a drive belt. The second sheave portion has a central passage that is rotationally mounted on the sleeve coupler. The engine braking assembly is operatively coupled to the second sheave portion and the sleeve coupler to axially move the second sheave portion toward the first sheave portion to engage first and second side faces of the drive belt when the sleeve coupler attempts to overrun the post of the first sheave portion in a rotational direction provided by a rotational output of an engine operatively coupled to the primary clutch.

BACKGROUND

Continuously variable transmission (CVT) systems are used in vehicles to change transmission ratios between an engine output and a drive train of the vehicle. In a typical CVT system, a primary clutch is coupled to receive a rotational output from an engine and a secondary clutch is coupled to provide a rotational output to the drive train. The primary clutch is coupled to provide rotation to the secondary clutch with an endless loop drive belt. In changing transmission ratios, typically the primary clutch is comprised of first and second conical-faced sheave portions that are configured in a way to move the second conical-faced sheave portion axially in relation to the first conical-faced sheave portion along an axis of rotation. In this system the distance between the sheaves of the primary clutch determines the positioning of the drive belt in relation to the rotational axis and hence the transmission ratio. In particular, the closer the first and second sheave portions are positioned together, the farther the drive belt is pinched on the conical-faces away from the rotational axis of the primary clutch. Likewise, the farther the first and second sheave portions are positioned away from each other, the closer the drive belt is the rotational axis of the primary clutch. When the engine is at idle speeds, the first and second sheaves of the primary clutch are axially positioned at a select distance from each other so at least one of the conical faced sheave portions does not engage a side of the drive belt. In this situation, the limited friction between the drive belt and the primary clutch allows the belt to slip so no rotational force is applied to the secondary sheave and hence no power is provided to the drive train by the engine.

Typically CVT systems as described above do not allow for engine braking. Engine braking is a term used to describe when the engine of a vehicle is used to provide at least some of the braking for the vehicle. An example situation where engine braking is beneficial occurs when a vehicle is going down a steep incline and the operator cuts back on the throttle. In this situation the engine's rotational output will be slower than the rotation of the drive train. In an engine braking scheme, the slow rotation of the engine is used to slow down the rotation of the drive train. However, since the drive belt on a typical CVT system is designed to slip on the primary clutch during idle speeds of the motor, the engine effectively is disconnected from the drive train. This disconnection between the engine and the drive train prevents a typical CVT system from implementing engine braking. In this situation, other traditional braking means must be employed which may or may not be effective in a given situation.

SUMMARY OF INVENTION

The above-mentioned problems of current systems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification. 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 invention.

In one embodiment, a primary clutch assembly of a CVT system is provided. The primary clutch assembly includes first and second sheave assemblies, a cylindrical sleeve coupler and an engine braking assembly. The first sheave portion has a first conical-faced surface. The first conical-faced surface is configured to engage a first side face of a drive belt. The first sheave portion further has a post that centrally extends from the first conical-faced surface. The cylindrical sleeve coupler is rotationally mounted on a portion of the post proximate the first conical-faced surface. The sleeve coupler has an engaging surface that is configured to engage an inner face of the drive belt. The second sheave portion has a central passage that is rotationally mounted on the sleeve coupler. The second sheave portion has a second conical-faced surface positioned to face the first conical-faced surface of the first sheave portion. Moreover, the second conical-faced surface is configured to engage a second side face of the drive belt. The engine braking assembly is operatively coupled to the second sheave portion and the sleeve coupler to axially move the second sheave portion toward the first sheave portion to engage the first conical-faced surface of the first sheave portion with the first side face of the drive belt and the second conical-faced surface of the second sheave portion with the second side face of the drive belt when the sleeve coupler attempts to overrun the post of the first sheave portion in a rotational direction provided by a rotational output of an engine operatively coupled to the primary clutch.

DETAILED DESCRIPTION

Embodiments of the present invention provide an effective engine braking mechanism that engages three surfaces of a drive belt during situations where a secondary clutch has a faster rotational speed than a primary clutch. In embodiments, an engine braking assembly moves a second sheave portion towards a first sheave portion of a primary clutch to engage the drive belt as described above in response to a sleeve coupler of the engine braking assembly (which is driven by the drive belt) attempting to overrun, in a rotational direction, a post of the first sheave portion that is driven by a rotational output of an engine operatively coupled to the primary clutch.

Referring toFIG. 1, a side perspective view of a CVT system100of an embodiment is illustrated. As illustrated, the CVT system100includes a primary clutch102and a secondary clutch104. The primary clutch102is coupled to receive a rotational output from an engine (not shown). The secondary clutch provides a rotational output to a drive train (not shown). An endless looped drive belt106rotationally couples the primary clutch102and the secondary clutch104. The primary clutch102includes a first sheave portion108and a second sheave portion110. In this embodiment, the second sheave portion110is axially movable in relation to the first sheave portion108. In particular, a sheave moving assembly112of the primary clutch102is designed to selectively move the second sheave portion110in relation to the first sheave portion108. Further illustrated inFIG. 1, is a cover114and fasteners158that attach the cover114to the second sheave portion110.

FIGS. 2A and 2Billustrate a primary clutch102of one embodiment. In particular,FIG. 2Aillustrates an unassembled side perspective view of the primary clutch102andFIG. 2Billustrates an assembled cross-sectional side view of the primary clutch102. AsFIGS. 2A and 2Billustrate, the primary clutch102includes the first sheave portion108and the second sheave portion110. The first sheave portion108includes a first side108aand second side108b. The first side108aof the first sheave portion108includes a central opening122. The second side108bof the first sheave portion108includes a first conical-faced surface107designed to engage a first side face106bof a drive belt106. The first sheave portion108further includes a post120that centrally extends from the first conical-faced surface107. The post120includes a bore121centered about a rotational axis170of the primary clutch102as illustrated inFIG. 2B. The bore121is further aligned with the central opening122. Bore121is designed to receive a rotational output from an engine (not shown). For example, in one embodiment bore121is designed to engage a crankshaft (not shown) of an engine that is passed through the central opening122. In other embodiments, other mechanisms provide the rotational output of the engine to the primary clutch102. The first sheave portion108and the post120rotate in response to the rotational output of the engine.

A bearing136is received around a portion of the post120. In one embodiment, bearing136is a cylindrical bearing. In other embodiments other types of bearings are used including, but not limited to, roller element bearings, plain bearings and the like. A cylindrical sleeve coupler138is further received around bearing136so that bearing136is positioned between the sleeve coupler138and a surface120aof the post120. The sleeve coupler138in this embodiment has an engaging surface138cdesigned to engage an inner face106aof a drive belt106. The sleeve coupler138further includes a first end138aand a second end138b. The first end138ais positioned proximate the first conical faced surface107of the first sheave portion108. The second end138bof the sleeve coupler138includes a plurality of sleeve coupler dogs139.

The second sheave portion110of the primary clutch102includes a first side110aand a second side110b. The first side110aof the second sheave portion110includes a second conical-faced surface111. The second conical-faced surface111is designed to engage a second side face106cof a drive belt106. The second sheave portion110further includes a central sheave passage124. The central sheave passage124is received around the sleeve coupler138such that the first conical-faced surface107of the first sheave portion108faces the second conical-faced surface111of the second sheave portion110. A bushing128is positioned between a portion of a surface that defines opening124of the second sheave portion110and the sleeve coupler138. In one embodiment, bushing128is any type of plain bearing. The second sheave portion110further has a plurality of arm extending portions126(bosses) that extend out generally perpendicular proximate an outer perimeter115of the second side110bof the second sheave portion.

The primary clutch102further includes a ramp coupler140. The ramp coupler140has a first side140aand a second side140band a central ramp coupler passage141. The central ramp coupler passage141is received around a portion of the post120of the first sheave portion108. The first side140aof the ramp coupler has a plurality of ramp coupler dogs143configured to mate with the sleeve coupler dogs139of the sleeve coupler138to provide a rotational coupling between the ramp coupler140and the sleeve coupler138. The second end140bof the ramp coupler140includes at least one coupler ramp145. The primary clutch102further includes a one way clutch150(OWC) that has a central roller clutch passage151. The central roller clutch passage151is received around a portion of the post120of the first sheave portion108. The OWC150includes a first side150a, a second side150band outer perimeter150c. The OWC150further includes at least one clutch ramp155that extends radially out from a surface that defines the outer perimeter150c. In another embodiment (not shown), the at least one clutch ramp155extends axially. In still another embodiment (not shown) the OWC includes at least one follower and at least one clutch ramp155. The at least one clutch ramp155is positioned to selectively engage the at least one coupler ramp145of the ramp coupler140. Movement of the at least one clutch ramp155of the OWC150in relation to the at least one coupler ramp145of the ramp coupler140provides engine braking functions as further discussed in detail below.

Cover114, as briefly discussed above, includes a central cover opening115. The central cover opening115receives an end of the post120of the first sheave portion108. The cover114has a plurality of apertures that align with threaded bores (not shown) in the arm extending portions126(bosses) of the second sheave portion110. Fasteners158, such as bolts, are passed through the plurality of the apertures in the cover114and are threadably engaged with the threaded bores in the arm extending portions126of the second sheave portion110. The primary clutch102also includes a spider154. The spider154includes a first side154a, a second side154band a central spider passage153. The central spider passage153is received around and coupled to a portion of the post120of the first sheave portion108. In particular, the spider154is solidly coupled about connection160as illustrated inFIG. 2B. In one embodiment, the connection160is mated threads. This connection160keeps the spider154static in relation to the post120thereby preventing the spider154from moving axially along the axis of rotation170. The spider154is positioned between the cover114and the second sheave portion110as illustrated. The spider154further includes radially extending arms165. Each radially extending arm165holds an engaging pin/roller subassembly157. A washer152is positioned between the second side150bof the OWC150and surface154cof the first side154aof the spider154. A biasing member156is positioned between the second side154bof the spider154and the cover114. The biasing member156, which in this embodiment is a spring, provides a biasing force separating the spider from the cover114. Moreover, since the second sheave portion110is coupled to the cover114via fasteners158, the biasing force of the biasing member156forces the second sheave portion110away from the first sheave portion108and towards the spider154.

A plurality of flyweight members130are rotationally coupled the second side110bof the second sheave portion110. In particular, in this embodiment each flyweight130has a flyweight passage131that is rotationally mounted on a pivot rod132. Each pivot rod132is coupled to the second sheave portion110via connector134. The plurality of the flyweights130are designed to pivot on the pivot rod132such that an engaging surface130aof the flyweights130moves towards the first side154aof the spider154in response to select angular rotational speeds of the second sheave portion110. In particular, a centrifugal force created by the rotation of the second sheave portion110causes the flyweights130to pivot about pivot rods132causing the engaging surfaces130aof the flyweights130to push on the engaging pin/roller subassemblies157of spider154. The faster the rotation of the second sheave portion110, the more push force the flyweights130exert on the spider154. This push force counters the biasing force created by biasing member156thereby moving the second sheave portion110closer to the first sheave portion108and away from the spider154. During acceleration of the rotation of the CVT100, the movement of second sheave portion110toward the first sheave portion108causes the drive belt106to move farther away from the rotation axis170of the primary clutch102thereby changing into higher gearing of the CVT100. During de-acceleration of the rotation of the CVT100(where the biasing force becomes greater than the push force), the movement of second sheave portion110away from the first sheave portion108causes the drive belt106to move closer to the rotation axis170of the primary clutch102thereby changing into lower gearing of the CVT100. This is further discussed below in regards toFIGS. 5A and 5B. Although, a sheave moving member based on the rotational speed of the sheave implementing flyweights is described above, other types of the sheave moving members know in the art are contemplated and the present invention is not limited to flyweight systems.

As discussed above, embodiments of the present invention implement engine braking. In an engine braking situation, the second sheave portion110is not rotating fast enough for the push force of the flyweights130to counter the biasing force of the biasing member156. In embodiments however, during an engine braking situation, as the inner surface106aof drive belt contacts the engaging surface138cof the sleeve coupler138, the ramp coupler140and the OWC150work together to counter the biasing force of biasing member156. This causes the second sheave portion110to move towards the first sheave portion108so that the first conical-faced surface107of the first sheave portion108engages the first side face106bof the drive belt106and the second conical-faced surface111of the second sheave portion110engages the second side face106cof the drive belt106. The friction created between the drive belt106and the first and second conical-faced surfaces107and111and surface138cof the sleeve coupler138allow the engine to help slow down the vehicle. Further description of the engine braking mechanism is described below in regards toFIGS. 6A and 6B.

As further discussed above, one of the devices used in embodiments of the engine braking mechanism is the OWC150. An illustration of an embodiment of an OWC150is provided inFIGS. 3A through 3D. In particular,FIG. 3Aillustrates a top view of OWC150. As illustrated, the OWC150has a body that is generally ring shaped having an outer perimeter150cand a central passage151. As discussed above, the central clutch passage151is received around surface portion120aof post120of the first sheave portion108. This embodiment of the OWC150includes a plurality of clutch ramps designated as155a,155band155c(moving members). Ramps155a,155band155cin this embodiment generally extend radially outward from a surface that defines the outer perimeter150cof the OWC150. In another embodiment (not shown) the ramps extend forward axially. Hence, the direction of the clutch ramps155a,155band155cis not limited to extending radially. In a corresponding embodiment of the ramp coupler140, the ramp coupler140has three coupler ramps145to respectively engage the three clutch ramps155a,155band155c. As illustrated in the cross-sectional views along section line AA and along section line BB of the embodiment inFIGS. 3B and 3C, the OWC150includes pin roller182athat is positioned between a first plain bearing180aand a second plain bearing180b. The plain bearings180aand180bare pressed into their respective positions. In other embodiments, other types of bearings are used. A cover181is positioned on the first side150aof the OWC150to keep dust out of the OWC150. A set screw opening184aprovides access to a set screw186a. Set screw opening184cand set screw186cis further illustrated in the side view of the OWC150ofFIG. 3D.FIG. 3Dfurther illustrates the shape of ramps155aand155bin this embodiment. As illustrated the clutch ramps155a,155band155cinclude a flat section155e. The clutch flat section155eengages a corresponding flat section on a corresponding coupler ramp145of a ramp coupler140in an overrunning mode described further below.

A cross-sectional view along section line CC ofFIG. 3Dis illustrated inFIG. 3E.FIG. 3Efurther illustrates set screws186a,186band186c. As illustrated, each set screw186a,186band186chas an associated opening184a,184band184cthat allow access to the respective set screws186a,186band186cthat are threadably engaged with internal threads of respective biasing member passages185a,185band185c. The set screw passages185a,185band185cextend from the outer perimeter150cof the OWC150to the associated internal cavities190a,190band190c. The set screws186a,186band186care each respectively engaged with pin roller biasing members188a,188band188c. The biasing members188a,188band188care received in respective plungers189a,189band189c. The plungers189a,189band189ccontact respective pin rollers182a,182band182cthat are in respective cavities190a,190band190c. The biasing members can be made from any type of material that provides a biasing force such as, but not limited to, compression springs, wire form springs, rubber elements, and the like.

The shape of the respective cavities190a,190band190cand contact of the respective plungers189a,189band189con the respective pin rollers182a,182band182conly allow the OWC150to rotate in one direction in relation to post120of the first sheave portion108. In particular, a biasing force from the biasing members188a,188band188cforce the associated pin rollers182a,182band182calong associated ramped surfaces197a,197band197cin the respective cavities190a,190band190csuch that a portion of the pin rollers182a,182band182cengage a shaft, such as post120, received in passage151of the OWC150to prevent the OWC150from rotating in respect to the post120in a first direction. However, the pin rollers182a,182band182care received within the respective cavity190a,190band190cto allow the OWC150to rotate in relation to the post120in a second direction.

