Patent ID: 7234345

Claim:
A vehicle tire air pressure detection system comprising: a transmitter unit attached to a wheel having a tire, wherein the transmitter includes a first transmitter/receiver for receiving a first electromagnetic wave for electric charging and for transmitting data with a second electromagnetic wave, a charger for charging electric power therein with the first electromagnetic wave, a sensor for detecting air pressure of the tire, and a first controller operated with the electric power for driving the first transmitter/receiver to transmit detection data of the air pressure of the tire with the second electromagnetic wave in a same frequency band as the first electromagnetic wave; a receiver unit attached to a chassis of the vehicle, wherein the receiver unit includes an antenna, a second transmitter/receiver for transmitting the first electromagnetic wave from the antenna toward the first transmitter/receiver and receiving the detection data through the antenna, and a second controller for driving the second transmitter/receiver to transmit the first electromagnetic wave and determining air pressure of the tire based on the detection data, wherein the second controller includes means for driving the second transmitter/receiver to transmit the first electromagnetic wave for a predetermined period, and wherein the first controller drives the first transmitter/receiver to transmit the detection data after an elapse of the predetermined period from being made operable with the electric power of the charger.