PURPOSE: To make sure of sealability despite simplicity in a manufacturing process, by forming a piston ring with a plastic member, and installing a metallic backup ring, which gives force in an expanding direction to this piston ring almost over the whole circumference, in the inner circumferential surface.
CONSTITUTION: Since a piston ring 13 is made up of a plastic member having elasticity such as, for example, a Teflon (fluorpacarbon polymers) compound or the like the outer circumferential surface 13b is subjected to deformation and wear after the form of an inner circumferential wall of a cylinder bore 2 and forcedly pressed by expanding force of a backup ring 17. And, it is almost uniformly pressed whereby the occurrence of partial damage in the piston ring 13 is chaecked. In addition, the plastic member is lightweight so that the promotion of lightweightiness in a reciprocating part is attainable, thus fluttering of the ring 13 inside a piston ring groove 11 attributable to reciprocation of a piston 3 is hard to occur, and with this fact, a leak of blow-by gas and so on becomes reduced. Therefore, a manufacturing process is simple and positive sealability is enjoyed an, what is more excellent in durability.
ISHIKAWA MITSURU
NAKAMURA KENICHI
OKADA KEIJI
NAKAMORI MASAHARU
SHIOZAKI TOMOO
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