DEVICE AND METHOD FOR FLUSHING A GAS FLOW LOADED WITH HYDROGEN VAPOR

Description

[Domaine technique]

[0001] The invention relates to the treatment of hydrocarbon vapors in a motor vehicle, and more particularly to a device for purging hydrocarbon vapors in a motor vehicle's internal combustion engine. The invention is especially applicable to hybrid vehicles and vehicles with purely internal combustion engines. Throughout this text, the term "fuel" advantageously refers to at least one hydrocarbon. [Etat de la technique antérieure]

[0002] In a motor vehicle with an internal combustion engine, the fuel stored in the tank requires venting to both release the fuel vapors and allow air into the tank as the fuel level drops. It is therefore necessary to regulate the pressure of the gases inside the tank to prevent significant pressure fluctuations that could cause both material damage and personal injury. One known solution is to create an exhaust vent in the tank's filler cap to expel these hydrocarbon vapors directly from the vehicle while allowing air into the tank to equalize the pressure. However, such a release of hydrocarbon vapors into the atmosphere has the major drawback of causing significant environmental pollution.However, such discharges are becoming less and less desirable and possible today in view of the various legislations which are becoming increasingly restrictive in this area and some of which require drastically limiting the emissions of hydrocarbon vapors into the atmosphere.

[0003] Other purging devices and methods are known from DE 10 2017 210768 A1, DE 10 2017 223277 A1, WO 2018 / 162038 A1 or DE 10 2018 220403 A1 for example.

[0004] Therefore, to limit pollution, it is now common practice to install a filtering device in the vehicle's fuel intake system. Such a device is connected, on one side, to the fuel tank and, on the other, to the outside of the vehicle. In a known solution, this device includes a carbon degassing filter, hereafter referred to as an "absorbent filter" (commonly called a "canister" by those skilled in the art), which absorbs hydrocarbon vapors from the tank so that the fuel emissions released into the atmosphere by the exhaust system are in the form of a gas significantly purified of the polluting components contained in the hydrocarbon vapors.

[0005] However, such an absorbent filter has a limited absorption capacity, called the maximum filter load. At this point, the absorbent filter is said to be "full" or "filled," or to be saturated. In this case, the filter can no longer retain hydrocarbon vapors, which then escape into the atmosphere. More generally, whether the absorbent filter is saturated or not, it is characterized at any given moment by its load, which corresponds to the percentage of fuel mass stored in the filter relative to its saturation value, that is, relative to its maximum load.

[0006] To limit harmful fuel emissions into the atmosphere when the filter is saturated, it is necessary to purge it regularly, ideally before it becomes saturated with hydrocarbon vapors. To achieve this, the system is connected to the vehicle's internal combustion engine in such a way that the hydrocarbon vapors absorbed by the filter are injected directly into the combustion chambers of the engine cylinders while the engine is running, where they are burned. In other words, the absorbent filter is regularly charged with hydrocarbon vapors from the fuel tank, and then the engine control unit periodically discharges this vapor into the combustion chambers of the engine cylinders while the engine is running.

[0007] The transfer of hydrocarbon vapors from the filter to the internal combustion engine is carried out through a purge circuit via a purge valve, which allows for the evacuation of this circuit. However, with the advent of hybrid vehicle technologies, purging hydrocarbon vapors from the filter is becoming increasingly difficult because evacuating the purge circuit is more challenging in a hybrid vehicle. Indeed, in a hybrid vehicle, the internal combustion engine is primarily used at the required high engine speeds. At high engine speeds, the air intake throttle is open, which reduces the vacuum in the purge circuit. Furthermore, due to this operating mode, there are fewer and fewer moments when the internal combustion engine is running to perform the purge, which can lead to hydrocarbon vapor releases into the atmosphere, as the filter is more frequently saturated without the possibility of purging.

[0008] A known solution to this problem involves using a radial pump, called an active purge pump, between the filter and the engine to circulate hydrocarbon vapors through the purge circuit to the engine. This requires compensating the amount of hydrocarbon vapors introduced into the engine cylinders with a corresponding volume of air to maintain the stoichiometric air-fuel ratio necessary for proper combustion of the mixture in the internal combustion engine.

[0009] In an existing solution, it is known to estimate the concentration of hydrocarbon vapor in the gas flow circulating between the filter and the engine and to control the introduction of said flow into the engine cylinders in the proportion corresponding to the stoichiometric ratio as a function of said concentration.

[0010] Naturally, any error in flow control results in a deviation from the stoichiometric ratio, leading to a variation in the hydrocarbon vapor concentration of the absorbing filter. This, in turn, impacts the real-time estimation of said hydrocarbon vapor concentration. Thus, the estimated hydrocarbon vapor concentration can vary between 0 and 200%, while in practice, the actual hydrocarbon vapor concentration cannot exceed 80%. Consequently, the flow control is flawed and deviates as soon as any control error occurs. The system remains relatively stable, however, because the control is performed in a closed loop via an oxygen sensor (called a lambda sensor) located in the engine's exhaust gas circuit. Nevertheless, such control proves slow compared to the rapid injection frequency. It is therefore crucial to be able to accurately estimate the hydrocarbon vapor concentration.

