Vehicle seat reclining device

A seat reclining device for swingably connecting a seat back to a seat cushion, the seat reclining device comprising:

• a base member connected to one of the seat back and the seat cushion;
• a rotating member connected to the other of the seat back and the seat cushion, the rotating member being rotatable relative to the base member, an internal gear being formed on an inner peripheral surface of the rotating member;
• a lock tooth having an external gear, which is engageable with the internal gear of the rotating member, the lock tooth being swingable in the direction of engaging and disengaging the external gear with and from the internal gear, the lock tooth having a bearing portion which has an arc shaped bearing surface;
• a shaft portion integrally formed with the base member, the shaft portion having an inner-periphery guiding surface, on which the bearing surface of the lock tooth slides in contact with the inner-periphery guiding surface of the shaft portion, the shaft portion being aligned with the external gear along a circumferential direction about a rotational center of the rotating member;
• a pair of guide portions integrally formed with the base member;
• a cam pushing the lock tooth to engage the external gear with the internal gear;
• and
• a weak portion formed at an end portion of the lock tooth opposite to the external gear across the shaft portion.