Piston ring with localized nitrided coating
AssigneeMahle International GmbH
InventorJohn C. Lahrman
Life of this patent
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Abstract
A piston ring comprising upper face, a lower face, an inner perimeter wall, and an outer perimeter wall that extends around the piston ring from the upper face to the lower face, where the outer perimeter wall has upper corner region disposed adjacent the upper face, a lower corner region disposed adjacent the lower face, and a band of a nitrided conversion layer extending between the upper corner region and the lower corner region, and where a PVD nitride layer is disposed on the upper corner region and on the lower corner region.
Claims19
A piston ring comprising:
- an upper face;
- a lower face;
- an inner perimeter wall;
- and
- an outer perimeter wall that extends around the piston ring from the upper face to the lower face;
- wherein the outer perimeter wall has upper corner region disposed adjacent the upper face, a lower corner region disposed adjacent the lower face, and a band of a nitrided conversion layer extending along the outer perimeter wall between the upper corner region and the lower corner region, wherein the nitrided conversion layer penetrates an exterior layer of the outer perimeter wall;
- and
- wherein the upper corner region and the lower corner regions have outer surfaces that coincide with the outer perimeter wall.
A method of making a crack-resistant piston ring, comprising:
- providing a piston ring, wherein the piston ring has an upper face, a lower face, an inner perimeter wall, and an outer perimeter wall that extends around the piston ring from the upper face to the lower face;
- the outer perimeter wall having upper corner region disposed adjacent the upper face, a lower corner region disposed adjacent the lower face, and an annular cavity in the central portion of the outer perimeter wall extending between the upper corner region and the lower corner region along the length of the outer perimeter wall;
- forming a nitrided conversion layer penetrating an exterior layer of the piston ring;
- performing a grinding process on the piston ring, thereby removing some of the nitrided conversion layer;
- and
- depositing a PVD nitride layer on the outer perimeter wall of the piston ring.
A piston ring comprising:
- upper face;
- a lower face;
- an inner perimeter wall;
- and
- an outer perimeter wall that extends around the piston ring from the upper face to the lower face, the outer perimeter wall comprising an upper corner region disposed adjacent the upper face along the length of the outer perimeter wall and having an outer surface that coincides with the outer perimeter wall, a lower corner region disposed adjacent the lower face along the length of the outer perimeter wall and having an outer surface that coincides with the outer perimeter wall, and a band of nitrided conversion layer disposed between the upper corner region and the lower corner region, the nitrided conversion layer penetrating an exterior layer of the outer perimeter wall, the band of nitrided conversion layer extending along the length of the outer perimeter wall and having an outer surface that is generally coplanar with the outer surfaces of the upper and lower corner regions;
- and
- a PVD nitride layer disposed on and extending along the length of the outer perimeter wall from the upper face to the lower face, and covering the outer surfaces of the upper and lower corner regions and the nitrided conversion layer.
Dependencies are inferred from the claim text.