DIRECT FUEL-INJECTION ENGINE

摘要

A direct fuel-injection engine equipped with a pent-roof type piston, wherein the cross-section shape, the central axis (Lp) of the piston included, of a cavity recessed in the center of the piston having the height of the top surface changing in the circumferential direction is basically set identical at each position in the circumferential direction (refer to the chained line). The size of each cross-section shape of the cavity does not agree with each other in a region closer to the central axis (Lp) side of the piston than intersections (el, d1) near the fuel injection point (Oinj). Therefore, in order to compensate for the disagreement of the size, at a cross-section remote from the direction of a piston pin, a correction is made from the cross-section shape shown by the chained line to the shape shown by a solid line in an enlarging direction, and hence the size of the cross-section shape is made more uniform at each position in the circumferential direction of the cavity. Consequently, the mixing state of fuel and air is made uniform to enhance the engine output and reduce the noxious substances in the exhaust gas.