Reducing of Scuffing Phenomenon at HCR Spur Gearing

Abstract

The article deals with possibility of increasing the resistance of HCR spur gearing from a scuffing point of view. Scuffing is the process that occurs when the surfaces of two contacting bodies are joined by localized welding and then pulled apart. A material transfer occurs between the two contacting surfaces due to high metal-to-metal contact and hence produces a weld. Since there are great pressures between teeth flanks and the load is higher, the scuffing is the most important damage of teeth flanks of HCR involute gears. The scuffing traces appear in the form of streaks or scratches with rough bottoms and sides, often appearing as bands of variable depth width oriented in the direction of the height of the tooth, and affect isolated zones or their whole width. In the case of warm scuffing; the combination of high pressure exists between teeth surfaces, high sliding speeds, and excessive contact temperature, resulting from pressure and sliding speed values, which cause oil film rupture between the teeth flanks. HCR profiles are more complicated than standard involute profiles, they have greater predisposition for occurring interference, pointed tip thickness, but also undercut of teeth during the production (primary production interference). Due to increased addendum height, there is larger possibility of occurring some interference or pointed tooth tip. Therefore it should prevent these errors and check if all equation and constraints are satisfied. This paper describes finding optimal solutions for geometry of the tooth curve profile. It will be defined certain values addendum heights for meshing wheel according to criteria of specific slips and corrected head shape of the teeth of both wheels. In the same time, this optimization is joined with assessment and theoretical analysis of the impact of the HCR tooth profile resistance to scuffing on the basis of integral temperature criterion according to Winter-Michaelis criterion. A significant benefit in a theoretical area is generalization of the integral temperature criterion for involute HCR gearing.