DEVICE FOR THE FLUID SUPPLY OF A MOTOR VEHICLE

Description

Technical field of the invention

[0001] The invention relates to a fluid supply device for a motor vehicle. The invention also relates to a fluid reservoir for a motor vehicle comprising a fluid supply device according to the invention. Furthermore, the invention relates to a selective catalytic reduction device for a motor vehicle comprising a fluid reservoir according to the invention. Finally, the invention relates to a motor vehicle comprising a fluid reservoir according to the invention. Technical background

[0002] Liquid injection systems for vehicles are already known in the prior art. These systems are used, for example, to inject an additive solution, such as an ammonia precursor, into the exhaust system of an internal combustion engine to perform selective catalytic reduction (SCR). SCR reduces nitrogen oxides (NOx) emitted by light and heavy vehicles equipped with internal combustion engines, thereby decreasing pollution and helping to comply with nitrogen oxide emission regulations. Selective catalytic reduction requires the use of a reducing agent, such as ammonia, at a precise concentration and of high quality.An ammonia precursor, such as urea, is generally used as an additive. This requires precise metering and injection into the exhaust gas stream, where it is hydrolyzed before converting nitrogen oxides (NOx) into nitrogen (N2) and water (H2O). To achieve this, vehicles must be equipped with a tank containing the additive solution, as well as a device for metering and injecting the desired quantity of additive into the exhaust system. Such a tank is described in document DE102013211254A1.

[0003] To prevent clogging the additive solution injector with impurities that may be present in the additive solution, it is known to filter the additive solution before injection. In the prior art, a filter element is arranged in the additive tank at the inlet of an additive supply pump, allowing the additive solution to be pumped through the filter element. This arrangement cleans the additive solution of its impurities before it is injected into the exhaust line, upstream of the catalyst in the selective catalytic reduction (SCR) reaction. This also protects the supply pump from impurities present in the aspirated additive solution.

[0004] After a certain period of use, impurities clog the filter element. Clogging occurs more rapidly when the impurities are numerous and large. This is particularly true in highly polluted areas. As the level of clogging increases, the filtration capacity of the filter element decreases, and the flow rate of the liquid through the filter element becomes lower than the suction flow rate of the feed pump. Consequently, the pump draws in some or all of the air, causing pressure losses in the liquid injection by the feed pump. This results in difficulties in accurately metering the injected additive and therefore a reduction in the efficiency of the selective catalytic reduction. Air intake is even more pronounced when the liquid level in the tank is low, thus exposing part of the filter element to air. Summary of the invention

[0005] The invention aims in particular to reduce the risk of loss of fluid injection pressure in a motor vehicle fluid supply device over time.

[0006] To this end, the invention relates to a liquid supply device for a motor vehicle, comprising: a supply pump intended to pump liquid from a liquid reservoir to a device for consuming that liquid, and a filtration assembly intended to filter the liquid pumped by the supply pump, the filtration assembly comprising a housing in which a filtration element is housed, in which the housing forms a siphon connected to a suction inlet of the feed pump and has an open end intended to open into the liquid contained in the liquid reservoir such that a path of this liquid in the siphon passes through a so-called high level, which, when the level of the liquid in the liquid reservoir is below a predetermined threshold, is higher than the level of the liquid in the liquid reservoir, in which the filtration element comprises a filtration zone in the form of a bag of filter material extending vertically in the siphon-forming housing, and in which the liquid supply device further comprises a supply conduit extending vertically in the bag between high and low points of the bag,The first upper end of the supply conduit is connected to the suction inlet of the supply pump, and the second lower end opens into the inside of the bag.

[0007] Thus, during the priming of the feed pump, it initially draws in the air present in the siphon housing. This air intake creates a vacuum that raises the liquid level in the siphon, thereby immersing the filter element in the liquid. Consequently, after the feed pump priming period, the filter element is no longer in contact with air, or at least remains sufficiently submerged, even when the liquid level in the tank is below the predetermined threshold, to prevent the feed pump from drawing in air during operation. Furthermore, because the filter element remains sufficiently submerged even when the liquid level in the tank is low, the risk of clogging the filter element, which would otherwise impede liquid flow, is effectively minimized.

