Method and device for detecting a deflated tire on a vehicle
First Claim
1. A method of detecting a deflated tire on a vehicle comprising the steps of:
- comparing the rolling radii of the tires by comparing angular velocity signals from wheel speed sensors one at each wheel;
calculating an error value (DEL'"'"') where ##EQU5## where C1, C2, C3 and C4 are angular velocity values for left-hand front, right-hand front, left-hand rear and right-hand rear wheels of the vehicle respectively;
determining a correction factor;
calculating a corrected error signal (DEL) where
space="preserve" listing-type="equation">DEL=DEL'"'"'-DELCORwherein
space="preserve" listing-type="equation">DELCOR=(LAT×
A)+(B×
LAT.sup.2)whereinA and B are vehicle related constants;
outputting a warning signal when a magnitude of the corrected error signal is between 0.05 and 0.5; and
operating a tire warning indicator indicating that at least one tire is deflated when said warning signal is output.
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Accused Products
Abstract
A method and device for detecting a deflated tire on a vehicle by comparing the rolling radii of the tires by means of comparing angular velocity speed signals from wheel speed sensors, one at each wheel, characterized by calculating an error value DEL'"'"', where ##EQU1## wherein C1, C2, C3 and C4 are angular velocity values for left-hand front, right=hand front, left-hand rear and right-hand rear wheels of the vehicle respectively, determining a correction factor LAT, calculating a corrected error value DEL where
DEL=DEL'"'"'-DELCOR
wherein
DELCOR=(LAT×A)+(B×LAT.sup.2)
wherein A and B are vehicle related constants, and operating a tire warning indicator provided in the vehicle to indicate that at least one tire is deflated when it is sensed that the magnitude of the corrected error value DEL is in the range 0.05 to 0.5.
6 Citations
25 Claims
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1. A method of detecting a deflated tire on a vehicle comprising the steps of:
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comparing the rolling radii of the tires by comparing angular velocity signals from wheel speed sensors one at each wheel; calculating an error value (DEL'"'"') where ##EQU5## where C1, C2, C3 and C4 are angular velocity values for left-hand front, right-hand front, left-hand rear and right-hand rear wheels of the vehicle respectively; determining a correction factor; calculating a corrected error signal (DEL) where
space="preserve" listing-type="equation">DEL=DEL'"'"'-DELCORwherein
space="preserve" listing-type="equation">DELCOR=(LAT×
A)+(B×
LAT.sup.2)wherein A and B are vehicle related constants; outputting a warning signal when a magnitude of the corrected error signal is between 0.05 and 0.5; and operating a tire warning indicator indicating that at least one tire is deflated when said warning signal is output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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3. A method of detecting a deflated tire according to claim 2, wherein the centralizing constant K has a value in the range 0.250125 to 0.250625.
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4. A method of detecting a deflated tire according to claim 2, wherein the centralizing constant K has a value of 0.25025.
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5. A method of detecting a deflated tire according to claim 2, further comprising calculating a deflation indicating factor IMC1, IMC2, IMC3, IMC4 for each wheel respectively and indicating the wheel having the numerically greater deflation indicating factor as being deflated, where the calculation of the deflation indicating factors comprises:
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space="preserve" listing-type="equation">IMC1=C1,then if the first deciding factor MC1 is greater than the central deciding factor MPSD then
space="preserve" listing-type="equation">IMC2=C2/[((C4/C3)/2)+0.5]
space="preserve" listing-type="equation">IMC3=C3/[((C4/C2)/2)+0.5]
space="preserve" listing-type="equation">IMC4=C4/[[((C4/C3)/2)+0.5]×
[((C4/C2)/2+0.5]];if the second deciding factor MC2 is greater than the central deciding factor MPSD then
space="preserve" listing-type="equation">IMC2=C2/[((C4/C3)/2)+0.5]
space="preserve" listing-type="equation">IMC3=C3/[((C3/C1)/2)+0.5]
space="preserve" listing-type="equation">IMC4=C4/[[((C4/C3)/2)+0.5]×
[((C3/C1)/2)+0.5]];if the third deciding factor MC3 is greater than the central deciding factor MPSD then
space="preserve" listing-type="equation">IMC2=C2/[((C2/C1)/2)+0.5]
space="preserve" listing-type="equation">IMC3=C3/[((C3/C1)/2)+0.5]
space="preserve" listing-type="equation">IMC4=C4/[[((C2/C1)/2)+0.5]×
[((C4/C2)/2)+0.5]];if the fourth deciding factor MC4 is greater than the central deciding factor MPSD then
space="preserve" listing-type="equation">IMC2=C2/[((C2/C1)/2)+0.5]
space="preserve" listing-type="equation">IMC3=C3/[((C3/C1)/2)+0.5]
space="preserve" listing-type="equation">IMC4=C4/[[((C2/C1)/2)+0.5]×
[((C3/C1)/2)+0.5]];or if none of the deciding factors MC1, MC2, MC3, MC4 is greater than the central deciding MPSD factor then
space="preserve" listing-type="equation">IMC2=C2/[(((C2+C4)/(C1+C3))/2)+0.5]
space="preserve" listing-type="equation">IMC3=C3/[(((C3+C4)/(C1+C2))/2)+0.5]
space="preserve" listing-type="equation">IMC4=C4/[[(((C3+C4)/(C1+C2))/2)+0.5]×
[(((C2+C4)/(C1+C3))/2)+0.5]].
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6. A method of detecting a deflated tire according to claim 1 wherein said outputting step is performed when the magnitude of the corrected error signal DEL is in the range 0.1 to 0.3.
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7. A method of detecting a deflated tire according to claim 1 wherein the value of the vehicle related constant A is in the range -5.0E-7 to +5.0E-7 and the value of vehicle related constant B is in the range -4.0E-9 to +4.0E-9.
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8. A method of detecting a deflated tire according to claim 1 wherein the value of the vehicle related constant A is in the range -2.0E-7 to +2.0E-7 and the value of the vehicle related constant B is in the range -2.0E-9 to +1.0E-9.
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9. A method of detecting a deflated tire according to claim 1 wherein the value of the vehicle related constants A and B are -1.8E-7 to -6.2E-10 respectively.
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10. A method of detecting a deflated tire according to claim 1 wherein the value of the vehicle related constants A and B are -1.0E-7 to +4.6E-10 respectively.
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11. A method of detecting a deflated tire according to claim 1 wherein the value of the vehicle related constants A and B are -3.3E-8 to -1.8E-10 respectively.
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12. A method of detecting a deflated tire according to claim 1 wherein the value of the vehicle related constants A and B are +1.4E-7 to -1.4E-9 respectively.
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13. A deflated tire detector comprising:
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a plurality of speed sensors each provided for a corresponding tire of a plurality of tires on a vehicle, each of said speed sensors outputting an angular velocity of said corresponding tire; means for comparing rolling radii of said tires including means for calculating an error signal (DEL'"'"') where ##EQU6## where C1, C2, C3 and C4 are angular velocity output by said speed sensors for left-hand front, right-hand front, left-hand rear and right-hand rear tires of the vehicle respectively, means for determining a correction factor (LAT), means for determining a corrected error signal (DEL) where
space="preserve" listing-type="equation">DEL=DEL'"'"'-DELCORwherein
space="preserve" listing-type="equation">DELCOR=(LAT×
A)+(B×
LAT.sup.2)wherein A and B are vehicle related constants, and means for determining when a magnitude of said corrected error signal is between 0.05 and 0.5 and for outputting a warning signal in response thereto; and a warning indicator, receiving said warning signal and providing a warning in accordance therewith. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification