阅读说明：本技术 测试车辆液体储箱的至少一个内部加固元件的状态的方法 (Method for testing the condition of at least one internal stiffening element of a liquid tank of a vehicle ) 是由 保罗·丹尼尔·鲁瑟 大卫·希尔 安托万·肖锡南 于 2019-08-06 设计创作，主要内容包括：本发明涉及一种测试车辆的液体储箱的至少一个内部加固元件的状态的方法。所述至少一个内部加固元件连接所述液体储箱的至少两个相对的壁,该液体储箱至少包括可由液位传感器测量的初始液体量,该方法包括以下步骤：a)基于由液位传感器测量的初始液体量和由压强传感器测量的液体储箱的初始内部压强,来确定第一阈值；b)监控液位传感器的输出和压强传感器的输出；c)如果压强传感器的输出高于所述第一阈值,则根据液体消耗演变、所述压强传感器的输出和在大气压下的储箱中的液体液位来确定第二阈值和第三阈值；d)将液位传感器的输出与第二和第三阈值作比较；e)-如果液位传感器的输出高于第二阈值,则发送指示连接相对的壁的至少一个内部加固元件断裂或可能断裂的第一预定信号,和/或；-如果液位传感器的输出低于第三阈值,则发送指示连接相对的壁的至少一个内部加固元件断裂或可能断裂的第二预定信号。(The invention relates to a method for testing the condition of at least one internal reinforcing element of a liquid tank of a vehicle. Said at least one internal stiffening element connects at least two opposite walls of said liquid tank comprising at least an initial quantity of liquid measurable by a level sensor, the method comprising the steps of: a) determining a first threshold value based on an initial amount of liquid measured by the liquid level sensor and an initial internal pressure of the liquid tank measured by the pressure sensor; b) monitoring the output of the liquid level sensor and the output of the pressure sensor; c) determining a second threshold and a third threshold from a liquid consumption evolution, an output of the pressure sensor and a liquid level in the tank at atmospheric pressure, if the output of the pressure sensor is higher than the first threshold; d) comparing the output of the level sensor to second and third thresholds; e) -if the output of the level sensor is higher than a second threshold value, sending a first predetermined signal indicating the breakage or possible breakage of at least one internal stiffening element connecting the opposite walls, and/or; -sending a second predetermined signal indicative of a breakage or possible breakage of at least one internal stiffening element connecting the opposite walls, if the output of the level sensor is lower than a third threshold value.)

1. Method for testing the condition of at least one internal stiffening element (1) of a liquid tank (2) of a vehicle, which connects at least two opposite walls (3, 4) of the liquid tank, the liquid tank comprising at least an initial amount of liquid (6) measurable by a level sensor (5), the method comprising the steps of:

a) determining a first threshold value based on an initial amount of liquid measured by the level sensor, preferably at atmospheric pressure, and an initial internal pressure of the liquid tank, preferably equal to atmospheric pressure, measured by a pressure sensor (7);

b) monitoring the output of the liquid level sensor and the output of the pressure sensor;

c) determining a second threshold value and a third threshold value from a liquid consumption evolution, an output of the pressure sensor and a liquid level in the tank, preferably measured at atmospheric pressure, if the output of the pressure sensor is higher than the first threshold value;

d) comparing the output of the level sensor to the second and third thresholds;

e) -if the output of said level sensor is higher than said second threshold value, sending a first predetermined signal indicating the breakage or possible breakage of at least one internal stiffening element connecting said opposite walls, and/or;

-sending a second predetermined signal indicative of a breakage or possible breakage of at least one internal stiffening element connecting said opposite walls, if the output of said level sensor is lower than a third threshold value.

2. Method according to claim 1, wherein during step c) the determination of the second and third threshold values is also done depending on the temperature of the liquid in the tank (2).

3. The method of any one of the preceding claims, comprising the step of incrementing a counter (9) if the output of the level sensor (5) is between the second threshold and the third threshold.

4. Method according to claim 3, wherein at least steps a), b) and c) of claim 1 are performed again, preferably using a plurality of first thresholds, if the counter (9) is below a fourth predetermined threshold.