[0008] The fact that the feed pump does not draw in air during operation prevents any instability or pressure loss for the liquid injected by the pump. This is particularly advantageous when the injected liquid must be precisely metered, for example, when the liquid is an ammonia precursor intended for injection into the exhaust system of an internal combustion engine for use as an additive in a selective catalytic reduction (SCR) reaction. The liquid feed system can be used with other liquids, such as water or fuel.

[0009] It is understood that the liquid supply device according to the invention allows the use of large-sized filtration elements without risking a decrease in the injection pressure of the liquid by the supply pump since the filtration element is no longer in contact with air or, at the very least, the filtration element remains sufficiently immersed.

[0010] Furthermore, since the air in the housing is expelled when the feed pump is primed, the level of clogging of the filter element has little impact on the liquid filtration flow rate, as the filter element is not in contact with air and can therefore only filter liquid. Thus, the liquid feed device according to the invention remains functional even with significant clogging of the filter element. The lifespan of the filter element is therefore increased, particularly in polluted areas where it tends to clog quickly.

[0011] The siphon housing, by its very function, includes a wall that is airtight and impermeable to the liquid in the reservoir. This further protects the filter element from any impurities present in the stored liquid, thus extending its lifespan. Specifically, any oily residues in the liquid remain on its surface and are trapped by the siphon housing, preventing them from reaching the filter element.

[0012] The term "impurity" refers to any foreign matter in the liquid, such as dust, soil, insects, shavings from the tank, oils, or solid particles. These foreign matter items may be floating, suspended, or settled at the bottom of the liquid tank.

[0013] The passage of the liquid through a so-called high level allows a significant immersion of the filtration element in the liquid regardless of the filling level of the reservoir, within the limit of a minimum filling level.

[0014] The predetermined threshold corresponds, for example, to the liquid level in the reservoir at which at least part of the siphon housing is no longer submerged. Preferably, the predetermined threshold corresponds to the liquid level in the siphon housing at which the filter element is no longer in contact with the air. This ensures that the filter element remains sufficiently submerged in the liquid even when the liquid level in the reservoir is lower than the so-called high level inside the housing.

[0015] It is understood that a "pocket" comprises at least one wall delimiting a cavity open at one end and closed at the other, forming the bottom of the pocket. According to the present invention, it is understood that the pocket wall is made of a filtration material and that liquid can be filtered through this wall into the interior of the pocket.

[0016] Because the filter area, in the form of a bag, extends vertically within the housing, when the bag is fully immersed in liquid—for example, once the pump has been primed and the air has been expelled from the housing—the available filtration surface area is optimized. This is because all sides of the bag, across their entire height and width, can be used to filter unfiltered liquid. This allows for a particularly compact filtration system and, consequently, a more compact liquid supply device.

[0017] The invention may also include one or more of the following optional features, taken alone or in combination.

[0018] The V / h ratio, where V is the volume of the filter element and h is its height, is between 400 mm² and 800 mm², preferably around 600 mm². This ratio represents the filtering surface area of ​​the filter element. Such filter elements exhibit good filtration properties. The presence of the siphon housing makes the use of such filter elements advantageous. Indeed, a filter element with these dimensions has good filtration properties but, with prior art liquid supply devices, creates a significant risk of liquid injection pressure loss due to its large volume, which can easily fill with air.The liquid supply device according to the invention makes it possible to expel air from the siphon-forming housing during priming, so that the use of such filtration devices is possible without encountering this problem.

[0019] According to the invention, the liquid supply device comprises a supply conduit extending vertically within the pouch between high and low points of the pouch, with a first upper end of the supply conduit connected to the suction inlet of the supply pump and a second lower end opening into the interior of the pouch. This is a simple means of facilitating pump suction by allowing liquid to be drawn in close to the liquid level in the siphon-forming housing.

