Detection of fuel leaks in the fuel system

Abstract

The present invention relates to a method for determining whether or not there is a fuel leak in a pressurized fuel system (1) of a vehicle equipped with a heat engine (2), comprising the step of measuring the pressure value in the system (1) at predetermined different points in time within a certain period of time after the vehicle's heat engine (2) has been stopped. This method, - A step of determining the two time points in time where the pressure values ​​are furthest apart from each other, - A step in which, if the absolute value of the difference between these two pressure values ​​is less than or equal to a predetermined pressure difference threshold, the conclusion is drawn that there is a fuel leak in system (1), - A step (230) to determine whether there are two time points in each period where the temperature difference exceeds a predetermined temperature difference threshold, and where the pressure values ​​at these two time points are below a predetermined pressure threshold and exceed the opposite value of this pressure threshold, - If it is determined that these two points in time exist, step (240) to conclude that there is a fuel leak in system (1) and This includes methods.

Description

Technical Field

[0001] The present invention relates, inter alia, to the detection of fuel leakage in a vehicle fuel system after the heat engine of the vehicle has stopped. More particularly, the present invention relates to passive detection methods, especially methods that do not perform suction within the system.

Background Art

[0002] In the prior art, especially according to Patent Document 1, a passive determination method for the presence or absence of fuel leakage in a pressurized fuel system of a vehicle equipped with a heat engine is already known. This method is carried out after the heat engine has stopped. This method includes a step of measuring pressure and temperature at several points within a certain period of time, and a step of calculating a first maximum temperature difference between each of these points following this step. If this first temperature difference exceeds a predetermined temperature difference threshold value, this method includes a step of calculating the pressure difference between the corresponding two points. If this pressure difference is below a predetermined pressure difference threshold value, this method concludes that there is fuel leakage in the fuel system.

[0003] The drawback of this method is that it cannot detect all fuel leaks.

[0004] Patent Documents 2, 3, 4, 5, 6, 7, 8 and 9 each present a method for determining leakage within a fuel system.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

[0006] The primary objective of this invention is to provide a more accurate method for determining fuel leaks within a fuel system, regardless of whether the fuel is in liquid or gaseous form. [Means for solving the problem]

[0007] For this purpose, the present invention provides a method for determining whether or not there is a fuel leak in a pressurized fuel system of a vehicle equipped with a heat engine, comprising the steps of measuring the pressure value and temperature value of the fuel vapor gas in the system at predetermined different points in time within a certain period of time after the vehicle's heat engine has been shut down, wherein the method is - A step of determining the two time points in time where the pressure values ​​are furthest apart from each other, - A step in which, if the absolute value of the difference between these two pressure values ​​is less than or equal to a predetermined pressure difference threshold, a conclusion is drawn that there is a fuel leak in the system. - A step of determining whether there are two time points within each time point in time where the temperature difference exceeds a predetermined temperature difference threshold, and where the pressure values ​​at these two time points are below a predetermined pressure threshold and exceed the opposite value of this pressure threshold, - If it is determined that these two points in time exist, the step of concluding that there is a fuel leak in the system is: Its purpose is to include methods that encompass such methods.

[0008] Thus, in the pressure-only step, concluding that there is a fuel leak only requires measuring the pressure over a certain period of time and determining the maximum pressure difference, i.e., the difference between the minimum and maximum pressures measured over that period. In fact, these steps are based on the fact that if the pressure difference falls below a predetermined threshold, i.e., if the pressure change over the relevant period of time is extremely small, it can be concluded with high accuracy that there is a fuel leak in the fuel system without considering temperature. In other words, these steps are extremely easy to perform.

[0009] In the steps involving both temperature and pressure, the temperature at each point in time is measured. These steps aim to detect whether two points in time satisfy the aforementioned conditions: a temperature difference above a threshold and a pressure value below a threshold and above the opposite value of that threshold. There is no particular need to look for the maximum temperature difference or maximum pressure difference. In other words, these steps are based on the fact that by linking particularly large temperature changes over time with pressure values ​​within a specific range, it is possible to conclude with high accuracy that there is a fuel leak in the fuel system.

[0010] These two sets of steps can each be used to conclude that a leak exists on their own. Implementing these two sets of steps, each based on different facts, increases the probability of detecting potential leaks.

[0011] Even if these steps do not lead to a conclusion that there is a fuel leak, this does not necessarily mean that there is no fuel leak. In this case, other steps can be performed to reach one of these conclusions.

[0012] "Point in time" is understood to refer to a single point within a certain period of time corresponding to a certain pressure within the fuel system.

