A seat belt system which does not interfere with the ingress and egress of rear seat passengers, and can detect the presence of an occupant without being influenced by the seat belt tension to provide the accurate weight detection. In one embodiment, the seat belt system comprises a retractor disposed in the rear door, an anchor of the seat belt webbing, and a rail member that allows the anchor of the seat belt webbing to slide in the vehicular longitudinal direction. The front end of the rail member is attached substantially on the seat side above a weight detecting device. The weight detecting device is disposed between the front seat and the floor panel, while the buckle capable of engaging the tongue of the seat belt webbing is disposed on the seat above the weight detecting device.
A seatbelt system for a front seat of a vehicle having such a double door that a front door (2) and a rear door (3) open outwardly forward and rearward, respectively, to form an uninterrupted doorway (14) to a passenger compartment (A) and the front door (2) overlaps the rear door from the outside so as to allow the rear door (3) to open and close while the front door is open comprises a retractor (28) installed in the rear door (3) and retracting a seatbelt (27) therein, a seatbelt lock mechanism (37) operative to lock the seatbelt (27) when the seatbelt (27) attains a predetermined acceleration, and a lock canceling mechanism (38) operative to put the seatbelt lock mechanism (37) inoperative when activated, The seatbelt system activates the lock canceling mechanism (38) to put the seatbelt lock mechanism (37) inoperative when the seatbelt (27) is unbuckled while the front door and/or the rear door is open or not properly closed and deactivates the lock canceling mechanism (38) to put the seatbelt lock mechanism (37) operative when the seatbelt (27) is buckled up while the front door and/or the rear door is open or not properly closed.
A vehicle seat for receiving an occupant is placed on a slider so as to move along a guide rail. A pair of belt anchor brackets for anchoring each end of a lap belt at each side of the seat is provided under the guide rail, and a weight sensor for sensing weight variation of the seat is provided under the belt anchor bracket. The tension of a seat belt (lap belt) does not affect the weight sensing functionality of the weight sensor and the state of the seat can accurately be determined.
