HCR Gearing and Optimization of its Geometry

Abstract

A special kind of the basic involute profile of non-standard gearing is called high contact ratio (HCR) gearing, where the contact ratio is higher, there are always at least two pairs of teeth in contact and the unit addendum height is not equal to one like for standard gearing. Thus, the tooth height is increased. When HCR gearing is used, it is not necessary to achieve a greater gear load capacity, but nevertheless there is a greater risk of interference due to the greater tooth height. The advantages of HCR gearing is higher resistance (load is distributed on more pairs of teeth at the same time) and a lower relative noise level of gearing, which can be significantly reduced by using an integer HCR factor. HCR profiles are more complicated than standard involute profiles, they have a greater predisposition for interference, pointed tip thickness and undercut of teeth during production (primary production interference). Due to increased addendum height, there is a larger possibility of some interference or pointed tooth tip occurring. Therefore, these issues need to be prevented in the design phase, and ensured that all relevant equations and constraints are satisfied. The described method of finding optimal gear parameter values uses a Generalized Particle Swarm (GPS) optimization algorithm and MATLAB. The GPS optimization is shown to be a very fast and reliable method.