Exhaust gas treatment device

Abstract

An exhaust gas treatment device (1), for an exhaust system (1) of an internal combustion engine, includes a housing (2), providing an exhaust path (3), an injector (4) arranged on the housing (2) for introducing a reduction agent into an exhaust gas flow following the exhaust gas path (3), and a mixer (7) arranged in the housing (2). The mixer (7) includes a shell (8), which encloses a mixer cross section (10) through which the exhaust gas flow can flow. The mixer (7) includes multiple guide blades (11), which on a shell inside project from the shell (8) and project into the mixer cross section (10). A simplified producibility is obtained with the mixer (7) including multiple straps (13), on a shell outside (14), which project from the shell (8) and project into a strap opening (16) formed on the housing (2) and penetrate a housing wall (15).

Claims

1. An exhaust gas treatment device for an exhaust system of an internal combustion engine, the device comprising: a housing through which an exhaust gas path leads; an injector arranged on the housing for introducing a reduction agent into an exhaust gas flow following the exhaust gas path; and a mixer arranged in the housing for mixing-through the reactant with the exhaust gas flow, wherein: the mixer comprises a shell, which encloses a mixer cross section through which the exhaust gas flow can flow; the mixer comprises multiple guide blades, which on a shell inside project from the shell and project into the mixer cross section; the mixer comprises multiple straps, which on a shell outside project from the shell and in each case project into a strap opening formed on the housing and penetrate a housing wall of the housing; the mixer is a shaped single sheet metal part comprised of a single sheet metal piece, in which the shell, the guide blades and the straps are formed by the single sheet metal piece; the mixer, on a shell outside, is radially supported via supporting zones on a wall inside of the housing wall; the supporting zones are arranged distributed in a circumferential direction of the shell and spaced from one another; and radially, between the shell outside and the wall inside, an air gap is formed outside the straps and outside the supporting zones.

2. A device according to claim 1, wherein: the straps are each fastened to the housing from an outside by means of a welded connection; and the respective welded connection closes off the associated strap opening.

3. A device according to claim 1, wherein the supporting zones are formed by elevations, which, through forming, are integrally shaped only on the housing wall or only on the shell or both on the housing wall and also on the shell.

4. A device according to claim 1, wherein that the supporting zones are each formed in a region of the straps.

5. A device according to claim 1, wherein that the housing is configured in a two-shelled manner with at least a housing section containing the mixer such that a shell outside extends along a first housing shell in a first circumferential section and extends along a second circumferential section along a second housing shell.

6. A device according to the claim 5, wherein: in a region of the first housing shell in the region of the second housing shell at least one of the supporting zones is formed.

7. A device according to claim 5, wherein at least one such strap opening is formed on the first housing shell and on the second housing shell.

8. A device according to claim 1, wherein the shell has a flat cross section with a width is greater than a height.

9. A device according to claim 1, wherein the guide blades are straight and run parallel to one another.

10. The device according to claim 1, wherein the guide blades, at each end, are connected to the shell in a fixed manner and are also arranged on another end in a free-standing manner.

11. The device according to claim 1, wherein: the shell, on at least one of an inflow-sided mixer side and on an outflow-sided mixer side comprises a first circumferential section and a second circumferential section which are located opposite one another; the first circumferential section comprises guide blades, which project from the first circumferential section in the direction of the second circumferential section; the second circumferential section comprises guide blades, which project from the second circumferential section in a direction of the first circumferential section; and the guide blades of the first circumferential section are arranged, in the flow direction of the exhaust gas flow, offset from the guide blades of the second circumferential section.

12. A device according to claim 1, wherein that the housing wall defines a flat cross section with a width that is greater than a height.

13. A device according to claim 1, wherein: the guide blades are straight and run parallel to one another; and the guide blades, at each end, are connected to the housing wall in a fixed manner and are also arranged on another end in a free-standing manner.

