Determination and optimization of the contact pattern of worm gears

The load capacity of worm gears is mainly influenced by the size and the position of the contact pattern. A new method was developed that allows for the determination and optimization of the idle and load contact patterns in the design stage. By this method, the contours of worm and worm wheel are simulated point by point, taking into account the boundary conditions of the manufacturing process. The idle contact pattern can be derived from these contours by pairing them together in such a way that the assembly deviations define the position of worm and wheel. The load contact pattern can be determined from the idle contact pattern by adding the deflections of the teeth and gear bodies and the elastic deformations of the bearings and the housing. This procedure can also be used for automated optimization of the contact pattern, so optimum machine settings can be found without a trial manufacturing. Comparisons of these theoretical contact patterns with real contact patterns of gears in practice showed a good correlation.