Gear Geometry for Reduced and Robust Transmission Error and Gearbox Noise

Gear geometry was optimized for decreased transmission error in order to reduce gearbox noise. Robustness with respect to gear deviations and varying torque was considered in order to find a gear geometry giving low noise in the appropriate torque interval despite deviations from the nominal geometry due to manufacturing tolerances. Static and dynamic transmission error as well as noise and housing vibration were measured using a gear test rig. The correlation between dynamic transmission error, housing vibration, and noise was investigated. In speed sweeps from 500 to 2500 rpm at constant torque, no correlation was found between dynamic transmission error and noise. Static transmission error seems to be the excitation of dynamic transmission error as well as housing vibration and noise, but different natural frequencies for different degrees of freedom of the dynamic system consisting of gears shafts, bearings, and housing lead to lack of correlation between dynamic transmission error and noise. Introduction Noise from gearboxes can be a problem for vehicles such as passenger cars, buses, trains, and trucks and for construction machines such as wheel loaders. This noise can be reduced by optimizing the macroand microgeometry of a gear pair. The macrogeometry involves parameters such as the number of teeth, module, face width, pressure angle, and helix angle, whereas the microgeometry involves modifications to the gear flank, for example tip relief and helix angle crowning. When designing a gear pair, compromises are necessary because some of the characteristics of a gear pair are contradictory. For example, different gear macrogeometry factors influence the gear tooth bending strength, noise, efficiency, size, weight, cost, scoring resistance, and pitting resistance. The characteristics of the gear pair are also affected by parameters like the type and viscosity of the oil used, the operating temperature, and deflections of shafts, bearings, and housing [1].