Patent ID: 7669931

Claim:
A seat reclining mechanism designed to be mounted to a seat cushion and a seat back so as to allow said seat back to be reclined, said seat reclining mechanism comprising: a guide bracket adapted to be mounted to either one of said seat cushion and said seat back; an internal gear member adapted to be mounted to a remaining one of said seat cushion and said seat back, said internal gear member being coupled to said guide bracket in a rotatable manner about a rotation axis thereof with respect to said guide bracket, and formed with internal teeth along a circle having a center on said rotation axis; a plurality of lock gear members disposed between said guide bracket and said internal gear member to extend radially from said rotation axis, each of said lock gear members being formed with external teeth meshingly engageable with said internal teeth, and supported by said guide bracket in such a manner as to be slidable in both a lock direction causing said external teeth to be brought into meshing engagement with said internal teeth and an unlock direction causing said external teeth to be released from the meshing engagement with said internal teeth; a fitting portion provided in either one of said guide bracket and said internal gear member; a rotatable cam rotatably supported by said fitting portion, and adapted to be rotatable in both a lock-causing rotation direction causing said lock gear members to be slidingly moved in said lock direction and an unlock-causing rotation direction causing said lock gear members to be slidingly moved in said unlock direction; and a lock spring biasing said rotatable cam in said lock-causing rotation direction, wherein: said fitting portion comprises a fitting hole formed in said either one of said guide bracket and said internal gear member, said rotatable cam has a fitting boss adapted to be fitted into said fitting hole, said fitting boss has an annular-shaped boss body, and a plurality of protrusions that protrude radially from said boss body toward an inner peripheral surface of said fitting hole to come into sliding contact with said inner peripheral surface.