Research On Temperature Field Prediction Of Wet Clutch In Electronically Controlled Torque Active Distribution Transfer Case )

The changes in road excitation affect the temperature of the wet clutch friction element in the transfer case when a four-wheel drive vehicle operates in the timely four-wheel drive mode,then excessive temperature causes the clutch dual steel plate to lose efficacy due to overheating.In order to ensure the use efficiency and service life of the wet clutch,this paper studies the calculation method of the heat flux distribution coefficient,temperature field distribution,and its variation law between friction components,establishes a dynamic heat flux distribution temperature prediction model for friction components,and proposes a thermal protection strategy for the electrically controlled torque active distribution transfer case wet clutch.A friction pair contact heat transfer model and a fluid solid convective heat transfer model were established.Considering the temperature continuity of the friction contact surface,a dynamic heat flow distribution temperature prediction model was established.The heat flow density distribution coefficient and temperature field of the dual steel sheet were obtained using the finite difference method.By comparing and analyzing the experimental results,it is found that using the constant heat flow distribution coefficient calculation will cause the predicted surface temperature of the dual steel sheet to be higher,and the temperature difference between the friction elements will increase over time.The maximum deviations between the dynamic heat flow distribution temperature prediction model and the constant heat flow distribution temperature prediction model are 8.1K and22.2K,respectively.A circumferential periodic temperature prediction model considering the influence of radial grooves on the friction plate is established,and the thermal interaction coefficient matrix of the circumferential periodic model is proposed.Under the premise of ensuring the accuracy of temperature prediction results,the model iteration procedure is simplified.The distribution coefficient of surface heat flux density and temperature field of dual steel sheets over time were studied under different relative speed differences,actuation pressure,cooling lubricating oil flow rate,and inlet temperature conditions.The results show that the distribution coefficient of heat flux density and the temperature of the dual steel sheet exhibit a sudden step change in the initial stage of sliding friction,with the former decreasing in a concave manner and gradually approaching a fixed value,while the latter increasing in a convex manner and gradually approaching a fixed value.By analyzing the simulation results,the influence of different relative speed differences,actuation pressure,cooling lubricating oil flow rate,and inlet temperature on the equilibrium time and equilibrium temperature of the sliding surface temperature of the dual steel sheet was obtained.The equilibrium time of the sliding surface temperature of the dual steel sheet increases with the increase of the actuating pressure,cooling lubricating oil flow rate,and inlet temperature,but decreases with the increase of the relative speed difference;The equilibrium temperature increases with the increase of relative speed difference,actuation pressure,cooling lubricating oil flow rate,and inlet temperature.The radial surface temperature of the dual steel sheet exhibits a parabolic distribution,reaching its highest at the mid diameter;The actuating pressure and the inlet temperature of cooling lubricating oil have little influence on the circumferential temperature distribution;The greater the cooling oil flow,the more uniform the circumferential temperature distribution.This paper establishes a temperature estimation model for the wet clutch during vehicle operation and an overheat protection strategy for the transfer case by analyzing the heat generation of bearings and transmission sprockets in the transfer case,as well as the heat dissipation of the transfer case housing,The simulation of the vehicle’s rescue working conditions was conducted,and the results showed that the change curve of the lubricating oil temperature will continue to rise and the surface temperature of the dual steel plate will also rapidly rise was obtained.The results showed that:,The maximum temperature of the dual steel plate fluctuates below the safe temperature under the control of the transfer case overheat protection strategy.