Patent ID: 7699397

Claim:
A seat reclining device, comprising: reclining mechanisms that are respectively provided on right and left sides of a seat so as to adjust an inclination angle of a seat back; and a connection member for synchronizing locking and unlocking motion of the reclining mechanisms, the connection member being disposed between the right and left reclining mechanisms, wherein the connection member connects operation shafts for respectively switching the right and left reclining mechanisms between a locking condition and an unlocking condition thereof in a condition that power can be transmitted therebetween, wherein the reclining mechanisms are disposed such that axes of their operation shafts are normally aligned with each other, wherein when a load is laterally disproportionately applied to the seat back in the locking condition of the reclining mechanisms, one of the reclining mechanisms relatively rotates together with the operation shaft thereof with respect to the other of the reclining mechanisms, so as to rotate the operation shaft of the other of the reclining mechanisms, thereby relatively releasing the locking condition of the other of the reclining mechanisms, wherein the connection member and the operation shaft of the other of the reclining mechanisms are connected by a coupling connection in which they are axially inserted to each other, so that the power can be transmitted therebetween, wherein the coupling connection portion of the connection member and the operation shaft of one of the reclining mechanisms is provided with a transmission preventing mechanism that is capable of preventing the transmission of the power between the operation shaft and the connection member when the load is laterally disproportionately applied to the seat back, and wherein the transmission preventing mechanism is constructed such that when the load is laterally disproportionately applied to the seat back, the one of the reclining mechanisms relatively rotates together with the operation shaft thereof and the connection portion of the operation shaft of one of the reclining mechanisms and the connection member is expanded in a width direction so as to be bent in a V-shape, thereby preventing the transmission of the power between the operation shaft and the connection member.