Patent ID: 8182039

Claim:
A coupling device of a vehicle seat, which couples two subject members in a manner such that one of the two subject members is rotated relative to the other of the two subject members, and relative rotation of the two subject members is locked at a given position, comprising: a first coupling member and a second coupling member, each of which includes a disc portion, wherein the first coupling member and the second coupling member are integrally coupled to the respective subject members, and the first coupling member is combined with the second coupling member in a manner such that the first coupling member and the second coupling member are rotated relative to each other, and the disc portions of the first coupling member and the second coupling member face each other; at least two lock members disposed between the first coupling member and the second coupling member, wherein, when outer peripheral tooth surfaces formed in the lock members are engaged with respective inner peripheral tooth surfaces formed in the second coupling member, relative rotation of the first coupling member and the second coupling member is locked; a plurality of pairs of guide portions formed in the first coupling member, wherein side surfaces of each pair of guide portions are disposed on sides of the corresponding lock member in a circumferential direction, wherein: each of the lock members is placed in the first coupling member so that a gap is formed between the lock member and each of the corresponding pair of the guide portions disposed on the sides of the lock member; when the outer peripheral tooth surface of each of the lock members is engaged with the corresponding inner peripheral tooth surface of the second coupling member, the lock member is rotated so that the lock member is inclined with respect to the side surfaces of the corresponding pair of the guide portions, and a portion of each of both side surfaces of the lock member contacts the side surface of the corresponding guide portion; and the lock members are arranged in the circumferential direction in the first coupling member, and at least one of the lock members is rotated in a rotational direction opposite to a direction in which at least one of the other lock members is rotated, to contact the side surfaces of the corresponding pair of the guide portions; and a slide cam disposed between the two lock members, the slide cam including inclination surfaces formed therein; wherein: the two lock members are symmetric to each other with respect to a line orthogonal to a rotational axis of the coupling device; when the slide cam slides in one direction along the line, the two lock members are guided by respective inclination surfaces formed in the slide cam so that the two lock members are rotated in the rotational directions opposite to each other while the two lock members are pushed outwardly in a radial direction of the first coupling member.