Patent ID: 7205886
Filing Date: 2007-04-17
Classification: B60C

Abstract:
1. A tire pressure monitoring system comprising: a wheel vibration detection means which detects vibrations of a wheel mounted to a vehicle; a speed detection means which detects wheel speed; a vibration frequency spectrum data producing means which applies a predetermined converting process to detection values from the wheel vibration detection means and produces vibration frequency spectrum data consisting of vibration frequency and a gain of the vibration frequency caused by a rotation of the wheel; a vibration frequency reference spectrum data storage means which stores a plurality of vibration frequency reference spectrum data in a manner associated with wheel speed, the vibration frequency reference spectrum data being used as a reference for a case where air pressure of a tire attached to the wheel is a normal value; and an air pressure determination means which reads the vibration frequency reference spectrum data from the vibration frequency reference spectrum data storage means on the basis of a current wheel speed or a current vehicle speed, compares a pattern of the thus read vibration frequency reference spectrum data with a pattern of current vibration frequency spectrum data produced by the vibration frequency spectrum data producing means, and determines that the tire is underinflated if a comparison result of these patterns exceeds a predetermined value.