Evolutionary calibration of fuel gauge law.

Abstract

Calibration method for the gauge law of a liquid gauging system, the system comprising a tank, a gauging device, a display device and an electrical circuit, the gauging device comprising a computer parameterized for carrying out the calculations necessary for the operation of the gauging service.The process includes a pre-calibration step of the gauging system, performed when the tank is empty, which consists of integrating complete minimum and maximum gauging laws into the computer and defining pre-calculated complete generic gauging laws between the minimum and maximum laws; a partial filling step of the tank, said step following the pre-calibration step; a step of determining a partial gauging law corresponding to the partial filling of the tank; and a step of determining the complete gauging law corresponding to the partial filling of the tank by selecting the pre-calculated complete generic law that most closely covers the partial gauging law. Figure for the abstract: Fig. 6.

Description

Title of the invention: Evolutionary calibration of fuel gauge law. technical field

[0001] The invention relates to the field of motor vehicles such as cars, motorcycles, trucks or buses, and concerns a device for measuring a liquid level in a tank. The invention relates more particularly to the measurement of a fuel level. Previous techniques

[0002] Motor vehicles generally include several tanks, including, for those with internal combustion engines, a fuel tank.

[0003] Manufacturers design fuel tanks with shapes that can be more or less complex, conforming to the available space in the vehicle. The tanks are equipped with a device for measuring their liquid level, in this case fuel, called a gauging device. This device makes it possible to determine the volume of liquid contained.

[0004] A measuring device generally comprises an arm ending in a float to form a sensing unit housed in the tank. The arm is hinged on a support incorporating a gauge, for example, consisting of a variable resistor. Rotation of the arm relative to the support changes the value of the variable resistor. The gauge is integrated into an electrical circuit that delivers an output signal reflecting the value of the variable resistor and, therefore, the liquid level in the tank.

[0005] The combined operation of a display device, located on the vehicle's dashboard, and a measuring device, installed in the fuel tank, allows the driver to be informed of the remaining fuel volume. The fuel level information is displayed by means such as an analog gauge, a digital indicator with discrete or continuous display, or other means. The fuel level information provided by the gauge is supplemented by a warning light indicating when the fuel level is low, in a reserve zone. A digital indicator of the distance that can be traveled with the available fuel volume may also be provided.

[0006] The driver therefore has information to check the vehicle's range and can plan a journey, adding fuel as needed. The information is generally reliable enough for the vehicle to actually reach its destination. However, it sometimes happens that the information presents discrepancies with reality.

[0007] Indeed, it has sometimes been observed that the fuel level is not displayed on the dashboard, that the gauge is inaccurate, or that the gauge gets stuck at full, which in this case means that a considerable amount of time elapses before the display indicates a decrease, even though the tank has been full and the vehicle has begun its journey. Cases of false low fuel warnings have also been observed.

[0008] In fact, in a significant number of cases, the fuel level information on the dashboard is inaccurate or even false. There is an inconsistency between the actual volume of fuel in the tank and the fuel level displayed on the vehicle's dashboard. This inconsistency leads to a feeling of inaccuracy in the information, non-linearity in the display, and a loss of driving range for the driver.

[0009] It appears that a gauging system, such as the one described above, exhibits a degree of variability, which is the source of the problems stated. The variability of the complete system comprises variations in the tank, the gauging device, their assembly, and, to a lesser extent, the electrical wiring and the computer performing the measurements. The gauging device transmits a resistance value related to the fuel level. The computer measures the resistance and transforms the resistance value into useful information, in this case the fuel volume in the tank, using software. The computer uses a fixed gauging law, calibrated for each vehicle family. In practice, there is a discrepancy between the fixed calibrated gauging law and the actual gauging law for each vehicle, due to the variations in the gauging system.

[0010] To overcome the aforementioned drawbacks, it has been proposed to increase the accuracy of fuel level measurement by improving the sensor used in the gauging device.

