AGMA 17FTM11 PDF

Tooth flank modifications are used to optimize the excitation behavior and durability of gears. In the first step, design is often done via guidelines, and afterwards, a variety of tooth flank modifications is checked via local calculation approaches to determine the best micro geometry in order to enhance operational behavior. Modifications are subject to statistical deviations due to the manufacturing process. Their sizes are in the range of micrometers and therefore in the same dimension as the tooth flank modification itself. However, deviations are often not taken into account during the design of modifications today, although they can lead to an uncertain influence on the operational behavior.

The authors developed a method to evaluate the quality and stability of flank modifications (like: tip reliefs, profile angle modifications, profile crownings, lead angle modifications, helix crownings, end reliefs, and root reliefs) regarding manufacturing tolerances during the design process. An FE-based tooth contact analysis is used to simulate characteristics of the excitation behavior and durability of a gear pair. In addition to the standard design process, the tolerance field of the tooth flank modification is taken into account. In order to choose an optimized micro geometry, a weighting function is used to compare the results by quality (level of target value such as transmission error or stress) and stability (variability of target value) under consideration of all relevant combinations of relevant modification parameters on pinion and gear in their respective tolerance fields. By means of the developed method, the planetary gear and cylindrical gear stages of a wind turbine are optimized. Regarding the target values (Hertzian pressure, transmission error, and root stresses) the characteristics for quality and stability are calculated, and the best constellation of tooth flank modifications is chosen. Results suggest that the quality of tooth flank modifications can differ between chosen tolerance fields while some variants are more susceptible than others. The presented design process provides a method to examine those influences and enables the engineer to choose the most robust micro geometry in terms of quality and stability already in the design process.