Patent ID: 7656282

Claim:
A tire inflation pressure detecting apparatus comprising: a pressure sensor provided on a wheel of a vehicle, the pressure sensor working to sense inflation pressure of a tire fitted on the wheel and generate a pressure signal representative of the sensed inflation pressure of the tire; a first transceiver provided on the wheel of the vehicle, the first transceiver being configured to selectively operate in a first receiver mode, in which the first transceiver is allowed to receive a radio wave, and a first transmitter mode in which the first transceiver transmits both an informing signal and the pressure signal, the informing signal being informative that the pressure signal is to be transmitted by the first transceiver following the informing signal; an electric power storage device provided on the wheel of the vehicle, the electric power storage device being configured to be charged with electric power, which is induced by the radio wave received by the first transceiver, and supply the electric power to both the pressure sensor and the first transceiver; a second transceiver provided on a body of the vehicle, the second transceiver being configured to selectively operate in a second transmitter mode, in which the second transceiver transmits the radio wave to the first transceiver, and a second receiver mode in which the second transceiver is allowed to receive both the informing signal and the pressure signal transmitted by the first transceiver; a pressure determiner provided on the body of the vehicle, the pressure determiner working to determine the inflation pressure of the tire based on the pressure signal received by the second transceiver, wherein the second transceiver changes operation thereof alternately between the second transmitter and second receiver modes, thereby intermittently transmitting the radio wave, the first transceiver operates in the first receiver mode to receive the radio wave intermittently transmitted by the second transceiver, when the electric power charged in the electric power storage device has reached a predetermined level, the first transceiver changes its operation from the first receiver mode to the first transmitter mode to transmit the informing signal and the pressure signal, and when the informing signal is received by the second transceiver in the second receiver mode, the second transceiver keeps its operation in the second receiver mode until the pressure signal that follows the informing signal is completely received by the second transceiver, and wherein in the first transmitter mode, the first transceiver repeatedly transmits in a discontinuous manner the informing signal at predetermined time intervals for a predetermined time period and then transmits the pressure signal.