Effect of lubricant viscosity on dynamics of high-precision gear considering lubricant-induced backlash reduction

The effect of lubricant viscosity on dynamics of a high-precision spur gear pair with near-zero backlash is investigated under deterministic and uncertain conditions via a tribo-dynamic model. This model, for the first time, considers the backlash reduction induced by the lubricant film between meshing teeth. In general, increasing viscosity can mitigate vibration in off-line-of-action (OLOA) direction and decrease dynamic transmission error (DTE) but can hardly mitigate vibration in line-of-action (LOA) direction. Moreover, increasing viscosity can suppress the uncertainty of OLOA vibration caused by the uncertain backlash, supporting stiffness and meshing stiffness but cannot suppress the uncertainty of DTE. Therefore, gear dynamic performance can be improved by increasing lubricant viscosity. However, to what extent the gear dynamic performance can be improved depends on the operating condition and surface roughness.