Bladder for a fuel tank

Abstract

The invention relates to an assembly (1) comprising a bladder (2) that defines a variable-volume sealed enclosure for a fuel tank of a vehicle fuel system, the bladder (2) comprising a ventilation port (3) configured to place the interior (4) of the sealed enclosure in fluid communication with the exterior of the fuel tank via a ventilation line of the fuel system, characterised in that the assembly comprises a ventilation system (5) for ventilating the bladder (2), wherein the ventilation system (5) is sealingly coupled to the ventilation port (3), and the ventilation system (5) comprises an overflow-prevention device configured to prevent fuel from overflowing out of the fuel tank in the event that the fuel tank is overfilled and the bladder (2) develops a leak, and a flow-prevention device configured to prevent fuel from flowing out of the fuel tank in the event that the fuel tank is overturned and the bladder (2) develops a leak.

Description

fuel tank bladder Technical field of the invention

[0001] The present invention relates generally to the control of fuel vapor pressure in a vehicle fuel tank, particularly for hybrid vehicles. A hybrid vehicle is a vehicle equipped with a heat engine (also called an "internal combustion engine") combined with one or more electric motors. The term "vehicle" refers to any vehicle, whether land-based such as a motor vehicle (car, motorcycle, truck, bus, train, machine, including construction equipment, etc.), marine such as a ship, or aerial such as an aircraft.

[0002] More specifically, the invention relates to an assembly comprising a bladder for a fuel tank of a vehicle fuel system.

[0003] The invention also relates to a vehicle fuel system comprising a fuel tank and an assembly according to the invention.

[0004] The invention also relates to a vehicle, in particular a motor vehicle, in particular a hybrid vehicle, comprising a fuel system according to the invention.

[0005] The invention also relates to a method of manufacturing a vehicle fuel system comprising an assembly according to the invention.

[0006] The invention also relates to a method of manufacturing by extrusion blow molding a fuel tank of a vehicle fuel system comprising an assembly according to the invention.

[0007] The invention finally relates to the use of an assembly according to the invention in a vehicle fuel system.

[0008] Fuel stored in a vehicle's fuel tank is subject to temperature fluctuations primarily dependent on the ambient temperature. Depending on the climate, the fuel temperature can vary significantly, especially when the vehicle is parked or in the open air. A rise in the fuel temperature in the tank causes some of it to evaporate. Since the fuel tank is a predetermined, sealed, and airtight volume, the generation of fuel vapors leads to a pressure increase in the gaseous phase inside the tank. This high fuel vapor pressure creates mechanical stress on the tank walls, which can damage them and lead to leaks if the pressure increase is not controlled. Technical background of the invention

[0009] It is known in the prior art, for example from document WO 2021 / 013940 A1, to place an inflatable bladder inside a fuel tank. This bladder is connected to an air inlet and outlet duct leading from the fuel tank and allows, alternatively, the bladder to be supplied with air or some of the air contained within it to be expelled. In this way, depending on the fluctuation in the amount of fuel vapors in the fuel tank, the bladder can inflate or deflate to modify the volume available for fuel vapors and thus limit variations in fuel vapor pressure within the fuel tank. Document US10926625 B2 also provides an example of a tank equipped with a bladder connected to a vent duct.

[0010] While bladder-type systems effectively reduce the risk of pressure spikes in the fuel tank, they do present some problems. Specifically, if the bladder is damaged, particularly if punctured or torn, fuel can enter it. Once fuel is present, some of it can escape through the vent. This can occur when there is too much fuel in the bladder (overfilling the tank) or when the tank is tilted excessively or even inverted. Safety standards mandate that fuel cannot escape from the tank, even in cases of overfilling, excessive tilting, or inverted tanks.

[0011] The invention aims in particular to solve the problems identified in the prior art by limiting the pressure rise of fuel vapors in the fuel tank while avoiding or mitigating the disadvantages posed by the bladder of the prior art.

