Method and system for determining the pressure of an aircraft tire

Description

[0001] The present invention relates to the field of aeronautics, and more particularly to the field of maintenance and servicing of aircraft tires. More specifically, the invention relates to monitoring the pressure of aircraft tires.

[0002] We know that improperly inflating aircraft tires can cause many problems. Over-inflation can lead to tread degradation, either through uneven wear or by making it more susceptible to mechanical damage. Conversely, under-inflation significantly increases stress and heating in the tire, which can reduce the tire's lifespan or even create safety risks such as tire bursting or detreading.

[0003] To remedy this situation, tire manufacturers recommend performing a daily tire pressure check. It is also generally recommended to always perform this check when the tires are cold, i.e., when the internal temperature of the tires is roughly equal to the ambient temperature. It is also not recommended to deflate a hot tire.

[0004] We are aware of documents containing recommendations for the cold inflation of aircraft tires, and the set pressures (Pc) to be applied depending on the type of tire, their dimensions, and possibly the aircraft load. These documents also indicate pressure maintenance recommendations, depending on the deviations from Pc.

[0005] In addition, the technical documentation provided by aircraft manufacturers indicates procedures to follow for pressure monitoring. These procedures indicate that since the pressure monitoring must be carried out when cold, it is advisable to wait three hours after stopping the aircraft before taking the measurements.

[0006] However, it has been found that such a procedure has two major drawbacks. The first is the uncertainty associated with this measurement. Indeed, it has been found that the temperature within the tire is inhomogeneous, with variations of up to forty degrees Celsius. In addition, the difference between the internal temperature and the ambient temperature after 3 hours can be as much as fifteen degrees Celsius, since it turns out that in reality the time required for complete cooling of the tire is more like five hours. This leads to errors of up to eleven PSI (0.76 bars) between the determined pressure and the actual cold pressure.

[0007] The second major drawback is the aircraft's downtime, which prevents airlines from increasing the rotation rate of their aircraft.

[0008] Document WO2019 / 081746 A1 describes a method for measuring the pressure of an aircraft tire by determining a cold pressure based on a pressure and temperature measurement.

[0009] The present invention therefore aims to remedy these drawbacks by proposing a method and a system for determining the cold pressure of a tire based on measurements taken when hot.

[0010] For this purpose, it appears necessary to know the transfer function between a hot tire and a cold tire.

[0011] However, it was surprisingly found that this transfer function was not identical throughout the tire. Thus, depending on the position of the sensor at the time the measurements are taken, the results can be distorted. Indeed, when the vehicle stops, the hot air present in the tire tends to rise, the temperature at the bottom of the tire will be lower than the temperature at the top of the tire. The inventors therefore carried out numerous measurements in order to construct the charts present in figure 1 These charts show the temperature / pressure transfer function in a tire as a function of the position of the sensor in the tire during measurement, the different positions being shown on the second diagram of the figure 1 .

[0012] Based on this research, the inventors were able to propose solutions to limit the uncertainty due to this positioning of the sensor.

[0013] Thus, the present invention relates to a method for determining the pressure in a mounted aircraft tire, comprising the following steps: a step during which a first internal gas temperature is measured at a first position in the tire with a first sensor installed in the tire, a step during which a second internal gas temperature is measured at a second position in the tire with a second sensor installed in the tire, the first and second positions being separated by an angular distance of between 160 and 200 degrees, a step during which a "retained" temperature is determined as a function of the first and second temperatures, a step during which an internal air pressure of the tire is determined, a step during which a cold pressure of the tire is determined as a function of the retained temperature, as a function of the pressure and as a function of a predetermined transfer function.

[0014] This process is intended to be implemented shortly after the vehicle has stopped, and the pressure measured is therefore called "hot". We will speak of "cold" pressure to designate the reference pressure generally used in aircraft manufacturers' recommendations, which is a pressure measured when the temperature inside the tire is substantially equal to the ambient temperature.

[0015] In a particular embodiment, the step of determining a pressure of the inflation gas of the tire comprises a step of measuring pressure with a pressure sensor installed in the tire, or a step of obtaining a pressure determined by a device external to the tire.

