Fuel tank ventilation system

Abstract

The invention relates to a fuel tank ventilation system (10) for a motor vehicle, comprising: a fuel tank (1) comprising a vapor dome; a refueling pipe (2); a fuel vapor trap (3) connected to the fuel tank (1) via an inlet pipe (4), wherein the inlet pipe (4) is connected to the fuel tank (1) via at least one continuously open hole (5), which hole is arranged in the vapor dome of the fuel tank (1) under static conditions; and a normally closed switch (CVS) (6) connected to the atmosphere and connected to the fuel vapor trap (3) via an outlet pipe (7), the normally closed switch (6) comprising an electric valve, which closes when the electric valve is de-energized; wherein the normally closed switch (6) is arranged to open during the vehicle refueling process and to close when the fuel in the fuel tank (1) reaches a predetermined filling level and when the vehicle is in normal operation.

Description

Technical Field

[0001] The present invention relates to a fuel tank venting system for a motor vehicle and a motor vehicle comprising such a system. More particularly, the present invention relates to an on-board refueling vapor recovery system on a motor vehicle, especially a hybrid motor vehicle. Background Art

[0002] This type of fuel vapor recovery system has a fuel vapor trap or canister to capture fuel vapors, a refueling valve, and one or more vent valves located on top of the fuel tank to handle fuel vapors in the fuel tank.

[0003] In the prior art literature, US2020 / 0198462A1 discloses a valve module for operating a fluid container system, GB2588778A discloses a vapor canister for a vehicle evaporative emission control system, US2018 / 0087475A1 discloses a fuel tank system including an evaporative emission control system, and US2016 / 0298576A1 discloses a fuel tank evaporative emission control and diagnostic system.

[0004] For example, a rollover valve (ROV) is used to shut off the fuel system in the event of a rollover event due to a vehicle accident, and a fill limit vent valve (FLVV) is used to prevent overfilling of the tank. However, the use of these valves makes the fuel tank system very expensive and complex to produce. Moreover, the valves take up a lot of space in the fuel system, especially inside the fuel tank, which means that the capacity of the tank may not be satisfactory. Summary of the invention

[0005] The object of the present invention is to overcome the disadvantages of known venting systems by providing a fuel tank venting system which is less expensive, simpler and saves space, in particular space inside the fuel tank.

[0006] The present invention thus provides a fuel tank venting system for a motor vehicle, comprising:

[0007] - fuel tanks including vapor domes;

[0008] - fuel pipe;

[0009] a fuel vapor trap connected to the fuel tank via an inlet duct, wherein the inlet duct is connected to the fuel tank via at least one continuously open hole, which hole is arranged to be located in the vapor dome of the fuel tank under static conditions, the hole being preferably arranged in a wall of the fuel tank, more preferably in a top wall of the fuel tank;

[0010] - a normally closed opening and closing device, which is communicated with the atmosphere and connected to the fuel vapor trap through an outlet pipe, the normally closed opening and closing device comprising an electric valve, which is closed when the electric valve is de-energized;

[0011] The normally closed switch is configured to open during the vehicle refueling process and to close when the fuel in the fuel tank reaches a predetermined filling level and when the vehicle is in normal operating conditions. Normal operating conditions refer to all conditions except refueling operations and conditions of excessive overpressure or underpressure.

[0012] Preferably, a pressure release valve is arranged between the normally closed opening and closing device and the fuel vapor trap, and the valve is arranged in parallel with the normally closed opening and closing device.

[0013] Thus, after refueling and during normal operation of the vehicle, the entire fuel system is shut down, which helps to increase the pressure in the fuel tank in a closed environment. It is known that the volatility of the fuel decreases when the pressure in the fuel tank increases. Therefore, in a closed fuel tank system, no fuel vapor enters the fuel vapor trap and nothing is loaded on the fuel vapor trap.

[0014] The fuel tank ventilation system is particularly useful for reducing CO2 emissions in hybrid electric vehicles. In fact, depending on the model of the vehicle, hybrid electric vehicles either use only the motor, only the engine, or both when running. A specific operating principle is as follows:

[0015] During static conditions (when the vehicle is not moving), both the combustion engine and the electric motor are shut down;

[0016] At start-up, it is the electric motor that causes the vehicle to move, up to a higher speed;

[0017] When higher speeds are reached, the combustion engine takes over;

[0018] In the case of hard acceleration, it is observed that both the combustion engine and the electric machine operate simultaneously, thus making it possible to reach accelerations equivalent to those of an engine with the same power, or even greater accelerations;

[0019] • During deceleration and braking phases, depending on the model of vehicle, kinetic energy may be used to recharge the battery.

