Investigation on Dry-clutch Transmissibility Characteristic for Vehicle Launch Shudder 2018-01-1225
Vehicle launch shudder is the terminology used in automotive industry to describe severe longitudinal oscillation during clutch engagement under start-up condition. This paper presents and implements detailed investigation for dry-clutch engagement and disengagement process, in order to deeply analyze vehicle launch shudder phenomenon which seriously deteriorates ride comfort. Firstly, diaphragm spring and cushion spring and link strip, which are three elastic components related to dry-clutch engagement and disengagement process in axial direction, are studied for their elastic properties, respectively, to obtain relationship between load and deflection. The elastic properties of these three elastic components are taken into considerations to establish nonlinear relationship between release bearing travel and clutch clamp force. Then, based on multi-body system dynamics theory, the lumped mass method is used to model the powertrain of front-engine and front-wheel-drive vehicle equipped with manual transmission, six-degree-of-freedom powertrain torsional vibration model is used to simulate vehicle launch shudder phenomenon numerically, and the performance of vehicle launch is evaluated by shock extent and dissipated energy. The speed of release bearing travel is used to reflect different launch intentions: fast launch and normal launch and slow launch. Finally, by comparing evaluation parameters of these three launch modes, it can be known that the longer synchronous moment or release bearing travel time, the smaller shock extent, and the better launch performance, but dissipated energy is negatively correlated with shock extent. Through the research of this paper, the launch shudder during dry-clutch engagement process is analyzed, which can provide theoretical references for structural optimization and launch control strategy.