| 摘要 |
PROBLEM TO BE SOLVED: To reliably cool an area between exhaust port inlets in an upper wall of a combustion chamber. SOLUTION: In a cylinder head 1, a water jacket 21 is demarcated by a lower wall portion 4 forming the upper wall of the combustion chamber and an upper wall portion 13 separated upward thereof, inlets 6, 6 of at least two exhaust ports 3, 3 per cylinder are opened in the lower wall portion 4, and a rib 29 which is protruded downward of the upper wall portion 13 and reduce a passage in a jacket is provided above an area between the exhaust port inlets 6, 6. The flow speed of the cooling water is reliably increased at the position between the exhaust port inlets to reliably cool the area between the exhaust port inlets in the upper wall of the combustion chamber.
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