| 摘要 |
PROBLEM TO BE SOLVED: To make it difficult to damage a molded sand core at a time of opening upper and lower dies for sand core molding in a course of manufacturing a sand core inserted into a casting mold used to form an EGR passage 2.SOLUTION: A plurality of upper fins 3 and a plurality of lower fins 4 provided in an EGR passage 2 are provided adjacently at intervals of predetermined spaces (5A to 5C, 6A to 6C) in a direction orthogonal to an exhaust gas flow direction, respectively. The upper fins 3 and the lower fines 4 are made to be gradually narrower toward a protrusion direction, thereby forming inclined surfaces on both sides of each fin 3, 4 in a width direction. An inclination angle &bgr; of the inclined surface of the lower fins 4 are set greater than an inclination angle α of the inclined surface of the upper fins 3. |
