Liquid supply device for a motor vehicle

Abstract

A liquid supply device for a motor vehicle comprises a supply pump for pumping a liquid from a liquid tank to a consumption device of the liquid, and a filtration assembly (7) for filtering the liquid pumped by the supply pump. The filtration assembly (7) has a compartment (8) in which a filtration element (9) is accommodated. The compartment (8) forms a siphon connected to the suction port of the supply pump and has an open end adapted to open into the liquid contained in the liquid tank, whereby when the level of the liquid in the tank is below a predetermined threshold, the path followed by the liquid in the siphon passes through an "elevated" level above the level of the liquid in the tank. The filtration element (9) comprises a filtration zone in the form of a pocket of filtration material extending vertically in the compartment (8).

Description

Technical Field

[0001] The present invention relates to a liquid supply device for a motor vehicle. The present invention also relates to a liquid tank for a motor vehicle comprising the liquid supply device according to the present invention. The present invention also relates to a selective catalytic reduction device for a motor vehicle comprising the liquid tank according to the present invention. Finally, the present invention relates to a motor vehicle comprising the liquid tank according to the present invention.

Background Art

[0002] For the purpose of performing selective catalytic reduction (also called "SCR" for short, the initials of "Selective Catalytic Reduction" in English), a liquid supply device for vehicles used for injecting an additive solution, particularly an ammonia precursor, into the exhaust line of an internal combustion engine is already known. This selective catalytic reduction can reduce nitrogen oxides (NO x ) emitted from ordinary vehicles and large vehicles equipped with internal combustion engines, thereby reducing the pollution caused by these vehicles and leading to compliance with laws and regulations regarding nitrogen oxide emissions. In selective catalytic reduction, it is required to use a reducing agent such as ammonia at an accurate concentration level and high quality. Generally, ammonia precursors such as urea are used as additives, and the ammonia precursor that needs to be accurately formulated and injected into the exhaust gas stream is hydrolyzed there to convert nitrogen oxides (NO x ) into nitrogen (N2) and water (H2O). For this purpose, it is necessary to equip the vehicle with a tank for containing the additive solution and a device for distributing the required amount of the additive and injecting it into the exhaust line.

[0003] To prevent clogging of the additive solution injector due to impurities that may be contained in the additive solution, it is known to filter the additive solution before its injection. In the prior art, a filter element is disposed in the additive tank at the inlet of the supply pump for the additive solution, so that the additive solution can be pumped through the filter element. By taking such measures, the additive solution has impurities removed upstream of the catalyst for the selective catalytic reduction reaction before being injected into the exhaust line. It also serves to protect the supply pump from impurities contained in the sucked additive solution.

[0004] The filter element tends to become clogged with impurities after being used for a while. If there are many impurities and they are large in size, the clogging progresses rapidly. This tendency is particularly prominent in areas with severe contamination. As the degree of clogging increases, the filtering performance of the filter element deteriorates, and the filtering flow rate of the solution passing through the filter element becomes lower than the suction flow rate of the supply pump. As a result, the pump will suck in all or part of the air, thereby causing a situation where the injection pressure of the liquid by the supply pump decreases. Then, it becomes difficult to accurately blend the injected additive, etc., leading to a decrease in the efficiency of selective catalytic reduction. The air suction becomes even more prominent if the liquid level in the tank is low enough for part of the filter element to be exposed to the air.

Summary of the Invention

Problems to be Solved by the Invention

[0005] It is a particular object of the present invention to reduce the risk of a time-dependent loss of liquid injection pressure in a liquid supply device for a motor vehicle.

Means for Solving the Problems

[0006] Therefore, the present invention is a liquid supply device for a motor vehicle, - a supply pump intended to pump a liquid from a liquid tank to a consuming device of the liquid, - A filtration assembly for the purpose of filtering a liquid pumped by a supply pump, the filtration assembly having a compartment in which a filtration element is housed, comprising the compartment forms a siphon connected to the suction port of the supply pump and has an open end adapted to open into the liquid contained in the liquid tank, whereby when the level of the liquid in the liquid tank is below a predetermined threshold, the path followed by the liquid in the siphon passes through a "raised" level above the level of the liquid in the liquid tank, in a liquid supply device, characterized in that the filtration element comprises a filtration zone in the form of a pocket of filtration material extending vertically in the compartment forming the siphon, for a liquid supply device.

