Method and system for making-safe a motor vehicle using dihydrogen as an energy or fuel source

Abstract

Method for making-safe a motor vehicle using dihydrogen as a source of energy or fuel in a circuit, the method comprising measuring pressure in the circuit, estimating a dihydrogen flow rate likely to be released as a function of the measured pressure, determining a target ventilation flow rate required to reduce a dihydrogen concentration in the air and determining and then applying a strategy for controlling a motor-fan unit and / or mobile flaps so as to implement the determined ventilation flow rate.

Description

[0001] TITLE: Method and system for securing a motor vehicle using dihydrogen as an energy source or fuel

[0002] The invention relates to a method for securing a motor vehicle using dihydrogen as an energy source or fuel, in particular a vehicle whose thermal powertrain or fuel cell is powered by dihydrogen. The invention also relates to a security system capable of implementing such a method and a vehicle comprising such a system.

[0003] In a global context of global warming linked to human activity, vehicle power sources are diversifying. Electric vehicles are developing, and it is known to integrate an electrochemical cell powered by dihydrogen in addition to the electric drive battery in order to optimize the autonomy and power of such vehicles. In addition, the market for hydrogen-powered vehicles, including a thermal powertrain using dihydrogen as fuel, is growing.

[0004] The introduction of tanks and / or circuits containing dihydrogen in vehicles is accompanied by an on-board safety management issue. Indeed, the dihydrogen molecule being the smallest existing molecule, the risks of leakage within the vehicle are higher than for other gases. Also, dihydrogen is particularly flammable and reactive, forming explosive mixtures with air above a low volume concentration, of the order of 4%. Finally, the amount of energy required to cause the ignition of dihydrogen, also known as minimum ignition energy, or MIE, is low, of the order of 0.01 mJ. It is therefore essential to integrate safety measures into the vehicle to prevent the accumulation of dihydrogen in localized areas in the event of a leak.

[0005] In the case of vehicles comprising a fuel cell, it is known to integrate the latter within a closed housing equipped with a fan dedicated to diluting the dihydrogen in the event of leak detection or as a preventive measure in order to prevent the accumulation of dihydrogen. Such a safety system is conventionally applied in installations comprising dihydrogen stored and distributed at low pressure, i.e. at pressures below 15 bar, or even of the order of 10 bar, which makes it unsuitable for installations implementing the storage and distribution of dihydrogen at high pressure, i.e. at pressures above 20 bar, in particular above 100 bar. Furthermore, the integration of such a fan within a fuel cell module generates additional space requirements and manufacturing costs.

[0006] It is also known to incorporate safety systems that interrupt the hydrogen supply if a leak is detected. However, such systems tend to detect small leaks, for example those with a diameter of less than 0.3 mm, late. As a result, hydrogen can accumulate in localized areas of the vehicle to dangerous concentrations. This disadvantage presents particularly significant risks in the case of vehicles using high-pressure hydrogen, i.e. at pressures greater than or equal to 20 bar.

[0007] The invention falls within this context and aims to provide a system and a method for securing a motor vehicle using dihydrogen as an energy source or fuel, overcoming the above drawbacks. In particular, the invention proposes a method for securing a motor vehicle comprising a drive chain at least partly supplied with dihydrogen, a dihydrogen circuit and at least one motor-fan unit and / or a set of controlled movable flaps. The method comprises:

[0008] - measuring a pressure in the dihydrogen circuit via at least one pressure sensor;

[0009] - the estimation of a mass flow rate and / or a volume flow rate of dihydrogen likely to be released, at atmospheric pressure, for at least one leak of predefined diameter located in the circuit as a function of the measured pressure

[0010] - the determination of a required target ventilation flow rate, corresponding to a forecast air flow rate necessary to reduce a concentration of dihydrogen in the air to a value less than or equal to a predefined safety threshold based on the estimated mass flow rate and / or volume flow rate of dihydrogen likely to be released;

[0011] - determining a strategy for controlling the motor-fan unit and / or the set of shutters so as to implement the determined target ventilation flow rate;

[0012] - the application of the strategy determined by controlling the motor-fan unit and / or the set of shutters by means of a control means, in particular a calculator of a thermal module comprising the motor-fan unit and / or the set of shutters.

[0013] Notably :

[0014] - the dihydrogen circuit is a high-pressure circuit configured to receive dihydrogen at a pressure greater than or equal to 20 bar, or even 50 bar or even 100 bar; and / or

[0015] - the estimation of the mass flow rate and / or the volume flow rate of dihydrogen likely to be released is carried out for a leak of a determined diameter, in particular a diameter greater than or equal to 0.1 mm.

