3ff2c1cd_Kosuke___Patent_applications__Description
[Patent application number] 20140144263 [Published] 05-29-2014 [Description] 
BALL SCREW AND ELECTRIC POWER STEERING SYSTEM INCLUDING BALL SCREW - There are provided a ball screw that makes it possible to prevent a situation where a large load is applied to a part of a plurality of balls, and an electric power steering system including the ball screw. The ball nut is a component that surrounds a part of the male thread groove, and has a nut inner surface and a female thread groove. The female thread groove is formed in the nut inner surface, and forms a part of the rolling path. A female thread diameter varies according to a position in an axial direction of the ball nut. The female thread diameter is larger at each of axially ends of the ball nut than at an axially intermediate portion of the ball nut, and the female thread diameter is larger at one of the axially ends than at the other of the axially ends.
Kosuke - Patent applications