[0007] Therefore, at the start of the supply pump, the supply pump initially sucks in the air in the compartment forming the siphon. The suction of this air creates a negative pressure, whereby the liquid level in the siphon is raised and the filtration element is immersed in the liquid. As a result, when the start-up phase of the supply pump is completed, the filtration element is no longer in contact with the air, or at least, even when the liquid level in the tank is lower than the predetermined threshold, the filtration element remains sufficiently immersed to the extent that the supply pump does not suck in air during the operation of the supply pump. Furthermore, since the filtration element remains sufficiently immersed even when the liquid level in the tank is low, the clogging effect of the filtration element that hinders the passage of the liquid is effectively suppressed.

[0008] Thus, by the supply pump not sucking in air during its operation, the instability and loss of pressure for liquid injection obtained by the supply pump are avoided. This is particularly advantageous when an accurate formulation of the liquid injected by the pump is required, for example, when the liquid is an ammonia precursor for use as an additive in a selective catalytic reduction reaction by being injected into the exhaust line of an internal combustion engine. The liquid supply device can be used for other liquids, such as water or fuel.

[0009] Since the filtering element is prevented from coming into contact with air, or at least the filtering element remains in a sufficient immersion state, it is understood that the liquid supply device according to the present invention enables the use of a large filtering element without risking a reduction in the injection pressure of the liquid by the supply pump.

[0010] Also, since the air in the compartment is discharged when the supply pump is started, the degree of clogging of the filtering element hardly affects the filtration flow rate of the liquid. This is because the filtering element is not in contact with air and the object of filtration is only the liquid. Thus, the liquid supply device according to the present invention functions even when the filtering element is considerably clogged. Therefore, the lifespan of the filtering element is extended even in a contaminated area where clogging tends to progress rapidly.

[0011] The compartment forming the siphon is provided with a wall having airtightness and liquid tightness with respect to the liquid in the tank for its function. Therefore, the filtering element is also protected against impurities that may sometimes be present in the liquid stored in the tank, thereby extending the lifespan of the filtering element. In particular, oily residues that may be present in the liquid remaining on the surface of the tank are blocked by the compartment forming the siphon and are prevented from reaching the filtering element.

[0012] "Impurities" refers to any foreign matter unrelated to the liquid, such as dust, sand, insects, tank cuttings, oils and fats, or solid particles. Such foreign matters may be floating, suspended, or deposited at the bottom of the liquid tank.

[0013] By passing through the "raised" level of the liquid, the filtering element can be immersed quite deeply in the liquid within the range of the minimum filling level regardless of the filling level of the tank.

[0014] The predetermined threshold value corresponds to, for example, the liquid level in the tank at which at least a part of the section forming the siphon no longer gets immersed. Preferably, the predetermined threshold value corresponds to the liquid level within the section forming the siphon, at which the filtering element no longer comes into contact with air. Thus, even if the liquid level in the tank is lower than the "raised" level inside the section, it is understood that the filtering element is sufficiently immersed in the liquid.

[0015] A "pocket" is understood to comprise at least one wall defining a cavity, one end of which is open and the other end of which is closed to form the bottom of the pocket. According to the present invention, the wall of the pocket is made of a filtering material, and it is understood that the liquid passes through the wall towards the inside of the pocket and is filtered.

[0016] Since the pocket-shaped filtering zone extends vertically within the section, when the pocket is completely immersed in the liquid, for example, when the pump is started and air is discharged from the section, the available filtering surface is optimized. This is because all surfaces of the pocket can be used to filter the liquid that has not yet been filtered, over the entire height and the entire width of each surface. Therefore, a particularly compact filtering assembly can be provided, and thus a compact liquid supply device can be provided.

[0017] The present invention can incorporate and include any one or more of the following optional features, either alone or in combination.

