METHOD OF MANUFACTURING A CRANKSHAFT FROM A HIGH SHRINK METAL ALLOY

摘要

A crankshaft includes a pin bearing journal, and a counterweight. The pin bearing journal defines a hollow pin core. The hollow pin core includes a first pin core section and a second pin core section, and an enlarged central section disposed between the first pin core section and the second pin core section. The first and second pin core sections each define a cross section having a first and second cross sectional area respectively, and the enlarged central section defines a third cross section defining a third cross sectional area, with the third cross sectional area larger than the first and second cross sectional areas. An isolation window extends through the counterweight. The crankshaft is cast from a high shrink steel alloy having a shrinkage factor equal to or greater than 1%. The enlarged central section and the isolation window improve the castability of the high shrink steel alloy.

主权项

1. A method of manufacturing a crankshaft, the method comprising:
positioning a casting core within a cavity of a mold having a first half and a second half forming an exterior shape of the crankshaft, wherein the exterior shape of the crankshaft includes a pin bearing journal, a main bearing journal, a first crank arm and a second crank arm supporting the pin bearing journal, and a counterweight extending radially outward from the second crank arm relative to a crank axis; casting the crankshaft by introducing a molten metal alloy into the cavity to form the crankshaft, wherein the molten metal alloy flows into the cavity and around the casting core to form a hollow pin core extending through the first crank arm, the pin bearing journal and the second crank arm, a hollow main core extending through the second crank arm and into the main bearing journal, and an isolation window extending at least partially through the counterweight, wherein the isolation window is disposed radially between an outer radial edge of the counterweight and the second crank arm; wherein the hollow pin core is shaped to include a first pin core section extending through the first crank arm, a second pin core section extending through the second crank arm, and an enlarged central section extending through the pin bearing journal between the first pin core section and the second pin core section, with the enlarged central section sized larger than the first pin core section and the second pin core section respectively to minimize a cross sectional thickness of the metal alloy between a radially inner surface of the hollow pin core and a bearing surface of the pin bearing journal, without interfering with the main bearing journal; cooling the molten metal alloy in the cavity around the casting core to solidify the metal alloy forming the crankshaft; and removing the casting core from the cast crankshaft; wherein the metal alloy is a high shrink alloy having a shrinkage factor equal to or greater than 1% during cooling of the molten metal alloy.