Bladder for a fuel tank

Abstract

The invention relates to a bladder (1) defining a variable-volume sealed enclosure for a fuel tank, wherein the sealed enclosure comprises a bellows (2) that is compressible in a Z-axis direction, the bellows (2) comprises a set E1 of folds (3), the folds of the set E1 of folds (3) not all being identical to one another, characterised in that each fold (31; 32, ..., 31(31-1,..., 3n) of a subset E2 of folds of the set E1 of folds (3) is in the shape of an elongate, flat, closed ring A when it is projected orthogonally onto a plane XY perpendicular to the Z-axis, the ring A having an outer length Lext and an inner length Lint in a longitudinal direction of axis X in the plane XY, the ring A also having an outer width lext and an inner width lint in a transverse Y-axis direction in the plane XY, the Y-axis being perpendicular to the X-axis, such that the ratio (Lext - Lint) / (lext - lint), referred to as ratio R, is strictly greater than 1.

Description

fuel tank bladder Technical field of the invention

[0001] The present invention relates generally to the control of the pressure of fuel vapors in a fuel tank for a motor vehicle, in particular for a hybrid vehicle. 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 "motor vehicle" means any mobile equipment, in particular, vehicles on road, rail, sea, air, space.

[0002] More particularly, the invention relates to a bladder for a fuel tank for a motor vehicle.

[0003] The invention also relates to an assembly comprising a protective casing and a bladder according to the invention.

[0004] The invention also relates to a fuel tank for a motor vehicle comprising at least one bladder according to the invention.

[0005] The invention also relates to a fuel tank for a motor vehicle comprising at least one assembly according to the invention.

[0006] The invention also relates to a use of at least one bladder according to the invention in a fuel tank for a motor vehicle.

[0007] The invention also relates to a motor vehicle, in particular a hybrid vehicle, comprising a fuel tank according to the invention.

[0008] The invention also relates to a method of manufacturing a fuel tank for a motor vehicle comprising at least one bladder according to the invention.

[0009] The invention also relates to a method of manufacturing by extrusion-blow molding a fuel tank for a motor vehicle comprising at least one bladder according to the invention.

[0010] The invention finally relates to a method of operating a fuel tank according to the invention.

[0011] The fuel stored in a motor vehicle fuel tank is subject to temperature fluctuations that depend primarily on the outside temperature. Depending on the climate to which the vehicle is exposed, the fuel temperature can vary greatly, particularly if the vehicle is outside when driving and when parked. An increase in the temperature of the fuel stored in the fuel tank causes a quantity of it to evaporate. Since the fuel tank defines a predetermined, closed and sealed volume, the generation of fuel vapors causes a rise in pressure in the gaseous phase inside the fuel tank. High fuel vapor pressure generates mechanical stresses on the walls of the fuel tank, which can damage them or even constitute a risk of explosion of the fuel tank if the rise in pressure is not controlled. Technical background of the invention

[0012] It is known in the prior art, for example from document WO 2021 / 013940 A1, to place a bellows inside a fuel tank. This bellows is connected to an air inlet and outlet duct leaving the fuel tank and allows, alternatively, to supply the bellows with air or to evacuate part of the air contained in the bellows. In this way, depending on the fluctuation in the quantity of fuel vapors present in the fuel tank, the bellows can compress or decompress to modify the volume available for the fuel vapors and thus limit the variations in fuel vapor pressure.

[0013] This bellows system does indeed reduce the risk of experiencing pressure peaks in the fuel tank, but it does pose certain problems. Indeed, the Applicant has found that a bellows with a cylindrical external shape must have a relatively large diameter to be effective. However, the larger the diameter of the bellows, the more complex it becomes to insert and fix it in the fuel tank. Complex manufacturing of the fuel tank implies an increase in the cost and manufacturing time of the fuel tank, which is not desirable.

[0014] Furthermore, a bellows having identical folds does not behave in a predictable manner when the bellows is compressed. Indeed, the Applicant has observed the appearance of buckling of the folds when a bellows having identical folds is compressed. Due to this uncontrolled buckling, the geometry of the compressed bellows differs from one compression to another, which is not desirable.

[0015] Document DE 10 2018 203006 A1 describes a bladder defining a variable volume sealed enclosure for a fuel tank in which the sealed enclosure comprises a compressible bellows, said bellows comprising a set of folds, the folds of said set of folds not all being identical to each other.

[0016] The invention aims in particular to solve the problems identified in the state of the art by limiting the rise in pressure of fuel vapors in the fuel tank while avoiding or mitigating the drawbacks posed by the bladder of the state of the art.

