Tire condition monitoring system and installation position ascertaining method

A tire condition monitoring system provided on a vehicle having a plurality of tires including two tires arranged adjacently on a dual wheel, the tire condition monitoring system comprising:

• a plurality of tire condition measuring devices, each provided on one of the tires;
• and
• a monitoring apparatus provided on a main body of the vehicle, each of the tire condition measuring devices being configured to measure an air pressure and a temperature of a tire and transmit by a wireless signal a measurement result together with identification information unique to the particular tire condition measuring device, the monitoring apparatus comprising:
• a receiver configured to receive signals transmitted from the tire condition measuring devices via at least one receiving antenna provided on a main body of the vehicle;
• a storage device configured to store measurement results and identification information received by the receiver;
• a comparator configured to compare the received measurement results to a past measurement results stored in the storage device;
• a dual wheel count storage device to receive information indicating how many dual wheels are provided and to store the number of dual wheels;
• a reset switch;
• an initial temperature value storage device configured to store temperature values received from the tire condition measuring devices after the reset switch has been pressed and the monitoring apparatus has been reset as initial temperature values that are associated with the identification information of the respective tire condition measuring devices that measured the temperature values;
• and
• an inside tire determining device configured to compare a temperature value received from the tire condition measuring device to an initial temperature value stored in the initial temperature value storage device for each identification information, and when one of the received temperature values exceeds the initial temperature value corresponding to the same identification information by an amount equal to or larger than a preset temperature difference (T degrees), the inside tire determining device ascertains which of the identification information corresponds to a tire condition measuring device installed in a tire mounted on an inside wheel of a dual wheel of the vehicle by arranging calculated values that are calculated based on the temperature values received from each of the tire condition measuring devices in an order and determining that a number of the calculated values high in the order are calculated values of temperatures of tires mounted on the inside wheel of a dual wheel, where the number of calculated values is equivalent to the number of dual wheels of the vehicle.