Scalable calibration of fuel gauge law.

Abstract

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.The method comprises a step of pre-calibration of the gauging system, carried out when the tank is empty, which consists of integrating minimum (N0) and maximum (N9) complete limit gauging laws into the calculator, and defining pre-calculated complete generic gauging laws (N1, N2, N3, N4, N5, N6, N7, N8) between the minimum law (N0) and the maximum law (N9), a step of partial filling 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 (N1, N2, N3, N4, N5, N6, N7, N8) which most closely covers the partial gauge law. Figure for 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, in particular, for those with a thermal engine, a fuel tank.

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

[0004] A measuring device generally comprises an arm terminated by a float to constitute a detection unit housed in the tank. The arm is articulated on a support comprising a gauge consisting for example of a variable resistor. The rotation of the arm relative to the support modifies the value of the variable resistor. The gauge is integrated into an electrical circuit delivering an output signal which reflects the value of the variable resistor and, therefore, which reflects the level of liquid in the tank.

[0005] It is the combined operation of a display device, present on the dashboard of the vehicle, and a measuring device, installed in the fuel tank, which makes it possible to indicate to a driver of the vehicle the volume of fuel remaining. The fuel level information is displayed by means such as a needle meter, a digital indicator with discrete display or continuous display, or other. The fuel level information given by the gauge is supplemented by a warning light making it possible to indicate that the fuel level is low, in a reserve zone. A digital indicator of the distance that can be traveled with the volume of fuel available in the tank may also be provided.

[0006] The driver therefore has information to check the vehicle's range, and can organize a journey by topping up the fuel level if necessary. The information is generally sufficiently reliable for the vehicle to actually be able to reach its destination. However, it happens that the information presents deviations from reality.

[0007] Indeed, it has sometimes been observed that the fuel level is not displayed on the dashboard, that the gauge is not accurate, or that the gauge is stuck at full, which means in this case that a fairly long time elapses before the display indicates a drop even though the fuel level has been filled and the vehicle has started its journey. Cases of false reserve have also been observed.

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

[0009] It appears that a gauging system, as presented above, has a dispersion, which is the source of the problems stated. The dispersion of the complete system is composed of dispersions at the level of the tank, the gauging device, their assembly and, to a lesser extent, the electrical wiring and the computer carrying out the measurements. The gauging device transmits a resistance value linked to the fuel height. The computer measures the resistance and transforms the resistance value into useful information, in this case the volume of fuel in the tank, using software. The computer uses a fixed gauging law, calibrated for each vehicle family. In practice there is a gap between the fixed calibrated gauging law and the actual gauging law for each vehicle, because of the dispersions of the gauging system.

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

[0011] For example, document US 11,175,171 B2 teaches the use of a capacitive level sensor. By implementing this sensor, the fuel level measurement is actually more accurate. However, it still happens that the fuel level information on the dashboard is inaccurate or false. In addition, a capacitive sensor makes the gauging system expensive, compared to a conventional system equipped with a variable resistor. Statement 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 aim is to make the fuel level display true to reality. The invention also seeks to minimize the cost of a system intended for level measurement.

[0013] To do this, the invention proposes a 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.

[0014] The method comprises learning 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 partial filling 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 the complete gauge law corresponding to the partial filling of the tank, by selecting the pre-calculated complete generic law which most closely covers the partial gauge law.

[0015] The calibration of the gauge law defines the performance of the fuel gauging function. It makes it possible to define the transfer law between the gauging device and the corresponding fuel volume for a given system, that is to say for an assembly comprising a tank, a gauging device, a display device, an electrical circuit and a computer. The calibration makes it possible to define the display law of the human-machine interface in relation to the calculated fuel volume, as well as some parameters necessary for calculating the fuel volume under load of the thermal engine. In practice, the gauge law is learned for each vehicle individually. This provides great precision for measuring the fuel volume. Among the advantages that result from this, we note greater safety in the preparation of journeys, in the sense that the risk of unforeseeable fuel shortage is reduced, or even absent.

