US Patent 7678007 Reclining device incorporation by reference

The present invention relates to a reclining device that includes an external teeth gear and an internal teeth gear and in which the rotation axis of one of the external teeth gear and the internal teeth gear revolves around the rotation axis of the other. The present invention aims to provide a reclining device of which the operation force is small and the operation force varies little. To achieve the aim, one of (a) the plane of each of the external teeth 31b that engages with the internal teeth 32b and (b) the plane of each of the internal teeth 32b that engages with the external teeth 31b is arranged to be flat, and the other of (a) and (b) is arranged to be convex.