[0011] For example, US patent 11,175,171 B2 teaches the use of a capacitive level sensor. By implementing this sensor, the fuel level measurement is indeed more accurate. However, the fuel level information on the instrument panel may still be inaccurate or false. Furthermore, a capacitive sensor makes the gauging system more expensive compared to a conventional system with a variable resistor. Description of the invention

[0012] The invention seeks to overcome the aforementioned drawbacks and has the general aim of improving the accuracy and reliability of fuel level measurement in a tank. One objective is to make the fuel level display conform to reality. The invention also seeks to minimize the cost of a system for measuring fuel level.

[0013] To this end, the invention proposes a method for calibrating the gauge law of a liquid gauging system, the system comprising a reservoir, a gauging device, a display device and an electrical circuit, the gauging device comprising a computer parameterized for carrying out the calculations necessary for the operation of the gauging service.

[0014] The method includes a learning of the gauge law in the lower part of the tank, said learning comprising the following steps: a pre-calibration step of the gauging system, carried out when the tank is empty, which consists of integrating complete minimum and maximum limit gauging laws into the computer, and defining pre-calculated complete generic gauging laws between the minimum law and the maximum law, a partial filling step of the tank, said step following the pre-calibration step, a step of determining a partial gauge law corresponding to the partial filling of the tank, a step of determining a complete gauge law corresponding to the partial filling of the tank, by selecting the pre-calculated complete generic law that most closely covers the partial gauge law.

[0015] The calibration of the gauge law defines the performance of the fuel gauging function. It allows the transfer law between the gauging device and the corresponding fuel volume to be defined for a given system, i.e., for an assembly comprising a tank, a gauging device, a display device, an electrical circuit, and a computer. Calibration allows the display law of the human-machine interface to be defined in relation to the calculated fuel volume, as well as some parameters necessary for calculating the fuel volume under load of the internal combustion engine. In practice, the gauge law is learned for each vehicle individually. This provides high accuracy for measuring the fuel volume. Among the resulting advantages is greater safety in trip planning, in that the risk of unexpected running out of fuel is reduced, or even eliminated.

[0016] The method includes a gauge law learning in the upper part of the tank, said learning comprising the following steps: steps of retrieval and storage by the computer of data measuring the fuel volume relative to a target level, for different full tank fills, said data being provided by a gauge of the gauging device, steps of calculation of averages of said data provided by the gauge, steps of determination of complete gauge law corresponding to the complete filling of the tank, on the basis of said averages of said data, by selection of the pre-calculated generic complete law which most closely covers said complete gauge law.

[0017] This is in fact, if necessary, to adjust for the vehicle user the calibration previously carried out in the factory at the end of manufacturing and just before marketing. This optimizes the accuracy of fuel level measurement during normal vehicle use.

[0018] The method includes steps for determining the actual gauge law, said law being an average of the full gauge law corresponding to the partial filling of the tank and the last full gauge law corresponding to the complete filling of the tank.

[0019] This allows for further refinement of the calibration. For example, the process allows differentiation between a nominal full tank, a slight underfill, and a slight overfill. The process also allows for consideration of vehicle aging, that is, the evolution of the dispersions of the components of the gauging system.

[0020] In the process, the data measuring the fuel volume are resistance values ​​from a variable resistor in the gauge of the gauging device. The use of this component minimizes the manufacturing costs of the gauging system because the price of a variable resistor is low. It also results in the advantage that the system is both simple and reliable.

[0021] In the process, the gauge law is learned based on an average of the resistance values ​​measured during a significant number of recent full fills. This allows for gradual adjustments to the gauge law. In other words, exceptions to the operating procedure, such as a very high fill level, will have their impact minimized.

[0022] In the process, the data comes from a number of fills between 3 and 10. Usage has shown that these values ​​give good results.

[0023] In the process, the partial filling of the tank is between 5 and 30% of a full fill. This results in significant savings for the vehicle manufacturer.

[0024] In the method, the display device is a digital indicator. Reading a digital value is easier than interpreting the position of a needle.

[0025] The invention also relates to a liquid gauging system implementing a gauging law method as mentioned above.

