Effect of base oil viscosity of grease on lubricating condition of ball type linear motion rolling bearing

In the ball type linear motion rolling bearing, no methods of selecting the grease considered the lubricated condition. The ball type linear motion rolling bearing and the ball bearing usually have similar defective modes. In the ball bearing, the wear life and the friction loss depend on the lubricated condition at the rolling contact area. So, the influence of the viscosity of the base oil which forms the oil film at the rolling contact area in the ball type linear motion rolling bearing was examined. Results reveal that the speed of forming the oil film depends not only on the thickener, but on the viscosity of the base oil. Moreover, when the calculated (the ratio of elastohydrodynamic oil film thickness and average roughness of two surfaces) is less than 0.6, the lubricated condition deteriorates. Therefore, when selecting the grease for the ball type linear motion rolling bearing, it is necessary to consider the viscosity and the lubricating condition of the base oil.