Research On The Impact Of Rolling Bearing Friction Torque For The Resistance Of Subcompact Vehicles Rear Axle Assembly

Drive axle is an important power transmission device in a car, and its power loss, as an important technical indicator, directly affects the dynamic property and fuel economy of a vehicle. This paper takes mini-car’s drive axle as the research object, and analyze the rear axle resistance in terms of bearings. From the perspective of decreasing the bearing’s self-resistance and working resistance of bearings, internal structure parameters, assembly preferences, radial clearance and lubrication parameters were optimized. The main research works are as follows:(1) The point contact and line contact basic equations were established through the contact analysis between the rolling elements and rolling nest of bearings and the application of Hertzian elastic contact theory. Besides, the load distribution was confirmed through statics analysis of bearings. In addition, the minimum oil film thickness formulas of point contact and line contact were acquired through the theoretical analysis of elasto-hydrodynamic lubrication;(2) The mathematical model of friction torque of tapered roller bearing and deep groove ball bearing were build, and the impact factors of friction torque were analyzed. Specifically, by analyzing the formation mechanism of friction torque of bearing in tapered roller bearing and deep groove ball bearing, the friction torque of bearing’s mathematical model were set up based on elastic contact, hydrodynamic lubrication and statics analysis, and the influences on friction torque of bearing resulting from bearing internal structure parameters, bearing operating conditions and machining precision of bearing were investigated by using MATLAB to simulate the bearing friction torque function;(3) Based on optimization design theory, the mathematical model of optimization design was established with the internal structure parameters of the bearing as design variables, bearing friction torque and basic dynamic load rating as the goals, genetic algorithm as the optimization algorithms, and the internal structure parameters of tapered roller bearings and deep groove ball bearing were optimized using MATLAB genetic algorithm toolbox. The experimental research of bearing friction torque was conducted, and the test results showed that the bearing friction torque has been improved;(4) The optimization of lubrication parameters, assembly preferences and radial clearance of rear axle bearings and the experimental verification were conducted based on the purpose of reducing the friction torque of rolling bearings on the rear axle. The resistance of rear axle before and after optimization were tested on the Chassis dynamometer respectively, and the test results showed that the resistance of the rear axle assembly was reduced.