CLEARANCE EXPANSION METHOD OF DRIVE SCREW, AND CONTROL ROD DRIVE MECHANISM USING DRIVE SCREW

摘要

PROBLEM TO BE SOLVED: To provide a clearance expansion method of a drive screw for controlling increase in torque for a motor due to a convex projection accompanying an occurrence of a scratch on a running surface of a screw shaft of the drive screw, and to provide a control rod drive mechanism using the drive screw.SOLUTION: A drive screw is provided in a control rod drive mechanism and used in an underwater environment in which rotational movement of a motor is converted into a vertical motion through a driving shaft, and a hollow piston is elevated. By making a diameter of a ball provided in the drive screw smaller than an existing article, a clearance between a ball running surface of the screw shaft and the ball, and a clearance between the ball and a ball running surface of a ball nut are expanded.