Quantitative Measurement of Soot Particles in Oil-Film by Image Analysis and Laser Scattering Method for Research on Mechanism of Friction and Wear

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(1)The effect of lowering the oil viscosity from SAE10W-30 to SAE5W-30 on the reduction of frictional power loss in diesel engines becomes larger when the class is modified from the CD oils to the DH oils, that is DH-1 or DH-2, lower in sulfated ash, phosphorous and sulfur named as Low-SAPS oils to protect the diesel particulate filter and the deNOx catalyst.(2)Shot-peening is more desirable than grinding as the surface finish for the sintered cam lobes of compound camshafts in the valve train with roller followers because the influence of surface finish and roughness on the friction loss and wear is quite small. The surface roughness should be larger than one micron and smaller than around three microns root mean square. Also, the friction loss from the roller follower supported by the needle bearing is larger than that from the one supported by the slide bearing.(3)The oil viscosity hardly changes the friction between cam and roller is small but it reduces the friction of other eleme … More nts in the valve train.(4)The additional supplement of the anti-wear and friction modifier additives, ZnDTP and MoDTC, into semi-used engine oils is effective to reduce the friction and wear for the cam and slipper follower. When contaminated with the soot kinds more than one in mass percentage, however, the effect for the wear becomes remarkably low while the effect for the friction is scarcely kept obvious. In order to reduce both the friction and the wear rate, the supplement of the additives into the oil should be more than around six in mass percentage and the allowable rate of soot contamination in the oil is less than around one in mass percentage.(5)The size distribution of soot particles in engine oils measured by the image analysis coincides with that measured by the laser scattering method so that both methods have high accuracy in measurement for the soot size. The amount of the dispersant markedly influences the size distribution of soot particles in the oil. The friction is low but the wear rate is somewhat high when the soot contamination is slight, while both the friction and the wear rate are remarkably high when that is much. Also, both the friction and the wear rate are low when the size of soot is small, while the both of them increase as the size of soot becomes large because of the coagulation. Accordingly, not only the soot coagulation causing the oil starvation in the sliding contact area namely the increase of soot size should be prevented by the dispersant but any soot particles coagulated with the wear debris and the hard sludge causing the abrasive wear should be removed from engine oils. Less