Design, simulation study and preliminary experimental results of the electromechanical clutch unit for the split-crankshaft engine

The Split-Crankshaft Engine (SCE) is an engine layout for passenger cars with a two-piece disengageable crankshaft. The secondary cranktrain can be disconnected through the electromechanically actuated Split-Clutch Unit (SCU). The efficiency gain due to increasing the load point is hereby enhanced by elimination of friction losses of the non-firing cylinders. In the present publication, the challenges encountered while developing such a crankshaft connecting clutch unit in terms of constructive practicability, control strategy for the angular synchronization of the crankshafts, as well as preliminary experimental results regarding the friction behavior of the SCU in engine oil are discussed. The principal feasibility of the SCU can be confirmed and design optimizations have been developed. A first control strategy for the SCU and its angular synchronization over 360°, which ensures the coupling of the partial engines during the full vehicle simulation of the common driving cycles like NEDC and WLTP, has been designed.