[0017] To this end, the invention relates to a bladder defining a variable-volume sealed enclosure for a fuel tank, in which the sealed enclosure comprises a compressible bellows in a Z-axis direction, said bellows comprising a set E1 of folds, the folds of said set E1 of folds not all being identical to each other, characterized in that each fold of a subset E2 of folds of the set E1 of folds has the shape of an elongated, flat, closed ring when projected orthogonally onto an XY plane perpendicular to the Z-axis, said ring having an external length L ext . and an interior length L int.along a longitudinal direction of axis X in the XY plane, said ring also having an external width l ext . and an interior width l int . along a transverse direction of axis Y in the XY plane, the axis Y being perpendicular to the axis X, such that the ratio (L ext . L int . ) / (L ext . L int . ), called ratio R, is strictly greater than 1.

[0018] Thus, the bellows of the prior art is here replaced by a bellows having a non-cylindrical external shape, in other words, a bellows having folds whose orthogonal projection on a plane perpendicular to the compression axis of the bellows does not have the shape of a flat and closed circular ring. This arrangement facilitates the introduction and fixing of the bladder in a fuel tank. The facilitated introduction of the bladder inside a fuel tank can be done through an opening made in a wall of the fuel tank, for example, a bung hole of the fuel tank. A bung hole is used for the introduction into the fuel tank of one or more components internal to the fuel tank, for example, a fuel pump to be installed at the bottom of the fuel tank.After the installation of the internal component(s) in the fuel tank and before putting the fuel tank into service, the bung hole is hermetically sealed. Alternatively, when the fuel tank is manufactured by a parison extrusion blow molding process, the bladder may be easily introduced into the fuel tank during the manufacture of the fuel tank, in particular, during a step of introducing one or more components into the parison.

[0019] Furthermore, because the folds of the bellows are not all identical, the occurrence of uncontrolled buckling of the folds when the bellows is compressed is avoided or at least limited.

[0020] The expression "the folds of the bellows are not all identical to each other" means that the bellows includes at least one fold which has a general shape different from the general shape of another fold of the bellows, the shape of a fold referring to its geometric shape.

[0021] Furthermore, without any other adaptation of the prior art bellows than those mentioned above, the Applicant found that the compression of the bellows is greater in the long sides of the bellows than in the short sides of the bellows, in other words, the bellows does not compress homogeneously, which is not desirable. The long sides of the bellows are the sides of the bellows bearing the longest pleats and the short sides of the bellows are the sides of the bellows bearing the shortest pleats. By carrying out numerical simulations, the Applicant discovered the existence of a causal link between the geometry of the longest pleats, the geometry of the shortest pleats and the homogeneity of the compression of the bellows. In particular, a bellows having pleats whose orthogonal projection on a plane perpendicular to the compression axis of the bellows has the shape of an elongated flat and closed ring compresses more homogeneously when (Lext . L in t . ) (L ext . L in t . ), in other words, when (L ext . L int. ) / (L ext . L int . ) 1, where L ext . is the outer length and L int. the internal length of the ring in a longitudinal direction in the plane perpendicular to the compression axis of the bellows, and where l ext . is the outer width and l int . the internal width of the ring in a transverse direction in the plane perpendicular to the compression axis of the bellows.

[0022] Preferably, the set E1 of folds is a set of adjacent folds connected to each other by first fold lines and each fold of said set E1 of folds consists of two adjacent half-folds connected to each other by a second fold line.

[0023] Advantageously, the bellows is made of an elastic material, i.e. a flexible, deformable material that returns to its initial shape when it is no longer mechanically stressed. In one example, the bellows is made of a thermoplastic elastomer material, for example thermoplastic polyurethane (TPU).

[0024] Alternatively, the bellows is made of polyethylene (PE), polyamide (PA), ethylene vinyl acetate (EVA) or as a multi-layer material comprising polyethylene (PE), preferably high density polyethylene (HDPE), and ethylene vinyl alcohol (EVOH).

[0025] Preferably, the polyethylene is high density polyethylene (HDPE), and the polyamide is polyamide 6, 11 or 12 (PA6, PA11 or PA12).

[0026] 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.

[0027] Different materials can therefore be chosen to make the bellows in order to give it a choice of characteristics, such as low cost, mechanical resistance, flexibility, deformability or impermeability to fuel.

[0028] The term "fuel" means a hydrocarbon suitable for powering heat engines. For particular heat engines, the fuel may be based on alcohol, for example, ethanol, bioethanol, butanol, methanol, or mixtures thereof, for example with hydrocarbons.

[0029] The term "fuel tank" means a sealed container, capable of storing fuel under various and varied conditions of use and environment. The fuel tank according to the invention comprises a wall, also called a casing, delimiting a hollow body. A fuel tank wall comprises an inner wall and an outer wall. The inner wall is a wall facing the interior volume of the hollow body while the outer wall is a wall facing the volume outside the hollow body. The inner wall comprises a lower inner wall, called the bottom wall, and an upper inner wall opposite the lower inner wall. Under normal conditions of use, the fuel rests on the bottom wall. The hollow body according to the invention is made of metal or plastic, preferably plastic.In the latter case, it comprises at least one synthetic resin polymer which is in a solid state under ambient conditions. Hollow plastic bodies are preferred due to their greater elasticity and their superior ability to be formed into complex shapes.

