Patent ID: 7678007

Claim:
A reclining device that includes an external teeth gear and an internal teeth gear and in which a rotation axis of one of the external teeth gear and the internal teeth gear revolves around a rotation axis of the other, the external teeth gear having external teeth on an outer circumferential surface thereof and being disposed with one of a member on a seat cushion side and a member on a seat back side, and the internal teeth gear having internal teeth of which a number of teeth is larger than that of the external teeth of the external gear teeth gear and that are configured so as to engage with the external teeth and being disposed with the other of the member on the seat cushion side and the member on the seat back side, wherein one of a plane of contact of the external teeth whereat the sides of external teeth engage with the sides of internal teeth and a plane of contact of the internal teeth whereat the sides of internal teeth engage with the sides of external teeth is flat, and the other of the plane of contact of the external teeth and plane of contact of the internal teeth is convex.