Direct fuel injection engine

摘要

A direct fuel injection engine is provided that is capable of forming an appropriate stratified fuel-air mixture and conducting good stratified combustion inside the combustion chamber (1) of the engine. The engine has a fuel injection valve (11) that is arranged at an upper surface of the combustion chamber (1) on or near the center reciprocation axis of the piston (4) and oriented such that the injection center axis (15) of the fuel stream injected therefrom is slanted with respect to the center reciprocation axis of the piston (4). An outer cavity (17) and an inner cavity (18) are provided in the top surface of the piston (4) in an overlapping arrangement such that the inner cavity (18) is in the outer cavity (17). Each cavity has a cavity center axis that runs parallel to the center reciprocation axis of the piston (4) and intersects the top surface of the piston (4) at a cavity center point (17a, 18a). The outer cavity (17) is arranged such that the cavity center point (17a) of the outer cavity (17) passes through the injection center axis (15) of the fuel stream injected from the fuel injection valve (11) when the piston (4) is in a position within the range of fuel injection timings at which a stratified fuel-air mixture is formed chiefly by the outer cavity (17). The inner cavity (18) is arranged such that the cavity center point 18a of the inner cavity (18) passes through the injection center axis (15) of the fuel stream injected from the fuel injection valve (11) when the piston (4) is in a position within the range of fuel injection timings at which a stratified fuel-air mixture is formed chiefly by the inner cavity (18).