Design Studies of Continuously Variable Transmissions for Electric Vehicles

Preliminary design studies were performed on four continuously variable transmission (CVT) concepts for use in advanced electric vehicles. A 1700 kg (3750 lb) vehicle with an energy storage flywheel was specified. Requirements of the CVTs were a maximum torque of 450 N-m (330 lb-ft), a maximum output power of 75 kW (100 hp), and a flywheel speed range of 28 000 to 14 000 rpm. The design of each concept was carried through the design layout stage. Power losses were determined over the ranges of operating conditions, and transmission efficiencies were calculated. The design studies were performed under contracts to NASA for DOE by Garrett/AiResearch (toroidal traction CVT), Battelle Columbus Labs (steel V-belt CVT), Kumm Industries (flat belt variable diameter pulley CVT), and Bales-McCoin Tractionmatic (cone-roller traction CVT).