| 摘要 |
PROBLEM TO BE SOLVED: To resist abrasion in the inner peripheral surface of a cylinder even when the cylinder is arranged in the moving region of a male screw part. SOLUTION: An electric power steering device includes: a steering shaft 5 having a male screw 51 with a flat surface 51a on its top and moving in the longitudinal direction of the shaft according to steering operation; a ball screw mechanism 8 having a nut 81 relatively rotatably screwed to the male screw 51 through a plurality of balls 82, and converting the rotation force of an electric motor 7 into a moving force in the longitudinal direction of the shaft and transmitting it to the steering shaft 5; and the cylinder 10 freely fitted to the steering shaft 5 and limiting the deflection quantity of the steering shaft 5. The width of the flat surface of the male screw 51 is set to be 0.7-1.5 times as wide as the diameter of the ball 82, thereby the abrasion in the inner surface of the cylinder hardly occurs even when the male screw part contacts the inner peripheral surface of the cylinder. COPYRIGHT: (C)2005,JPO&NCIPI
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