Vehicle tire pressure monitoring system

Claim 1

Vehicular tire pressure monitoring system for a plurality of wheels (10) to be monitored, having a plurality of pressure transducers (11, 12), one each being associated with a wheel of the vehicle and providing, respectively, "correct pressure" or "low pressure" signals upon each revolution of the respective wheel, said signals forming a plurality of signal trains (S1, S2) associated with the respective wheels; a signal processing and evaluation network (15) having counters (22), each having a reset terminal, one each associated with a respective wheel; and a plurality of warning indicators (26, 27), one each associated with a respective wheel and providing a warning indication of low tire pressure, said system comprising a combining logic circuit (23) including a NOR-function element (23), having its input connected to the outputs (21) of the transducers (11, 12) of all the wheels, in parallel, to receive the signal trains (S1, S2) of all the wheels, combine said signal trains, and provide combined output signals (S3); a connection means (J) from said combining logic circuit, the output from the combining logic circuit being formed by said connection means (J) to form common junction which, in turn, is connected to the count inputs (37) of all of said counters (22); means (13, 14) for connecting the respective transducers (11, 12) to the respective reset terminals (R) of the associated counters (22) to reset the respective counters when the transducer provides to the respective counters "correct pressure" signals, but failing to reset the respective counter upon providing "low pressure" signals; means (24, 25, 28) for connecting the shift output of the respective counters to the respective associated indicators, shifting of the counters to fully loaded condition being indicated by the respective warning indicator (26, 27) to thereby provide a warning indication signal indicative of low pressure at the respective tire after the associated counter has been fully loaded by the combined output signals (S3) derived from those transducers which have still provided "correct pressure" signal trains (S2); and an oscillator (28) energizeable by connection of a vehicle main switch (29), the output of the oscillator (28) being connected to a further input of said NOR-function element (23) to pretest the warning indicators (26, 27) and operability of the combining logic circuit (23), the connection means (J) from said combining logic circuit, the counters (22) and the connection means (24, 25, 28) connecting the shift output of the respective counters to the respective associated indicators.