METHOD FOR DETECTING LEAKAGE OF A VEHICLE TIRE

• US 20130274988A1
• Filed: 04/11/2013
• Published: 10/17/2013
• Est. Priority Date: 04/12/2012
• Status: Active Grant

• Current Assignee: Continental Automotive France (Continental AG), Continental Automotive GmbH (Continental AG)
• Original Assignee: Continental Automotive France (Continental AG), Continental Automotive GmbH (Continental AG)
• Inventors: REYNES, Jean-Luc
• Granted Patent: US 9,162,541 B2
• Time in Patent Office: Days
• US Class Current: 701/29.4
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: B60C 23/0476 Temperature compensation of measured pressure values
• CPC Class Codes: B60C 23/0477 Evaluating waveform of pressure readings

Abstract

In order to avoid the risk of false alarms by supplementing the pressure and temperature measurements with a particular monitoring of their change over time, there is proposed a method which includes: converting referenced pressure measurements (ΔP) into values of a magnitude calibrated in temperature called converted pressure (ΔP_T); monitoring for at least two sampling periods (n1, n2) multiples of a measurement period, the change in a difference called significant (ΔQ) at each measurement moment between the values of the converted pressure (ΔP_T) and a referenced temperature (ΔT). The slope (p(n)) of these variations is monitored and signifies either an absence of leakage or an air leakage at a fast or slow rate.

Claims

1. A method for detecting air leakage from each tire of a vehicle, wherein two parameters of temperature (T) and of pressure (P) of the air inside the tire are measured at successive moments separated by a measurement period, the measurements of the two parameters (P, T) are referenced (Δ

T, Δ

P), said method being characterized in that it consists;

in converting the referenced pressure measurements (Δ

P) into values of a magnitude calibrated in temperature called converted pressure (Δ

P_T),

in monitoring for at least two sampling periods (n1, n2, n3) the change in a difference called significant (Δ

Q) at each measurement moment between the values of the converted pressure (Δ

P_T) and the referenced temperature (Δ

T), these variations in the parameters being established over one and the same processing period greater than or equal to the highest sampling period (n3),

in determining slopes (p(n)) of variation in the significant difference (Δ

Q) for each sampling (n1, n2, n3) over the processing period and,

when the slope of variation (p(n)) of the difference (Δ

Q) remains negative for at least one sampling (n1, n2, n3) over the processing period, in estimating that an air leakage is detected (E1, E2, E3) with a fast or slow level of flow rate associated with threshold values (S1a, S2a;

S1b, S2b;

S1c, S2c) for the sampling period(s) in question.

2. The detection method as claimed in claim 1, wherein the number of samplings is equal to three (n1, n2, n3) with a first period sampling (n1) equal to a measurement period and the other two sampling periods (n2, n3) equal to multiples of the measurement period (n1).

3. The detection method as claimed in claim 1, characterized in that the pressure measurements (P1, P2, P3) and temperature measurements (T1, T2, T3) of the air of each of the tires of a vehicle are supplied by sensors (101, 102) according to the measurement period (n1), transmitted to a central processor unit (110) at the moments set by the measurement period (n1), the measurements corresponding to the moments set by each sampling period (n1, n2, n3), called sampling measurements, are selected on the basis of the measured values, stored in a memory (114) when the vehicle starts and is running, and processed in the central unit (110) in order to supply the slopes (p(n)) of variation in the significant difference (Δ

Q).

4. The detection method as claimed in claim 1, wherein, for each tire, the parameters are referenced (Δ

T, Δ

P_T) on the basis of the values of temperature (T) and of pressure (P) minus reference measurements (T_ref, P_ref) taken on startup, and the conversion of the pressure into temperature (Δ

P_T) is determined by the application of a coefficient (KT) equal to the ratio between a reference temperature measurement (T_ref) and a reference pressure measurement (P_ref) to the values taken by the converted pressure (Δ

P_T).

5. The detection method as claimed in claim 1, characterized in that, for each tire, the parameters are referenced (Δ

T, Δ

T_P) on the basis of the values of temperature (T) and of pressure (P) minus reference measurements (T_ref, P_ref) taken on startup, and the conversion of the temperature into pressure (Δ

T_P) is determined by the application of a coefficient (K′

P)equal to the ratio between a reference pressure measurement (T_ref) and a reference temperature measurement (P_ref) to the values taken by the converted temperature (Δ

T_P).

