Importance

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Abstract

An internal combustion engine has first and second cylinders (12, 14), the first cylinder (12) having a larger swept volume than the second cylinder (14) and the second cylinder being formed in the crown of the first cylinder. First and second pistons (16, 18) are reciprocable respectively in the first and second cylinders (12, 14), the second piston (18) being formed as a protrusion on the crown of the first piston (16). The first cylinder has an air inlet (25) and an exhaust outlet (27) whilst a first fuel source (34) provides fuel to the second cylinder (14). The second piston has a crown (35) which is spaced from and connected to the crown (36) of the first piston and which has an edge (37) which is relatively thin in the axial direction compared to the spacing of the first piston crown from the second piston crown. This defines a combustion space (20) between the piston crowns and a side wall (14a) of the second cylinder (14) when the pistons are substantially at the inner dead center position. The combustion space (20) communicates with both cylinders (12,14) during part of the expansion stroke. A spark plug (52) is provided communicating with the combustion space. The ignition process is started with a spark and allowed to continue by compression ignition. After the spark ignition process begins, the flame raises the pressure and temperature of the gas in the combustion space sufficiently to cause compression-ignition of the remainder of the vaporized fuel as it ingresses into the combustion space under the action of the smaller piston and mixes with more air.

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First Claim