[0020] Preferably, the difference Δ between the second lower end of the supply line and the bottom of the bag is between 10 and 90% of the bag height p; preferably, the difference Δ is approximately 25% of the bag height p. This positioning of the second lower end of the supply line optimizes fluid aspiration by the supply pump through the supply line, both during pump priming and subsequent aspiration.

[0021] The bag comprises at least two lateral filtration faces, each positioned opposite and at a distance from a wall of the housing. This optimizes the surface area available for filtration. Indeed, in this arrangement, the lateral filtration faces are not in contact with the housing wall and can therefore come into direct contact with unfiltered liquid. Thus, liquid can enter the bag not only through the bottom but also through the lateral filtration faces. The filtration area of ​​the filter element is thereby increased. Depending on the embodiment, the number of lateral faces can vary, for example, from two to six.

[0022] The liquid supply system includes heating elements for the siphon housing. This allows any frozen liquid in the siphon housing to thaw, thus enabling the liquid supply system to function. It should be noted that the heating elements only need to heat the volume of liquid present in the siphon housing. Since this volume is small, thawing the liquid within it is facilitated.

[0023] The feed pump is housed in a casing, with the filtration assembly arranged outside and supported by the casing. The casing allows for the simple and efficient grouping and connection of the various functional units of the liquid supply system. This simplifies the manufacturing of the liquid supply system and results in a compact liquid supply unit.

[0024] Preferably, the liquid supply system also includes means for removable attachment of the filtration assembly to the housing. This facilitates maintenance of the liquid supply system. It is then easy to detach the filtration assembly from the housing in order, for example, to check the condition of the filter element, particularly its level of clogging. It is also easy to replace the filter element when necessary. In particular, it is possible to replace the filter element without having to perform any manipulations on the rest of the liquid supply system, especially the feed pump. This reduces the risk of wear on the rest of the supply system, thus increasing its service life.Removable fastening methods may consist of any means known to those skilled in the art for easily and quickly attaching and detaching the filter assembly from the housing. Preferably, these removable fastening methods do not require the use of a tool to attach or detach the filter assembly from the housing. For example, removable fastening methods are clip-on or screw-on methods that allow the filter assembly to be clipped or screwed directly onto the housing. Screw-on fastening refers to the fact that the filter assembly includes a thread that complements a thread on the housing, so that the filter assembly can be screwed directly onto the housing.Preferably, the threads of the filter assembly and the housing form quarter-turn screw-type fastening means, allowing the filter assembly to be attached and detached from the housing by rotating the filter assembly a quarter turn, or 90°. Attaching and removing the filter assembly is thus particularly easy, even when space is limited.

[0025] The liquid is an aqueous solution, preferably an ammonia precursor. If the liquid is an ammonia precursor, the liquid supply device can advantageously be used in a selective catalytic reduction reaction to purify the exhaust gases of an internal combustion engine. In another embodiment, the aqueous solution is water.

[0026] The invention also relates to a fluid reservoir for a motor vehicle equipped with a fluid supply device as described above. Thus, depending on the embodiment, the reservoir can be, for example, a reservoir for an aqueous solution such as water or urea, or a fuel reservoir. The reservoir can be made of any material. In the specific case of a urea solution reservoir, the material of the reservoir is preferably a material having good chemical resistance to urea. This is generally a plastic material. Polyolefins, in particular polyethylene and, more particularly, high-density polyethylene (HDPE), are preferred materials. This reservoir can be manufactured by any known processing method. One known method is injection molding. A preferred method is extrusion blow molding.In this process, a parison—in one or more parts—is obtained by extrusion and then shaped by blow molding. Molding the tank in one piece from a single-part parison gives good results.

[0027] The invention also relates to a selective catalytic reduction device for purifying the exhaust gases of an internal combustion engine of a motor vehicle. The selective catalytic reduction device comprises a liquid reservoir as described above, in which the liquid is an ammonia precursor. The ammonia precursor is, for example, urea. The catalytic reduction device is thus improved by being equipped with a liquid supply device according to the invention, which reduces the risk of a loss of injection pressure of the ammonia precursor over time. This is particularly advantageous since, as mentioned above, it is important to precisely meter the ammonia precursor injected during selective catalytic reduction, and a loss of injection pressure of the ammonia precursor impairs the accuracy of this metering.

