Thermal characteristics analysis and experimental study of the planetary roller screw mechanism

The thermal characteristics of the planetary roller screw mechanism (PRSM) under various working conditions are investigated both analytically and experimentally. Firstly, thermal boundary conditions including the thermal contact resistance, thermal constriction resistance, conductive and convective resistance are particularly characterized and formulated, based on the fractal theory and heat transfer theory. Secondly, a thermal model based on the thermal network method (TNM), is established to predict the PRSM temperature evolution. The thermal balance equation set is solved by considering the influence of lubricant viscosity drop and the change of heat generation. Thirdly, the main factors affecting the thermal characteristics of the PRSM system, such as the external load, screw speed, and lubricating grease, are discussed and analyzed. The correlation between the experimental data and the calculated values confirms the validity of the proposed thermal model for the transient thermal analysis. Results indicate that the external load, operating speed, and lubricant consistency have a significant influence on the temperature rise level, even leading to the thermal failure of the PRSM. This study provides an in-depth understanding of the thermal behavior and heat transfer mechanism of the PRSM, and thus can be applied to its design and development.