Research On The Torque Characteristic Of Friction Pairs In Hydro-viscous Clutch

In order to improve speed regulation characteristic, widen speed range, improve speedstability and optimize structural design for the double arc oil grooves friction pairs ofhydro-viscous clutch, the theoretical prediction and experimental research on frictioncharacteristics and torque transmission characteristics in speed regulation process havebeen studied. The fluid torque caused by shear stress, the impact and optimization of oilgrooves, the mixed friction characteristics and torque, the torque stability and the otherfactors on torque performance were obtained along with various film thicknesses.The mathematical model of fluid flow characteristics was established to determine thefluid torque. The analytical solution of flow characteristics were solved by step analyticalmethod. Film equivalent radius model and fluid torque by shear stress model wereintroduced under Reynolds boundary condition. The equivalent temperature model wasachieved by taking the temperature increase and the fluid viscosity-temperaturecharacteristic into account. Iterative method was employed to determine the equivalenttemperature and output speed. The flow characteristics and fluid torque of friction pairswere calculated under different operating conditions.In the stage of mixed friction, the film average flow model by considering asperityeffect on film lubrication properties and fractal contact model of rough surface in whichasperity contact properties was describe were established respectively. The change ofcontact friction coefficient along with specific pressure was studied especially. Based on thetwo models mentioned above, the mixed friction model of friction pairs was coupled. Thefriction torque characteristics and the main factors were analyzed.Aiming at the impact of oil grooves on fluid torque, the flow characteristics and fluidtorque by shear stress were analyzed utilizing the numerical simulation research throughwhich the mathematical model of fluid torque by shear stress was modified. The integratedoptimization design platform of oil grooves was built. The influence of width, depth andnumber of oil grooves on fluid torque was investigated. Choosing maximum fluid torque asoptimization target, the grooves’ structure parameters were optimized. The results indicatethat the fluid torque and speed regulation characteristic can be improved by shallowing the groove depth, narrowing the width and increasing the number of oil grooves.For the condition of torque instability in speed regulation process, the torque stabilityin stage of fluid torque was described by stability of film thickness. In mixed friction stage,the torsional vibration model was proposed by discussing the effect of friction coefficienton torque stability. The phase plane analysis method was applied to study the torquestability, and the main factors were analyzed.The test rig for torque characteristics of hydro-viscous clutch was designed. Thechange of film thickness was measured in speed regulation process. The torquecharacteristics of copper based powder metallurgy friction material were obtained throughwhich the theoretical prediction models can be validated in stages of fluid torque and mixedfriction. Besides, the speed regulation characteristic of copper-based powder metallurgyfriction material and carbon fiber paper-based friction material were researched respectively.The conclusion was that the carbon fiber paper-based friction material has a wider speedregulation range and better speed regulation performance.