Device and method for purging a gas stream laden with hydrocarbon vapors

Abstract

A device (10) for purging vapors from fuel stored in a tank (30) of a combustion engine vehicle (1), comprising a control module (130) configured, in particular, to determine the contribution of gas flow convection to the temperature of said gas flow from a measurement of the received gas flow temperature and a measurement of the received pump internal temperature; to determine the contribution of flow conduction to the gas flow temperature from the mass flow rate, a temperature of the received gas flow, and a measurement of the received pump internal temperature; to estimate the temperature of the gas flow circulating in a purge circuit (120) from the determined adiabatic compression, convection, and conduction contributions; and to calculate the fuel vapor concentration of the flow from the estimated temperature. Figure for the abstract: Fig. 1

Description

Title of the invention: Device and method for purging a gas flow loaded with hydrocarbon vapors Technical field

[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 heat engine. The invention finds its application in particular in hybrid vehicles and in vehicles with a pure heat engine. Prior art

[0002] In a motor vehicle with a thermal engine, the fuel stored in the tank requires a vent to allow both the vapors emitted by the fuel to escape and air to enter the tank when the fuel level decreases. It is therefore necessary to regulate the pressure of the gases contained in the tank in order to avoid large pressure variations which could cause damage to both material and personal injury. To do this, a known solution consists of forming an exhaust orifice in the closing cap of the tank in order to evacuate these hydrocarbon vapors directly outside the vehicle while allowing air to enter the tank to equalize the pressure. Such a release of these hydrocarbon vapors into the atmosphere has the major disadvantage of significantly polluting the environment.However, such discharges are becoming less and less desirable and possible today in light of the various legislations which are becoming more and more restrictive in this area and some of which require drastic limits to be placed on the emissions of hydrocarbon vapours into the atmosphere.

[0003] Also, in order to limit pollution, it is nowadays known to install a filtering device in the fuel intake system of the vehicle. Such a device is connected, on the one hand, to the tank and, on the other hand, to the exterior of the vehicle. In a known solution, this device comprises a carbon degassing filter hereinafter called an "absorbent filter" (commonly referred to by the Anglicism of "canister" by those skilled in the art) which makes it possible to absorb the hydrocarbon vapors coming from the tank so that the fuel fumes discharged into the atmosphere by the discharge device are in the form of a gas significantly purified of the polluting components contained in the hydrocarbon vapors.

[0004] However, such an absorbent filter has a limited absorption capacity, called the maximum load of the filter. We then say that the absorbent filter is "full" or "filled" or that it is saturated. In this case, the filter can no longer retain the hydrocarbon vapors which then escape into the atmosphere. More generally, that the absorbent filter whether saturated or not, it is characterized at a given moment by its load which corresponds to the percentage of mass of fuel stored in said filter in relation to its saturation value, that is to say in relation to its maximum load.

[0005] In order to limit harmful fuel releases into the atmosphere when the filter is saturated, it is necessary to purge it regularly, preferably before it becomes saturated with hydrocarbon vapors. For this, the device is connected to the vehicle's heat engine so as to allow the injection of hydrocarbon vapors absorbed by the filter directly into the combustion chambers of the cylinders of the engine in operation in order to burn them. In other words, the absorbent filter is regularly loaded with hydrocarbon vapors from the tank and then the engine control computer discharges it episodically into the combustion chambers of the cylinders of the heat engine when said engine is in operation.

[0006] The hydrocarbon vapors are conveyed from the filter to the heat engine in a purge circuit via a purge valve which allows said purge circuit to be placed under vacuum. However, with the advent of hybrid vehicle technologies, it is becoming increasingly difficult to purge the hydrocarbon vapors from the filter because creating a vacuum in the purge circuit is more difficult in a hybrid vehicle. Indeed, in a hybrid vehicle, the heat engine is preferably used at the required high speeds. However, at high speeds, the air intake throttle is open, which reduces the vacuum in the purge circuit. Furthermore, due to this mode of operation, there are fewer and fewer available moments during which the heat engine is operating to perform the purge, which can lead to releases of hydrocarbon vapors into the atmosphere, the filter being more often saturated without the possibility of purging.

