Seat belt retractor employing ultrasonic motor

摘要

A reel of a seat belt retractor equipped in a automobile for reeling a seat belt is integral with a shaft of an ultrasonic motor. The ultrasonic motor is rotated either one direction or the other so as to retract or draw out the seat belt. A control device for controlling the rotation of the ultrasonic motor by supplying a control signal based on the signals sensed by a buckle sensor which senses a buckle is locked, a tension sensor which senses tension of a seat belt, a speed sensor which senses speed of the automobile, a rotation sensor which senses the rotation degree and a child seat sensor which senses whether child seat is set on a passenger seat.