[0011] The hydrocarbon vapor concentration can be estimated from the pressure difference at the inlet and outlet of the active purge pump. This pressure difference depends on the pump's rotational speed and the density of the gases flowing through it. Since the pump's rotational speed is determined by the required purge flow rate that the engine can absorb, it can vary very rapidly, for example, from 10,000 to 60,000 rpm in 1 second and from 60,000 to 10,000 rpm in 2 seconds. This change in speed implies a change in the operating point, modifying both the pressure and the temperature, and therefore the gas density due to the adiabatic compression of the radial pump. This density is also a function of the ambient pressure (i.e., the atmospheric air pressure entering the absorption filter), the temperature of the gas flow, and the hydrocarbon vapor concentration.Thus, it is necessary to know precisely the values ​​of the ambient pressure and the temperature of the gas flow in order to determine, from the pressure difference and therefore the density, the concentration of hydrocarbon vapors in order to correct the injection parameters as quickly and accurately as possible, such an injection correction being applied for example every 20 ms.

[0012] Ambient pressure is measured using a pressure sensor mounted on the purge circuit or supplied by another sensor connected to the engine control unit, for example, near the active purge pump. In existing solutions, temperature is measured using a sensor placed before or after the active purge pump and employing a passive NTC (Negative Temperature Coefficient) temperature sensor. However, with this technology, the temperature measurement response time depends on the gas flow velocity, which varies, for example, between 0 and 80 l / min, and can therefore be particularly long. For example, the response time can be around 25 seconds when the flow velocity is zero and around 5 seconds when the flow velocity is 80 l / min. Other temperature sensors, such as thermocouples, can be used.However, the response time of these sensors depends on their intrinsic technology, the cost of which increases inversely with their response time. Therefore, fast-response thermocouple sensors are used in laboratories and are too expensive for use in mass-produced vehicles. In any case, the response times of low-cost temperature sensors used in the automotive industry are too long to allow for accurate, real-time estimation of hydrocarbon vapor concentration and precise, rapid control of the gas flow entering the engine cylinders. It is therefore advantageous to offer a solution that at least partially addresses these drawbacks. [Exposé de l'invention]

[0013] One of the aims of the invention is to accurately and quickly estimate the temperature of the gas flow circulating in the purge circuit. Another aim of the invention is to accurately measure the fuel vapor concentration of the gas flow circulating in the purge circuit. A further aim of the invention is to precisely control the flow rate of the purged gas entering the engine cylinders.

[0014] To this end, the invention first relates to a device for purging vapors from fuel stored in a tank of a hybrid or internal combustion motor vehicle, said vehicle comprising an internal combustion engine and a fuel storage tank intended to be burned in said engine, said device comprising: an absorbent filter capable of filtering the vapors generated by the fuel stored in said tank in the form of hydrocarbons, a so-called "purge" circuit connected to the absorbent filter and intended to be connected to the engine and comprising: o a pump, preferably radial (or centrifugal), capable of allowing the circulation of a gas flow containing hydrocarbon vapors from the absorbent filter to the engine, o an "upstream" pressure sensor located upstream of the pump, o a "downstream" pressure sensor located downstream of the pump, o at least one temperature sensor configured to measure the temperature of the gas flow, preferably located at least upstream of the pump, o a purge valve configured to switch between an open position, in which said purge valve allows the circulation of the gas flow from the absorbent filter to the engine, and a closed position in which the absorbent filter is isolated from the engine, a control module configured to,In a purge mode: ∘ receive measurements from the upstream pressure sensor and the downstream pressure sensor, o calculate the pressure difference of the gas flow between the pump inlet and outlet from the received upstream and downstream pressure measurements, ∘ receive temperature measurements from the temperature sensor, the pump rotation speed and the internal temperature of the pump, ∘ determine the mass flow rate of the gas flow from the received pump rotation speed, o determine the contribution of adiabatic compression of the gas flow to the temperature of said gas flow from the calculated pressure difference and the received temperature measurement of the gas flow, o determine the contribution of convection of the gas flow to the temperature of said gas flow from the received temperature measurement of the gas flow and the received internal temperature measurement of the pump,o Determine the contribution of flow conduction to the gas flow temperature from the determined gas flow mass flow rate, the received gas flow temperature, and the received pump internal temperature measurement; o Estimate the temperature of the gas flow circulating in the purge circuit from the determined adiabatic compression, convection, and conduction contributions; o Calculate the fuel vapor concentration of the flow from the estimated temperature, received pressure measurements, and the received pump rotation speed; o Control the purge valve to regulate the flow rate entering the engine cylinders according to the calculated concentration, respecting the stoichiometric ratio of the air-fuel mixture combustion for said cylinders.

