Seat reclining apparatus

A seat reclining apparatus, comprising:

• a first member configured to be attached to one of a seat cushion and a seat back and including an internal gear and a first tubular portion positioned coaxially with the internal gear and arranged at an inner circumferential side of the internal gear;
• a second member configured to be attached to the other of the seat cushion and the seat back and including an external gear and a second tubular portion into which the first tubular portion is inserted, the external gear having teeth fewer than teeth of the internal gear and engaging with the internal gear, the second tubular portion being positioned coaxially with the external gear and arranged at an inner circumferential side of the external gear;
• a pair of wedge members arranged in an annular accommodating chamber formed between an outer circumferential surface of the first tubular portion and an inner circumferential surface of the second tubular portion, each of the wedge members including a protruding portion axially protruding from the accommodating chamber;
• a biasing member biasing the pair of wedge members in a direction to separate the pair of wedge members from each other in a circumferential direction of the pair of wedge members;
• an input member having a central axis coaxial with the first tubular portion, the input member rotating to press the protruding portion along the circumferential direction to rotate the pair of wedge members in the circumferential direction to move an engagement position between the internal gear and the external gear in the circumferential direction;
• a pressing point via which the input member presses the wedge member;
• a radially inward contact point via which the wedge member is contactable with the first tubular portion;
• and
• a radially outward contact point via which the wedge member is contactable with the second tubular portion,
• wherein in a state where a biasing force of the biasing member is largest because of a dimensional variation in manufacturing, a pressing force line passing through the pressing point via which the input member presses the wedge member is designed to be identical to an intermediate line between a first tangent line passing through the radially inward contact point and a second tangent line passing through the radially outward contact point.