Patent ID: 7439632

Claim:
A vehicle door control system comprising: a portable device for receiving are request signal and transmitting a response signal including an ID code thereof in response to the request signal; and a vehicle unit mounted in a vehicle for transmitting the request signal, receiving the response signal from the portable device through intercommunications, checking the ID code included in the response signal and controlling conditions of vehicle doors according to a check result of the ID code, wherein the vehicle unit includes a lock condition control unit that controls lock and unlock conditions of the vehicle doors; an automatic opening/closing unit that automatically opens and closes the vehicle doors, an inferring means that infers whether a holder of the portable device is going to ride in the vehicle; and a riding-time control means that unlocks the vehicle doors by the lock condition control unit and automatically opens the vehicle doors by the automatic opening/closing unit when the check result of the ID code included in the response signal responding to the request signal transmitted to an exterior of the vehicle with the vehicle doors locked is determined as OK, and it is inferred by the inferring means that the holder of the portable device is going to ride in the vehicle, wherein the vehicle unit repeatedly performs intercommunications with the portable device and acquires information on receiving levels of plural request signals in the portable device through the intercommunications repeatedly performed; and the inferring means infers that the holder of the portable device is going to ride in the vehicle when the plural receiving levels are larger than a predetermined threshold value and a fluctuation range of the receiving levels is within a predetermined range.