Decision Method of Optimum Specification of Involute Helical Gears for High Load Carrying Capacity (2nd Report, Design Algorithm and Endurance Test)

Abstract

Motor power of vehicles is increasing to accomplish more speedy and comfortable drive. On the other hand, smaller and lighter drive train is required to expand the internal space of vehicles. Gears used for those drive trains must therefore have high load carrying capacity. In this report, gearbox whose center distance, gear ratio and face width are fixed, is treated and the influence of module, number of teeth and profile modification of tooth flank on load carrying capacity is investigated, where pressure angle, helix angle, addendum modification factor and tooth depth are optimized by the method proposed in the previous report. There is an optimum value of module in load carrying capacity and the characteristic of the optimum module depends on tooth number. Tooth profile modification for larger module gear contributes to improve load carrying capacity, but that has small effects for small module gears. Asymmetrical tooth profile form correction has little advantage if gear dimensions are optimized. Total decision method of gear specification for high load carrying capacity is proposed, which includes the decision of module, number of teeth, pressure angle, helix angle, addendum modification factor and tooth depth and profile modification of tooth flank as well. Endurance test of the gears designed by the proposed method is carried out and the improvement in gear life is confirmed.