Tire initial difference correcting process and tire air-pressure reduction detecting apparatus

Claim 2

A tire initial-difference correcting process for use in a tire air-pressure reduction detecting apparatus for detecting rotational angular velocities of four tires attached to a four-wheeled vehicle and detecting a reduction in tire air pressure based on the detected rotational angular velocities, said process comprising the steps of: calculating forward/backward accelerations based on the rotational angular velocities; judging whether or not the calculated forward/backward accelerations are lower than a predetermined threshold level; determining to employ the rotational angular velocities, only when the calculated forward/backward accelerations are lower than the threshold level, for correcting an initial difference in dynamic load radii of the tires based on a variation in performance and air pressure of the respective tires; obtaining correction factors based on the rotational angular velocities determined to be employed for correcting the initial difference; and correcting the initial difference based on the correction factors thus obtained.

Claim 3

A tire initial-difference correcting process as set forth in claim 1 or 2, further comprising the step of calculating a vehicle traveling distance based on the rotational angular velocities, wherein the initial difference is corrected by using the rotational angular velocities collected until the calculated vehicle traveling distance reaches a predetermined straight traveling distance.

Claim 4

A tire initial-difference correcting process as set forth in claim 3, further comprising the step of calculating an average of the correction factors calculated based on the rotational angular velocities collected until the calculated vehicle traveling distance reaches a predetermined straight traveling distance, wherein the initial difference set forth in claim 1 or 2 is corrected based on the calculated average of the correction factors.

Claim 5

A tire air-pressure reduction detecting apparatus including a rotational angular velocity calculating means for calculating rotational angular velocities of tires attached to a vehicle, an air-pressure reduction judging means for judging whether or not a tire air pressure is reduced based on the rotational angular velocities calculated by the rotational angular velocity calculating means, and a warning means for issuing and stopping a warning in accordance with a judgement result obtained by the air-pressure reduction judging means, said tire air-pressure reduction detecting apparatus comprising: a counting means for counting the number of judgement results obtained by the air-pressure reduction judging means in an ascending or descending order which depends on whether a judgement result obtained by the air-pressure reduction judging means indicates that the tire air pressure is reduced or that the tire air pressure is not reduced, said counting means being adapted to prevent a count value from exceeding a predetermined steady-state count which supports the judgement that the tire air pressure is not reduced; and said warning means being adapted to issue a warning when the count value reaches a predetermined warning threshold count which supports the judgement that the tire air pressure is reduced.

Claim 6

A tire air-pressure reduction detecting apparatus as set forth in claim 5, comprising: said counting means being adapted to prevent the count value from exceeding a predetermined upper counting limit which supports the judgement that the tire air pressure is reduced, and said warning means being adapted to stop the warning when the count value reaches a predetermined warning stopping threshold count which supports the judgement that the tire air pressure is not reduced.

Claim 7

A tire air-pressure reduction detecting apparatus including a rotational angular velocity calculating means for calculating rotational angular velocities of tires attached to a vehicle, an air-pressure reduction judging means for judging whether or not a tire air pressure is reduced on a predetermined cycle based on the rotational angular velocities calculated by the rotational angular velocity calculating means, and a warning means for issuing and stopping a warning in accordance with judgement results obtained by the air-pressure reduction judging means, said tire air-pressure reduction detecting apparatus comprising: a time-measuring means; a memory means for storing the judgement results obtained by the air-pressure reduction judging means during a predetermined time period; a count judging means for judging, when the length of a time period measured by the time measuring means reaches a predetermined time length, whether or not a count value stored in the memory means for the judgement results indicating that the tire air pressure is reduced is not less than a predetermined first count value; and said warning means being adapted to issue a warning when it is judged by the count judging means that the count value is not less than the predetermined first count value.

Claim 8

A tire air-pressure reduction detecting apparatus as set forth in claim 7, wherein said count judging means is adapted to judge, when the length of a time period measured by the time measuring means reaches the predetermined time period, whether or not the count value stored in the memory means for the judgement results indicating that the tire air pressure is reduced is less than a predetermined second count value which is set to be less than the first count value, and said warning means is adapted to stop the warning when it is judged by the count judging means that the count value is less than the predetermined second count value.

Claim 9

A warning issuing/stopping process for use in a tire air-pressure reduction detecting apparatus, comprising the steps of: calculating rotational angular velocities of tires attached to a vehicle; and issuing and stopping a warning in accordance with judgement results of whether or not a tire air pressure is reduced, based on the calculated rotational angular velocities; wherein the warning is issued when the counting of judgement results indicating that the tire air pressure is reduced is repeated a predetermined number of times, and the warning is stopped when the counting of judgement results indicating that the tire air pressure is not reduced is repeated a predetermined number of times.