[0012] To this end, the invention relates to an assembly comprising a bladder defining a fuel-tight, variable-volume enclosure for a fuel tank in a vehicle fuel system. The bladder includes a vent orifice configured to establish fluidic communication between the interior of the sealed enclosure and the exterior of the fuel tank via a fuel system vent line. The assembly includes a bladder venting system hermetically coupled to the vent orifice. This venting system comprises both:

[0013] - an overfill prevention device configured to prevent fuel from overflowing from the fuel tank when a situation of fuel tank overfilling and bladder leakage occurs, and

[0014] - a leak prevention device configured to prevent fuel from flowing out of the fuel tank when a fuel tank overturning situation and bladder leakage occurs.

[0015] In the context of the invention, the expression "to prevent" means "to stop" or, at the very least, "to limit".

[0016] Furthermore, for the aforementioned situations to occur, the conditions must all be met. Regarding the overfill prevention device, it is most effective when both of the following conditions are present: the fuel tank is overfilled and the bladder is leaking. Regarding the leak prevention device, it is most effective when both of the following conditions are present: the fuel tank is at a steep angle, or even inverted, and the bladder is leaking.

[0017] Thus, the prior art bladder is equipped here with a ventilation system capable of preventing fuel from the bladder from escaping the fuel tank through the air outlet duct when the tank is overfilled and / or when the tank is significantly tilted or even inverted. Indeed, such scenarios are likely to occur when the variable-volume sealed enclosure is no longer airtight against the fuel in the fuel tank, for example, when the bladder is punctured, torn, or even ripped off. Furthermore, combining an overflow prevention device and a leak prevention device in the ventilation system prevents fuel from the bladder from escaping the fuel tank through the air outlet duct, regardless of the fuel leak scenario.

[0018] Advantageously, the bladder is made of an elastic material, that is, a flexible and deformable material that ideally returns to its original shape when no longer subjected to mechanical stress. In one example, the bladder is made of a thermoplastic elastomer material, for example, thermoplastic polyurethane (TPU).

[0019] Alternatively, the bladder is made of polyethylene (PE), polyamide (PA), ethylene-vinyl acetate (EVA) or as a multilayer material comprising polyethylene (PE), preferably high-density polyethylene (HDPE), and ethylene vinyl alcohol (EVOH).

[0020] Alternatively, the bladder is manufactured as a multilayer material comprising thermoplastic polyurethane (TPU) and ethylene vinyl alcohol (EVOH).

[0021] Alternatively, the bladder is manufactured as a multilayer material comprising thermoplastic polyurethane (TPU) and polyamide (PA).

[0022] Preferably, polyethylene is high-density polyethylene (HDPE), and polyamide is polyamide 6, 11 or 12 (PA6, PA11 or PA12).

[0023] Advantageously, the multilayer comprises an adhesive layer provided between the polyethylene (PE) layer, preferably high-density polyethylene (HDPE), and the ethylene vinyl alcohol (EVOH) layer.

[0024] Different materials can be chosen to make the bladder in order to give it a choice of characteristics, such as low cost, mechanical resistance, flexibility, deformability or fuel impermeability.

[0025] The term "fuel" refers to a hydrocarbon suitable for powering internal combustion engines. For specific internal combustion engines, the fuel may be alcohol-based, for example, ethanol, bioethanol, butanol, methanol, or mixtures thereof, for example with hydrocarbons.

[0026] The package may also include one or more of the following optional features, taken alone or in combination:

[0027] - The overflow prevention device is located within the overflow prevention device. This reduces the size and therefore the footprint of the bladder ventilation system. Preferably, the overflow prevention device is located within and below the overflow prevention device, with the vertical axis of the vehicle as the reference point.

[0028] - The overflow prevention device is a normally open float valve. This allows for a simple, inexpensive, and reliable overflow prevention system.

[0029] The flow prevention device is a ball or spring-loaded ROV (Reverse Orbital Valve). This allows for a simple, inexpensive, and reliable flow prevention device. Preferably, the flow prevention device is a spring-loaded ROV with a pre-calibrated spring. This is because a spring-loaded ROV is more compact and less expensive to manufacture than a ball-loaded ROV.