[0016] In a particular embodiment, the determination of the retained temperature is carried out by choosing the highest temperature between the first and second temperatures, or by taking the average of the first and second temperatures.

[0017] In a particular embodiment, a method according to the invention further comprises the step of determining the altitude of the sensor having measured the highest temperature, and in which the step of determining the cold pressure of the tire takes this altitude into account.

[0018] The invention also relates to a system for determining the pressure in a mounted aircraft tire, the system comprising at least two temperature sensors installed inside the tire, the sensors being positioned so that the angular distance between the two sensors is between 160 and 200 degrees, each of the sensors is preferably placed between 80° and 100° relative to the rolling direction, a means for determining the pressure inside the tire, calculation means making it possible to determine, as a function of a temperature and a pressure, a cold pressure of the tire.

[0019] In a particular embodiment, the pressure determining means is included in the group comprising: a pressure sensor installed in the tire, a pressure sensor installed on the associated rim, or an external measuring device such as a pressure gauge.

[0020] In a particular embodiment, the temperature sensors include accelerometers for determining the altitude of the sensor.

[0021] In a particular embodiment, a system according to the invention further comprises means for determining the temperature of the brake associated with the tire.

[0022] We will now describe various examples of embodiments of the invention. It is specified here that these examples will describe both a method according to the invention, but also constituent elements of a system according to the invention.

[0023] Thus, an example of a complete system allowing the implementation of all the embodiments of the present invention comprises the following elements: at least two temperature sensors installed in the tire, a mobile device, which may take the form of a mobile phone or a reader of any type, comprising means for reading the measurements made by the sensors, and means for transmitting these measurements to calculation means, calculation means, installed either in the mobile device or on a remote server, and in this case the mobile device comprises means capable of allowing the exchange of data between the mobile device and the remote server, advantageously, a user interface allowing an operator to consult data on the mobile device, or to enter certain data necessary for the implementation of a method according to the invention (for example data concerning the ambient temperature, tire pressure, brake temperature, etc.)

[0024] Further, a system according to some embodiments of the invention may optionally comprise: accelerometers installed in temperature sensors, means of determining the pressure in the tire.

[0025] In a first embodiment, a system is used comprising two temperature sensors attached to the inner rubber of a mounted tire. These two sensors are located diametrically opposite each other. Thus, when the vehicle is stationary, and the tire therefore no longer has any rotational movement relative to the ground, there is a guarantee of having a sensor located in the upper part of the tire, namely above a horizontal diameter of the tire, and a sensor located in the lower part of the tire.

[0026] The two sensors measure the temperature inside the tire. Advantageously, the sensors are equipped with wireless communication means allowing them to communicate with a mobile device on which an application developed specifically for implementing the invention is installed.

[0027] Thus, the mobile device can read the values ​​of the measurements made by the sensor. Depending on the embodiments, the implementation of the method can continue directly at the level of the mobile device, equipped with calculation or storage means, or in a remote server with which the mobile device communicates.

[0028] When the temperatures measured by the two sensors are known, a method according to the invention comprises the step of determining a temperature retained for the rest of the calculation; Two options are possible: in one example, the temperature retained is the highest temperature. Indeed, the highest temperature comes from the sensor located in the upper part of the tire, and it has been observed that in the upper part of the tire, the transfer function between hot tire and cold tire varies little and is independent of the temperature or the braking energy.

[0029] In another example, used advantageously in the case where the two sensors are located at approximately the same height, an average of the two measured values ​​can be taken to determine the retained value.

[0030] There are different ways to implement this determination of the retained temperature: either one or other of the options stated above is systematically used, whatever the situation, or the method to be used is determined based on selection criteria: for example, if it is determined that the difference between the two measured temperatures is less than a certain value, for example 2°C with an accuracy of + / - 1°C of the temperature measurement, or if it is determined that the difference in altitude between the two sensors is less than a certain value, for example 5 mm, in this case the average is chosen, and in other cases the maximum method is used.

