| The differential is an important element of the vehicle’s drive axle, and reduce its power loss is becoming increasingly important in auto transmission efficiency, but its power loss characteristics are not widely studied around the world. The differential power loss mainly focused on transmission of bevel gears. In the process of meshing efficiency model of bevel gears, the chance of each meshing point what load distribution, the oil film thickness and other factors on, is ignored easily. Gears pair lubricating state is always considered as a single mixed lubrication or elastohydrodynamic lubrication, and the driveline efficiency as a constant. Those could not reflect the power characteristics of differential well. Regard symmetric planetary gear differential as research object, a theoretical model and simulation analysis of bevel gear meshing efficiency under various lubrication conditions was established by using the rational model of load distribution, oil film thickness and other factors, which combined with the literature at home and abroad. The detailed contents are as follows:Firstly, vehicle driveline efficiency and differential power loss characteristics were summarized, and structure of differential, working principle as well as main parameters which directly influences differential performance were analyzed.Secondly, according to the real problem that influence of tooth surface roughness and the gear working condition, a theoretical model of friction coefficient under integrated lubrication which consist of boundary lubrication, mixed elastohydrodynamic lubrication and elastohydrodynamic lubrication was established by using calculating oil film-thickness ratio to determine the lubrication condition. A math model of load distribution was established, and a math model of sliding and rolling friction power loss was also established with a variable of pressure angle and pitch radius, which erased the error of the prevailing power loss integral calculation to accurate calculate average sliding and rolling power loss by introducing integration method for a meshing cycle, and a bevel gear meshing efficiency prediction model based on MATLAB was built.Thirdly, three-dimensional modeling of differential was built. Then the mechanism and component of inner friction torque was analyzed based the force analysis and kinematic analysis of the planetary gear and half axle gear under typical working condition. In addition, a math model of friction torque is established to analyze the torque performance of differential, and gain the calculated relationship of left and right half-axle, which provided a reference for torque distribution of differential.Finally, based on theoretical models of bevel gear power loss, churning loss, windage loss and bearing power loss, the differential transmission efficiency is simulated, then combined transmission efficiency of the main reducer form related literature to gain the transmission efficiency of driving axle, which compared the dates from experimental measurement to illustrate theoretical model of power loss. |
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