5. Method according to claim 4, wherein, if said counter (9) is higher than said fourth threshold value, said method comprises the step of sending a signal indicating that at least one internal stiffening element (1) connecting said opposite walls (3, 4) is not broken.

6. Method according to any of the preceding claims, wherein the monitoring step b) depends on a rise or a fall of the pressure inside the tank (2) resulting solely from a rise or a fall of the temperature outside the tank.

7. Method according to any of claims 1 to 5, wherein the monitoring step b) comprises a step of commanding means for increasing or decreasing the pressure inside the tank (2), preferably in response to a signal from a vehicle collision sensor.

8. Method according to claim 7, wherein the step of commanding means for increasing or decreasing the pressure inside the tank (2) is carried out by:

-using an external pump not forming part of the vehicle;

-using a device forming part of the vehicle, such as a pump or a heater; and/or

-commanding the release of the pressure inside the tank using a valve of the tank.

9. A method according to any one of the preceding claims, wherein the method is performed when the power of the vehicle is off, preferably only when the power of the vehicle is off.

10. A method as claimed in any preceding claim, wherein the method is triggered when the vehicle is in a service mode.

11. The method according to any one of the preceding claims, wherein a leak detection step is performed before step a).

12. Method for testing the condition of at least one internal stiffening element (1) of a liquid tank (2) of a vehicle, which connects at least two opposite walls (3, 4) of the liquid tank, comprising the steps of:

-performing a leak detection step, and

-sending a signal indicating a possible breakage of at least one internal stiffening element (1) connecting at least two opposite walls (3, 4) of the liquid tank, if the result of the leak detection step is of a predetermined type.

13. Vehicle liquid tank (2) comprising control means (8) for implementing the method according to any one of the preceding claims.

14. Vehicle comprising a liquid tank (2) and a control device (8) for implementing a method according to any one of claims 1 to 12.

15. A computer readable medium comprising instructions which, when executed by a computer, cause the computer to perform the steps of the method of any one of claims 1 to 12.

Technical Field

The present invention relates to a method for testing a liquid tank, such as a vehicle fuel tank.

Background

Fuel tanks often require internal reinforcing structures such as welded posts, or external structures such as welded patches. During accidents that are not severe enough to require significant replacement of the tank, the internal reinforcing structure may be damaged, which, if these damages remain undetected, may cause noise or, in the worst case, may compromise the integrity of the tank after repeated use. We do not know any way to detect such damage without disassembling the tank and without internal inspection. Disassembling the tank is not advisable because it is time-consuming, costly and complicated. However, depending on the nature of the damage, the internal stiffening element detecting a rupture in the tank may protect the driver against the risk of future leaks, liquid residues or ventilation losses and bursts.

Disclosure of Invention

The present invention aims to provide a test method that addresses these drawbacks. The invention relates to a method for testing the condition of at least one internal stiffening element 1 of a liquid tank 2 of a vehicle, said at least one internal stiffening element connecting at least two opposite walls 3, 4 of the liquid tank, which liquid tank comprises at least an initial quantity of liquid 6 measurable by a level sensor 5, said method comprising the following steps:

a) determining a first threshold value based on an initial quantity of liquid measured by a level sensor, preferably at atmospheric pressure, and an initial internal pressure of said liquid tank, preferably equal to atmospheric pressure, measured by a pressure sensor 7;

b) monitoring the output of the liquid level sensor and the output of the pressure sensor;

c) determining a second threshold value and a third threshold value from a liquid consumption evolution, an output of the pressure sensor and a liquid level in the tank, preferably measured at atmospheric pressure, if the output of the pressure sensor is higher than the first threshold value;

d) comparing the output of the level sensor to the second and third thresholds;

e) -if the output of said level sensor is higher than said second threshold value, sending a first predetermined signal indicating the breakage or possible breakage of at least one internal stiffening element connecting said opposite walls, and/or;

-sending a second predetermined signal indicative of a breakage or possible breakage of at least one internal stiffening element connecting said opposite walls, if the output of said level sensor is lower than a third threshold value.

