METHOD FOR EXPLOITING PRESSURE AND TEMPERATURE MEASUREMENTS OF A VEHICLE TIRE

Abstract

A method for processing inflation defects of a tyre of a vehicle is disclosed, the tyre being equipped with sensors for measuring the pressure and the temperature of the internal cavity of said tyre. The pressure and the temperature of the internal cavity of the tyre are measured periodically and, as soon as an inflation defect of a tyre is detected, an alert is signalled to the driver of the vehicle, in which there is also transmitted to the driver of the vehicle a maximum speed setpoint: which, when the measured inflation pressure of the tyre is greater than or equal to a first inflation pressure threshold value p.sub.1, is a first maximum speed setpoint value V.sub.1; and which, when the measured inflation pressure of the tyre is less than said first pressure threshold value p.sub.1 and greater than or equal to a second pressure threshold value p.sub.2, decreases as a function of said measured inflation pressure of the tyre.

Claims

1.-17. (canceled)

18. A method for processing inflation defects of a tire of a vehicle, the tire being equipped with sensors for measuring a pressure and a temperature of an internal cavity of the tire, comprising the steps of: periodically measuring the pressure and temperature of the internal cavity of the tire; as soon as an inflation defect of a tire is detected, signaling an alert to a driver of the vehicle; and transmitting a maximum speed setpoint to the driver, wherein the maximum speed setpoint, when the measured inflation pressure of the tire is greater than or equal to a first inflation pressure threshold value p1, is a first maximum speed setpoint value V1, and wherein the maximum speed setpoint, when the measured inflation pressure of the tire is less than the first pressure threshold value p1 and greater than or equal to a second pressure threshold value p2, decreases as a function of the measured inflation pressure of the tire.

19. The method according to claim 18, wherein the first maximum speed setpoint value V1 lies between 90 and 130 km/h.

20. The method according to claim 18, wherein, when the measured inflation pressure of the tire lies between the first pressure threshold p1 and the second pressure threshold p2, the maximum speed setpoint transmitted decreases progressively between the first maximum speed setpoint value V1 and a second maximum speed setpoint value V2 as a function of the measured inflation pressure of the tire.

21. The method according to claim 18, wherein, when the measured inflation pressure of the tire lies between the first pressure threshold p1 and the second pressure threshold p2, the maximum speed setpoint transmitted decreases by speed levels between the first maximum speed setpoint value V1 and a second maximum speed setpoint value V2 as a function of the measured inflation pressure of the tire.

22. The method according to claim 18, wherein, when the measured inflation pressure of the tire is less than the second inflation pressure threshold value p2, the maximum speed setpoint transmitted is zero.

23. The method according to claim 18, wherein the first pressure threshold value p1 is equal to a nominal inflation pressure of the tire when cold.

24. The method according to claim 18, wherein the first pressure threshold value p1 lies between 1.5 and 2.5 bar.

25. The method according to claim 18, wherein the second pressure threshold value p2 lies between an unseating pressure of the tire from a rim of the tire while rolling and the unseating pressure plus 0.3 bar.

26. The method according to claim 18, wherein the second pressure threshold value p2 lies between 0.5 bar and 1 bar.

27. The method according to claim 18, wherein the tire comprises structural elements allowing the tire to roll at zero inflation pressure, and, when the measured inflation pressure is less than the second threshold p2, the maximum speed setpoint transmitted is the speed recommended by a manufacturer of the tire and is of the order of 80 km/h.

28. The method according to claim 18, wherein the inflation defect of the tire is a detection of a loss of pressure.

29. The method according to claim 28, wherein, in order to detect an inflation defect of the tire: a pressure p.sub.g and a temperature of the gas of the internal cavity of the tire are recorded periodically; and the measured pressure p.sub.g is transformed into absolute pressure P.sub.g, the temperature is transformed into absolute temperature T, a P.sub.g/T ratio is calculated, and a series of values is obtained; and a leak is detected when a variation over time of the series of values satisfies a predetermined relationship.

30. The method according to claim 29, wherein, the tire having a given nominal inflation pressure value when cold p.sub.0, the pressure variation threshold p lies between 3 and 7% of the nominal inflation pressure value when cold.

31. The method according to claim 29, wherein, from the P.sub.g/T values, a linear regression is performed, the slope of the linear regression straight line is calculated, the time needed for the inflation pressure p.sub.g to drop below a critical pressure threshold is estimated, and the estimated time is transmitted to the driver of the vehicle.

32. The method according to claim 18, wherein the inflation defect of the tire is the detection of an abnormal rise in temperature.

33. The method according to claim 18, wherein the tire comprises, on its inner wall, a layer of self-sealant product.

34. The method according to claim 18, wherein the vehicle comprises an autonomous driving mode.

Description

DESCRIPTION OF THE FIGURES

[0048] The invention is now described using the attached drawing in which; [0049] FIG. 1 presents a first example of trend of the maximum speed setpoint in a diagram of speed as a function of inflation pressure; [0050] FIG. 2 presents a second example of the trend of the maximum speed setpoint; and [0051] FIG. 3 presents a trend of the maximum speed setpoint in the case of tyres with extended mobility.

DETAILED DESCRIPTION OF THE INVENTION

[0052] The first step of the method according to one of the objects of the invention consists in detecting an inflation defect of a tyre at the earliest possible moment.

[0053] The detection of a pressure defect can be made in different ways.