Adjustment of force on the pin rollers182a,182band182cis accomplished by adjusting the respective set screws186a,186band186cin this embodiment. In operation, the pin rollers182a,182band182care set to lock the OWC150to rotate with the post120of the first sheave portion108in a first direction and allow the OWC150to move independent (overrunning mode) of the rotation of the post120in the other direction as described above. A further illustration of the OWC is provided in the cross-sectional side perspective view ofFIG. 3F. In another embodiment, pin rollers are set at the manufacture and set screws are not used. An example of a pre-set embodiment is illustrated inFIG. 9Bbelow. OWC150is one example of an OWC that can be used. Any type of OWC or roller OWC known in the art that allows relative rotation in a first direction and disallows relative rotation in a second direction can be used.

Further illustrations describing the operation of the primary clutch102are provided inFIGS. 4A through 6B.FIGS. 4A and 4Billustrate cross-sectional views of the primary clutch102and drive belt106.FIG. 4Bis a close up view of relevant portions of the primary clutch102and drive belt106. In particular,FIGS. 4A and 4Billustrate the primary clutch102during an idle operation mode. During idle situations, only the inner face106aof the drive belt engages the engaging surface138cof the sleeve coupler138. The second conical-faced surface111of the second sheave portion110is spaced a distance away from the first conical-faced surface107of the first sheave portion108so there is a gap151between a second side face106cof the drive belt106and the second conical-faced surface111of the second sheave portion110. A gap may also be (or may be in place of gap151) between the first side face106bof the drive belt106and the first conical-faced surface107(not shown). The gap151between the first conical-faced surface107of the first sheave portion108and the second conical-face surface111of the second sheave portion110is maintained by biasing member156during the idle operational mode. During an idle operation mode, friction between the inner face106aof the drive belt106and the engaging surface138cof the sleeve coupler138prevents sleeve coupler138and bearing136from turning while post120rotates with the rest of the primary clutch102that is engaged to receive the rotational output of the engine. Hence, in the idle operational mode, the engine is disconnected from the drive train because the drive belt is coupled only to the sleeve coupler138, the ramp coupler140and the OWC150which is overrunning and therefore provides no moving force to the secondary clutch104. Further in the idle operation mode, the second side140bof the ramp coupler140abuts the first side150aof the OWC150. This is illustrated inFIG. 4B. Hence, in the idle operation mode, the at least one ramp145extending from the second side140bof the ramp coupler140and the at least one ramp (generally designated as155) on the OWC150are not engaged to ramp up the ramp coupler140from the OWC150since the OWC150is overrunning about surface portion120aof the post120. Further, flats145eon the at least one ramp145of the ramp coupler are coupling flats155eon the at least one ramp155of the OWC during idle mode operation. Also in idle mode operation, the engaging surface130aof the flyweight130is in a neutral position that is away from the first side154aof the spider154.

Cross-sectional views of the primary clutch102in an activation operational mode are illustrated inFIGS. 5A and 5B.FIG. 5Bis a close up view of relevant portions of primary clutch102. AsFIGS. 5A and 5Billustrate, during activation operational mode, the flyweights130are pivoted towards the first surface154aof the spider154due to the centrifugal forces caused by the rotation of the primary clutch102. As a result of the pivoting of the flyweights, a push force is generated by the engaging surface130aof the flyweights130on the engaging pin/roller subassemblies157of the spider154. This push force counters the biasing force of the biasing member156on the spider154thereby moving the second sheave portion110closer to the first sheave portion108of the primary clutch102. The faster the rotation of the primary clutch102, the stronger the centrifugal force (and hence the push force) and the closer the second sheave portion110is moved towards the first sheave portion108. AsFIGS. 5A and 5Billustrate, as the second sheave portion110moves towards the first sheave portion108the first conical-faced surface107of the first sheave portion108and the second conical-faced surface111of the second sheave portion110engage respective side faces106band106cof the drive belt. As the second sheave portion110moves closer yet to the first sheave portion108(indicated by arrow190inFIG. 5A), the drive belt106is forced farther away from the rotational axis170(as indicated by arrow192ofFIG. 5A). The primary clutch102is designed to only allow the second sheave portion110to move a select distance towards the first sheave portion108so the drive belt106remains contained between the first and second conical-faced surfaces107and111.

When the rotational speed of the primary clutch slows, the centrifugal force on the flyweights130is reduced and the biasing force causes the second sheave portion110to move away from the first sheave portion108(as indicated by arrow191ofFIG. 5A). As a result the drive belt106moves closer towards the rotational axis170(as indicated by arrow193ofFIG. 5A). The continuously changing distance between the drive belt106and the rotational axis170provides continuously changing transmission ratios. In addition to changing the transmission ratios with the spacing of the first and second conical-faced surfaces107and111, the friction between the engaged side faces106band106cof the drive belt106with the respective conical-faced surfaces107and111cause the drive belt106to move with the rotation of the primary clutch102. The drive belt106in turn provides rotation to the secondary clutch104to power the drive train in the non-engine braking operational mode.

