Particle filter and method for producing a particle filter

Abstract

The invention relates to a particle filter (1) for an exhaust gas system (2), and to a method for producing a particle filter. The particle filter (1) comprises a plurality of flow channels (5), which extend from a first end face (6) towards a second end face (7) and which are separated from one another by porous channel walls (8). On the end faces (6, 7), the flow channels (5) each have mutual closing means (9) such that an exhaust gas (10) enters a flow channel (5) that is open on the first end face (6), flows through the channel wall (8), and escapes from the particle filter (1) by way of an adjacent flow channel (5) that is open on the second end face (7). In a direction of flow (11), the channel wall (8) has, in succession, the following layers: a particle filter layer (13); an intermediate layer (14) comprising a first SCR coating (15) having a first catalytic activity (16); a second SCR coating (18) having a second catalytic activity (19), wherein the second catalytic activity (19) is different from the first catalytic activity (16).

Claims

1-9. (canceled)

10. A particle filter (1) for an exhaust gas system (2), the particle filter (1) comprising: a first end face (6); a second end face (7); a plurality of porous channel walls (8); and a plurality of Sow channels (5) extending from the first end face (6), at which an exhaust gas (10) enters, through to the second end face (7), the flow channels (5) being separated from one another by respective ones of the porous channel walls (8), the flow channels (5) each having a closure (9) arranged alternately at the first and second end laces (6, 7) so that the exhaust gas (10) entering a flow channel (5) that is open at the first end face (6) flows through the channel wall (8) and flows out from the particle filter (1) through an adjacent flow channel (5) that is open at the second end face (7), each channel wall (8) having at least the following layers in succession in a flow direction (11): a particle filter layer (13) having a porosity of from 5 to 50% and an average pore size, of from 5 to 15 μm on the exhaust gas entry side (12); an intermediate layer (14) having a porosity of from 55 to 95% and an average pore size of from 15 to 100 μm, the intermediate layer (14) comprising a first selective catalytic reduction (SCR) coating (15) having a first catalytic activity (16); and a second SCR coating (18) having a second catalytic activity (19), different from the first catalytic activity (16), arranged on an exhaust gas exit side (17).

11. The particle filter (1) as claimed in claim 10, wherein the second catalytic activity (19) is greater than the first catalytic activity (16).

12. A process for producing a particle filter (1), the process comprising: providing a plurality of flow channels (5) each extending from a first end face (6) to a second end face (7) and being separated from one another by porous channel walls (8); alternately arranging closures (9) in the flow channels (5) at the first and second end faces (6, 7); coating the porous channel wall (8) with a first selective catalytic reduction (SCR) coating (15) having a first catalytic activity (16); coating the channel walls (8) of the flow channels (5) that are open at the second end face (7) with a second SCR coating (18) having a second catalytic activity (19), the second catalytic activity (19) being different from the first catalytic activity (16); arranging a particle filter layer (13) on channel walls (8) of the flow channels (5) that are open at the first end face (6), the particle filter layer (13) having a porosity of from 5 to 50% and an average pore size of from 5 to 15 μm.

13. The process as claimed in claim 12, wherein at least fee channel walls (8) and the particle filter layer (13) are produced by a printing process.

14. The process as claimed in claim 12, wherein the particle filter layer (13) is applied by a coating process.

15. The process as claimed in claim 12, wherein the second catalytic activity (19) is greater than the first catalytic activity (16).

16. The process as claimed in claim 12, wherein the first SCR coating (15) has a first viscosity (20) and fee second SCR coating (18) has a second viscosity (21), wherein the first viscosity (20) is less than the second viscosity (21).

17. A motor vehicle (3) comprising: an internal combustion engine (4); and an exhaust gas system (2), the exhaust gas system (2) having a particle filter (1) as claimed in claim 10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention and also the wide technical field are explained in more detail below with reference to the figures. It may be pointed out that the figures and in particular the size ratios depicted in the figures are purely schematic. In the drawings:

[0044] FIG. 1: shows a motor vehicle having an exhaust gas system;

[0045] FIG. 2: shows a section of a particle filter;

[0046] FIG. 3: shows a detail of FIG. 2;

[0047] FIG. 4: shows a process step a);

[0048] FIG. 5: shows a process step b);

[0049] FIG. 6: shows a process step c);

[0050] FIG. 7: shows a process step d); and

[0051] FIG. 8: shows a process step e).

