Coated piston ring for an internal combustion engine

Patent metadata

Field	Value
Publication number	US-2021071760-A1
Application number	US-201916564852-A
Country	US
Kind code	A1
Filing date	Sep 9, 2019
Priority date	Sep 9, 2019
Publication date	Mar 11, 2021
Grant date	—

Abstract

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.

First claim

What is claimed is:

1 . A piston ring, comprising:
a ring body extending circumferentially around a center axis between opposite end surfaces, said end surfaces of said ring body presenting a gap therebetween, said ring body having an outer surface facing away from said center axis, said outer surface including end sections adjacent said end surfaces, said end sections of said outer surface being rough, a coating disposed on said end sections of said outer surface, and said coating including chromium nitride (CrN) or diamond-like carbon (DLC).

2 . The piston ring of claim 1 , wherein said coating consists essentially of DLC or CrN.

3 . The piston ring of claim 1 , wherein end sections are spaced from one another by a middle section of said outer surface, and said middle section is not coated with said coating including CrN or DLC.

4 . The piston of claim 1 , wherein said end sections have a surface roughness greater than a surface roughness of said middle section of said outer surface.

5 . The piston ring of claim 1 , wherein said coating includes a plurality of grains disposed at angles relative to one another.

6 . The piston ring of claim 1 , wherein said coating includes CrN.

7 . The piston ring of claim 6 , wherein said coating is applied by physical vapor deposition.

8 . The piston ring of claim 1 , wherein said coating includes DLC.

9 . The piston ring of claim 1 , wherein said end surfaces of said ring body are parallel to said center axis,
said ring body has an inner surface facing toward said center axis, said ring body has a top surface extending from said inner surface to said outer surface and a bottom surface spaced from said top surface and extending from said inner surface to said outer surface, said inner surface is parallel to said center axis and said outer surface, said top surface is perpendicular to said center axis and parallel to said bottom surface, said ring body is formed of steel, said end sections are spaced from one another by a middle section of said outer surface, said middle section of said outer surface is not coated with said coating including CrN or DLC. said end sections of said outer surface have a surface roughness which is greater than a surface roughness of said middle section, said coating consists essentially of DLC or CrN, and said coating includes a plurality of grains disposed at angles relative to one another.

10 . A piston assembly for an internal combustion engine, comprising:
a piston body including at least one ring groove extending circumferentially around a center axis, a ring body disposed in one of said at least one ring groove, said ring body extending circumferentially around the center axis between opposite end surfaces, said end surfaces of said ring body presenting a gap therebetween, said ring body having an outer surface facing away from said center axis, said outer surface including end sections adjacent said end surfaces, said end sections of said outer surface being rough, a coating disposed on said end sections of said outer surface, and said coating including chromium nitride (CrN) or diamond-like carbon (DLC).

11 . The piston assembly of claim 10 , wherein said piston body includes a crown and a skirt depending from said crown, and said at least one ring groove is located in said crown.

12 . A method of manufacturing a piston ring comprising the steps of:
providing a ring body extending circumferentially around a center axis between opposite end surfaces, the end surfaces presenting a gap therebetween, the ring body having an outer surface facing away from the center axis; texturing end sections of the outer surface located adjacent the end surfaces so that the end sections of the outer surface are rough; and applying a coating to the rough end sections of the outer surface, the coating including chromium nitride (CrN) or diamond-like carbon (DLC).

13 . The method of claim 12 including applying the coating by physical vapor deposition.

14 . The method of claim 13 , wherein the coating includes CrN.

15 . The method of claim 12 , wherein the coating includes DLC.

16 . The method of claim 12 , wherein the end sections are spaced from one another by a middle section of the outer surface, and applying none of the coating to the middle section of the outer surface.

17 . The method of claim 16 , wherein the texturing step provides the end sections of the outer surface with a surface roughness which is greater than a surface roughness of the middle section.

18 . The method of claim 12 , wherein the end surfaces of the ring body are parallel to the center axis, the ring body has an inner surface facing toward the center axis, the ring body has a top surface extending from the inner surface to the outer surface and a bottom surface spaced from the top surface and extending from the inner surface to the outer surface, the inner surface is parallel to the center axis and the outer surface, the top surface is perpendicular to the center axis and parallel to the bottom surface, the ring body is formed of steel, the end sections are spaced from one another by a middle section of the outer surface which is not textured, the end sections have a surface roughness which is greater than a surface roughness of the middle section, the coating consists essentially of DLC or CrN, and the coating includes a plurality of grains disposed at angles relative to one another being applied to the outer surface; and applying none of the coating to the middle section of the outer surface.

19 . A method of manufacturing a piston assembly comprising the steps of:
providing a piston body including at least one ring groove extending circumferentially around a center axis, providing a ring body extending circumferentially around the center axis between opposite end surfaces, the end surfaces presenting a gap therebetween, the ring body having an outer surface facing away from the center axis, texturing end sections of the outer surface adjacent the end surfaces so that the end sections of the outer surface are rough, applying a coating to the rough end sections of the outer surface, the coating including chromium nitride (CrN) or diamond-like carbon (DLC), and disposing the coated piston ring in one of the at least one ring groove of the piston body.

20 . The method of claim 19 , wherein the end sections are spaced from one another by a middle section of the outer surface, and applying none of the coating to the middle section of the outer surface.

Assignees

• Tenneco Inc

Inventors

• Aharonov Robert Reuven
• Irrgeher Marc

Classifications

• C23C28/042

  including a refractory ceramic layer, e.g. refractory metal oxides, ZrO2, rare earth oxides · CPC title

• C23C28/04 Primary

  only coatings of inorganic non-metallic material · CPC title

• C23C28/044

  coatings specially adapted for cutting tools or wear applications · CPC title

• C23C14/0641

  Nitrides (C23C14/0617 takes precedence) · CPC title

• F16J9/26 Primary

  characterised by the use of particular materials · CPC title