Abstract: In a ball screw according to the present invention, four circulation passages forming a circulation route are respectively arranged in the axial direction of the ball screw. The mounting positions of the second and third circulation passages A2 and A3 are set at positions which are reversed 180 degrees in the circumferential direction thereof with respect to the mounting positions of the first and fourth circulation passages A1 and A4. Accordingly, it is possible to provide a ball screw which can reduce variations in a load distribution along the axial direction of the ball screw caused by moments around a surface perpendicular to the axis of the ball screw that are generated by shifting circumferential-direction phases between circulation passages forming a circulation route from one another.

Abstract: There is provided a return pipe type ball screw capable of accurately positioning and fixing return pipes on and to a nut member even when a troublesome positioning operation is not carried out, and circulating balls endlessly and smoothly for a long period of time without the possibility that dust enters the interior of the nut member. In such a ball screw, ball passing holes formed so as to extend through the nut member are inclined at an angle equal to a lead angle of a ball rolling groove of a screw shaft, and each of the return pipes is formed by combining together a pair of return pieces adapted to be fitted in the ball passing holes.

Abstract: A ball screw apparatus is provided with a screw shaft having a spiral ball screw groove, a nut member having a screw groove, and a plurality of balls. A smoothly continuous worked portion is formed at a portion of the screw groove by grinding a corner portion between the screw groove and a connecting way. The worked portion is formed such that the distance between the screw grooves is gradually reduced regarding an advancing direction of the ball entering from the connecting way in between the screw grooves. This worked portion extends from an end of the connecting way in a circumferential direction of the nut member and within a range of 90° from the corner portion along the circumferential direction of the nut member.

Abstract: A rolling-body screw drive (10) comprises a threaded spindle and a threaded nut (12) enclosing the threaded spindle. A helically running threaded channel (16) is provided between an outer circumferential surface of the threaded spindle and an inner circumferential surface (12a) of the threaded nut (12). The threaded channel (16) forms, together with a return channel (22) in the nut (12) which connects the two end regions (16a, 16b) of the threaded channel (16), an endless circulatory channel (24) in which an endless series of rolling bodies is accommodated. Each of the two end regions (16a, 16b) of the threaded channel (16) is assigned a deflecting element (18) which is retained on the threaded nut (12) and has a deflecting channel (20) for transferring the rolling bodies between the threaded channel (16) and the return channel (22). At least one of the deflecting elements (18) is made up of at least two deflecting-element parts (26, 28) which together bound the deflecting channel (20).

Abstract: This invention relates to improvement of a ball screw unit in which a nut member meshes with a screw shaft via a plurality of balls circulating endlessly. The balls are disposed freely rotatably in line at a predetermined interval in a ball arranging member formed in a belt-like shape. If a relative rotation occurs between the nut member and screw shaft, the balls circulate in the infinite circulation path with the ball arranging member. Guide pieces are projected to both sides of the ball arranging member and guide grooves for accommodating each of the guide pieces are formed along the entire circumference of the infinite circulation path. Therefore, the ball arranging member is introduced by the guide grooves and circulates in the infinite circulation path without being fluttered.