[0030] A hollow plastic body can be produced using any known processing method. A known method is the injection process. Extrusion blow molding and rotational molding processes are also known.

[0031] The term "plastic material" refers to both the generally homogeneous material of a single-layer structure and the heterogeneous material of a multi-layer structure.

[0032] 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.

[0033] The term "polymer" refers to both homopolymers and copolymers (binary or ternary in particular). Examples of such copolymers are, but are not limited to, random distribution copolymers, block copolymers, block copolymers and graft copolymers.

[0034] Any type of thermoplastic polymer or copolymer with a melting temperature below the decomposition temperature is suitable. Thermoplastic polymers with a melting range of at least 10 degrees Celsius (10°C) are particularly suitable. Examples of such materials include those with a polydispersity in their molecular weight.

[0035] In particular, polyolefins, thermoplastic polyesters, polyketones, polyamides and their copolymers may be used. A mixture of polymers or copolymers may also be used, as well as a mixture of polymeric materials with inorganic, organic and / or natural fillers such as, for example, but not limited to, carbon, salts and other inorganic derivatives, natural or polymeric fibers. It is also possible to use multilayer structures consisting of stacked and integral layers comprising at least one of the aforementioned polymers or copolymers.

[0036] A commonly used polymer is polyethylene. Excellent results have been achieved with high-density polyethylene (HDPE).

[0037] In one example, the hollow body comprises a multilayer structure comprising at least one layer of thermoplastic material and at least one additional layer which may advantageously be made of a barrier material to liquids and / or gases. Preferably, the nature and thickness of the barrier layer are chosen so as to limit as much as possible the permeability of liquids and gases in contact with the wall of the fuel tank. Preferably, this layer is based on a barrier material, i.e. a fuel-impermeable resin such as EVOH for example (partially hydrolyzed ethylene-vinyl acetate copolymer). Alternatively, the hollow body may be subjected to a surface treatment (fluorination or sulfonation) intended to make it fuel-impermeable.

[0038] The bladder according to the invention alternatively comprises one or more of the following optional features, taken alone or in combination.

[0039] The ratio R is between 1.1 and 2.0. Preferably, the ratio R is chosen to be substantially equal to 1.5. This makes it possible to obtain even more uniform compression of the bellows.

[0040] The E1 set of folds contains an odd number of folds. This allows a second fold line to be found in a midplane parallel to the XY plane rather than a first fold line. This arrangement makes the compression of the bellows even more uniform.

[0041] The subset E2 of folds contains the same number of folds as the set E1 of folds. This makes it possible to attribute the advantages of the invention to all the folds of the bellows.

[0042] The area of ​​a ring of a first ply of the subset E2 of plies is strictly greater than the area of ​​a ring of a second ply adjacent to the first ply of the subset E2 of plies and includes the latter in the XY plane. This allows the first ply to extend radially beyond the radial extension of the second ply adjacent to the first ply. Thus, when the bellows is compressed, the radial end of the first ply is prevented from interfering with the radial end of the second ply adjacent to the first ply on the one hand, and the axial distance between the two adjacent plies is reduced on the other hand. In other words, the radial ends of two adjacent plies are interposed whereas, in the prior art, the radial ends of two adjacent plies are stacked in the direction of the Z axis. Thanks to this arrangement, the bellows is more compact when it is compressed.

[0043] The terms "radially" and "radially" refer to a direction perpendicular to the Z axis, away from the Z axis.

[0044] The first ply, respectively the second ply, of the subset E2 of plies has a first height, respectively a second height, in the direction of the Z axis, and the bellows is configured to have: a first configuration, called the working configuration, in which the bellows is compressed in the direction of the Z axis, and a second configuration, called the rest configuration, in which the bellows is not compressed in the direction of the Z axis and in which the first height of the first ply is strictly greater than the second height of the second ply. This makes it possible to make certain plies less resistant to compression than others. Thanks to this arrangement, the bellows is more compact when it is compressed.

[0045] The bellows consists of two opposite half-bellows, mutually symmetrical with respect to a median plane P parallel to the XY plane, each half-bellows having a general external shape substantially inscribed in a fictitious pyramid with a rectangular base, said rectangular base being included in the median plane P. This makes it possible to obtain an even more homogeneous compression of the bellows.

[0046] Ring A has an inner radius r i nt . and an outer radius r ext . in the XY plane, such that the ratio r ext . / r int . is strictly greater than 1. Preferably, the ratio r ext . / r int . is between 1.1 and 2.0. This allows for even more uniform compression of the bellows.

