Influence factors of friction-induced oscillation during wet clutch engagement

A simplified 4 degree-of-freedom (DOF) power-train dynamic model with an integrated damping induced by the friction effect of a wet clutch was developed to investigate the friction-induced oscillation (judder) during engagement, which may worsen the clutch engagement quality and result in the clutch failure. The stability criteria were obtained based on the eigenvalue analysis method. The numerical simulation in Matlab/Simulink was performed to evaluate the influence of different parameters such as the coefficient of friction, the variation process of control oil pressure, the moment of inertia of the clutch and the stiffness of drive shafts on the clutch judder. The results indicate that the system instability occurs when the integrated damping, which is determined by the coefficient of friction and the oil pressure, is negative. The results further show the clutch judder attenuates with the increase of the moment of inertia of the clutch driven component and the rise of the stiffness of the transmission output shaft. When the oil pressure rises rapidly at the early stage then followed by a slow rate, the amplitude of the friction-induced oscillation decreases.