CAST HOLLOW CRANKSHAFT AND METHOD OF MANUFACTURING THE SAME

摘要

A cast hollow crankshaft for an internal-combustion engine and its manufacturing method are provided, which can reduce the weight by coring-out, can prevent bending of a core during manufacturing and floating of the core during pouring of molten metal so as to achieve precise manufacturing and provide the good productivity, and can eliminate the need of machining of oil holes. In the cast hollow crankshaft, a hollow portion has an elliptical cross section at a journal portion and/or a pin portion. Oil holes of the journal portion and the pin portion are formed by coring-out. The hollow portion also has an elliptical cross section at an arm portion. The manufacturing of this crankshaft uses a core that bends in a horizontal direction and has an elliptical cross section in which a major axis extends in a vertical direction at a journal part and/or a pin part. The hollow portion and the oil holes are formed integrally with each other by enveloped-casting with the use of the core that bends in the horizontal direction and includes a plurality of baseboard portions extending toward a mold or extending vertically toward the mold at the journal part and/or the pin part.