Importance

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Abstract

An internal combustion engine has at least one set of first and second cylinders (12,14), the first cylinder (12) having a larger swept volume than the second cylinder (14), and respective first and second pistons (16,18) movable in the cylinders. The pistons are coupled together such that they are movable in the cylinders in a cyclic manner at the same frequency. An air inlet (24) and an exhaust outlet open into the first cylinder and a fuel injector (34) provides fuel to the second cylinder. A combustion space (20) is also provided which communicates with both cylinders during at least a portion of the expansion stroke. The second piston has a crown (35) and a body portion (19), with the crown being spaced from and connected to the body portion and having an edge (37) which is relatively small in the axial direction compared to the distance between the crown and the body portion in the axial direction. The combustion space (20) is defined between the piston crown and body portion and a side wall (14 a) of the second cylinder. The gap (128) between the crown edge (37) and the cylinder wall (14a) serves to inhibit ingression of fuel into the combustion space (20) until towards the end of the compression stroke. Access means (30) associated with the second cylinder for admitting fuel and/or air to the second cylinder during the induction stroke comprises a port (33) opening into the second cylinder and a valve (31) for controlling port.

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First Claim