[0028] Finally, the invention also relates to a vehicle comprising a liquid reservoir as described above. Brief description of the figures

[0029] The invention will be better understood upon reading the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which: [ Fig.1 ] is a schematic representation of a vehicle comprising a tank equipped with a liquid supply device according to the invention; [ Fig. 2 ] is a perspective view of the liquid supply system of the [ Fig.1 ] ; ] Fig.3 ] is a cross-sectional view of part of the liquid supply system of the [ Fig.1 ] ; ] Fig. 4 ] is a perspective view of a filtration assembly forming part of the liquid supply system of the [ Fig.1 ] ; ] Fig. 5 ] is a front view of part of the filtration assembly of the [ Fig. 4] ; ] Fig. 6 ] is a longitudinal cross-sectional view of the portion of the filtration assembly shown in the [ Fig. 5 ] ; And [ Fig. 7 ] is a schematic representation of the operation of the liquid supply system of the [ Fig.1 ]. Detailed description

[0030] We have represented on the figures 1 to 7 an embodiment of a liquid supply device 1 2 according to the invention. In the present case, the liquid supply device 1 2 is mounted on a lower wall of a liquid tank 3 which is itself mounted on a motor vehicle 4 ([ Fig.1 ]).

[0031] In this case, the liquid is an ammonia precursor, such as urea. The liquid reservoir 3 and the liquid supply device 1 are thus part of a selective catalytic reduction device 18 intended to purify the exhaust gases of an internal combustion engine (not shown) of the motor vehicle 4.

[0032] The material from which the liquid reservoir 3 is made is preferably one with good chemical resistance to urea. It is generally a plastic. Polyolefins, particularly polyethylene and, more specifically, high-density polyethylene (HDPE), are preferred materials. This reservoir can be manufactured by any known processing method. One known method is injection molding. A preferred method is extrusion blow molding. In this process, a parison—in one or more parts—is obtained by extrusion and then shaped by blow molding. Molding the reservoir in one piece from a single parison gives good results.

[0033] The liquid supply device 1 2 includes in particular a housing 5, a supply pump 6 and a filtration assembly 7 ( figures 2 , 3 ,4 And 7 ).

[0034] The housing 5 forms a support element for the various functional units of the liquid supply device 2. In this case, the supply pump 6 is housed inside the housing 5 and the filtration assembly 7 is arranged outside the housing 5 and supported by this housing 5 ( figures 2 ). More specifically, the liquid supply device 1 2 includes removable fastening means (not shown) for the filtration assembly on the housing 5. Preferably, these removable fastening means do not require the use of a tool to attach or detach the filtration assembly 7 and the housing 5. For example, the removable fastening means are clip-on or screw-on means allowing the filtration assembly 7 to be clipped or screwed directly onto the housing 5.

[0035] The other functional units of the liquid supply device 1 2 are conventional and are not shown for clarity. The housing 5 can be made of any material with good chemical resistance to urea. For example, the housing 5 is made of thermoplastic material.

[0036] The supply pump 6 is designed to pump liquid from the liquid reservoir 3 to a liquid consumption device (not shown). In this case, since the liquid is an ammonia precursor, the liquid consumption device is a catalyst for a selective catalytic reduction reaction. It is understood that the liquid consumption device will differ depending on the intended use of the liquid supply device 2, and more specifically, depending on the nature of the liquid 2 contained in the liquid reservoir 3. The supply pump 6 used is known in itself and will not be described in further detail here. It is understood that the supply pump 6 could, in particular, be a supply pump typically used for injecting ammonia precursors in a selective catalytic reduction reaction in a motor vehicle 4.

[0037] The filtration assembly 7 is intended to filter the liquid 2 pumped by the feed pump 6 in order to ensure that the liquid 2 injected into the selective catalytic reduction reaction is substantially free of impurities. The filtration assembly 7 includes in particular a housing 8 in which is housed a filtration element 9 ([ Fig. 4 ]).

