Development of the Epicycloidal Roller Control System for the Torotrak Full-Toroidal Infinitely Variable Transmission 2009-01-1540
Application of high torque capacity Infinitely Variable Transmissions (IVT's) utilizing Torotrak variable ratio traction technology have delivered 20% fuel economy improvement in vehicles ranging from V8 SUV's to diesel city buses.
The fuel economy improvement results from a combination of optimised engine operation and significant reduction of launch parasitic losses by the replacement of the torque convertor with a “Geared Neutral” capability inherently provided by the IVT architecture.
The conventional Torotrak Variator comprises two toroidal cavities with three rollers per cavity. Each roller is attached to a reaction piston via a carriage assembly, resulting in the active division of the transmission load across the six available power paths. Hydraulic pressure is applied to each roller piston assembly, defining the torque reacted within the Variator.
Attaching each roller to a single control would not only reduce the parts count and cost of the transmission but would allow a drum output from the centre of the Variator so eliminating an epicyclic gear set and further simplifying the transmission design whilst improving its overall efficiency.
A novel Epicycloidal Roller Control (ERC) system has therefore been developed, connecting all six rollers to a single actuator by exploiting the inherent accuracy available from conventional involute gearing.
The result is a significant parts count and hence cost reduction together with improvements in system efficiency, performance and package.
This paper describes the ERC system in detail together with the testing and validation of the system.