Direct fuel injection engine

摘要

The object is to provide a direct fuel injection engine equipped with a pentroof-shaped piston, the conditions under which air and fuel are mixed within a cavity being made uniform in the circumferential direction. In order to do so, when a cavity 25 recessed in a central part of a top face of a piston is divided into six virtual cavity sections 25A to 25F, each having an included angle of 60º, by six half planes X1 to X6, the volumes of the cavity sections 25A to 25F are made substantially equal, the number of cavity sections, which is six, is made equal to the number of fuel injection axes Li1 and Li2, and when viewed in a piston central axis Lp direction the bisectors of the included angles of the cavity sections 25A to 25F are made to coincide with the fuel injection axes Li1 and Li2 and, moreover, a fuel spray angle γ of the fuel injection axes Li1 and Li2 is made to coincide with the included angle. It is thereby possible to minimize unused air in the cavity 25 and make the conditions under which air and fuel are mixed uniform in the circumferential direction, thus improving the engine output and reducing harmful exhaust materials.