Power Losses in a Gearbox Lubricated with Axle Gear Oils

Three axle gear oils (75W90-A, 80W90-A and 75W140-A), available on the market and labeled as “Fuel Efficient”, and two candidate products (75W85-B and 75W90-B) were selected and their physical and chemical properties were measured and compared. The friction torque inside rolling bearings lubricated with the five axle gear oils was measured in a dedicated test rig. The measurements and the corresponding numerical simulations indicate that friction torque inside rolling bearings is strongly dependent on the operating conditions and on the axle oil formulations. The model was then applied with success to predict the torque loss in gearbox rolling bearings, in particular, those used in the FZG machine slave and test gearboxes. Gear power loss tests were realized on the FZG gear test machine, using type A10 gears and severe operating conditions. The torque loss measurements and the corresponding numerical simulations clearly pointed out the influence on the base oil type, of the oil viscosity and of the additive package on gear torque loss promoted by different axle oil formulations. An average coefficient of friction between meshing gears was devised from the experimental results. Several aspects regarding the meshing gears power loss were investigated like gear loss factor, the coefficient of friction and the influence of gear oil formulation (axle gear oils). A gearbox total power loss can be predicted by estimating the several power loss sources dissipated in gears, bearings and seals.