Method of detecting a deflated tire on a vehicle

Abstract

A method of detecting a deflated tire on a vehicle by comparing the rolling radii of the tires by means of comparing angular velocity speed signal values C1, C2, C3 and C4 from wheel speed sensors on wheels 1-4 at the left-hand front, the right-hand front, the left-hand rear and the right-hand rear wheel position respectively, comprising the step of calculating an error value DEL' in normal driving by processing the four angular velocity speed signal values C1-C4 in a central processing unit (10) which subtracts the sum of the signal values from one pair of diagonally opposite wheels from the sum of the signal values from the other pair of diagonally opposite wheels and expressing the results as a percentage of the mean of the sums DEL'=(C1+C4-C2-C3).times.50/((C1+C2+C3+C4)/4), sensing when the magnitude of the error value DEL' is between a DEL' min value of 0.05 and a DEL' max value of 0.5 and when it is carrying out the step of deciding which tire is apparently deflated by comparison of the angular velocity speed signal values C1-C4 with each other, and finally operating a tire warning indicator in the vehicle to warn the driver that that particular tire is deflated, wherein there is determined from the wheel speed signal values C1-C4 the vehicle speed SPD in which SPD=(C1+C2+C3+C4)/(4.times.KPHFAC) and wherein KPHFAC is a constant representing the number of wheel speed signals per wheel speed sensor per unit of speed, deriving a corrected error value DEL by dividing the error value DEL' by a correction factor SPDELCOR related to the vehicle speed SPD and using the corrected error value DEL in place of the error value DEL' to warn of a deflated tire.

Dependencies are inferred from the claim text.