JP2009138914A5 - - Google Patents

Claims (5)

  A screw shaft having a shaft screw groove formed on an outer peripheral surface thereof, and a ball nut having a nut screw groove positioned outside the screw shaft and facing the shaft screw groove, the relative rotation of the screw shaft and the ball nut Accordingly, a ball circulation path is provided which causes the ball to roll along the ball load rolling path between the both screw grooves, and has a larger inner diameter than the inner diameter of the ball load rolling path, and circulates the ball. A ball screw device provided with a circulation member having a ball guide passage inside and communicating between a load rolling path and the ball circulation path at two locations, wherein the ball nut is connected at the joint between the ball nut and the circulation member. The ball screw device is characterized in that a buffer portion for expanding the diameter of the nut screw groove to the outside is provided so that no step is generated between the circulating member and the ball guide passage.   The buffer portion includes an inclined portion that is inclined from the nut screw groove and expands outward in diameter, and a flat portion that is connected to the inclined portion and smoothly connected to the ball guide passage of the circulation member. Item 2. The ball screw device according to Item 1. The ball circulation path is the ball screw apparatus according to claim 1 or 2 was formed on the ball nut. The ball screw device according to any one of claims 1 to 3 , wherein notches are provided at both ends of the ball nut, and the circulation member is incorporated in these notches. The ball screw device according to any one of claims 1 to 4 , wherein the circulation member is integrally provided at both ends of a return tube having the ball circulation path.