Seat reclining device

摘要

A seat reclining device includes a lower arm, an upper arm, and a locking mechanism including a cam rotatable relative to either the lower arm or the upper arm and restricting a relative rotation between the lower arm and the upper arm. The seat reclining device further includes a spring disposed in a space formed between the cam and either one of the lower arm or the upper arm for biasing the cam in a direction in which the locking mechanism restricts the relative rotation between the lower arm and the upper arm. The spring is wound around a rotational axis of the cam and disposed in an opening hole formed at either one of the lower arm or the upper arm. The spring includes an inner engaging portion to be engaged with the cam and an outer engaging portion to be engaged with the opening hole.