Experimental study on transmission rattle noise behaviour with particular regard to lubricating oil

The analysis of the angular relative motion indicates that gear tooth impacts during rattling lead to elastic deformation of meshing gear pairs. High contact forces during impacts cause Hertzian flattening of gear tooth flanks and rising fluid viscosity with pressure in the contact zone (elastohydrodynamic lubrication regime). The elastic deformation of meshing gear pairs lead to deviations from the angular velocity ratio between two gears of a gear pair and thus from the Law of Gearing. The main source for the gear rattle noise level is the additional presence of meshing impacts at the beginning of each gear pair meshing. Gear rattle noise reduction can be achieved by avoiding meshing impacts, e.g. by using low traction gear lubricants.