Sensor for an aircraft tank

Abstract

The invention relates to a sensor (24) for measuring at least an amount and / or density of a fuel (18) in an aircraft tank (10), comprising: - at least one probe (26), which is configured to measure at least the amount and / or density of the fuel, and intended to be placed in an internal space (16) of the tank (10); - a memory (38), placed in the internal space (16) and configured to store at least values of calibration parameters of the probe (26); and - a single communication bus, intended to connect the probe (26) and the memory (38) to remote measurement electronics (20), via a harness (22) passing through a wall (14) of the tank (10).

Description

[0001] DESCRIPTION

[0002] TITLE: Sensor for aircraft tank

[0003] Technical field of the invention

[0004] The invention relates to a sensor installed in an aircraft tank, in particular a sensor for measuring at least one quantity of fuel in an aircraft tank, as well as an assembly comprising such a sensor and an associated control method.

[0005] State of the prior art

[0006] Fuel control in an aircraft tank is of great importance during a flight. Therefore, it is necessary to be able to monitor the quantity and density of fuel in the tank in real time during the flight with a high degree of accuracy.

[0007] For this purpose, it is known to install suitable sensors, such as gauges, densimeters and thermometers, in fuel tanks. Such sensors are connected to measuring electronics, located outside the tank, via a harness extending through a wall of the tank. However, such a fuel tank constitutes a particularly difficult environment, forming in particular an explosive atmosphere due to fuel vapors, which leads to significant constraints in the choice of the type of sensors as well as their functionalities and their controls.

[0008] In particular, the electronic components used must not, on the one hand, heat up or generate hot spots, particularly above 200°C, and, on the other hand, store energy, particularly likely to generate a spark of more than 200 pJ.

[0009] Usually, these sensors are analog and passive, excited at low power, so as not to risk having a component that could heat up or, in the event of a fault, generate a spark.

[0010] However, it is desirable to limit the measurement uncertainty of the sensors linked to manufacturing variations and thus improve the reliability of the measurement. Indeed, the manufacturing tolerances of the sensors mean that the fuel volume and density measurements can show dispersion from one sensor to another.

[0011] However, such improvements are made complex by the purely analog nature of the sensors.

[0012] It is also important not to significantly increase the aircraft weight through such improvements, nor to implement changes requiring substantial modifications to the tank and harness, which would prove very costly. Finally, it is necessary for the sensors to be of the simplest possible design in order to maximize their reliability, particularly considering the difficulties of accessing them inside the tank in the event of a need for replacement.

[0013] Presentation of the invention

[0014] The invention thus aims to improve the accuracy of measurements of a quantity and / or density of fuel present in tanks of an aircraft, without requiring significant reconfiguration of the harness or the tank.

[0015] To this end, the invention relates to a sensor for measuring at least one quantity and / or density of a fuel in an aircraft tank, comprising: at least one probe, configured to measure at least the quantity and / or density of the fuel, intended to be arranged in an internal space of the tank; a memory, in particular of the electrically erasable and programmable read-only memory type, arranged in the internal space of the tank and configured to store at least calibration parameter values ​​of the probe; and a single communication bus, in particular composed of at least two conductors, intended to connect the probe and the memory to remote measurement electronics, by an electrical harness passing through a wall of the tank.

[0016] Such a sensor allows access to specific calibration data from the measuring probe by measuring electronics, in particular remote electronics, which improves the accuracy and reliability of measurements, without requiring modifications to the tank and the electrical harness.

[0017] In particular, the communication bus is of the type known as “One-Wire”.

[0018] Thus, according to the invention, to a purely analog probe, it is proposed to add a memory configured to store at least the values ​​of calibration parameters of the probe made accessible via the same conductors as those used by the probe, devoid of such a memory.

[0019] The probe may be a gauge, in particular a capacitive measuring gauge, comprising two electrodes connected respectively to a low impedance conductor and a high impedance conductor of the communication bus protected by a shielding layer.

[0020] Furthermore, the memory is, for example, connected between the high impedance conductor of the communication bus and the shielding layer.

