| abstract |
A two ring piston and piston ring assembly has an upper thin steel compression ring (15) and a lower ring (17) which is thicker than the compression ring and which acts both as a compression ring and an oil control ring. The lower piston ring (17) is made of a material which is more conformable than steel, for example a plastics material, which may be reinforced. In this way, effective sealing is provided using only two piston rings, while the frictional forces between the piston (10) and an associated cylinder (18) are reduced. |