Patent ID: 8261606

Claim:
An apparatus for detecting a tire attached to a vehicle having a decreased air pressure, comprising: a rotation velocity detection means for periodically detecting rotation velocities of tires of the respective wheels of the vehicle; a rotating wheel speed ratio calculation means for calculating, based on rotation velocity information obtained from the rotation velocity detection means, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle; a wheel torque calculation means for calculating a wheel torque of the vehicle; an initialization means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels; a storage means for storing the relation obtained by the initialization means; a comparison means for comparing the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the relation stored in the storage means; and a judgment means for judging whether a tire air pressure is decreased or not based on a comparison result by the comparison means.