Pressure compensation device for a fuel tank

Abstract

The invention relates to a pressure compensation device (1) for a fuel tank of a fuel system for a vehicle, comprising an assembly (8) comprising a bladder (2) and configured to be positioned inside a tank. According to the invention, the assembly further comprises a support (3) and attachment means (4) for attaching the bladder to the support. The support comprises a wall (3a) having an inner face (3b) and an opening (3c) extending through the wall. The attachment means comprise a first attachment member (4a) secured to the bladder and a second attachment member (4b) fixed to the first attachment member (4a). The first attachment member (4a) comprises a bearing surface (4aa) bearing against the inner face (3b) of the wall (3a) of the support (3) and a receiving surface (4ab) for the second attachment member (4b). The first attachment member (4a) passes through the opening (3c) such that the wall is sandwiched between the second attachment member (4b) and the bearing surface (4aa).

Description

Fuel tank pressure compensation device

[0001] The invention relates to plastic fuel tanks for vehicles. The invention also relates to fuel systems. More particularly, the invention relates to a pressure compensation device for a plastic fuel tank of the aforementioned fuel system, a vehicle comprising the aforementioned fuel system, a method for assembling the aforementioned fuel system, and methods for manufacturing the aforementioned system.

[0002] The invention can be used in the field of vehicles, particularly hybrid vehicles. The term "vehicle" refers to any motor vehicle such as a car, motorcycle, truck, bus, train, or machine, including construction equipment for example.

[0003] Fuel stored in a plastic vehicle 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 tank is a closed volume, the generation of fuel vapors leads to a pressure increase inside the tank, which can generate mechanical stress on the tank walls, potentially damaging them and causing leaks.

[0004] To limit air pollution, manufacturers of internal combustion engine vehicles install a canister in the fuel tank's ventilation system. A canister contains an activated carbon filter that collects fuel vapors from the fuel tank. These vapors are stored in the canister until it is saturated. When the canister is full, it must be purged to prevent fuel from being released into the atmosphere. Purged canisters are opened to flow through the canister to the engine's intake system while the engine is running, allowing the fuel vapors to be burned in the combustion chamber, thus preventing any fuel vapors from being released into the atmosphere.

[0005] However, in the case of hybrid vehicles, which combine an internal combustion engine with an electric motor, the internal combustion engine shuts down when the electric motor is running. Since the canister is no longer purged, fuel vapors accumulate inside the plastic fuel tank, leading to an increase in internal pressure. This can generate mechanical stress on the tank walls, potentially damaging them and causing leaks.

[0006] Faced with this situation, it was necessary to develop technical solutions to obtain a plastic fuel tank that is not affected by variations in internal pressure.

[0007] One known technical solution involves positioning reinforcing elements, such as pillars, inside the plastic fuel tank to stiffen the fuel tank.

[0008] A second known technical solution involves attaching a bladder inside a plastic fuel tank. This bladder's function is to fill and empty with air depending on the amount of fuel vapors present in the tank. This technical solution ensures that when fuel vapors are present in large quantities in the fuel tank, the bladder occupies a small space (and is therefore only partially filled with air), and when fuel vapors are present in small quantities in the fuel tank, the bladder occupies a large space (and is therefore largely filled with air). The size of the bladder thus adjusts according to the amount of fuel vapors present in the fuel tank so that the pressure inside the tank does not exceed acceptable limits (to prevent damage to the fuel tank).US patent 2020 / 406745 A1 describes an example of a fuel tank equipped with a variable-volume bladder. In addition, US patent 2007 / 290414 A1 relates to a method for attaching an accessory mounting plate to the wall of a fuel tank to allow the mounting of various accessories.

[0009] These technical solutions have drawbacks. Using pillars in the fuel tank requires a significant number of parts and is limited in terms of the maximum pressure that can be achieved within the fuel tank. As for using a bladder in the fuel tank, this technical solution is unsatisfactory because the bladder's structure lacks robustness.

[0010] The invention aims in particular to overcome the drawbacks of the prior art.

[0011] More specifically, an objective of the invention, in at least one of its embodiments, is to provide a device enabling a plastic vehicle fuel tank to remain unaffected by variations in internal pressure while avoiding the aforementioned disadvantages.

[0012] An objective of the invention, in at least one of its embodiments, is also to provide a fuel system comprising a device enabling a plastic vehicle fuel tank not to be affected by variations in internal pressure, and a vehicle comprising said fuel system.

[0013] An objective of the invention is also to provide, in at least one of its embodiments, a method for assembling a device enabling a plastic vehicle fuel tank not to be affected by variations in internal pressure, but also a method for manufacturing a fuel system comprising a device enabling a plastic vehicle fuel tank not to be affected by variations in internal pressure, as well as a vehicle comprising said fuel system.

[0014] To this end, the invention relates to a vehicle fuel system comprising a plastic fuel tank inside which a pressure compensation device is fixed. The pressure compensation device for a plastic fuel tank comprises an assembly configured to be positioned inside a plastic fuel tank, the assembly comprising a bladder.

[0015] According to the invention, such a device is such that: the assembly also includes a support and means for fixing the bladder to the support; the support includes a wall having an inner face turned towards the bladder and an opening through the wall; the fixing means include a first fixing member attached to the bladder and a second fixing member fixed to the first fixing member; the first fixing member includes a bearing surface against the inner face of the wall of the support and a receiving surface for the second fixing member, preferably by cooperation or complementarity of form between the first fixing member and the second fixing member; the first fixing member passes through the opening so that the wall is sandwiched between the second fixing member and the bearing surface of the first fixing member.

[0016] The general principle of the invention is based on the fact that the configuration of the fastening means allows the bladder to be secured to the support so that the support and therefore the bladder can be configured to be positioned inside the fuel tank so that the inside of the bladder is in fluidic communication with the outside of the fuel tank, to limit the pressure in the fuel tank.

