Patent ID: 7334843

Claim:
A seat reclining apparatus comprising: a base plate fixedly attached to one of a seat bottom and a seatback and including a plurality of guiding portions extending in a radial direction of the base plate; a gear plate fixedly attached to the other one of the seat bottom and the seatback, the gear plate rotatably assembled at the base plate and formed with internal teeth; a lock gear assembled at the base plate and guided by the guiding portions of the base plate to be movable in the radial direction, the lock gear being formed with external teeth engageable with the internal teeth of the gear plate, at least one external tooth, which is positioned at at least one of a front end and a rear end from a rearward tilting direction of the seatback, having a radius of a pitch circle being smaller than a radius of a pitch circle of the internal teeth of the gear plate; a cam member rotatable and controlling a radial movement of the lock gear so that the lock gear is engaged with or disengaged from the internal teeth of the gear plate; and a biasing member for biasing the cam member to rotate in a direction for engaging the lock gear with the internal teeth.