Abstract
Keywords - bearing seal, oil pump, CO2 emissions, oil flow, crankshaft
A newly developed, patented crankshaft seal makes it possible to reduce the oil flow rate through the main bearing clearance and increase oil pressure. This means that the size and weight of oil pumps can be reduced and power input cut by over 200 W, which in turn means lower fuel consumption and fewer CO2 emissions.
At high operating temperatures, differences in the coefficients of thermal expansion of light metal engine blocks and steel crankshafts cause large bearing gaps to open up and the viscosity of engine oil to drop. In the past, in order to provide the larger oil volume flow rates needed both for these large gaps and for hot idle, and to ensure adequate lubrication, pumps were designed with this critical operating situation in mind. As a result, either pumps that were too large for normal operation or costly variable capacity pumps were used.
The new PTFE-compound crankshaft bearing seals are inserted into grooves to the left and right of the oil groove in the upper bearing shell, which is subjected to a smaller load. The serviceability of these crankshaft bearing seals has been verified on a component test bench with a bearing diameter of 48 mm. In these tests, the oil volume flow rate was reduced by up to 55 percent. The new crankshaft bearing seals were also tested in fired 1.1- and 1.6-liter engines. Thanks to the crankshaft bearing seals, the total oil volume flow rate was reduced by up to 20 percent and the total oil pressure increased by 8 percent.
As a result of the reduced oil volume flow rate and the increased oil pressure, smaller oil pump designs can now be used. By using smaller oil pumps with lower operating energy input and taking into account the low frictional losses of the sealing elements, it is realistic to say that 200 W per engine can be saved. This potential saving is the result not only of minimized throttling losses, but also of the reduction in pump performance, which no longer has to be designed for the hot idle operating point as it is today.
This crankshaft bearing seal is used in sealing packages that are specially designed to minimize friction, cut fuel consumption, and reduce CO2 emissions.