[0017] Thus, the invention is based on a completely new and inventive approach that eliminates the need for pillars positioned inside the fuel tank and also for a bladder whose structure could be easily damaged, particularly during its integration inside the fuel tank. Indeed, by being attached to a support, the bladder according to the invention is configured to be positioned efficiently and easily inside the fuel tank, while maintaining fluidic communication with the outside of the fuel tank so as to fill with air when the pressure in the fuel tank is relatively low and to empty of air when the pressure in the fuel tank is relatively high. It is understood that the bladder is attached to a separate support, which does not constitute a wall of the tank. In other words, this support cannot be a structural wall of the tank.This support allows for easy positioning of the bladder within a parison during the fuel system manufacturing process. The support prevents any contact between the bladder and the parison, thus avoiding potential damage to the bladder.

[0018] Using pillars, as opposed to a bladder and support system, requires a significantly larger number of components. Indeed, a greater number of pillars are necessary to reinforce the overall strength of the fuel tank, particularly to withstand increasing pressure within the tank. Furthermore, using a bladder and support system within the fuel tank, compared to pillars, allows for operation at higher internal pressures.

[0019] According to one embodiment, the support wall covers the entire face of the bladder towards which the inner face of the support wall is turned.

[0020] Thus, this configuration allows for optimal bladder protection.

[0021] According to one embodiment, the pressure compensation device according to the invention is such that the first fixing member protrudes on an external surface of the bladder.

[0022] Thus, the fact that the first fixation organ protrudes on the external surface of the bladder allows for easier cooperation or complementarity of form between the first fixation organ and the second fixation organ, and therefore allows for adequate bonding between the first fixation organ and the second fixation organ.

[0023] According to a preferred embodiment of the preceding embodiment, the pressure compensation device according to the invention is such that the first fixing member has an elongated shape, preferably cylindrical, and the second fixing member is chosen from one of the following: a fork, a pin, a circlip, a clip-on fixing means, such as a clip.

[0024] Thus, due to this configuration, the first fastening element has a shape that allows it to easily pass through the opening in the support. Furthermore, the fact that the second fastening element can be selected from the following options—a fork, a pin, a circlip, or a clip-on fastener—allows the second fastening element to be secured to the first at the support. Consequently, the first fastening element, due to the positioning of the second fastening element, is immobilized in contact with the support. Positioning the second fastening element in contact with the first prevents any separation between the support and the bladder.

[0025] The term "fork" refers to a piece, preferably a piece made of metal or plastic, equipped with two arms that surround another piece in order to lock or block the two pieces together.

[0026] The term "pin" refers to a part, preferably made of metal or plastic, designed to pass through the end of certain components so that the resulting assembly is both securely connected and separable. Both parts to be joined must have a bored hole. The pin then passes simultaneously through the hole in each part to secure them together.

[0027] The term "clip" (or "fastener" in French) refers to a piece, preferably made of metal or plastic, used to fasten several objects together, notably by surrounding the objects to keep them pressed together.

[0028] According to one embodiment, the pressure compensation device according to the invention is such that the first fixing member is immovable with respect to the bladder.

[0029] Thus, the fact that the first fixation organ is fixed relative to the bladder allows for a more reliable connection between the first fixation organ and the bladder. Indeed, the fixation mechanisms used between the first fixation organ and the bladder are more robust.

[0030] According to one embodiment, the pressure compensation device according to the invention is such that the first fixing member is configured to support the weight of the bladder.

[0031] This configuration ensures a robust connection between the first fixation organ and the bladder. Indeed, the risk of the first fixation organ detaching from the bladder due to the bladder's significant weight is eliminated.

[0032] According to one embodiment, the pressure compensation device according to the invention is such that the second fixing member is removable after having been secured to the first fixing member.

[0033] Thus, the fact that the second fastening element can be separated from the first fastening element after being attached to it facilitates the positioning of the bladder and its support inside the fuel tank. Indeed, when manipulation of the bladder relative to the support is necessary inside the fuel tank, the fact that the bladder can be attached and then separated from the support allows for greater freedom during the positioning operations of the bladder and its support within the fuel tank.

[0034] According to one embodiment, the pressure compensation device according to the invention comprises at least two first fixing members.

[0035] Thus, the fact that the pressure compensation device includes at least two initial fixing elements allows the bladder to be secured to the support at several points.

[0036] According to one embodiment, the pressure compensation device includes at least two second fastening members.

[0037] Thus, in the same way as for the first fixation organs, the fact that the pressure compensation device includes several second fixation organs makes it possible to secure the bladder to the support in several places.

[0038] According to one embodiment, the pressure compensation device according to the invention comprises at least two openings.

[0039] Thus, and also in the same way as for the first and second fixing organs, the fact that the pressure compensation device includes several openings allows the bladder to be secured to the support in several places.

[0040] According to one embodiment, the pressure compensation device according to the invention comprises two first fixing members, two second fixing members and two openings.

[0041] Thus, due to this configuration, the pressure compensation device allows a compromise between sufficient effective bonding between the bladder and the support and a simplification of the assembly steps between the bladder and the support.

[0042] According to one embodiment, the pressure compensation device according to the invention is such that one of the first two fixing members includes a conduit configured to put the inside of the bladder into fluidic communication with the outside of the plastic fuel tank.

[0043] According to one embodiment, the pressure compensation device according to the invention is such that the bladder has a superior face and the first fixing member is positioned on the superior face of the bladder.

[0044] Positioning the first fastening element on the upper surface of the bladder reduces the risk of bladder tears and stresses, while increasing its compensating capacity. Positioning the first fastening element (and therefore the fluid communication conduit between the inside of the bladder and the outside of the fuel tank) on the upper surface of the bladder also minimizes the distance between the bladder inlet and the end of the conduit connecting the bladder to the fuel tank outlet.

[0045] The expression "upper surface of the bladder" refers to the surface of the bladder closest to the support.

[0046] According to one embodiment, the pressure compensation device according to the invention comprises at least 'n' assemblies comprising a bladder and a support, 'n' being a natural number between 2 and 6.

[0047] Therefore, the fact that the pressure compensation device comprises 'n' assemblies (each containing a bladder and a support) allows for easier integration of the assemblies, and thus the bladders, into the fuel tank. This is because individual bladders have a smaller volume compared to the volume of a single bladder.

