Mixer arrangement for mixing an injection medium with the exhaust gas of an internal combustion engine

Abstract

A mixer arrangement for mixing an injection medium with the exhaust gas of an internal combustion engine, comprising: an exhaust gas guide section (4) in the interior of which the exhaust gas of the internal combustion engine can be guided, an injector (3) which is attached to an outside of the exhaust gas guide section (4), wherein the exhaust gas guide section (4) has an injection opening (10) which extends along an injection axis (L_10) and through which the injection medium can be injected from the injector (3) into the interior of the exhaust gas guide section (4), wherein a first recess (60) is formed on the outside of the exhaust gas guide section (4), and the first recess (60) is arranged in a direction parallel to the injection axis (L_10) in overlap with the injector (3) and the injector (3) is spaced apart in this direction from the outside of the exhaust gas guide section (4).

Description

[0001] The present invention relates to a mixer arrangement for mixing an injection medium with the exhaust gas of an internal combustion engine.

[0002] For exhaust gas aftertreatment, reactants are introduced into the exhaust stream to reduce environmentally harmful components. For example, in diesel engines, a urea-water solution is injected into the exhaust gas to reduce the nitrogen oxide content in a downstream SCR catalyst arrangement. A mixer arrangement can be installed upstream of the catalyst arrangement to mix the reactant injected into the exhaust stream with the exhaust gas to improve the effectiveness of the catalyst.

[0003] EP 3 808 949 A1 discloses a mixer arrangement for an internal combustion engine, comprising: a base element, wherein a reactant inlet opening is formed in the base element, which is open in the direction of a radially expanding reactant receiving volume. On an outer side of the base element, a fastening arrangement is formed, via which a fastening flange of an injector can be fixed to the base element. The fastening arrangement has a flat contact surface for the contact of the injector and a plurality of internal threads arranged around the reactant inlet opening at a circumferential distance from one another. The shape of the contact surface and the positioning of the internal threads are coordinated with the shape of the fastening flange of the injector.

[0004] The present invention is based on the object of providing a mixer arrangement for mixing an injection medium with the exhaust gas of an internal combustion engine, which prevents overheating of the injector.

[0005] To achieve the object underlying the invention, a mixer arrangement for mixing an injection medium with the exhaust gas of an internal combustion engine is proposed, comprising: an exhaust gas guide section, into the interior of which the exhaust gas of the internal combustion engine can be guided, an injector which is fastened to an outer side of the exhaust gas guide section, wherein the exhaust gas guide section has an injection opening which extends along an injection axis and through which the injection medium can be injected from the injector into the interior of the exhaust gas guide section, wherein a first recess is formed on the outer side of the exhaust gas guide section, and the first recess is in register with the injector in a direction parallel to the injection axis and the injector is spaced apart from the outer side of the exhaust gas guide section in this direction.

[0006] The mixer arrangement according to the invention has the advantage that the contact surface of the injector, which rests against the exhaust gas guide section carrying the hot exhaust gas, is reduced, while the surface of the injector around which ambient air can flow is increased. Thus, less thermal energy is transferred from the exhaust gas guide section to the injector, and the injector can more effectively dissipate the thermal energy to the environment without requiring additional installation space.

[0007] In one possible embodiment, the first recess can be open in a direction parallel to the injection axis and away from the exhaust gas guide section. When the injector is assembled, the first recess can extend further in a radial direction with respect to the injection axis than the injector. The first recess can be delimited in the axial direction by a bottom surface of the recess. In the radial direction, the first recess can be surrounded at least in sections by an intermediate shoulder. At least one ventilation gap can be formed between the injector and the intermediate shoulder, through which ventilation gap ambient air can flow into the first recess.

[0008] In a further possible embodiment, the injector can be fastened to an outer side of the exhaust gas guide section in an alternative installation position. The alternative installation position can also be referred to as a second installation position. A second recess can be formed on the outer side of the exhaust gas guide section. The second recess can be arranged in a direction parallel to the injection axis, overlapping the injector in the second installation position. The injector can be spaced apart from the outer side of the exhaust gas guide section in this direction.

[0009] In a further possible embodiment, the first recess and the second recess can be designed to be mirror-symmetrical with respect to a mirror plane that includes the injection axis.

[0010] An exemplary embodiment of a mixer arrangement according to the invention is explained in more detail below with reference to the accompanying drawings. Herein: Fig. 1 a side view of an exhaust gas aftertreatment arrangement with a mixer arrangement according to the invention; Fig. 2 a longitudinal section through the mixer arrangement of Fig. 1; Fig. 3 a perspective view of the exhaust aftertreatment arrangement from Fig. 1 without the injector; Fig. 4 another side view of the exhaust aftertreatment arrangement from Fig. 1 in a first installation position without injector; Fig. 5 the flange element from Fig. 1 in a perspective view; Fig. 6 the view from Fig. 4 with the injector mounted in the first installation position; and Fig. 7 the view from Fig. 4 with attached injector in the second installation position.