[0013] "Fuel system" refers to a device incorporated into a vehicle equipped with a heat engine, and its functions include storage, purification, measurement, or transportation of fuel supplied to the heat engine. The fuel system includes at least one fuel tank and a fuel supply pipeline to the heat engine. The fuel system can also include one or more accessories, namely, a ventilation valve and ventilation pipeline of the fuel tank, a filling tube, a canister, a fuel filter, a fuel pump, a fuel tank gauge, an electrical connector, a lid, and any member through which fuel in a liquid and / or gaseous state usually passes inside, such as a fuel vapor circulation pipe.

[0014] A vehicle equipped with a heat engine can be, among other things, a hybrid vehicle.

[0015] Other optional features adopted alone or in combination are listed below.

[0016] Advantageously, this method is passive in that neither the temperature measurement nor the pressure measurement is carried out after or during the suction generation or evacuation of the fuel system, nor after or during any other mechanical operation on the fuel container or the fuel vapor container.

[0017] Thus, the determination of the presence or absence of leakage is carried out within the framework of the passive method.

[0018] Preferably, this method is carried out in the following steps before the above-mentioned step of determining the two time points when the pressure values are farthest apart from each other: - A step of determining the number of time points indicating the absolute value of the pressure value exceeding a predetermined pressure threshold among each time point; - A step of deriving the conclusion that there is no fuel leakage in the system when the determined number of time points exceeds a predetermined time point threshold and includes.

[0019] Thus, these steps implemented after the step of determining pressure can quickly conclude that there is no fuel leakage, and therefore it is possible to stop this method without further continuation. These steps are based on the fact that when the pressure maintains an extremely high level over time, it can be concluded with high accuracy that there is no fuel leakage in the system.

[0020] Advantageously, this method includes a step of measuring the temperature value at each time point. As a result of the above steps, if no conclusion can be drawn regarding the presence or absence of fuel leakage and a temperature value exceeding a predetermined boiling point threshold is shown at at least one time point, the following steps - a step of determining two time points within each time point where the temperature decreases over time and the temperature difference between them is the largest; - a step of comparing this temperature difference with a predetermined temperature difference threshold; - a step of determining the pressure difference between these two time points; - a step of comparing this pressure difference with a predetermined pressure difference threshold; - a step of comparing the pressure at the time point with the lower temperature among these two time points with a predetermined pressure threshold; - a step of deriving the conclusion that there is no fuel leakage in the system when this temperature difference exceeds the predetermined temperature difference threshold, this pressure difference exceeds the pressure threshold or is lower than the opposite value of this threshold, and the pressure at the time point with the lowest temperature exceeds the predetermined pressure threshold or is lower than the opposite value of this threshold are included.

[0021] That is, these steps are based on the fact that for fuel showing an extremely high temperature, if an extremely large pressure change occurs with an extremely large temperature decrease and the pressure maintains a sufficiently high level when this temperature decrease stops, it can be concluded with high accuracy that there is no fuel leakage.

[0022] These steps are performed only if none of the above steps lead to a conclusion regarding the presence or absence of a leak, and only if the boiling point threshold is exceeded at any point in time. In other words, these steps make it possible to conclude, within a very specific framework, that there is no fuel leak in the fuel system when the preceding, more general steps fail to reach a conclusion.

[0023] The boiling point threshold is a theoretical value determined by interpolation and / or extrapolation, for example, 30°C. In reality, fuel may boil before or after reaching this theoretical value. Both depend on the temperature and atmospheric pressure conditions in which the vehicle equipped with the fuel system is located. For example, in mountainous areas with relatively low atmospheric pressure, boiling of fuel may be observed before reaching 30°C.

[0024] Preferably, this method includes a step of measuring the temperature value at each point in time, and if, as a result of the above steps, no conclusion is reached and no temperature value exceeding a predetermined boiling point threshold is shown at any point in time, the following steps are taken: - A step to determine the two time points with the largest temperature difference among all the time points, - A step of comparing this maximum temperature difference with a predetermined temperature difference threshold, - A step to determine the pressure difference between these two points in time, - A step of comparing this pressure difference with a predetermined pressure difference threshold, - A step of concluding that there is no fuel leak in the system if this maximum temperature difference exceeds a predetermined temperature difference threshold, and this pressure difference exceeds a pressure threshold or falls below the opposite value of this threshold. Includes.

[0025] These steps are based on the fact that, for fuel that remains below the boiling point threshold over time, if the temperature and pressure change significantly, it can be concluded with high accuracy that there is no fuel leak in the system.

