Definition of a coefficient to evaluate a moving contact pattern in planetary gearboxes

Planetary gearboxes are often used for their high power density. Designs featuring a rotating carrier are popular because of their high gear ratio and potentially good efficiency. Especially in bigger constructions as in wind turbine gearboxes, it has been observed that the contact pattern moves in the width direction while the carrier rotates. This may lead to higher damage on the tooth flanks or reduced lifetime of the planet bearings underneath the mesh due to oscillating loads. The main influences on this phenomenon have yet to be investigated and no characteristic value has been defined to describe the moving contact pattern. It is only with this type of coefficient that the complex results of contact analysis can be evaluated clearly so that disadvantageous constructions can be distinguished from better ones. Therefore in this paper a coefficient to evaluate moving contact pattern is defined and used in a theoretical study about the influence of a radially displaced sun shaft on the contact pattern movement.