[0015] The use of adiabatic compression, convection and conduction contributions advantageously allows reliable, fast and precise control of the gas flow rate in the engine cylinders in order to respect the stoichiometric ratio of the engine, without depending on the latency of the sensors.

[0016] According to the invention, the contribution of the adiabatic compression of the gas flow to the temperature of said gas flow T Flow _ Adb is determined according to the following equation: T Flow _ Adb = T Inlet ∗ P Flow P Inlet γ − 1 γ Or T Inlet is the temperature of the gas flow received from the flow temperature sensor upstream of the pump, P Flow is the gas flow pressure received from the downstream pressure sensor, P Inlet is the gas flow pressure measured by the upstream pressure sensor, and γ is the ideal gas constant. Considering γ constant over the temperature and pressure range considered, the contribution of gas flow convection to the temperature of said gas flow, from the received gas flow temperature measurement and the received pump internal temperature measurement, is determined according to the following equation: Δ T Flow _ Conv = HeatFac Conv ∗ T Body − T Inlet Or HeatFac Conv represents the exchange of heat by convection and radiation between the pump material and the gas flow, T Body is the temperature of the pump body, which corresponds to the internal temperature of the pump and T Inlet is the temperature of the gas flow measured by the flow temperature sensor, and the contribution of conduction (or absorption) of the flow to the temperature of the gas flow from the determined mass flow rate of the gas flow, the temperature of the received gas flow and the measurement of the internal temperature of the received pump is determined according to the following equation: Δ T Flow _ Cond = Q ˙ flow ∗ HeatFac Cond ∗ T Body − T Inlet Or Q̇ flow is the mass flow rate of the gas flow through the pump (in kg / h), HeatFac Cond heat exchange by conduction between the pump material and the gas flow, T Body is the internal temperature of the pump and T Inlet is the temperature of the gas flow measured by the flow temperature sensor, and in which the control module then calculates an estimate of the temperature of the gas flow circulating in the purge circuit from the adiabatic compression, convection and conduction contributions determined according to the following equation: T Flow = T Flow _ Adb + Δ T Flow _ Conv + Δ T Flow _ Cond

[0017] According to one aspect of the invention, the control module is configured to calculate the fuel vapor concentration of the flow from the estimated temperature according to the following equation: HC _ vol gas = ρ gas − ρ air ρ but − ρ air where ρ gas is the density of the gas in the pump, ρ air is the density of the air at the pressure and temperature in the pump and ρ but is the density of the butane at the pressure and temperature in the pump.

[0018] Advantageously, the radial pump is an electric pump.

[0019] Even more advantageously, the temperature sensor is placed at the inlet and / or outlet of the pump.

[0020] Preferably, the control module is configured to determine a time when hydrocarbon vapor purging is complete, to close the purge valve, and to control the pump so that it operates, in a so-called "non-purge" mode, at a predetermined minimum speed. Indeed, in the absence of a purge phase (i.e., no flow), if the turbine continues to rotate at very high speed, for example, 60,000 rpm, the airflow over the pump blades becomes unstable, generating significant stresses on the shaft and the turbine. If this operating mode is prolonged, it leads to premature pump aging. Therefore, the pump's rotational speed must be reduced to eliminate these instabilities.If the temperature sensor is located far from the pump outlet, for example, more than 10 cm away, heat will not propagate to the sensor, or will propagate very slowly, because there is no flow, resulting in a very long sensor response time, for example, more than 30 seconds. In this case, the temperature inside the pump cannot be calculated from the temperature information provided by the sensor located downstream of the pump. A model must be used instead of the sensor value. In this case, the temperature at the pump outlet will be equivalent to the temperature due to adiabatic compression. If the temperature sensor is located close to the pump outlet, for example, less than 10 cm away, the heat generated by the pump will propagate to the sensor, and the sensor temperature value can be used instead of the model value.Furthermore, since there is no flow, the heat generated by the pump is pushed back to the pump inlet. Consequently, the temperature across the pump is almost uniform, and the inlet temperature is then equal to the adiabatic contribution temperature.

[0021] The invention also relates to a motor vehicle comprising a device as previously described, a heat engine comprising at least one cylinder and a fuel storage tank intended to be burned in said at least one cylinder of the engine.