[0011] The Fig.1 to 7, which are described together below, show part of an exhaust gas aftertreatment system 1 of an internal combustion engine with a mixer system 2 according to the invention for mixing an injection medium, which can be injected by an injector 3, with the exhaust gas of the internal combustion engine. In the present case, to reduce the nitrogen oxide content in the exhaust gas, a water-urea solution is injected into the exhaust gas through the injector 3 as an injection medium and mixed with it. The exhaust gas is then fed to a catalyst (not shown), in which the nitrogen oxides contained in the exhaust gas are converted into water and nitrogen by means of selective catalytic reduction.

[0012] The injector 3 is optionally liquid-cooled. For this purpose, the injector 3 is supplied with coolant from a coolant source (not shown) via a partially illustrated coolant supply line 56. The coolant flows through the injector 3 and is subsequently returned to the coolant source via a partially illustrated coolant discharge line 57.

[0013] The mixer arrangement 2 comprises a first exhaust gas guide section 4, which can also be referred to as the first exhaust gas guide element. The first exhaust gas guide section 4 is essentially pot-shaped and has a circular connecting opening 5, via which the first exhaust gas guide section 4 can be fluidically connected to a not-shown upstream section of the exhaust gas aftertreatment arrangement 1. The upstream section of the exhaust gas aftertreatment arrangement 1 can be a particulate filter, for example. The imaginary normal of the connecting opening 5 defines the main inflow direction of the exhaust gas into the first exhaust gas guide section 4.

[0014] The first exhaust gas guide section 4 also comprises an insert opening 8 in which a flange element 9 is arranged. The first exhaust gas guide section 4 and the flange element 9 are firmly connected to one another, in particular welded. The flange element 9 comprises an injection opening 10, which extends along an injection axis L_10 and through which the injector 3 can inject the injection medium into the interior of the first exhaust gas guide section 4.

[0015] For this purpose, the injector 3 is firmly connected to the first exhaust gas guide section 4. The flange element 9 has, on an outer side facing away from the interior of the first exhaust gas guide section 4, a fastening arrangement with three first internal threads 14, 14', 14", which together form a first threaded hole pattern. The internal threads can also be generally referred to as threaded holes. The three first internal threads 14, 14', 14" are each inserted into an internal thread boss 15, 15', 15" and extend along a central axis.

[0016] The injector 3 has three mounting holes 54, 54', 54", which together form a mounting hole pattern. The mounting holes 54, 54', 54" are designed as cylindrical through holes and can therefore also be referred to as mounting holes.

[0017] The first threaded hole pattern of the flange element 9 is designed to complement the mounting hole pattern of the injector 3. Thus, the first threaded hole pattern and the mounting hole pattern can be aligned, so that a screw 55, 55', 55" extends through one of the three mounting holes 54, 54', 54" into and engages one of the three first internal threads 14, 14', 14". The injector 3 is then clamped to the flange element 9 via three screws 55, 55', 55" and frictionally connected. This positioning of the injector 3 is performed in a first installation position of the exhaust gas aftertreatment system 1 and is also referred to as the first installation position of the injector.

[0018] The flange element 9 also has three second internal threads 17, 17', 17", which together form a second threaded hole pattern. The second threaded hole pattern is arranged rotationally symmetrically to the first threaded hole pattern with respect to the injection axis L_10. In the present case, the second threaded hole pattern is arranged offset by 180 degrees to the first threaded hole pattern with respect to the injection axis, without being limited thereto. The three second internal threads 17, 17', 17" are each introduced into an internal thread slug 18, 18', 18" and extend along a central axis.

[0019] The second threaded hole pattern of the flange element 9 is also designed to complement the mounting hole pattern of the injector 3. Thus, the second threaded hole pattern and the mounting hole pattern can be aligned, so that a screw 55, 55', 55" extends through one of the three mounting holes 54, 54', 54" into and engages one of the three second internal threads 17, 17', 17". The injector 3 is then clamped to the flange element 9 via the three screws 55, 55', 55" and frictionally connected. This positioning of the injector 3 is performed in a second installation position of the exhaust aftertreatment system 1.