[0048] According to one embodiment, the pressure compensation device according to the invention is such that the first fixing member includes a conduit configured to put the inside of the bladder into fluidic communication with the outside of the plastic fuel tank.

[0049] Thus, positioning a conduit that connects the inside of the bladder to the outside of the fuel tank facilitates the supply of air to the bladder and the evacuation of the air initially contained within it. Similarly, when using multiple bladders, positioning conduits that connect the inside of the bladders to the outside of the fuel tank allows for easier positioning of the individual bladders relative to the fuel tank wall.

[0050] According to one embodiment, the pressure compensation device according to the invention is such that the bladder wall describes a parallelepiped such as a rectangular parallelepiped or a square parallelepiped, a prism or a sphere.

[0051] Thus, the fact that the bladder has a shape describing a rectangular parallelepiped, a square parallelepiped, a prism, or a sphere ensures easy integration of the bladder into the fuel tank. Indeed, the bladder is not constrained by its shape and can therefore adapt to different fuel tank shapes.

[0052] According to a particular embodiment, the pressure compensation device is such that in the case of 'n' sets each comprising a bladder, at least two of them have a bladder having a different shape.

[0053] Having at least two bladders with different shapes makes it easier to integrate them, and therefore the entire bladder assembly, into the fuel tank. This allows the shape of at least one bladder to be adapted to the constraints within the fuel tank, particularly the remaining available space.

[0054] According to one embodiment, the pressure compensation device according to the invention is such that the bladder is fixed by a face adjacent to the upper face to the support protecting them.

[0055] Thus, such a configuration makes it easier to integrate the bladder into the tank, especially when the latter has a complex shape.

[0056] According to one embodiment, the pressure compensation device according to the invention is such that the bladder comprises an elastically deformable wall.

[0057] Thus, the bladder has a variable volume and can therefore receive a larger volume of air than if the bladder wall were not elastically deformable.

[0058] Preferably, the bladder is made of a lightweight, flexible material with low permeability to fuel and fuel vapors. "Low permeability" means permeability sufficient to prevent the bladder from becoming contaminated with fuel or fuel vapors in a way that would impair its optimal performance. Preferably, the bladder is made of polyethylene (PE), preferably high-density polyethylene (HDPE), polyamide (PA), thermoplastic polyurethane (TPU), or a multilayer material comprising at least one layer of thermoplastic polyurethane (TPU) or polyethylene (PE), preferably high-density polyethylene (HDPE), and more preferably thermoplastic polyurethane (TPU). The multilayer material preferably includes a fuel barrier layer, the barrier layer being based on ethylene vinyl alcohol or polyamide. Preferably, the polyamide is polyamide 6, 11, or 12 (PA6, PA11, or PA12).More preferably, the multilayer structure includes an adhesive layer sandwiched between the polyethylene (PE) layer, preferably high-density polyethylene (HDPE), and the ethylene vinyl alcohol (EVOH) layer. The materials forming the bladder are chosen based on considerations of cost, mechanical strength, or impermeability to fuel and fuel vapors.

[0059] According to one embodiment, the pressure compensation device according to the invention is such that the bladder is configured to inflate and deflate in at least ten different directions; preferably, the bladder is configured to inflate and deflate in at least twenty different directions. More preferably, the bladder is configured to inflate and deflate in at least thirty different directions. Most preferably, the bladder is configured to inflate and deflate in at least fifty different directions.

[0060] According to one embodiment, the pressure compensation device according to the invention is such that the bladder is configured to deform, during its inflation or deflation, in two opposite directions.

[0061] According to one embodiment, the pressure compensation device according to the invention is such that the bladder is configured to deform along a Z axis which is perpendicular to the wall of the support.

[0062] According to one embodiment, the pressure compensation device includes a bladder protection means attached to the support, the bladder protection means covering at least partially the bladder.

[0063] Thus, the bladder protection means covering at least partially the bladder (i.e. at least part of the faces adjacent to the upper face of the bladder) allows rigid protection for the bladder, which, due to its ability to deform, could be damaged as a result of contact with the parison.

[0064] The term "cover" in the phrase "bladder protection means covers the bladder" means that the bladder protection means is positioned relative to the bladder so as to conceal the bladder when an observer looks in the direction in which the bladder protection means covers the bladder (i.e., in the direction through the bladder protection means and the bladder).

[0065] In the context of the present invention, the word "partially" in the expression "the bladder protection means covers at least partially the bladder" means that the bladder protection means extends over all or part of at least one of the faces adjacent to the upper face of the bladder.

[0066] According to one embodiment, the pressure compensation device according to the invention is such that the bladder protection means includes an anti-ballooning device.

[0067] Therefore, positioning a bladder protection device that includes an anti-sloshing mechanism protects the bladder from fuel sloshing (known as "slosh") within the fuel tank, particularly during acceleration and rapid cornering. Protecting the bladder is essential because its deformable structure lacks resistance to these sloshing forces.

[0068] According to one embodiment, the pressure compensation device according to the invention is such that the shape of the bladder support-protection means assembly is obtained by scaling the bladder shape to a ratio greater than one. Preferably, the bladder is a rectangular parallelepiped and the bladder support-protection means assembly is a rectangular parallelepiped. According to an alternative embodiment, the bladder is a square parallelepiped and the bladder support-protection means assembly is a square parallelepiped. According to another alternative embodiment, the bladder is a prism and the bladder support-protection means assembly is a prism. According to yet another alternative embodiment, the bladder is a sphere and the bladder support-protection means assembly is a sphere.

[0069] According to one embodiment, the pressure compensation device according to the invention is such that the bladder protection means comprises perforated areas, preferably the perforated areas extend vertically.

[0070] The perforated areas serve to reduce the weight of the bladder protection device without affecting the anti-ballooning function.

[0071] According to one embodiment, the pressure compensation device according to the invention includes an additional fastening member configured to fix the support inside the plastic fuel tank.

[0072] Preferably, the additional fastening element is mounted movably on the support.

[0073] The additional mounting bracket is fixed to the support and is also attached to the fuel tank. The fact that the additional mounting bracket is movable on the support allows it to compensate for the fuel tank's shrinkage as it cools. Indeed, when the additional mounting bracket is attached to the parison, the parison is at a high temperature. Therefore, it is desirable that the additional mounting bracket, due to its mobility relative to the support, can move with the fuel tank as it cools.

