A systematic approach to profile relief design of low and high contact ratio spur gears

Abstract

This is the first of a series of papers on the design of the tooth profile relief of both low and high contact ratio spur gears and its effects on transmission error (TE) and tooth loads. A systematic approach to profile relief design is introduced. The process of profile relief analysis is based on a number of simplifying assumptions to ease the understanding of the relief design. Useful relief cases determined during the simplified analysis are further investigated, with realistic parameter values such as variable stiffness, manufacturing tolerances and so on, in other papers of the series. Experimental validation of the cases proven to be good are also given in forthcoming papers. In the present paper, the systematic approach is applied to low contact ratio (LCR) spur gears first with some design regions and to high contact ratio (HCR) spur gears with some new and promising design regions and rules. Several smooth transmission error curves at different loads are shown to be possible for the relief designed, hence allowing a range of loads with uniform motion transfer. The advantages of HCRG over LCRG in terms of smooth TE curves and tooth load values are noted.