METHOD FOR DETECTING A LEAK IN A TIRE OF A STATIONARY VEHICLE

Description

Field of invention

[0001] The present invention relates to a method for detecting a leak in a vehicle tire. More particularly, it relates to the use of measurements taken when the vehicle is stationary. State of the art

[0002] Knowing tire inflation pressures is not enough to provide a vehicle driver with reliable and useful information. Constantly consulting these indications risks being more tedious than actually useful. Indeed, the pressure and / or temperature measurements of the inflation gas in the internal cavity of the tires vary enormously during driving due to heating caused by hysteretic losses of the constituent mixtures, the influence of heat released by the brakes and load transfers which cause slight variations in tire volume. This is why standard vehicle tire pressure monitoring systems or TPMS (acronym for Tire Pressure Monitoring System) most often limit themselves to alerting the driver in the event of a tire inflation pressure that is around 20% lower than the nominal cold inflation pressure for passenger vehicles.This nominal cold inflation pressure is given by the vehicle manufacturers. These standard systems also alert when the inflation pressure is below 1.5 bar for passenger vehicles, the minimum inflation pressure value according to the recommendations of the ETRTO (European Tyre and Rim Technical Organization).

[0003] For several years now, tires have been marketed with a layer of self-sealing product on their inner surface. These elastic, viscous or pasty products are designed to seal holes caused by a perforating object passing through the wall of a tire.

[0004] These self-sealing products do not completely eliminate the risk of a tire going flat following a puncture, but have nevertheless made it possible to significantly reduce this risk. It is also noted that a very large proportion of residual leaks are slow or very slow leaks which can occur for several days or even several weeks before being detected by current tire monitoring systems or TPMS and very often it is the vehicle user who discovers when picking up their vehicle that one of its tires is flat and therefore unfit for any driving.

[0005] Leak detection methods are known in particular from US2006 / 082451, US6545599 and DE102022003712. Description of the invention

[0006] The subject of the invention is a method for detecting a leak in a vehicle tire, the tire comprising a tire monitoring member with pressure and temperature measuring sensors and with a driving operating mode and a stationary operating mode, in which: the vehicle is stopped; then said operating mode is launched at a standstill to detect during said stopping of the vehicle the presence or absence of a leak of inflation gas from the tire, - after having launched the operating mode at a standstill of the member: the pressure pg and the temperature θ of the gas in the internal cavity of the tire are periodically measured; the series of pressure and temperature values ​​and the times of the measurements are recorded in non-volatile memory; the measured pressure pg is transformed into absolute pressure P and the measured temperature θ into absolute temperature T, the ratio P / T is calculated and a series of values ​​is obtained; when the series of values ​​decreases by a value greater than a given threshold, an alert is triggered.

[0007] When the vehicle is stationary, the sources of disturbance to the measurements of the measuring device are reduced and it is easier to detect small variations in inflation pressure linked to slow or very slow leaks.

[0008] Monitoring the P / T ratio allows, as is well known to those skilled in the art, to minimize the consequences of temperature variations on the accuracy of measurements. This ratio is proportional to the number of moles of gas present in the internal cavity of the tire.

[0009] According to one embodiment, the measurement period is constant and between 30 minutes and 60 minutes.

[0010] According to this embodiment, a measurement is taken every 30 minutes, for example.

[0011] According to an alternative embodiment, the measurement period is continuously increasing between two measurements, at least for a given number of measurements.

[0012] The measurement period can increase after each measurement by a factor of between 1.5 and 4.

[0013] For example, this period can be doubled after each measurement. This would result in a first measurement at the start of the operating mode when the device is switched off, then a second 15 minutes later, a third 30 minutes later, then 1 hour later, then 2 hours later, and so on. This method of implementation makes it possible to limit the number of measurements and thus the consumption of the device's energy source.

[0014] It should be noted, however, that taking measurements and processing them consumes much less energy than sending an alert message outside the organ.

[0015] According to an advantageous embodiment, the measurement period is constant when it exceeds a given threshold, and preferably when said period is greater than or equal to one week.

[0016] The alert trigger threshold can be between 2 and 7% of the P / T ratio.

[0017] According to an alternative embodiment, the threshold for triggering the alert may correspond to a variation of between 50 and 200 mbar and preferably between 100 and 150 mbar in the pressure of the gas in the internal cavity of the tire.

[0018] The last pressure and temperature measurements obtained in the rolling operating mode of the component can be taken as a reference. It is also possible to take as a reference the first measurements obtained after the start of the operating mode when the component is stopped.

[0019] According to a preferred embodiment, when the alert is triggered, an alert message is sent to at least one pre-identified recipient.

[0020] These recipients may include the vehicle user, the address of a garage where the leak can be repaired and / or a tire dealer.

[0021] According to a preferred embodiment, the vehicle comprising a central unit for monitoring the vehicle's tires, when an alert is triggered by a component of a tire, this alert is transmitted to at least one pre-identified recipient via the central monitoring unit.

