| Straight-toothed bevel gears are widely used in modern automotive main reducers and differentials due to the space-interlaced shaft drive.When the load transmitted by the straight bevel gear and the sliding speed of the tooth surface are too large,if the lubrication between the tooth surfaces is improper,the tooth surfaces of the two bevel gears are susceptible to friction and wear.In this paper,the automotive differential bevel gear is taken as the research object.Firstly,the infinite long-line contact isothermal elastohydrodynamic lubrication model of the straight-toothed bevel gear is established.Secondly,the elastohydrodynamic lubrication problem under the time-varying micro-profile of the straight-toothed bevel gear is studied.The influence of profile modification on the lubrication characteristics of straight-toothed bevel gears is carried out.Then the lubrication mechanism of differential bevel gears under differential conditions was studied,and the lubrication characteristics under straight-line driving conditions and turning conditions were studied in turn,and analyzed simultaneously.The problem of thermal elastohydrodynamic lubrication under differential conditions was studied.Finally,the thermoelastic lubrication characteristics of spur bevel gears with finite-line contact were studied.The steady-state elastic hydrodynamic lubrication model of the infinite-line contact of the straight-toothed bevel gear is established.The multi-grid method is used to solve the steady-state elastohydrodynamic lubrication numerical solution of 11 points from the big end to the small end of the straight bevel gear.The oil film pressure and oil film thickness of the large end and small end of the straight bevel gear are discussed.The effects of straight-toothed bevel gear modulus,indexing cone angle,elastic modulus,dimensionless velocity and dimensionless load on oil film pressure and oil film thickness at the small end point are discussed.Considering the variation of the comprehensive radius of curvature,the entrainment speed and the load with time when the single-toothed gear of the straight-toothed bevel gear is engaged,the influence of Gaussian surface roughness distribution and cosine roughness distribution on the time-varying elastohydrodynamic lubrication is studied.The time-varying microscopic elastic flow numerical solution of the bevel gear during the whole meshing period is solved,and the maximum oil film pressure,minimum oil film thickness,center oil film thickness and center oil filmpressure are solved.On the basis of time-varying elastohydrodynamic lubrication of straight-toothed bevel gears,the influence of tooth profile modification on lubrication characteristics is considered.The oil film pressure and oil film of tooth profile modification on instantaneous and instantaneous piercing points are studied.The influence of thickness on the lubrication characteristics of the straight-toothed bevel gear after trimming,the oil film pressure and oil film thickness at three speeds were compared.The influence of the shape modification parameters on the lubrication characteristics was studied,the transient lubrication characteristics for two maximum trim and trim lengths were discussed,The oil film pressure distribution along the tooth width direction of the straight bevel gear after the profile modification is studied.Based on the time-varying elastohydrodynamic lubrication model of infinite-line contact,the lubrication characteristics of the differential bevel gear under straight-line driving condition and differential working condition are studied.The change of the sliding ratio,the center pressure,the central film thickness,the minimum film thickness and the maximum pressure is compared when the planetary gear meshes with the half-shaft gear under two working conditions.The elastohydrodynamic lubrication values of the planetary gears and the left and right side gears in the whole meshing interval under variable working conditions are calculated.The meshing thermal characteristics of the bevel gear under differential conditions,and the temperature field variation of the planetary gear are also studied.Taking the differential planetary gear and the semi-axle gear as the research object,the finite-line contact elastohydrodynamic lubrication model of the straight-toothed bevel gear is established,and the comprehensive radius of curvature and the entrainment speed of the entire contact line of the bevel gear are calculated.The oil film pressure,oil film thickness and the temperature of the solid and oil film intermediate layers on the entire contact line of the bevel gear are calculated by the grid method and the column-by-column scanning method. |
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