Nippon Piston Ring Co., Ltd.

Kazuo Shimizu

Motonobu Onoda

Katsuaki Ogawa

Takeji Tsuchiya

Tohru Watanabe

Yukio Tateishi

According to an embodiment of the present invention a piston ring for internal combustion engines for use with a piston and a cylinder, is provided that has an external circumferential sliding surface adapted to slid against the internal wall of the cylinder. The piston ring has an ion-plating deposition layer formed over the externtal circumferential sliding surface, the deposition layer having pores and being made of a mixture of a first chromium nitride of CrN type and a second chromium nitride of Cr N type. The mixing ratios in the mixture are more than 45.5 and less than 98.0 weight percent for the first chromium nitride and the balance portion for the second chromium nitride. According to another embodiment of the present invention, a piston ring for internal combustion engines for use with a piston and a cylinder, is provided that has an external circumferential sliding surface adapted to slid against the internal wall of the cylinder. The piston ring having an ion-plating deposition layer formed over the external circumferential sliding surface thereof, the deposition layer having pores and being made of a mixture of a first chromium nitride of CrN type, a second chromium nitride of Cr N type, and metallic chromium. The mixing ratios in the mixture are more than 45.0 and less than 98.0 weight percent for the first chromium nitride, more than 0.5 and not more than 15.0 weight percent for the metallic chromium, and the balance portion for the second chromium nitride. According to a further embodiment of the present invention, the ion-plating deposition layer formed over the external circumferential sliding surface of the piston ring, made of the mixture described in the above embodiments, is formed to have porosity of more than 0.5 and not more than 20.0 percent.

Nitride-plated piston ring for internal combustion engines

The present invention provides a chrome-plated sliding member free from periodical decreases in wear resistance or seizure resistance without the necessity to intentionally bend a multi-layer hard chrome plating film. This is a sliding member having a multi-layer hard chrome plating film on the sliding surface of the substrate . Microcracks opening to the outer surface side of the individual hard chrome plating layers are distributed in hard chrome plating layers and . The microcracks of the individual hard chrome plating layers comprise relatively shallow portions where bottoms stop within a single layer, and relatively deep portions and where cracks run through two or more layers. The quantities of the microcracks expressed by the area ratios of microcracks on a cross-section of the hard chrome plating film include a quantity of the portions where cracks stop within a single layer within a range of from 1.5 to 35.0%, a quantity of the portions where cracks run through two or more layers within a range of from 0.5 to 25.0%, and a total quantity of microcracks within a range of from 2.0 to 40.0%.

Chrome-plated sliding member and manufacturing method thereof

A laminated chromium plating layers providing improved wear resistance and fatigue strength for use in mechanical parts of an internal combustion engine. The lamination is formed on a base body and contains a plurality of high hardness chromium plating layer and a plurality of low hardness chromium plating layer, and each high hardness chromium plating layer is formed upon each low hardness chromium plating layer to provide the lamination of alternating high hardness chromium plating layer and low hardness chromium plating layer.

Growing community of inventors

Yono, Japan

Kazuo Shimizu