[0026] These steps are performed only if none of the above steps lead to a conclusion regarding the presence or absence of a leak, and only if no temperature values ​​exceeding the boiling point threshold are observed at any point. In other words, these steps make it possible to conclude, within a very specific framework, that there is no fuel leak when the preceding, more general steps fail to reach a conclusion.

[0027] Preferably, this method includes a step of measuring the temperature value at each point in time, and if, as a result of the above steps, no conclusion is reached and no temperature value exceeding a predetermined boiling point threshold is shown at any point in time, the following steps are taken: - A step to determine the two time points with the largest temperature difference among all the time points, - A step of comparing this maximum temperature difference with a predetermined temperature difference threshold, - A step to determine the pressure difference between these two points in time, - A step of comparing this pressure difference with a predetermined pressure difference threshold, - A step of concluding that there is a fuel leak in the system if this maximum temperature difference exceeds a predetermined temperature difference threshold, and this pressure difference is less than or equal to a pressure threshold or the opposite of this threshold. Includes.

[0028] In other words, these steps are based on the fact that if the temperature of a fuel remains below its boiling point threshold for a given period of time, while the temperature changes very significantly, the corresponding pressure changes very little, it can be concluded with high accuracy that there is no fuel leak in the system.

[0029] To our advantage, this method is, - Prior to the above steps, when the heat engine is started after a predetermined time, for example, 2 hours, *Steps to measure pressure and temperature values ​​within the system Includes, Next, this method proceeds to at least one of the following two groups of steps, namely *In the first group of steps, **A step of comparing the absolute value of the pressure value with the minimum pressure threshold, **A step that suggests there is no fuel leak in the system if the absolute value of the pressure exceeds the minimum pressure threshold,** *In a different set of steps, **A step of comparing the pressure value with another pressure threshold, **A step of comparing temperature and boiling point threshold, **A step that suggests there is no fuel leak in the system when the absolute value of the pressure exceeds another pressure threshold and the temperature is below the boiling point threshold.** Steps including, - If, as a result of at least some of the steps described above, no conclusion is reached regarding the presence or absence of a fuel leak, and a tentative suggestion that there is no fuel leak is given, then the step of deriving the conclusion that there is no fuel leak is... Includes.

[0030] In this way, when the vehicle's heat engine is operating for a certain period of time, such as two hours, the pressure and temperature values ​​are determined and compared to thresholds. In other words, these steps do not require measuring the changes in the system's pressure and temperature over time, and are therefore extremely easy to perform.

[0031] These steps tentatively suggest that there is no fuel leak. In other words, these steps alone do not lead to a conclusion. However, if, after the subsequent shutdown of the heat engine, at least some, preferably all, of the steps described above fail to result in a conclusion regarding the presence or absence of a leak, these tentative suggestions may be considered as necessary to conclude that there is no fuel leak. That is, these measurements performed with the engine ignited can provide an answer regarding the presence or absence of a fuel leak, even if a conclusion could not be reached after performing the steps with the engine stopped.

[0032] Preferably, the duration is 6 hours from the time the vehicle's heat engine is shut down, and the number of time points is preferably at least 5, distributed within this 6-hour period.

[0033] Thus, a duration of 6 hours is the duration required by various standards, including the US standard known as "CARB" ("California Air Resources Board"). In other words, the present invention is particularly compliant with this standard.

[0034] Advantageously, the fuel system includes fuel tanks and canisters connected to each other, and this method involves the following steps before the measurement step. - The step of releasing the connection between the tank and the canister, - Steps to isolate the tank and canister from the heat engine and the atmosphere, Includes, - The measurement step is performed in a tank or canister.

[0035] Thus, the method described allows for the detection of fuel leaks within the fuel system, including the tank and canister. The steps described are performed within this system, isolated from the outside, i.e., from the heat engine and the atmosphere. The pressure and temperature changes described are the pressure and temperature changes within this system.

[0036] According to the present invention, a data processing device including a processor adapted to the steps of the method described above is also conceivable for carrying out the steps of the method described above.

[0037] This device is, in particular, a vehicle-mounted processing unit.

[0038] According to the present invention, a vehicle fuel system equipped with a heat engine is also envisioned, wherein the system includes a pressure sensor configured for measuring pressure within the fuel system and a data processing device as described above, the data processing device being configured to perform the steps of the method described above within the fuel system.

[0039] According to the present invention, a vehicle equipped with a heat engine including the fuel system described above is also conceivable.

[0040] According to the present invention, a computer program is also conceivable that includes instructions to cause a computer to perform the steps of the method described above when the program is executed by the computer.

[0041] According to the present invention, a computer-readable recording medium is also conceivable, which includes instructions that cause a computer to perform the steps of the above-described method when the instructions are executed by a computer.

