| 摘要 |
PROBLEM TO BE SOLVED: To provide a ball screw suppressing the number of part items to the minimum, setting the length of a nut to short, uniformizing the load distribution in the nut, and obtaining large load capacity. SOLUTION: A circulation passage 8 is constituted by providing balls 3 in a spiral passage 6 formed of a screw shaft 1 and screw grooves 4 and 5 of the nut 2 and by providing a return tube 7. In the return tube type bell screw, the circulation passage 8 is unified. A ball unloading region 11 is provided in a phase part of the spiral passage 6 opposite to a circumferential phase provided with the return tube 7.
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