Development of an Efficient Powertrain with an Automated Multi-Speed-Transmisson and Two-Drive-Transmission for uninterrupted Traction Force
Cooperation: Institut für Elektrische Energiewandlung (TU Darmstadt)
The aim was to optimize a novel, highly efficient electric powertrain for a application as a traction drive in vehicles. The electric machines were designed as high speed drives with the highest possible torque and power density. The transmission should be designed to be as compact and efficient as possible with at least two stages and two gears per coupled electric machine.
Automated manual transmissions in a layshaft design are the simplest way for realizing multiple gears. With the Two-Drive-Transmission shown in the picture (an automated manual transmission (AMT) driven via two input paths) it is possible to avoid uncomfortable interruptions in tractive force during gear changes.
The use of two smaller electric motors also leads to an increase in efficiency compared to an electric vehicles with only one powerful electric motor. In partial load operation, only one of the two electric motors provides propulsion, resulting in higher specific load and thus better efficiency of the electric machine.
By coupling a combustion engine, a series-parallel hybrid architecture is created, which allows the operating modes “pure electric driving”, “series hybrid mode”, “parallel hybrid mode” and “pure combustion engine driving”.
First simulation results showed a considerable increase in efficiency and thus CO2 savings. In the New European Driving Cycle (NEDC), energy consumption is 17% lower than for an electric vehicle with only one electric motor and a 1-speed transmission.