Tire pressure drop detecting device and method
First Claim
1. A tire-pressure drop detecting device for a four-wheel vehicle having four tires, comprising:
- rotational angular velocity detecting means for each tire, each rotational angular velocity detecting means includingpulse outputting means respectively provided in relation to a corresponding tire for outputting pulses at a rate proportional to the speed of rotation of the corresponding tire,counting means connected to the pulse outputting means for counting the pulses applied from the pulse outputting means within a predetermined measuring period,storing means for storing the time when the last pulse within each of the measuring periods is applied to the counting means,means for calculating the time elapsed from the time when the last pulse in the preceding measuring period is applied to the time when the last pulse in the present measuring period is applied, which calculated time is stored in the storing means as a reference time of the present measuring period,means for dividing the number of pulses applied within the present measuring period by said reference time, to calculate a number of pulses per unit time, andmeans for calculating the rotational angular velocity of the corresponding tire on the basis of said calculated number of pulses per unit time;
vehicle state judging means for judging whether or not said four-wheel vehicle is in a state previously determined to be unsuitable for detection of a tire pressure reduction;
operating means fornot performing an operation if said vehicle state judging means judges that the four-wheel vehicle is in a state previously determined to be unsuitable for the detection, andfinding, from the rotational angular velocities of the four tires detected by said rotational angular velocity detecting means, the ratio of the sum of the rotational angular velocities of a first pair of tires to the sum of the rotational angular velocities of a second pair of tires, the first pair of tires being spatially arranged on a diagonal line relative to the four tires of the vehicle, if said vehicle state judging means does not judge that the four-wheel vehicle is in a state previously determined to be unsuitable for the detection; and
reduced pressure tire judging means for judging that the pneumatic pressure of a tire is reduced depending on whether the ratio found by said operating means is larger or smaller than a predetermined value.
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Accused Products
Abstract
The present invention is directed to a device for and a method of detecting a tire pressure drop for a four-wheel vehicle. When F1, F2, F3 and F4 are respectively taken as the rotational angular velocities of four tires, a judged value dF given by the following equation (A) is found:
dF=(F1+F4)/(F2+F3) (A)
The judged value dF is the ratio of the sum of the rotational angular velocities (F1+F4) of a pair of tires on a diagonal line to the sum of the rotational angular velocities (F2+F3) of the other pair of tires. If the pneumatic pressures of the four tires are all normal, (F1+F4)=(F2+F3), so that dF=1. On the other hand, if the pneumatic pressure of any one of the tires drops, dF≠1. Accordingly, it is judged that the pneumatic pressure of a tire drops by comparing the judged value with a predetermined value.
62 Citations
50 Claims
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1. A tire-pressure drop detecting device for a four-wheel vehicle having four tires, comprising:
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rotational angular velocity detecting means for each tire, each rotational angular velocity detecting means including pulse outputting means respectively provided in relation to a corresponding tire for outputting pulses at a rate proportional to the speed of rotation of the corresponding tire, counting means connected to the pulse outputting means for counting the pulses applied from the pulse outputting means within a predetermined measuring period, storing means for storing the time when the last pulse within each of the measuring periods is applied to the counting means, means for calculating the time elapsed from the time when the last pulse in the preceding measuring period is applied to the time when the last pulse in the present measuring period is applied, which calculated time is stored in the storing means as a reference time of the present measuring period, means for dividing the number of pulses applied within the present measuring period by said reference time, to calculate a number of pulses per unit time, and means for calculating the rotational angular velocity of the corresponding tire on the basis of said calculated number of pulses per unit time; vehicle state judging means for judging whether or not said four-wheel vehicle is in a state previously determined to be unsuitable for detection of a tire pressure reduction; operating means for not performing an operation if said vehicle state judging means judges that the four-wheel vehicle is in a state previously determined to be unsuitable for the detection, and finding, from the rotational angular velocities of the four tires detected by said rotational angular velocity detecting means, the ratio of the sum of the rotational angular velocities of a first pair of tires to the sum of the rotational angular velocities of a second pair of tires, the first pair of tires being spatially arranged on a diagonal line relative to the four tires of the vehicle, if said vehicle state judging means does not judge that the four-wheel vehicle is in a state previously determined to be unsuitable for the detection; and reduced pressure tire judging means for judging that the pneumatic pressure of a tire is reduced depending on whether the ratio found by said operating means is larger or smaller than a predetermined value. - View Dependent Claims (2, 3, 4)