[0018] When V is the volume of the filtering element and h is the height of the filtering element, the V / h ratio is between 400 mm 2 and 800 mm 2 Preferably, the V / h ratio is about 600 mm 2This ratio can represent the filtration area of the filtration element. Such a filtration element has excellent filtration characteristics. The presence of the section forming the siphon enables the advantageous use of such a filtration element. In fact, although filtration elements of such dimensions have good filtration characteristics, in the liquid supply devices of the prior art, due to their large volume which can easily be filled with air, there is a significant risk that the liquid injection pressure is lost. In the liquid supply device according to the present invention, since air can be discharged outside the section forming the siphon at startup, such a filtration element can be used without encountering such problems.

[0019] This liquid supply device further comprises a supply pipe that extends vertically between an upper portion and a lower portion of the pocket within the pocket, wherein a first upper end of the supply pipe is connected to the suction port of the supply pump and a second lower end of the supply pipe opens into the interior of the pocket. This is a simple means to smooth the suction of the pump, especially by causing the suction of the liquid to be carried out near the liquid level in the section forming the siphon.

[0020] Preferably, the distance Δ between the second lower end of the supply pipe and the bottom of the pocket is between 10% and 90% of the height p of the pocket, and preferably the distance Δ is about 25% of the height p of the pocket. This arrangement of the second lower end of the supply pipe enables the optimization of the suction of the liquid by the supply pump through the supply pipe, whether at the start-up of the pump or at subsequent suction times.

[0021] The pocket has at least two lateral filtration surfaces, and each lateral filtration surface is arranged facing each other and at a distance from the wall of the section. Thereby, the area available for filtration is optimized. In fact, in this layout, it can be seen that the lateral filtration surfaces are not in contact with the wall of the section and can therefore come into direct contact with the liquid that has not yet been filtered. Therefore, the liquid can enter the pocket not only from the bottom of the pocket but also from the lateral filtration surfaces. Thereby, the filtration zone of the filtration element is widened. The number of lateral sides can vary, for example, from 2 to 6 according to the embodiment.

[0022] The liquid supply device includes heating means for a section that forms a siphon. Therefore, if the liquid freezes in the section that forms the siphon, it can be thawed to make the liquid supply device available. It should be noted that the heating means heats only the volume of the liquid contained in the section that forms the siphon. Since that volume can be kept small, thawing the liquid contained therein becomes easy.

[0023] The supply pump is housed in the housing, and the filtration assembly is disposed outside the housing and supported by the housing. The housing enables various functional units of the liquid supply device to be simply and efficiently assembled and connected. Thereby, the manufacture of the liquid supply device becomes easy, and a compact liquid supply device can be obtained.

[0024] Preferably, the liquid supply device further comprises means for removably fixing the filtration assembly to the housing. Thereby, the maintenance of the liquid supply device becomes easier. In fact, it becomes easier to separate the filtration assembly from the housing for purposes such as checking the state of the filtration element, particularly its degree of clogging. Furthermore, it also becomes easier to replace the filtration element at a desired timing. In particular, the filtration element can be replaced without having to perform any operation on other parts of the liquid supply device, particularly the supply pump. Thereby, the risk of wearing out other parts of the supply device is reduced and its lifespan is prolonged. The means for removable fixing can be any means known to those skilled in the art and can consist of means that can simply and quickly couple or separate the filtration assembly and the housing. Preferably, such means for removable fixing do not require the use of tools to couple or separate the filtration assembly and the housing. For example, the means for removable fixing can be a clip or screw fixing means that can directly clip or screw the filtration assembly to the housing. Screw fixing here means that the filtration assembly is provided with screws complementary to the screws made on the housing so that the filtration assembly can be directly screwed into the housing. Preferably, the screws of the filtration assembly and the screws of the housing form a 1 / 4 turn screw type fixing means that allows the filtration assembly and the housing to be coupled and separated by applying a 1 / 4 turn, i.e., a 90° rotation, to the filtration assembly. Therefore, the fixing and removal of the filtration assembly are very easy even in cases where there is little space for manual work.

[0025] The liquid is an aqueous solution and is preferably an ammonia precursor. When the liquid is an ammonia precursor, the liquid supply device can advantageously be used within the framework of a selective catalytic reduction reaction for purifying the exhaust gas of an internal combustion engine. In another embodiment, the aqueous solution is water.