6. The detection method as claimed in claim 1, characterized in that the slope (p(n)) of variation in the significant difference (Δ

Q) is established, for each sampling, by an average variation in this significant difference over a number of consecutive sampling periods defining the processing period.

7. The detection method as claimed in claim 1, in which the number of periods taken into account is sufficient to confirm the reproducibility of the difference variation slope values with the aid of at least two determined threshold values, an amplitude threshold value (S1a, S1b, S1c) and a period confirmation threshold value (S2a, S2b, S2c).

8. The detection method as claimed in claim 7, wherein, during a period at least equal to the confirmation threshold (S2), for each sampling (n) in standard running conditions, the slope (p(n)) is substantially zero in the event of no air loss (E1), greatly negative in the event of fast leakage (E2) for at least the shortest period sampling (n1), and constant for at least the longest period sampling (n3), after a drop at least equal to the amplitude threshold (S1c).

9. The detection method as claimed in claim 1, wherein the measurement period (n1) is chosen between 15 seconds and one minute.

10. The detection method as claimed in claim 2, characterized in that the pressure measurements (P1, P2, P3) and temperature measurements (T1, T2, T3) of the air of each of the tires of a vehicle are supplied by sensors (101, 102) according to the measurement period (n1), transmitted to a central processor unit (110) at the moments set by the measurement period (n1), the measurements corresponding to the moments set by each sampling period (n1, n2, n3), called sampling measurements, are selected on the basis of the measured values, stored in a memory (114) when the vehicle starts and is running, and processed in the central unit (110) in order to supply the slopes (p(n)) of variation in the significant difference (Δ

Q).

11. The detection method as claimed in claim 2, wherein, for each tire, the parameters are referenced (Δ

T, Δ

P_T) on the basis of the values of temperature (T) and of pressure (P) minus reference measurements (T_ref, P_ref) taken on startup, and the conversion of the pressure into temperature (Δ

P_T) is determined by the application of a coefficient (KT) equal to the ratio between a reference temperature measurement (T_ref) and a reference pressure measurement (P_ref) to the values taken by the converted pressure (Δ

P_T).

12. The detection method as claimed in claim 2, characterized in that, for each tire, the parameters are referenced (Δ

T, Δ

T_P) on the basis of the values of temperature (T) and of pressure (P) minus reference measurements (T_ref, P_ref) taken on startup, and the conversion of the temperature into pressure (Δ

T_P) is determined by the application of a coefficient (K′

P) equal to the ratio between a reference pressure measurement (T_ref) and a reference temperature measurement (P_ref) to the values taken by the converted temperature (Δ

T_P).

13. The detection method as claimed in claim 2, characterized in that the slope (p(n)) of variation in the significant difference (Δ

Q) is established, for each sampling, by an average variation in this significant difference over a number of consecutive sampling periods defining the processing period.

14. The detection method as claimed in claim 2, in which the number of periods taken into account is sufficient to confirm the reproducibility of the difference variation slope values with the aid of at least two determined threshold values, an amplitude threshold value (S1a, S1b, S1c) and a period confirmation threshold value (S2a, S2b, S2c).

15. The detection method as claimed in claim 3, wherein, for each tire, the parameters are referenced (Δ

T, Δ

P_T) on the basis of the values of temperature (T) and of pressure (P) minus reference measurements (T_ref, P_ref) taken on startup, and the conversion of the pressure into temperature (Δ

P_T) is determined by the application of a coefficient (KT) equal to the ratio between a reference temperature measurement (T_ref) and a reference pressure measurement (P_ref) to the values taken by the converted pressure (Δ

P_T).

16. The detection method as claimed in claim 3, characterized in that, for each tire, the parameters are referenced (Δ

T, Δ

T_P) on the basis of the values of temperature (T) and of pressure (P) minus reference measurements (T_ref, P_ref) taken on startup, and the conversion of the temperature into pressure (Δ

T_P) is determined by the application of a coefficient (K′

P) equal to the ratio between a reference pressure measurement (T_ref) and a reference temperature measurement (P_ref) to the values taken by the converted temperature (Δ

T_P).