[0020] In fact, during the emptying of the fuel vapor trap, vapors are drawn from the fuel vapor trap by the engine intake vacuum that occurs at low engine loads. As a result, the combustion engine is operated in an inefficient operating mode; when supplementing the engine with an electric machine, the aim is to avoid operating the engine in an inefficient operating mode. In fact, for example during the Worldwide Harmonized Light Vehicle Test Cycle (WLTC), it was found that greater fuel savings and CO2 emissions can be achieved when the hybrid engine is not operated in a low load (inefficient) mode; some plug-in hybrid vehicles do completely shut down the combustion engine whenever possible, in order to operate in pure EV mode without any CO2 emissions. In this latter specific case, it is important to avoid a completely full fuel vapor trap, since this would require the engine to be emptied, in which case the engine would have to be started only for the fuel vapor trap to be emptied, resulting in unnecessary CO2 emissions.

[0021] In view of the above, the claimed fuel tank vent system allows for such a closed fuel tank system that helps to increase the pressure in the fuel tank and thereby reduce the loading of the fuel vapor trap, thereby allowing for reduced CO 2 emissions.

[0022] Moreover, on the one hand, valves commonly present in the prior art, such as ROV, OPV (overpressure valve) or FLVV, are replaced by the at least one hole in the claimed fuel tank venting system, which frees up more space for the fuel. Thus, the capacity of the fuel tank is increased. On the other hand, the removal of the above-mentioned valves makes the fuel tank venting system simpler and less expensive.

[0023] It will be appreciated that the claimed at least one hole or vent hole may be implemented by a simple connection between the fuel tank and the inlet conduit, such as a venting nipple allowing liquid and gas to pass through. No moving parts are arranged in the hole for controlling the communication between the fuel tank and the inlet conduit. Preferably, there are no moving parts in the wall of the fuel tank. It will be appreciated that the at least one hole is arranged to be non-continuously submerged.

[0024] It will also be appreciated that the inlet conduit is arranged to maintain continuous vapor communication between the fuel vapor trap and the fuel tank under static conditions. Static conditions refer to when the vehicle is not moving and is not being refueled.

[0025] An optional feature of the present invention is that the normally closed opening and closing device is only opened during the vehicle refueling process or when the pressure in the fuel tank reaches a predetermined pressure level. Thus, the fuel tank venting system allows such a closed fuel tank system that helps to increase the pressure in the fuel tank and thereby reduce the loading of the fuel vapor trap, thereby allowing to reduce CO2 emissions while avoiding pressure in the fuel tank that exceeds the tolerance of the fuel tank and may damage the fuel tank, that is, avoiding its internal pressure from becoming too extreme while ensuring the safety of the tank. Therefore, the predetermined pressure level is predetermined as a pressure level when the vehicle is not in normal operating conditions.

[0026] Another optional feature of the present invention is that the electric valve is opened only during the vehicle refueling process. Thus, the active actuation (or active actuation, active actuation) of the normally closed opening and closing device in which the electric valve is energized is only performed during the vehicle refueling process.

[0027] A further optional feature of the present invention is that the normally closed opening and closing means comprises a single electric valve. Thus, the fuel tank venting system is less expensive and simpler, particularly because the control of the fuel tank venting system is simplified.

[0028] Another optional feature of the present invention is that the fuel tank ventilation system includes at least two holes, both of which are connected to the inlet pipe through a ventilation tube located outside the fuel tank, and the holes are preferably arranged in different areas on the top wall of the fuel tank.

[0029] Thus, in the case of large and / or complex tanks, tilting of the vehicle may cause the liquid level to reach one or more holes, so that the holes concerned are immersed in the fuel. Providing a plurality of holes in different areas on the top wall of the fuel tank ensures that when the fuel tank is tilted, at least one or some of the holes are still able to operate, which allows to ensure a continuous vapor communication between the fuel vapor dome and the fuel vapor trap. Since the vent pipe is outside the fuel tank, there is more space in the fuel tank. Moreover, the assembly of the vent pipe to the tank is relatively simple. The cost of the fuel tank ventilation system can also be reduced.

