Effects of Hunting Gear Ratio Upon Surface Durability of Gear Teeth

Abstract

It was clearly shown that the pitting limits of gear pairs with a hunting gear ratio were appreciably lower than those of gear pairs with a unity gear ratio. This was ascribed to the difference in effectiveness of running-in between the mating tooth surfaces. Test gears with hardnesses ranging from 185 HB to 850 Hv were finished by hobbing, skiving or grinding. The contact fatigue damage was estimated from work-hardening at the tooth surfaces. The critical plastic strain which might cause pitting cracks was shown in terms of Brinell hardness. The availability of face-width was calculated from the two different pitting limits for gear pairs with two different gear ratios. It ranged from 0.23 to 0.80 in the present experiments because pitting limits of gear pairs with a unity gear ratio were appreciably greater. This suggested that there was a strong possibility to increase the load carrying capacity of tooth surfaces of gear pairs having gear ratios other than unity.