Urea injector and method for producing urea injector

Abstract

The invention relates to a method for producing a sealing seat component of a urea injector, comprising the following steps: producing the sealing seat component from a substrate, the sealing seat component having at least one through-opening and a sealing seat, the sealing seat is used for releasing and closing the through opening together with a closing element (5); hardening a region of a surface of the seal seat member including the seal seat; the region of the surface of the sealing seat component, including the sealing seat, is finished by means of a finishing process.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a sealing seat component for a urea injector, a method for manufacturing a urea injector, and a urea injector. Background Technology

[0002] In internal combustion engines, it is known to meter urea solutions, deionized water, or other corrosive media for exhaust aftertreatment. Besides the corrosiveness of these media (which erode surfaces and components they contact over their service life), another problem is the risk of particulate matter introduction when replenishing these media, for example in off-road applications, in construction machinery such as excavators, trucks, and agricultural machinery such as combine harvesters. For instance, such particles may also be introduced when purging the injector to prevent the medium from freezing. However, the introduction of these particles causes significant wear during operation, especially at the seals. This can lead to leaks and dislodgement at the injector. Due to the corrosive nature of this medium, which results in a high risk of corrosion, concepts used in other injector applications, such as gasoline injectors, cannot be applied to urea injectors. Summary of the Invention

[0003] In contrast, the method for manufacturing a sealing seat member for a urea injector according to the present invention has the following advantages: it enables the sealing seat member, especially in the sealing seat region, to achieve particular robustness. It should be noted that the term "urea injector" herein includes injectors that must introduce corrosive media, such as urea or deionized water, into subsequent spaces.

[0004] The method according to the invention can be implemented very simply and cost-effectively, and provides additional robustness to the urea injector. In particular, this robustness is achieved even in the presence of undesirable particles within the injector that could lead to sealing problems. The method according to the invention includes the step of manufacturing a sealing member from a substrate, wherein the sealing member has at least one through-opening and at least one sealing seat, wherein the sealing seat, together with a closing element, is configured to release and close the through-opening. In a next step, at least one region of the surface of the sealing member including the sealing seat is hardened. Preferably, the hardened region including the sealing seat is slightly larger than the actual sealing seat, particularly the sealing line. In a final step, the surface of the sealing member including the sealing seat is finished using a finishing process. This results in a sealing seat with very high surface hardness and minimal roughness. Another advantage of the method according to the invention is that no geometric changes are required on the urea injector, particularly the sealing member. Therefore, even under extreme operating conditions of the urea injector, especially under high-risk conditions with particulate input into the fluid circuit of the urea injector, reliable sealing and reduced leakage can be achieved throughout the entire service life of the urea injector.

[0005] The preferred embodiments of the present invention show a preferred extended configuration.

[0006] Preferably, the base material of the sealing seat component is stainless steel. Stainless steel is especially austenitic stainless steel. The nickel content of austenitic stainless steel is preferably between about 8% (by weight) and 13% (by weight), the chromium content is greater than 13.5% (by weight), and the carbon content is less than 0.07% (by weight).

[0007] More preferably, the hardening step of this method is performed using a hardening material comprising carbon and / or nitrogen and / or boron. This allows for the achievement of a surface hardness preferably in the range of 600HV0.05 to 1200HV0.05 (HV = Vickers hardness).

[0008] More preferably, during the hardening step, the hardening material is permeated to a penetration depth C, wherein the penetration depth C is in the range of 1µm≤C≤50µm, and particularly in the range of 10µm≤C≤25µm.

[0009] Particularly preferably, the temperature during the hardening step is less than or equal to 500°C. This effectively prevents nitrogen and carbon from reacting with chromium to form nitrides. This has a particular advantage: the weldability of the sealing component thus manufactured allows it to be connected to adjacent components via welded joints during the subsequent manufacture of the urea injector.

[0010] Preferably, through a finishing process, the average surface roughness Ra of the surface in the region where the seal seat is located is less than or equal to 0.1 µm. This allows for an absolute fluid seal of the urea injector at the seal seat using only metallized sealing members, rather than elastomers. More preferably, the average surface roughness Ra is less than or equal to 0.05 µm.

[0011] Precision finishing processes preferably include processes such as honing and / or grinding and / or rolling and / or polishing.

[0012] When the area of ​​the sealing element, including the sealing seat, is a narrowed region, especially a tapered region, a particularly good seal and reduced leakage are achieved. Preferably, the area with the sealing seat narrows towards the through opening of the sealing element.

[0013] Particularly preferably, the entire surface of the sealing member is treated by hardening. Then, preferably, only the area around the sealing member is machined by finishing. Alternatively, the entire surface of the sealing member is also machined by finishing.

[0014] Furthermore, the present invention also relates to a urea injector having a sealing seat component manufactured according to the method of the present invention. This urea injector is not limited to introducing urea, but should be interpreted broadly as being used to introduce corrosive media, such as deionized water in addition to urea.

