Ultra low device volume piston system

A piston and ring assembly operative within a cylinder bore of an internal combustion engine, the piston having a crown and an annular side wall for movement along the bore wall, comprising:

• (a) walls defining one or more grooves in said side wall each with a step;
• (b) a pair of superimposed mating split compression rings in each groove, each effective to exert a resilient circumferential sealing force against said bore wall but together are effective to act in unison as a result of friction therebetween, said rings being sized to permit said upper ring to engage both said step and lower ring when said lower ring is sealing against a side of said groove;
• (c) an elastomeric ring acting between only said step and lower ring to resiliently bias said lower ring against said bore wall at temperatures as low as -20.degree. F. and to thermally expand as the temperature rises up to as high as 300.degree. F. to augment the sealing force of said lower ring;
• and
• (d) solid film lubricant coating said groove and non-mating surfaces of said rings to insure low friction engagement therebetween, said solid film lubricant being at least two of graphite, MoS.sub.2 and BN.

An ultra low crevice volume piston and ring assembly operative within a cylinder bore wall, the piston having a crown with a depending annular side wall for movement along the bore wall, comprising:

• (a) walls defining one or more annular grooves in said side wall each having at least on step;
• (b) at least two split compression rings in each of said grooves having split ends, each effective to exert a resilient circumferential sealing force against said bore wall, said rings having mating surfaces superimposed one upon another to act in unison to provide sealing between said piston and bore wall, the split ends of said rings being out of superimposed alignment, the lower of said rings having a thickness generally commensurate with the height of the step to permit the upper ring to engage both said step and lower ring during sealing;
• (c) an elastomer ring associated with each pair of compression rings and operative to resilient bias only the lower of said rings against said bore wall;
• and
• (d) a solid film lubricant coating said groove and the non-mating surfaces of said superimposed rings.