FIGS. 6A and 6Billustrate a cross-sectional side view of the primary clutch102in an engine braking operational mode.FIG. 6Bis a close up view of relevant portions of the primary clutch102. In an engine braking situation without an engine braking system (EBS), the primary clutch102will not be rotationally connected to the secondary clutch104that is coupled to a drive train of the vehicle. An example situation where this can occur is when the operator of the vehicle lets off on the gas while the vehicle is traveling down a steep incline. In a typical CVT system the drive belt, in this situation, will be essentially disconnected (in an idle configuration as discussed above) from the primary drive because slip will occur when the conical faced surfaces107and111no longer engage the sides106band106cof the belt106and the inner surface106aof the belt106moves away from the post120to allow free rotational movement of the post120and engine during idle. Hence, in a typical CVT system without EBS, the vehicle must rely on other braking means during this situation. Other braking means, however, may not be adequate in all situations.

AsFIGS. 6A and 6Billustrate, in the engine braking operational mode, the flyweights130are not subject to significant centrifugal forces that cause the engaging surface130aof the flyweight130to pivot towards the first side154aof the spider154. This is because the rotation speed of the primary clutch102is relatively low (and hence so is the rotational output of the engine as the result of letting up on the throttle) in an engine braking situation. Therefore, the flyweights130cannot be used to force the second sheave portion110towards the first sheave portion108in this situation. In the engine braking situation, the secondary clutch104is pushing the belt106to a maximum radius on the secondary clutch104and thus to a minimum radius on the primary clutch102. Hence, the drive belt106that is rotationally coupled to the secondary clutch104will move the sleeve coupler138(which the inner face106aof the belt drive is engaged with) faster than the post120of the first sheave portion108. Therefore, the sleeve coupler138will rotate in relation to the post120of the first sheave portion108to try and overrun the post120.

Since, the sleeve coupler dogs139are engaged with the ramp coupler dogs143of the ramp coupler140, the ramp coupler140also rotates in relation to post120. This rotation of the ramp coupler140causes the at least one coupler ramp145to slideably engage the at least one ramp155of the OWC150. The OWC150is designed to remain synchronous with the belt and the ramp coupler while allowing the post to rotate (engine idling) but lock up with the post120in the other direction of rotation while engine braking where the at least one coupler ramp145of the ramp coupler140will rotate in relation to the at least one clutch ramp155of the OWC150. The rotation of the at least one ramp145in relation to the at least one ramp155causes second side140bof the ramp coupler140to axially move away from the first side150aof the OWC150to form a gap195. Since the second side150bof the OWC150is positioned against the thrust washer152and the thrust washer152abuts surface154cof the non-axially moving spider154, the ramp coupler140is forced to move axially towards the second sheave portion110. In particular, the first side140aof the ramp coupler140pushes on bushing128(which is a flanged plain bearing in this embodiment) countering the biasing force of the biasing member156to move the second sheave portion110towards the first sheave portion108a select distance. Free play in the rotational coupling between the sleeve coupler dogs139of the sleeve coupler138and the ramp coupler dogs143of the ramp coupler140allows movement of the ramp coupler140axially towards the second sheave portion110. The movement of the second sheave portion110towards the first sheave portion108causes the drive belt106to be frictionally engaged on three sides. That is, the inner face106aof the drive belt106is engaged with the engaging surface138cof the sleeve coupler138, the first side face106bof the drive belt106is engaged with the first conical-faced surface107of the first sheave portion108and the second side face106cof the drive belt106is engaged with the second conical-faced surface111of the second sheave portion110. This action reconnects the engine to the drive train via the drive belt106and the primary and secondary clutches102and104to allow for engine braking. The engagement of each of the three of the drive belt face surfaces106a,106band106care needed to create enough friction to overcome the rotation forces provided by the drive train in applications were the vehicle is relatively heavy.

The engagement of the drive belt106as described above in the engine braking operation mode will continue as long as the secondary clutch104is providing a force on the drive belt106as the result of the drive train trying to move the secondary clutch104faster than the primary clutch102. When the force provided by the secondary clutch104subsides, rotation of the post120of the first sheave portion108of the primary clutch102will be faster than the rotation of the secondary clutch104. Hence, rotation of the sleeve coupler138and the ramp coupler140will be slower than the rotation of the OWC150. As a result, the at least one coupler ramp145of the ramp coupler140will rotate in relation to the at least one ramp155of the OWC150in the opposite direction as described above. This rotation causes the second side140bthe ramp coupler140to be positioned once again proximate the first side150ato the OWC150where the flat145eof the at least one coupler ramp145of the ramp coupler140couples the flat155eof the at least one ramp155of the OWC150thereby removing the force on the second sheave portion110by the ramp coupler140. Moreover, the biasing force provided by biasing member156further provides the biasing force to push the second side140bthe ramp coupler140to be against the first side150aof the OWC150when returning to the idle operational mode.

Another embodiment of a primary clutch200is illustrated inFIGS. 7A and 7B. In particular,FIG. 7Aillustrates a first unassembled front-side perspective view of the primary clutch200andFIG. 7Billustrates a second unassembled rear-side view of the primary clutch200. AsFIGS. 7A and 7Billustrate, the primary clutch200includes a first sheave portion208and a second sheave portion210. The first sheave portion208includes a first side208aand second side208b. The first side208aof the first sheave portion208includes a central opening222. The second side208bof the first sheave portion208includes a first conical-faced surface207designed to engage a first side face106bof a drive belt106. The first sheave portion208further includes a post220that centrally extends from the first conical-faced surface207. The post220includes a bore221centered about a rotational axis270of the primary clutch200as illustrated at least inFIG. 10A. The bore221is further aligned with the central opening222. Bore221is designed to receive a rotational output from an engine (not shown). For example, in one embodiment, bore221is designed to engage a crankshaft (not shown) of an engine that is passed through the central opening222. In other embodiments, other mechanisms provide the rotational output of the engine to the primary clutch200. The first sheave portion208and the post220rotate in response to the rotational output of the engine.

The second sheave portion210of the primary clutch200includes a first side210aand a second side210bas illustrated inFIGS. 7A and 7B. The first side210aof the second sheave portion210includes a second conical-faced surface211. The second conical-faced surface211is designed to engage a second side face106cof a drive belt106. The second sheave portion210further includes a central sheave passage224. A sleeve coupler306is received around a first portion220aof the post220of the first sheave portion208. In this embodiment, the sleeve coupler306includes a first internal set of needle bearings307aand a second set of needle bearings307bthat engage a surface of the first portion220aof the post220. An illustration of the sleeve coupler306received on the first portion220aof the post220is illustrated inFIGS. 10A through 10C. Sleeve coupler306included a flange306bthat protrudes from an outer surface306aof the sleeve coupler306. A first thrust washer302and a first seal304are position between an end of the sleeve coupler306and the second side208bof the first sheave208as illustrated inFIG. 10A through 10C. As further illustrated inFIGS. 10A through 10C, a bushing311in the central opening224of the second sheave portion210contacts a portion of the outer surface306aof the sleeve coupler306. Moreover, an edge of the bushing311abuts one side of the flange306bof the sleeve coupler306.

The second sheave portion210further has a plurality of arm extending portions226(bosses) that extend out generally perpendicular proximate an outer perimeter217of the second side210bof the second sheave portion210. This is illustrated in the rear perspective view of the second sheave portion210ofFIG. 8. Further illustrated inFIG. 8, is a braking ramp rim500that extends around an opening to the central passage224of the second sheave portion210. The braking ramp rim500has a height from the second side210bof the second sheave portion210that varies. In particular, in this embodiment, the braking ramp rim500varies from three low height positions500bto three high height positions500a. In one embodiment, the different between a low height position500band a high height position500ais in a range of 0.020 of an inch to 0.500 of an inch. However, the difference can be more or less depending on the application (i.e. the size of the vehicle, the brake torque needed, etc). Torque buttons412a,412band412c(moving members) in a one way clutch314described below engage the braking ramp rim500to selectively move the second sheave portion210towards the first sheave portion208during an engaging braking situation in this embodiment as described below.

An example embodiment of a one way clutch (OWC)314is illustrated inFIGS. 9A through 9F. The OWC314includes a housing402with a first side402a, a second side402band a central passage402c. Similar to the embodiment described above, the housing402includes internal cavities408a,408band408cas illustrated inFIG. 9B. Pin rollers404a,404band404care received in the respective internal cavities408a,408band408c. Pin roller biasing members406a,406band406care also received in the internal cavities408a,408band408c. The biasing members406a,406band406cexert a biasing force on the respective pin rollers404a,404band404ctowards one end of the respective cavities408a,408band408c. Each of the cavities408a,408band408chas an opening into the central passage402cof the housing402. The central passage402cis received around the outer surface306aof the sleeve coupler306as illustrated inFIGS. 10A through 10C. The shape of the internal cavities408a,408band408cand the biasing members406a,406band406callow the OWC314to rotate independent of the rotation of the sleeve coupler306in one direction and lockup the OWC314with the sleeve coupler306in the other direction (i.e. where the respective pin rollers404a,404band404cengage the outer surface306aof the sleeve coupler306).

Referring back toFIG. 9B, the cross section view illustrates additional cavities410formed in the housing402of the OWC314in this embodiment. The additional cavities410are used to change the direction of the OWC314. Hence, if a OWC314is needed that locks in an opposite direction, the pin rollers404a,404band404cand the pin roller biasing members406a,406band406care repositioned in respective cavities410. In one embodiment, each pin roller biasing member406a,406band406cincludes a spring block retainer440a,440band440cand a plunger442a,442b,442cas seen inFIGS. 9D and 9E. The spring block retainers440a,440band440care designed to receive a first end of respective biasing members406a,406band406c(which are springs in this embodiment). The plungers442a,442band442care designed to receive a second end of the respective biasing members406a,406band406c. The spring block retainers440a,440band440chelp retain the first end of the biasing members406a,406band406cwithin the respective cavities408a,408band408c. The plungers442a,442band442con the second end of the biasing members406a,406band406cengage the respective pin rollers404a,404band404c.