[0015] Here, the urea injector includes a welded connection that is constructed between the sealing seat member and another component of the urea injector, such as the valve sleeve.

[0016] More preferably, the sealing seat component has a linear sealing seat. Particularly preferably, the sealing seat is composed of a metal ball-cone assembly. Attached Figure Description

[0017] The 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 preferred embodiment of the present invention is shown; Figure 2 Show Figure 1 A schematic enlarged partial cross-sectional view of the sealing seat component of the urea injector in the invention is shown to illustrate the method according to the invention. Detailed Implementation

[0018] Below, refer to Figure 1 and Figure 2 The following describes in detail the urea injector 1, the method for manufacturing the sealing seat member 7 for the urea injector 1, and the method for manufacturing the urea injector 1.

[0019] The urea injector 1 is configured to introduce a medium, particularly an aqueous urea solution or deionized water, into a suitable part of the internal combustion engine or into the exhaust aftertreatment system of the internal combustion engine.

[0020] The urea injector 1 here includes an electromagnetic actuator 20 having an armature 2, an inner pole 3 and a coil 4. The inner pole 3 is fixed in the valve sleeve 13.

[0021] The urea injector 1 also includes a metal shut-off element 5, which is operatively connected to the armature 2. In this embodiment, the shut-off element 5 is a valve ball 50, which has a flat portion 51 on its side for allowing the medium to be introduced to flow through. The valve ball 50 is preferably connected to the armature 2 by means of a welded connection.

[0022] The closing element 5 seals the through opening 8 at the sealing seat member 7. Figure 1 This shows the urea injector in the off state.

[0023] The sealing seat component 7 has a tapered region 71 on which a sealing seat 6 is constructed. The sealing seat 6 is a linear sealing seat and is provided by a ball-cone assembly consisting of a valve ball 50 and the tapered region 51. Figure 1 As can be seen, the sealing seat 6 is constructed on the end of the valve ball 50 that is away from the armature 2.

[0024] Depend on Figure 1 It can also be seen that the armature 2 is constructed as a hollow cylinder and has a central hole 16 and multiple lateral holes 17 for guiding the medium to be introduced through. Figure 1 The direction of flow of the medium to be introduced is schematically indicated by arrows.

[0025] The medium to be introduced can be guided to the sealing seat 6 on the side of the flat section 51. When the urea injector 1 is activated, the armature moves in the direction of arrow A while overcoming the armature gap 14 between the armature and the inner pole 3, causing the valve ball 50, which is fixedly connected to the armature 2, to be lifted from the sealing seat 6. Thus, the medium can be introduced through the through opening 8.

[0026] Here, a guide area 11 leading to the valve sleeve 13 is provided on the outer periphery of the armature 2. Figure 1 The central axis is represented by the line XX.

[0027] The armature and the closing element 5 are reset by means of the reset element 9, in particular the cylindrical spring, which is arranged in the hollow region of the inner pole 3.

[0028] Depend on Figure 1It can also be seen that a welded connection 12 is provided between the sealing seat component 7 and the valve sleeve 13. Thus, the sealing seat component 7 is fixed to the valve sleeve 13 adjacent to it.

[0029] Depend on Figure 2 As can be seen in detail, the sealing seat component 7 here has a tapered region 71 and a welding region 70 located on the outer periphery, where a welding connection 12 to the valve sleeve 13 is made in a subsequent manufacturing step.

[0030] Depend on Figure 2 It can also be seen that the sealing seat member 7 has a hardened edge layer 72. The hardened edge layer 72 covers the entire surface of the sealing seat member 7.

[0031] The sealing component 7 is made of a base material, which is austenitic stainless steel. The austenitic stainless steel here has a nickel content in the range of 8% to 13% (weight percentage), a chromium content in the range of more than 13.5% (weight percentage), and a carbon content of less than 0.07% (weight percentage).

[0032] The hardened edge layer 72 enables resistance to corrosive media, particularly urea solutions or deionized water, from being introduced. This also allows for an improved seal at the sealing seat 6.

[0033] Here, the hardened edge layer 72 has a penetration depth C into the substrate of the sealing member 7, which is in the range of 1µm ≤ C ≤ 50µm, and especially in the range of 10µm ≤ C ≤ 35µm.

[0034] Here, the sealing member 7 is manufactured such that, in the first step, it is preferably shaped from austenitic stainless steel using a machining process. A through opening 8 is also formed here. Next, the surface of the sealing member 7 is hardened, wherein this hardening includes at least the area of ​​the sealing seat 6. That is, it is also possible to harden only the sealing seat 6, which is a linear sealing seat in this embodiment, and a certain range, for example, 1 cm, on both sides of the linear sealing seat. However, in the embodiment described above, the entire sealing member 7 is hardened.

[0035] In the final step of this method, the entire surface of the sealing seat component 7 is finished using a precision machining process. This ensures minimal leakage throughout the entire service life of the urea injector 1.

