Improved drag torque model for wet clutch

An improved drag model for wet clutch is proposed based on the surface tension of lubricant, surface waviness and nonparallelism of friction pairs. The radial pressure distribution equation is derived by considering the surface tension and surface wettability. The thickness of oil film is deduced under the influences of surface waviness and nonparallelism of the friction pairs. Results of numerical calculation indicate that the surface tension, surface waviness and nonparallelism of friction pairs all lead to increase in the drag torque of wet clutch. The drag torque increases rapidly with rise of the nonparallelism, while the influence of the surface waviness is not obvious. The effectiveness of proposed model is verified by comparison of this model with existing model and with test data.