[0007] A known solution to this problem is to use a radial pump, called an active purge pump, between the filter and the engine in order to circulate the hydrocarbon vapors in the purge circuit to the engine. In doing so, it is necessary to compensate the quantity of hydrocarbon vapors introduced into the engine cylinders with a corresponding volume of air in order to respect the stoichiometric air-fuel ratio necessary for the proper combustion of the mixture in the heat engine.

[0008] In an existing solution, it is known to estimate the hydrocarbon vapor concentration of 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.

[0009] Obviously, any error in flow control implies a deviation from the stoichiometric ratio which leads to a variation in the concentration in hydrocarbon vapor from the absorbent filter impacting the estimation of said hydrocarbon vapor concentration in real time. Thus, the estimated hydrocarbon vapor concentration can vary between 0 and 200% while in practice, the actual hydrocarbon vapor concentration cannot exceed 80%. As a result, the flow control is erroneous and deviates as soon as any control error occurs. The system remains relatively stable, however, because the control is carried out in a closed loop via an oxygen sensor (called a lambda probe) placed in the engine's exhaust gas circuit. However, such control is slow compared to the rapid frequency of injections. It is therefore important to be able to accurately estimate the hydrocarbon vapor concentration.

[0010] 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 rotation speed of the pump and the density of the gases circulating in the pump. Since the rotation speed of the pump is set by the purge flow rate requirement that can be absorbed by the engine, it can therefore vary very quickly, for example from 10,000 to 60,000 revolutions per minute in 1 second and from 60,000 to 10,000 revolutions per minute in 2 seconds. This change in speed involves a change in the operating point, modifying both the pressure and the temperature and therefore the density of the gases due to the adiabatic compression of the radial pump. However, this density is also a function of the ambient pressure (i.e. the pressure of the atmospheric air entering the absorbent 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 precisely as possible, such an injection correction being for example applied every 20 ms.

[0011] The ambient pressure is measured using a pressure sensor mounted on the purge circuit or supplied by another sensor connected to the engine control, for example near the active purge pump. In existing solutions, the temperature is measured using a sensor placed before or after the active purge pump and using a passive temperature sensor of the NTC type for "Negative Temperature Coefficient". However, with this technology, the response time of the temperature measurement depends on the speed of the gas flow, which varies for example between 0 and 80 1 / min, and can therefore be particularly long. For example, the response time can be of the order of 25 seconds when the flow speed is zero and of the order of 5 seconds when the flow speed is 80 1 / min. Other temperature sensors, of the thermocouple type, can be used. However, the response time of these sensors depends on their intrinsic technology, the cost of which increases inversely proportionally to their response time. Also, fast-response thermocouple sensors are used in laboratories and are too expensive to be used in mass-produced motor vehicles. In any case, the response times of low-cost temperature sensors used in the automotive industry are too long to allow accurate estimation of the hydrocarbon vapor concentration in real time and allow precise and rapid control of the gas flow entering the engine cylinders at the same time. It is therefore advantageous to propose a solution that can at least partially overcome these drawbacks. Statement of the invention

[0012] One of the aims of the invention is to estimate the temperature of the gas flow circulating in the purge circuit accurately and quickly. Another aim of the invention is to accurately measure the fuel vapor concentration of the gas flow circulating in the purge circuit. Another aim of the invention is to accurately control the flow rate of the purged gas flow entering the engine cylinders.

[0013] To this end, the invention firstly relates to a device for purging the vapors of a fuel stored in a tank of a hybrid or thermal motor vehicle, said vehicle comprising a thermal engine and a storage tank for a fuel 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: • a pump, preferably radial (or centrifugal), capable of allowing the circulation of a flow of gas containing hydrocarbon vapors from the absorbent filter to the engine, • an “upstream” pressure sensor placed upstream of the pump, • a so-called “downstream” pressure sensor placed downstream of the pump, • at least one temperature sensor configured to measure the temperature of the gas flow, preferably placed at least upstream of the pump, • a purge valve configured to switch between an open position, in which said purge valve allows the flow of gas 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 pressure sensor downstream, • calculate the pressure difference of the gas flow between the inlet and outlet of the pump from the upstream and downstream pressure measurements received, • 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 rotation speed of the received pump, • 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 received gas flow temperature measurement, • determine the contribution of the convection of the gas flow to the temperature of said gas flow from the temperature measurement of the gas flow received and the internal temperature measurement of the pump received, • 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 internal pump temperature measurement, • estimate the temperature of the gas flow circulating in the purge circuit from the determined adiabatic compression, convection and conduction contributions, • calculate the fuel vapor concentration of the flow from the estimated temperature, the received pressure measurements and the received pump rotation speed, • control the purge valve in order to control the flow rate entering the engine cylinders according to the concentration calculated while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

[0014] The use of the contributions of adiabatic compression, convection and conduction advantageously makes it possible to reliably, quickly and precisely control the flow rate of the gas flow in the engine cylinders in order to respect the stoichiometric ratio of the engine, without depending on the latency of the sensors.