[0030] A roll-over valve (ROV) is designed to prevent fuel from escaping the tank when the vehicle rolls over, for example, in an accident. The ROV closes automatically when the vehicle rolls over. A rollover is defined as a movement of sufficient magnitude for the fuel level in the tank to reach the ROV under the force of gravity alone. Specifically, this term also refers to any situation in which the ROV becomes submerged in fuel from the tank. More precisely, it refers to a situation in which the fuel tank has rotated 180° from its original, designed position.

[0031] - The ventilation opening is provided in a wall of the bladder's sealed enclosure, and the ventilation system passes through said wall of the bladder's sealed enclosure. This allows for the most compact assembly possible.

[0032] The assembly also includes a bracket for attaching the bladder to the inner wall of the fuel tank. Preferably, the bladder mounting bracket is welded to the inner wall of the fuel tank, allowing for a simple, inexpensive, and reliable attachment of the bladder. Furthermore, the mounting bracket allows for the attachment of additional components (e.g., gauge, valve, retaining clip, sensor) to the assembly.

[0033] The invention also relates to a vehicle fuel system comprising a fuel tank, a ventilation line, and an assembly conforming to the aforementioned assembly. The fuel tank includes a wall delimiting a hollow body in which the bladder of said assembly is housed, said hollow body defining an internal volume intended to contain fuel outside the sealed enclosure of said bladder. The ventilation system is arranged within said ventilation line.

[0034] A "fuel system" is defined as any device incorporated into a vehicle equipped with an internal combustion engine whose function is to store, purify, measure, or transport fuel intended to power the internal combustion engine. A fuel system includes at least one fuel tank and a fuel supply line to the internal combustion engine. It may also include one or more of the following accessories: a fuel tank vent valve, flap, and line; a filler neck; a canister; a fuel filter; a fuel pump; a fuel tank gauge; an electrical connector; a fuel cap; and any component, in general, through which fuel passes in liquid and / or gaseous form, for example, a fuel vapor recirculation line.

[0035] A "fuel tank" is defined as a sealed container suitable for storing fuel under various operating and environmental conditions. The fuel tank according to the invention comprises a wall, also called a casing, enclosing a hollow body. A fuel tank wall includes an inner wall and an outer wall. The inner wall faces the interior volume of the hollow body, while the outer wall faces the exterior volume of the hollow body. The inner wall includes a lower inner wall, called the bottom wall, and an upper inner wall opposite the lower inner wall. Under normal operating conditions, the fuel rests on the bottom wall. The hollow body according to the invention is made of plastic. In this case, it comprises at least one synthetic resin polymer that is in a solid state under ambient conditions.Hollow bodies made of plastic are preferred because of their better elasticity and superior ability to be shaped into complex forms.

[0036] A hollow body made of plastic can be produced by any known manufacturing process. One known method is injection molding. Extrusion blow molding and rotational molding are also known processes.

[0037] The term "plastic material" refers both to the generally homogeneous material of a single-layer structure and to the heterogeneous material of a multi-layer structure.

[0038] The hollow body advantageously comprises at least one thermoplastic polymer, that is to say, a polymer which, under the influence of heat, melts or softens sufficiently to allow it to be shaped.

[0039] The term "polymer" refers to both homopolymers and copolymers (including binary and ternary copolymers). Examples of such copolymers include, but are not limited to, random-distributed copolymers, sequenced copolymers, block copolymers, and grafted copolymers.

[0040] Any type of thermoplastic polymer or copolymer with a melting point below its decomposition point is suitable. Thermoplastic polymers with a melting range of at least ten degrees Celsius (10°C) are particularly well-suited. Examples of such materials include those exhibiting polydispersity of their molecular mass.

[0041] In particular, polyolefins, thermoplastic polyesters, polyketones, polyamides, and their copolymers can be used. A mixture of polymers or copolymers can also be used, as well as a mixture of polymeric materials with inorganic, organic, and / or natural fillers such as, but not limited to, carbon, salts and other inorganic derivatives, and natural or polymeric fibers. It is also possible to use multilayer structures consisting of stacked and bonded layers comprising at least one of the aforementioned polymers or copolymers.

[0042] A commonly used polymer is polyethylene. Excellent results have been obtained with high-density polyethylene (HDPE).

