Abstract: A method for manufacturing a linear motion shaft includes: manufacturing a first shaft portion, and connecting the first shaft portion and a second shaft portion by friction welding. A first input section is formed in a material for the first shaft portion to obtain the first shaft portion and then a gripped section for centering is formed on the outer peripheral surface of an axially end portion of the first shaft portion on the side connected to the second shaft portion based on the first input section. The friction welding is performed by abutting the axially end portions of the first shaft portion and the second shaft portion in a state where the gripped section is gripped by a first gripping tool for centering, the first shaft portion is rotated with the first gripping tool, and the second shaft portion remains without rotating.

Abstract: With respect to a linear motion shaft in which a rack shaft part and a ball screw shaft part are joined to each other by friction welding, coaxiality of a portion having a rack shaft part and a portion having a ball screw shaft part is improved. In a state where a gripped portion 56 formed on the screw shaft part 29 is gripped by a first gripping tool 57 for centering, and a rack shaft part 28 is gripped by a second gripping tool 58 for centering, end portions in the axial direction of the rack shaft part 28 and the screw shaft part 29 are abutted to each other while the screw shaft part 29 and the rack shaft part 28 are relatively rotated by rotating the first gripping tool 57, so that the rack shaft part 28 and the screw shaft part 29 are joined to each other by friction welding.

Abstract: An electric power steering apparatus includes an input shaft, an output shaft, a torsion bar coaxially coupling the input and output shafts to each other, and a torque detection sleeve. One of the input and output shafts includes a cylindrical portion. On the inner peripheral surface of the cylindrical portion, a female stopper is provided. The other of the input and output shafts includes a male stopper to be engaged with the female stopper, and a torque detection concave-convex section adjacent to the male stopper in the axial direction. The male stopper includes a plurality of male grooves. The torque detection concave-convex section includes a plurality of detection grooves. The torque detection sleeve is arranged radially outside the torque detection concave-convex section. The diameter of a groove bottom circle of the male stopper is smaller than the diameter of a groove bottom circle of the torque detection concave-convex section.

Abstract: An electric power steering apparatus includes an input shaft, an output shaft, a torsion bar coaxially coupling the input and output shafts to each other, and a torque detection sleeve. One of the input and output shafts includes a cylindrical portion. On the inner peripheral surface of the cylindrical portion, a female stopper is provided. The other of the input and output shafts includes a male stopper to be engaged with the female stopper, and a torque detection concave-convex section adjacent to the male stopper in the axial direction. The male stopper includes a plurality of male grooves. The torque detection concave-convex section includes a plurality of detection grooves. The torque detection sleeve is arranged radially outside the torque detection concave-convex section. The diameter of a groove bottom circle of the male stopper is smaller than the diameter of a groove bottom circle of the torque detection concave-convex section.