[0021] Such a feature allows for simple and reliable measurement of the quantity and / or density of fuel in the tank, in a fully analog manner and without involving significant current or heating. Such a feature also allows for greater accuracy than known state-of-the-art probes.

[0022] The sensor may include at least one diode connected in parallel with the memory and / or at least one resistor connected in series with the memory.

[0023] Such a feature allows effective protection of the memory and sensor against overvoltages.

[0024] The memory can be mounted on an electronic card placed in a box located in the internal space of the tank, in particular on the probe.

[0025] More specifically, the housing is capable of containing a resin that submerges the electronic board and memory. This feature allows for insulation of the electrical components from the fuel present in the tank.

[0026] The memory can be of the electrically erasable and programmable read-only memory type. This feature allows data to be stored on a component requiring little energy and limiting any risk of heating.

[0027] The calibration parameter values ​​may include two probe capacitance values ​​measured at two different tank fill rates.

[0028] Furthermore, depending on the linearity of the sensor, more than two calibration parameters can be stored.

[0029] Such a feature allows correction of measurement results, in particular by linear interpolation or by segmentation of a non-linear response curve, in order to correct variations due to manufacturing tolerances of the probe.

[0030] Furthermore, the probe can also be a densimeter composed of two windings forming a transformer connected to an excitation.

[0031] The calibration parameter values ​​of the probe, as a density meter, may include mechanical correction parameters related to manufacturing. Such a feature allows compensation of density measurement results by eliminating manufacturing-related variations.

[0032] Thus, according to the invention, the probe is capable of measuring a fuel height, and / or a density of the fuel passing through it or in which it is partially or entirely immersed.

[0033] The sensor may further comprise a measuring probe, in particular a passive one, capable of measuring any other physical quantities characteristic of the fuel, such as a temperature, a permittivity, etc.

[0034] More particularly, the sensor may further comprise a temperature measuring probe, in particular a digital temperature measuring probe, in particular integrated into the memory and accessible via the communication bus. Such a feature makes it possible to take into account measurement variations due to the temperature of the fuel. In particular, the communication bus may be of the two-wire type comprising two conductors and their insulation, such as a coaxial cable, a twisted pair, etc.

[0035] The invention also relates to an assembly comprising a reservoir and a measuring system comprising at least:

[0036] - a sensor as described previously,

[0037] - control electronics, and

[0038] - an electrical harness extending between the sensor and the control electronics, in particular through a wall of the tank.

[0039] The invention further relates to a method for measuring at least one quantity and / or density of fuel in a tank, using a sensor as described above and measuring electronics connected to the sensor.

[0040] The measuring method comprises at least:

[0041] An obtaining step, during which at least one value of calibration parameters of the probe is obtained;

[0042] A storage step, during which the calibration parameter values ​​are stored in memory;

[0043] A read step, during which the calibration parameter values ​​are read from the memory by the measuring electronics each time the measuring electronics are started; and

[0044] A step of obtaining measurements of the quantity of fuel and / or the density of fuel, in particular periodic, during which the measuring electronics, by implementing the probe using the calibration parameter values, obtains measurements of the quantity and / or the density of fuel.

[0045] Brief description of the figures

[0046] The present invention will be better understood and other characteristics and advantages will become apparent upon reading the detailed description which follows, comprising embodiments given for illustrative purposes with reference to the appended figures, presented as non-limiting examples, which may serve to complete the understanding of the present invention and the description of its embodiment and, where appropriate, contribute to its definition, in which:

[0047] [Fig. 1] Figure 1 is a schematic view of an assembly comprising a reservoir and a measuring system comprising a sensor according to the invention, and

[0048] [Fig. 2] Figure 2 is a schematic view of the sensor of Figure 1. Detailed Description of the Invention

[0049] Figure 1 schematically represents a fuel tank 10, in particular for an aircraft, and a measuring system 12, capable of determining a quantity and / or a density of a fuel 18 present in the tank 10. Advantageously, the measuring system 12 is in particular configured to measure both the quantity and / or the density of the fuel 18 present in the tank 10.

