Patent ID: 8376464

Claim:
A seat recliner for a vehicle, the seat recliner comprising: a holder equipped with a lock gear guide portion in a receiving portion opened at one side thereof, the lock gear guide portion having an arc shaped guide surface; an upper gear comprising inside gear teeth formed at an inner peripheral edge of the upper gear, the upper gear being engaged with the holder; an actuating cam located in the holder to be engaged with a rotation shaft extending through center of the holder, and the actuating cam having a transporting projection and a first supporting projection at predetermined intervals on an outer peripheral edge thereof; and a lock gear including outside gear teeth at outside surface and with a contacting surface, a first supporting surface and a first engagement surface at a rear surface with the guide surface of the lock gear guide portion contacting with an outside of the lock gear, wherein the actuating cam is provided with a second supporting projection at an opposite side of the first supporting projection with regard to the transporting projection of the actuating cam, wherein the lock gear is provided with the contacting surface at a center thereof so that the lock gear pushed by the transporting projection can be pushed with regard to a center of the rotation shaft, and is provided with the first supporting surface and a second supporting surface at both sides of the contacting surface so that the first supporting projection and the second supporting projection can be supported, wherein the arc shaped guide surface is formed by a vertex of an equilateral triangle, wherein the equilateral triangle is formed by contact lines of the outside and inside gear teeth and the each of the contact lines is perpendicular to a line, which joins the center of the rotation shaft with the each of the contact lines, and wherein the lock gear further comprises a second engagement surface for separating the inside and outside gear teeth at time of releasing a locking state by engaging with the actuating cam.