[0030] Another optional feature of the present invention is that the fuel tank vent system includes a vent tube located inside the fuel tank, the vent tube connected to the aperture and having at least one secondary aperture that is continuously open to allow communication between the fuel tank and the inlet conduit.

[0031] Thus, an alternative solution for solving the risk of flooding some holes in case of a tilted fuel tank is provided, which is not subject to any permeability requirements for fuel vapor. Since the vent pipe is inside the tank, the assembly of the fuel tank vent system on the vehicle is simplified and less permeation of fuel vapor occurs.

[0032] It is understood that the inlet of the vent pipe for fuel vapors should advantageously be arranged in the vapor dome. Thus, when the vent pipe is inside the fuel tank and at least partially in contact with the liquid, the inlet opening should be arranged above the maximum liquid level in the fuel tank, which means in the vapor dome of the fuel tank.

[0033] A further optional feature of the invention is that the fuel tank ventilation system comprises a liquid vapor separator in the inlet duct, which is arranged between the fuel vapor trap and the orifice, preferably above the maximum fuel level in the fuel tank. The liquid vapor separator is preferably above the liquid level in the fuel tank even in the case of a slope. For this purpose, the liquid vapor separator is preferably arranged as high as possible.

[0034] In a preferred embodiment, the liquid vapor separator includes at least one rollover valve arranged at and above the maximum fuel level of the liquid vapor separator. The rollover valve (ROV) is arranged to close the communication between the fuel tank and the fuel vapor trap in the event of a pipeline rupture or rollover event. By means of the ROV, the fuel is retained in the fuel system and cannot be released to the atmosphere.

[0035] Preferably, a high flow rollover valve is used that can accommodate vapor flow in all conditions, such as refueling conditions or some specific driving conditions with different temperatures and atmospheric pressures.

[0036] In another preferred embodiment, the fuel vapor trap is placed in a vent area configured according to the geometry of the fuel tank so that the fuel vapor trap always remains away from the fuel when the vehicle is tilted at least 12%, preferably up to 15%, and more preferably up to 30% in any direction. For example, when the vehicle is on a flat surface, the fuel vapor trap is placed at a sufficiently high position above the fuel tank. Moreover, the fuel vapor trap should have a gap with the fuel tank in the lateral direction to avoid being submerged when the fuel tank is tilted in any direction.

[0037] Yet another optional feature of the present invention is that the fuel tank vent system includes a recirculation line connecting the liquid vapor separator and the header of the refueling pipe to reduce vapor generation in the tank and reduce loading on the fuel vapor trap, thereby allowing for reduced CO2 emissions.

[0038] Another optional feature of the present invention is that the fuel tank vent system includes a level sensor located inside the fuel tank, the level sensor being capable of sending a signal when the fuel reaches a predetermined level, the signal relating to the closing of the normally closed switch.

[0039] The liquid level detection signal can trigger the closing of the normally closed switch device immediately or with a time delay. No other electronic device is required to control the action, thus saving costs.

[0040] Alternatively, the system may be operated without any level sensor and the normally closed switch is timed, the timer being calculated by the fuel tank volume and the refueling rate.

[0041] Another feature of the present invention is that the normally closed opening and closing device includes a valve pair, which includes an over-pressure relief (OPR) valve and an under-pressure relief (UPR) valve, or includes a combined pressure / vacuum relief valve (P / VRV) to ensure the safety of the storage tank and prevent its internal pressure from becoming too extreme.

[0042] The present invention also provides a motor vehicle comprising the fuel tank ventilation system as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The attached diagram shows some preferred variations. Figures 1 to 7 The invention is presented in a non-limiting manner.

[0044] [ Figure 1 ] Figure 1 is a schematic diagram of a fuel tank venting system according to a first embodiment of the present invention;

[0045] [ Figure 2 ] Figure 2 is a schematic diagram of a fuel tank venting system according to a second embodiment of the present invention;

[0046] [ Figure 3 ] Figure 3 is a schematic diagram of a fuel tank venting system according to a third embodiment of the present invention;

[0047] [ Figure 4 ] Figure 4 is a schematic diagram of a fuel tank venting system according to a fourth embodiment of the present invention;

[0048] [ Figure 5 ] Figure 5 is a schematic diagram of a fuel tank venting system according to a fifth embodiment of the present invention;

[0049] [ Figure 6 ] Figure 6 is a schematic diagram of a fuel tank venting system according to a sixth embodiment of the present invention;