[0047] The invention also provides an assembly comprising the aforementioned bladder, characterized in that the assembly further comprises a protective casing for the bladder. This makes it possible to protect the bladder throughout its life, in particular, during its introduction and fixing in the fuel tank.

[0048] The invention also provides a fuel tank for a motor vehicle comprising at least one bladder conforming to the aforementioned bladder, the at least one bladder extending inside the fuel tank.

[0049] The invention also provides a fuel tank for a motor vehicle comprising at least one assembly conforming to the aforementioned assembly, the at least one assembly extending inside the fuel tank.

[0050] The term "fuel tank for a motor vehicle" means any device incorporated in the motor vehicle whose function is to store, purify, measure or transport fuel intended to supply the heat engine. A fuel tank is part of a fuel system as soon as it is coupled to a fuel supply line for the heat engine. A fuel system may also include, but is not limited to, one or more of the following accessories: fuel tank vent valve and line, filler pipe, canister, fuel filter, fuel pump, fuel tank gauge, electrical connector, closing cap as well as any member, in general, through which fuel passes in the liquid or gaseous state, for example, a fuel vapor circulation pipe.

[0051] The fuel tank according to the invention further comprises a ventilation duct connecting the inside of the bladder to the outside of the fuel tank. In the case where the material of the bladder is impermeable to fuel and fuel vapors, the connection to the outside of the fuel tank opens into the atmosphere, thus the fuel tank allows, alternatively, to supply the bladder with air or to evacuate part of the air contained in the bladder. In the case where the material of the bladder is permeable to fuel and / or fuel vapors, the connection to the outside of the fuel tank opens into a fuel vapor circulation duct towards a canister, thus the fuel tank allows, alternatively, to supply the bladder with gas or to evacuate part of the gas contained in the bladder towards the canister. The gas supplying the bladder is either air coming directly from the atmosphere, or air passing through the canister.

[0052] Advantageously, the fuel tank further comprises at least one heat storage member, extending inside the fuel tank, comprising a phase change material having a melting point of between 18° and 40°C, the phase change material being preferentially chosen from the following list: calcium chloride hexahydrate (CaCl2.6H2O), octadecane (C 18 H 38 ), cyclohexanol (C6H 12 O), a derivative of glycerin.

[0053] The at least one heat storage member makes it possible to absorb heat, in particular when the fuel has a temperature close to the melting point of the phase change material. Indeed, the fusion reaction being endothermic, it consumes heat from the fuel. The at least one heat storage member thus makes it possible to limit the rise in temperature of the fuel and therefore to limit the generation of fuel vapor in the fuel tank. Thanks to this arrangement, the bladder can be sized with a smaller volume, so that the disadvantages linked to the volume of the bladder are reduced, in particular the limitation of the useful volume of the tank. It is thus understood that the combined effects of the at least one heat storage member and the bladder surpass the effects provided by the at least one heat storage member and the bladder considered in isolation.

[0054] The invention also provides for the use of at least one bladder, conforming to the aforementioned bladder, in a fuel tank, the at least one bladder being intended to limit the increase in pressure inside the fuel tank, in order to limit the mechanical stresses on the fuel tank.

[0055] The invention also provides a motor vehicle, in particular a hybrid vehicle, comprising a fuel tank conforming to the aforementioned fuel tank.

[0056] The invention also provides a method for manufacturing a fuel tank for a motor vehicle, comprising the following steps:

[0057] a) have a fuel tank,

[0058] (b) have at least one bladder conforming to the aforementioned bladder,

[0059] c) compress the bellows along the Z axis direction,

[0060] (d) introducing the at least one bladder inside the fuel tank through an opening made in a wall of the fuel tank,

[0061] e) securing the at least one bladder inside the fuel tank such that the at least one bladder extends inside the fuel tank.

[0062] In one example, step d) of introducing the at least one bladder inside the fuel tank through an opening provided in a wall of the fuel tank is carried out manually by an operator.

[0063] In one example, the opening in the fuel tank wall is a bung hole.

[0064] Advantageously, in the aforementioned method, step e) of fixing the at least one bladder inside the fuel tank is carried out by means of clipping, snap-fastening, fitting, gluing, clamping, pinching or welding the at least one bladder to an internal wall of the fuel tank.

[0065] Preferably, the inner wall of the fuel tank is an upper inner wall of the fuel tank.

[0066] The invention also provides a method of manufacturing by extrusion-blow molding a fuel tank for a motor vehicle, comprising the following steps:

[0067] (a) have at least one bladder conforming to the aforementioned bladder,

[0068] b) opening an extrusion blow mold and extruding a parison into the open mold,

[0069] c) introducing at least one bladder into the parison using an insertion rod,

[0070] d) bringing the extrusion-blow mold into an intermediate closing position in order to fix the at least one bladder inside the parison by pressing the parison either against the at least one bladder or against a protective casing of the at least one bladder,

[0071] e) remove the insertion rod,

[0072] f) bringing the extrusion blow mold into a final closing position in order to preform a fuel tank,

[0073] (g) introducing a pressurized gas into the extrusion blow mold to form the fuel tank by blow molding,

[0074] h) open the extrusion blow mold and remove the fuel tank thus formed.