[0074] According to a preferred embodiment of the two preceding embodiments, the pressure compensation device according to the invention is such that the additional fixing member is made of polyethylene.

[0075] According to an alternative embodiment, the additional fastening member is directly fixed to the support, without being mounted movably on the support and without the addition of an elastic element between the additional fastening member and the support.

[0076] 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 for powering the internal combustion engine. A fuel system includes at least one plastic 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.

[0077] The Z-axis along which the bladder is configured to deform is perpendicular to a plane (which may be horizontal). This plane may be the plane coinciding with the ground (when the ground is flat) on which the vehicle is positioned in its normal operating position.

[0078] According to one embodiment, the fuel system according to the invention is such that the plastic fuel tank includes a fuel tank filling conduit, a fuel vapor venting conduit and an injection conduit.

[0079] According to one embodiment, the fuel system according to the invention is such that the position of the bladder is chosen so that the bladder occupies a central position in the fuel tank.

[0080] In cases where multiple bladders are planned, the position of the bladders is chosen so that the bladders are evenly distributed in the fuel tank.

[0081] According to one embodiment, the fuel system according to the invention is such that the volume of the bladder is chosen so that the bladders occupy a sufficient space enabling them to fulfill their function in the fuel tank when the bladders are totally filled with air.

[0082] More specifically, according to one embodiment, the bladder volume is calculated using the following formula:

[0083] Equation 1

[0084] With :

[0085] - V b being the volume of the bladder.

[0086] - V Pmin being the vapor pressure of the fuel at the minimum temperature,

[0087] - V Pmax being the vapor pressure of the fuel at maximum temperature,

[0088] - P t being atmospheric pressure,

[0089] - V being the total volume of the fuel tank, i.e. taking into account the volume of fuel and the volume dedicated for the occupation of the fuel vapor.

[0090] The bladder volume is calculated by taking into account the temperature cycle in question (for example, the CARB temperature cycle (California Air Resources Board)) and the fuel vapor pressure, which can be 7.7 PSI. The values ​​of the temperature cycle in question allow the determination of the minimum and maximum temperatures necessary for determining V Pmin et de V Pmax The CARB temperature cycle is a 24-hour reference temperature cycle with a temperature increase from 18°C ​​to 40°C during the first 12 hours and a temperature decrease from 40°C to 18°C ​​during the last 12 hours.

[0091] In order to calculate the bladder volume, other factors such as the bladder compression rate (accounting for the residual volume in the bladder after it has shrunk) and the various heat transfers through the fuel tank wall can also be taken into account.

[0092] According to one embodiment, the fuel system according to the invention is such that the volume of the bladder is between 5 and 30 liters. In one embodiment of the invention, one of the bladders of the pressure compensation device has a different volume than another bladder of the pressure compensation device.

[0093] The fuel system may further include one or more of the following optional features, taken alone or in combination: a plastic fuel tank inside which at least m pressure compensation devices are fixed, m being an integer between 1 and 6; an air circuit comprising: a node, supply sections connecting the node to the internal volume of each of the bladders (the supply sections forming the conduits), and an outlet section connecting the node to an outlet of the tank; a node of the air circuit being preferably positioned between the bladder and the wall of the fuel tank. The term "node," in the context of the present invention, corresponds to a fluid connection between the supply sections and the outlet section; a node of the air circuit being positioned between the fastening means and the wall of the fuel tank.an air circuit node preferably being a four-way valve; a bladder equipped with a valve or flap; a bladder equipped with a component configured to restrict (or limit or prevent) the inflation or deflation of the bladder according to a specific flow rate; a plastic fuel tank outlet leading to a filter, preferably an activated carbon filter or canister, located outside the fuel tank; at least one heat storage device, extending inside the fuel tank, comprising a phase-change material having a melting point between 18° and 40°C; a phase-change material housed in a casing impermeable to this material and to the fuel so that no exchange of matter between the fuel and the heat storage device occurs within the casing; a phase-change material selected from one of the following: calcium chloride hexahydrate (CaCl2.6H2O), octadecane (C. 18 H 38 ), cyclohexanol (C6H 12 O), a derivative of glycerin.

[0094] The invention also relates to a vehicle, in particular a hybrid vehicle, comprising a fuel system conforming to the aforementioned fuel system.

[0095] The invention also relates to a method for assembling a pressure compensation device conforming to the aforementioned pressure compensation device. This method comprises the following steps: positioning the bladder relative to the support so that the first fastening element passes through the opening; fixing the second fastening element onto the first fastening element so that the wall is sandwiched between the second fastening element and the bearing surface of the first fastening element.

[0096] This method thus protects the bladder thanks to a support that is easily attached to the bladder due to the reduced number of manipulations and training required by the user. Thanks to the support, the bladder, which has limited rigidity, is protected, in particular, from contact with the parison that could damage it.

[0097] The invention also relates to a method for manufacturing a fuel system by extrusion blow molding, conforming to the aforementioned fuel system. This method comprises the following steps: positioning a parison in an open mold, inserting the pressure compensation device according to the invention, comprising an additional fastening member conforming to the aforementioned additional fastening member, into the parison, closing the mold, and blowing the parison into the mold to form a fuel tank.

[0098] In the context of the present invention, the term "paraison" refers to a paste of a material in a molten state (comprising or being made of plastic), having a relatively high temperature, configured to be molded by extrusion blow molding in a mold so that it takes the desired shape of the fuel tank to form its walls.

[0099] The extrusion blow molding process for manufacturing a fuel system may further include one or more of the following optional features, taken alone or in combination: between the step of inserting the pressure compensation device inside the parison and the step of bringing the parison into contact with the additional fixing member, the extrusion blow molding process includes the following step: pre-blowing the parison.

[0100] - between the positioning step of a parison in an open mold and the insertion step of the pressure compensation device inside the parison, the extrusion blow molding manufacturing process includes the following steps: holding the pressure compensation device by a robot arm, positioning, via the robot arm, the pressure compensation device on an insertion rod.