[0022] The invention also relates to a method for controlling the flow rate of a gas circulating in a purge device as described above, said method, implemented by the control module of said purge device, comprising the steps of: receiving at least one measurement of the flow pressure upstream of the pump, receiving at least one measurement of the flow pressure downstream of the pump, calculating the pressure difference of the flow between the inlet and outlet of the pump, receiving at least one temperature measurement from the flow temperature sensor, receiving at least one measurement of the pump rotational speed and the internal temperature of the pump, determining the mass flow rate of the gas flow from the received pump rotational speed, determining the contribution of the adiabatic compression of the gas flow to the temperature of said gas flow from the calculated pressure difference and the received temperature measurement of the gas flow, determining the contribution of the convection of the gas flow to the temperature of said gas flow from the received temperature measurement of the gas flow and the received internal temperature measurement of the pump,Determination of the contribution of flow conduction to the gas flow temperature from the determined gas flow mass flow rate, the received gas flow temperature, and the internal temperature measurement of the received pump; estimation of the temperature of the gas flow circulating in the purge circuit from the determined adiabatic compression, convection, and conduction contributions; calculation of the fuel vapor concentration of the flow from the estimated temperature; control of the purge valve to regulate the flow rate entering the engine cylinders according to the calculated concentration, respecting the stoichiometric ratio of the combustion of the air-fuel mixture for said cylinders.

[0023] According to the invention, the contribution of the adiabatic compression of the gas flow to the temperature of said gas flow T Flow _ Adb is determined according to the following equation: T Flow _ Adb = T Inlet ∗ P Flow P Inlet γ − 1 γ Or T Inlet is the temperature of the gas flow received from the flow temperature sensor, P Flow is the gas flow pressure received from the downstream pressure sensor, P Inlet is the gas flow pressure measured by the upstream pressure sensor, and γ is the ideal gas constant, considering γ to be constant over the temperature and pressure range considered. The contribution of gas flow convection to the temperature of said gas flow, based on the temperature measurement of the received gas flow and the internal temperature measurement of the received pump, is determined according to the following equation: Δ T Flow _ Conv = HeatFac Conv ∗ T Body − T Inlet Or HeatFac Conv represents the exchange of heat by convection and radiation between the pump material and the gas flow, T Body is the internal temperature of the pump and T Inlet is the temperature of the gas flow measured by the flow temperature sensor and the contribution of the conduction of the flow to the temperature of the gas flow from the determined mass flow rate of the gas flow, the temperature of the received gas flow and the measurement of the internal temperature of the received pump is determined according to the following equation: Δ T Flow _ Cond = Q ˙ flow ∗ HeatFac Cond ∗ T Body − T Inlet Or Q̇ flow is the mass flow rate of the gas flowing through the pump, HeatFac Cond heat exchange by conduction between the pump material and the gas flow, T Body is the internal temperature of the pump and T Inlet is the temperature of the gas flow measured by the flow temperature sensor, and in which the control module then calculates an estimate of the temperature of the gas flow circulating in the purge circuit from the adiabatic compression, convection and conduction contributions determined according to the following equation: T Flow = T Flow _ Adb + Δ T Flow _ Conv + Δ T Flow _ Cond

[0024] Advantageously, the calculation of the fuel vapor concentration of the flow from the estimated temperature is carried out according to the following equation: HC _ vol gas = ρ gas − ρ air ρ but − ρ air where ρ gas is the density of the gas in the pump, ρ air is the density of the air at the pressure and temperature in the pump and ρ but is the density of the butane at the pressure and temperature in the pump.

[0025] According to one aspect of the invention, the method further comprises the steps, implemented by the control module, of determining an end time for purging hydrocarbon vapors, closing the purge valve and controlling the pump so that said pump operates, in a so-called "non-purge" mode, at a predetermined minimum speed.

[0026] The invention also relates to a computer program product characterized in that it comprises a set of program code instructions which, when executed by one or more processors, configure the processor(s) to implement a process as previously described. [Description des dessins]

[0027] Other features and advantages of the invention will become apparent upon reading the following description. This description is purely illustrative and should be read in conjunction with the accompanying drawings, in which: [ Fig. 1 ] There figure 1 schematically illustrates one embodiment of the vehicle according to the invention. Fig. 2 ] There figure 2 schematically illustrates one embodiment of the process according to the invention. [Description des modes de réalisation]

[0028] The device according to the invention is intended to be mounted in a vehicle and allows both the evaporation of vapors from the fuel stored in the tank of a hybrid or thermal motor vehicle and the purging of hydrocarbon vapors generated by said fuel by combustion in the engine.

[0029] We represented at the figure 1 such a vehicle 1. The vehicle 1 comprises a device 10 according to the invention, a thermal engine 20 and a tank 30 for storing a fuel intended to be burned in said engine 20. The engine comprises in a known manner cylinders (not shown) allowing the fuel and air to be mixed in order to allow combustion.

[0030] The device 10 includes an absorbent filter 110, a so-called "purge" circuit 120 and a control module 130.

[0031] The absorbent filter 110 filters the vapors generated by the fuel stored in the tank 20 in the form of hydrocarbons. For this purpose, the absorbent filter 110 is connected to the tank 30 via a conduit 31.