[0075] Finally, according to the invention, there is provided a method of operating a fuel tank conforming to the aforementioned fuel tank, characterized in that the method comprises, in response to an increase in the pressure inside the fuel tank, a step of compressing the bellows to pass from the rest configuration to the working configuration.

[0076] The compression step of the bellows to move from the rest configuration to the working configuration is achieved by increasing the pressure inside the fuel tank.

[0077] Other features and advantages of the invention will become clear from the description given below, for information purposes only and in no way limiting, with reference to the appended drawings, in which:is a sectional view of a part of a fuel tank according to the invention, in which the bellows is shown in the rest configuration;is a view similar to, in which the bellows is shown in the working configuration;Figures 3 and 4 are sectional views of the bellows in the rest configuration;is a view of an elongated, flat and closed ring A in the XY plane;is a view of a ring A i including an A ring i+1in the XY plane;is a perspective view of the bellows in the rest configuration;Figures 8 to 10 are views from different sides of the bellows in the rest configuration;is a schematic view of the bellows in the working configuration;is a perspective view of a motor vehicle according to the invention.Detailed description of at least one embodiment of the invention

[0078] In the various figures, identical or similar elements bear the same references, possibly with the addition of an index. The description of their structure and function is therefore not systematically repeated.

[0079] In all that follows, the 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.

[0080] Figures 1 and 2 illustrate a fuel tank 10 comprising a bladder 1 according to the invention. The bladder 1 extends inside the fuel tank 10, it is mechanically coupled to the fuel tank 10 and the interior of the bladder 1 is fluidically connected to the exterior of the fuel tank 10 via a ventilation connection 7 of a ventilation duct (not shown).

[0081] The fuel tank 10, generally made of plastic, is configured to store the fuel which is used by the motor vehicle in particular for its propulsion. The fuel tank 10 comprises a wall delimiting a hollow body defining an internal volume in which the fuel extends both in liquid form and in gaseous form, according to a distribution depending in particular on the pressure and temperature conditions inside the fuel tank 10. The fuel tank generally comprises a filling duct, allowing the tank to be filled with fuel, a ventilation duct allowing the fuel vapors to be evacuated under certain conditions and an injection duct allowing the fuel to be conveyed to the engine of the motor vehicle.These three conduits are well known in the state of the art, so they are not shown in the figures and will not be described further in the following.

[0082] The bladder 1 defines a variable-volume sealed enclosure. The sealed enclosure comprises a bellows 2 that is compressible along a Z-axis direction. The bellows is here made of an elastic material, i.e., a flexible, deformable material that returns to its initial shape when it is no longer mechanically stressed. In one example, the bladder is made of a thermoplastic elastomer material, for example, thermoplastic polyurethane (TPU).

[0083] In another example, the bellows is made of polyethylene (PE), polyamide (PA), ethylene vinyl acetate (EVA) or in the form of a multilayer comprising polyethylene (PE) and ethylene vinyl alcohol (EVOH). Preferably, the polyethylene is high density polyethylene (HDPE), the polyamide is polyamide 6, 11 or 12 (PA6, PA11 or PA12), and the multilayer comprises an adhesive layer provided between a layer of high density polyethylene and the layer of ethylene vinyl alcohol. Advantageously, the multilayer comprises an adhesive layer provided between the layer of polyethylene (PE), preferably high density polyethylene (HDPE), and the layer of ethylene vinyl alcohol (EVOH).

[0084] The bellows 2 is configured to have a first configuration, called the working configuration, and a second configuration, called the rest configuration. In the working configuration, the bellows 2 is compressed in the direction of the Z axis (see), while in the rest configuration, the bellows 2 is not compressed, in other words, the bellows 2 retains its initial shape (see).

[0085] Illustrates a bellows 2 comprising a set E1 of folds 3 in which E1 contains an odd number of folds, here five.

[0086] The folds of the set E1 of folds 3 are not all identical to each other and each fold 31, 32, 33 of a subset E2 of folds of the set E1 of folds 3 has the shape of an elongated, flat and closed ring A when it is projected orthogonally onto an XY plane perpendicular to the Z axis.

[0087] Still in the example shown in, three folds are shown in the subset E2. However, when the subset E2 of folds contains the same number of folds as the set E1 of folds 3, all the folds in the set E1 of folds 3 each have the shape of an elongated, flat, closed ring A when projected orthogonally onto an XY plane perpendicular to the Z axis.

