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The “Two-Drive-Transmission with Range-Extender” (called DE-REX) is an innovative hybrid powertrain concept using two electric motors and an internal combustion engine. The two electric motors are permanent magnet synchronous motors with a maximum power of 48 kW each. As combustion engine a 3 cylinder, turbocharged engine with a power of 65 kW is used. The aggregates are coupled to a transmission whose layout is characterized by consisting of two parallel 2-speed sub-transmissions. This layout offers a high flexibility and enables both parallel and series hybrid driving. The hybrid control unit (HCU) has to select the optimal driving mode and power distribution between the aggregates in regard to in some extend competing objectives like efficiency, emissions or driving comfort. In particular, the operation of the internal combustion engine with only two gear ratios is challenging.

Modern vehicles need to fulfil challenging requirements with respect to emissions, noise and fuel consumption. Up to the EU5 legislation a sound steady state application was sufficient for passenger car Diesel engines to meet these requirements, and fuel consumption was less in the focus than the emissions of nitrous oxides and soot, hydrocarbons and carbon monoxide. Future legislation will require not only tighter limits in emissions but additionally will set fuel consumption targets. More demanding drive cycles will make it even more difficult to achieve these targets. Additional to measures on the combustion engine, moderate electrification for energy recuperation as well as the supply of electrical generated torque to the drive train will increasingly find its way into modern passenger cars. The presence of an electric machine can be used not only to reduce the fuel consumption but also the emissions of the combustion engine.