Patent ID: 8500580

Claim:
A torque sensing device for a belt-driven conical-pulley transmission, said torque sensing device comprising: a first ramp surface rigidly connected to a shaft that carries a pair of conical disks; a second ramp surface rigidly connected to a sensing piston that surrounds the shaft and that is axially movable along and rotatable relative to the shaft, wherein the ramp surfaces face each other and are configured so that upon a change in torque between the sensing piston and the input shaft the axial position of the sensing piston changes through the rolling of balls positioned between and contacting the ramp surfaces; a radially inwardly facing guide surface fixedly positioned relative to an axially movable conical disk, wherein the balls contact the guide surface; wherein the axially movable disk is non-rotatably and axially movably connected to the shaft for axial movement relative to an axially fixed disk that is rigidly connected to the shaft, and wherein axial movement of the axially movable conical disk is effected by a hydraulic pressure that is a function of the axial position of the sensing piston and that acts against a face of the axially movable conical disk; and wherein the guide surface is configured in such a way that a radial distance between the balls and the axis of the shaft is a function of the axial distance between the axially movable disk and the axially fixed disk, wherein in the circumferential direction of the torque sensing device the guide surface includes a plateau region on each side of which is a convexly-curved region, and the contact points of a particular ball with the ramp surfaces, the contact point of that ball with the guide surface, and the center point of that ball each lie in a radially oriented plane, wherein the radially-oriented plane is relative to the shaft longitudinal axis.