Patent ID: 7683769

Claim:
A tire inflation pressure detecting apparatus comprising: a plurality of antennas each of which is provided on a body of a vehicle at a predetermined distance from a corresponding one of a plurality of wheels of the vehicle; a transmitter provided on the body of the vehicle and working to transmit a plurality of radio waves respectively through corresponding ones of the antennas; a plurality of pressure sensors each of which is provided on a corresponding one of the wheels of the vehicle and works to sense inflation pressure of a tire fitted on the corresponding wheel; a plurality of transceivers each of which is provided on a corresponding one of the wheels of the vehicle in connection with a corresponding one of the pressure sensors on the corresponding wheel, each of the transceivers working to receive a corresponding one of the radio waves transmitted through the corresponding antenna and transmit a pressure signal indicative of the inflation pressure sensed by the corresponding pressure sensor; a plurality of charging units each of which is provided on a corresponding one of the wheels of the vehicle in connection with a corresponding one of the transceivers on the corresponding wheel, each of the charging units being configured to be charged with electric power, which is induced by the corresponding radio wave received by the corresponding transceiver, and supply the electric power to the corresponding pressure sensor and transceiver; a receiver provided on the body of the vehicle and working to receive, through the corresponding antennas, the pressure signals transmitted by the transceivers; a pressure determiner provided on the body of the vehicle in connection with the receiver, the pressure determiner working to determine the inflation pressures of the tires based on the corresponding pressure signals received by the receiver; and a controller provided on the body of the vehicle and working to control the transmitter to transmit the radio waves through the corresponding antennas, wherein at least two of the radio waves are transmitted at different times, so as to minimize interference therebetween, and wherein at least one pair of the radio waves are transmitted at the same time with such a phase difference therebetween that when the pair of the radio waves intersect, strength of a resultant wave thereof is lower than both strengths of the pair of the radio waves.