[0043] In one example, the hollow body comprises a multilayer structure including at least one layer of thermoplastic material and at least one additional layer which may advantageously be made of a liquid and / or gas barrier material. Preferably, the nature and thickness of the barrier layer are chosen to minimize the permeability of liquids and gases in contact with the fuel tank wall. Preferably, this layer is based on a barrier material, i.e., a fuel-impermeable resin such as EVOH (ethylene-vinyl acetate copolymer, partially hydrolyzed). Alternatively, the hollow body may undergo a surface treatment (fluorination or sulfonation) to render it fuel-impermeable.

[0044] The fuel system may also include one or more of the following optional features, taken alone or in combination:

[0045] - The ventilation system passes through the fuel tank wall. This allows all the functions of the ventilation system to be performed simply and compactly.

[0046] - The vent line includes a flow limiter, for example, a calibrated orifice. This allows control of bladder deformation during tank filling when pressure and fuel level increase inside the tank.

[0047] - The flow limiter is integrated into the ventilation system. This allows for the integration of functions within the ventilation system.

[0048] - The ventilation line includes a canister. This prevents fuel vapors from escaping into the atmosphere when the bladder material is permeable to fuel vapors.

[0049] - Alternatively, the ventilation line opens directly into the atmosphere without passing through a canister. This allows for direct fluidic communication between the inside of the sealed enclosure and the atmosphere.

[0050] The invention also relates to a vehicle, in particular a motor vehicle, in particular a hybrid vehicle, comprising a fuel system conforming to the aforementioned fuel system.

[0051] The invention also relates to a method for manufacturing a fuel system conforming to the aforementioned fuel system, characterized in that it comprises the following steps:

[0052] a) have a fuel tank,

[0053] b) to have a set conforming to the aforementioned set,

[0054] c) compress the bladder,

[0055] d) insert the bladder into the fuel tank through an opening in a wall of the fuel tank,

[0056] e) secure the bladder inside the fuel tank using a bladder mounting bracket,

[0057] f) connect the inside of the sealed bladder enclosure to a fuel system vent line in a leak-proof manner.

[0058] This process allows the aforementioned fuel system to be manufactured in a simple manner.

[0059] The aforementioned process may further include one or more of the following optional features, taken alone or in combination:

[0060] - step d) of introducing the bladder into the fuel tank through an opening made in a wall of the fuel tank is carried out manually by an operator.

[0061] In one example, the opening in the wall of the fuel tank is a drain hole.

[0062] - step e) is carried out by means of clipping, snapping, fitting, gluing, tightening, pinching or welding the bladder fixing support onto an internal wall of the fuel tank.

[0063] Preferably, the bladder is attached inside the fuel tank using a clip. This method of attaching the bladder inside the fuel tank is simple, inexpensive, and reliable.

[0064] Preferably, the inner wall to which the bladder is attached is an upper inner wall of the fuel tank. Thus, the bladder is positioned inside a vapor dome of the fuel tank, above a surface of liquid fuel.

[0065] The invention also relates to a method for manufacturing a fuel tank for a fuel system conforming to the aforementioned fuel system by extrusion blow molding, characterized in that it comprises the following steps:

[0066] a) to have a set conforming to the aforementioned set,

[0067] b) open a blow mold and extrude a parison into the open mold,

[0068] (c) to insert said assembly into the parison using an insertion rod,

[0069] d) bring the extrusion blow mold into an intermediate closed position in order to fix said assembly inside the parison by pressing the parison against said assembly,

[0070] e) remove the insertion rod,

[0071] f) bring the extrusion blow mold into a final closed position in order to pre-form a fuel tank,

[0072] (g) introduce a pressurized gas into the extrusion blow mold in order to form the fuel tank by blowing,

[0073] h) open the extrusion blow mold and remove the fuel tank thus formed.

[0074] This process makes it possible to manufacture the aforementioned fuel system in an even simpler way.

[0075] The invention also provides for the use of an assembly conforming to the aforementioned assembly in a fuel system, said assembly being intended to limit the increase in pressure inside the fuel tank, in order to limit the mechanical stresses on the fuel tank, while preventing fuel from escaping from the fuel tank when the bladder is damaged and fuel is present in the bladder.