[0101] Before the pressure compensation device is inserted into the parison, it is positioned on the insertion rod. In one embodiment of the invention, after the pressure compensation device has been positioned on the insertion rod, a draping table is actuated to raise the insertion rod, on which the pressure compensation device is positioned. The pressure compensation device is thus positioned inside the parison at the desired location.

[0102] - at the stage of insertion of the pressure compensation device inside the parison, the support includes a mechanism configured to prevent premature deployment or expansion of the bladder.

[0103] - During the insertion of the pressure-compensating device into the parison, premature bladder deployment or expansion is prevented by a mechanism, and after the insertion of the pressure-compensating device into the parison, the mechanism is deactivated so that premature bladder deployment or expansion is possible. In one embodiment of the invention, the mechanism is configured to be deactivated by the insertion rod or the robot arm.

[0104] - during the step of bringing the parison into contact with the additional fixing element, the additional fixing element welds itself to the parison permanently.

[0105] - The support (or bladder protection means) is made of high-density polyethylene (HDPE), polyoxymethylene (POM), polyphthalamide (PPA), or a thermoplastic material. In one embodiment of the invention, the support material (or bladder protection means) has a higher melting point than the parison material. In one embodiment of the invention, the support material (or bladder protection means) has a higher melting point than polyethylene.

[0106] - the parison includes a multilayer system comprising at least one layer of ethylene vinyl alcohol (EVOH) sandwiched between two layers of high-density polyethylene (HDPE).

[0107] - the support (or the means of protecting the bladder) includes a housing configured to receive the robot arm, used during the manufacture of a fuel tank by extrusion blow molding.

[0108] In this process, the pressure compensation device is positioned on the insertion rod and before closing the mold, the insertion rod is removed.

[0109] Given that the manufacturing process for a fuel tank involves blow molding, during which the parison is heated to a sufficiently high temperature to become malleable, and given that the bladder itself lacks rigidity (due to its deformation capacity), it is essential to provide a bladder protection system that includes a support for the bladder. Specifically, the hot parison could heat the bladders or come into contact with them, potentially causing localized deformation, which is undesirable, especially since bladders are typically quite thin, on the order of a millimeter. Such deformation could compromise the bladders' mechanical strength and therefore their functionality.

[0110] Thus, the positioning of a support covering at least partially the bladder makes it possible to obtain a rigid structure attached to the bladder, making it easier to handle the bladder by means of the support (and the means of protecting the bladder) during the loading of the components (when the fuel tank is manufactured by extrusion blow molding) into the parison (i.e. the molten material configured to form the fuel tank at the end of the extrusion blow molding) and also to protect the bladder during the extrusion blow molding in order to avoid contact between the parison and the bladder.

[0111] Indeed, thanks to the support (and the bladder protection system) attached to the bladder, the fuel system's manufacturing process is less complex, as some of its manufacturing steps are less demanding. In particular, fewer fastening operations are required inside the hot parison or the molded tank, which is advantageous in configurations where the internal volume of the parison or tank is difficult to access.

[0112] The invention also relates to a method of manufacturing a fuel system conforming to the aforementioned fuel system, the method comprising the following steps: having a plastic fuel tank including a vent, introducing the pressure compensation device including an additional fastening member conforming to the aforementioned additional fastening member into the plastic fuel tank through the vent, fixing the support inside the plastic fuel tank by means of the additional fastening member.

[0113] In this latter process, the fuel tank may have been made by injection or by extrusion blow molding.

[0114] According to an additional feature of the fuel system manufacturing process, the step of attaching the support inside the fuel tank using the additional fastener is carried out by welding. For this step, the additional fastener has been previously attached to the support.

[0115] This latter process, due to the positioning of a support linked to the bladder, limits the number of fixing operations and therefore facilitates handling during the loading of components into the fuel tank.

[0116] Other features and advantages of the invention will become more apparent upon reading the following description of a preferred embodiment, given by way of simple illustration and not limitation, and the accompanying drawings, among which: a fuel tank pressure compensation device for a vehicle, where the bladder is attached to the support by fastening means, according to an embodiment of the invention; an exploded view of the pressure compensation device where the fastening means can be observed; and a cross-sectional view of the inside of a fuel tank where two pressure compensation devices are attached. In this figure, fluid communication channels between the inside of the bladders and the outside of the fuel tank can be observed.

[0117] In relation to Figures 1 and 2, an embodiment of the invention is presented in which a pressure compensation device 1 for a fuel tank of a vehicle fuel system comprises an assembly 8 configured to be positioned inside a plastic fuel tank.

[0118] The assembly 8 comprises a bladder 2, a support 3, and means 4 for attaching the bladder 2 to the support 3. The support 3 comprises a wall 3a having an inner face facing the bladder 2 and an opening 3c passing through the wall 3a. The means 4 comprise a first attachment element fixed to the bladder 2 and a second attachment element attached to the first attachment element. The first attachment element comprises a bearing surface against the inner face of the wall 3a of the support 3 and a receiving surface for the second attachment element. The first attachment element passes through the opening 3c so as to sandwich the wall 3a between the second attachment element and the bearing surface of the first attachment element.

[0119] In the embodiment shown in Figures 1 and 2, a bladder protection means 3' is depicted. This bladder protection means 3' is integral with the support 3. The bladder protection means 3' is positioned to at least partially cover the bladder 2. The bladder protection means 3' may cover some or all of the faces adjacent to the upper surface of the bladder 2 that it covers. Only the configuration where the support 3 covers the bladder over its entire upper surface and where the bladder protection means 3' covers the bladder over almost all of its four faces adjacent to the upper surface is shown. The configuration in which the bladder protection means 3' is not included in the pressure compensation device is not shown. Only configurations that include the bladder protection means 3' are shown.

[0120] In figures 1 and 2, support 3 covers the entire upper surface of the bladder.

[0121] In the illustrated example (Figures 1 and 2), the first fixation organ protrudes from an external surface of bladder 2 and has an elongated, preferably cylindrical, shape. Bladder 2 has a superior surface, and the first fixation organ is positioned on the superior surface of bladder 2.

