| 摘要 |
PROBLEM TO BE SOLVED: To improve longevity and to reduce noise by preventing early damages of a rolling element and a guide surface due to shortage of oil film strength of a lubricant. SOLUTION: A ball screw device has: a screw shaft 3 extended in the axial direction and having a thread groove 2 extending in the axial direction; a ball nut 6 having a thread groove 4 facing the thread groove 2 of the screw shaft 3 and supported on the screw shaft 3 so as to be relatively movable along the axial direction through rolling of a large number of balls 5 inserted between these thread grooves 2, 4; and a holding piece arranged between each of the balls 5 and to hold the balls 5. A lubricant combined with a lubricant base oil kinematic viscosity of which is more than 150 mm<SP>2</SP>/S (40 degrees C) is used as the lubricant. COPYRIGHT: (C)2004,JPO
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