Simplified Calculation Method for the Efficiency of Involute Helical Gears

The traditional methods for the calculation of the efficiency of cylindrical gear transmissions are based on the hypotheses of constant friction coefficient and uniform load distribution along the line of contact. However, the changing rigidity of the pair of teeth along the path of contact produces a non uniform load distribution, which has significant influence on the friction losses, due to the different relative sliding at any point of the line of contact. In previous works, the authors obtained a non-uniform model of load distribution based on the minimum elastic potential criterion, which was applied to preliminary calculations of the efficiency of spur and helical gears. Recently, a new analytic formulation of the load distribution has been found. In this work, this new model of load distribution is applied to study the efficiency of involute spur gears with transverse contact ratio between 1 and 2, assuming the friction coefficient to be constant along the path of contact. Analytical expressions for the power losses due to friction, for the transmitted power and for the efficiency are presented.