DETECTION OF LEAKS IN A DEVICE FOR EVAPORATING VAPORS OF A FUEL STORED IN A VEHICLE HEAT ENGINE TANK

Abstract

Disclosed is a device for evaporating vapors of a fuel stored in a motor vehicle tank. The evaporation device includes a bypass circuit and a bypass valve configured to move between a so-called absorption position, in which the bypass valve allows the gases to flow between the tank and an absorbent filter and a so-called leak detection position, in which the bypass valve allows the gases to flow between a purge circuit and the tank via the bypass circuit.

Claims

1. A device (13) for evaporating vapors of a fuel stored in a motor vehicle tank (12), said vehicle comprising an engine (11) and a tank (12) for storing a fuel for burning in said engine (11), said evaporation device (13) comprising: an absorbent filter (131) suitable for filtering the vapors generated by the fuel stored in said tank (12), a so-called absorption circuit (132) connecting the absorbent filter (131) to the tank (12) so as to allow the gas vapors to be conveyed to the absorbent filter (131), a so-called ventilation circuit (135) connecting the outside of the vehicle to the absorbent filter (131) comprising an outlet valve (130) configured to switch between an open position in which the outlet valve allows the gases filtered by the absorbent filter (131) to escape to the outside, and a closed position in which the evaporation device (13) is isolated from the outside of the vehicle, a so-called purge circuit (133) connecting the absorbent filter (131) to the engine (11) of the vehicle and comprising an electric pump (136), suitable for allowing the fuel vapors absorbed by the absorbent filter (131) to flow to the engine (11), a pressure measurement sensor (137) and a purge valve (134) configured to switch between an open position, in which said purge valve allows the gases to flow from the absorbent filter (131) to the engine (11), and a closed position in which the absorbent filter (131) is isolated from the engine (11), said evaporation device (13) further comprising a bypass circuit (138) and a bypass valve (139) mounted between the absorption circuit (132), the purge circuit (133) and the tank (12), which is configured to move between a so-called absorption position, in which the bypass valve (139) allows the gases to flow between the tank (12) and the absorbent filter (131), via the absorption circuit (132), and a so-called leak detection position, in which the bypass valve (139) allows the gases to flow between the purge circuit (133) and the tank (12) via the bypass circuit (138), the electric pump (136) being configured to draw in gases from the outside to convey them, via the ventilation circuit (135), the absorbent filter (131) and the bypass circuit (138), to the tank (12), in order to pressurize said tank (12) and thus allow the detection of a leak in the evaporation device (13) by means of the pressure measurement sensor (137).

2. The evaporation device (13) as claimed in claim 1, comprising a control module (14) that is electrically connected to the measurement sensor (137) in order to receive the pressure value measurements therefrom and configured to detect the presence of a leak when the absolute value of the change in said value of the pressure inside the evaporation device (13) measured for a predetermined period is greater than or equal to a predetermined threshold.

3. The evaporation device (13) as claimed in claim 2, in which the control module (14) is also configured to determine the size of the leak detected as a function of the change in the value of the pressure measured by the measurement sensor (137).

4. The evaporation device (13) as claimed in claim 3, in which the control module (14) is configured to determine the flow rate of the leak or the dimensions of the orifice linked to the leak.

5. The evaporation device (13) as claimed in claim 4, in which the control module (14) is configured to control the outlet valve (130), the purge valve (134), the bypass valve (139) and the electric pump (136) so that they switch to their different positions.

6. A vehicle comprising an evaporation device (13) as claimed in claim 1.

7. A method for detecting a leak in a device (13) as claimed in claim 1 for evaporating vapors of a fuel stored in a motor vehicle tank (12), said vehicle comprising an engine (11) and a tank (12) of fuel for burning in said engine (11), said method comprising: placing (S1) the bypass valve (139) in the leak detection position, the outlet valve (130) in the open position and the purge valve (134) in the closed position, activating (S2) the electric pump (136) so as to draw in gases from the outside of the vehicle to convey them, via the ventilation circuit (135), the absorbent filter (131), the purge circuit (133) and the bypass circuit (138), to the tank (12), in order to pressurize said tank (12), placing (S3) the outlet valve (130) in the closed position at a first time, measuring (S4) the change in pressure by means of the pressure measurement sensor (137) between the first time and a second time in order to determine a pressure difference between said first time and said second time, and detecting (S5) the presence of a leak when the pressure difference determined is greater than or equal to a predetermined pressure difference threshold.

