PRETENSIONER, RETRACTOR, AND SEAT BELT DEVICE

Provided are a pretensioner, a retractor, and a seat belt device which can achieve both securing of the strength of a power transmission member in an initial driving stage and reduction of the sliding resistance against the power transmission member in a steady driving stage. The retractor includes a spool for winding up webbing for restraining an occupant and a pretensioner for winding up the webbing in an emergency to remove slack. The pretensioner includes a ring gear connected to the spool and a power transmission device for transmitting power to the ring gear in an emergency. The power transmission device includes a rod-shaped power transmission member which transmits power to the ring gear while being plastically deformed. A tip end of the power transmission member has an enlarged portion formed thicker than other portions of the power transmission member . The enlarged portion is made of the same material as the power transmission member