Abstract：The service life and the performance of wet clutch are affected by the clutch engagement process.Based on the hydrodynamics theory and the elastic contact theory of rough surfaces, the mathematical models of the oil slick thickness and the transmission torque were established for the engagement process of wet clutchs.The mathematical models were solved by the Runge-Kutta method, then the influences of pilot oil pressure, lubricant viscosity and permeability of friction material on the oil film thickness and the transmission torque of wet clutch were obtained. The simulation results show that increase of pilot oil pressure can effectively improve transmission torque of wet clutch and cut down engagement process time of wet clutch, and as the lubricating oil viscosity increases or the permeability of friction material decreases, the response speed of transmission torque during the wet clutch engagement process slows down, and the clutch engagement time is prolonged. The lubricating oil viscosity and the permeability of friction material have a great effect on the transmission torque of wet clutch during the compression and compaction stage, but have little influence on transmission torque during the rough contact stage.

Keyword：wet clutch;transmission torque;thickness of oil slick;engagement time;