Piston ring

Abstract

According to a first embodiment of the present invention, a piston ring 1 is provided that has a stainless steel base material 2 having an upper surface, a lower surface, an inner circumferential surface and an outer circumferential surface, the surfaces each having a nitride layer 3 formed thereon, where the nitride layer 3 each is first formed to have a compound layer 4 and a diffusion layer 5, where the diffusion layer 5 of the outer circumferential surface is then exposed by removing the compound layer 4 of the outer circumferential surface, where the exposed diffusion layer 5 has thereafter an ion-plating deposition layer 8 of hard ceramic formed thereon. The piston ring 1 is characterized in that the exposed diffusion layer 5 is removed on the upper and lower corners 7 of the upper and lower surfaces and the outer circumferential surface by chamfering corner regions 6 located around the upper and lower corners 7 before the ion-plating deposition layer 8 is formed. According to a second embodiment of the present invention, a piston ring 1a is provided that has a stainless steel base material 2a having an upper surface, a lower surface, an inner circumferential surface and an outer circumferential surface, the surfaces each having a nitride layer 3a formed thereon, where the nitride layer 3a each is first formed to have a compound layer 4a and a diffusion layer 5a, where the diffusion layer 6a of the outer circumferential surface is then exposed by removing the compound layer 4a of the outer circumferential surface, where the exposed diffusion layer 5a has thereafter an ion plating deposition layer 8a of hard ceramic formed thereon. The piston ring 1a is characterized in that the exposed diffusion layer 45a is reduced in the thickness thereof to 30% or less of the nitride layer in the thickness thereof on the upper and lower corners 7a of the upper and lower surfaces and the outer circumferential surface by chamfering corner regions 6a located around the upper and lower corners 7a before the ion-plating deposition layer 8a is formed. With a piston ring 1, 1a implemented as described above, advantages are effected in that degradation of the fatigue strength is prevented that otherwise would be caused by cracks occurring in the ion-plating deposition layer 8, 8a of such piston ring 1, 1a; better adhesion is obtained compared with the ion-plating deposition layer formed directly on the stainless steel base material, as in prior art; scuffing would not occur even if the ion-plating deposition layer on the outer circumferential surface wears out.

Dependencies are inferred from the claim text.