Patent ID: 8579756

Claim:
A reclining mechanism comprising: a ring-shaped first plate fixed to a seat back; a ring-shaped second plate capable of rotating with respect to the first plate and fixed to a seat cushion; a plurality of planetary gears in meshing engagement with internal gears provided in respective inner peripheries of the first plate and the second plate; a sun gear in meshing engagement with the planetary gears; a holding member rotatably holding the planetary gears and having an inner peripheral wall surrounding the sun gear; and a restriction member for restricting a rotation of the holding member with respect to the sun gear, wherein: the sun gear has an opposing wall section opposed to the inner peripheral wall of the holding member; the opposing wall section of the sun gear and the inner peripheral wall of the holding member define therebetween a wedge-shaped space in which the restriction member is displaceably disposed; and the opposing wall section of the sun gear is formed such that a width of the wedge-shaped space is gradually narrowed toward a counter direction with respect to a specific direction, where the specific direction is a direction along which the first plate is urged to be rotated according to a force applied to the seat back in a rearward tilting direction, and the counter direction is a direction opposite to the specific direction.