Tire air-pressure reduction detecting method and apparatus

Claim 2

A tire air-pressure reduction judging method of: detecting the rotational angular speeds of the four tires attached to a four-wheeled vehicle; obtaining, according to a judging formula based on the detected rotational angular speeds, a judgement value for judging whether or not a tire is reduced in air pressure; comparing the judgement value thus obtained with threshold values; and judging based on the result of comparison whether or not a tire is reduced in air pressure, said method comprising the steps of: travelling, at each of predetermined speeds, the vehicle with the tires thereof individually depressurized, obtaining judgement values at said speeds according to said judging formula, setting, as a reference judgement value, the judgement value for a predetermined reference speed out of said obtained judgement values, storing the relationship between the ratios of said other obtained judgement values to said reference judgement value, and said speeds; calculating the speed of the vehicle while the vehicle actually travels; obtaining, based on said stored relationship, the ratio corresponding to said calculated speed; and correcting, based on said ratio thus obtained, said judgement value obtained according to said judging formula, or said threshold values.

Claim 3

A tire air-pressure reduction detecting apparatus having: rotational angular speed detecting means (1) for detecting the rotational angular speeds of the four tires attached to a four-wheeled vehicle; judgement value operating means (2b) for putting, in a judging formula, said rotational angular speeds detected by said rotational angular speed detecting means (1), thereby to obtain a judgement value for judging whether or not a tire is reduced in air pressure; comparing means (2b) for comparing said judgement value obtained by said judgement value operating means (2b) with threshold values; and judging means (2b) for judging, based on the result of comparison made by said comparing means (2b), whether or not a tire is reduced in air pressure, said tire air-pressure reduction detecting apparatus comprising: memory means (2c) for travelling, at each of predetermined speeds, the vehicle with the tires thereof individually depressurized, for obtaining judgement values at said speeds according to said judging formula, for setting, as a reference judgement value, the judgement value for a predetermined reference speed out of said obtained judgement values, and for storing the relationship between the ratios of the said other obtained judgement values to said reference judgement value, and said speeds; and speed calculating means (2b) for calculating the vehicle speed while the vehicle actually travels; said judgement value operating means (2b) being adapted to obtain, based on said relationship stored in said memory means (2c), the ratio corresponding to said calculated speed and to correct, based on said ratio thus obtained, said judgement value obtained according to said judging formula, or said threshold values.

Claim 4

A tire air-pressure reduction judging method of detecting the rotational angular speeds of the four tires attached to a four-wheeled vehicle, putting said detected rotational angular speeds in a judging formula, thereby to obtain a judgement value for judging whether or not a tire is reduced in air pressure, comparing said judgement value thus obtained with threshold values, and detecting a reduction in the air pressure of a tire based on the result of such comparison, said tire air-pressure reduction judging method comprising the steps of: obtaining judgement values according to the judging formula while the vehicle is travelled with the tires thereof individually depressurized, setting a reference tire out of said tires, and storing the ratios of the judgement values for other tires than said reference tire, to the judgement value for said reference tire, said ratios being stored as respectively corresponding to said tires; specifying, based on said detected rotational angular speeds, a tire which satisfies a predetermined specific condition relating to a reduction in air pressure, such specifying operation being made when the vehicle actually travels; reading the ratio stored as corresponding to said specified tire; and correcting, based on said read ratio, said judgement value obtained according to said judging formula, or said threshold values.

Claim 5

A tire air-pressure reduction judging method according to claim 4, wherein said specifying step comprising: selecting a tire which has generated the greatest rotational angular speed out of the rotational angular speeds detected, storing tire data for a predetermined period of time representing said selected tire, selecting the most frequently stored tire data thus stored, and only when the rate of the number of said selected tire data to the total number of all the tire data stored, is not less than a predetermined value, specifying the tire corresponding to said selected tire data as a tire which satisfies a predetermined specific condition relating to a reduction in air pressure.

Claim 6

A tire air-pressure reduction judging method according to claim 4, wherein said specifying step comprising: selecting a tire which has generated the greatest rotational angular speed out of the rotational angular speeds detected, storing tire data for a predetermined period of time representing said selected tire, selecting the tire corresponding to the latest tire data out of the tire data thus stored, as a tire which satisfies a predetermined specific condition relating to a reduction in air pressure.