[0016] According to an exemplary embodiment, the safety threshold is selected from a plurality of safety thresholds corresponding to different percentages of the lower explosive limit of dihydrogen, in particular corresponding to 25%, 50% 70% and / or 75% of the lower explosive limit of dihydrogen.

[0017] Optionally, the determination of the target ventilation flow rate comprises a sub-step of determining a plurality of target ventilation flow rates, each defined by a safety threshold and / or a leak diameter specific to it, and a sub-step of selecting one of the target ventilation flow rates as a function of at least one criterion selected from the pressure measured in the circuit, a safety margin compensating for an inaccuracy in calculating the mass flow rate and / or the volume flow rate of dihydrogen likely to be released, the energy consumption of the vehicle and / or the comfort of a user.

[0018] In particular, the determination of a control strategy for the motor-fan unit and / or the set of flaps includes the determination of the flow rate of an outside air flow circulating naturally through the motor-fan unit and / or the set of flaps:

[0019] - the determination of the flow rate of the outside air flow taking into account a useful surface area of ​​a heat exchanger included in the thermal module comprising the motor-fan unit and / or the set of shutters; and / or

[0020] - the vehicle comprising a means for measuring and / or estimating a longitudinal speed of the vehicle and determining the flow rate of the exterior air flow taking into account a measured or estimated longitudinal speed of the vehicle.

[0021] Optionally, the determination of a control strategy for the motor-fan unit and / or the set of movable flaps comprises the determination of a forecast control setpoint intended for the potential dilution of dihydrogen released in the event of a leak and the reception of a forecast control setpoint intended for the thermal management of at least one element to be thermally treated, each of said setpoints defining at least one degree of opening of the set of controlled flaps and / or a rotation speed of the powertrain, the ventilation strategy to be applied being the forecast setpoint having the highest values ​​of degree of opening and / or rotation speed or a combination of the different setpoints aimed at applying the highest values ​​of degree of opening and rotation speed.

[0022] Optionally but preferably, the vehicle comprises at least one means for regulating the circulation of dihydrogen in the circuit, such as a valve or solenoid valve, the method comprising the detection of a state, closed or open, of said regulating means and the interruption of the method when it is detected that the regulating means is in the closed state.

[0023] According to an exemplary embodiment, the vehicle comprises a measuring or estimating member configured to measure or estimate an effective ventilation flow rate circulating in a front compartment of the vehicle, the method comprising checking and adjusting the control in real time when it is detected that the effective ventilation flow rate differs from the target ventilation flow rate.

[0024] The invention also relates to a security system for a motor vehicle comprising a drive chain configured to be at least partly supplied with dihydrogen, the security system comprising hardware and / or software elements configured to implement the method according to the invention, the hardware elements comprising at least one processing unit, at least one pressure sensor and a means for controlling a motor-fan unit and / or a set of controlled flaps of the vehicle, in particular a computer of a thermal module comprising the motor-fan unit and / or the set of flaps.

[0025] The invention also relates to a motor vehicle comprising:

[0026] - a drive chain configured to be at least partly supplied with dihydrogen;

[0027] - a circuit configured to allow the circulation of dihydrogen; - a motor-fan unit and / or a set of controlled flaps; and

[0028] - a security system according to the invention.

[0029] In particular, the motor-fan unit and / or a set of shutters are included in a thermal module further comprising at least one heat exchanger.

[0030] The invention may also extend to a computer or calculator program product comprising program code instructions recorded on a computer-readable medium for implementing the steps of the method according to the invention when said program operates on a computer. Alternatively, the computer program product is downloadable from a communication network and / or recorded on a data medium readable by a computer and / or executable by a computer, said program comprising instructions which, when the program is executed by the computer, lead the latter to implement the method according to the invention.

[0031] The invention may also relate to a computer-readable data recording medium on which is recorded a computer program comprising program code instructions for implementing the method according to the invention or to a computer-readable recording medium comprising instructions which, when executed by a computer, cause the latter to implement the method.

[0032] The invention finally extends to a signal from a data medium carrying the computer program product as set out above.

[0033] Other details, characteristics and advantages will emerge more clearly on reading the detailed description given below, for informational and non-limiting purposes, in relation to the various exemplary embodiments illustrated in the following figures: Figure 1 is a simplified schematic representation of an exemplary embodiment of a vehicle equipped with a security system.

[0034] Figure 2 is a flowchart of an example of the execution of a security process.

[0035] Figure 3 is a flowchart of an alternative example of executing the securing process.

[0036] Figure 4 is a flowchart of an alternative example of executing the securing process.

[0037] Figure 5 is an example of a table containing values ​​of mass and volume flow rates of dihydrogen likely to be released as a function of the pressure of a circuit and different leak diameters.

[0038] Figure 6 is a representation of the evolution of different target ventilation rates as a function of pressure.

