| 摘要 |
PURPOSE: A cooling structure of a cylinder head is provided to improve processibility by avoiding the interference of a groove with an exhaust port core and to reduce thermal loads to the exhaust port by connecting an upper water jacket with the groove via a drill hole. CONSTITUTION: Exhaust ports(2,3) and intake ports(4,5) are formed in a cylinder head. A mounting hole(7) for fitting a fuel injection nozzle is formed in the cylinder head facing the center of a combustion chamber. Water jackets(8,9) for cooling are formed in the upper portion of the exhaust and intake ports. A groove(10) whose bottom is exposed is formed in the lower portion of the cylinder head to surround the exhaust ports. A cooling water flow hole(13) is communicated with the groove to flow cooling water from a water jacket(12) of a cylinder block(11) and with the upper water jacket via a drill hole(14). As the groove is spaced apart from the exhaust port, the interference with an exhaust port core in insertion is avoided.
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