[0088] The set E1 of folds 3 is a set of adjacent folds connected to each other by first fold lines 4.

[0089] It also illustrates that a first fold 3 i of the subset E2 of folds has a first height h i , for example fold 31 has a height h1, and that a second fold 3 i+1 adjacent to the first fold 3 i of the subset E2 of folds has a second height h i +1 , for example fold 32 has a height h2. Each height h i , h i +1is measured between two nearest neighboring first fold lines 4, in the direction of the Z axis.

[0090] Illustrates that each fold of said set E1 of folds 3, for example fold 31, is made up of two adjacent half-folds, for example 3 1a and 3 1b , connected to each other by a second fold line 5.

[0091] Also illustrates a preferred embodiment of the invention in which the bellows 2 consists of two opposite half-bellows 2a, 2b, mutually symmetrical with respect to a median plane P parallel to the XY plane. Each half-bellows 2a, 2b has a general external shape substantially inscribed in a fictitious pyramid with a rectangular base, the rectangular base being included in the median plane P.

[0092] Figure 5 illustrates the aforementioned ring A. Ring A has an outer length L ext . and an interior length L int.along a longitudinal direction of axis X in the XY plane. Ring A also has an external width l ext . and an interior width l int . along a transverse direction of axis Y in the XY plane, the axis Y being perpendicular to the axis X. According to the invention, the ratio (L ext . L int . ) / (L ext . L int . ), called ratio R, is strictly greater than 1. In other words, the difference in length (L ext . L int . ) is strictly greater than the difference in width (l ext . L int . ).

[0093] In the example illustrated in, the ratio R is approximately equal to 2. In practice, a ratio R between 1.1 and 2.0 is suitable and a ratio R equal to 1.5 is particularly suitable.

[0094] Also illustrates the area S, the inner radius r i nt . and the outer radius r ext . of ring A. The inner radius r i nt . connects the interior of a short side of ring A to the interior of a long side of ring A, while the outer radius r i nt . connects the outside of a short side of ring A to the outside of a long side of ring A. The inner rays r i nt . and exterior r ext . are such that the ratio r ext . / r int . is strictly greater than 1. Still in the example illustrated in, the ratio r ext . / r int . is approximately equal to 1.7. In practice, a ratio R between 1.1 and 2.0 is suitable.

[0095] Illustrates the area S i of a ring A i of a first fold 3 iof the subset E2 of folds and the area S i +1 of a ring A i +1 of a second fold 3 i+1 adjacent to the first fold 3 i of the subset E2 of folds. In one embodiment of the invention, the area S i is strictly greater than the area S i +1 and area S i includes area S i +1 in the XY plane.

[0096] In one embodiment of the invention, when the bellows 2 is in the rest configuration, the first height h i of the first fold 3 i is strictly greater than the second height h i +1 of the second fold 3 i+1 (see).

[0097] In the working configuration, the bellows 2 is compressed so as to give the bellows 2 a first geometric shape having a first volume (see). In the illustrated example, the first geometric shape is a generally prismatic shape. In the rest configuration, the bellows 2 is decompressed so as to give the bellows 2 a second geometric shape having a second volume (see). In the illustrated example, the second geometric shape is also a generally prismatic shape. In all cases, the first volume is strictly less than the second volume.

[0098] In practice, the second volume is proportional to the volume of fuel in the fuel tank 10. Advantageously, the second volume is between 20% and 50% of the volume of fuel in which the bladder 1 is immersed, preferably the second volume is between 20% and 30% of the volume of fuel in which the bladder 1 is immersed.

[0099] The maximum volume of the bladder 1 is chosen according to the volume and shape of the fuel tank 10, the range of values ​​proposed being able to be adapted to certain types of motor vehicle tanks.

[0100] As seen in Figures 1 and 2, the bladder 1 is part of an assembly further comprising a protective casing 6 for the bladder 1. In one example, the protective casing 6 is made of plastic, for example, polyoxymethylene (POM).

[0101] Figures 7 to 10 illustrate from different angles a bellows 2 in the rest configuration.

[0102] Illustrates a bellows 2 in the working configuration.

[0103] Illustrates a motor vehicle 20, for example, a hybrid vehicle, comprising the fuel tank 10.

[0104] Another object of the invention is a method of manufacturing the fuel tank 10 for a motor vehicle, comprising the following steps:

[0105] a) have a fuel tank 10,

[0106] b) have at least one bladder 1,

[0107] c) compress the bellows 2 along the Z axis direction,

[0108] d) introducing the at least one bladder 1 inside the fuel tank 10 through an opening provided in a wall of the fuel tank 10,

[0109] e) securing the at least one bladder 1 inside the fuel tank 10 such that the at least one bladder 1 extends inside the fuel tank 10.

[0110] In one example, step d) of introducing the at least one bladder 1 inside the fuel tank through an opening made in a wall of the fuel tank is carried out manually by an operator.

