Optimization of HCR gearing geometry from a scuffing point of view

Abstract

The paper deals with an issue of increasing the resistance of HCR external involute gearing from a scuffing point of view. It reports on a difference between involute gears with low contact ratio (LCR) and those with high contact ratio (HCR). The paper describes scuffing as the most significant damage done to the teeth flanks of HCR involute gears. In the case of warm scuffing, it is the combined action of high pressure between surfaces, high sliding speeds, and excessive contact temperature, resulting from pressure and sliding speed values, which consequently cause oil film rupture between the teeth flanks. Adopting a suitable geometry of the tooth curve profile, certain values of addendum heights for the meshing wheel will be defined according to the criteria of specific slips and corrected head shapes of the teeth of both wheels. The paper deals with the assessment and theoretical analysis of the impact of the HCR tooth profile resistance to scuffing on the basis of integral temperature criterion according to the Winter-Michaelis criterion. The basic relations for assessing the scuffing properties of an HCR involute gearing profile are derived, as well as the optimization of geometrical parameters of HCR gearing based on theoretical considerations on the properties of HCR gearing in terms of its resistance to warm scuffing combined with geometrical constraints against interferences. Finally, the results of the obtained optimization are compared with experimental results provided in previous research. A significant benefit in a theoretical area is the generalization of the integral temperature criterion for involute HCR gearing. By optimizing the criterion for the integral temperature of involute HCR gearing, the minimal flash temperature is obtained and the condition for the occurrence of scuffing is minimized.