Seat belt retractor with automatic locking mechanism

摘要

A seat belt retractor (14) includes a spool (16) upon which vehicle seat belt webbing (12) is wound. The spool (16) is supported for unwinding rotation under the influence of tension in the webbing (12). An emergency locking mechanism (40) dissipates energy by resisting unwinding rotation of the spool (16), while permitting a limited amount of such rotation, when the level of the tension in the webbing (12) is greater than a predetermined elevated level. A sensor assembly (190) senses a vehicle occupant characteristic and/or a vehicle collision characteristic. A control assembly (180) varies the amount of dissipated energy in response to a signal from the sensor assembly (190).