Abstract
Vehicles that are operated fuel-e.ciently su.er from shift shocks (automatic transmissions) or reluctant/inverse acceleration response (continuously variable transmissions), when a fast increase in wheel power is asked for, e.g., in a kick-down. This phenomenon is somewhat alleviated by applying smoothened shift strategies, or by forcing the driver to deliberately choose between a sport and economy driving-mode. Both methods either compromise performance or fuel-economy. A new type of drive train, referred to as Zero Inertia (ZI) Powertrain, augments a CVT powertrain, with a planetary gear set and a compact steel .ywheel, enabling the combination of fuel-economy and driveability without compromise. A prototype transmission has been experimented on, both at a test rig and in a test vehicle.
This paper evaluates the new powertrain, its components and the way they are operated, with respect to e.ciency. Measurements of component e.ciencies are analyzed for stationary situations, and suggestions for improvements are given. The power loss of the additional .ywheel is shown to be marginal. Furthermore, fuel-optimal operation of the (combination of) internal combustion engine, the torque converter and the CVT is discussed. Between 15 and 25% fuel is saved with respect to a 4 speed automatic transmission.