The method facilitates determining the condition of the tank, more specifically of the internal reinforcing element. For example, it may indicate a suspected fracture of the at least one internal stiffening element. The method relies on pressure evolution and volume evolution taking into account the evolution of the liquid consumption, which information is captured by sensors commonly available on the system. Therefore, it is not costly. Taking into account the evolution of the liquid consumption at least allows to adjust the expected amount of liquid in the tank. This method is particularly useful when the ambient temperature change is insufficient to generate an internal pressure that would exceed the first threshold. Taking into account the evolution of liquid consumption means that the method can be done during days or several drives. Thus, there are more possible variations to reach the first threshold and the method may be performed more frequently.

The liquid consumption may be measured or estimated, for example, by an engine control unit, a fuel pump, or a mathematical model.

The two opposing walls are preferably a bottom wall and a top wall. Opposite walls may be provided, being the two side walls of the tank.

The initial amount of liquid that can be measured by the level sensor ensures that there is at least a minimum detectable amount of liquid in the tank before the process is carried out, so that the process can be carried out. For example, the method will not work if the tank does not contain any liquid.

The initial internal pressure of the liquid tank is preferably equal to atmospheric pressure. Since the initial liquid amount is measured at atmospheric pressure, the tank is not initially deformed, which improves the accuracy of the method.

The first threshold may be higher, lower or equal to atmospheric pressure. For example, the first threshold may be +50mbar higher or-50 mbar lower than the initial pressure. Preferably, the first threshold is +100mbar higher or-100 mbar lower than the initial pressure. More preferably, the first threshold is +200mbar higher or-200 mbar lower than the initial pressure.

"initial" refers to the first measurement at whatever time of measurement. This measurement may be made, for example, at vehicle power start or prior to an accident or crash.

The signal may be, for example, an audio or visual signal.

Thereby, the signal alerts the operator or driver, for example by indicating that the at least one internal stiffening element is broken or possibly broken. The operator or driver may then take action to confirm and/or repair the fault. For example, the visual signal may be a message or light displayed on the dashboard. In an alternative embodiment, the settable signal does not specifically indicate that the at least one internal stiffening element is broken or possibly broken, but merely indicates that there is a fault requiring repair.

The monitoring of the output of the level sensor and the output of the pressure sensor may be continuous or on-time monitoring.

The evaluation of the second and third threshold values may be done by mapping. There may be a table relating the liquid level and liquid consumption evolution in the tank at atmospheric pressure to a first threshold. Thus, the liquid level inside the tank can be compared with an expected level according to the pressure inside the tank.

It may be provided that if neither of the conditions of step e) is satisfied, a predetermined signal is sent indicating that at least one internal stiffening element is not broken.

The liquid tank may for example be a tank for fuel, urea or water.

Preferably, during step c), the determination of said second and third threshold values is also done as a function of the temperature of the liquid in said tank.

Thus, the evaluation of the second or third threshold value is more accurate, since the temperature may affect the liquid level in the tank. In fact, an increase in temperature causes the liquid to expand, i.e. causes thermal expansion of the liquid. Thus, for example, an increase in temperature results in an expected increase in the liquid level in the tank.

Advantageously, the method comprises the step of incrementing a counter if the output of the level sensor is between the second threshold and a third threshold.

Preferably, if the counter is below a fourth predetermined threshold, at least steps a), b) and c) of the method are performed again, preferably using a plurality of first thresholds.

Thus, the significance of the method is increased.

Advantageously, if said counter is higher than a fourth threshold value, the method comprises a step of sending a signal indicating that at least one internal stiffening element connecting said opposite walls is not broken.

Therefore, it is mandatory to repeat the method to ensure that it is statistically run a sufficient number of times, for example it meets the condition of verifying that at least one internal stiffening element is not broken. This is especially interesting when the method relies on natural pressure variations inside the tank.

Preferably, said monitoring step b) is dependent on an increase or decrease of the pressure inside said tank resulting solely from an increase or decrease of the temperature outside the tank.

The method thus relies on temperature changes (possibly natural changes) caused by the environment of the tank and no additional elements are required to run the method. In this case, the first threshold value is preferably +100mbar higher or-100 mbar lower than the initial pressure.

