Combustion chamber of in-cylinder direct fuel injection engine

A combustion chamber of an in-cylinder direct fuel injection spark ignition engine comprising:

• a roof having an intake valve side and an exhaust valve side,
• an intake port provided on the intake valve side of the roof at an acute angle including zero degrees upward with respect to an extended line from said exhaust valve side of the roof so as to form a tumble flow of intake air along the exhaust valve side of the roof,
• an intake valve provided in the intake port for introducing intake air into the combustion chamber,
• an exhaust valve provided at the exhaust valve side of the roof for discharging exhaust gas from the combustion chamber,
• a cylinder,
• a fuel injector disposed between the intake valve side of the roof and the exhaust valve side of the roof and inclined at a first inclination angle toward the exhaust valve side of the roof with respect to an axis of the cylinder,
• a piston provided in the cylinder, the piston having a top surface defining a piston cavity therein, the piston cavity being curved so as to reflect fuel spray injected from the fuel injector together with the tumble flow of the intake air in the direction of the intake valve side of the roof to gather reflected fuel spray at the intake valve side of the combustion chamber, and
• a single spark plug having an electrode projecting from the intake valve side of the roof toward the piston cavity so as to be exposed to the tumble flow and the fuel spray reflected by the piston cavity.