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

An apparatus for detecting a tire attached to a vehicle having a decreased air pressure, comprising:

• a rotation velocity detection means for periodically detecting rotation velocities of tires of the respective wheels of the vehicle;
• a rotating wheel speed ratio calculation means for calculating, based on rotation velocity information obtained from the rotation velocity detection means, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle for a predetermined plurality of speed regions;
• a wheel torque calculation means for calculating a wheel torque of the vehicle;
• an initialization means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels for the respective speed regions;
• a storage means for storing the relation obtained by the initialization means;
• a comparison means for comparing, for the respective speed regions, the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the relation stored by in storage means;
• and
• a judgment means for judging whether a tire air pressure is decreased or not based on a comparison result by the comparison means.

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

• a rotation velocity detection step of periodically detecting rotation velocities of tires of the respective wheels of the vehicle;
• a rotating wheel speed ratio calculation step of calculating, based on rotation velocity information obtained in the rotation velocity detection step, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle;
• a wheel torque calculation step of calculating a wheel torque of the vehicle;
• an initialization step of obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels;
• a storage step of storing the relation calculated in the initialization step;
• a comparison step of comparing the rotating wheel speed ratio with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque and the stored relation;
• and
• a judgment step of judging whether a tire air pressure is decreased or not based on a comparison result obtained in the comparison step.

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

• a rotation velocity detection step of periodically detecting rotation velocities of tires of the respective wheels of the vehicle;
• a rotating wheel speed ratio calculation step of calculating, based on rotation velocity information obtained in the rotation velocity detection step, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle for a predetermined plurality of speed regions;
• a wheel torque calculation step of calculating a wheel torque of the vehicle;
• an initialization step of obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels for the respective speed regions;
• a storage step of storing the relation obtained in the initialization step;
• a comparison step of comparing, for the respective speed regions, the rotating wheel speed ratio with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque and the stored relation;
• and
• a judgment step of judging whether a tire air pressure is decreased or not based on a comparison result in the comparison step.

A program for causing, in order to detect a decrease in an air pressure of a tire attached to a vehicle, a computer to function as;

• a rotating wheel speed ratio 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, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle;
• a wheel torque calculation means for calculating a wheel torque of the vehicle;
• an initialization means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels;
• a comparison means for comparing the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the relation obtained by the initialization means;
• and a judgment means for judging whether a tire air pressure is decreased or not based on a comparison result by the comparison means.

A program for causing, in order to detect a decrease in an air pressure of a tire attached to a vehicle, a computer to function as;

• a rotating wheel speed ratio 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, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle for a predetermined plurality of speed regions;
• a wheel torque calculation means for calculating a wheel torque of the vehicle;
• an initialization means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels for the respective speed regions;
• a comparison means for comparing, for the respective speed regions, the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the relation obtained by the initialization means;
• and a judgment means for judging whether a tire air pressure is decreased or not based on a comparison result by the comparison means.