| 摘要 |
<p>An object of the present invention is to provide a technique for improving a strength, especially a fatigue strength of a power transmission shaft provided with a serrated portion for torque transmission such as a spline shaft. A power transmission shaft is serration-fitted to an inner joint member of respective constant velocity joints (2, 3). A driveshaft (1) is provided with a serrated portion (A) as well as a smooth portion (B) having a cylindrical outer circumferential surface (4a). A cut-up portion (13) is formed at the end portion of the serrated portion (A). When applying an induction hardening to the smooth portion (B) and the serrated portion (A), a hardening ratio of the smooth portion (B) is set at a different value from that of the serrated portion (A), and such that a fatigue strength of the smooth portion (A) becomes equal to or greater than that of the serrated portion (A).</p> |
