Allocation of Gear Tolerances to Minimize Gearbox Noise Variability

We consider a gearbox fitted out with a single helical gear and a housing with only one elastic face which radiates noise. For a gearbox manufactured in large number, a high noise level variability can result from variability of geometry faults induced by tolerances on each gear design parameter. In this paper, this noise variability is assumed to be induced by only tolerances on two gear design parameters: profile and helix angle. Two main issues are addressed here: the first goal is to rank the influences of each geometrical parameter and to analyze their interaction on the total radiated sound power with a full factorial experiments and a variance analysis. The second issue consists of an estimation of the mean value and the standard deviation for noise level using a modified Taguchi's method. For two quality classes of the gear, the obtained results reveal a predominance of helix angle error on the variability of the radiated sound power. Furthermore, interaction between the two studied parameters has been demonstrated.