Speed change control device for continuously variable transmission

摘要

A speed change control device for a continuously variable transmission has a carrier adapted to rotate about a predetermined axis, a twin cone adapted to rotate integrally with the carrier while being held by the carrier and rotatable about a central axis which is inclined with respect to the predetermined axis, and a pair of track rings disposed around the outer periphery of the carrier and movable along the predetermined axis. A part of the inner peripheral surface of each track ring is in frictional engagement with the outer peripheral surface of the twin cone. A screw shaft having left-hand threads of a large lead angle on one half and right-hand threads of a large lead angle on the other half is provided rotatably about the axis thereof in parallel with the predetermined axis, a nut on one track ring being engaged with the left-hand thread portion and a nut on the other track ring engaged with the right-hand thread portion so that with rotation of the screw shaft both track rings are moved in opposite directions. The lead angle of the threads of the screw shaft is set large so that the screw shaft is rotated also by axial forces acting on the track rings, the fore end portion of a rod of a hydraulic cylinder adapted to slide in parallel with the above predetermined axis is connected to one track ring so that a sliding motion of the rod causes a force to be applied to the one track ring, thereby allowing the screw shaft to rotate to move both track rings in opposite directions.