Patent attributes
A vehicle seat recliner for reclining a seat back with respect to a seat base, includes an internal gear member, an external gear member, a drive member, a lock member, a biasing member, and a cover. The drive member causes relative rotation between the internal gear member and the external gear member. The lock member and the biasing member operate for selectively locking and unlocking relative rotation between the internal gear member and the external gear member. The cover covers an outside of the external gear member. The outside of the external gear member includes fitting projections, wherein the fitting projections project toward the cover, and are arranged concentrically. Each of the fitting projections includes a radial inside fixed to the cover by press-fitting and recess-projection fitting, and includes a radial outside configured to be fitted to a mounting hole of the second frame.