Patent ID: 8052535

Claim:
A motor vehicle steering shaft that rotates responsively to steering of a steering member, the motor vehicle steering shaft comprising: an inner shaft and a tubular outer shaft fitted in a manner to relatively slide in a shaft direction and to transmit a torque to and from each other; a rigid coupling element for rigidly coupling the inner shaft and the outer shaft in a circumferential direction of the inner shaft when a relative rotation amount of the inner shaft and the outer shaft exceeds a predetermined range; and an elastic coupling element for elastically coupling the inner shaft and the outer shaft in the circumferential direction of the inner shaft when the relative rotation amount of the inner shaft and the outer shaft is within the predetermined range; the elastic coupling element including a resin member that extends across a first shaft-direction groove formed on an outer circumferential surface of the inner shaft and a second shaft-direction groove formed on an inner circumferential surface of the outer shaft; the inner shaft and the outer shaft being elastically supported mutually via the resin member at a central position of the predetermined range when no torque is loaded to the steering shaft; the resin member including a cylindrical surface that has a contact portion linearly contacting the second shaft-direction groove; the second shaft-direction groove and the contact portion forming a predetermined contact angle; the second shaft-direction groove including a pair of opposite surfaces facing the circumferential direction of the inner shaft and the cylindrical surface of the resin member; contact portions linearly contacting the cylindrical surface being formed on each of the pair of the opposite surfaces; a distance between one contact portion of the pair of the opposite surfaces and a center of the inner shaft being equal to a distance between the other contact portion of the pair of the opposite surfaces and the center of the inner shaft; the first shaft-direction groove including a pair of fixing surfaces aligned in the circumferential direction of the inner shaft; and the resin member including a pair of flat surfaces fixed on the pair of fixing surfaces.