Patent ID: 7227457

Claim:
A tire inflation pressure sensing apparatus comprising: a pressure sensor provided on a wheel of a vehicle, said pressure sensor working to sense an inflation pressure of a tire mounted on the wheel and generate a pressure signal representative of the sensed inflation pressure of the tire; a transmitter provided on the wheel of the vehicle, said transmitter including a first antenna and being configured to consecutively send out through the first antenna an informing signal and the pressure signal generated by said pressure sensor, the informing signal being informative of that the pressure signal is to be sent out from said transmitter following the informing signal; a receiver provided on a body of the vehicle, said receiver including a second antenna and being configured to send out through the second antenna a radio wave for providing electrical power for said transmitter, receive through the second antenna the informing signal and pressure signal from said transmitter, and determine the inflation pressure of the tire based on the received pressure signal, said receiver selectively operating in an ON-mode, in which said receiver sends out the radio wave without simultaneously receiving the informing signal and pressure signal from said transmitter, and an OFF-mode in which said receiver stops sending out the radio wave and is allowed to receive the informing signal and pressure signal from said pressure sensor; and a charging unit provided on the wheel of the vehicle, said charging unit being configured to be charged with an electrical power, which is induced by the radio wave received by said transmitter through the first antenna, and supply the electrical power to said pressure sensor and said transmitter, wherein said receiver changes an operation thereof alternately between the ON-mode and OFF-mode so as to keep the operation in the ON-mode for a first predetermined time period T 1 and in the OFF-mode for a second predetermined time period T 2 until it receives the informing signal from said transmitter in the OFF-mode, and then keeps the operation thereof in the OFF-mode until it completes receiving the informing signal and pressure signal from said transmitter, and wherein said transmitter starts, when a level of the electrical power charged in said charging unit has increased to a predetermined level, to repeatedly send out the informing signal a plurality of times for a third predetermined time period T 3 , which is no shorter than (T 1 +T 2 ), and then sends out the pressure signal.