Study of Energetic Characteristics in Power Split Drives for on Highway Trucks and Wheel Loaders

Continuously variable transmissions (CVT) have been gaining popularity because they decouple the engine of a vehicle from the vehicle wheels, providing seamless shifting in vehicle operation and allowing the engine to operate in a speed range where fuel consumption and emissions are minimized. In particular, the power-split CVT, or power split drive (PSD), combines the variability of a CVT with the high efficiency of a mechanical transmission, providing potential benefits for both on road and off road vehicles. Hybrid PSDs allow further fuel savings by transferring the vehicle's kinetic energy to an energy storage device such as a battery, flywheel, hydraulic accumulator or other means during braking and utilizing the stored energy during the next propulsion cycle. While many power split configurations exist in literature (Miller 2005), this paper focuses on a dual stage input coupled PSD with a flywheel energy storage device. The objective of this research work is to describe the mechanism of energy recovery for the dual stage PSD with flywheel energy storage and demonstrate the transmission's energy recovery capabilities. To accomplish the latter task simulations for two specific applications, a wheel loader and a highway truck, demonstrate the energy saving potential of the hybrid dual stage PSD when compared to the standard dual stage PSD.