Dip lubrication of gears with low immersion depth

The lubricant in transmissions has two major duties: a load carrying lubricant film shall be built up between the flanks of the gears in order to reduce friction and wear, and the generated heat shall be dissipated. In contrast, there are power losses because of the oil drag of the rotating pails in the oil sump. For the reduction of parasitic losses a general trend in automotive applications is the reduction of the oil level in sump lubricated transmissions. Bulk temperatures of pinion and gear increase with reduced immersion depth. A higher bulk temperature is observed with increasing rotational speed, load, and oil temperature. Flank damages are activated by insufficient lubrication conditions. A low oil film thickness results from high bulk temperatures and thus a decreased oil viscosity as it happens with insufficient heat dissipation. The no-load losses decrease with decreasing immersion depth, as expected, especially at high speed. This is an abstract of a paper presented at the 15th International Colloquium Tribology - Automotive and Industrial Lubrication (Ostfildern, Germany 1/17-19/2006).