Combustion chamber shape of direct injection type diesel engine

摘要

An object of the present invention is to provide a combustion chamber shape of a direct injection type diesel engine in which a black smoke generation amount can be suppressed during no-load operation while suppressing NOx and fuel consumption. The combustion chamber 5 is formed in a recessed shape in a piston top wall 3 and injecting fuel at a predetermined nozzle hole angle alpha into the combustion chamber 5 from a nozzle hole 20 of a fuel injection valve having a nozzle hole center O1 substantially on a cylinder center line. A wall face of the combustion chamber 5 includes: a conical mountain portion 12 formed at a central portion in the combustion chamber and having such a slope angle and skirt end diameter D2 that fuel spray does not collide with the mountain portion; a slope portion 14 that inclines downward and outward from a skirt end of the mountain portion 12 at a smaller angle than the slope angle of the mountain portion 12 and with which the fuel spray collides; and a saucer portion 15 which rises in an arc shape from an outer peripheral end of the slope portion 14 to reach an outer peripheral end of the combustion chamber and with which the fuel spray collides.