[0016] The method comprises a learning of the 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 relative to a target level, for different complete fills 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.

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

[0018] The method 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 of the last complete gauge law corresponding to the complete filling of the reservoir.

[0019] This allows the calibration to be further refined. For example, the method allows for differentiation between a nominal full tank, a slight underfilling and a slight overfilling. The method also allows for taking into account the aging of the vehicle, i.e. the evolution of the dispersions of the components of the gauging system.

[0020] In the method, the data measuring the fuel volume are resistance values ​​of a variable resistor of 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 contained. It also advantageously follows that the system is both simple and reliable.

[0021] In the method, 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. This allows progressive adjustments of the gauging law. In other words, exceptions to the operating mode, such as a very high level fill-up, will see their impact minimized.

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

[0023] In the method, the partial filling of the tank is between 5 and 30% of a complete filling. 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 gauge 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 aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0028] - [Fig. 1] is an example of 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.l], but additionally shows inter gauge laws mediators,

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

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

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

[0033] - [Fig.6] is a flowchart relating to the calculation of the gauge law obtained by ap full learning,

[0034] - [Fig.7] is a flowchart relating to the calculation of the real gauge law,

[0035] - [Fig.8] is similar to [Fig.5], but shows the real, precise gauge law, which evolves with the aging of the vehicle. Detailed description

[0036] A motor vehicle equipped with a thermal engine comprises a system for gauging liquid, such as 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 comprises a computer configured to perform the calculations necessary to carry out the gauging service. This involves calibrating the gauge law to define the performance of the fuel gauging function. In practice, the gauge law defines the transfer law between a variable resistance, which is measured, and the volume of fuel. Indeed, the gauging device comprises an arm terminated by a float to constitute a detection unit, housed in the tank. The arm is articulated on a support comprising a gauge, constituted by the variable resistance. The rotation of the arm relative to the support modifies 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, reflects the level of liquid 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 from the thermal 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° slope, fuel volume when underfilled and overfilled. For example, a click at the A fuel pump nozzle clicks below the desired pressure, while more than three clicks indicates overfilling.

[0040] One objective is to ensure linearity of the gauging service. This involves detecting a variation in fuel volume sufficiently early after filling the tank and detecting a low volume of fuel added. This facilitates the management of a journey, particularly when the vehicle is rented and it needs to be refueled. It is also a matter of avoiding running out of fuel.

[0041] For this, 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 we will see later.

[0042] First of all, the gauge law is learned in the lower part of the tank, at the factory, at the end of the assembly line during the first fuel supply.

[0043] To enable its delivery, the vehicle receives, during its manufacture, a fuel supply which allows it to complete all the logistical stages. But this supply is low and generally represents only one eighth of the tank capacity. In fact, the vehicle is not delivered with a full tank.

[0044] A pre-calibration is integrated into the vehicle, before the first fuel supply, in order to specify parameters, approximately 80, which allow the calculations necessary for the operation of the gauging service to be carried out. In other words, the pre-calibration is carried out while the fuel tank is completely empty.

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

[0046] The calculations still correspond, as shown in [Fig. 1], to the definition of the limit gauging laws N0, N9 of the system, that is to say the minimum and maximum acceptable tolerances, for an entire population of vehicles. More precisely, a minimum law N0 corresponds to the smallest volume that can be recorded on the population of vehicles taking into account all the dispersions, such as the dimensional differences of the parts or their wear, for a given resistance value. A maximum law N9, for its part, corresponds to the maximum volume that can be recorded on the population of vehicles for a given resistance value.

[0047] As soon as the pre-calibration is done, the calculator of the gauging device stores a whole network of curves covering all the tolerances, calculated from minimum NO and maximum N9 gauging laws, as shown in [Fig.2].

[0048] A set of intermediate laws NI, N2, N3, N4, N5, N6, N7, N8 is defined, the laws corresponding to intermediate volumes between the minimum volume and the maximum volume of fuel for an identical resistance value.

