A piston ring (10) for forming a seal between a piston (26) and piston housing (28). The piston ring (10) has first and second orthogonal axes (12, 14) and a body portion (18) which is resiliently deformable in the direction of the first axis (12) and is substantially rigid in the direction of the second axis (14).

A piston ring (10) for forming a seal between a piston (26) and piston housing (28). The piston ring (10) has first and second orthogonal axes (12, 14) and a body portion (18) which is resiliently deformable in the direction of the first axis (12) and is substantially rigid in the direction of the second axis (14).

A seal ring is in contact with an outer peripheral surface of a plunger. A biasing ring is made of a material having a lower fuel resistance than the seal ring, and is provided radially outwardly with respect to the seal ring in a seal chamber so as to bias the seal ring against the plunger. An axial position of a portion of the seal ring where a surface pressure on the plunger is maximum is defined as a maximum surface pressure position. The seal ring has diameter changing portions in both axial directions with respect to the maximum surface pressure position. The diameter changing portions are formed so as to have an outer diameter smaller than that of the portion corresponding to the maximum surface pressure position.

A seal ring is in contact with an outer peripheral surface of a plunger. A biasing ring is made of a material having a lower fuel resistance than the seal ring, and is provided radially outwardly with respect to the seal ring in a seal chamber so as to bias the seal ring against the plunger. An axial position of a portion of the seal ring where a surface pressure on the plunger is maximum is defined as a maximum surface pressure position. The seal ring has diameter changing portions in both axial directions with respect to the maximum surface pressure position. The diameter changing portions are formed so as to have an outer diameter smaller than that of the portion corresponding to the maximum surface pressure position.

An oil ring to be attached to a ring groove of a piston for an engine is provided. The oil ring includes two annular ring bodies having a common axis and arranged in tandem, and an expander for biasing the ring bodies radially outward. A sliding surface is formed at an outer circumference of each ring body to bulge radially outward and slides on a cylinder inner circumferential surface. The sliding surface of one of the ring bodies has a tip portion and first and second curved surfaces. In cross sections of the first and second curved surfaces, the first and second curved surfaces are connected while tangent lines to the cross sections at the tip portion align with each other, and when positional change rates are compared between points on the first and second curved surfaces, a change rate of the first curved surface is lower.

An oil ring to be attached to a ring groove of a piston for an engine is provided. The oil ring includes two annular ring bodies having a common axis and arranged in tandem, and an expander for biasing the ring bodies radially outward. A sliding surface is formed at an outer circumference of each ring body to bulge radially outward and slides on a cylinder inner circumferential surface. The sliding surface of one of the ring bodies has a tip portion and first and second curved surfaces. In cross sections of the first and second curved surfaces, the first and second curved surfaces are connected while tangent lines to the cross sections at the tip portion align with each other, and when positional change rates are compared between points on the first and second curved surfaces, a change rate of the first curved surface is lower.

A piston for an internal combustion engine includes a cylindrical piston body defining a longitudinal axis and having a top end and an outer cylindrical surface. A first piston ring groove is formed in the outer cylindrical surface and includes a groove root, an upper surface and a lower surface. The groove root has a variable depth about a circumference of the cylindrical piston body.

The present disclosure provides a sealing ring assembly having a ring and one or more gap cover elements, configured to seal a high-pressure region from a lower pressure region of a piston and cylinder device. The ring may be segmented, and the gap cover elements may engage with interfaces between the ring segments. The gap cover elements are configured to move radially outward and wear as the ring wears. The gap cover elements may include, for example, wedge-shaped features that engage with corresponding wedge recesses in the interfaces. The sealing ring assembly may include a high-pressure boundary and a low-pressure boundary. As the sealing ring wears, the gap cover elements stay engaged with the interfaces, so that ring gaps do not form on the low pressure boundary.

The present disclosure provides a sealing ring assembly having a ring and one or more gap cover elements, configured to seal a high-pressure region from a lower pressure region of a piston and cylinder device. The ring may be segmented, and the gap cover elements may engage with interfaces between the ring segments. The gap cover elements are configured to move radially outward and wear as the ring wears. The gap cover elements may include, for example, wedge-shaped features that engage with corresponding wedge recesses in the interfaces. The sealing ring assembly may include a high-pressure boundary and a low-pressure boundary. As the sealing ring wears, the gap cover elements stay engaged with the interfaces, so that ring gaps do not form on the low pressure boundary.

A piston ring system for an internal combustion engine includes a first compression piston ring (2), a second compression piston ring (4), and an oil scraper piston ring (6). The first compression piston ring (2) has a first ring body (8) with a first upper ring flank (10), a first lower ring flank (12), a first ring inner side (14), a first ring outer side (16), as well as two first abutting surfaces. A first contact region (18) of the first ring body (8) is arranged with a cylinder running surface (20) above a first piston ring center (22). At least one first oil pocket (24) is arranged below the first contact region (18) in the circumferential direction. The second compression piston ring (4) having a second ring body (26) a second upper ring flank (28), a second lower ring flank (30), a second ring inner side (32), a second ring outer side (34), as well as two second abutting surfaces. A second contact region (36) of the second ring body (26) is arranged with the cylinder running surface (20) above or below a second piston ring center (38). At least one second oil pocket (40) is arranged below the second contact region (36) in the circumferential direction. The oil scraper piston ring (6) is formed in one piece, two pieces, or three pieces.