Sailing/Coasting Enabled by Mechatronic Starting Devices

Abstract

Engine start quality and seamless engine start/stop are key elements of drive quality and customer acceptance in today’s electrified propulsion architectures. Two novel mechatronic devices have been created for premium engine start/stop. One concept uses a motor/generator in place of the traditional alternator, coupled to a mechatronic switching device for selectable geared or belted operation of the motor/generator. The second starter concept uses a two-speed gear scheme inserted between the starter motor and crankshaft flywheel for smooth engine starts. In the present work, the use of these starter devices in vehicles with sailing/coasting mode as well as in mild hybrid propulsion systems is described. Sailing/coasting mode of operation is enabled by the quick engine re-start capability of these starters allowing seamless switching between fuelled and unfuelled engine operation. This could reduce fuel consumption by about 3–6% on the NEDC driving cycle, without regenerative braking. One may further hybridize the propulsion system by adding a battery for storing regenerative braking energy. Using such an architecture, a 6–8% fuel economy improvement on the WLTP certification driving cycle may be achieved, depending on voltage and power levels implemented, as well as energy storage systems included.