[0031] Once the retained temperature has been determined, and knowing the tire pressure at the time of the temperature measurement, the pressure in the cold tire can then be determined using the following formula: P_cold=Pmeasured -A*(Tretained-Tambient), in which A is a constant depending on the characteristics of the sensors and the tire. The pressure measurement can be carried out by any means described in this document.

[0032] It should be noted here that the use of two sensors has other advantages compared to existing systems: on the one hand, two temperature measurements are carried out, which means that even in the event of damage to a sensor, it is still possible to determine a cold pressure; to this end, in an exemplary embodiment, a method according to the invention provides that in the case where a temperature measurement is absent, the temperature retained is equal to the single temperature measured, on the other hand, the fact of positioning two diametrically opposed sensors makes it possible to better balance the tire, and to avoid unbalance phenomena which cause premature wear or risks of failure.

[0033] Finally, it is also possible to consider the case where an operator, having to interrogate the temperature sensors, simply interrogates the sensor located in the upper part of the tire, which is more accessible than the sensor located in the lower part, or even in the contact area of ​​the tire on the ground, which makes it difficult to access. In this case, the lower sensor, which would not be interrogated, could be considered a faulty sensor.

[0034] We will now describe a second example of embodiment of the invention. In this example, described using the figure 2 , temperature sensors are also used, which are equipped with a 3-axis accelerometer. The accelerometer is installed on the sensor or nearby, so that these axes ( xc , including , zc ) correspond to the cylindrical markers ( n , y , t) of the tire. This makes it possible to know the altitude of the accelerometer and therefore of the sensor by starting by determining the azimuth β, from the accelerations measured along the normal axis and the tangential axis of the accelerometer, which are components of the acceleration of gravity, using the following formula: β = π 2 + atan a n a t

[0035] Knowing this azimuth, we can then calculate the precise altitude Zsensor in two ways: Either with the crushed radius Re and the inflated radius Rg of the tire: Z sensor = Re + Rg * sinβ either with a pre-established law Z_sensor (β) to take into account the “ovalization” of the tire with crushing, because the radius Rg varies according to the angle β.

[0036] In this embodiment, the cold pressure of the tire is determined by taking into account the altitude of the sensor whose temperature measurement was retained, using the following formula: P cold = Pm - ( B * Z sensor + C ) * ( Tretenue - Tamb ) where B and C are constants, dependent on the characteristics of the sensor and the tire.

[0037] In a third exemplary embodiment, a method according to the invention takes into account an additional parameter for determining the cold pressure, namely the brake temperature. Indeed, it has been found that, in particular when a temperature sensor is located in the lower part of the tire, close to the contact patch, the cooling dynamics depend on the brake temperature. Thus, taking this temperature into account makes it possible to improve the accuracy of a method according to the invention.

[0038] This brake temperature can be obtained in different ways: it can be received directly from the aircraft, for example by a wireless connection between the mobile device and telecommunications means installed in the aircraft, it can be entered directly on the mobile device by an operator in charge of maintaining the aircraft, it can be estimated by the calculation means according to certain usage quantities of the aircraft, for example by using the following formula: Tfrein = AT ∗ W frein 2 + BT ∗ W frein + CT with : W frein = ∫ freinage Ma ∗ ax − F poussée 1 − R ∗ ActivREv + Faéro ∗ dD Faéro = − 1 2 ∗ ρ ∗ S ∗ C x 0 ∗ V 2 C x 0 = Ma ∗ ax 0 1 2 ∗ ρ ∗ S ∗ V 0 2

[0039] Where: Ma: the aircraft weight at landing, ax: longitudinal acceleration, Fthrust: designates the thrust of the engines, ActivRev: the indicator of the opening of the doors of the reverse system: 0 if open, 1 if closed, R: the ratio of thrust directed towards the front of the aircraft, Faero: the aerodynamic drag, D: the distance traveled, Cx: the drag coefficient, S: master-couple surface of the wing, ρ: the density of the air, V: aircraft speed / V0 landing speed AT, BT and CT are constants dependent on the characteristics of the brake and the aircraft.