The first side402aof the housing402of the OWC314in this embodiment includes bores411a,411band411c. The bores411a,411band411care illustrated inFIGS. 9B and 9D. Torque buttons412a,412band412care received in the respective bores411a,411band411c. The torque buttons412a,412band412ceach have an end that extends out beyond the first side402aof the housing402of the OWC314as illustrated inFIG. 9C. The end of the torque buttons412a,412band412care aligned with the braking ramp rim500of the second sheave portion210. When the OWC314is rotating independent of the sleeve coupler306, torque buttons412a,412band412care positioned proximate the low height positions500bof the braking ramp rim500. When the OWC314locks onto the sleeve coupler306, the rotation of the OWC314and the sleeve coupler306, causes the torque buttons412a,412band412cto rotate from the low height positions500btowards the high height positions500aalong the ramp profile of the braking ramp rim500. This action forces the second sheave210toward the first sheave208in an engine braking situation as further discussed below. Referring toFIG. 9D, a seal422and a bearing424are positioned proximate the first side402aand central passage402cof the housing402of the OWC314. Although in this embodiment the torque buttons412a,412band412care coupled to the OWC314and the braking ramp rim500is on the second sheave portion210, an opposite arrangement could be used having the same desired effect. Moreover, any engine braking assembly that effectively moves the second sheave portion210towards the first sheave portion208as the result of the sleeve coupler306attempting to overrun the post220is contemplated. Further, although the OWC314is described as roller pin OWC, any type of OWC can be used such as, but not limited to, roller clutches, sprag clutches, etc.

The second side402bof the housing402of the OWC314includes three slots414a,414band414c. Three return biasing members320a,320b,320care received in the respective three slots414a,414band414cas illustrated inFIG. 9F. One end of each return biasing members320a,320b,320cis coupled to a respective biasing pin connector430a,430band430c. Spider pins254aand254b(and a third pin not shown inFIG. 7A) on spider254passing though apertures317in thrust washer316(shown inFIG. 7A) are designed to be received in respective connectors430a,430band430cof the return biasing members320a,320band320c. This arrangement of the return biasing members320a,320b, and320callows the OWC314to return to a non-torque position (i.e. the torque buttons being position proximate the low height position500bof the braking ramp rim500) after an engine braking situation has passed. Further illustrated inFIG. 10Ais bearing426positioned proximate the second side402bof the housing402of the OWC314and seal318that is positioned about the second side402bof the housing402of the OWC.

Referring back toFIGS. 7A and 7B, the primary clutch200includes a cover214with a central opening214a. The central cover opening214areceives an end of the post220of the first sheave portion208. The cover214has a plurality of apertures that align with threaded bores (not shown) in the arm extending portions226(bosses) of the second sheave portion210. Fasteners258, such as bolts, are passed through the plurality of the apertures in the cover214and are threadably engaged with the threaded bores in the arm extending portions226of the second sheave portion210. The primary clutch200also includes the spider254. The spider254includes a first side254a, a second side254band a central spider passage254c. The central spider passage254cis received around and coupled to a portion of the post220of the first sheave portion208. In particular, the spider254is solidly coupled about connection260as illustrated inFIG. 10A. In one embodiment, the connection260is mated threads. This connection260keeps the spider254static in relation to the post220thereby preventing the spider254from moving axially along the axis of rotation270. The spider254is positioned between the cover214and the second sheave portion210as illustrated. The spider254further includes radially extending arms265. Each radially extending arm265holds an engaging pin/roller subassembly257. A washer318is positioned between an end of the sleeve coupler306and the first side254aof the spider254. A biasing member256is positioned between the second side254bof the spider254and the cover214. The biasing member256, which in this embodiment is a spring, provides a biasing force separating the spider254from the cover214. Moreover, since the second sheave portion210is coupled to the cover214via fasteners258, the biasing force of the biasing member256forces the second sheave portion210away from the first sheave portion208and towards the spider254.

A plurality of flyweight members230are rotationally coupled the second side210bof the second sheave portion210. In particular, in this embodiment each flywheel230has a flyweight passage231that is rotationally mounted on a pivot rod232. Each pivot rod232is coupled to the second sheave portion210via connector234. The plurality of the flyweights230are designed to pivot on the pivot rod232such that an engaging surface230aof the flyweights230moves towards the first side254aof the spider254in response to select angular rotational speeds of the second sheave portion210. In particular, a centrifugal force created by the rotation of the second sheave portion210causes the flyweights230to pivot about pivot rods232causing the engaging surfaces230aof the flyweights230to push on the engaging pin/roller subassemblies257of spider254. The faster the rotation of the second sheave portion210, the more push force the flyweights230exert on the spider254. This push force counters the biasing force created by biasing member256thereby moving the second sheave portion210closer to the first sheave portion208and away from the spider254. During acceleration of the rotation of the CVT100, the movement of second sheave portion210toward the first sheave portion208causes the drive belt106to move farther away from the rotation axis270of the primary clutch200thereby changing into higher gearing of the CVT100. During de-acceleration of the rotation of the CVT100(where the biasing force becomes greater than the push force), the movement of second sheave portion210away from the first sheave portion208causes the drive belt106to move closer to the rotation axis270of the primary clutch200thereby changing into lower gearing of the CVT100. This is further discussed below. Although, a sheave moving member based on the rotational speed of the sheave implementing flyweights is described above, other types of the sheave moving members know in the art are contemplated and the present invention is not limited to flyweight systems.

