Patent ID: 8256843

Claim:
A vehicle seat reclining device comprising: a stationary member; a movable member having an internal toothed portion; a plurality of lock tooth blocks, each having an external toothed portion meshable with the internal toothed portion; a cam configured to be in cam-connection with each of the lock tooth blocks; a coiled torsion spring provided to bias the cam in a locked direction such that the external toothed portion meshes with the internal toothed portion; and an operating lever configured to rotate the cam against a spring force of the coiled torsion spring in an unlocked direction such that the external toothed portion demeshes from the internal toothed portion, wherein a plurality of guide protrusion pairs are formed integral with an inside face of the stationary member, for guiding the respective lock tooth blocks, wherein two opposing circular-arc concave portions are formed on two opposing faces of two circumferentially adjacent sets selected out of the plurality of guide protrusion pairs, wherein a circumferential space between the two opposing circular-arc concave portions is dimensioned to be wider on a radially outward side so as to define a spring accommodation space for the coiled torsion spring on the radially outward side, and dimensioned to be narrower on a radially inward side so as to form convex portions, circumferentially opposed to each other, on the radially inward side, wherein the coiled torsion spring has a pair of engagement portions formed by outwardly bending both ends of a winding portion and configured to engage with the respective convex portions under preload, and one of the engagement portions is further configured to have a spring-force application portion hooked to the cam for permanently forcing the cam in the locked direction, and wherein an anti-rotation protrusion is formed on an outside face of the stationary member at a specified position conforming to the spring accommodation space.