[0040] In the embodiments described so far, it is considered that the temperature measurements are carried out shortly after the aircraft stops, i.e. within 15 min to 2 h following this stop.

[0041] In this fourth embodiment, we will describe an advantageous way of determining the cold pressure, regardless of when the temperature measurements are taken.

[0042] To do this, from the estimation of the temperature at the start of parking Tstop, we estimate the time from the tire stop during which the pressure is likely to increase dtMaxStrat, and the increase in Pressure dPMaxStrat, due to thermal exchanges with the brake.

[0043] We know the time dt that has elapsed since the tire stopped, from component 3 of the solution: If dt > dtMaxStrat: the pressure of the inflation gas decreases, following a decreasing exponential law, which makes it possible to estimate the tire pressure after a certain time dt from the current time such that: P tm + dt = Pm − P froid ∗ exp dt τ + P froid

[0044] Or: the time constant τ depends on the characteristics of the tire, Pcold is the estimated cold pressure, tm is the current measurement time, Pm: pressure measured at the current time dt: time elapsed since time tm

[0045] We can also estimate the time dtCold, from the current instant, at the end of which the pressure will reach Pcold+εP, εP being the desired measurement precision, i.e.: dtFroid = ln εP Pm − P froid τ

[0046] If dt < dtMaxStrat: the gas pressure increases more or less quickly during dtMaxStrat, depending on the temperature Tstop at the start of parking. Then the pressure evolution follows a decreasing exponential law from tMaxStrat, which makes it possible to estimate the tire pressure after a certain time dt (=tMaxSrat-tm+dt') from the current time tm: P dt = Pmax − P froid ∗ exp dt − tMaxStrat − tm τ + P froid

[0047] Where Pmax: the maximum pressure during parking measured at tMaxStrat,

[0048] We can also estimate the time dtCold, from the current instant, at the end of which the pressure will reach Pcold+εP, εP being the desired measurement precision, i.e.: dtFroid = ln εP Pmax − P froid τ + tMaxStrat − tm

Claims

1. Method for determining the pressure in a mounted aircraft tyre, involving the following steps: - a step during which a first internal gas temperature is measured at a first position in the tyre, with a first sensor installed in the tyre, the method being characterized in that it comprises the following steps: - a step during which a second internal gas temperature is measured at a second position in the tyre, with a second sensor installed in the tyre, the first and the second positions being separated by an angular distance of between 160 and 200 degrees, - a step during which a "retained" temperature is determined, as a function of the first and second temperatures, - a step during which a pressure of the internal air of the tyre is determined, - a step during which a cold pressure of the tyre is determined, as a function of the retained temperature, as a function of the pressure and as a function of a predetermined transfer function.

2. Determination method according to Claim 1, wherein the step of determining a pressure of the internal air of the tyre comprises a step of measuring pressure with a pressure sensor installed in the tyre, or a step of obtaining a pressure determined by a device outside the tyre.

3. Determination method according to Claim 1, wherein the retained temperature is determined by selecting the highest temperature out of the first and second temperatures, or by averaging the first and second temperatures.

4. Determination method according to one of the preceding claims, further comprising the step of determining the altitude of the sensor that has measured the highest temperature, and wherein the step of determining the cold pressure of the tyre takes this altitude into account.

5. System for determining the pressure in a mounted aircraft tyre, the system having - at least two temperature sensors installed inside the tyre, the sensors being positioned such that the angular distance between the two sensors is between 160 and 200 degrees, - a means for determining the pressure inside the tyre, - calculation means making it possible to determine, as a function of a temperature and a pressure, a cold pressure of the tyre.

6. Determination system according to Claim 5, wherein the means for determining the pressure is included in the group comprising: a pressure sensor installed in the tyre, a pressure sensor installed on the associated rim, or an external measuring device such as a manometer.

7. Determination system according to Claim 5 or 6, wherein the temperature sensors comprise accelerometers making it possible to determine the altitude of the sensor.

8. Determination system according to any one of Claims 5 to 7, further comprising means for determining the temperature of the brake associated with the tyre.