[0020] The flange element 9 has bearing surfaces 16, 16', 16" at the axial ends of the internal threaded studs 15, 15', 15" and bearing surfaces 19, 19', 19" at the axial ends of the internal threaded studs 18, 18', 18" which are flat and lie in a common contact plane.

[0021] The flange element 9 has a central sealing shoulder 11 that annularly encloses the injection opening 10. The sealing shoulder 11 has a sealing surface 12 at its axial end, which lies in the contact plane.

[0022] In the first installation position, the support surfaces 16, 16' 16" of the internal threaded studs 15, 15', 15" together with the sealing surface 12 form a contact surface of the flange element 9, on which the injector rests with a complementary contact surface.

[0023] In the second installation position, the contact surfaces 19, 19', 19" of the internally threaded studs 18, 18', 18" together with the sealing surface 12 form a contact surface of the flange element 9, on which the injector rests with the complementary contact surface.

[0024] The injector 3 is thus fastened to the outside of the first exhaust gas guide section 4 via the fastening arrangement. A first recess 60 is formed on the outside of the first exhaust gas guide section 4. The first recess 60 is open in a direction parallel to the injection axis L_10 and away from the first exhaust gas guide section 4. In the first installation position, the injector 3 is arranged in a direction parallel to the injection axis L_10, overlapping at least sections of the first recess 60. The injector 3 is spaced from the outside of the exhaust gas guide section 4 in this direction. A gap is thus formed between the outside of the exhaust gas guide section 4 and the injector 3 in the region of the first recess 60.In other words, the injector 3 has regions which are arranged in axial overlap with the first recess 60, wherein in these regions the injector 3 is spaced from the outside of the exhaust gas guide section 4.

[0025] In the first installation position of the injector 3, the first recess 60 extends further in a radial direction relative to the injection axis L_10 than the injector 3. The outer side of the exhaust gas guide section 4 thus has sections in the region of the first recess 60 that are arranged in a direction parallel to the injection axis L_10 without overlapping the injector 3. This allows ambient air to enter the first recess 60 unhindered and flow behind the injector 3, so that thermal energy can be efficiently dissipated from the injector 3 to the ambient air.

[0026] The first recess 60 is bounded in the axial direction by a bottom surface 61 with respect to the injection axis L_10 and is surrounded at least partially in the radial direction by an intermediate shoulder 62. At least one ventilation gap is formed between the injector 3 and the intermediate shoulder 62, through which ambient air can flow into the first recess 60. This also allows air to flow behind the injector 3, so that thermal energy can be efficiently dissipated from the injector 3 to the ambient air.

[0027] A second recess 60' is formed on the outside of the first exhaust gas guide section 4. The second recess 60' is open in a direction parallel to the injection axis L_10 and away from the first exhaust gas guide section 4. In the second installation position, the injector 3 is arranged in a direction parallel to the injection axis L_10 in overlap with at least sections of the second recess 60'. The injector 3 is spaced apart from the outside of the exhaust gas guide section 4 in this direction. A gap is thus formed between the outside of the exhaust gas guide section 4 and the injector 3 in the region of the second recess 60'. In other words, the injector 3 has regions that are arranged in axial overlap with the second recess 60', wherein in these regions the injector 3 is spaced apart from the outside of the exhaust gas guide section 4.

[0028] In the second installation position of the injector 3, the second recess 60' extends further in a radial direction relative to the injection axis L_10 than the injector 3. The outer side of the exhaust gas guide section 4 thus has sections in the region of the second recess 60' that are arranged in a direction parallel to the injection axis L_10 without overlapping the injector 3. This allows ambient air to enter the second recess 60' unhindered and flow behind the injector 3, so that thermal energy can be efficiently dissipated from the injector 3 to the ambient air.

[0029] The second recess 60' is bounded in the axial direction by a bottom surface 61' with respect to the injection axis L_10 and is surrounded at least partially in the radial direction by the intermediate shoulder. At least one ventilation gap is formed between the injector 3 and the intermediate shoulder 62, through which ambient air can flow into the second recess 60'. This also allows air to flow behind the injector 3, so that thermal energy can be efficiently dissipated from the injector 3 to the ambient air.

[0030] In the first installation position, the injector 3 is arranged in a direction parallel to the injection axis L_10, overlapping at least sections of the second recess 60'. In the second installation position, the injector 3 is arranged in a direction parallel to the injection axis L_10, overlapping at least sections of the first recess 60.

[0031] The first recess 60 and the second recess 60' are designed to be mirror-symmetrical with respect to a mirror plane E_sym, which encompasses the injection axis L_10. It is conceivable that the first recess 60 and the second recess 60' are connected to each other via a connecting recess.

