Patent ID: 8627798

Claim:
A direct fuel-injection engine comprising: a piston; a cavity recessed in a central part of a top face of the piston; and a fuel injector which injects fuel into the cavity at a plurality of different injection angles (δ), the fuel injector performs main injection along a fuel-injection axes (Li 1 , Li 2 ′) oriented toward an inner wall face of the cavity when the piston is located at a first point located near a top dead center of the piston, and performs secondary injection along the fuel-injection axes (Li 1 , Li 2 ′) when the piston is located at a second position defined further away from the top dead center of the piston than the first point, wherein a shape of the inner wall face of the cavity is configured so that, with N as a whole number of 2 or more, when the cavity is divided into N virtual cavity sections by the inner wall face of the cavity and N half planes extending radially from a piston central axis (Lp) and having equal included angles, the fuel injection axes (Li 1 , Li 2 ′) are arranged correspondingly to the respective virtual cavity sections and depths of the respective virtual cavity sections are differentiated so as to correspond to the injections angles (δ) of the fuel infection axes (Li 1 , Li 2 ′), so that volumes of the virtual cavity sections are substantially equal, and when an intersection point of each fuel-injection axis (Li 1 , Li 2 ′) with the inner wall face of the cavity during the main injection is defined as a main injection collision point (P 1 m , P 2 m ′), and an intersection point of each fuel-injection axis (Li 1 , Li 2 ′) with the inner wall face of the cavity during the secondary injection is defined as a secondary injection collision point (P 1 s , P 2 s ′), a main injection collision angle (α 1 m , α 2 m ′) formed between the fuel-injection axis (Li 1 , Li 2 ′) and the inner wall face on the open end side of the cavity relative to the main injection collision point (P 1 m , P 2 m ′) is set at an obtuse angle, and a secondary injection collision angle (α 1 s , α 2 s ′) formed between the fuel-injection axis (Li 1 , Li 2 ′) and the inner wall face on the open end side of the cavity relative to the secondary injection collision point (P 1 s , P 2 s ′) is set at one of a right angle and an acute angle.