Preferably, said monitoring step b) comprises the step of commanding means for increasing or decreasing the pressure inside said tank, preferably in response to a signal from a vehicle collision sensor.

Here, the pressure change is directed and not only a result from a change in the environment (or, to say, driven by the environment). Thus, the implementation of the method is controlled to a greater extent, since the pressure target, i.e. the first threshold value, will be reached on command. Thus, the method can be triggered whenever desired or needed. This approach is shorter than the one based on the evolution of ambient pressure (or rather, environmentally driven). In such an embodiment of the step of implementing said means for commanding an increase or decrease in the pressure inside said tank in response to a signal from a vehicle collision sensor, the method is forced to be completed when an event monitored by an external sensor (e.g. a collision sensor) suspects that an impact has occurred. The sensor may for example be an accelerometer for an airbag or for a dedicated use.

More preferably, the step of commanding the means for increasing or decreasing the pressure inside the tank is carried out by:

-using an external pump not forming part of the vehicle;

using devices forming part of the vehicle, such as pumps or heaters; and/or

-commanding the release of the pressure inside the tank using a valve of said tank.

When an external pump is used, which does not form part of the vehicle, the external device can exert pressure inside the tank during maintenance and require the completion of the diagnosis. Control of a valve of the system, such as a Fuel Tank Isolation Valve (FTIV) or a purge valve, may be provided to allow pressure from an external pump to be applied to the system. The external pump can apply positive and/or negative pressure. When an external pump is used, which does not form part of the vehicle, the first threshold value may for example be +100mbar higher than the initial pressure, preferably +200mbar higher than the initial pressure.

The devices forming part of the vehicle are devices already in the vehicle for other purposes, such as leak detection pumps, canister purge pumps, engine manifold vacuums, or others. Thus, it is inexpensive and requires no external intervention. When using a device forming part of a vehicle, the first threshold value is preferably +50mbar higher or-50 mbar lower than the initial pressure.

When using a tank valve to implement a command to relieve the internal pressure of the tank, it is possible to use an existing valve (for example an FTIV or E-valve) and at low cost and without external intervention. The valve may be used only to reduce the pressure, but the occurrence of the relief pressure may be associated with a fueling event, for example. In this case, the first threshold value is preferably equal to the atmospheric pressure.

Advantageously, the method is performed when the power of the vehicle is off, preferably only when the power of the vehicle is off.

Thereby, sloshing of the liquid in the tank is limited. Sloshing refers to fluctuations in the liquid in the tank that make noise to the measurement of the fuel level. In order to make the method as relevant as possible, the level sensor should not be moved dynamically. Thus, avoiding sloshing improves the accuracy of the liquid level measurement.

Preferably, the method is triggered when the vehicle is in a service mode.

Thus, the method is performed when this information is particularly useful. The tank can thus be investigated more deeply and replaced if necessary. The method is triggered, for example, by an external computer.

Advantageously, said step a) is preceded by a leak detection step.

The leak detection step tests the integrity of the tank shell. In the case of passive systems (i.e. increase or decrease of pressure based on changes in external temperature), tests that are usually done using a constant tank volume fail because there is a change in volume due to breakage of the internal stiffening element.

The leak detection method is intended to detect a leak in a liquid tank of a vehicle. An example of a leak detection method is described in JP 2013-.

The invention also relates to a method for testing the condition of at least one internal stiffening element of a liquid tank of a vehicle, which connects at least two opposite walls of the liquid tank, comprising the steps of:

-performing a leak detection step, and

-sending a signal indicating a possible breakage of at least one internal stiffening element connecting at least two opposite walls of said liquid tank, if the result of the leak detection step is of a predetermined type.

Advantageously, the predetermined type of result is such a result indicating that a leak is suspected. The result can be derived from the outcome of the leak detection method. If the leak test reveals a problem, this may be caused by an unexpected volume change due to a broken internal stiffening element. Thereby, the method may facilitate servicing of a liquid tank, also referred to as a liquid system, e.g. a fuel system.