[0026] The present invention also targets a liquid tank for a motor vehicle equipped with the liquid supply device described above. Therefore, depending on the embodiment, the tank can be a tank for an aqueous solution such as water or an aqueous urea solution, a fuel tank, or the like. The tank can be made of any material. In particular, when it is a tank for a urea solution, the material of the tank is preferably a material having excellent chemical resistance to urea. Generally, it is a plastic material. Preferred materials include polyolefins, particularly polyethylene, and more specifically high-density polyethylene (HDPE). This tank can be manufactured by any known processing method. One of the known embodiments is an injection molding method. One of the preferred embodiments is an extrusion blow molding method. In this method, a parison (consisting of one or more parts) is produced by extrusion and blow molded in a mold. By integrally molding the tank from a continuous parison, good results can be obtained.

[0027] The present invention also targets a selective catalytic reduction device for purifying the exhaust gas of an internal combustion engine of a motor vehicle. In the selective catalytic reduction device provided with the liquid tank as described above, the selective catalytic reduction device in which the liquid is an ammonia precursor is also within the scope of the present invention. The ammonia precursor is, for example, urea. In that case, the catalytic reduction device is improved because it is equipped with the liquid supply device according to the present invention, which can reduce the risk of the injection pressure of the ammonia precursor being lost over time. This is particularly advantageous because, as already explained, in selective catalytic reduction, it is important to accurately dose the injected ammonia precursor, and the loss of the injection pressure of the ammonia precursor will impair the accuracy of the dosing.

[0028] Finally, the present invention also targets a motor vehicle equipped with the liquid tank described above.

[0029] A better understanding of the present invention will be obtained by reading the following non-limiting description only as an example with reference to the accompanying drawings.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0031] One embodiment of the liquid 2 supply device 1 according to the present invention is shown in FIGS. 1 to 7. Here, the liquid 2 supply device 1 is attached to the lower wall of the liquid tank 3 attached to the motor vehicle 4 (FIG. 1).

[0032] In this case, the liquid is an ammonia precursor such as urea. Thus, the liquid tank 3 and the liquid supply device 1 form part of a selective catalytic reduction device 18 for purifying the exhaust gas of an internal combustion engine (not shown) of the motor vehicle 4.

[0033] The material for manufacturing the liquid tank 3 is preferably a material having excellent chemical resistance to urea. Generally, it is a plastic material. Examples of preferred materials include polyolefins, particularly polyethylene, and more specifically high-density polyethylene (HDPE). This tank can be manufactured by any known processing method. One of the known embodiments is the injection molding method. One of the preferred embodiments is the extrusion blow molding method. In this method, a parison (which may consist of one or more parts) is produced by extrusion and then blow molded in a mold. Good results can be obtained by integrally molding the tank from a continuous parison.

[0034] The liquid 2 supply device 1 particularly includes a housing 5, a supply pump 6, and a filtration assembly 7 (Figs. 2, 3, 4, and 7).

[0035] The housing 5 forms a support for the various functional units of the liquid 2 supply device 1. In this case, the supply pump 6 is housed in the housing 5, and the filtration assembly 7 is arranged outside the housing 5 and supported by the housing 5 (Fig. 2). More specifically, the liquid 2 supply device 1 further includes means (not shown) for removably fixing the filtration assembly to the housing 5. Preferably, such means for removable fixing do not require the use of tools to couple or separate the filtration assembly 7 and the housing 5. For example, the means for removable fixing may be a clip or screw fixing means that can directly clip or screw the filtration assembly 7 to the housing 5.

[0036] The other functional units of the liquid 2 supply device 1 are conventional and not shown for clarity. The housing 5 can be made of any material having excellent chemical resistance to urea. For example, the housing 5 is made of a thermoplastic material.

[0037] The supply pump 6 is intended to pump liquid from the liquid tank 3 to a liquid consuming device (not shown). In this case, the liquid is an ammonia precursor, and the liquid consuming device is a catalyst for selective catalytic reduction reaction. It is understood that depending on what kind of use is required of the liquid consuming device with respect to the liquid supply device 1, and in particular depending on the nature of the liquid 2 contained in the liquid tank 3, it will be different. The supply pump 6 to be used is obvious, and no further detailed description will be given here. It is understood that the supply pump may particularly correspond to the supply pump 6 that has been conventionally used for injecting an ammonia precursor in the selective catalytic reduction reaction in the motor vehicle 4.