[0050] [ Figure 7 ] Figure 7 is a schematic diagram of a fuel tank venting system according to a seventh embodiment of the present invention;

[0051] [ Figure 8 ] Figure 8 is a schematic diagram of a fuel tank venting system according to an eighth embodiment of the present invention. DETAILED DESCRIPTION

[0052] Reference Figure 1 A fuel tank venting system 10 for a motor vehicle according to a first embodiment of the present invention comprises a fuel tank 1, a refueling pipe 2 closed by a fuel cap, and a fuel vapor trap 3, which is, for example, a canister containing activated carbon, carbon or other material that absorbs and desorbs fuel vapor. The fuel vapor trap 3 thus receives and stores fuel vapor from the fuel tank 1 and then delivers these stored fuel vapors to a fuel filling device for combustion in a vehicle engine. The fuel vapor trap 3 is connected to the fuel tank 1 via an inlet pipe 4.

[0053] In this embodiment, the inlet duct 4 is connected to the fuel tank 1 only via one hole 5 which is continuously open when the vehicle is in static conditions. Thus, the inlet duct 4 is arranged to maintain a continuous vapour communication between the fuel vapour trap 3 and the fuel tank 1 under static conditions. The hole 5 is arranged in the top wall 11 of the fuel tank 1 so that the hole 5 is not continuously immersed in liquid. Preferably, the hole 5 is carried by a vent connection capable of connecting the inlet duct 4 to the fuel tank 1. For example, the vent connection can be a vent nipple fixed to the tank wall.

[0054] Moreover, the fuel vapor trap 3 is connected to a normally closed opening and closing device 6 arranged to communicate with the atmosphere. The normally closed opening and closing device 6 is connected to the fuel vapor trap 3 via an outlet pipe 7. The normally closed opening and closing device 6 comprises an electric valve, in particular a single electric valve, such as a solenoid valve, which is closed when the electric valve is de-energized. The normally closed opening and closing device 6 is arranged to be opened during the vehicle refueling process, and closed when the fuel in the fuel tank 1 reaches a predetermined filling level and when the vehicle is in a normal operating state. In other words, the normally closed opening and closing device 6 is opened only during the vehicle refueling process. Alternatively, the normally closed opening and closing device 6 is opened only in the following cases: a first case, during the vehicle refueling process; and a second case, when the pressure in the fuel tank 1 reaches a predetermined pressure level. In the second case, the vehicle is not in a normal operating state. The predetermined pressure level is, for example, an overpressure or underpressure relative to the ambient pressure, for example, determined relative to the pressure tolerance performance of the fuel tank 1. The overpressure is, for example, selected to be 0.3 bar to 1 bar higher than the ambient pressure, and may occur, for example, in summer when the vehicle is parked in a sunny area for a long time. The low pressure is, for example, selected to be -0.1 bar to -0.3 bar below the ambient pressure. In the second case, i.e. when the pressure in the fuel tank 1 reaches a predetermined pressure level, in order to open the normally closed opening and closing device 6, the normally closed opening and closing device 6 includes a passive valve (or passive valve, passivevalve), such as a mechanically actuated valve, which is passively opened when the predetermined pressure level is reached, i.e. opened under the action of the pressure difference between the ambient pressure and the pressure in the fuel tank, and in other cases, passively closed when the predetermined pressure level is not reached or no longer reached. For example, the above-mentioned electric valve and the above-mentioned passive valve are arranged in parallel, each of which connects the outlet pipe 7 to the atmosphere when opened. For example, as a passive valve, the normally closed opening and closing device includes a valve pair, which includes an overpressure release (OPR) valve and an underpressure release (UPR) valve, or includes a combined pressure / vacuum release valve (P / VRV) to ensure the safety of the tank and avoid its internal pressure from becoming too extreme. In any case, the electric valve is opened only during the vehicle refueling process. Thus, active actuation (or active actuation) of the normally closed on-off valve, in which the electric valve is energized, is only performed during the vehicle refueling process.

[0055] The fuel tank venting system may include a level sensor located inside the fuel tank 1 , which is capable of sending a signal to close the normally closed opening and closing device 6 when the fuel reaches a predetermined level.

[0056] Reference Figure 2, a second embodiment of the present invention is disclosed. In addition to the features already described in the first embodiment, the fuel tank ventilation system further comprises a liquid vapor separator (LVS) 8 located in the inlet duct 4, the liquid vapor separator 8 being arranged between the fuel vapor trap 3 and the orifice 5. In this embodiment, the liquid vapor separator 8 is arranged above the maximum fuel level in the fuel tank 1.

