Gear rattle dynamics under non-stationary conditions: The lubricant role

Abstract

Multi-stage-constant-mesh gearboxes contain two different kinds of gear pairs, called active and inactive stages. The latter are engaged but not transferring energy to the output shaft, whilst the former transmits power from the input to the output shaft. Due to the interaction between these stages, undesirable impacts are provoked, which could result in the failure of elements connected to the gearbox. This phenomenon is called gear rattle. The lubricant is the only element between teeth in contact, and therefore, its role is the key to understand the system behaviour and to palliate the potential consequences of this non-stationary phenomenon. In this regard, it was proven in previous gear rattle analysis performed by the authors that two lubricant effects must be considered to correctly model this phenomenon; the effect of the fluid entraining in the conjunction and the lubricant squeeze produced when profiles are approaching. In light of these factors, in this work, low-loaded gear transmissions dynamic behavior were analysed, making special emphasis on the fluid viscosity influence on the dynamic behavior and on hydrodynamic forces under non-stationary conditions.