[0036] Precision finishing processes preferably include processes such as honing and / or grinding and / or rolling and / or polishing.

[0037] With the aid of a finishing process, the average surface roughness Ra of the produced surface is preferably less than or equal to 0.1µm, and more preferably less than or equal to 0.05µm.

[0038] In the hardening step, a hardening material containing carbon and / or nitrogen and / or boron is used. More preferably, the hardening temperature is selected to be less than or equal to 500°C, thereby preventing nitrogen from reacting with chromium and / or carbon to form nitrides. This results in the significant advantage that, in the next manufacturing step of the urea injector, the sealing seat member 7 can be connected to the adjacent member without problems by means of the welded connection 12. Here, no limitations are imposed on the welding process used, thus the overall manufacturing cost of the urea injector 1 can be kept very low despite the improved resistance to corrosive media and / or solid materials that may be introduced into the medium to be sealed.

[0039] During the hardening step, the Vickers hardness (HV) of the hardened edge layer is preferably in the range of 600HV0.05 to 1200HV0.05.

[0040] Therefore, during hardening, carbon and / or nitrogen and / or boron diffuse into the edge layer 72 of the sealing member 7. This generates inherent compressive stress, particularly in the surface region, which leads to the desired improvement in hardness.

[0041] Regarding the substrate of the sealing member, it should also be noted that an excessively high nickel content may cause problems during the subsequent welding process used to attach the sealing member 7 to the adjacent member via the welded connection 12. Therefore, the nickel content of the substrate should not exceed 13% (by weight).

[0042] Furthermore, it should be noted that the lower the carbon content and the lower the processing temperature in austenitic stainless steel, the less likely so-called hot cracking will form during subsequent welding. This prevents the risk of intergranular cracking during the operation of the injector under the influence of corrosive media and / or hot exhaust gases and their potentially corrosive components.

[0043] Therefore, according to the present invention, a method for significantly improving the sealing seat member 7 can be provided, making the sealing seat member 7 significantly more robust than in the prior art in terms of resistance to corrosive media and resistance to potentially introduced particles. Here, it is not necessary to change the geometry of the urea injector, and the necessary method steps can be easily integrated into the manufacturing process from a manufacturing technology perspective. Since such injectors are batch-produced components, a reduced scrap rate is also achieved during manufacturing, resulting in significant economic advantages in the manufacture of urea injectors.

Claims

1. A method for manufacturing a sealing seat component (7) for a urea injector (1), the method comprising the following steps: The sealing seat member (7) is manufactured from a substrate, wherein the sealing seat member (7) has at least one through opening (8) and a sealing seat (6), and the sealing seat (6) is configured to release and close the through opening together with the closing element (5); The surface of the sealing member (7), including the area of ​​the sealing seat (6), is hardened; The surface of the sealing seat component (7), including the area of ​​the sealing seat (6), is finished using a finishing process.

2. The method according to claim 1, wherein, The base material of the sealing seat component is stainless steel, especially austenitic stainless steel.

3. The method according to claim 2, wherein, The substrate comprises nickel in the range of 8% to 13% by weight, chromium in a content of 13.5% or more by weight, and carbon in a content of 0.07% or less by weight.

4. The method according to any one of the preceding claims, wherein, The hardening is carried out using a hardening material, which includes carbon and / or nitrogen and / or boron or compounds having these components.

5. The method according to any one of the preceding claims, wherein, During the hardening step, the penetration depth C is in the range of 1 μm ≤ C ≤ 50 μm, especially in the range of 10 μm ≤ C ≤ 35 μm.

6. The method according to any one of the preceding claims, wherein, During the hardening process, the temperature is less than or equal to 500°C, thereby preventing nitrogen from reacting with chromium and / or carbon to form nitrides.

7. The method according to any one of the preceding claims, wherein, The average surface roughness Ra of the area including the sealing seat and the surface processed by a finishing process is less than or equal to 0.1 μm, especially less than or equal to 0.05 μm.

8. The method according to any one of the preceding claims, wherein, The finishing process includes honing and / or grinding and / or rolling and / or polishing.

9. The method according to any one of the preceding claims, wherein, The area where the sealing seat (6) is arranged is a narrowing area, especially a tapered narrowing area.

10. The method according to any one of the preceding claims, wherein, The entire surface of the sealing seat component (7) is processed by hardening.

11. The method according to claim 10, wherein, The entire hardened surface of the sealing seat component is machined using finishing processes.

12. The method according to any one of the preceding claims, wherein, During the hardening step, the Vickers hardness (HV) of the hardened edge layer reaches the range of 600HV0.05 to 1200HV0.

05.

13. A urea injector having a sealing seat member (7) manufactured according to any one of claims 1 to 12.

14. The urea injector according to claim 13, wherein, The sealing seat component (7) is connected to another component of the urea injector by means of a welded connection (12).

15. The urea injector according to claim 13 or 14, wherein, The sealing seat component (7) has a linear sealing seat (6).

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