[0038] The filtration assembly 7 is intended to filter the liquid 2 pumped by the supply pump 6 so that the liquid 2 injected into the selective catalytic reduction reaction contains almost no impurities. The filtration assembly 7 particularly includes a compartment 8 in which a filtration element 9 is accommodated (Figure 4).

[0039] The compartment 8 is generally in the shape of a parallelepiped and has a closed first end in the longitudinal direction and an open second end on the opposite side of the first end in the longitudinal direction. In this case, the compartment 8 is formed of two parts. The first part forms the main body 10 of the compartment 8, and the second part forms a closing cover 11 for closing the first end of the compartment 8 so as to have airtightness with respect to the air contained in the liquid tank 3 and liquid tightness with respect to the liquid 2. Alternatively, the compartment 8 can be manufactured such that the main body 10 and the cover 11 are integrally molded.

[0040] Compartment 8 forms a siphon that is connected at the level of its closed first longitudinal end via supply pipe 13 to the suction port 12 of supply pump 6. The open second longitudinal end of compartment 8 that forms the siphon opens into the liquid 2 contained within liquid tank 3, such that when the level of the liquid within liquid tank 3 is below a predetermined threshold, the path that liquid 2 follows within the siphon passes through a "raised" level that is above the level of the liquid 2 within liquid tank 3 (see Figure 7). The predetermined threshold can be located approximately at the level of the open first longitudinal end of compartment 8 that forms the siphon. Preferably, the predetermined threshold is the liquid level within compartment 8 that forms the siphon and corresponds to the liquid level at which filtering element 9 is submerged in liquid 2.

[0041] Filtering element 9 is made of a flexible filtering mesh fixed to a rigid framework. The filtering mesh is flexible and can be wound around from above or below the rigid framework, etc. Advantageously, the filtering mesh and the rigid framework are made of a thermoplastic material and are welded to each other. Alternatively, the flexible filtering mesh is manufactured integrally with the rigid framework (Figures 5 and 6).

[0042] Filtering element 9 comprises a filtering zone that extends vertically within compartment 8 that forms the siphon. In other words, when filtering element 9 is attached to housing 5 (Figures 2, 3 and 7), it is arranged perpendicular to compartment 8 which is itself arranged vertically. More specifically, the filtering zone of filtering element 9 comprises pockets 14 of filtering material formed by the filtering mesh.

[0043] Pocket 14 comprises at least one wall that defines a cavity, with one end of the wall being open and the other end being closed to form the bottom of the pocket. In this case, the supply pipe 13 can pass through the opening of pocket 14. According to this embodiment, pocket 14 has two lateral filtering surfaces 19, 20, and each of the lateral filtering surfaces 19, 20 is arranged facing each other and at a distance from the wall of compartment 8 (Figures 3 and 7).

[0044] In this case, when V is the volume of the filtering element 9 and h is the height of the filtering element 9, the V / h ratio is 400 mm 2 to 800 mm 2 and preferably, the V / h ratio is about 600 mm 2 In this embodiment, the filtering pocket 14 has a height p of about 68 mm which is slightly lower than the height h of the filtering element (Fig. 5).

[0045] The supply pipe 13 generally has an inverted "L" shape and extends vertically between the upper and lower portions of the pocket 14 within the pocket 14. The first upper end 15 of the supply pipe 13 is connected to the suction port 12 of the supply pump 6, whereby the interior of the section 8 forming the siphon can be put into fluid communication with the suction port 12 of the supply pump 6 (Figs. 3 and 7). The second lower end 16 of the supply pipe 13 opens into the pocket 14 (Figs. 5 and 6). The height at which the second lower end 16 of the supply pipe 13 opens into the pocket 14 varies depending on the embodiment. In this case, also advantageously, the gap Δ between the second lower end 16 of the supply pipe 13 and the bottom of the pocket 14 is about 15.5 mm, which corresponds to about 23% of the height p of the pocket 14 (Fig. 5). Advantageously, the gap Δ between the second lower end 16 of the supply pipe 13 and the bottom of the pocket 14 is between 10% and 90% of the height of the pocket, and preferably the gap Δ is about 25% of the height of the pocket.

