Method and device for the detection of a pressure drop in a tire of a vehicle wheel

• US 6,691,059 B1
• Filed: 02/06/2002
• Issued: 02/10/2004
• Est. Priority Date: 08/06/1999
• Status: Expired due to Fees

• Current Assignee: Continental Teves AG & Co. OHG (Continental AG)
• Original Assignee: Continental Teves AG & Co. OHG (Continental AG)
• Inventors: Griesser, Martin
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Le, John
• Application Number:
  US10/049,082
• Time in Patent Office: 734 Days
• Field of Search: 702/138, 702/140, 702/148, 731/462, 731/463, 731/464, 731/465, 701/70, 340/442, 340/443, 340/444, 340/445
• US Class Current: 702/140
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00

Abstract

A method for the detection of a pressure drop in a tire of a wheel of a vehicle including the steps of determining a test variable from the wheel radii or from variables representing these wheel radii of the wheels of the vehicle, wherein the test variable is a quotient of two sums of each two wheel radii or variables representing these wheel radii of each one pair of vehicle wheels, comparing the test variable with a threshold value, and detecting a pressure drop with respect to the result of the comparison, wherein several test variables are determined with respect to several different wheel pair combinations, and pressure drop is considered to have been identified only if a defined vehicle wheel is identified by all found test variables as a wheel with a possible pressure drop.

Claims

1. A method of detecting pressure drop in a tire of a vehicle having a plurality of tires, comprising the steps of:

a) determining a test variable value for each respective vehicle tire, each said test variable being a function of its associate tire'"'"'s pressure, or a variable which is a function of tire pressure;

b) placing two test variable values in a first group;

c) placing two other test variables in a second group;

d) adding the test variables in the first group;

e) adding the test variables in the second group;

f) dividing the sum derived in step d) by the sum derived in step e);

g) comparing the quotient derived in step f) with a predetermined nominal tire pressure threshold value;

h) placing two test variables in a third group, wherein the two vehicle tires represented in the third group are different than the two vehicle tires represented in the first group;

i) placing two test variables in a fourth group, wherein the two vehicle tires represented in the fourth group are different than that two vehicle tires represented in the second group;

j) adding the test variables in the third group;

k) adding the test variables in the fourth group;

l) dividing the sum derived in step j) by the sum derived in step k);

m) comparing the result of step l) with a predetermined nominal tire pressure threshold value;

n) comparing the results of step g) with the result of step m) to determine if the results of step l) and step m) exceed said nominal tire pressure threshold value, and if a vehicle tires is common to at least two of said groups used in steps b), c), h), or i).

2. Method as claimed in claim 1,

wherein a pressure drop is considered to have been detected only if a defined vehicle wheel is detected as a faster turning wheel.

3. Method as claimed in claim 2,

wherein a pressure drop is considered to have been detected only if the discrepancy of the rotational speed of the faster turning wheel from the rotational speed of the other wheels or the discrepancy of the dynamic rolling radius (Δ

R_dyn) from the dynamic rolling radii of the other wheels exceeds a predetermined threshold value (th₁).

4. Method as claimed in claim 3,

wherein as a limit value (th₁) a discrepancy of the dynamic rolling radius (Δ

R_dyn) of roughly 0.8% to 1% from the dynamic rolling radii (Δ

R_dyn) of the other wheels is predetermined.

5. Method as claimed in claim 1,

wherein a pressure drop is considered to have been detected when a defined vehicle wheel is identified as a faster turning wheel or a slower turning wheel compared to the remaining vehicle wheels.

6. Method as claimed in claim 5,

wherein a pressure drop is considered to have been detected only if the discrepancy of the rotational speed of the wheel turning faster or more slowly or the discrepancy of the dynamic rolling radius (Δ

R_dyn) of the faster or slower turning wheel from the dynamic rolling radii of the remaining wheels exceeds predetermined limit values (th₁, th₃).

7. Method as claimed in claim 6,

wherein as a limit value (th₁) for the detection of a pressure drop of a faster turning wheel, a discrepancy of the dynamic rolling radius (Δ

R_dyn) of this wheel of roughly 0.8% to 1% from the dynamic rolling radii (Δ

R_dyn) of the remaining wheels is predetermined, and as a limit value (th₃) for the detection of a pressure drop of a wheel turning more slowly a discrepancy of the rolling radius of this wheel of roughly 15% is predetermined.

8. Method as claimed in claim 7,

wherein a first test variable is determined initially with respect to a first wheel pair combination, and further test variables are determined with respect to further wheel pair combinations only if the comparison of the first test variable provides an indication of a pressure drop.

9. Method as claimed in claim 8,

wherein the two pairs of wheels at the vehicle diagonal represent the first wheel pair combination.

10. Method as claimed in claim 1, wherein said first test variable is for a first wheel pair combination concerning the two pairs of wheels at the two vehicle diagonals, wherein the second test variable is for a second wheel pair combination concerning the two pairs of wheels on the two vehicle sides, and wherein the third test variable is for a third wheel pair combination concerning the two pairs of wheels at the two vehicle axles.

11. Method as claimed in claim 1,

wherein the test variable of step a) are determined with respect to correction values that are learned.

12. Method as claimed in claim 1,

wherein when a quotient is compared with a threshold value, considerations are made over a defined period of time or by way of statistical analysis.

13. Method as claimed in claim 12,

wherein the period of time used to determine learned correction values is shorter than the period of time needed to determine non-corrected test variables.

14. Method as claimed in claim 1,

wherein a test variable PG is determined with respect to the formula $\mathrm{PG}=\frac{\mathrm{Wp1r1}+\mathrm{Wp1r2}}{\mathrm{Wp2r1}+\mathrm{Wp2r2}},$

wherein Wp1r1 is the speed of the first wheel of the first pair, Wp1r2 is the speed of the second wheel of the first pair, Wp2r1 is the speed of the first wheel of the second pair, and Wp2r2 is the speed of the second wheel of the second pair.