[0076] Other features and advantages of the invention will become clear from the following description, which is by way of example and not limitation, with reference to the accompanying drawings, in which: 1a is a cross-sectional view of part of a fuel system according to the invention; 2a illustrates an alternative embodiment of the fuel system of the invention; 3a is a cross-sectional view of a ventilation system without a flow prevention device; 4a is a cross-sectional view of a ventilation system without an overflow prevention device; 5a is a cross-sectional view of a ventilation system according to the invention; 6a is a perspective view of a vehicle according to the invention. Detailed description of at least one embodiment of the invention

[0077] In the various figures, identical or similar elements bear the same references, possibly with an additional subscript. Therefore, a description of their structure and function is not systematically repeated.

[0078] In all that follows, orientations are the orientations of the figures. In particular, the terms "upper", "lower", "left", "right", "above", "below", "forward" and "backward" are generally understood in relation to the direction in which the figures are represented.

[0079] Figures 1 and 2 illustrate a fuel system 10 for a vehicle, particularly for a motor vehicle, comprising a fuel tank 11, a ventilation line 12, and an assembly 1 according to the invention. In this example, the fuel tank 11 is made of plastic.

[0080] Assembly 1 includes a bladder 2 defining a leak-proof enclosure with variable volume. The bladder 2 is made of an elastic material, i.e., a flexible and deformable material. The bladder 2 includes a vent 3 configured to establish fluidic communication between the interior 4 of the leak-proof enclosure and the exterior of the fuel tank 11 via the vent line 12 of the fuel system 10. Assembly 1 includes a venting system 5 for the bladder 2, which is hermetically sealed to the vent 3. The venting system 5 comprises both:

[0081] - an overfill prevention device configured to prevent fuel from overflowing from the fuel tank 11 when a situation of overfilling of the fuel tank 11 and a leak in the bladder 2 occurs, and

[0082] - a leak prevention device configured to prevent fuel from flowing out of the fuel tank 11 when a situation of fuel tank 11 overturning and bladder 2 leakage occurs.

[0083] The fuel tank 11 includes a wall 13 delimiting a hollow body in which the bladder 2 of assembly 1 is housed. The hollow body defines an internal volume intended to contain fuel outside the sealed enclosure of the bladder 2. Assembly 1 further includes a support 9 for securing the bladder 2 inside the fuel tank 11. The ventilation system 5 is arranged in the ventilation line 12. The ventilation system 5 has an inlet port 5a and an outlet port 5b. The inlet port 5a is in fluidic communication with the interior of the sealed enclosure, and the outlet port 5b is in fluidic communication with the exterior of the fuel tank 11.

[0084] In the example illustrated in the figure, the ventilation line 12 includes a canister 17.

[0085] In the example illustrated in the figure, the ventilation line 12 opens into the atmosphere without passing through a canister.

[0086] In an example not shown, the ventilation system 5 passes through the wall 13 of the fuel tank 11.

[0087] Figure 1 illustrates an embodiment in which the ventilation system 5 includes an overflow prevention device but does not include a flow prevention device. In this example, the overflow prevention device is a normally open float valve 6.

[0088] The illustration shows an embodiment in which the ventilation system 5 includes a flow prevention device but not an overflow prevention device. In this example, the flow prevention device is a dense ball "ROV" reversing valve 7. Advantageously, two dense balls 7, 7' are provided, arranged one above the other such that the lower ball 7 can close the inlet orifice 5a of the ventilation system 5 and the upper ball 7' can close the outlet orifice 5b of the ventilation system 5.

[0089] When a motor vehicle equipped with this type of reversing valve is operating normally, the axis of the reversing valve is substantially vertical. In this position, the lower ball 7 rests on a lower conical seat and hermetically seals the inlet orifice 5a. In this position, the outlet orifice 5b is open because the upper ball 7' rests on the lower ball 7 and a free space remains between the upper ball 7' and an upper conical seat.

[0090] If an overpressure occurs inside 4 of the sealed enclosure sufficient to momentarily lift the lower ball 7 and the upper ball 7', overpressure air will exit through the outlet 5b.

