| 摘要 |
PROBLEM TO BE SOLVED: To increase combustion efficiency and improve emission of exhaust gas by forming a surface shape of a swelling part into a projecting partial spherical face shape in a diesel engine in which a cavity which becomes narrower in an upper part is formed on a top face of a piston and the swelling part protrudes in a central part on a bottom face of the cavity. SOLUTION: In a direct injection type diesel engine E, a tip part faces a cavity 3 formed on a top face 2a of a piston 2 fitted in a cylinder bore 1, and a fuel injector 10 is provided in a cylinder head 21. In this case, the cavity 3 on the piston top face 2a is formed in such a way that it becomes narrower in an upper part, and a swelling part 4 of which surface shape is formed into a projecting partial spherical face protrudes in a central part on a bottom face of the cavity 3. Consequently, it is possible to leave the minimum required amount of air in the central part of the cavity 3, ensure a large quantity of air in a peripheral part, and prevent an increase of NOx by supplying a small amount of air in the central part of the cavity for combustion at the time of light, load. |
