Patent ID: 7874589

Claim:
A seat belt retractor comprising: at least one spool for winding up a seat belt, a locking mechanism having a locking member which is prevented from rotating in a belt withdrawing direction in an event of an emergency, and a seat belt load limiting mechanism for limiting load applied to the seat belt when the spool rotates relative to the locking member, wherein the seat belt load limiting mechanism comprises a torsion bar which rotationally connects the spool and the locking member and is torsionally deformable when the spool rotates relative to the locking member, and a shearing member which is disposed to extend both in the spool and the locking member and is shear-deformable when the spool rotates relative to the locking member, wherein limited load characteristics of the seat belt load limiting mechanism are set such that a limited load is first a load limited only by shear deformation of the shearing member when the spool rotates relative to the locking member, and a load limited by torsional deformation of the torsion bar is added to the load limited by the shearing member after the load limited by the shearing member becomes a maximum limited load.