To provide an internal combustion engine in which cooling oil jetted from a piston jet to an up-and-down stroking piston reaches a ceiling reverse surface as long as possible without being blocked by reinforcing walls to efficiently cool the piston.
The piston 23 includes a pair of skirt parts 52 suspended down from a ceiling surface 51, a pair of connection walls 53 connecting the pair of skirt parts 52 to each other, and the pair of reinforcing walls 56 connecting the pair of connection walls 53 to each other between each skirt part 52 and each piston pin boss 54. The reinforcing walls 56 are each bridge-shaped with an opening portion 60 provided between the ceiling reverse surface 58 and itself. At the top dead center position and the bottom dead center position of the piston 23, the piston jet 28 jets the cooling oil from a plurality of jet orifices 71, 72, 73 in different directions to reach the ceiling reverse surface 58 through the opening portions 60 of the reinforcing walls 56.
TANABE KAZUYA
INO SATORU
NOMURA AKIHITO
Shinya Motoyama