Effect of backup ratio and cutter tip radius on uniform bending strength design of spur gears

In the higher speed ratio and profile shifted gear drives, the maximum fillet stress in the pinion and the gear is not equal. The load-carrying capacity of the gear drives can be improved by removing this unbalanced maximum fillet stress. This paper has explained an idea to remove this unbalanced maximum fillet stress and design the spur gear drives with uniform fillet strength. This uniform fillet strength of the gear drive can be achieved by changing the tooth thickness of basic racks on the pitch lines from the standard tooth thickness (0.57 pi m) in to a non-standard one (k(gc)pi m, k(gc)not equal 0.5). The influence of gear parameters such as backup ratio, cutter tip radius and addendum modification factors on the maximum fillet stress has been analyzed through FEM with different values of tooth thickness coefficient and finally the optimum value of tooth thickness coefficient are suggested for the given spur gear drive that improve the fillet capacity in bending. (C) 2014 Elsevier Ltd.