Tank device, exhaust aftertreatment system

Abstract

Tank device (1) for an exhaust gas aftertreatment system (2), in particular of a motor vehicle, with a tank (4) for storing liquid exhaust gas aftertreatment agent (3) and with a removal device (5) for removing the liquid exhaust gas aftertreatment agent (3) from the tank (4), wherein the removal device (5) has a suction nozzle (8) which ends in a filter box (9) arranged in the tank (4), wherein a wall (13) lying at the top of the filter box (9) in the tank (4) is formed at least in regions by an upper filter element (15) and a wall (14) lying at the bottom of the filter box (9) in the tank (4) is formed at least in regions by a lower filter element (16), characterized in that the upper filter element (15) consists of a hydrophobic material and the lower filter element (16) consists of a hydrophilic material.

Description

The invention relates to a tank device for an exhaust gas aftertreatment system, in particular of a motor vehicle, having a tank for storing liquid exhaust gas aftertreatment agent and having a removal device for removing the liquid exhaust gas aftertreatment agent from the tank, wherein the removal device has at least one suction connection which ends in a filter box arranged in the tank, wherein a wall lying at the top of the filter box in the tank is formed at least in regions by an upper filter element and a wall lying at the bottom of the filter box in the tank is formed at least in regions by a lower filter element.The invention further relates to an exhaust gas aftertreatment system having a corresponding tank device and to a motor vehicle.Prior ArtTank devices and exhaust gas aftertreatment systems of the type mentioned at the beginning are known from the prior art. In order to reduce the pollutant emission of motor vehicles, it is known to posttreat the exhaust gas of an internal combustion engine of the motor vehicle. To reduce NOx emissions, the so-called SCR method (SCR=selective catalytic reduction) is frequently used in this case, in which a liquid exhaust gas aftertreatment agent, for example an aqueous urea solution, is mixed with the exhaust gas, which reacts together with the exhaust gas in a downstream catalyst and in the process reduces NOx to nitrogen and water. This method requires that a tank device be carried in the motor vehicle, in which the liquid exhaust gas aftertreatment agent can be stored and made available. The tank device has a tank in which the liquid exhaust gas aftertreatment agent is stored, and a removal device by means of which the exhaust gas aftertreatment agent can be removed and fed, for example, to a metering module or injection valve assigned to the exhaust system. For removal, a suction connection arranged in the tank is provided. In order to prevent contaminants from entering the injection system, the suction connection ends in a filter box which is arranged in the tank, so that only previously filtered exhaust gas after-treatment agent can enter the suction connection.Due to the required small pore size of the filter elements, the filter box does not fill itself when the exhaust gas aftertreatment agent is first filled into the tank. At present, the air in the filter box must be actively removed from the filter box by a removal device or by means of an external pump or syringe, so that the filter box is filled with the exhaust gas after-treatment agent. This is awkward, long and undesirable by the customer in the vehicle manufacturing process.DE 10 2009 029 400 A1 discloses a vehicle tank for storing liquids, having a filter device which has a porous filter material. From JP 2005-299 441 A it is known to equip a urea water tank with a concentration measuring element. The publication WO 2004 / 082 804 A1 describes a fuel filter, which is preceded by a coalescer element.Disclosure of the InventionThe tank device according to the invention having the features of claim 1 has the advantage that the filter box automatically fills when the tank is filled for the first time with the liquid exhaust gas aftertreatment agent and the air located therein automatically leaves the filter box. For this purpose, it is provided according to the invention that the upper filter element consists of a hydrophobic material and the lower filter material consists of a hydrophilic material. In the hydrophobic filter element, the filter pores are not immediately filled with liquid. Despite wetting of the surface, the smallest pores remain initially filled with air. Only after a certain time do these pores also fill with liquid. In the hydrophilic filter element, the pores are immediately filled with liquid. The pores filled with liquid block the path of the air. This means that the hydrophobic material offers a small pressure loss for air and the hydrophilic material a small pressure loss for the liquid exhaust gas after-treatment agent. The arrangement of the hydrophobic material at the top and of the hydrophilic material at the bottom ensures that the respective pressure losses are kept low both at the top and at the bottom, and that the liquid exhaust gas aftertreatment agent thereby penetrates into the filter box from the bottom and at the same time the air escapes from the filter box at the top. As a result, already when the tank is initially filled, the filter box is vented or filled with the exhaust gas aftertreatment agent without additional measures.Preferably, the filter elements are supported by a filter frame. The filter frame is box-like and sealingly adjoins the filter elements and the suction connector, respectively, so that it is ensured that only filtered exhaust gas after-treatment agent can pass into the filter box and thus to the suction connector. The side walls of the filter frame are preferably designed closed, so that a preferred flow direction or filling direction of the filter box is ensured.According to an advantageous development of the invention, it is provided that at least the upper filter element is designed to be elastically deformable. As mentioned, the pores of the hydrophobic material fill with liquid over time. This liquid then forms a barrier layer for air. This results in that even when parts of the upper filter element are in contact with air, not the air but liquid is drawn in. In the event that the outer surface of the upper filter element is in contact with air in whole or in large parts, the elastic deformability of the filter element ensures that air is nevertheless not drawn into the filter box, but that the filter element deforms inward into the filter box and thus suction of air into the suction connection is prevented even when the tank is almost empty. The filter box thus offers a kind of reservoir effect.According to an advantageous development of the invention, it is provided that at least one side wall of the filter element is formed at least in regions by a further filter element. As a result, the filling process of the filter box can be accelerated if necessary.The filter box preferably has at least one support foot, so that the lower filter element is always arranged at a distance from the base of the tank. This prevents the filter box with the lower filter element from resting on the tank bottom, for example, during a first filling, as a result of which exhaust gas aftertreatment means could only pass into the filter box with difficulty or not at all through the lower filter element. The support foot thus serves as a spacer, which always