Patent ID: 7431119

Claim:
A seat belt retractor comprising: a spool capable of winding and unwinding a seat belt; an electric motor; a power transmission mechanism disposed between the electric motor and the spool to achieve a connected state when the electric motor and the spool are connected and a disconnected state when the connected state is cancelled; and a control mechanism to control the electric motor and the power transmission mechanism to switch between a power transmission operation mode in which the electric motor is driven and the power transmission mechanism is in the connected state, a power transmission allowing mode in which the driving of the electric motor is stopped and the power transmission mechanism is in the connected state, and a power transmission disconnection mode in which the power transmission mechanism is in the disconnected state, wherein when a vehicle door corresponding to the seat belt moves from the closed state to an open state, the control mechanism switches to the power transmission operation mode to conduct the seat belt winding-up action by the spool and, after the seat belt winding-up action, the control mechanism switches to the power transmission allowing mode to maintain the power transmission mechanism in the connected state.