| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston capable of suppressing oil consumption and blow-by gas, and reducing coagulation which a pressure ring holds by itself and a sudden rise of blow-by gas amount caused by fluttering under light load high rotation. SOLUTION: A straight abutment is used for a top ring 22, and an annular groove 34 having a wedge cross section which is diametrically increased in the size thereof near the top ring groove and downwardly decreased in a size is formed in a second land 31 under a top land groove. The straight abutment positively releases combustion gas in a high pressure side to a low pressure side, so that oil stored in the second land 31 is descended to return to an oil pan. Consequently, a piston capable of reducing both of oil consumption and blow-by gas can be obtained. Coagulation or a sudden rise of the blow-by gas can be prevented by using the straight abutment for the top ring 22.
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