[0039] Figure 1 schematically illustrates a motor vehicle 1 equipped with an embodiment of a security system 2 according to the invention. The vehicle 1 can be of any type, that is to say it can be a private vehicle, a utility vehicle, a truck or a bus. Also, the vehicle 1 can be an autonomous or non-autonomous vehicle.

[0040] In particular, the vehicle 1 comprises a drive chain 3 which is configured to be at least partly supplied with dihydrogen. In a known manner, at least part of said chain is arranged in a front compartment of the vehicle 1, for example at least one powertrain in the broad sense, in particular a thermal powertrain.

[0041] According to an exemplary embodiment, the vehicle 1 is electrically powered and comprises at least one fuel cell. In this sense, it comprises an electric drive train 3 comprising an electric powertrain and an electric drive battery, also capable of being referred to as a “battery”, “battery module” or even “battery pack” in English, allowing the storage of electrical energy and the supply of at least one component of the drive train 3 with electrical energy. In addition, the vehicle 1 comprises a fuel cell device comprising at least one fuel cell configured to be supplied with dihydrogen and to supplement the capacities of the electric drive battery by giving the vehicle 1 additional autonomy in addition to the autonomy provided by the battery. The fuel cell device comprises one or more fuel cells.

[0042] Alternatively, the vehicle 1 is hydrogen-powered, that is to say it comprises a drive train 3 comprising a thermal powertrain configured to use dihydrogen as fuel.

[0043] Regardless of the type of engine used, the vehicle 1 comprises a dihydrogen circuit 4, i.e. a circuit capable of allowing the circulation of dihydrogen. The dihydrogen circuit 4 comprises at least one tank, or a bottle, capable of storing dihydrogen. The dihydrogen circuit 4 also comprises at least one dihydrogen supply line configured to allow the circulation and distribution of dihydrogen between the tank and the components requiring it, namely the thermal powertrain or the fuel cell device depending on the type of vehicle 1 considered. The dihydrogen circuit 4 is at least partly, or even entirely, arranged at the front compartment of the vehicle 1. Also, the dihydrogen circuit 4 is equipped with at least one means 5 for regulating the flow of dihydrogen, such as a valve or a solenoid valve, configured to vary the flow of dihydrogen, or even interrupt it.Optionally, the hydrogen circuit 4 includes at least one pressure reducer.

[0044] In particular, the hydrogen circuit 4 is a high-pressure circuit 4, configured to receive hydrogen at a pressure greater than or equal to 20 bar, or even 50 bar or even 100 bar. Such a pressure is caused to vary within the tank depending on its filling state. For example, as illustrated in Figure 5 or 6, the pressure can rise, in a non-limiting manner, to a pressure of 700 bar when the tank is completely filled. Such a principle advantageously makes it possible to carry a larger quantity of hydrogen within the vehicle 1 while limiting the space required by the tank.

[0045] Conventionally, the vehicle 1 further comprises at least one motor-fan unit 62 and a set of controlled flaps 63. According to a particular embodiment, the vehicle 1 comprises a thermal module 6 comprising a heat exchanger 61, such as a radiator, and comprising the set of flaps 63, the function of which is then to vary the flow rate of air admitted into the thermal module 6 proportionally to the longitudinal speed of the vehicle 1 and to its degree of opening, and the motor-fan unit 62. The motor-fan unit 62 can in particular be controlled so as to implement different rotation speeds, or different percentages of a maximum rotation speed, in order to vary a flow rate of air outside the vehicle 1 entering the front compartment and circulating through the heat exchanger 61.In particular, by knowing the flow rate generated by the motor-fan unit 62 at its maximum speed, the control thereof can be implemented to obtain a target flow rate, the air flow rate being linearly proportional to the rotation speed of the motor-fan unit 62.

[0046] The different flaps of the flap assembly 63 are configured to be moved according to different degrees of opening, between a closed position, in which they block the circulation of the air flow through the heat exchanger 61 and the front compartment, and an open position, allowing the circulation of said air flow. It is understood that the vehicle 1 may also comprise a plurality of motor-fan units 62 and / or flap assemblies 63. Also, the vehicle 1 may comprise a plurality of thermal modules 6. Optionally, the thermal module 6 may comprise a plurality of motor-fan units 62 and / or flap assemblies 63.

[0047] The vehicle 1 is also equipped with a security system 2 according to the invention. Said system comprises the hardware and / or software elements necessary for implementing a security method according to the invention, as set out below.

[0048] The security system 2 comprises at least one processing unit 7, at least one pressure sensor 8 and a control means 9, or actuator, configured to control the motor-fan unit 62 and / or the set of controlled flaps 63. In this way, the motor-fan unit 62 and / or the set of flaps 63 are capable of being controlled as part of thermal management functions and / or as part of securing the vehicle in order to dilute and disperse a possible accumulation of dihydrogen resulting from a leak or in order to implement the thermal management of an element of the vehicle 1.

