Patent ID: 7227458

Claim:
A tire inflation pressure sensing apparatus comprising: a transmitter provided on a wheel of a vehicle, said transmitter including a pressure sensor that works to sense an inflation pressure of a tire mounted on the wheel and being configured to transmit a signal representative of the inflation pressure of the tire sensed by the pressure sensor; and a receiver provided on a body of the vehicle, said receiver including an antenna and being configured to receive the signal transmitted from said transmitter through the antenna and determine the inflation pressure of the tire depending on the received signal, wherein said transmitter further includes an acceleration sensor that works to generate a signal as a function of a component of gravitational acceleration in a sensing direction of the acceleration sensor, the component of gravitational acceleration varying with rotation of the wheel, and wherein said transmitter is configured to determine a position of said transmitter relative to the antenna of said receiver depending on the signal generated by the acceleration sensor and transmit the signal representative of the inflation pressure of the tire toward the antenna of said receiver when a transmitting request is issued and the determined position of said transmitter falls in a predetermined range.