ensures filling of the filter box from below.It is particularly preferably provided that the suction connection is connected to a conveying device of the extraction device, wherein the conveying device is arranged outside the filter box in the tank. Particularly preferably, the conveying device and the filter box together can form a removal module arranged in the tank. The delivery module is expediently connected or connectable on the pressure side to a metering module or injection valve by a corresponding line which leads outwards through a wall of the tank.The exhaust gas aftertreatment system according to the invention is distinguished by a tank device as has been described above. The advantageous embodiment of the exhaust gas aftertreatment system has the result that, when the tank is initially filled, the filter box is automatically filled with liquid exhaust gas aftertreatment agent and vented.The invention further relates to a motor vehicle which is distinguished by an exhaust gas aftertreatment system which is designed as described above.The invention will be explained in more detail below with reference to the drawings. The only one is shown for this purpose.FIG. shows an advantageous tank device in a schematic illustration.The FIGURE shows a schematic illustration of a tank device 1 for an exhaust gas aftertreatment system 2 of a motor vehicle, which is not illustrated in any more detail here. By means of the exhaust gas aftertreatment system 2, a liquid exhaust gas aftertreatment agent 3, which is stored in a tank 4 of the tank device 1, is intended to be injected or sprayed into the exhaust gas stream of an internal combustion engine of the motor vehicle, with the result that said exhaust gas reacts with the exhaust gas in order to reduce pollutant emissions.For this purpose, the tank device 1 has a removal device 5 which comprises a conveying device 6 which is connected or can be connected on the pressure side to a metering module 7 which is designed, for example, as a pressure-controlled injection valve. On the suction side, the conveying device 6 is connected to a suction connection 8 which is located in the tank 4 and draws in the exhaust gas aftertreatment agent 3 located therein.The suction connection 8 terminates in a filter box 9. the filter box 9 has a filter frame 10 which surrounds an end 11 of the suction connection. For this purpose, the filter frame 10 has two oppositely arranged end faces 12 which are at least substantially closed, wherein the end 11 of the suction connection 8 projects through one of the end faces 12 into the filter box. The end walls 12 are connected to one another via likewise closed side walls, which are not shown here. The filter box 9 further has an upper wall 13 and a lower wall 14. The filter box 9 is disposed in the tank 4 such that the top wall 13 is located at the top of the tank 4 and the bottom wall 14 is located at the bottom. The upper wall 13 is formed substantially by an upper filter element 15 which consists of a hydrophobic material. The bottom wall 14, on the other hand, is substantially formed by a bottom filter element 16 made of a hydrophilic material. In the present embodiment, the upper filter element 15 and the lower filter element 16 each extend over the entire length of the filter box 9 between the end walls 12, and the filter elements 15 and 16 are thereby held by the filter frame 10. Of course, it is also conceivable to provide a plurality of upper and / or a plurality of lower filter elements 15 and 16 in each case next to one another, which are held in each case by the filter frame 10 at the top and bottom on the filter box 9.The hydrophobic design of the filter element 15 and the hydrophilic design of the filter element 16 ensure that, when the tank 4 is initially filled with the liquid exhaust gas aftertreatment agent 3, the buoyancy force of the air initially present in the filter box 9 is greater than the pressure loss of the filter elements 15 and 16 to be overcome. Despite wetting of the surface, the smallest pores remain initially filled with air. After a certain time, however, these pores also fill with liquid. The pressure loss through the upper filter element 15 is thus small.In the lower filter element 16, the pores of the hydrophilic material immediately fill with liquid. The pores filled with liquid then block the path to the outside of the air. Thus, for the hydrophilic filter element 16, the pressure loss is small for liquid but large for air. By arranging the hydrophobic filter element 15 at the top and the hydrophilic filter element 16 at the bottom, both pressure losses are small. When the exhaust gas aftertreatment agent 3 is initially introduced into the tank 4, the filter box 9 itself is filled with exhaust gas aftertreatment agent 3, since the pressure losses for penetration into the filter box for the exhaust gas aftertreatment agent 3 and for escape from the filter box for the air are each small. Overall, this means that the buoyancy force is greater than the sum of the pressure losses at the lower filter element 16 and the upper filter element 15, with the result that the air can permeate through the upper filter element 15 by overcoming an initial pressure and subsequent flow pressure losses and, at the same time, the liquid exhaust gas aftertreatment agent 3 flows through the lower filter element 16 with the same volume of the outflowing gas or of the outflowing air into the interior by overcoming the initial pressure loss of the lower filter element 16 and subsequent flow pressure losses. The decisive force for the self-filling and venting of the filter box 9 is thus the buoyancy force of the air.Since the pores of the hydrophobic material of the upper filter element 15 also fill with liquid over time, they form a barrier layer for the air located in the filter box after some time. This air-blocking effect results in the filter box 9 having the property that even if parts of the filter surface of the upper filter element 15 are in contact with air, not the air but always only liquid is sucked in, which leads to a so-called reservoir effect. If the upper filter element 15 is also designed to be elastically deformable, it is achieved at a low fill level of the tank 4 that the total volume of the filter box 9 is initially reduced before air is drawn in. This increases the readiness of the tank device 4, even in the case of a low fill level, to reliably prevent air from being drawn in and entering the interior of the filter box 9.The advantageous tank device 1 thus allows the filter box 9 to be automatically filled with exhaust gas after-treatment agent during a first filling, and prevents air from re-entering the interior of the filter box 9 after the first filling. The tank device 1 thus combines the advantage of self-filling with the advantage of the reservoir effect.In order to ensure reliably that the lower filter element 16 is always in contact with exhaust gas aftertreatment means 3, in particular when the tank 4 is first filled, the end walls 12 are designed to be so large that they form a support foot 17 at least downwards, in the present exemplary embodiment also upwards, which serves as a spacer of the lower filter element 16 to the base 18 of the tank 4. The support feet 17 thus ensure that, when the exhaust gas aftertreatment agent 3 is introduced into the tank 4, the latter always comes into contact with the lower filter element 16 and can thus enter the filter box 9.