[0050] The measuring system 12 can also be configured to measure a temperature of the fuel 18 present in the tank 10.

[0051] The tank 10 comprises walls 14 defining a substantially closed internal space 16, containing a fuel 18, in particular in single-phase or two-phase form.

[0052] The number of phases and the density of fuel 18 may vary depending on altitude, temperature and / or filling rate.

[0053] Due to the flammable nature of the fuel 18 and the presence of fuel vapor in the internal space 16, the internal space 16 constitutes a hazardous environment governed by the standards associated with explosive atmospheres.

[0054] The measuring system 12 comprises measuring electronics 20, an electrical harness 22 and at least one sensor 24 arranged in the internal space 16 of the tank 10. In particular, the sensor 24 can be immersed at least partially in the fuel 18.

[0055] The measurement electronics 20 comprises, for example, at least one processor and at least one memory, not shown in the figures. The measurement electronics 20 is, for example, integrated into an on-board computer and can be connected to other avionics equipment.

[0056] The measuring electronics 20 are arranged outside the tank 10 and away from the fuel 18. In fact, the measuring electronics 20 are not suitable for operating in an explosive atmosphere.

[0057] The electrical harness 22 is a connection assembly comprising one or more electrical cables grouped in a protective casing. The electrical harness 22 extends from the measuring electronics 20, through the walls 14 of the tank, to the sensor 24, in order to allow the connection of electrical signals between the sensor 24 and the measuring electronics 20.

[0058] The electrical harness 22 may be of considerable length, for example between 10 and 50 meters.

[0059] The sensor 24 comprises at least one probe 26 arranged in the internal space 16 of the tank 10.

[0060] According to one embodiment, the probe 26 is of the capacitive measurement type arranged in the internal space 16 of the tank 10. According to another embodiment, the probe 26 is of the transformer ratiometric measurement type, arranged in the internal space 16 of the tank 10.

[0061] Figure 2 is a schematic view of the sensor 24 of Figure 1.

[0062] More specifically, according to an embodiment shown in FIG. 2, the probe 26 is a level gauge or a densimeter for measuring the density of fuel in the tank 10.

[0063] Such a probe 26 is likely to be at least partially arranged in the fuel 18. The probe 26 may comprise a first electrode 28 and a second electrode 30, respectively cylindrical, concentric, arranged vertically, in particular in the case of a capacitive gauge. In particular, the first electrode 28 may constitute an external electrode 28 and the second electrode 30 may constitute an internal electrode 30, according to the example illustrated in FIG. 2.

[0064] The first electrode 28 and the second electrode 30 define between them an annular space 32 in which the fuel 18 rises during filling and falls during consumption. The level of fuel 18 in the annular space 32 thus modifies the capacitance value of the probe 26.

[0065] The capacity of the probe 26 varies in particular linearly with the fuel level 18 in the internal space 32.

[0066] In particular, an electrical signal sent by the measuring electronics 20 to the probe 26 makes it possible to determine a capacitance value of the probe 26 for a given fuel level. Such a capacitance value can then be used by the measuring electronics 20 to determine the fuel level 18 and the quantity of fuel 18 in the tank 10. According to another embodiment, the probe 26 is a densimeter, advantageously arranged entirely immersed in the fuel 18 and capable of measuring a density of the fuel 18 in the tank 10.

[0067] According to another embodiment, the sensor 24 comprises the probe 26, capable of determining the level of fuel 18 in the tank 10 and a densimeter, capable of measuring the density of the fuel 18 in the tank 10.

[0068] Optionally, the sensor 24 may further comprise a temperature probe.

[0069] The sensor 24 further comprises an electronic card 34, capable of being arranged in the internal space 16 of the tank 10. For example, the electronic card 34 is placed in a protective housing 36.

[0070] The electronic card 34 comprises a certain number of electronic components used in the measurement by the probe 26, in particular depending on the type of gauging.

