| 摘要 |
PROBLEM TO BE SOLVED: To improve accuracy of a warning by detecting reduction in tire air pressure by using a phenomenon that a dynamic load radius of a tire reduces when air pressure reduces and rotating speed of the tire relatively increases, and correcting a judging value of a warning by a position sensitivity factor by an installing position of the tire. SOLUTION: Wheel speed sensors 1 are respectively arranged on respective tires W1 to W4 of a four-wheel vehicle, and respective sensor signals are inputted to a control unit. In this control unit 2, when a position sensitivity factor by a position of the vehicle is denoted by Pi (i=1 to 4) and a tire sensitivity factor by the tires is denoted by Ti and wheel speed under normal air pressure is denoted by V and wheel speed at pressure reduced time is denoted byαV, the position sensitivity ratio : P2/P1, P3/P1, P4/P3, and the tire sensitivity ratio : T2/T1, T3/T1, T4/T3 are found, and respective wheel speeds after correction are found these values, and a judging value (a DEL value) to give a warning is calculated. The DEL value after correction and a warning threshold value are compared with each other, and a warning is given with constant sensitivity.
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