[0046] The liquid supply device 1 further includes heating means 17 for the section 8 forming the siphon. In this case, the heating means 17 is formed by a heating mat that partially covers the section 8 forming the siphon. In another embodiment, any heating means that can be disposed in the liquid 2 tank 3 can be used to heat the section 8 forming the siphon. For clarity, the heating means 17 is shown only in Fig. 3.

[0047] An operating example of the liquid 2 supply device 1 according to the present invention will be described below with reference to Fig. 7.

[0048] As already described, the liquid 2 supply device 1 is used in this case for selective catalytic reduction reaction, here for the purpose of injecting the liquid 2, which is an ammonia precursor, into the exhaust gas flow of the motor vehicle 4, where the liquid 2 is hydrolyzed to nitrogen oxides (NO x ) which are converted to nitrogen (N2) and water (H2O).

[0049] Figure 7A shows the liquid 2 supply device 1 before its use, i.e., in the state before the start of operation of the supply pump 6. Here, the liquid 2 level in the liquid tank 3 is relatively low, so a corresponding part of the filtration assembly 7, especially a corresponding part of the section 8 forming the siphon, is not immersed in the liquid 2. There is air present in the section 8 forming the siphon.

[0050] When it is required to inject the liquid 2 into the exhaust gas flow, the supply pump 6 is started. In the first step of starting, the supply pump 6 sucks in the mixture of air and liquid 2 in the section 8 forming the siphon through its suction port 12 and further along the supply pipe 13. The suction of air creates a negative pressure, which causes the liquid 2 level inside the section 8 forming the siphon to rise (Figure 7B).

[0051] When the start-up period ends, all or most of the air in the section 8 forming the siphon is sucked in by the supply pump 6, and the section 8 forming the siphon is filled with the liquid 2 up to the point where the filter element 9 is completely or almost completely immersed (Fig. 7C). It can be seen that the level of the liquid 2 in the section 8 forming the siphon is here higher than the level of the liquid 2 in the liquid 2 tank 3. At that time, the filter element 9 is immersed in the liquid and not in contact with air. Therefore, at this stage, the supply pump 6 stops sucking in air or almost stops. Therefore, the risk of loss of the injection pressure of the liquid 2 is reduced or eliminated. Also, the immersed state of the filter element 9 at the stage when the start-up of the pump is completed can be obtained regardless of the degree of clogging of the filter element 9. Therefore, even if the filter element 9 is in a state of advanced clogging, it is possible to continue using the filter element 9 in the liquid 2 supply device 1 according to the present invention. This is because air has been previously discharged from the section 8 forming the siphon, and in any case, air is not sucked in by the supply pump 6 to cause a decrease in the liquid 2 injection pressure.

[0052] (Example) Hereinafter, the results of tests aimed at measuring the effectiveness of the liquid 2 supply device 1 according to the present invention in relation to the degree of clogging of the filter element 9 will be described. In the test, the filter element 9 was tested with the degree of clogging represented as 0% (control), 10%, 20%, 30%, 40%, 50% of the height h of the filter element 9. To control the degree of clogging, the clogging was reproduced by artificially covering the filter element 9 with epoxy resin starting from the lower end of the filter element 9 up to the height corresponding to the percentage of the desired degree of clogging. The effectiveness of the liquid 2 supply device 1 according to the present invention was tested by measuring the amount of the aqueous solution, here an aqueous urea solution, that could be injected using only the filter element 9 as in the prior art or using the filter element 9 housed in the section 8 forming the siphon of the filter assembly 7 according to the present invention. The test results are as shown in Table 1.

[0053] [Table 1]

[0054] To facilitate measurement, the amount of urea is measured in kilograms rather than in liters. Alternatively, the test could also be conducted by measuring the amount of urea in liters. In this test, for the case where the liquid supply device 1 includes only the filtration element (a case representing the prior art) and for the case where the filtration assembly 7 according to the present invention in which the filtration element 9 is housed in the compartment 8 forming the siphon, 5 kg of urea is to be injected.