[0042] The present invention will be better understood by referring to the attached drawings and reading the following description, which is merely an example. [Brief explanation of the drawing]

[0043] [Figure 1] This is a schematic diagram of the fuel system according to the present invention. [Figure 2] This is a flowchart of the method according to the present invention. [Modes for carrying out the invention]

[0044] Figure 1 shows one embodiment of the fuel system 1 of the present invention. This fuel system 1 is a pressurized fuel system for a vehicle's heat engine 2. This system is mounted on a vehicle (not shown). The vehicle may be a hybrid vehicle or otherwise. This system includes a data processing unit 3, a fuel tank 4, a canister 5, and a dual valve 6.

[0045] The data processing device 3 includes a processor 7 adapted to the steps of method 100, which will be described later, in order to carry out the steps of method 100. The word "adapted" means that the processor 7 is configured specifically for carrying out this method. The data processing device 3 further includes a computer-readable recording medium 8 which includes instructions that cause a computer to carry out the steps of method 100 when the instructions are executed by the computer, more specifically by the processor 7. In particular, the recording medium 8 includes a computer program 9 which includes instructions that cause a computer to carry out the steps of method 100 when the program 9 is executed by the computer, more specifically by the processor 7. In this example, the data processing device 3 is an "electronic control unit" (ECU), the processor 7 is a microprocessor, and the computer-readable recording medium 8 is a non-volatile memory adapted for storing the computer program 9.

[0046] The fuel tank 4 contains fuel consisting of a liquid phase and a gas phase, as illustrated by double dashed lines. The fuel tank 4 includes a temperature sensor 10 and a pressure sensor 11 located in the upper part of the fuel tank 4, i.e., within the zone of the fuel tank 4 where the gas phase fuel is present under the normal operating conditions of the vehicle. The pressure sensor 11 and temperature sensor 10 are connected to the data processing device 3.

[0047] The canister 5 is connected to the vehicle's heat engine 2 by means not shown.

[0048] Canister 5 is connected to the fuel tank 4 and the atmosphere 12, shown by the tree illustration, respectively, by the tubes and double valve 6 shown schematically.

[0049] The dual valve 6 can open and close the connection between the canister 5 and the fuel tank 4 on the one hand, and between the canister 5 and the atmosphere 12 on the other hand. This dual valve 6 is preferably a solenoid valve controlled by the data processing device 3. This dual valve 6 may be replaced with two separate valves, in particular an FTIV ("fuel tank isolation valve") type valve capable of opening and closing the connection between the fuel tank 4 and the canister 5, and a CVS ("canister isolation valve") type valve capable of opening and closing the connection between the canister 5 and the atmosphere 12.

[0050] In Figure 1, the double valve 6 is configured to open the connection between the canister 5 and the fuel tank 4, and to close the connection between the canister 5 and the atmosphere 12. In this way, the fuel tank 4 and the canister 5 form a system isolated from the outside.

[0051] From here, the method 100 for determining the presence or absence of fuel leaks in System 1 will be described with reference to Figure 2. This method is performed within System 1 and allows for the detection of fuel leaks in the subassembly formed from the fuel tank 4 and canister 5, which are isolated from the outside. Thus, when referring to the presence or absence of fuel leaks in System 1, the subassembly formed from the canister 5 and fuel tank 4 is usually assumed. However, this method is thought to be applicable to other subassemblies or the entire system. In this method 100, predetermined thresholds and numerical values ​​are both calculated using mathematical functions (not described in detail) or input in advance into the data processing device 3 by a person skilled in the art. When predetermined thresholds and numerical values ​​are calculated using mathematical functions, the variables of these mathematical functions are atmospheric pressure.

[0052] It should be noted that some of the steps described later allow us to conclude that a fuel leak exists if the presented tests are successful, but we cannot conclude that there is no fuel leak even if these tests fail. Conversely, in the other steps, we can conclude that there is no fuel leak if the presented tests are successful, but we cannot conclude that there is a fuel leak even if these tests fail. By performing this series of tests, it becomes possible to conclude with a very high degree of probability whether or not there is a fuel leak in System 1.

[0053] It should be noted that all tests described later are passive, meaning they do not require suction generation or vacuuming of fuel system 1, nor any other mechanical operation on containers 4 and 5.

[0054] In step 110, the vehicle's heat engine 2 is started by the vehicle's driver. The data processing device 3 determines the previous shutdown time of the heat engine 2 prior to this start. If this time is longer than a predetermined time, particularly two hours, step 120 is performed. In fact, two hours is sufficient to obtain appropriate pressure and temperature values ​​in subsequent measurements. In modified embodiments, step 120 may be performed even if this time is not observed or if a different time is set.