[0049] The processing unit 7 comprises at least one calculation unit comprising hardware and software resources, in particular at least one processor, or microprocessor, cooperating with memory elements. The memory elements are included in the security system 2 or, alternatively, equipped in the vehicle 1. The processing unit 7 is capable of executing instructions for the implementation of a computer program and of receiving data from the at least one pressure sensor 8.

[0050] The at least one pressure sensor 8 is arranged in the hydrogen circuit 4. It makes it possible to measure the pressure of the hydrogen present in the circuit 4 at at least one point, for example at the tank, at the outlet of the latter or within the at least one supply line. It should be noted that, when the means 5 for regulating the circulation of the hydrogen is open, the measured pressure of the hydrogen is uniform over at least part of the hydrogen circuit 4, in particular in the tank and at at least one portion of the at least one supply line connected to the tank and located upstream of the pressure reducer according to the direction of circulation of the hydrogen.

[0051] The control means 9 is configured to control the set of flaps 63 and / or the motor-fan unit 62 independently of each other according to instructions communicated by the processing unit 7. The control means 9 is capable of adjusting the rotation speed of the motor-fan unit 62 and the degree of opening of the different flaps of the set of flaps 63 as required. In particular, the control means 9 is a computer included in the thermal module 6 comprising the motor-fan unit 62 and / or the set of flaps 63.

[0052] Optionally, the security system 2 and / or the vehicle 1 further comprises a measuring means and / or an estimation means capable of detecting or estimating a longitudinal speed of the vehicle 1 and communicating it to the processing unit 7, such as a speed sensor, a driving assistance system, a means of locating the vehicle 1 or any other known means.

[0053] Optionally, the security system 2 and / or the vehicle 1 comprises a device for measuring or estimating a flow rate of the exterior air circulating in the front compartment.

[0054] The various measurements, relating to pressure, longitudinal speed and / or flow rate, are carried out at regular time intervals or, preferably, in real time.

[0055] An example of execution of the method 100 for securing the vehicle 1 is described below with reference to FIGS. 2 to 4. The method 100 for securing can also be considered as being a method of operation of the security system 2 as described above or of a motor vehicle 1 equipped with such a system.

[0056] The securing method 100 firstly comprises a step E01 of measuring the pressure in the hydrogen circuit 4 via the at least one pressure sensor 8. Such a measurement is carried out at at least one point in the circuit 4, for example at the tank and / or at the at least one supply pipe connecting said tank to the element to be supplied. For example, the at least one pressure sensor 8 is arranged at the outlet of the tank, at the means 5 for regulating the circulation of hydrogen in the circuit 4. The measurement is carried out at regular time intervals or, alternatively, in real time.

[0057] As indicated above, circuit 4 is in particular a high-pressure circuit 4, configured to store and circulate dihydrogen at a pressure greater than or equal to 20 bar, or even 50 bar or even 100 bar.

[0058] The safety system 2 then executes, via the processing unit 7, a step E02 of estimating a mass flow rate d_mas and / or a volume flow rate d_vol of dihydrogen likely to be released, at atmospheric pressure, for at least one leak of predefined diameter located in the dihydrogen circuit 4, as a function of the measured pressure. In this way, the system makes it possible to estimate in advance a quantity of dihydrogen likely to be released into the front compartment as a function of the previously measured pressure if a leak were to form, even in the absence of a leak or detection of a leak by conventional safety systems at the time of implementing such an estimation.

[0059] In particular, the estimation of the mass flow rate d_mas and / or the volume flow rate d_vol of dihydrogen likely to be released is at least carried out for a leak with a diameter greater than or equal to 0.1 mm and a diameter less than or equal to 0.5 mm, or even less than or equal to 0.30 mm. In particular, the estimation of the mass flow rate d_mas and / or the volume flow rate d_vol of dihydrogen likely to be released is carried out for a plurality of leak diameter values ​​included in a range of predefined diameters, for example included in an interval of [0.1; 0.5 mm] or [0.1; 0.25 mm], or even [0.1; 0.2 mm].

[0060] In particular, such estimations are made for a predefined temperature, such a parameter negligibly affecting the mass flow rate d_mas or the volume flow rate d_vol. Alternatively, such estimations are made by taking into account a temperature measured in the engine compartment or in the environment outside the vehicle 1 via at least one temperature sensor.