[0122] A conduit is provided in the first mounting bracket to connect the inside of the bladder 2 to the outside of the plastic fuel tank via a tube. An additional mounting bracket secures the support 3 inside the fuel tank. This additional mounting bracket is movably attached to the support 3.

[0123] Figure 10 shows a fuel system comprising a plastic fuel tank 5 equipped with a pressure compensation device 1. In one embodiment of the invention, the additional fastening member is attached to the plastic fuel tank 5 and also to the support 3 such that the support 3 is integral with the fuel tank 5. The configuration of the first fastening member and the second fastening member allows the bladder to be attached to the support 3, and the configuration of the additional fastening member allows the assembly 8 comprising the bladder and the support 3 to be attached to the fuel tank 5 by being positioned inside it. More specifically, the first fastening member is attached to the bladder.

[0124] In order to secure the bladder to the support 3 as illustrated in the figure, the first fixing member is positioned relative to the bladder so as to pass through the opening of the support 3 and so that the bearing surface of the first fixing member is in contact with the support 3. The second fixing member is then fixed to the first fixing member so that the wall 3a is sandwiched between the second fixing member 4b and the bearing surface of the first fixing member.

[0125] Advantageously, the conduit providing fluidic communication between the inside of the bladder and the outside of the fuel tank 5 via the tubing 5b, illustrated in the figure, allows the bladder to fill with outside air when the pressure of the fuel tank 5 decreases and to empty of the air initially contained inside the bladder when the pressure of the fuel tank 5 increases.

[0126] Preferably, the shape of the fuel tank 5 is designed to best fit the shape of the vehicle in which it is positioned. In the illustrated example, the fuel tank 5 is made of plastic. The fuel tank 5 is configured to store the fuel used by the vehicle, particularly for propulsion. The tank 5 defines an internal volume in which the fuel is contained in both liquid and gaseous forms, according to a distribution that depends, among other things, on the pressure and temperature conditions inside the tank 5. The tank advantageously includes a filler neck for filling the tank with fuel, a vent for venting fuel vapors under certain conditions, and an injection line for delivering the fuel to the vehicle's engine.These three conduits (the filling conduit, the ventilation conduit and the injection conduit) are not shown in the figures.

[0127] Preferably, as illustrated, one or more bladders (e.g., two, three, four, five, or six bladders) are provided in the fuel tank 5. Therefore, there can be several pressure compensation devices 1 (e.g., two, three, four, five, or six pressure compensation devices 1) in the fuel tank 5. In the illustrated example, the shape of the bladder(s) is a rectangular parallelepiped; alternatively, this shape can be a square parallelepiped, a prism, or a sphere. One bladder can have a different shape from another bladder. Only configurations with one or two bladders (and therefore one or two pressure compensation devices 1) are shown in the figures.

[0128] According to an advantageous example, the position of the bladder or bladders is chosen so that they occupy a central place in the fuel tank 5 and if there are several that they are evenly distributed in the fuel tank 5. At the, only the configuration where two bladders are present in the fuel tank is represented.

[0129] Advantageously, the volume of bladder 2 or bladders 2 is chosen so that they occupy sufficient space for their function within the fuel tank 5 when fully filled. Thus, the volume of bladder 2 or bladders 2 is chosen based on the total volume of the tank 5 and the maximum fuel capacity of the tank 5, ensuring, in particular, that the bladder(s) 2 have a volume suitable for the amount of fuel vapor that may be generated within the tank 5. Generally, the volume of bladder 2 or bladders 2 is between 5 and 30 liters. One bladder 2 may have a different volume than another bladder 2.

[0130] Preferably, the bladder(s) are fixed by their upper surface to the support 3 protecting them (as illustrated in Figure 3). The bladder(s) 2 may also be fixed by a surface adjacent to the upper surface 2a to the support protecting them (not shown in the figures). The configuration in which the bladder 2 is fixed to the support 3 by fixing the upper surface 2a to the support 3 is preferable to that in which the bladder 2 is fixed to the support 3 by fixing a surface adjacent to the upper surface 2a to the support 3, in order to reduce the risk of bladder tears and stresses on the bladder and to increase its compensating capacity.

[0131] Preferably, the bladder(s) 2 comprise an elastically deformable wall allowing inflation and deflation without plastic deformation. Preferably, the bladder(s) 2 are made of polyethylene (PE), preferably high-density polyethylene (HDPE), polyamide (PA), thermoplastic polyurethane (TPU), or are in the form of a multilayer comprising at least one layer of thermoplastic polyurethane (TPU) or polyethylene (PE), preferably high-density polyethylene (HDPE), and more preferably thermoplastic polyurethane (TPU). The multilayer includes a fuel barrier layer, the barrier layer being based on ethylene vinyl alcohol or polyamide. Preferably, the polyamide is polyamide 6, 11, or 12 (PA6, PA11, or PA12).

[0132] 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.

[0133] Preferably, the bladders are configured to inflate and deflate in multiple directions. This configuration simplifies manufacturing because the bladder can then have the same thickness throughout its entire length. Advantageously, the bladders are configured to deform, during inflation or deflation, in two opposite directions. According to another embodiment of the invention, the bladders are configured to deform along a Z-axis, which can be vertical when the fuel system 10 equipping a vehicle is on a horizontal plane and the vehicle is positioned on a horizontal surface in its normal operating position.

[0134] This provides greater freedom in the positioning of the bladders within the tank. If the bladders were configured to deform in only one direction, a large amount of travel in that direction would be required. This is not the case with the configuration where deformation occurs in two opposite directions or in multiple directions.

[0135] Advantageously, the fuel system 10 includes an air circuit comprising: a node (not shown in the figures), supply sections connecting the node to the internal volume of each of the bladders, the supply sections forming the conduits 5a, and an outlet section (not shown in the figures) connecting the node to an outlet of the tank.

[0136] Thus, to allow the inflation and deflation of the bladders, the bladder(s) operate with an air circuit connected on one side to bladder(s) 2 and on the other side to an air supply system located outside the reservoir 5. This configuration greatly simplifies the arrangement of the bladder(s) within the reservoir, as only a single opening is required in the reservoir 5 to allow air to enter and exit the bladders. More specifically, thanks to the air circuit, it is possible to alternately fill bladder(s) 2 with air so that they occupy a larger total volume in the reservoir 5, and to evacuate some of the air contained in bladder(s) 2 so that they occupy a smaller total volume in the reservoir 5.