Claim 7

A tire air-pressure reduction judging method according to claim 4, wherein said specifying step comprising: selecting a tire which has generated the greatest rotational angular speed out of the rotational angular speeds detected, storing tire data for a predetermined period of time representing said selected tire, selecting the most frequently stored tire data thus stored, and when the rate of the number of said selected tire data to the total number of all the tire data stored, is less than a predetermined value, specifying the tire corresponding to the latest tire data out of the tire data thus stored, respectively as a tire which satisfies a predetermined specific condition relating to a reduction in air pressure.

Claim 8

A tire air-pressure reduction detecting apparatus having: rotational angular speed detecting means (1) for detecting the rotational angular speeds of the four tires attached to a four-wheeled vehicle; judgement value operating means (2b) for putting, in a judging formula, said rotational angular speeds detected by said rotational angular speed detecting means (1), thereby to obtain a judgement value for judging whether or not a tire is reduced in air pressure; comparing means (2b) for comparing said judgement value obtained by said judgement value operating means (2b) with threshold values; and judging means (2b) for judging, based on the result of comparison made by said comparing means (2b), whether or not a tire is reduced in air pressure, said tire air-pressure reduction detecting apparatus comprising: ratio operating means (2b) for previously obtaining judgement values according to the judging formula while the vehicle is travelled with the tires thereof individually depressurized, for setting a reference tire out of said tires, and for obtaining the ratios of the judgement values for other tires than said reference tire, to the judgement value for said reference tire; memory means (2c) for storing said ratios obtained by said ratio operating means (2b), said ratio being stored as respectively corresponding to said tires; and specifying means (2b) for specifying, based on said detected rotational angular speeds, a tire which satisfies a predetermined specific condition relating to a reduction in air pressure, such specifying operation being made when the vehicle actually travels; said judgement value operating means (2b) being adapted to read, from said memory means (2c), the ratio obtained and stored as corresponding to said tire specified by said specifying means (2b), and to correct, based on said read ratio, said judgement value obtained according to said judging formula, or said threshold values.

Claim 9

A tire air-pressure reduction detecting apparatus according to Claim 8, wherein the specifying means (2b) comprises: a selecting unit for selecting a tire which has generated the greatest rotational angular speed out of the rotational angular speeds detected by the rotational angular speed detecting means (1); and a memory unit capable of storing tire data representing said tire selected by said selecting unit, said tire data taken for a predetermined period of time being stored; and said specifying means (2b) is adapted such that said specifying means (2b) selects the most frequently stored tire data out of said tire data stored in said memory unit, and that, only when the rate of the number of said selected tire data to the total number of all the tire data stored in said memory means, is not less than a predetermined value, the tire corresponding to said selected tire data is specified as a tire which satisfies a predetermined specific condition relating to a reduction in air pressure.

Claim 10

A tire air-pressure reduction detecting apparatus according to Claim 8, wherein the specifying means (2b) comprises: a selecting unit for selecting a tire which has generated the greatest rotational angular speed out of the rotational angular speeds detected by the rotational angular speed detecting means (1); and a memory unit capable of storing tire data representing the tire selected by said selecting unit, said tire data taken for a predetermined period of time being stored; and said specifying means (2b) is adapted to specify, as a tire which satisfies a predetermined specific condition relating to a reduction in air pressure, the tire corresponding to the latest tire data out of the tire data stored in said memory unit.

Claim 11

A tire air-pressure reduction detecting apparatus according to Claim 8, wherein the specifying means (2b) comprises: a selecting unit for selecting a tire which has generated the greatest rotational angular speed out of the rotational angular speeds detected by the rotational angular speed detecting means (1); and a memory unit capable of storing tire data representing the tire selected by said selecting unit, said tire data taken for a predetermined period of time being stored; and said specifying means (2b) is adapted such that said specifying means (2b) selects the most frequently stored tire data out of said tire data stored in said memory unit, and that, when the rate of the number of said selected tire data to the total number of all the tire data stored in said memory means, is less than a predetermined value, the tire corresponding to the latest tire data is specified as a tire which satisfies a predetermined specific condition relating to a reduction in air pressure.