Functional unit for a reducing agent storage tank and reducing agent storage tank

Abstract

Functional unit (1) for a reducing agent storage tank, wherein the reducing agent is preferably an aqueous urea solution for the aftertreatment of exhaust gases from an internal combustion engine, comprising a housing (2) for receiving at least one electrical or electronic component and a support (3) by means of which the housing (2) can be connected to the reducing agent storage tank, in particular welded, characterized in that the housing (2) and the support (3) have interlocking collar sections (4, 5) between which a sealing element (6) is arranged to form a radial seal, wherein a support element (7) is integrated into the radially outer collar section (5).

Description

[0001] The invention relates to a functional unit for a reducing agent storage tank with the features of the preamble of claim 1. Furthermore, the invention relates to a storage tank for a reducing agent, in particular an aqueous urea solution for the aftertreatment of exhaust gases from an internal combustion engine, with such a functional unit. State of the art

[0002] To reduce nitrogen oxide (NOx) emissions, the exhaust gases from modern combustion engines, especially diesel engines, undergo aftertreatment in a reduction catalyst. Before the exhaust gases enter the reduction catalyst, they are treated with an aqueous urea solution as a reducing agent. This aqueous urea solution causes the formation of ammonia, which reacts with the nitrogen oxides in the downstream reduction catalyst to form harmless nitrogen and water. The aqueous urea solution is stored in a reducing agent reservoir and metered into an exhaust gas channel via a metering module. A conveying module is provided to supply the reducing agent from the reservoir to the metering module. This conveying module is usually located within the reservoir, often in conjunction with a heating device to prevent the aqueous urea solution from freezing at low ambient temperatures.

[0003] German patent application DE 10 2014 210 799 A1 discloses, by way of example, a heating device for a reducing agent storage tank. This device, together with a pump, is mounted on a housing, thus forming a functional unit that facilitates installation in the storage tank. The housing can be attached from below to an opening at the bottom of the storage tank and connected to the tank via a support structure, such that the heating device and the pump are located inside the tank. For this purpose, the heating device and the pump are preferably mounted on the support structure, which is then welded to the storage tank. In this way, the support structure simultaneously provides a media-tight separation, preventing the electrical or electronic components housed within the casing from coming into contact with the aqueous urea solution.

[0004] DE 10 2010 014 314 A1 discloses a device for providing liquid reducing agent, DE 10 2010 004 614 A1 discloses a tank arrangement and a metering system for a reducing agent, and DE 10 2009 000 101 A1 discloses a further tank design.

[0005] Based on the aforementioned prior art, the present invention aims to provide a functional unit for a reducing agent storage tank in which it is ensured that no moisture enters the housing from the outside and impairs the functionality of the electrical or electronic components housed in the housing.

[0006] The problem is solved by a functional unit for a reducing agent storage tank with the features of claim 1. Advantageous embodiments of the invention are described in the dependent claims. Furthermore, a reducing agent storage tank with such a functional unit is described. Disclosure of the invention

[0007] The functional unit proposed for a reducing agent storage tank comprises a housing for receiving at least one electrical or electronic component and a support by means of which the housing can be connected to the reducing agent storage tank, in particular by welding. The reducing agent stored in the storage tank is preferably an aqueous urea solution for the aftertreatment of exhaust gases from an internal combustion engine. According to the invention, the housing and the support have interlocking collar sections between which a sealing element for forming a radial seal is arranged, with a support element integrated into the radially outer collar section.

[0008] The two interlocking collar sections allow for a detachable connection between the housing and the support. This is particularly advantageous if an electrical or electronic component housed within the casing, such as a circuit board or other electronic component, is defective and needs to be replaced. If the functional unit is connected to a reducing agent reservoir, the housing can be opened without removing the support.

[0009] The desired seal to the outside is achieved via the sealing element located between the two collar sections. The gap accommodating the sealing element is preferably dimensioned such that the sealing element is compressed or bears against the two collar sections under radial preload. In this way, the sealing effect can be maximized.

[0010] To permanently maintain the radial preload of the sealing element, it is essential to prevent the gap from widening. This task is accomplished by the support element, which, according to the invention, is integrated into the radially outer collar section. Due to the integration of the support element into the radially outer collar section, this section can no longer expand, or only to a very limited extent, relative to the radially inner collar section when heated. The gap dimension thus remains largely unchanged, which in turn ensures that the radial preload of the sealing element relative to the collar sections is maintained.

[0011] The integration of a support element into the radially inner collar section is unnecessary. This is because thermally induced expansion of the radially inner collar section compared to the radially outer collar section leads to a narrowing of the gap. This means that the sealing element is compressed more effectively, thus increasing the sealing effect.

[0012] The support element allows the housing and the support structure to be made of different materials, particularly materials with different coefficients of thermal expansion. This means the support element enables a functionally appropriate material selection. For example, the support structure can be made of a weldable material, allowing for welding to a reducing agent storage tank. In contrast, the housing material does not need to be weldable. Here, the material's strength and stiffness are the primary considerations. Ideally, the housing and the support structure are therefore made of different materials.

