| 摘要 |
PROBLEM TO BE SOLVED: To simplify a device installed inside a tire so that a power source including a battery is not needed, the device installation being a method for measuring the tire air pressure while the tire is static or revolving. SOLUTION: A hollow object (tube 1) processed for reflecting radio wave (electromagnetic wave) has an increased inner pressure and is installed inside the tire, wherein the outer shape change of the hollow object (tube 1), caused by a pressure difference between the time of a low tire air pressure and the time of a proper tire air pressure, is to be a radio wave reflection change upon irradiation of the radio wave (electromagnetic wave) on the hollow object (tube 1) by a radio wave (electromagnetic wave) duplex device 2 installed outside of the tire. The reflected radio wave is received at the radio wave (electromagnetic wave) duplex device, where the tire air pressure value is obtained by a change in the reflected radio wave (electromagnetic wave).
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