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0052] FIG. 1 shows a motor vehicle 3 having an internal combustion engine 4 and an exhaust gas system 2. The exhaust gas system 2 comprises an addition unit 22 for a reducing agent or a reducing agent precursor, which can be taken from a tank 23. A particle filter 1 is arranged downstream of the addition unit 22. An exhaust gas 10 flows through the exhaust gas system 2 from the internal combustion engine through to the particular filter The exhaust gas 10 enters the particle filter 1 via a first end face 6 and leaves it again via a second end face 7.

[0053] FIG. 2 shows a section of the particle filter 1 as shown in FIG. 1. The particle filter comprises a plurality of flow channels 5 which extend, parallel to one another and separated from one another by porous channel walls 8, from the first end face 6 to the second end face 7. Closures 9 are arranged alternately in the flow channels 5 at the end faces 6 and 7. The exhaust gas 10 enters the open flow channels 5 via the first end face 6 and is forced by closure 9 to flow through the channel walls 8 in the flow direction 11. Thus, the flow channels 5, which are open at the first, end face 6 form the exhaust gas entry side 12 and the flow channels 5, which are open at the second end face 7 form the exhaust gas exit side 17.

[0054] FIG. 3 shows a detail III of FIG. 2. A channel wall 8 extends from the first end face 6 through to the second end face 7. An exhaust gas 10 flows in the flow direction 11 through the porous channel wall 8. A particle filter layer 13 is arranged on the channel wall 8 on the exhaust gas entry side 12. Downstream of the particle filter layer 13, an intermediate layer 14 which comprises a first SCR coating 15 having a first catalytic activity 16 is present in the porous channel wall 8. Downstream of the intermediate layer 14, on the exhaust gas exit, side 17 of the channel wall 8, there is a second SCR coating 18 having a second catalytic activity 19.

[0055] It can be seen in FIG. 3 that the second SCR coating 18 has been applied only after arrangement of the closures 9 and that the particle filter layer 13 has been applied before arrangement of the closures 9.

[0056] Particle filter layer 13, intermediate layer 14 and second SCR coating 18, each having different thicknesses 24, form the channel wall 8 in the finished particle filter 1.

[0057] FIG. 4 shows process step a), i.e., the still uncoated channel walls B that form the flow channels 5.

[0058] FIG. 5 shows process step b), in which closures 9 are arranged alternately, so that the flow direction 11 is then prescribed by the channel walls 8.

[0059] FIG. 8 shows process step c), in which the porous channel wall 8 is provided with a first SCR coating 15f which has a first viscosity 20, so as to form an intermediate layer 14. This process step can, in particular, also be carried out before process step b).

[0060] FIG. 7 shows process step d), in which the second SCR coating 18, which has a second viscosity 21, is arranged on the intermediate layer 14 on the exhaust gas exit side 1 of the channel wall 8, The second viscosity 21 is greater than the first viscosity 20 of the first SCR coating 15, so that it is not possible for the second SCR coating 18 to penetrate into the intermediate layer 14.

[0061] FIG. 8 shows process step e), in which the particle filter layer 13 is arranged on the intermediate layer 14 on the exhaust gas entry side 12 of the channel wall 8.

[0062] It may be pointed out as a precaution that the combinations of technical features shown in the figures are not absolutely necessary in general. Thus, technical features of one figure can be combined with other technical features of a further figure and/or of the general description. Anything different only applies when the combination of features has been explicitly stated here and/or a person skilled in the art sees that the basic functions of the apparatus/of the process otherwise can no longer be performed.

[0063] Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described, in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated, by the scope of the claims appended hereto.

LIST OF REFERENCE NUMERALS

[0064] 1 Particle Filter [0065] 2 Exhaust gas system [0066] 3 Motor vehicle [0067] 4 Internal combustion engine [0068] 5 Flow channel [0069] 6 First end face [0070] 7 Second end face [0071] 8 Channel wall [0072] 9 Closure [0073] 10 Exhaust gas [0074] 11 Flow direction [0075] 12 Exhaust gas entry side [0076] 13 Particle filter layer [0077] 14 Intermediate layer [0078] 15 First SCR coating [0079] 16 First catalytic activity [0080] 17 Exhaust gas exit side [0081] 18 Second SCR coating [0082] 19 Second catalytic activity [0083] 20 First viscosity [0084] 21 Second viscosity [0085] 22 Addition unit [0086] 23 Tank [0087] 24 Thickness