Patent ID: 9599218
Date: 2017-03-21
CPC Classifications: F16H

Claim:
1. A toroidal variable speed traction drive comprising: a driving toroidal disc assembly and a driven toroidal disc assembly, said driving toroidal disc assembly and said driven toroidal disc assembly having a common axis of rotation; a plurality of roller assemblies interposed between said driving toroidal disc and said driven toroidal disc, each roller assembly comprising at least one roller; wherein said toroidal discs are urged together against the interposed roller assemblies by an axially directed clamping force, wherein each roller of each roller assembly contacts the driving toroidal disc and the driven toroidal disc at respective contact points so as to define gear ratios between the driving toroidal disc assembly and said driven toroidal disc assembly, said gear ratios comprising higher gear ratios and lower gear ratios; the driving toroidal disc assembly being driven by an input drive shaft which provides an input torque; the driven toroidal disc driving an output structure that rotates around the common axis of rotation, said output structure driving an output shaft; wherein an interposed ball ramp clamping arrangement is provided between said driven toroidal disc and said output structure, said interposed ball ramp clamping arrangement providing the axially directed clamping force, the axially directed clamping force being proportional to an output torque experienced by said output shaft such that when the toroidal variable speed traction drive is at one of the higher gear ratios the clamping force is sufficient to prevent slippage between the driving toroidal disc assembly and the driven toroidal disc assembly, and when the toroidal variable speed traction drive is at one of the lower gear ratios the clamping force is substantially greater than necessary to prevent slippage between the driving toroidal disc assembly and the driven toroidal disc assembly for a then prevailing input torque.