[0015] According to the invention, the contribution of the adiabatic compression of the gas flow to the temperature of said gas flow TF / ow,_AÆ is determined according to the following equation: where TInlet is the temperature of the gas stream received from the * 3?»« * flow temperature sensor upstream of the pump, PFlow is the gas flow pressure received from the downstream pressure sensor, PIniet is the gas flow pressure measured by the upstream pressure sensor, and y is the ideal gas constant, considering y constant over the temperature and pressure range considered, the contribution of the gas flow convection to the temperature of said gas flow from the received gas flow temperature measurement and the received internal pump temperature measurement is determined according to the following equation: where HeatFaccom represents the convection and radiation heat exchange between the pump material and the gas stream, TBody is the pump body temperature which corresponds to the internal temperature of the pump and TInlet is the gas stream temperature measured by the stream temperature sensor, and the contribution of flow conduction (or absorption) to the gas flow temperature from the determined gas flow mass flow rate, the received gas flow temperature and the received internal pump temperature measurement is determined according to the following equation: Or q is the mass flow rate of the gas stream through the pump (in kg / h), HeatFacCond the conduction heat exchange between the pump material and the gas stream, T Body is the internal temperature of the pump and TItdet is the gas stream temperature measured by the stream temperature sensor, and wherein 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: Fl wfewv According to one aspect of the invention, the control module is configured to calculate the fuel vapor concentration of the stream from the estimated temperature according to the following equation: “ P / KLwL.,, - —— ,fe: ~ iron where pgas is the density of the gas in the pump, even is the density of air at the pressure and temperature in the pump and pbut is the density of butane at the pressure and temperature in the pump.

[0016] Advantageously, the radial pump is an electric pump.

[0017] Advantageously, the temperature sensor is placed at the inlet and / or outlet of the pump.

[0018] Preferably, the control module is configured to determine an end time for purging the hydrocarbon vapors, to close the purge valve and to control the pump so that said pump operates, in a mode called "non-purge", 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 air flow on the pump blades becomes unstable, generating significant forces on the rotation axis and on the turbine. If this operating mode continues, it leads to premature aging of the pump. It is therefore necessary to reduce the rotation speed of the pump so that the instabilities disappear. If the temperature sensor is placed far from the pump outlet, for example at a distance greater than 10 cm, the heat does not propagate or only with great difficulty to the sensor because there is no flow, causing the sensor's reaction time to be too long, for example greater than 30 seconds. In this case, the temperature in the pump cannot be calculated from the temperature information provided by the sensor placed 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 placed close to the pump outlet, for example at a distance of less than 10 cm, the heat generated by the pump propagates to the sensor and the sensor temperature value can be used instead of the model value. In addition, since there is no flow, the heat generated by the pump is forced back to the pump inlet. Therefore, the temperature across the pump is almost homogeneous and the inlet temperature is then equal to the adiabatic contribution temperature.

[0019] The invention also relates to a motor vehicle comprising a device as presented previously, a heat engine comprising at least one cylinder and a storage tank for a fuel intended to be burned in said at least one cylinder of the engine.

