A piston ring structure includes a piston ring having an opening, and at least one positioning clip mounted on the opening of the piston ring. The at least one positioning clip is provided with two insertion slots corresponding to two sides of the opening. The at least one positioning clip is provided with a spacing rib located between the insertion slots. Each of the insertion slots of the at least one positioning clip are mounted on each of the two sides of the opening of the piston ring, with each of the two sides of the opening being inserted into each of the insertion slots of the at least one positioning clip.

Embodiments of a combination piston and piston ring reduce the volume of a crevice defined between the circumferential wall of a cylinder and a portion of the outer wall of a piston within the cylinder, the portion extending down from the top of the piston. The combination piston and piston ring is configured such that pressurized fluid within the cylinder reliably urges a radial face of the piston ring to sealingly engage the circumferential wall of the cylinder, even as the piston reciprocates within the cylinder.

Embodiments of a combination piston and piston ring reduce the volume of a crevice defined between the circumferential wall of a cylinder and a portion of the outer wall of a piston within the cylinder, the portion extending down from the top of the piston. The combination piston and piston ring is configured such that pressurized fluid within the cylinder reliably urges a radial face of the piston ring to sealingly engage the circumferential wall of the cylinder, even as the piston reciprocates within the cylinder.

A piston ring which is resinous includes an annular main body portion having an inner peripheral surface and an outer peripheral surface facing each other and a pair of side surfaces interconnecting the inner peripheral surface and the outer peripheral surface and a joint portion 3 formed in the main body portion. The joint portion has a step shape when viewed from at least one of the pair of side surfaces and the outer peripheral surface. The outer peripheral surface has a tapered surface having an outer diameter increasing from a side of one side surface of the pair of side surfaces of the main body portion toward a side of the other side surface.

A piston ring which is resinous includes an annular main body portion having an inner peripheral surface and an outer peripheral surface facing each other and a pair of side surfaces interconnecting the inner peripheral surface and the outer peripheral surface and a joint portion 3 formed in the main body portion. The joint portion has a step shape when viewed from at least one of the pair of side surfaces and the outer peripheral surface. The outer peripheral surface has a tapered surface having an outer diameter increasing from a side of one side surface of the pair of side surfaces of the main body portion toward a side of the other side surface.

In ported engine constructions, cooling of piston crowns and cylinder liners results in reduction or elimination of bore/liner distortions, thus ensuring circularity of the bore/piston interface throughout engine operation. Consequently, the need for heavily-tensioned piston rings is eliminated. Such engine constructions incorporate annular low-tension compression seals on the pistons, which substantially reduce port bridge wear during all phases of engine operation while also limiting blow-by during combustion.

In ported engine constructions, cooling of piston crowns and cylinder liners results in reduction or elimination of bore/liner distortions, thus ensuring circularity of the bore/piston interface throughout engine operation. Consequently, the need for heavily-tensioned piston rings is eliminated. Such engine constructions incorporate annular low-tension compression seals on the pistons, which substantially reduce port bridge wear during all phases of engine operation while also limiting blow-by during combustion.

A piston ring with a coated outer surface is provided. The coating is disposed on end sections of the outer surface adjacent a gap. Typically, a middle section of the outer surface located between the end sections is not coated. The coating can be formed of CrN or DLC, and the CrN coating can be applied by physical vapor deposition (PVD). The end sections of the outer surface, upon which the coating is applied, are rough. For example, the outer surface can be blasted or otherwise textured to achieve the rough surface. The rough surface retains oil and distributes stress better than a smooth surface, and thus reduces crazing and flaking of the coating.

A sealing system for sealing a cylindrically shaped surface containing a first annular seal and a second annular seal. Each annular seal has a gap penetrating from the outer diameter to the inner diameter. The angle of the gap in the first annular seal and the angle of the gap in the second annular seal and the arrangement of the seals relative to an expander ring and a biasing ring minimizes leakage without the need for an anti-rotation pin or other means that would significantly decrease efficiency and reliability.

A sealing system for sealing a cylindrically shaped surface containing a first annular seal and a second annular seal. Each annular seal has a gap penetrating from the outer diameter to the inner diameter. The angle of the gap in the first annular seal and the angle of the gap in the second annular seal and the arrangement of the seals relative to an expander ring and a biasing ring minimizes leakage without the need for an anti-rotation pin or other means that would significantly decrease efficiency and reliability.