[0055] In step 120, the device 3 measures the pressure value inside the tank using the pressure sensor 11 and measures the temperature inside the tank using the temperature sensor 10.

[0056] In step 130, the device 3 compares the absolute value of the pressure with a predetermined minimum pressure threshold within the first group of steps.

[0057] In step 140, if the pressure value is above the minimum pressure threshold in absolute terms, device 3 tentatively suggests that there is no fuel leak in the system.

[0058] If no preliminary indications are given as a result of step 140, steps 150 and 160 are performed.

[0059] In step 150, the apparatus 3 performs a comparison between the pressure value and another predetermined pressure threshold, and a comparison between the temperature and the boiling point threshold, within a separate group of steps.

[0060] In step 160, if the pressure value is above this other pressure threshold in absolute value and the temperature is below this boiling point threshold, device 3 tentatively suggests that there is no fuel leak in the system.

[0061] Alternatively, first perform steps 150 and 160, and only if the results of step 160 do not provide any preliminary indications, then perform steps 130 and 140.

[0062] If the results suggest that there is no fuel leak, this result is stored in memory by device 3 and retrieved again in step 380 as needed, as described later. Thus, it is not possible to draw conclusions from these steps alone. However, these preliminary suggestions are considered as needed to conclude that there is no fuel leak if no conclusion is reached in steps 170 to 370, as described later. In other words, these measurements performed with the engine ignited can provide an answer regarding the presence or absence of a fuel leak, even if no conclusion is reached after performing the steps with the engine stopped. Alternatively, these measurements could be considered relatively early in this method.

[0063] In step 170, the vehicle's heat engine 2 is stopped by the driver.

[0064] In step 180, the device 3 uses the temperature sensor 10 and the pressure sensor 11 to measure the pressure and temperature values ​​in the fuel tank 4 at predetermined different points in time within a certain period. Here, this period is 6 hours. This means that if the vehicle is restarted before this period has elapsed, the steps from step 190 onward will not be performed due to insufficient stopping time. Conversely, unless the heat engine 2 is restarted, it can be assumed that measurements will continue to be performed even after this period has elapsed. This 6-hour duration corresponds to the shortest time required by the CARB standard to which the present invention conforms. However, it is also possible to set a different duration. In this example, when the duration is 6 hours, each point in time corresponds to 30 minutes, 2 hours 30 minutes, 3 hours 30 minutes, 4 hours 30 minutes, and 6 hours after the heat engine 2 has stopped, respectively. It is also possible to assume more or fewer points in time than this. However, when the duration is 6 hours, it is advantageous to set at least 5 points in time. Also, it is advantageous not to set too many points in time in order to save energy required for determining whether or not there is a fuel leak.

[0065] In step 190, the device 3 determines the number of time points in step 180 that show a pressure absolute value exceeding a predetermined pressure threshold.

[0066] In step 200, if the number of time points determined in step 190 exceeds a predetermined time point threshold, the device 3 concludes that there is no fuel leak in the subassembly of system 1 formed from the canister 5 and the fuel tank 4, and method 100 is stopped. In this case, none of the steps described below are performed. In a modified embodiment, even if the result of step 190 concludes that there is no leak, this method is not stopped, and the steps described below are performed. The predetermined time point threshold can be, for example, 3 time points when a total of 5 time points are set for a 6-hour duration. It can be any other number, or it can be changed according to the number of measurements performed in step 180, i.e., the number of time points set during this time.

[0067] This analysis is extremely simple and quick because it focuses solely on pressure measurements. Performing this analysis allows for a rapid conclusion that, in some cases, there is no fuel leak. This analysis is based on the fact that if a significant amount of pressure remains high in system 1 within this timeframe, there is a very high probability that there is no fuel leak in system 1 at all.

[0068] If no conclusion is reached as a result of Step 200, Step 210 will be carried out.

[0069] In step 210, the device 3 determines the two time points in step 180 whose pressure values ​​are furthest apart from each other.

[0070] In step 220, if the absolute value of the difference between these two pressure values ​​is less than or equal to a predetermined pressure difference threshold, device 3 concludes that there is a fuel leak in the system. This process is stopped, and none of the subsequent steps are performed.

[0071] This analysis also allows for very simple conclusions to be drawn without temperature. This analysis is based on the fact that if the pressure changes very little over time, there is a possibility of fuel leakage within system 1. The given pressure difference threshold corresponds to the threshold below which fuel leakage is observed in all systems under test, in particular.