[0111] In one example, the opening in the fuel tank wall is a bung hole (not shown).

[0112] Advantageously, in the aforementioned method, step e) of fixing the at least one bladder 1 inside the fuel tank 10 is carried out by means of clipping, snap-fastening, interlocking, gluing, clamping, pinching or welding the at least one bladder 1 to an internal wall of the fuel tank 10. In the example illustrated, the fixing of the at least one bladder 1 inside the fuel tank 10 is carried out with clipping clips 8 (see) and the internal wall of the fuel tank 10 is an upper internal wall of the fuel tank 10.

[0113] Another subject of the invention is a method of manufacturing by extrusion-blow molding the fuel tank 10 for a motor vehicle, comprising the following steps:

[0114] a) have at least one bladder 1,

[0115] b) opening an extrusion blow mold and extruding a parison into the open mold,

[0116] c) introducing by means of an insertion rod the at least one bladder 1 inside the parison,

[0117] d) bringing the extrusion-blow mold into an intermediate closed position in order to fix the at least one bladder 1 inside the parison by pressing the parison against the at least one bladder 1 or against a protective casing 6 of the at least one bladder 1,

[0118] e) remove the insertion rod,

[0119] f) bringing the extrusion blow mold into a final closing position in order to preform a fuel tank,

[0120] (g) introducing a pressurized gas into the extrusion blow mold to form the fuel tank by blow molding,

[0121] h) open the extrusion blow mold and remove the fuel tank thus formed.

[0122] The use of the bladder 1 in the fuel tank 10 for a motor vehicle serves to limit the increase in pressure inside the fuel tank 10.

[0123] Indeed, when the fuel contained inside the fuel tank 10 rises in temperature, for example when the outside temperature becomes higher than the temperature of the fuel, part of the fuel is evaporated, which generates fuel vapors in the fuel tank 10. Given that the fuel tank 10 defines a closed and sealed volume, the increase in the quantity of fuel vapors causes the pressure in the gaseous phase inside the fuel tank 10 to increase. We will now describe how the fuel tank 10 according to the invention makes it possible to limit this increase in pressure.

[0124] The bellows 2 is compressed under the action of the pressure in the gaseous phase inside the fuel tank 10. The bellows 2 comprising a deformable wall, a balance of the stresses applied to the wall of the bellows 2 is established, this balance leads to the evacuation of all or part of the air contained in the bellows 2 by a ventilation connection 7 of a ventilation duct (not shown). The ventilation duct is connected, on one side, to the bellows 2, more precisely, to the interior volume of the bellows 2 via the ventilation connection 7, and, on the other side, to the outside of the fuel tank 10. In this way, the volume of the bellows 2 extending into the fuel tank 10 decreases, and the volume occupied by the fuel vapors increases, which results in a reduction in the pressure due to the fuel vapors.When the fuel temperature eventually decreases, for example when the outside temperature becomes lower than the fuel temperature, some of the fuel vapors condense. The amount of fuel vapors in the fuel tank 10 then decreases, as does the fuel vapor pressure. A new equilibrium of the stresses on the wall of the bellows 2 is established, this equilibrium leading to a filling of the bellows 2 by the ventilation duct via the ventilation connector 7 and to an increase in the volume of the bellows 2 extending into the fuel tank 10. Although the ventilation duct is not illustrated in the figures, it is connected to the bellows 2 before the introduction of the bellows 2 inside the fuel tank 10. The ventilation duct is made of a flexible material allowing it to be deformed with the bellows 2 during its introduction inside the fuel tank 10.

[0125] Thus, when the bladder 1 is in operation inside the fuel tank 10, the bellows 2 compresses in response to an increase in the pressure inside the fuel tank 10 causing the bellows 2 to change from the rest configuration to the working configuration. The aforementioned compression is part of a method of operating the aforementioned fuel tank 10. List of references

[0126] 1: bladder2: bellows2a, 2b: half-bellows3, ​​31, 32,…, 3 i , 3 i +1 ,…: pli31 a , 3 1b ,…, 3 ia , 3 ib ,…: half-fold4: first fold line5: second fold line6: protective casing7: ventilation connection8: clip10: fuel tank20: vehicleA, A i , HAS i +1 ,…: rings, S i , S i +1 ,…: area of ​​a ringL ext . : outer length of a ring L int. : interior length of a ring ext . : outer width of a ring int . : interior width of a ring int . : inner radius of a ring ext . : outer radius of a ringZ: compression axis of the bellowsXY: plane perpendicular to the axis ZP: median plane parallel to the plane XYE1: set of pleatsE2: subset of plish1, h2,…, h i , h i +1 ,…: height of a fold

