Flat belt continuously variable transmission with geared speed ratio

Abstract

A flat belt CVT is disclosed in which a geared control system is employed to establish and maintain the effective diameter of each pulley assembly by determining the mutual angular relationship between sets of inner and outer guideway disks provided with spirals oriented in the opposite sense and supporting belt engaging elements at their intersections. The sets of guideway disks are coupled through a planetary gear system which includes a component which can be externally manipulated to adjust the angular relationship between the sets of inner and outer guideway disks while rotating. The planetary gear system includes a first sun gear which meshes with star gears whose shafts are fixed in position with respect to the first sun gear. A second sun gear meshes with planet gears which may orbit around the second sun gear while rotating on a planet carrier. The star and planet gears each mesh with the same internal ring gear, and an external ring gear on the planet carrier meshes with a pinion which is coupled to an external positioning structure such as a hand crank for the driving pulley assembly and a load device for the driven pulley assembly. In one embodiment especially suitable for certain applications, a harmonic drive is interposed between one of the sun gears and the set of guideway disks to which it is coupled to increase precision and reduce torque and power requirements.