ELECTRIC POWER STEERING APPARATUS OF BALL SCREW TYPE

摘要

A rack-driven auxiliary power steering apparatus prevents a ball nut and a nut pulley from idling due to a slip thereof and increases durability when the drive belt is operated by driving of a motor, and minimizes vibrations and noise transferred through the rack bar, the ball nut, and the nut pulley when the rack bar is slid while the nut pulley and the ball nut are rotating, thereby providing a comfortable steering feeling to the driver.

主权项

1. An electric power steering apparatus of a ball screw type comprising:
a rack bar having a spiral outer peripheral screw groove on an outer peripheral surface thereof; a ball nut coupled to a rack bar via a ball and having a spiral inner peripheral screw groove corresponding to the outer peripheral screw groove on an outer peripheral surface thereof and a ball circulation passage axially penetrating between the inner peripheral screw groove and the outer peripheral screw groove; and an end cap coupled to two inner peripheral surfaces of the ball nut respectively and having a ball moving passage wherein one side thereof passes through the ball circulation passage and the other side thereof passes through the outer peripheral screw groove and the inner peripheral screw groove, wherein a center radius of the ball of the inner peripheral screw groove gradually increases toward an inlet of the ball moving passage or a distance from a central axis to an outermost of the inner peripheral screw groove gradually increases from the center of the ball nut to two sides thereof.