Patent ID: 8726724

Claim:
A system for detection of deflated tires based on a resonance frequency of tires attached to a vehicle and a relative comparison index of rotation speeds of the tires, comprising: a rotation information detection means for detecting rotation information of the tires; a rotation speed calculation means for calculating rotation speeds of the tires based on the rotation information detected by the rotation information detection means; a resonance frequency assumption means for assuming a resonance frequency of the tires based on the rotation information of the tires; and a determination means for detection of deflated tires using a decreased pressure determination index calculated by a relative comparison of the rotation speeds of the tires and the resonance frequency assumed by the resonance frequency assumption means, wherein the determination means is so configured, assuming that the first determination index at which warning is issued when the resonance frequency exceeds the first threshold a predetermined number of times is 100 in detecting deflated tires based on the resonance frequency and when the first determination index has a converted percentage equal to or higher than 10 and lower than 100, as to reduce the second threshold to be compared with the decreased pressure determination index to a value equal to or higher than 1% and equal to or lower than 90% and to detect deflated tires having a decreased pressure when the decreased pressure determination index exceeds the reduced threshold.