8. The detection method as claimed in claim 7, comprising after the step (S9) of detecting the presence of a leak, a step (S10) of determining the size of said detected leak on the basis of the pressure difference measured.

9. The detection method as claimed in claim 7, in which the predetermined pressure difference threshold is between 5 and 50 hPa.

10. The detection method as claimed in claim 7, in which the evaporation device (13) comprises a control module (14) electrically connected to the measurement sensor (137), in order to receive the pressure value measurements therefrom, and to the outlet valve (130), the purge valve (134), the bypass valve (139) and the electric pump (136), in order to control them, the steps of the method being implemented by said control module (14).

11. The evaporation device (13) as claimed in claim 3, in which the control module (14) is configured to control the outlet valve (130), the purge valve (134), the bypass valve (139) and the electric pump (136) so that they switch to their different positions.

12. The evaporation device (13) as claimed in claim 4, in which the control module (14) is configured to control the outlet valve (130), the purge valve (134), the bypass valve (139) and the electric pump (136) so that they switch to their different positions.

13. A vehicle comprising an evaporation device (13) as claimed in claim 2.

14. A vehicle comprising an evaporation device (13) as claimed in claim 3.

15. A vehicle comprising an evaporation device (13) as claimed in claim 4.

16. A vehicle comprising an evaporation device (13) as claimed in claim 5.

17. A method for detecting a leak in a device (13) as claimed in claim 2 for evaporating vapors of a fuel stored in a motor vehicle tank (12), said vehicle comprising an engine (11) and a tank (12) of fuel for burning in said engine (11), said method comprising: placing (S1) the bypass valve (139) in the leak detection position, the outlet valve (130) in the open position and the purge valve (134) in the closed position, activating (S2) the electric pump (136) so as to draw in gases from the outside of the vehicle to convey them, via the ventilation circuit (135), the absorbent filter (131), the purge circuit (133) and the bypass circuit (138), to the tank (12), in order to pressurize said tank (12), placing (S3) the outlet valve (130) in the closed position at a first time, measuring (S4) the change in pressure by means of the pressure measurement sensor (137) between the first time and a second time in order to determine a pressure difference between said first time and said second time, and detecting (S5) the presence of a leak when the pressure difference determined is greater than or equal to a predetermined pressure difference threshold.

18. A method for detecting a leak in a device (13) as claimed in claim 3 for evaporating vapors of a fuel stored in a motor vehicle tank (12), said vehicle comprising an engine (11) and a tank (12) of fuel for burning in said engine (11), said method comprising: placing (S1) the bypass valve (139) in the leak detection position, the outlet valve (130) in the open position and the purge valve (134) in the closed position, activating (S2) the electric pump (136) so as to draw in gases from the outside of the vehicle to convey them, via the ventilation circuit (135), the absorbent filter (131), the purge circuit (133) and the bypass circuit (138), to the tank (12), in order to pressurize said tank (12), placing (S3) the outlet valve (130) in the closed position at a first time, measuring (S4) the change in pressure by means of the pressure measurement sensor (137) between the first time and a second time in order to determine a pressure difference between said first time and said second time, and detecting (S5) the presence of a leak when the pressure difference determined is greater than or equal to a predetermined pressure difference threshold.

19. A method for detecting a leak in a device (13) as claimed in claim 4 for evaporating vapors of a fuel stored in a motor vehicle tank (12), said vehicle comprising an engine (11) and a tank (12) of fuel for burning in said engine (11), said method comprising: placing (S1) the bypass valve (139) in the leak detection position, the outlet valve (130) in the open position and the purge valve (134) in the closed position, activating (S2) the electric pump (136) so as to draw in gases from the outside of the vehicle to convey them, via the ventilation circuit (135), the absorbent filter (131), the purge circuit (133) and the bypass circuit (138), to the tank (12), in order to pressurize said tank (12), placing (S3) the outlet valve (130) in the closed position at a first time, measuring (S4) the change in pressure by means of the pressure measurement sensor (137) between the first time and a second time in order to determine a pressure difference between said first time and said second time, and detecting (S5) the presence of a leak when the pressure difference determined is greater than or equal to a predetermined pressure difference threshold.