[0032] Arranged in the interior of the first exhaust gas guide section 4 is a mixing tube 36 that extends along a longitudinal axis L_36. The longitudinal axis L_36 is arranged transversely, in particular orthogonally, to the main inflow direction of the exhaust gas in the first exhaust gas guide section 4. The longitudinal axis L_36 is also arranged coaxially to the injection axis L_10. The mixing tube 36 has an injection opening 37 at a first axial end, which is oriented in the direction of the injection opening 10 of the flange element 9. In other words, the injection opening 37 and the injection opening 10 are opposite one another. The injector 3 thus injects the injection medium into the mixing tube 36. The mixing tube 36 engages in recesses in the flange element 9, such that the mixing tube 36 is supported at the first axial end by the flange element 9 in the axial and radial directions.

[0033] The mixing tube 36 comprises a swirl section 38 designed to swirl the exhaust gas flowing through it, so that improved mixing of the exhaust gas and injection medium can be achieved in the mixing tube 36. The swirl section 38 extends from the injection opening 37 along the longitudinal axis L_36 and widens conically with increasing distance from the injection opening 37.

[0034] In the region of the swirl section 38, the mixing tube 36 has a plurality of inlet openings 39 distributed over the circumference, through which the exhaust gas from the internal combustion engine can enter the mixing tube 36. In other words, the mixing tube 36 is fluidly connected to the first exhaust gas guide section 4 via the inlet openings 39. The inlet openings 39 are each delimited in sections by a guide vane 40, which is shaped such that the exhaust gas from the internal combustion engine enters the swirl section 38 with swirl. The swirl section 38 of the mixing tube 36 can thus be referred to as a mixing arrangement.

[0035] A cylindrical section 41 adjoins the swirl section 38 in the direction of the longitudinal axis L_36 of the mixing tube 36. The cylindrical section 41 can also be referred to as a mixing section. The cylindrical section 41 includes an outlet opening 42 of the mixing tube 36 at its second axial end.

[0036] The cylindrical section 41 extends through a passage opening 6 of the first exhaust gas guide section 4, which extends along a passage axis L_6. The passage axis L_6 of the passage opening 6 and the longitudinal axis L_36 of the mixing tube are arranged coaxially to one another. The cylindrical section 41 extends into a second exhaust gas guide section 25, which can also be referred to as a second exhaust gas guide element. The second exhaust gas guide section 25 is arranged downstream of the first exhaust gas guide section 4. The mixing tube 36 thus fluidically connects the first exhaust gas guide section 4 to the second exhaust gas guide section 25.

[0037] The cylinder section 41 is partially surrounded by a sleeve element 43, which extends along a longitudinal axis L_43. The longitudinal axis L_43 of the sleeve element 43 is arranged coaxially with the longitudinal axis L_36 of the mixing tube 36. The sleeve element 43 also extends from the interior of the first exhaust gas guide section 4 through the passage opening 6 of the first exhaust gas guide section 4.

[0038] A gap 52 is formed between the sleeve element 43 and the mixing tube 36. The gap 52 extends between an inlet opening 45 and an outlet opening 46, each formed between the mixing tube 36 and the sleeve element 43. The gap 52 is fluidically connected to the first exhaust gas guide section 4 via the inlet opening 45. The gap 52 is fluidically connected to the second exhaust gas guide section 25 via the outlet opening 46. It is also conceivable in principle for the gap 52 to be optionally fluidically connected to the mixing tube 36.

[0039] The gap 52 thus fluidically connects the first exhaust gas guide section 4 to the second exhaust gas guide section 25. The hot exhaust gas of the internal combustion engine can enter the gap 52 from the interior of the first exhaust gas guide section 4 via the inlet opening 45 and flow through it toward the second exhaust gas guide section 25. The hot exhaust gas effectively transfers the thermal energy contained therein to the mixing tube 36, heating it evenly. This prevents colder spots in the mixing tube 36 where the injection medium can condense and subsequently deposit.

[0040] The mixer arrangement 2 comprises a second exhaust gas guide section 25, which can also be referred to as a second exhaust gas guide element. The second exhaust gas guide section 25 is essentially pot-shaped and has a circular connecting opening 26, via which the second exhaust gas guide section 25 can be fluidically connected to a downstream section (not shown) of the exhaust gas aftertreatment arrangement 1. The downstream section of the exhaust gas aftertreatment arrangement 1 can be, for example, an SCR catalyst.