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5. A tire pressure drop detecting device for a four-wheel vehicle having four tires, comprising:
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rotational angular velocity detecting means for each tire, each rotational-angular velocity detecting means including pulse outputting means provided in relation to a corresponding tire for outputting pulses at a rate proportional to the speed of rotation of the corresponding tire, counting means connected to the pulse outputting means for counting the pulses applied from the pulse outputting means within a predetermined measuring period, first storing means for storing the time when the last pulse within each of the measuring periods is applied to the counting means, means for calculating the time elapsed from the time when the last pulse in the preceding measuring period is applied to the time when the last pulse in the present measuring period is applied, which calculated time is stored in the first storing means as a reference time of the present measuring period, means for dividing the number of pulses applied within the present measuring period by said reference time, to calculate a number of pulses per unit time, and means for calculating the rotational angular velocity of the corresponding tire on the basis of said calculated number of pulses per unit time; correcting means for correcting the rotational angular velocity of each of the-tires detected by the rotational angular velocity detecting means based upon the behavior of said four-wheel vehicle; operating means for finding the ratio of the sum of the rotational angular velocities of a first pair of tires to the sum of the rotational angular velocities of a second pair of tires on a the basis of the rotational angular velocities of the respective tires corrected by said correcting means, the first pair of tires being spatially arranged on a diagonal line relative to the four tires of the vehicle; and reduced pressure tire judging means for judging that the pneumatic pressure of a tire is reduced based upon whether the ratio found by said operating means is larger or smaller than a predetermined value. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A tire pressure drop detecting device for a four-wheel vehicle having four tires, comprising:
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rotational angular velocity detecting means for each tire, for respectively detecting the rotational angular velocity F1 of a left front tire W1, the rotational angular velocity F2 of a right front tire W2, the rotational angular velocity F3 of a left rear tire W3 and the rotational angular velocity F4 of a right rear tire W4 of the four-wheel vehicle, each rotational angular velocity detecting means including pulse outputting means provided in relation to a corresponding tire for outputting pulses at a rate proportional to the speed of rotation of the corresponding tire, counting means connected to the pulse outputting means for counting the pulses applied from the pulse outputting means within a predetermined measuring period, storing means for storing the time when the last pulse within each of the measuring periods is applied to the counting means, means for calculating the time elapsed from the time when the last pulse in the preceding measuring period is applied to the time when the last pulse in the present measuring period is applied, which calculated time is stored in the storing means as a reference time of the present measuring period, means for dividing the number of pulses applied within the present measuring period by said reference time, to calculate a number of pulses per unit time, and means for calculating the rotational angular velocity of the corresponding tire on the basis of said calculated number of pulses per unit time; operating means for finding, from the detected rotational angular velocities of the respective tires, a ratio dF of the sum of the rotational angular velocities (F1+F4) to the sum of the rotational angular velocities (F2+F3); and reduced pressure tire judging means for judging that there is no tire whose pneumatic pressure is reduced if the ratio dF found by said operating means is in the range of (1+a1) to (1-a2), where a1 and a2 are constants determined by the vehicle, and judging that there is a tire whose pneumatic pressure is reduced if said ratio dF is not within said range. - View Dependent Claims (16, 17, 18, 19, 21)
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22. A tire pressure drop detecting device for a four-wheel vehicle having four tires, comprising:
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rotational angular velocity detecting means for each tire, each rotational angular velocity detecting means including pulse outputting means provided in relation to a corresponding tire for outputting pulses at a rate proportional to the speed of rotation of the corresponding tire; counting means connected to the pulse outputting means for counting the pulses applied from the pulse outputting means within a predetermined measuring period; storing means for storing the time when the last pulse within each of the measuring periods is applied to the counting means; means for calculating the time elapsed from the time when the last pulse in the preceding measuring period is applied to the time when the last pulse in the present measuring period is applied, which calculated time is stored in the storing means as reference time of the present measuring period; means for dividing the number of pulses applied within the present measuring period by said reference time, to calculate a number of pulses per unit time; and means for calculating the rotational angular velocity of the corresponding tire on the basis of said calculated number of pulses per unit time; and reduced pressure tire judging means for comparing the calculated rotational angular velocities of the four tires, to judge whether or not the pneumatic pressure of one of the tires is reduced. - View Dependent Claims (20, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A tire pressure drop detecting method for a four-wheel vehicle having four tires, comprising:
