Seat belt pretensioner with brake

摘要

An apparatus (10) for helping to protect an occupant of a vehicle seat (14) comprises a seat belt (20) and a seat belt retractor (30) including a spool (60) supported for rotation about a spool axis (64) in a seat belt withdrawal direction (68) and an opposite seat belt retraction direction (66). An electric motor (110) is energizable to rotate the spool (60) in the seat belt retraction direction (66) and is de-energizable. The electric motor (110) is energizable to rotate the spool (60) in the seat belt retraction direction (66) to apply a predetermined amount of tension to the seat belt (20). An electrically actuatable brake (140) associated with the motor (110) is actuatable to maintain the predetermined amount of tension on the seat belt (20) after the motor applies the predetermined amount of tension to the seat belt.