The piston ring unit includes a plurality of piston rings and an inner contact ring. A plurality of piston rings are disposed adjacent to each other in an axial direction of the piston such that joints of plurality of the piston rings do not overlap with each other in the axial direction. An inner contact ring is interposed between an outer circumferential surface of the piston and an inner circumferential surface of the piston ring in a state where the inner contact ring extends over all of the plurality of piston rings in the axial direction, and is disposed such that an opening of the inner contact ring does not overlap with the joint of the at least one piston ring as viewed in a radial direction of the piston.

A piston ring includes a first ring portion which is fitted onto an outer circumferential portion of a piston and which is capable of sliding relative to an inner wall surface of a cylinder, and a second ring portion which is fitted onto the outer circumferential portion of the piston, arranged side-by-side with the first ring portion in the axial direction, and which is capable of sliding relative to the inner wall surface of the cylinder. The second ring portion is fitted onto the outer circumferential portion of the piston in such a way as to be positioned on a side opposite to a compression chamber inside the cylinder, relative to the first ring portion, and has a greater hardness than the first ring portion has.

The present disclosure provides an open-faced piston with a circumferential groove into which a piston ring assembly is arranged. Openings at the bottom of the circumferential groove and between a front land of the open-faced piston and the piston face are provided. The openings are arranged to allow for a combustion reaction to propagate through the volume defined between the bottom of the piston ring assembly and the piston face such that at least a portion of an air and fuel mixture located in that volume is reacted.

The present disclosure provides an open-faced piston with a circumferential groove into which a piston ring assembly is arranged. Openings at the bottom of the circumferential groove and between a front land of the open-faced piston and the piston face are provided. The openings are arranged to allow for a combustion reaction to propagate through the volume defined between the bottom of the piston ring assembly and the piston face such that at least a portion of an air and fuel mixture located in that volume is reacted.

A piston ring includes a ring body that has a first ring body end and a second ring body end and a ring joint. The first and second ring body ends are arranged opposite one another to define the ring joint. The ring body has a radial ring surface as a sliding contact surface axially displaceable relative to an inner barrel surface and an inclined ring surface that rests on an inclined ring groove surface. The first ring body end has a projection section with a projection section separating surface. The second ring body end has a base section with a base section separating surface and a base section contour. The base section defines a receiving contour. The projection section engages in the receiving contour, and a receiving contour cross section and a projection contour cross section coincide. The projection section separating surface and the base section separating surface are opposite one other in an areal and sealing physical contact and define a plane that has an inverse inclination with respect to the inclined ring surface. The plane intersects the radial ring surface and defines an outer separating line at an intersection line of the plane with the radial ring surface. The plane intersects the inclined ring surface and defines an inner separating line at a second intersection line of the plane with the inclined ring surface. The separating lines define the separating surfaces, and at least one of the separating lines has a curvature radius concentric with the body.

A piston ring includes a ring body that has a first ring body end and a second ring body end and a ring joint. The first and second ring body ends are arranged opposite one another to define the ring joint. The ring body has a radial ring surface as a sliding contact surface axially displaceable relative to an inner barrel surface and an inclined ring surface that rests on an inclined ring groove surface. The first ring body end has a projection section with a projection section separating surface. The second ring body end has a base section with a base section separating surface and a base section contour. The base section defines a receiving contour. The projection section engages in the receiving contour, and a receiving contour cross section and a projection contour cross section coincide. The projection section separating surface and the base section separating surface are opposite one other in an areal and sealing physical contact and define a plane that has an inverse inclination with respect to the inclined ring surface. The plane intersects the radial ring surface and defines an outer separating line at an intersection line of the plane with the radial ring surface. The plane intersects the inclined ring surface and defines an inner separating line at a second intersection line of the plane with the inclined ring surface. The separating lines define the separating surfaces, and at least one of the separating lines has a curvature radius concentric with the body.

A stepped piston ring (2) includes a ring outer side (5), an upper ring flank (6), and a lower ring flank (8). The ring outer side (5) on the upper edge has a notch (10, so that only a lower portion of the ring outer side (5) forms a contact surface (4).

A stepped piston ring (2) includes a ring outer side (5), an upper ring flank (6), and a lower ring flank (8). The ring outer side (5) on the upper edge has a notch (10, so that only a lower portion of the ring outer side (5) forms a contact surface (4).

Embodiments of a combination piston and piston ring to 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 to 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.