14. A device according to claim 1, wherein said shell comprises a first wall portion, a second wall portion, a third wall portion and a fourth wall portion, said first wall portion, said second wall portion, said third wall portion and said fourth wall portion being integrally connected to one another to form a one-piece shell, at least the first wall portion, the second wall portion, the third wall portion and the fourth wall portion defining the mixer cross section through which the exhaust gas flow can flow, said one-piece shell comprising a shell outer surface, said shell outer surface comprising a plurality of housing wall contact surfaces, said housing wall comprising a housing wall inner surface, said housing wall inner surface comprising a plurality of shell contact surfaces, each of said housing wall contact surfaces being in direct contact with one of said shell contact surfaces in a respective supporting zone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic lateral view of an exhaust gas treatment device;

(3) FIG. 2 is a schematic view of the exhaust gas treatment device corresponding to view direction II in FIG. 1;

(4) FIG. 3 is a schematic sectional view of the exhaust gas treatment device corresponding to section lines III in FIG. 2;

(5) FIG. 4 is a schematic enlarged view of a detail IV from FIG. 3;

(6) FIG. 5 is a schematic view of the exhaust gas treatment device according to view direction V in FIG. 1;

(7) FIG. 6 is a schematic sectional view of the exhaust gas treatment device according to section lines VI in FIG. 5;

(8) FIG. 7 is a schematic enlarged detail VII from FIG. 6;

(9) FIG. 8 is a schematic view as in FIG. 2, however showing another embodiment;

(10) FIG. 9 is a schematic sectional view corresponding to section lines IX in FIG. 8;

(11) FIG. 10 is a schematic enlarged detail X from FIG. 9;

(12) FIG. 11 is a schematic view as in FIG. 5, however showing the other embodiment;

(13) FIG. 12 is a schematic sectional view corresponding to section lines XII from FIG. 11;

(14) FIG. 13 is a schematic enlarged detail XIII from FIG. 12;

(15) FIG. 14 is a schematic front view of a mixer;

(16) FIG. 15 is a schematic lateral view of the mixer corresponding to view direction XV in FIG. 14;

(17) FIG. 16 is a schematic lateral view of the mixer corresponding to view direction XVI in FIG. 14;

(18) FIG. 17 is a schematic sectional view of the mixer corresponding to section lines XVII in FIG. 16;

(19) FIG. 18 is a schematic enlarged detail XVIII from FIG. 17.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(20) Referring to the drawings, according to FIG. 1, an exhaust gas treatment device 1, which is only partly shown here, which is provided for use in an exhaust system of an internal combustion engine, comprises a housing 2 which is likewise only partly shown, through which leads an exhaust gas path 3 indicated by arrows. The exhaust gas treatment device 1 additionally comprises an injector 4, which is arranged on the housing 2, and with which a reactant can be introduced into an exhaust gas flow, which during the operation of the exhaust system follows the exhaust gas path 3. According to a preferred embodiment, the exhaust gas treatment device 1 is an SCR-system, with which with the help of the injector 4, watery urea solution can be sprayed into the exhaust gas flow. In the housing 2, an SCR-catalytic converter 5 is then arranged in the exhaust gas path 3 downstream of the injector 4, which makes possible reducing nitrogen oxides to nitrogen and water by means of ammonia and carbon dioxide. In the housing 2, a static mixer 7 is additionally arranged in a mixing region 6 indicated by a brace, which is evident in the sectional views of FIGS. 3, 4, 6, 7, 9, 10, 12, 13 and in the views of the FIGS. 14 to 18. The mixer 7 serves for mixing-through the reactant with the exhaust gas flow. To this end, the mixer 7 is arranged in the exhaust gas path 3 downstream of the injector 4 and upstream of the SCR-catalytic converter 5.

(21) As is evident in particular from the views of FIGS. 14 to 18, the mixer 7 comprises a shell 8, which in a circumferential direction 9 encloses a mixer cross section 10 through which an exhaust gas flow can flow. Furthermore, the mixer 7 comprises multiple guide blades 11, which on a shell inside 12 project from the shell 8 and project into the mixer cross section 10. As is evident in particular from the detail views of the FIGS. 4, 7, 10, 13 and 18, the mixer 7 additionally comprises multiple straps 13 which in each case project on a shell outside 14 from the shell 8 to the outside. Complementarily to the straps 13, strap openings 16 are formed in a housing wall 15 of the housing 2, wherein each strap 13 projects into such a strap opening 16. In this case, a separate strap opening 16 is provided for each strap 13. The straps 13 engaging in the strap openings 16 bring about fixing of the mixer 7 in the housing 2. This fixing in this case is effected by way of a positive connection. Final fixing of the mixer 7 in the housing 2 in this case can be effected by means of welded connections 17, with which the respective strap 13 is fastened to the housing wall 15 on a housing outside 18 namely practically in such a manner that in the process the associated strap opening 16 is closed off at the same time. In particular, the respective welded connection 17 can be formed as a weld seam which surrounds the respective strap 13 along the strap opening 16 in a closed manner. Instead of a surrounding weld seam, a pendulum seam can also be provided, which runs over and beyond the respective strap opening 16.

