Investigations on the pitting load capacity of internal spur and helical gears

Abstract

Planetary gear boxes are suitable for numerous applications due to their compact design and high power density with coaxial in- and output. Especially in wind energy and industrial transmission systems but also in automotive applications such as automatic transmissions, planetary gear drives are commonly used. As a consequence of the continuous increase in the required power, the risk for flank damages has increased recently. Mostly, planetary transmissions are designed as helical gears due to improved NVH behavior and higher pitting resistance acc. to ISO 6336. However, systematic experimental investigations on the flank load carrying capacity of internal helical gears are not known so far. Based on the theoretical and experimental investigations in the research project FVA 482/II, the existing standardized load carrying capacity calculation method for pitting considering the maximum load could be verified. Thereby, the influence of the helix angle and material pairing of the planet and ring gear on the pitting resistance was studied. Certainly, it is shown that the maximum contact stress is not necessarily located at the pitch point C. Therefore, a detailed analysis of the load distribution and an adapted calculation approach is recommended especially for internal helical gears.