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respectively detecting the rotational angular velocities of the four tires by, for each tire, outputting pulses at a rate proportional to the speed of rotation of the respective tire, counting the outputted pulses within a predetermined measuring period, storing the time when the last pulse within each of the measuring periods is counted, calculating the time elapsed from the time when the last pulse in the preceding measuring period is counted to the time when the last pulse in the present measuring period is counted, and storing the calculated time as a reference time of the present measuring period, dividing the number of pulses counted within the present measuring period by said reference time, to calculate a number of pulses per unit time and calculating the rotational angular velocity of the respective tire on the basis of said calculated number of pulses per unit time; finding, from said detected rotational angular velocities of the four tires, the ratio of the sum of the rotational angular velocities of a first pair of tires to the sum of the rotational angular velocities of a second pair of tires, the first pair of tires being spatially arranged on a diagonal line relative to the four tires; judging that the pneumatic pressure of a tire is reduced based on whether said found ratio is larger or smaller than a predetermined value; judging whether said four-wheel vehicle is in a state previously determined to be unsuitable for detection of a tire pressure reduction; and inhibiting judgement of a tire pressure reduction when it is judged that said four-wheel vehicle is in a state previously determined to be unsuitable for the detection of a tire pressure reduction. - View Dependent Claims (32, 33, 34, 35, 36, 37)
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38. A tire pressure drop detecting method for a four-wheel vehicle having four tires, comprising the steps of:
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respectively detecting the rotational angular velocity F1 of a left front tire W1, the rotational angular velocity F2 of a right front tire W2, the rotational angular velocity F3 of a left rear tire W3 and the rotational angular velocity F4 of a right rear tire W4 of the four-wheel vehicle by, for each tire, outputting pulses at a rate proportional to the rotation of the respective tire, counting the pulses outputted within a predetermined measuring period, storing the time when the last pulse within each of the measuring periods is counted, calculating a time elapsed from the time when the last pulse in the preceding measuring period is counted to the time when the last pulse in the present measuring period is counted, and storing the calculated time as a reference time of the present measuring period, dividing the number of pulses counted within the present measuring period by the reference time, to calculate a number of pulses per unit time, and calculating the rotational angular velocity of the respective tire on the basis of said calculated number of pulses per unit time; finding, from the detected rotational angular velocities of the respective tires, a ratio dF of the sum of the rotational angular velocities (F1+F4) to the sum of the rotational angular velocities (F2+F3); and judging that there is no tire whose pneumatic pressure is reduced if the found ratio dF is in the range of (1+a1) and (1-a2), where a1 and a2 are constants determined by the vehicle, while judging that there is a tire whose pneumatic pressure is reduced if the found ratio dF is outside said range. - View Dependent Claims (39, 40, 41, 42, 43, 44)
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45. A tire rotational angular velocity determining device, for use with a tire pressure drop detecting device in a vehicle with a tire, the tire rotational angular velocity determining device comprising:
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pulse outputting means provided proximal to the tire, for outputting pulses at a rate proportional to the rotation of the tire; counting means connected to the pulse outputting means for counting the pulses applied from the pulse outputting means within each of a plurality of sequential predetermined measuring periods; storing means for storing the time when the last pulse within each of the measuring periods is applied to the counting means; means for calculating the time elapsed from the time when the last pulse in a preceding measuring period is applied to the time when the last pulse in a present measuring period is applied, which calculated time is stored in the storing means as a reference time of the present measuring a period; means for dividing the number of pulses applied within the present measuring period which are counted by said counting means by said reference time, to calculate a number of pulses per unit time; and means for calculating the rotational angular velocity of the tire on the basis of said calculated number of pulses per unit time. - View Dependent Claims (46, 47, 48, 49, 50)
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Specification