Patent ID: 9695918
Date: 2017-07-04
CPC Classifications: F16H,Y02E,Y10T

Claim:
1. A method for gap expanding in a ball screw, the method comprising: disposing the ball screw in a control rod drive mechanism, the ball screw converting via a driving shaft rotational motion of an electric motor to vertical motion to thereby move a hollow piston up or down, wherein the ball screw has a screw shaft and a ball nut engaged with the screw shaft via traveling balls, the gap coefficient (A) is given by: A=((2×R−L)−D)÷(2×R−L)), in which R is a distance between a curved surface forming a ball traveling side and a curvature center point thereof, R being determined for two different curved surfaces, each of the two different curved surfaces having a different curvature center point, L is a distance between the two curvature center points, and D is a diameter of the traveling balls, the gap coefficient is more than 0.03 and less than 0.17, and determining the diameter of the traveling balls to satisfy the expression given by A, in which A has the value of more than 0.03 and less than 0.17, thereby expanding a gap between the ball traveling side of the screw shaft and the traveling balls and a gap between the traveling balls and a ball traveling side of the ball nut.