Method and apparatus for alarming decrease in tire air-pressure, and program for judging decompression of tire

An apparatus for alarming decrease in tire-air-pressure, which alarms decrease in internal pressure of a tire on the basis of rotational information obtained from tires attached to a vehicle, the apparatus comprising:

• rotational information detecting means which detects rotational information of respective tires;
• a first calculating means which respectively calculates and stores a wheel speed, a vehicle acceleration, a slip ratio between front and rear wheels, a running distance and a turning radius on the basis of the rotational information of the respective tires;
• a second calculating means which performs moving averaging of the vehicle acceleration and the slip ratio between front and rear wheels;
• an accumulating means which accumulates the running distance, the moving-averaged vehicle acceleration and the slip ratio between front and rear wheels when the turning radius is not less than a specified value;
• a third calculating means which obtains a linear regression coefficient and a correlation coefficient of the vehicle acceleration and the slip ratio between front and rear wheels when the accumulated running distance has reached a specified distance;
• a decompression judging means which judges whether at least a driving wheel tire has decompressed upon comparing a judged value of the linear regression coefficient and a reference value for internal pressure of the linear regression coefficient which has been preliminarily calculated when the tires are reference internal pressure, the linear regression coefficient when the correlation coefficient is not less than a specified value being set as the judged value;
• and an alarming means which issues an alarm of decrease in tire air-pressure on the basis of the result of judgment of decompression.

A computer program on a computer readable medium for judging decompression of a tire, wherein a computer is made to function, for judging decrease in tire air-pressure, as a first calculating means which respectively calculates and stores a wheel speed, a vehicle acceleration, a slip ratio between front and rear wheels, a running distance and a turning radius on the basis of the rotational information of the respective tires;

• a second calculating means which performs moving averaging of the vehicle acceleration and the slip ratio between front and rear wheels;
• an accumulating means which accumulates the running distance, the moving-averaged vehicle acceleration and the slip ratio between front and rear wheels when the turning radius is not less than a specified value;
• a third calculating means which obtains a linear regression coefficient and a correlation coefficient of the vehicle acceleration and the slip ratio between front and rear wheels when the accumulated running distance has reached a specified distance;
• and a decompression judging means which judges whether at least a driving wheel tire has decompressed upon comparing a judged value of the linear regression coefficient and a reference value for internal pressure of the linear regression coefficient which has been preliminarily calculated when the tires are of reference internal pressure, the linear regression coefficient when the correlation coefficient is not less than a specified value being set as the judged value.