Patent ID: 8040229

Claim:
A method for alarming decrease in tire air-pressure of tires on wheels installed on a vehicle, comprising the steps of: a) detecting rotational information obtained from the wheels; b) respectively calculating a wheel speed, a vehicle acceleration and a slip ratio of a front wheel and a slip ratio of a rear wheel from the rotational information of the respective wheels; c) accumulating the vehicle acceleration and the slip ratio of the front wheel and the slip ratio of the rear wheel; d) obtaining a primary regression coefficient of the vehicle acceleration and the slip ratio of the front wheel or the slip ratio of the rear wheel; and e) judging whether or not the tires are decreased in the air pressure upon comparing the primary regression coefficient and a reference value of the primary regression coefficient preliminarily calculated in step d) when air pressure in the tires is at a reference internal pressure, wherein in the case where sampling data of the accumulated slip ratio and the accumulated vehicle acceleration are continuously changed by a change amount within a fixed range of the slip ratio and the vehicle acceleration, the primary regression coefficient is calculated based on an average value of at least one point or two points in the vicinity of a start point of the sampling data and an average value of at least one point or two points in the vicinity of an end point of the sampling data.