| With the rapid development of national economy, the number of automobile is increasing continually, and the fuel consumption resulting from automobile application is also growing year by year. The most direct consequence of vehicle fuel consumption is a large increase in exhaust emissions, which will lead to huge environmental pollution. In order to deal with the increasingly serious environmental problems, emission regulations have become increasingly stringent. To improve the vehicle fuel economy, and reduce the environmental pollution caused by fuel consumption, has become a significant subject that almost all automobile enterprises have to be faced with.As the technology condition of transmission system has great influence on automobile fuel economy, enhancing the efficiency of transmission system is of great significance for improving vehicle fuel economy. In order to make the optimization work carried out purposefully, a new testing method for the measurement of transmission resistance distribution of FR automobile is proposed in this paper. Using this method to diagnose several domestic mini-cars can reach the following conclusion: the fact that the friction power loss of pedestal bearing for mini-car half-shaft is too large is one of the important reasons that affecting the fuel economy of domestic mini-car.Therefore, pedestal bearing for half-shaft(including differential bearing and hub bearing) is chosen as the research object, and improving the efficiency of transmission system is taken as the research objective in this paper. This article mainly makes study from these three aspects: internal structure optimization of pedestal bearing for half-shaft, control of preload force for differential bearing, and control of working clearance for hub bearing and differentiated design of hub bearing. The main research work can be summarized as the following aspects:(1)A mathematical model of multi-objective optimization design is built, optimal solution on the internal structure parameters of differential bearing has been carried out based on genetic algorithm, and the validity of the mathematical model is verified through testing. Based on the friction moment test, the relationship between the friction moment of hub bearing and the filling amount of grease is studied, the mathematical relationship is established through curve fitting, the reliability of the formula is verified through testing. By conducting the test, the influence of hub bearings seals' structure on friction moment of hub bearing has been studied. The existing shortcomings of hub bearings have been analyzed after the discussion for operating conditions of hub bearings, and an improved scheme is presented in view of these weaknesses. In addition, after the simulation analysis it can be found that the optimization scheme is not only helpful to improve the stress distribution of hub bearing, but also advantageous to raise the fatigue life of hub bearing.(2) A mathematical model of friction torque for differential bearing in pre-tightening condition is proposed basing on Hertz contacting theory and energy theory. A numerical model of differential bearing is developed, and the validity of the numerical model is verified. The relationship between preloading force and preloading deformation is discussed with this numerical model, and the mathematical relationship between preloading force and preloading deformation is concluded through analysis. Combined with the working conditions of mini-car, force analysis of differential bearing will be conducted, and the minimum preloading deformation will be determined after calculating the minimum preloading force of differential bearing. In order to study the influence of preloading deformation to transmission efficiency of drive axle, a special test-bed for testing transmission efficiency of drive axle is designed, and a new test method used for measuring transmission efficiency of drive axle is proposed.(3)Through systematically studying the key factors influencing working clearance of hub bearing, a mathematical model considering the influences of interference fit, temperature distribution, external load and oil film thickness is put forward, and the validity of the model is verified through testing. Based on industry characteristics and manufacturing level of domestic mini-car, a method is used to control the working clearance of hub bearing will be designed. This method can realized the precise control of hub bearing clearance through selection, and overcome the limitations of traditional methods which depend on recommended value to control working clearance of hub bearing. A mathematical model of internal load distribution is built based on statics, and the corresponding relationship between working clearance and the fatigue life of hub bearing has been simulated according to the fatigue life theory. Simulation results show that when the working clearance of hub bearing is controlled between-10? and 10?, hub bearing can obtain ideal fatigue life. Within the scope the influence of working clearance to transmission efficiency of drive axle is studied by bench scale test, and a group of desirable working clearance of hub bearing has been acquired through comparative analysis.(4)On the basis of above research, vehicle test has been conducted to validate related research results, and the test content mainly includes fuel consumption testing and transmission resistance testing. The test results indicate that the application of research results in mini-car driveline can make fuel consumption reduced by more than 0.4 L/100 km, and make transmission resistance of driveline decreased about 40%, which is of high applied value in engineering. |
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