[0049] For example, in a non-limiting manner, if when carrying out a dispersion study it is realized that there is a possible inaccuracy of 5 liters for the same resistance value, 10 intermediate laws can be provided with deviations of 0.5 liters between them.

[0050] Once the pre-calibration has been carried out, a partial fuel filling is carried out in the factory. The fuel filling machine communicates with the vehicle to provide the successive values ​​of the volumes of fuel actually introduced into the tank. The volumes delivered by the machine are measured very precisely and assumed to be perfect, knowing that the filling is incomplete, for example limited to 10 liters.

[0051] As shown in [Fig.3], the information on 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] We therefore know the curve of resistance as a function of volume for this vehicle, but only for small volumes, less than 10 liters for example, and not for the entire volume of the tank, up to full, since a complete full tank is not provided in 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 precalculated gauging law curves passing closest to the point defined by the measured resistance and volume.

[0054] Concretely, for the real volume value, the calculator determines the resistance associated with the volume for each intermediate law. The calculator compares the measured resistance to the different 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, knowledge of the actual volume of fuel introduced into the tank and the associated resistance value allows 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 authorized and the law applied for this vehicle is the pre-calibrated gauge law.

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

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

[0058] In fact, from the factory outlet, 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 carried out. As a result, the evolution of the lower part of the law is not verified. However, it is possible to access an indication that a full fill has been made. It is an object of the invention to recognize this event and to deduce therefrom an evolution, then a correction, of the gauge law.

[0059] Learning the gauge law in the upper part of the tank throughout the lifetime of the vehicle, each time the tank is completely filled, is done as follows.

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

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

[0062] The target level is pre-calibrated in the calculator. [Fig.5] visualizes this level, constructed as the smallest useful capacity that could be measured on a population of vehicles. The target level corresponds to a minimum full tank, from which a safety margin is subtracted, the value of which is a few liters, for example 2.

[0063] The volume of fuel inserted into the tank is not known, but the dispersion of the volume at standstill when full is known. The volume at full is assumed to be fixed and calibrated for each family of vehicles.

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

[0065] As for factory learning, at full fill-up, a complete gauge law is defined from the selection of one of the precalculated gauging law curves passing closest to the point defined by the measured resistance and the calibrated volume. Concretely, in relation to [Fig.7], for the calibrated volume value the computer determines the resistance at full fill-up which is associated with this volume for each intermediate law. The computer compares the measured resistance with the resistances which result 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 curve learned at the factory and the curve learned at full fill-up.

[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 precise, 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 method described is based solely on an evolution in the programming of the calculator, by adding functionalities to a classic management logic. In other words, these are known components which 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 is integrated into the planned development or series developments. In addition, the method makes it possible to identify systems which would present non-compliant dispersions. Again, the method allows learning of the real system mounted on the vehicle and the evolution over time.

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

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

Claims

1.

2.

3. Claims 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 (NO) and maximum (N9) complete limit gauging laws into the calculator, and defining pre-calculated complete generic gauging laws (NI, N2, N3, N4, N5, N6, N7, N8) between the minimum law (NO) and the maximum law (N9), - a step of partial filling 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 reservoir, - a step of determining the complete gauge law corresponding to the partial filling of the reservoir, by selecting the pre-calculated complete generic law (NI, N2, N3, N4, N5, N6, N7, N8) which most closely covers the partial gauge law. Method according to claim 1, which comprises learning the gauge law in the upper part of the reservoir, 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 for calculating averages of said data provided by the gauge, - steps for determining the complete gauge law corresponding to the complete filling of the tank, on the basis of said averages of said data, by selecting the pre-calculated complete generic law (NI, N2, N3, N4, N5, N6, N7, N8) which most closely covers said complete gauge law. The method of claim 2, which comprises steps of deter- real gauge law mination, said law being an average of the complete gauge law (NI, N2, N3, N4, N5, N6, N7, N8) corresponding to the partial filling of the reservoir and of 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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