To increase the effect such as knocking suppression due to intension of a reverse squish stream at the initial time in an expansion process while preventing the interference of an air intake valve and an air exhaust valve even when a valve lift amount at an air intake top dead center is large. 吸気上死点におけるバルブリフト量が大きい場合でも吸・排気弁との干渉が生じないようにしつつ、膨張行程初期の逆スキッシュ流の強化によるノッキング抑制等の効果を高める。 - 特許庁