(22) As is evident in particular from the FIGS. 14 to 17, the mixer 7 is preferentially configured as a shaped sheet metal part 19, which is formed by a single sheet metal piece 20, which comprises the shell 8, the guide blades 11 and the straps 13. In a starting state, the sheet metal piece 20 is flat. The guide blades 11 and the straps 13 are cut clear, for example by a punching process or a cutting process. Following this, the guide blades 11 and the straps 13 are angled relative to the remaining sheet metal piece 20. The remaining region of the sheet metal piece 20 thereby forms the shell 8, which by bending over in the circumferential direction 9 is preferably bent over so far that its longitudinal ends from a joint 21.

(23) Practically, the mixer 7 on its shell outside 14 is radially supported on a wall inside 23 of the housing wall 15 via supporting zones 22. In this case, multiple such supporting zones 22 are provided, which are arranged distributed in the circumferential direction 9 of the shell 8 and spaced from one another. With the help of these supporting zones 22 it is achieved that the mixer 7 only supports itself on the housing 2 only locally via these supporting zones 22. In particular, the mixer 7 because of this does not have any physical contact with the housing 2 outside these supporting zones 22 and outside the plug connections, which in each case are formed by a strap 13 inserted in the associated strap opening 16. Accordingly, an air gap 24 is formed radially between the shell outside 14 and the wall inside 23 outside the straps 13 and outside the supporting zones 22. With the help of this air gap 24, an air gap insulation between mixer 7 and housing 2 is created.

(24) The supporting zones 22 are formed by elevations 25, which in the case of the embodiments shown here are each integrally shaped on the housing wall 15 by forming. Accordingly, the elevations 25 project from the housing 2 or from the housing wall 15 to the inside in the direction of the mixer 7. In the embodiments shown in the FIGS. 1 to 7, the supporting zones 22 are positioned spaced from the straps 13 in the circumferential direction 9, in the view of FIG. 2, a supporting zone 22 is arranged in the circumferential direction 9 between two adjacent straps 13. In the view of FIG. 5, by contrast, a strap 13 is arranged in the circumferential direction 9 between two adjacent supporting zones 22.

(25) In contrast with this, the FIGS. 8 to 13 show an embodiment, in which the supporting zones 22 are each formed in the region of the straps 13. In this case, the respective strap opening 16 is located within the respective supporting zone 22. Accordingly, the respective strap 16 is also arranged within the respective supporting zone 22. In the view of FIG. 8, two supporting zones 22 are evident, in which, in each case, the interaction between strap 13 and strap opening 16 takes place centrally. In contrast with this, only one supporting zone 22 is evident in the view of FIG. 11, in which the respective strap 13 engages in the associated strap opening 16.

(26) As is evident in particular from the FIGS. 3, 6, 9 and 12, the housing 2, in the housing section 26 shown here, which contains the mixer 7, is configured in a two-shelled manner so that a first shell 27 and a second shell 28 are provided, which are inserted into one another or attached to one another. In the shown example, a substantially flat connection zone 29 is provided, in which the two housing shells 27, 28 are attached to one another.

(27) The mixer 7 is installed in the two-shelled housing section 26 so that a first circumferential section 30 of the shell 8 extends along the first housing shell 27, while a second circumferential section 31 of the shell 8 extends along the second housing shell 28. In the examples shown here, the first circumferential section 30 comprises two straps 13, and the first housing shell 27 comprises the two associated strap openings 16. The second circumferential section 31 by contrast comprises only a single strap 13. The second housing shell 28 comprises the strap opening 16 fitting the same. Both on the first housing shell 27 and also on the second housing shell 28, the elevations 25 in the mixer region 6 are shaped by a stamping process or the like in order to form the contact zones 22.

