Research On Frictional Convection Heat Transfer And Temperature Field Distribution Of Friction Pairs In Hydro-viscous Clutch

The hydro-viscous clutch uses the oil film shearing force and the mutual contact between the friction surfaces to transmit power to realize the soft start of the device.A large amount of frictional heat will be generated during the relative sliding process,which makes the temperature of the friction pairs rise sharply,especially uneven temperature rise is easy to cause deformation of the friction pairs,thus affecting the performance of the hydro-viscous clutch.In order to reduce the thermoelastic deformation of the friction pairs of the hydro-viscous clutch,the temperature field of the friction pair should be predicted accurately.This paper takes the double-arc oil groove friction pair of the hydro-viscous clutch as the research object.The finite element simulation analysis is used to obtain the convective heat transfer coefficient between the friction pair and the working oil firstly,then the temperature field distribution of one set of friction pairs is obtained,so is the temperature field distribution of multiple sets of friction pairs in the axial direction through simulation.Finally,the effectiveness of the numerical simulation method is verified through experiments.In order to obtain the accurate convective heat transfer coefficient of the friction pairs,the fluid-solid coupling finite element model of the friction pairs was established using CFX.The parameters such as the heat transfer surface shape,friction plate speed,oil inlet pressure and oil physical properties were taken into account to obtain the relationships between factors and the convection heat transfer coefficient respectively.The results show that the convective heat transfer coefficient changes from the inner diameter to the outer diameter with the change of the cross-sectional area of the oil tank;the smaller the oil viscosity,the greater the inlet pressure,the greater the convective heat transfer coefficient.In order to obtain the temperature field distribution of the friction pairs,the temperature field model of the friction pair was established in ABAQUS.The heat distribution coefficient obtained according to the theoretical calculation was input as the heat source.The convection heat transfer coefficient was used as the boundary condition.So that the temperature field distribution of the friction pair was obtained.The results show that the temperature of the friction plate and the dual steel plate gradually increase from the inner diameter to the outer diameter,the center temperature of the diamond-shaped area between the oil grooves is higher than that of the surrounding area,and hot spots are easy to form;the normal load of the friction pair will affect the temperature value of the friction element,but has little effect on the distribution law of the temperature field.The temperature field distribution of multiple sets of friction pairs is obtained by numerical simulation.The results show that the temperature of the friction pair in the axial direction increases firstly,and then decreases,and the temperature value of the fifth friction element area on the piston side reaches the maximum;The temperature in the outer diameter area is significantly higher than the inner diameter area.The difference in material properties between the friction pairs causes the temperature of the dual steel plate to be higher than that of the friction plate as a whole,and the temperature of the friction pair shows an alternating distribution of high and low in the axial direction.The frictional force at the spline causes the pressure of the friction pair to decrease in the axial direction,resulting in a gradient in the axial temperature.A test bench for the thermal load characteristics of the friction pairs of the hydro-viscous clutch was built.The method of using a given drive motor speed and a given load motor torque is used to imitate the soft start process.A temperature sensor is embedded in the dual steel plate,the temperature of the dual steel plate is monitored by the computer data acquisition system under slip conditions,and the temperature field distribution under different clutch pressures and different slip times is obtained.The results of test and simulation are basically consistent.