In the event of a vehicle collision, the ECU controller will trigger the pre-tensioning of the seatbelt's inflator. At this point, the webbing will quickly retract inward, effectively pulling the occupant back toward the seatback for restraint. When the external load force is too large, the webbing is pulled out, and the retractor then enters a locked state under the action of vehicle sensing and webbing sensing. The webbing pulls the spool, which in turn drives the load-limiting rod to rotate, exerting a relatively constant force on the occupant. This effectively protects the pressure on the occupant's chest and waist and can significantly reduce the injury value to the occupant.