[0038] The housing 8 has a general parallelepiped shape with a first closed longitudinal end and a second open longitudinal end, opposite the first. In this case, the housing 8 is formed in two parts: a first part forming the main body 10 of the housing 8, and a second part forming a closing cover 11 intended to seal the first longitudinal end of the housing 8 airtight and to prevent the liquid 2 present in the liquid reservoir 3 from entering. Alternatively, the housing 8 can be manufactured so that the body 10 and the cover 11 are made from a single piece of material.

[0039] The housing 8 forms a siphon which is connected to a suction inlet 12 of the supply pump 6 at its first closed longitudinal end via a supply conduit 13. The second open longitudinal end of the siphon-forming housing 8 opens into the liquid 2 contained in the liquid reservoir 3 such that a path of this liquid 2 in the siphon passes through a so-called high level, which, when the liquid level in the liquid reservoir 3 is below a predetermined threshold, is higher than the liquid level in the liquid reservoir 3 (see [ Fig. 7 For example, the predetermined threshold can be located approximately at the level of the first open longitudinal end of the siphon-forming housing 8. Preferably, the predetermined threshold corresponds to the liquid level in the siphon-forming housing 8 at which the filtering element 9 is immersed in the liquid 2.

[0040] The filtration element 9 is made from a flexible filter mesh fixed to a rigid frame. The filter mesh is flexible and is, for example, wound over or under the rigid frame. Advantageously, the filter mesh and the rigid frame are made of thermoplastic material and are welded to each other. Alternatively, the flexible filter mesh is manufactured as a single piece with the rigid frame ( figures 5 and 6 ).

[0041] The filtration element 9 includes a filtration zone that extends vertically within the siphon-forming housing 8. In other words, the filtration element 9 is arranged vertically within the housing 8, which is itself arranged vertically when mounted on the casing 5 ( figures 2 , 3 And 7 ). More specifically, the filtration zone of the filtration organ 9 includes a pocket 14 of filtration material formed by the filter mesh.

[0042] The bag 14 includes at least one wall delimiting a cavity open at one end and closed at the other, forming a bottom of the bag. In this case, the opening of the bag 14 allows the passage of the supply conduit 13. According to this embodiment, the bag 14 includes two lateral filtration faces 19, 20, each lateral filtration face 19, 20 being arranged opposite and at a distance from a wall of the housing 8 ( figures 3 And 7 ).

[0043] In the present case, the V / h ratio, where V is the volume of the filtration unit 9 and h is the height of the filtration unit 9, is between 400 mm² and 800 mm², preferably the V / h ratio is approximately 600 mm². In the present embodiment, the filtration bag 14 has a height p of approximately 68 mm, which is slightly less than the height h of the filtration unit ([ Fig. 5 ]).

[0044] The supply conduit 13 has a general inverted "L" shape and extends vertically in the pocket 14 between high and low points of the pocket 14. A first upper end 15 of the supply conduit 13 is connected to the suction inlet 12 of the supply pump 6 and thus allows fluid communication between the interior of the siphon-forming housing 8 and the suction inlet 12 of the supply pump 6 ( figures 3 And 7 ). A second lower end 16 of the supply conduit 13 opens into the inside of the pocket 14 ( figures 5 and 6 ). Depending on the embodiment, the height at which the second lower end 16 of the supply conduit 13 opens into the pocket 14 varies. In the present case, and advantageously, the gap Δ between the second lower end 16 of the supply conduit 13 and the bottom of the pocket 14 is approximately 15.5 mm, which represents approximately 23% of the height p of the pocket 14 ([ Fig. 5Advantageously, the gap Δ between the second lower end 16 of the supply conduit 13 and the bottom of the pocket 14 is between 10% and 90%, preferably the gap Δ is about equal to 25% of the height of the pocket.

