Numerical studies on the dynamic characteristics of a wet multi-disc clutch during the disengaging process

A comprehensive numerical model was proposed to investigate the disengaging process of a wet multi-disc clutch, which included the hydrodynamic lubrication, the micro elastic-plastic contact, the spline resistance, and the impact between the piston and clutch hub. The clutch disengaging process was divided into the boundary, mixed, and hydrodynamic lubrication stages to discuss the variations in friction pair gaps and friction torque. Moreover, the nonuniformity coefficient was employed to characterize the disengaging uniformity of friction pair gaps. During the disengaging process, the friction pair gaps increased slowly, increased rapidly, and stabilized after fluctuating. The increase in spline friction coefficient and the decline in pressure decrease rate dramatically deteriorated the disengaging uniformity; the decline in pressure decrease rate also significantly prolonged the disengaging time. This research demonstrated for the first time evidence for the dynamic characteristics of the clutch disengaging process.