Global Synthesis Of Speed Increasing Spiral Bevel And Hypoid Gears

The public experience for design, manufacturing and application of spiral bevel and hypoid gears mainly considers the speed reducing case. The works specifically aimed at the speed increasing case or even referred to the comparison of these two different cases are seldom reported in the literature. For the same drive sides of a gear pair, the significant differences between speed increasing and reducing cases are: (a) the direction of friction reverses and (b) the approach contact and the recess contact interchange. These differences can have an effect on gear performance and their adjustment needs the full control of the entire contact point paths on gear tooth surfaces. The current design of spiral bevel and hypoid gears is usually based on the local synthesis approach, proposed by Litvin, which is restricted to one single (mean) point and cannot ensure the contact performance along the entire contact point path, resulting in uncontrolled contact ellipses with different sizes and unavoidable transmission errors. For the design of speed increasing spiral bevel and hypoid gears, the global synthesis approach proposed by the authors is employed in this paper. By this approach, the entire contact point path and the contact performance (instantaneous transmission ratio and instantaneous relative curvatures) for each point of the entire contact point path can be directly predesigned to achieve any shape of motion graph and any type of contact pattern. The desired tooth surfaces can be generated on five-axis CNC machines, and the corresponding machine settings can make full use of the capability of modern CNC machines. By dynamic contact analysis, the design parameters of global synthesis for speed increasing spiral bevel and hypoid gears can be verified and optimized further. For illustration and demonstration, an example of face milled spiral bevel gears for speed increasing application will be provided. The meshing difference between speed reducing and speed increasing, and the improved speed increasing design by global synthesis will also be present. The global synthesis approach can also be used for the design and manufacturing of other gears, such as face gears and worm gears.