Patent attributes
A seat belt retractor includes at least one frame having a back board and side walls extending from side rims of the back board, a spool supported by the at least one frame configured to wind up a seat belt, a motor configured to rotate the spool, and an electronic control unit mounted to the frame for controlling the driving of the motor. The electronic control unit includes a base, an electronic control unit board fixed to the base, and a cover attached to the base to cover the electronic control unit board. The electronic control unit includes an opening at a lower end that opens an interior of the electronic control unit to an exterior.