20. A method for detecting a leak in a device (13) as claimed in claim 5 for evaporating vapors of a fuel stored in a motor vehicle tank (12), said vehicle comprising an engine (11) and a tank (12) of fuel for burning in said engine (11), said method comprising: placing (S1) the bypass valve (139) in the leak detection position, the outlet valve (130) in the open position and the purge valve (134) in the closed position, activating (S2) the electric pump (136) so as to draw in gases from the outside of the vehicle to convey them, via the ventilation circuit (135), the absorbent filter (131), the purge circuit (133) and the bypass circuit (138), to the tank (12), in order to pressurize said tank (12), placing (S3) the outlet valve (130) in the closed position at a first time, measuring (S4) the change in pressure by means of the pressure measurement sensor (137) between the first time and a second time in order to determine a pressure difference between said first time and said second time, and detecting (S5) the presence of a leak when the pressure difference determined is greater than or equal to a predetermined pressure difference threshold.

Description

[0041] FIG. 1 schematically illustrates an evaporation device of the prior art.

[0042] FIG. 2 schematically illustrates an evaporation device according to one embodiment of the invention, in which the bypass valve is in the absorption position.

[0043] FIG. 3 is a schematic representation of the evaporation device in FIG. 2, in which the bypass valve is in the leak detection position.

[0044] FIG. 4 schematically illustrates one embodiment of the method according to the invention.

[0045] FIGS. 2 and 3 show an example of an evaporation device 13 according to the invention, suitable for being installed in a motor vehicle. However, the present invention also relates any installation in a different context, in particular on any vehicle comprising an engine for which it is necessary to detect the presence of a leak of vapors of fuel stored in a tank.

[0046] As is known, a combustion engine of a motor vehicle comprises one or more hollow cylinders each delimiting a combustion chamber into which a mixture of air and fuel is injected. With reference to FIG. 2, the fuel is stored in a tank 12, from which it is drawn by an injection pump (not shown) to be conveyed to the engine 11. More specifically, the injection pump conveys the fuel into an injection rail (not shown) so as to allow the injection of the fuel into each combustion chamber.

[0047] As the pressure of the gases contained in the tank 12 must be controlled to avoid any damage or accidents and limit pollution due to the fuel vapors, the vehicle comprises an evaporation device 13, connected to the tank 12, the engine 11 and the outside of the vehicle, that makes it possible to absorb the vapors and convey them into the combustion chambers of the engine 11 so that they can be burned therein, so that the gases discharged into the atmosphere are significantly purified of the polluting components. The evaporation device 13 also makes it possible to control the presence of a leak of the fuel vapors, as will be described in greater detail hereinafter.

[0048] Still with reference to FIGS. 2 and 3, the evaporation device 13 comprises a control module 14, an outlet valve 130, an absorbent filter 131, a so-called absorption circuit 132, a so-called purge circuit 133, a purge valve 134, a so-called ventilation circuit 135, an electric pump 136, a pressure measurement sensor 137, a bypass circuit 138, a bypass valve 139 and a connection circuit 140.

[0049] The electric pump 136 is mounted in one portion of the purge circuit 133. The electric pump 136 operates in one direction in order to cause a stream of gas coming from the absorbent filter 131 to flow, in the portion of the purge circuit 133 in which it is mounted, to the engine 11 or the tank 12. However, when the electric pump 136 is not operating, the stream of gas can flow in two directions in order to cause the stream of gas to flow both in one direction and in the opposite direction in the portion of the purge circuit 133 in which it is mounted.

[0050] The ventilation circuit 135 connects the outside (i.e. the atmosphere) of the evaporation device 13 to the absorbent filter 131 via the outlet valve 130. The outlet valve 130 is configured to move between an open position in which the outlet valve 130 allows a stream of gas to pass from the outside to the absorbent filter 131 or from the absorbent filter 131 to the outside, and a closed position in which the outlet valve 130 prevents a stream of gas from passing from the outside to the absorbent filter 131 or from the absorbent filter 131 to the outside. In other words, the outlet valve 130 makes it possible to open or close the ventilation circuit 135 so as to isolate and seal the evaporation device 13 from the outside of the vehicle.

