Improvement of lubrication for cam and follower

In order to improve the lubrication between cam and follower of internal co mbustion engines, the influences of materials or oil viscosity and additive s on the friction and scuffing characteristics have been examined,with a te st rig by increasing the contact load at a constant revolution speed. Also the effects of oil supply through the oil-hole of the camshaft on the reduc tion of friction and the prevention of scuffing have been examined. From th e experiments the following results were made obvious. Firstly: the effect of the material on the reduction of friction or the prevention of scuffing is dependent upon the combination of earn and follower materials. The follo wer material of hard sintered metal ol silicon nitride ceramics is superior in both effects to chilled cast iron when mating with the cam material of hardened S48C steel cam. Secondly, as the viscosity of base-oil becomes low, the friction increases or decreases depending on oil additives, but the scuffing resistance always becomes small. The organo-molybdenum compounds, MoDTP and MoDTC, decrease the friction and the zinc dialkyl-dithiophosphates are effective in prevent ing scuffing. In the case of mixed additive with such Molybdenum friction m odifiers, primary ZnDTP and secondary ZnDTP enhance the effect to modif' th e friction when mixed with MoDTP, however primary ZnDTP becomes inferior in scuffing resistance to secondary ZnDTP. Specifically the mixed additive of MoDTC and primary ZnDTP improves the lubrication in both respects of the f riction and the anti-scuffing. Lastly the oil supply from cam surface oil-hole is an effective means of im proving the lubrication. The effect becomes largest when the oil-hole is ar ranged between the flank and shoulder of the cam-lobe corresponding to the valve opening.