Drive clutch for a continuously variable transmission with engine braking and built in belt protection

A drive clutch for a continuously variable transmission comprising:

• an input shaft adapted to engage with an engine drive component, the input shaft having a rotational axis;
• a first sheave disposed about a portion of the input shaft and having a rotational axis coincident with the rotational axis of the input shaft, the first sheave being rotatable relative to the input shaft, the first sheave having a belt-engaging surface formed on a portion of one face;
• a support housing engaged to and extending outward from the face on the first sheave and having a central axis coincident with the rotational axis of the input shaft, the first sheave adapted to rotate in combination with the support housing;
• a first centrifugal clutch assembly disposed about the input shaft, the centrifugal clutch assembly adapted to provide controlled engagement between the first sheave and the input shaft, the centrifugal clutch assembly including a clutch hub mounted to the input shaft, an engagement surface formed on or attached to the first sheave, a plurality of shoes disposed in the hub and spaced about a portion of the input shaft, the shoes mounted so as to be movable radially outward from the input shaft upon rotation of the input shaft above a threshold RPM, the radial translation of the shoes being restrained by springs, the shoes being disposed within the hub such that rotation of the input shaft produces concurrent rotation of the shoes, the shoes having a frictional surface on one end for engaging with the engagement surface on the first sheave when the shoes are radially displaced from the input shaft;
• a bearing assembly located between the input shaft and the first sheave or support housing, the bearing assembly configured to permit the first sheave and support housing to remain substantially rotationally disengaged from the input shaft;
• a second sheave disposed about the support housing and mounted so as to be axially movable relative to the support housing, the second sheave having a belt-engaging surface formed on a portion of one face and that faces the belt-engaging surface of the first sheave, the belt-engaging surfaces defining a groove for receiving a belt that is adapted to engage a driven clutch;
• a second centrifugal clutch assembly with an engagement surface formed on or attached to the second sheave, a centrifugal clutch hub, a plurality of shoes located on the hub and mounted so as to be movable radially outward upon rotation of the input shaft above a threshold RPM, the radial movement of the shoes being restrained by springs, the shoes being disposed within the centrifugal clutch hub such that rotation of the input shaft produces concurrent rotation of the shoes, the shoes having a frictional surface on one end for engaging with the engagement surface on the second sheave when the shoes are radially displaced;
• and
• a tower assembly including:
• a base disposed about the input shaft,
• a plurality of flyweights pivotally attached to the base,
• a spider disposed adjacent to the flyweights, the spider including surfaces against which the flyweights bear as the flyweights pivot, the spider being displaceable relative to the base, the spider being attached to the input shaft, and
• a spring mounted between the spider and a tower cover, the spring arranged to urge the second sheave away from the first sheave,
• wherein the second sheave is mounted so as to be separately rotatable from the tower assembly until the input shaft rotates above a threshold speed.

A drive clutch for a continuously variable transmission comprising:

• an input shaft adapted to engage with an engine, the input shaft having a rotational axis;
• a sheave assembly including first and second sheaves mounted on a support housing so as to rotate in combination with the support housing, one of the sheaves being axially movable relative to the other, the sheave assembly being disposed about the input shaft and being rotationally disconnected from the input shaft;
• a bearing assembly located between the input shaft and the sheave assembly for providing some support for the sheave assembly on the input shaft while permitting rotation of input shaft relative to the sheave assembly,
• a first centrifugal clutch assembly disposed about the input shaft, the first centrifugal clutch assembly adapted to provide controlled engagement between the first sheave and the input shaft, the first centrifugal clutch assembly including a clutch hub mounted to the input shaft, a torque transfer surface formed on or attached to the sheave assembly, and means for frictionally engaging the clutch hub to the torque transfer surface upon the input shaft rotating at a speed relative to the sheave assembly that is above a threshold value, the means for engaging the clutch hub to the torque transfer surface include a plurality of shoes and springs disposed on the clutch hub, the shoes being radially displaceable in response to rotational motion of the clutch hub, the springs biasing the shoes radially toward the input shaft, and wherein the torque transfer surface is a drum surface mounted or formed within a recess in a rear face of the first sheave;
• and
• an axial control mechanism mounted on the input shaft adjacent to the second sheave, the axial control mechanism controlling the movement of the second sheave toward and away from the first sheave as a function of the speed of the input shaft, wherein the second sheave is mounted so as to be separately rotatable from the axial control mechanism until the input shaft rotates above a threshold speed.