[0057] There are mainly two types of LVS: the so-called "passive" LVS, known for example from patent EP1020670 in the name of the applicant, which comprises in its base a simple valve which opens under the weight of the liquid it contains; and the so-called "active" LVS, known for example from US patent No. 6698475, which discharges by active means (a pump, for example a jet pump).

[0058] Reference Figure 3 , a third embodiment of the present invention is disclosed. In addition to the features already described in the second embodiment, the fuel tank venting system comprises a rollover valve 9 disposed in the liquid vapor separator 8. The rollover valve 9 serves to automatically close the fuel tank 1 as soon as the fuel tank 1 begins to tip over. For example, the rollover valve comprises a high-density ball device resting in a cage, the bottom of the cage having a conical shape so that the ball moves upwards to push the valve that closes the inlet pipe 4 leading to the fuel vapor trap 3. In this embodiment, the rollover valve 9 is disposed above the maximum fuel level of the liquid vapor separator 8.

[0059] Figure 4 A fourth embodiment of the invention is shown in which a recirculation line 12 is used to connect the liquid vapor separator 8 and the head of the refueling pipe 2 to reduce vapor generation in the fuel tank 1 .

[0060] Figure 5 A fifth embodiment of the present invention is shown, which is an improvement of the fourth embodiment to target the use of large and / or complex fuel tanks. In this embodiment, the fuel tank 1 includes a second hole 5'. The two holes 5, 5' are arranged in different areas on the top wall 11 of the fuel tank 1, and the two holes 5, 5' are connected to the inlet pipe 4 through a vent pipe 13. In this embodiment, the vent pipe 13 and the LVS 8 communicating with the holes 5, 5' are arranged outside the fuel tank 1.

[0061] Figure 6 An alternative to the fifth embodiment is shown, in which the fuel tank ventilation system comprises a ventilation pipe 13' located inside the fuel tank 1. The ventilation pipe 13' is connected to the hole 5 provided on the top wall 11 of the fuel tank 1. Moreover, the ventilation pipe 13' comprises a continuously open secondary hole 51. Thus, both the hole 5 and the secondary hole 51 are in communication with the inlet pipe 4 through the ventilation pipe 13'.

[0062] Preferably, the fuel vapor trap 3 is placed in a ventilation area configured according to the geometry of the fuel tank 1 so that the fuel vapor trap 3 always remains away from the fuel when the vehicle is tilted in any direction by at least 12%, preferably up to 15%, more preferably up to 30%. In the above embodiment, the LVS 8 is placed above the liquid level in the fuel tank 1. However, as long as the holes and the secondary holes are arranged in the vapor dome, the inlet pipe 4 can be arranged inside the fuel tank and in contact with the liquid. In this case, as Figure 7 As shown, the LVS 8 and the fuel vapor trap 3 may be arranged below the fuel tank 1 and below the liquid level. Alternatively, in order to better protect the fuel vapor trap 3, the inlet pipe 4 may have a Figure 8 The U-shape shown, and thus the shape of the inlet pipe, has a raised point configured to prevent liquid fuel from entering the fuel trap. Thus, no liquid can enter the fuel vapor trap 3, which avoids fuel liquid from contaminating the fuel vapor trap 3.

[0063] Reference numerals list:

[0064] 1: Fuel tank

[0065] 2: Fuel pipe

[0066] 3: Fuel vapor trap

[0067] 4: Inlet pipe

[0068] 5. 5': Hole

[0069] 6: Normally closed switch

[0070] 7: Export pipeline

[0071] 8: Liquid vapor separator

[0072] 9: Rollover valve

[0073] 10: Fuel tank ventilation system

[0074] 11: Top wall

[0075] 12: Recirculation line

[0076] 13, 13': Ventilation pipe

[0077] 51: Secondary hole

Claims

1. A fuel tank venting system (10) for a motor vehicle, comprising: - a fuel tank (1) comprising a vapour dome; - a refueling pipe (2); a fuel vapor trap (3) connected to the fuel tank (1) via an inlet duct (4), wherein the inlet duct (4) is connected to the fuel tank (1) via at least one permanently open hole (5) which is arranged in the vapor dome of the fuel tank (1) under static conditions; The fuel tank ventilation system (10) is characterized in that it comprises: - a normally closed opening and closing device (6) communicating with the atmosphere and connected to the fuel vapor trap (3) through an outlet pipe (7), the normally closed opening and closing device (6) comprising an electric valve, the electric valve being closed when the electric valve is de-energized; The normally closed opening and closing device (6) is configured to open during the vehicle refueling process and to close when the fuel in the fuel tank (1) reaches a predetermined filling level and when the vehicle is in normal operation. And wherein the inlet conduit (4) is arranged to maintain continuous vapor communication between the fuel vapor trap (3) and the fuel tank (1) under static conditions.