[0032] The absorbent filter 110 is connected to the outside of the vehicle (atmospheric air) by a conduit 111 in which an air valve 112 is mounted. The air valve 112 is configured to switch between an open position, in which the air valve 112 allows the exhaust of the gases filtered by the absorbent filter 110 to the outside, and a closed position in which the device 10 is isolated from the outside of the vehicle 1. The air valve 112 is optional and can be used for leak detection.

[0033] The absorbent filter 110 is also connected to the engine cylinders 20 via the purge circuit 120.

[0034] The purge circuit 120 connects the absorbent filter 110 to the engine cylinders 20 of vehicle 1 and includes a radial (or centrifugal) pump 121, an upstream pressure sensor 122, a downstream pressure sensor 123, a flow temperature sensor 124 and a purge valve 125.

[0035] The radial pump 121, which is preferably an electric pump, is suitable for circulating a flow of gas containing hydrocarbon vapors in the purge circuit 120, from the absorbent filter 110 to the motor 20. The pump 121 is also suitable for measuring its rotational speed and internal temperature, in particular to prevent overheating of its electric motor and electronics, and for sending these measurements to the control module.

[0036] The upstream pressure sensor 122 is mounted upstream of the pump 121 and is capable of measuring the pressure of the gas flow circulating between the absorbent filter 110 and the pump 121.

[0037] The downstream pressure sensor 123 is mounted downstream of the pump 121 and is suitable for measuring the pressure of the gas flow circulating between the pump 121 and the purge valve 125. Preferably, the downstream pressure sensor 123 uses a pressure model based on the air intake into the engine after the air filter to determine and provide the temperature of the gas flow at said downstream pressure sensor 123.

[0038] The flow temperature sensor 124 is mounted in this example upstream of the pump 121 and is configured to measure the temperature of the gas flow circulating between the absorbent filter 110 and the pump 121. In another embodiment, the flow temperature sensor 124 could be mounted downstream of the pump 121. In another embodiment, the device 10 could include two temperature sensors: one downstream and one upstream of the pump 121 to improve the accuracy of the temperature model.

[0039] The purge valve 125 is configured to switch between an open position, in which said purge valve 125 allows the flow of gas from the absorbent filter 110 to the engine 20, and a closed position in which the absorbent filter 110 is isolated from the engine 20. The purge valve 125 is capable of being controlled by the control module 130 in opening or closing, including in several open positions in order to allow the injection of the gas flow from the absorbent filter 110 into the cylinders at different flow rates.

[0040] The control module 130 is configured to control the pump 121, specifically the operating regime of said pump 121.

[0041] The control module 130 is configured to receive measurements from the upstream pressure sensor 122 and the downstream pressure sensor 123.

[0042] The control module 130 is configured to calculate the pressure difference of the gas flow between the inlet and outlet of the pump 121 from the upstream and downstream pressure measurements received from the upstream pressure sensor 122 and the downstream pressure sensor 123.

[0043] The control module 130 is configured to receive temperature measurements from the flow temperature sensor 124.

[0044] The control module 130 is configured to periodically determine, preferably at a high frequency (i.e. continuously), the mass flow rate of the gas flow through the purge valve 125 and the pump 121. Since the gas flow through the pump 121 is the same as the gas flow through the purge valve 125, the mass flow rate of the gas flow can be determined from a predefined model using as inputs the pressure of the gas flow measured by the downstream pressure sensor 123, the temperature of the gas flow at the inlet of the purge valve 125, the temperature of the gas flow at the outlet of the purge valve 125 and the opening position of the purge valve 125.To this end, temperature sensors (not shown) can be positioned on either side of the purge valve 125, or the temperature information can be derived from an independent model based on the electrical characteristics of the purge valve 125, or from the temperature information that can also be provided by the pressure sensor 123, or from a model using the downstream temperature model of the pump 121, which is known per se. Preferably, these last three pieces of information are combined to improve accuracy depending on the operating modes. The opening position information of the purge valve 125 can be received from the purge valve itself or determined by the control module 130, for example, using a model based on the opening command of the purge valve 125, taking into account the opening and closing times of the purge valve 125, such a model being known per se.

[0045] The control module 130 is configured to receive internal temperature measurements of the pump 121 of vehicle 1, for example via a CAN type data communication bus.

[0046] The control module 130 is configured to determine the contribution of the adiabatic compression of the gas flow to the temperature of said gas flow from the calculated pressure difference and the temperature measurement of the received gas flow.

[0047] The control module 130 is configured to determine the contribution of gas flow convection to the temperature of said gas flow from the temperature measurement of the received gas flow and the internal temperature measurement of the pump 121.

[0048] The control module 130 is configured to determine the contribution of the conduction of the flow to the temperature of the gas flow from the determined mass flow rate of the gas flow, the temperature of the received gas flow and the internal temperature measurement of the pump 121.

[0049] The control module 130 is configured to estimate the temperature of the gas flow circulating in the purge circuit 120 from the determined adiabatic compression, convection and conduction contributions.

[0050] The 130 control module is configured to calculate the fuel vapor concentration of the flow from the estimated temperature.

