| 摘要 |
PURPOSE:To facilitate removal of sand after completion of casting, by casting core for an opening to form one body with the core of the exhaust port and forming a heat-insulating space surrounding the outside of port liner. CONSTITUTION:Port liner 7 in the form of a double-sleeve structure is formed in exhaust port 4 by way of casting, and a heat-insulating space 10 is formed between liners 7a and 7b. In order to achieve casting of port liner 7 and to form heat-insulating space 10, an opening 12 for inserting valve guide 6 is pre-formed in port liner 7 in the form of a double-sleeve structure, and port core 13 and jacket core 14 for forming heat-insulating space 10 are fixed respectively on the inside and on the outside of port liner 7 by way of burning. The jacket core 14 is removed at opposite end portions of port liner 7 for forming supports 15a, 1b after casting. These portions serve as outlet port for discharging core and therefrom, so that removal of core sand can be facilitated greatly. |
