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Surface scuffing related to gas nitrided piston rings is attracting more attention as the effective cylinder pressure is increased in the recent years. However, the mechanism behind scuffing induced in long-term operations remained unknown. This study focuses on clarifying the mechanism behind scuffing related to gas nitrided piston rings. In addition, application of a thin composite plated surface film containing dispersed particles is proposed as an effective measure for preventing surface scuffing during long-term operations. Furthermore, factors enabling maintenance of high scuffing resistance on the ring surface after the thin plated composite film wears off and the underlying nitrided surface is exposed were analyzed. The dominant factor was discovered to be the difference in the resulting sliding surface profile, after initial wear, between a ring surface with composite plating and a ring surface with only gas nitriding treatment.

A recent increase in detergent additives to gasoline has resulted in an increase in the accumulation of deposits inside the engine's combustion chamber (this type of deposit will be hereinafter referred to as “CCD”;Combustion Chamber Deposit). Along with this tendency, authors have observed an engine noise generated during warm up, which may be attributable to the CCD accumulation. It was reported that the engine noise was identified as carbon knocking caused when the piston and cylinder head physically come in contact because of these CCDs(1X2) This paper deals with another noise generated by the CCD trapped between the piston ring and piston ring groove.

To reduce the oil consumption in diesel engines, the combination of top ring gap clearance (C1) and second ring gap clearance (C2) (ring gap balance) was applied. The effect of the ring gap balance on piston ring axial motion and second land pressure was observed and factors to control oil consumption were analyzed. The authors obtained a technique to reduce oil consumption by decreasing second land pressure and thus making second ring liable to lift off. Blow up gas was significantly concerned about oil consumption of blow-by gas.

Today preservation of the global environment is an international challenge, and air pollution has attracted more concern than ever. Especially, pollution due to exhaust emission from automobiles is a serious matter, and among others, the improvement of exhaust emission is urgent. For this purpose, regulations have been tightened on exhaust emission such as particulate control and NOx control. Thus, it is essential for oil consumption of diesel engines to reduce oil consumption and employ Exhaust Gas Recirculation (EGR), and piston rings are the important key to solve these problems. This paper clarifies the effect of top rings, among piston rings, on oil consumption through engine tests and theoretical calculation of oil film thickness, and suggests techniques to reduce oil consumption.

Although various factors affecting oil consumption of an internal combustion engine can be considered, a technique to predict the amount of oil consumed within a cylinder that passes across a running surface of a ring was developed in this study. In order to predict the effect of cylinder deformation on oil consumption, a simple and easy technique to calculate the oil film thickness in deformed cylinder was proposed. For this technique, the piston ring was assumed to be a straight beam, and the beam bends with ring tension, gas pressure, and oil film pressure. From the calculated oil film thickness, amount of oil passing across the running surface of the TOP ring and into the combustion chamber was calculated. The calculated results were then compared to the oil film thickness of the ring and oil consumption measured during engine operation, and their validity was confirmed.