[0013] The housing is preferably cup-shaped and open at the top. This opening facilitates the insertion of the electrical or electronic component into the housing. The housing can then be closed by attaching the support, which is positioned so that the two collar sections interlock. Preferably, the collar section of the support surrounds the collar section of the housing, so that the collar section of the support is located radially outside. Accordingly, the collar section of the support incorporates the support element. This provides the support with additional stiffening.

[0014] According to a preferred embodiment of the invention, the support element is designed as a closed ring. The ring shape prevents the support element from deflecting radially under load. This means that the support function of the support element is optimized by the ring shape.

[0015] Furthermore, the support element is preferably made of a material with a coefficient of thermal expansion that is essentially equal to or less than that of the material from which the radially inner collar section is made. This ensures that the gap between the two collar sections does not widen when heated, as the linear expansion of the radially outer collar section is limited to the linear expansion of the integrated support element.

[0016] The support element can be integrated into the radially outer collar section in different ways.

[0017] According to a first preferred embodiment of the invention, the support element is overmolded with the material of the radially outer collar section. In this case, the integration takes place simultaneously with the production of the carrier or the housing. The support element is first inserted into an injection mold as an insert and then overmolded with the material of the carrier or the housing.

[0018] According to a second preferred embodiment of the invention, the radially outer collar section has a recess into which the support element is inserted by potting. In this case, the support element is inserted subsequently, which simplifies the manufacture of the carrier or the housing.

[0019] According to a third preferred embodiment of the invention, the support element is inserted into an end-face groove of the radially outer collar section. This means that the support element and the carrier or housing are manufactured independently of each other and subsequently joined. The connection can be made by achieving a force-fit, form-fit, and / or material connection that prevents the support element from falling out of the groove. For example, the support element can be connected to the collar section by clipping, pressing, crimping, and / or bonding.

[0020] In a further development of the invention, it is proposed that the groove be bounded radially on the outside by a groove flank that is freestanding relative to the support element. This freestanding groove flank helps to compensate for internal stresses resulting from the restricted longitudinal expansion of the radially outer collar section due to the integrated support element. Because the radially outer groove flank is freestanding, the groove can open when heated. This leads to partial deformation of the collar section, which relieves internal stresses. Furthermore, the deformation occurs in a non-critical area of ​​the collar section, so it has no effect on the function of the carrier or the housing. The sealing function of the sealing element is also not impaired, since the radially inner groove flank is held in position by the adjacent support element.

[0021] Advantageously, the radially inner collar section is formed on the housing and the radially outer collar section on the support. This means that the collar section of the support encompasses the collar section of the housing. In this way, the potential contact area of ​​the support with a reducing agent storage tank is increased, thus facilitating the connection of the functional unit to the storage tank. Furthermore, it is ensured that in the event of a leak in the area of ​​the connection between the support and the storage tank, no reducing agent can penetrate the housing.

[0022] The housing is preferably made of a first plastic, preferably a high-strength plastic with or without fillers, for example polyamide or polybutylene terephthalate (PBT). These and comparable plastics exhibit sufficiently high strength and / or stiffness.

[0023] The support is preferably made of a second plastic, preferably high-density polyethylene (HDPE) or polypropylene (PP). HDPE has the advantage of being weldable, thus allowing the support to be connected to a reducing agent storage tank via a weld. Since HDPE is also resistant to urea and ammonia, the support and the storage tank can be made of the same material.

[0024] Since the advantages of the invention are particularly evident in combination with a reducing agent storage tank, a reducing agent storage tank with a functional unit according to the invention is further proposed. The functional unit is preferably attached to the reducing agent storage tank in the area of ​​an opening at the bottom and welded to the reducing agent storage tank via the support. The welded connection ensures the sealing of the storage tank to the outside, while the support simultaneously prevents the housing of the functional unit from coming into contact with the reducing agent stored in the tank. The housing can therefore be made of a material that is neither weldable nor otherwise adapted to the material of the support. In particular, a material can be selected that has a higher strength than the material of the support.Different coefficients of thermal expansion of the materials can be disregarded, as an integrated support element counteracts thermally induced changes in length of the support relative to the housing. This ensures that the sealing contact of a sealing element located between the support and the housing is maintained, thus guaranteeing the sealing of the housing to the outside.

[0025] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic section through a functional unit according to the invention in a first preferred embodiment, Fig. 2 an enlarged section of the Fig. 1 in the area of ​​the radial seal between housing and support, Fig. 3 a schematic section through a functional unit according to the invention in a second preferred embodiment in the area of ​​the radial seal between housing and support, Fig. 4 a schematic section through a functional unit according to the invention in a third preferred embodiment in the area of ​​the radial seal between housing and support as well as Fig. 5 a schematic section through a functional unit according to the invention in a fourth preferred embodiment in the area of ​​the radial seal between housing and support. Detailed description of the drawings

[0026] The Fig. Figure 1 shows a functional unit 1 comprising a housing 2 and a support 3. The functional unit 1 can be connected, in particular, to a reducing agent storage tank (not shown). The connection is made via the support 3 by means of welding. The welding takes place in the area of ​​a web 11 formed on the upper surface of the support 3.

