Abstract: The nut has a first fitting surface provided with a first retaining ring groove on an end portion on the other side in the axial direction; the fitting cylinder, at an end portion on the one side in the axial direction, has a second fitting surface provided with a second retaining ring groove in a portion facing the first retaining ring groove with regard to a radial direction; and the retaining ring is engaged so as to span between the first retaining ring groove and the second retaining ring groove.

Abstract: To provide a nut that can suppress increase in the number of components. The nut according to the present disclosure includes a nut main body and a circulation component. The nut main body includes a housing part having a bow shape when viewed from an axial direction, a seat surface, a through hole, and a pair of side surfaces. The circulation component includes a circulation component main body, two arm parts extending toward both sides in a seat surface direction from the circulation component main body, ribs projecting from the respective two arm parts, and caulking parts obtained by caulking the ribs. Recessed parts that the caulking parts enter are disposed on the pair of side surfaces. A ball passage is disposed in the circulation component main body.

Abstract: A linear motion actuator has a ball screw device having a screw shaft, a nut, and a plurality of balls, a piston mounted on one end of the screw shaft, and a stroke limiting mechanism setting an operation starting point in time of the screw shaft toward a first direction pointed by the one end. The nut has one end face directed to the first direction and a protruding part protruding from the one end face.

Abstract: A ball screw has a screw shaft including a spiral-shaped ball rolling groove formed in an outer peripheral surface thereof; a nut including a spiral-shaped ball rolling groove formed in an inner peripheral surface thereof; a plurality of balls disposed in a raceway formed by the two rolling grooves; and, a return path for moving the balls from the terminal point of the raceway to the start point of the raceway, the two end portions of the return path respectively including a rising surface rising from the ball rolling groove of the nut and a stopper portion disposed opposed to the rising surface to form the end portion of the raceway, wherein a boundary portion between the rising surface and the ball rolling groove of the nut is formed a round portion having the radius of curvature 0.05 times the diameter of the ball or more.

Abstract: A rolled ball screw has a screw shaft having a ball screw groove so as to engaging with rolling elements of a ball screw, the screw shaft is formed by rolling while a thread rolling die is pressed against a cylindrical bar-shaped member to thereby roll the ball screw groove, wherein the number of waves per circumference per lead of said ball screw groove is set different from the integer multiples of the number of said rolling elements per lead of said ball screw groove.

Abstract: In the ball screw, a ball circulation tube 20 is formed to have such a shape that the movable amount of balls 15 in a first direction (X) intersecting at right angles to the axis of the tube 20 is larger than the movable amount of the balls 15 in a second direction (Y) intersecting at right angles to the first direction (X), and the ball circulation tube 20 is fixed to a nut 13 in such a manner that the outer surface 20a of the tube 20 extending in parallel with the first direction (X) is opposed to the outer surface of the nut 13.

Abstract: In the ball screw, a ball circulation tube 20 is formed to have such a shape that the movable amount of balls 15 in a first direction (X) intersecting at right angles to the axis of the tube 20 is larger than the movable amount of the balls 15 in a second direction (Y) intersecting at right angles to the first direction (X), and the ball circulation tube 20 is fixed to a nut 13 in such a manner that the outer surface 20a of the tube 20 extending in parallel with the first direction (X) is opposed to the outer surface of the nut 13. Accordingly, it is possible to provide a ball screw which can restrict variations in the torque of the ball screw caused by the mutual sliding movements of balls occurring within a ball circulation tube.

Abstract: A ball screw device has a screw shaft having a helical thread groove provided on an outer surface thereof; a ball nut having a thread groove provided on an inner surface thereof, the ball nut being movably fitted on the screw shaft; a number of balls rollably interposed between the two thread grooves; and a ball circulating member fixed to the ball nut for forming a ball circulation path through which the balls rolling on a gap between the two thread grooves are endlessly circulated, wherein the ball has a distribution of residual compressive stress including a maximum value &sgr;s of 1,000 MPa or less after polishing in a production process involving surface hardening followed by hardening and tempering and the residual compressive stress &sgr;D at the depth of 1% of the ball diameter Dw from the surface of the ball is the maximum value &sgr;s or less.

Abstract: A ball screw has a screw shaft including a spiral-shaped ball rolling groove formed in an outer peripheral surface thereof; a nut including a spiral-shaped ball rolling groove formed in an inner peripheral surface thereof; a plurality of balls disposed in a raceway formed by the two rolling grooves; and, a return path for moving the balls from the terminal point of the raceway to the start point of the raceway, the two end portions of the return path respectively including a rising surface rising from the ball rolling groove of the nut and a stopper portion disposed opposed to the rising surface to form the end portion of the raceway, wherein a boundary portion between the rising surface and the ball rolling groove of the nut is formed a round portion having the radius of curvature 0.05 times the diameter of the ball or more.

Abstract: A rolled ball screw has a screw shaft having a ball screw groove so as to engaging with rolling elements of a ball screw, the screw shaft is formed by rolling while a thread rolling die is pressed against a cylindrical bar-shaped member to thereby roll the ball screw groove, wherein the number of waves per circumference per lead of said ball screw groove is set different from the integer multiples of the number of said rolling elements per lead of said ball screw groove.

Abstract: In the ball screw, a ball circulation tube 20 is formed to have such a shape that the movable amount of balls 15 in a first direction (X) intersecting at right angles to the axis of the tube 20 is larger than the movable amount of the balls 15 in a second direction (Y) intersecting at right angles to the first direction (X), and the ball circulation tube 20 is fixed to a nut 13 in such a manner that the outer surface 20a of the tube 20 extending in parallel with the first direction (X) is opposed to the outer surface of the nut 13. Accordingly, it is possible to provide a ball screw which can restrict variations in the torque of the ball screw caused by the mutual sliding movements of balls occurring within a ball circulation tube.