Claim 10

A tire air-pressure reduction judging process for judging whether or not a tire air-pressure is reduced based on rotational angular velocities of tires attached to a vehicle which are calculated on a predetermined cycle of first time period, said tire air-pressure reduction judging process comprising the steps of: detecting on the cycle of first time period a vehicle traveling state in relation to such factors as a velocity of the vehicle, a radius of curvature of a road on which the vehicle is traveling, lateral and forward/backward accelerations of the vehicle; judging on the cycle of first time period whether or not the detected vehicle traveling state is suitable for judging whether or not the tire air pressure is reduced; and judging whether or not the tire air pressure is reduced, by employing the rotational angular velocities calculated only when it is judged that the detected vehicle traveling state is suitable for judging whether or not the tire air pressure is reduced, without employing the rotational angular velocities calculated when it is judged that the detected vehicle traveling state is not suitable for judging whether or not the tire air pressure is reduced.

Claim 11

A tire air-pressure reduction judging apparatus including a rotational angular velocity calculating means for calculating rotational angular velocities of tires attached to a vehicle on a cycle of first time period, and an air-pressure reduction judging means for judging whether or not a tire air-pressure is reduced based on the rotational angular velocities calculated by the rotational angular velocity calculating means, said tire air-pressure reduction judging apparatus comprising: a traveling state detecting means for detecting on the cycle of first time period a vehicle traveling state in relation to such factors as a velocity of the vehicle, a curvature radius of a road on which the vehicle is traveling, lateral and forward/backward accelerations of the vehicle; a traveling state judging means for judging on the cycle of first time period whether or not the vehicle traveling state detected by the traveling state detecting means is suitable for judging whether or not the tire air pressure is reduced; a memory means for storing data of a judgement result obtained by the traveling state judging means which indicates that the vehicle traveling state detected by the traveling state detecting means is not suitable for judging whether or not the tire air-pressure is reduced, if it is so judged by the traveling state judging means; an adder means for adding up the rotational angular velocities calculated by the rotational angular velocity calculating means during a cycle of second time period which is equivalent to an integer multiple of the first time period; and said air-pressure reduction judging means being adapted to refer to the data stored in the memory means to judge whether or not the tire air pressure is reduced based on a sum of the rotational angular velocities added up by the adder means, if there is not stored the data of the judgement result indicating that the vehicle traveling state is not suitable, and to prohibit judging whether or not the tire air pressure is reduced during the cycle of second time period, if there is stored the data of the judgement result indicating that the vehicle traveling state is not suitable.

Claim 12

A tire air-pressure reduction judging apparatus including a rotational angular velocity calculating means for calculating rotational angular velocities of tires attached to a vehicle on a cycle of first time period, and an air-pressure reduction judging means for judging whether or not a tire air-pressure is reduced based on the rotational angular velocities calculated by the rotational angular velocity calculating means, said tire air-pressure reduction judging apparatus comprising: a traveling state detecting means for detecting on the cycle of first time period a vehicle traveling state in relation to such factors as a velocity of the vehicle, a curvature radius of a road on which the vehicle is traveling, lateral and forward/backward accelerations of the vehicle; a traveling state judging means for judging on the cycle of first time period whether or not the vehicle traveling state detected by the traveling state detecting means is suitable for judging whether or not the tire air pressure is reduced; an adder means for adding up the rotational angular velocities calculated by the rotational angular velocity calculating means during a cycle of second time period which is equivalent to an integer multiple of the first time period; and said air-pressure reduction judging means being adapted to judge whether or not the tire air pressure is reduced based on a sum of the rotational angular velocities added up by the adder means, only when a judgement is continuously made a predetermined number of times by the traveling state judging means that the vehicle traveling state detected by the traveling state detecting means is suitable for judging whether or not the tire air pressure is reduced.

Claim 13

A tire air-pressure reduction detecting apparatus including a rotational angular velocity calculating means for calculating rotational angular velocities of tires attached to a vehicle on a predetermined cycle of first time period, and an air-pressure reduction judging means for judging whether or not a tire air-pressure is reduced based on the rotational angular velocities calculated by the rotational angular velocity calculating means, said tire air-pressure reduction detecting apparatus comprising: a traveling state detecting means for detecting on the cycle of first time period a vehicle traveling state in relation to such factors as a velocity of the vehicle, a curvature radius of a road on which the vehicle is traveling, lateral and forward/backward accelerations of the vehicle; a traveling state judging means for judging on the cycle of first time period whether or not the vehicle traveling state detected by the traveling state detecting means is suitable for judging whether or not the tire air pressure is reduced; an adder means for adding up the rotational angular velocities calculated by the rotational angular velocity calculating means if it is judged by the traveling state judging means that the vehicle traveling state detected by the traveling state detecting means is suitable for judging whether or not the tire air pressure is reduced; said air-pressure reduction judging means being adapted to judge whether or not the tire air pressure is reduced based on a sum of the rotational angular velocities added up by the adder means, when a count of judgement results obtained by the traveling state judging means which indicate that the vehicle traveling state detected by the traveling state detecting means is suitable for judging whether or not the tire air pressure is reduced reaches a predetermined count.

Claim 14

A tire air-pressure reduction detecting apparatus as set forth in claim 13, further comprising: means for clearing the sum of the rotational angular velocities added up by the adder means, when it is continuously judged a predetermined number of times by the traveling state judging means that the vehicle traveling state detected by the traveling state detecting means is not suitable for judging whether or not the tire air-pressure is reduced.