Urea injector

Abstract

This invention relates to a urea injector for introducing urea into an exhaust aftertreatment system of an internal combustion engine, comprising an electromagnetic actuator having an armature, an inner pole, and a coil; a closing element operatively connected to and releasing the armature and closing a through opening at a sealing seat; wherein the armature has a stop surface pointing toward the inner pole and a guide surface arranged on the outer periphery of the armature, the guide surface protruding radially outward from the cylindrical body of the armature; wherein the guide surface is arranged adjacent to the stop surface, and a first conical transition region is arranged between the guide surface and the stop surface, the first conical transition region forming a first angle α with respect to the stop surface; and wherein a second conical transition region is arranged between the guide surface and the cylindrical body, the second conical transition region forming a second angle b with respect to the central axis X-X of the urea injector.

Description

Technical Field

[0001] This invention relates to a urea injector for introducing urea into an exhaust aftertreatment system of an internal combustion engine or combustion equipment, such as a heating device. Background Technology

[0002] This type of internal combustion engine or equipment includes an exhaust system with a catalytic converter to reduce nitrogen oxides in the exhaust gases. Urea is typically introduced as an aqueous solution of urea. During operation, crystallization problems may occur, which can restrict the movement of moving parts, particularly the armature of electromagnetic actuators. This can hinder the opening and / or closing of the urea injector, and in extreme cases, may even cause obstruction of the armature of the electromagnetic actuator. Summary of the Invention

[0003] In contrast, the urea injector according to the invention for introducing urea into an exhaust aftertreatment system of an internal combustion engine or into a device has the following advantages: reliable mobility of the moving parts of the urea injector can be achieved even if crystallization occurs in the internal region of the urea injector. The measures for implementing the invention can be implemented very simply and cost-effectively on existing urea injectors, and can also be added if necessary. Thus, the urea injector is significantly more robust in operation, so that, for example, during engine shutdown (such as during start-stop operation), water evaporation due to high temperatures in the exhaust system may lead to crystallization, but this will not have an impact on the next start of the engine. To prevent freezing damage due to the urea aqueous solution, the injector can be emptied after the engine is finally shut down, even without problematic crystallization, although crystallization may still occur after emptying due to the evaporation of the urea aqueous solution. Therefore, the invention particularly ensures that the urea injector will not fail, thus enabling adequate exhaust aftertreatment at all times, especially to meet legal requirements.

[0004] According to the invention, this is achieved by the following: the urea injector has an electromagnetic actuator having an armature, an inner pole, and a coil. Furthermore, the urea injector includes a closing element operatively connected to the armature and releasing and closing the through opening at a sealing seat. The armature has a stop surface pointing towards the inner pole, which the armature stops against the inner pole when the urea injector is open. Additionally, the armature has a guide surface arranged on its outer periphery, protruding radially outward from the cylindrical body of the armature. The guide surface protrudes radially outward, particularly circumferentially, from the outer periphery of the cylindrical body. The guide surface is arranged adjacent to the stop surface of the armature. A first conical transition region is arranged between the guide surface and the stop surface. The first conical transition region is arranged at a first angle α relative to the stop surface. A second conical transition region is provided, arranged at a second angle b relative to the central axis XX of the urea injector, and is arranged between the guide surface and the cylindrical body of the armature.

[0005] Therefore, the outer periphery of the armature is modified in such a way that it has an annular, radially outward-protruding guide surface, which connects to the adjacent area via a first transition area and a second transition area.

[0006] This urea injector can introduce not only urea, but also other media that tend to crystallize, such as deionized water.

[0007] The preferred embodiments of the present invention provide preferred extended configurations.

[0008] Preferably, the first angle α is not equal to the second angle b. This measure ensures that if crystals form in the armature region, particularly in the region adjacent to the guide surface, movement of the armature can be achieved at least in the axial direction of movement. Because crystals are typically constructed to be substantially the same size during formation, it can be ensured that the armature can also move in at least one direction to disrupt the crystals in that direction, thereby reducing the crystal size. The armature can then also typically move in that axial direction as well, because the armature impacts the crystals formed on the other side of the guide surface at a predetermined speed over a longer stroke, applying an increased impact force to break the crystals.

[0009] Particularly preferably, the first angle α is configured such that the following inequality is satisfied: 1° ≤ a ≤ 70°. Particularly preferably, the first angle α is in the range of 30° ≤ a ≤ 60°, and particularly approximately 45°.

[0010] More preferably, the second angle b is configured such that the second angle is in the range of 30°≤b≤89°, particularly in the range of 50°≤b≤70°, and even more particularly in the range of about 60°.

[0011] According to a preferred embodiment of the invention, a coating is provided on the guide surface of the armature. This coating facilitates the movement of the armature in the axial direction by reducing friction. This improves the movement of the armature, so that crystallization that may form in the region of the guide surface can be disrupted by the flexibility of the armature.

[0012] More preferably, a coating is also provided on the armature stop surface and / or on the first tapered transition region between the guide surface and the stop surface. Preferably, coatings are formed on multiple surfaces during the manufacturing process. Preferably, the second tapered transition region also has a coating.

[0013] To prevent the armature from jamming due to crystallization, the transition between the stop surface and the first conical transition region, and / or the transition between the first conical transition region and the guide surface, and / or the transition between the guide surface and the second conical transition region, are preferably constructed without sharp edges. In other words, at the transitions between the aforementioned regions of the armature, any edges that may exist after manufacturing can be rounded to ensure the armature's mobility even in the event of crystallization.

[0014] More preferably, the first length L1 of the first conical transition region in the direction of the central axis XX of the urea injector is greater than or equal to the second length L2 in the direction of the central axis XX of the second conical transition region.

[0015] More preferably, the third length L3 of the guide surface in the direction of the central axis XX is less than or equal to the first length L1 of the first conical transition region.

[0016] The coating on the armature area is preferably a chromium coating, a carbon coating, or a coating that includes a combination of chromium and carbon. Attached Figure Description

[0017] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the drawings: Figure 1 A schematic cross-sectional view of a urea injector according to a first preferred embodiment of the present invention is shown; Figure 2 Show Figure 1 A schematic partial cross-sectional view of the armature of a urea injector; and Figure 3 A schematic partial cross-sectional view of the armature of a urea injector according to a second embodiment of the present invention is shown. Detailed Implementation

[0018] Below, refer to Figure 1 and Figure 2 A urea injector 1 according to a first preferred embodiment of the present invention is described in detail.

[0019] The urea injector 1 is configured to introduce an aqueous urea solution into the exhaust gas aftertreatment system of an internal combustion engine.

[0020] The urea injector 1 includes an electromagnetic actuator 20, which has an armature 2, an inner pole 3 and a coil 4.

[0021] The inner pole 3 is fixed in the valve sleeve 13.

[0022] The urea injector 1 also includes a spherical shut-off element 5, which is fixedly connected to the armature 2. The sealing seat member 7 preferably has a through opening 8, which is centrally configured. The shut-off element 5 releases and closes the through opening 8 at the sealing seat 6.

[0023] like Figure 1 As shown, the sealing seat 6 is annularly constructed between the closing element 5 and the sealing seat member 7.

[0024] The closing element 5 includes a notch 50 that allows urea to flow past when the element is open.

[0025] Figure 1 The flow path through the urea injector 1 is schematically shown by arrows. The urea solution can be guided through the internal region of the shut-off element 5 and along the outer periphery of the shut-off element 5.

[0026] XX represents the central axis of the urea injector. For example... Figure 1 As further shown, in the closed state, there is an armature gap 14 between the armature 2 and the inner pole 3, the gap being as follows: Figure 1 As shown.