[0020] The invention also relates to a method for controlling the flow rate of a gas flow circulating in a purge device as presented previously, 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 difference in flow pressure between the inlet and the outlet of the pump, - receiving at least one temperature measurement from the flow temperature sensor, - receiving at least one measurement of the rotation speed of the pump and the internal temperature of the pump, - determination of the mass flow rate of the gas flow from the rotation speed of the received pump, - determination of 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 gas flow temperature measurement, - determination of the contribution of the convection of the gas flow to the temperature of said gas flow from the temperature measurement of the gas flow received and the internal temperature measurement of the pump received, - 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 received internal pump temperature measurement, - 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 in order to control the flow rate of the flow entering the engine cylinders according to the concentration calculated while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

[0021] According to the invention, the contribution of the adiabatic compression of the gas flow to the temperature of said gas flow is determined according to the following equation: y-1 r - vy 'Ordet- * « * / nîet where TInlet is the temperature of the gas flow received from the flow temperature sensor, P Flow is the pressure of the gas flow received from the downstream pressure sensor, PInlet is the pressure of the gas flow measured by the upstream pressure sensor, and y is the ideal gas constant, considering y constant over the temperature and pressure range considered, the contribution of the convection of the gas flow to the temperature of said gas flow from the received gas flow temperature measurement and the received internal pump temperature measurement is determined according to the following equation: where HeatFacconv represents the convection and radiation heat exchange between the pump material and the gas stream, TBody is the internal temperature of the pump, and T Inlet is the gas stream temperature measured by the stream temperature sensor and 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 is determined according to the following equation: Or q is the mass flow rate of the gas stream passing through the pump, HeatFacCond the conduction heat exchange between the pump material and the gas stream, TBody is the internal temperature of the pump and TInlet is the temperature of the gas stream measured by the stream temperature sensor, and in which the control module then calculates an estimate of the temperature of the gas stream circulating in the purge circuit from the adiabatic compression, convection and conduction contributions determined according to the following equation: Advantageously, the calculation of the fuel vapor concentration of the stream from the estimated temperature is carried out according to the following equation: pm;- FC WF.. —--— ' Pw - where pgas is the density of the gas in the pump, even is the density of air at the pressure and temperature in the pump and pbut is the density of butane at the pressure and temperature in the pump.

[0022] 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 the 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.

[0023] 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 method as presented previously. Brief description of the drawings

[0024] Other characteristics and advantages of the invention will become apparent from reading the description which follows. This is purely illustrative and must be read in conjunction with the appended drawings in which: [Fig.l] [Fig.l] schematically illustrates an embodiment of the vehicle according to the invention. [Fig.2] [Fig.2] schematically illustrates an embodiment of the method according to the invention. Description of the embodiments

[0025] The device according to the invention is intended to be mounted in a vehicle and allows both the evaporation of the vapors of the fuel stored in the tank of a hybrid or thermal motor vehicle and the purging of the hydrocarbon vapors generated by said fuel by combustion in the engine.

[0026] [Fig. 1] shows 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) for mixing the fuel and air in order to allow combustion.

[0027] The device 10 comprises an absorbent filter 110, a so-called “purge” circuit 120 and a control module 130.

[0028] The absorbent filter 110 makes it possible to filter the vapors generated by the fuel stored in said tank 20 in the form of hydrocarbons. For this purpose, the absorbent filter 110 is connected to the tank 30 via a conduit 31.

[0029] The absorbent filter 110 is connected to the exterior of the vehicle (the 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 escape of the gases filtered by the absorbent filter 110 to the exterior, and a closed position in which the device 10 is isolated from the exterior of the vehicle 1. The air valve 112 is optional and can be used for leak detection.

[0030] The absorbent filter 110 is also connected to the cylinders of the engine 20 via the purge circuit 120.

[0031] The purge circuit 120 connects the absorbent filter 110 to the cylinders of the engine 20 of the vehicle 1 and comprises a radial (or centrifugal) pump 121, a so-called “upstream” pressure sensor 122, a so-called “downstream” pressure sensor 123, a flow temperature sensor 124 and a purge valve 125.

[0032] The radial pump 121, which is preferably an electric pump, is capable of allowing the circulation of 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 capable of measuring its rotation speed and its internal temperature, in particular to avoid overheating of its electric motor and its electronics, and of sending these measurements to the control module.

[0033] 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.

[0034] The downstream pressure sensor 123 is mounted downstream of the pump 121 and is capable of 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.

[0035] 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 stream flowing between the absorbent filter 110 and the pump 121. In another embodiment, the stream 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.

[0036] The purge valve 125 is configured to switch between an open position, in which said purge valve 125 allows the circulation of the gas flow 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, in particular in several open positions in order to allow the gas flow coming from the absorbent filter 110 to be injected into the cylinders at different flow rates.

[0037] The control module 130 is configured to control the pump 121, in particular the operating speed of said pump 121.

