Advanced Powertrain Functions of 48 V Hybrid Vehicles: Efficient powertrains does not exclude driving pleasure

摘要

48 V mild hybrid systems are one of the key technologies to achieve compliance with future emission and CO_2 limits. They enable high energy recuperation capabilities and thus offer considerable CO_2 reduction potentials at reasonable additional system cost. Moreover, the 48 V technology provides great opportunities to improve additional powertrain functionalities and also the driving pleasure. A 48 V system supports improved stop-start functionalities and additional boosting by electrical supercharging or torque assist by belt-driven starter generators (BSG). FEV Europe GmbH has designed a full-featured 48 V mild hybrid demonstrator vehicle on the basis of a Mercedes Benz AMG A45 vehicle with 280 kW internal combustion engine power. The 48 V system consists of a 8 Ah high power battery with lithium iron phosphate (LFP) technology and a 3 kW bidirectional DC/DC converter. The 12.5 kW electric machine is integrated in the belt drive system of the combustion engine (PO architecture). In addition, a 6.5 kW electrical compressor is used to significantly improve the engine intake air boosting dynamics. The paper summarizes the key findings of the evaluation of the full featured 48 V mild hybrid vehicle in terms of powertrain functionality. The functions relating to fuel economy are regenerative braking, intelligent load point shifting and "sailing". The "sailing" operation can be realized with an idling or with a fully stopped engine. The performance and comfort related functions are optimized engine start and combined boosting with the belt-driven starter generator and the electric compressor. Especially, the drive mode selection, deciding between regenerative braking and engine off "sailing" can be supported by predictive driving functions. Thereto, environmental information from onboard or offboard sensors can be used.