[0061] For example, such an estimate may be calculated by the processing unit 7 or extracted from previously calculated data, recorded on the memory element. According to a non-limiting example embodiment, illustrated in FIG. 5, this data is presented in the form of a table grouping together estimates of the mass flow rate value d_mas and / or the volume flow rate d_vol of dihydrogen likely to be released at a given time as a function of the measured pressure, for different possible leak diameters. Such a table may also take into account the temperature, as described above.

[0062] Indeed, it has been found that 95% of hydrogen leaks observed in vehicles result from holes with a diameter between 0.1 and 0.2 mm. However, the detection of such leaks by conventional safety systems of the prior art is more complex and time-consuming due to their small size. As a result, the interruption of the hydrogen supply can be delayed and the hydrogen can then accumulate in the front compartment at critical concentrations, above the lower explosive limit, or LEL, also known as the lower flammability limit or "Lower Flammability Limit" in English. Such a risk is particularly critical in the case of a high-pressure hydrogen circuit 4.

[0063] The method according to the invention is thus capable of ensuring the safety of users at all times, regardless of the detection of a leak.

[0064] The safety method 100 then comprises the determination E03 of a required target ventilation flow rate d_vent. The target ventilation flow rate d_vent corresponds to the estimation of an air flow rate that would be necessary to reduce a possible concentration of dihydrogen in the air, in particular in the front compartment, to a value less than or equal to a predefined safety threshold S_sec as a function of the previously estimated mass flow rate d_mas and / or volume flow rate d_vol of dihydrogen released.

[0065] The target ventilation flow rate d_vent is calculated independently of the detection of a hydrogen leak. In this way, the method according to the invention makes it possible to anticipate the accumulation of hydrogen at critical concentrations in the event of a leak and to plan a ventilation level adapted to reduce and disperse a possible accumulation of hydrogen in the air at any time. It is thus possible to overcome the delay in triggering conventional safety measures observed before the detection of a leak.

[0066] The target ventilation flow rate d_vent thus calculated is a function of the pressure measured in circuit 4, and, consequently, a function of the filling level of the tank of said circuit 4. Preferably, the target ventilation flow rate d_vent is determined based on the assumption that the dihydrogen concentration is homogeneous in space, in particular in the front compartment, in order to simplify the calculations carried out.

[0067] For example, the safety threshold S_sec is set to the value of the lower explosive limit of dihydrogen. Optionally but preferably, in order to ensure effective and robust dilution of dihydrogen in the event of a leak, the safety threshold S_sec is selected from a plurality of safety thresholds S_sec corresponding to different percentages of the lower explosive limit of dihydrogen, in particular, but not limited to, 25%, 50% 70% and / or 75% of the lower explosive limit of dihydrogen.

[0068] Such values ​​make it possible to integrate a more or less significant safety margin allowing, on the one hand, to compensate for the different estimates made and, on the other hand, to compensate for the hypotheses applied to the different calculations made, such as the fact that the concentration of dihydrogen is homogeneous in space.

[0069] The processing unit 7 then performs a step E04 of determining a strategy for controlling the motor-fan unit 62 and / or the set of movable flaps 63 so as to implement the determined target ventilation flow rate d_vent. As indicated above, the control strategy comprises determining a degree of opening of all or part of the flaps of the set of flaps 63 and / or a rotation speed of the motor-fan unit 62.

[0070] Then, the method comprises the application of the strategy E05 determined by controlling the motor-fan unit 62 and / or the set of movable flaps 63 via the control means 9.

[0071] The ventilation thus implemented makes it possible to ensure the safety of the vehicle 1 even when a leak has not yet been detected, in particular when the said leak is too small to allow immediate detection by conventional safety systems.

[0072] Figures 3 and 4 illustrate particular examples of execution of the method that can be implemented. Optionally, the step E03 of determining the target ventilation flow rate d_vent comprises a sub-step E031 of determining a plurality of target ventilation flow rates d_vent, each defined by a safety threshold S_sec specific to it and / or by a leak diameter specific to it, and a sub-step E032 of selecting one of the target ventilation flow rates d_vent based on at least one criterion.

[0073] For example, the different target ventilation flow rates d_vent are defined in order to achieve one of the different examples of safety thresholds of concentration S_sec of dihydrogen defined previously. The processing unit 7 is then able to select a target ventilation flow rate d_vent, and by extension a ventilation strategy and a control strategy, the most suitable on the basis of at least one criterion. For example, such a criterion is selected from the pressure measured in the circuit 4, a safety margin compensating for any inaccuracy in calculating the mass flow rate d_mas and / or the volume flow rate d_vol of dihydrogen likely to be released, the energy consumption of the vehicle 1 and / or the comfort of a user.

