Abstract

A reclining device for seat which has circular inwardly and outwardly toothed portions as a full meshing lock element, which permits for reducing pitches in the teeth of them for fine adjustment of reclining angle. A male lock member having the circular outwardly toothed portion and a female lock plate having the circular inwardly toothed portion are provided coaxially on a shaft. The male lock member is so accommodated in a base housing as to be movable along the longitudinal axis of the shaft in an irrotational way via a guide element. A rotary cam member and an array of cam follower regions are provided as an actuation element, which works with the guide element to insure stable positioning and displacement of the male lock member relative to the female lock plate. Hence, the arcuate outwardly toothed protion may be positively brought to and out of meshed engagement with the arcuate inwardly toothed portion, without any incomplete unlocking problem.