[0051] The absorption circuit 132 connects the absorbent filter 131 to the bypass valve 139. The purge circuit 133 connects the absorbent filter 131 to the engine 11 of the vehicle via the electric pump 136 and the purge valve 134. The bypass circuit 138 connects the bypass valve 139 to the purge circuit 133 at a connection point CP situated between the electric pump 136 and the purge valve 134. The connection circuit 140 connects the tank 12 to the bypass valve 139.

[0052] The bypass valve 139 is mounted between the absorption circuit 132, the purge circuit 133 and the connection circuit 140. The bypass valve 139 is configured to move between a so-called absorption position and a so-called leak detection position.

[0053] The absorption position of the bypass valve 139, shown in FIG. 2, corresponds to the position in which the bypass valve 139 allows gases to be conveyed from the tank 12 to the absorbent filter 131, via the absorption circuit 132, thus allowing the absorption of the fuel vapors by the absorbent filter 131. The absorbent filter 131 is configured to capture and filter the vapors generated by the fuel stored in the tank 12 in order to retain the polluting elements thereof.

[0054] The leak detection position of the bypass valve 139, shown in FIG. 3, corresponds to the position in which the bypass valve 139 allows a stream of gas coming from the outside and making it possible to pressurize the tank 12 when the purge valve 134 is closed and the outlet valve 130 is open, to be drawn in by means of the electric pump 136 and via the ventilation circuit 135, the absorbent filter 131, the purge circuit 133 and the bypass circuit 138.

[0055] The purge circuit 133 connects the absorbent filter 131 to the engine 11 of the vehicle so as to allow said absorbent filter 131 to be purged by releasing the gas vapors retained by said absorbent filter 131 and by conveying them into the combustion chambers of the engine 11 so as to allow the combustion thereof. This is achieved by actuating the electric pump 136 so that it draws in a stream of gas coming from the outside (for example air), via the ventilation circuit 135 and the absorbent filter 131, and conveys said stream, loaded with the toxic vapors stored in the absorbent filter 131, into the cylinders of the engine 11.

[0056] The different circuit portions of the evaporation device 13 preferably take the form of tubes or pipes.

[0057] The purge valve 134, mounted in the purge circuit 133 between the electric pump 136 and the engine 11, is configured to open or close said purge circuit 133. More specifically, the purge valve 134 is configured to move between a closed position in which it prevents the flow of a gaseous stream to the engine 11, and an open position in which it permits a gaseous stream to pass to the engine 11. The purge circuit 133 thus makes it possible, depending on the position of the purge valve 133, to convey the fuel vapors stored in the absorbent filter 131 to the engine 11 or to isolate the evaporation device 13 from the engine 11.

[0058] The pressure measurement sensor 137 is mounted in the purge circuit 133 between the connection point CP and the purge valve 134. The pressure measurement sensor 137 is configured to measure the pressure of the gases contained in the purge circuit 133. The measurement sensor 137 particularly makes it possible to measure the reduction in the internal pressure of the purge circuit 133 and the tank 12 following the pressurization of said tank when there is a leak in the evaporation device 13, particularly in the tank, as will be explained below.

[0059] As a variant, the pressure measurement sensor 137 could be mounted in a different place in the purge circuit 133, or in the bypass circuit 138 or in the connection circuit 140, or even in or on the tank 12 in order to measure the internal pressure thereof.

[0060] The control module 14 takes the form for example of a main computer for controlling the engine 11 of the vehicle or a dedicated microcontroller.

[0061] The control module 14 is configured to control the electric pump 136 in order to start it. More specifically, the control module 14 is configured to control the electric pump so as to allow either fuel vapors to be conveyed from the absorbent filter 131 to the engine 11 in order for them to be burned, or gas to be drawn in from the outside to the tank 12 to pressurize it.

[0062] The control module 14 is configured to control the outlet valve 130 and the purge valve 134 to their open or closed positions.

[0063] More specifically, the control module 14 is configured to control the purge valve 134 so as to allow either fuel vapors to be conveyed from the absorbent filter 131 to the engine 11, or the evaporation device 13 to be isolated from the engine 11 so that the tank 12 can be pressurized. Similarly, the control module 14 is configured to control the outlet valve 130 so as to allow a stream of gas to be conveyed from the tank 12 to the outside via the absorbent filter 131, which retains the toxic vapors therefrom, or from the outside to the tank 12 to pressurize it via the absorbent filter 131 and the purge circuit 133, or the evaporation device 13 to be isolated from the outside.