[0027] The carrier 3 is connected to the housing 2 via a collar section 5, which engages a collar section 4 of the housing 2. An elastomeric sealing element 6 is inserted between the two collar sections 4 and 5, bearing against them under radial preload. This creates a seal between the housing 2 and the outside.

[0028] The housing 2 is made of a first plastic of high strength and low thermal expansion, for example, polyamide, polybutylene terephthalate (PBT), or a comparable material. The support 3 consists of a second plastic, which is essentially adapted to the material of the reducing agent storage tank. This can be, in particular, high-density polyethylene (HDPE) or polypropylene (PP). Thus, the support 3 and the housing 2 have different coefficients of thermal expansion. This means that they expand to different degrees when heated. To ensure that the sealing contact between the sealing element 6 and the collar sections 4 and 5 is maintained, the collar section 5 of the support 3 has an annular support element 7 integrated into the collar section 5.The circumferential annular support element 7 limits the longitudinal expansion of the carrier 3 relative to the housing 2, so that the gap in which the sealing element 6 is received does not widen or only widens negligibly. The sealing function of the sealing element 6 is thus maintained.

[0029] As in particular the Fig. As can be seen from Figure 2, the support element 7 is completely enclosed within the collar section 5 of the carrier 3 and encased by the carrier 3 material. Therefore, a material can be selected for the support element 7 that primarily fulfills its supporting function. The coefficient of thermal expansion should be as equal to or less than that of the housing 2 material as possible to reliably prevent any widening of the sealing gap.

[0030] The support function of the support element 7 can lead to undesirable bulging of the carrier 3. This is because the lack of expansion in the radial direction may be compensated for by expansion in the axial direction. This can be counteracted by inserting the support element 7 into an end-face groove 9 of the collar section 5, the radially outer groove flank 10 of which is free of the support element 7. This embodiment is exemplified in the Fig. Figure 3 shows that the free-standing groove flank 10 allows the groove 9 to open when heated, causing the support 3 to undergo partial deformation, which compensates for internal stresses and thus counteracts buckling of the support 3.

[0031] In the Fig. Figure 4 shows another preferred embodiment of a functional unit 1 according to the invention, wherein the illustration is again limited to the sealing area between the housing 2 and the support 3. Here, a potting compound is introduced into a recess 8 of the collar section 5 of the support 3 to form the support element 7.

[0032] As exemplified in the Fig. As shown in Figure 5, the support element 7 can also be integrated into the collar section 5 of the beam 3 in such a way that a positive fit is achieved between the support element 7 and the collar section 5. In the Fig. The support element 7 was subsequently inserted from below into the end-face groove 9 of the collar section 5 and clipped into place. Locking lugs 12 are provided on the support element 7 for this purpose.

Claims

[1] Functional unit (1) for a reducing agent storage tank, wherein the reducing agent is preferably an aqueous urea solution for the aftertreatment of exhaust gases from an internal combustion engine, comprising a housing (2) for receiving at least one electrical or electronic component and a support (3) by means of which the housing (2) can be connected to the reducing agent storage tank, in particular welded, characterized by , that the housing (2) and the support (3) have interlocking collar sections (4, 5) between which a sealing element (6) is arranged to form a radial seal, wherein a support element (7) is integrated into the radially outer collar section (5). [2] Functional unit according to claim 1, characterized by , that the support element (7) is designed as a closed ring. [3] Functional unit according to claim 1 or 2, characterized by, that the support element (7) is made of a material which has a coefficient of thermal expansion which is essentially equal to or less than that of the material from which the radially inner collar section (4) is made. [4] Functional unit according to any one of the preceding claims, characterized by , that the support element (7) is overmolded with the material of the radially outer collar section (5). [5] Functional unit according to any one of claims 1 to 3, characterized by , that the radially outer collar section (5) has a recess (8) into which the support element (7) is inserted by potting. [6] Functional unit according to any one of claims 1 to 3, characterized by , that the support element (7) is inserted into an end-face groove (9) of the radially outer collar section (5) and is preferably clipped, pressed, crimped and / or glued. [7] Functional unit according to claim 6, characterized by , that the groove (9) is radially bounded on the outside by a groove flank (10) which is free from the support element (7). [8] Functional unit according to any one of the preceding claims, characterized by , that the radially inner collar section (4) is formed on the housing (2) and the radially outer collar section (5) is formed on the carrier (3). [9] Functional unit according to any one of the preceding claims, characterized by , that the housing (2) is made of a first plastic, preferably of polyamide or polybutylene terephthalate (PBT), and the support (3) is made of a second plastic, preferably of high-density polyethylene (HDPE) or polypropylene (PP). [10] Reducing agent storage tank with a functional unit (1) according to one of the preceding claims, wherein the functional unit (1) is attached to the reducing agent storage tank in the area of ​​a bottom opening and is welded to the reducing agent storage tank via the support (3).

Images