Patent ID: 8387907

Claim:
A seat belt device, comprising: a retractor frame; a spindle that is rotatably attached to the retractor frame and configured to have a webbing wrapped around an outer periphery thereof; a lock member that is rotatable with respect to the retractor frame and configured to be locked thereby preventing rotation during an emergency; a pin connecting the spindle and the lock member such that the spindle and the lock member rotate integrally with each other in an initial state, the pin being breakable when a predetermined relative rotational force acts between the spindle and the lock member, to separate the spindle from the lock member in a second state where the spindle and the lock member can rotate relatively to each other; an emergency lock configured to lock during the emergency, locking the lock member to the retractor frame, thereby hindering rotation of the spindle in a webbing draw-out direction; a pretensioner configured to cause the spindle to rotate in a take-up direction in order to take up a predetermined length of the webbing before the emergency lock operates, during the emergency, to lock the lock member; an energy absorption mechanism having one end fixed to the spindle and another end fixed to the lock member, and which is configured to absorb collision energy while allowing relative rotation between the spindle and the lock member, when, during the emergency, a rotational force equal to or greater than a predetermined value acts, in the webbing draw-out direction, on the spindle, in a state where the lock member is locked by the emergency lock, wherein the pin having first and second breaking loads depending on the direction of relative rotation between the lock member and the spindle, the breaking load being greater when the spindle is about to rotate relative to the lock member in the webbing draw-out direction than the breaking load when the spindle is about to rotate relative to the lock member in a webbing take-up direction.