Alternatively, the predetermined type of result is a result derived from an outcome of the leak detection method, which result indicates that the at least one internal stiffening element may break despite no leak being detected. This can be accomplished by pumping air into and out of the liquid tank to pressurize or depressurize it and measuring the internal pressure of the liquid tank. If no leak is suspected after the leak detection method has been performed, the method comprises the step of defining a relation between:

volume of air pumped into and out of the liquid tank, denominated V_air(t)；

Vapor dome volume, denominated V_dome(t); and

-the internal pressure of the liquid tank, denominated P_int(t) and comparing the value C (t) calculated using the above relationship with a predetermined threshold valueWhere t in parentheses means that the parameter of interest is time dependent. The predetermined threshold may for example be a calibrated value calculated using the above relation when the tank condition is known to be intact.

From pump performance F_pump(t) and Pump activation time duration Δ t_actDeducing the air volume V_air(t) wherein the vapor dome volume V_dome(t) is calculated as the total volume V of the liquid tank_tot(t) and the name V_liquid(t) the difference in liquid volume in the liquid tank is as follows:

V_dome(t)＝V_total(t)-V_liquid(t)

pump Performance F_pump(t) is defined as a function of, for example, the volume of air V_air(t), pump efficiency, and pump current consumption.

For example, the value c (t) may be calculated according to the following steps:

-step 1: calculating the energy consumption E of the pump_pump(t) Pump Performance F_pump(t) and tank internal pressure P_int(t) to obtain A (t), wherein the pump performance F_pump(t) is dependent on the volume of air V_air(t) parameters.

A(t)＝E_pump(t)*F_pump(t)*P_int(t)

-step 2: during pump activation time Δ t_actIntegrating A (t) to obtain B (t), wherein the pump activation time period Δ t_actIs dependent on the volume V of air_air(t) parameters.

-step 3: calculating B (t) and vapor dome volume V_dome(t) to obtain C (t).

C(t)＝B(t)*V_dome(t)

If the value C (t) is higher than a predetermined threshold value, the method comprises a step of indicating a possible breakage of at least one internal stiffening element.

On the contrary, no signal is sent indicating a possible breakage of at least one internal stiffening element connecting at least two opposite walls of the liquid tank.

The invention also relates to a vehicular liquid tank comprising control means for implementing the method as described above.

The invention also relates to a vehicle comprising a liquid tank and a control device for implementing the method as described above.

The invention also relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method as described above.

Drawings

The above-mentioned and other features, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The reference figures quoted below refer to the attached drawings, in which:

figure 1 is a schematic view of an embodiment of a tank that can be used for implementing the method according to the invention;

figure 2 is a schematic view of another embodiment of tank that can be used for implementing the method according to the invention;

figure 3 is a flow chart illustrating a first embodiment of the method according to the invention;

figure 4 is a flow chart illustrating a second embodiment of the method according to the invention; and

fig. 5 is a flow chart illustrating a third embodiment of the method according to the invention.

Detailed Description

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto.

First embodiment (FIGS. 1 and 3)

The first embodiment describes a method for testing the condition of at least one internal stiffening element 1 of a liquid tank 2 of a vehicle, wherein the internal stiffening element 1 connects at least two opposite walls, preferably a bottom and a top wall 3, 4, of the liquid tank 2. The stiffening element 1 is, for example, a column.

The tank 2 has a level sensor 5 for measuring the level of the liquid 6 inside the tank 2.

The tank 2 has a pressure sensor 7 for measuring the internal pressure of the tank 2.

The tank 2 is associated to a control device 8, the GAI control device 8 being able to process the data provided by the level sensor 5 and the pressure sensor 7 and command the steps of the method.

The tank 2 comprises at least an initial amount of liquid 6 measurable by a level sensor 5. For example, the tank 2 comprises at least 2mL of liquid 6, for example 20L of liquid 6. The first threshold value is determined by the control means 8 on the basis of the initial quantity of liquid 6 measured by the liquid level sensor 5 and the initial internal pressure of the liquid tank 2 measured by the pressure sensor 7 (step a, not shown). For example, the first threshold value may be determined using a two-dimensional look-up table using the initial internal pressure and the initial liquid amount as input data.