[0038] The control module 130 is configured to receive the measurements from the upstream pressure sensor 122 and the downstream pressure sensor 123.

[0039] The control module 130 is configured to calculate the pressure difference of the gas flow between the inlet and the 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.

[0040] The control module 130 is configured to receive the temperature measurements from the flow temperature sensor 124.

[0041] 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 passing through the purge valve 125 and the pump 121. The gas flow passing through the pump 121 being the same as the gas flow passing 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.For this purpose, temperature sensors (not shown) can be arranged on either side of the purge valve 125 or by an independent model based on the electrical characteristics of the purge valve 125 or by the temperature information which can also be provided by the pressure sensor 123 or by a model using the model of the downstream temperature of the pump 121 in a manner known per se. Preferably, these last three pieces of information are combined to improve the precision depending on the modes of use. The information of . The opening position of the purge valve 125 may be received from the purge valve 125 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 time of the purge valve 125, such a model being known per se.

[0042] The control module 130 is configured to receive measurements of the internal temperature of the pump 121 of the vehicle 1, for example via a CAN type data communication bus.

[0043] 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 received temperature measurement of the gas flow.

[0044] The control module 130 is configured to determine the contribution of the convection of the gas flow to the temperature of said gas flow from the received gas flow temperature measurement and the internal temperature measurement of the pump 121.

[0045] The control module 130 is configured to determine the contribution of the flow conduction to the temperature of the gas flow from the determined mass flow rate of the gas flow, the received temperature of the gas flow and the internal temperature measurement of the pump 121.

[0046] 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.

[0047] The control module 130 is configured to calculate the fuel vapor concentration of the stream from the estimated temperature.

[0048] 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 of the flow entering the cylinders of the engine 20 as a function of the concentration calculated while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

[0049] The control module 130 comprises a processor capable of implementing a set of instructions making it possible to carry out these functions.

[0050] Implementation

[0051] It is considered as a prerequisite that the device first operates in non-purge mode. When the control module determines that it is necessary to perform a purge of the absorbent filter (purge mode), the control module 130 controls the pump 121 so that the pump 121 operates at a predetermined speed, for example minimum, and opens the purge valve 125.

[0052] When the flow of gas loaded with hydrocarbon vapors circulates from the absorbent filter 110 towards the engine 20 through the purge circuit 120, the upstream pressure sensor 122 and the downstream pressure sensor 123 periodically measure the pressure of the gas flow and send their measurements to the control module 130 (respectively steps E1 and E2). The control module 130 then calculates the pressure difference of the flow between the inlet and the 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).

[0053] At the same time, 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).

[0054] At the same time, 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.

[0055] The control module 130 then determines the mass flow rate of the gas flow from the rotation speed of the pump 121 and the pressure and temperature values ​​on either side of the purge valve 125 (step E6). The rotation speed of the pump makes it possible to characterize the air passage section in the purge valve 125, this section being used to calculate the mass flow rate in a manner known per se. 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 can be used, this model being in the form of a table having as inputs the ambient atmospheric pressure and the air flow rate entering the engine.

[0056] The control module 130 then determines:

[0057] 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 gas flow temperature measurement (step E7),

[0058] the contribution of the convection of the gas flow to the temperature of said gas flow from the temperature measurement of the gas flow received and the internal temperature measurement of the pump 121 received (step E8),

[0059] the contribution of the flow conduction to the temperature of the gas flow from the mass flow rate of the gas flow, the received temperature of the gas flow and the received internal temperature measurement of the pump (step E9).

[0060] In theory, the calculations require the temperature value of the body of the pump 121 rather than the internal temperature of the pump 121. The pump 121 includes an internal sensor for measuring the internal temperature but not the temperature of the body of the pump 121. However, the internal temperature of the pump 121 and the temperature of the

[0061]

[0062]

[0063]

[0064]

[0065]

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[0067]

