| 摘要 |
PROBLEM TO BE SOLVED: To make determination of deterioration degree of lubricating grease easier to feed new lubricating grease, efficiently and without waste. SOLUTION: In a ball screw A, a thread groove 1a and a thread groove 2a are formed on an outer diameter face of a screw shank 1 and an inner diameter face of a nut 2, respectively. A plurality of balls 4 are held, capable of rolling in a circulating passage constituted of a spiral passage 3 and its connecting passage that are formed, when both of the thread grooves are oppositely disposed. The nut 2 and screw shank 1 are held via the balls 4 to be capable of rolling in the spiral passage 3. The lubricating grease lubricates the plural balls 4 and the circulating passage. The lubricating grease has lightness of 1 and is made by thickening base oil which has 3.0-7.5 mm2/s for viscosity at 100 deg.C by using a urea thickener. |
