International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Scuffing is a spontaneous gear failure mechanism resulting in a disrupted surface. Scuffed gears are more sensitive to dynamic excitation and friction. Besides the lubricant and the material, the scuffing load capacity is mainly dependent on the gear geometry. High contact ratio gears exhibit a lower load carrying capacity due to an increased dissipation of frictional heat in the outer mesh positions. In this paper this phenomenon is addressed with experiments and simulative analysis. Based on these works, recommendations for adequate profile modifications are derived to maximize the load carrying capacity regarding scuffing of high contact ratio gears.

Crossed helical gear units are used in many applications. They range from actuators and power take-offs to household appliances and functions in automotive engineering and production processes. The design is often based on a material combination of steel-worm and plastic-wheel. Based on the research on high efficient plastic materials, they already replace a large number of steel applications. In order to improve the load capacity and performance of crossed helical gears, they must be understood in detail. This article deals with a new calculation method to design optimized flank geometries and to investigate them with regard to their properties in gear mesh. In addition, the deformation and the load distribution in the gear mesh will be examined in more detail. The observation is made in the normal section. In this section, all relevant influences on the performance of the gearing can be analyzed. The pressure and deformation are verified with the help of an FEM-simulations.

The contact pattern and contact line calculation is an essential part of the design of worm gears. The existing calculation algorithms are based on the law of gearing. For this reason, cases like meshing interferences can only be analysed to a limited extent. The simulation of the hobbing process of enveloping wormwheels, introduced here, makes it possible to generate any wheel flank precisely. For the contact pattern calculation, one wheel flank is generated from the cutter geometry and one from the worm geometry. These two generated flanks are brought into contact. For each flank coordinate, the distance to the opposite flank is obtained. The graphical
application of this distance over the wheel coordinates results in a contour diagram that is known as the contact pattern. The contact linecalculation of worm gears also shows on which part of the flanks power is transmitted at a certain rotational position. For this calculation, the wheel flank generated from the cutter is brought into contact with the worm flank at any angular positions.