[0068] pump body 121 are not strictly identical, but their dynamics are similar. The internal temperature of pump 121 is therefore a good image of the temperature of pump body 121. 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: y-1 * Ftov * « where TInlet is the gas flow temperature received from the flow temperature sensor, PFlow is the gas flow pressure received from the downstream pressure sensor 123 and PInlet is the gas flow pressure measured by the upstream pressure sensor 122 and gamma y is the ideal gas constant which is between 1.2 and 1.4 depending on the gases considered. The contribution of the gas flow convection to the temperature of said gas flow from the received gas flow temperature measurement and the received internal temperature measurement of the pump 121 is determined according to the following equation: where HeatFacConv represents the convection and radiation heat exchange between the pump material and the gas stream, TBody is the internal temperature of the pump 121 and TInlet is the gas stream temperature measured by the stream temperature sensor 124. The contribution of flow conduction to the gas flow temperature from the gas flow mass flow rate, the received gas flow temperature, and the received pump 121 internal temperature measurement is determined according to the following equation: where is the mass flow rate of the gas stream passing through the pump, HeatFacCond re shows the conduction heat exchange between the material of the pump 121 and the gas stream, TBody is the internal temperature of the pump 121 and TInlet is the temperature of the gas stream measured by the stream temperature sensor 124. 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: Once the temperature has been estimated, the control module 130 calculates in a step El 1 the fuel vapor concentration of the gas flow from the temperature estimated according to the following formula:

[0069]

[0070] where pgas is the density of the gas in the pump 121, even is the density of the air at the pressure and temperature in the pump 121 and pbut is the density of the butane at the pressure and temperature in the pump 121.

[0071] Then, the control module 130 controls the purge valve 125 in a step E12 in order to control the flow rate of the flow entering the cylinders of the engine 20 as a function of the concentration calculated while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

[0072] 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 correspondences are stored between the hydrocarbon vapor concentration 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.

[0073] When the control module 130 determines that the purge mode is finished (step E13), it closes the purge valve 125 (step E14) and controls the pump 121 (step E15) to avoid premature aging of the material(s) constituting the pump 121, for example by controlling the pump 121 at its minimum speed.

[0074] The invention therefore advantageously makes it possible to control in a simple, reliable and precise manner the flow rate of the gas flow in the cylinders of the engine 20 in order to respect the stoichiometric ratio of the engine 20.

Claims

Claims

1. Device (10) for purging vapors from a fuel stored in a tank of a hybrid or thermal motor vehicle (1), said vehicle (1) comprising a thermal engine (20) and a tank (10) for storing a fuel intended to be burned in said engine (20), said device comprising: - an absorbent filter (110) capable of filtering the vapors generated by the fuel stored in said tank (10) in the form of hydrocarbons, - a circuit (120) called “purge” connected to the absorbent filter and intended to be connected to the engine (20) and comprising: • a pump (121) capable of allowing the circulation of a flow of gas containing hydrocarbon vapors from the absorbent filter (110) to the engine (20), • an “upstream” pressure sensor (122) placed upstream of the pump (121), • a so-called “downstream” pressure sensor (123) placed downstream of the pump (121), • a flow temperature sensor (124) configured to measure the temperature of the gas flow, • a purge valve (125) configured to switch between an open position, in which said purge valve 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), - a control module (130) configured to, in a purge mode: • receive the measurements from the upstream pressure sensor (122) and the downstream pressure sensor (123), • calculate the pressure difference of the gas flow between the inlet and the outlet of the pump (121) from the upstream and downstream pressure measurements received, • receive the temperature measurements from the flow temperature sensor (124), the rotation speed of the pump (121) and the internal temperature of the pump (121), • determine the mass flow rate of the gas flow from the rotation speed of the pump (121) received, • determine the contribution of the adiabatic compression of the gas flow to the temperature of said gas flow TFiow_Adb, from the calculated pressure difference and the temperature measurement of the gas flow received, and according to the following equation: r—* where TInlet is the gas stream temperature received from the stream temperature sensor, PFlow is the gas stream pressure received from the downstream pressure sensor (123), PInlet is the gas stream pressure measured by the upstream pressure sensor (122) and y is the ideal gas constant, • determine the contribution of the convection of the gas flow to the temperature of said gas flow from the temperature measurement of the gas flow received and the internal temperature measurement of the pump (121) received, according to the following equation: where HeatFacconv represents the convection and radiation heat exchange between the pump material (121) and the gas stream, TBody is the internal temperature of the pump (121) and TInlet is the gas stream temperature measured by the stream temperature sensor (124), • determine the contribution of the flow conduction to the temperature of the gas flow from the determined mass flow rate of the gas flow, the received temperature of the gas flow and the received internal temperature measurement of the pump (121), according to the following equation: where q is the mass flow rate of the gas stream passing through the pump (121), HeatFaccond the conduction heat exchange between the pump material (121) and the gas stream, TBody is the internal temperature of the pump (121) and TInlet is the gas stream temperature measured by the stream temperature sensor (124), • estimate the temperature of the gas flow circulating in the purge circuit from the determined adiabatic compression, convection and conduction contributions, according to the following equation: • calculate the fuel vapor concentration of the flow from the estimated temperature, the pressure measurements received and the rotation speed of the pump received, • control the purge valve (125) in order to control the flow rate of the flow entering the cylinders of the engine (20) according to the calculated concentration while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

