Patent ID: 7438044

Claim:
A small diesel engine comprising: a small cylinder having a cylinder head defining a pre-combustion chamber therein, the pre-combustion chamber being in the shape of a broadened shallow bowl; a piston reciprocally mounted within said cylinder, the piston having a piston crown in the shape of a dome for protruding within the bowl-shaped pre-combustion chamber during a combustion event before and after top dead center, the piston protruding so as to enter the pre-combustion chamber; wherein the piston is further shaped such that the opening between the pre-combustion chamber and the cylinder head progressively enlarges when the piston is moving down after the top of its stroke so as to provide a variable geometry combustion chamber; a fuel injector for injecting fuel spray plumes into said pre-combustion chamber to facilitate the combustion process during the downward stroke of the piston; and a glow plug in the cylinder head and protruding into the bowl-shaped pre-combustion chamber in close proximity to an injected fuel spray plume but not in direct contact with the injected fuel to thereby facilitate fuel ignition at moderate compression ratios during engine starting, thereby facilitating use of a small cylinder displacement; wherein a minimal squish area is defined between the bowl-shaped chamber and edges of the piston as the piston approaches top dead center.