Research On Slipping And Thermal Characteristics Of Wet Clutch During Starting Conditions

Wet clutches are widely used in automobile automatic transmission because of their large engagement torque,reliable operation,and stable wear.During the start of the car,the friction disks of the wet clutch and the separator plates are quickly engaged in a short period of time.A large amount of frictional heat will be generated on the sliding surface and the temperature will rise.Excessive temperature will cause the thermal failure of the friction pairs and affect the driving safety.In order to deeply understand the slip and thermal load characteristics of the wet clutch for starting conditions,the school-enterprise cooperation project is used to simulate the friction characteristics,coolant temperature and transient temperature field of the wet clutch at the starting conditions.The specific research contents are as follows:First,by analyzing the friction torque generation mechanism of the wet multi-plate clutch,the transmission torque and the disengagement state torque of the coupling process were modeled and simulated.Second,by combining the power transmission model of starting conditions and the calculation of friction torque,the mathematical model of wet clutch slip power and coolant temperature was derived,the slip power and the effect of the coolant temperature of different start loads,ramp angles and coolant flow rate were studied.Then,according to the finite difference method,the transient thermal calculation program was written in Matlab,and the transient temperature field of the wet multi-plate clutch for ramp start,racing start and continuous multiple start conditions,as well as different starting conditions and different friction materials to the temperature were simulated.It is found that the temperature difference of the same contact surface is related to the radial position,and the temperature of the friction pair of different contact surfaces is significantly affected by the constraints;different starting conditions have different effects on the radial and axial temperature difference of the wet multi-plate clutch,and thermal ablation is more likely to be caused by starting multiple times.An optimized solution for the self-adjustment of coolant flow was designed for multiple consecutive starts,which could effectively reduce the maximum temperature of the friction pair for multiple consecutive starts.Finally,a thermal load test was carried out on the wet clutch bench,and a continuous coupling test with different coolant flow rates was conducted by embedding thermocouples on the surface of the dual steel sheet and the coolant outlet.According to the coMParison between the test results and the simulation results,the reliability of the finite difference thermal programming calculation of the wet multi-plate clutch transient temperature field is verified,which can provide a reference for the research of the enterprise wet clutch thermal model.