Driven pulley for a continuously variable transmission
The driven pulley is part of a continuously-variable transmission (CVT). The driven pulley comprises two coaxially-disposed sheaves defining between them a belt-receiving groove. It also has at least two axisymmetric ramp surfaces attached to one of the sheaves and at least two axisymmetric followers attached to the other sheave, each ramp surface being engageable by a corresponding one of the followers. At least some of the ramp surfaces are provided on corresponding ramp holders that are independent from the sheaves. A method of modifying the settings of a driven pulley and a method of assembling a driven pulley also disclosed.
1. A driven pulley for a continuously-variable transmission, the driven pulley having a rotation axis and comprising:
two coaxially-disposed sheaves, each sheave having an interior surface and an exterior surface opposite the interior surface, the interior surfaces defining between them a belt-receiving groove;
at least two axisymmetric ramp surfaces attached to one of the sheaves and facing away from the two sheaves; and
at least two axisymmetric followers attached to the other sheave and positionable outside the exterior surface of said one of the sheaves, each ramp surface being engageable by a corresponding one of the followers; wherein
at least two of the ramp surfaces are each provided on a top side of a corresponding separate ramp holder that is individually and removeably connected to said one of the sheaves, each of the separate ramp holders having a bottom side, opposite the top side, located in and in engagement with a corresponding ramp holder slot provided on the exterior surface of said one of the sheaves.
2. The driven pulley as defined in claim 1 , wherein the ramp holders, once connected to said one of the sheaves, are immovable relative to said one of the sheaves.
3. The driven pulley as defined in claim 1 , wherein each ramp holder slot is provided on a back side of a wall of said one of the sheaves, the wall having a front side, opposite the back side, defining one edge of the belt-receiving groove of the driven pulley.
4. The driven pulley as defined in claim 1 , wherein each ramp holder is removeably connected to said one of the sheaves using a single fastener, each fastener comprising a threaded portion and said one of the sheaves comprising a corresponding threaded portion located in the corresponding ramp holder slot to receive the threaded portion of the fastener.
5. The driven pulley as defined in claim 4 , wherein each threaded portion of said one of the sheaves longitudinally extends in a direction that is substantially parallel to the rotation axis of the driven pulley.
6. The driven pulley as defined in claim 5 , wherein the fasteners are inserted through corresponding holes made across the ramp holders where a ramp surface height between the top and bottom sides of each ramp holder is substantially maximum.
7. The driven pulley as defined in claim 6 , wherein each fastener has an enlarged tool-engaging head, the heads of the fasteners being hidden inside corresponding chamfered hole sections once the ramp holders are connected to said one of said sheaves.
8. The driven pulley as defined in claim 1 , wherein the ramp holders are individually removable from the driven pulley even when the two sheaves of the driven pulley are connected together.
9. The driven pulley as defined in claim 1 , wherein the ramp surfaces are at least four in number and are all provided on a corresponding one of the ramp holders, the ramp surfaces comprising first ramp surfaces and second ramp surfaces in equal number, each first ramp surface being engageable by one of the followers while the followers are out of engagement with the second ramp surfaces, each second ramp surfaces being engageable by one of the followers when the followers are out of engagement with the first ramp surfaces.
10. The driven pulley as defined in claim 9 , wherein each first ramp surface and a corresponding one of the second ramp surfaces are alternatively engageable by the same corresponding follower.
11. The driven pulley as defined in claim 9 , wherein each first ramp surface and each second ramp surface are engageable by a different one of the followers, each follower being engageable with only one of the ramp surfaces.
12. The driven pulley as defined in claim 9 , wherein each second ramp surface comprises:
a first section substantially axially extending with reference to the rotation axis of the driven pulley;
a second section extending in a direction that is generally parallel to a corresponding adjacent one of the first ramp surfaces; and
a third section extending in a direction that is generally perpendicular to the second section, the third section being engageable by a corresponding one of the followers to prevent the continuously-variable transmission from upshifting when operated in a reverse mode.
13. The driven pulley as defined in claim 12 , wherein the second section of each second ramp surface has one end merging with a corresponding end of the first section, the second section having a second end, opposite the first end, merging with a corresponding end of the third section, the three sections being substantially continuous.
14. The driven pulley as defined in claim 1 , wherein the ramp holder slots receive the bottom side of the ramp holders regardless of a direction of rotation of the driven pulley corresponding to a forward mode of the continuously-variable transmission.
15. A method of modifying settings of a driven pulley of a continuously-variable transmission, the method comprising:
removing a plurality of individual ramp holders that are each separately and individually connected to an exterior surface of a sheave of the driven pulley, each individual ramp holder having a bottom side engaging the exterior surface of the sheave and having a top side opposite the bottom side, the bottom side of each individual ramp holder being located inside a corresponding ramp holder slot provided on the exterior surface of the sheave, the top side of each individual ramp holder facing away from the exterior surface of the sheave and including a corresponding ramp surface configured to engage a corresponding follower; and then
inserting a plurality of new individual ramp holders into the corresponding ramp holder slots on the exterior surface of the sheave of the driven pulley and connecting them to the sheave, the new individual ramp holders having ramp surfaces that are different in shape compared to the ramp surfaces they replace.
16. The method as defined in claim 15 , wherein the step of removing includes removing a single fastener to remove each ramp holder from the corresponding ramp holder slot.
17. The method as defined in claim 15 , wherein the step of removing and the step of inserting are carried out while the sheave of the driven pulley is connected to another sheave of the driven pulley.
18. The method as defined in claim 15 , wherein the step of removing and the step of inserting are carried out while the sheave of the driven pulley is connected to another sheave of the driven pulley and the driven pulley is mounted in a vehicle.