Engines and pistons for them

摘要

An engine in which an oil consumption and a leakage of blow-by gas can be stably reduced for a long period of time has a piston including a first land 3, a first ring groove 4, a second land 5, a second ring groove 6, a third land 7, a third ring groove 8, and a piston skirt 9 formed on a piston peripheral wall 1 in this order from the head of the piston. A first pressure ring 10 is fitted in the first ring groove 4; a second pressure ring 11 is fitted in the second ring groove 6; an oil ring 12 is fitted in the third ring groove 8. A corner at a boundary between an outer peripheral face 5a of the second land 5 and a second-land-side end face 6a of the second ring groove 6 is bevelled, with a tapered face 14 having a diameter reducing toward the second ring groove 6 to form an indentation for the suppression of variation in gas pressure in the space 17 facing the second land during upward and downward movements of the piston.