TIRE PRESSURE MONITORING SYSTEM

摘要

PURPOSE: To detect a pressure of a tire when necessary by providing a response unit for radio wave transmitting to a questioning unit the output data of a pressure sensor detecting a pneumatic pressure of a tire and selectively supplying a battery power selected by an identifying code transmitted by a questioning unit and displaying the output data on a display. CONSTITUTION: A modulating unit 10a of a questioning unit 10 provided in a driver's seat modulates a transmitting output of a transmitting unit 12 with a modulating circuit 13 according to an identifying code output by an identifying code generating circuit 11 and transmits the modulated output to response units 20-50 of each wheel via an antenna 14. Among the response units 20-50, only the response unit which detects a signal coincident with the identifying code turns on a switch 27 to supply electric power 28 to a pressure sensor 25 and a transmitting unit 26. The pressure sensor 25 thus becomes under operating conditions and detects a pneumatic pressure of a tire and then transmits the output thereof to the questioning unit 10 as a radio wave by a transmitting unit 26 via an antenna 29. When an antenna 15 of a demodulating assembly 10b receives the output, the output is processed by a band-pass filter 16 and a demodulating circuit 18 to display it on a display 19.