1. Field of the Invention
The present invention relates to an improvement in a vehicular passive seat belt arrangement for selectively automatically restraining a vehicle occupant and releasing the occupant from restraint, and more particularly to a control system for such a passive seat belt arrangement to prevent its malfunction so as to improve safety for the vehicle occupant.
2. Description of the Prior Art
Recently passive seat belt arrangement has been increasingly mounted on automotive vehicles. A typical passive seat belt arrangement is configurated as follows: An upper end section of a seat belt is movably engaged with a guide rail extending in the fore-and-aft direction of the vehicle, so that the seat belt upper end section is selectively driven forward and rearward, i.e., toward its restraining position at which the vehicle occupant is restrained by the seat belt and toward its releasing position at which the vehicle occupant is released from restraint. Such driving of the seat belt is carried out in response to ON-OFF actions of a door switch adapted to be turned ON and OFF respectively when the door is opened and closed. This driving control manner is adopted upon paying attention to the fact that the door is necessarily opened when the vehicle occupant gets off the vehicle while closed during vehicle cruising, i.e., the seat belt arrangement is controlled t release the vehicle occupant from restraint upon the door switch being turned ON when the door is opened, while to restrain the vehicle occupant upon the door switch being turned OFF when the door is closed.
However, with such a conventional control manner of the passive seat belt arrangement, even in case the door is opened contrary to the vehicle occupant's will, for example, owing to trouble of a door locking device, the door switch is turned ON and accordingly the seat belt upper end section is unavoidably moved to the releasing position at which the seat belt arrangement releases the vehicle occupant from restraint. This is because the driving control of the passive seat belt arrangement is made only in accordance with ON-OFF actions of the door switch. Such a control manner provides a possibility of the vehicle occupant being released from restraint with the seat belt arrangement during vehicle cruising, and therefore very dangerous for the vehicle occupant.