Rolling Bearing Stress Forecast System Of Drive Rear Axle Main Speed Reducer

The main reducer of drive axle can change the transmission direction of torque, and solve the problem in torque distribution between the left and right driving cartwheel. The quality of drive axle affects the quality of whole car directly. As a key part of the main spindle in the drive axle, the tapered roller bearing, with performance index including precision, vibration and reliability, plays an important role in the performance and life of drive axle. The operation condition of tapered roller bearings in spindle has the following characteristics:â‘ under high speed, between 1000~2800n/min.â‘¡under great loading, generally under heavy loading.â‘¢Exist radial run out, as bearings are running. All of these negative factors will make the roller slide and deflect, and cause friction between the roller and ball track, which will make bearings over hot and wear, then lead to premature failure. The bearing failure will always shorten the life of the main reducer of drive axle.The conventional designing method have disadvantage of complex computing process, difficult, low precision. It cannot meet the need of present market economy, and restrict the improvement of innovation ability of production. Recently, the commercial FEA soft have great improvement in solving the contact problem, and provide advanced research tool for FEA numerical calculation and analysis.This paper studies the mechanical model of tapered roller bearing of main reducer in the drive axle, including following part: (1) the engagement force of angle gear acts on the bearing by shaft, which will make the inner raceway, outer race and roller under load. (2) when the roller bearing is preloaded, acting force will generate between the inner raceway and outer race under load.(3) the angle gear shaft runs under the drive torque and mesh force, which will cause radial runout at the bearing location, and causes relative displacement between the inner raceway and outer race of roller bearing, and then the bearing is under load.Consider the elastic hydrodynamic characteristics, and refer to the roller bearing tribology, elastic hydrodynamics and lubricate theory. The classical Herzz theory is base on the hypothesis that the surfaces are smooth. However, the surfaces of inner raceway, outer race and roller of the tapered roller bearing are not smooth, and lubricant exists between them. Actually, the surface lubricated is impossible smooth absolutely; ant the roughness has a great influence on the lubrication pressure, which will have important effect on the drag force. The development of elastic hydrodynamics play an important role in the research on the roller bearing, and it's helpful to improve the service life and reliability of bearings. Many experiments shows that the life of bearings will increase above one time when the oil film thickness is 3 to 4 times as much as the roughness of tow contact surfaces.Empolder a user interface by mathematic soft and analysis the variation regularity of the oil film thickness when contact on surfaces with different roughness, and then gain the curves of drag coefficient correspondingly, which are the friction factors between the roller and inner/outer raceway. Import the physical parameters of the lubricant and the operation condition of external load, then export the friction factors. Then build a forecast testing module for the tapered roller bearing by development language UIDI in FEA soft ANSYS. Add a menu for it to the main menu of ANSYS, and input the friction factors, which have been calculated in last part, to ANSYS to compute the external load, inertia force and contact stress distribution.This thesis comprises six chapters. Chapter 1 presents the background and significance of this research work. A general statement of the development of bearing theories is given. Finally, the main coverage of the study is described. Chapter 2 analysis the external load on the tapered roller bearings. In addition, discusses the load distribution of the tapered roller bearings and the computing formula of linear velocity firstly. Studies the classical Herzz contact theory, and concludes that the contact stress calculated by FEA soft is close to the value calculated by the classical Herzz contact theory. Chapter 3 summarizes the theory of isothermal linear elastic lubrication theory, and emphasis the calculating methodof combined iteration. Finally discusses the influence of surface roughness on the oil film distribution and the influence of surface roughness and oil distribution on the friction factors. Chapter 4 introduces the stress analysis of the tapered roller bearings under preload, axial load, inertia load and the entire external load. Chapter 5 presents the bearing testing program. The program comprises of two parts. In the first part, develop the user interface, and import the oil physical parameters and the conditions of external load, then output the friction factors. The second part describes the development language UIDI in FEA soft ANSYS and its control files, and builds a testing module of the tapered roller bearings in ANSYS. Then add a menu for it to the main menu of ANSYS, and input the friction factors, which have been calculated in chapter 1, to ANSYS to compute the bearing stress distribution. Chapter 6 summarizes the conclusions of the thesis and presents the defaults and improvement of the thesis.