Ball screw

A ball screw comprising:

• a screw shaft formed with a spiral screw groove on an outer peripheral surface thereof;
• a nut formed with a spiral screw groove on an inner peripheral surface thereof and provided with a notch portion on an outer peripheral surface thereof;
• balls configured to roll between the screw groove of the screw shaft and the screw groove of the nut;
• and
• a circulation part forming a ball circulation path for circulating the balls rolling between both screw grooves of the screw shaft and the nut and attached to the notch portion,
• wherein the nut is formed with, in the notch portion, an elongated hole that penetrates in a radial direction, and whose longitudinal direction is formed along a lead angle and parts of both longitudinal side surfaces parallel to each other guide the balls,
• wherein the circulation part includes
• a first circulation component that is disposed in the notch portion so as to abut against a bottom wall surface of the notch portion and has a tongue portion accommodated in the elongated hole,
• a second circulation component that is disposed in the notch portion so as to cover the first circulation component and accommodated in the elongated hole, and has a wall portion facing the tongue portion, and
• a pipe that is disposed in an abutting surface where the first circulation component and the second circulation component abut against each other, constitutes a part of the ball circulation path, and has a higher strength than materials of the first and second circulation components,
• wherein the notch portion includes a first bottom wall surface and a second bottom wall surface, the first bottom wall surface being deeper into the notch than the second bottom wall surface,
• wherein the elongated hole is at least partially formed in the second bottom wall surface,
• wherein the first circulation component contacts the first bottom wall surface and the first circulation component has a tongue portion, and
• wherein the second circulation component has an extending portion that contacts the second bottom wall surface.