[0022] This central unit can then validate the leak detection diagnosis and use its means of communication to transmit an alert message adapted to the pre-identified recipient.

[0023] Depending on the situation, the alert message may be relayed to an external server or website, or directly to a predetermined cell phone or smartphone. It may also be sent by email.

[0024] Several means can be used to determine the vehicle shutdown. For example, since the vehicle has a dashboard power-up circuit, the vehicle shutdown can be determined when the power-up circuit is open.

[0025] When the device includes an accelerometer to detect a rotational movement of the tire, the stopping of the vehicle can be determined by the absence of a signal linked to the rotation of the tire for a period greater than a given threshold.

[0026] The threshold for triggering the vehicle shutdown and launching the stationary mode can be between 15 and 20 minutes for example.

[0027] Finally, the operating mode when the device is stationary switches to the operating mode when it is identified that the vehicle is no longer stationary.

[0028] The tire advantageously comprises on at least part of its inner wall a layer of self-sealing product.

[0029] The vehicle may also include an autonomous driving mode. In this case, the term "vehicle driver" refers to all the elements that enable the vehicle to drive autonomously.

[0030] The method according to one of the objects of the invention is particularly suitable in the case of such vehicles because it has the advantage of warning of a tire problem before any attempt to put the vehicle back into service. Definitions

[0031] The following abbreviations are used in the application text: p, relative inflation pressure of the gas in the internal cavity of a tire; P, absolute inflation pressure; P = p + p atm; p atm, atmospheric pressure, equal to 101.325 kPa under standard conditions; θ, temperature in degrees Celsius of the gas in the internal cavity of a tire; T, absolute temperature in kelvins (degrees Celsius + 273.16). Description of the figure

[0032] There figure 1 attached illustrates a diagram of the operating mode when a monitoring device is stopped. Description of an embodiment of the invention

[0033] There figure 1 illustrates a diagram of the main steps of the operating mode when a monitoring device is stopped according to one of the objects of the invention.

[0034] The monitoring device in question is arranged in the internal cavity of a vehicle tire and is equipped in particular with a pressure sensor, a temperature sensor, a microprocessor, a non-volatile memory, a clock. The device can transmit and receive radio signals. The device has an operating mode while the vehicle is moving and an operating mode when the vehicle is stationary.

[0035] The operating mode while driving usually allows the driver of the vehicle to be warned in the event of a loss of tire pressure, in particular when the pressure decreases by more than 20% of the nominal cold relative pressure value given by the vehicle manufacturer.

[0036] This monitoring unit is part of a vehicle tire monitoring system consisting of four monitoring units, one per tire, and a central unit or CPU. In driving mode, the CPU periodically receives the measurements taken by the units, processes them, and sends messages tailored to the condition of the tires to the driver or any other pre-identified recipient.

[0037] In step 100, the monitoring device is in driving operating mode. The vehicle is either driving or stopped but without the criteria for detecting a stop being satisfied.

[0038] In step 110, the device tests for detection of a stop. This detection may be related to the opening of the dashboard power-up circuit, the absence of a signal related to tire rotation for a period exceeding 15 or 20 minutes, or any other agreed test.

[0039] If the stop detection criterion(s) are not met, the driving mode continues (loop 102).

[0040] Otherwise, the operating mode of the monitoring device switches to the off operating mode (loop 104).

[0041] At the time of switching to the stationary operating mode, at t 0 , the member carries out a measurement at least of the relative inflation pressure p 0 and the temperature θ 0 of the gas in the internal cavity of the tire (step 130).

[0042] The organ calculates the absolute inflation pressure P 0 from the relative pressure as well as the absolute temperature in kelvins: P 0 = p 0 + p atm , where pm is atmospheric pressure; and T 0 = θ 0 + 273 , 16

[0043] The organ then calculates the ratio P 0 / T 0 (step 140).

[0044] The organ then periodically measures the relative pressure and temperature of the gas in the internal cavity of the tire.

[0045] For example, at t=t+ Δt, it measures pt and θ t (step 150).

[0046] The organ then obtains the absolute pressures and absolute temperatures and calculates the ratio: P t / T t (step 160).

[0047] At step 170, the organ tests the value of the ratio P t / T t relative to the initial ratio taken as reference: P 0 T 0 − P t T t ≻ S

[0048] If the difference is less than the threshold S (loop 172), the organ tests whether the vehicle is still stopped or not (step 180). In the embodiment of the figure 1 , we test whether or not we have detected a rotation of the tire, for example with an accelerometer of the monitoring device.

[0049] If both tests 170 and 180 are negative, measurement step 150 is repeated after a period Δt greater than or equal to the previous one (loop 172).

[0050] If test 170 is positive, that is to say that the difference between the two values, initial and at t, is greater than test S, the unit concludes in step 190 that there is a leak of gas from the internal cavity of the tire. The unit then sends a wake-up and alert signal to the central unit UC of the vehicle tire monitoring system (step 200). The UC then transmits to at least one pre-identified recipient a leak alert message from the corresponding tire.