[0054] The usual TPMS systems trigger an alert when the relative inflation pressure of a tyre is measured below a predefined threshold suited to the tyre-vehicle pairing.

[0055] It is also possible to analyse the pressure variations between two tyres of one and the same axle as proposed by the document EP0786361 A1. The tracking of the pressure deviations between these two tyres makes it possible to alert the driver as soon as this deviation exceeds a given threshold. That allows for early alerts, in particular before the inflation pressure of the tyre concerned crosses the abovementioned triggering threshold.

[0056] It is also possible to analyse the trend of the pressure of the tyres, tyre by tyre. It is then preferable to track the quantity of gas present in the internal cavity of the tyres by applying the ideal gas law as proposed in the document EP0315885 B1. The trend of the ratio between the absolute inflation pressure and the absolute temperature is then calculated. This ratio is linked to the number of moles of gas. This tracking also allows for an early detection of a leak.

[0057] FIG. 1 presents a first example of maximum speed setpoint to be transmitted to the driver of a vehicle as a function of the measured inflation pressure of one of its tyres and after the detection of an inflation defect.

[0058] At the point A.sub.1, an inflation defect has been detected by one of the methods indicated previously. The measured inflation pressure of the tyre concerned is greater than the first pressure threshold p.sub.1. The tyre is still in conformity with its range of operation as described by the ETRTO.

[0059] Upon the detection, an alert is transmitted to the driver of the vehicle to prompt him or her not to exceed the speed V.sub.1. V.sub.1 is sufficiently high to make it possible to continue his or her journey in acceptable conditions but makes it possible to limit the risks of ejection of a perforating object, if the latter is responsible for the detected leak. V.sub.1 preferably lies between 130 and 90 km/h, very preferentially between 90 and 110 km/h.

[0060] At the point A.sub.2, the inflation pressure corresponds to the first critical threshold p.sub.1. Below this value the tyre is no longer in conformity with the recommendations of the constructor of the vehicle, even those of the ETRTO. p.sub.1 is preferably equal to 1.5 bar or to the recommended inflation pressure when cold of the tyre/vehicle pairing concerned.

[0061] From this particular moment, according to the method according to one of the objects of the invention, the driver of the vehicle is allowed to continue his or her route but by prompting him or her to much more markedly reduce his or her speed to remain in good conditions of safety.

[0062] At the point A.sub.3, the inflation pressure corresponds to the second critical threshold p.sub.2. The maximum setpoint speed is then of the order of 50 km/h to conserve a good vehicle steering capacity.

[0063] Below this second critical pressure threshold, rolling is no longer allowed. The maximum speed setpoint transmitted is zero, or immediate stop.

[0064] Preferably, this second pressure threshold value p.sub.2 lies between the pressure of unseating of the tyre from its rim while rolling and this unseating pressure plus 0.3 bar. Realistic values can lie between 0.5 and 1 bar, preferentially between 0.6 bar and 0.8 bar.

[0065] The document EP1650543 A2 presents a method for determining the resistance to unseating of a tyre mounted on a rim and inflated to a predetermined pressure.

[0066] This method consists in equipping a vehicle with the tyre on a position of a steering axle; setting the vehicle in motion and stabilizing it at a predetermined speed of the order of 40 to 60 km/h; imposing, by rotation of the steering wheel, a steering wheel angle, and maintaining it for a predetermined time, the vehicle advancing at the predetermined speed such that the tyre travels a portion of its trajectory in a circular arc; repeating the preceding step by progressively increasing the steering wheel angle until at least one condition, chosen from among (i) the unseating of the tyre, or (ii) the arrival of the steering wheel of the vehicle at the end stop, is satisfied.

[0067] This method makes it possible to obtain a fine estimation of the resistance to unseating of the tyres.

[0068] In FIG. 1, the maximum speed setpoint decreases progressively between V1 and V2. The decrease being more rapid in proximity to the point A.sub.2.

[0069] FIG. 2 presents a second example of a maximum speed setpoint to be transmitted to the driver of a vehicle as a function of the measured inflation pressure of one of its tyres and after the detection of an inflation defect.

[0070] In this example, the maximum speed setpoint decreases by speed levels between 130 and 50 km/h.

[0071] FIG. 3 presents a third example of maximum speed setpoint to be transmitted to the driver of a vehicle as a function of the measured inflation pressure of one of its tyres and after the detection of an inflation defect.

[0072] In this example, the tyre affected by the detection of a leak comprises structural elements allowing it to roll at zero inflation pressure with a speed and a distance that are limited.

[0073] When the measured inflation pressure becomes less than the second threshold p.sub.2, the maximum setpoint speed transmitted is no longer zero but the speed recommended by the manufacturer of the tyre and is of the order of 80 km/h. The distance that such a tyre can travel at zero pressure is also limited, of the order of 80 km.

[0074] The three figures thus indicate two zones, an authorised shaded first zone I and an unauthorised unshaded second zone II.

[0075] This method of transmission to the driver of a vehicle of a maximum speed setpoint that changes as a function of the inflation pressure is a useful addition to the methods for early detection of inflation anomalies by giving the driver precise setpoints to be observed to remain safe while allowing him or her to continue rolling outside of the usual pressure range.

[0076] This method is particularly advantageous in the case of tyres comprising self-sealant products and autonomous vehicles by greatly limiting the cases of enforced stoppage of the vehicles.