Analysis Of Friction Characteristics Of Inclined Gear Based On Point Contact Ejection

Helical gear,as an important mechanical transmission component,is widely used in reducer of aerospace turbine,drive component of automobile and ship power system because of its smooth transmission,strong load-carrying capacity,compact structure and small axial force.For involute helical gears,with the development of gear train toward high speed and heavy load,more and more attention has been paid to reducing friction between tooth surfaces of gears and improving lubrication performance of gear train.Using the principles of point of contact elastohydrodynamic lubrication and the principles of structural mechanics and driving characteristics of helical gears,this paper combines the friction,wear and lubrication problems of gears,comprehensively considers the influence of gear modification and roughness,establishes a model of point helical gear contact thermal elastohydrodynamic lubrication,solves the full numerical solution of the model,and analyses the elastohydrodynamic lubricant characteristics of helical gears.The major points of this study are as follows:(1)Theoretical analysis of EHL based on point contact.Firstly,the mathematical model of elastohydrodynamic lubrication has been established on a point-to-point basis,and the oil film pressure and temperature in point-contact elastohydrodynamic lubrication were solved by multi-grid algorithm and row-by-row scanning algorithm respectively.The Fortran language was used to program the numerical calculation,and the effects of load,entrainment speed and slip-roll ratio on the thermal elastohydrodynamic of point-contact were analyzed.Through numerical analysis of calculation,it is found that the temperature of oil film is significantly affected by slip roll,which has a great influence on loading load and entrainment speed based on Point Contact Elastohydrodynamic lubrication.In addition,in point-contact elasticity,the non-Newtonian fluid effect of lubricants mainly affects the temperature and shear stress of the oil film.In most cases,the film temperature and shear stress of non-Newtonian fluid lubricants are lower than that of Newtonian fluid lubricants.(2)Helical gear thermal EHL characteristics.The point contact elastohydrodynamic theory is applied in the transmission of helical gear train.Based on the numerical calculation results,the changes of the contact load,the line distance,the entrainment velocity,the radius of curvature and the slip-roll ratio of the gearwheels along the line meshing line of gears are studied.Influence of various geometric parameters and operational constraints parameters of helical gears on lubrication characteristics is analyzed.The results show that proper selection of geometric and operating parameters of helical gears is of great help to improve lubrication and friction of helical gears.(3)The influence of modification on the characteristics of gear EHL.The effect of crown modification and various barrel modifications on the EHL of helical gears based on point contact is analysed.Through comparative analysis,moderate modification is beneficial to uniform distribution of transverse loads on helical gears.Excessive modification may cause higher oil film pressure and shear heating,which will result in gear lubrication failure seriously.(4)Thermal Elastohydrodynamic analysis of helical gear with rough tooth surface.Calculation and analysis of thermal elastohydrodynamic lubrication of helical gears with rough surface considered.The rough tooth surface of helical gear is simulated by random roughness,transverse roughness and three-dimensional roughness model respectively,and the related value of Micro-Elastohydrodynamic lubrication is calculated by inserting roughness model function into the main program.The influence of the roughness texture,the roughness amplitude and the roughness wavelength on the elasto-hydrodynamic lubrication characteristics of helical gears is analysed.The data show that the thickness of the oil film on the rough surface of the gear tooth is obviously thinner than that on the smooth surface of the tooth.The change of roughness texture will change the pressure and film thickness.Increasing the roughness amplitude or roughness wavelength will decrease the thickness of lubricant film.