IMPACT-ABSORBING STEERING DEVICE

PROBLEM TO BE SOLVED: To solve a problem wherein impact absorbing load varies due to minute relative rotational motion on a pair of jackets under a normal condition in a column contraction type impact-absorbing steering device. SOLUTION: In this impact-absorbing steering device 1, an outer jacket 5 and an inner jacket 6 of a steering column 4 fitting each other are retained with a designated retention force under the normal condition and are allowed to relatively slide under an impact absorbing condition. At least a contact part 37 of an outer circumference 35 of the inner jacket 6 is subjected to surface hardening treatment such as carbo-nitriding. Consequently, difference of Vickers hardness between contact parts 33, 37 of fitting parts 31, 36 is maintained at least 200 or more. Occurrence of welding and irregular wear is controlled when both of the jackets 5, 6 relatively rotate minutely to suppress variation of impact absorbing load. An inner periphery 30 of the outer jacket 5 can be subjected to the surface hardening treatment instead of the outer circumference 35 of the inner jacket 6. COPYRIGHT: (C)2004,JPO