Contact Performance Analysis And Experimental Study Of Planetary Gear Considering Elastohydrodynamic Lubrication

Gears are widely used as basic transmission parts.When they collide with each other in the meshing process,the gear surface will move relative to each other,resulting in gear surface wear.Due to the action of lubrication fluid,oil film will be formed on the contact surface to reduce gear wear and prolong the service life of the gear.In this thesis,aiming at the contact performance of gear pairs under elastic fluid lubrication,the contact performance of gear pairs in planetary gear trains was further studied by comprehensively considering the tooth surface morphology.Firstly,the motion state of gear pairs was analyzed,the elastohydrodynamic lubrication contact model was established based on the lubrication contact theory,and the oil film state parameters were analyzed.Then,simulation data was compared with theoretical data.The contact characteristics of oil film pressure,thickness and fatigue during gear meshing were analyzed.The main research contents are as follows:Firstly,the contact state of the planetary gear pair under elastohydrodynamic lubrication was analyzed.The contact analysis of the gear pair was simplified according to the relative slip velocity and the equivalent curvature radius of the gear pair during meshing,and the gear motion state was analyzed.The generalized Reynolds equation was established based on the relationship between pressure,lubrication fluid viscosity and density.The meshing contact process and contact state of planetary gear pairs were analyzed based on the elastohydrodynamic lubrication contact equation.The established elastohydrodynamic contact model and the simplified Hertz contact model were compared and analyzed.Secondly,the influence of tooth surface morphology on the contact performance of planetary gear pairs was analyzed,the gear surface morphology was characterized by three-dimensional mathematics,and the characteristic factors affecting the microscopic morphology were analyzed.By comparing with the measurement results of tooth surface morphology,the three-dimensional contour variation rule of gear under different morphological fractal characteristic parameters was obtained,and the normal contact stiffness model of gear was established based on the microscopic morphology.Based on ANSYS finite element simulation software,the contact fatigue of gear pairs in the meshing process was simulated and evaluated,and the influencing factors of gear dynamic meshing contact performance were analyzed.At the same time,the pressure in the contact area would change the lubrication contact state.Then the gear time-varying meshing stiffness model and oil film stiffness model were established,and the influencing factors of stiffness were analyzed.The influence of different working conditions,gear parameters and tooth surface roughness on the contact properties is considered.Finally,the contact characteristic experiment of gear pairs was carried out based on the planetary gear contact test bench to observe the temperature distribution of the entire transmission working system.The temperature point of gear pairs in thermal equilibrium was measured by thermocouple,and the contact strain was measured by stress-strain gauge.Based on the contact experiment of planetary gear,the influence of different speed and torque on temperature and contact stress is studied,which is of great significance for the analysis of contact characteristics of planetary gear.