Abstract
To elucidate the aspects of lubrication of oil impregnated sintered bearings which are set in real high speed revolution machinery and tools, the sintered bearings which compositions are Cu-9%Sn and Cu-9%-Sn-1% C were tested using the high and low viscosity lubricant oils.
The results obtained are as follows:
1) When oil impregnated sintered bearings were set into real high speed revolution machinery and tools, it was found that they are driven under an extremely severe boundary condition, because no sufficient time can be given for the geometrical conformity of the bearings, as the number of revolution of the shafts reaches the fixed high speed one just after the starting. Consequently, large amounts of wear of the bearings occurred at this stage and it was supposed that the bearings may seize in the worst case.
2) The coefficient of friction of the start-up was affected extremely by the viscosity of the lubricant oil. Consequently, the values of the coefficient of friction did not indicate the degree of the severity of the state of lubrication.
3) Adding solid lubricants alleviated the severe state of boundary lubrication of the start-up. It was considered, however, that solid lubricants added by the conventional way into the bearing matrix increase the apparent viscosity of the oil and consequently increase the coefficient of friction and the bearing temperature after transferring to the hydrodynamic conditions at the regular state.
