Engine and method for improved crankcase fatigue strength with fracture-split main bearing caps

摘要

The present invention provides reduced fatigue stress levels in a stressed area of an engine crankcase by lowering the outer edges of the crankshaft bearing cap fracture-split lines without changing the central axis location of the crankshaft in the crankcase. This is accomplished by causing the fracture-split lines of the bearing caps to angle downward from the horizontal plane of the crankshaft axis to a slightly lower position at the outer edges of the bearing caps. This lowers the outer edges of the bearing caps sufficiently to allow larger radii to be formed on the lateral connectors of the crankcase support webs with the adjacent sidewalls of the crankcase. Accordingly, the fatigue stress levels in the crankcase web members are reduced without requiring a significant change in the crankcase dimensions.