The method is triggered by an operator when the vehicle is in a service mode and the vehicle is powered off. After triggering the method, the overpressure in the tank is initiated by an external device, for example by increasing the pressure in the tank by an external pump. Of course, it is possible to provide for the use of other means, such as means forming part of the vehicle, for increasing the pressure in the tank. There may be one or more steps of increasing the pressure, and the pressure may be increased gradually (pressure ramp). In another embodiment, it may be provided to use a pressure reduction that causes a low pressure in the tank. Such a low pressure may be caused, for example, by an external pump.

The pressure and the liquid level are monitored by the control means with the sensors (step b) until the tank pressure measured by the pressure sensor 7 is above a first threshold value.

If the output of the pressure sensor 7 is higher than the first threshold value, a second threshold value and a third threshold value are determined by the control means 8 depending on the evolution of the liquid consumption, the output of the pressure sensor 7 and the level of the liquid 6 in the tank 2 at atmospheric pressure (step c, not shown). For example, the second and third threshold values may be determined using a three-dimensional look-up table using as input data the evolution of the liquid consumption, the output of the pressure sensor 7 and the level of the liquid 6 in the tank 2 at atmospheric pressure. The look-up table may be arranged to include a fourth dimension relating primarily to the temperature of the liquid in the tank. As mentioned above, the thermal expansion of the liquid can thus be taken into account.

The control means 8 then compares the output of the level sensor 5 with the second and third threshold values to see if the output of the level sensor 5 differs from the expected level value (step d).

If the output of the level sensor 5 is above the second threshold value, this may indicate that the inner stiffening element 1 (or at least one of the inner stiffening elements 1) is broken. Thereby, a signal is sent indicating a breakage or possible breakage of at least one internal stiffening element 1 (step e). Preferably, the signal is sent to the driver at a first time. The signal may be a visual signal, for example the signal may consist of a message or light displayed on the dashboard. The signal corresponding to the diagnosis may be stored in a storage medium to alert an operator of the repair shop during an internal electrical inspection of the vehicle.

If the output of the level sensor is below a third threshold value, this may indicate that the internal stiffening element 1 (or at least one of the internal stiffening elements 1) is broken. Thereby, a signal is sent indicating that the at least one internal stiffening element is broken or possibly broken.

If the output of the level sensor 5 is below the second threshold value and above a third threshold value, this may indicate that the column 1 is intact. Thereby, it may be provided to send a signal indicating that the internal stiffening element 1 (or at least one internal stiffening element 1) is intact.

Second embodiment (FIGS. 2 and 4)

In this embodiment, the method is also used for testing the condition of at least one internal stiffening element 1 of a liquid tank 2 of a vehicle, wherein the internal stiffening element 1 connects at least two opposite walls of the liquid tank, preferably a bottom wall 3 and a top wall 4. For example, the at least one stiffening element is a post.

The tank 2 may for example be the same as described above in relation to the first embodiment.

The first step of the method consists in performing a leak detection method. In the present case, the leak detection method used is an active leak detection method. Of course, any suitable leak detection method may be used with the arrangement, such as the leak detection methods described in WO 2018/002054 or WO 2013/164463, the contents of which are incorporated herein by reference.

If the result of the leak detection method indicates the possible presence of a leak, a predetermined signal is sent by the control device 8 indicating the breakage or possible breakage of at least one internal stiffening element 1. In fact, this result may actually be a false positive result caused by a broken internal stiffening element 1. Thereafter, the operator may conduct further investigations to verify or override the presence of a leak in the tank. The above-mentioned leak detection result is likely to be caused by a broken reinforcing member if it seems that there is no leak.

If the result of the leak detection method indicates that no leak is present in the tank 2, the counter 9 (e.g. the predetermined counter 9 of the control device 8) is reset and the status of the vehicle is observed.

