VENTILATION DEVICE EQUIPPED WITH A MEMBRANE FOR A VEHICLE LIQUID TANK

Abstract

The ventilation device (4) for a vehicle liquid tank, comprises: a membrane (20) impermeable to a predetermined liquid and permeable to a vapor likely to be produced by this liquid, and at least one pipe (52) suitable for discharging liquid found on the membrane from the device. The or each pipe has an end contiguous with the membrane, the rest of the or each pipe extending at an altitude lower than this end when a main axis of the device is vertical.

Claims

1. A ventilation device for a vehicle liquid tank, which comprises: a membrane impermeable to a predetermined liquid and permeable to a vapor likely to be produced by this liquid, and at least one pipe suitable for discharging liquid found on the membrane from the device, the or each pipe having an end contiguous with the membrane, the rest of the or each pipe extending at an altitude lower than this end when a main axis of the device is vertical.

2. The device according to claim 1, configured to allow a gas communication between the outside of the device and an upper side of the membrane while limiting the intrusion from the outside of the device toward this side of the membrane of any element foreign to the device having a smallest total dimension above a predetermined threshold.

3. The device according to claim 1, wherein said device comprises a main body and a cover configured to be fastened to the body while allowing a gas communication between the outside of the device and an upper side of the membrane while limiting the intrusion from the outside of the device toward this side of the membrane of any element foreign to the device having a smallest total dimension above a predetermined threshold.

4. The device according to claim 1, comprising a main body and a cover configured to be fastened to the body, wherein the membrane is fastened by a circumferential edge, so as to be watertight, to the body at an opening of the latter, this opening being formed by an inner flange, wherein the cover comprises a side wall provided with an inner face such that the inner face of the wall is facing an outer face of the inner flange while being separated from the latter by a distance smaller than a predetermined threshold.

5. The device according to claim 3, wherein the cover is welded to the body.

6. The device according to claim 1, wherein said device comprises an open-worked wall extending at a distance from the membrane, facing a lower wall of the membrane.

7. The device according to claim 1, wherein said device comprises a body and a base having a largest transverse dimension (S) greater than a largest transverse dimension (U) of the body.

8. The device according to claim 7, wherein the body comprises at least two external inclined faces oriented toward the base.

9. A tank that comprises a device according to claim 1.

10. A liquid tank for a vehicle, which comprises: a membrane impermeable to the liquid and permeable to a vapor likely to be produced by this liquid, and at least one pipe suitable for discharging liquid found on the membrane from the device, the or each pipe having an end contiguous with the membrane, the rest of the or each pipe extending at an altitude lower than this end when a main axis of the tank is vertical.

11. The tank according to claim 10 that comprises an open-worked wall extending at a distance from the membrane, facing a side of the membrane oriented toward the inside of the tank.

12. The tank according to claim 9, wherein said tank is a water tank.

13. The tank according to claim 9, wherein said tank is a fuel tank.

14. The tank according to claim 9, wherein said tank is an ammonia precursor tank.

15. A vehicle that comprises a device according to claim 1.

16. A vehicle that comprises a tank according to claim 9.

Description

[0038] We will now describe two embodiments of the invention given as non-limiting examples and supported by the appended figures, in which:

[0039] FIGS. 1 and 2 are perspective and elevation views of a tank according to a first embodiment of the invention,

[0040] FIGS. 3 to 5 are elevation views, in vertical axial cross-section and top view, of the ventilation device of the tank of the preceding figures,

[0041] FIG. 6 is a perspective view of the ventilation device according to a second embodiment, in which the cover and the membrane are not shown, and

[0042] FIG. 7 is a perspective view of the device of FIG. 6.

[0043] In reference to FIGS. 1 to 5, we will describe a vehicle tank 2 provided with a ventilation device 4 according to a first embodiment of the invention. It is a fuel tank such as diesel fuel, in the present example.

[0044] The tank 2 here is formed by two lower 6 and upper 8 shells made from thermoplastic material. The two shells will be welded to one another at a weld plane 10 extending in a median zone of the height of the tank.

[0045] In the lower part, the tank comprises a platen 12 closing a lower opening of the lower shell 6 and bearing different members gathered to form a module 14 extending in the tank. These members in particular comprise a pump for injecting liquid from the tank outside the latter for use thereof on board a vehicle. Such a module is known in itself and will not be described in more detail here.

[0046] The ventilation device 4 is located in the uppermost point of the tank or one of its highest points. Here, this point forms an upper recess 16. The device is arranged on an opening 18 of the upper shell 8, this opening being provided in one of the main walls of the tank.