[0074] For example, as illustrated in Figure 6, for a pressure of the order of 100 bar measured in the dihydrogen circuit 4, target ventilation flow rates d_vent aimed at reaching safety thresholds S_sec corresponding to 25%, 50% or 75% of the lower explosive limit do not have a major impact on the energy consumption of the vehicle 1 or the comfort of a user. The processing unit 7 can then select any of said flow rates. On the other hand, for a measured pressure greater than or equal to 500 bar, the target ventilation flow rate d_vent required to reach a safety threshold S_sec equal to 25% of the lower explosive limit is much greater than that required to reach a safety threshold S_sec equal to 75% of the lower explosive limit.It will therefore be necessary to open the flaps of the flap assembly 63 further and to operate the motor-fan unit 62 at higher power, which will increase the energy consumption of the vehicle 1 and is likely to generate noise and / or vibrations affecting the comfort of the user. It may then be preferable to opt for a higher safety threshold S_sec in such a situation. The determination of the control strategy is then implemented according to the target ventilation flow rate d_vent selected as described above.

[0075] Additionally or alternatively, the target ventilation flow rate d_vent is selected based on a preference of a user of the vehicle 1, for example entered via a human-machine interface.

[0076] Figure 3 illustrates a separate exemplary embodiment that can be combined with the exemplary embodiments described previously in which the determination of a control strategy E04 comprises, firstly, a sub-step E041 of determining a flow rate of an outside air flow circulating through the motor-fan unit 62 and / or the set of flaps 63, in particular through the at least one thermal module 6. The term “flow rate of the outside air flow” means the useful flow rate of the air flow circulating naturally in the front compartment, in particular through the motor-fan unit 62 and / or the set of flaps 63, before application of a control strategy to be applied at a given time when the vehicle 1 is in motion. In particular, the useful flow rate of the air flow circulating naturally through the at least one thermal module 6 is considered.Such a flow rate, resulting from the advancement of the vehicle 1, can be measured or estimated by means of a member for measuring or estimating the flow rate of the air flow as a function of the degree of opening of the flaps of the set of flaps 63 and the longitudinal speed at a given instant. For example, the degree of opening of the flaps is transmitted to the processing unit 7 by the control means 9. The target ventilation flow rate d_vent then corresponds to the sum of the flow rate of the outside air flow and a generated air flow rate, corresponding to a flow rate resulting from the control of the motor-fan unit 62 and / or of the set of movable flaps 63 within the framework of the securing method according to the invention. The determination of the flow rate of the outside air flow takes into account a useful surface area of ​​the heat exchanger 61 and / or the longitudinal speed of the vehicle 1 at a given instant.In particular, the longitudinal speed is measured by a measuring means and / or any means of estimating the longitudinal speed as explained above. Such a principle advantageously makes it possible to optimize the control of the motor-fan unit 62 and the energy consumption of the vehicle 1 by adjusting the opening of the flaps of the flap assembly and the rotation speed of the motor-fan unit 62 only as needed.

[0077] For example, when the vehicle 1 is stationary and its longitudinal speed is zero, the outside airflow rate is zero. The target ventilation flow rate d_vent is then only defined by the generated airflow rate. In order to implement the target ventilation flow rate d_vent, the control means 9 must actuate the motor-fan unit 62 and open the flaps of the flap assembly 63.

[0078] When the vehicle 1 is moving, the longitudinal speed of the vehicle 1 is non-zero and the flow of outside air circulating naturally in the front compartment participates in the dilution of the dihydrogen. The determination of the control strategy of the motor-fan unit 62 and / or of the set of movable flaps 63 then comprises a sub-step E042 of comparing the flow rate of the outside air flow with the target ventilation flow rate d_vent.

[0079] When the outside air flow rate is greater than or equal to the value of the target ventilation flow rate d_vent, in particular due to the longitudinal speed of the vehicle 1, the flaps of the flap assembly 63 are controlled to the minimum opening degree necessary to achieve the target ventilation flow rate d_vent and the motor-fan unit 62 remains off. The motor-fan unit 62 is then not necessary, the dilution of the hydrogen in the front compartment being able to be ensured by the sole movement of the vehicle 1 and the control of the flap assembly 63. The aerodynamic and energy performance of the vehicle 1 is then optimized.

[0080] When the outside air flow rate is strictly lower than the target ventilation flow rate value d_vent, the control strategy provides, for example, increasing the opening of the flaps of the flap assembly 63 and, if necessary, activating the motor-fan unit 62 in order to increase the generated air flow rate to reach the target ventilation flow rate value d_vent. The motor-fan unit 62 is controlled so as to implement the minimum rotation speed required to reach the target ventilation flow rate so as to optimize the energy performance of the vehicle 1.