[0051] The control module 130 is configured to, in a so-called "purge" mode, control the purge valve 125 in order to control the flow rate entering the engine cylinders 20 according to the calculated concentration while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

[0052] The control module 130 includes a processor capable of implementing a set of instructions to perform these functions. Implementation

[0053] As a prerequisite, it is assumed that the device initially operates in non-purge mode. When the control module determines that it is necessary to purge the absorbent filter (purge mode), the control module 130 commands the pump 121 to operate at a predetermined speed, for example minimum, and opens the purge valve 125.

[0054] When the gas flow laden with hydrocarbon vapors circulates from the absorbent filter 110 towards the motor 20 through the purge circuit 120, the upstream pressure sensor 122 and the downstream pressure sensor 123 periodically measure the gas flow pressure and send their measurements to the control module 130 (steps E1 and E2, respectively). The control module 130 then calculates the pressure difference of the flow between the inlet and outlet of the pump 121 from the current pressure values ​​received from the upstream pressure sensor 122 and the downstream pressure sensor 123 (step E3).

[0055] Simultaneously, the flow temperature sensor 124 also periodically measures the temperature of the gas flow and sends its measurements to the control module 130 (step E4).

[0056] In parallel, the control module 130 also receives in a step E5 the rotation speed of the pump 121 and the internal temperature of the pump 121, sent directly by the pump 121, for example via a data communication bus of the vehicle 1.

[0057] The control module 130 then determines the mass flow rate of the gas flow based on the rotational speed of the pump 121 and the pressure and temperature values ​​on either side of the purge valve 125 (step E6). The pump's rotational speed characterizes the cross-sectional area of ​​the air passage through the purge valve 125, which is used to calculate the mass flow rate using a known-perceived method. The pressure and temperature values ​​on either side of the purge valve 125 can be established from a predefined model stored in a memory area of ​​the control module 130. This model is in the form of a table with ambient atmospheric pressure and the air flow rate entering the engine as inputs.

[0058] The control module 130 then determines: the contribution of the adiabatic compression of the gas flow to the temperature of said gas flow from the calculated pressure difference and the temperature measurement of the received gas flow (step E7), the contribution of the convection of the gas flow to the temperature of said gas flow from the temperature measurement of the received gas flow and the internal temperature measurement of the received pump 121 (step E8), the contribution of the conduction of the flow to the temperature of the gas flow from the mass flow rate of the gas flow, the temperature of the received gas flow and the internal temperature measurement of the received pump (step E9).

[0059] In theory, the calculations require the temperature of the pump body 121 rather than its internal temperature. Pump 121 includes an internal sensor for measuring the internal temperature, but not the temperature of the pump body 121. However, the internal temperature of pump 121 and the temperature of the pump body 121 are not exactly the same, but their dynamics are similar. Therefore, the internal temperature of pump 121 is a good indicator of the temperature of the pump body 121.

[0060] The contribution of the adiabatic compression of the gas flow to the temperature of said gas flow TFlow_Adb is determined according to the following equation: T Flow _ Adb = T Inlet ∗ P Flow P Inlet γ − 1 γ where Tlnlet is the temperature of the gas flow received from the flow temperature sensor, PFlow is the pressure of the gas flow received from the downstream pressure sensor 123 and Plnlet is the pressure of the gas flow measured by the upstream pressure sensor 122 and gamma γ is the ideal gas constant which is between 1, 2 and 1.4 depending on the gases considered.

[0061] The contribution of gas flow convection to the temperature of said gas flow, based on the received gas flow temperature measurement and the received internal temperature measurement of pump 121, is determined according to the following equation: Δ T Flow _ Conv = HeatFac Conv ∗ T Body − T Inlet where HeatFacConv represents the heat exchange by convection and radiation between the pump material and the gas flow, TBody is the internal temperature of pump 121 and Tlnlet is the temperature of the gas flow measured by the flow temperature sensor 124.

[0062] The contribution of the conduction of the flow to the temperature of the gas flow, from the mass flow rate of the gas flow, the temperature of the received gas flow and the internal temperature measurement of the pump 121 received, is determined according to the following equation: Δ T Flow _ Cond = Q ˙ flow ∗ HeatFac Cond ∗ T Body − T Inlet Or Q̇ flow is the mass flow rate of the gas flow through the pump, HeatFacCond represents the heat exchange by conduction between the pump material 121 and the gas flow, TBody is the internal temperature of the pump 121 and Tlnlet is the temperature of the gas flow measured by the flow temperature sensor 124.

[0063] The control module 130 then calculates in a step E10 an estimate of the temperature of the gas flow circulating in the purge circuit 120 from the adiabatic compression, convection and conduction contributions determined according to the following equation: T Flow = T Flow _ Adb + Δ T Flow _ Conv + Δ T Flow _ Cond Once the temperature is estimated, the control module 130 calculates, in step E11, the fuel vapor concentration of the gas stream from the estimated temperature according to the following formula: HC _ vol gas = ρ gas − ρ air ρ but − ρ air where ρgas is the density of the gas in pump 121, ρair is the density of the air at the pressure and temperature in pump 121 and ρbut is the density of the butane at the pressure and temperature in pump 121.

