Patent ID: 7333008

Claim:
A tire deflation warning system including a means for detecting rotational speeds of wheels on a vehicle having driving wheels and following wheels, for obtaining rotational speed information of the wheels, and a means for judging tires with reduced air pressure from the rotational speed information of the wheels, the system comprising: a means for determining whether (1) the vehicle has run a fixed distance from starting and (2) the speed of the vehicle is more than a fixed value; a means for judging whether driving force works to respective wheels or not; a means for calculating a vehicle speed when driving force works to respective wheels; a means for comparing (1) a ratio R of an average of the rotational speeds of the driving wheels against an average of the rotational speeds of the following wheels, in running state in which the vehicle has driving force, with (2) an initial value of an average of the rotational speeds of the driving wheels against an average of the rotational speeds of the following wheels at normal air pressure, in running state in which the vehicle has driving force, to obtain a ratio R/initial value; and a means for judging that the air pressures of the all wheels which are mounted on the vehicle are simultaneously reduced, or that the air pressures of the driving wheels are reduced by comparing the ratio R/initial value with (1) a preliminarily determined judging threshold for reduced pressures of all wheels or (2) a preliminarily determined judging threshold for reduced pressures of the driving wheels.