[0026] The invention also relates to a motor vehicle comprising a liquid gauging system as mentioned above. Brief description of the drawings

[0027] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0028] - [Fig. 1] is an example of a representation of the minimum gauge law and the law of maximum gauge of a given vehicle, for the implementation of a process according to the invention,

[0029] - [Fig.2] is similar to [Fig.1], but also shows inter gauge laws medians,

[0030] - [Fig.3] is a logic diagram relating to the calculation of the gauge law obtained by ap factory pre-assembly,

[0031] - [Fig.4] is similar to [Fig.1] and [Fig.2], but shows a gauge law for the vehicle in brand new condition,

[0032] - [Fig.5] is similar to [Fig.1], [Fig.2] or [Fig.3], for a configuration group gauge display,

[0033] - [Fig.6] is a logic diagram relating to the calculation of the gauge law obtained by ap Prentissage au plein,

[0034] - [Fig.7] is a logic diagram relating to the calculation of the actual gauge law,

[0035] - [Fig.8] is similar to [Fig.5], but shows the actual, precise gauge law, which changes as the vehicle ages. Detailed description

[0036] A motor vehicle equipped with an internal combustion engine includes a liquid gauging system, such as for fuel. The gauging system includes, in particular, a tank, a gauging device, a display device and an electrical circuit, not shown.

[0037] The gauging device includes a computer configured to perform the calculations necessary for the gauging function. This involves calibrating the gauging law to define the performance of the fuel gauging function. In practice, the gauging law defines the relationship between a variable resistance, which is measured, and the fuel volume. The gauging device comprises an arm ending in a float to form a sensing unit, housed in the tank. The arm is hinged on a support incorporating a gauge, which is the variable resistance. Rotation of the arm relative to the support changes the value of the variable resistance. The gauge is integrated into the electrical circuit and delivers an output signal, which reflects the value of the variable resistance and, therefore, the fuel level in the tank.

[0038] The calibration of the gauge law also defines the display law in relation to the calculated fuel volume, as well as some parameters necessary for calculating the fuel volume under load of the internal combustion engine.

[0039] The calibration of the gauge law must ensure acceptable performance for all of the following dispersion cases: filling volume and gauge law when new and after aging, filling volume on a 2° slope and on a 2° incline, fuel volume underfilled and overfilled. For example, a click at One click of a fuel pump nozzle indicates underfilling, while more than three clicks indicate overfilling.

[0040] One objective is to ensure the linearity of the fuel gauging service. This involves detecting a variation in fuel volume sufficiently early after the tank has been filled and detecting a small amount of fuel added. This facilitates trip management, particularly when the vehicle is rented and refueling is required. It also helps prevent running out of fuel.

[0041] For this purpose, the gauge law is learned for each vehicle individually. The gauge law is the transfer function between the volume of fuel contained in the tank and the measured resistance. It corresponds to a function, or curve, as will be seen later.

[0042] Firstly, a learning of the gauge law is carried out in the lower part of the tank, at the factory, at the end of the assembly line during the first fueling.

[0043] To enable its delivery, the vehicle receives, during its manufacture, a fuel allocation that allows it to complete all the logistical stages. However, this allocation is small and generally represents only one-eighth of the tank's capacity. Indeed, the vehicle is not delivered with a full tank.

[0044] A pre-calibration is integrated into the vehicle, before the first refueling, in order to specify approximately 80 parameters that enable the calculations necessary for the operation of the fuel gauging service. In other words, the pre-calibration is performed when the fuel tank is completely empty.

[0045] The calculations correspond to the estimation of the level of fuel remaining in the tank, the use of the standard gauge law if learning is not activated or impossible, the determination of the minimum fuel volume allowing the detection of a fuel addition and the conditions of entry into the different modes of updating the displayed gauge, and also the display law allowing the fuel volume to be translated into a percentage of display.

[0046] The calculations, as shown in [Fig. 1], correspond to the definition of the system's limit gauging laws, that is, the minimum and maximum acceptable tolerances, for an entire population of vehicles. More precisely, a minimum law corresponds to the smallest volume that can be measured across the vehicle population, taking into account all variations, such as dimensional differences in parts or their wear, for a given resistance value. A maximum law, on the other hand, corresponds to the maximum volume that can be measured across the vehicle population for a given resistance value.