[0091] If, for any reason, the motor vehicle tilts, the axis of the inlet 5a and outlet 5b ports also tilts and forms an angle with the vertical. If this tilt exceeds the angle of the lower conical seat, the lower ball 7 will tend to roll on this seat, opening the inlet 5a. Under these conditions, when the variable-volume sealed chamber is no longer sealed against the fuel in the fuel tank 11, fuel may enter the reversing valve. However, by rolling on the lower conical seat, the lower ball 7 pushes the upper ball 7' upwards, pressing against the upper conical seat. This ball then seals the outlet 5b, preventing the fuel that has entered the reversing valve from flowing out.

[0092] In the event of the fuel tank 11 being overturned, the lower ball 7 then occupies the upper position and presses the upper ball 7' against its conical seat, which results in the closure of the outlet 5b.

[0093] This illustrates an embodiment of the invention in which the ventilation system 5 comprises both the overflow prevention device and the overflow prevention device. Advantageously, the overflow prevention device is disposed within and below the overflow prevention device, with the vertical axis of the motor vehicle as a reference. The overflow prevention device is a normally open float valve 6, and the overflow prevention device is a spring-loaded ROV (reversing valve) 8. In this example, the ventilation system 5 comprises a body 15, and the ventilation line 12 comprises a flow restrictor 16. In this example, the flow restrictor 16 is a calibrated orifice arranged in the body 15 of the ventilation system 5.

[0094] Still in the example illustrated in the, the ventilation orifice 3 is provided in a wall 2a of the sealed enclosure of the bladder 2 and the ventilation system 5 passes through the wall 2a of the sealed enclosure of the bladder 2.

[0095] The ventilation line 12 includes a ventilation fitting 12a. The ventilation fitting 12a is the section of the ventilation line 12 arranged inside the fuel tank 11.

[0096] The vent fitting 12a has two ends, each end connected to a fluid connector 12b, 12c. The first fluid connector 12b provides a leak-proof connection between the inside of the sealed bladder 2 enclosure and the vent fitting 12a, via the venting system 5. The second fluid connector 12c provides a leak-proof connection between the vent fitting 12a and the section of the vent line 12 arranged outside the fuel tank 11. Advantageously, the first fluid connector 12b forms part of the body 15 of the venting system 5.

[0097] Laillustrates a motor vehicle 20, for example, a hybrid vehicle, including the fuel system 10.

[0098] Another object of the invention is a method for manufacturing a fuel system 10 for a vehicle comprising the following steps:

[0099] a) have a fuel tank 11,

[0100] b) to have a set 1,

[0101] c) compress the bladder 2,

[0102] d) insert the bladder 2 into the fuel tank 11 through an opening provided in a wall of the fuel tank 11,

[0103] e) secure the bladder 2 inside the fuel tank 11 by means of a bladder 2 fixing bracket 9,

[0104] f) connect the inside 4 of the sealed enclosure of the bladder 2 to a vent line 12 of the fuel system 10.

[0105] Advantageously, in the aforementioned process, step e) is carried out by means of clipping, snapping, fitting, gluing, tightening, pinching or welding the support 9 for fixing the bladder 2 to an internal wall 14 of the fuel tank 11.

[0106] Another object of the invention is a method for manufacturing a fuel tank 11 of a fuel system 10 for a vehicle by extrusion blow molding, comprising the following steps:

[0107] a) to have a set 1,

[0108] b) open a blow mold and extrude a parison into the open mold,

[0109] c) insert assembly 1 into the parison using an insertion rod,

[0110] d) bring the extrusion blow mold into an intermediate closed position in order to fix assembly 1 inside the parison by pressing the parison against assembly 1,

[0111] e) remove the insertion rod,

[0112] f) bring the extrusion blow mold into a final closed position in order to pre-form a fuel tank 11,

[0113] (g) introduce a pressurized gas into the extrusion blow mold in order to form the fuel tank 11 by blowing,

[0114] h) open the extrusion blow mold and take out the fuel tank 11 thus formed. Reference list