[0041] The second exhaust gas guide section 25 has a passage opening 27 that extends along a passage axis L_27. The passage axis L_27 of the passage opening 27 and the longitudinal axis L_36 of the mixing tube 36 are arranged coaxially to one another. A connecting tube 28 extends along a longitudinal axis L28 through the passage opening 27 of the second exhaust gas guide section 25. The passage axis L_27 of the passage opening 27 and the longitudinal axis L_28 of the connecting tube 28 are arranged coaxially to one another. The connecting tube 28 extends from an interior of the second exhaust gas guide section 25 through the passage opening 27. The connecting tube 28 has a cylindrical section 29 and an adjoining conical section 30, the conical section 30 forming an axial end of the connecting tube 28.In the area of ​​the passage opening 27, the cylinder section 29 of the connecting pipe 28 and the second exhaust gas guide section 25 are firmly connected to one another.

[0042] The connecting pipe 28 encloses the mixing pipe 36 and the sleeve element 43 at least in sections. In other words, the respective axial ends of the mixing pipe 36 and the sleeve element 43 arranged outside the interior of the first exhaust gas guide section 4 extend into the connecting pipe 28.

[0043] The connecting pipe 28 and the sleeve element 43 are detachably connected to one another by a connecting arrangement 32, so that the connecting pipe 28 and the sleeve element 43 are arranged without contact with one another. The connecting arrangement 32 connects the connecting pipe 28 and the sleeve element 43 in a region outside each of the first exhaust gas guide section 4 and the second exhaust gas guide section 25.

[0044] In the interior of the second exhaust gas guide section 25, a baffle plate 31 is arranged, which optimizes the flow of the exhaust gas. List of reference symbols 1 exhaust aftertreatment arrangement 2 mixer arrangement 3 Injector 4 first exhaust gas section 5 Connection opening 6 Passage opening 8 Insert opening 9 Flange element 10 Injection opening 11 central sealing shoulder 12 Sealing surface 14 First threads 15 threaded studs 16 support surface 17 Second thread 18 threaded studs 19 Support surface 25 Second exhaust gas guide section / element 26 Connection opening 27 Passage opening 28 Connecting pipe 29 Cylinder section 30 cone section 31 baffle plate 32 Connection arrangement 36 mixing tube 37 Injection port 38 swirl section 39 Inlet opening 40 guide vane 41 Cylinder section 42 Outlet opening 43 Sleeve element 45 Inlet opening 46 Outlet opening 52 gap 54 fixing holes 55 screws 56 Coolant supply line 57 Coolant drainage 60 recess 61 floor area 62 subparagraph L axis QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 808 949 A1

[0003]

Claims

[1] Mixer arrangement for mixing an injection medium with the exhaust gas of an internal combustion engine, comprising: an exhaust gas guide section (4), in the interior of which the exhaust gas of the internal combustion engine can be guided, an injector (3) which is attached to an outer side of the exhaust gas guide section (4), wherein the exhaust gas guide section (4) has an injection opening (10) which extends along an injection axis (L_10) and through which the injection medium can be injected from the injector (3) into the interior of the exhaust gas guide section (4), characterized by , that a first recess (60) is formed on the outside of the exhaust gas guide section (4), wherein the first recess (60) is arranged in a direction parallel to the injection axis (L_10) in overlap with the injector (3) and the injector (3) is spaced from the outside of the exhaust gas guide section (4) in this direction. [2] Mixer arrangement according to claim 1, characterized by that the first recess (60) is open in a direction parallel to the injection axis (L_10) and away from the exhaust gas guide section (4). [3] Mixer arrangement according to one of claims 1 or 2, characterized by that in the assembled state of the injector (3), the first recess (60) extends further in a radial direction with respect to the injection axis (L_10) than the injector (3). [4] Mixer arrangement according to one of claims 1 to 3, characterized by that the first recess (60) is bounded in the axial direction by a bottom surface (61) and is surrounded in the radial direction at least in sections by an intermediate shoulder (62). [5] Mixer arrangement according to one of claims 1 to 4, characterized by that at least one ventilation gap is formed between the injector (3) and the intermediate shoulder (62), through which ambient air can flow into the first recess (60). [6] Mixer arrangement according to one of claims 1 to 5, characterized by , that the injector (3) can be fastened to an outer side of the exhaust gas guide section (4) in an alternative installation position, and that a second recess (60') is formed on the outside of the exhaust gas guide section (4), wherein the second recess (60') is arranged in a direction parallel to the injection axis (L_10) in overlap with the injector (3) in the second installation position and the injector (3) is spaced from the outside of the exhaust gas guide section (4) in this direction. [7] Mixer arrangement according to one of claims 1 to 6, characterized by that the first recess (60) and the second recess (60') are designed to be mirror-symmetrical with respect to a mirror plane (E_sym) which includes the injection axis (L_10).

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