[0047] As soon as the pre-calibration is completed, the gauging device's computer stores a whole network of curves covering all the tolerances, calculated from minimum and maximum gauging laws, as shown in [Fig.2].

[0048] A set of intermediate laws is defined, the laws corresponding to intermediate volumes between the minimum and maximum volume of fuel for an identical resistance value.

[0049] For example, in a non-limiting way, if in carrying out a dispersion study it is realized that there is a possible inaccuracy of 5 liters for the same resistance value, it is possible to provide 10 intermediate laws with differences of 0.5 liters between them.

[0050] Once the pre-calibration is complete, a partial fuel filling is carried out at the factory. The fuel filling machine communicates with the vehicle to provide successive readings of the fuel volumes actually added to the tank. The volumes delivered by the machine are measured with high precision and assumed to be perfect, given that the filling is incomplete, for example limited to 10 liters.

[0051] As schematically shown in [Fig.3], the information of the actual volume is transmitted, the measurement of the resistance of the gauge is triggered, which makes it possible to know the resistance value of the gauge for the volume introduced, for this vehicle.

[0052] The resistance curve as a function of volume for this vehicle is therefore known, but only for small volumes, less than 10 liters for example, and not for the entire tank volume up to full, since it is not designed to be fully filled at the factory. It is therefore necessary to extend the curve for larger volumes.

[0053] A first complete gauge law is defined from the selection of one of the pre-calculated gauge law curves passing closest to the point defined by the measured resistance and volume.

[0054] Specifically, for the actual volume value, the calculator determines the resistance associated with the volume for each intermediate gauge law. The calculator compares the measured resistance to the various pre-calculated resistances. The selected intermediate gauge law is the one for which the pre-calculated resistance is closest to the measured resistance. Then, the resistance curve for small volumes is extended by the pre-calibrated generic gauge law.

[0055] In addition, knowing the actual volume of fuel introduced into the tank and the associated resistance value allows for a conformity check. Indeed, if the measured resistance is greater than the maximum value or less than the minimum value for the volume of fuel introduced, then the fuel tank is outside the tolerances. In this case, learning the gauge law is not permitted, and the law applied for this vehicle is the pre-calibrated gauge law.

[0056] In the case of a compliant factory learning process, the gauging system has a fairly precise gauging law, given that the vehicle is in new condition. This law is visible on [Fig.4], by the curve which has the most points, in accordance with the legend.

[0057] But at this stage, neither the aging of the vehicle nor subsequent filling variations are taken into account. This is why a learning process for the gauge law is planned for the upper part of the tank.

[0058] In fact, from the factory gate, no means of directly measuring the volume of fuel introduced into the tank is available. In particular, no measurement of the partial-fill volume is taken. As a result, the evolution of the lower part of the law is not verified. However, it is possible to obtain an indication that a full fill has been completed. An object of the invention is to recognize this event and to deduce from it an evolution, and then a correction, of the gauge law.

[0059] Learning the gauge law in the upper part of the tank throughout the life of the vehicle, at each full tank fill, is done as follows.

[0060] After adding fuel to the full tank, the resistance of the fuel gauge is measured to update the displayed gauge reading, according to a known readjustment logic. This logic allows the update during a vehicle state transition, i.e., when the ignition is switched from off to on, just before the engine actually starts. The update is permitted if the volume of fuel added, and therefore measured by the gauge, is greater than a calibrated readjustment threshold. For example, 4 liters added. To achieve this, a first fuel level is measured before refueling, when the vehicle is stopped. A second fuel level is measured after refueling, when the vehicle is restarted. If the second level is greater than the first level plus the calibrated readjustment threshold, then the display update is permitted.

[0061] When the fuel level reaches a pre-calibrated target level, identified as a full tank level in the most unfavorable dispersion case, the minimum fill, then the learning of the gauge law called "full" is effective.

[0062] The target level is pre-calibrated in the computer. Figure 5 shows this level, calculated as the smallest usable capacity that could be measured across a population of vehicles. The target level corresponds to a minimum fill-up, from which a safety margin of a few liters, for example 2, is subtracted.

[0063] The volume of fuel inserted into the tank is not known, but the variation in volume from stationary to full is known. The full volume is assumed to be fixed and calibrated for each vehicle family.