[0072] If no conclusion is reached as a result of step 220, step 230 will be performed.

[0073] In step 230, the device 3 determines whether there are two points in time where the temperature difference exceeds a predetermined temperature difference threshold, and the pressure value falls below a predetermined pressure threshold and exceeds the inverse value of this pressure threshold. The temperature difference threshold is 3°C, and the pressure threshold is determined according to atmospheric pressure (not explained here).

[0074] If, in step 240, it is determined that there are two points in time from step 230, the device 3 concludes that there is a fuel leak in system 1, and method 100 is stopped.

[0075] In other words, this analysis is based on the fact that a fuel leak is possible if, within a 6-hour period including, for example, 5 time points being measured, there are two time points where the temperature changes significantly and the pressure is within a specific range (between a threshold and its opposite).

[0076] Steps 230 and 240 can be performed alternatively before steps 210 and 220, and steps 210 and 220 may be performed only if no conclusion is reached as a result of step 240. In other modified embodiments, steps 210 and 220 are performed in parallel, while steps 230 and 240 are performed in parallel.

[0077] If no conclusion is reached as a result of steps 200 through 240, step 250 is performed.

[0078] In step 250, the apparatus 3 determines whether the temperature exceeds a predetermined boiling point threshold at least once. If so, step 260 is performed. Otherwise, the process continues from step 320.

[0079] In step 260, if at least one of the time points in step 180 shows a temperature value exceeding a predetermined boiling point threshold, the apparatus 3 determines the two time points that show the greatest temperature decrease within that time period and have the largest temperature difference.

[0080] In step 270, the apparatus 3 compares this temperature difference with a predetermined temperature difference threshold. This threshold is 3°C. Other values ​​may also be used.

[0081] In step 280, the device 3 determines the difference between the pressure values ​​at these two points in time.

[0082] In step 290, the apparatus 3 compares this pressure difference with a predetermined pressure difference threshold. This threshold changes according to atmospheric pressure (not described here).

[0083] In step 300, the device 3 compares the pressure at the time point with the lower temperature among two time points with a predetermined pressure threshold. This threshold also changes according to atmospheric pressure (not described here).

[0084] In step 310, if the temperature difference exceeds a predetermined temperature difference threshold, the pressure difference exceeds a pressure threshold or falls below the inverse of this threshold, and the pressure at the lowest temperature exceeds a predetermined pressure threshold or falls below the inverse of this threshold, the device 3 concludes that there is no fuel leak in the system. In this case, the subsequent steps are not performed, and method 100 is terminated.

[0085] Thus, this analysis is more accurate than other analyses. This analysis is performed only if the results of the preceding steps have not led to a conclusion regarding the presence or absence of a fuel leak, and only if the boiling point is reached at least at one point in time. In other words, this analysis is suitable when the temperature is extremely high or when the temperature rises at least at one point in time. Alternatively, this analysis could be performed relatively early in Method 100.

[0086] In step 320, if no temperature value exceeding a predetermined boiling point threshold is shown at any point in step 180, the apparatus 3 determines the two points in time from which the temperature difference is largest.

[0087] In step 330, the apparatus 3 compares this maximum temperature difference with a predetermined temperature difference threshold. This threshold is 3°C, but other values ​​may also be used.

[0088] In step 340, the device 3 determines the difference between the pressure values ​​at these two points in time.

[0089] In step 350, the apparatus 3 compares this pressure difference with a predetermined pressure difference threshold. This threshold changes according to atmospheric pressure (not described here).

[0090] In step 360, if the maximum temperature difference exceeds a predetermined temperature difference threshold and the pressure difference exceeds a pressure threshold or falls below the opposite of this threshold, the device 3 concludes that there is no fuel leak in the system. In this case, method 100 is stopped.

[0091] Thus, this analysis is more precise than the others and applies to cases where none of the measured temperatures correspond to the boiling point. This analysis is performed only if the results of the preceding steps have not led to a conclusion regarding the presence or absence of a fuel leak. Alternatively, this analysis could be performed relatively early in Method 100.

[0092] Alternatively, the analysis performed in steps 320 through 350 may conclude that there is a fuel leak. In step 370, which is performed in place of or in parallel with step 360, if the maximum temperature difference exceeds a predetermined temperature difference threshold, but the pressure difference falls below a pressure threshold or exceeds the inverse of this threshold, the device 3 concludes that there is a fuel leak in the system. In this case, method 100 is stopped.

[0093] Step 370 is performed using the thresholds from steps 330 and 350, but it may also be performed using other thresholds.

