Patent ID: 7347181

Claim:
A direct injection spark ignition engine comprising: a cylinder; a piston which is reciprocally movably arranged in said cylinder and defines with said cylinder a combustion chamber; a fuel injector arranged at one side of a center axis of said cylinder for directly injecting fuel into said combustion chamber; and a smoothly continuous lowered recess formed on a top surface of said piston capable of receiving at least part of fuel injected from said injector, said recess having a first cross section along a first plane including said cylinder center axis and a nozzle end of said injector, said first recess cross section having first and second lower contours substantially of arc shape with its center above said recess, said first and second contours being smoothly connected through a lowest point of said first recess cross section, said first lower contour being located at said one side of said cylinder center axis, said second lower contour being located at the other side of said cylinder center axis, and said first contour having a larger radius than a radius of said second contour.