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 and a control rod drive mechanism using the drive screw capable of suppressing a torque increase for the electric motor due to a convex projection accompanying an occurrence of a scratch on a running surface of a screw shaft of 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. The drive screw includes a screw shaft and a ball nut engaged with the screw shaft via a plurality of balls, and expands a clearance between a running surface of the screw shaft and the running surface of the ball by making a groove shape of the ball running surface of the screw shaft large.SELECTED DRAWING: Figure 5