[0137] According to one example, the node is positioned between the bladder(s) (i.e. between the fastening means 4) and the outlet of the fuel tank 5.

[0138] Preferably, the node simply forms a fluidic connection between the supply and outlet sections, but it can be expected to be formed by a four-way valve.

[0139] Preferably, each bladder 2 is equipped with a valve (not shown) configured to alternately allow or prevent their inflation and deflation. This allows the bladders to be used according to the pressure inside the tank. The valve for each bladder is located on its supply line. The valves allow each bladder 2 to be activated or deactivated at any time. In other words, when a valve is closed, the air contained in the bladder 2 to which it is connected remains trapped in bladder 2 until the valve is opened.

[0140] More specifically, the bladder(s) 2 are compressed by the pressure in the gaseous phase inside the tank 5. Since the wall of the bladder(s) 2 is deformable, a balance of stresses acting on these walls is established. This balance leads to the release of some of the air contained in the bladder(s) 2 through the air circuit for bladders with an open valve. In this way, the volume of the bladder(s) 2 extending into the tank 5 decreases, and the volume occupied by the fuel vapor increases, resulting in a decrease in fuel vapor pressure. When the fuel temperature eventually decreases, for example, when the outside temperature falls below the fuel temperature, some of the fuel vapor condenses. The amount of fuel vapor in the tank 5 then decreases, as does the fuel vapor pressure.A new equilibrium of the stresses on the wall of the bladder(s) 2 is established, this equilibrium leading to the filling of the bladder(s) 2 by means of the air circuit and to an increase in the volume of the bladder(s) 2 extending into the reservoir 5.

[0141] Advantageously, the bladder(s) 2 are to be equipped with a restriction to allow inflation or deflation according to a specific flow rate.

[0142] Preferably, the tank outlet leads to a filter, such as an activated carbon filter or canister, located outside the tank. This way, even if fuel vapor enters the bladders and mixes with the surrounding air, the fuel vapor is not released into the atmosphere but is captured by the filter. The filter is not shown in the figures.

[0143] Advantageously, the fuel system 10 further includes at least one heat storage element (not shown in the figures), extending inside the tank, comprising a phase-change material having a melting point between 18° and 40°C. More specifically, the phase-change material is housed in a casing that is impermeable to both the material and the fuel, such that the casing does not allow any exchange of matter between the fuel and the heat storage element. Conversely, the casing of the heat storage element is heat-conductive, thus allowing heat exchange between the fuel and the phase-change material. The at least one heat storage element absorbs heat, particularly when the fuel temperature is close to the melting point of the phase-change material. Indeed, since the melting reaction is endothermic, it consumes heat from the fuel.At least one heat storage device thus limits the temperature rise of the fuel and therefore limits the generation of fuel vapor in the tank and thus the increase in pressure within the tank. The phase change material is preferably chosen from the following list: calcium chloride hexahydrate (CaCl2.6H2O), octadecane (C. 18 H 38 ), cyclohexanol (C6H 12 O), a derivative of glycerin.

[0144] Thanks to this limitation of fuel vapor generation, the bladder or bladders can be sized with a smaller total volume, so that the choice of the volume of bladder 2 or the total volume of bladders 2 can no longer be impacted by the total volume of tank 5 and / or by the maximum volume of fuel that can be contained in fuel tank 5. It is thus understood that the combined effects of at least one heat storage element and the bladders surpass the effects provided by at least one heat storage element and the bladders considered in isolation.

[0145] Preferably, as illustrated, the support 3 has a shape that conforms to the shape of the bladder 2. The shape of the assembly (support 3 - bladder protection device 3') can be obtained by scaling the shape of the bladder 2 with a ratio greater than 1. Thus, if the bladder 2 is a rectangular parallelepiped, the assembly (support 3 - bladder protection device 3') is at least partially a rectangular parallelepiped. Conversely, if the bladder 2 is a square parallelepiped, the assembly (support 3 - protection device 3') is at least partially a square parallelepiped.

[0146] Advantageously, as illustrated in Figures 1 and 2, the bladder protection means 3' comprises an anti-ballooning device and perforated areas. The perforated areas extend vertically.

[0147] The support 3 (or the bladder protection means 3') also includes a housing for the robot arm used in the extrusion blow molding of a fuel tank 5. This housing is not shown in the figures.

[0148] As illustrated, the first fixation element 4a is positioned on the bladder 2. The bladder 2 has a superior surface 2a. The first fixation element 4a is integral with the superior surface 2a of the bladder 2. The first fixation element 4a forms a protrusion extending in space away from the bladder 2. The first fixation element 4a has an axis of symmetry 7 in the direction of its extension. For example, such that in planes perpendicular to the axis of symmetry 7, the first fixation element 4a describes a circle.

[0149] Advantageously, the second fastening element 4b is chosen from a fork, a pin, a circlip and a clip-on fastening means, such as a clip.

[0150] As illustrated in, the elements forming the first fixing organ 4a and the second fixing organ 4b are chosen so that they can function by cooperation or complementarity of form.

[0151] The first fixation device 4a is fixed relative to the bladder 2. The first fixation device 4a is configured to support the weight of the bladder 2 on which it is positioned. The second fixation device 4b is removable after being secured to the first fixation device 4a.

[0152] Preferably, the first fastening element 4a is made of thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), polyamide (PA), polyethylene (PE), polyoxymethylene (POM), or polyphthalamide (PPA). The first fastening element 4a can also be made of two materials, for example, a polyamide (PA) body and a thermoplastic polyurethane (TPU) weld edge. The fact that the first fastening element 4a is made of two materials allows for a rigid and watertight first fastening element 4a thanks to the polyamide (PA), while also enabling it to weld to the bladder (which is made of thermoplastic polyurethane (TPU)) thanks to the thermoplastic polyurethane (TPU).