[0094] Step 380 is performed only if no conclusion has been reached in any of the preceding steps, that is, if the device 3 has not reached any conclusion regarding the presence or absence of a fuel leak. In this case, in step 380, the device 3 checks whether the results from steps 100 to 160 have been saved. If the device determines that the results from steps 100 to 160 indicate a provisional indication that there is no fuel leak, the device 3 concludes in step 380 that there is no fuel leak in system 1.

[0095] If no preliminary indications are given, device 3 determines that it cannot draw any conclusions about the presence or absence of a fuel leak in system 1. In such cases, this method is continued, that is, the measurement in step 180 is continued until the heat engine 2 is restarted, or if the measurement was stopped, it can be resumed. Thus, after the next shutdown of the vehicle's heat engine, the method, particularly from step 170 onward, is resumed for a new duration, for example, 6 hours or more. The more measurements taken within the time period, the higher the likelihood that the comparison steps performed will be able to draw a conclusion about the presence or absence of a fuel leak.

[0096] Prior to the steps described above, if the double valve 6 is configured differently from the configuration shown in Figure 1, Method 100 assumes a step of returning to the configuration shown in Figure 1, which is carried out by a device 3 that controls the opening of the connection between the fuel tank 4 and the canister 5 and the isolation of the fuel tank 4 and the canister 5 from the heat engine 2 and the atmosphere.

[0097] The present invention is not limited to the embodiments presented, and other embodiments will be obvious to those skilled in the art.

[0098] Thus, the present invention is compatible with any fuel system as defined at the beginning, and can be implemented in containers other than the fuel tank 4 and canister 5. In particular, it can be implemented in a standalone fuel tank 4 isolated from the canister 5, or in a standalone canister 5, or in any container in which a pressure sensor and a temperature sensor can be installed and connected to the data processing device 3. [Explanation of Symbols]

[0099] 1. Fuel System 2. Vehicle heat engine 3. Data Processing Devices 4 Fuel tank 5 Canister 6 Double valve 7 Processors 8. Computer-readable recording media 9. Computer Programs 10 Temperature Sensor 11. Pressure Sensor 12 Atmosphere 100 Method for determining whether or not there is a fuel leak

Claims

1. A method (100) for determining whether or not there is a fuel leak in a pressurized fuel system (1) of a vehicle equipped with a heat engine (2), the method comprising the step (180) of measuring the pressure value and temperature value of the fuel vapor gas in the system (1) at predetermined different time points within a certain period of time after the heat engine (2) of the vehicle has been stopped (170), - A step (210) of determining the two time points in which the pressure values ​​are furthest apart from each other, - Step (220) of concluding that there is a fuel leak in the system (1) if the absolute value of the difference between these two pressure values ​​is less than or equal to a predetermined pressure difference threshold, - A step (230) to determine whether there are two time points within each of the aforementioned time points where the temperature difference between the respective temperatures exceeds a predetermined temperature difference threshold, and where the pressure values ​​at these two time points are below a predetermined pressure threshold and exceed the opposite value of this pressure threshold, - Step (240) to conclude that there is a fuel leak in the system (1) when it is determined that the two aforementioned time points exist. A method (100) characterized by including the following.

2. The method according to claim 1 (100), wherein the temperature measurement and the pressure measurement are passive in that they are not performed after or during suction generation or vacuuming of the fuel system (1), nor after or during any other mechanical operation on the fuel container or fuel evaporator gas container (4, 5).

3. The following steps are performed before step (210) of claim 1, which determines the two time points in time when the pressure values ​​are furthest apart from each other: - A step (190) to determine the number of time points in the aforementioned time points in which the absolute value of the pressure exceeds a predetermined pressure threshold, - A step (200) in which, if the number of determined time points exceeds a predetermined time point threshold, the conclusion is drawn that there is no fuel leak in the system. The method according to claim 1 or 2 (100), including the method according to claim 1 or 2.

4. The process includes a step of measuring the temperature value at each of the aforementioned time points (180), and if, as a result of the steps in at least one of claims 1 to 3, no conclusion is reached regarding the presence or absence of a fuel leak, and a temperature value exceeding a predetermined boiling point threshold is observed at at least one time point (250), the following steps are taken: - A step (260) to determine the two time points in the aforementioned time period in which the temperature decreases and the temperature difference is greatest, - A step (270) of comparing this temperature difference with a predetermined temperature difference threshold, - A step (280) to determine the pressure difference between these two points in time, - A step (290) of comparing this pressure difference with a predetermined pressure difference threshold, - A step (300) of comparing the pressure at the time point with the lower temperature among the two aforementioned time points with a predetermined pressure threshold, - Step (310) of concluding that there is no fuel leak in the system if the temperature difference exceeds the predetermined temperature difference threshold, the pressure difference exceeds the pressure threshold or falls below the inverse of this threshold, and the pressure at the lowest temperature exceeds the predetermined pressure threshold or falls below the inverse of this threshold. The method according to any one of claims 1 to 3, including (100).

