| 摘要 |
<p>A cylinder head (1) includes a water jacket (4) formed around an ignition plug mounting hole (5). Upper surfaces (12 to 14) of portions of the water jacket (4) between intake ports (7) and the ignition plug mounting hole (5) and between exhaust ports (8) and the ignition plug mounting hole (5) are set to be lower than upper surfaces (15 to 17) of the remaining portions of the water jacket (4) around the ignition plug mounting hole (5) to increase the rigidity. Thereby, deformation of the cylinder head (1) due to cylinder internal pressure is limited, and the stress concentration around the ignition plug mounting hole (5) due to such deformation is reduced.</p> |