[0051] Optionally, after waking up the CPU, the device can transmit to the CPU all the measurements taken during the stopped operating mode (step 220).

[0052] This optional step has the advantage of allowing the CPU to validate or invalidate the leak diagnosis as well as adapt the message sent to the pre-identified recipient depending on the intensity of the detected leak: If the leak rate is less than, for example, 0.05 or 0.10 bar per month, these are natural inflation losses and no message is useful when the inflation pressure is correct; if the leak rate is greater than 0.10 bar / month and less than 1 bar per week, this is an abnormal leak and the pre-identified recipient should be alerted and advised to have the affected tire inspected; if the leak rate is greater than 1 bar per week, it is a rapid leak and the message can be to inspect the affected tire as soon as possible And to prohibit all driving if the inflation pressure is close to or below 1.5 bar.

[0053] Of course, the messages sent can be adapted according to the measured relative inflation pressure of the tire.

[0054] Finally, if test 180 is positive, the monitoring device switches from stationary operating mode to driving operating mode (loop 182) until the vehicle is next stopped.

[0055] To implement the method of the invention, a monitoring device such as that presented in the applicant's patent EP1354219B1 can be used.

Claims

1. Method for detecting a leak from a tyre of a vehicle, said tyre including a member for surveillance of said tyre with sensors for measuring the pressure and the temperature and having a driving operating mode (102) and a stationary operating mode (104), in which: - it is determined that the vehicle is stationary (110); then - said stationary operating mode (104) is launched to detect when the vehicle is stationary the presence or the absence of a leak of inflating gas from the tyre, characterized in that after the stationary operating mode of the member has been launched: - there are periodically measured the pressure pg and the temperature θ of the gas in the internal cavity of said tyre (130, 150); - the series of pressure and temperature values and the measurement times are stored in nonvolatile memory; - the measured pressure pg is converted to an absolute pressure P and the measured temperature θ is converted to an absolute temperature T, the ratio P / T (140, 160) is calculated and a series of values is obtained; - if said series of values decreases by an amount above a given threshold (S), an alert is triggered (190).

2. Detection method according to claim 1, in which the measurement period is constant and between 30 minutes and 60 minutes inclusive.

3. Detection method according to claim 1, in which the measurement period increases continuously during at least a given number of measurements.

4. Detection method according to the preceding claim, in which the measurement period increases after each measurement by a factor between 1.5 and 4 inclusive.

5. Detection method according to claim 3 or 4, in which the measurement period is constant if it exceeds a given threshold (S) and preferably if said period is greater than or equal to one week.

6. Detection method according to any one of claims 1 to 5, in which said threshold (S) is between 2 and 7% inclusive of said ratio P / T.

7. Detection method according to any one of claims 1 to 5, in which said threshold (S) corresponds to a variation between 50 and 200 mbar inclusive and preferably between 100 and 150 mbar inclusive of the pressure of the gas from the internal cavity of the tyre.

8. Detection method according to claim 6 or 7, in which there is taken as the reference for the ratio P / T the last measurement or measurements of pressure and of temperature obtained in the driving operating mode of the member.

9. Detection method according to claim 6 or 7, in which there is taken as the reference for the ratio P / T the last measurement or measurements of pressure and of temperature obtained in the stationary operating mode of the member.

10. Detection method according to any one of the preceding claims, in which, upon triggering of the alert, an alert message is sent to at least one pre-identified addressee.

11. Detection method according to the preceding claim, in which, the vehicle including a central unit (UC) for surveillance of the tyres of the vehicle, upon the triggering of an alert the member of said tyre transmits the alert message to at least one pre-identified recipient via said surveillance central unit (UC).

12. Detection method according to any one of claims 1 to 11, in which, said vehicle including a circuit for powering up the dashboard, that the vehicle is stationary is determined when said power up circuit is open.

13. Detection method according to any one of claims 1 to 11, in which it is determined that the vehicle is stationary by virtue of the absence of weight on the seat of the driver.

14. Detection method according to any one of claims 1 to 11, in which the member including an accelerometer for detecting a movement of rotation of said tyre, it is determined that the vehicle is stationary by the absence of any signal linked to the movement in rotation of the tyre for a time above a given threshold.

15. Detection method according to the preceding claim, in which it is determined that the vehicle is stationary after between 15 and 60 minutes inclusive.

16. Detection method according to any one of the preceding claims, in which the stationary operating mode of said vehicle switches to the driving operating mode if it is identified that the vehicle is no longer stationary and preferably if a movement in rotation of said tyre is detected.

17. Detection method according to any one of the preceding claims, in which the tyre includes on at least a part of its interior wall a layer of a self-blocking product.

18. Detection method according to any one of the preceding claims, in which the vehicle has an autonomous driving mode.