BALL SCREW DEVICE

PROBLEM TO BE SOLVED: To provide a ball screw device of a long service life converting the linear motion of a nut once into swing motion of a swing arm, and converting the swing motion again into rotary motion to drive a driven body. SOLUTION: In the swing arm 21 swinging around a driven shaft 23 for taking out rotary motion, and a groove 13a of a nut 13 screwed with a ball screw shaft 12 driven by a motor 18, contact points between a false triangular tip part 21a which is a constant width pattern of the swing arm 21 and a groove 13a of a nut 13 are points P1, P2 including the centerline of a ball screw shaft 12 when the swing arm 21 is in a vertical position. When the nut 13 moves to the right, the tip part 21a inclines within the groove 13a of the nut 13, and the contact points move to P3, P4, but even if the swing arm 21 inclines by 30° from the vertical position, the moving quantity d is small, and large rotational moment having adverse effect on a ball circulating passage of the nut 13 does not occur. COPYRIGHT: (C)2007,JPO&INPIT