Patent ID: 7895986

Claim:
A diesel engine comprising: a cavity provided on a top surface of a piston of said engine, the cavity having a concave cross section along a moving direction of said piston, and forming a combustion chamber; and a fuel injection nozzle located such that the fuel injection nozzle is facing a substantially center portion of said combustion chamber and is configured to inject fuel to a side wall of said combustion chamber; wherein said concave cross section has a shape in which a center of a bottom portion is raised up toward an opening of said concave cross section, the center being located along a radial direction of said piston: wherein said fuel injection nozzle has a plurality of injection hole groups, each group having two injection holes respectively; wherein a distance between said two injection holes, an angle between longitudinal axes of said two injection holes and an angle between horizontal axes of said two injection holes of each of said injection hole groups are each set such that fuel sprays injected from said two injection holes will form a single fuel spray cloud for each of the injection hole groups after the fuel sprays collide with a wall of said combustion chamber, and such that the distance between collision points of the fuel sprays injected from said two injection holes at a time of their collision with said wall of said combustion chamber will be in a predetermined range in which a penetration force of said fuel spray cloud along a longitudinal direction of said combustion chamber received after collision with said wall of said combustion chamber is at or near a predetermined maximum value; and wherein said predetermined range is a range in which said penetration force of said fuel spray cloud along the longitudinal direction of said combustion chamber will be 120% or more as large as a penetration force of said fuel spray cloud along a lateral direction of said combustion chamber.