Electric seat belt retractor system

摘要

An electric retractor extracts and retracts a seat belt in response to tension in the seat belt. The electric retractor may include a spool rotatably attached to a retractor frame. A seat belt is wound on the spool. The spool is rotated by a motor via a worm gear system that permits limited axial motion of the worm, but generally prevents the motor from being back-driven by tension in the seat belt to prevent forced seat belt extraction. The gear system may also cut off power to the motor in the event of excessive seat belt tension to prevent further payout of the seat belt. A senses tension in the seat belt and activates the motor to retract or extract the seat belt from the retractor. An emergency control system may override the web guide control in response to abnormal vehicle dynamics to provide reversible pre-crash pretensioning and/or crash pretensioning.