Method for producing piston ring with recess

Patent metadata

Field	Value
Publication number	US-10514097-B2
Application number	US-201715672942-A
Country	US
Kind code	B2
Filing date	Aug 9, 2017
Priority date	Nov 30, 2009
Publication date	Dec 24, 2019
Grant date	Dec 24, 2019

Abstract

A method for producing a piston ring for a cylinder that moves in a sliding direction includes providing a piston ring base material having an upper surface, a lower surface and an outer circumferential surface having a first recess between the upper surface and the lower surface, forming a hard film in the first recess and on a cylindrical surface at a predetermined thickness, and removing, by performing a polishing process on the sliding surface, the hard film formed on the cylindrical surface and a part of the piston ring base material disposed adjacent to the removed hard film, to form a second recess. The second recess is formed by removing an area of the removed part of the piston ring base material as a result of polishing the sliding surface due to a difference in the hardness of the hard film and the piston ring base material.

First claim

The invention claimed is:

1. A method for producing a piston ring cylinder that moves in a sliding direction, comprising:
providing a piston ring base material having an upper surface, a lower surface and an outer circumferential surface between the upper surface and the lower surface,
forming a first recess by removing a first part of the piston ring base material in a part of the outer circumferential surface, a remaining part of the outer circumferential surface being a cylindrical surface formed directly below the first recess in the sliding direction, the first recess having a bottom surface parallel to the outer circumferential surface and in inclined surface extending from the bottom surface to the cylindrical surface;
forming a hard film on the bottom surface and the inclined surface of the first recess and on the cylindrical surface at a predetermined thickness, the hard film having a higher hardness than the piston ring base material, an outer surface of the hard film on the bottom surface of the first recess establishing a sliding surface;
forming a second recess by performing a polishing process on the sliding surface including:
removing the hard film formed on the cylindrical surface;
removing the hard film formed on a part of the inclined surface of the first recess and a second part of the piston ring base material disposed adjacent to the cylindrical surface, to a point substantially flush with the sliding surface, and
removing a third part of the piston ring base material from a section of the piston ring base material exposed by removal of the second part of the piston ring base material by the second step,
wherein the second recess is directly connecting the first recess and forming a connecting vertex with the inclined surface of the first recess.

2. The method according to claim 1 , further comprising:
forming a nitride diffusion layer on the piston ring base material after forming the second recess.

3. The method according to claim 2 , wherein the nitride diffusion layer is directly formed on the upper surface and the lower surface of the piston ring base material and on the second recess.

4. The method according to claim 1 , wherein the first recess is formed on the piston ring base material by at least one of cutting, grinding and polishing the piston ring base material.

5. The method according to claim 1 , wherein
the inclined surface forms an angle 10°-30° with the sliding surface.

6. The method according to claim 1 , wherein the first recess has a higher depth from the sliding surface than the second recess.

7. The method according to claim 1 , wherein the first recess has a depth of 10 μm to 60 μm.

8. The method according to claim 1 , wherein the second recess has a depth of 1 μm to 20 μm.

9. The method according to claim 1 , wherein a length of the second recess in the sliding direction is about 5%-25% of a distance between the upper surface and the lower surface of the piston ring base material in the sliding direction.

10. The method according to claim 1 , wherein the hard film is formed by a PVD method.

11. The method according to claim 1 , wherein the hard film comprises a Cr—N type film or a Cr—B—N type film.

12. The method according to claim 1 , wherein the second recess has a curved surface extending from the connecting vertex.

13. The method according to claim 12 , wherein the second recess further has a flat surface extending from the lower surface of the piston ring base material and the curved surface.

14. The method according to claim 1 , wherein the predetermined thickness for the hard film formed in the first recess and on the cylindrical surface is substantially the same as a depth of the first recess after removing the hard film on the part of the inclined surface of the first recess and the second part of the piston ring base material disposed adjacent to the cylindrical surface at the second step.

15. The method according to claim 1 , wherein the sliding surface is polished such that the sliding surface is parallel with the sliding direction.

16. The method according to claim 1 , wherein the sliding surface is polished such that the sliding surface is curved relative to the sliding direction.

17. The method according to claim 16 , wherein the sliding surface has a barrel face shape.

18. The method according to claim 16 , wherein the sliding surface has an eccentric barrel face shape.

Assignees

• Nippon Piston Ring Co Ltd

Inventors

• Fujimura Kazuhiro
• Chiba Atsushi
• Akimoto Naoyuki
• Hiraishi Iwao

Classifications

• F16J9/26 Primary

  characterised by the use of particular materials · CPC title

• F16J9/206

  One-piece oil-scraping rings · CPC title

• F16J9/20

  Rings with special cross-section (L-section rings F16J9/02); Oil-scraping rings {(F16J9/06 takes precedence)} · CPC title

• B23P15/065

  from metal strip · CPC title

• B23P15/06

  piston rings from one piece · CPC title