Study on Elastohydrodynamic Lubrication Characteristics of Grease-Lubricated Spur Gears

Abstract

To reveal the evolution mechanism of the lipid film at the meshing interface of involute spur gears, an elastohydrodynamic lubrication (EHL) numerical model for line contact of lipid-lubricated spur gears was established based on the Ostwald constitutive equation. The oil film pressure and thickness distributions along the meshing line were obtained by using a numerical iterative algorithm combined with the multi-grid technique. On this basis, the influence laws of key operating parameters (gear speed, transmitted torque and lipid viscosity) on the elastohydrodynamic lubrication characteristics were systematically investigated. The results show that under lipid lubrication conditions, when the gear speed increases, the entrainment velocity increases accordingly, which is more conducive to the formation of the lubricating oil film, resulting in an increase in the oil film thickness. When the transmitted torque increases, the oil film thickness will slightly decrease. In addition, when the lipid viscosity increases, the position of the secondary pressure peak in the gear contact area shifts towards the inlet area, significantly increasing the oil film thickness. However, it is not advisable to pursue excessively high lipid viscosity, as the macroscopic rheology of the lipid, gear churning loss and lipid supply state should also be comprehensively considered. Therefore, in practical applications, when selecting a lipid for gears, the specific working conditions must be fully considered to ensure the best lubrication performance.