A Research On Wet Multi-plate Clutches’ Drag Torque And Its Influence Factors

Wet multi-plate friction clutch is widely used in the transmission system of heavy vehicles because of its high power density,long service life and excellent controllability.Working heat is an important factor that determinate life cycle and working performance of wet clutch.There are two inducements that cause excessive heating:friction heating during engagement and oil’s viscous shear heating in condition of disengagement(drag torque).This passage focus on drag torque and look into a few typical issues of wet clutch on a track-laying vehicle.Main work can be summarized as follows:1.Build a mathematical model of drag torque between friction pairs.There propose a two-phase flow model that can precisely describe the pressure,velocity distribution in fluid area between friction pairs.This model successfully explains some phenomenon:sharply descend in high rotational speed and slight ascend in higher rotational speed.Base on the model,the relation between drag torque and some factors(such as flow rate of lubricating oil,interval between friction plates)are numerically calculated.In addition,there propose a concept--oil fraction which is then used to evaluate the accuracy of model by FEA.2.Thermal-fluid-solid coupling simulation of friction pairs.VOF model is used to evaluate the accuracy of mathematical model.Multi-field coupling FEA method is used to simulate fluid field distribution and friction plate’s stress-strain character.Analyze results of orthogonal test and use grey correlation analysis to evaluate stress-strain character’s sensitiveness against some factors.Finally,interval between friction plates is chosen as optimization index.3.Dynamically optimize the structure of clutch’s flow field.Here choose standard deviation of average pressure values in different intervals as objective function to ensure equally distribution of different friction pairs.Then use the result of optimization to design the structure of testbed.4.Use the automatic drag torque measuring system to conduct single variable test.Compare experimental data with mathematical model calculated data.