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It is very important for the control of particulate emissions in diesel engines to reduce oil consumption. In order to control oil consumption in diesel engines, the mechanism by which sliding surface profiles of piston top rings are changed during endurance testing and the effect of the profiles on oil consumption were determined. The results obtained indicate that oil consumption depends largely upon the ratio of barrel face drop (e) to effective sliding surface width(B) of top ring profiles after endurance testing. The results also indicate that when the e/B is less than 6 /1000, oil consumption increases greatly. A technique is proposed for reducing oil consumption by controlling the e/B ratio through optimizing the top ring design.

In order to extend the oil drain interval and to prolong the engine service life, we have investigated the effects of engine load and wear on heavy-duty diesel engine oil deterioration and oil filter plugging. Furthermore, effects of oil quality on oil deterioration has also been studied. We have found in this study that the increase of blow-by gas flow due to excessive wear of engine components causes severe nitro-oxidation in heavy-duty diesel engines at a high engine load conditions similar to that observed in gasoline engines. The nitro-oxidation of engine oil also causes filter plugging. From the oils tested, the high ash oil showed better anti-nitro-oxidation performance than those with low ash.

KOMATSU achieved the first practical application in the world of the nodular cast iron piston to high speed four stroke diesel engines with a bore of 125mm, and since then this application has expanded to larger engines. In order to improve the casting quality and productivity we also developed the permanent mold casting process for the nodular cast iron pistons. In this paper, aims in the development of the nodular cast iron pistons and its design features and casting technology are presented.

This paper deals with the antiseizure properties of connecting rod bearing for which the overlay is worn due to extended engine operation. Trimetal bearings from operating engines were collected and their surface condition was evaluated. It was found that there were some bearings where the Ni-compound layer had been exposed. For such bearings the seizure-load-limit was lower than that for bearings whose overlay was still intact. In order to understand this tendency quantitatively, the effect of the bearing materials on anti-seizure properties were studied. Using these results, the authors analysed the correlation between bearing seizure and some parameters which can estimate the work load of the bearing. It was found that the “mean unit load of the bearing X velocity” can serve as a practical parameter for bearing seizure.