[0045] The liquid supply device 1 further includes means 17 for heating the siphon housing 8. In this case, these heating means 17 are formed by a heating mat partially covering the siphon housing 8. According to other embodiments, any heating means suitable for being placed inside a liquid reservoir 3 2 in order to heat the siphon housing 8 may be used. For clarity, the heating means 17 are shown only on the [ Fig.3 ].

[0046] The following is described, with reference to the [ Fig. 7 ], an example of the operation of the liquid supply device 1 2 according to the invention.

[0047] As previously stated, the liquid supply device 1 is implemented in this case for a selective catalytic reduction reaction in order to inject liquid 2, here an ammonia precursor, into the exhaust gas stream of the motor vehicle 4 where it is hydrolyzed in order to convert nitrogen oxides (NOx) into nitrogen (N2) and water (H2O).

[0048] There figure 7A This represents the state of the liquid supply device 1 2 before its use, i.e., before the start-up of the supply pump 6. Here, the liquid level 2 in the liquid reservoir 3 is relatively low, so that a significant portion of the filtration assembly 7, and in particular the siphon housing 8, is not immersed in the liquid 2. Air is present inside the siphon housing 8.

[0049] When injection of liquid 2 into the exhaust gas stream is desired, the supply pump 6 is activated. During an initial priming stage, the supply pump 6 draws, via its suction inlet 12 and along the supply conduit 13, a mixture of air present in the siphon housing 8 and liquid 2. The air intake creates a vacuum which causes an increase in the level of liquid 2 inside the siphon housing 8 ( figure 7B ).

[0050] At the end of the priming period, all or most of the air that was present inside the siphon housing 8 was drawn out by the supply pump 6 so that the siphon housing 8 is filled with liquid 2 at least so as to completely or almost completely immerse the filtering element 9 ( figure 7CIt is observed that the level of liquid 2 in the siphon-forming housing 8 is higher than the level of liquid 2 in the liquid 2 reservoir 3. The filter element 9 is therefore immersed in the liquid and is not in contact with air. At this stage, the feed pump 6 can no longer, or practically no longer, draw in air. Thus, the risk of a loss of injection pressure of liquid 2 is reduced or even eliminated. Furthermore, the immersion of the filter element 9 after the pump has primed is achieved regardless of the degree of clogging of the filter element 9.Thus, even with high clogging of the filtration organ 9 it is possible to continue to use this filtration organ 9 with a liquid supply device 1 2 according to the invention since the air having been expelled from the housing 8 forming a siphon, it can in all cases no longer be sucked up by the supply pump 6 and generate a drop in injection pressure of the liquid 2. Examples

[0051] The results of a test designed to measure the efficiency of the liquid supply device 1 according to the invention, as a function of the clogging level of the filtration element 9, are described below. The filtration elements 9 were tested for clogging levels, expressed as a percentage of the height h of the filtration element 9, of 0% (control), 10%, 20%, 30%, 40%, and 50%. To control the clogging level, it was artificially induced by coating the filtration element 9 with an epoxy resin to a height corresponding to the desired clogging percentage, starting from the lower end of the filtration element 9.The efficiency of the liquid supply device 1 2 according to the invention was tested by measuring the quantity of aqueous solution, here urea, that can be injected using the filtration element 9 alone, as in the prior art, or housed in a siphon-forming compartment 8 of a filtration assembly 7 according to the invention. The test results are presented in Table 1. [Table 1] Clogging level Volume of urea to be injected (kg) Volume of urea injected with a prior art liquid feeding device (kg) Volume of urea injected with a liquid supply device according to the invention (kg) 0 % 5,000 4,821 Not applicable (NA) 10 % 5,000 4,540 4,824 20 % 5,000 4,459 4,844 30 % 5,000 3,685 4,821 40 % 5,000 3,343 4,810 50 % 5,000 3,247 4,841

[0052] The volume of urea is measured in kilograms rather than liters to facilitate measurements. Alternatively, this test could be carried out by measuring the volume of urea in liters. According to this test, 5 kg of urea are to be injected through a liquid supply device 1 comprising either a filtration element alone (the prior art case), or a filtration assembly 7 according to the invention in which the filtration element 9 is housed in a siphon-forming compartment 8.

