| 摘要 |
PROBLEM TO BE SOLVED: To optionally adjust the inclination of a seat back. SOLUTION: A seat back is connected in a rising/falling manner to the rear part of a seat cushion, and a fixed ring 11 and a rotating ring 12 are provided on the rising/falling center shaft. The fixed ring 11 is fixed to a seat cushion, and the rotating ring 12 is fixed to the seat back. A V-shape cam groove 21 deep at the circumferential center and gradually shallowed toward both ends is formed at the outer periphery of the fixed ring 11. A rolling element 23 is interposed between the cam groove 21 and a cylindrical surface 22 at the inner periphery of the rotating ring 12, and the seat back is locked in the inclination adjusted position by the frictional contact of the rolling element with a bottom face 21a of the cam groove 21 and the cylindrical surface 22. An operating member 51 provided coaxially with a retainer 24 is rotated to axially press the retainer by a cam face 53 so as to engage a positioning protruding part 42 provided at the retainer 24, with a positioning recessed part 41 formed at the fixed ring 11. This engagement holds the rolling element 23 in a neutral position contactless with the cylindrical surface 22 to adjust the inclination of the seat back. Frictional resistance imparting mechanism 70 for imparting frictional resistance to the rotating ring 12 is provided to prevent the play of the seat back.
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