[0027] like Figure 2 As shown in detail, a guide region 11 for the armature is constructed between the armature 2 and the valve sleeve 13. The armature 2 has a guide surface 24 here (see...). Figure 2 The guide surface protrudes radially outward from the cylindrical body 2a of the armature 2. Therefore, the entire armature 2 is not guided on the valve sleeve 13, but only in the area of ​​the guide surface 24.

[0028] The guide surface 24 is arranged adjacent to the stop surface 23 of the armature 2. Here, when the urea injector 1 is continuously open, the armature 2 is pressed against the inner pole 3 by the stop surface 23.

[0029] A first conical transition region 21 is provided between the stop surface 23 and the guide surface 24. A second conical transition region 22 is provided between the guide surface 24 and the cylindrical body 2a of the armature 2.

[0030] The first conical transition region 21 and the second conical transition region 22 are as follows: Figure 2As shown in detail, the first tapered transition region 21 is constructed at a first angle α relative to the stop surface 23. The first angle α is preferably 45° to 60°, and more particularly 50°.

[0031] The second conical transition region 22 is constructed at a second angle b between the guide surface 24 and the cylindrical body 2a relative to the central axis XX of the urea injector. The second angle b is preferably 60°.

[0032] During the opening process, coil 4 is energized, causing armature 2 to move along the central axis XX towards the inner pole 3, thus eliminating the armature gap 14. At this point, reset element 9 is pressed together; after energizing coil 4 is stopped, this reset element allows armature 2 and closing element 5 to return to their original positions. Figure 1 In the off state shown.

[0033] like Figure 2 As shown, in the direction of the central axis XX, the first length L1 of the first tapered transition region 21 is greater than the second length L2 of the second tapered transition region 22. Here, the third length L3 of the guide surface 24 in the axial direction is equal to the first length L1.

[0034] like Figure 2 As schematically shown, if crystals 15 form in the region on the inner wall of the valve sleeve 13 and in the region on the outer periphery of the armature 2, this may impede the movement of the armature. Figure 2 The double arrow A is used to indicate this. Crystallization from the urea aqueous solution is particularly likely to occur when the injector is emptied after the internal combustion engine is shut down to prevent it from freezing, and the urea aqueous solution remaining on the wall of the component evaporates or dries, leaving urea crystals. The same situation (crystallization) may also occur after the internal combustion engine is shut down, due to the very high temperatures in the area of ​​the exhaust aftertreatment system, even if the water in the urea aqueous solution present in urea injector 1 evaporates without emptying.

[0035] The invention relates to the provision of a first conical transition region 21 and a second conical transition region 22 at the two ends of the guide surface 24, pointing in the direction along the central axis XX. Therefore, with this design, the movement of the armature 2 can be ensured even when crystals 15 are formed, and the crystals 15 can be broken down, so that these crystals are broken down into such small particles that the armature is no longer obstructed. Here, the conical transition surface and the inner circumferential region of the valve sleeve 13 form a gap that continuously decreases as the armature moves relative to the fixed-position crystals 15, thereby grinding the crystals 15 present therein into small particles. These small particle components of the crystals no longer interfere with the movement of the armature 2 and, for example, can quickly dissolve in the urea aqueous solution due to their small size during subsequent refilling, for example, if the urea injector 1 has been emptied.

[0036] To further improve the formation of crystal 15, a transition portion without sharp edges is preferably provided. Specifically, a first transition portion without sharp edges 31 is constructed between the stop surface 23 and the first conical transition region 21. A second transition portion without sharp edges 32 is constructed between the first conical transition region 21 and the guide surface 24. A third transition portion without sharp edges 33 is constructed between the guide surface 24 and the second conical transition region 22 (see [link]). Figure 2 ).

[0037] The edgeless transition portions 31, 32, and 33 are achieved, for example, by rounding the edges present after the armature 2 is manufactured. The edgeless transition portions ensure that jamming is prevented, especially between the edges and the crystals, particularly in the region between the second transition portion 32 and the third transition portion 33, during the formation of the crystal 15.

