If torque conversion with high gear ratio, compact installation space and 90-degree axis-crossing angle is needed, often worm gears are used. Due to their high power density and sliding speeds within the tooth contact, frictional heat and thermal stresses are higher compared to helical, bevel and hypoid gears, and thus the thermal load capacity of worm gears is lower.

In the selection of lubricating greases for plastic worm gears, the user needs to know the influence of each grease constituent on the tribological performance in order to choose the appropriate lubricant. In this work, the effect of NLGI class, viscosity, base oil and thickener type are investigated separately regarding the efficiency and temperature close to the tribocontact. With the help of this contribution the user understands the effect of each parameter and learns about the potentially reachable efficiency and temperature ranges.

In this work a physically based method for the tribological investigation of worm gears is presented.