5. The process includes measuring the temperature value at each of the aforementioned time points, and if, as a result of the steps described in at least claim 1 or 2, no conclusion is reached and no temperature value exceeding a predetermined boiling point threshold is shown at any of the time points, the following steps are taken: - A step (320) to determine the two time points with the largest temperature difference among the aforementioned time points, - A step (330) of comparing this maximum temperature difference with a predetermined temperature difference threshold, - A step (340) to determine the pressure difference between these two points in time, - A step (350) of comparing this pressure difference with a predetermined pressure difference threshold, - Step (360) of concluding that there is no fuel leak in the system when the maximum temperature difference exceeds the predetermined temperature difference threshold and the pressure difference exceeds the pressure threshold or falls below the opposite value of the threshold. The method according to any one of claims 1 to 3, including (100).

6. The process includes measuring the temperature value at each of the aforementioned time points, and if, as a result of the steps described in at least claim 1 or 2, no conclusion is reached and no temperature value exceeding a predetermined boiling point threshold is shown at any of the time points, the following steps are taken: - A step (320) to determine the two time points with the largest temperature difference among the aforementioned time points, - A step (330) of comparing this maximum temperature difference with a predetermined temperature difference threshold, - A step (340) to determine the pressure difference between these two points in time, - A step (350) of comparing this pressure difference with a predetermined pressure difference threshold, - Step (370) of concluding that there is a fuel leak in the system when the maximum temperature difference exceeds the predetermined temperature difference threshold and the pressure difference is less than or equal to the pressure threshold or the opposite value of the threshold. The method according to any one of claims 1 to 3, including (100).

7. A method (100) according to any one of claims 1 to 6, - Prior to the step of claim 1, when the heat engine (2) is started after a predetermined time, for example, 2 hours, * Step (120) to measure the pressure and temperature values ​​within the system. Includes, Next, the method proceeds to at least one of the following two groups of steps, namely, *In the first group of steps, **Step (130) of comparing the absolute value of the pressure value with the minimum pressure threshold, **Step (140) in which it is tentatively suggested that there is no fuel leak in the system if the absolute value of the pressure exceeds the minimum pressure threshold, *In a different set of steps, **Step (150) of comparing the aforementioned pressure value with another pressure threshold, **Step (150) of comparing the above temperature with the boiling point threshold, **Step (160) in which it is tentatively suggested that there is no fuel leak in the system when the absolute value of the pressure exceeds the other pressure threshold and the temperature falls below the boiling point threshold.** Steps including, - A step (380) to derive the conclusion that there is no fuel leak when, as a result of at least the steps described in claim 1, no conclusion has been reached regarding the presence or absence of a fuel leak, and a provisional suggestion has been given that there is no fuel leak. Method (100), including the method (100).

8. The method according to any one of claims 1 to 7 (100), wherein the duration is 6 hours from the time the heat engine (2) of the vehicle is stopped, and the number of time points is preferably at least 5, distributed within this 6-hour period.

9. The fuel system includes a fuel tank (4) and a canister (5) connected to each other, and the following steps are taken before the measurement step: - A step of disconnecting the connection between the tank (4) and the canister (5), - A step of isolating the tank (4) and the canister (5) from the heat engine (2) and the atmosphere. Includes, - The method according to any one of claims 1 to 8 (100), wherein the measurement step (180) is performed in the tank (4) or the canister (5).

10. A data processing device (3) comprising a processor adapted to the steps of the method according to any one of claims 1 to 9 for carrying out the steps of the method according to any one of claims 1 to 9.

11. A fuel system (1) for a vehicle equipped with a heat engine (2), wherein the system includes a pressure sensor (11) configured for measuring pressure within the fuel system and a data processing device (3) according to claim 10, wherein the data processing device is configured to carry out the steps of the method according to any one of claims 1 to 9 within the fuel system.

12. A vehicle comprising a heat engine (2) including the fuel system (1) according to claim 11.

13. Computer program (9), which, when the program is executed by a computer, includes instructions causing the computer to perform the steps of the method according to any one of claims 1 to 9.

14. A computer-readable recording medium (8), the recording medium (8) comprising instructions causing the computer to perform the steps of the method according to any one of claims 1 to 9 when the instructions are performed by the computer.

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