Minimising gear losses

The emissions of CO₂ worldwide are actually an often discussed topic. To reduce these emissions, gear boxes offer several starting points. There are possibilities for loss reduction in gears, bearings and oil supply. Load dependent gear losses provide a big potential to improve efficiency at operating points with high load. At no-load, bearings, oil viscosity and oil supply can be optimized. Aim of this study was the reduction of losses in power trains by about 30%. Main target of this project was the experimental investigation and verification of measures for loss reduction within one optimized gear box. Several approaches were combined for that. Load-dependent gear losses can be reduced by about 60% by using lowloss gears. In this case, basic idea is to concentrate the gear contact around the pitch point for lower sliding speeds. Different surface topologies were investigated. These were manufactured by deterministic laser structuring, grinding or superfinishing. Especially for running conditions at low speed power loss reduction could be achieved by very smooth superfinished tooth flank surfaces. Reduction of power losses could also be reached by applying diamond like carbon (DLC) coatings. Loss savings by DLC coatings were measured especially at higher speeds with thick surface separating lubricant films. This is caused by a thermal isolation effect of coatings.