Abstract
The advanced engineering concept of a 48V electric machine application that addresses the trade-off between superior four wheel drive driving dynamics and highest efficiency is presented. The aim of the contribution is to give functional insights on the progressive concept, to discuss the application and give some outlooks on the development. The system is developed for vehicles with a powertrain architectures that feature a longitudinal mounted engine and the rear axle as primary driven axle. The system is located in the area of a conventional transfercase. The main components of the system architecture are the planetary gear set, used as a powersplit gear, the 48V hollow-shaft electric machine and the mode shift device. This arrangement enables the system to operate in three modes: The four wheel drive mode offers full four wheel drive performance incorporating longitudinal torque vectoring. In the four wheel drive mode the torque transmitted from the main transmission output to the front axle is piloted by the torque of the 48V electric machine. The powersplit function of the planetary gear set enables the system to pilot high internal combustion engine power with limited power of the 48V electric machine. Additional advantages regarding traction, wear and driving dynamics are incorporated as well. The recuperation and e-drive mode connects the electric machine to the rear axle. In this mode the electric machine acts as drivetrain generator and recups energy. The P3 location of the electric machine is beneficial regarding efficiency and drag torque. An indication of the reduction of energy demand in the emission cycle WLTP is given in the paper. Further e-drive functionalities like electric driving in parking situations or traffic-jams as well as e-sailing and boosting are covered additionally. By providing full four wheel drive longitudinal torque vectoring functionality and reducing the vehicles CO2 emissions with the recuperation function the system is a serious option for future highest performant powertrain architectures.