2. The fuel tank vent system (10) of claim 1, wherein: The hole (5) is provided in the wall of the fuel tank (1).

3. The fuel tank vent system (10) of claim 1, wherein: The hole (5) is provided in a top wall (11) of the fuel tank (1).

4. The fuel tank venting system (10) according to any one of claims 1 to 3, wherein: The normally closed opening and closing device (6) opens only during the vehicle refueling process or when the pressure in the fuel tank (1) reaches a predetermined pressure level.

5. A fuel tank venting system (10) according to any one of claims 1 to 3, comprising at least two holes (5, 5'), both of which are connected to the inlet pipe (4) through a vent pipe (13) located outside the fuel tank (1).

6. The fuel tank vent system (10) of claim 5, wherein: The at least two holes (5, 5') are arranged in different areas on the top wall (11) of the fuel tank (1).

7. A fuel tank ventilation system (10) according to any one of claims 1 to 3, comprising a ventilation pipe (13') located inside the fuel tank (1), the ventilation pipe (13') being connected to the hole (5) and having at least one secondary hole (51) which is continuously open.

8. The fuel tank venting system (10) according to any one of claims 1 to 3, wherein: The hole (5) is carried by a vent connection capable of connecting the inlet duct (4) to the fuel tank (1).

9. The fuel tank venting system (10) of claim 8, wherein: The vent connection is a vent joint.

10. The fuel tank vent system (10) of claim 8, wherein: The vent connection is fixed to the wall of the fuel tank (1).

11. A fuel tank venting system (10) according to any one of claims 1 to 3, comprising a liquid vapor separator (8) in the inlet duct (4), the liquid vapor separator (8) being arranged between the fuel vapor trap (3) and the aperture (5).

12. The fuel tank vent system (10) of claim 11, wherein: The liquid vapor separator (8) is arranged above the maximum fuel level in the fuel tank (1).

13. The fuel tank vent system (10) of claim 11, wherein: The liquid-vapor separator (8) comprises at least one rollover valve (9), which is arranged at and above a maximum fuel level in the liquid-vapor separator (8).

14. The fuel tank venting system (10) according to any one of claims 1 to 3, wherein: The fuel vapor trap (3) is placed in a ventilation area configured according to the geometry of the fuel tank (1) so that the fuel vapor trap (3) always remains away from the fuel when the vehicle is tilted at least 12% in any direction.

15. The fuel tank vent system (10) of claim 14, wherein: The fuel vapor trap (3) is placed in a ventilation area configured according to the geometry of the fuel tank (1) so that the fuel vapor trap (3) always remains away from the fuel when the vehicle is tilted up to 15% in any direction.

16. The fuel tank vent system (10) of claim 14, wherein: The fuel vapor trap (3) is placed in a ventilation area configured according to the geometry of the fuel tank (1) so that the fuel vapor trap (3) always remains away from the fuel when the vehicle is tilted up to 30% in any direction.

17. The fuel tank venting system (10) of claim 11, comprising a recirculation line (12) connecting the liquid vapor separator (8) and the head of the refueling pipe (2).

18. A fuel tank ventilation system (10) as claimed in any one of claims 1 to 3, comprising a liquid level sensor located inside the fuel tank (1), the liquid level sensor being capable of sending a signal when the fuel reaches a predetermined liquid level, the signal being related to the closing of the normally closed opening and closing device (6).

19. The fuel tank venting system (10) according to any one of claims 1 to 3, wherein: The normally closed on-off device (6) comprises a valve pair or a combined pressure / vacuum release valve (P / VRV), wherein the valve pair comprises an overpressure release (OPR) valve and an underpressure release (UPR) valve.

20. A motor vehicle comprising a fuel tank venting system (10) according to any one of claims 1 to 19.

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