GLE-03 MODEL OF EFFICIENCY OF HIGH TRANSVERSE CONTACT RATIO SPUR GEARS(GEAR LUBRICATION AND EFFICIENCY)

Abstract

The traditional methods for computation 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. This load distribution was applied to compute the efficiency of spur and helical gears, resulting in slightly greater values of the efficiency than those obtained if the load distribution along the line of contact is assumed to be uniform. In this work, this non-uniform model of load distribution is applied to study the efficiency of involute spur gears with transverse contact ratio greater than 2 (named high transverse contact ratio gears). In this kind of gear transmissions, the load is shared among two or three pairs of teeth, reducing significantly the load, and consequently the friction losses, at the contact points in which the relative sliding is greater. Analytical expressions for the power losses due to friction, for the transmitted power and for the efficiency are presented, as well as a study of the influence of some transmission parameters (as the gear ratio, the pressure angle, etc.) on the efficiency.