Hybridization Requires New Clutch Systems

Abstract

Double clutch transmissions hold a significant share in worldwide passenger cars, thanks to its combination of dynamic, efficiency and comfort. Current systems with dry as well as wet clutches show good compatibility for electrification through the integration of P2 hybrid modules. However, this requires a disconnect clutch C0 in addition to the existing double clutch. New highly integrated clutch systems are required to minimize the axial installation space, with strong focus on overall efficiency. Electric vehicle launches with P2 hybrid systems lead to a significant reduction in clutch energy allowing innovative designs of compact triple clutch systems. Schaeffler has developed production solutions for wet and dry triple clutch systems and is currently industrializing those for different drivetrains. This article shows how the clutch loads change as a result of the P2 hybridization, resulting in compact triple clutches integrated into the rotor of the electric motor. Furthermore, the overall thermal balance is analyzed and related differences in efficiencies between dry and wet triple clutch solutions are presented. The clutch systems are enhanced through further development of the tribological system as well as a smart and modular actuation.