Patent ID: 8448692

Claim:
A gravity casting method for integrally gravity casting a turbine housing having a twin scroll unit and a bypass unit and an exhaust manifold having a plurality of exhaust runner units, the gravity casting method comprising: forming a first mold; forming a second mold combined with the first mold configured to form a cavity of the turbine housing so that an end portion of the twin scroll unit is upward disposed on a lower inner side between the first mold and the second mold; forming an exhaust runner mold disposed on an upper side between the first mold and the second mold, configured to form a cavity of the exhaust manifold connected to the cavity of the turbine housing so that the exhaust runner units are disposed in parallel in a width direction between the first mold and the exhaust runner mold and also to connect to an exhaust manifold-side riser over the cavity of the exhaust manifold, and configured to form a sprue along with an injection port for injecting molten metal into the cavity of the turbine housing between the second mold and the exhaust runner mold and also to form a turbine housing-side riser based on the end portion of the twin scroll unit; forming a twin scroll mold installed between the first mold and the second mold so that the twin scroll mold forms a lower portion of the cavity of the turbine housing; forming a twin scroll auxiliary mold installed between the first mold and the twin scroll mold and between the exhaust runner mold and the twin scroll mold so that the twin scroll auxiliary mold forms one side of the cavity of the turbine housing; forming a core support mold installed between the first mold and the second mold on the other side of the cavity of the turbine housing; forming a turbine housing-side riser based on the end portion of the twin scroll unit within the first mold and the second mold in a state where a cavity of the turbine housing is formed so that the end portion of the twin scroll unit which is an outlet of the turbine housing is upward disposed; and injecting molten metal into the injection part.