| 摘要 |
PROBLEM TO BE SOLVED: To provide the method and device which can detect the air pressure drop of a tire accurately with a simple processing. SOLUTION: The maximum material frequency f0max which is the torsional natural frequency around the axis center of the tire at the maximum time of the air pressure of the tire or the frequency fmax near thereto and the minimum natural frequency f0min which is the torsional natural frequency around the axis center of the tire at the minimum time of the air pressure of the tire or the frequency fmin near thereto are decided, and the torsional vibration amplitudes|θ2(fmax)|,|θ2(fmin)|of the tire in the maximum natural frequency f0max or the frequency fmax near thereto and the minimum natural frequency f0min or the frequency fmin near thereto are found out respectively, and the ratio M between the torsional vibration amplitude|θ2(fmax)|of the tire in the maximum natural frequency f0max or the frequency fmax near thereto and the torsional vibration amplitude|(θ2(fmin)|of the tire in the minimum natural frequency f0min or the frequency fmin near thereto is calculated, and based on this ratio M, the air pressure drop of the tire is detected.
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