Seat reclining apparatus

Abstract

A seat reclining apparatus includes a base plate, a ratchet plate, guide grooves formed on the base plate, lock members installed in the guide grooves and guided thereby between engaged and disengaged positions, a first cam positioned between the base plate and the ratchet plate and rotates relative thereto by an operation of an operating member between locked and unlocked positions, and a single second cam which presses one of the lock members to the engaged position by receiving a force from the first cam when the first cam rotates from the unlocked position to the locked position, wherein the single second cam is positioned in one of the guide grooves that serves as a second-cam accommodating guide groove, and the single second cam can come in sliding contact with an inner surface of the one of the guide grooves.

What is claimed is: 
     
         1 . A seat reclining apparatus comprising:
 a base plate which is fixed to one of a seat cushion side frame and a seatback side frame;   a ratchet plate which includes an internal gear, said ratchet plate being fixed to the other of said seat cushion side frame and said seatback side frame so as to face said base plate while being rotatable relative thereto;   a plurality of guide grooves which are formed on a surface of said base plate which faces said ratchet plate;   a plurality of lock members which are installed in said guide grooves and guided by said guide grooves, respectively, so that each of said lock members can move between an engaged position, in which an outer toothed portion formed on an outer peripheral surface of said each lock member is engaged with said internal gear of said ratchet plate, and a disengaged position, in which said outer toothed portion of said each lock member is disengaged from said internal gear of said ratchet plate toward an inner peripheral side;   a first cam which is positioned between said base plate and said ratchet plate and rotates relative to said base plate and said ratchet plate in association with an operation of an operating member between a locked position to position each said lock members in said engaged position and an unlocked position to position each said lock members in said disengaged position; and   a single second cam which presses one of said lock members to said engaged position thereof by receiving a force from said first cam when said first cam rotates from said unlocked position to said locked position, wherein said single second cam is positioned in one of said guide grooves that serves as a second-cam accommodating guide groove, and wherein said single second cam is capable of coming in sliding contact with an inner surface of said one of said guide grooves.