| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of an impact absorption type steering shaft, in which galling of a serration is prevented in the process for relatively shifting an outer shaft and an inner shaft. SOLUTION: Previous to combination with the outer shaft, in the inner shaft 23, a male serration 31 is formed on the outer peripheral surface of an enlarged diameter part 29, but at this time, a chamfer is not applied on the end surface of the enlarged diameter part 29. That is, under condition of forming the end part of the enlarged diameter part 29 to the perfect cylindrical shape, the inner shaft 23 is set in a roll forming device to form the male serration 31 while roll contacting with a roll-forming tool 41. In this way, at the tip part of the enlarged diameter part 29, a blank is shifted in the tip direction by pushed out with the roll-forming tool 41 and a curl part whose shape is smoothly shrunk, is formed at the tip part of the male serration 31. Further, in this way, the galling on a female serration at the outer shaft side is not developed and such effect that resistance is reduced at the time of relatively shifting the outer shaft and the inner shaft 23, is brought about. |
