Patent ID: 8237544

Claim:
A door control system in which, by performing mutual communication that a portable device returns a response signal including an ID code in response to a request signal transmitted from a vehicle unit, the vehicle unit receives the response signal from the portable device, and matches the ID code included in the response signal with a predetermined ID code specific to a vehicle, and controls the state of a vehicle door, wherein the vehicle unit comprises: an internal communication unit that communicates with the portable device in a vehicle compartment as a communication area; an automatic open/close device that automatically closes the vehicle door; a detecting unit that detects a distance between the portable device and the vehicle; a main control unit that, with the vehicle door opened, after determining that the portable device has moved out of a predetermined range of a periphery of the vehicle from a detection result by the detecting unit, automatically closes the vehicle door by the automatic open/close device when ID code matching is not confirmed as a result of mutual communication with the portable device by the internal communication unit; wherein: the detecting unit includes an external communication unit that defines the predetermined range outside the vehicle as the communication area of the portable device; the main control unit determines that the portable device has moved out of the predetermined range of the vehicle, when the code matching is changed from being confirmed to not being confirmed after a predetermined time as a result of mutual communication with the portable device by the external communication unit, with the vehicle door opened; the main control unit outputs a low sensitivity signal to the portable device, the low sensitivity signal instructing the portable device to drop reception sensitivity level thereof for the request signal; the portable device changes its reception sensitivity level to a lower sensitivity level when receiving the low sensitivity signal; and the main control unit outputs the low sensitivity signal after the code matching is confirmed at least once as a result of mutual communication with the portable device by the external communication unit with the vehicle door being open.