Claims

Bladder (1) defining a variable-volume sealed enclosure for a fuel tank, in which the sealed enclosure comprises a bellows (2) compressible in a Z-axis direction, said bellows (2) comprises a set E1 of folds (3), the folds of said set E1 of folds (3) not all being identical to each other, characterized in that each fold (31, 32,…, 3 i , 3 i+1 ,…, 3 n ) of a subset E2 of folds of the set E1 of folds (3) has the shape of an elongated, flat and closed ring A when projected orthogonally onto an XY plane perpendicular to the Z axis, said ring A having an external length L ext . and an interior length L int. along a longitudinal direction of axis X in the XY plane, said ring A also having an external width l ext . and an interior width l int .along a transverse direction of axis Y in the XY plane, the axis Y being perpendicular to the axis X, such that the ratio (L ext . L int . ) / (L ext . L int . ), called ratio R, is strictly greater than 1. Bladder (1) according to the preceding claim, characterized in that the ratio R is between 1.1 and 2.0, preferably, the ratio R is chosen to be substantially equal to 1.

5. Bladder (1) according to any one of the preceding claims, characterized in that the set E1 of folds (3) contains an odd number of folds. Bladder (1) according to any one of the preceding claims, characterized in that the subset E2 of folds contains the same number of folds as the set E1 of folds (3). Bladder (1) according to any one of the preceding claims, characterized in that the area S iof a ring A i of a first fold (3 i ) of the subset E2 of folds is strictly greater than the area S i +1 of a ring A i +1 of a second fold (3 i+1 ) adjacent to the first fold (3 i ) of the subset E2 of folds and includes the latter in the XY plane. Bladder (1) according to the preceding claim, characterized in that the first fold (3 i ), respectively the second fold (3 i+1 ), of the subset E2 of folds has a first height h i , respectively a second height h i +1, in the direction of the Z axis, and the bellows (2) is configured to have:a first configuration, called the working configuration, in which the bellows (2) is compressed in the direction of the Z axis, anda second configuration, called the rest configuration, in which the bellows (2) is not compressed in the direction of the Z axis and in which the first height h i of the first fold (3 i ) is strictly greater than the second height h i +1 of the second fold (3 i+1 ). Bladder (1) according to any one of the preceding claims, characterized in that the bellows (2) consists of two opposite half-bellows (2a, 2b), mutually symmetrical with respect to a median plane P parallel to the XY plane, each half-bellows (2a, 2b) having a general external shape substantially inscribed in a fictitious pyramid with a rectangular base, said rectangular base being included in the median plane P. Bladder (1) according to any one of the preceding claims, characterized in that the ring A has an internal radius r i nt . and an outer radius r ext . in the XY plane, such that the ratio r ext . / r int . is strictly greater than 1. Assembly comprising a bladder (1) according to any one of claims 1 to 8, characterized in that it further comprises a protective casing (6) for the bladder (1). Fuel tank (10) for a motor vehicle comprising at least one bladder (1) according to any one of claims 1 to 8 extending inside the fuel tank (10). Use of at least one bladder (1) according to any one of claims 1 to 8 in a fuel tank (10) for a motor vehicle, the at least one bladder (1) being intended to limit the increase in pressure inside the fuel tank (10). Motor vehicle (20), in particular hybrid vehicle, comprising a fuel tank (10) according to claim 10. A method of manufacturing a fuel tank (10) for a motor vehicle according to claim 10, comprising the following steps: a) providing a fuel tank (10), b) providing at least one bladder (1) according to any one of claims 1 to 8, c) compressing the bellows (2) in the Z-axis direction, d) introducing the at least one bladder (1) into the fuel tank (10) through an opening in a wall of the fuel tank (10), e) fixing the at least one bladder (1) into the fuel tank (10) such that the at least one bladder (1) extends into the fuel tank (10). Method for manufacturing a fuel tank (10) for a motor vehicle according to claim 13, in which step e) of fixing the at least one bladder (1) inside the fuel tank (10) is carried out by means of clipping (8), snap-fastening, fitting, gluing, clamping, pinching or welding the at least one bladder (1) on an internal wall of the fuel tank (10). A method of manufacturing by extrusion-blow molding a fuel tank (10) for a motor vehicle according to claim 10, comprising the following steps: a) providing at least one bladder (1) according to any one of claims 1 to 8, b) opening an extrusion-blow mold and extruding a parison into the open mold, c) introducing the at least one bladder (1) inside the parison by means of an insertion rod, d) bringing the extrusion-blow mold into an intermediate closed position in order to fix the at least one bladder (1) inside the parison by pressing the parison either against the at least one bladder (1) or against a protective casing (6) of the at least one bladder (1), e) removing the insertion rod, f) bringing the extrusion-blow mold into a final closed position in order to preform a fuel tank,g) introducing a pressurized gas into the blow mold to form the fuel tank by blowing,h) opening the blow mold and removing the fuel tank thus formed.,

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