| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a torsion bar for a seat belt winding device capable of further increasing energy absorbing function, suppressing enlargement, and being formed inexpensively. SOLUTION: Even when higher stress generates on the surface part side of a torsion part 20 when the torsion bar 7 is twisted, the stress on the surface part is suppressed low because hardness of the surface part is set lower than the central part. Therefore, torsion rotational speed until the torsion bar 7 is cut off is higher than a prior art. Rotation amount of a reel after the start of torsion of the torsion part 20 can increase. Therefore, a belt drawing amount of a seat belt after the seat of torsion of the torsion part 20 is sufficiently secured, and energy absorbing ability further increases.</p> |