[0064] In order to provide stability to the system, the gauge law is learned on an average of the resistances measured over a significant number of the last Completely full. For example, 5 full. Figure 6 shows in particular the obtaining of the new gauge law curve which results from the calculation of the average resistances.

[0065] As with factory learning, at full tank, a complete gauge law is defined by selecting one of the pre-calculated gauge law curves that passes closest to the point defined by the measured resistance and the calibrated volume. Specifically, with reference to [Fig. 7], for the calibrated volume value, the computer determines the resistance at full tank associated with that volume for each intermediate law. The computer compares the measured resistance to the resistances derived from the laws. The intermediate law for which the resistance value is closest to the measured resistance value is selected. The law curve applied to the vehicle, the actual curve, is an average of the factory-learned curve and the full-tank-learned curve.

[0066] The display law, as well as some parameters allowing the calculation of the fuel level during driving, also evolve.

[0067] At this stage, as shown in [Fig.8], the gauge law is accurate, evolves with the aging of the vehicle, and adapts to the uses of the driver(s), in particular for underfilling and overfilling of the fuel tank.

[0068] In summary, the described method relies solely on an evolution in the computer's programming, adding functionalities to a conventional management logic. In other words, known components are used in a new and improved way. These components are simple and inexpensive, and consequently, the implementation of the method is simple and inexpensive. This implementation integrates into planned development or series production upgrades. Furthermore, the method makes it possible to identify systems that exhibit non-conforming variations. Moreover, the method allows the actual system mounted on the vehicle to learn and adapt over time.

[0069] The invention is not limited to the implementation described, and includes all equivalents that may fall within the scope of the following claims.

[0070] In particular, various sensor variants can be provided for the gauging device, and applications for any type of liquid or fluid.

Claims

Claims

1. Method for calibrating the gauge law of a liquid gauging system, the system comprising a tank, a gauging device, a display device and an electrical circuit, the gauging device comprising a computer configured to carry out the calculations necessary for the operation of the gauging service, characterized in that it comprises a learning of the gauge law in the lower part of the tank, said learning comprising the following steps: - a step of pre-calibration of the gauging system, carried out when the tank is empty, which consists of integrating minimum and maximum complete limit gauging laws into the computer, and defining pre-calculated complete generic gauging laws between the minimum law and the maximum law, - a step of partially filling the tank, said step following the pre-calibration step,- a step of determining a partial gauge law corresponding to the partial filling of the reservoir, - a step of determining a complete gauge law corresponding to the partial filling of the reservoir, by selecting the pre-calculated complete generic law which most closely covers the partial gauge law.,

2. Method according to claim 1, which comprises a learning of gauge law in the upper part of the tank, said learning comprising the following steps: - steps of recovery and storage by the computer of data measuring the volume of fuel in relation to a target level, for different fillings of the tank, said data being provided by a gauge of the gauging device, - steps of calculating averages of said data provided by the gauge, - steps of determining the complete gauge law corresponding to the complete filling of the tank, on the basis of said averages of said data, by selection of the pre-calculated complete generic law which most closely covers said complete gauge law.

3. Method according to claim 2, which comprises steps of determining the actual gauge law, said law being an average of the complete gauge law corresponding to the partial filling of the reservoir and the last complete gauge law corresponding to the complete filling of the reservoir.

4. A method according to claim 2 or 3, wherein the data measuring the fuel volume are resistance values ​​of a variable resistor of the gauge of the gauging device.

5. Method according to claim 4, in which the learning of the gauge law is done on an average of the resistance values ​​measured during a significant number of last complete fill-ups.

6. A method according to any one of claims 2 to 5, wherein the data comes from a number of fills between 3 and 10.

7. A method according to any one of claims 1 to 6, wherein the partial filling of the reservoir is between 5 and 30% of a complete filling.

8. A method according to any one of claims 1 to 7, wherein the display device is a digital indicator.

9. A liquid gauging system implementing a gauge law calibration method according to any one of claims 1 to Q

10. O. A motor vehicle comprising a liquid gauging system according to claim 9.

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