[0064] Next, the control module 130 commands the purge valve 125 in a step E12 in order to control the flow rate entering the engine cylinders 20 according to the calculated concentration while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

[0065] This control can be carried out for example from a table stored in a memory area accessible to the control module 130 and in which are stored correspondences between the concentration of hydrocarbon vapor of the gas flow and the opening of the purge valve 125, these correspondences making it possible to respect the stoichiometric ratio of the engine 20.

[0066] When the control module 130 determines that the purge mode is complete (step E13), it closes the purge valve 125 (step E14) and commands the pump 121 (step E15) to prevent premature aging of the material(s) constituting the pump 121, for example by commanding the pump 121 at its minimum speed.

[0067] The invention therefore advantageously allows the flow rate of the gas in the cylinders of the engine 20 to be controlled in a simple, reliable and precise manner in order to respect the stoichiometric ratio of the engine 20.

Claims

1. Device (10) for purging the vapours of a fuel stored in a tank of a hybrid or combustion-engine motor vehicle (1), said vehicle (1) comprising a combustion engine (20) and a tank (10) for storing a fuel that is intended to be burned in said engine (20), said device comprising: - an absorbent filter (110), which can filter the vapours generated by the fuel stored in said tank (10) in the form of hydrocarbons; - a circuit (120) referred to as "purging" circuit, which is connected to the absorbent filter, intended to be connected to the engine (20) and comprises: o a pump (121), which can allow a stream of gas containing hydrocarbon vapours to circulate from the absorbent filter (110) towards the engine (20); o a pressure sensor (122) referred to as "upstream" pressure sensor and placed upstream of the pump (121); o a pressure sensor (123) referred to as "downstream" pressure sensor and placed downstream of the pump (121); o a stream temperature sensor (124) configured to measure the temperature of the stream of gas; o a purging valve (125) configured to switch between an open position, in which said purging valve allows the stream of gas to circulate from the absorbent filter (110) towards the engine (20), and a closed position in which the absorbent filter (110) is isolated from the engine (20); - a control module (130), which is configured, in a purging mode, to: o receive the measurements from the upstream pressure sensor (122) and from the downstream pressure sensor (123) ; o calculate the pressure difference of the stream of gas between the inlet and the outlet of the pump (121) based on the upstream and downstream pressure measurements received; o receive the temperature measurements from the stream temperature sensor (124), the speed of rotation of the pump (121), and the internal temperature of the pump (121) ; o determine the mass flow rate of the stream of gas based on the speed of rotation received for the pump (121) ; o determine the contribution of the adiabatic compression of the stream of gas to the temperature of said stream of gas TFlow_Adb, based on the pressure difference calculated and on the measurement received for the temperature of the stream of gas, and according to the following equation: T Flow _ Adb = T Inlet ∗ P Flow P Inlet γ − 1 γ where TInlet is the temperature of the stream of gas received from the stream temperature sensor, PFlow is the pressure of the stream of gas received from the downstream pressure sensor (123), PInlet is the pressure of the stream of gas measured by the upstream pressure sensor (122), and γ is the ideal gas constant; o determine the contribution of the convection of the stream of gas to the temperature of said stream of gas based on the measurement received for the temperature of the stream of gas and on the measurement received for the internal temperature of the pump (121), according to the following equation: Δ T Flow _ Conv = HeatFac Conv ∗ T Body − T Inlet where HeatFacConv represents the exchange of heat by convection and radiation between the material of the pump (121) and the stream of gas, TBody is the internal temperature of the pump (121), and TInlet is the temperature of the stream of gas measured by the stream temperature sensor (124); o determine the contribution of the conduction of the stream to the temperature of the stream of gas based on the mass flow rate determined for the stream of gas, on the temperature received for the stream of gas, and on the measurement received for the internal temperature of the pump (121), according to the following equation: Δ T Flow _ Cond = Q ˙ flow ∗ HeatFac Cond ∗ T Body − T Inlet where Q̇flow is the mass flow rate of the stream of gas passing through the pump (121), HeatFacCond is the exchange of heat by conduction between the material of the pump (121) and the stream of gas, TBody is the internal temperature of the pump (121), and TInlet is the temperature of the stream of gas measured by the stream temperature sensor (124); o estimate the temperature of the stream of gas circulating in the purging circuit based on the adiabatic compression, convection and conduction contributions determined, according to the following equation: T Flow = T Flow _ Adb + ΔT Flow _ Conv + Δ T Flow _ Cond o calculate the concentration of fuel vapours of the stream based on the temperature estimated, at the pressure measurements received, and at the speed of rotation received for the pump; o control the purging valve (125) in order to control the flow rate of the stream entering the cylinders of the engine (20) according to the concentration calculated, while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

2. Device (10) according to Claim 1, wherein the control module (130) is configured to determine a time of end of purging of the fuel vapours, to close the purging valve (125), and to control the pump (121) such that said pump (121) operates, in this mode referred to as "non-purging" mode, at a predetermined minimum rate.