[0038] Therefore, the present invention solves the crystallization problem in urea injectors in a surprisingly simple manner. This improves the robustness of the urea injector, as it continues to operate even after venting and crystallization, especially to meet legal requirements regarding exhaust aftertreatment of internal combustion engines. Here, the solution according to the invention can be implemented very simply and cost-effectively on the armature 2.

[0039] Figure 3 The armature of a urea injector according to a second embodiment of the present invention is shown.

[0040] Unlike the first embodiment, the second embodiment additionally provides a coating 40. For example... Figure 3 As shown, coating 40 is applied to three regions, having a first coating 41 on the stop surface 23, a second coating 42 on the first tapered transition region 21, and a third coating 43 on the guide surface 24. A fourth coating 44 may also be provided on the second tapered transition region 22. Here, coating 40 is constructed such that there are no sharp edges at the transitions between the different regions. This is particularly important in the case of coating, because the increased layer thickness, especially at the transitions, can cause problems during armature movement, particularly at the transition to the guide surface 24. Coating 40 is preferably an electroplated chromium layer or a carbon coating or a combination thereof. It is also possible to coat only a selected single surface, especially the guide surface 24.

Claims

1. A urea injector (1) for introducing urea into an exhaust aftertreatment system of an internal combustion engine, the urea injector comprising: An electromagnetic actuator (20) having an armature (2), an inner pole (3) and a coil (4); The closing element (5) is operatively connected to the armature (2) and is released at the sealing seat (6) to close the through opening (8). The armature (2) has a stop surface (23) pointing toward the inner pole and a guide surface (24) arranged on the outer periphery of the armature, the guide surface protruding radially outward from the cylindrical body (2a) of the armature (2); The guide surface (24) is arranged adjacent to the stop surface (23), and a first conical transition region (21) is arranged between the guide surface (24) and the stop surface (23), the first conical transition region forming a first angle α with respect to the stop surface (23); and A second conical transition region (22) is arranged between the guide surface (24) and the cylindrical body (2a), and the second conical transition region forms a second angle b with respect to the central axis XX of the urea injector.

2. The urea injector according to claim 1, wherein, The first angle a is not equal to the second angle b.

3. The urea injector according to any one of the preceding claims, wherein, The first angle a is in the range of 1°≤a≤60°, especially in the range of 20°≤a≤40°, and even more particularly in the range of 30°.

4. The urea injector according to any one of the preceding claims, wherein, The second angle b is in the range of 30°≤b≤89°, especially in the range of 50°≤b≤70°, and especially in the range of 60°.

5. The urea injector according to any one of the preceding claims, wherein the urea injector further has a coating (43) on the guide surface (24).

6. The urea injector according to claim 5, wherein the urea injector further comprises a coating on the stop surface (23) and / or the first conical transition region (21) and / or the second conical transition region (22).

7. The urea injector according to any one of the preceding claims, wherein, The first transition portion (31) between the stop surface (23) and the first conical transition region (21) is edgeless, and / or the second transition portion between the first conical transition region (21) and the guide surface (24) is edgeless, and / or the third transition portion between the guide surface (24) and the second conical transition region (22) is edgeless.

8. The urea injector according to any one of the preceding claims, wherein, The first length L1 of the first conical transition region (21) in the axial direction of the central axis XX of the urea injector is greater than or equal to the second length L2 of the second conical transition region (22) in the direction of the central axis XX.

9. The urea injector according to claim 8, wherein, The third length L3 of the guide surface (24) in the direction of the central axis XX is less than or equal to the first length L1 of the first conical transition region (21).

10. The urea injector according to any one of claims 5 to 9, wherein, The coating is a chromium coating, a carbon coating, or a coating that includes both chromium and carbon.

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