Referring toFIG. 10Aa cross-sectional view of the primary clutch200in an activation operational mode is illustrated. AsFIG. 10illustrates, during an activation operational mode, the flyweights230are pivoted towards the first surface254aof the spider254due to the centrifugal forces caused by the rotation of the primary clutch200. As a result of the pivoting of the flyweights, a push force is generated by the engaging surface230aof the flyweights230on the engaging pin/roller subassemblies257of the spider254. This push force counters the biasing force of the biasing member256on the spider254thereby moving the second sheave portion210closer to the first sheave portion208of the primary clutch200. The faster the rotation of the primary clutch200, the stronger the centrifugal force (and hence the push force) and the closer the second sheave portion210is moved towards the first sheave portion208. As the second sheave portion210moves towards the first sheave portion208the first conical-faced surface207of the first sheave portion208and the second conical-faced surface211of the second sheave portion210engage respective side faces106band106cof the drive belt106. As the second sheave portion210moves closer to the first sheave portion208, the drive belt106is forced farther away from the rotational axis270. As with the embodiment discussed above, the primary clutch200is designed to only allow the second sheave portion210to move a select distance towards the first sheave portion208so the drive belt106remains contained between the first and second conical-faced surfaces207and211.

InFIG. 10B, the primary clutch200is illustrated during an idle operation mode. During idle situations, only the inner face106aof the drive belt engages the surface306aof the sleeve coupler306. The second conical-faced surface211of the second sheave portion210is spaced a distance away from the first conical-faced surface207of the first sheave portion208so there is a gap501between a second side face106cof the drive belt106and the second conical-faced surface211of the second sheave portion210. A gap may also be (or may be in place of gap501) between the first side face106bof the drive belt106and the first conical-faced surface207(not shown). The gap501between the first conical-faced surface207of the first sheave portion208and the second conical-face surface211of the second sheave portion210is maintained by biasing member256during the idle operational mode. During an idle operation mode, friction between the inner face106aof the drive belt106and the outer surface306aof the sleeve coupler306prevents sleeve coupler306from turning while post220rotates with the rest of the primary clutch200that is engaged to receive the rotational output of the engine. Hence, in the idle operational mode, the engine is disconnected from the drive train because the drive belt106is coupled only to the sleeve coupler306and the OWC314(which is overrunning) provides no moving force to the secondary clutch104. Further in the idle operation mode, the torque buttons412a,412band412cof the OWC314are in a non-torque position (i.e. the torque buttons being position proximate the low height position500bof the braking ramp rim500of the second sheave portion210.

FIG. 10Cillustrates the primary clutch200in the engine braking operational mode. In the engine braking operational mode the flyweights230are not subject to significant centrifugal forces that cause the engaging surface230aof the flyweight230to pivot towards the first side254aof the spider254. This is because the rotation speed of the primary clutch200is relatively low (and hence so is the rotational output of the engine as the result of letting up on the throttle) in an engine braking situation. Therefore, the flyweights230cannot be used to force the second sheave portion210towards the first sheave portion208in this situation. In the engine braking situation, the secondary clutch104is pushing the belt106to a maximum radius on the secondary clutch104and thus to a minimum radius on the primary clutch200. Hence, the drive belt106that is rotationally coupled to the secondary clutch104will move the sleeve coupler306(which the inner face106aof the belt drive is engaged with) faster than the post220of the first sheave portion208. Therefore, the sleeve coupler306will rotate in relation to the post220of the first sheave portion208to try an overrun the post220.

As stated above, the OWC314is designed to rotate independently of the sleeve coupler306while the sleeve coupler rotates in one direction in relation to the OWC314(engine idling) but lock up with the sleeve coupler306when the sleeve coupler306rotates in the other direction of rotation in relation to the OWC (engine braking). When the OWC314locks up on the sleeve coupler306, the rotation of the OWC314and the sleeve coupler306, causes the torque buttons412a,412band412cto rotate to engage the ramp rim500moving towards the high height positions500afrom the low positions500b. This action forces the second sheave210toward the first sheave208thereby countering the bias force supplied by bias member256. This action reconnects the engine to the drive train via the drive belt106and the first and second clutches200and104to allow for engine braking. The engagement of each of the three of the drive belt face surfaces106a,106band106care needed to create enough friction to overcome the rotation forces provided by the drive train in applications were the vehicle is relatively heavy.

The engagement of the drive belt106as described above in the engine braking operation mode will continue as long as the secondary clutch104is providing a force on the drive belt106as the result of the drive train trying to move the second clutch104faster than the first clutch200(primary clutch). When the force provided by the secondary clutch104subsides, rotation of the post220of the first sheave portion208of the first clutch200will be faster than the rotation of the secondary clutch104. The return biasing members320a,320b, and320callows the OWC314to return to a non-torque position (i.e. the torque buttons being position proximate the low height position500bof the braking ramp rim500) after an engine braking situation has passed.

Embodiments of the CTV100system can be used with any type of vehicle including, but not limited to, all-terrain vehicles (ATVs), utility vehicles, golf carts, cars, trucks, boats etc. Moreover, the drive belt106used with the CVT system may be made from any type of material that provides adequate rotational communication between the primary sheave102,200and the secondary sheave104for a given application. Examples of drive belt materials include, but are not limited to, rubber, polyurethane, urethane, neoprene, fiber reinforced materials as well has as drive belts made from metals.