A cylindrical retainer configured to retain balls in a rollable manner is provided inside a ball screw nut. The retainer has retainer grooves each having a shape of an elongated hole that extends in an axial direction of a ball screw shaft so as to be inclined at a predetermined angle. A first end of the ball screw nut and a first end of the retainer, which is one of two ends of the retainer that is closer to the first end of the ball screw nut, are spaced away from each other by a distance. The terminal end of the retainer groove closest to the second end of the retainer and a ball that is closest to the second end of the ball screw nut are spaced away from each other by a distance. The distance is set equal to or larger than the distance.

A ball screw device is provided, including a retainer that can properly retain balls. The difference between a diameter being the pitch circle diameter of the ball screw device and the outside diameter of the rack shaft is set to be equal to or larger than the difference between the bore diameter of a ball screw nut and the diameter. The thickness center diameter of the retainer is set to be smaller than the diameter. Even when the inclination angle is reduced, the clearance between the inclined surfaces of each retainer groove on the radial inside can be easily set to be smaller than the diameter of the balls because the bore diameter of the retainer is set to be smaller. Thus, even when the inclination angle of the inclined surfaces is set to be smaller, the balls can be properly retained.

A ball screw device and a steering system that include a retainer having more uniform stiffness are provided. Between a rack shaft and a ball screw nut, a cylindrical retainer having a plurality of retainer grooves that retain balls in a rollable manner is provided. Each retainer groove has two short inner surfaces that intersect the extending direction of the retainer groove and two long inner surfaces that intersect these short inner surfaces and extend along the extending direction of the retainer groove. In each of interior-angle portions where the short inner surfaces and the long inner surfaces intersect, a corner round surface is formed. The radius of the corner round surface is set to be smaller than one half of the width of the retainer groove.

A ball screw mechanism that allows a reduction in contact and friction between a retainer and a nut is provided. In a ball screw mechanism, a nut is threadedly engaged with a screw groove of a rack shaft through balls retained in a retainer groove of a retainer, and an axial force is applied to the rack shaft in accordance with rotation of the nut. The nut includes a uniform diameter portion having a uniform inside diameter and enlarged diameter portions each having an inside diameter larger than that of the uniform diameter portion. The enlarged diameter portions are provided at opposite axial ends of a region on an inner circumferential surface of the nut. The region faces the retainer groove and retainer ends adjoining to opposite axial ends of the retainer groove.

A ball screw assembly is disclosed herein. The assembly includes a nut having an outer raceway, and at least one notch. A spindle extends inside of the nut, and the spindle defines an inner raceway. A ball-spring assembly includes a plurality of balls supported between the outer raceway and the inner raceway, and at least one reset spring engaged against at least one ball of the plurality of balls At least one end-stop component is engaged against a terminal end of the ball-spring assembly and positioned within the at least one notch. A radially inner side of the at least one end-stop component abuts the spindle. A method of forming the nut for a ball screw assembly is also disclosed herein.

There is provided a ball screw mechanism for which a return of a sphere, such as a conventional circulating ball screw, need not to be considered, and that can prevent vibration and noise and avoid an increase in heat by ensuring smooth movement of a sphere without causing ball jam or the like of a sphere on a screw shaft. The present invention includes a screw shaft 2 that has a spiral groove 2a and extends linearly, a housing 30 that surrounds a periphery of the screw shaft 2, and a plurality of spheres 4 and ball bearings 5 that transmits thrust of the screw shaft 2 to the housing 30. Each ball bearing 5 includes an outer ring 7 attached and fixed to the housing 30 at regular intervals along the spiral groove 2a of the screw shaft 2, and an inner ring 6 provided with a concave spherical contact surface 5a in contact with the sphere 4 on a side surface facing the screw shaft 2. Each inner ring 6 is rotatably disposed about rotation axes N.sub.1 to N.sub.4 orthogonal to a rotation axis O of the screw shaft 2. The spheres 4 are arranged, each in contact with the contact surface 5a of each of the ball bearings 5, at regular intervals adjacent to each other in the spiral groove 2a of the screw shaft 2.

The invention relates to mechanical engineering, and more particularly to a curved groove ball bearing mechanism, in which a pair of curved groove ball bearings without a retainer are symmetrically arranged to enable the conversion between the rotary motion and the reciprocating linear motion. The bearing mechanism includes an inner ring, a first outer ring, a second outer ring, a plurality of first steel balls and a plurality of second steel balls. The invention is capable of achieving the conversion between the rotary motion of the inner ring into the reciprocating linear motion of the first and second outer rings.

There is provided a ball screw mechanism for which a return of a sphere, such as a conventional circulating ball screw, need not to be considered, and that can prevent vibration and noise and avoid an increase in heat by ensuring smooth movement of a sphere without causing ball jam or the like of a sphere on a screw shaft. The present invention includes a screw shaft 2 that has a spiral groove 2a and extends linearly, a housing 30 that surrounds a periphery of the screw shaft 2, and a plurality of spheres 4 and ball bearings 5 that transmits thrust of the screw shaft 2 to the housing 30. Each ball bearing 5 includes an outer ring 7 attached and fixed to the housing 30 at regular intervals along the spiral groove 2a of the screw shaft 2, and an inner ring 6 provided with a concave spherical contact surface 5a in contact with the sphere 4 on a side surface facing the screw shaft 2. Each inner ring 6 is rotatably disposed about rotation axes N.sub.1 to N.sub.4 orthogonal to a rotation axis O of the screw shaft 2. The spheres 4 are arranged, each in contact with the contact surface 5a of each of the ball bearings 5, at regular intervals adjacent to each other in the spiral groove 2a of the screw shaft 2.

A ball screw assembly is disclosed herein. The assembly includes a nut having an outer raceway, and at least one notch. A spindle extends inside of the nut, and the spindle defines an inner raceway. A ball-spring assembly includes a plurality of balls supported between the outer raceway and the inner raceway, and at least one reset spring engaged against at least one ball of the plurality of balls. At least one end-stop component is engaged against a terminal end of the ball-spring assembly and positioned within the at least one notch. A radially inner side of the at least one end-stop component abuts the spindle. A method of forming the nut for a ball screw assembly is also disclosed herein.

A ball screw assembly includes a guider, an open nut, open shields, a first circulator, a second circulator, and ball circulating assemblies. The open nut is slidably fitted over the guider and includes an axial cylinder having an axial opening. Inner spiral channels of the axial cylinder and spiral channels of the guider form inner ball races. The open shields are coaxially fitted over the axial cylinder. An inner peripheral wall of each of the open shields and an outer annular wall of the axial cylinder form an outer ball race. The first circulator and the second circulator are disposed on the axial cylinder corresponding to the open shields. The inner ball races, first curves of the first circulator, the outer ball races, and second curves of the second circulator form ball circulating races, and the ball circulating assemblies roll in the ball circulating races.