Claims

Tank device (1) for an exhaust gas aftertreatment system (2), in particular of a motor vehicle, having a tank (4) for storing liquid exhaust gas aftertreatment agent (3) and having a removal device (5) for removing the liquid exhaust gas aftertreatment agent (3) from the tank (4), wherein the removal device (5) has a suction connection (8) which ends in a filter box (9) arranged in the tank (4), wherein a wall (13) lying at the top of the filter box (9) in the tank (4) is formed at least in regions by an upper filter element (15) and a wall (14) lying at the bottom of the filter box (9) in the tank (4) is formed at least in regions by a lower filter element (16), characterized in that the upper filter element (15) consists of a hydrophobic material and the lower filter element (16) consists of a hydrophilic material.Tank device according to claim 1, characterised in that the filter elements (15, 16) are held by a filter frame (10).Tank device according to one of the preceding claims, characterized in that at least the upper filter element (15) is designed to be elastically deformable.Tank device according to one of the preceding claims, characterized in that at least one side wall of the filter box (9) is formed at least in regions by a further filter element.Tank device according to one of the preceding claims, characterized in that the filter box (9) has at least one support foot (17), so that the lower filter element (16) is always arranged at a distance from a base (18) of the tank (4).Tank device according to one of the preceding claims, characterized in that the suction connection piece (8) is connected to a conveying device (6) of the extraction device (5), wherein the conveying device (6) is arranged in particular outside the filter box (9) in the tank (4).Exhaust gas aftertreatment system (2), in particular for a motor vehicle, having a tank device (1) for storing and providing a liquid exhaust gas aftertreatment agent (3), characterized bythe configuration of the tank device according to one or more of the preceding claims.Motor vehicle having an exhaust gas aftertreatment system according to Claim 7.

Images