| 摘要 |
In a collapsible steering shaft a collapse load is decreased while assuring the heat resistance of a coupling portion between an outer shaft and an inner shaft. In addition, a time during which a great collapse load is needed is also decreased. Female serration grooves on an inner surface of the outer shaft are engaged with male serration grooves on an outer surface of the inner shaft. A recess is formed on the outer surface of the inner shaft and is aligned with a root in the male serration grooves, and a steel ball is set in the recess. A part of this steel ball intrudes into a top part of a thread in the female serration grooves. A flat portion is formed by removing a part of the male serration grooves, whereby the top part crushed by the steel ball can be prevented from frictionally engaging with the male serration grooves. |