[0153] Advantageously, the second fastening element 4b is made of thermoplastic polyurethane (TPU), polyamide (PA), high-density polyethylene (HDPE), polyoxymethylene (POM), or polyphthalamide (PPA). The second fastening element 4b may also be made of steel, stainless steel, or aluminum. Preferably, the pressure compensation device 1 comprises several first fastening elements 4a. The pressure compensation device 1 comprises several second fastening elements 4b. The pressure compensation device 1 comprises several openings 3c. The pressure compensation device 1 comprises the same number of first fastening elements 4a as second fastening elements 4b and openings 3c, so that each first fastening element 4a is associated with a distinct second fastening element 4b and a distinct opening 3c.It is possible, for example, that the pressure compensation device comprises two first fixing members 4a and two second fixing members 4b and that the wall has two openings 3c. In this configuration, one of the two first fixing members 4a includes the conduit 5a which provides fluid communication between the inside of the bladder 2 and the outside of the fuel tank 5. Only the configuration where the pressure compensation device 1 comprises two first fixing members 4a, two second fixing members 4b and two openings 3c is shown in the figures.

[0154] Advantageously, the additional fastening member 6 is configured to secure the support 3 to the fuel tank 5. However, in order to prevent stress on the additional fastening member 6 from causing rupture in the tank wall during the cooling of the fuel tank 5 (during the manufacture of a fuel tank 5 by blow molding a parison) and therefore during the shrinkage of the material constituting the tank, the additional fastening member 6 is mounted to be movable or to have elasticity relative to the support 3. The additional fastening member 6 is therefore positioned on a flexible element (not shown, which may be made of plastic and may be in the shape of a chicane, for example, describing a broken line forming rounded angles that are alternately protruding and re-entrant) whose role is to accompany the movement of the additional fastening member 6 during the cooling of the tank 5.The additional fastening element 6 is positioned against a flexible element.

[0155] In an advantageous example, the additional fastening element 6 is made of high-density polyethylene (HDPE). Preferably, the additional fastening element 6 is directly fixed to the support 3, without being mounted to move and without the addition of an elastic element.

[0156] Of course, the invention is not limited to the examples of embodiment mentioned above.

[0157] List of references: 1: pressure compensation device 2: bladder 2a: upper face 3: support 3a: wall 3b: inner face 3c: opening 3': bladder protection means 4: fastening means 4a: first fastening member 4aa: bearing surface 4ab: receiving surface 4b: second fastening member 5: fuel tank 5a: conduit 5b: tubing 6: additional fastening member 7: axis of symmetry 8: assembly 10: fuel system 20: vehicle Z: vertical axis

Claims

Fuel system (10) for a vehicle comprising a plastic fuel tank (5) inside which a pressure compensating device (1) is fixed, the pressure compensating device (1) comprising an assembly (8) configured to be positioned inside the plastic fuel tank (5), the assembly (8) comprising a bladder (2), the device is characterized in that: the assembly (8) also comprises a support (3) and means for fixing (4) the bladder (2) to the support (3), the support (3) comprises a wall (3a) having an inner face (3b) facing the bladder (2) and an opening (3c) through the wall (3a), the fixing means (4) comprise a first fixing member (4a) integral with the bladder (2) and a second fixing member (4b) fixed to the first fixing member (4a),The first fixing member (4a) comprises a bearing surface (4aa) against the inner face (3b) of the wall (3a) of the support (3) and a receiving surface (4ab) for the second fixing member (4b). The first fixing member (4a) passes through the opening (3c) such that the wall (3a) is sandwiched between the second fixing member (4b) and the bearing surface (4aa) of the first fixing member (4a). System (10) according to the preceding claim, wherein the first fixing member (4a) is projecting on an external surface of the bladder (2). System (10) according to the preceding claim in which the first fastening member (4a) has an elongated shape, preferably cylindrical, and the second fastening member (4b) is chosen from one of the following: a fork, a pin, a circlip, a clip fastening means. System (10) according to any one of the preceding claims wherein the bladder (2) has an upper face (2a) and the first fixing member (4a) is positioned on the upper face (2a) of the bladder (2). System (10) according to any one of the preceding claims wherein the first fastening member (4a) comprises a conduit (5a) configured to put the inside of the bladder (2) into fluidic communication with the outside of the plastic fuel tank. System (10) according to any one of the preceding claims comprising a bladder protection means (3') integral with the support (3), the bladder protection means (3') covering at least partially the bladder (2). System (10) according to the preceding claim in which the bladder protection means (3') comprises an anti-ballooning device. System (10) according to any one of the preceding claims comprising an additional fastening member (6). System (10) according to the preceding claim in which the additional fastening member (6) is mounted movable. Vehicle (20), in particular hybrid vehicle, comprising a fuel system (10) according to any one of the preceding claims. Method of assembling a fuel system (10) according to any one of claims 1 to 9 comprising the following steps: positioning the bladder (2) relative to the support (3) so that the first fastening member (4a) passes through the opening (3c), fixing the second fastening member (4b) onto the first fastening member (4a) so that the wall (3a) is sandwiched between the second fastening member (4b) and the bearing surface (4aa) of the first fastening member (4a). A method for manufacturing a fuel system (10) by extrusion blow molding according to any one of claims 1 to 9, the method comprising the following steps: positioning a parison in an open mold, inserting the pressure compensation device (1) of the fuel system (10) according to any one of claims 8 to 9 into the parison, bringing the parison into contact with the additional fixing member (6), closing the mold, blowing the parison into the mold so as to form a fuel tank made of plastic material (5). Extrusion-blowing manufacturing method of a fuel system (10) according to the preceding claim, the method comprising between the step of inserting the pressure compensation device (1) inside the parison and the step of bringing the parison into contact with the additional fixing member (6), the following step: pre-blowing the parison. Method of manufacturing a fuel system (10) according to any one of claims 1 to 9, the method comprising the following steps: having a plastic fuel tank (5) including a vent, introducing the pressure compensation device (1) of the fuel system (10) according to any one of claims 8 to 9 into the plastic fuel tank (5) through the vent, fixing the support (3) inside the plastic fuel tank (5) by means of the additional fixing member (6).

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