Design of Axial Profiling and Investigation of the Influence of Pocket Position on Lubricant Flow in Planetary Journal Bearings in Applications with Low Sliding Speeds and High Loads

The application of plain bearings has become very famous in planetary gear stages in recent years. To improve load-carrying capacity, this study investigates a design method for axial profiling in which a sixth-order polynomial is iteratively derived from the curve of local minimum film thickness for each axial grid position. Two load cases with specific bearing loads of 12.0 MPa and 6.0 MPa at 0.5 m/s are considered for profile design. Calculation results and computational effort of strategies assuming rigid or elastic geometries during the optimization are compared. Results indicate that the consideration of deformation is already necessary in the design phase and a maximization of minimum film thickness leads to much higher load-carrying capacity than the minimization of the maximum film pressure. Furthermore, the impact of the lube oil pocket position on oil flow rate is experimentally and theoretically investigated to identify the optimization potential of this parameter. Results show that the oil flow varies by the factor of three if the lube oil pocket is shifted incrementally over an angular span of 180° outside the load zone. The results and possible extensions are critically discussed under the consideration of practically relevant restrictions in mechanically highly loaded planetary gearboxes.