[0081] Optionally, as illustrated in Figure 3, the determination of a control strategy E04 of the motor-fan unit 62 and / or of the set of movable flaps 63 is configured so as to take into consideration a control instruction intended for the thermal management of at least one element to be thermally treated of the vehicle 1, in particular a control instruction of the at least one thermal module 6. For example, the processing unit 7 implements a sub-step of determining E043 a forecast control instruction intended for the potential dilution of dihydrogen released in the event of a leak as described previously and a sub-step of receiving or determining E044 a forecast control instruction intended for the thermal management of the at least one element to be thermally treated. Each of these instructions is defined by a degree of opening of the flaps of the set of flaps 63 and / or a rotation speed of the motor-fan unit 62.

[0082] The processing unit 7 then executes a sub-step E045 of comparing the opening degree values ​​of the flaps of the set of flaps 63 and / or the rotation speed values ​​of the motor-fan unit 62 specific to each of the instructions. The ventilation strategy to be applied is then the forecast instruction having the highest opening degree and rotation speed values ​​or a combination of the different instructions aimed at applying the highest opening degree and rotation speed values ​​taken from said instructions.

[0083] In this way, the security system 2 according to the invention can use components already embedded in the vehicle 1, in particular at least one thermal module 6, conventionally associated with the thermal management of at least one element to be thermally treated equipping the vehicle 1, without however hindering the proper functioning of the thermal management of the vehicle 1. It should be noted that the invention, described in the context of a vehicle comprising a thermal module 6, also extends to a vehicle comprising a plurality of thermal modules 6.

[0084] Optionally, the securing method 100 comprises a step E06 of verifying the control strategy. Such a verification comprises a sub-step E061 of measuring an effective ventilation flow rate d_eff circulating in the front compartment corresponding to the ventilation flow rate actually implemented following the application of a control strategy previously determined during an execution of the method according to the invention at a previous time tx. The verification of the control strategy then comprises a sub-step E062 of adjusting the control strategy of the motor-fan unit 62 and / or the set of movable flaps 63 when it is detected that the measured effective ventilation flow rate d_eff differs from the determined target ventilation flow rate d_vent. In particular, such an adjustment is carried out in real time. Such a principle aims to refine the control of the motor-fan unit 62 and the set of flaps 63.In particular, the verification step E06 is executed in a closed loop, simultaneously with the determination of the control strategy E04 at a time t. Also, such a verification can be accompanied by learning the adjustment of the control strategy.

[0085] According to an optional but preferred exemplary embodiment, the method comprises a step of detecting a state E07, closed or open, of the regulating means 5 and comprises the interruption E071 of the method when it is detected that the regulating means 5 is in the closed state. In particular, the interruption of the process is carried out prior to the pressure measurement E01. In this way, the method is only executed when the dihydrogen is distributed to the drive chain 3, that is to say when the risk of leakage is present.

[0086] The invention thus proposes a method and a system for securing a vehicle comprising a drive chain supplied with dihydrogen making it possible to ensure, at all times, a sufficient ventilation level to dilute dihydrogen below a safety threshold, in particular below the lower explosive limit, in the areas of the vehicle where dihydrogen is present and likely to accumulate in the event of a leak. The invention is capable of continuously ensuring the safety of the vehicle regardless of the detection of a leak, which advantageously makes it possible to protect users in the event of small leaks, conventionally detected later, by limiting the accumulation of dihydrogen. The invention is particularly advantageous in the case of vehicles using high-pressure dihydrogen as an energy source or fuel.

[0087] Furthermore, the invention is inexpensive, using components already embedded in the vehicle, conventionally associated with the thermal management of at least one element of the vehicle.

[0088] The present invention cannot, however, be limited to the means and configurations described and illustrated here and it also extends to any equivalent means or configuration and to any technically operative combination of such means insofar as they ultimately fulfill the functionalities described and illustrated in the present document.

Claims

CLAIMS 1. Method for securing (100) a motor vehicle (1) comprising a drive chain (3) at least partly supplied with dihydrogen, a dihydrogen circuit (4) and at least one motor-fan unit (62) and / or a set of controlled movable flaps (63), the method comprising: - measuring a pressure (E01) in the hydrogen circuit (4) via at least one pressure sensor (8); - the estimation (E02) of a mass flow rate (d_mas) and / or a volume flow rate (d_vol) of dihydrogen likely to be released, at atmospheric pressure, for at least one leak of predefined diameter located in the circuit (4), as a function of the measured pressure; - the determination (E03) of a required target ventilation flow rate (d_vent), corresponding to a forecast air flow rate necessary to reduce a concentration of dihydrogen in the air to a value less than or equal to a predefined safety threshold (S_sec) based on the estimated mass flow rate (d_mas) and / or volume flow rate (d_vol) of dihydrogen likely to be released; - the determination (E04) of a strategy for controlling the motor-fan unit (62) and / or the set of flaps (63) so as to implement the determined target ventilation flow rate (d_vent); - the application of the strategy (E05) determined by controlling the motor-fan unit (62) and / or the set of flaps (63) by means of a control means (9), in particular a calculator of a thermal module (6) comprising the motor-fan unit (62) and / or the set of flaps (63).

