Apparatus and method for detecting decrease in tire air pressure and program for detecting decrease in tire air pressure

A method for detecting a decreased air pressure of a tire attached to a vehicle, comprising:

• a rotation velocity detection step of periodically detecting rotation velocities of tires of the respective wheels of the vehicle;
• an acceleration calculation step of calculating, based on rotation velocity information obtained in the rotation velocity detection step, accelerations of the respective tires;
• an acceleration variation calculation step of calculating, based on accelerations of the respective tires calculated in the acceleration calculation step, acceleration variations of the respective tires;
• a comparison step of comparing acceleration variations of the respective tires calculated in the acceleration variation calculation step;
• an estimation step of estimating, when the comparison by the comparison step shows that an acceleration variation of a certain tire is greater than acceleration variations of the other tires, a decrease in air pressure of the certain tire;
• a test step of determining, based on the tire rotation velocity information of the respective wheels, a tire having a rotation velocity that is faster than the rotation velocities of the other tires or that is further slower than a predetermined reference;
• and
• a judgment step of judging, when a certain tire identified in the estimation step is identical with the tire identified in the test step, a decrease in air pressure of the certain tire.

A program for causing, in order to detect a decreased air pressure of a tire attached to a vehicle, a computer to function as:

• an acceleration calculation means for calculating, based on rotation velocity information obtained from a rotation velocity detection means for periodically detecting rotation velocities of tires of the respective wheels of the vehicle, accelerations of the respective tires;
• an acceleration variation calculation means for calculating, based on the accelerations of the respective tires calculated by the acceleration calculation means, acceleration variations of the respective tires;
• a comparison means for comparing the acceleration variations of the respective tires calculated by the acceleration variation calculation means;
• an estimation means for estimating, when a comparison result of the comparison means shows that an acceleration variation of a certain tire is greater than acceleration variations of the other tires, a decrease in air pressure of the certain tire;
• a test means for determining, based on the tire rotation velocity information of the respective wheels, a tire having a rotation velocity that is faster than the rotation velocities of the other tires or that is further slower than a predetermined reference;
• and a judgment means for judging, when a certain tire identified by the estimation means is identical with the tire identified by the test means, a decrease in air pressure of the certain tire.