[0115] 1: assembly 2: bladder 2a: wall 3: vent port 4: inside of sealed enclosure 5: venting system 5a: venting system inlet port 5b: venting system outlet port 6, 6': normally open float valve 7, 7': ROV ball rollover valve 8: ROV spring rollover valve 9: mounting bracket 10: fuel system 11: fuel tank 12: vent line 12a: vent fitting 12b: first fluid connector 12c: second fluid connector 13: wall 14: inner wall 15: venting system body 16: flow restrictor 17: canister 20: vehicle

Claims

Assembly (1) comprising a bladder (2) defining a variable-volume sealed enclosure for a fuel tank of a vehicle fuel system, said bladder (2) comprising a vent port (3) configured to connect the interior (4) of the sealed enclosure to the exterior of the fuel tank via a fuel system vent line, the assembly comprising a venting system (5) for the bladder (2) sealed to the vent port (3), characterized in that the venting system (5) comprises both: an overfill prevention device configured to prevent fuel from overflowing from the fuel tank when a situation of fuel tank overfilling and bladder (2) leakage occurs,and a leak prevention device configured to prevent fuel from flowing out of the fuel tank when a fuel tank overturns and the bladder (2) fails to seal properly. Assembly (1) according to the preceding claim, characterized in that the flow prevention device is disposed within the overflow prevention device. Assembly (1) according to any one of the preceding claims, characterized in that the overflow prevention device is a normally open float valve (6, 6'). Assembly (1) according to any one of the preceding claims, characterized in that the flow prevention device is a ball (7) or spring (8) ROV reversing valve. Assembly (1) according to any one of the preceding claims, characterized in that the ventilation orifice (3) is provided in a wall (2a) of the sealed enclosure of the bladder (2) and the ventilation system (5) passes through said wall (2a) of the sealed enclosure of the bladder (2). Assembly (1) according to any one of the preceding claims, characterized in that it further comprises a support (9) for fixing the bladder (2). Fuel system (10) for vehicle comprising a fuel tank (11), a vent line (12) and an assembly (1) according to any one of the preceding claims, the fuel tank (11) comprising a wall (13) delimiting a hollow body in which is housed the bladder (2) of said assembly (1), said hollow body defining an internal volume intended to contain fuel outside the sealed enclosure of said bladder (2), the vent system (5) is arranged in said vent line (12). Fuel system (10) according to the preceding claim, characterized in that the ventilation system (5) passes through the wall (13) of the fuel tank (11). Fuel system (10) according to claim 7 or 8, characterized in that the ventilation line (12) includes a flow limiter (16). Fuel system (10) according to any one of claims 7 to 9, characterized in that the vent line (12) comprises a canister (17). Vehicle (20), in particular motor vehicle, in particular hybrid vehicle, comprising a fuel system (10) according to any one of claims 7 to 10. A method for manufacturing a vehicle fuel system (10) comprising the following steps: a) having a fuel tank (11), b) having an assembly (1) according to any one of claims 1 to 6, c) compressing the bladder (2), d) introducing the bladder (2) into the fuel tank (11) through an opening in a wall of the fuel tank (11), e) fixing the bladder (2) inside the fuel tank (11) by means of a bladder fixing support (2), f) sealingly connecting the inside (4) of the sealed bladder housing (2) to a vent line (12) of the fuel system (10). Method of manufacturing a fuel system (10) for a vehicle according to the preceding claim, wherein step e) is carried out by means of clipping, snapping, fitting, gluing, clamping, pinching or welding the bladder mounting support (2) onto an internal wall (14) of the fuel tank (11). A method for manufacturing a fuel tank (11) of a fuel system (10) for a vehicle by extrusion blow molding, comprising the following steps: a) having an assembly (1) according to any one of claims 1 to 6, b) opening an extrusion blow mold and extruding a parison into the open mold, c) inserting said assembly (1) into the parison by means of an insertion rod, d) bringing the extrusion blow mold into an intermediate closed position to secure said assembly (1) inside the parison by pressing the parison against said assembly (1), e) removing the insertion rod, f) bringing the extrusion blow mold into a final closed position to preform a fuel tank (11), g) introducing pressurized gas into the extrusion blow mold to form the fuel tank (11) by blowing, h) opening the extrusion blow mold and removing the fuel tank (11) thus formed.

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