Spiral Bevel Gears and Hypoid Gears

Abstract

In this chapter, the geometry of the main types of spiral bevel gears is first defined and considerations about the spiral angle are made. The corresponding cutting processes are then briefly described, and the generation of active flank surfaces of the teeth is defined. The main geometrical quantities of these gears are then determined as well as those concerning the equivalent cylindrical gears obtained using the Tredgold approximation. The load analysis of spiral bevel gears is then performed, also defining the thrust characteristic on shafts and bearings. Subsequently, the concepts concerning these gears are extended to the most general gearing case represented by the hypoid gears. The fundamentals of these gears are then provided, based on the kinematics already described for the hyperboloid gears. Two approaches to theoretical analysis are described, the first of more limited validity, and the second more general, but both capable to provide reliable results in terms of geometric and kinematic characteristics of these types of gears. The load analysis is extended to these types of gears, and some indications on the design choices inherent to them to improve their efficiency are provided. Finally, the unified ISO procedure, which allow us to calculate the geometric quantities of spiral bevel and hypoid gears is summarized.