[0047] The device 4 comprises a ventilation member comprising a membrane 20 that is impermeable to water and permeable to diesel vapor, steam and air. This membrane here is microporous and for example made from polytetrafluoroethylene (PTFE). The membrane 20 has a thickness of between 250 and 350 m. The membrane 20 is for example made in a planar form, such as a disc. It extends horizontally and is fastened by its circumferential circular edge so as to be watertight to a support 22 of the ventilation device at a circular opening of this support, here formed by an inner cylindrical flange 24.

[0048] The device further comprises a cover 33 able to be fastened to the support 22: [0049] while preserving a gas passage through the membrane 20 toward the outside of the device along the cover, and [0050] while limiting the intrusion into the device of any element foreign to the device having a smallest total dimension above a predetermined threshold, in particular 2 mm, or even 1.5 mm. To that end, in the present example, the cover comprises a disc-shaped upper wall 36 and a cylindrical side wall 38.

[0051] The base 22 comprises an outer cylindrical flange 34 extending around the inner flange 24 and at a distance from the latter in reference to a main axis 32 of the device. This axis is oriented vertically during the use of the device and the tank embedded in the vehicle. The outer flange 34 also extends higher than the inner flange 24. The cylindrical wall 38 of the support is fastened to its upper wall 36 at a distance from the peripheral edge of the latter. In this way, the peripheral edge zone of the wall 36 is left free and serves to fasten the cover directly on the outer cylindrical flange 34, in the case at hand by ultrasonic welding. This welding produces a continuous junction along the entire inner edge over a closed loop.

[0052] The cylindrical wall 38 of the cover therefore, by its outer face, is facing the inner face of the outer flange 34. Additionally, the inner face of the wall 38 is facing the outer face of the inner flange 24 while being separated by the latter by a distance d smaller than 2 mm, preferably than 1.5 mm. This distance is illustrated in FIG. 4. It procures the aforementioned anti-intrusion effect.

[0053] The inner flange 24 is topped in the present example by curved indentations 48 arranged in a circular configuration in planar view like in FIG. 5; here, there are six of them. The apex of the indentations 48 is facing and at a distance from the inner face of the upper wall 36 of the cover. The indentations 48 are arranged at a distance from one another such that their side edges 49 extend facing and at a distance from one another. This distance arranges respective spaces 50 between the indentations 48 that place the membrane 20 in communication with the outside of the flange 24. In this way, each of the spaces 50 is part of a pipe 52 whose upstream end is contiguous with the circumferential circular edge of the membrane 20 at the apex of the flange. The terms upstream and downstream here refer to the flow of water from the membrane toward the outside of the device. In the downstream direction, each pipe 52 continues while being formed by the space 50, then descends between the outer face of the flange 24 and the inner face of the cylindrical wall 38 of the cover. Lastly, orifices 51 are arranged in the frustoconical wall 44. These orifices are in respective communication with the spaces 50 and/or in the same angular position as those around the axis 32. These orifices form the downstream end of the pipes. The presence of these multiple orifices makes it possible to reduce the risk of obstruction of the device. It is observed that the upstream end of each pipe contiguous to the membrane 20 forms the uppermost point of the pipe when the axis 32 is vertical, that is to say, when the device and the tank are in their normal usage position. The downstream end of the pipe, formed by the orifice 51, constitutes the lowermost point thereof. Furthermore, the fact that these orifices are distributed angularly around the axis 32 allows a good discharge of any liquids potentially present on the membrane and therefore limits the accumulation thereof on the membrane, thus making it possible to preserve the ventilation function thereof, for example during ford crossing.

[0054] The support 22 comprises a planar horizontal lower wall 55 perpendicular to the axis 32, extending below the membrane 20, opposite and at a distance therefrom. The wall has orifices or apertures 57 (see FIGS. 4 and 5), These orifices 57 make it possible to discharge the water that could be located above the wall so that it falls back into the reservoir. They also place the membrane 20 in gas communication with the inside of the tank. This wall also provides protection of the membrane with respect to masses of liquid or blocks of frozen liquid that could damage the membrane.

[0055] The ventilation device further comprises a base 40. The support 22 is rigidly fastened to the upper wall of the base 40. The part of the support 22 that is contiguous to the base 40 forms a cylindrical face 42 with a diameter smaller than that U of the outer cylindrical face of the flange 34. The junction between these two faces is formed by a frustoconical face 44. This narrowing of the support toward the base therefore offers inclined faces that facilitate the gripping of the support by a tool during the fastening of the device to the tank.