[0071] Advantageously, the housing 36 is filled with a resin embedding the electronic card 34 to prevent possible contact between the electronic card 34 and the fuel 18. The electronic card 34 notably comprises a memory 38, in particular of the electrically erasable and programmable read-only memory type, also known by the acronym EEPROM for “Electrically Erasable Programmable Read Only Memory” in English.

[0072] For example, memory 38 has a storage capacity of 1024 bits.

[0073] Such a type of memory 38 is a component capable of passively storing data without requiring a power supply, so that the stored information is not lost when the power supply is lost.

[0074] Moreover, such memory 38 requires very low electrical current and low voltage to access the stored data

[0075] Finally, such a memory 38 generates only a small amount of heat, which can be considered negligible.

[0076] According to the exemplary embodiment, the memory 38 is self-powered between a ground wire 40 and a data wire 42, according to a so-called “parasitic power supply” arrangement.

[0077] The memory 38 is configured to store at least values ​​of calibration parameters of the probe 26, in particular at least values ​​of two calibration parameters of the probe 26.

[0078] Such values ​​are specific to probe 26, and allow for manufacturing tolerances to be taken into account.

[0079] The calibration parameter values ​​may include, for example, a value of the capacitance of the probe 26 measured when the tank 10 is empty and a value of the capacitance of the probe 26 measured when the tank 10 is filled with fuel 18.

[0080] More generally, the calibration parameter values ​​may comprise capacity values, in particular two capacity values, measured at various fuel levels 18 in the tank 10, in particular two fuel levels 18 in the tank 10, corresponding to distinct known filling rates of the tank 10.

[0081] Alternatively, the calibration parameter values ​​may comprise, for example, an offset value of the probe 26 and a gain value of the probe 26, i.e. respectively values ​​of the ordinate at the origin and slope of the affine function linking the measured capacity of the probe 26 and the fuel level 18 in the tank 10, or filling rate of the tank 10, and / or the density of the fuel 18.

[0082] Furthermore, in the case where the probe 26 is a densimeter, the calibration parameters can be voltage ratios corresponding to density values, temperature compensations or others.

[0083] Optionally, other parameters can be stored in the memory 38 to be read by the measuring electronics 20.

[0084] For example, the memory 38 can store coefficients of variation of the relationship between the capacity of the probe 26 and the fuel level 18 in the tank 10, or filling rate of the tank 10, with the temperature, or any other relevant data in order to adjust the precision of the measurement carried out by the sensor 24.

[0085] Optionally, in the case where the sensor 24 comprises several probes 26, for example a gauge and a densimeter, the memory 38 can comprise calibration parameter values ​​for each probe 26.

[0086] The measuring electronics 20 is configured to calculate a quantity measurement result and / or a density measurement result of the fuel 18 in the tank 10, in particular from the measured capacity of the probe 26 and the calibration parameter values. The calculation is done, for example, by linear interpolation.

[0087] The probe 26 is connected to the measuring electronics 20 by a communication bus allowing a connection with only two wires, namely a data wire and a ground wire. Such a communication bus is of the “One-Wire” type, also known as a “Dallas bus”). Such a communication bus allows a two-wire electrical connection.

[0088] According to the example presented, the two-wire electrical connection is of the coaxial type, comprising a high-impedance central core 42 and a shielding layer radially surrounding the central core as well as a low-impedance wire 47. Such a connection is represented schematically in FIG. 2, by a ground wire 40, and by a data wire 42 connected to the internal electrode 30 of the sensor 24.

[0089] Such a “One-Wire” type communication bus allows digital communication by multiplexing on the same conductors as those used for the transmission of analog signals relating to the measurement of the probe 26 and this, without degradation of the latter.

[0090] A terminal block 44 is arranged downstream of the electrical harness 22, on the electronic card 34, to allow connection of the probe 26.

[0091] Thus, thanks to the multiplexing implemented in the measuring electronics 20, the data stored in the memory 38 can be read by digital communication on the data wire 42.

