| 摘要 |
PROBLEM TO BE SOLVED: To provide a ball screw device of a circulation type to circulate a group of balls capable of preventing deterioration of lubrication performance of track surfaces of a screw shaft and a nut member and ball surfaces, and achieving high service life. SOLUTION: Balls 4 are provided between mutually facing surfaces of a screw groove in the screw shaft and a screw groove in the nut member, and the downstream side of the screw groove in the screw shaft or the screw groove in the nut member are communicatively connected to the upstream of it by ball circulation ways 33 and 34. A holder ring 5 for rotatably holding the balls is provided between the screw shaft and the nut member. Grease sumps 53 are formed in the holder ring 5, and grease 6 is filled in the grease sumps 53. The grease sumps 53 are formed as pockets 51 to hold the balls 4 in the holder ring 5.
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