Patent ID: 8128169

Claim:
A seat reclining apparatus for a vehicle, comprising: a first arm adapted to be supported by one of members respectively arranged at a seat cushion and a seat back of a seat; a second arm adapted to be supported by the other of the members respectively arranged at the seat cushion and the seat back of the seat; an internal gear formed at the first arm; an external gear formed at the second arm and engaging with the internal gear that is formed at the first arm, the external gear including at least one fewer teeth than the internal gear of the first arm; a first circumferential portion formed coaxially with the internal gear at the first arm; a second circumferential portion formed coaxially with the external gear at the second arm; first and second wedge members accommodated in an accommodating space formed between the first circumferential portion and the second circumferential portion under a condition where one of the first circumferential portion and the second circumferential portion eccentrically contacts the other of the first circumferential portion and the second circumferential portion so that the internal gear and the external gear engage with each other, each of the first and second wedge members including a pressure portion pressed by the one of the first circumferential portion and the second circumferential portion and a circumferential contact surface frictionally contacting the other of the first circumferential portion and the second circumferential portion to thereby bring the first and second wedge members into a wedged state; a spring arranged between the first and second wedge members and biasing the first and second wedge members in a direction toward first and second ends of the accommodating space, respectively, to thereby realize the wedged state; a drive shaft rotatably driven by a drive unit around a rotation axis of either one of the first arm and the second arm, the drive shaft moving one of the first and second wedge members in a direction away from one of the first and second ends of the accommodating space depending on a rotation direction of the drive unit in order to release the wedged state of the one of the first and second wedge members and pressing the other of the first and second wedge members into the other of the first and second ends of the accommodating space to move one of the internal gear and the external gear eccentrically relative to the other of the internal gear and the external gear to thereby rotate the second arm relative to the first arm depending on a difference of the number of teeth between the internal gear and the external gear; and a retention groove retaining a lubricant and formed on the circumferential contact surface of each of the first and second wedge members frictionally contacting the other of the first circumferential portion and the second circumferential portion, the retaining groove extending along a direction of the rotation axis of either one of the first arm and the second arm.