[0055] Regarding the case where the degree of clogging is 0%, the test was conducted only on the prior art liquid supply device to obtain a reference value. As a result, in the prior art, in the case of a filtration element that has not clogged generally because it is still new, the amount of urea injected from the original 5 kg of urea was 4.821 kg.

[0056] When the filtration element 9 has a 10% clogging, it can be seen that the injected urea has decreased in the prior art liquid supply device. The amount of injected urea is 4.540 kg compared to 4.821 kg when the filtration element 9 is not clogged, and the urea has decreased by 0.281 kg. In the liquid supply device 1 according to the present invention, 4.824 kg of urea can be injected, and such a decrease is not seen. On the contrary, it can be seen that the urea injection amount even slightly increases (by 0.003 kg) compared to the control example. That is, when the degree of clogging is 10%, the filtration ability of the filtration assembly 7 according to the present invention is superior to that of the prior art, and it can maintain a filtration level almost equivalent to the filtration level obtained when the filtration element 9 is new.

[0057] Even when the filtration element 9 is 20% clogged, it can be seen that the amount of urea injected by the prior art liquid supply device has decreased. The amount of urea injected is 4.459 kg as compared with 4.821 kg when the filtration element 9 is not clogged, and the urea has decreased by 0.362 kg. Also here, it can be seen that 4.844 kg of urea is injected by the liquid 2 supply device 1 according to the present invention, and such a decrease is not seen. And it can also be seen that the urea injection amount has increased slightly (0.023 kg) compared with the comparative example. That is, when the clogging degree is 20%, the filtration ability of the filtration assembly 7 according to the present invention is superior to that of the prior art, and it is possible to maintain a filtration level almost equivalent to the filtration level obtained when the filtration element 9 is new.

[0058] Even when the filtration element 9 is 30% clogged, it can be seen that the amount of urea injected by the prior art liquid supply device has decreased. The amount of urea injected is 3.685 kg as compared with 4.821 kg when the filtration element 9 is not clogged, and the urea has decreased by 1.136 kg. Also here, it can be seen that 4.821 kg, that is, the same amount of urea as the new filtration element 9, is injected by the liquid 2 supply device 1 according to the present invention, and such a decrease is not seen. That is, when the clogging degree is 30%, the filtration ability of the filtration assembly 7 according to the present invention is superior to that of the prior art, and it is possible to maintain a filtration level almost equivalent to the filtration level obtained when the filtration element 9 is new.

[0059] Even when the filtration element 9 is 40% clogged, it can be seen that the amount of urea injected is reduced in the prior art liquid supply device. The amount of urea injected is 3.343 kg as compared with 4.821 kg when the filtration element 9 is not clogged, and the urea has decreased by 1.478 kg. In the liquid 2 supply device 1 according to the present invention, 4.810 kg of urea is injected, and it can be seen that the decrease in urea is only 0.011 kg, which is not so large. That is, when the clogging degree is 40%, the filtration ability of the filtration assembly 7 according to the present invention is superior to that of the prior art, and a filtration level substantially equivalent to the filtration level obtained when the filtration element 9 is new can be maintained.

[0060] Even when the filtration element 9 is 50% clogged, it can be seen that the amount of urea injected is reduced in the prior art liquid supply device. The amount of urea injected is 3.247 kg as compared with 4.821 kg when the filtration element 9 is not clogged, and the urea has decreased by 1.574 kg. Also here, in the liquid 2 supply device 1 according to the present invention, 4.841 kg of urea is injected, and it can be seen that it is 0.020 kg more than in the control example and such a decrease is not seen. That is, when the clogging degree is 50%, the filtration ability of the filtration assembly 7 according to the present invention is superior to that of the prior art, and a filtration level substantially equivalent to the filtration level obtained when the filtration element 9 is new can be maintained.