[0053] The case where the clogging level is at 0% was tested only on the liquid supply device of the prior artery in order to provide a reference value. Thus, in the prior artery, with a filtration unit that is not clogged, generally because it is new, the volume of urea injected from 5 kg of urea is 4.821 kg.

[0054] In the case where the filtration element 9 is 10% clogged, a decrease in the urea injected into the prior art liquid supply device is observed. The volume of urea injected is 4.540 kg instead of 4.821 kg when the filtration element 9 is not clogged, representing a loss of 0.281 kg of urea. It is noted that this decrease is not observed with the liquid supply device 2 according to the invention, since 4.824 kg of urea were injected. Thus, a slight increase in the volume of urea injected is even observed compared to the control case (an increase of 0.003 kg). At 10% clogging, the filtration capacities of the filtration assembly 7 according to the invention are therefore better than those of the prior art and allow for maintaining a level of filtration substantially equivalent to that obtained when the filtration element 9 is new.

[0055] In the case where the filtration element 9 is 20% clogged, a decrease in the volume of urea injected for the prior art liquid supply device is again observed. The volume of urea injected is 4.459 kg instead of 4.821 kg when the filtration element 9 is not clogged, representing a loss of 0.362 kg of urea. Again, this decrease is not observed with the liquid supply device 2 according to the invention, since 4.844 kg of urea were injected. Thus, a slight increase in the volume of urea injected is observed compared to the control case (an increase of 0.023 kg). At 20% clogging, the filtration capacities of the filtration assembly 7 according to the invention are therefore better than those of the prior art and allow for maintaining a level of filtration substantially equivalent to that obtained when the filtration element 9 is new.

[0056] In the event that the filtration element 9 is 30% clogged, a decrease in the volume of urea injected for the prior art liquid supply device is again observed. The volume of urea injected is 3.685 kg instead of 4.821 kg when the filtration element 9 is not clogged, representing a loss of 1.136 kg of urea. Again, this decrease is not observed with the liquid supply device 2 according to the invention, since 4.821 kg of urea were injected, the same amount as with a new filtration element 9. At 30% clogging, the filtration capacities of the filtration assembly 7 according to the invention are therefore better than those of the prior art and allow for maintaining a level of filtration substantially equivalent to that obtained when the filtration element 9 is new.

[0057] In the event that the filtration element 9 is 40% clogged, a decrease in the volume of urea injected into the prior art liquid supply device is again observed. The volume of urea injected is 3.343 kg instead of 4.821 kg when the filtration element 9 is not clogged, representing a loss of 1.478 kg of urea. It is noted that this decrease is not very significant with the liquid supply device 2 according to the invention, since 4.810 kg of urea were injected, representing a loss of only 0.011 kg of urea. At 40% clogging, the filtration capacities of the filtration assembly 7 according to the invention are therefore better than those of the prior art and allow for maintaining a level of filtration substantially equivalent to that obtained when the filtration element 9 is new.

[0058] In the case where the filtration element 9 is 50% clogged, a decrease in the volume of urea injected for the prior art liquid supply device is again observed. The volume of urea injected is 3.247 kg instead of 4.821 kg when the filtration element 9 is not clogged, representing a loss of 1.574 kg of urea. Again, this decrease is not present with the liquid supply device 2 according to the invention, since 4.841 kg of urea were injected, an increase of 0.020 kg of urea compared to the control case. At 50% clogging, the filtration capacities of the filtration assembly 7 according to the invention are therefore better than those of the prior art and allow for maintaining a level of filtration substantially equivalent to that obtained when the filtration element 9 is new.

