Patent ID: 7231901

Claim:
A direct-injection engine comprising: two intake valves and two exhaust valves provided at a pent roof type a cylinder head; a spark plug provided at the substantial center of said cylinder head; and a fuel injection valve for directly injecting a fuel into a cylinder, and which is installed on the intake valve side with respect to the center of said cylinder head, said engine is further configured to performs stratified combustion by injecting a fuel at a compression stroke in a state where a tumble flow is formed in the cylinder, wherein said engine further comprising a piston having a piston crown with a recessed curved surface and a pair of arc-shaped grooves, wherein said recessed curved surface is deeply recessed at the vicinity immediately below said spark plug on said piston crown, and said pair of arc-shaped grooves are formed on said recessed curved surface, located on the intake valve side with respect to the center of said piston crown, disposed so as to symmetric with respect to a piston diameter line linking between a point directly below said fuel injection valve and the center of said piston crown, and extended from the circumference side of said piston crown toward the center thereof, wherein said fuel injection valve is configured to form a first concentrated fuel spray band directed to said spark plug and a second concentrated fuel spray bands directed to said arc-shaped grooves.