The Influence of Free End Surfaces on Elastohydrodynamic Lubrication of Involute Spur Gears with Different Pressure Angles

A finite-length elastohydrodynamic lubrication (EHL) model of involute spur gears with consideration of free end surfaces was established based on the solution to the finite-length space, which was different from the conventional EHL model of spur gears based on half-space theory. The overlapping method was used to construct the free end surfaces. Matrix formulation and semi-analytical method were utilized to solve the effect of free end surfaces and FFT algorithm was utilized to speed up the calculation of the elastic deformation. The unified Reynolds equation method was used to obtain the oil film pressure and thickness. The effect of free end surfaces on EHL of involute spur gears with different pressure angles was analyzed and compared at the pitch point. The results showed that, compared with the conventional half-space model, the free end surfaces reduced the peak pressure, homogenized the distribution of pressure and increased the minimum oil film thickness. The level of pressure decreased and the film thickness increased as the pressure angle increased. When different pressure angles were adopted, the influence of free end surfaces on the peak pressure of the EHL of involute spur gears was approximately identical and that on the minimum film thickness was significant.