| 摘要 |
PROBLEM TO BE SOLVED: To realize low torque without alteration of specifications in spite of base oil dynamic viscosity and consistency equal to those of conventional grease. SOLUTION: A ball screw device is provided with a ball screw shaft 10 having a ball thread groove 12 and extending rectilinearly, a ball nut 20 having a ball thread groove 24 opposite to the ball thread groove 12 of the screw shaft 10 and guided by the screw shaft 10 through a number of balls 30 inserted between the ball thread grooves 12, 24 to relatively move rectilinearly, and a tube type circulating path 40 having a ball circulating path for circulating the balls 30 inserted between the ball thread grooves 12, 24. In the ball screw device, a grease composition containing a metallic soap-base thickener having long fibrous material with a major axis part of 3μm or more in base oil obtained by mixing lubricating oil having a polar group in a molecular structure with non-polar lubricating oil is sealed in the ball nut 20. |