2. Device (10) according to claim 1, in which the control module (130) is configured to determine an end time for purging the fuel vapors, to close the purge valve (125) and to control the pump (121) so that said pump (121) operates, in this so-called “non-purge” mode, at a predetermined minimum speed.

3. Device (10) according to claim 1 or 2, wherein the control module (130) is configured to calculate the fuel vapor concentration of the flow from the estimated temperature according to the following equation: P,... -fev i / C wL.... - —-------- * fetf ~ fer where pgas is the density of the gas in the pump (121), even is the density of the air at the pressure and temperature in the pump (121) and pbut 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 thermal engine (20) comprising at least one cylinder and a tank (30) for storing a fuel intended to be burned in said at least one cylinder of the engine (20).

5. Method for controlling the flow rate of a gas flow circulating in a purge device (10) according to any one of claims 1 to 3, said method, implemented by the control module (130) of said device, comprising the steps of: - reception (El) of at least one measurement of the pressure of the flow upstream of the pump (121), - reception (E2) of at least one measurement of the pressure of the flow downstream of the pump (121), - calculation (E3) of the pressure difference of the flow between the inlet and the outlet of the pump (121), - reception (E4) of at least one temperature measurement from the flow temperature sensor (124), - reception (E5) of at least one measurement of the rotation speed of the pump (121) and of the internal temperature of the pump (121), - determination (E6) of the mass flow rate of the gas flow from the rotation speed of the pump (121) received, - determination (E7) of 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 gas flow temperature measurement, according to the following equation: W On kf * T where TInlet is the gas stream temperature received from the stream temperature sensor, PFlow is the gas stream pressure received from the downstream pressure sensor, PIntel is the gas stream pressure measured by the upstream pressure sensor (122) and y is the ideal gas constant, - determination (E8) of the contribution of the convection of the gas flow to the temperature of said gas flow from the temperature measurement of the gas flow received and the internal temperature measurement of the pump received, according to the following equation: where HeatFacconv represents the heat exchange by convection and radiation between the pump material (121) and the gas flow, TBody is the internal temperature of the pump (121) and TInlet is the gas flow temperature measured by the flow temperature sensor (124), - determination (E9) of the contribution of the 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, according to the following equation: where ç is the mass flow rate of the gas flow passing through the pump (121), HeatFaccond the conduction heat exchange between the material of the pump (121) and the gas flow, TBody is the internal temperature of the pump (121) and TInlet is the temperature of the gas flow measured by the flow temperature sensor (124), - estimation (E10) of the temperature of the gas flow circulating in the purge circuit from the determined adiabatic compression, convection and conduction contributions, according to the following equation: - calculation (El 1) of the fuel vapor concentration of the flow from the estimated temperature, - control (El2) of the purge valve in order to control the flow rate of the flow entering the cylinders of the engine (20) according to the calculated concentration while respecting the stoichiometric ratio of the combustion of the air-fuel mixture relative to said cylinders.

6. Method according to claim 5, further comprising the steps, implemented by the control module, of determining (El3) an end time for purging the fuel vapors, closing (El4) the purge valve (125) and controlling (E15) the pump (121) so that said pump (121) operates, in this so-called “non-purge” mode, at a predetermined minimum speed.

7. A method according to claim 5 or 6, wherein the calculation of the fuel vapor concentration of the stream from the estimated temperature is carried out according to the following equation: HC P^t " P^ where pgas is the density of the gas in the pump (121), even is the density of the air at the pressure and temperature in the pump (121) and pbut is the density of the butane at the pressure and temperature in the pump (121).

8. 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 method according to any one of claims 5 to 7.

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