2. Method for securing (100) a motor vehicle (1) according to the preceding claim in which: - the dihydrogen circuit (4) is a high pressure circuit configured to receive dihydrogen at a pressure greater than or equal to 20 bar, or even 50 bar or even 100 bar; and / or - the estimation of the mass flow rate (d_mas) and / or the volume flow rate (d_vol) of dihydrogen likely to be released is carried out for a leak of a given diameter, in particular a diameter greater than or equal to 0.1 mm.

3. Method for securing (100) a motor vehicle (1) according to one of the preceding claims, in which the safety threshold (S_sec) is selected from a plurality of safety thresholds (S_sec) corresponding to different percentages of the lower explosive limit of dihydrogen, in particular corresponding to 25%, 50% 70% and / or 75% of the lower explosive limit of dihydrogen.

4. Method for securing (100) a motor vehicle (1) according to one of the preceding claims, in which the determination (E03) of the target ventilation flow rate (d_vent) comprises a sub-step of determining (E031) a plurality of target ventilation flow rates (d_vent), each defined by a safety threshold (S_sec) and / or a leak diameter specific to it, and a sub-step of selecting (E032) one of the target ventilation flow rates (d_vent) as a function of at least one criterion selected from the pressure measured in the circuit (4), a safety margin compensating for an inaccuracy in calculating the mass flow rate (d_mas) and / or the volume flow rate (d_vol) of dihydrogen likely to be released, the energy consumption of the vehicle (1) and / or the comfort of a user.

5. Method for securing (100) a motor vehicle (1) according to one of the preceding claims, in which the determination (E04) of a strategy for controlling the motor-fan unit (62) and / or the set of flaps (63) comprises the determination (E041) of the flow rate of an external air flow circulating naturally through the motor-fan unit (62) and / or the set of flaps (63): - determining the flow rate of the outside air flow taking into account a useful surface area of ​​a heat exchanger (61) included in the thermal module comprising the motor-fan unit and / or the set of shutters; and / or - the vehicle (1) comprising a means for measuring and / or estimating a longitudinal speed of the vehicle (1) and determining the flow rate of the exterior air flow taking into account a measured or estimated longitudinal speed of the vehicle (1). 6.Method for securing (100) a motor vehicle (1) according to one of the preceding claims, in which the determination of a strategy (E04) for controlling the motor-fan unit (62) and / or the set of movable flaps (63) comprises the determination of a forecast control instruction (E043) intended for the potential dilution of dihydrogen released in the event of a leak and the reception of a forecast control instruction (E044) intended for the thermal management of at least one element to be thermally treated, each of said instructions defining at least one degree of opening of the set of controlled flaps (63) and / or a rotation speed of the powertrain, the ventilation strategy to be applied being the forecast instruction having the highest values ​​of degree of opening and / or rotation speed or a combination of the different instructions aimed at applying the highest values ​​of degree of opening and rotation speed.

7. Method for securing (100) a motor vehicle (1) according to one of the preceding claims, in which the vehicle (1) comprises at least one means (5) for regulating the circulation of dihydrogen in the circuit (4), such as a valve or solenoid valve, the method comprising the detection (E07) of a state, closed or open, of said regulating means (5) and the interruption (E071) of the method when it is detected that the regulating means (5) is in the closed state.

8. Method for securing (100) a motor vehicle (1) according to one of the preceding claims, in which the vehicle (1) comprises a measuring or estimating member configured to measure or estimate an effective ventilation flow rate (d_eff) circulating in a front compartment of the vehicle (1), the method comprising the verification (E06) and the adjustment (E062) in real time of the control when it is detected that the effective ventilation flow rate (d_eff) differs from the target ventilation flow rate (d_vent).

9. Safety system (2) for a motor vehicle (1) comprising a drive chain (3) at least partly configured to be supplied with dihydrogen, the safety system (2) comprising hardware and / or software elements configured to implement the method according to one of the preceding claims, the hardware elements comprising at least one processing unit (7), at least one pressure sensor (8) and a means (9) for controlling a motor-fan unit (62) and / or a set of controlled flaps (63) of the vehicle (1), in particular a computer of a thermal module comprising the motor-fan unit and / or the set of flaps.

10. Vehicle (1) motor vehicle comprising: - a drive chain (3) configured to be at least partly supplied with dihydrogen; - a circuit (4) configured to allow the circulation of dihydrogen; - a motor-fan unit (62) and / or a set of controlled shutters (63); and - a security system (2) according to the preceding claim.

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