Abstract

A continuously variable friction drive is used to phase a cam plate attached to the camshaft relative to a sprocket plate driven by the crankshaft. Discs are received within the cavity between the sprocket and cam plate. The discs are free to rotate about an axis of rotation, and is fixed relative to the cam and the sprocket, so that when the sprocket plate rotates, the cam plate is rotated by the discs in the opposite direction. The axis of rotation of the discs can be tilted by an actuator, so that the discs themselves contact the plates at different distances from their axes of rotation, which changes the speed of rotation of one plate relative to the other. When the speed of rotation of the crank and cam differ, the phase angle between the two shafts is changed.