| 摘要 |
PROBLEM TO BE SOLVED: To lubricate oil for a long period in a ball screw. SOLUTION: This ball screw is provided with a screw shaft 2 having a spiral groove 2a in the outer circumferential surface, a nut body 3 externally fitted around it and having a spiral groove 3a, a retainer 5 interposed between the outer circumferential surface of the screw shaft 2 and the inner circumferential surface of the nut body 3 and retaining a plurality of balls 4 rotatably engaged with the respective spiral grooves 2a and 3a, and an approximately cylindrical cover member 6 fixed to a flange 30 of the nut body 3 and covering the outer circumference of the screw shaft 2. An oil bearing sheet 8 is installed on the inner circumferential surface 6a of the cover member 6. In operating the ball screw, the balls 4 subjected to a centrifugal force is brought in contact with the oil bearing sheet 8, and as a result, the oil is seeped out from the inside of the oil bearing sheet 8 for a long period. This constitution can prevent the seizure and abrasion of the rolling surfaces caused by the absence of the oil film.
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