[0092] Advantageously, the electronic card 34 may also comprise at least one resistor 45, connected in series at the input of the memory 38. The resistor 45 thus has sufficient input resistance, for example of the order of 6 KOhm.

[0093] The electronic card 34 may also include at least one diode 46, mounted in parallel with the memory 38. This makes it possible to protect the memory 38 from potential overvoltages and to improve the system's resistance to lightning strikes.

[0094] During operation, the measurement system 12 constitutes an acquisition system in which the measurement electronics 20 are configured to: read the data stored in the memory 38 at each start-up; detect any change in the sensor 24; and / or where appropriate, update the values ​​of the calibration parameters stored in the memory 38.

[0095] Reading of the memory 38 is done digitally on the data wire 42, for example according to the “One-Wire” communication protocol.

[0096] Once the reading of the data stored in the memory 38 is complete, the memory 38 is isolated at the level of the measuring electronics 20.

[0097] The monitoring of the level, or rate or quantity, and / or density of fuel 18 in the tank 10 is then implemented by the measuring electronics 20 by means of the probe 26. The capacity values ​​of the probe 26 thus measured are established from the values ​​of the calibration parameters previously recovered to deduce, precisely and reliably, the quantity and / or density of fuel 18 present in the tank 10.

Claims

CLAIMS 1. Sensor (24) for measuring at least one quantity and / or density of a fuel (18) in an aircraft tank (10), comprising: at least one probe (26), configured to measure at least the quantity and / or density of the fuel, intended to be arranged in an internal space (16) of the tank (10); a memory (38), in particular of the electrically erasable and programmable read-only memory type, arranged in the internal space (16) and configured to store at least calibration parameter values ​​of the probe (26); and a single communication bus, in particular composed of at least two conductors, intended to connect the probe (26) and the memory (38) to remote measurement electronics (20), by an electrical harness (22) passing through a wall (14) of the tank (10).

2. Sensor (24) according to claim 1, characterized in that the probe (26) is a gauge, in particular a capacitive measuring gauge, comprising two electrodes connected respectively to a low impedance conductor (47) and a high impedance conductor (42) of the communication bus protected by a shielding layer (40).

3. Sensor (24) according to claim 2, characterized in that the memory (38) is connected between the high impedance conductor (42) of the communication bus and the shielding layer (40).

4. Sensor (24) according to any one of the preceding claims, characterized in that it comprises at least one diode (46) connected in parallel with the memory (38) and / or at least one resistor (45) connected in series with the memory (38).

5. Sensor (24) according to any one of the preceding claims, in which the memory (38) is mounted on an electronic card (34) placed in a housing (36) located in the internal space (16) of the tank (10).

6. Sensor (24) according to any one of the preceding claims, in which the calibration parameter values ​​comprise two capacitance values ​​of the probe (26) measured at two different filling rates of the tank (10).

7. Sensor (24) according to any one of the preceding claims, in which the probe (26) is a densimeter composed of two windings forming a transformer connected to an excitation.

8. Sensor (24) according to any one of the preceding claims, wherein the sensor (24) further comprises a temperature measuring probe.

9. Assembly comprising a tank (10) and a measuring system (12) comprising at least: a sensor (24) according to any one of the preceding claims, control electronics (20), and an electrical harness 22, extending between the sensor (24) and the control electronics (20), in particular through a wall (14) of the tank (10).

10. Method for measuring at least one quantity and / or density of fuel (18) in a tank (10), using a sensor (24) according to any one of claims 1 to 8 and measuring electronics (20) connected to the sensor (24), the measuring method comprising at least: An obtaining step, during which at least one value of calibration parameters of the probe (26) is obtained; A storage step, during which the calibration parameter values ​​are stored in the memory (38); A reading step, during which the calibration parameter values ​​are read from the memory (38) by the measuring electronics (20) each time the measuring electronics (20) is started; and A step of obtaining measurements of the quantity and / or density of fuel (18), during which the measuring electronics (20) by implementing the probe (26), by means of the calibration parameter values ​​obtains measurements of the quantity and / or density of fuel (18).

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