The tank 2 comprises at least an initial amount of liquid 6 measurable by a level sensor 5. For example, the tank comprises at least 2mL of liquid 6, for example 20L of liquid 6. The first threshold value is determined by the control means 8 on the basis of the initial quantity of liquid 6 measured by the liquid level sensor 5 and the initial internal pressure of the liquid tank 2 measured by the pressure sensor 7 (step a, not shown). For example, the first threshold value may be determined using a two-dimensional look-up table using the initial internal pressure and the initial liquid amount as input data.

If the vehicle is powered on, a valve or pump 10 is activated in order to release pressure from the inside of the tank 2, and the method can be performed again from the leak detection step. The valve is for example an FTIV or E-valve. If the power of the vehicle is shut down, the control means 8 commands an increase in the pressure in the tank using, for example, means forming part of the vehicle, such as a vehicle pump. This results in an overpressure in the tank 2. There may be one or more pressure increase steps and the pressure may be increased gradually (pressure ramp). In another embodiment, it may be provided to use a pressure reduction that causes a low pressure in the tank 2. Such low pressure may be caused, for example, by an on-board pump.

The pressure and the liquid level are monitored by the control means 8 and the sensors 5, 7 (step b) until the tank pressure measured by the pressure sensor 7 is above a first threshold value.

If the control means 8 determines that the output of the pressure sensor 7 is higher than the first threshold value, a second and a third threshold value are determined by the control means 8 depending on the evolution of the liquid consumption, the output of the pressure sensor 7 and the level of the liquid 6 in the tank 2 at atmospheric pressure (step c, not shown). For example, the second and third threshold values may be determined using a three-dimensional look-up table using as input data the evolution of the liquid consumption, the output of the pressure sensor 7 and the level of the liquid 6 in the tank 2 at atmospheric pressure. The look-up table may be arranged to include a fourth dimension relating primarily to the temperature of the liquid in the tank. As mentioned above, the thermal expansion of the liquid can thus be taken into account.

The control means 8 then compares the output of the level sensor with the second and third threshold values to see if the output of the level sensor differs from the expected level value (step d).

If the output of the level sensor is above the second threshold value, this may indicate that the inner stiffening element 1 (or at least one of the inner stiffening elements 1) is broken. Thus, a signal is sent indicating the breakage or possible breakage of at least one internal stiffening element 1 (step e).

If the output of the level sensor 5 is below a third threshold value, this may indicate that the internal stiffening element 1 (or at least one of the internal stiffening elements 1) is broken. Thus, a signal is sent indicating the breakage or possible breakage of at least one internal stiffening element 1 (step e, not shown).

If the output of the level sensor 5 is below the second threshold value but above a third threshold value, the counter 9 is incremented. If the counter 9 is below a fourth predetermined threshold, at least steps a), b) and c) of the method are carried out again at the command of the control device 8, preferably using a plurality of first thresholds. If the counter 9 is higher than the fourth threshold value, the method comprises sending a signal indicating that at least one internal stiffening element 1 connecting the opposite walls 3, 4 is not broken.

Third embodiment (FIGS. 2 and 5)

The third embodiment is the same as the second embodiment except for the points discussed below.

In a third embodiment, the leak detection method is not an active leak detection method, but a method based on pressure and temperature analysis, such as the method described in EP 17305638. Moreover, the leak detection test is carried out by the control device 8 in parallel with the test of the condition of at least one internal stiffening element 1 of the liquid tank 2 of the vehicle. Thus, in contrast to the second embodiment, the test is performed even if the leak detection method detects a leak.

In the third embodiment, there is no step of actively increasing the internal pressure in the tank after the vehicle power shut-down is observed. Instead, the monitoring step b) relies on an increase or decrease of the pressure inside the tank 2, which is only caused by an increase or decrease of the temperature outside the tank. When the ambient temperature rises, the pressure inside the tank rises. When the ambient temperature decreases, the pressure inside the tank decreases.

The temperature and the liquid level inside the tank 2 are monitored by the control means 8 until the output of the pressure sensor 7 is higher than the first threshold, as in the second embodiment, and all the following steps are identical to those of the second embodiment.

While the principles of the invention have been described above in connection with specific embodiments, it is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention, as defined in the appended claims.