[0059] This test allows us to determine the filtration efficiency of a filter element 9 over time, that is, as it becomes clogged. The loss of filtration efficiency for prior art filter elements corresponds in practice to an increased risk of injection pressure loss during the use of the liquid supply device 2. As previously mentioned, this injection pressure loss is disadvantageous, particularly in cases where the quantity of liquid 2 to be injected must be precisely measured, since it prevents an acceptable level of accuracy regarding the quantity of liquid 2 injected.Thus, this test shows that the use of a liquid supply device 1 2 according to the invention makes it possible to preserve the filtration capacities of the filtration organ 9 over time, even for significant clogging, and thus to reduce the risk of loss of injection pressure of the liquid 2 over time. List references

[0060] 1: Liquid supply device 2: Liquid 3: Reservoir 4: Motor vehicle 5: Housing 6: Supply pump 7: Filtration assembly 8: Housing 9: Filtration element 10: Housing body 11: Housing cover 12: Supply pump suction inlet 13: Supply conduit 14: Filtration element bag 15: First upper end of the supply conduit 16: Second lower end of the supply conduit 17: Housing heating means forming a siphon 18: Selective catalytic reduction device 19, 20: Filtration side faces h: Height of the filtration element p: Height of the filtration bag Δ: Distance between the second lower end of the supply conduit and the bottom of the bag

Claims

1. A device (1) for supplying liquid (2) for a motor vehicle (4), comprising: - a supply pump (6) intended to pump liquid (2) from a liquid (2) tank (3) to a device consuming said liquid (2), and - a filtration assembly (7) for filtering the liquid (2) pumped by the supply pump (6), the filtration assembly (7) comprising a housing (8) in which a filtration member (9) is housed, wherein the housing (8) forms a siphon connected to a suction inlet (12) of the supply pump (6) and has an open end intended to open into the liquid (2) contained in the liquid (2) tank (3) such that a path of said liquid (2) through the siphon passes through a so-called high level, which, when the level of the liquid (2) in the liquid (2) tank (3) is below a predetermined threshold, is higher than the level of the liquid (2) in the liquid (2) tank (3), wherein the filtration member (9) comprises a filtration zone in the form of a pocket (14) of filtration material extending vertically within the housing (8) forming the siphon, characterized in that the device (1) for supplying liquid (2) further comprises a supply conduit (13) extending vertically within the pocket (14) between high and low points of the pocket (14), a first high end (15) of the supply conduit (13) being connected to the suction inlet (10) of the supply pump (6) and a second low end (16) opening into the interior of the pocket (14).

2. The device (1) for supplying liquid (2) according to claim 1, wherein the ratio V / h, where V is the volume of the filtration member (9) and h is the height of the filtration member (9), is between 400 mm2 and 800 mm2, preferably the ratio V / h is approximately equal to 600 mm2.

3. The device (1) for supplying liquid according to claim 1 or 2, wherein the distance (Δ) between the second low end (16) of the supply conduit (13) and the bottom of the pocket (14) is between 10 and 90% of the height (p) of the pocket (14), preferably, the distance (Δ) is approximately equal to 25% of the height (p) of the pocket (14).

4. The device (1) for supplying liquid (2) according to any one of the preceding claims, wherein the pocket (14) comprises at least two filtration side walls (19, 20), each filtration side wall being arranged opposite and at a distance from a wall of the housing (8).

5. The device (1) for supplying liquid (2) according to any one of the preceding claims, comprising means (17) for heating the housing (8) forming the siphon.

6. The device (1) for supplying liquid (2) according to any one of the preceding claims, in which the supply pump (6) is housed in a casing (5), the filtration assembly (7) being arranged outside the casing (5) and mounted on said casing (5).

7. The device (1) for supplying liquid (2) according to claim 6, further comprising means for removably attaching the filtration assembly (7) to the casing (5).

8. The device (1) for supplying liquid (2) according to any one of the preceding claims, wherein the liquid (2) is an aqueous solution, preferably an ammonia precursor.

9. A liquid (2) tank (1) for a motor vehicle (4), characterized in that it is equipped with a device (1) for supplying liquid (2) according to any one of the preceding claims.

10. A selective catalytic reduction device (18) for purifying exhaust gases from an internal combustion engine of a motor vehicle, characterized in that it comprises a liquid (2) tank (3) according to claim 9, wherein the liquid (2) is an ammonia precursor.

11. Motor vehicle (4) characterized in that it comprises a liquid (2) tank (3) according to claim 9.