| 摘要 |
PROBLEM TO BE SOLVED: To prevent damping of swirl, to suppress outflow of fuel spray to the outside of a cavity as transfer ability of fuel spray is ensured, and to suppress the generation of smoke and accumulation of carbon, in a spark ignition type direct injection engine where a cavity is formed in a manner to be offset to the suction side. SOLUTION: A step is formed between a part (U) on the side situated upper stream of a swirl and a part (L) on the side situated downstream of a swirl of the crown surface of a piston in a pent roof shape having a cavity 13 offset to the suction side. A side wall part 13a on the side situated upper stream of a swirl at the peripheral edge on the exhaust side of the cavity 13 is raised, a squish clearance of the part (U) on the side situated upper stream is approximately uniformly decreased in the central direction of a cylinder, and a clearance of the part (L) on the side situated downstream is gradually increased in the central direction of a cylinder. Outflow of fuel spray is suppressed by the height of a side wall part 13a on the side situated upper stream of a swirl and damping of a swirl due to a squish flow on the side situated downstream of a swirl is suppressed.
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