Patent ID: 7073861

Claim:
A seat back hinge construction comprising: a center hinge to be provided between seat backs arranged by being divided into right and left, and said right and left seat backs to be supported by said center hinge so as to be reclinable, said center hinge including a mounting bracket of which one end portion to be installed to one seat back, a center hinge bracket to be installed to a vehicle body, and a hinge shaft for connecting said mounting bracket to said center hinge bracket; said right and left seat backs to be supported via said center hinge so as to be turnable by inserting said hinge shaft through the other end portion of said mounting bracket and said center hinge bracket and by fixing said hinge shaft to a seat frame of the other seat back; the other end portion of said mounting bracket and said center hinge bracket each are provided with a through hole through which a cylindrical collar is installed, and said hinge shaft is arranged by being inserted in said collar; said collar is formed with an engagement portion for holding the other end portion of said mounting bracket; the mounting bracket is held on the engagement portion on the end of the collar, and the hinge shaft is inserted through the installation bracket and is then directly installed to the seat frame; wherein said hinge shaft is formed by a shoulder bolt having a large-diameter portion and a small-diameter portion, and is configured so that a shoulder is in contact with the side surface of a seat frame of said seat back in a state in which said hinge shaft is tightened and fixed; and wherein a child seat attachment member extending in the transverse direction is fixed to said center hinge bracket.