(28) As is evident in particular from the FIGS. 14 to 17, the mixer cross section 10 is practically flat so that a width 32 of the mixer 7 is greater than a height 33 of the mixer 7. In this case, the inner dimensions are drawn in FIG. 14. The same then applies also to the outer dimensions. In the example, the width 32 is at least twice the size as the height 33.

(29) Furthermore, all guide blades 11 are configured as straight guide blades 11 in this case, which are each orientated parallel to the height direction. Accordingly, all guide blades 11 run parallel to one another. Furthermore, the guide blades 11 in each case project into the mixer cross section 10 in a free-standing manner. They consequently have free ends which do not have any contact with the shell 8.

(30) In the case of the mixer 7 introduced in this case, a total of four guide blade rows 34 are formed, namely a first guide blade row 34.sub.1, a second guide blade row 34.sub.2, a third guide blade row 34.sub.3 and a fourth guide blade row 34.sub.4. In FIG. 15, a flow direction 35 of the exhaust gas flow is indicated by an arrow. On the inflow sided mixer side 36 and on the outflow-sided mixer side 37, the shell 8 comprises a first circumferential section 30 and a second circumferential section 31 each, which with the flat mixer cross section 10 are located opposite one another. The first circumferential section 30 of the inflow-sided mixer side 36, which can also be called inflow side 36 or inlet side 36, comprises guide blades 11, which from the first circumferential section 30 project in the direction of the second circumferential section 31 and which in the example form the fourth guide blade row 34.sub.4. On the inflow-sided mixer side 36, which can also be called inflow side 36 or inlet side 36, the second circumferential section 31 comprises guide blades 11, which project from the second circumferential section 31 in the direction of the first circumferential section 30. These guide blades 11 in the example form the third guide blade row 34.sub.3. On the outflow-sided mixer side 27, which can also be called outflow side 37 or outlet side 37, the first circumferential section 30 comprises guide blades 11, which project from the first circumferential section 30 in the direction of the second circumferential section 31, and which in the example form the second guide blade row 34.sub.2. Finally, on its outflow-sided mixer side 37 on the second circumferential section 31, the shell 8 comprises guide blades 11 which project from the second circumferential section 31 in the direction of the first circumferential section 30 and which in the example form the first guide blade row 34.sub.1.

(31) On the respective mixer side 36, 37, the guide blades 11 of the first circumferential section 30 are arranged offset in the flow direction 35 relative to the guide blades 11 of the second circumferential section 31. Accordingly, the exhaust gas flow consecutively flows about or flows through the four guide blades rows 34 shown in this case. The two guide blade rows 34.sub.3 and 34.sub.4 of the inflow-sided mixer side 36 each extend over the entire height 33 of the mixer 7. In this case, the guide blades 11 of the third guide blade row 34.sub.3 and the guide blades 11 of the fourth guide blade row 34.sub.4 are set at an angle opposite to the exhaust gas flow.

(32) Opposite blade angles are also provided in the case of the two guide blade rows 34.sub.1 and 34.sub.2 of the outflow-sided mixer side 37. There it is additionally provided that the guide blades of the first guide blade row 34.sub.1 and of the second guide blade row 34.sub.1 are designed differently in size. In particular it is evident that the guide blades 11 of the first guide blade row 34.sub.1 and of the second guide blade row 34.sub.1 each do not extend over the entire height 33 of the mixer 7. It is rather evident from the FIGS. 14 and 17 that a guide blade 11 each of the first guide blade row 34.sub.1 and a guide blade 11 each of the second guide blade row 34.sub.2 jointly reach the height 33 of the mixer 7. In particular, a separating plane 38 is evident, which is located between the two circumferential sections 30, 31. The guide blades 11 of the first guide blade row 34.sub.1 extend from the second circumferential section 31 only as far as to the separating plane 38. The guide blades 11 of the second guide blade row 34.sub.2 by contrast extend from the first circumferential section 30 only as far as to the separating plane 38.

(33) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.