[0064] The control module 14 is configured to control the bypass valve 139 so as to place it in its absorption position or in its leak detection position, depending on the desired configuration. Advantageously, the control module 14 is configured to place the bypass valve 139 in its leak detection position when certain leak diagnosis conditions are met (for example below a predetermined speed of the vehicle to avoid vibrations generated by the movement of the vehicle or the running of the engine interfering with the measurements of the pressure sensor 137, depending on the temperature and ambient pressure) in order to ensure the robustness of the leak detection and the accuracy of the estimate of the size of the leak of the diagnosis.

[0065] The control module 14 is configured to receive from the measurement sensor 137 the pressure measurements that it takes, to analyze the change in these values, for example the gradient thereof, over a predetermined time interval, and to detect the presence of a leak when the pressure drop inside the evaporation device 13 is greater than or equal to a predetermined threshold following the pressurization of the tank 12 and when the purge valve 134 and the outlet valve 130 are in the closed position.

[0066] During a leak test, the evaporation device 13 is initially pressurized, then the pressurization is stopped and the change in internal pressure is analyzed for a predetermined period, for example 10 seconds. When the internal pressure remains substantially stable for the predetermined period, there is no leak. Conversely, when the pressure reduces and the absolute value of the pressure difference between the start and end of the predetermined period is greater than or equal to the predetermined threshold, this reveals the presence of a leak. The predetermined pressure difference threshold is advantageously between 5 and 50 hPa, and preferably of the order of 15 hPa.

[0067] The control module 14 is configured to determine the size of the leak detected as a function of the change in the pressure value measured by the measurement sensor 137, i.e. as a function of the pressure gradient, making it possible for example to anticipate the operations necessary to repair the leak. The greater and faster the pressure drop, the larger the leak detected. If there is a leak, the change in pressure can be evaluated using the pressure gradient, which can then be compared to predetermined gradient values, for example empirically predetermined, corresponding to given leak flow rates or given leak orifice sizes. In this preferred example, the control module 14 is configured to determine the flow rate of the leak or the dimensions of the orifice linked to the leak.

[0068] The invention will now be described in terms of one exemplary embodiment with reference to FIG. 4. The method according to the invention makes it possible to detect the presence of a leak of fuel vapors in an evaporation device 13 as described previously.

[0069] According to a preferred embodiment, in order to allow the detection of a leak, the outlet valve 130 is initially in its open position so as to allow a stream of gas to flow into the evaporation device 13, the purge valve 134 is initially in its closed position so as to isolate the evaporation device 13 from the engine 11, and the bypass valve 139 is initially placed in its absorption position so as to allow the fuel vapors to be absorbed by the absorbent filter 131.

[0070] When it is necessary to carry out a leak detection test, the control module 14, in a step S1, places the bypass valve 139 in its leak detection position, the outlet valve 130 in its open position and the purge valve 134 in its closed position.

[0071] The control module 14 then activates the electric pump 136 in a step S2 so as to create a stream of gas from the outside to the tank 12 via the ventilation circuit 135, the absorbent filter 131, the purge circuit 133 and the connection circuit 140 and thus pressurize the tank 12.

[0072] When the pressure in the tank has reached the threshold of 15 hPa, in a step S3 the control module 14 then places the outlet valve 130 in its closed position at a first time and then in a step S4 collects the measurements of the change in pressure sent by the pressure measurement sensor 137 between the first time and a second time in order to determine a pressure difference between said first time and said second time.

[0073] In a step S5, the control module 14 then detects the presence of a leak when the absolute value of the pressure difference determined (which in this case corresponds to a pressure drop) is greater than or equal to a predetermined pressure difference threshold.

[0074] In a preferred embodiment, the control module 14 also optionally determines, in a step S6, the size of the leak detected as a function of the pressure difference calculated.

[0075] Such a method according to the invention advantageously makes it possible to detect the presence of a leak in the evaporation device simply, quickly and effectively, particularly whether the engine 11 is in a running or static state. Such a method also makes it possible to detect a leak without requiring the incorporation into the evaporation device 13 of specific NVLD equipment, thus allowing effective, low-cost leak detection.