[0056] The support 22 and the base 40 are made from thermoplastic material. The base is fastened, for example by welding, to the main wall of the tank forming the upper shell 8 facing the opening 18. In the present example, the upper face of the base bears against an outer face of the main wall. The opening 18 is thus in gas communication with the membrane 20. Lastly, the membrane is in gas communication with the outside of the tank along the cover 36. One can see that the device 4 is able to be attached on a tank 2 in order to ventilate it. The membrane is in fact able to place the inside of the tank in gas communication with the outside of the tank.

[0057] The tank also comprises a filling tube 54.

[0058] The base, the cover and the support are for example made from polyethylene, other thermoplastic materials nevertheless being conceivable.

[0059] The device works as follows.

[0060] When the tank experiences an overpressure due to an increase in the temperature or altitude, since this increase generally occurs slowly, the steam or fuel vapor can pass slowly through the opening 18 of the tank, through the openings 57 until reaching the membrane 20 and passing through it. These gases pass above the flange and below the wall 36 of the cover, then between the flange and the side wall 38, then escape through the orifices 51 into the atmosphere.

[0061] When the tank experiences an underpressure due to a drop in the temperature or the altitude, the same phenomenon occurs in reverse, except that this time it is ambient air that penetrates below the cover 36 through the membrane 20 until reaching the inside of the tank to reestablish a normal pressure therein.

[0062] The membrane also procures effective protection against the intrusion of foreign elements. Additional protection is procured by the cooperation between the cover 33 and the support 22 for the elements having a smallest total dimension of less than 2 mm. Indeed, debris and particularly insects or spiders for the most part cannot penetrate through the orifices 51, much less between the flange 24 and the side wall 38 of the cover in light of the distance d. In this context, the inner flange 24 and the cover 33 form a labyrinth that is more effective because it is sinuous. If the water arrives on the membrane 20 for example on the occasion of a ford crossing, this water is immediately discharged by gravity through the drainage pipes 52, by first crossing the drainage spaces 50 and lastly the drainage orifices 51.

[0063] The ventilation device can be attached on the tank once the latter is made or integrated into the tank during the manufacture, in particular by injection or by blowing, of the latter. In this respect, the frustoconical wall 44 offers an engagement for a tool allowing holding of the support 22 during the placement and fastening of the device on a tank. Additionally, the upper face 53 of the base, left free by the support, allows a tool to bear for this fastening, which for example takes place by hot welding of the plastic material of the base on that of the tank. This disengagement results from the fact that the largest transverse dimension U, which corresponds to the largest diameter of the support 22, is smaller than the largest diameter S of the base 40.

[0064] One can see that the device is compact.

[0065] Below, several examples are described of sizings for producing the invention, non-limitingly, with the understanding that other sizings can be considered.

[0066] In the Case of a Water Tank

[0067] For a water tank, it is possible to give the membrane 20 a diameter of 30 mm. It will allow to procure a head loss of 50 mbar (50 hPa or 5000 Pa) in the tank with a gas flow rate of 80 liters per hour. Indeed, during operation, the pump of the tank will apply a flow rate of 80 liters per hour, and it is not desirable for the underpressure in the tank to exceed 50 mbar.

[0068] In the Case of a Tank for a Urea Solution

[0069] For a tank of a urea solution, it is possible to give the membrane 20 a diameter of 20 mm. It will allow to procure a head loss of 45 mbar (4500 Pa) in the tank with a gas flow rate of 15 liters per hour.

[0070] In the case of a fuel tank such as diesel fuel

[0071] For a fuel tank such as diesel fuel, it is possible to give the membrane 20 a diameter of 30 mm. It will allow to procure a head loss of 45 mbar (4500 Pa) in the tank with a gas flow rate of 30 liters per hour.

[0072] The invention is not limited to the described embodiment.

[0073] The cover can also be fastened to the support by clipping.

[0074] The second embodiment, shown in FIGS. 6 and 7, is identical to the first embodiment except for the following points: [0075] a journal cross 61 extends from the open-worked wall 55 toward the membrane 20 (see FIG. 6). The journal cross 61 delimits four compartments that each comprise one of the orifices 57 of the open-worked wall 55. This journal cross 61 makes it possible, inter alia, to reinforce the open-worked wall 55, and [0076] the outer flange 34 has an inner face and an outer face in reference to the main axis 32 of the device. A screwing thread 60 is present on the outer face of the outer flange 34 (see FIGS. 6 and 7). This screwing thread 60 in particular allows the screwing of a welding tool during the method for assembling the device 4 on the tank 2.