Dynamic Characterization and Modeling of Wet Clutch Actuator for High-Fidelity Propulsion System Simulations 2020-01-1414
Innovations in mobility are built upon a management of complex interactions between sub-systems and components. A need of CAE tools that are capable of system simulations is well recognized, as evidenced by a growing number of commercial packages. However impressive they are, the predictability of such simulations still rests on the representation of base components. Among them, a wet clutch actuator continues to play a critical role in next generation propulsion systems. It converts hydraulic pressure to mechanical force to control torque transmitted through a clutch pack. The actuator is typically modeled as a hydraulic piston opposed by a mechanical spring. Because the piston slides over a seal, some models have a framework to account for seal friction. However, there are few literatures to describe the effects of seals on clutch actuator dynamics. In practice during a routine simulation, a spring constant is tuned to match vehicle data, assuming that it captures the effects of seal friction. The validity of this approach is not well established. This article describes the dynamic characterization of wet clutch actuator. The effect of seal friction is examined in detail during stroking and de-stroking. It is found that the seal friction is directional, highly non-linear, and discontinuous under certain conditions. It introduces a significant error in clutch apply force calculation unless it is explicitly accounted. A new clutch actuator model is proposed to represent seal friction based on empirical observation of its complex behaviors. It is shown that the model has a sizable impact on the quality of propulsion system simulations.
Hiral Haria, James McCallum, Yuji Fujii, Takahiro Tsuchiya, Masatoshi Miyagawa, Shinji Nakamura, Matthew Wendel, Nikolaos Katopodes
Ford Motor Company, FCC Co., Ltd., University of Michigan