[0061] This test makes it possible to draw conclusions about the effectiveness over time of the filtration by the filtration element 9, i.e., its effectiveness during the process of clogging progression. The decrease in the effectiveness of filtration in the filtration elements of the prior art actually corresponds to an increase in the risk of injection pressure loss during the continued use of the liquid 2 supply device 1. As already pointed out, this loss of injection pressure is disadvantageous especially when the injection volume of the liquid 2 must be accurately metered. This is because it becomes impossible to obtain an acceptable level of accuracy regarding the amount of the injected liquid 2. In such circumstances, this test shows that the liquid 2 supply device 1 according to the present invention can maintain the filtration capacity of the filtration element 9 over time even in the case of severe clogging, thereby reducing the risk that the injection pressure of the liquid 2 decreases over time.

[0062] The present invention is not limited to the described embodiments, and other embodiments will be apparent to those skilled in the art.

Explanation of Reference Numerals

[0063] 1 Liquid supply device 2 Liquid 3 Tank 4 Automobile vehicle 5 Housing 6 Supply pump 7 Filtration assembly 8 Compartment 9 Filtration element 10 Compartment body 11 Compartment cover 12 Suction port of supply pump 13 Supply pipe 14 Pocket of filtration element 15 First upper end of supply pipe 16 Second lower end of supply pipe 17 Heating means of compartment forming siphon 18 Selective catalytic reduction device 19, 20 Lateral filtration surfaces h Height of filtration element p Height of filtration pocket The gap between the second lower end of the Δ supply pipe and the bottom of the pocket

Claims

1. A liquid (2) supply device (1) for a motor vehicle (4), comprising: - A supply pump (6) for pumping liquid (2) from a liquid (2) tank (3) to a consumption device of the liquid (2); - A filtration assembly (7) for filtering the liquid (2) pumped by the supply pump (6), the filtration assembly (7) having a compartment (8) containing a filtration element (9); characterized in that the compartment (8) forms a siphon connected to the suction port (12) of the supply pump (6) and has an open end opening into the liquid (2) contained in the liquid (2) tank (3), such that when the level of the liquid (2) in the liquid (2) tank (3) is below a predetermined threshold, the path followed by the liquid (2) in the siphon passes through an "elevated" level above the level of the liquid (2) in the liquid (2) tank (3). In the liquid (2) supply device (1), the filtration element (9) comprises a filtration zone in the form of a pocket (14) of filter material extending vertically in the compartment (8) forming the siphon.

2. When V is the volume of the filtration element (9) and h is the height of the filtration element (9), the V / h ratio is between 400 mm ２ and 800 mm ２ and preferably the V / h ratio is about 600 mm ２ The liquid (2) supply device (1) according to claim 1, wherein the liquid (2) supply device (1) is as described above.

3. The liquid (2) supply device (1) according to claim 1 or 2, further comprising a supply pipe (13) extending vertically between an upper portion and a lower portion of the pocket (14) within the pocket (14), wherein a first upper end (15) of the supply pipe (13) is connected to the suction port (10) of the supply pump (6) and a second lower end (16) opens into the interior of the pocket (14).

4. The liquid (2) supply device (1) according to claim 3, wherein the gap (Δ) between the second lower end (16) of the supply pipe (13) and the bottom of the pocket (14) is between 10% and 90% of the height (p) of the pocket (14), preferably the gap (Δ) is approximately 25% of the height (p) of the pocket (14).

5. The liquid (2) supply device (1) according to any one of claims 1 to 4, wherein the pocket (14) has at least two lateral filtration surfaces (19, 20), each lateral filtration surface being arranged facing each other and at a distance from the wall of the compartment (8).

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

7. The liquid (2) supply device (1) according to any one of claims 1 to 6, wherein the supply pump (6) is housed in the housing (5), and the filtration assembly (7) is arranged outside the housing (5) and supported by the housing (5).

8. The liquid (2) supply device (1) according to claim 7, further comprising means for removably fixing the filtration assembly (7) to the housing (5).

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

10. A liquid (2) tank (3) for a motor vehicle (4), characterized in that it is equipped with the liquid (2) supply device (1) according to any one of claims 1 to 9.

11. A selective catalytic reduction device (18) for purifying the exhaust gas of an internal combustion engine of a motor vehicle, comprising the liquid (2) tank (3) according to claim 10, wherein the liquid (2) is an ammonia precursor.

12. A motor vehicle (4), characterized in that it comprises the liquid (2) tank (3) according to claim 10.

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