Combustion Chamber Structure for Diesel Engine

A combustion chamber structure in a diesel engine including a piston having a crown surface formed with a reentrant cavity, and a multi-hole fuel injection nozzle disposed on a center line of the cavity, wherein

• a lip portion defining a minimum diameter in an entrance portion of the cavity is located below an opening brim,
• a spray center axial line extending from a spray point of the fuel injection nozzle is oriented to point to a position slightly below the lip portion at a position at or near a top dead center,
• a height position of a top of a raised portion formed centrally in a bottom of the cavity is set substantially equal to a height position of the lip portion, and
• a conical surface of the raised portion is formed at one of an angle pointing to the spray point of the fuel injection nozzle at a piston position at the top dead center, and an angle steeper than the angle pointing to the spray point, to form a region where an excess air rate is highest, on a center line of the raised portion.