3. Device (10) according to Claim 1 or 2, wherein the control module (130) is configured to calculate the concentration of fuel vapours of the stream based on the temperature estimated, according to the following equation: HC _ vol gas = ρ gas − ρ air ρ but − ρ air where ρgas is the density of the gas in the pump (121), ρair is the density of the air at the pressure and temperature in the pump (121), and ρbut is the density of the butane at the pressure and temperature in the pump (121) .

4. Motor vehicle (1) comprising a device (10) according to any one of Claims 1 to 3, a combustion engine (20) comprising at least one cylinder and a tank (30) for storing a fuel that is intended to be burned in said at least one cylinder of the engine (20).

5. Method for controlling the flow rate of a stream of gas circulating in a purging device (10) according to any one of Claims 1 to 3, said method, which is implemented by the control module (130) of said device, comprising the steps of: - receiving (E1) at least one measurement of the pressure of the stream upstream of the pump (121); - receiving (E2) at least one measurement of the pressure of the stream downstream of the pump (121); - calculating (E3) the pressure difference of the stream between the inlet and the outlet of the pump (121) ; - receiving (E4) at least one temperature measurement from the stream temperature sensor (124); - receiving (E5) at least one measurement of the speed of rotation of the pump (121) and of the internal temperature of the pump (121); - determining (E6) the mass flow rate of the stream of gas based on the speed of rotation received for the pump (121); - determining (E7) the contribution of the adiabatic compression of the stream of gas to the temperature of said stream of gas TFlow_Adb, based on the pressure difference calculated and on the measurement received for the temperature of the stream of gas, according to the following equation: T Flow _ Adb = T Inlet ∗ P Flow P Inlet γ − 1 γ where TInlet is the temperature of the stream of gas received from the stream temperature sensor, PFlow is the pressure of the stream of gas received from the downstream pressure sensor, PInlet is the pressure of the stream of gas measured by the upstream pressure sensor (122), and γ is the ideal gas constant; - determining (E8) the contribution of the convection of the stream of gas to the temperature of said stream of gas based on the measurement received for the temperature of the stream of gas and on the measurement received for the internal temperature of the pump, according to the following equation: Δ T Flow _ Conv = HeatFac Conv ∗ T Body − T Inlet where HeatFacConv represents the exchange of heat by convection and radiation between the material of the pump (121) and the stream of gas, TBody is the internal temperature of the pump (121), and TInlet is the temperature of the stream of gas measured by the stream temperature sensor (124); - determining (E9) the contribution of the conduction of the stream to the temperature of the stream of gas based on the mass flow rate determined for the stream of gas, on the temperature received for the stream of gas, and on the measurement received for the internal temperature of the pump, according to the following equation: Δ T Flow _ Cond = Q ˙ flow ∗ HeatFac Cond ∗ T Body − T Inlet where Q̇flow is the mass flow rate of the stream of gas passing through the pump (121), HeatFacCond is the exchange of heat by conduction between the material of the pump (121) and the stream of gas, TBody is the internal temperature of the pump (121), and TInlet is the temperature of the stream of gas measured by the stream temperature sensor (124); - estimating (E10) the temperature of the stream of gas circulating in the purging circuit based on the adiabatic compression, convection and conduction contributions determined, according to the following equation: T Flow = T Flow _ Adb + ΔT Flow _ Conv + Δ T Flow _ Cond - calculating (E11) the concentration of fuel vapours of the stream based on the temperature estimated; - controlling (E12) the purging valve in order to control the flow rate of the stream entering the cylinders of the engine (20) according to the concentration calculated, while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

6. Method according to Claim 5, furthermore comprising the steps, which are implemented by the control module, of determining (E13) a time of end of purging of the fuel vapours, of closing (E14) the purging valve (125), and of controlling (E15) the pump (121) such that said pump (121) operates, in this mode referred to as "non-purging" mode, at a predetermined minimum rate.

7. Method according to Claim 5 or 6, wherein the concentration of fuel vapours of the stream based on the temperature estimated is calculated according to the following equation: HC _ vol gas = ρ gas − ρ air ρ but − ρ air where ρgas is the density of the gas in the pump (121), ρair is the density of the air at the pressure and temperature in the pump (121), and ρbut is the density of the butane at the pressure and temperature in the pump (121) .

8. Computer program product, characterized in that it comprises a set of program code instructions that, when they are executed by one or more processors, configure the one or more processors to implement a method according to any one of Claims 5 to 7.