Seat reclining device

摘要

A seat reclining device includes a first circular shaped concave portion formed in a first arm and a second concave portion which is concentric with the first concave portion and formed inwardly of the first concave portion. The device also includes an engaged portion which is engaged by an engaging portion. The engaged portion is dividing into two engaged portions in which a first engaged portion is formed on the inner surface of the first concave portion and a second engaged portion is formed on the inner surface of the second concave portion. The engaging portion is divided into two engaging portions such that a first engaging portion is engaged with the first engaged portion and a second engaging portion is engaged with the second engaged portion. All the engaging and engaged portion have gears possessing the same angular piths as each other.